Fullscreen HTML5Med Res (??MB)HTML4

AUGUST 2020 ISSN 1030-2662 08 9 771030 266001 The VERY BEST DIY Projects! 9 95*NZ $12 90 $ INC GST INC GST The ULTIMATE in High Fidelity Audio Recording and Playback . . . NEW HIGH POWER ULTRASONIC CLEANER You Too Can OBD2 LIDAR & SODAR: They’ve got your range . . . and speed! awesome projects by On sale 24 July 2020 to 23 August 2020 Our very own specialists have developed this fun to build project to keep you entertained this month with special prices exclusive to Club Members. BUILD YOUR OWN: High Efficiency Power Supply Learn the basics of electronics making this high efficiency 5V power supply. Using the professional standard LM2678 5V step down ( or “buck” ) regulator, you can design a power supply that takes any voltage between 5-37V and bring it down to a constant and stable 5V rail. You will also learn how to read and understand datasheets. 1995 $ SKILL LEVEL: Beginner TOOLS REQUIRED: Soldering Iron SAVE 30% WHAT YOU NEED: 1 x Voltage Regulator LM2678T-5 +5V step-down 5A TO-220-7 1 x Universal Pre-Punched Experimenters Board - Small 1 x 100�H 3A Prewound Ferrite Choke 2 x 2 Way PCB Mount Screw Terminals 5mm Pitch 1 x 1N5819 Schottky Diode - 40V 1A DO41 1 x 0.47�F 50VDC Monolithic Capacitor 2 x 220�F 16VDC Low ESR Electrolytic Capacitor 1 x 10nF 50VDC Ceramic Capacitors - Pack of 2 3 x 22�F 63VDC Low ESR Electrolytic Capacitor CLUB OFFER BUNDLE DEAL ZV1636 HP9550 LF1272 HM3172 ZR1020 RC5498 RE6312 RC5348 RE6342 $11.95 $4.95 $4.95 $1.35 EA 80¢ 75¢ 46¢ EA 46¢ 42¢ EA KIT VALUED AT $28.74 SEE STEP-BY-STEP INSTRUCTIONS AT: www.jaycar.com.au/high-efficiency-psu See other projects at www.jaycar.com.au/arduino Essential Tools For Your Project 240V Soldering Iron Ideal for the hobbyist and handy person. Stainless steel barrel and orange cool grip impact resistant handle. Fully electrically safety approved. 25W TS1465 $14.95 (shown) 40W TS1475 $19.95 FROM 1495 $ 200G DURATECH SOLDER 60% Tin / 40% Lead. Resin cored. 2 sizes available. 0.71mm NS3005 1.00mm NS3010 SOLDER FLUX PASTE Provide superior fluxing and reduce solder waste. Nonflammable, non-corrosive. 56g tub. NS3070 ONLY 1795 $ SOLDERING IRON TIP CLEANER ONLY Static-safe, suitable for lead-free solders. Supplied with spare insert. TS1510 16 $ 95 EA Got a great project or kit idea? If we produce or publish your electronics, Arduino or Pi project, we’ll give you a complimentary $100 gift card. Upload your idea at projects.jaycar.com Shop the catalogue online! Free delivery on online orders over $99* Exclusions apply - see website for full T&Cs. * ONLY 1795 $ Looking for other projects to do? See our full range of Silicon Chip projects at jaycar.com.au/c/silicon-chip-kits or our kit back catalogue at jaycar.com.au/kitbackcatalogue www.jaycar.com.au 1800 022 888 Contents Vol.33, No.8 August 2020 SILICON CHIP www.siliconchip.com.au Features & Reviews 10 Measuring distance & motion with lidar and SODAR While radar has been a staple for use in detecting stationary or moving objects over large distances, sometimes precise measurements need to be made over much smaller ranges. This is where light (lidar) and sound (SODAR) are much more useful – by Dr David Maddison 31 Microchip’s new Hello FPGA kit The Hello FPGA (Field Programmable Gate Array) is an evaluation kit from Microchip intended to be a gentle introduction to FPGAs. It costs approximately $250 and includes a 480 x 320 LCD display (similar to the one in our Micromite BackPack V3), colour camera, 8GB of RAM and more – by Tim Blythman Lidar can be used to make detailed 3D maps or track moving objects, while SODAR is mainly used to remotely monitor the movement of water or air – Page 10 Constructional Projects 24 SuperCodec: the ultimate in computer sound cards With performance so good our Audio Precision test gear has difficulty measuring it, we believe the USB SuperCodec is better than nearly everything on the market. If you’re serious about your computer audio, you’ll want to build this one! - by Phil Prosser 38 A homemade Switchmode 78XX replacement Here’s an efficient drop-in replacement to the well-used 78XX series of regulators that you can easily build yourself for a variety of voltages – by Tim Blythman This USB SuperCodec is a must-have multi-function audio device, with high-fidelity audio recording and playback – Page 24 66 1MHz-6GHz Arduino-based Digital RF Power Meter This RF power meter uses an Arduino Nano and measures from 1MHz-6GHz at power levels up to 3mW (5dBm), and its range can be easily extended by using low-cost fixed attentuators – by Jim Rowe 88 The Colour Maximite 2 – part two The final part of this series covers assembly, setup and writing your own BASIC programs with this miniature computer – by Geoff Graham and Peter Mather Your Favourite Columns 46 Serviceman’s Log Fixing heaters – it’s a gas – by Dave Thompson These DIY switchmode regulators can replace 78XX linear regulators with better efficiency (no heatsink required!), and can be built for 3.3V all the way to 24V – Page 38 61 Circuit Notebook (1) (2) (3) (4) (5) Four USB power supplies from a laptop charger Preamplifier power supply runs from 5V DC Modifying the Ultra-LD Mk.2 to drive a hearing loop Altitude readout for the Boat Computer Heelometer for boats 83 Vintage Radio Velco 1937 ‘kit’ radio restoration – by Ken Kranz 98 Vintage Workbench Tektronix T130 LC Meter, Part 3 – by Alan Hampel Everything Else 2 Editorial Viewpoint 4 Mailbag – Your Feedback 65 Product Showcase siliconchip.com.au 87 SILICON CHIP ONLINE SHOP 106 Ask SILICON CHIP 111 Market Centre 112 Notes and Errata Australia’s electronics magazine 112 Advertising Index A Wideband RF Power Meter has never been simpler to build. It goes up to 6GHz, and is powered by an Arduino Nano – Page 66 August 2020  1 www.facebook.com/siliconchipmagazine SILICON SILIC CHIP www.siliconchip.com.au Publisher/Editor Nicholas Vinen Technical Editor John Clarke, B.E.(Elec.) Technical Staff Jim Rowe, B.A., B.Sc Bao Smith, B.Sc Tim Blythman, B.E., B.Sc Technical Contributor Duraid Madina, B.Sc, M.Sc, PhD Art Director & Production Manager Ross Tester Reader Services Ann Morris Advertising Enquiries Glyn Smith Phone (02) 9939 3295 Mobile 0431 792 293 glyn<at>siliconchip.com.au Regular Contributors Dave Thompson David Maddison B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Ian Batty Cartoonist Brendan Akhurst Founding Editor (retired) Leo Simpson, B.Bus., FAICD Silicon Chip is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 626 922 870. ABN 20 880 526 923. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Subscription rates (12 issues): $105.00 per year, post paid, in Australia. For overseas rates, see our website or email silicon<at>siliconchip.com.au Editorial office: Unit 1 (up ramp), 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9939 3295. E-mail: silicon<at>siliconchip.com.au ISSN 1030-2662 * Recommended & maximum price only. Printing and Distribution: Editorial Viewpoint Businesses need to handle ‘black swan’ events better Some businesses have clearly handled the COVID-19 crisis better than others. In some cases, they continue to operate as usual; you would never know that their workforce has been relocated and their internal operations disrupted. Others have significantly reduced their quality of service since early this year, and are obviously struggling to adjust to the current situation. I think that those who have reacted by cancelling (or ignoring) contracts, and have cut back on their activities, are making a long-term mistake. There is that saying that “every dark cloud has a silver lining”, and perhaps the silver lining of the current situation is the fact that it’s forcing us to re-evaluate what is really important and perhaps focus a bit more on our long-term goals. Sure, times are tough, but life has to go on, and businesses need to continue to operate. Clearly, many ‘bricks and mortar’ retail operations have suffered badly (with some exceptions, like supermarkets). But for the most part, at least in Australia, mail-order businesses are doing very well, and many service-based companies have remained open. I do feel very sorry for those businesses which were forced to close by government edict and many will probably never re-open; eg, restaurants, bars, pubs, clubs etc. I think the situation could have been handled in such a way to avoid much of that pain and suffering (but that’s a discussion for another day). Nobody knows how long this situation will last; it could be years. Life can’t just stop in the meantime. We have to adapt and find ways to keep the economy running, and continue to supply the goods and services that people want and need. We certainly haven’t let COVID-19 interfere with SILICON CHIP (apart from some mailing disruptions, which are unfortunately out of our control). Over the last few months, I have dealt with several organisations that have seemingly seen increased demand for their products and services. While it’s understandable that they are busy, the lack of communication and resulting poor service are not justified. Lots of people are out of work, so if your business is booming and you can’t cope with the demand, why not hire some extra people? With all that extra money coming in, plus government stimulus support, surely they can afford to hire new employees. And I would imagine there are plenty of people looking for work at the moment. (On a related topic, we are hiring; see the ad on page 37). Many companies are now refusing even to answer the phone and take weeks to answer e-mails (if they ever do). That is not the way to conduct business. We are still answering the phone and replying to e-mails as best we can, although our office occasionally closes a bit earlier than usual due to reduced staff presence. But at least you can get a hold of us. Even if you have many employees working from home, it is not hard to forward e-mails and redirect phone calls. So I think that those companies which have closed their phone lines are really just using the crisis as an excuse to avoid dealing with customers (except for new sales, of course). In fact, I get the impression that many businesses and individuals are exploiting the crisis by crying poor and trying to shirk their responsibility when really, they are not doing that badly. Some are also taking advantage of the situation to reduce after-sales support and prioritise on making sales, which is not likely to lead to happy customers. So let’s keep the economy going and find ways to work around the voluntary or enforced isolation we are currently experiencing. It may go on for a while yet. We can keep the country and the economy going, despite the unfortunate situation. Nicholas Vinen 24-26 Lilian Fowler Pl, Marrickville 2204 2  Silicon Chip Australia’s electronics magazine siliconchip.com.au MAILBAG your feedback Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd may edit and has the right to reproduce in electronic form and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman”. New Zealand delivery delay I’m happy with the result and they and the silicone recommended in the work well. My old A/V amp/receiver article hardened in a day. For a VicThanks for your explanation of why my June 2020 issue was so late. Ironi- has a subwoofer output, so I am con- torian winter (don’t forget Tassie and cally, it arrived today, just after I read sidering adding a single subwoofer NZ), you will probably need more than a week. your e-mail (about a month late). I eventually. Also, the bricks need to be perfectI used the Altronics drivers. I debatthink you people must have waved RAYMING TECHNOLOGY ed whether to recess the drivers into ly dry; it will not adhere well to old, your magic wand. mossy bricks. Once the silicone is dry, the cabinet as IPCB thought that they were I would like to pass on my thanks PCB Manufacturing and Assembly Services it is almost impossible to remove and susceptible to damage if mounted on and appreciation to you and your staff Fuyong Bao'an Shenzhen China therefore would require destruction to for producing such an excellent and the outside. 0086-0755-27348087 Some comments against mounting replace an internally mounted speaker informative technical publication. I Sales<at>raypcb.com purchased my first issue of Electronics them inside were that the acoustics should it fail. Gaps can be the result of irregular Australia in 1971, and built the Delta- would be compromised, but surely www.raypcb.com het receiver, which is still operation- only an acoustic pedant would notice concrete, so spend some time selecting your bricks and ensuring that the sural. I stayed with EA, purchasing each the difference. Anyway, if they were mounted in- face is smooth and true. It helps to rub monthly edition until Jamieson Rowe side, the ports would have to be per- two blocks together to remove small moved to Silicon Chip. I followed. I always look forward to receiving fect, and mine were not. so I mount- chunks or just run an angle grinder my monthly dose of Silicon Chip. Well ed them outside. I used the silicone lightly over it. Also, check that the sealant, as suggested, but I found that timber is not warped and only select done to all of you. there is small side-slip still possible the best timber. Ray Clarkson, You can mount the Altronics drivwith pressure. It might harden with Dunedin, New Zealand. time, however; maybe Liquid Nails ers inside the larger concrete block, and it will help the bass end without would be better. Feedback on Concreto speakers having to buy the more expensive subAlso, I may have overdone the I endeavour to keep an interest in woofer drivers. things electronic, mainly via your mag- amount required for adhesion, as there Use the same dimensions for the azine. I have been an Amateur Radio is a small gap between the timber and port as shown in the sub diagram, and licence holder for some 40+ years, and brick in one of the “cabinets”. reduce the driver mounting hole diRaymond Reaburn, I am a musician (still playing). So I was ameter to suit. Our original prototype Mont Albert North, Vic. interested enough in your Besser brick used this configuration, and it worked bookshelf speaker project (June 2020; Allan Linton-Smith responds: Thanks siliconchip.com.au/Article/14463) to for your comments! I built the pro- well, but our final setup with the small totype speakers during hot weather, and large bricks worked better. have a go. RAYMING TECHNOLOGY Fuyong Bao'an ,Shenzhen, China Tel: 0086-0755-27348087 email: sales<at>raypcb.com web: www.raypcb.com PCB Manufacturing and PCB Assembly Services 4  Silicon Chip Australia’s electronics magazine siliconchip.com.au Use neutral-cure silicone with concrete I have enjoyed many projects provided and read all articles with interest. I am one of the silent majority. The Concreto Speaker System, June 2020 edition, is impressive for its simplicity and reported good performance. It is on the list of projects I want to undertake. In the assembly instructions, you mention Parfix Kitchen & Bathroom silicone sealant was used. This is an acetic cure silicone suitable for glass, tile and stainless steel surfaces. The blocks used as the base structure of the speakers are concrete and so are alkaline in nature. Acetic cure silicone is unsuitable for concrete as the acetic acid produced in the curing process will react with the concrete and degrade the “adhesion surface” interface, causing the sealant to release from the blocks in time. It often takes months to manifest itself as a problem. For adhesion to concrete surfaces, it is best to use one of the many neutral-cure silicones on the market, nominally called “concrete” or “roofing” silicone. Charles Camenzuli, Wentworthville, NSW. Concern over chemical spill handling I have some concern in your article on anodising aluminium (May 2020; siliconchip.com.au/Article/14423). You are using suggesting the use of sodium bicarbonate to neutralise sodium hydroxide spills. Both of these are basic (alkaline), not acidic. Sodium hydroxide (NaOH) is extremely dangerous when not carefully used. Basic (alkaline) burns usually are much more severe (rapid-acting) than acidic burns. Get it in your eye, and you will be permanently blind. With acid, you have a small chance if you are quick enough to wash it out. NaOH has a pH of 14 while sodium bicarbonate (NaHCO3) is a weak base with a pH of 8.4. On the pH side of things, you are better off using water with a pH near 7.0 to weaken NaOH. Ideally, a weak acid should be used to neutralise sodium hydroxide. For example, citric acid (lemon juice), acetic acid (vinegar) or dilute hydrochloric acid could be used. Boric acid or ammonium chloride are sometimes used. For non-industrial situations, vinegar or lemon juice are the easiest 6  Silicon Chip to obtain and safe to use. Remember that mixing acids and bases will create an exothermic reaction with likely splattering consequences, the degree of which is determined by the way, quantity and rate of mixing. Be sure to wear the appropriate protective equipment. The above information is based on safety processes learned while working for a major chemical company, starting as an instrument technician and then as an engineer. Wolf-Dieter Kuenne, Bayswater, Vic. Response: you are right that NaHCO3 would be of no use in the case of a NaOH spill. The bicarbonate of soda was only intended to be used to clean up any spilled acid (specifically, the sulfuric acid), and that is the only purpose that we mentioned for it. The reason why we did not suggest keeping a weak acid on hand is that NaOH is only used in that process in a very weak solution (one spoonful in a tub of water). It might still be possible to create a hazard by accidentally dropping a large number of NaOH granules into the water while making that solution. In that case, you are right that having a jug of vinegar on hand would be a good idea. Preamp for acoustic guitar I would like to suggest that you design an acoustic guitar preamp in pedal format. Commercially available guitar preamps are expensive for what they are (well, the good ones anyway). I don’t think the circuits are all that complex. LR Baggs makes some popular ones. The ideal list of features would include a DI (direct injection) output, six-band graphic equaliser, phase switch, volume and gain controls. It could also include a notch filter, if there is room. (J. C., Point Cook, Vic) Comment: thanks for the suggestion; it is a good one. Thumbs up for Colour Maximite 2 Thanks for producing another Silicon Chip with great content under the somewhat difficult global conditions we are currently experiencing. I am pleased that I can keep up by having a combined print & online subscription, because the June printed issue has yet to arrive in New Zealand. I perused my online version of Silicon Chip earlier today and am pleased Australia’s electronics magazine to see Geoff Graham’s and Peter Mather’s Colour Maximite 2 included. I look forward to more on it in the future. I am fortunate to have a singleboard version of the CMM2 sitting on my bench, and am awed by its performance. It is a huge step up from the original Maximite, so I must congratulate the originators of this design. The future for the CMM2 and Micromite is now really only limited by our imaginations. Warwick Guild, Dunedin, New Zealand. Response: the CMM2 is a potent little computer, and pleasingly easy to build. Sorry about the delays for New Zealand subscribers; it took around six weeks for the June issues to arrive. Unfortunately, there isn’t much we can do about it. We hope the postal system will recover soon. Fire and inversion layers affect radio signals I was prompted to write in by the letter about radio communications during bushfire emergencies in the June 2020 issue (pages 10 & 11). I read a Scientific American article in late 1968/ early 1969 with comments from a fire chief (from memory, in New York) on what he experienced at the scene of a very intense fire. He said that the department had introduced new UHF portables and were using them at this fire when he attempted to communicate with one of his men that he could see through the shimmering air. There was no response from his radio, even though he could see his man using his portable. He, the fire chief, had no reception of those signals obviously being transmitted, so he assumed his radio was faulty. At the end of the day, he had a technician check both radios, and they worked OK, both one-to-one and as part of the whole system. Investigations were ordered, and after extensive tests, it was assumed that the intense fire had created a vertical air shear, like a mirror wall, that deflected the radio signals at the shear between the two radios. The lower frequency (longer wavelength) of their earlier low-band VHF was assessed side-by-side through the tests, and VHF worked OK. We know that horizontal layering (inversion layer), temperature and air density go hand-in-hand. siliconchip.com.au A further anecdote, if I may, is that long hop HiBand VHF over about 100km between Barrow Island and Onslow on the mainland of WA was problematic when the sea was calm, and there was no wind. When the sea was rough, we assumed that scatter was occurring to give a path between the inversion layer and the sea surface through ducting – a perfect mirror on top and bottom causing the radio wavefront to move past or fall short (skip). A similar effect was experienced when I set up a HiBand VHF link between a high building in Fremantle and an oil rig being serviced in Gage Roads. When the rig floated higher on the tide, the antenna set on the top of the derrick would move above the low inversion layer, and comms failed until the tide lowered or after sundown when we assumed the inversion layer disappeared. My point here is that this effect must be considered for any proposed upgrade in fire comms. It also might explain why short-wavelength mobile phones and the current UHF radios issued to firefighters failed at times during the last Black Summer events. Some HF manufacturers might be approached to create a small HF portable, particularly as both Australian manufacturers of HF have created almost FM-like clarity using HF. I also recall setting up some AM-HF at around 2MHz for the CFA at Werribee while I was at the RAAF radio school in 1967 (in my spare time of course) and that seemed to work well, despite the cumbersome equipment. Robert Sherwood, Perth, WA. Properly aligning AM radio dial low end In Dr Hugo Holden’s article on his H-Field Transanalyser, he gives some instructions on how to use it to align an AM radio (June 2020, p90; siliconchip. com.au/Article/14471). Hugo observes that the low-end antenna alignment can be done by sliding a ferrite rod’s coil one way or the other. As he points out, many cannot be so adjusted. When it was possible, I have not found a case where this adjustment was sufficient for optimal alignment. This is a method that lots of folks repeat, without having challenged its usefulness. The preferred method is to adjust the oscillator coil for maximum output siliconchip.com.au at 600kHz, while ‘rocking’ the gang. In effect, the adjustable oscillator circuit is being brought into alignment with the unadjustable/limited-adjustable antenna circuit. I have detailed this method in my articles. Also, the accepted top-end alignment consists of (i) setting the oscillator trimmer for 1600kHz with the gang fully open, (ii) re-checking the bottom end, then (iii) setting the signal generator to 1400kHz, tuning to that signal, and adjusting the antenna trimmer for max output. There are sound and accepted theoretical and practical reasons for the above procedures, in that they consistently deliver the best performance figures from broadcast-band radios of all kinds. Ian Batty, Rosebud, Vic. Clarification of H-fields Based on some of the feedback I’ve received on my H-Field Transanalyser design (May & June 2020; siliconchip. com.au/Series/344), I realised that I could have done a better job of explaining some aspects of the design, and how the unit got its name. Generally, a transistor radio with a ferrite rod responds to the magnetic component of the electromagnetic wave, or the H-field as it is known. The E-field is the electric component of the field, not received to any great extent unless the radio has an external wire antenna. So the idea of the Transanalyser was to produce a controlled and known near H-field to apply to the radio’s ferrite rod. This field is produced by the current in the one-turn loop. This current is set by the open circuit source voltage from the attenuator output applied across a 150W resistance, 75W being the generator output impedance and the other 75W being a series resistor. The loop is on the “ground” side, as capacitively coupled voltages to the rod’s coils are to be avoided. The point is that the loop which generates the H-field has a controlled current. The loop voltage is not important. Therefore, the controlled H-field at the radio’s ferrite rod is reduced by the attenuator to very low values, analogous to the H-field from a far off, or weak, radio station. And this amount of field is the same for each radio tested, as the loop passes directly around the radio’s ferrite rod. Australia’s electronics magazine August 2020  7 One problem with external loops some distance away from the radio is that the near-field H-radiation depends on the spacing of the loop from the radio and the rotational axis of the loop, with respect to the radio’s rod, and the other factors I noted in the article. My direct loop avoids that, and helps with comparisons and uniformity between testing different radios. But of course, seeing a wire loop around the ferrite rod being fed by an RF source, one is tempted to think of transformers and the efficiency of the coupling. But the voltage on the one turn loop and the voltages on the tuned circuit or other secondary windings on the radio’s ferrite rod (due to turns ratios etc) will vary by radio. This does not matter, because it is the radio’s overall response to the H-field applied to the ferrite rod that is important – just as it is in use, when the radio is responding to the H-far-field of the electromagnetic wave from a radio station. Also, the noise performance of the radio is better assessed on a listening test. As the audible modulation on the carrier of the received H-field drops, you can hear into the noise floor, which is exactly what happens with weak and far off radio stations as you get further away from them. This is the main reason why any RF test generator, however it is coupled to the radio, requires a decent attenuator. One other thing I could have mentioned was that if a thin wire is used to make the loop, the wire pair can be twisted together for a considerable length (30cm or more). Then the radio’s PCB can be flipped around for repairs and adjustments without being hindered by the presence of the loop. Teflon-covered hookup wire or enamelled copper wire is fine. When finished, the small loop near the rod can just be cut to remove it, and the wire discarded. Dr Hugo Holden, Minyama, Qld. Hazards swapping Active & Neutral I was delighted to read your article on assembling “Concreto” speaker enclosures. I still use my 3-foot Humes concrete pipe with an 8-inch Wharfedale speaker on top, standing on two timber slats to provide an air vent, assembled around 1960. In the same issue (June 2020), a correspondent asked why it was dangerous to swap Active and Neutral wires in domestic power points, and I would like to comment. I spent many years living in rental accommodation, in old buildings that had (presumably) been wired before a standard existed for the orientation of Active and Neutral pins. One day, a friend visited and offered to prepare a meal. She brought her electric frypan, one which she had used for years. We discovered that it worked with some of my power points but not with others. I checked and found that Neutral and Earth had been swapped inside the frying pan. Since Earth and Neutral leads are joined at the switchboard, the appliance worked correctly with no indication to the user that anything was wrong -- provided it was plugged into a correctly-wired powerpoint. When the incoming Active and Neutral were reversed, the element was connected between Neutral and Earth, while the body of the pan was connected directly to 240V! 8  Silicon Chip I have come across the same behaviour with an extension cord in which Neutral and Earth were inadvertently swapped at one end. Appliances worked (with and without the extension cord) when plugged into a correctly worked socket, but failed – and had a live outer casing – when plugged into outlets that had Active and Neutral reversed. If ever an appliance works with some power points and not others, switch off and beware! Congratulations on an excellent magazine. Mike Emery, Fern Tree, Tas. Flywheels are not to be trifled with I was interested to read John Walker’s account of flywheel storage in your June 2020 issue (Mailbag, p4). It brought to mind a similar situation I encountered many years ago. As a young graduate student, I used to spend my summers working at Culham Laboratory in Oxfordshire, on the fringes of nuclear fusion research. During my first month, I joined a tour to see JET (the Joint European Torus) and some of its ancillary research tools. One that stuck in my mind was an enormous flywheel weighing many tons. I believe it was spun up over several hours, then connected to a generator that would bring it to a halt in a matter of seconds, thereby delivering a huge pulse of current to one of the particle accelerators. The flywheel was mounted in a shallow pit with its axle vertical, and one of the party asked why. Surely the bearings would be easier to maintain if the axle was horizontal? The tour guide agreed, but pointed out that the designer had considered a range of risks, one of which was the bearings failing and the flywheel tearing itself loose when spun up to full speed. If this had happened, some back-of-the-envelope calculations had shown that the flywheel would break its way out of the building and roll as far as London, destroying everything in its path before it came to a halt! Hence the pit, which would at least contain the damage in the case of a failure. I greatly enjoy your magazine and look forward to reading many more issues. Andrew Colin, Brisbane, Qld. Adding altitude display to Touchscreen Boat Computer The speedo in my elderly LandCruiser went berserk, and the pointer broke off. I solved this problem by building the April 2016 Touchscreen Boat Computer with GPS (siliconchip.com.au/Article/9887) and installing it in a bespoke (3D-printed) ABS case above the dashboard. With the software upgrade published soon after, it has served well for nearly four years. One addition I would have liked would be to show the altitude – not a great need for this as a Boat Computer, but inspired by your Car Altimeter in the May 2020 issue (siliconchip.com.au/Article/14431). I wondered if the boat computer software could be tweaked to extract the current altitude from either the GGA or GSN lines or the NMEA messages. It could then be shown on the screen along with the latitude and longitude, assuming a spot could be found for it. Australia’s electronics magazine siliconchip.com.au One change I did make that could be of interest to the current project; I have a transistor shorting across the trimpot, which adjusts the screen brightness for maximum daytime driving. When the headlights are turned on, a wire from that relay activates to turn the transistor off, so the screen brightness is at the trimpot setting for night driving. Maybe this is only possible on older cars where you can access this sort of wiring. Ron Walker, King Creek, NSW. Response: As luck would have it, we’ve actually finished the modifications for the Altimeter, and it can be viewed on page 64 of this issue. Combining block control with DCC UG85-W LoRaWAN Gateway (Wi-Fi) The Ursalink UG85 is an intelligent, performant and configurable LoRaWAN indoor gateway for smart IoT applications. The UG85 is based on the Semtech SX1301 chipset, allowing to operate on multiple channels at the same time. SKU: ULC-014 Price: $560.50 ea + GST UC11-N1 LoRaWAN Sensor Node I found your article on an Arduino DCC system interesting (January 2020; siliconchip.com.au/Article/12220). However, not all model railway enthusiasts want to use DCC. Many of us are happy to stick with block control, which for many prototypes is more practical. But there are DCC features we would like such as constant lighting, switchable lighting in coaches/trains, on/off loco traction and switchable sound. Constant lighting is possible using low-voltage lamps, LEDs or 12V intermittent pulses plus capacitors, or highfrequency AC. (However, locos are now appearing with Faulhaber coreless motors which don’t like AC). It would seem to me to be possible to use an imposed track DCC signal (once) to switch on/off a latching decoder to achieve most of the above features. That shouldn’t damage existing motors. Greg Procter, Hukerenui, NZ. Tim responds: I certainly do see the benefits on block control, but do not see it as mutually exclusive with DCC. A layout set up with block control is well suited to making the most of conversion to DCC. Most DCC decoders are ‘backwards-compatible’ with analog DC tracks. The blocks can be configured into ‘power districts’ to ensure that electrical faults are isolated. The blocks can also be connected to individual track current sensors to provide inputs to a signalling system, opening up the possibility of automatic train control. Current sensing is easier to do in a DCC system as there is always power present, which is not the case in a basic analog DC system. We’ve looked at designing our own DCC decoders, and while we think it would be interesting to create a ‘hackable’ design which can be customised by the end-user, there is no way we can compete with existing commercial decoders on price point or miniaturisation. Presuming that you do not want to simply install DCC for motor control, which would give the desired features, you could consider what was suggested in Mailbag in March 2018 (p7, “WiFi model railway control is already available”). Such a system could sit alongside existing analog DC hardware. The problem of getting steady power still exists, and there doesn’t appear to be a broadly accepted standard to work with (another of DCC’s benefits). A miniature WiFi controller would also be handy for many applications outside of model railways. SC siliconchip.com.au Helping to put you in Control The UC11-N1 is a fully integrated, battery powered LoRaWAN node with multiple communication interfaces for connecting to a wide range of external sensors. SKU: ULC-015 Price: $258.00 ea + GST AM100 Ambience Monitoring LoRaWan Sensor Ursalink AM100 Series consists of multiple smart sensors that are built specifically for indoor ambient measurements. It has a clean and modern design that makes it discrete in indoor ambience. SKU: ULC-019 Price: $285.00 ea + GST ITP14 Universal Process Indicator 0-10 V / 4-20 mA Easy to mount the ITP14 fits into a standard 22.5 mm borehole for signal lamps and can be connected to 0-10V or 4-20mA signals. The measured values are scalable and there is NPN output for control or alarm function. SKU: AKI-010 Price: $149.95 ea + GST TCW122B-RR - Remote relay control across a LAN Each TCW122B-RR is an Ethernet based I/O module that has two digital inputs and two relay outputs. Two units can be paired in order to seamlessly send digital IO data to the other paired device. SKU: TCC-003 Price: $144.70 ea + GST Slim Multi-Function Timer SPCO MINI-1M Slim Line, DIN Rail mount, multi-function timer. SPCO output, dual LEDs indication. Multiple time range 0.1 s to 100 hours. 12 to 240 VAC/VDC powered. SKU: NTR-101 Price: $74.95 ea + GST Relayduino USB/RS-485 IO Module 8-28VDC Arduino-compatible controller with eight relay outputs, four optoisolated inputs and three 4 to 20 mA or 0 to 5 VDC analog inputs. USB and RS-485 serial interfaces. Windows, Mac OS X and Linux compatible. 8~28VDC powered. SKU: KTA-223 Price: $164.95 ea + GST For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Prices are subjected to change without notice. Australia’s electronics magazine August 2020  9 Measuring distance & motion with Lidar & Sodar Radar has been used for more than a century to detect moving or stationary objects at great distances. But sometimes you need to make precise measurements over much smaller distances – mapping a building or a crime scene, for example. Or you may want to measure wind or water currents. For these tasks, light and sound are more useful than radio waves. Hence, the invention of lidar and SODAR. D istance and motion can be measured using radio waves, light or sound. Radar (RAdio Detection And Ranging) is the most well known of such technologies, and the use of sound for sonar (SOund Navigation Ranging) on ships and submarines is also well known. In this article, we look at the use of light and sound waves for sensing technologies and how they differ from radar and sonar. Experiments with radar started in the late 19th century, but it wasn’t fully developed until the early 20th century, with rapid advances occurring between 1935 and 1945. It was used mainly to detect by Dr David 10  Silicon Chip ships and later, aircraft at great distances. Sonar developed over a similar period, and was used both for marine navigation and to detect submarines. We previously described Airborne Weather Radar in the April 2015 issue (siliconchip.com.au/Article/8449) and Broadband Marine Radar in the November 2010 issue (siliconchip.com.au/Article/343). Plus, we discussed sonar in the context of bathymetry in June 2019 (siliconchip.com. au/Article/11664). More recent developments include SODAR (SOnic Detection And Ranging) and ultrasonic ranging, both of which utilise sound waves, Maddison Australia’s electronics magazine siliconchip.com.au but they operate quite differently to sonar. You may have also heard of lidar (LIght Detection And Ranging), which uses light rather than radio waves. We’ll also briefly discuss infrasound detection, which is at the opposite end of the frequency spectrum to ultrasound. We previously discussed some uses of lidar, for Google Street View and Apple Look Around mapping, in the SILICON CHIP article on Digital Cartography in the March 2020 issue (siliconchip.com.au/Article/12577). Many autonomous ground vehicles also carry lidar units to sense their surroundings, and some such vehicles also use pre-scanned 3D maps for safe navigation. Radar vs lidar and SODAR The main differences between radar, lidar, SODAR and ultrasonic ranging are as follows: Compared to radar, SODAR and ultrasonic ranging, lidar gives much-improved object detail because of its shorter wavelength (in the hundreds of nanometres). Similarly, smaller objects can be detected, such as dust particles. Lidar and SODAR can be used to measure wind strength and direction at a distance. Lidar senses the motion of aerosol particles in the air, while SODAR is sensitive to air density differences. For example, the Windfinder AQ500 (siliconchip. com.au/link/ab2q) SODAR unit is designed for meteorological measurements. Ultrasonic ranging is superficially similar to SODAR, in that ultrasound is used to determine the range in both cases. But SODAR uses an array of microphones and sound ‘beams’, while ultrasonic ranging uses a single microphone and beam. It is often used in older autofocus cameras, and also small robots, for obstacle detection and avoidance. Radar gives a much greater detection range than lidar or SODAR. The laser beams used for lidar are readily absorbed by atmospheric particles like fog, smoke or dust, whereas Fig.1: lidar measurements taken as Apollo 15 orbited the Moon on two different orbits (numbers 15 and 22) in 1971. The lines indicate elevations and depression relative to a sphere 1738km from the centre of mass of the Moon. those hardly affect radar or SODAR. Radar detection distances are generally limited by lineof-sight considerations. Airborne radar can have a range of several hundred kilometres, while over-the-horizon radars (which reflects a beam off the ionosphere) can have a range of several thousand kilometres. One example of the latter is Australia’s Jindalee Operational Radar Network (JORN). Lidar can have a range of tens to hundreds of metres, or in extreme cases, up to about 4km. SODAR typically operates over a maximum range of about 200-2000m. Ultrasonic ranging is typically is used at distances between centimetres and a few metres. Fig.2: a lidar image of a forest. Source: Oregon State University. siliconchip.com.au Australia’s electronics magazine August 2020  11 Fig.3: a lidar-derived flood model for an area in South Carolina along the Saluda River. Source: USGS. Note that lidar will work through a glass window, but ultrasonic ranging will not, since sound waves will bounce off the glass but light waves can pass through. This was a limitation of early ultrasonic autofocus cameras such as the SX-70 (described below). Operating principles In all cases, the operating principles of radar, lidar and SODAR are essentially the same. A pulse of radio energy, light or sound waves is emitted. That pulse is reflected off an object or objects and the reflected pulse returns to the receiver. The elapsed time between emission and the detection of the reflected pulse is recorded and, in some cases, so is the frequency difference. The distance to the object is determined by multiplying the elapsed time by the speed of light or sound, and dividing the result by two. This accounts for the fact it has to travel there and back. For example, if a pulse of radio waves or light takes 3 microseconds to return to the place of emission, then the range, R = 3µs x 300,000,000m/s ÷ 2 = 450m. 300,000,000m/s is approximately the speed of light. The object’s velocity can be determined by the Doppler shift (if measured), and the angle from the transmitter/receiver can also be determined by knowing the direction of the strongest return. Lidar usually uses a single beam. It may be fixed, to measure a distance, or scanned in two or three dimensions to establish a 2D or 3D map of an area. SODAR generally uses multiple beams to develop a 2D or 3D map. In contrast, ultrasonic ranging typically uses a single beam Fig.5: a 2D (horizontal) DIAL map showing methane emissions above a landfill area. Source: Innocenti et al. (https://doi.org/10.3390/rs9090953) 12  Silicon Chip Fig.4: a photograph (left) and lidar image (right) revealing otherwise almost invisible remains from an archeological site in New England, USA. Source: Kate Johnson, University of Connecticut. to establish distance, but it is possible to move the beam to create a 2D or 3D map of an area. So why use lidar rather than a camera, as both sense visible light? A single lidar sensor can have a 360° field of view (360° cameras exist, but are composed of multiple cameras). But its main advantage is that the distance to each ‘pixel’ in the image is accurately known. Our brains are good at extracting approximate range information from a photo, but it’s very hard for a computer to do that. With a lidar image, though, it is clear to the computer exactly where each sensed object is located relative to the lidar device, as the result is a 3D ‘point cloud’. That’s much easier to use for tasks like obstacle avoidance. The point cloud can also be shown as a 2D image and rotated in place; something you can’t easily do with still images without using multiple cameras and a lot of image processing. Uses for lidar The idea of using a laser to measure distance came about in 1960, just after the laser was invented. It was then used by the US National Centre for Atmospheric Research to measure clouds. It was later used in 1971 by Apollo 15 to make topographic measurements of the Moon (Fig.1) and by Apollo 16 and 17, both in 1972. Earlier measurements with lidar were relatively simple distance measurements, or small collections of distance measurements, because of limited computer storage capabilities. But now, highly-detailed and complex 3D ‘point clouds’ representing detailed photo-like models of the environment can be produced. Fig.6: a partial photo and drawing of the Apollo 15 laser ranging retroreflector. This was the largest reflector left during the Apollo missions and is still in use. Australia’s electronics magazine siliconchip.com.au Fig.7: the NASA Clementine topographic map of the Moon from 1994. The colours indicate elevation, as shown on the scale. This data was gathered from an altitude of ~500m. Fig.8: lidar observations of Martian clouds on 3rd September 2008 from NASA’s Phoenix Mars Lander. Fall streaks are suggestive of falling of water snow (not CO2 snow). Lidar can be used from the air or space, with topography mapped as the terrain is traversed, or it can be performed at ground level, either in a fixed location or on a moving platform. Examples of the latter are Google and Apple cars making 3D maps of entire cities from a ground perspective. Airborne or ground-based lidar can be used in forestry to measure the height of trees, their rate of grown and their volume (to estimate when to harvest or for fire management purposes) – see Fig.2 overleaf. Airborne lidar can also be used to make accurate 3D maps, for example, to determine where flooding will occur (Fig.3). Lidar can be used for pollution modelling, by detecting particles in the air that are approximately the same size as the wavelength of the light used. Lidar has several uses in digital mapping and urban planning; these were described in our March 2020 article on Digital Cartography (siliconchip.com.au/Article/12577). Coastlines can be accurately mapped with lidar, and with special lidar that penetrates water calls LADS (Laser Airborne Depth Sounder), the submarine environment can also be mapped. LADS was described in our June 2019 article on sonar (siliconchip.com.au/Article/11664). Lidar is also useful for mobile phone network planning, so that line of sight locations from proposed towers can be determined. This is particularly important for 5G because of poor building and foliage signal penetration. In mineral exploration and mine management, lidar can be used for high-accuracy surveys of existing and proposed mine sites, and also to measure dust and pollutants. In archeology, lidar can be used to map ruins beneath jungle canopies, where they would otherwise be invisible, or to reveal micro-topography in other areas suggestive of buried remains (see Fig.4). Lidar can be used in architecture and building restoration to make precise models of buildings, and in the case of restorations, parts can be scanned and reproduced if necessary. It can also be used for geology; for example, to study changes in topography due to a volcanic eruption or ground movements such as landslides or avalanches. stances in the atmosphere such as pollution, or natural emissions such as from hydrocarbon deposits. The latter can be used to locate such deposits (see Fig.5). This technique was developed in the late 1970s by BP and the National Physical Laboratory in the UK. In DIAL, laser beams of two specific frequencies are emitted. One frequency is tuned to a known absorption band of a molecule of interest, and the other is at a slightly different wavelength which is not absorbed by the molecule of interest. Both beams are backscattered by atmospheric dust etc. The beam that is tuned to the absorption band will be absorbed more than the other, indicating the amount of gas of interest and its location. A map can then be drawn showing the concentration of the gas of interest as a function of range. This technique can also be used to find trace emissions of gases from hydrocarbon deposits, thus locating them, even if they are under the surface. Differential Absorption Lidar (DIAL) DIAL is a remote sensing technique and a form of lidar. It is used to determine the chemical composition of subsiliconchip.com.au Lunar laser ranging experiments On several trips to the Moon, laser retroreflectors were left behind, providing a reflective surface from which a laser could be bounced. This allows the distance from the Earth to the Moon to be measured accurately. Reflectors were placed by Apollos 11, 14 and 15 (Fig.6) and the two Soviet Lunokhod missions. All five arrays are Human echolocation Some people with visual impairments have taught themselves to echolocate similarly to bats, whales and dolphins. They use natural “passive” environmental echos while others actively produce clicks with their mouth and listen to the echos from those. Research has shown that in such people, the brain uses the visual cortex to process this information, since it is not being used for its normal function of eye vision. See the video titled “Daniel Kish: How I use sonar to navigate the world” at https://youtu.be/uH0aihGWB8U and read about the organisation he established to promote and teach this technique, World Access for the Blind at https://waftb.net Australia’s electronics magazine August 2020  13 Fig.9: the RPLIDAR A1 360° laser range scanner. still being used today to make measurements. To determine the lunar distance, a laser pulse is fired from Earth and the round trip time measured. The range is computed, based on the known speed of light. Measurements can be made with millimetre-level accuracy. When a laser is fired from Earth, the beam diameter is 6.5km on the Moon’s surface and on average, about three photons per laser pulse return to the detector on Earth. The precise calculation of the distance is not as simple as it sounds. Many variables have to be taken into account. These factors include the very slight variations of the speed of light in different parts of the atmosphere (which also have to be taken into account for satellite navigation systems) and the motion of the observing station due to tides in the Earth’s crust. The “crustal tide” due to the Moon’s gravitational pull can be as much as 384mm. Relativistic effects and many other small effects also have to be accounted for. Some facts established from the measurements are: the Moon is becoming more distant from Earth at the rate of 3.8cm per year; the Moon has a liquid core; Newton’s gravitational constant has changed less than 1 part in 100 billion in the last 50 years; and Einstein’s general theory Fig.10: this shows how the RPLIDAR A1 can scan a room in and make a 2D map of the area. of relativity is correct within the accuracy allowed by the measurements. There was a plan to install a new reflector on the Moon (called MoonLIGHT) in July 2020. This was to be placed by the MX-1E lander being built by Moon Express, but the mission was cancelled and the fate of this experiment is unknown. It would have improved the measurement accuracy by about 100 times. Lunar and Martian lidar The Moon surface has been mapped from orbit using lidar (Fig.7), and Martian cloud patterns have been observed by the Phoenix lander (Fig.8). There are also proposals by the SETI Institute to use robotic vehicles to map the surfaces of the Moon and Mars using lidar, to map interior structures such as possible caves or lava tubes. Inexpensive hobbyist or consumer lidar There are several inexpensive lidar devices available that SILICON CHIP readers may wish to use or experiment with. One example is the US$150 GARMIN LIDAR-Lite v3HP (siliconchip.com.au/link/ab2l). This has a range of 5cm to 40m, an accuracy of ±2.5cm, an update rate of more than Fig.11: a 3D map of the Jenolan Caves (near Sydney) created with the Zebedee lidar device. Source: CSIRO. See the video titled “Real science from caves to the classroom” at https://youtu.be/jt38pF_TJvY 14  Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.13: the 20-20 Ultralyte 100LR with DBC or “distance between cars” feature, showing the distance in feet on the left and time in seconds on the right, as well as speed in miles per hour. The DBC feature is used to enforce ‘tailgating’ laws. 1kHz and an I2C or PWM interface. The GARMIN LIDARLite V3 for US$130 is similar; the main difference is that the maximum update rate is lower, at 500Hz. The Seeedstudio Grove TF Mini LiDAR (siliconchip.com. au/link/ab2m) is a US$40 device with a range of 0.3m to 12m, an accuracy of 1-2% depending on range, and a UART (serial) interface. The devices mentioned above establish range only and cannot produce a two-dimensional map unless they are rotated and scanned on a mount. The Slamtec RPLIDAR A1 (see Figs.9 & 10 and www. slamtec.com/en/Lidar/A1) is a 360° laser range scanner with a sampling rate of 8kHz and a scan rate (rotation rate) of 2-10Hz, a range of 12m and an accuracy of 2mm with a serial and USB interface. It can produce a two-dimensional map and costs about US$115. Note that there are some devices marketed as “lidar” which do not use a laser but rather a regular LED, and therefore are not true lidar devices. For example, the US$60 GARMIN LIDAR-Lite V4 LED, with a 5cm to 10m range and accuracy of ±1cm to ±5cm depending on range, an update rate of around 200Hz and I2C or ANT wireless interfaces. Lidar mapping of confined spaces Lidar can be used to map the inside of caves and other enclosed spaces. If the lidar unit is stationary, then one room can be easily captured (see Fig.11). But if a “walk through” is required such as in a cave, mine or large building, a location reference is needed. It is usually not possible to use GPS as the signal does not work in such places, so the location of the lidar as it moves is determined by SLAM or Simultaneous Location and Mapping. This is where the location is determined by the use of three-axis accelerometers, which provide data about the movement of the device. siliconchip.com.au Fig.14: the Remtech PA-XS, a small SODAR unit weighing only 7kg, with a range of 400m. Lidar sensors for consumer drones Relatively inexpensive lidar devices are now available for consumer-level drones. As an example, the Livox Mid-40 LIDAR can be purchased in Australia for A$899. Lidar for crash investigation In Australia, the NSW and Victorian police forces are both known to use lidar to map vehicle crash scenes; specifically, they use the RIEGL VZ-400i, as shown on page 10. Lidar police speed enforcement Police in many countries use lidar for speed limit enforcement. One advantage of lidar over radar is that there is much less beam divergence with lidar, so theoretically, if the equipment is used correctly, it is possible to measure the speed of a specific vehicle in a stream of traffic. Speed-detecting radar, on the other hand, has difficulty in distinguishing between nearby vehicles. When used incorrectly, it has even been known to measure the speed of other objects such as windmills, aircraft and tree branches blowing in the wind! Very high levels of operator attention and training are required to ensure the accurate operation of police radar. Models of police handheld lidar used in Australia and New Zealand include the LTI TruCAM, LTI TruSpeed, LTI 20-20 Ultralyte 100 LR, LTI TruSpeed SE, LTI Ultralyte Compact, Australia’s electronics magazine August 2020  15 Fig.15: a SODAR result for Niwot Ridge in Colorado, USA, showing how the wind speed and direction vary with the height above ground level and time of day. The arrow colour indicates the wind speed while the arrow orientation shows the direction. Kustom Signals ProLaser III, Kustom Signals ProLaser 4 and Kustom Signals Pro-Lite+. See www.lasertech.com/default. aspx and https://kustomsignals.com for more details. Note that while lidar for speed enforcement is theoretically accurate (within error margins), its use in Australia has been successfully challenged, reported by the ABC at siliconchip. com.au/link/ab2n Lidar is also used by police in some areas to measure the distance between vehicles as they travel down a road (see Fig.13). SODAR SODAR is a meteorological instrument that uses sound in a similar way that lidar uses light. SODAR is generally designed to determine wind speeds as a function of height above the instrument. This type of device is also known as Fig.16: a Metek Doppler SODAR PCS.2000 with RASS temperature profiler operating at 482MHz, 915MHz or 1290MHz. This setup is used for vertical profiling of temperatures, temperature gradients and inversion layers synchronously with the SODAR wind profiling. The RASS antennae are placed on either side of the SODAR unit. The vertical range for RASS is up to 500m. 16  Silicon Chip a wind profiler (see Fig.14). They take advantage of the Doppler effect, where the frequency of an echo is altered by the motion of the object it bounces off. This is related to the effect where a moving vehicle with sirens or a horn blaring appears to change in pitch as it passes you. Apart from sound waves, wind profiler instruments can also use radar or lidar to perform measurements using the same basic principle. Applications of SODAR include: assessment of sites for wind generators, to prove there is a suitable wind speed profile throughout the height of the windmill; wind shear detection at airports; wind studies to examine dispersal of Fig.17: how RASS works. A radio beam is reflected off acoustic waves from the SODAR unit, and the backscattered signal can be used to determine the speed of sound as a function of altitude, which can be then be converted to temperature. Australia’s electronics magazine siliconchip.com.au Fig.18: lidar measurements from an aircraft over the Atlantic on 27th September 2016, testing the ALADIN Airborne Demonstrator (A2D) prototype lidar. This was used on the European Space Agency Aeolus satellite, launched on 22nd August 2018. It shows wind speed as a function of height along the flight path. Aeolus is the first satellite capable of making global wind measurements and can measure from the surface to an altitude of 30km. pollutants from smokestacks etc; and determining existing wind patterns for environmental impact studies. The ‘echo’ of the sound wave returning to a receiver from the atmosphere is known as backscatter. Backscatter can occur from substances such as atmospheric dust or rain. But due to the way SODAR operates, it generally arises from small changes in the ‘sonic refractive index’ due to the changes in wind speed or temperature. A change in wind speed of 1m/s corresponds to a change in the sonic refractive index of 0.3%; for a change in temperature of 1°C, the change is 0.17%. For radio frequency signals, the change in refractive index due to a 1°C temperature change is 1ppm (part per million) and radio waves are unaffected by changes in wind speed.Therefore, it is best to use sound to measure wind speed, as RF is very insensitive. See siliconchip.com.au/link/ab2o for more details on this. A SODAR system may be mono-static or bi-static. In a mono-static system, both the transmitted and received beam use the same ‘antenna’ (one transducer is used as both a microphone and a speaker). Backscattering is thus due to temperature fluctuations, which are carried along with the wind, enabling its speed to be determined (Fig.15). In a bi-static system, separate transmitting and receiving devices are used, and backscatter occurs from both temperature and speed fluctuations; however, all commercial SODARs are mono-static. Mono-static SODAR systems use a series of antennas pointed upward in different directions, or they may have a phased-array arrangement with the ‘beam’ electronically steered. A minimum of three beams are required to resolve the three components of wind speed, being in the x, y and z directions. More beams give better results, as with ADCP, which is discussed later. Usually, there is a vertical beam and two beams at right angles, offset from the vertical by about 15-30°. In operation, multiple transmitted pulses are backscattered (reflected) from a moving turbulent patch of air. The reflected pulses incur a Doppler shift according to the speed of the air patch, and the shift of consecutive pulses will change as the patch moves along. When the data from multiple different beams are analysed, the individual vesiliconchip.com.au Fig.19: Japan’s National Institute of Advanced Industrial Science and Technology (AIST) mounted a lidar wind profiler on a windmill to measure upwind speed and direction, for optimising the windmill’s yaw angle and blade pitch for maximum power and service life. locity components can be calculated. The sound a SODAR unit makes in operation can be heard in the video titled “Sound from SODAR wind measurements” at https://youtu.be/8HUyExuFMFI Looking at a range of typical SODAR devices such as those from Remtech, Inc (www.remtechinc.com), the audio frequency is from 1-5.5kHz with an acoustic power level from 5-150W, giving a maximum analysis altitude of 400-3000m. A single unit may use multiple frequencies. SODAR and RASS A RASS or radio acoustic sounding system may be used in conjunction with SODAR to measure the atmospheric lapse rate, which is the measure of how temperature changes with altitude. A radio signal, typically in the UHF frequency range, is directed vertically into the SODAR beam (see Figs. 16 & 17). When certain conditions are met, due to the way the acoustic beam changes the dielectric properties of the atmosphere (it causes either compression or rarefaction), this alters the amount of the radio beam which is backscattered. This provides a measure of the Doppler shift due to vertical motion of the air caused by the acoustic beam. The speed of sound in the air can be determined from this, and thus the temperature, as it alters the speed of sound. As an example of how the speed of sound varies with temperature, between -10°C and 30°C at standard sea-level atmospheric pressure, the speed of sound varies from 325m/s to 350m/s. Measurements are made at different altitudes, so the “pressure altitude” also has to be taken into account. Lidar for wind profiling Doppler lidar can also be used for wind profiling. As with SODAR, the light is backscattered, and the Doppler shift is measured to determine wind speed. Data obtained can be used to optimise windmill performance or for meteorological applications (see Figs.18 & 19). ADCP in water An equivalent device to SODAR for use in water is the acoustic doppler current profiler (ADCP). It uses the same basic principles as SODAR. The frequency range used is Australia’s electronics magazine August 2020  17 Fig.20 (above): a variety of ADCP and DVL instruments from Rowe Technologies, Inc. Note the differing numbers of transducers, as some units utilise more beams than others. typically from 38kHz to several megahertz. Figs.20, 21 & 23 show various ADCP units, while Figs.22 & 24 show how they can be used. The results are visible in Figs.25 & 26. The predecessor to the ADCP was the Doppler speed log, used to measure the speed of a ship through the water. The first commercial ADCP produced in the mid-1970s was an adaption of that system. ADCP works by sending out pulses of ultrasound which are backscattered from particles in the water column of interest. The backscattered signal yields two main pieces of information: the Doppler frequency shift, which gives information about the speed of the particle and the time delay to receive the backscattered signal, giving the range of the particle. An ADCP can also yield information about the distribution of particles in the water column, such as sediments or plankton. When the ADCP is attached to a ship or other maritime platform, the depth of the water and platform speed are also known. When the ADCP is on the seafloor, information about surface waves can be obtained. An ADCP uses two beams for horizontal measurements (2D H-ADCP) or three or more beams (3D case) to resolve water motion in two or three directions. In the 3D case, a fourth beam provides more accuracy. Additional beams Fig.21: the Teledyne RD Instruments ChannelMaster H-ADCP. It uses two beams to produce a 2D velocity profile for a water channel. Different versions can measure across a channel with a width from 20m to 300m. Such devices are often permanently mounted. can be used to make measurements at other frequencies to provide either better accuracy (high frequency) or greater range (low frequency). Three is the minimum number of beams needed for measuring the three velocity components of flow in the x, y and z directions. But the standard configuration uses four beams, as this provides redundancy plus an estimate of the measurement error. A five-beam system is a fourbeam system with an additional vertical beam for measuring waves and ice when upward-looking or depth when downward-looking. Some dual-frequency systems have seven beams; three beams per frequency plus a vertical beam, while there are also eight-beam dual-frequency systems with four beams per frequency. An ADCP can measure the flow of water current through a column. Fig.22 shows a variety of ways in which this is useful. It may be mounted horizontally, such as on the shore of a river, to measure the flow of water from shore to shore. Or it can be mounted on bridge pilings or seawalls to measure flow in streams and irrigation channels (H-ADCP). Alternatively, it may be mounted on the seafloor to look vertically through a column of water all the way to the surface, or on a ship’s hull to take measurements of current Fig.22: the variety of ways in which ACDP can be used, on mobile or fixed platforms. The direction of the multiple beams is shown. DVL refers to Doppler Velocity Logging, for measuring vehicle speed relative to the seafloor. Source: Rowe Technologies, Inc. 18  Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.24: a StreamPro ADCP attached to a small flotation device is dragged across the Boise River in the USA to measure the flow volume and speed. The velocity profile is measured continuously on the laptop computer. The device is usually connected to the computer via Bluetooth, plus the data is recorded onboard as a backup. Source: Tim Merrick, USGS. Also see the video at https:// youtu.be/E69Y3JaBIiQ Fig.23: the popular Teledyne RD Instruments StreamPro ADCP for measuring velocity and discharge in shallow streams. It is designed for measurements in water 15225cm deep and uses four beams at 2MHz. The whole system weighs just 5kg and is powered by AA cells. The transducer head overhangs the front of the float while the electronics package is in the other blue housing. flow along the path of the vessel (a transect). In H-ADCP, the instrument is set horizontally looking across a stream, irrigational channel etc at a fixed height. Current profiling is often done in two dimensions, rather than three – see Fig.25. If only a 2D slice is measured, then the total flow can be inferred by using an appropriate velocity model for rectangular, circular, trapezoidal, multi-point, or polynomial shaped channels. Relevant dimensions are entered into the measurement software. Three-dimensional ACDP readings are typically in the form of measurements for North-South, East-West and vertical flows. Ultrasonic ranging Ultrasonic or ultrasound ranging uses an ultrasonic pulse to measure the distance to an object. It can also detect if an object has moved in front of a beam. Ultrasonic ranging is used for camera autofocus systems, motion detection, robotics guidance, proximity sensing, measurement of tank liquid levels, measurement of wind speed and direction and object ranging. Parking sensors in cars are an everyday use of ultrasonic ranging. These help motorists manoeuvre vehicles without striking cars or other objects which they may not be able to see, or cannot easily estimate the distance to (Fig.28). The sensors are built into the bumpers of cars, and typically, Fig.25: measurements of the Antarctic Circumpolar Current with velocity profiles as a function of time in the N-S, E-W and vertical directions (left) with the measurement path (above). These were taken with an ADCP attached to an SD 1020 Saildrone USV (unmanned surface vehicle) at 300kHz, 90m deep. Six days of data are shown. Source: Saildrone. siliconchip.com.au Australia’s electronics magazine August 2020  19 Fig.26: typical data that can be obtained from the StreamPro. The middle image shows the measurement matrix while the measurements are at the bottom, with the flow rate indicated by colour. This 3D measurement determines the velocity profile at all depths. Source: Kyutae Lee. 20  Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.27: an ultrasonic anemometer, the Gill Instruments Ltd WindObserver II. An advantage of this type of instrument is that it contains no moving parts. there are four in the front and four in the back, although some vehicles have twelve sensors in total. Similar sensors may also be used to provide automatic parking features, for example, to measure the distance from the vehicle to the curb, or an already parked vehicle. Wind speed and direction can also be measured with an ultrasonic anemometer (see Fig.27). The time of flight of an ultrasonic pulse depends on the speed of the wind passing in front of it. With two pairs of ultrasonic sensors, the individual velocity components can be resolved to give speed and direction. Ultrasound is typically defined as sound waves with a frequency above 20kHz, which is the upper limit that any human can hear (some people have a much lower bound; it generally drops as we age). Dogs can hear up to 45kHz, cats 64kHz. Some animals such as porpoises can detect frequencies up to 160kHz. At average sea-level atmospheric pressure, 20kHz sound waves have a wavelength of 1.9cm and higher frequencies will be less than that. Ultrasound is used because it gives a more accurate range measurement due to its shorter wavelength than lower sound frequencies. Fig.29: the Polaroid SX70 camera with “Sonar” autofocus from 1978. The ultrasonic transducer is the large perforated disc above the lens. It is a valuable collector’s item today, and has a niche following. siliconchip.com.au Fig.28: a range of Bosch ultrasonic sensors for automated car parking, parking assistance and manoeuvering systems, including emergency braking. They can detect a 7.5cm “standard pole” from 15cm to 5.5m (depending on model), have a horizontal field of view of ±70°, a vertical field of view of ±35°, use frequency modulation and have dedicated ICs to make interfacing easier. The Polaroid Sonar Ranging Module In 1978, Polaroid introduced the SX-70 instant camera which featured an innovative ultrasonic rangefinding system to focus the camera automatically (see Fig.29). The technology was licensed to other users for different applications, and Polaroid built a business around the supply of this ultrasonic transducer circuit board. It was known as the 6500 Series Sonar Ranging Module (Fig.30), and it was suitable for use with a range of Polaroid transducers such as the 600 Series Instrument Grade Electrostatic Transducer (Fig.32). It was intended for use by experimenters and commercial developers alike. Its data sheet can be seen at www.robotstorehk.com/6500.pdf These modules were prized by robotics experimenters, and possibly still are, judging by the amount written about them. Some people have sourced modules from old Polaroid cameras, although the modules are not the same as those that were sold separately. There are notes (last updated 2005) on salvaging them from old cameras at www.uoxray. uoregon.edu/polamod/ Before salvaging these from old cameras, be aware of the possible value of the camera as a collector’s item – especially the SX-70! Fig.30: the Polaroid 6500 Ultrasonic Ranging Module with 600-series transducer. The scale is in inches. Note the discrete components and DIP (dual in-line package) ICs. Australia’s electronics magazine August 2020  21 Experimenting with ultrasonic distance sensors Jaycar and Altronics both sell ultrasonic sensor modules. Jaycar has Cat AU5550 (an all-in-one transmitter/receiver) and also the very popular dual HC-SR04 module, Cat XC4442. Altronics also has the HC-SR04, Cat Z6322. One interesting way to experiment with the HC-SR04 ultrasonic rangefinder module is to build the Jaycar Cat KR9292 “Duinotech Mini Smart Car Robot Kit”. The HC-SR04 module is elementary to drive, as demonstrated by our March 2016 project, the Ultrasonic Garage Parking Assistant (siliconchip.com.au/Article/9848). That was one of our first projects based on Geoff Graham’s Micromite LCD BackPack, which has built-in support for the HC-SR04 sensor module. It requires just two connections to the microcontroller: one digital output to trigger a pulse and a digital input, to determine when the echo is received. Measuring the time between one changing state and then the other tells you the distance from the front of the sensor to the closest object. The 6500 module was capable of driving a transducer such as the 600 Series at 50kHz. This provides range detection over about 2-17m, with 1% accuracy. SensComp (www.senscomp.com) bought Polaroid’s portfolio of ultrasonic ranging modules and transducers and remarkably, a modern SMT (surface mount) version of the 6500 module is still available today (Fig.31). Fig.31: the SensComp 615078LF SMT 6500 Ranging Module, a derivative of the original Polaroid 6500 module but using surface-mount components. It has the same specifications as the original Polaroid device and the parts appear to correspond directly to those shown in Fig.30. Infrasound is at the opposite end of the acoustic spectrum to ultrasound, and is defined as being acoustic frequencies less than 20Hz, the typical lower limit of human hearing. Infrasound arises in nature from some animals such as whales and elephants and natural phenomena such as earthquakes, ocean waves and aurorae. Infrasound listening arrays have been used to locate avalanches, nuclear detonations and tornadoes. The volcanic explosion of Krakatoa in 1883 was detected as small pressure fluctuations on traditional barometers around the world, as infrasonic waves circled the Earth three to four times in each direction. The low-frequency array or LOFAR is a radio astronomy observatory in the Netherlands, but the infrastructure of LOFAR is also used for sensors to perform infrasound observations. According to KNMI’s website (they are a member organisation), the observatory consists of “a temporary 80 element high density array, a permanent 30 element microbarometer array with an aperture of 100km and, at the same locations, a 20 to 30 element seismological component”. The microbarometers can be used to probe processes in the upper atmosphere above 30km and other infrasound phenomena, and also to study seismo-acoustic phenomena since seismic events are also measured at the same site. See http://siliconchip.com.au/link/ab2p Infrasound is also used by the comprehensive nucleartest-ban treaty organization (or CTBTO, of which Australia is a member) to monitor for unauthorised nuclear tests. Australia has infrasound stations located Warramunga, NT; Hobart, TAS; Shannon, WA; Cocos Islands and Davis Station, Antarctica (see Fig.33). For more information on this network, see the video titled “The Infrasound Network and how it works” at https:// youtu.be/GVWOA5pZG6o SC Fig.32: a SensCorp 604142 Series 600 Instrument Grade Ultrasonic Sensor for use with the 6500 module. This is a modern version of Polaroid’s original 600 sensor. Fig.33: the Australian infrasound monitoring station “IS03” at Davis Base, Antarctica. This is one of about 300 stations around the world maintained by CTBTO member states. Apart from infrasound, Australia monitors seismic, radionuclide and hydroacoustic phenomena to detect unauthorised nuclear tests as part of the International Monitoring System (IMS). Infrasound 22  Silicon Chip Australia’s electronics magazine siliconchip.com.au Cable Assembly & Box Build Assembly Metal Work Label and Wire Marker CNC Engraving and Machining Functional Test and Logistic Service Electrical box assembly <at>Ampec we specialise in manufacturing of custom design cable assemblies as well as turnkey electronic and electric product assemblies. Fully automatic cut, strip and crimp machines High mix low volume and quick turnaround +61 2 8741 5000 e sales<at>ampec.com.au w www.ampec.com.au Part 1 – By Phil Prosser • 192kHz • 24-bit USB This beauty is the ultimate in high-fidelity audio recording and playback. You could use the SuperCodec for digitising LPs, recording your own music or playing music with a very high-quality stereo amplifier driving excellent speakers. It can also turn your PC into an advanced audio analyser, capable of measuring harmonic distortion down to 0.0001% and signal-to-noise ratios up to 110dB (or even more, with suitable attenuators). T his project was inspired by a reader who wanted to digitise his LP collection, and asked if we had a USB sound interface that would let him record with very high fidelity. If you want better quality audio for your PC, including the ability to record and playback at high sampling rates and bit depths (up to 192kHz, 24-bit), read on. In addition to recording and playback of music or other audio, this project enables your PC to become an advanced audio quality analyser. You 24  Silicon Chip just need the right software; we’ll get to that later. With the addition of the SILICON CHIP Balanced Input Attenuator for Audio Analysers and Scopes from the May 2015 issue (siliconchip.com.au/ Article/8560), you will have a potent measurement tool indeed. It allows you to measure the distortion performance of the very best amplifiers, preamps, equalisers and other audio devices. In designing this project we started by looking for a simple IC CODEC as the solution. There are some all-in-one Australia’s electronics magazine USB audio chips available, but they fall short on several fronts. They generally limit you to the use of 48kHz, 16bit audio but more importantly, they generally have quite high distortion figures of around 0.1%, with signal-tonoise ratios topping out at about 85dB. We need better performance than that. The first prototype for this project used the same analog-to-digital converter (ADC) and digital-to-analog converter (DAC) boards from the DSP Active Crossover (May-July 2019; siliconchip.com.au/Series/335). Those boards use the Cirrus Logic siliconchip.com.au CS5381 and CS4398 chips respectively. While they are a few years old, their performance is phenomenal. The CS4398 DAC has a dynamic range of 120dB and signal-to-noise ratio (SNR) of 107dB; the CS5381 ADC achieves an SNR of 110dB, or 0.0003%. So we decided to stick with those chips but put as much as possible onto one board, to make it easier to build and give a nice, compact result. The performance this USB Sound Card delivers should fulfil even the most ardent hifi enthusiasts’ desires. We did make several changes and improvements compared to that earlier project, though. This design teases the maximum performance from these parts, in a ‘no-compromise’ approach to low noise and low distortion. Plus it provides ‘plug-and-play’ operation for Windows, Mac and Android computers. We tested it on Windows, but trust the vendor’s promise of Mac and Android compatibility. During the development process, we made several key decisions: • To get the best performance, we need to isolate the PC’s ground from the USB Sound Card. Computers are noisy things, so we must break the ground loop. • It must be supported by proper drivers in Windows and ideally, all other common operating systems. • The ability to handle different sampling rates is important, though once set, it will generally be left alone. • The PCB layout must minimise noise, plus we need to be able to connect the inputs and outputs in a variety of ways. Features • • • • • • • • Stereo input & output with very low distortion and noise Connects to computer via USB Windows, macOS & Android driver support Asynchronous sampling rate conversion (completely transparent) Full galvanic isolation between computer and audio connectors Housed in a sleek aluminium instrument case Power by 12V DC (eg, from plugpack) Power and clipping indicator LEDs • Putting a transformer in the box would introduce measurable 50Hz related noise, even if we took measures to minimise it. Since we don’t want a complicated power supply arrangement, we chose a DC plugpack. • For the cleanest project for SILICON CHIP constructors, everything should be on one PCB. As we have noted in the past, the use of some surface-mount components is unavoidable in projects like this. We need to use specific parts to get this level of performance, and in many cases, they only come in SMD versions. In this case, that includes the USB interface and the ADC and the DAC chips. Where possible, though, we have used through-hole components. This has resulted in the PCB being a bit larger than an all-SMD version would be, but we have found a very nice case that fits it neatly. Principle of operation Fig.1 shows the block diagram of the SuperCodec. It consists of a USB to I2S (serial digital audio) interface with galvanic isolation to the remainder of the circuit, a local clock generator for the ADC and DAC with bidi- rectional asynchronous sampling rate conversion (ASRC), the power supply section and the aforementioned ADC and DAC sections. We have chosen to use a MiniDSP MCHStreamer to provide the USB interface. This is a pre-built device that we have integrated into our design. This avoids us having to develop the hardware and USB driver software for the PC which is complex, expensive and needs to be done very well to deliver you an easy-to-use product. It is essential that constructors can reliably install the sound driver software for this project and have it work with a minimum of fuss. The investment in this component is well worth the ease of use it will deliver you. This project appears to a Windows computer as a sound interface that you select and use just like any other – we show you how to in the box titled “Setting up the MCHStreamer”. This is essentially a regular audio device then, just one of very high quality. The MCHStreamer is a very clever device that can provide 10 input and output channels (five stereo pairs) with sampling rates of 32-384kHz at 24 bits. It supports I2S as well as TDM and other audio formats. We are using it as a two-channel Fig.1: the concept of the USB SuperCodec is deceptively simple, since much of the complexity is hidden in the prebuilt MiniDSP MCHStreamer module. That USB interface module produces a serial digital audio stream which passes through a galvanic isolation section and onto the ASRC, then the separate ADC and DAC sections. It’s all powered from the PC USB 5V and a 12V DC plugpack. siliconchip.com.au Australia’s electronics magazine August 2020  25 Fig.2: spectral analysis (large window FFT) of the data from the SuperCodec’s ADC when fed a sinewave from a Stamford Research Ultralow Distortion Function Generator. This gives an excellent result of 0.0001% THD (-121.4dB). That’s despite an Earth loop causing a largerthan-normal spike at 50Hz, which was fixed with some extra isolation in the final version of the Sound Card. Fig.3: a close-up of the 980-1020Hz portion of the spectral analysis, showing very little evidence of clock jitter in the ADC system. That’s because the crystal oscillator, digital isolators and ASRCs are all low-jitter devices. High jitter can distort signals since the sampling rate effectively changes between samples. (stereo) audio interface. This leaves pack, along with power for the rest of download the PC driver software. We have laid out our sound card so many channels unused, but that is the circuit. You can buy the MCHStreamer from that the MCHStreamer plugs straight not the aim of this project. If you want onto the underside of to use this design as the board. This avoids the basis of a multiSpecifications having to send highchannel recorder, be • Sampling rate: 32-192kHz speed digital signals our guest! • Resolution: 16-32 bits (24 bits actual) over a ribbon cable. The MCHStreamer • Loopback total harmonic distortion (THD): 0.0001% (-120dB) When purchasing parts is powered from the • DAC THD+N: 0.00050% (-106dB) for this, be very careful USB cable and breaks to get the header speciout the I2S audio in• ADC THD+N: 0.00063% (-104dB) fied in the parts list. terface that we need • Loopback THD+N, no attenuator: 0.00085% (-101.4dB) Any alternative needs on a pair of headers. • Loopback THD+N, 8dB resistive attenuator: 0.00076% (-102.5dB) a pin pitch of 2mm and The chip we’re us• Recording signal-to-noise ratio (SNR): 110dB a minimum height of ing for galvanic isola• Playback SNR: 107dB 10mm; otherwise, you tion requires a pow• Dynamic range: 120dB will not be able to seat er supply on both • Input signal level: up to 1V RMS the MCHStreamer fully. sides of the barrier. • Output signal level: up to 2.4V RMS; 2.0-2.2V RMS Luckily, the MCHPerformance (-1.5 to -0.75dB) for best performance Streamer has a 3.3V measurements output available on We used three methan expansion header which we can use to power the com- www.minidsp.com/products/usb- ods to measure the performance of the puter side of that chip. The audio side audio-interface/mchstreamer Once USB SuperCodec, and these measurepower supply is derived from the plug- you register and order it, you can ments aided us in improving it over Fig.6: the noise floor of the complete DAC+ADC system. It’s higher than the ADC alone, but still very low at around -130dB. 26  Silicon Chip Fig.7: here the 1kHz test signal has been reduced in amplitude by 10dB, dropping from around 1V RMS to around 0.1V (100mV) RMS. That’s below most normal ‘line level’ signals, but despite this, distortion performance is still excellent, with THD measuring as -112dB/0.0002%. Australia’s electronics magazine siliconchip.com.au Fig.4: the first loopback test, measuring the performance of the complete DAC+ADC system. Performance is still excellent with only slightly higher harmonic distortion than the ADC alone, at -118dB (still rounding to 0.0001%). To verify that clock jitter is not a problem, we then ‘zoomed in’ to the 1kHz fundamental, as shown in Fig.3. This plot shows spectral data for 1kHz ±20Hz. This shows that the fundamental is 120dB down at about ±2Hz from the fundamental. That’s about as good as you can expect, and suggests that jitter in the clock source and digital signal path is minimal and has little effect on performance. Loopback testing Importantly, there is no spike at 25kHz, 12.5kHz or related frequencies, suggesting that the switchmode regulators are not squegging, ie, are free from subharmonic oscillation that could affect audible frequencies. The harmonics of the very slightly distorted 1kHz fundamental are visible at 2kHz, 3kHz etc up to 8kHz, then 11kHz and 12kHz. The strongest harmonic is 2kHz (second harmonic), at around -118dB. The result is a very low THD figure of -118dB/0.00013%. Remember that this now includes any distortion from the DAC plus the ADC, so this is very impressive. But this measurement does not include noise. To calculate the THD+N figure and signal-to-noise ratio, the inputs to the The second test method was to connect the unit’s outputs to its inputs via a stereo RCA-RCA cable. This lets us conduct ‘loopback’ tests using PC audio analysis software. The result of the first such test is shown in Fig.4. You can see that we’ve solved the SuperCodec DAC THD+N vs Frequency Earth loop now as the .01 50Hz peak is at -130dB! 22kHz BW 0dB You can also see the 22kHz BW -1dB .005 50kHz spike from the 22kHz BW -2dB 22kHz BW -7.5dB switchmode circuitry. Total Harmonic Distortion (%) several iterations until we arrived at the final design. The first method was to feed in a very low distortion sinewave from a Stamford Research DS360 Ultralow Distortion Function Generator. Very large sample sets were run through an FFT so we could inspect the close-in phase noise. The reason for doing this (rather than merely looping the output back to the input) is that we need independent clocks for the signal generator and ADC to pick up any distortion caused by clock jitter. With both devices running off the same clock, those effects are liable to cancel each other out, at least partially. The results of this first test are shown in Fig.2. Note that we had an Earth loop during this test, leading to a greater than usual spike at 50Hz (this was fixed later); despite this, the reading is extremely promising with just a THD figure of just 0.0001% (-118dB) THD. Fig.5: the noise floor of the ADC, measured with the inputs shorted. The biggest spike in the audible range is at 50Hz due to mains hum pickup, but this is hardly a problem, being below -140dB. 19/05/20 14:37:19 80kHz BW 0dB .002 .001 .0005 .0002 .0001 Fig.8: the 1kHz test signal has been increased to the maximum DAC output level of a bit more than 2V RMS. You can see that in this case, more isn’t necessarily better, as the THD figure is slightly worse than the 1V test case, yielding a THD figure of -111dB/0.0003%. That’s still excellent, though! siliconchip.com.au 20 50 100 200 500 1k 2k Frequency (Hz) 5k 10k 20k Fig.9: THD+N (not THD) at four different signal levels for the SuperCodec’s DAC, asFig.9 measured with our Audio Precision System Two. The fifth curve has a wider measurement bandwidth of 20Hz-80kHz, to get a more realistic idea of distortion levels at higher frequencies. Unfortunately, measurements with 80kHz bandwidth also have an unrealistically high noise level. Australia’s electronics magazine August 2020  27 .01 SuperCodec ADC THD+N vs Frequency 19/05/20 14:51:30 .01 Total Harmonic Distortion (%) Total Harmonic Distortion (%) 19/05/20 15:20:11 .005 .005 1V RMS (0dB) 0.5V RMS (-6dB) .002 .001 .0005 No attenuator 8.0dB attenuator .002 .001 .0005 .0002 .0002 .0001 SuperCodec loopback THD+N vs Freq. 20 50 100 200 500 1k 2k Frequency (Hz) 5k 10k 20k Fig.10: THD+N (not THD) at two different signal levels for Fig.10Audio Precision System the SuperCodec’s ADC, using our Two as the signal source. The rise in distortion with increasing frequency seems to be an artefact of the way the audioTester software calculates THD+N. We don’t think it is a real effect. The true THD+N level for the ADC is well below 0.001% across the whole frequency range. .0001 20 50 100 200 500 1k 2k Frequency (Hz) 5k 10k 20k Fig.11: THD+N (not THD) calculated in a loopback manner, ie, using just the SuperCodec with its outputs feeding its inputs. As the nominal DAC output level is 2.4V RMS and the maximum input level is 1V RMS, its performance is best with an 8dB resistive attenuator (1.5k/1k) between the outputs and inputs. Otherwise, the SNR is degraded by an additional 7dB or so. ADC were shorted out, and a new spec- other test frequencies ranging from decent results at the maximum output trum captured (Fig.5). We then rein- 20Hz up to 19kHz, all with virtual- signal level, if that’s what you need. stated the loopback cables and meas- ly identical results, so the plots are ured the input level with the DAC si- not worth reproducing. We also ran Audio Precision testing lent (Fig.6). These give us an idea of 1kHz tests with lower and higher sigThe third measurement method we the noise floor, which is around -104dB nal levels. used was to hook the SuperCodec up for the ADC alone and -102dB for the Fig.7 shows the results with the to an Audio Precision System Two anDAC+ADC. Both figures are limited by output level reduced by 10dB. This alyser. This was mainly to verify that 50Hz hum pickup. only increases the THD figure to the above results were all correct, and Since these levels are significantly -112dB/0.0002%, indicating that you we weren’t somehow fooling ourselves higher than the THD alone, that means aren’t sacrificing much performance by using the Sound Card to measure that the THD+N performance figures by operating the codec at lower signal its own performance. for the Sound Card are determined just levels when necessary. We ran three tests: one to test the by the noise levels. Fig.8 is at the maximum output sig- DAC in isolation, one to test the ADC By the way, since the DAC has to nal level, which increases second and in isolation, and one to test the whole have its output level set no higher third harmonic distortion so that the system. than -7.5dB to avoid overloading the THD figure is -111dB/0.0003%. This The first test involved feeding digital ADC in the loopback test, we could indicates that the optimal signal lev- sinewaves to the SuperCodec’s DAC, have gotten better results by inserting el for low distortion is a few decibels with its outputs then fed into the AP2’s a resistive divider between the output below maximum. But you’ll still get distortion analyser. This yielded SNR and input. Indeed, if you are and THD+N measurements using this device as part of both of 106dB, and the distora measurement system, you tion vs frequency and level would need resistive dividplot of Fig.9. ers, especially if the device These figures match the exyou are measuring has gain pected performance given in (eg, an audio amplifier). the CS4398 IC data sheet pretSo when used as a measty much precisely, suggesting urement system, you can we’ve built the circuit around expect slightly better perforit correctly! mance than the figures givThe second test involved en here suggest. Essentially, feeding the AP2’s low distorthe loopback THD+N (and tion sinewave generator into thus the measurement limit) the SuperCodec’s ADC and will approach the 0.00063% plotting similar curves, shown (-104dB) figure given for the in Fig.10. ADC alone. These curves are a bit ‘wonky’ The back end of the SuperCodec has all the input and We made many other output connectors (the RCA sockets) along with the USB due to the weird way that the loopback measurements at connector and the 12V DC power socket. software we used (audioTester) 28  Silicon Chip Australia’s electronics magazine siliconchip.com.au Parts list – USB SuperCodec 1 PCB assembly – see below 1 Hammond 1455N2201BK extruded aluminium instrument case with black panels [Altronics H9125, Mouser 546-1455N2201BK] 1 MiniDSP MCHStreamer USB-to-I2S interface [www.minidsp.com/products/usb-audio-interface/mchstreamer] 1 12V DC plugpack, 1.5A+ [Altronics M8936D, Jaycar MP3486] 2 white (or black) insulated panel-mount RCA sockets (CON6a,CON7a) [Altronics P0220, Jaycar PS0496] 2 red insulated panel-mount RCA sockets (CON6b,CON7b) [Altronics P0218, Jaycar PS0495] 2 plastic TO-220 insulating bushes 2 M3 x 6mm panhead machine screws 1 M3 x 10mm panhead machine screw 2 M3 flat washers 3 M3 shakeproof washers 1 M3 hex nut 2 3mm inner diameter solder lugs 2 3mm inner diameter fibre washers 1 8mm tall adhesive rubber foot [Altronics H0930, Jaycar HP0825] 4 12mm round slim adhesive rubber feet [Altronics H0896] 1 1m length of heavy-duty figure-8 shielded audio cable [Altronics W2995, Jaycar WB1506] 1 30cm length of 2.4-3mm diameter black or clear heatshrink tubing 1 30cm length of 5mm diameter black or clear heatshrink tubing PCB assembly parts 1 double-sided PCB coded 01106201, 99.5 x 247.5mm 1 150µH 5A toroidal inductor (L1) [Altronics L6623] 2 47µH 0.5A bobbin-style inductors (L2,L4) [Altronics L6217] 1 100µH 5A toroidal inductor (L3) [Altronics L6622, Jaycar LF1270] 13 4-5mm ferrite suppression beads (FB1-FB13) [Altronics L5250A, Jaycar LF1250] 2 M205 fuse clips (F1) 1 5A fast-blow M205 fuse (F1) 3 16x22mm TO-220 PCB-mount heatsinks (HS1-HS3) [Altronics H0650, Jaycar HH8516] 1 PCB-mount DC barrel socket, 2.1mm ID (or to suit plugpack) (CON1) [Altronics P0620, Jaycar PS0519] 2 tall 6x2-pin header sockets, 2.0mm pitch (CON2,CON3) [Samtec ESQT-106-03-F-D-360; available from Mouser] 2 4-pin polarised headers with matching plugs, 2.54mm pitch (CON4,CON5) [Altronics P5494+P5474+P5471, Jaycar HM3414+HM3404] 3 mica or rubber TO-220 insulating washers 3 plastic TO-220 insulating bushes 3 M3 x 6mm panhead machine screws 3 M3 flat washers 3 M3 shakeproof washers 3 M3 hex nuts 1 60 x 70mm rectangle of Presspahn, Elephantide or similar insulating material Semiconductors 1 CS5381-KZZ stereo 192kHz ADC, TSSOP-24 (IC1) [#] 7 NE5532AP or NE5532P dual low-noise op amps, DIP-8 (IC2-IC5,IC8,IC10,IC11) 2 CS8421-CZZ stereo audio sample rate converters, TSSOP-20 (IC6,IC7) [#] 1 CS4398-CZZ stereo 192kHz DAC, TSSOP-28 (IC9) [#] 1 MAX22345SAAP+ 4-channel high-speed digital isolator, SSOP20 (IC12) [#] siliconchip.com.au 1 DS1233A-10+ 3.3V supply supervisor, TO-92 (IC13) [#] 1 4N28 optocoupler, DIP-6 (OPTO1) [Altronics Z1645] 1 ACHL-25.000MHZ-EK 25MHz clock oscillator module (XO1) [#] 2 LM2575T-ADJG 1A buck regulators, TO-220-5 (REG1,REG2) [#] 3 LM317T 1A positive adjustable regulators, TO-220 (REG3,REG6,REG8) [Altronics Z0545, Jaycar ZV1615] 1 LM337T 1A negative adjustable regulator, TO-220 (REG4) [Altronics Z0562, Jaycar ZV1620] 1 LP2950ACZ-3.3 100mA 3.3V low-dropout regulator, TO-92 (REG5) [Altronics Z1025] 1 AZ1117H-ADJ 1A adjustable low-dropout regulator, SOT-223 (REG7) [Altronics Y1880] 1 BC547 or BC549 100mA NPN transistor (Q1) 2 high-brightness 5mm LEDs (LED1,LED2) 9 1N4004 400V 1A diodes (D1,D22-D29) 2 1N5822 40V 3A schottky diodes (D2,D3) 12 BAT85 30V 200mA schottky diodes (D5-D16) [Altronics Z0044] Capacitors 1 2200µF 25V low-ESR electrolytic [Altronics R6204, Jaycar RE6330] 1 2200µF 10V low-ESR electrolytic [Altronics R6238, Jaycar RE6306] 4 470µF 25V low-ESR electrolytic [Altronics R6164, Jaycar RE6326] 1 470µF 6.3V low-ESR organic polymer electrolytic [Panasonic 6SEPC470MW] [#] 1 220µF 25V low-ESR electrolytic [Altronics R6144, Jaycar RE6324] 4 100µF 25V low-ESR electrolytic [Altronics R6124, Jaycar RE6322] 8 47µF 50V low-ESR electrolytic [Altronics R6107, Jaycar RE6344] 1 33µF 25V low-ESR electrolytic [Altronics R6084, Jaycar RE6095] 4 22µF 50V bipolar electrolytic [Altronics R6570A, Jaycar RY6816] 14 10µF 50V low-ESR electrolytic [Altronics R6067, Jaycar RE6075] 1 1µF 63V electrolytic [Altronics R4718, Jaycar RE6032] 2 1µF 25V X7R SMD ceramic, 2012/0805 size [Vishay VJ0805Y105KXXTW1BC or VJ0805Y105KXXTW1BC] [#] 1 220nF 63V MKT 19 100nF 63V MKT 17 100nF 25V X7R SMD ceramic, 2012/0805 size [Kemet C0805C104M3RACTU] [#] 4 22nF 63V MKT 7 10nF 63V MKT 9 10nF 50V X7R SMD ceramic, 2012/0805 size [Kemet C0805C103J5RACTU] [#] 2 2.7nF 100V NP0/C0G SMD ceramic, 2012/0805 size [TDK C2012C0G2A272J125AA] [#] 4 1.5nF 63V MKT 8 470pF 50V NP0/C0G ceramic [TDK FG28C0G1H471JNT00] [#] 1 220pF X7R SMD ceramic, 2012/0805 size [AVX 08052C221K4T2A] [#] 2 100pF NP0/C0G/SL ceramic [Altronics R2822, Jaycar RC5324] 2 33pF NP0/C0G ceramic [Altronics R2816, Jaycar RC5318] Resistors (1/4W 1% metal film types) 5 47k 6 10k 2 5.6k 4 2.4k 2 1.5k 14 1.2k 3 1k 4 750 4 680 1 560 2 330 2 270 4 240 2 220 4 91 1 0 (or 0.7mm diameter tinned copper wire) 4 10 Resistors (1/10W 1% SMD types, 2012/0805 size) [#] 2 47k 5 2k 2 1k 1 220 1 22 1 10 All components marked with [#] are available from Mouser. Australia’s electronics magazine August 2020  29 To whet your appetites for the construction details to be presented next month, here’s the “naked” SuperCodec PCB before it was placed in its case. As we explained in the text, there are mainly through-hole components but also a few SMDs, mainly because they’re not available in throughhole versions. calculates THD+N, as we will explain in a later article. But despite this, they confirm that the ADC performance is just slightly worse than the DAC performance, mainly to do with its lower signal levels. The final test involved running more loopback tests, but this time using the audioTester software to measure THD+N, so that we can make a direct comparison to the Audio Precision figures. This yielded the curves shown in Fig.11. This time, there appears to be an artificial drop at higher frequencies, which we think can be ignored. Our assumed real performance is pretty much flat, as shown by the dashed lines. So it seems that a measurement system based around a personal computer, the SuperCodec and some low-cost software has performance approaching that of our Audio Precision System Two, which cost many thousands when new. Even good used AP2s are priced at four figures. Plus, you gain some additional functions and features with this solution compared to the AP2, such as THD-only measurements (rather than THD+N). SC Next month: As the USB SuperCodec circuit is fairly complicated, we don’t have enough room left to describe it in this article. So we’ll be presenting all the circuit diagrams next month, along with an in-depth description of how it all works. Following that, we’ll describe how to build and test it in detail, along with some tips on how best to use it. In the meantime, if you’re interested in building the USB Sound Card, we suggest that you get busy ordering all the parts that you will need, as per the parts list. Our test setup. We initially built a version of this card without the asynchronous sample rate conversion (ASRC) components, shown at right. The performance is pretty much identical but it’s less flexible, so we decided to stick with the design that included ASRC. 30  Silicon Chip Australia’s electronics magazine siliconchip.com.au “First look” at Microchip’s new FPGA kit . . . by Tim Blythman Hello FPGA Field Programmable Gate Arrays (FPGAs) are powerful chips which are getting easier to use all the time. This Microchip Hello FPGA Kit is targeted towards entry-level users. It comes with demonstration software for image processing, signal processing and artificial intelligence. We took one for a test-drive, to see what’s possible for even those with minimal knowledge of FPGAs. F ield programmable gate arrays are incredibly powerful and useful. They are regularly used to simulate many microchip designs before they are committed to ASICs (application-specific integrated circuits). Making custom chips is a very costly process, so you want to be sure your chip will work before pulling the trigger! FPGAs are one of the essential tools to achieve that. An FPGA is effectively a lot of configurable logic gates; it’s a bit like the old 300-in-1 electronics kits with the spring connectors and wires, but more like 1,000,000-in-1, much smaller in size and electronically configurable. Having basic elements equivalent to individual logic gates and flip-flops means that they can emulate almost any chip. Most modern FPGAs also have specialised functional blocks to provide, siliconchip.com.au for example, RAM, adders, multipliers, DSP functions and even complete microprocessor cores! In some respects, they are a counterpoint to microcontrollers and microprocessors. Microcontrollers and microprocessors typically work in a linear fashion, processing instructions one at a time. On the other hand, the gates in an FPGA can all work in a massively parallel manner, doing many things simultaneously. We’ve described some FPGA boards previously. The Arduino Vidor MKR utilises an FPGA to produce HDMI video (amongst other things). We reviewed this in March 2019; see siliconchip.com.au/Article/11448 The Vidor also allows the FPGA to be configured to provide custom peripherals, although, for the most part, it is a microcontroller board. We also reviewed the Lattice iceAustralia’s electronics magazine Stick in April 2019 (siliconchip.com. au/Article/11521). That is a development board that can be programmed using the open-source IceStorm software and even the block-based IceStudio software. The iceStick combined with the IceStudio software is one of the cheapest and easiest ways to get an introduction to FPGAs. We even showed our readers how to turn the iceStick into a VGA Terminal for displaying retro computer text and graphics in that issue (siliconchip. com.au/Article/11525). So to sum up, FPGAs are incredibly powerful but also very complicated and sometimes difficult to work with. The Hello FPGA Kit The Hello FPGA Kit is an evaluation board, originally from a company called Microsemi. For many years, they were known as a supplier of elecAugust 2020  31 The Hello FPGA Kit consists of an LCD board, a main FPGA board and a camera board which are usually sandwiched together, as seen on page 31. tronics for military, aerospace and other high-reliability applications. Some of their products were used in the Mars Curiosity rover and unsurprisingly, one of their key product lines is FPGAs; their PolarFire FPGA was named Product of the Year in 2017 by Electronic Products China and 21ic.com. In 2018, they were taken over by Microchip Technology, better known as manufacturers of PIC microcontrollers (and now also Atmel AVR microcontrollers since their takeover of Atmel). The Hello FPGA Kit reviewed here was kindly loaned to us by Microchip Technology Australia. The Hello FPGA Kit is a set of three boards which are sandwiched together. One board has a camera lens poking out and a set of headers; it is fitted with an OmniVision OV7725 camera. There aren’t many electronic components on that board; a switchmode regulator and its associated passives take 5V in to provide a 1.8V rail for the camera. Its underside has headers to attach to the FPGA motherboard, labelled as “Expansion” and “Arduino”. Its top sports a MikroBus socket. The second outer board features an LCD panel. The PCB itself is not much larger than the LCD, although neither the board nor schematics give any indication about the model or capabilities of the LCD controller. It measures 3.5in (89mm) diagonally, and the documentation states that it has a resolution of 480 x 320 pixels. 32  Silicon Chip A solitary DFN-6 package and two passives provide PWM control of the display’s LCD backlighting. The schematic indicates that the LCD uses a parallel 8-bit bus. It connects to the FPGA board via an “Expansion” header. The LCD panel appears to be similar to the type used in our Micromite LCD Backpack V3 (siliconchip.com. au/Article/11764). The main board (see below), sandwiched and normally hidden in between the other two, carries the FPGA and a microcontroller. But the block User Push Buttons Power LEDs 20-pin Expansion Header diagram, Fig.2, shows that there’s a lot more on the board than just those two chips. The PIC32MX795F512 micro provides an interface for uploading of the demonstration software to the FPGA and monitoring its operation. The PIC32MX795F512 is the same chip that we used for both the Maximite and Colour Maximite computers (see siliconchip.com.au/Series/30 and siliconchip.com.au/Series/22 for more information). The FPGA is a Microsemi SmartUser LEDs FPGA JTAG Header PICkit Header SmartFusion FPGA PIC32MX79SFS12L USB 2.0 20-pin Expansion Header Arduino Compatible Interface Australia’s electronics magazine Fig.1: there is no shortage of connectivity on the Hello FPGA main board. USB, JTAG and even Arduinocompatible headers are provided. siliconchip.com.au Fig.2: the Hello FPGA main board consists of an M2S010VF256 FPGA communicating with a PIC32MX795F512 micro. The PIC32MX795F512 communicates with the GUI app over a USB-serial link, while the FPGA connects with the camera and LCD board via headers. Fusion2 M2S010-VF256 in a BGA (ball grid array) package, with 256 ‘pins’ (actually lands). Microsemi M2S010-VF256 FPGA The M2S010-VF256 is described as an SoC (system on a chip). It incorporates a 166MHz 32-bit ARM Cortex M3 processor, which has 64KB of integrated RAM and 512KB of embedded non-volatile memory. The processor also has, among other typical microcontroller peripherals such as SPI, I2C and UART, a USB OTG controller, an Ethernet controller and a CAN bus controller. It can interface directly to the FPGA as well, since they are on the same die. Such an arrangement appears to be typical of many modern FPGA devices. While it is certainly possible to create a processor in the ‘FPGA fabric’, to do so is less efficient in terms of power and FPGA resources than having dedicated silicon for this purpose. And since the processor is on the same die as the FPGA, communication is much faster than if the processor was a separate chip. In terms of ‘power’, it is interesting to compare the M2S010-VF256 to the Lattice iCE40HX1K chip used in the iceStick that we previously reviewed. It isn’t always easy to make a direct comparison between FPGAs from different brands or even families, as their siliconchip.com.au Fig.3: the GUI app is simple and easy to use. The main things to remember are to use the controls at top right to connect to the Hello FPGA Kit and ensure that the correct Action is selected before clicking Run. internal structures can be quite different, even though they achieve a similar result. Nonetheless, we can say that the M2S010-VF256 has roughly 9.5 times the logic elements of the Lattice FPGA, at 12,084 total, compared to 1280. It also has many more Logic Array Blocks (1007 vs 160). Its maximum operating frequency is not given, but we suspect that it will be lower than the 1066MHz for the iCE40HX1K, given that the M2S010 series is designed for power efficiency. Low power normally does not translate to blistering clock speeds. Despite that, its large number of logic blocks means that it can be configured to do a lot of work per clock cycle. One of the interesting features of the Hello FPGA Kit is that it can measure and report its own power consumption. So it’s clear that making the best use of power is a focus of the SmartFusion2 range. Their power analysis tool can estimate and evaluate power usage before committing to a design. The FPGA component of the M2S010-VF256 also has several ‘SerDes’ interfaces. SerDes is an abbreviation for “Serialiser-Deserialiser”, and as the name suggests, they convert data between serial and parallel formats. For example, the SerDes on the M2S010-VF256 can be configured to Australia’s electronics magazine provide a 10Gbps Ethernet interface. Many modern high-speed buses are serial in nature; HDMI and USB are other examples. The SerDes may include features such as clocking, encoding and framing. Data is processed internally in parallel and then serialised for output. Beyond this, there are many socalled ‘IP cores’ that can add further configurable peripherals to the chip. Their page also notes some potential applications in fields such as medical imaging, radar processing, automotive and military systems. Medical imaging and radar processing are examples of applications which require a large amount of data to be processed; the parallel nature of an FPGA allows it to process this data in parallel and the results to be then fed to the processor for storage and display. See siliconchip.com.au/link/ab3o for more information on the FPGA chip. A guide for the Hello FPGA Kit can be found at siliconchip.com.au/ link/ab3p Now let’s have a look at some features on the Hello FPGA Kit’s main PCB (see Fig.1). The block diagram for the FPGA board is shown in Fig.2. The FPGA itself is labelled U1 while the PIC microcontroller is labelled U13. The latter has an 8MHz crystal (Y1), while a 50MHz oscillator (X1) provides the clock signal for the FPGA. August 2020  33 Fig.4: the FPGA Demo tab for the AI Demo offers several sample digit sets to test out the AI recognition system, and displays the output from the FPGA too. Four regulators are present: U9, U10, U11 and U16. U16 derives 3.3V from the 5V rail. This feeds into U9, providing 1.2V for the FPGA core; and U10, supplying 1.5V for a DRAM chip. U11 provides the VTT (terminator voltage) for the DDR DRAM. U2 is a current-monitoring device with an I2C interface; it is used to measure the FPGA current via a current sense resistor connected to the output of the 1.2V regulator which powers the FPGA core. The USB function is not provided by the PIC (although it is capable of doing so), but by a dedicated USB-serial IC (U5; MCP2221A). This can also interface to an I2C bus. There are also a great many passive devices on this side of the PCB; the power decoupling section shows over 50 bypass capacitors connecting across several rails. The underside of the board is not quite as busy, although still littered with many tiny parts, including the 8Gb MT41K1G8RKB DRAM IC (U4), in a BGA package. There is also non-volatile storage in the form of U8, a 64Mb SST26VF064B serial flash IC. Many FPGAs are designed to load their configuration from a flash IC during startup. On the other hand, the Microsemi M2S010 has its own internal flash, which reduces power consumption and is more secure in that the flash 34  Silicon Chip Fig.5: the Image Processing Demo is simple enough, offering some sliders to change the way the image from the camera is displayed on the LCD screen. memory cannot be easily read by unauthorised persons. The remaining ICs on this side of the PCB are U14 (a 74CBTLV3257 four-channel multiplexer) and U15 (a 74LVC1G157 single-channel multiplexer), which combine into a fivechannel multiplexer to switch the JTAG programming lines between the PIC and a set of header pins. This is controlled from the PIC and defaults to the header pins, allowing the PIC to take control of these lines if needed, but allowing connection to the JTAG header when it is not. Software While we earlier alluded to the fact that some FPGAs are hard to work with, the demonstration software for the Hello FPGA Kit is the opposite. We could only see downloads for the Windows operating system; our test system used Windows 10. You will need a Microsemi account to download the software. Registration is simple and does not require a confirmation email (but does need an email address). This is done at the following web page: https://soc.microsemi.com/ Portal/Default.aspx?v=2 You can then go to www.microsemi. com/existing-parts/parts/150925 and click on the Resources tab and download the Hello FPGA GUI Application. The design project files are listed Australia’s electronics magazine separately, but the necessary demonstration files are included with the GUI application. You can download the various user guides too. The installer is packaged in a zip file, so you should extract the entire file and then run the installer. While the zip file was around 250MB, the install only appears to be 9MB. After installing the software, we were prompted to disable fast-start, which we did not do. But we did need to reboot the computer to complete the installation. A copy of the MCP2221 drivers is included. We found the files at C:\Microchip\Hello_FPGA_GUI\MCP2221_ Drivers on our system, although they installed automatically. It appears that a copy of the PIC firmware image (HEX file) is also installed along with the software. Fig.3 shows the rather terse screen you are greeted with when you open the GUI app (it has an “M” icon). At upper right, connecting to the Hello FPGA Kit requires selecting its COM port and pressing the connect/disconnect button next to it. If it lights up green, then you have successfully connected. AI digit recognition We found the AI Digit Recognition demonstration to be the most interesting. Once the Hello FPGA Kit is connected to the host application, siliconchip.com.au Fig.6: the FIR demo shows several stages in the signal processing sequence, from defining and selecting a filter to testing it and validating the result through FFT analysis of the output. the demo firmware is easy to upload. Under “DAT File”, browse to the file named “Demo3_HF10_DIGIT_ CNN_FF_V1.1.dat”. On our system, this was located at C:\Microchip\ Hello_FPGA_GUI\DatFiles. Ensure “PROGRAM” is selected under the “Action” drop-down and then click Run. The process takes almost a minute, and prompts you to unplug and replug the board; this appeared to be unnecessary, although we did need to press the “Connect” button to restart communication. One upside of this demo is that it doesn’t need the GUI app to work, as much information is displayed on the onboard LCD screen. The LCD should show what the camera sees, with some other information overlaid. The centre of the LCD is marked by a green square, which indicates the area that the FPGA is processing. This is scaled down to a 28x28 greyscale image, a preview of which is shown in the LCD’s upper-left corner. It shows the AI Digit Recognition output at lower left, as a digit between 0 and 9. You can click on the FPGA Demo tab of the GUI app to see some more information (Fig.4). Some testing digit sets are available. It is a simple case of pointing the camera at the digits in the GUI app to see that it recognises them. The Hello FPGA Kit had no trouble identifying the sample digits shown, siliconchip.com.au Fig.7: a major focus of the Hello FPGA Kit is on power consumption, and the Power Graph tab allows this to be seen in real time, including during and after applying the Flash Freeze mode. as long as the camera was correctly aligned with the image. Since this is how the ‘AI’ has been trained, that is to be expected. The More Info button and CNN Structure tab both show some background about how the neural network in the AI is organised. AI and neural networks are a field which is seeing more interest of late. The demo on the Hello FPGA kit is impressive, but also telling of how narrow its capabilities are. Other demos There are two other demos included with the Hello FPGA GUI App. These are the FIR Filter demo (found by loading and programming the “Demo1_ FIR_FILTER_V1.3.dat” file) and the CAM LCD demo (“Demo2_HF10_ CAM_LCD_FF_V1.1.dat”). These both rely on the GUI App to control and interface to the Hello The LCD screen on the Hello FPGA Kit displays the number that it recognises, so the AI demo can be used without the GUI app or even a computer connected. Australia’s electronics magazine August 2020  35 Fig.8: the Libero design software allows graphical editing of advanced functional blocks. The design files for the three supplied demos can be viewed and edited, so you can see how they work. That makes it much easier to design your own firmware, rather than starting from scratch. FPGA Kit. Select the appropriate DAT file, select “PROGRAM” and click Run. The CAM LCD demo (Fig.5) shows some basic image processing; the controls are seen in the accompanying image and include brightness, contrast and colour balance. The image from the camera is processed by the FPGA and then displayed on the LCD. The FIR filter demo (Fig.6) shows how the Hello FPGA Kit can be used in a signal processing application. FIR stands for Finite Impulse Response and is a technique usually used to implement a digital filter. An FIR filter consists of several coefficients which are applied to a window of samples to produce the output. The important thing is that the process involves a large number of multiplications (by coefficients) happening almost simultaneously. Since the Smartfusion2 FPGA has many hardware multipliers, this becomes a lot easier to implement in real-time. Having the multipliers in hardware means the processing is fast, which can be critical if the processing needs to occur with low latency. An FIR filter has advantages over discrete filters in that the characteristics are set by the coefficients. The same hardware can be set to behave as low-pass, high-pass, bandpass or band-stop by changing the coefficients. The cut-off frequencies can be changed, and the filter may even be Fig.9: 16 sets of digits are supplied for use with the AI Demo. They shows that it can recognise digits regardless of how they are drawn. You could test it with your own writing, too! 36  Silicon Chip something that is not even possible with discrete components. With the FIR Filter demo, a filter is generated and the coefficients can be seen. This filter can then be applied to a signal to see its effect; the FFT (Fast Fourier Transform) is also displayed so that the frequency response of the filter can be validated. Power and Flash Freeze As we noted earlier, power use and monitoring is an important feature of the Hello FPGA Kit. The app provides a Power tab to explore this. A time vs power graph dominates this view (Fig.7), with a live power reading at lower left. There are also buttons to switch the Flash Freeze feature on and off. Flash Freeze is akin to sleep or suspend modes in microcontrollers, and the demos allow users not only to see the standby power levels, but also measure how long it takes for the unit to wake up from Flash Freeze. Libero design software The demonstration programs are quite interesting, but somewhat limited in scope. To develop further applications requires the Libero design Australia’s electronics magazine siliconchip.com.au software. To program and debug a device requires a licence, but it’s also possible to get a 60-day free licence which allows you to see how the Libero design software works. As mentioned earlier, we tested on Windows 10, although there are also versions for Linux. The Libero design software is a 7GB download from the Microsemi website, at http://siliconchip.com.au/link/ab3q You will need to register to do this. The install involves unzipping the file and then installing it, which requires another 15GB of hard drive space. During the install, you’ll also be prompted to provide a license; the trial license can be requested as part of this process, although it may take up to 45 minutes to be processed. Once granted, follow the instructions to install the license; this involves setting an environment variable to a path. We also downloaded the design files for the three demos from www.microsemi.com/existing-parts/ parts/150925#resources There is even a design guide for using the Libero software with the Hello FPGA hardware, at siliconchip.com. au/link/ab3r You’ll need to unzip these to work with them. The actual project is another compressed archive inside this. We opened the Image Processing demo project (“HF10_OV7725_LCD_ FF.prjx”). As shown in Fig.8, the overall view is a similar block-based editor to what we saw when we reviewed the iceStick hardware and tested the IceStudio software (siliconchip.com.au/ Article/11521). So even if you have minimal experience with FPGAs or coding in HDL, it is possible to create a custom design using the Hello FPGA hardware, al- though you will need a different license to do so, on top of the cost of the board. Conclusion The Hello FPGA Kit is simple to use and demonstrates several diverse features and applications. The GUI app is straightforward to use. The free trial license of the Libero design software is a good way to investigate its suitability for designing for your custom applications. The Hello FPGA Kit is well-provisioned; it is currently listed for sale at around AU$300. The FPGA chip costs around AU$50 by itself, in multiples of 119 (in a 7 x 17 chip tray). You can order a Kit from Digi-key (siliconchip.com.au/link/ab3s) or Mouser (siliconchip.com.au/link/ab3t). Both companies offer free international express (courier) delivery for this item (and any other items you order at the SC same time). Would you like to work for Australia's No.1 electronics magazine? We have an entry-level, full-time position available that's ideal for someone who's enthusiastic about electronics. If you enjoy reading about the projects we publish – and probably even build some of them – we want to hear from you! You don't have to be an expert – just keen to learn! Or maybe you already have plenty of knowledge but are looking for a change of pace in your employment. IS HIRING! It will require travel to our office in Brookvale (on Sydney’s Northern Beaches) each weekday. We are only one minute away from the major bus route from the city and ferry wharf, or a car space is available. On-the-job training will be provided. There are definitely opportunities for advancement in this position. To start with, we need someone who can: Identify components and create kits of parts from a parts list. Program microcontrollers using existing software (HEX files). Yes, we’ll train you! Order components and manage stock. Pick parts and pack orders. Help subscribers with renewals, changes of address and other queries. Answer and direct e-mails and take phone calls. Proofread articles. Maybe even write some articles! Ideal applicants will be self-motivated and able to work well by themselves as well as in a small team. If you are unable to work full-time, we may be able to accommodate you. Successful candidates will be given a six-month paid trial, followed by a permanent position, if you have what it takes! If this sounds like we're talking about you, email your resume/CV (along with contact details!) to jobs<at>siliconchip.com.au siliconchip.com.au Australia’s electronics magazine August 2020  37 A Switchmode Replacement for 78xx regulators By Tim Blythman The 78xx series of three-terminal linear regulators started as the LM109/309 in 1969. So they’ve been around for about 50 years, and they are undeniably still useful today. Their biggest disadvantage is inefficiency, especially with a large input/output voltage difference. If only there was an efficient, drop-in alternative! W Of course, there are plenty of switch- efficiency at higher currents and volte have been using 78xx series linear regulators since the mode ICs which do a similar job, but age differentials. It’s built on a board first issue of SILICON CHIP in they almost always require quite a few that’s roughly the same size as a TONovember 1987 and we still use them extra ‘support’ components, possibly 220 package and has the same three including a bulky inductor. And some- connecting leads. And it’s relativeextensively today. There is no doubt that they are a times selecting the right components ly inexpensive and doesn’t use very simple and effective way of getting is a bit of a ‘black art’. Even then, the many components. However, we must point out that a well-controlled fixed voltage sup- result may not match the performance ply between 3.3V and 24V. They’re of a 78xx; for example, the allowable sometimes, a linear regulator is precheap, they’re available everywhere range of input voltages may be more ferred, mainly because its output does limited. not have switching artefacts (such as and they’re easy to use. This article describes a switchmode high-frequency ripple). Linear regulaFor example, our 45V Bench Supply from October and November 2019 regulator that can be used as a direct tors may also have better line and load (siliconchip.com.au/Article/12014) replacement for a 78xx type regulator regulation. Switchmode regulators are used three 78xx series positive regula- in most cases, but with much greater continually improving in this regard, but we understand that there tors and one 7905 -5V regulawill always be cases where a tor to provide regulated rails Features & specifications linear regulator is required. for its circuitry. The ideal solution is often But being linear devices, • Input voltage: 4-30V to combine a switchmode they can be inefficient, and • Output voltage: 2-24V pre-regulator with a lowthis causes two major prob- • Output current: up to 1A dropout linear post-regulalems. Not only is much of • Quiescent current: around 80µA tor. That gives you the best the supplied energy wasted, • Efficiency: typically 90-96% of both worlds. Our Hybrid but it must be adequately • Dropout voltage: 0.5V Bench Supply from Aprilremoved from the device to • Size: equivalent to a TO-220 package semiconductor device June 2014 used this apprevent overheating. In oth- • Heatsinking: not required proach; see siliconchip.com. er words, more inefficiency • PWM frequency: 500kHz; lower at light loads au/Series/241 means more dissipation and • External capacitance required: 1µF+ at input, 22µF+ at output Thus, in the space taken up more dissipation means more • Other features: under-voltage lockout (4V), thermal shutdown, over-current/short circuit protection by two TO-220 parts, you can heatsinking is required. 38  Silicon Chip Australia’s electronics magazine siliconchip.com.au even implement such a hybrid regulator arrangement by using our design and then passing its output to a discrete linear regulator. The latter should ideally be a low-dropout type, but a 78xx could be used if maximum efficiency is not required. The IC at the centre of this design can deliver any voltage from 2V to 24V, with the output voltage of our Regulator set by just one resistor value. So this design can replace not just one part, but many. You might also be wondering about parts like the ubiquitous LM317 adjustable regulators. They have a different pinout to the 78xx series, so it isn’t possible to make a one-size-fits-all solution that addresses both of these families. While it is possible to fit this device in place of an LM317 in many cases, you would need to make some changes to the surrounding circuitry, including deleting the external resistors which set its voltage. Our replacement device The 78xx we know and love is the one we find in a TO-220 package. This version alone appeared in half a dozen circuits that we published last year. There are also variants in the smaller TO-92 package (the 78Lxx) and SMD TO-252 (78Mxx in surface-mounting D-PAK) packages. It’s the TO-220 package that we’re targeting, because if you can get away with one of the smaller variants, the chances are that you don’t have too much dissipation to worry about. Also, it’s harder to cram the necessary parts into the smaller spaces that these packages offer. If your intended application has a 78xx bolted onto a chunky heatsink, then you’re going to benefit most from our upgrade. And that’s precisely what this project is; a drop-in replacement regulator for the hot, inefficient IC that’s wasting energy on your design. Our design is easily adaptable for Our switchmode Regulator has a very similar outline to the 78xx linear regulator it is intended to replace. With careful choice of parts, the thickness The design can be kept much the same too. If you We wanted our Regulator to be as have space available, you may wish to close as possible to a direct substiuse a larger inductor or larger capacitors tute for the 78XX in a TO-220 packto improve its performance. many voltages; it can be used in place of a 7833 (3.3V), 7805, 7806, 7808, 7809, 7810, 7812, 7815 or 7824. It might also be suitable to replace one of the many low-dropout three-terminal fixed regulators on the market (although their pinouts don’t always match the 78xx). age, and the first item we considered was the size. The body of a TO-220 part is around 10mm x 15mm; a minuscule size for a PCB. But it would not be a dropin replacement if it doesn’t fit in the same space. We decided to leave off the tab mounting hole, since our design will How switchmode regulators work There are many types of switchmode regulators in use today. This includes step-down (buck), boost, flyback, buck/boost, SEPIC, resonant and fully isolated types. But step-down/buck is probably the most common configuration and is also, in a sense, the simplest (with boost not far behind). This is a step-down/buck design. A linear regulator reduces its output voltage by simply introducing a controlled resistance in series with the load. If the input voltage is twice the output voltage, this means that 50% of the power going into the regulator is turned into heat. That means poor efficiency. If your aim was to vary the power to something like a LED or lamp, which only responds to the average current, you could get much greater efficiency by applying the full input voltage to it but only doing so 50% of the time. This could be done using pulse width modulation (PWM), and indeed that is how most DC lamp dimmers and simple motor speed controllers work. The voltage is normally switched by a transistor, with the transistor either fully off (and passing no current) or fully on (dropping no voltage). Little power is lost in the switching element, with real-world efficiencies coming quite close to 100%. But such an arrangement is not suitable for powering ICs or other devices which expect a more-or-less constant supply voltage. Thus, to get a similar efficiency to the PWM approach when siliconchip.com.au powering such devices, we need to ‘filter out’ the rapidly changing part of the waveform (the AC component), giving us just an average voltage level (the DC component). An LC low-pass filter is a simple way to do this. We can’t use an RC filter since we would have half the voltage across the resistor, so efficiency would be no better than a linear regulator. But with an LC filter, energy is stored in both elements (the inductor and the capacitor). Most of that is returned later, so losses and heating are minimal. In the case of the inductor, excess energy is briefly stored in its magnetic field. One way to think of this approach is that applying pulses of voltage to an inductor forms something like a constant current source. At the same time, the capacitor makes the load impedance very low at high frequencies, resulting in a fairly unchanging voltage across the load, despite the pulses applied by the transistor. There will still be some amount of ripple present at the load, but with the correct choice of components, it can be reduced to a manageable amount. In fact, the amount of tolerable ripple dictates the required switchmode frequency and capacitor and inductor values. The best way to reduce ripple is to use the largest inductor and capacitor values possible. In practice, size is an issue, particularly with inductors, so we are forced to compromise (too large an inductor can also affect the regulator’s response to load transients). Australia’s electronics magazine August 2020  39 CON1 OUTPUT GND INPUT 3 2 L1 22 H /1A 4 1 3 1 F 35V 2 1 F 6.3V X7R SC 2020 VIN EN VOUT 6 7 REG1 BOOST MCP16311 VFB VCC AGND 8 100nF R1 52.3k 1 F 1 6.3V X7R PGND 5 10k HIGH EFFICIENCY SWITCHMODE REGULATOR (5V) Fig.1: the circuit of the Regulator is just about straight out of the MCP16311 data sheet, except that the input and output capacitors are lower than recommended. That’s because these are supplemented by external capacitance on the host board. The values in red need to change for a different output voltage. 40  Silicon Chip package (eight-pin micro small outline package). We found a device that came in this package, with a good compromise of most of the features we wanted. By the way, MSOP packages have varying pin pitch, sometimes 0.635mm (the same as SSOP and TSSOP) and sometimes even smaller, at 0.5mm. But they’re also narrower than SSOP and TSSOP, so are one of the most compact packages that can be hand-soldered without too much difficulty. Switchmode operation If you aren’t familiar with the operation of switchmode regulators, see our panel “How switchmode regulators work”. This also explains some 6 5 OUTPUT VOLTS not need to dissipate anywhere near as much heat. So there is no need to attach it to a heatsink. While this does also remove the option of using a mounting screw to secure the part, our Regulator uses sturdy pin headers which are thicker than the leads on most discrete parts. If absolutely necessary, silicone sealant or other adhesive can be used to provide mechanical support. In any case, the Regulator PCB with all its parts is typically around half the weight of a TO-220 device, so the mechanical stresses will be less. With a PCB size set, we started looking for the best switchmode regulator IC to use. We needed to choose one which we could fit on this small PCB, including all the required supporting components. We found it difficult to find suitable parts that could work up to the nominal 35V input that the 78xx series can tolerate. In the end, we settled for a part with a 30V rating, as this covers most use cases. We considered using a device in a user-friendly SOIC-8 SMD package, but one of these would take up around a quarter of the available space on the PCB. Other parts we found came in QFN (quad flat no-lead) and DFN (dual flat no-lead) packages, but we decided that these would be too difficult for many people to solder. You need a reflow oven or hot air station to have much chance of success. So we limited our search to parts with leads. A decent compromise between size and ease of soldering is the MSOP-8 of the other design considerations we had to take into account. While sorting through the (huge number of) switchmode regulator ICs that are available, we looked at several features. Firstly, high-frequency operation is necessary. This means that a lower inductor value is needed, which reduces its physical size. A higher frequency also means less ripple and noise. We also looked for parts which operate synchronously, rather than requiring an external diode. While it is only one extra part, the diode does carry a fair amount of current, so choosing a synchronous part means that some space and dissipation is saved. The voltage drop across the low-side Mosfet (which replaces the diode’s function in synchronous designs) is less than that of the diode. Ultimately, we settled on the Microchip MCP16311. It has a switching frequency of 500kHz and operates synchronously with a minimum number of external components for an adjustable output. As noted earlier, it can operate with up to 30V on its input. We initially tried to lay out the PCB using 3216-size (1206 imperial) passive components. These measure 3.2mm x 1.6mm, but were too large, so we switched to 2012-size (0805 imperial) parts measuring 2.0 x 1.2mm. These save a significant amount of space on the PCB, but aren’t too much harder than 3216-size parts to solder. The footprints that we’ve provided on the PCB are actually a tiny bit larg- SWITCHMODE 4 7805 3 2 1 0 0 1 2 3 4 5 6 7 8 9 INPUT VOLTS Fig.2: the Switchmode Regulator does not operate with an input supply below 4V. At 4V and above, though, it has a much lower dropout voltage than the 7805 and attains a 5V output with only 5.5V at its input (ie, 0.5V dropout). The 7805 needs nearly 7V on its input before it is in regulation. Australia’s electronics magazine siliconchip.com.au er than 3216/1206 parts, so you might be able to use the slightly larger 1206 parts anyway. The circuit The circuit for our design is shown in Fig.1, with the components for a 5V output. IC1 is the MCP16311 integrated switchmode controller. It works with 4.4-30V at its input (pin 4, VIN) and can deliver 2-24V at up to 1A. Pin 3, the enable (EN) input, is tied to VIN so that the IC is enabled as long as there is a sufficiently high supply voltage. The input supply is bypassed by a 1µF capacitor. While this is less than the recommended capacitance in IC1’s data sheet, any application using a 7805 requires an external bypass capacitor anyway, which will supplement the capacitance fitted to the PCB. Pins 5 and 8 are connected to ground, with pin 5 being the highcurrent return for the synchronous switch, while pin 8 is the low-current reference ground to which the output voltage is referred. Both are connected to large copper pours on the PCB. IC1 has an internal low-voltage regulator for its control circuitry, which should be bypassed by a 1µF capacitor connected between pin 2 and ground. This pin sits around 5V, so a 6.3V capacitor is adequate. Pin 1 is connected to IC1’s internal regulator feedback circuitry. The voltage at pin 1 is compared to a precision 0.8V reference, so this pin should be Desired Vout R1 (E96) Nominal Vout R1 (E24) L1 3.3V 31.6k 3.328V 30k 3.2V 15µH (eg, SRN6028-150M) 5V 52.3k 4.984V 51kV 4.88V 22µH (eg, SRN6028-220M) 6V 64.9k 5.992V 62k 5.76V 27µH (eg, ASPI-6045S-270M) 8V 88.7k 7.896V 91k 8.08V 39µH (eg, ASPI-6045S-390M) 9V 102k 8.96V 100k 8.8V 39µH (eg, ASPI-6045S-390M) 10V 115k 10V 110k 9.6V 47µH (eg, SRN6028-470M) 12V 140k 12V 130k 11.2V 56µH (eg, SRN6045TA-560M) 15V 178k 15.04V 180k 15.2V 68µH (eg, TYS6045680M-10) 24V 287k 23.76V 300k 24.8V 120µH (eg, SRN6045TA-121M*) * current rating is 850mA, so don’t draw more than this (the output voltage may drop before reaching that level). For more current, you can probably get away with a 100µH inductor, part code ASPIAIG-S6055-101M. Table 1: Component choices connected to the midpoint of a voltage divider between the output and ground. The ratio of this divider sets what fraction of the output voltage is seen at pin 1 and thus dictates the output voltage. The MCP16311 data sheet recommends a 10k resistor for the lower part of the divider, so changing the output voltage is simply a case of setting the upper resistor. For a 5V output, the upper resistor should ideally be 52.5k. While From left to right, a 3.3V Regulator, a 5V Regulator and a 12V Regulator. Note that the inductor needed is much larger for higher voltage versions. This version is only 6mm thick, which is more than the 5mm of many 78xx regulators, but still slim enough to fit in most places where one would be used, especially as no heatsink is normally required. siliconchip.com.au Nominal Vout Australia’s electronics magazine changing this resistance will set a different output voltage, for optimum performance, other components must be adjusted too. In practice, 52.3kis the closest commonly available value, from the E96 (96 values per decade) series. This gives a nominal 4.984V output. For comparison, a 51k resistor (found in the more common E24 series) would give a nominal 4.88V output. Unless you need a precision voltage reference, either of these would be close enough for most 5V supplies. You probably should not use a switchmode device as a precision reference anyway! Pin 6 is the switch (SW) terminal, which is connected to the two internal Mosfets. One switches the output to ground (pin 5), the other to VIN (pin 4). A non-synchronous part would require an external diode (typically a schottky diode) in place of the lower transistor, to allow inductor current to circulate while the upper Mosfet is off. Between the switch terminal and the output is an LC low-pass filter comprising a series inductor and a capacitor to ground. Like the input capacitor, we’re using a lower capacitor value than recommended in the view that more external capacitance will be fitted. However, it would be possible to fit a higher capacitance in the space available if necessary. The output of the LC filter is fed to August 2020  41 Setting the output voltage The MCP16311 data sheet recommends different inductors for different output voltages. The rule-of-thumb value is 4.5µH per volt at the output. In choosing an inductor, keep an eye on the DC resistance specification too. Values around 100mare recommended, meaning that the inductor will drop 0.1V, dissipating 100mW when the regulator is supplying 1A. If you are planning to run your regulator near 1A, this will probably be the biggest loss. Another critical point is the voltage rating of the output filter capacitor. You need a 6.3V or higher rating for a 5V output, but we’ve specified 50V for all capacitors to keep things simple. Advanced constructors may wish to use devices with a lower voltage rating but higher capacitance, as long as they still have a sufficient voltage rating for their particular role. Table 1 shows some choices for both the top resistor value (from both the 42  Silicon Chip TOP VIEW 1 F 18105201 1 BOTTOM VIEW L1 1 52.3k 10k 1 F 100nF REG1 1 1 F REG1 1 1 F CON1 100nF L1 1 R1 R1 52.3k 10k 1 F 18105201 CON1 the output pin of CON1, which forms the interface with the external circuitry; its other two pins are connected to the VIN pin of IC1 and the ground pour. This output voltage is also fed to the upper resistor in the feedback voltage divider mentioned earlier. The final component on the board is a 100nF capacitor between pins 6 (switch or SW) and pin 7 (BOOST). Because the internal high-side Mosfet is an N-channel device for maximum efficiency, it needs its gate to be brought above its source to conduct. As the source is connected to the SW pin, a voltage above SW (and possibly above VIN) is required to drive its gate. An internal charge pump provides this higher voltage, which is stored in this 100nF capacitor until it is needed to switch the Mosfet. The overall operation is as follows. IC1 produces a pulse-width modulated (PWM) square wave at the SW pin (pin 6) which is filtered by the LC circuit. The output voltage is monitored by the voltage divider connected to pin 1, which causes IC1 to change its PWM duty cycle to maintain the desired output voltage. With a light load at its output, IC1 can also ‘drop’ or skip PWM cycles, reducing power consumption. Three-pin header CON1 has 0.1in (2.54mm) spacing, to match a TO-220 package. 1 F 1 (WITHOUT LABELS) Fig.3: we’ve shown the component overlays same size (above) as we IN GND OUT OUT GND IN normally do but thought a veryBOTTOM VIEW (300%) TOP VIEW (300%) much-enlarged view (at right) would help you with assembly. Inductor L1 is fitted to the top side of the PCB, opposite to the other parts. It is easiest to solder IC1 first, as access to its pins is not as good once the surrounding parts are in place. The part that controls the output voltage is resistor R1 at upper left. Here it is a 52.3kresistor, to give a 5V output. Pin header CON1 can be fitted to either side, depending on the needs of your application. This can be fitted last, so you can test fit the board before soldering it. E24 and E96 series) and also a suggested inductor value. Note that the E24 resistor values do not allow for a high level of accuracy, but may still be close enough, depending on your application. Performance Naturally, we ran some tests to ensure that the Regulator has equivalent performance to its linear predecessor. As per the data sheet recommendations, we connected around 10µF extra capacitance at the input and 22µF at the output. Efficiency is very high compared to a linear device. We connected our prototype 5V Regulator to an 8 load (a wirewound power resistor), drawing a nominal 625mA. For low values of input voltage (up to around 12V), efficiency was 96%, dropping off above 12V. This agrees well with the information in the MCP16311 data sheet. Our calculations suggest that well over half of these losses are simply due to dissipation in the inductor’s DC resistance. Hence, the importance of low DC resistance in this part. During this test, we noted the Regulator was warming up above ambient, but was never too hot to touch. Another quick measurement indicated that the quiescent current of the Regulator (under no-load conditions) is around 80µA, close to the Australia’s electronics magazine value from the data sheet, and a lot less than a 78xx regulator at around 5mA (60 times higher!). Fig.2 shows how the output voltage varies with the input voltage, comparing the Regulator with the expected performance of a standard 7805. This also indicates the dropout voltage. Interestingly, the 7805 passes more voltage at very low input voltages. This is not unexpected, as the MCP16311 does not even come out of the under-voltage lockout until its input reaches around 4V. Once it starts up, it has a much lower dropout, needing an input of only 5.5V to supply 5V at the output; a dropout voltage of around 0.5V. On the other hand, the 7805 is not regulating correctly until its input reaches around 7V; a 2V dropout. In battery-powered applications, both the lower quiescent current and the low dropout voltages are big advantages. Not only does the higher efficiency mean that less energy is wasted, but the Regulator is also capable of operating with much lower input voltages, making better use of the same battery. One advantage of the MCP16311’s low-voltage shutdown feature is that in a battery situation, the 7805 would continue to pass current, completely flattening the battery (which could be fatal if it’s a rechargeable type), while the MCP16311 will switch off when siliconchip.com.au Again reproduced very much larger than in real life, these photos show front and back of the regulator – in this case set up to replace a 7805 (5V) regulator. Changing the regulation voltage is as simple as changing R1 and L1 to suit. its input gets too low, preventing this. Since the output is below 5V by the time the input reaches 4V, the connected circuit will probably not be operating to specification anyway. Scope1-Scope4 show more details of the circuit’s performance. Scope1 shows that the Regulator takes around 350µs to start up, which is quick enough for most applications. Scope2 shows output ripple. This is one area in which the 7805 will be superior, although this small amount of ripple is tolerable for most applications. Scope3 and Scope4 show the response to load and line changes; the output varies by around ±150mV for a 625mA load step, recovering in less than 100µs, while line regulation is around 1%, ie, an output variation of around 17mV for an input ripple of 1.88V. Construction Taking note of what is described above, choose your components before starting construction. Many of the components are quite small, and their marking will be barely legible. The capacitors will probably be unmarked, so take care not to mix them up (or lose them!). Check that you have the appropriate tools for working with small surfacemounted components. At a minimum, we recommend a fine-tipped soldering iron (preferably siliconchip.com.au with adjustable temperature), a pair of fine-tipped tweezers, a magnifier as well as some flux paste and solder braid (wick). Something to secure the very small PCB would be handy. If you don’t have a PCB clamping tool, then Blu-Tack may be sufficient. The Regulator is built on a double-sided PCB coded 18105201 which measures 15 x 10mm and is 0.6mm thick (a standard PCB is 1.6mm thick, which would make the device 1mm thicker). Refer to the PCB overlay diagram (Fig.3) during construction, to see which parts go where. IC1 has the finest pins, so start by fitting it. Check and confirm where the pin 1 dot is and align it with the markings on the PCB. If you have CON1 at the bottom then IC1’s pin 1 is at lower left. If you cannot find a dot, then the part may have a chamfer along one edge; this edge should be closest to CON1. IC1’s pins are on a 0.65mm pitch with only a 0.2mm spacing. You will probably bridge some pins while soldering it, so the solder braid is essential. Apply some flux to the pads and hold the IC in place with the tweezers. Solder one pad down (or one even one side if your iron tip is broad). Check and double-check that all the pins are entirely within their pads; if they are not, then they may short to adjacent pads even after any solder bridges are removed. Also check that the part is flat. Once you are sure of this, solder the pins on the other side. Don’t be concerned about bridges; in this case, they are almost inevitable. Just ensure that each pin is soldered to its correct pad in some fashion. With the IC soldered in place on both sides, you can clean up any bridges. Apply some more flux paste to the pins and press the braid against the pins with the soldering iron on one side. Gently draw the braid away from the part. It should draw up any excess solder, leaving a clean fillet. Inspect this with the magnifier and compare it to our photo above. Apart from IC1, none of the parts are polarised, so do not be concerned about the orientation after IC1 is installed. Follow with the 100nF capacitor which goes near IC1’s pins 1 and 8. Apply flux to the pads and solder Australia’s electronics magazine Parts list – ‘78XX’ 1 double-sided PCB coded 18105201, 15 x 10 x 0.6mm 1 3-pin right-angle header, 2.54mm pitch (or straight header, depending on application) (CON1) 1 22µH 6mm x 6mm 1.1A inductor* (eg, BOURNS SRN6028-220M) 1 MCP16311 switchmode IC, MSOP8 package (Digi-key, Mouser) Capacitors (all X7R SMD ceramics, size 2012/0805) 3 1µF 50V^ 1 100nF 50V (code 105) (code 104) Resistors (all 1% SMD size 2012/0805) 1 52.3kW (R1)* (code 5232) 1 10kW (code 1002) * parts for 5V output; see Table 1 for other voltages ^ increase to 2.2µF if an external lowESR input bypass capacitor of at least 1µF is not possible one lead only. Confirm that the part is flat and square within the pads before soldering the other lead. Go back and retouch the first lead with some fresh solder or a bit of extra flux. Use the same technique to fit the three 1µF capacitors. While they don’t all need to be 50V types, the price difference is small, so it’s easier to just use 50V types for all three as stated in the parts list. That also makes assembly easier since you don’t have to worry about which one goes where. The two remaining parts on this side are the resistors. Fortunately, these are usually marked so are more difficult to mix up. The 10kresistor will be marked as 103 or 1002. The other resistor value will vary depending on your selected output voltage. For the 52.3kresistor we’ve recommended for a 5V output, expect a code of 5232. The last component, inductor L1, is on the other side of the PCB. So now is a good time to clean up any flux residue on the top before flipping the PCB over. If you don’t have a dedicated flux solvent, isopropyl alcohol may work (assuming you can get some at a reasonable price… even metho is getting hard to find!). In any case, take care, as many of these cleaning substances are flammable. Allow the PCB to thoroughly dry before resuming soldering. L1 is a larger part and will generally have more thermal mass, so may August 2020  43 Scope1: this shows the response of the Regulator to having 8V applied with an 8  load (625mA). Its startup time is limited mostly by having to charge the output capacitance, which would be the case for most regulator circuits. require more heat. We’ve sized the pads for a nominal 6mm x 6mm part although up to 8mm x 8mm may fit. In this case, you may need to apply heat to the inductor leads. The technique is much the same as for other two-lead parts. Apply flux, solder one lead, check that the part is where you would like it and then solder the remaining lead. Then clean up the flux that’s been applied to this side of the PCB. You may need to install straight or right-angle headers for CON1, depending on how you wish to use the Regulator. We’ve fitted right-angle headers to our units to make them install just like a TO-220 device. This is also ideal for use on a breadboard. If using right-angle headers, check which side is the best fit (they can be soldered on either side), in case space is tight in your application. We fitted the headers at the rear (IC1 side) of the PCB by removing the pins from the plastic frame and threading them into the frame from the other side. This allows the pins to be held in position while soldering. This arrangement can also be used to mount the Regulator flat against the PCB by bending the leads a further 90°, just as you would for a discrete part, but a more rigid option would be to mount a straight header at the back. This may not work if you have components very close to where the Regu44  Silicon Chip Scope2: under the same test conditions as Scope1, we’ve zoomed into the output waveform after it has had time to stabilise to show the output ripple. We see around 50mV of ripple at the MCP16311’s 500kHz PWM frequency; more output filter capacitance would reduce this. This ripple is the main downside of using a switchmode regulator. lator will need to mount, but will be a lot more secure as the shorter leads will not be able to flex as much. Testing One of the worst things that could happen is that R1 is open circuit, which would mean that IC1 is not able to regulate the output as it cannot see any voltage at its output; effectively, the input voltage will appear at the output. If this is your first foray into surface mounted parts, you might want to double-check your soldering against our photos. You should ideally also test that the Regulator works correctly before deploying it to your circuit. 3-pin header CON1 will make it easy to plug into a breadboard or use jumper wires to rig up a test circuit. Note that the front of the Regulator is the side with the inductor and the CON1 header and pin 1 markings are on this side. Apply 4-30V to pin 1 of CON1 (with respect to GND at pin 2). Use a currentlimited supply if possible (eg, a bench supply) or series resistor to limit the current; this will minimise damage in the event of a fault with the circuit. You should be able to measure the desired output voltage at pin 3. You may also like to load the output (for example, with a resistor) to check that the circuit works under load. If it works as expected, you are ready to Australia’s electronics magazine solder it into your final circuit. Installation Because it is intended to replace a single component, the Regulator could be used in any number of designs, so we can only offer general advice. Any design using a 78xx or similar should have separate bypass and filter capacitors already included. We’ve put some modest capacitance on the Regulator PCB, but as mentioned earlier, not as much as recommended by the MCP16311 datasheet; mostly due to space considerations. The MCP16311 should ideally have at least 2µF at its input and 20µF at its output; we’ve provided around 1µF For some variants, we squeezed in slightly larger 3216/ 1206-sized capacitors across the input and output pins. It’s generally easier to get these larger valued or higher-rated parts in the larger part sizes, so it is worth considering if space is not critical. siliconchip.com.au Scope3: here we connected a 68  load to the Regulator and switched a second 8  load in and out using a Mosfet (gate voltage in blue, the yellow trace is the supply voltage). Thus the output current jumps from 75mA to 700mA and back. The green trace shows the output voltage, which in all cases stays within 200mV of the setpoint. More output capacitance will stabilise this further. for each. Thus an extra 1µF on the input and at least 22µF at the output is recommended. One option to add more capacitance directly to the Regulator PCB is to stack capacitors vertically. We’ve even seen part manufacturers do this to create discrete capacitors with more capacitance! You might also be able to get discrete capacitors with a higher value that will fit onto the board, depending on the actual input and output voltages you’ll be using. Check what parts are available in the 2012/0805 size (or 3216/1206 size, if you’re willing to jam them in). We recommend that you stick with types having an X5R, X6S or X7R dielectric. For example, 2.2µF 50V X5R capacitors are available in 2012/0805 size, if you can’t fit a 1µF external ceramic bypass capacitor on your host board. We’ve also built some variants with larger 1206 (3216 metric) sized input and output capacitors; you can see these in the photos. On the other hand, if your design can tolerate some ripple at the output, then you may be able to reduce the output capacitance below the recommended value. Just be careful to check that this doesn’t affect stability under the range of load conditions the regulator will experience. When fitting the Regulator to your siliconchip.com.au Scope4: the same 8  load as before but with the input supply being fed from an AC transformer and bridge rectifier with a 1000µ µF filter capacitor. Around 2V of ripple (at 100Hz) from the supply produces less than 20mV of ripple at the Regulator’s output, an attenuation of around 100 times. PCB, keep in mind that there are bare component leads on the back of the Regulator PCB which may short against (for example) the existing 78xx mounting hole. Some insulating tape (eg, polyimide) applied to the PCB should be sufficient to avoid problems here. Under low load conditions, thermal dissipation will be quite low, so you could probably even seal the entire part in heatshrink tubing, although we haven’t tested this. Alternatively, if you have space, extend the headers pins of CON1 so that there is clearance between the Regulator PCB and the PCB underneath. If your design is subject to vibration, some neutral-cure silicone sealant between the two will reduce mechanical fatigue. If you are using the right-angle mounting arrangement, then you will also lose the option to mechanically secure the Regulator PCB because it lacks a mounting hole. You should also ensure clearance between the Regulator PCB and any case parts that might short against the components on the Regulator PCB. Again, some tape and sealant may be required to maintain clearance and insulation. If you have space, the right angle connector CON1 can be mounted at the front (rather than the back) of the PCB. This will increase the clearance behind it. SC Australia’s electronics magazine EVERY ARTICLE IN EVERY BACK ISSUE OF Nov 1987 Dec 2019 CAN NOW BE YOURS FOREVER INDIGITAL FORMAT YOURS(PDF) FOREVER IN DIGITAL (PDF) FORMA A Storing 30+ years of SILICON CHIP magazines takes up a lot of space. Now you can save all that space and still have all the issues available. Or maybe you simply want the convenience of searchable files plus index - so you can find that feature or article you want without trawling through back issues! The choice is yours. The digital edition PDFs are supplied on a quality metal USB flash drive, at least 32GB. Each flash drive contains a fiveyear block (60 issues), covering: Nov 87 - Dec 94 Jan 00 - Dec 04 Jan 10 - Dec 14 Jan 95 - Dec 99 Jan 05 - Dec 09 Jan 15 - Dec 19 Each five-year block is priced at just $100, and yes, current subscribers receive the normal 10% discount. If you order the entire collection, the 6th block is FREE (ie, pay for five, the sixth is a bonus!). All PDFs are high resolution (some early editions excepted). Save the files to your PC hard disk, and the USB Flash Drive can be used over and over! For more information, or to place an order, visit www.siliconchip.com.au/ shop/digital_pdfs AUGUST 2020 45 SERVICEMAN'S LOG Fixing heaters – it’s a gas Dave Thompson I usually only repair electronic and mechanical devices, not gas appliances. But when our heater started acting up in the middle of winter, I thought I’d better look into it. It turned out to be an electrical problem after all, so it was up my alley! It’s almost the middle of winter here in Christchurch, and as is usual for this time of year, the weather is gloomy and cold. Because of the ‘lockdown’, we are spending a lot more time inside than we usually would, and subsequently spending a lot more on keeping the house warm as well! Then again, as we aren’t driving our cars that much, the money saved and extra money spent probably cancel out. I know what you are thinking; LPG isn’t the most efficient way to heat a 46  Silicon Chip home. I agree, but the 6.5kW Masport gas stove (or fire, depending on where you went to school) installed in our lounge was already here when we moved in. And given that we no longer have a reticulated natural gas supply in town, it is bottled gas or nothing. We never actually intended to keep this fire; we knew the people we purchased this house from and spent many nights enjoying dinners here, but because they didn’t use the fire much, we thought it wasn’t much chop. Australia’s electronics magazine We planned to replace the gas fire with a pellet fire (or stove, depending on where you went to school). We’d used a pellet fire in our old home for the previous decade or so and we were very happy with it. While some love and some loathe pellet fires, for efficiency, they’re tough to beat. The fuel is simply compressed sawdust, which is cheap to make and widely available, and emissions are next-to-nothing. The ash pot only needs emptying once every few weeks siliconchip.com.au when the fire is used all day, every day. Our old Canadian-made Evolution 2 pellet stove (which replaced a log burner) could throw out around 10kW, but we only ever used it on the lowest of five heat settings; otherwise, we’d have melted! Before we moved in, I purchased an identical, almost-new Evolution 2 pellet fire salvaged from a quake-damaged home. It was a bargain, and all we’d need to do was swap out the gas fire with this one, although I’d have to get resource consent and a registered installer to do that work. I could do it, of course; but I had to pay a professional to do it, to satisfy the insurance company. But once we moved in, we discovered that the gas fire could produce some decent heat (about 6.5kW worth), so it wasn’t worthwhile to replace it. That spare pellet fire is now taking up valuable bench and power tool space in my workshop, so if anyone is looking for a cheap, good-condition Evolution 2, drop me a line! fires is the noise of the fan and auger motor. On the low setting, the auger runs for about three seconds twice per minute; on high, more often. It isn’t that loud, and we found after the first few nights we no longer heard it, but visitors would often ask what it was. The fan noise is similar to a small fan heater; not too intrusive but certainly audible. Many people think they couldn’t put up with these noises, but it really isn’t that intrusive, and we soon got used to it. Another downside is that a pellet stove needs electricity, so it was initially rendered useless in the quakes, when we had prolonged periods without mains power. However, I soon had it rigged it up to our generator, so we could at least keep warm if the power failed. And that is pretty much it as far as operation goes. Keeping it as dustfree inside as possible, and emptying the ash pan once in a while is about all that is required; plus a flue clean every couple of years. An introductory course on pellet heaters The problems begin For those who don’t know what a pellet stove is, or how they work, they are actually very clever. Most work similarly, regardless of make or model. (Don’t worry, this is leading to a repair story, I promise…) The top part of the machine is a hopper into which pellets are poured. Pellets are available from supermarkets and hardware stores in 10, 15 or 20-kilo bags, with the largest bags being the hardest to carry, but also the best value. Thankfully, since we usually ran our heater on low, it would only burn through about 15kg of pellets each week. A motorised auger system in the bottom of the pellet hopper periodically feeds pellets into a burn pot, usually within a sealed burn chamber in the bottom half of the fire. You can generally see this burn pot through the glass front door of the chamber, and this is where the visible flames sprout from as well, giving that cosy ‘fireplace’ effect. A blower fan spreads the hot air outwards from the fire. Once the fire is alight, the more pellets you feed in, the hotter it burns. Drop in the pellets less-frequently, and the heat output is reduced. Besides having to feed the hungry fire, the other main gripe with pellet siliconchip.com.au As you’d expect, there are lots of moving parts in a pellet heater, and they need to be in good condition to ensure they are operating effectively. The first problem I had with our Evolution stove was a common one: a failed igniter. Usually, to get the fire going, you just push a button. It starts the auger motor and an internal fan. The auger drops pellets into the burn pot. When they have built up into a small pile, the igniter, which protrudes slightly into the burn pot, glows red-hot and sets the pellets burning. It’s helped along by the calibrated airflow in the chamber. When the chamber temperature rises to a set level, the main blower fan kicks in, and it’s away. This usually takes about 10 minutes or so, but after a few years, it took increasingly longer, and eventually failed to ignite altogether. This wasn’t as disastrous as you’d think, because I could easily start the fire by opening the door, manually igniting a small number of metho-soaked pellets in the burn pot and then closing the door; the stove would then be going almost instantly. However, this took away some of the convenience, so I looked into replacing that igniter. I ended up getting the supplier to send out their maintenance guy who Australia’s electronics magazine Items Covered This Month • • • • Fixing a pellet heater Upgrading a Labtech Q1590 frequency counter Asus monitor repair LG TV power board repair *Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz replaced it, telling me that poor design meant that as long as the stove was ‘on’, the igniter was powered and glowing red hot. This makes little sense, as once the thing was alight, it didn’t need any other ignition source and all this did was considerably shorten the life of the igniter. It went again after another two years and that time I replaced it, at considerably less cost. When it failed again two years after that, I left it as-is and simply used the metho starting method. After about 10 years, the auger motor bearings failed, and that made a really nasty noise. Fortunately, they are standard bearings and easily replaced, but it goes to show that the more complex a system, the more breakdownprone it becomes. All this influenced our decision not to replace the Masport gas fire/stove. For one, it is relatively cheap to run (compared to electricity) and as we use the gas for cooking as well, it makes no real sense to replace it. Even the fire is sick of the lockdown So it was a bit ironic that barely a few weeks into the lockdown, the fire would periodically go out. I never saw it going out; I just noticed that while the built-in fan was still running, there was no fire on the fake logs. Re-lighting it was also difficult. At first, I thought that the 45kg bottle was empty and needed swapping (I use a manual switching system, so I know when one of the bottles needs replacing). Usually, all I have to do is open the tap on the fresh bottle and flick the gas switch over, and all is well. But this time, I could see the go/no-go indicator in the gas line was still showing green, so the tank wasn’t empty after all. August 2020  47 I went back inside and tried to ignite the fire to no avail. To start it, I push and turn the main gas valve to ‘light’ and hold it down while I press the piezo igniter. Typically, it takes a few strikes to light the pilot lamp, and after about five seconds I can let up on the valve and the pilot stays alight while I hear gas enter the burn chamber, beneath the fake rocks. A few ‘WOOFS’ later and the thing is going. We rarely have to turn this one up either, with level one or two sufficient to warm our space. However, this time I needed to keep the valve pressed much longer, and even then the pilot barely lit up. Once going, we needed to run it on level five just to keep it alight. Something was obviously wrong… While I know a little about a lot of things, I know next to nothing about how gas fires work. But a quick internet search gave me all the information I needed, as well as an excellent service manual for the appliance. At least that allowed me to investigate what could be wrong. I know one thing though; messing around with gas and fittings is something that absolutely should be left to 48  Silicon Chip the professionals. I can still clearly recall sitting at my workshop desk a few months back, and feeling/hearing the massive bang as a house about four kilometres from me literally blew to bits because of a gas fire leak. Lesson learned! Gas is not to be trifled with. Editor’s note: as detailed in this column in the past, just because you get a professional to do the job doesn’t necessarily mean that you will get a good result. Our newly-built house had a recurring gas leak (as did our neighbours, in the other half of the duplex). That was despite it being checked and approved by the relevant authorities! The good news is that as there was some electronics involved, I had a legitimate reason to at least have a poke around. These fires are actually very clever; all gas fires must have a fail-safe system that shuts off the flow if either the pilot light goes out or the main gas valve is opened without lighting the fire. This stops the room filling up with gas and suffocating anyone, or converting the home into a bomb. The gas-flow system is controlled by a solenoid which is held open (and Australia’s electronics magazine thus allows gas to flow) only while a flame heats a thermocouple (or thermopile). If the pilot flame goes out, the thermocouple cools, its output voltage drops and the solenoid closes, stopping the gas flow. It’s simple and highly effective, as long as all the components in the system are working. So based on the symptoms, I could at least start to troubleshoot this problem without having to take any gas lines apart. The first possibility was a blocked or partially blocked gas line. If the blockage was further up the line, towards the bottles and the fittings, I wouldn’t be able to do anything without a gasfitter’s ticket. However, we use the same system for cooking, and our gas hob rings all burned at full noise, so it was unlikely to be a problem with the lines, at least to the junction where the fire and gas hob feeds split off – which is situated handily right behind the heater. That meant that it was unlikely that the gas lines to the heater were blocked. But we could have simply had a blocked pilot light, and that assembly is readily accessible after removing the escutcheon and one glass panel from the front of the heater. Once exposed, I used a bent piece of copper wire that just fit into the pilotlight jet to clear any potential blockage. It felt clear, and a quick puff with one of my rubber-bulb circuit-board dusters ensured that it was clear of obstructions. The pilot light on this fire has three flame paths: one towards the bare-copper igniter wire, one to the thermocouple, positioned opposite the igniter wire, and one into the main part of the fire. I used a pipe-cleaner soaked in white spirit to clean these out, and as they came out remarkably clean, that was likely not the fault. I could hold the gas valve down and turn the main gas input tap at the back of the fire on and off, and could hear a decent gas flow through the system. So I doubted that it was a flow problem. The next thing to check was the thermocouple. These are a known consumable, and replacements are widely and cheaply available. After removing the rear access panel, I could see where the thermocouple connected into the main valve. This is a plumbing-type fitting that is easily removed/undone with an open-ended spanner. siliconchip.com.au Once free, the copper tube-like electric lead can be unfurled to bring the connection out so I could get my multimeter probes onto it. The tube is grounded, while the internal wire is the ‘hot’ lead (LOL!). With the meter set to volts, I played the flame of my small gas torch over the thermocouple tip, where the pilot flame usually hits it. I measured just on 9mV. According to the book, I should read at least 15mV, so this was a potential (haha!) problem; 9mV may be barely enough to hold the solenoid in. A replacement M9x1 thermocouple was only $39 including delivery, so it made sense to replace it and see what happened. I tested the new one when it arrived, and got a reading of 16mV. Fitting it was as easy as loosening a retaining nut and bolt, removing the old one and threading the new one in. I re-connected it to the main valve, and the fire’s been going perfectly for a month now, so I think that’s job done! Labtech Q1590 frequency counter upgrade C. K., of Croydon, Vic, went a bit beyond the usual remit in this column of making something that’s broken work again. Instead, he took an older test instrument that was functional but a bit inaccurate, and modernised it so that it is super-accurate. As you can imagine, it took a bit of doing... What can we do with test equipment, years old but still functional, The interior view of the Q1590 frequency counter. There is an oscillator module inside the centre metal enclosure. that is well off the pace in regards to accuracy and stability? This was my dilemma when I tried to calibrate a Labtech Q1590 multi-function counter. I bought it probably in 1989, and it has never failed me. But these days, digital communication technology requires extreme frequency accuracy. Only a few Hertz out, and digital messages cannot be decoded. I tried to calibrate the counter using a GPS-disciplined source of 10MHz, but the readout was about 150Hz too low. Taking the case off revealed an oscillator module inside a metal case, with two trimcaps which can be accessed through holes in the top (shown above). One trimmer is for a 10MHz crystal, and the other is for a 3.906250MHz crystal, the purpose of which is not clear to me. As the readout was low, the 10MHz oscillator frequency was too high. But adjusting the trimmer still did not give me a correct reading. Adding an 18pF capacitor across it helped, but the adjustment was difficult and tended to jump. By replacing the trimmer capacitor and the parallel fixed capacitor with new ones, and with very careful adjustment, I could get to within about 3Hz. But I wasn’t satisfied with that. Fig.1: the small circuit designed to utilise a cheap TCXO found online as a replacement oscillator module in the Q1590. siliconchip.com.au Australia’s electronics magazine August 2020  49 The original oscillator module shown without the metal cover (left) and with the oven and NPN transistor removed (right) Also, on turning the counter on, the reading started about 50Hz low and after a couple of minutes overshot by about 8Hz, then over several hours, it gradually crept to within 3Hz. Both crystals are wrapped in a piece of copper that is heated by an NPN power transistor (shown above). A thermistor glued to the copper sheath provides feedback so that it maintains a more-or-less constant temperature. But apparently, the temperature still was not stable enough. Since I hate to throw things out, I decided to come up with an improved oscillator design using a TCXO (Temperature Compensated Crystal Oscillator). These can be expensive, but I found a 10MHz model on AliExpress for less than $20. That seemed suspiciously cheap, but I decided to take a punt anyway. The 3.906250MHz crystal was a problem – I couldn’t find a TCXO at that frequency. So I decided to use a DDS (Direct Digital Synthesis) chip like the Analog Devices AD9850 (as described in the September 2017 issue; siliconchip.com.au/ Article/10805). Modules using this chip are available cheaply on eBay and elsewhere, but there was not enough space in the Frequency Counter to fit such a module and associated micro. Fortunately, I had a couple of the bare chips in my stock of parts. Virtually any microcontroller can be used to load the tuning word into this chip, and as I have heaps of Atmel AVRs on hand, I decided to use an ATtiny2313. The circuit I came up with is shown on the previous page. If it looks familiar, that might be because it’s quite similar to my Circuit Notebook entry on pages 96-97 of January 2020 (siliconchip.com.au/Article/12231). But that circuit used an Arduino and an AD9850-based module, compared to the more basic approach taken here. There is a small problem in that when the AD9850 has a 10MHz input frequency, the 3.90625MHz we want at the output is a bit too close to the The fixed frequency counter with new oscillator module – the repair cost totalled less than $50. 50 SILICON CHIP Australia’s electronics magazine siliconchip.com.au The finished replacement module was made using a custom PCB. Nyquist frequency of 5MHz, resulting in a very distorted output with many spurs that could read as false edges. I solved this with a tuned circuit that cleans up the waveform, based on transformer T1 plus one fixed and one variable capacitor. I managed to locate the original counter schematic and discovered that the 3.90625MHz crystal is driven by one stage of a 74HC04 hex inverter, operating as an oscillator amplifier. So I just had to remove the old crystal and feed the output of the AD9850 chip into pin 13 of the 74HC04. All that the ATtiny2313 does is load five bytes into the AD9850 to set up the correct output frequency. The tuning word is 0x64000000 (hex). Obviously, there is some magic power-of-two relationship between the two frequencies to get such a simple number (and this hints at why a seemingly odd frequency was chosen). Designing the PCB was a bit tricky, as there is not much room available, so I mostly used surface-mount components. Some resistors and capacitors are on the underside of the board. It was fortunate that the pins connecting the oscillator board to the motherboard were at 5.08mm (0.2in) centres. I used socket strips on the motherboard and matching pins on the oscillator board so that it became a plug-in module. Once the custom PCB arrived, I loaded the components and plugged the module in (shown at left). Holding my breath, I connected the 10MHz reference to the input. And up came 10000000 – spot on! I decided to leave it running several hours, in which time there was the rare jump to 10000001, but only for one count period. I was quite surprised and pleased that the cheap TCXO is so accurate. There is a sticky label on the oscillator which gives access to an adjustsiliconchip.com.au ment, but I am rather glad that I did not have to fiddle with that. I still don’t know what the 3.96250MHz frequency is used for. I believe it has to do with the 100MHz to 1GHz range of the counter. Having spent considerable time on this repair/ upgrade, I did not feel inclined to do a full analysis of the original design. Has the exercise been worth it? Not if I count the (unpaid) hours I spent on it. As I already had most of the components, I spent less than $50 in total. But the satisfaction of extending the life of an otherwise useless instrument certainly made it worthwhile. Asus monitor repair Poor, innocent bugs are often unfairly targeted as the cause of electronics misbehaving. But in the case of one particular monitor, B. P., of Dundathu, Qld, found the culprit to be of the reptilian variety instead... We’ve been using an Asus computer monitor in our camper as a TV, with it connected to a personal video recorder (PVR). Recently, my wife told me that the monitor was dead. I found that she was right, so I had to take it apart to see if it could be repaired. Often something that is totally dead is easier to repair than something that partly works; I was hoping that would be the case here. Opening the monitor up proved to be quite tricky. Computer monitors, in general, don’t seem to be built with repair in mind, as they are clipped and Australia’s electronics magazine not screwed together. So it’s often difficult to get them apart without damage. The usual way of opening them is to pull the front plastic surround away from the screen carefully, making sure not to damage the screen in the process. I’ve opened up quite a few monitors over time, but this one proved to be a lot more difficult than most of the others I’ve worked on. Still, I eventually got it open. I then sat the monitor face-down on a towel and lifted the back off. I could then see why the monitor had stopped working; there was a blown-up gecko at the side of the metal housing. I could see that the gecko had been burnt by high voltage electricity. Despite that, it had clearly crawled some distance from where it had been zapped. After removing the gecko, I proceeded to disconnect the cables necessary to turn the metal housing over so I could access the circuit boards on the other side. While doing this, I found a dead cockroach in the corner of the video board. I’ve previously had a computer power supply blown up by a roach, but this time, the culprit was the gecko. There was a considerable carbon deposit between the two tracks where the gecko had come in contact. I’ve seen other devices where tracks have been shorted by some wildlife, but this is the first time I’ve seen this carbon between the tracks. I would need to rectify this before I looked into what else might have been destroyed. August 2020  51 I started by scraping all the carbon out of the burnt section of the PCB until it was back to clean fibreglass. This was to ensure that it would not arc when voltage was applied. Next, I touched up the corner of the blown-off pad with solder, although this may not have been entirely necessary. I checked the fuse next, and it had blown. That was potentially a good sign, but it didn’t rule out damage to other components. I searched for a replacement fuse, but as this fuse was a leaded type that was soldered to the PCB, I was unable to find a suitable replacement. I then thought of fitting fuse clips, so that I could use a regular fuse, but I didn’t have any clips of a suitable size. I wondered what junk circuit board I might have that I could salvage some smaller fuse clips from, and I located an old CRT TV board that I hadn’t yet stripped of components. It had suitable clips and even a fuse with the correct rating, so I removed them from the board and considered how I could fit them to the monitor PCB. Because the replacement fuse was shorter than the original fuse, I decided to re-use one of the original fuse pads and fit the other clip to a section of the PCB with no tracks. I drilled 1/16in holes for the clips, fitted them and bent the pins over, then soldered the first one to the pad. It was then just a matter of soldering a wire from the pins on the other clip to the original track. This would save me effort in future if the fuse ever blew again. It’s always hit and miss replacing a blown fuse, as it might just blow again the instant that power is applied, or perhaps it wouldn’t blow but something else would. So before applying power, I decided The dead gecko and the damage done shown below. 52  Silicon Chip Australia’s electronics magazine to make some further checks. I checked the bridge rectifier, and it tested good. I then checked across the power terminals and as there was no short circuit apparent, I decided to apply power to see what would happen. I plugged in a power cable and turned the monitor over, then pressed the power button and the monitor came to life. That was a good sign; it appears that the fuse had done its job in protecting the circuit from the killer gecko. I just had to reassemble the monitor and put it back into service. It has been working well since the repair and I’m hoping for no more wildlife invasions. Unfortunately, there are large openings in the monitor for ventilation, so that is still a possibility. This was another successful repair at no cost, which was a win-win situation. It saved the monitor from landfill and avoided us having to find a replacement. It’s worth having a go at repairing devices, but always remember that electricity kills, so proceed with extreme care. LG TV power board repair R. S., of Fig Tree Pocket, Qld found some damaged parts on a TV power supply PCB and replaced them. But it seems that the damage was more widespread than he thought... This LG TV power supply board had a strange fault on the 5V standby supply. It uses a 3B0365 IC (IC500) with an internal high-voltage FET, which shorted out. When this and the 1.2W currentsense resistor (which I found to be open circuit) were replaced, the 5V supply would still not power up. The circuit (siliconchip.com.au/ link/ab3a and siliconchip.com.au/ link/ab3b) shows that the auxiliary supply generated for the 3B0365 comes from an extra winding on the transformer. This also supplies two other integrated circuits on the board, via a transistor controlled by a powerup signal from the main board. This transistor was shorted out, as was the L6599 IC (IC100), so the auxiliary supply for the 3B0365 was being shunted, stopping it from working. Once these additional faulty parts were replaced, the board sprang to life. What I am not sure about is whether the L6599 failed first and damaged the other components, or whether the 3B0365 failed first and caused the other problems. SC siliconchip.com.au Test and measure your projects Hardcore electronics by On sale 24 July 2020 to 23 August 2020 DUINOTECH ESP32 WIRELESS DEVELOPMENT BOARD The ESP32 Development Board has a 58mm diameter and is designed to be sewn onto fabric to create wearable electronic jewellery. Arduino® Compatible. • 5V Input power • Wi-Fi and Bluetooth® • Smartphone control • Dual power option - USB, or JST XC3810 ONLY Conductive thread (WW4100 $8.95) sold separately. MULTIFUNCTION ENVIRONMENT METER WITH DMM Sound level meter, light meter, humidity meter, & temperature meter all in one unit. • 600V, 4000 count • AC/DC voltages up to 250V • AC/DC current up to 10A QM1594 FLEXIBLE HOOK UP WIRE Made from silicone rubber for extreme flexibility making it ideal for sewing and for use in your e-clothing project. • Temperatures from -60°C up to 150°C. • Handy 8m roll Red WH3034 Black WH3036 JUST ONLY 139 $ CLAMP METER 600A True RMS AC/DC. Packed with features found on more expensive units such as True RMS, non contact voltage etc. • CAT III, 4000 count • AC/DC voltages up to 600V • AC/DC current up to 600A QM1632 JUST 8995 $ BODY STRIP THERMOMETERS Contains heat-sensitive liquid crystals that change colour to indicate different temperatures. Pack of 4. • 35 to 40°C Range • Non-Invasive • 90(L) x 15(W)mm QM7450 ONLY 4 $ 11 $ 95 EA. 3D PRINTING PEN Create amazing 3D artwork. Mobile and lightweight. Includes power adaptor, stand and 3 x 10m filaments. A great way to enter the world of 3D printing. Ages 14+. • Comfortable to hold • 1.75mm PLA / ABS filament compatible TL4253 PRICE BREAKTHROUGH 7995 $ 10 PIECE FILAMENT PACK 1.75mm PLA. To suit the TL4253 3D Printing Pen. Convenient 3m lengths. TL4255 ONLY 1495 99 $ SPARKLE STITCH KIT Learn simple sewing and electronics and make spectacular light-up wearable technology. Kit includes everything you need to get started - felt cloth, needles, thimble, thread, glue gun, multimeter, electronic components, 62 page guide & more. KM1080 ONLY See website for details. VALUED AT OVER $125 Covers atomic structure to DC and AC theory, semiconductors, integrated circuits, digital electronics and communications. ONLY • Softcover. 734 pages with illustrations. BM7108 6495 $ DESKTOP 3D SCANNER V2 WITH SOFTWARE Watch real life objects become digitized before your eyes. Scans up to 250 x 180mm. Sleek, foldable design for workspace storage. Comes packed with MFStudio software with +Quickscan. • Scans up to 250(H) x 180(D)mm TL4420 See website for details. ONLY 1499 $ 48 PIECE SCREWDRIVER SET WITH CARRY CASE 35 PIECE ELECTRONIC TOOL KIT SUPER PRO GAS SOLDERING IRON ONLY ONLY ONLY 27 $ 95 Free delivery on online orders over $99* Exclusions apply - see website for full T&Cs. * 79 $ • CAPTURES GEOMETRY IN AS FAST AS 1 MINUTE! • SCAN OBJECTS WITH AN ACCURACY WITHIN +/- 0.1MM RESOLUTION. Made from S2 tool steel and hardened to 58HRC for continued reliability. Suitable for phone, game consoles and computer repairs. • Magnetic bits • 168(L) x 65(W) x 15(H)mm TD2134 TEACH YOURSELF ELECTRICITY AND ELECTRONICS Shop the catalogue online! 3995 $ MAKE YOUR OWN E-CLOTHING Comprehensive tool set in a quality zipped storage case. • Slotted, Philips, Pozi, Torx, Hex • Cutters, pliers, flexible shaft, tweezers TD2117 39 $ 95 • Adjustable temperature up to 580°C • 120 min (approx.) operating time • Internal piezo crystal ignitor • Stainless steel finish • 234mm long TS1320 139 $ www.jaycar.com.au 1800 022 888 YOUR DESTINATION FOR DIY & RASPBERRY PI PROJECTS. Think. Possible. BUILD YOUR OWN: WI-FI IFTTT DATALOGGER Do you have a garden or home-brewing set up that you need to monitor multiple things at once? This project uses the popular “IF THIS THEN THAT” service (IFTTT) with the MCP3008 chip to send your sensor data to the cloud! Example code has Google sheets and Gmail functionality, and 3 sensors are bundled below. Try out all 3 or mix and match your own. SKILL LEVEL: Beginner TOOLS: Drill, Soldering Iron WHAT YOU NEED: 1 × Wi-Fi Mini ESP8266 Main Board 1 × MCP3008 8 Channel 10 Bit ADC DIP16 1 × Temperature Sensor Module 1 x Socket to Socket Jumper Leads 40-pce 1 × Soil Moisture Sensor Module 1 × Universal Experimenters Board - Small 1 × Large Light Dependent Resistor (LDR) 1 x 28-pin Header Terminal Strip 1 x 10k Ohm 0.5W Metal Film Resistors Pk8 XC3802 ZK8868 XC4494 WC6026 XC4604 HP9550 RD3485 HM3211 RR0596 $24.95 $16.95 $6.95 $5.95 $4.95 $4.95 $3.95 95¢ 85¢ 4995 $ SAVE 25% SEE PARTS & STEP-BY-STEP INSTRUCTIONS AT: www.jaycar.com.au/wifi-ifttt-datalogger See other projects at www.jaycar.com.au/arduino KIT VALUED AT: $70.45 Accessories to suit Raspberry Pi RASPBERRY PI BEGINNER'S GUIDE 2ND EDITION Learn how to set up your Raspberry Pi, install its operating system, and start coding projects, with step-by-step guides using the Scratch and Python programming languages. 252 pages. BM7164 ALSO AVAILABLE: Retro Gaming With Raspberry Pi BM7166 $34.95 ONLY An aluminium heatsink with adhesive thermal transfer tape. Suitable for Rasberry Pi and other BGA devices. HH8581 ONLY 95 95 ONLY ONLY ONLY Helps dissipate extraneous heat. Self adhesive pads for peel and stick use. Pack of 2. HH8584 7 95 $ Set of 3. Angled & duckbill 120mm. Superfine 135mm. TH1760 ¢ ONLY EA 19 $ 95 Buy online & collect in store Comes pre-loaded with NOOBS software for easy installation of Raspbian operating system. Full size SD card adaptor included. XC9030 2495 95 STAINLESS STEEL TWEEZER SET - ESD SAFE click & collect 6995 $ 16GB NOOBS SD CARD 4 75 INCLUDES 3.7V 3800MAH LI-ION BATTERY COPPER HEATSINK 2 PACK $ Diffused tower type LEDs that fit into a 1.8mm hole in a panel or enclosure. • 20mA Typical forward current • 60° Viewing angle • Diffused lens Yellow ZD0050 $0.75 Orange ZD0060 $0.75 FROM Red ZD0040 $0.75 Blue ZD0080 $0.75 Green ZD0070 $0.95 Used this module to create your own Raspberry Pi based music player or just improve the sound quality from your Raspberry Pi. XC9048 STACKABLE HEADER 2MM TOWER-TYPE LEDS 54 ONLY 29 Essential for building your own custom hat for Raspberry Pi. Perfect fit for the 40 pin GPIO header. • 2 x 20 stackable header HM3228 3 $ DIGITAL AUDIO CONVERTER $ HEATSINK PIN GRID ARRAY ONLY POWER PACK WITH LI-ION BATTERY Portable power expansion board with 2 x USB output ports. • Attaches directly to Raspberry Pi XC9060 2795 $ CLUB OFFER BUNDLE DEAL $ STAINLESS STEEL WIRE STRIPPER & CUTTER SCREWDRIVER SET - 22 PIECE Strips wire up to 2.6mm and cut steel wires up to 3.0mm. • Soft rubber handle TH1841 • Includes popular slotted, Phillips, Star and TRI bits • Storage case included TD2114 ONLY ONLY 19 $ 95 3495 $ ON SALE 24.07.2020 - 23.08.2020 YOUR DESTINATION FOR ARDUINO, SHIELDS & MODULES. BUILD YOUR OWN: Think. Possible. Arduino® TEMPERATURE / ENVIRONMENT MONITOR to detect humidIty, temperature, and air quality AIR QUALITY SENSOR WITH CO2+TEMPERATURE DUST SENSOR MODULE Detect a wide range of volatile organic compounds (TVOCs), including equivalent carbon dioxide (eCO2) and metal oxide (MOX) levels. ONLY • 5V Input Power • CCS811B chip • Precision NTC thermistor • Board Measures 36 x 20mm XC3782 Detect airborn micro-particulate particles as small as 0.8μm with this photoelectric dust sensor module. Sensitive enough to detect cigarrette smoke. • Sharp GP2Y1014AU optical sensor • Ultra low power consumption • 0.5V/(0.1mg/m3) Sensitivity XC3780 34 $ $ TEMPERATURE AND HUMIDITY SENSOR MODULE DIGITAL TEMPERATURE SENSOR MODULE Measure both temperature and humidity. Features resistive-type humidity measurement. • 0 ºC - 50 ºC +/- 2 ºC temp range • 20 – 80% +/- 5% humidity • 1Hz sample rate XC4520 ONLY Provides up to 12 bits of resolution and 0.5° accuracy through a single digital IO pin. Multiple devices can even be connected to the same pin. XC3700 ONLY 9 $ ONLY 2395 95 695 95 TEMPERATURE SENSOR MODULE Provides simple way to measure temperature. The module outputs an analogue voltage that varies directly with temperature. Connect it straight to one of your Duinotech analogue inputs. Max 100°C. • 21cm breakout ONLY cable included XC4494 695 $ $ BLUETOOTH® V4.0 BLE MODULE 2 X 16 LCD CONTROLLER MODULE JUMPER LEAD - 100 PIECE ACTIVE BUZZER MODULE ONLY ONLY ONLY ONLY Brings the latest Bluetooth® 4.0 standards to your Arduino® project. Configurable as master or slave. Provides a serial communication channel. Serial interface with AT commands. XC4382 29 $ Allows you to create a user friendly interface for your project. Comes with a built-in 16 character by 2 line LCD display with backlight. • Contrast adjust knob • 4 Bit Arduino® LCD Library XC4454 19 95 $ 14 95 $ SMART WI-FI RELAY KIT SCREW TERMINAL SHIELDS ONLY FROM An ESP8266 Wi-Fi controlled SPDT relay that you can trigger with an App from anywhere in the world. 5VDC Input power or 9-12VDC via regulator. • 10A <at> 250VAC Contact rating • ESP8266 Module and microcontroller • Screw terminal blocks • 45(L) x 28(W) x 20(H)mm XC3804 17 $ $ BREADBOARD LAYOUT PROTOTYPING BOARDS HP95 70 4 95 In the Trade? 9 $ 95 $ Over 200 parts to get your new Arduino® project up and running with a minimum of fuss. Includes wires, components, 400 point breadboard and a 170 page instruction book to get you started. • Classic Arduino® Uno board • Includes a buzzer, motor and servo for interactive output • Light sensors, pushbuttons, LEDs and more! XC9200 ONLY 169 $ XC3 8 90 Strip of eight RGB LEDs which can be controlled by a single Arduino® pin. Up to 1000 LEDs can be daisy chained and run from one pin. • Each channel has 256 brightness levels • Current draw 500mA per module maximum XC4380 JUST 495 95 See website for details RGB LED STRIP MODULE A prototyping board that lets you transfer your breadboard design without having to rework it. Includes five holes on each side per row and power rails running the length of the board. Small 400 Hole HP9570 $4.95 (Shown) Large 862 Hole HP9572 $9.95 $ 95 The easy way to add sound to your project. Hook up a digital pin and ground, and use the tone() function to get your Arduino® beeping. XC4424 ARDUINO® STARTER KIT A screw terminal block to simplify wiring for your Arduino® Uno & Nano boards. Includes a large prototyping area with through-plated holes for any components that require soldering. Suits Nano XC3892 $9.95 Suits Uno XC3890 $15.95 9 95 FROM A mixed pack of jumper leads for your Arduino®, breadboarding and prototyping projects. WC6027 BREADBOARD POWER MODULE BREADBOARD WITH 830 TIE POINTS ONLY JUST Adds a compact power supply to your breadboard. Power from a USB socket or DC. 3.3V or 5V switchable. XC4606 9 $ 95 With labeled rows and columns and adhesive back for mounting, it is ideal for electronic prototyping and Arduino® projects. 200 distribution holes. • 630 terminal holes PB8815 1495 $ 55 YOUR DESTINATION FOR ENCLOSURES, ELECTROMECH & MORE. Think. Possible. NEMA-4 IP65 waterproof sealed enclosures Jaycar stocks a comprehensive range of enclosures suitable for professional applications in harsh environments, prototyping or even general utility uses. Excellent value for money!* More than 120 enclosures available. • Sealed lid with recessed neoprene gasket • Protects against the ingress of moisture and dust LISTED ARE SOME OF OUR POPULAR SELLERS. *See in-store for details. DIECAST ALUMINIUM (METAL): ABS (DARK GREY): POLYCARBONATE (LIGHT GREY): • Operating temperature: -40°C to +125°C • Lid fixing screws are M4 stainless steel (non-magnetic) into threaded brass inserts • Some sizes available with flange or clear lid Small 82 x 80 x 55mm HB6230 $14.95 Medium 115 x 90 x 55mm HB6216 $17.95 Large 171 x 121 x 80mm HB6224 $26.95 Extra Large 222 x 146 x 55mm HB6220 $34.95 HB5050 HB6230 • Operating temperature: Up to +400°C • Screw holes for lid fixing are roll threaded • Captive recessed lid screws • Some sizes available with flange mount Small 64 x 58 x 35mm HB5030 $13.95 Medium 115 x 90 x 55mm HB5042 $25.95 Large 171 x 121 x 55mm HB5046 $36.95 Extra Large 222 x 146 x 55mm HB5050 $39.95 • Operating temperature: -20°C to +80°C • Lid fixing screws are M4 stainless steel (non-magnetic) into threaded brass inserts • Some sizes available with flange mount Small 64 x 58 x 35mm HB6120 $6.95 Medium 115 x 65 x 55mm HB6124 $13.95 Large 171 x 121 x 80mm HB6129 $23.95 Extra Large 240 x 160 x 90mm HB6134 $39.95 SEE OUR WEBSITE FOR A FULL RANGE OF ENCLOSURES! HB FROM 9 612 SELF-POWERED LED PANEL METERS 20% OFF SELECTED PANEL METERS & ACCESSORIES 1495 95 $ HEAVY DUTY CURRENT SHUNTS Super simple to install, these units connect straight up, with no fuss! Auto zero calibration and easy to read red LED display. • Automatic polarity sensing Voltmeter 4.5-30V QP5581 WAS $14.95 NOW $11.95 Ammeter 0-50A QP5588 WAS $39.95 NOW $31.95 These shunt bars allow you to measure high current draw without needing a high current ammeter. 50mV max current. 5A 10.0mΩ QP5410 WAS $14.95 NOW $11.95 50A 1.0mΩ QP5412 WAS $14.95 NOW $11.95 100A 0.5mΩ QP5415 WAS $19.95 NOW $15.95 200A 0.25mΩ QP5417 WAS $19.95 NOW $15.95 10 NOW FROM 11 95 19MM IP67 METAL PUSHBUTTON SWITCHES Durable and stylish stainless steel switch with LED ring illumination. • 12V LED illumination • DPDT momentary action • Spade or solder connection Red DPDT SP0800 $19.95 Blue DPDT SP0802 $19.95 Green DPDT SP0804 $19.95 Blue SPDT SP0810 $20.95 SP 08 04 $ SP0810 (Front) 1995 click & collect Moving Coil Type. • 44mm meter hole • MU45 • 59(W) x 52(H)mm WAS $17.95 EA 0-1mA QP5010 0-50μA QP5012 0-1A QP5013 0-5A QP5014 0-10A QP5015 0-20A QP5016 0-20V QP5020 0-30V QP5022 QP5016 QP5022 7 1395 $ EA. SAVE 20% IP67/65 waterproof switches Jaycar stocks a great range of high quality electromechanical switches to suit every application and every budget. Our range is so huge that it would be impossible to feature all of them here. So if you are looking for any of these features for your project, talk to us now. *See in-store for details. • Heavy duty plastic or metal body • SPST, SPDT or DPDT configurations • Momentary or On/Off action • Round, square or rectangular bezels • Black, red, green, blue or metal silver buttons • lluminated or non-illuminated LED status • Spade or solder lugs connection PUSHBUTTON SWITCHES SPST IP67 SEALED MINI TOGGLE SWITCHES IP67 ROCKER SWITCH SPDT IP65 ONLY FROM ONLY 4 SP0810 (Back) PANEL METERS NOW 1 QP54 SAVE 20% $ FROM $ 95 • Contact rating: 100mA <at>50VAC • Momentary action Black Button SP0656 Red Button SP0657 (with Power Symbol) QP54 NOW FROM 11 $ SAVE 20% 56 FROM 13 $ HB 95 4 6 $ 613 FROM • Contact rating: 2A <at>250VAC • On-On action SPDT ST0554 $6.95 DPDT ST0555 $7.95 6 $ 95 EA 95 • Contact rating: 21A<at>14VDC • On-Off-On action • Red/green illumination SK0999 1695 $ YOUR ONE-STOP-SHOP! HEAD TO OUR WEBSITE FOR ALL YOUR MECHANICAL SWITCH REQUIREMENTS. Buy online & collect in store ON SALE 24.07.2020 - 23.08.2020 YOUR DESTINATION FOR COMPONENTS & MORE. Exclusive club offer Think. Possible. 15A 2 CORE TINNED POWER CABLE 25A 2 CORE TINNED POWER CABLE Suitable for automotive and marine applications. Double insulated. • Resistance (20°C): 0.0123 ohm/m • Max Temp: 80°C Per Metre WH3079 RRP $2.85 CLUB $2.40 CLUB Per 30m Roll WH3077 FROM RRP $74.95 CLUB $62.95 2 $ Suitable for auto, marine or general purpose wiring. • Resistance (20°C): 0.0053 ohm/m • Max Temp: 80°C WH3087 RRP $4.95/m $ /m CRIMPING TOOL FOR NONINSULATED LUGS ONLY 95 RESISTOR PACKS CLUB 5 $ NOW FROM SAVE 20% SAVE 20% 15 AMP DC POWER CABLE HANDY PACK 7.5A TINNED HEAVY DUTY HANDY PACKS CLUB CLUB Suitable for general purpose automotive and marine applications. 15A rated current. • 10m roll black cable WH3055 RRP $12.95 $ EA Quality connectors Whether you’re working with micro power digital signals, or high current automotive equipment, we’ve got the connectors to suit your application. Solder, crimp or screw terminals, Jaycar is your one stop shop for everything electrical. HEAVY DUTY WIRE STRIPPER / CUTTER / CRIMPER WITH WIRE GUIDE Strip all types of cable from AWG 10-24 gauge (0.13-6.0mm). TH1827 ONLY 32 $ More ways to pay: 95 1995 FROM FROM TERMINAL STRIPS D' BACKSHELLS 12 way & capable of being divided with a sharp knife. Supplied with a sturdy retention hole. • Temperature: -35°C to 110°C 6A HM3194 $2.15 10A HM3196 $2.45 FROM 215 $ 20% OFF SAVE 20% ‘D’ CONNECTORS 1 EA SELECTED PROTOTYPING PACKS $ WEIDMULLER PCB MOUNT SCREW TERMINALS $ 35 $ NOW 95 These are 5.08mm spacing. Interlocking. 10A rated. 2-Way HM3130 $1.35 3-Way HM3132 $1.75 1270 00 100 pieces. Contains 3mm and 5mm LEDs of mixed colours. Even includes 10 x 5mm mounting hardware FREE! ZD1694 WAS $24.95 7 9 $ 95 Silicone rubber insulation, very flexible with high temperature rating. Suitable for 250V wiring and general heavy duty work. 10m roll length. • Resistance (20°C): 0.0237 ohm/m • Max Temp: 80°C RRP $14.95 EA Red WH3035 Black WH3037 ASSORTED LED PACK Ceramic 10pF - 100nF - 60 Pieces RC5399 WAS $9.95 NOW $7.95 Greencap 0.001μF - 0.22μF - 60 Pieces RG5199 WAS $14.95 NOW $11.95 Electrolytic 1μF - 470μF - 55 Pieces RE6250 WAS $13.50 NOW $10.80 NOW FROM /m 11 00 CAPACITOR PACKS 0.25W 5% Carbon Film - 300 Pieces RR1680 WAS $12.95 NOW $9.95 0.50W 1% Metal Film - 300 Pieces RR0680 WAS $19.95 NOW $15.95 SELECTED HIGH CURRENT GENERAL PURPOSE POWER CABLES. 840 $ /m Flexible heavy duty cable suitable for general purpose wiring up to 250V. 10m roll length. • Resistance (20°C): 0.0237 ohm/m • Max Temp: 80°C RRP $5.95 EA Red WH3045 Black WH3046 Green WH3047 16 $ For even higher current applications where twin core cabling is required. • Resistance (20°C): 0.0024 ohm/m • Max Temp: 80°C WH3063 RRP $9.95/m CLUB 7.5A TINNED HANDY PACKS Comfortable handles and spring-loaded.14-18 AWG and 22-26 AWG. TH1834 $ CLUB 420 40 15% OFF 56A 2 CORE TINNED POWER CABLE Quality solder-type connectors with gold plated contacts and nickel plated shells. 9-Pin Plug PP0800 $1.45 9-Pin Socket PS0804 $1.95 15-Pin Plug PP0820 $1.95 15-Pin Socket PS0824 $1.95 1 $ 45 Quality range of backshells in plastic, metal & ABS flameproof. 9-pin to 25pin available. See website for details. 9-Pin Plastic PM0808 $2.25 9-Pin ABS PM0810 $2.95 9-Pin Metal PM0812 $3.95 FROM 2 $ 25 METAL BANANA PLUGS Gold plated, designed for monster type speaker cable. The hole will accept another banana plug or a thick cable. Red PP0426 $4.95 Black PP0427 $4.95 Red Locking PP0416 $7.95 Black Locking PP0417 $7.95 FROM 495 $ BANANA SOCKET - SCREW TYPE Top quality speaker terminal with gold banana sockets which also have a huge hole (6mm) to accept high gauge speaker cable. • Suppled with gasket. PT3008 ONLY 1095 $ 57 YOUR DESTINATION FOR THE BEST REWARDS & PERKS love jaycar? you're going to love our rewards! SHOP In store & online EARN POINTS For dollars spent 1 point = $1 CLUB OFFER GET REWARDS eCoupons for future shops in store 200 points = $10 eCoupon CLUB OFFER 139 249 $ SAVE $20 account profile and more... CLUB OFFER 139 $ + PERKS offers, event invitations, $ SAVE $30 300W HOT AIR REWORK STATION SAVE $50 PROFESSIONAL 400K LUX METER • Temp range: 100-500°C • Air flow control: Rotary dial • 240V powered TS1645 RRP $159 PROFESSIONAL SOUND LEVEL METER WITH CALIBRATOR • Selectable Lux or fc scale • Data hold • Relative mode • Includes carry case. QM1584 RRP $169 • Wide dynamic range from 30dB to 130dB. • Min, Max & Data hold • A & C Weighting* Fast (125ms) or Slow (1s) response. • USB connectivity QM1598 RRP $299 CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE RATCHET CRIMPING TOOL TRANSISTOR CLAMPS CORROSION BUSTER PEN 20A 6.5-100V DC POWER METER WITH BUILT-IN SHUNT 25% Heavy duty. Crimp F-type CAT-V connectors onto RG6 or RG59 coax. TH1831 RRP $39.95 CLUB $29.95 20% Clamp TO-220 devices to a heatsink. Pack of 100. HH8602 RRP $24.95 CLUB $19.95 20% Remove rust, wax and dirt. NA1410 RRP $24.95 CLUB $19.95 20% Display power, voltage, energy, current. QP2320 RRP $29.95 CLUB $22.95 CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE ANALOGUE BENCH VOLTMETER 0-15V TINNED COPPER WIRE REVERSIBLE GEARHEAD MOTOR BATTERY SECURING TRAYS 25% Quick and easy to read display of volts. QP5040 RRP $19.95 CLUB $14.95 25% Tin plated. 100g. WW4030 RRP $19.95 CLUB $14.95 CLUB OFFER SAVE 20% 25% 50kg.cm torque at 55RPM at load and up to 160RPM at No load. YG2738 RRP $43.95 CLUB $34.95 Heavy duty. 2 sizes available. Small HB8104 RRP $14.95 CLUB $10.95 Large HB8106 RRP $16.95 CLUB $11.95 CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE BENCH ENCLOSURE 4-IN-1 USB TYPE-C CONNECTION LEAD 10 WAY BLADE FUSE BLOCKS 4P/6P/8P MODULAR CRIMP TOOL WITH NETWORK/POE TESTER 10% Comply with standard IEC297 rack heights. 88(H) x 279(D) x 304(W)mm. HB5556 RRP $69.95 CLUB $59.95 20% Connects most portable USB devices. 1m long. WC7764 RRP $24.95 CLUB $19.95 15% Screw or spade terminals with LED indicator. SZ2097 or SZ2098 RRP $26.95EA. CLUB $21.95EA. 10% OFF EXCLUSIVE CLUB OFFER DESKTOP MAGNIFIERS* *See T&Cs for details. 58 click & collect Buy online & collect in store 15% Tests both UTP and STP cable. Detachable cable tester. TH1939 RRP $74.95 CLUB $62.95 YOUR CLUB, YOUR PERKS KEEP UP TO DATE WITH THE LATEST OFFERS & WHAT'S ON! Visit www.jaycar.com.au/makerhub ON SALE 24.07.2020 - 23.08.2020 YOUR DESTINATION FOR WORKBENCH ESSENTIALS Think. Possible. 1. VACUUM BENCH VICE WITH 75MM JAW • Made from hard-wearing diecast aluminium • Vacuum base and ball joint clamp • 75mm opening jaw • 160mm tall (approx) TH1766 ONLY 39 $ 95 2. MAGNETIC PICKUP TOOL • Magnetic tip with claw • Flexible spring steel shaft • LED illumination TH1864 ONLY 1495 $ 4. 100MHZ DUAL CHANNEL OSCILLOSCOPE WITH DIGITAL STORAGE 849 $ 1795 $ Contains wash-free RMA flux and conforms to MIL- F- 14256F. • Plastic reels • 1.5m long 1.5mm NS3026 3.0mm NS3028 139 SAVE $20 6. DIGITAL MICROSCOPE • Suitable for laboratory work, jewellers etc. • Up to 600X Magnification USB with 3MP Camera QC3191 (Shown) WAS $99.95 NOW $69.95 SAVE $30 1080P with 4.3" Screen QC3193 WAS $129 NOW $99 SAVE $30 EA ELECTRONIC CLEANING SOLVENT 175G Highly efficient fast drying solvent for use on delicate electronic, electrical equipment. NA1004 ONLY 1150 $ SAVE $30 Easy and inexpensive alternative to welding, soldering and brazing. Two part epoxy resin. Bonds to almost any surface. NA1518 ONLY 1695 $ Bond, build, fix and fill anything in seconds. A solvent free formula stays liquid until cured with the included UV LED Light. NA1530 44 $ • Temp range up to 320°C • Exceptional heat recovery • High insulation, low current leakage • Electrically safety approved TS1430 ONLY 89 $ 95 95 More ways to pay: 95 10% OFF SELECTED WATCH TOOLS. • 08mm punch • 2 spare pin punches • Assortment of 2 pins TH2014 WAS $10.95 NOW 950 $ JEWELLER'S SCREWDRIVER SET BONDIC LIQUID PLASTIC WELDING KIT 2 15W 240V SOLDERING IRON PIN EXTRACTOR PRESS J-B WELD EPOXY JUST 6995 $ Japanese built quality, with a large vacuum chamber for strong suction. • 330mm long. TH1856 31 95 3 NOW FROM DESOLDERING TOOL $ 5 $ 4 $ ONLY ONLY 1 • Up to 5A current • Input Voltage: 100-240VAC <at> 50/60Hz • Output voltage: 0-16V/5A, 0-27V/3A, 0-36V/2.2A • Constant current and voltage options • Includes banana to alligator clamp leads NOW • 53(W) x 300(D) x 138(H)mm MP3842 WAS $159 Quality soldering irons & accessories by goot. DESOLDER BRAID 6 5. 80W SLIMLINE LAB POWER SUPPLY 3. VERNIER CALIPERS • 5-digit LCD • 0-150mm (0-6”) measurement range • Metric & imperial measurement Budget TD2081 $17.95 Stainless Steel TD2082 $39.95 FROM 5 • Lightweight and compact unit for greater control and data storage options • 7" colour LCD • Built-in waveform generator NOW • High accuracy • PC connection via USB • SD card support SAVE $50 QC1936 WAS $899 Set of six, housed in a handy storage case • Slotted: 1.0, 1.2 & 1.6mm • Phillips: #00, #0 & #1 TD2023 WAS $9.95 NOW 8 $ 95 65W 240V TEMPERATURE CONTROLLED SOLDERING STATION • Adjustable temperature (200-480°C) • Excellent temperature stability and anti-static characteristics • Electrically safety approved • 146(L) x 115(W) x 98(H)mm TS1440 WAS $329 NOW 299 $ SAVE $30 2 PIECE WATCH CASE OPENER KIT Consists of an adjustable opener that engages the little recesses on the back of a watch. Also includes an oyster shucker style NOW opening tool. TH1929 WAS $24.95 2195 $ 4 PIECE WATCHMAKER'S KIT Case retainer with 18 retaining lugs, a large dusting bulb pump, No. 7 tweezers and fine dusting brush. TH1932 WAS $34.95 NOW 3095 $ WATCH CASE HOLDER TH1934 WAS $15.95 NOW 1395 $ 59 What’s DUINOTECH LEONARDO ATMEGA32U4 DEVELOPMENT BOARD DUINOTECH ATTINY85 MICRO USB DEVELOPMENT BOARD 4 X 4 X 4 LED CUBE KIT Take your soldering skills to the next level by building a dazzling array of ultra-bright blue LEDs. Using the supplied template, you will arrange this 4 x 4 x 4 matrix into a work of art. Fifteen different psychedelic patterns are included, with instructions on how to create your own. With some ingenuity, you could even create a 3D version of your favourite retro platform game! • 64 Ultra-Bright LEDs ONLY • 65(W) x 88(H) x 65(D)mm KM1097 1395 95 $ Suit Windows and Android Smartphones. Omnidirectional with a 2m long cable. Includes wind sock to reduce noise and a convenient carry pouch. • 35Hz - 18kHz frequency response • Electrostatic pickup • -30dB sensitivity AM4015 Components may differ slightly to the one shown. 12V 850A DON'T FORGET YOUR BATTERIES! 179 CR123A 3V LITHIUM BATTERIES - 6 PACK Commonly used in LED torches and cameras. • 1600mAh capacity • Not rechargeable SB2324 Jaycar stock a huge range of batteries from tiny button cells to rechargeable batteries to suit your requirement. See in-store or online for our full range! Extremely light and portable. Capable of jump starting just about anything. Charges via USB C socket. • 850A cranking current • Qi Charger • Lithium rechargeable battery • 2 x USB ports • LED torch with SOS function MB3764 $ 2995 $ JUMP STARTER & POWERBANK Send high definition AV signals to a screen in another room up to 150m away using a Cat5e/6 cable through a common router or Ethernet switch. • 100m (Cat5e), 150m INCLUDES TRANSMITTER, (Cat6) RECEIVER AND POWER Transmission distance SUPPLIES • HDMI pass-through ONLY • Multicast receiver support • Infrared remote control extender AC1752 ONLY ONLY 19 $ SAMSUNG HIGH DRAIN 2500MAH LI-ION BATTERY Samsung 3.6V lithium ion (Li-Ion) 18650 battery for high drain applications up to 20A. • 2500mAh capacity • Samsung model ONLY INR18650-25RM SB2298 $ 95 ONLY 249 $ 21 95 1995 $ Requires Arduino® Compatible UNO Board (XC4410 $29.95) available separately. 1080P HDMI CAT5E/CAT6 OVER IP EXTENDER USB TYPE-C LAPEL MICROPHONE 4x4x4 KIT & Arduino® Compatible UNO Board! KM1097 + XC4410 Total Value $49.90 BUILD A JUST 21 $ PANASONIC EVOLTA AA BATTERIES - 18 PACK Internationally recognised as the longest lasting AA alkaline battery. • Up to 20% more energy • Power: 1.5V SB2903 ONLY 2695 $ TERMS AND CONDITIONS: REWARDS / CLUB MEMBERS FREE GIFT, % SAVING DEALS, & MEMBERS OFFERS requires ACTIVE Jaycar Rewards / membership at time of purchase. Refer to website for Rewards / membership T&Cs. IN-STORE ONLY refers to company owned stores and not available to Resellers. Page 2: Club Offer: Wi-Fi Datalogger project includes 1 x each of XC3802, ZK8868, XC4494, WC6026, XC4604, HP9550, RD3485, HM3211 & RR0596 for $49.95. Page 4: 20% OFF Selected Panel Meters & Accessories applies to QP5581, QP5588, QP5410/12/15/17, QP5010/13/14/15/16/20/22. Page 5: Club Offer: 15% OFF Selected Power Cables applies to WH3077/79, WH3087, WH3045/46/47, WH3063, WH3055 & WH3035/37. 20% OFF Selected Prototyping Packs apply to RR1680, RR0680, RC5399, RG5199, RE6250 & ZD1694. Page 6: Club offer: 10% OFF Desktop Magnifiers applies to Jaycar 013A: Deskstop Magnifiers product category. Page 7: 10% OFF Selected Watch Tools applies to TH2014, TD2023, TH1932, TH1929 & TH1934. Page 8: Bundle Deal: 1 x KM1097 + 1 x XC4410 for $39.90. SERVIC E NSW ELIZABE CANL BAB BUNT Y ING LE RD EY VA SUPER CH AUTO EAP GOOD GUYS OFFIC WORK E S HORSLEY For your nearest store & opening hours: TH ST ONLY SAVE $10 Features an ATtiny85 8-bit microcontroller that you can program using the Arduino® IDE. 8k Flash Memory. • 6 x I/O connections • Integrated 5V Regulator XC3940 A smaller version of the popular Leonardo board. Perfect for small footprint projects. Powered by a 32u4 ATMEL processor, it features a 16MHz clock and 32kB of flash memory. • 10 x digital pins • 5 x analogue pins • 4 PWM pins • Tiny form factor, 23mm x 20mm XC4431 BOTH FOR 3990 $ RAY WHITE DR EY RSL HO DR N NEW STORE Wetherill Park Shop 52, 1183-1187 The Horsley Drive Wetherill Park, NSW (02) 9604 7411 1800 022 888 www.jaycar.com.au Over 100 stores & 130 resellers nationwide HEAD OFFICE 320 Victoria Road, Rydalmere NSW 2116 Ph: (02) 8832 3100 Fax: (02) 8832 3169 ONLINE ORDERS www.jaycar.com.au techstore<at>jaycar.com.au Arrival dates of new products in this flyer were confirmed at the time of print but delays sometimes occur. Please ring your local store to check stock details. Occasionally there are discontinued items advertised on a special / lower price in this promotional flyer that has limited to nil stock in certain stores, including Jaycar Authorised Resellers. These stores may not have stock of these items and can not order or transfer stock. Savings off Original RRP. Prices and special offers are valid from catalogue sale 24.07.2020 - 23.08.2020. CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions will be paid for at standard rates. All submissions should include full name, address & phone number. Four USB power supplies from laptop charger AC/DC adaptors for notebooks and laptops are widely available at low prices. These usually have an output voltage of 19-20V and output current between 3.5A and 7A. They are reliable, compact, have low RFI/EMI emissions and do not dissipate much heat. There are also many devices designed to run from a USB +5V power supply. Also, many devices designed to be powered from 6V or 4.5V work well when powered from +5V. So it is handy to have a way to power such devices from the laptop supplies previously mentioned. This circuit accomplishes that. It’s based on four identical sub-circuits built around MIC4576-5.0 fixed output voltage buck regulator chips. These can deliver up to 3A at 5V. Their switching frequency is nominally 200kHz. The circuit is protected with a fuse at the input and diode D9 will cause the fuse to blow immediately if the supply polarity is accidentally reversed. LED5 lights up to indicate when power is applied. The output of a switchmode laptop supply can have some noise and ripple, so this is reduced by the CLC pi filter comprising numerous capacitors on the input side, a 220µH choke and the bypass capacitors for REG1-REG4 which are all effectively in parallel. This filter also helps to prevent switching noise from REG1-REG4 being radiated out of the input supply leads. Each regulator has three input bypass capacitors of various values, to provide a low-impedance supply over a wide range of frequencies. They also require freewheeling schottky diodes (D1-D4), filter inductors (L1-L4) and output filter capacitors, which each comprise a parallel pair, 100µF and 1000µF. LEDs1-4 indicate the presence of voltage at each output, while diodes D5-D8 protects the circuit against back-fed negative voltages. With up to 15W delivered to each USB output, the total maximum power is 60W. If we assume that efficiency is around 80%, we need an adaptor that can deliver 72W. If the output voltage is 19V, this means a current draw of up to 4A, hence the value chosen for F1. Most laptop supplies can handle that. REG1 to REG4 need to be connected to large copper areas to help remove heat from them. For output currents above about 1.5-2A, it would also be a good idea to attach small finned heatsinks to each regulator. If you can’t get the MIC4576-5.0 regulators, you could substitute LM25965.0 or LM2576-5.0 regulators, but then the values of inductors L1-L4 might have to change. Petre Petrov, Sofia, Bulgaria. ($75) 61 Preamplifier power supply runs from 5V DC I wanted to build the Ultra-Low Distortion Preamp with Tone Controls and Six-input Preamp published in the March, April & September 2019 issues (siliconchip.com.au/Series/333 & siliconchip.com.au/Article/11917). However, I decided that I wanted to run my preamp from a single 5V DC supply. So I started researching the use of a Linear Technology LT1930 power converter chip. From their application sheet, I built up a supply that could deliver ±15V at 70mA per side from a 5V DC input. The chip switches at 1.2MHz, which means the inductor and capacitors can be physically small. One problem with the chip is its surface-mount footprint which makes it a bit difficult to design the board and solder the 5-pin chip. In the application notes, they mentioned using the copper PCB to provide heatsinking since the chip is switching a lot of power for its size. It works like a boost converter feeding into a charge pump. When REG1’s pin 4 shutdown input (SHDN) is high, it periodically sinks current into its switch pin (SW, pin 1). This causes current to flow through inductor L1, charging up its magnetic field. When REG1’s internal switch turns off, the voltage at pin 1 shoots up. This rise is coupled through capacitor C1, forward-biasing schottky diode D2, charging up output filter capacitor C3. When pin 1 of REG1 goes low again, C1 discharges through D1, so it’s ready to repeat the cycle. When the voltage at pin 1 goes up, capacitor C2 is also charged up via diode D3. When pin 1 goes low, the negative transition is coupled through C2, pulling the cathode of diode D4 negative and charging up output filter capacitor C4. The +15V output voltage is divided down and applied to REG1’s feedback pin (FB, pin 3) so that it can adjust its duty cycle to maintain a constant +15V output regardless of load. The load on the -15V output is assumed to be similar, and so the -15V output should be reasonably close to the desired voltage. I have run the supply for more than three months without any problems. I measured its efficiency at 75%. I used the recommended 2.2µF multi-layer ceramic capacitors and a 22µF tantalum capacitor for input bypassing. Although I have no means of measuring the audio quality from the preamp, it sounds fine to me. Since the chip runs at 1.2MHz, I doubt it will have much effect on audio frequency signals, although it may interfere with RF tuners. But I have never noticed any such problem. The inductor I used is an SMD 10µH ferrite-core type from Altronics, Cat L8200, which is rated at 2.3A with a DC resistance of 70mW. The LT1930 is available from element14. The diodes must be schottky devices to keep up with the high switching frequency. Although I haven’t tried it, the circuit should run from a 3.7V lithiumion rechargeable battery. Bob Temple, Churchill, Vic. ($80) The LT1930 regulator is soldered to the copper side of the PCB. Modifying the Ultra-LD Mk.2 to drive a hearing loop As shown here, it’s quite easy to modify one of our Ultra-LD amplifier modules (or indeed, just about any discrete amplifier published in Silicon Chip in the last 10 years) to drive a hearing loop. The additional components can be mounted on a piece of protoboard, with the double-pole switch mounted on a panel or bracket. There are three connections to the amplifier labelled X, Y and Z. Connec62  Silicon Chip tion X can be made by carefully soldering a wire to a pad on the top side of the PCB while Y and Z are made through the speaker output connector. The switch is included to allow the amplifier to be switched from constant current back to constant voltage mode if desired. With switch S1 in the position shown here, the current through the external loop is sensed by a 0.5W Australia’s electronics magazine shunt resistor and the voltage developed across this resistor is AC-coupled back to the base of PNP transistor Q2, in the input pair of the amplifier. This overrides the normal voltage feedback signal because it has a much lower impedance of around 12.5W compared to the original 489W (510W ∥ 12kW). The two added 1N4148 diodes are to protect the electrolytic coupling capacitor from damage under overload siliconchip.com.au conditions. The 2.5W resistor limits the peak loop current. This must be a high-wattage resistor. With S1 in the alternative position, the shunt resistor is shorted out so that the negative terminal of the speaker connects to ground as it usually would, and the current feedback path is disconnected, allowing the usual voltage feedback to resume. You still have the 2.5W resistor in series with the speaker, but that won’t stop the speaker from working. It will reduce the maximum power and damping factor, however. The hearing loop comprises two turns of figure-8 light-duty cable, 25 AWG (14 x 0.12mm). I’ve mounted it in the ceiling of a room measuring 5.2 x 5.0 meters. The two turns of the figure-8 cable provide a four-turn loop. An under-carpet loop may work too, but there would be some attenuation and field distortion from the steel in a concrete floor. The amplifier sensitivity is 0.5V peak input for a 5A peak output, or 20 amp-turns in the loop. I’m also using a PreChamp preamplifier (July 1994; siliconchip.com.au/Article/5252) provides a small amount of gain to accommodate typical auxiliary line-level inputs. I also added a volume control potentiometer to the preamp. I am very grateful to Associate Professor Catherine Birman, director of the Sydney Cochlear Implant Centre, and numerous others who gave me the ability to hear again. From a technical perspective, Cochlear implants are mind-blowing, particularly for someone who started in the days of vacuum tube technology. Anthony Leo, Cecil Park, NSW. ($80) siliconchip.com.au Australia’s electronics magazine August 2020  63 Altitude readout for the Boat Computer We had a request to add an altitude display to the Touch-Screen Boat Computer project from April 2016 (siliconchip.com.au/Article/9887). We briefly pondered what this chap might be doing with his boat that would require an altimeter, but he noted that he was using the unit in his four-wheel drive. The apparent utility of an altimeter readout is now obvious! As the data from the GPS module includes an altitude reading, we figured that it would not be too hard to arrange. If you have already built the Boat Computer, the update is easy to perform and does not require hardware changes. With the revised software, the altitude is shown (in metres) on the latitude/longitude display screen, as shown in the photo. Using MMedit or similar (eg, TeraTerm and the XMODEM command), simply load the “BoatComputerV7altitude.bas” file in place of the existing BASIC file. You can download this new code from siliconchip.com. au/Shop/6/3372 After the program has been run once, it will run automatically whenever power is applied. If you are starting from a blank Micromite (loaded only with the BASIC interpreter), then you will still need to configure the LCD and load the fonts before loading the BASIC program. See the original article for details. Alternatively, you can use a PIC32 programmer to load the HEX file directly into the PIC’s flash memory. This will work whether or not you already had the Boat Computer up and running. Our correspondent also noted a small hardware modification he has made to his Boat Computer (which can be applied to just about any Micromite BackPack project). He added a transistor across the trimpot which adjusts the screen brightness. When the headlights are on, a wire from that relay activates to turn the transistor off, so the screen brightness is at the trimpot setting for night driving. The rest of the time, this added transistor is on, enabling maximum display brightness. Tim Blythman, SILICON CHIP. Heelometer (heel meter) for boats Once upon a time, the heel or lean of a boat was measured with a passive, gravity-powered device like the one shown in the photo below. Nowadays, we can use an accelerometer instead. I realised that the Digital Spirit Level project from August 2011 (siliconchip. com.au/Article/1122) could easily be modified to perform this task. So I modified the software, as follows. It only measures the angle with A classic style heel meter which uses gravity to determine angles. 64  Silicon Chip a resolution of 1° and prefixes the reading with “P” for port or “S” for starboard, depending on which way it is leaning. For readings beyond 90°, it displays “OOPS”. This provides a handy way of knowing whether your boat has capsized! It also records the maximum heel encountered, which is displayed for a couple of seconds the next time it is turned on. The original software was written in C and compiled with Microchip’s C18 compiler. It has been migrated to the current Microchip XC8 compiler and modified to give the above facilities. The revised source code and HEX file are available as a free download from the Silicon Chip website (siliconchip. com.au/Shop/6/5507). Geoff Champion, Mount Dandenong, Vic. ($80) The heel meter showing a reading of port 19° 19°. Australia’s electronics magazine siliconchip.com.au PRODUCT SHOWCASE Industrial-use Arduino from NOVUS Automation The new DigiRail NXprog from NOVUS combines the ease of Arduino programming with the robustness of a controller designed for industrial usage. In addition to the features shown on the right, the DigiRail NXprog modules also allows for 35mm DIN rail mounting and screw terminal connections. Through its RS485 interface running Modbus RTU protocol, the DigiRail NXprog communicates with other devices acting either as a master or as a slave. It also incorporates an industrial Ethernet port running Modbus TCP protocol, making it suitable for industry 4.0 applications. In addition, the DigiRail NXprog can work with protocols from the Arduino community library as well as with other proprietary protocols. Unlike most PLCs which impose certain programming difficulties to the average user, the DigiRail NXprog programming is Arduino compatible, allowing for the use of high-level programming languages, such as C and C++. This way, users can program complex algorithms such as recursive logic, state machines, statistical analysis and mathematical equations in a very simple way. The Arduino library provided ensures quick and easy programming for reading temperatures using thermocouples, RTDs, Modbus communications and other tasks. Ocean Controls RS485 Port Ethernet Port 44 Frankston Gardens Dr Carrum Downs 3201 VIC Tel: (03) 9708 2390 Website: www.oceancontrols.com.au Maxim Integrated Summer Shen Tel: (+86 021) 5330 8100 www.maximintegrated.com summer.shen<at>maximintegrated.com Designers of compact consumer devices can now slash solution size by half and extend battery life by up to 20% with the MAX77654 single inductor, multiple output (SIMO) power management IC (PMIC) from Maxim. This next-generation SIMO PMIC delivers 3 outputs with just one insiliconchip.com.au ductor at 91% efficiency, which is 16% greater than traditional 4-chip systems. With significantly reduced size, system designers can pack more functionality into applications such as wearables, hearables or other compact consumer devices when compared to using traditional power solutions. The Australia’s electronics magazine USB Programming Port Universal Analog Inputs for thermocouples, RTDs etc Analog Outputs (4-20mA / 0-10V) Isolated Digital Inputs Digital Transistor or Relay Ouputs (depending on model) MAX77654 builds on Maxim’s robust portfolio of SIMO PMICs. Small Size: highly integrated, threeoutput buck-boost converter delivers a 19mm2 solution size that is 50% smaller than traditional discrete solutions. It consists of a SIMO PMIC, nine capacitors and an inductor. Long Battery Life: with 91% efficiency, as well as 500nA shutdown current and 6µA supply current, this solution provides 20% longer battery life and 7 times lower heat dissipation compared to discrete solutions. Cost-effective: up to 40% fewer components and 23% lower BOM cost compared to discrete solutions. The MAX77654 is available at Maxim Integrated’s website for $2 US (1000-up, FOB USA); it’s also available from authorised distributors. The MAX77654EVKIT evaluation kit is available for $119 US. August 2020  65 by Jim Rowe Low-cost, Wideband Digital RF Power Meter Simple to build and low in cost, this RF Power Meter will be very useful for anyone who needs to measure radio frequency signals from 1MHz to 6GHz. By itself, it can only handle power levels up to about 3mW (5dBm), but its range can easily be extended using fixed attenuators. W hile reviewing Banggood’s little RF Power Meter to extend its power range. I freely admit this last idea was that was published last month (siliconchip.com. copied from Banggood’s RF Power Meter... au/Article/14498), it occurred to me that we could design a similar device that wouldn’t cost much more to The Meter’s heart The Analog Devices AD8313 demodulating logarithmic build, but would handle much higher frequency signals. I also realised that its construction could be made easy amplifier chip in the RF Detector module forms the heart by using other low-cost prebuilt modules that I had re- of the Meter. It accurately converts an RF signal into a corresponding decibel-scaled DC output voltage. It maintains viewed recently. The concept quickly solidified around using an Arduino accurate log conformance for signals from 1MHz to 6GHz Nano module as the ‘brains’, together with the Banggood and provides useful operation to 8GHz. The input range is typically 60dB (referenced to 50), RF Detector module I reviewed in the March 2018 issue with errors less than ±1dB up to 5.8GHz. (siliconchip.com.au/Article/11005). Fig.1 shows how the AD8318 works. It has nine cascaded In a sense, this is a simpler and lower-cost replacement for my Digital RF Level and Power Meter from the October amplifier/limiter stages, each with a gain of 8.7dB. The outputs of each amplifier 2008 issue. stage are connected to At the same a full-wave detector time, it offers some cell, and the output worthwhile encurrents of the detechancements, like tor cells are summed a much wider freand fed to a currentquency range (from to-voltage converter 1MHz up to above S which produces out6GHz), the ability put voltage VOUT. to send the results The voltage-to-curof each measurerent converter at upment to your PC for per right allows addata logging, and Fig.1: an internal block diagram for the AD8318 log detector IC. The justment of the slope an allowance for differential input signal passes through a string of nine amplifiers/limits and of VOUT. For example, fixed attenuators at the outputs of each one go to full-wave detectors. The direct currents from the Meter’s input, each detector are summed and converted to a voltage which appears at VOUT. when the VSET and 66  Silicon Chip Australia’s electronics magazine siliconchip.com.au Features and Specifications Function: A compact, low-cost RF power and level meter with LCD screen and USB interface Frequency range: from 1MHz to over 6.0GHz Input impedance: 50 nominal Maximum input power level: +5dBm (3.2mW/398mV RMS) Minimum input power level: -60dBm (1nW/224µV RMS) Measurement range: -60dBm (224µV RMS) to +33dBm (10V RMS) with recommended attenuators Measurement linearity: about ±1dBm, 10MHz to 1GHz, +6dBm/-4dBm, 1MHz to 4.0GHz (see measurement plots) Measurement resolution: approximately ±0.1% Power supply: 5V DC at less than 120mA via USB micro-B socket SC Ó VOUT pins are tied together, this sets the output slope to a nominal -25mV/ dB. The AD8318 also includes an internal temperature sensor and bias stabilisation on the cascaded gain stages, so that changes in ambient temperature do not unduly affect accuracy. And all of this impressive technology is squeezed into a tiny 4 x 4mm 16-lead LFCSP surface-mount package. Fig.2 shows the measured transfer characteristic of an AD8318 at four different frequencies: 100MHz, 1GHz, 2GHz and 4GHz. It’s very close to linear at -25mV/dB at all four frequencies, between 0dBm and -60dBm. Fig.3 is the full circuit of the Banggood log detector module we are using. There’s very little in it apart from the AD8318 and a 78L05 regulator, which provides the AD8318 with a regulated +5V supply. (We are actually bypassing the 78L05 in this project, as you’ll learn shortly.) The full circuit The full circuit for our new RF Power Meter is shown in Fig.4. The Banggood AD8318-based log detector module is at upper left, connected to the rest of the circuit via CON2. The Arduino Nano MCU ‘brain’ is on the right. IC1 in the centre an LTC2400CS8 high-resolution (24-bit) ADC (analog-to-digital converter) used to digitise the output voltage from the log detector module. siliconchip.com.au Fig.2: a plot of VOUT vs input signal level for the AD8318 at four different frequencies (with the default slope setting of -25mV/ dB). As you can see, the linearity is excellent, and the frequency has minimal effect on the measured RF power level. This ADC requires a reference voltage to set its input scaling, and this is provided by accurate 2.500V reference REF1, an LT1019ACS8. IC1 digitises its input voltage under the control of the Arduino MCU via an SPI interface using Nano pins 1 (SCK), 30 (MISO) and 28 (SS-bar). After the MCU processes the digitised sample data, it displays the calculated RF power and voltage levels on the 16x2 LCD module via CON1. This is via an I2C interface using MCU pins 8 (SDA) and 9 (SCL) – the LCD module is an I2C serial type. Three pushbutton switches (S1-S3) are connected to MCU pins 25, 23 and 21. These are used to tell the unit when      SC 1MHZ – 8GHZ LOGARITHMIC DETECTOR MODULE  Fig.3: the circuit of the pre-assembled log detector module is very simple. The RF signal is terminated with a 51Ω resistor (52.3Ω might be better) and coupled to the inputs of IC1 via a pair of 1nF capacitors. The output from IC1 is fed to a pin header, while power is supplied via a 2-way terminal block. We’re bypassing 5V regulator REG1 in this project. Australia’s electronics magazine August 2020  67        16 x 2 LCD SC  WIDEBAND DIGITAL RF POWER METER Fig.4: thanks to the use of three prebuilt modules, the circuit of the RF Power Meter is not too complicated. The Arduino Nano uses 24-bit analog-to-digital converter IC1 to read the output of the log detector with high precision. 2.5V reference REF1 ensures that IC1 measures that signal with reference to a very stable voltage. The whole circuit is powered from the 5V pin of the Nano, which gets its power from a USB charger or computer. you have connected one or more external RF attenuators ahead of the Meter’s RF input, to increase its measurement range. It then adjusts its display to give correct readings. Since the Meter is designed to operate from a 5V DC supply derived via the USB cable connected to the Arduino Nano, the supply for the rest of the Meter circuitry is taken from MCU pin 12. This goes directly to the LCD module (again via CON1). For the rest of the circuitry, it is filtered by inductor RFC1 and several bypass capacitors. We are making a few minor modifications to the Banggood Log Detector module to simplify using it in the RF Meter project. The 78L05 regulator on the module needs an input of at least 7V for proper regulation, but we don’t have that. Instead, we have a well-filtered 4.75V rail after the 4.7 series resistor. So we are bypassing the 78L05 in the module by connecting the supply wire from CON2 directly to its output pin 1. To make sure that the 78L05 isn’t damaged by reverse current, it’s a good idea to remove the 10k resistor in series with the LED at the input of the 78L05. It’s pretty unlikely that such a small current would damage the regulator, but the LED won’t be visible once the case is on anyway, so it just wastes power if left in-circuit. The only other modification needed is to fit a 1nF SMD ceramic capacitor (2012/0805-size) across the two pads just to the left of the 2-pin output connector on the log detector 68  Silicon Chip PCB. This provides additional filtering for the AD8318’s internal feedback loop – it’s shown as COBP on Fig.4. All of these modifications should be clear from both the notes on the circuit (Fig.3) and the close-up photo of the log detector module PCB below. CONNECT +5V WIRE TO THESE PADS REMOVE THIS RESISTOR ADD 1nF CAPACITOR ACROSS THESE PADS A few minor modifications need to be made to the Banggood module before fitting it to the PCB. Australia’s electronics magazine siliconchip.com.au       Pin 8 of IC1 (the LTC2400 ADC) is taken to the centre pin of JP1, a three-pin header. This allows the sampling frequency of IC1 to be set for optimum rejection of any power line frequency components in its input signal. When the jumper shunt fitted to JP1 is in the lower position, the sampling frequency is set to reject 60Hz components (as you’d need in the USA), but if the jumper shunt is fitted in the upper position, the sampling frequency is set to reject 50Hz components. So the latter position is the best one for use in Australia, New Zealand or the UK.  What the firmware does The firmware sketch for the RF Power Meter is called “RF_Power_Meter_sketch.ino” and is available for free downloading from the SILICON CHIP website. When uploaded to the Arduino Nano’s ATmega328P micro, it does several things. Its main task is to direct IC1, the ADC, to take a sequence of 10 measurements of the output voltage VOUT from the log detector module. It then averages each group of measurements and calculates from that the corresponding RF power level in dBm and the equivalent voltage level in millivolts or microvolts. These figures are then sent to the LCD module for display, and are also sent out via the Meter’s USB data line for display and possible logging on a computer. The firmware’s other main task is to check between measurement cycles for any presses of the Select Attenuation pushbutton switch, S1. If S1 has been pressed, it then swings into ‘change attenuation’ setting mode and it monitors any presses of switches S3 (‘Increase’) or S2 (‘Decrease’) and adjusts its setting for the external attenuation in steps of 1dB. Then when S1 is pressed again, it saves the new external attenuation figures and returns to its normal measurement mode. The attenuation value is set to zero each time the unit is powered up. SILICON CHIP Fig.5: this PCB overlay diagram and the photo below shows which parts go where. The only polarised parts are IC1, REF1 and the Arduino Nano module. Pushbutton switches S1-S3 are mounted on the lid and wired back to the board using flying leads, while the header on the LCD screen (also mounted on the lid) is soldered directly to the pins of CON1 as the last step in the assembly. Construction The complete RF Power Meter is housed in a diecast aluminium box measuring 119 x 93.5 x 56.5mm. Pushbutton switches S1-S3 and the LCD module all mount on or behind the box lid/front panel. All of the other modules and components are mounted on a double-sided PCB measuring 109 x 83mm and coded 04106201. This also mounts behind the box lid/front panel, via four pairs of spacers. Begin construction by first fitting the passive SMD components to the main PCB, using the overlay diagram of Fig.5 and the matching photo as a guide. Then fit RFC1, which is larger and will probably need a hotter iron. It’s best to smear a thin layer of flux paste on its pads before soldering it in place. After this, install IC1 siliconchip.com.au and REF1, which are both in SOIC-8 SMD packages. Next mount 4-pin SIL headers CON1 and CON2, along with the 3-pin header for JP1. Then you can fit the four PCB terminal pins, which all push through their matching holes in the main PCB and are soldered to the pads underneath. Two are to the left of RFC1 (TPGND and TP5V), while a third pin (TP2.5V) is to the right of REF1 and the fourth (TP VOUT) is to the right of CON2. You should then be able to fit the Arduino Nano module to the PCB, with its 30 pins passing down through the Australia’s electronics magazine August 2020  69 matching holes and soldered to the pads underneath. The final step in assembling the main PCB is to fit the AD8318 log detector module. It mounts on the top of the main PCB using four 10mm long M3 machine screws, with an M3 nut used on each screw as a spacer, and then further M3 nuts underneath to complete the job. Once it has been secured, plug a 4-pin SIL socket into header CON2 and solder four short lengths of lightduty hookup wire to its pins, then to the matching points on the module using Fig.5 as a guide. By the way, although the log detector module shown in the photos and diagrams is fitted with a small two-way terminal block power and a two-pin header for Vout, the module as supplied may not have these. Neither connector is required in this application, as you can simply solder the wires to the pads on the PCB. Case preparation There are only two holes to be cut in the box proper: an 11mm diamFig.6: only two holes need to be made in the main part of the case, with the eter round hole in the front, and a 9 locations and sizes shown here. The round hole is for the SMA RF input x 11mm rectangular hole in the rear. connector while the rectangular cutout allows a USB micro-B plug to be inserted The location of each of these holes is into the socket on the Nano board shown in Fig.6. There are 12 holes to be cut in the box lid, which becomes the Meter’s front panel. The locations and sizes of these holes are shown in Fig.7. There are three 12.5mm holes for the three pushbutton switches and a 65 x 15mm rectangular hole for the LCD ‘window’. The remaining small holes are for mounting the LCD module and the main PCB. After you have made and deburred all the holes in the lid/front panel, it’s a good idea to attach a dress front panel to the front for a professional appearance. We have prepared an actual-size artwork for this, which can be downloaded from the SILICON CHIP website as a PDF file. You can print this out in colour and then hot-laminate it in an A5 laminating pouch. After this you can cut it to size, punch four 3mm holes (one in each corner) and then attach it to the front of the lid using either thin double-sided cellulose tape or contact adFig.7: most of the holes that need to be made are actually in the case lid, including hesive. Once it is securely attached, a large rectangular cutout for the LCD screen. This is best made by drilling a cut out the remaining holes using a series of small (say 2mm) holes around the inside of the perimeter, knocking the inside part out, then filing the edges to shape. You can use a similar technique for sharp hobby knife. For other options to make a panel the USB socket hole in the base. 70  Silicon Chip Australia’s electronics magazine siliconchip.com.au Photos of the front (above) and rear (at right) of the assembled project showing the holes required, These photos match Fig.6, opposite. label, see siliconchip.com.au/Help/FrontPanels The next step is to attach an 80 x 25mm rectangle of thin clear plastic (say, 0.4mm thick) behind the LCD window cutout, to protect the screen from dirt and damage. This can be attached using standard cellulose tape, taking care not to cover the LCD module mounting holes. The lid assembly can now be finished. Mount the LCD module behind the window using four 16mm-long M2.5 countersunk screws, four 9mm-long untapped spacers, three or four Nylon washers and then four M2.5 nuts as shown in Fig.8 and the photos. Then you can mount the three pushbutton switches using the supplied plastic nuts, and finally attach a 25mmlong M3 tapped spacer near each corner using a 6mm long M3 machine screw. The rear of your lid/front panel should now look like the photo. Next, cut six 25mm lengths of single-core hookup wire (three red and three black) and strip off about 4-5mm of the insulation at both ends of each. Then solder one end of each red and black pair of wires to the connection lugs at the rear of each pushbutton switch. These are to connect the switches to their matching pads on the main PCB. After plugging a four-pin SIL socket into CON1, attach the main PCB using four 12mm M3 screws through each corner of the PCB, with a 6mm long untapped spacer between the PCB and each 25mm long tapped spacer – see Fig.8. The only trick is making sure that the wires from each pushbutton pass through their matching holes in the main PCB, although you can adjust them later if necessary. Once all the switch wires are through their corresponding PCB pads, upend the assembly and solder the wires to those pads. The final step is to solder the four pins of the SIL header on the LCD module to the corresponding pins at the top of the SIL socket you fitted to CON1. You may need to slightly bend the LCD header pins using a pair of needle-nose pliers, so that they are close to the pins of the SIL socket, allowing them to be soldered together. If this proves a little tricky, it can help to temporarily remove the nearby tapped spacers, which can be replaced easily once the connections have been made. Don’t fit this assembly into the box just yet, since it’s a good idea to check a few key voltages at this stage. It may also be necessary to adjust the contrast of the LCD to get the clearest display once the Meter firmware has been uploaded. Testing and setup First, connect the Meter up to a USB 5V power supply siliconchip.com.au using a mini-B cable. As soon as power is applied, the LCD’s backlight should illuminate. Get out your DMM and check a few voltages relative to the TPGND pin at the left Parts list – Wideband Digital RF Power Meter 1 diecast aluminium box, 119 x 93.5 x 56.5mm [Jaycar HB5064 or similar] 1 double-sided PCB coded 04106201, 109 x 83.5mm 1 Arduino Nano or compatible module 1 1-8000MHz AD8318-based RF Logarithmic Detector module [eBay, AliExpress, Banggood] 1 16x2 LCD module with LED backlight and I2C serial interface [SILICON CHIP Cat SC4198] 3 panel-mounting SPST pushbutton switches (S1-S3) [Jaycar SP0700 or similar] 1 100µH RF choke, SMD 12 x 12 x 8mm [Jaycar LF1402 or similar] 4 25mm-long M3 tapped spacers 4 9mm-long untapped spacers 4 6mm-long untapped spacers 4 M3 x 12mm panhead machine screws 4 M3 x 10mm panhead machine screws 4 M3 x 6mm panhead machine screws 8 M3 hex nuts 4 M2.5 x 16mm countersunk machine screws 4 M2.5 hex nuts 4 Nylon flat washers, 3mm inner diameter 2 4-pin SIL headers, 2.54mm pitch 1 3-pin SIL header, 2.54mm pitch 2 4-pin SIL header sockets, 2.54mm pitch 1 2-pin SIL header socket, 2.54mm pitch 1 jumper shunt/shorting block 2 100mm lengths of light-duty hookup wire (red & black) Semiconductors 1 LTC2400-CS8 24-bit ADC, SOIC-8 (IC1) [Digi-Key LTC2400CS8#PBF-ND] 1 LT1019ACS8-2.5 voltage reference (REF1) [Digi-Key LT1019ACS8-2.5#TRPBFCT-ND] Capacitors 2 100µF 10V X5R SMD ceramic, 3216/1206-size 2 10µF 16V X7R SMD ceramic, 3216/1206-size 7 100nF 50V X7R SMD ceramic, 3216/1206-size 2 1nF 50V C0G or NP0 SMD ceramic, 2012/0805-size Resistors (all SMD 1%, 3216/1206 size) 1 5.6Ω (code 5R6 or 5R60) 1 4.7Ω (code 4R7 or 4R70) Australia’s electronics magazine August 2020  71 Fig.8: this side profile view shows how it all goes together and fits into the case. If you don’t have untapped 6mm spacers, you could use tapped 6.3mm spacers instead. Note how the log detector module is spaced off the main PCB using nuts. The last step before dropping the whole thing into the case is to bend the 4-pin header on the LCD over to make contact with CON4 on the main board, then solder the pins together. rear of the main PCB. You should measure close to 5V on the adjacent TP5V pin, around 4.75V on the VCC pin of the socket plugged into CON2, and very close to 2.5V at TP2.5V. If you get all of these readings, remove the power and download the Meter’s Arduino sketch from the SILICON CHIP website. You will need the Arduino IDE (Integrated Development Environment) to compile and upload the sketch. If you don’t have it already installed, it’s a free download from www.arduino.cc/en/Main/Software Our sketch, “RF_Power_Meter_sketch.ino”, uses libraries: SPI.h, Wire.h and LiquidCrystal_I2C.h. The first two come as standard with the Arduino IDE, but you’ll probably have to install the last one via the Library Manager or download it from siliconchip.com.au/link/ab2k Once ready, plug the Meter’s USB cable into a free port of your PC. If you are running Windows 10, go into Settings -> Bluetooth & Other Devices and then go down to Other devices. You should find an entry like USB-SERIAL CH340 (COMxx), where the digits after “COM” indicate the virtual COM port that Windows has assigned the Meter’s Nano – or strictly, its CH340 USB-serial interface chip. Next, start up the Arduino IDE, and go into the Tools menu. Then click on Board, which will produce a list of possible Arduino modules; select Arduino Nano from that list. Then click on Processor and select “ATmega328P (old Bootloader)”, since this is the appropriate one to communicate with the Meter’s Nano MCU via its CH340 serial interface. After this, click on Port, which should give a listing of any virtual COM ports that IDE has found available. Select the COM port address that corresponds to the Meter. If you didn’t already load the LiquidCrystal_I2C library via the Library Manager, do so now. If you downloaded the ZIP file instead, add it via the “Add .ZIP Library” option near the top of the Sketch -> Included Library list. Now open the downloaded sketch file and click Sketch -> Verify/Compile, After 20 or 30 seconds, you should get the message “Done compiling” in the box near the bottom of the IDE window, plus some statistics regarding the compilation. If all has gone well, the final step is to go into the Sketch menu again and click on Upload. When this is completed, the Meter should spring into life. The LCD should first display the initial greeting: This photo is from the same direction as Fig.8 above . . . . . . while this shot is from the opposite direction. 72  Silicon Chip Silicon Chip RF Power Meter Then, after a few seconds, it should begin displaying the results of its RF input sampling and calculations. With nothing connected to the Meter’s RF input, you should get a display like this: RF Pwr= -68.5dBm =83.2uV At=00dB If the display on the LCD is not clear and well defined – perhaps just two lines of blocks – that indicates that the contrast trimpot on the back of the LCD module needs to be adjusted. Rotate the trimpot in one direction or the other using a small screwdriver. The trimpot is just above RFC1 and the TP5V and TPGND terminal pins. The last thing to test before fitting the Meter assembly into its box is to make sure it is sending the test readings back to the PC. Australia’s electronics magazine siliconchip.com.au An end-on photo (above) with a shot showing the display board and pushbuttons, obviously before they were wired in! Note how the standoffs are lengthened to make the required spacing between the main board and front panel. To do this, go to the Arduino IDE and open the Tools menu. Click on Serial Monitor and it will open up another window. This should show the Meter’s virtual COM port address at the top, and at the top of the centre area you should see: Silicon Chip Digital RF Power Meter Then, after a few seconds, you should see the results of the first reading on a single line: RF Pwr= -68.6dBm = 82.6uV At=00dB Further readings will appear every few seconds. If you don’t see this display in the Serial Monitor window, or if all you see is a string of weird graphic symbols, check at the bottom right of the window to make sure that the serial data rate is set to 115,200 baud (bits per second). This is the data rate at which the Meter’s Arduino Nano sends the reading data. If you click on the “Show timestamp” checkbox at bottom left of the same window, a timestamp will be added to the start of each line of readings to allow data logging. If you have access to the equipment necessary to finetune the Meter’s calibration, as described at the start of the section below, you may wish to do that now. Otherwise, you can accept the default calibration we have built into the firmware. In that case, unplug the USB cable and lower the Meter assembly it into the box, securing it with the four supplied mounting screws. Your Digital RF Power Meter is then ready for use. Calibration To fine-tune the Power Meter’s calibration, you’ll need a DMM able to measure DC voltages up to 2.5V with high accuracy, and a UHF signal generator which can be set to provide CW signals at 1GHz (1000MHz) with an accurate amplitude of between +5dBm and -65dBm. The first step is to remove the Meter assembly from its box (if you’ve already finished the assembly) and apply 5V power via the USB cable. After allowing a few minutes for it to stabilise, use the DMM to measure the reference voltage at TP2.5V, up near the right rear corner of the main PCB, relative to the TPGND pin. This should be very close to 2.5000V, but whatever the siliconchip.com.au reading you get, record it carefully as VREF. Next, transfer the positive test lead of the DMM to monitor the voltage at the TP VOUT terminal pin, just to the right of CON2 at the rear of the log detector module. Then connect the input of the Power Meter to the output of the signal generator via a short length (say 150mm) of SMA-SMA cable. The short length is to minimise cable losses. Set the generator to provide a CW (continuous wave, ie, unmodulated) signal at 1.000GHz, with an initial level of +5dBm (1.78V RMS). The DMM should show the log detector’s VOUT voltage to be around 0.5V. Record the actual value of this reading, this time with the label “Vo5dBm”. Next, reduce the generator output level to 0dBm (224mV RMS), and again record the DMM reading (it should be around 0.56V) with the label “Vo0dBm”. Repeat this exercise with the generator set to -55dBm (398µV), which should give a reading of around 1.9V, and -65dBm (126µV), which should give a reading of around 2.1V. These figures should be recorded as “Von55dBm” and Von65dBm” respectively. Now remove the DMM test leads and go back to the Arduino IDE, which presumably still has the RF Power Meter sketch open. Scroll down about 50 or so lines from the top, where you’ll find three lines reading: byte S1 = 0; byte S2 = 0; byte S3 = 0; then you’ll see a blank line, followed by a line reading: const float Von65dBm = 2.0451; In place of that figure of 2.0451, type in the reading you recorded for Von65dBm. Similarly, replace the values on the next four lines with the other readings that you noted earlier. Make sure that, in replacing these figures, you don’t remove the semicolons after each one. Otherwise, the sketch won’t compile. Save the modified sketch file and recompile it by going to the Sketch menu and clicking on Verify/Compile. Then Australia’s electronics magazine August 2020  73 +20 Even with a longer cable between the generator and the Meter (allowing for the cable losses), there was still a peak at 2.5GHz. But if you know the frequency of the signal you are measuring (as you usually would), you can use Fig.9 to make allowances for this behaviour. +10  +5 398mV 0 224mV –10 71mV Suitable attenuators To make the Meter truly useful, you should ideally also get a few inline attenuators. These can be used to extend its meas–30 7.1mV urement range above +5dBm. Banggood has a range of very compact SMA–40 SMA fixed coaxial attenuators, for the 2.24mV reasonable price of A$10.65 each or A$28.11 for three. They are rated at –50 2W and 0-6GHz, and are available with 710mV attenuation figures of 3dB, 6dB, 10dB, 20dB and 30dB. –60 224mV The 10dB attenuator could be used to extend the range of the RF Pow–70 er Meter to +15dBm (1.26V RMS, or 71mV 32mW), while the 20dB unit would extend its range to +25dBm (3.98V –80 RMS or 316mW). Similarly, the 30dB 5 5 2 2 500 1GHz 50 200 20 10 10 100 1 unit would extend its range to at least FREQUENCY +33dBm (10.0V RMS or 2W into 50Ω). Fig.9: the measured performance of the finished product for nine different I ordered the 10dB, 20dB and 30dB input levels over a range of frequencies from 1MHz to 4GHz. The readings are units, and thanks to the COVID-19 pangenerally within about ±1dB up to 1GHz, but a peak at around 2.5GHz makes demic they took about seven weeks to readings from higher frequencies less accurate. You can use this diagram to arrive. But they did turn up eventucompensate the readings, as long as you know the signal frequency. ally, and they seem to be well made. if it compiles correctly as before, click on Sketch→Upload They’re pictured in the photo below. to load the revised firmware to flash memory on the PowAs mentioned earlier, when you power up the Meter, er Meter’s Nano. the external attenuation figure is set to zero – displayed Your Power Meter should now be calibrated. Just to as “00dB” at the right-hand end of the second line of the verify that this has been achieved, you can set the signal LCD. When you change the attenuation figure to allow generator output to say -40dBm (2.24mV RMS), where- for any attenuator(s) you are using via buttons S1-S3, upon the Meter should give a reading very close to this the Meter will display this new figure on the LCD in the figure; within ±1dBm. same position. The calibration is then complete. You can remove the If at a later stage you remove the external attenuator(s) power from the Meter assembly and reinstall it in its box, and wish to reset the Meter’s attenuation figure to zero, so it’s ready for use. this can be done either by using the trio of pushbuttons again, or simply by removing power from the Meter for Typical response plot about 10 seconds and then reapplying it. SC After calibrating the prototype RF Power Meter shown in the photos, we measured its response over a range of signal levels and between 1MHz and 4.0GHz (the upper A selection of attenuators, in limit of the Gratten GA1484B Signal Generator). The results are shown in Fig.9. This shows that the this case 10, Meter response at most signal levels is within ±2dB up 20 and 30dB, to 1.0GHz, rising to a peak of around +6dB at 2.5GHz, which will rather significantly before falling away again. increase the The peak at 2.5GHz is presumably related to the com- power handling ponents (and possibly the PCB tracks) at the input of the of your RF meter. log detector module. We wondered whether the 51Ω in- These were also put load resistor was responsible, as the AD8318 data sheet sourced from suggests 52.3Ω intead. But swapping that resistor out with Banggood, at less some 52.3Ω samples we bought did not eliminate the peak. than $30 for the three. So it’s probably a PCB layout problem. RF INPUT LEVEL in dBm  –20 22.4mV 74  Silicon Chip Australia’s electronics magazine siliconchip.com.au Build It Yourself Electronics Centres® 240V power from a lithium battery! M 8199A SAVE $20 299 $ Carry 240V Power Anywhere! 8 pages of great deals on This portable solar generator is fitted with 14Ah battery bank & 240V mains inverter. Allowing you cable free power for both AC and DC appliances anywhere! Plus 2.1mm DC power & USB charging. 40W solar panel (N0040F) to suit $115. useful electronics. NEW! 1.5” screen on rear LED Magnifier for micro tasks Add on an MicroSD card 16GB $9.95 (DA0328). 1080p GPS WiFi Dash Cam Protect yourself with this feature packed dash cam! 1080p footage and includes high end features such as GPS, wi-fi footage transfer, G-sensor triggering & parking mode. Theft deterrent magnetic bracket. 68.95 $ D 2322 NEW! SAVE $19 50 $ Bluetooth® BBQ Temperature Monitor X 7015 Love your slow cooked meats? Cook to perfection with the EasyBBQ dual probe monitor. Makes cooking easy! Android or iOS compatible. 0-300°C range. Requires 2xAAA batteries. Build wireless charging into your desk An ultra-slim desk mount 10W wireless fast charger. Requires 60mmØ hole. Includes power adaptor & USB cable. Why pay $300 for a MaggyLamp? The inspect-a-gadget illuminated desk magnifier is an absolute bargain at $69, we believe ours is every bit as useful. An incredible visual Say aid for detailed inspection and e to work on fine items with full clarity goodby ! eye strain through the 5 dioptre lens. Tackle complex miniature tasks with confidence! SAVE 12% X 4205 69 $ See notifications while you recharge. 45.95 $ D 2324 Handy upright 15W wireless charging stand allows you to read incoming notifications at a glance without having to stop charging. Requires QC3.0 USB wall charger (such as our M8863) Joondalup Store OPENS AUGUST 3RD 2/182 WINTON RD JOONDALUP, WA. OPEN 7 DAYS. D 2320 59.95 $ ADD ON DEAL: USB QC 3.0 wall charger for $10 (M 8863) Wireless Charger Alarm Clock A stylish USB powered clock with in-built 10W wireless charging for your phone & 8 colour night light. Clock auto dims at night time. Dual alarms so you’ll always wake up on time! USB output also lets you charge your watch. *Phone for illustration purposes. Desk Mount Power Delivery Charger 135 $ Charges a laptop, a phone & tablet at the same time! D 2323 A 96W USB type C charger, plus dual QC 3.0 USB charging in the one compact near flush mount unit. Requires 60mmØ mounting hole. Includes power supply. MERCER LANE FANTASTIC FURNITURE dalup Joon DELAGE STREET JOONDALUP DRIVE S 9442 WINTON RD. 139 $ *Devices shown for illustration purposes. SAVE $50 Order online <at> altronics.com.au | Sale pricing ends August 31st 2020. Top deals on power solutions. NEW! D 0511B 79.95 $ Power your camping fridge without risk of draining your battery! Recharges faster thanks to USB C input! Jumbo QC3.0/USB C Power Bank PRE ORDER! NEW! Arrives Mid August. 269 $ M 8197 Offering both the latest QuickCharge 3.0 charging and 18W USB-C PD output, this enormous 20,000mAh power bank will keep your devices charged away from mains power. 136x70x25mm SAVE $30 N 1130F Carry 240V Power Anywhere! This air travel friendly portable power generator is fitted with 5Ah battery bank, 80W 240V mains inverter, 18W power delivery USB C charger & QC3.0 USB charger. Offers you cable free power for both AC and DC appliances! Recharge by USB or included power adaptor. 209 $ USB C Panel Mount Charger 130W Remote Power Folding Solar Panel A combination Quick Charge 3.0 and 18W USB C power delivery charger for the car, 4WD or caravan. Going bush? Have power wherever you go on your next 4WD/camping adventure. Includes 130W panel, solar regulator, battery connection cables and canvas carry case. 3 stage solar charger. Adjustable stand for best sun placement. 664x631x75mm (folded). NEW! 34.95 $ P 0696 179 $ NEW! M 8539 105 $ M 8994 S 2682 SAVE $40 Charges any USB-C laptop 119 $ SAVE $30 Need an extra laptop charger? Powerhouse® 7 Stage 12V High Output Battery Charger This 90W USB-C power delivery (PD) charger offers fast recharging for MacBooks, Nintendo Switch and other type “C” devices. Plus a standard 2.4A USB charger output. S 4732 With Tags SAVE 32% 20 16 $ $ M 8863 Home QC3.0 Wall Charger S 4736 Standard 18650 Lithium Batteries 18 $ SAVE 12% 3.7V 2600mAh. Quality Samsung brand cells. Unprotected. 5.2A discharge current. 18.6Ø x 65mmL. QC 3.0 for 4x faster charging. 3A output. Compact case doesn’t block outlets. Dual 12V Car Battery Isolator Kit Offers support for batteries up to 300Ah with an output current up to 12A. 7 stage charging delivers the appropriate charge current to maintain best performance & battery life. Can also recover deeply discharged cells. Suits permanent connection, making it great for seldom used vehicles. Auto reconnect starts charging again as soon as you connect the unit to mains! Provides everything you need to wire up a secondary battery in your vehicle - vital for powering appliances at campsites, inverters etc, and isolating the primary battery so you have enough juice to start your car! Instructions included. Do-It-All Battery Charger SAVE 32% 44 $ Powered by USB, allowing you to stay powered up Charges: Li-Ion, Ni-Mh & Ni-Cd anywhere. Works with 10440 to 26650 size lithium and AAAA to C size .95 $ Ni-MH/Ni-Cd. 22 M 8881 Super saving! Charge 8 USB devices at once. Got a family full of devices? This handy charger produces up to 12A of charging current to keep all your tablets and phones juiced up! Includes power cord. A 0289A Huge range of vehicle DC power products available NEW! High Current DC Power Distribution Posts High current DC power distribution posts with reinforced nylon base. Available in single, dual and bridging types. 48V DC max. Model Type NEW! P 2172 Single M8 Red P 2173 Single M8 Black $10.95 $10.95 $14.95 $14.95 $10.95 $10.95 $14.95 $14.95 $13.75 $13.75 P 2175 Dual M8 Red P 2176 Dual M8 Black P 2182 Single M10 Red P 2183 Single M10 Black P 2177 Dual M10 Red P 2179 Dual M10 Black P 2180 Bridging M8 Red P 2181 Bridging M8 Black SAVE 20% 26 $ SAVE 22% 19 per roll $ P 0690 Dual USB Charging Socket 3.1A max output. Suits standard switch recesses. W 2120 Must have for portable solar power systems SAVE 22% Q 0589 35 $ Figure 8 Power Cable Easy Read DC Energy Meter The cable of a million uses! A great general purpose electronics cable - don’t let your workshop run out. 7.5A rated. 24/0.20. 30m roll. Simultaneous display of voltage, current, power and energy (Wh) readings. Ideal for DC battery monitoring and small solar systems. Requires 85x45mm cutout. 20A max. See last page for store locations or visit altronics.com.au Sale pricing ends August 31st 2020. Expand your AV system & save. C 5285 C 0876 Magnetic ‘edge to edge’ grilles. 355 $ 229/pr $ 160 /pr /pr $ SAVE $100 NEW! SAVE $80 C 0881 8” C 0871 6.5” Includes easy to mount ball joint bracket Opus One® 2x30W Bluetooth® Wireless Ceiling Speakers 179/pr $ SAVE $80 Built to stream the best content from your favourite music streaming service, app or podcast player. Bluetooth 5.0 technology offers superb audio performance and range. Each speaker pair has an in-built high performance 2x30W RMS amplifier. The ideal way to add permanent wireless sound to any room in the house. A modern, low profile finish is provided by frameless magnetic fit grilles. Includes power supply. Sold in pairs. Premium sound in a tiny package. Stunning hi-fi clarity by Opus One® Redback® 2.75” Mini Satellite Speakers. Deliver full and rich sound you’d hardly believe these speakers are only 10cm tall! They’re the perfect home and small commercial sound solution - especially when paired with our C 5210 subwoofer and A 4860 bluetooth amplifier. 8Ω 10W rated. Suits flat TVs up to 84” The perfect partner for our A 1116 Bluetooth amplifier (see below). Can be installed yourself, fliplock brackets secure each speaker for flush mount screwless finish. Sold in pairs. Broken remote? No problem! With USB connection in base! SAVE $80 209 $ SAVE UP TO $50 H 8232A Dual SAVE $50 H 8126B 225 109 $ Cantilever Arm TV Bracket Active Optical HDMI Cables SAVE $20 $ H 8230 Single Desk Monitor Mounts Silky smooth cantilever adjustment, stays just where you want it to. It even has 14° of tilt adjustment! Engineered for flat screens up to 84” using 600 x 400mm VESA. Max weight, 45kg. Regain precious desk space! • Single or dual models with easy adjust arms • USB ports for easy peripheral connection • Monitors up to 30” • Desk clamp installation. • Max 9kg. SAVE 20% SAVE 25% 59 A 3089 A 3133B 50 $ $ 2 Way HDMI Splitter A handy switcher for connecting up to 5 HDMI sources to a 4k/2k or HD display. Includes plugpack. Sends one HDMI signal to two HDMI outputs (ie show the same on two TVs). 4K ready. Dynalink® F2 Pro Gaming Headset Multi-platform ready! Suits PC, Playstation, Xbox and Switch with included TRRS adaptor. Offers excellent comfort for long gaming sessions with RGB lighting effects (when USB is plugged in). 2m cable. C 9042 68.95 $ NEW! Cutting edge Active Optical Cable (AOC) HDMI technology supporting 4K resolutions at longer lengths than copper cable. Plus, it’s thinner, lighter & more flexible! Why use HDMI AOC? These cables totally eliminate the need for long distance baluns, UTP conversion and boosters for HDMI signals - get full 4K <at> 60Hz over the full distance! 42 $ A 3127 5 Way HDMI Switcher SAVE 25% Mini HDMI Repeater Extends HDMI leads up to 50m. Inline connection. Supports 4K <at> 60Hz. Model Length Normally NOW P 7427 10m $240 P 7428 12m $265 P 7429 15m $275 P 7430 20m $289 P 7432 30m $299 P 7434 50m $345 $185 $189 $199 $225 $235 $295 Listen while you walk, run or ride! NEW! C 9044 63.25 $ Flexible Wireless Sports Headphones Great sound and even better battery life! These over ear style headphones offer up to 16 hours listening time in a super comfortable & compact design. Bluetooth 5.0 for great range and audio quality. Buying for business? Save with a VIP-Trade Card Dog ate your remote? Enthusiastic toddler binged too hard on Paw Patrol? This handy replacement features IR learning plus preprogrammed codes for 100’s of popular equipment brands. A 1012A 34.50 $ SAVE $50 199 $ A 4201 Bluetooth® 2x50W Amp Stream audio directly from your device to your speakers in the study or entertaining area. 3.5mm and RCA inputs. Class D design. Includes power supply, banana speaker plugs & 3.5mm to RCA cable. Amazing Bluetooth Sound For Less! The perfect every day commuter earphones with top notch wireless sound, compact folding design and up to 18 hours of listening between recharges. 50 $ C 9034 SAVE 12% Sale pricing ends August 31st 2020. Upgrade the tool kit this month... FEATURE PACKED SAVE $39 41 $ .50 19 Range DMM With in-built AC mains detection. Featuring true RMS measurement, transistor and diode testing and backlit display. Q 1126A SAVE $25 50 READS AC & DC SAVE $21 80 $ 28 MANUAL RANGES NEW MODEL! ULTRA SLIM CASE SAVE $25 70 $ $ $ 9999 Count True RMS Multimeter Feature Packed 28 Range DMM 600A AC & DC Clamp Meter Not much bigger than your average mobile phone (16mm thickness), this auto ranging meter saves space in your tool box. Easy to use with volts, current, amps and resistance. Q 1064 With in-built AC mains detection. Featuring a striking easy to read reverse backlit screen and a massive 9999 count readout. Auto ranging with easy push button operation. Q 1090 Includes temperature probe at no extra cost! Excellent for service technicians or enthusiasts. Easy to use with an on screen guide for test lead connection. Massive 20A rating AC/DC to 1000V. Q 1067 Safe and easy measurement of AC & DC voltage/current. In-built non contact voltage detection indicates live AC wiring. Includes test probes, temperature probe & carry case. Q 0965 RCD Mains GPO Tester SAVE 23% Q 3003 35 $ Detect lethal AC voltages instantly. This non-contact probe detects cabling and power outlets with live AC power (100-1000V). An essential preventative tool for trades people. Waterproof case with in-built torch. Do-It-All Multimeter With in-built AC mains detection. This is one of the best DMMs we have evaluated when it comes to build quality and features. Its perfect for the serious enthusiast or tradesperson • LCD bargraph • 3.75 digit display • Mode assistance indicators. • Includes case, temp probe & insulated test leads. Q 1068 Powerful diagnosis tools in the palm of your hand. Tests mains power points for correct operation with simulation of an earth leakage to test your household RCD. Indicates unsafe wiring. A must have for P 8142 electricians. Measure and map UTP cable networks - simply! SAVE $40 105 80 $ Space Saver Multimeter Waterproof design for field use! TOP FEATURE SET NEW! 40 $ SAVE $44 Q 1347 The must have diagnostic tool kit for any IT technician or data installer Measures cable length up to 1000m, continuity testing and trace cable locations all with the one unit. Kit includes 8 remote identifiers for connection to cable runs, a ‘sniffer’ probe and main tester with easy to see backlit screen. Includes carry case, batteries and various connection adaptors 185 $ All the power of a benchtop oscilloscope in the palm of your hand. This compact digital storage oscilloscope and digital multimeter makes field testing easy, even when working in tight spaces or with equipment on site. Offers 2 channels with real time sampling of 125MSa/s per channel with waveform comparison tools and a full range of accessories (plus carry case). Q 0102 SAVE $81 319 $ 310 $ M 8205 0-30V 5A Network Cable Tracer SAVE $20 Q 1341 105 $ A must have for IT technicians! Combines a cable tracer & tester in one unit. Injects an audible signal down the line, making it easy to find specific lead. Requires 3 x AA and 1 x 9V batteries. 239 $ SAVE $80 D 3006A SAVE 12% 40 $ Linear Lab Power Supplies Our most popular models! Fully adjustable with LCD meters for precision adjustments. Great for R&D and workshops. • Precision linear toroidal design • Fixed 12V & 5V output rails • Fully regulated • Short circuit & overload protection. LAN Network Tester Instantly displays the status of all data cable conductors (shorted pins, straight or crossover cable identification). M 8200A 0-30V 3A er supply? Why choose a linear toroidal pow mode designs compared to switch Linear power supplies offer far lower noise s or analog circuits. They are device ve sensiti ing power to and are well suited or medical equipment. ions unicat comm ideal for use in labs, with See last page for store locations or visit altronics.com.au Sale pricing ends August 31st 2020. Electronics workbench essentials. Torque adjustment prevents chewed out screw heads! 375 SAVE $80 $ Not just for desoldering works great as a regular hot air gun! SAVE $30 T 2052 NEW! 160 $ 99 $ T 1289 SMD Hot Air Re-Work Desoldering Gun T 2128 Repair faster with a lithium screwdriver. Super fast desoldering for quick repairs or recycling parts Soldering & Vacuum Desoldering Station Provides 300W of hot air for quick and easy desolder and re-work of surface mount boards. Melts solder in seconds allowing you to remove devices easily. 200-500°C adjustable. Includes desk stand - plus narrow, medium and wide nozzles for different tasks. This USB rechargeable screwdriver features a fully adjustable torque drive for fast and accurate driving of precision screws found in modern high tech devices. Two way direction control. Standard 4mm driver bits (14 included). 3 hours use per charge. See web for full contents list. Save space on your bench with this top performing 60W soldering iron and 90W vacuum desoldering station. Removes a 16 pin through hole IC in 30 seconds! Sucks molten solder away from components & pads in no time and is easily cleaned. 160° to 480°C adjustable. Includes 0.2mm soldering tip and three desoldering tips. NEW! 49.95 Includes hard to find bit types for latest phones & laptops $ T 2164A SAVE 15% SAVE 15% 29 $ Pro 72pc Repair / Servicing Tool Set A premium finish aluminium driver handle with silent ball bearing ferrule top. Contains a huge variety of driver 4x28mm driver bits, double ended opening tools, spudger, curved tip tweezers and flexible drive extension. It makes servicing high tech devices easy! SAVE 30% SAVE 19% 16 T 2748A Superb build quality! T 2749 Stay sharp longer! 10 $ Rust free stainless steel! T 2741 T 2865A Side Cutter T 2870A Long Nose Plier T 2860A Bull Nose Plier SAVE 13% $ T 1490A T 2185A An aluminium driver handle with 48 4mm bits to open and repair all types of devices. Housed in an ultra slimline aluminium casing. Great for field repairs. See web for kit contents. A 35x26cm heat resistant silicon work mat to keep screws and materials organised while you work. Also includes a separate 25x20cm magnetic mat for keeping tiny metal parts from rolling away. 20 $ 48pc Compact Servicing Kit Never lose a tiny screw again! SAVE 18% 60 $ 29 $ T 4015A Must have for any tool kit SAVE 16% 22ea $ 5” Carbon Steel Side Cutters Tungsten Carbide Side Cutters Stainless Steel Long Nose Pliers Super Sharp Stainless Steel Scissor Snips 1000V Rated Electrical Tools Tough carbon steel blades, stay sharp longer. Ideal for cutting solid core wires. 130mm. Tough HRC 72° tungsten carbide construction for 5 times the life of standard side cutters. 130mm. Rust Resistant - great for the tackle box or use in moisture prone environments. 125mm. Multi-purpose snippers made from SK4 carbon steel. Spring loaded with comfort grip. 160mm. VDE 1000V rated electrical hand tools constructed from quality drop forged steel with comfort grip insulated handles. T 1499 SAVE 20% No more eye strain! 50 NEW! $ 11.50 $ T 2168A Screen Removal Suction Cup Pliers For removing outer glass from phones tablets & laptops. Cups rotate for larger screens. Pick Prying Set A handy plastic tool set for prying open adhesive surfaces on phones, laptops etc. SAVE $9.95 SAVE 23% 7 $ T 1498 Get a crisp close up view. Features 1/4” and 4mm drive handles SAVE 22% 36 25 $ $ X 0432 5x magnifier with LED backlight. Great for reading fine print, sewing etc. USB rechargeable. Includes carry case. 69pc Dual Ratchet Driver Kit 11 Pc Screwdriver Set T 2198B Quality set of flat blade and phillips screwdrivers for general repairs. Chrome vanadium. Buying for business? Save with a VIP-Trade Card Superb quality ratchet driver with a wide selection of bits for most electronic jobs. Includes both a 1/4” adjustable angle (<90°) ratchet handle and a smaller 4mm ratchet handle. Great for the home handyman or enthusiast. Sale pricing ends August 31st 2020. Print your own parts, models & more! K 8600 559 $ 30 x 30 x 40cm build volume for larger prints FREE! 1kg roll of PLA filament with every CR-10 or Ender 3 sold this month. Valued at $49.95 K 8606 1095 $ Print bigger with the Creality® CR-10 V2 3D Printer Creality® ‘Ender 3’ 3D Printer The CR-10 offers reliable large volume printing up to 30Wx30Dx40Hcm! The dual port fan cooled hot end offers reliable and precise print quality whilst the triangular design provides excellent stability. Heated print bed reduces warping, ensuring great prints every time. This printer is great for anyone who needs to print larger designs such as cosplay parts, architectural models & replacement parts. Creality’s top selling 3D printer is here! The Ender 3 is a compact 3D printer offering excellent print quality with a build volume of 22Wx22Dx25Hcm and is compatible with ABS, PLA and TPU filaments. Supplied mostly assembled and can be up and running within an hour. Creality® Premium PLA Filament ABS Filament We’re now stocking Creality’s premium 1.75mm PLA designed for use in many brands of 3D printer on the market. Creality have focused on making top quality non toxic filaments with a tolerance of just 0.02mm. Each filament is 100% bubble free and offers excellent tensile strength & fluidity. This all adds up to more reliable prints and less waste! Made from high quality materials for less brittle filament breakages. 49 $ .95 per kg. NEW! T 2370 T 2745A 18 $ .50 n K 8387A Silver n K 8388A Gold n K 8389A Pink n K 8391A Orange n K 8392A Green n K 8393A Yellow n K 8394A Purple n K 8395A Blue n K 8396A Red n K 8397A Black n K 8398A Grey n K 8399A White 35 $ Comfy Precision Snippers Remove rough edges and neaten up prints with this comfort grip external chamfer tool. Ideal for trimming plastic supports from prints. SAVE 24% T 1296 SAVE 12% 15 $ 5 Piece Needle File Set T 2352 Fine edge files for smoothing 3D prints. SAVE 15% Blow Brush 16 $ T 1480 Remove fine debris from prints when smoothing or reworking. 44.95 n K 8383A White n K 8384A Black $ Fluoro Filament A translucent fluoro yellow coloured PLA for brightly coloured prints! 1kg roll. 57 $ .95 K 8390A Cut, Polish, Grind, Sand & Carve. SAVE 16% Deburring Hand Tool Printing with ABS instead of PLA. We’ve also added to the range Creality ABS. 1kg rolls. 60 $ Fume Extractor & Fan Whisk away solder/print fumes from your workspace! Also works as a fan. Adjustable speed. Great for finishing and smoothing your 3D prints! Perfect for odd jobs and hobbies. Powerful 130W motor with variable speed between 8000 and 33000 RPM. Included is a 172pc accessory kit of grinding wheels, drills, cutters, sanding discs, polishing pads and more. See last page for store locations or visit altronics.com.au T 2120 SAVE 13% 75 $ Sale pricing ends August 31st 2020. Top deals for makers & builders. Raspberry Pi® 4 The latest Pi 4 is now capable of running two monitors at once - in 4K resolution too! It’s also equipped with USB 3.0, upgraded CPU and a choice of 4GB or 8GB RAM. Micro sized desktop computing has arrived! NEW MODEL! Z 6309A 144 $ 112 $144 $ Z 6302G 4GB RAM 7” Touchscreen to suit Raspberry Pi® New 8GB version now available! Create all-in-one, integrated projects such as tablets, infotainment systems and gaming consoles. Connects via DSI port on your Pi. 800x480 resolution. 10 finger capacitive touch. Screen dimensions 192x111mm (inc. bezel). Z 6302H 8GB RAM 10.95 $ NEW! Red Raspberry Pi® 4 Aluminium Cases P 1925 NEW! P 1993 Available in dual fan cooled or passive cooled versions. These cases provide protection and thermal dissipation for your Pi 4. *Pi not included. 8 $ .65 39.95 $ H 8959 Dual Fan 29.95 $ H 8954 Passive In Line Power Switch Micro HDMI Adaptor Switch your Pi 4 on or off. USB type C. S 1147 Use your HDMI cables with your Pi 4. SAVE $30 85 $ SAVE 28% SAVE 25% SAVE 34% 7 $ ea Colourful Arcade Gaming Switches Jumbo arcade machine momentary switches with 12V illumination and customisable button plate. 25mmØ hole. S 0910 Red S 0911 Green S 0912 Blue S 0913 Yellow S 0914 White 15 $ S 1148 USB Interface For Joystick & Buttons A handy interface board for a joystick and up to 12 arcade buttons. Includes pre-terminated cables. Heavy Duty Arcade Joystick 17 $ Great for retro gaming projects or for direction control in serious projects. Adjustable plate allows 2, 4 or 8 way control. 95x59mm mounting plate. Z 6518 64x32 RGB Full Colour LED Matrix Panel These linkable panels are ideal for making highly visible scrolling signs, information readouts, clocks and timers. Readable up to 52m away! 5mm pitch LEDs. 384x192mm. 60 LEDS per metre. 4 for $ Z 6393 28 SAVE 30% 16 $ SAVE 30% SAVE 25% 12 $ Z 6392 Lightweight SG90 Servo A great micro servo for lightweight robotics applications. 180 degree rotation (±90°). 3.5-6V operation. Z 6444 High Torque MG995 Servo MG90S Micro Metal Servo A high speed metal geared servo with 12kg/cm torque. Weighs 55 grams. 120 degree rotation (±60°) A high speed metal geared servo with 2kg/cm torque. Weighs 14.5 grams. 180 degree rotation (±90°). 22 $ A cut down version of our popular MegaBox which provides a backlit 16x2 LCD for simple readouts, plus room to customise the front panel with buttons or IR sensor. UNO (sold separately) fits neatly behind the screen and provides room for add-on shields as required. SAVE $50 85 $ 5050 size LEDs for superior light output! Create Amazing LED Light Effects! 5m reel of addressable RGB 5050 LED strip - this means you can program the colour of every individual LED using an Arduino/ Raspberry Pi. 60 LEDs per m. WS2812B chip on board. 10mm width, adhesive backed. 5V, 3.6A/m (max). Arduino Handheld Game Kit K 9675 SAVE 22% X 3223A per 5m roll. MegaStand Acrylic 16x2 LCD UNO Kit 2048 LEDs per panel! SAVE 19% SAVE 24% 40 60 $ $ Arduino Keypad Plate Arduino Control Plate Perfect for Arduino based access control designs, this handy wallplate has a atmega328p chip and is suitable for use with standard shields. K 9650 Perfect for Arduino based automation projects, this handy wallplate has a atmega328p chip and is suitable for use with standard shields. K 9655 Buying for business? Save with a VIP-Trade Card Provides all the hardware to build your own handheld console, then you can upload open source games from online communities or have a go at coding your own. Requires 2xAAA batteries. Have a go at coding your own games! Z 6457 SAVE $10 58 $ Sale pricing ends August 31st 2020. Great value security deals. 499 NEW! $ 120 $ S 9901J SAVE $100 IS PRICE! 20 SYSTEMS ONLY AT TH S 9018 Why settle for just HD? This system features 2K detail and clarity. Affordable 5 Megapixel CCTV Surveillance System. NEW! • HARD DRIVES TO SUIT: 1TB $120 (D 5514), 2TB $170 (D 5516). Great for monitoring in remote locations, temporary CCTV monitoring etc. Runs off batteries, so its quick & easy to set up anywhere you need to keep an eye on things. Weatherproof case with LCD screen. Requires 8xAA batteries & DA0322 16GB NEW! SD card $14.95. The safe & easy way to monitor the front door. Records photos of visitors when you’re not home. Easy to wire up yourself with 4 core cabling (ie: W 2341). Plus it hooks up to two extra CCTV cameras to monitor other parts of your home. Supports 2 doorbells, 4 indoor monitors & 2 CCTV cameras, plus remote door latching capability (when used with a door strike). 1080p video or 20MP still shot resolution. 189 $ 425 Cable Free Solar Light 12 $ SAVE 13% S 9179B With solar powered flashing red LED Dummy Bullet Camera With LED Deter vandals and thieves from your home or business with a pretend CCTV camera. NEW! S 9395 Indoor Monitor + S 9396 Outdoor Camera $ S 9178A Dummy Dome Camera Deter vandals and thieves from your home or business with a pretend CCTV camera. A 0326 35 $ Battery Free Door Bell Never change batteries again! Kinetic action of the button press powers the signal to a wireless chime unit inside your home. 25 ring tones. 100m range. Instant security light! Stylish motion activated design. Charges by day, lights at night. Weatherproof design. Requires no batteries or cabling. 145Wx96Hmm. SAVE 25% 22 $ X 2375 SAVE 25% 15 $ S 5327 Window/Door Open Alert Alerts you when a door or window opens with an alarm or chime. Great for notifying you when customers arrive at your business. Adhesive backed, installs in seconds! Requires 2xAAA batteries. Joondalup Store OPENS AUGUST 3RD 2/182 WINTON RD JOONDALUP, WA. OPEN 7 DAYS. Western Australia Build It Yourself Electronics Centres Sale Ends August 31st 2020 Phone: 1300 797 007 Fax: 1300 789 777 Mail Orders: mailorder<at>altronics.com.au » Joondalup: 2/182 Winton Rd » Perth: 174 Roe St » Balcatta: 7/58 Erindale Rd » Cannington: 5/1326 Albany Hwy » Midland: 1/212 Gt Eastern Hwy » Myaree: 5A/116 N Lake Rd Please Note: Resellers have to pay the cost of freight & insurance. Therefore the range of stocked products & prices charged by individual resellers may vary from our catalogue. Victoria 08 9428 2166 08 9428 2188 08 9428 2167 08 9428 2168 08 9428 2169 08 9428 2170 » Springvale: 891 Princes Hwy » Airport West: 5 Dromana Ave 03 9549 2188 03 9549 2121 New South Wales » Auburn: 15 Short St 02 8748 5388 Queensland » Virginia: 1870 Sandgate Rd 07 3441 2810 South Australia » Prospect: 316 Main Nth Rd Find a local reseller at: altronics.com.au/resellers © Altronics 2020. E&OE. Prices stated herein are only valid until date shown or until stocks run out. Prices include GST and exclude freight and insurance. See latest catalogue for freight rates. 08 8164 3466 B 0091 29 Get the full picture with 360° horizontal and 118° vertical motorised viewing. Kasa app allows easy swipe pan/tilt movements. Provides 1080p full HD video with object tracking mode and night vision. SAVE $170 SAVE 30% $ TP-Link Wi-Fi Pan/Tilt Indoor Camera 7” Touchscreen Video Door Intercom Covert CCTV Camera Video Recorder SAVE 26% S 9017 ® Crystal clear wide angle 1080p vision with instant alerts of movement, plus two way audio. Excellent night vision performance and easy remote viewing via the Kasa home app (Android/iOS). Simple to install with instructions supplied. Cameras can be remote viewed on iOS/Android. Each pack includes: • Hybrid digital video recorder (IP camera ready!) • Pro grade 5MP resolution weatherproof cameras • 20m connection leads • Power supply S 9446C 97 $ TP-Link® Wi-Fi Indoor Camera Vintage Radio Velco Velco 1937 1937 radio radio chassis chassis restoration restoration By Ken Kranz Back in the 1960s, I rescued this 1937 Velco radio chassis from the tip. I’m not sure what radio it came out of; it may have been a kit radio built into a custom cabinet. The cabinet was long gone, but I reckoned that one day, I could get the radio working again. Fast forward to 2019, and I finally had the chance to do just that. This chassis clearly was for a battery-powered radio, as it lacked a mains transformer and rectifier. I wasn’t sure which exact set it was from. Velco made several ‘kit’ radios so it could have been one of those. I searched the internet to get some information about the manufacturer, Velco. Arthur J. Veall Pty Ltd (247249 Swanston Street Melbourne, 302 Chapel Street Prahran) manufactured Velco-branded products from 1931 to 1955. From 1950, Velco Sound Systems Pty Ltd was at 65 Latrobe Street, Melbourne. siliconchip.com.au Velco-branded products included radios, signal generators, “set analysers”, volt-ohm meters, valve testers, multimeters and tape recorders. Velco manufactured a model 365B receiver in 1937. Its specifications were: Valves: 1C4, 1A6, 1C4, 1K6, 1D4 Intermediate Frequency: 175kHz Wave bands: broadcast band only Batteries: 2V (A) and 135V (B) Speaker: permanent magnet Case: timber Valve markings on my set indicate the valve lineup to be 1C4 (RF preamp), 1C6 (converter), 1C4 (first IF amplifier), 1B5 (demodulator & audio preamp) and 1D4 (audio output stage). A 1K6 dual-diode pentode had been fitted in the place of the 1B5, with the pentode triode-connected. This is very similar to, but not exactly the same as what’s specified for the 365B. The 1A6 pentagrid converter has the same pin connections as the 1C6 and very similar specifications. So I think that this radio is a 365B derivative. Circuit details Unfortunately, I could not locate a 83 Fig.1: the Velco 1937 radio circuit was traced from the original set and then modified. One modification was adding a set of diodes to clamp the filament supplies and protect it from any high voltages during repair. circuit diagram, so I had to create one by tracing out the circuit. It is shown in Fig.1. I drew the original version of this diagram using LTspice, so I am also able to simulate the operation of the radio. The component designators are unlikely to match the original schematics, as I had to number them myself. Excellent SPICE models are available for all the common audio valves and many RF valves, although it’s difficult to find models for pentagrid converters. You can download the files for my circuit diagram/model from siliconchip.com.au/Shop/6/5573 The download package also includes many handy valve models that could be used to simulate other sets. Looking at the circuit, there’s nothing really remarkable about this set. It does have an RF gain stage built around valve V1. The following mixer/oscillator is a conventional configuration, as are the IF transformers and sole IF gain stage. The two diodes in V4 are used to demodulate the audio signal and to derive an AGC control voltage, which is used to vary the bias conditions of the first three stages (V1-V3; RF amp, converter and IF amp). The audio output stage (V5) is a very basic Class-A configuration. Fixing it up The first thing I did after I got it on my workbench was to take a good look at it. I found that the tuning gang had a bent shaft, presumably due to the cramped nature of its storage location for the last 50 plus years. I removed the tuning capacitor and placed the shaft in a vice. Quite some force was required to make it almost straight. I feared one extra adjustment would break the shaft, so I stopped there and refitted to the chassis with new rubber mounting grommets, to replace the disintegrated originals. A number of the paper caps tested leaky, so I replaced all of them with Shown here is the underside of the Velco radio chassis before it was repaired, with the finished set shown adjacent for comparison. One of the biggest changes was the replacement of all the paper capacitors with newer film capacitors. 84  Silicon Chip Australia’s electronics magazine siliconchip.com.au modern types. The back-bias resistor was open-circuit; I was able to repair it by removing one turn of its wire and soldering that to its terminal. I also found some badly damaged wires and replaced them with 600Vrated black wires with silicone insulation. I decided to add eight silicon diodes, two sets of four in series in an inverse parallel arrangement across the 2V filament supply. This was to protect the radio against me accidentally connecting too high a voltage to this supply. The radio was initially designed to drive a loudspeaker fitted with an im- pedance matching transformer. So that I could drive a modern 8W speaker instead, I decided to fit a 100V line transformer, connecting the 0.5W tap (20kW impedance) between the anode of V5 (the 1D4 output pentode) and the B+ rail. I then connected my test speaker across the 8W winding. Testing the radio I applied 2V to the filament supply and measured the current drawn. It settled at around 700mA, which I thought was a reasonable figure to power the five valve heaters. I then slowly ramped up the B+ supply to 135V DC and measured a flow of about 10mA. Australia’s electronics magazine Some satisfactory noises were coming from the loudspeaker, so I fitted a short aerial and found that all local radio stations could be received with good fidelity, in spite of Pimpala (ABC 891kHz) transmitting 50kW only 3km from my location. I aligned the dial pointer with the actual transmitted frequencies and left it tuned to 1323kHz for some background music. A few days later, the radio was playing away in the background when the sound of silence hit me. The primary winding on one of the IF transformers had gone open circuit. My friend Andy (VK5AAQ) advised me that this was common on these 85 The coils for the replacement IF transformer was wound using a sewing machine with 0.1mm copper wire (left). The coils were placed on a wooden dowel, which is attached to the original mounting bracket as shown above. sets, as they only switched off the filament supply; the constant B+ voltage combined with moisture caused electrolytic corrosion, with this being a typical result. Rather than look for a replacement 175kHz IF transformer, I recalled that back in the early days of radio, many items were self-made. Inspired by B. B. Babani’s Coil Design and Construction Manual (1960), I decided to repair it with a home-made replacement coil. A replacement IF transformer The outer diameter of the coil former was about 10mm. A sewing machine bobbin is about 9mm; close enough for me. I measured the wire diameter at 0.1mm. So I ordered a reel of 0.1mm diameter enamelled copper wire and some clear sewing machine bobbins. I drilled a 1mm hole in the sidewall of the bobbin for the start of the winding, then placed it on the semi-automatic coil winder of a sewing machine. My daughter held a nylon rod with the spool of 0.1mm wire so it could unspool freely, and the machine ¾ filled the bobbin in no time. The spooling speed is fully adjustable from a crawl to frightening. In spite of the very low strength of the 0.1mm wire, we didn’t experience any breakages. I measured the inductance of the good coil on the old IF transformer at 7.4mH using a TH2821B LCR meter, and used a Fluke multimeter to determine that the DC resistance was 76W. As both trimmer capacitors had similar ranges (19-110pF), I decided to build the IF transformer using two identical 7.4mH inductors. I tested the freshly wound coil and found it to be over four times the required value, so we transferred about 86  Silicon Chip half of the wire onto another bobbin. I adjusted both coils by removing turns until the required 7.4mH was achieved. I found that the DC resistance and Q were very similar to those of the original coils. I cut the wires about 6mm from the coil former and soldered flexible ribbon cable leads onto the coil ends. I then covered the wire terminations in some ten-second ultraviolet cure resin. I then slid them onto a 6mm outer diameter wooden dowel, applied a generous amount of shellac to each end and fitted the assembly to the original mounting bracket. The wires were terminated as shown in the photos. The moment of truth: I powered the set on and turned the volume full up, but it was very quiet. A quick adjustment of the IF trimmer capacitors gave me lots of beautiful noise. I moved to a blank spot on the dial and used the trimmers to peak the noise at about ½ to ¾ compression. All the local stations came in loud and clear, including 5MU. An excellent result indeed. Although the slideable coils would allow adjustment of the coupling coefficient, the result was so pleasing that I immediately coated the former with shellac, including a small amount on the coil. As one would expect, the set stopped working. I did not re-tune the IFs and simply let the set dry out for a few days. At switch-on a few days later, the radio was again playing 1323kHz; most satisfactory. I refitted the IF cover and that hardly affecting the tuning. A quick re-tweak and the set ran for about a week until bench real estate required its movement back into storage. Conclusion All that’s left is to put the original can back in place. The repair of this set may offend some restoration purists. The radio was saved from landfill in the 1960s; it now works and might be enjoyed by somebody in the future. I saved all the components I removed. It could be reinstalled in a period cabinet by someone with the skills and inclination to do so. It still needs a replacement 2V dial lamp (not shown on the circuit diagram). I might make a screw-in replacement using a white LED and resistor. Some time in the future, I am hoping to find a diecast box that will locate over the large square hole, paint it a similar colour, and build a power supply into it so the set will run from a 12V plug pack. The radio consumes less than 3W, so I might even be able to power it from a 1A USB port. Velco references: siliconchip.com.au/link/ab31 siliconchip.com.au/link/ab32 www.kevinchant.com/velco.html SPICE references: siliconchip.com.au/link/ab33 siliconchip.com.au/link/ab34 siliconchip.com.au/link/ab35 Plotting valve curves using LTspice: https://youtu.be/VV3e_mNQ-dQ SC Australia’s electronics magazine siliconchip.com.au SILICON CHIP .com.au/shop ONLINESHOP PCBs, CASE PIECES AND PANELS HIGH POWER LINEAR BENCH SUPPLY ↳ HEATSINK SPACER (BLACK) DIGITAL PANEL METER / USB DISPLAY ↳ ACRYLIC BEZEL (BLACK) UNIVERSAL BATTERY CHARGE CONTROLLER BOOKSHELF SPEAKER PASSIVE CROSSOVER ↳ SUBWOOFER ACTIVE CROSSOVER ARDUINO DCC BASE STATION NUTUBE VALVE PREAMPLIFIER TUNEABLE HF PREAMPLIFIER 4G REMOTE MONITORING STATION LOW-DISTORTION DDS (SET OF 5 BOARDS) NUTUBE GUITAR DISTORTION / OVERDRIVE PEDAL THERMAL REGULATOR INTERFACE SHIELD ↳ PELTIER DRIVER SHIELD DIY REFLOW OVEN CONTROLLER (SET OF 3 PCBS) 7-BAND MONO EQUALISER ↳ STEREO EQUALISER NOV19 NOV19 NOV19 NOV19 DEC19 JAN20 JAN20 JAN20 JAN20 JAN20 FEB20 FEB20 MAR20 MAR20 MAR20 APR20 APR20 APR20 18111181 SC5168 18111182 SC5167 14107191 01101201 01101202 09207181 01112191 06110191 27111191 01106192-6 01102201 21109181 21109182 01106193/5/6 01104201 01104202 Subscribers get a 10% discount on all orders for parts $10.00 $5.00 $2.50 $2.50 $10.00 $10.00 $7.50 $5.00 $10.00 $2.50 $5.00 $20.00 $7.50 $5.00 $5.00 $12.50 $7.50 $7.50 REFERENCE SIGNAL DISTRIBUTOR H-FIELD TRANSANALYSER CAR ALTIMETER RCL BOX RESISTOR BOARD ↳ CAPACITOR / INDUCTOR BOARD ROADIES’ TEST GENERATOR SMD VERSION ↳ THROUGH-HOLE VERSION COLOUR MAXIMITE 2 PCB (BLUE) ↳ FRONT & REAR PANELS (BLACK) OL’ TIMER II PCB (RED, BLUE OR BLACK) ↳ ACRYLIC CASE PIECES / SPACER (BLACK) IR REMOTE CONTROL ASSISTANT PCB (JAYCAR) ↳ ALTRONICS VERSION APR20 MAY20 MAY20 JUN20 JUN20 JUN20 JUN20 JUL20 JUL20 JUL20 JUL20 JUL20 JUL20 CSE200103 06102201 05105201 04104201 04104202 01005201 01005202 07107201 SC5500 19104201 SC5448 15005201 15005202 $7.50 $10.00 $5.00 $7.50 $7.50 $2.50 $5.00 $10.00 $10.00 $5.00 $7.50 $5.00 $5.00 AUG20 AUG20 AUG20 01106201 18105201 04106201 $12.50 $2.50 $5.00 NEW PCBs USB SUPERCODEC SWITCHMODE 78XX REPLACEMENT WIDEBAND DIGITAL RF POWER METER PRE-PROGRAMMED MICROS As a service to readers, Silicon Chip Online Shop stocks microcontrollers and microprocessors used in new projects (from 2012 on) and some selected older projects – pre-programmed and ready to fly! Some micros from copyrighted and/or contributed projects may not be available. $10 MICROS ATtiny816 PIC12F202-E/OT PIC12F617-I/P PIC12F675-E/P PIC12F675-I/SN PIC16F1455-I/P PIC16F1455-I/SL PIC16F1459-I/P PIC16F88-I/P PIC16LF88-I/P $15 MICROS ATtiny816 Development/Breakout Board (Jan19) Ultrabrite LED Driver (with free TC6502P095VCT IC, Sep19) Temperature Switch Mk2 (Jun18), Recurring Event Reminder (Jul18) Door Alarm (Aug18), Steam Whistle (Sept18), White Noise (Sept18) Trailing Edge Dimmer (Feb19), Steering Wheel to IR Adaptor (Jun19) Car Radio Dimmer Adaptor (Aug19) Courtesy LED Light Delay (Oct14), Fan Speed Controller (Jan18) Tiny LED Xmas Tree (Nov19) Microbridge and BackPack V2 / V3 (May17 / Aug19) USB Flexitimer (June18), Digital Interface Module (Nov18) GPS Speedo/Clock/Volume Control (Jun19) Ol’ Timer II (Jul20) 5-Way LCD Panel Meter (Nov19), IR Remote Control Assistant (Jul20) UHF Repeater (May19), Six Input Audio Selector (Sept19) Universal Battery Charge Controller (Dec19) Garbage Reminder (Jan13), Bellbird (Dec13) GPS-synchronised Analog Clock Driver (Feb17) ATmega328P RF Signal Generator (Jun19) PIC16F1459-I/SO Four-Channel DC Fan & Pump Controller (Dec18) PIC32MM0256GPM028-I/SS Super Digital Sound Effects (Aug18) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sept19) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) GPS-Synched Frequency Reference (Nov18), Air Quality Monitor (Feb20) RCL Box (Jun20) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) $20 MICROS PIC32MX470F512H-I/PT Stereo Echo/Reverb (Feb 14), Digital Effects Unit (Oct14) PIC32MX470F512H-120/PT Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) PIC32MX470F512L-120/PT Micromite Explore 100 (Sept16) $30 MICROS PIC32MX695F512L-80I/PF PIC32MZ2048EFH064-I/PT Colour MaxiMite (Sept12) DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20) KITS & SPECIALISED COMPONENTS SWITCHMODE 78XX KIT (CAT SC5553) (AUG 20) COLOUR MAXIMITE 2 in stock now (JUL 20) Includes PCB and all onboard parts (choice of 3.3V, 5V, 8V, 9V, 12V & 15V versions) Short form kit: includes everything except the case, CPU module, power supply, optional parts and cables (SC5478) Short Form kit (with CPU module): includes the programmed Waveshare CPU modue and everything included in the short form kit above (SC5508) $12.50 $80.00 $140.00 VARIOUS MODULES & PARTS CAR ALTIMETER (BACKPACK V2 / V3 KIT) (MAY 20) SUPER-9 FM RADIO (NOV 19) MICROMITE EXPLORE-28 (CAT SC5121) (SEPT 19) $30.00 $20.00 BMP180 temperature/pressure sensor (Cat SC4343) DHT22 temperature/humidity sensor (Cat SC4150) CA3089E IC, DIP-16 (Cat SC5164) MC1310P IC, DIP-14 (Cat SC4683) 110mm telescopic antenna (Cat SC5163) Neosid M99-073-96 K3 assembly pack (two required) (Cat SC5205) Complete kit – includes PCB plus programmed micros and all onboard parts Programmed micros – PIC32MX170F256B-50I/SO + PIC16F1455-I/SL MICROMITE LCD BACKPACK V3 KIT (CAT SC5082) - 3.5-inch TFT LCD touchscreen (Cat SC5062) - DHT22 temp/humidity sensor (Cat SC4150) - BMP180 (Cat SC4343) OR BMP280 (Cat SC4595) temp/pressure sensor - BME280 temperature/pressure/humidity sensor (Cat SC4608) - DS3231 real-time clock SOIC-16 IC (Cat SC5103) - 23LC1024 1MB RAM (SOIC-8) (Cat SC5104) - AT25SF041 512KB flash (SOIC-8) (Cat SC5105) - 10µF 16V X7R through-hole capacitor (Cat SC5106) $5.00 $7.50 $3.00 $5.00 $7.50 $6.00ec (AUG 19) Includes PCB, programmed micros, 3.5in touchscreen LCD, UB3 lid, mounting hardware, Mosfets for PWM backlight control and all other mandatory on-board parts $75.00 Separate/Optional Components: - 16x2 I2C LCD (Digital RF Power Meter, Aug20) - DS3231 real-time clock SMD IC (Ol’ Timer II, Jul20) - WS2812 8x8 RGB LED matrix module (Ol’ Timer II, Jul20) - MAX038 function generator IC (H-Field Transanalyser, May20) - MC1496P double-balanced mixer (H-Field Transanalyser, May20) - AD8495 thermocouple interface (DIY Reflow Oven Controller, Apr20) - Si8751AB 2.5kV isolated Mosfet driver IC (Charge Controller, Dec19) - I/O expander modules (Nov19): PCA9685 – $6.00 ¦ PCF8574 – $3.00 ¦ MCP23017 – $3.00 - SMD 1206 LEDs, packets of 10 unless stated otherwise (Tiny LED Xmas Tree, Nov19): yellow – $0.70 ¦ amber – $0.70 ¦ blue – $0.70 ¦ cyan – $1.00 ¦ pink (1 only) – $0.20 - ISD1820-based voice recorder / playback module (Junk Mail, Aug19) - 23LCV1024-I/P SRAM & MCP73831T (UHF Repeater, May19) - MCP1700 3.3V LDO regulator (suitable for USB M&K Adapator, Feb19) - LM4865MX amplifier & LF50CV regulator (Tinnitus/Insomnia Killer, Nov18) - 2.8-inch touchscreen LCD module with SD card socket (Tide Clock, Jul18) - ESP-01 WiFi Module (El Cheapo Modules, Apr18) $30.00 $7.50 $5.00 $10.00 $3.00 $5.00 $1.50 $2.00 $7.50 $3.00 $15.00 $25.00 $2.50 $10.00 $5.00 $4.00 $11.50 $1.50 $10.00 $22.50 $5.00 $10 flat rate for postage within Australia. Overseas? Place an order via our website for a quote. All items subect to availability. Prices valid for month of magazine issue only. All prices in Australian dollars and included GST where applicable. PAYPAL (24/7) INTERNET (24/7) MAIL (24/7) PHONE – (9-5:00, Mon-Fri) eMAIL (24/7) To Use your PayPal account siliconchip.com.au/Shop Your order to PO Box 139 Call (02) 9939 3295 with silicon<at>siliconchip.com.au Place siliconchip.com.au Australia’s electronics magazine August silicon<at>siliconchip.com.au Collaroy NSW 2097 with order 2020  87 & credit card details Your You can also order and pay by cheque/money order (Orders by mail only). Make cheques payable to Silicon Chip Publications. Order: 08/20 Colour Maximite 2 Words and MMBasic by Geoff Graham Design and firmware by Peter Mather Part 2 We introduced the Colour Maximite 2 last month, but now we delve into the details of building it. As it turns out, that is quite easy because all the complex stuff is on the preassembled Waveshare CoreH743I CPU Board. The PCB that you need to populate is a simple double-sided board with mostly through-hole passive components. You should be able to finish it off it in an hour or two. B efore starting, take precautions against static electricity which could damage the STM32 processor. You do not need to go overboard here, but you should discharge yourself by occasionally touching a grounded point on your workbench and making sure that you do not unnecessarily handle the CPU board and its connecting pins, The main ‘motherboard’ PCB is labelled “Colour Maximite 2: V2.1” and measures 130 x 102mm. As shown in the PCB overlay diagram, Fig.5, it has cut-outs on either side to clear the moulded posts in its plastic case, and two small cut-outs at the front with a ‘peninsula’ in between that has three exposed copper pads on it. This is the “Nunchuk” connector. Start by soldering the two 80-pin sockets used for the plug-in CPU module. The trick here is to solder them in such a way that the solder does not wick up the pins, preventing the CPU module from being properly inserted. So use the following procedure. Place the motherboard on a flat surface and insert both 80-pin connectors in their correct places on the board. Then gently push the CPU board into these connectors. We say gently because you do not want to bend the pins 88  Silicon Chip on the connectors or the CPU board. Then, while holding the CPU board in place on the motherboard, turn the board over and solder all the connector’s pins. Don’t use a lot of solder; only a small amount is required for each pin. The CPU board can then be unplugged and placed aside while the remaining components are fitted. Next to go in should be the audio socket. The reason for this is that the PCB is a little crowded around it, and it is an SMD part, so if you leave the audio socket to last, it will be difficult to get your soldering iron in without causing damage. Solder its five large pins to the pads on the top of the board. Next, solder the SD card socket, which is also surface mounted. This This is the assembled motherboard without the Waveshare CPU board plugged in. Usually hidden by the CPU board are three capacitors, a resistor and the SD card socket. Note that this is a prototype and the final PCB will vary slightly in its layout (see the panel for details). Australia’s electronics magazine siliconchip.com.au The Colour Maximite 2 in its case. If you remember computers like the Tandy TRS80, Commodore 64 or Apple II from the 80s, you will be right at home playing with this. The differences are that this is about a hundred times faster, has a much better display and costs a fraction of the price! Fig.5: follow this PCB ► overlay diagram to build the ‘motherboard’. Once you’ve fitted the connectors and larger components, there isn’t much to it. The remaining components are a few small ceramic capacitors and 46 miniature 0.25W resistors. SMD resistors can be used instead, if desired. has two small posts on the underside which click into matching holes in the PCB to ensure perfect alignment. With the socket in position, solder the two tabs on the right side of the socket (viewed from the front) and five on the left side. Some are tiny and can be easily missed, so count them when you have finished (seven in total). Some are also close to the shield of the socket. So take care not to cause a solder bridge there. Note that the socket must be held firm to the PCB while soldering, as any gap between it and the PCB will prevent an inserted SD card from making reliable contact with the connector pins. Finish it off by soldering the nine pins at the rear. To do this, spread some flux paste over the pins and load up your fine-tipped soldering iron with a little solder; a small bump is all that you need. For each pin, slide the tip of your iron over the solder pad towards the connector so that the tip hits the connector’s pin, and the solder should magically flow around the pin. If you get a solder bridge, don’t worry and carry on with the other pins. Finally, examine your soldering using a powerful magnifier and clean up any solder bridges using solder wick. Be careful here, as solder wick can suck siliconchip.com.au up all the solder so you might have to come back and resolder any pins that look like they don’t have enough solder. The last device that is to be soldered on the top side of the PCB is the battery holder, so you might as well do that now. Its orientation is shown on the PCB silkscreen, and the pads are large, so this should be an easy job. Through-hole parts Next, it is worth soldering the highprofile connectors and the power switch. They will hold the PCB off the bench when you later place it upside down to mount the capacitors and vertically-mounted resistors. There is nothing complicated about soldering these components. It is just a case of placing them in position as shown in Fig.5 and the PCB silkscreen printing, and soldering their pins. After you have done this, go back with a magnifier to check and rectify any suspicious joints. You can then install the optional IR receiver and DS18B20+ temperature sensor if you wish. These can easily be added later, so they are not critical. There are only five capacitors on the motherboard. Three of these are situated under the CPU module, and they Australia’s electronics magazine should be mounted flat on their sides so that they will not obstruct the CPU module when it is plugged in. The board is designed to accept polarised Tantalum types for the 10µF and 1µF values, but we’ve specified ceramics as they perform better and are more reliable, and that is what we’re supplying in our kits. Unlike Tantalum capacitors, which are a type of electrolytic capacitor, they are not polarised, so you don’t need to worry about their orientations. Ten of the resistors sit flat on the PCB, and they can be soldered next (see the colour code table on page 97). The pads are spaced to suit 0.5W or 0.6W resistors, but you can use smaller 0.25W resistors if you want to (that’s what we supply in our kits). There is an additional eleventh resistor (4.7kW) near the back panel which is only required if you are installing the optional DS18B20+ temperature sensor. Still, you might as well install it now anyway, as it’s cheap and easy and you might want to add that sensor later (this is also supplied in our kit, even though the sensor itself isn’t). Then there are 35 resistors used in the R-2R ladders for the VGA analog outputs. As mentioned last month, August 2020  89 ► these are vertically mounted to save space, although you can also use 3216/1206-size surface mount resistors. Make sure that they match the silkscreen legend and will not get in the way of the CPU board when it is plugged in. The USB-serial converter chip comes in a 14-pin DIL package, and you should use an IC socket for this, so that you can pull the chip out if you suspect that something is wrong. Into this socket, you can plug the MCP2221A from Microchip or the Microbridge, as mentioned last month (our kit comes with the latter). Both work identically, but the MCP2221A does not need programming, so it will be the preferred option for some. The Microbridge (May 2017; siliconchip.com.au/Article/10648) is a PIC16F1455 or PIC16F1454 microcontroller programmed with the Microbridge firmware, which you can download for free from our website. There are six pads beside this chip for an optional six-pin header to allow you to program this chip, although the ones we supplied come pre-programmed, so that should not be necessary if you’re building it from a kit. The last item to install is the vertically-mounted LED module which indicates power and SD card activ- ity. Using this module makes it easy to get the correct alignment with the matching holes in the front panel, but you can use discrete 3mm LEDs if you wish. If using discrete LEDs, temporarily mount the motherboard in the case (see below and don’t forget the spacers). Then, fit the front panel and bend the leads of the two LEDs to suit the front panel holes. With the leads in place on the motherboard and the LEDs poking through the front panel, you can tack-solder one lead for each LED from the top of the motherboard to keep it in place. Finally, remove the motherboard and securely solder and trim the LED’s leads on the underside of the PCB. Initial testing Before you apply power, it is good insurance to go over both sides of the motherboard in detail with a magnifier, to confirm that all the solder joints are good and nothing has been missed. The current drawn by the motherboard and the STM32 processor is a good indication of the state of both. So, for the first test, make sure that the CPU module is not plugged in, place a CR1220 battery in the battery holder and do not connect anything else (VGA, SD card etc). Using a Type-A to Type-B USB ca- Fig.6: the current drawn by the motherboard and STM32 processor is a good indication of whether they are functioning correctly. You can easily measure this by plugging in the USB power cable with the front panel switch off and connecting a DMM set to measure milliamps across the switch terminals, as shown here. 90  Silicon Chip Australia’s electronics magazine ble, plug the motherboard into a 5V source but leave the front panel power switch off (up). Set your multimeter to measure direct current on the order of 200mA and place the probes across the switch contacts as shown in Fig.6. The reading should be 0mA. Next, prepare the Waveshare CPU module by removing any jumpers, set the power switch on the top side to “5VIN” and the BOOT CONFIG switch to “Flash”. Then plug the module into the motherboard. Make sure that the orientation is correct; the USB socket on the top of the module’s PCB should be to the rear of the computer and the 20pin IDC connector to the front. Again, with nothing else connected to the motherboard, plug it into a source of 5V. Measure the current across the power switch, which should now be about 45mA. If the CPU module has had the Colour Maximite 2 firmware loaded (your supplier might have done this), the current drawn will be about 180mA. Anything significantly different from these numbers indicates a problem; see the fault-finding steps below. Communicating with the STM32 processor The STM32 processor includes its own firmware loader/programmer so the Colour Maximite 2 firmware can be easily loaded via USB using a personal computer or laptop. You do not need any specialised hardware. First, go to the STM32 manufacturer’s website at siliconchip.com.au/ link/ab2x and download the STM32CubeProgrammer software. This is free software, but ST requires that you have an ST account or provide your name and email address. They will then email you a link to download the software. Windows, Linux and macOS versions of this software are available. Install the appropriate version on your computer and check that it runs. Now set the BOOT CONFIG switch to “SYSTEM” – this tells the STM32 processor to expect a firmware upload. Note that this is different from the position of the switch used in our initial tests above. Disconnect all cables, including the USB Type-B power cable. Use a USB Type-A to Type-A cable to connect the USB Keyboard port to a USB port on your desktop or laptop siliconchip.com.au 2 Select connect, refresh if needed 1 Select USB the screenshot (the USB port number may vary). Click on the “Connect” button. You should then see a series of messages as shown in Fig.7, concluding with the message “Data read successfully”. Any messages in red indicate an error. Programming the firmware 3 Check messages Fig.7: the STM32CubeProgrammer software is used to load the firmware into the STM32 processor. Select USB as the communications method; if the USB connection is not recognised, click on the small blue circle to refresh the entry. Your screen should look like this (the USB port number may vary). computer. This will power up the Colour Maximite 2 regardless of the position of the power switch. You should also hear a sound from your desktop computer as the Colour Maximite 2 connects to it. Note that if you don’t have a Type-A to Type-A cable, you can use a TypeA to micro Type-B cable and plug it into the USB power on the WaveShare STM32 module. But this won’t be accessible later when the case is assembled, and you have to unplug Fig.8: this is the “Erasing and Programming” mode. Select the firmware file (it will have an extension of .bin), tick the “Verify programming” checkbox and click on the “Start Programming” button. Then wait for the “Download verified successfully” dialog box. The operation will take under a minute, and any errors will result in a message in red. siliconchip.com.au the WaveShare module to get to this port, so it’s a good idea to get a hold of a Type-A to Type-A cable. Run the STM32CubeProgrammer software on your computer. On the top-right of the program window, select USB as the communications method (see Fig.7). If the program does not recognise the USB connection, click on the small blue circle to the right of the Port drop-down list to refresh the entry. Your screen should look like Now click on the download button on the left side of the STM32CubeProgrammer window. The software will switch to the “Erasing and Programming” mode, as illustrated in Fig.8. Use the “Browse” button to select the firmware file you downloaded from our website (it has a .bin extension) and tick the “Verify programming” checkbox. Then click on the “Start Programming” button. The STM32CubeProgrammer software will program the firmware into the flash memory on the STM32 (it calls this “downloading”). After a short time, a dialog box will pop up saying “File download completed”. Do not do anything at this point, as the software will then start reading back the firmware programmed into the flash. When this has completed successfully, another dialog box will pop up saying “Download verified successfully”, as shown in Fig.8. The whole operation will take under a minute, and any error messages will be shown in red. If all is OK, dismiss all the dialog boxes and close the STM32CubeProgrammer software. Remove the USB 1 Select programming 3 Tick verify 2 Load firmware 4 Start programming 5 Dismiss dialog boxes 6 Check messages Australia’s electronics magazine August 2020  91 Type-A to Type-A cable from the USB Keyboard port and plug in your VGA monitor and USB keyboard. On the CPU board, set the BOOT CONFIG switch back to “Flash” and plug the Colour Maximite 2 into power and set the power switch to on (down). You should now see the Maximite logo on the VGA monitor, along with the version number of the firmware that you have just loaded, as shown in Fig.9. Note that initially, some monitors may truncate the text on the margins or show an image that seems to shimmer or flicker. In most cases, this can be fixed by pressing the auto setup button on the monitor or, failing that, using the monitor’s image setup mode to adjust parameters such as the clock, phase and position. When MMBasic is first loaded, it will prompt for the keyboard type and the date/time. On subsequent firmware upgrades, MMBasic will preserve these settings (in addition to the real-time clock settings) and will not prompt for them again. All of these can be changed later using the relevant OPTION commands. As a final test, the current drawn with the STM32 running the Colour Maximite 2 firmware should be 160220mA, depending on the current drawn by your keyboard and SD card. If you wish to load another version of the firmware (eg, to upgrade it), this can be done by repeating the steps above. To avoid having to open the case up to change the position of the BOOT CONFIG switch when upgrading, MMBasic has a handy command: “UPDATE FIRMWARE”. This reboots the Colour Maximite 2 directly into bootloader mode. Case assembly The motherboard is designed to sit in a standard ABS plastic instrument case available from Altronics and Jaycar. Some suppliers will include the front and back panels made up as printed circuit boards, without copper tracks and with cut-outs in the correct places. In that case, they should just drop straight in. If not, you will have to manually make the cut-outs in the blank panels supplied with the enclosure by following the dimensions in Fig.10. The simplest way of doing this is to download this as a PDF file from the Silicon Chip website and print them with 1:1 scaling. You can use that as the template for the cut-outs. Fig.10 also includes the front panel artwork. We printed this onto heavyduty adhesive-backed paper and then covered the printed surface with adhesive clear plastic film, of the type used to cover books. After you have trimmed the label and made the cutouts using a sharp razor blade or hobby knife, stick it onto the front panel for a professional result. An additional benefit of this technique is that you can make the cut-outs in the plastic front panel slightly larger than necessary, and the adhesive label will hide any rough edges. The motherboard can be fastened to the pillars in the enclosure using four ordinary 8mm M3 screws (self-tappers are not required) – see Fig.11. You need to add 5mm spacers on each mounting pillar to elevate the PCB and its connectors to match the Fig.9: when you power up the Colour Maximite 2 with a VGA monitor plugged in, you will see a splash screen like this. It shows the version of MMBasic installed. Check this against the latest version on the Author’s website to see whether an upgrade is available. When MMBasic is first loaded, it will prompt for the keyboard type and the date/time. 92  Silicon Chip Australia’s electronics magazine cut-outs in the front and rear panels. You may be able to get away with two M3 nuts instead of the 5mm spacer, but it would be better to use the real thing. What can I do with it? Here are a few things that you can try out first, just to prove that you have a working computer. All of these commands should be typed at the command prompt (“>”). What you type is shown in bold, and MMBasic’s output is shown in normal text. Try a simple calculation: > PRINT 1/7 0.1428571429 See how much memory you have: > MEMORY Flash: 0K ( 0%) Program (0 lines) 516K (100%) Free RAM: 0K ( 0%) 0 Variables 0K ( 0%) General 5471K (100%) Free What is the current time? > PRINT TIME$ 09:04:01 Draw a circle: > CIRCLE 400, 100, 50 Draw a line: > LINE 0, 0, 799, 399 Fault-finding What if it does not work? The first step is to measure the current drawn by the assembled device. If it is 160220mA then that indicates that the firmware has been loaded and is running correctly. If this is OK but you cannot see anything on your VGA monitor, that probably means that something is wrong between the STM32 processor and the monitor. Try a different VGA cable, check for bent pins on the CPU module, check the ladder resistors and, of course, check your soldering. If the current drain is about 45mA then it’s likely that the firmware has not been correctly loaded into the STM32 processor, so you should re-run those steps. Anything other than the above indicates a serious problem. You can test the Waveshare CPU module by removing it from the mothsiliconchip.com.au Fig.10: these are the cut-outs required for the front and back panels. You can download this diagram from the Silicon Chip website, print them with 1:1 scaling and use them as templates for making the cuts. The front panel artwork can be printed onto adhesive-backed paper to make a label (see text). erboard, placing shorting jumpers on all header pins except PA9-VBUS and setting the power switch to USB and the BOOT CONFIG switch to SYSTEM. Then plug a USB cable into the micro USB connector on the top of the Waveshare module and the other end into your desktop computer. Both LEDs on the module should illuminate, and it should connect to your computer. If the VBUS LED does not illuminate, you probably have not configured the board correctly, or USB power is not available. If VBUS illuminates but the PWR LED doesn’t, check the 3.3V regulator on the underside of the module. Then, using the steps listed above, try loading the Colour Maximite 2 firmware onto the STM32 processor using this USB cable and your desktop computer. The procedure is the same as described above when loading the firmware via the USB keyboard port using the STM32CubeProgrammer software. If this process goes without a hitch, you can be sure that your Waveshare CPU module is perfectly OK and your problem must be something to do with the motherboard. By the way, this is an alternative method of loading the firmware if you siliconchip.com.au do not want to use a USB Type-A to Type-A cable to load the firmware via the USB Keyboard port. The motherboard itself is so simple that, if you suspect a fault with it, you can just use traditional troubleshooting steps. Check for bent pins (especially on the Waveshare CPU module), check all component leads/pads are soldered, check for short circuits between pads and pins etc. A table showing the pin layout of the Waveshare CPU module can be found overleaf. Calibrating the real-time clock (RTC) We have found that the out-of-thebox accuracy of the real-time clock in the STM32 is rather poor. This is not a huge problem, as usually the date/ time is only used for time-stamping files on the SD card. But if you would like it to be more accurate, the STM32 can be tweaked to correct for any drift. This is done in MMBasic with the OPTION RTC CALIBRATE command. This command takes a number between -511 and + 512; each step corresponds to a change of about 0.0824 seconds per day. Negative numbers will slow the clock down while positive will speed it up. With a bit of patience, you can get it spot-on. The best approach is to set the time accurately using an Internet time source, eg: TIME$ = “hh:mm:ss” Then, after (say) a week, check the current clock time with the following statement: PRINT TIME$ Fig.11: the motherboard fastens to four of the pillars in the enclosure using 8mm-long M3 machine screws (self-tappers are not required) and 5mm spacers. The spacers elevate the PCB and its connectors to match the cut-outs in the front and rear panels. Australia’s electronics magazine August 2020  93 Simple arithmetic (number of seconds offset ÷ [0.0824 × total days passed]) will then tell you the correction needed, and you can apply that as follows: OPTION RTC CALIBRATE ±nn Just make sure to get the correction sign right, ie, make it positive if the clock drifted behind the actual time, or negative if it was ahead. Interacting with MMBasic Communication with the Colour Maximite 2 is via the console at the command prompt (ie, the greater than symbol > on the console). On startup, MMBasic issues the command prompt and waits for a command to be entered. It will also return to the command prompt if your program ends or if an execution error is encountered. When the command prompt is displayed, you can issue commands related to the program that you are working on (EDIT, LIST and RUN). You can set some options (the OPTION command) and delete, copy and rename files and directories (FILES command). Almost any command can be entered at the command prompt; this is often used to test a command to see how it works. A simple example is the PRINT command, which you can test by entering the following at the command prompt: PRINT 2 + 2 Not surprisingly, MMBasic will print out the number 4 before returning to the command prompt. This ability to test a command at the command prompt is handy when you are learning to program in BASIC. The CTRL-C sequence (hold down the CTRL key then press the C key) is called the break key or character. When you type this on the console, it will interrupt whatever MMBasic is doing and immediately return control to the command prompt. Remember this, as it can get you out of all sorts of difficult situations. Test Program “bounce.bas” BOX 0, 0, 800, 600, 1, RGB(yellow), RGB(black) x = 400 y = 300 dx = 1 dy = 1 DO CIRCLE x, y, 30, 2, ,0, RGB(red) x = x + dx IF x = 31 OR x = 768 THEN dx = dx * -1 y = y + dy IF y = 31 OR y = 568 THEN dy = dy * -1 PAUSE 2 LOOP do with it. As you read the following, keep the user manual handy so that you can look up the details of the commands used. You can use the built-in editor to enter this program. If you have used a text editor before, you will find its operation familiar. The keyboard arrow keys move your cursor around the text while the Home and End keys take you to the beginning or end of the line. The delete key deletes the character at the cursor, while backspace deletes the character before the cursor. You must have a properly formatted card in the SD card slot, as this is where the editor will save your file when you have finished entering it. To start the editor, type EDIT “bounce. bas” at the command prompt and press Enter. Then type in the program shown above. Press the F2 key to save your program and run it. You should see a yellow boundary drawn around the edges of the screen and a red ball bouncing around inside it, as shown in Fig.12. As mentioned earlier, you may need to adjust your monitor to see all of the yellow boundary (ie, press the auto setup button on your monitor). If there was an error in your program, you will get a message with the line number and the error description. You can then re-enter the command EDIT (or press F4 at the command prompt) and you will be taken back into the editor, with the cursor positioned on the line that caused the error. Correct the error and then save/re-run the program by pressing F2. Program details This program demonstrates how BASIC and the graphics commands work. At the start, we draw a box which is as big as the screen using yellow for the outline and filled with black. The RGB() function returns a colour value so, for example, RGB(yellow) will return the value of the colour yellow, and that is passed to the BOX command as the colour to be used. The next two lines set the variables x and y to the initial coordinates (or position) of the centre of the ball that we are going to draw. By setting x = 400 and y = 300, we start by positionFig.12: if you’ve entered the test program correctly, once you run it, you will see a screen like this. The ball will bounce around the screen, changing direction each time it touches one of the edges. Test program This simple program will cause a red ball to zoom around the screen bouncing off the ‘walls’. It is not particularly complex, nor is it very useful, but it is worth exploring as it will give you a feel using the Colour Maximite 2 and what you can 94  Silicon Chip Australia’s electronics magazine siliconchip.com.au Table 1: Pin Layout of Waveshare STM32 Module LEFT No. 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 GND PE2 PE4 PE6 PI8 PC14 PI9 PI11 PF1 PF3 PF5 PF7 PF9 PH0 RST PC1 PC3 PA1 PH2 3.3V 3.3V PH4 PA3 PA5 PA7 PC5 PB1 PF11 PF13 PF15 PG1 PE8 PE10 PE12 PE14 PB10 PH6 PH8 PH10 3.3V RIGHT 5VIN PE3 PE5 VBAT PC13 PC15 PI10 PF0 PF2 PF4 PF6 PF8 PF10 PH1 PC0 PC2 VREF+ PA0 PA2 PH3 GND GND PH5 PA4 PA6 PC4 PB0 PB2 PF12 PF14 PG0 PE7 PE9 PE11 PE13 PE15 PB11 PH7 PH9 PH11 5VOUT PI7 PI5 PDR PE0 PB8 PB7 PB5 PB3 PG14 PG12 PG10 PD7 PD5 PD3 PD1 PC12 PC10 PA14 GND GND PI1 PH15 PH13 PA13 PA11 PA9 PC9 PC7 PG8 PG6 PG4 PG2 PD14 PD12 PD10 PD8 PB14 PB12 GND GND PI6 PI4 PE1 PB9 BOOTO PB6 PB4 PG15 PG13 PG11 PG9 PD6 PD4 PD2 PD0 PC11 PA15 PI3 PI2 3.3V 3.3V PI0 PH14 PA12 PA10 PA8 PC8 PC6 PG7 PG5 PG3 PD15 PD13 PD11 PD9 PB15 PB13 PH12 3.3V No. 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 Table 1: use this pin layout as a guide if you need to troubleshoot the Waveshare CPU module, as the silkscreen ends up upside-down relative to pin 1 and how the module is placed on the Colour Maximite 2 PCB. ing the ball in the centre of the screen. The coordinate system used by MMBasic involves two axes: the x or horizontal axis and y or the vertical axis. x = 0 and y = 0 refers to the pixel at the top left of the screen. The coordinates get larger as you move to the right and down the screen. So x = 799 and y = 599 is the position of the pixel in the bottom right corner (the default resolution of the screen is 800 x 600 pixels). dx and dy are the amounts by which we move the ball in the x and y-axis every time the program loops around siliconchip.com.au (d = delta). With these both set to 1, the ball moves right and down one pixel each time the loop is executed. When the ball hits a wall, the polarity of these is reversed (more on that below). DO…LOOP The program then enters a DO… LOOP which causes the enclosed code to be repeated forever (well, at least, until something stops it!). The first thing that we do in this loop is to draw a circle (ie, our ball) at the coordinates given by the variables x and y and with a radius of 30 pixels. The Australia’s electronics magazine outline of the ball is black and is two pixels thick, while the centre is filled with red. Drawing the outline in black means that when we move the ball and redraw it, the black outline will erase any part of the last ball’s image that was left behind. This works well because we only ever move the ball by one pixel at a time. We then either increment or decrement the value of x depending on the value of dx, which is 1 or -1. This results in the ball moving one pixel either left or right on the next loop, August 2020  95 when the ball is redrawn. The program line after that checks to see if the ball is about to hit the left or right boundaries and, if it is, it reverses the sign of dx, causing the ball to travel in the opposite direction. The same is done for the vertical direction (dy) and taken together, this means that the ball will appear to bounce off all four edges of the screen. The purpose of the PAUSE 2 command is to slow down the program so that you have time to see the ball move. To see how fast the Colour Maximite 2 can really go, change this to PAUSE 0 (or remove that line entirely) and then re-run the program. The ball will just turn into a blur. You will notice that while this program is running, you will not get the command prompt back. This is because MMBasic is now busy executing your program and drawing the bouncing ball. You can stop the program whenever you want to by Last-minute PCB changes The motherboard illustrated in the photographs has gone through a few changes and so may not exactly match the PCB overlay diagram and final board that you receive. Most changes were minor layout adjustments, but one significant change was the provision for an external 8MHz crystal oscillator to replace the 8MHz crystal on the Waveshare CPU board. In testing, it was found that some VGA modes (such as 800x600 pixel 16-bit colour) caused difficulty for some monitors. This was traced to instability in the on-chip 8MHz oscillator in the Cortex-M7 CPU. Most constructors will be unaffected and will not need to do anything. However, if this change is needed, it can be easily implemented by removing the 8MHz crystal on the Waveshare CPU board and installing the external oscillator and a capacitor on the motherboard. The parts required are one SMD 100nF 50V X7R ceramic capacitor in a 3216/1206 package, and one 5x7mm SMD 8MHz oscillator (QX7 XO 25ppm), eg, RS Cat 813-6194. 96  Silicon Chip entering CTRL-C at the console, and you should get the command prompt back again. best way to understand it is to get in there and try it out. Full-screen editor The File Manager is a great way of managing the files and directories on the SD card. You can always use the traditional BASIC commands at the command prompt (COPY, CHDIR etc) to do this, but the File Manager is much easier. It provides a graphical list of the contents of the SD card and, using the arrow and Page Up/Down keys, you can select a file or directory and rename it, delete it, edit it etc. To get into the File Manager, use the FILES command or press the F1 key at the command prompt. On startup, it defaults to listing the current directory. Fig.13 shows what it looks like. Files and directories are colour-coded, and the status lines at the bottom will tell you what file you have selected and the key commands that are available to you. You can choose a different sorting order for files and directories by using the CTRL-S key. Positioning the cursor on a directory and hitting Enter will take you into that directory; if the directory has a name consisting of two dots (ie, “..”), pressing Enter will take you up the directory tree by one level. Hitting Enter while a program file is selected will run that program, and pressing F4 will edit it. You can even play a WAV, FLAC or MP3 file via the audio output by selecting it and pressing Enter. CTRL-F will enter the search mode, which works similarly to search in the full-screen editor. This will prompt you for the search text and, as you type this in, the cursor will automatically be positioned on the first file or directory with a matching name. You can then use the down arrow key to search for the next occurrence, or the up arrow for the previous occurrence. As with the editor, the best way to get to know the File Manager is to fire it up and try it out. If you are familiar with the editor used in the original Colour Maximite and the Micromite, this editor is similar but it has extra features. These include a much larger clipboard (capable of holding many lines), the ability to edit very long lines (the screen will scroll sideways) and a much-enhanced search function. Entering the above program should have given you a feel for how the editor works and, as we said, its operation is reasonably intuitive. The colour-coded text makes it easier to understand the program (commands are in cyan, comments in yellow, constants in green and so on). The status bar at the bottom of the screen shows the name of the file being edited, and the location of the cursor within it. Below this, there is a summary of the common key commands. Two important functions of the editor need further explanation: search mode and mark mode. CTRL-F enters search mode. This will prompt you for the search text, and as you type this, the editor will automatically position the cursor at the first match found. You can then use the down arrow key to search for the next occurrence, or the up arrow for the previous occurrence. In this mode, the Enter key leaves the cursor where it is and returns to normal editing mode, while CTRL-V will replace the searched text with whatever is in the clipboard (see below). Escape (Esc) aborts the search. CTRL-S enters mark mode. In this mode, you can use the arrow keys, Home or End to mark (or select) text and copy it to the clipboard. It will be highlighted on the screen as you move the cursor around. Then CTRL-C will copy the selection to the clipboard while CTRL-X will copy and delete (cut) the selection. Delete (Del) will simply delete the selection without changing the clipboard, and Escape (Esc) will return to the normal editing mode without changing anything. You can use the editor to edit any text file, not just programs – all you need to do is specify the full file name, including the file’s extension (eg, EDIT “myfile.txt”). As we said before, the Australia’s electronics magazine File Manager The serial console Usually, a VGA monitor and USB keyboard are used as the console for MMBasic. But as mentioned last month, you can connect to a desktop or laptop computer via the serial console and use its keyboard and screen to siliconchip.com.au Resistor Colour Codes do the same job. This is handy if your Colour Maximite 2 does not have an attached monitor and keyboard; it also makes it easier to transfer programs and data between the two. To access the serial console, connect the Colour Maximite 2 to your personal computer via the USB Type-B connector on the rear panel (this also provides power). When you do this, the Colour Maximite 2 will appear as a USB virtual serial port, which acts much like a standard serial port. Windows 10 includes the required device driver. For Linux, Mac and earlier Windows versions, you can get a driver and instructions from Microchip at siliconchip.com.au/link/ab2y You will need a terminal emulator program on your desktop computer. This acts like an old-fashioned computer terminal; it will display text received via the serial link, and any key presses will be sent back. For Windows users, Tera Term is a good choice. You can download it from http://tera-term.en.lo4d.com/ For Mac users, a terminal emulator is built into macOS (Terminal); refer to the Colour Maximite 2 User Manual for instructions (siliconchip.com. au/link/ab2z). For Linux users, there are a few options like PuTTY (https:// www.putty.org/). The terminal emulator and the serial port that it is using should be set to the Colour Maximite 2 standard o o o o o o o o o No.   6   1   2   19   13   3   1   1 Value 10kΩ 4.7kΩ 1kΩ 240Ω 120Ω 75Ω 10Ω 2.2Ω 4-Band Code (1%) brown black orange brown yellow violet red brown brown black red brown red yellow brown brown brown red brown brown violet green black brown brown black black brown red red gold brown of 115,200 baud, eight data bits and one stop bit. When you have the serial port and terminal emulator set up, reset the Colour Maximite 2 and you should see the MMBasic banner and prompt on the terminal emulator. Loading a program from a PC If you have prepared a program on your computer, you can transfer it to the Colour Maximite 2 via the serial console using either the AUTOSAVE or XMODEM commands. The AUTOSAVE command looks like this: AUTOSAVE “filename” After this, you can simply copy the program to your desktop computer’s clipboard and paste it into the terminal emulator (eg, Tera Term). From the Colour Maximite 2’s perspective, this is the same as if a high-speed typist types in the program. After the pro- 5-Band Code (1%) brown black black red brown yellow violet black brown brown brown black black brown brown red yellow black black brown brown red black black brown violet green black gold brown brown black black gold brown red red black silver brown gram has transferred, press the F1 key and MMBasic will save the program to the SD card and return to the command prompt. The XMODEM command is a bit more complicated and uses the XModem protocol to transfer a BASIC program file, including an integrity check which will detect most transfer errors. The Colour Maximite 2 User Manual goes into the details of how to do this – it is reasonably straightforward. MMEdit Another convenient method of creating your programs and sending it to the Colour Maximite 2 is to use MMEdit, written by Jim Hiley from northern Tasmania. It can be installed on a Windows computer and it allows you to edit your program on the PC then, with a single button click, transfer it to the Colour Maximite 2 for testing. MMEdit is easy to use with colourcoded text, mouse-based cut and paste and many more useful features such as bookmarks and automatic indenting. Because the program runs on your PC, you can save and load your programs to and from the computer’s hard disk. MMEdit can be downloaded from Jim’s website at www.c-com.com.au/ MMedit.htm It is free, although he would appreciate a small donation. Conclusion Fig.13: one of the new features of the Colour Maximite 2 is the File Manager, shown here. Use the arrow keys and Enter to navigate the files and directories on the SD card. Other keyboard commands available are shown at the bottom of the screen. siliconchip.com.au Australia’s electronics magazine So there you have it. The Colour Maximite 2 is a powerful but inexpensive computer that is fun to use. Now would be a good time to download our tutorial “Introduction to Programming with the Colour Maximite 2” (siliconchip.com.au/link/ab30) and start working your way through it. Enjoy! For updates to MMBasic and more, go to the Author’s website at http:// geoffg.net/maximite.html SC August 2020  97 Vintage Workbench The The Tektronix Tektronix Type Type 130 130 LC LC Meter Meter –– Part Part 33 Calibration Calibration By Alan Hampel, B. Eng. (Electronics, Honours) In the last two articles, Alan Hampel described how the T-130 LC meter works and how he cleaned up the dirty and faulty unit that he got from eBay. In this last part of the series, he describes how he got it correctly calibrated and working again. Servicing the controls Checking with a multimeter, I found that the resistance of each contact in the RANGE SELECTOR switch varied with each engagement from around 5-15W. That isn’t very good, but the contacts looked OK to the eye, with no excessive wear. I applied contact cleaner/lubricant sparingly (just achieving a wet appearance), and rotated the switch through the whole range numerous times. Checking again with the multimeter, all contacts showed no perceptible resistance. Then I applied some grease to the clicker mechanism. I applied some contact cleaner/lubricant to the shafts of the COARSE ZERO and FINE ZERO variable capacitors. Everybody who is an electronics enthusiast or technician soon learns that pots need lubricant because of the racket dry pots make in audio gear. Variable capacitors need lubricant too. But the effect of dry capacitors is more subtle: a certain amount of oscillator frequency instability. Checking components I checked all 50 resistors for correct resistance and visual integrity. That was possible without unsoldering anything for all but 10, because unpowered valves are open circuits (normally). I checked the remaining 10 by powering up and checking for correct voltage division, and checking current by shorting each in the chain with a milliamp range of my multimeter. This revealed three things: 1) Resistor R96 was 20% high. R96 (470W) and R95 (33kW) back-bias the Restoring the manual When I restore a vintage electronic item, I like to have an immaculate manual to go with it. When I bought this T-130, the eBay seller threw in an original printed instruction manual. Unfortunately, it was for a different serial number, and was in very poor condition, with numerous stains and pages missing. I downloaded a manual from the Boat Anchor website (http://bama.edebris. com/manuals/), but it too had missing pages, and the scan quality was poor. I decided to re-create the manual in the Tektronix style by re-typing it and re-taking the photos from the same angles as Tektronix did. I also scanned the drawings and cleaned them up with Microsoft Paint and Media Impression (a software package that came with my PC and does much the same job as Photoshop). I have a Tektronix/US-style symbol library in my CAD system, so I re-drew the circuit diagram in Tektronix style. The Tektronix original had several errors, which I corrected. I also drew component layout diagrams, though Tektronix never included them in their manual. All this work on the manual was a good investment. It made me thoroughly familiar with the circuit, how it works, and what clever tricks the designer Cliff Moulton used to get excellent performance. That knowledge was invaluable for fault-finding and calibration. 98  Silicon Chip Australia’s electronics magazine charge and discharge diodes, balancing out contact potential. This would cause too much meter back-bias. 2) Resistor R405 (1.5W) was twice its correct value, which would starve the variable oscillator valve of heater current. 3) Valve V60 (a 6BE6) had about 50kW leakage between the first grid and the cathode. I checked electrolytic capacitor C401 (2 x 15µF) by measuring the ripple voltage on it. It was still good; I measured 7V versus the 8V stated in the manual. I saw no corrosion; this is sometimes seen when electrolytics leak electrolyte. I checked electrolytic C402 (6.25µF) by measuring the ripple voltage on it. It too was still good. Surprisingly, electrolytics C99 (5µF) and C100 (25µF), factory originals, were installed backwards! Not surprisingly, they each had only about 10% of their rated capacitance and were very leaky. As the ripple on the 150V rail was exactly as stated in the manual, that indicated that polyester capacitor C403 (22nF) was still good. The only other polyester capacitors are the range capacitors, which are Sprague Black Beauty polyester. I checked them insitu for leakage (even though leakage is unlikely) – all had no measurable leakage. All other capacitors are professional ceramic types that are known to almost never fail. Methodical checking I replaced the temporary and weak 6X4, and the 6U8 in the V30 socket, with the new 6X4 and one of the 6U8s siliconchip.com.au The right side interior of the T-130 chassis neatly houses all the valves, transformers and a few other parts. The large transformer marked “T-130 PA1” at bottom right (T400) is used to power the valve plates and heaters, T30 at upper right is part of the fixed oscillator (V30), while T1 is marked at lower left and and is part of the variable oscillator (V4). the seller sent me, following Rule 10 (from “14 rules of restoration” from the last article): Every single time you replace a component, do a comprehensive set of checks to verify both that the fault due to that component has been cleared, and that no new symptoms have appeared. siliconchip.com.au I replaced faulty heater dropping resistor R405, again following Rule 10. As it’s a wire-wound component, if it’s high, it’s most likely about to go open. I couldn’t find a source of resistors identical to the original, but I installed a Welwyn part that at least looks like a type available in the 1960s. Changing it made the instrument zero slightly Australia’s electronics magazine more stable, but still too far off to allow the 3pF range to be used. Now that I could deem the power supply good, I went through the rest of the instrument, stage by stage, checking waveforms. This revealed that: ● The 6U8 variable oscillator valve (V4) had low emission. I replaced it with another of the 6U8s the seller August 2020  99 The interior left side of the chassis houses nearly all the capacitors, resistors and other components mounted on ceramic strips and connected via point-to-point wiring. Note the two replacement silver-coloured electrolytics (C99 & C100) at the top right corner; Tektronix factory-installed the originals in backwards! sent me. That stopped over-deflection on the 3pF range. The instrument zero became a bit more stable, but now had a small backwards deflection. ● Since the 6BE6 mixer (V60) had extremely high grid-cathode leakage, it could well be about to fail completely. I replaced it with a NOS valve from eBay. This improved things – instead of the meter dropping back past about 80pF, it didn’t start to drop back until about 200pF. 100  Silicon Chip The low-pass filter is pretty crude, and its output falls somewhat as frequency increases. The low-emission valve from the old radio had offset the input to the Schmitt trigger, so that triggering up and down ceased past a certain point. ● Checking waveforms around the Schmitt trigger confirmed that it couldn’t follow the filter output past about 10.9kHz (200pF indicated). With resistor checks already done, presumAustralia’s electronics magazine ably, the problem was valve V70 (another 6U8). On plugging in a replacement, the T-130 now followed a variable capacitor up to 250pF. This was far from perfect, but as all other components have been checked, I assumed that I could correct it with 50kW symmetry trimpot R68, which adjusts the bias on the Schmitt input to centre the signal between the trigger levels. That turned out to be correct. ● I then replaced defective elecsiliconchip.com.au T-130 applications The obvious applications of the T-130 are checking small capacitors and inductors before soldering them into circuit and – via the probe lead – checking suspect parts in-circuit. The guard voltage output removes the need to isolate parts before checking them; a facility that most modern capacitance and inductance meters do not have. Something that almost all design engineers of valve circuits had to grapple with is the Miller effect, which affects amplifier frequency response and may make negative feedback circuits unstable, requiring compensation (see the panel in part one). The T-130 makes the measurement of Miller effect capacitance easy. First, the static (or stray) capacitance at a grid can be measured by the T-130 and probe lead with no HT on the circuit under test. Then the HT can be switched on, and there will be an increase in the measured capaci- tance – this increase is due to the Miller effect. The T-130 can be used to identify short lengths of coax (<< 1/4 wavelength of 140 kHz, ie, << 500m) without knowing the actual length. Just measure the capacitance with the far end open, and the inductance with the far end shorted. Then, Z ≈ √L ÷ C. For example, let’s say the inductance measured on the T-130 is 0.60µH and the capacitance is 104pF. Then Z is approximately 76W. If the sheath diameter is 10.3mm, the coax must be RG11/U. The T-130 with the Dielectric Test Adapter can help with evaluating the effect plastics and other insulators have on RF circuits, provided a flat sample of at least 55mm diameter is available. It can, by measuring relative permittivity (dielectric constant), assist in identifying plastics. There was another use for the T-130. The space charge increases the apparent grid-cathode capacitance of a valve – the denser the space charge, the greater the capacitance (this capacitance can appear to be negative at RF under certain conditions!). It’s useful to know this variation when designing stable oscillators. A valve produces both white noise and flicker noise due to the random emission of electrons from the cathode. Fortunately, both are reduced by the space charge. The denser the space charge, the lower the noise. This suggests an inverse correlation between noise level and grid-cathode capacitance, and indeed there is. In a noise-critical application, it may be desirable to predict the noise in a tube operated in conditions different to the that given as typical in data sheets. One can measure the noise in a prototype circuit directly, but it can be quicker and easier to measure the capacitance. trolytics C99 and C100 with new tantalum units, following Rule 10. No symptoms were cleared, and no new symptoms appeared. C99 and C100 are too small to provide any meter damping. They were only installed from serial number 6040 onwards. Presumably, the Schmitt trigger sometimes oscillated due to the transients in the meter circuit wiring getting back to the Schmitt input. ● Schmitt triggers can oscillate if the valve gm is very low. Sure enough, checking it (V70, 6U8 again) showed that was the case. I replaced it with a NOS valve (following Rule 10 of course). The wild pointer swings no longer occurred when rotating a tuning capacitor under test. ● V45 (another 6U8) had low emission in the triode, which works as the discharge diode in the meter circuit. This caused the backwards and somewhat unstable deflection of the meter, as its contact potential was too weak to balance out the back-bias from resistors R95 and R96. ● The output of the cathode follower was low, with a lot of hum. Changing the 6BH6 (V110) fixed it. movement plastic case was broken on the left-hand side. A previous owner had patched it up, but there was still a gap. That was unacceptable, as it would let dust in, eventually ruining the movement. The scale markings had faded as well. Damaged meter movement While not the original, the meter looks very close to some of the later models, which can be viewed at http://w140.com/tekwiki/wiki/130 As mentioned earlier, the meter siliconchip.com.au Australia’s electronics magazine Fortunately, I had another 4.5-inch meter that fitted the mounting holes and had the same full-scale deflection current. It even looks like the meter Tek fitted to later T-130s. It did not, of course, have the same scales. I photographed the scales in the bro- August 2020  101 Restoring the S-30 Delta Standards Box Users of the T-130 could send it back to the Tektronix factory for adjustment and calibration, but this would have been inconvenient, to say the least. Tektronix sold the S-30 Delta Standards Box as an accessory. The S-30 plugs into the UNKNOWN connector and enables you to check the T-130 accuracy. The S-30 contains preset capacitors for each range, an inductor, and a choice of 1MW and 100kW resistors. Only one inductor is needed because if all the capacitance ranges read correctly, and any one inductance range reads correctly, the other inductance ranges must be right. The resistors allow you to check the resistance compensation of the variable oscillator. The capacitors and the inductor in the S-30 were adjusted in the factory to within 1%. Combined with the T-130 basic accuracy and repeatability of ±1%, using the S-30 to calibrate the T-130 then gives you a T-130 with an accuracy of ±2%. Typical of reputable American companies, only ±3% accuracy was claimed in Tektronix marketing – a “safety” margin of an additional 1%. I purchased an S-30 from another eBay seller. It arrived with the outside marred by wear and tear and some gum from ownership stickers was present. I removed the single control knob, FRONT BACK C2 1.5-5.1 C4 1.5-5.1 -3µµF C6 2.3-14.2 +3µµF C7 3-12 C8 22 C10 82 C9 4.5-25 C12 285 C11 4.5-25 0µµF +10µµF +30µµF +100µµF +300µµF 1 MEG 100K SHORT CIRCUIT R2 1M 300µH R1 100K TYPE S-30 DELTA STANDARD the anodised front panel and the case, and gave them all a wash in the sink with dishwashing liquid. This easily removed the grime and the sticker gum, but made the wear and tear more obvious. I decided not to do anything about the wear and tear. What was more of a concern was that the inner chassis had rotated within the case, so that a connection could not be made. Further disassembly revealed that the inner chassis was secured only by the switch L15 220-330µH boss and nut – there was nothing to stop rotation when the switch knob was turned. Using a generous amount of Blu Tack to contain chips and prevent them spreading within the inner chassis, I carefully drilled a location hole and installed a nut and bolt to prevent rotation – something Tektronix should have done. The Blu Tack left a grease mark, so I used a cotton bud and isopropyl alcohol to get rid of it. This is one of the ‘old’ style S-30s, the ‘new’ style ones are slightly taller with a visible logo and smaller print (http://w140. com/tekwiki/ wiki/S-30). 102  Silicon Chip Australia’s electronics magazine siliconchip.com.au The capacitance and inductance trimmers are mounted on the sides of the S-30 chassis. They are meant to be adjusted as required with the aid of an RLC bridge, and can be accessed by removing the blue case. ken meter and converted them into a CAD file. I then jury-rigged a Rotring technical pen in a desktop NC milling machine and used that to inscribe new scales, complete with Tektronix logo, to fit the replacement meter movement. Adjustment and calibration T-130 owners could buy an S-30 Standards Box for calibration (see panel). This contained various adjustable capacitors that could be checked on a standard audio RLC bridge (see diagram at left). It also contained an adjustable inductor. Since this inductor was designed for 140kHz, it could not be checked on a standard RLC bridge. The T-130 manual describes an “Inductance Standardizer” which contains a 1% tolerance 4310pF capacitor. This resonates when connected in series with a correctly adjusted S-30 inductor at 140kHz. The T-130 is used as a 140kHz null resonance indicator. Tek didn’t sell the Inductance Standardizer – they expected S-30 owners to build it themselves. I bought an S-30 from another eBay seller, and I made an Inductance Standardizer with paralleled 1nF and 3.3nF 1% capacitors. However, calibration with a frequency counter is easier and more ac- curate. All you need is a Production Test Fixture, a 300pF 1% capacitor, a 100pF capacitor (accuracy unimportant) and two 0.5W carbon resistors, 100kW & 1MW. The resistors must be identical types. The Production Test Fixture (shown overleaf) ensures the stray capacitance in connecting the capacitor and resistors is always the same. The T-130 can easily resolve 0.05pF, so physical precision in connection is vital. Carefully zero the meter with the mechanical adjustment. Turn on the T-130 and leave it for one hour to warm up and stabilise. Connect a frequency counter to the output of the fixed oscillator buffer at R49 (1.5MW) and adjust T30 for a reading of precisely 140,000Hz. Then, with the COARSE ZERO adjusted for half-scale deflection on the 3pF range, adjust resistance compensation trimmer C7 until the deflection is the same for both the 100kW and 1MW resistors. The manual says adjustment should be made last, but since it has a significant effect on the adjustment of T1, it’s better to do it now. Next, connect a scope to the Schmitt trigger output on R74 (15kW). Select the 300pF range and insert the 300pF capacitor. Adjust R68 (symmetry) for the best waveform symmetry. Now connect a frequency counter to R74 (or leave the scope connected, if it has an inbuilt frequency counter). Adjust the COARSE and FINE ZERO controls for a dead beat on the 3pF range with nothing in the Production Test Fixture. Re-insert the 300pF capacitor and adjust T1 for precisely 15,477Hz. Repeatedly adjust COARSE ZERO, FINE ZERO and T1 until you get dead beat and 15,477Hz without further adjustments. Then, with the 300pF capacitor still inserted, adjust R78 for exactly full-scale deflection of the meter. At this point, the total tuning capacitance without the 300pF capacitor is 1136pF, T1 is 1136µH, and both the 300pF and 300µH ranges are correct. The Schmitt trigger output for all ranges is correct and the range trimpots R97 through R100 can then be adjusted. Insert the 100pF capacitor and adjust the COARSE and FINE ZERO controls to get precisely 5781Hz. Then adjust the 100pF range trimpot R97 for C1 3.3nF 1% RS 168-3336 S1 TO 130 C2 1.0nF 1% RS 168-3346 L1 330µH RS 104-8416 TO S-30 R1 7.5 RS 386-143 The circuit diagram for the Inductance Standardizer is shown above, with the INDUCTANCE STANDARDIZER interior shown slightly below actual size (64mm long diecast box). Inductance Standardizers were meant to be constructed from the circuit provided in the manual and as made obvious from the labelling, this wasn’t made by Tektronix. siliconchip.com.au Australia’s electronics magazine August 2020  103 Are Your S ILICON C HIP Issues Getting Dog-Eared? REAL VALUE AT $19.50 * PLUS P & P Keep your magazine copies safe, secure & always available with these handy binders Order now from www.siliconchip.com.au/Shop/4 or call (02) 9939 3295 and quote your credit card number. *See website for overseas prices. An excerpt form the Tektronix catalog from 1975 showing the T-130 and a photo of the Production Test Fixture, right at the end of its production life. A replica of the Production Test Fixture, made from stainless steel and a standard UHF-to-N adapter, was shown in the first article of this series in the June issue on page 39. 104  Silicon Chip Australia’s electronics magazine siliconchip.com.au exactly full-scale deflection. When I made this adjustment, I found that R97 was hopelessly noisy. Applying lubricant didn’t fix it. I could not locate an identical pot, so I moved the wire on one end of the track to the other end – that solved the problem. Next, remove the 100pF capacitor and adjust the remaining trimpots for full-scale deflection on the remaining ranges with the correct frequencies. Use the COARSE ZERO and FINE ZERO controls to get the listed frequencies: 1812Hz to adjust R98 (for 30pF range), 612Hz to adjust R99 (10pF) and 184Hz to adjust R100 (3pF). Finally, remove the Production Test Fixture, set COARSE ZERO to about 5° back from maximum and set FINE ZERO to its midpoint. Adjust zero span trimmer C2 for a dead beat on the 3pF range. Seal all adjustments with tamper-proof seal or red nail varnish. Performance after restoration The T-130 is very good. There is no perceptible drift in zero over the specified supply voltage range of 210-250V AC. The drift of the zero setting in the initial warm-up is less than 0.15pF indicated. After that, no drift in zero or full-scale deflection is perceptible on any range except the 3pF and 3µH ranges, which in any case remain within 5% and 1% when the FINE ZERO is Fun with screws! I re-assembled the instrument using new screws because the old ones were all corroded and unsightly. Typical for an American company, Tektronix used Unified Coarse (UNC) 6-32, 8-32 and 4-40 threaded screws to hold their instruments together. They used a mixture of CSK (countersunk), FH (flat head), PH (pan head) and TH (truss head – a wide version of pan head) screws. They used Keps nuts; these are the sort that have a star lock washer pre-attached to the nut. I found I had run out of some of the screws needed. There are three specialist fastener shops in Perth. I rang the first one and asked: “Do you have in stock screws UNC8-32 x 1/2 THS plated or stainless?” “Err, do you want wood screws?” “No, I’m asking for UNC-8-32 x 1/2 screws.” “Err, um, but what sort do you want, do they have a pointy end?” “Forget it, mate. You don’t understand UNC screw terminology – that tells me you don’t sell UNC.” I rang the second firm. The chap clearly knew his screws, and had them in stock. But his minimum sale quantity was 200 of each item. Cripes, I’ll never use that many in the rest of my life, and all the sizes I need would cost me more than the instrument is worth. I rang the third firm. That chap also understood the terminology, but he didn’t stock them. He told me to ring firm number 2. I fired up eBay and bought 20 of each size from a Chinese seller. They arrived within a week, post free, costing me about $4 for each size. And local shops wonder why they are losing sales... adjusted just before making a reading. Tek claimed that the oscillators will not pull in together above 1Hz separation (0.016pF indicated). Mine certainly betters that specification. a 25pF capacitor and got a stable reading. Clearly, with all the faults the T-130 had, it could not measure anything. Did he lie? Not necessarily. He probably connected the 25pF capacitor, selected the 100pF range and switched the T-130 on. The 1N2630 probably didn’t short the heaters until he shipped it to me. Because of the incorrect rectifier not being properly grasped by the socket, there was no HT, therefore no back-bias to oppose contact potential in the charge and discharge valves. One of them had weak emission, and it just so happened that the weak emission produces about 25% meter deflection. So it might have appeared that the instrument was working, at least in that one specific test case! SC Did the eBay seller lie? The seller claimed he tested it with ► siliconchip.com.au Australia’s electronics magazine The T-130 LC Meter with the Inductance Standardizer and S-30 Delta Standards Box connected together. August 2020  105 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Send your email to silicon<at>siliconchip.com.au How to program the PIC16F1459 I read with interest the article on the Infrared Remote Control Assistant project in your July 2020 issue (siliconchip.com.au/Article/14505). I note at the beginning of the article that PIC16F88 is not to be used in any new designs. I have MPLAB v8.20, which is pretty old now. I was interested to see if I would be able to program a PIC16F1459, as used in that project, but it is not listed in my version. I also have a PICkit 3 which has served me well, and was wondering what version of MPLAB you use and whether the PICkit 3 would work to program these devices. The PIC16F1459 datasheet does not show PGD or PGC pins on the device. A bit of web searching revealed that ICSPDAT is equivalent to PGD and ICSPCLK to PGC. Is that correct? (G. C., Toormina, NSW) • MPLAB version 8.92 can be used to program the PIC16F1459, and you should be able to use the PICkit 3 as we’ve programmed those chips with one without issue. However, it’s easiest to just switch over to MPLAB X entirely; it is a free download (although the free versions of the compilers are somewhat limited). Yes, ICSPDAT has the same programming function as PGD and PGED. Likewise, ICSPCLK is the same as PGC or PGEC. er (January-March 2017; siliconchip. com.au/Series/308). I have them hooked up to a pair of JBL 4312 control monitors. This is a truly superb stereo system, and you would have to pay a (very) large amount of money to acquire similar performance commercially. The USB codec in the DAC works flawlessly; however, you must have a computer with a USB port that recognises the codec to be able to use it. It’s OK for me but useless for the rest of the family. I see that the Maximite can read several music formats and send the digital data to the DAC in the STM32 chip. Now if the Maximite could send this data out the USB port to the codec in the CLASSiC DAC, or alternatively, output S/PDIF, we would have the necessary tools to create our own music player on the Maximite (with powerful graphics to enhance it). The 128GB SD card would allow around 300 full albums to be stored in FLAC format – surely enough for most music fans. (G. B., Strathalbyn, SA) • Geoff Graham responds: that’s an interesting idea, but we don’t want to add this feature to the CMM2. The main reason is that the CMM2 is designed as a fun BASIC computer and this would force it into a different, possibly conflicting, path. Also, the sole USB port is used for the keyboard and with that connected to a DAC, you would then have no way of controlling the CMM2 as a standalone computer. A suggestion for the Colour Maximite 2 Which type of infrared receiver to use The Colour Maximite 2 described in last month’s issue is a fabulous project. Well done to all concerned in its creation. I would like to suggest a possible enhancement or additional project which I think the Maximite would be able to handle. Like many of your readers, I built the CLASSiC DAC (February-May 2013; siliconchip.com. au/Series/63) plus the SC200 amplifi106  Silicon Chip In your March 2020 article on the Programmable Thermal Regulator (siliconchip.com.au/Series/342), the infrared receiver IRX1 doesn’t appear in the parts list. Is Jaycar Cat ZD1952 suitable? (B. W., Inner Park, Qld) • Yes, Jaycar Cat ZD1952 is suitable. We have also recommended Altronics Z1611A as an alternative in previous projects. Practically speaking, most 3-pin infrared receiver/decoders Australia’s electronics magazine can be used. Ideally, its bandpass filter (usually 36kHz, 38kHz or 40kHz) should be matched to your remote, but in practice, it isn’t critical, and a 38kHz receiver will generally work with any remote. Measuring very low distortion and noise I want to measure the specifications of the Ultra-LD Mk.4 amplifier that I have built (August-October 2015; siliconchip.com.au/Series/289). I mainly want to measure the signal-tonoise ratio (SNR) and total harmonic distortion plus noise (THD+N). You published photos of my amp in the Mailbag sections of the June 2016 and March 2018 issues. To measure the THD+N, I first looked at the Quant Asylum QA400 audio analyser you reviewed in the March 2015 issue (siliconchip.com. au/Article/8388), and for which you published a Balanced Input Attenuator in May 2015 (siliconchip.com.au/ Article/8560). However, this model has been discontinued by the manufacturer. Its replacement, the QA401, costs two and a half times as much! There are a couple of reviews available on the internet (siliconchip.com. au/link/ab42 and siliconchip.com. au/link/ab43), and they measure the THD+N at -99dB (0.0011%). According to the graph on page 37 in the August 2015 issue, the THD+N of the Ultra-LD Mk.4 amplifier is better than -106dB (0.0005%). So that won’t be suitable. I also looked at second-hand instruments like the Audio Precision analysers or the Rohde & Schwarz UPL units, but they trade at no less than a couple thousands of dollars used on eBay. Regarding the SNR, my understanding is that I need to measure the output at full power (though it could be done at lower power, say 20W only) against the noise measured with no input signal. Since the rated power into 8W is 135W, that means 32.86V RMS across its output at full power before siliconchip.com.au distortion if I am not mistaken. That translates into 30.33dBV. With an SNR rated at -124dB (unweighted at full power), I should measure -91dBV noise with no signal. So I built the High Resolution Audio Millivoltmeter (October 2019; siliconchip.com.au/Article/12018) along with its companion Precision Audio Signal Amplifier. After running my amp for more than an hour, I measured -75dBV at the output of each amplifier module. I remembered that the output had to be tuned to be below 0.5mV by adjusting VR2 on the board. I took this opportunity to re-calibrate the quiescent current of my two modules, but could not get a better output noise figure. With a 50W load on the Audio Millivoltmeter, it shows -89dBV, which should be just at the edge of the precision I need for this measurement. It seems very challenging to adjust the output of the amplifier closer to 0mV just with VR2. Is my methodology correct? Finally, in the June 2020 issue, you mention you would publish a USB SuperCodec. Would it allow measurements precise enough for audio gears like the Ultra-LD Mk.4? Keep up the great work, and thank you. (O. A., Singapore). • It is difficult to find test equipment that can measure the performance of the Ultra-LD Mk.4 amplifier for less than a few thousand dollars. That design, and some others we have published, are approaching the limit of practical distortion measurement, being down in the low single digits part-per-million range (approaching -120dB). Your approach to measuring its SNR is valid, but as the input of the Digital Audio Millivoltmeter is AC-coupled, any output DC offset from the amplifier should not affect its reading. Have you terminated the Ultra-LD Mk.4 input when making the measurement? You can use a 100W resistor, although simply shorting the input to ground is usually OK. If you leave the input open, you will get more noise due to the higher-than-usual input impedance. The signal source impedance usually is 100W or less when it’s connected to a device like a CD player, so you want to maintain that situation when testing the no-signal condition. The USB SuperCodec (starting on siliconchip.com.au page 24 in this issue) is probably the closest you will get to the performance of an Audio Precision or similar device for under $1000. We haven’t added up its parts cost, but we’re guessing it’s in the range of ‘a few hundred’ dollars. It certainly can measure very low distortion numbers. It isn’t as good as our Audio Precision System 2 at measuring THD+N or SNR. But there are ways around that. With appropriate software, some resistive dividers and some careful measurements, you could get accurate THD+N and SNR readings for the Ultra-LD Mk.4 using the SuperCodec. The main trick is to measure the distortion and noise separately, then combine the readings. You can use the bare SuperCodec to measure the noise floor with no signal, then measure the full-scale amplitude and THD using a divider feeding into the SuperCodec. Some RMS calculations should then give you the correct THD+N figure. If you still can’t get close to the -106dB/0.0005% THD+N figure that we quoted, it’s possible that your power supply is injecting noise into your amplifier outputs. Check the grounding carefully. Problem uploading DAB radio BASIC code I’ve built your DAB+/FM/AM Radio (January-March 2019; siliconchip. com.au/Series/330), and it’s powering up OK, but I’m having a lot of trouble trying to load the BASIC code into the Explore 100. For the life of me, I cannot get the ‘crunched’ file to load properly. I have the same problem as a previous constructor (July 2019, pages 106107 in Ask Silicon Chip); after the upload, it shows 64727 bytes saved and not 66104 bytes as expected. I have downloaded the file from your website several times, used both Stuffit Expander and 7Zip, at different stages, to decompress the file and Tera Term to upload the resultant crunched file to the Explore 100, but to no avail. I have tried to use MMEdit to load the uncrunched version and crunch it during load, but I don’t know how to load it into the Explore 100. Any tips would be greatly appreciated. (A. V., Ferntree Gully, Vic) • We haven’t been able to recreate this problem, but we think it may be a glitch with the XMODEM protocol that is used with TeraTerm. During the Australia’s electronics magazine development of this project, we used MMEdit to upload the BASIC program, so it should work using that method. It appears to use a different protocol. With MMEdit, you need to select CONNECT → NEW to set up a serial port, then the port will appear in the CONNECT menu and must be selected. After this, auto-crunch on load can be selected from the ADVANCED menu. Load the BASIC program and run it by using the button at top right that looks like a running man. MMEdit behaves differently to many other programs, so it can be a bit tricky to use. You can download the manual from www.users.on.net/~tassyjim/ stuff/MMedit.pdf We have another possible solution for you, which would allow you to continue using TeraTerm. We have split the BASIC file into a library CFUNCTION and the main BASIC code. Using TeraTerma and XMODEM RECEIVE, send the CFUNCTION.BAS file to the Explore 100, then issue the command LIBRARY SAVE. This moves the CFUNCTION out of the BASIC program space. Then send the “DAB FM AM Radio Firmware2.bas” file via XMODEM RECEIVE. It is crunched and smaller than 64727 bytes. Assuming that this transfer works, try running the program. More queries on uploading BASIC code I assembled the DAB+/FM/AM Radio project using a pre-programmed Explore 100 and a pre-loaded radio board, then uploaded and ran the radio BASIC program using MMedit and a USB-serial interface. It seems that something has gone wrong; while I get messages in the MMChat console that indicate the radio board is working (“booting radio… booted” etc), the BASIC code halts with the error “Invalid font number #14”. This makes me think that the BASIC code has not uploaded correctly. The display initially presents the four main buttons which do not respond to pressing; however, by touching different areas on the screen, most of the main screen finally appears. The radio does not activate in any of the three modes, of which AM is the first highlighted. Where to from here? (B. F., Mount Eliza, Vic) • While most people who have built the DAB+/FM/AM Radio got it up and August 2020  107 running, we’ve had about three people including yourself write in to say that the BASIC code will not run correctly. In the other cases, we’ve determined that this was because the upload was truncated (the number of bytes uploaded was smaller than the size of the BASIC code). The problem is that we have never been able to reproduce this on our own Explore 100; using MMEdit (as you have done), the upload is always successful. We haven’t been able to identify the common factor with people who have had this problem. So our recommendation is for you to get a PIC programmer (even the Snap programmer is sufficient) and load our supplied HEX file directly into the flash memory of the PIC. That way, you don’t have to upload the BASIC code as it is already loaded in the HEX file. No response from Explore 100 chip I am building your DAB+/FM/AM Radio which incorporates the Explore 100 module (September-October 2016; siliconchip.com.au/Series/304). Firstly, I have built two Explore 100s, but I can’t get either of them to work. I have gone through the faultfinding procedure in the articles and all appears OK. The current drain is 110mA. I’m using TeraTerm V4.88 Terminal Emulator and a serial converter. Hitting enter on the PC doesn’t give me the Micromite command prompt. Looking at the Tx pin with a CRO, when the Reset button is pressed, I see a DC change but nothing else. The chips are supposed to be preprogrammed. On the emulator, I see a flashing block prompt which stops flashing when I press Reset. What can be wrong? Also, when I plug in the assembled radio board and power the whole thing up, the current draw changes very little. I ran an infrared thermometer over the radio board to check for hot spots. There were none, just the opposite. Not even the radio chip, IC1 was heating up; I thought it should be getting warm, seeing there is so much crammed into it. I checked to see if the crystal oscillator was working and it wasn’t; there was nothing across the 12pF capacitors, yet there was on the Explore 100 board – about 2V peak-to-peak. I can measure 1.8V and 3.3V in vari108  Silicon Chip ous places around radio chip IC1. So it looks like there is a fault in the radio section. But most of those components came pre-soldered to the board, so why isn’t it working? (T. V., Burpengary, Qld) • Try pressing Ctrl-C in TeraTerm to get the MMBasic prompt; this will also interrupt any running commands. You should see any typed text echoed back in any case. Have you set the terminal baud rate to 38,400? The terminal will not work if the baud rate is not configured correctly. Have you tried connecting to the Explore 100 using the native USB serial port? This will at least narrow down whether the processor is ‘alive’. We suspect that the DC change you are seeing on reset is being detected as a ‘break’ condition by the Terminal, which might be why the flashing stops. It’s normal for the radio chip, IC1, to be drawing no power and for its crystal oscillator to be shut down until it is commanded to start up by the Explore 100. Clearly, that is not happening as you have not been able to load the BASIC firmware yet, given that you are having trouble accessing its console. Even if the Explore 100 is programmed, if the radio chip is not operating, most likely the fault will be in the connections between the two boards, rather than a problem with the radio chip itself. The radio board will do very little without the Explore 100 driving it. First, make sure that the Explore 100 is working and MMBasic is responding. Then ensure that the radio software is loaded and running on the Explore 100. If you purchased it from us, the radio firmware was pre-loaded on the flash chip. So as long as the interface (the dual-row headers) between the two boards is good, you can then expect radio chip IC1 to start drawing current and doing something. Getting CSV data from Arduino Seismograph Hello, I built your Arduino-based 3-axis Seismograph (April 2018; siliconchip.com.au/Article/11030). I have never worked with this chip (the MPU6050) before, nor WAV files. I’ve been able to get basic X, Y & Z information out of the chip, and your project works as it was intended to. I’d like to modify your project to Australia’s electronics magazine write this data to a CSV file on the SD card, along with the date and time from the real-time clock. I can then visualise it in all axes using the R programming language, which is more useful for me. The code for your April 2018 sketch is impressive (and works fine on a Nano, by the way) but it’s way over my head. Can you help? I need to be able to match the data within a few seconds to the microphone I’m using on another platform. I just need to get the data as numbers and write it into a CSV file. (M. M., via email) • The Seismograph delivers CSVcompatible data to the serial port, although this may not include timestamps. To change the format of the data saved to the card, you will need to change the file.write() command in the main loop. Instead of writing WAV audio data, this can be replaced by something like the data that is printed to the Serial port a few lines later. The dosync() and openfile() functions will also need to be changed. The name of the file created should be changed from having a .wav extension to .csv, and the line that prints the header should instead print an appropriate CSV header. The sync function will probably work if it is changed to do nothing; all it does is to update the WAV headers with the number of data bytes (which is not necessary for CSV files). The CSV format requires significantly more data to be written than WAV (this is one of the reasons we chose WAV), so you may find the Arduino struggles to keep up. If so, lower the sampling rate. Sync signal from Vintage TV RF Modulator I’ve constructed the Analog AV Modulator for Vintage TV Sets (March 2018; siliconchip.com.au/ Article/11007), and it’s working perfectly. It is a most useful device for helping me maintain my several 1956 Astor SJ receivers. It does indeed provide a true 1950s TV signal; a perfect solution. I’d like to take an output from the modulator to provide a composite sync signal to a TV waveform monitor. The required signal should have only sync/blanking pulses, not luminance or chrominance signals. Looking at the circuit on page 84, it appears that pin 1 siliconchip.com.au (the B1 input) of IC3 is being fed with the composite sync pulses I’m seeking, but I’m not entirely certain. I’m hoping either yourself or the article’s author, Ian Robertson, can assist me with advice on the following: Is there a point in the circuit at which all sync pulses (excluding luma and chroma signals) are aggregated? If so, what form would you suggest for a buffered take-off circuit with a 75W output impedance for connecting to an external device? (G. D., Bunyip, Vic.) • Ian Robertson replies: pin 1 of IC2 (the LM1881 sync separator), labelled CSout, delivers composite sync at TTL levels. It is not connected in the current design. Unfortunately, this output is not capable of driving a back-terminated load directly. You would need to add an emitter-follower, using a general-purpose NPN transistor such as a BC547. The collector of this transistor goes to +5V (Pin 8 of IC2), and the base goes to pin 1. To get approximately 1V into a 75W load you need a voltage divider of two 150W resistors, connected in series from the emitter of the BC547 to ground. The composite sync output comes from the junction of the two resistors. There will be a small DC offset, but that shouldn’t worry a monitor. Class-D amplifier is refusing to start One of my boys for the HSC has built the CLASSiC-D amplifier in mono form (November-December 2012; siliconchip.com.au/Series/17), powering it from the Ultra-LD Mk.3 power supply. We have a 40-0-40V toroidal transformer with 3.31A available. When I power up an amp, I always put a current limiting incandescent bulb (65R) in series with the mains supply as a safety limiter. This drops the supply to around 100V (measured) and the amplifier powers up and functions perfectly with a good audio output. The problem occurs when the current-limiting light bulb is taken out and full current is supplied. Then the amp does not progress out of red LED protect mode and into run blue mode. I measured the voltage out of the power supply board, and it had risen to ±60V, giving a head of 120V. siliconchip.com.au As the setup is a single amplifier module in mono format, the load is perhaps not as demanding as anticipated. I guess the current-limiting feature may be holding the amplifier in protect mode. At 120V, some of the caps and perhaps other parts will be nearing their tolerances as well. The student rather quickly suggested that we could hard-wire the light bulb into the amplifier and a special pulsating blue light could accompany his doof doof music! Ten points for initiative. Can we modify the amplifier in some way as an alternative? (D. K., Warriewood, NSW) • The problem is most probably the overvoltage protection that shuts down the amplifier at around ±60V (120V total). That’s via zener diode ZD5 and transistor Q5. The solution would be to lower the voltage of the amplifier supply. For the toroidal transformer, you can wind on two extra windings with a few turns that reduce the output of each of the two secondary windings. The windings need to be wound in the opposite direction to the original and then connected in series with the secondary using a similar or larger gauge wire. Before connecting again to the amplifier power supply, check that each secondary winding voltage has reduced to around 38VAC. If the voltage is more than the original, the added winding needs to be reversed. To find out how many turns are required, wind on say 10 turns and measure the voltage. That will give an estimate of how many volts per turn by dividing the measured voltage by 10. You will need to wind on enough turns for a reduction of about 2V AC on each secondary. Another alternative (that is not ideal) is to change the over-voltage threshold to be higher. To do this, add a diode (1N4004) in series with the zener (anode to anode). Add another diode in series if this is insufficient. sible to replace with TLC549? Or can you suggest another alternative part? (V. V., via email) • Yes, the TLC549 is a suitable substitute in this design. Identifying unknown SMD ICs I’m trying to fix a broken Bosch 30V 500mA battery charger for a cordless vacuum cleaner. I have no circuit diagram, and many of the parts are hard to identify. The feedback circuit on the low voltage side uses a 6-pin surfacemount IC marked OD=28X, instead of a TL431. Can anyone help me to identify this part? I am also trying to find some information on a 6-pin surface mount IC marked TV6PE. It seems to be a protective device. Based on how it is wired, I believe it to be a comparator with a built-in voltage reference. (R. S., Fig Tree Pocket, Qld) • Identifying SMD ICs from their markings can be frustrating. There are websites to help do this, but many ICs often share the same code (usually two or three letters), and it is usually hard to read the code. Sometimes there’s more than one sequence of letters, and you don’t know which one to search by. The best website we’ve found for doing this is https://alltransistors.com/ smd-search.php We think the first device you mention may be included in this list: alltransistors.com/smd-search. php?search=0D Note that we are searching for 0D and not OD, as SMD codes usually do not start with the letter O because they would be almost indistinguishable from a zero. There are a few six-pin devices on that list, so if you check their pinouts, hopefully you’ll find one that matches. The TV6PE device is a tricky one. TV6 does come up with a few possible matches in six-pin packages, but Alternative to TLC548 ADC chip I would like to build your Charger for Deep Cycle 12V Batteries (November & December 2004; siliconchip. com.au/Series/102). But one part is very difficult to buy anywhere, the TLC548 analog-to-digital converter (it has been discontinued). Is it posAustralia’s electronics magazine August 2020  109 none are comparators. You may have to search a vendor like Digi-key or Mouser that has a parametric search for components of your estimated type in that package, then check each data sheet until you find one with a matching pinout. X2 capacitor failure is too common I have repaired several small appliances which use a mains-rated capacitor to drop the voltage down to a low level for the circuit. These include a wireless doorbell, night light, LED globes etc. The mains-rated series capacitor slowly degrades, and the voltage supplied to the circuit is reduced until it stops working. Most would simply be discarded when they stop working and end up in landfill simply because of the failure of one component. Would an X1 capacitor be longer lasting than the recommended X2 type? X2 capacitors are designed to fail short circuit, which would destroy the device before the circuit breaker tripped. Would it be better to use a Y2 capacitor (designed to fail open-circuit) in these devices? (J. B., Mirani, Qld) • X2 capacitors are not designed to fail short-circuit. They are allowed to fail short-circuit, but in practice, as you’ve noticed, they tend to lose capacitance if abused and eventually just go open-circuit. X1 capacitors might be slightly more reliable given their higher voltage rating. But a good-quality X2 capacitor would probably be just as effective. It’s true that the X2 series capacitors supplied in mains-powered devices fail too often. Our experience is that if you replace them with a good quality X2 capacitor, they usually last a long time. The X2 capacitor typically has a series resistor for inrush current limiting that would likely fuse in the case where the capacitor does go short circuit (or the PCB track would). What are low-K ceramic capacitors I am restoring my Playmaster 101 valve amplifier, as described in Radio & Hobbies, August 1962. I built the amplifier back in 1966. All has gone well, but I’m confused about the feedback capacitors coupling the output trans110  Silicon Chip former secondary back to the cathode of the first valve. They are 220pF plastic or ceramic types and have been specified as being “not High K”. Originally I used polyester; I have searched the web for “low K capacitor” and come up blank. What type of capacitor would you recommend? (P. C., Balgal Beach, Qld) • Low-K (C0G, NP0 or similar) ceramic capacitors are close-tolerance, highstability ceramic capacitors for use in tuned circuits where low losses, high linearity or excellent temperature stability are required. High-K capacitors tend to have poor tolerances and high voltage and temperature coefficients, and are generally used for supply bypassing where the precise value is not critical. Modern capacitors can be classified according to the characteristics and properties of their insulating dielectric. Low-loss, high-stability capacitors include mica, low-K ceramic, polystyrene and polypropylene. Medium-loss, medium-stability capacitors include paper, polyester, and mediumK ceramics like X7R, X6S and X5R. For the 220pF low-K capacitors, you could safely use NP0/C0G ceramic, mica, polystyrene or polypropylene. Sourcing ultrasonic piezo speakers I recently came across an article featured in an old copy of Electronics Australia, November 1985, on page 40: “Pest Off” by Colin Dawson. I decided that I want to build it to try to reduce the number of rodents and pests around our property. The components are readily available from Jaycar, including a Piezo Tweeter, Cat CT1930 (RSN1005). But this does not meet the required frequency that the Pest Off delivers, 2364kHz. As no part number is provided in the article, I am hoping you can tell me whether or not this piezo tweeter would work in this project with a few modifications. Or can you suggest another I can use? (K. W., Hamilton, NZ) • The RSN1005 is the equivalent to the KSN1005 originally specified. So the Jaycar part is suitable. The output frequency from these piezo speakers does extend beyond 20kHz. Manufacturers do not tend to show the response above 20kHz, because this is the upper-most range of human hearing. Australia’s electronics magazine Some mains adaptors may not meet standards I bought a QNAP NAS (networkattached storage device) recently, and it came with a Delta DPS-65VB 12V/65W power adaptor. The NAS crashed when there was a very brief mains glitch that caused no malfunction of anything else of mine. That got me checking things, and it seems that the problem was caused by the 8ms sag time and 750ms recovery time of the power adaptor when under load. Not good, given our occasionally flaky mains on the Central Coast! There was no bad weather at the time. Anyway, the power adaptor is sealed and has a 3-pin IEC connector which suggests to me that it is Class I. But when I checked between the Earth pin and the 0V/sleeve connection on the 12V output plug, I determined that there are two diodes in inverse parallel and a 100nF capacitor in parallel between them. I know that sort of configuration used to appear years ago in various types of equipment, but is it actually legal? (J. R., Woy Woy, NSW) • We have never seen diodes between mains Earth and the 0V output of a DC supply. Such a device is probably not safe, as the diodes could fail open-circuit under a fault condition, possibly leaving the output at mains potential. We have seen many switchmode supplies with a floating DC output but a three-pin plug with a mains Earth connection. This is odd as they have plastic cases, but cannot qualify as Class II or ‘double insulated’ as that class has the requirement of no Earth connection. (However, there are valid reasons to use an Earth connection with such an insulated device, such as RFI/EMI suppression.) Possibly, those supplies have an internal Earthed metal chassis and therefore may qualify as Class I, despite being in a plastic case and having a floating output. This type of supply is commonly sold in Australian retail outlets, eg, with new laptop or notebook computers. One would therefore assume that they meet Australian/New Zealand standards; however, we are not 100% sure. If you are concerned that the device might not meet standards, it would be best to contact the Electrical continued on page 112 siliconchip.com.au MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP KIT ASSEMBLY & REPAIR FOR SALE PCB PRODUCTION VINTAGE RADIO REPAIRS: electrical mechanical fitter with 36 years ex­ perience and extensive knowledge of valve and transistor radios. Professional and reliable repairs. All workmanship guaranteed. $17 inspection fee plus charges for parts and labour as required. Labour fees $38 p/h. Pensioner discounts available on application. Contact Alan, VK2FALW on 0425 122 415 or email bigalradioshack<at>gmail. com GREAT VALUE PARTS and more are found in the Tronixlabs ebay store via tronixlabs.com.au - for enquiries or support please email support<at> tronixlabs.com PCB MANUFACTURE: single to multi­ layer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au DAVE THOMPSON (the Serviceman from S ILICON C HIP) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, NZ but service available Australia/NZ wide. Email dave<at>davethompson.co.nz KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com LEDs, BRAND NAME and generic LEDs. Heatsinks, fans, LED drivers, power supplies, LED ribbon, kits, components, hardware, EL wire. www.ledsales.com.au ASSORTED BOOKS FOR $5 EACH Selling assorted books on electronics and other related subjects like audio, video, programming etc. Many of them are in poor condition. Some of the books may have already been sold, but most are still available. Bulk discount available; post or pickup. All books can be viewed at: siliconchip.com.au/link/ aawx When referring to a book you might be interested in, it helps to state the number at the bottom of the photo. Email for a postage quote: Silicon Chip silicon<at>siliconchip.com.au ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus $1.20 for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone Glyn (02) 9939 3295 or 0431 792 293. WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable. siliconchip.com.au Australia’s electronics magazine August 2020  111 Coming up in Silicon Chip 5G Networks Dr David Maddison describes the benefits and challenges of this new fifthgeneration mobile communications technology. Based on how it’s being described, it’s as if 5G will be the best thing since sliced bread. But will it? Read our article and decide for yourself. High Power Ultrasonic Cleaner Advertising Index Altronics...............................75-82 Ampec Technologies................. 23 Dave Thompson...................... 111 Digi-Key Electronics.................... 3 Our new Ultrasonic Cleaner can deliver around 40W into a cleaning bath, ideal for cleaning larger parts in about four litres of water or solvent. It has an adjustable power level from 10-100%, a timer from 20 seconds to 90 minutes, over-current protection and runs from 12V, either from a battery or mains adaptor. OBD2 & Forscan – advanced automotive diagnostics Emona Instruments................. IBC Hare & Forbes....................... OBC Jaycar............................ IFC,53-60 You’ve probably seen the dirty cheap (in some cases, less than $10) Bluetooth car diagnostic dongles online. You may even have one or two. But dongles ain’t dongles; for just a bit more money, you can get one that can do more than just give you ‘trouble codes’. With the right (low-cost) gear, you can interrogate the dozens of electronic modules in modern vehicles and even reprogram them! Keith Rippon Kit Assembly...... 111 Satellite navigation – in space? And on the Moon? Microchip Technology.................. 5 Yes, it is possible (if tricky) to pick up navigation signals well above the orbits of the satellite constellations and even as far away as the Moon. NASA even has plans to launch navigation and communication satellites in orbit around the Moon too! Ocean Controls........................... 9 The History of Aussie GPOs Silicon Chip Binders............... 104 We use them every day but did you ever wonder where our power point design came from? Why is it different from the American, European and UK plugs? Why do some countries use similar sockets but in different orientations? This article describes all of that, as well as the history of Australian mains voltages and frequencies, why our sockets always have switches, and more besides. Note: these features are planned or are in preparation and should appear within the next few issues of Silicon Chip. The September 2020 issue is due on sale in newsagents by Thursday, August 27th. Expect postal delivery of subscription copies in Australia between August 25th and September 11th. LD Electronics......................... 111 LEDsales................................. 111 RayMing PCB & Assembly.......... 4 Silicon Chip Job....................... 37 Silicon Chip Shop.................... 87 The Loudspeaker Kit.com........... 7 Tronixlabs................................ 111 Vintage Radio Repairs............ 111 Wagner Electronics................... 50 Notes & Errata DIY Reflow Oven, April & May 2020: on page 32 of the April issue, in the parts list, the male/female chassis-mount IEC power connector is described as a 15A type, but a 10A type is needed. The catalog code given (Altronics P8330A) is correct, ie, it is the 10A type. Equipment Safety System team at www.eess.gov.au/about/contact-us/ Hazards of old mains wiring I am wondering if anyone has ever done a study of the decomposition of original latex coatings on ‘ancient’ wiring and the rotting of fabric bindings etc. (S. B., Bundamba, Qld) • See the Publisher’s Letter in the 112  Silicon Chip November 1995 issue (“Have you had your house wiring checked?”) and August 2008 (“Electrical wiring in older houses can be dangerous”). As Leo said in his 2008 column, “… if your home is 50 years old or more, the wiring is almost certain to be unsafe or in need of upgrading.” It’s amazing that fabric- and rubbercoated mains wires still are working, in some cases over 100 years after they were installed. But they’re bound to Australia’s electronics magazine fail sooner or later, and possibly start a fire, so even if there are no apparent problems, it’s still best to replace it all with modern vinyl-insulated mains wiring. Circuit breakers should be upgraded at the same time, to RCD versions. The new wiring and breakers should also allow you to upgrade each circuit to deliver more total current and power, reducing or eliminating nuisance tripping. SC siliconchip.com.au “Rigol Offer Australia’s Best Value Test Instruments” Oscilloscopes NEW 200MHz $649! New Product! Ex GST RIGOL DS-1000E Series RIGOL DS-1000Z/E - FREE OPTIONS RIGOL MSO-5000 Series 450MHz & 100MHz, 2 Ch 41GS/s Real Time Sampling 4USB Device, USB Host & PictBridge 450MHz to 100MHz, 4 Ch; 200MHz, 2CH 41GS/s Real Time Sampling 424Mpts Standard Memory Depth 470MHz to 350MHz, 2 Ch & 4Ch 48GS/s Real Time Sampling 4Up to 200Mpts Memory Depth FROM $ 429 FROM $ ex GST 649 FROM $ ex GST 1,569 ex GST Multimeters Function/Arbitrary Function Generators New Product! RIGOL DG-800 Series RIGOL DG-1000Z Series RIGOL DM-3058E 410MHz to 35MHz 41 & 2 Output Channels 416Bit, 125MS/s, 2M Memory Depth 425MHz, 30MHz & 60MHz 42 Output Channels 4160 In-Built Waveforms 45 1/2 Digit 49 Functions 4USB & RS232 FROM $ 479 FROM $ ex GST Power Supplies 725 ONLY $ ex GST Spectrum Analysers 789 ex GST Real-Time Analysers New Product! RIGOL DP-832 RIGOL DSA Series RIGOL RSA Series 4Triple Output 30V/3A & 5V/3A 4Large 3.5 inch TFT Display 4USB Device, USB Host, LAN & RS232 4500MHz to 7.5GHz 4RBW settable down to 10 Hz 4Optional Tracking Generator 41.5GHz to 6.5GHz 4Modes: Real Time, Swept, VSA & EMI 4Optional Tracking Generator ONLY $ 749 FROM $ ex GST 1,321 FROM $ ex GST 3,210 ex GST Buy on-line at www.emona.com.au/rigol Sydney Tel 02 9519 3933 Fax 02 9550 1378 Melbourne Tel 03 9889 0427 Fax 03 9889 0715 email testinst<at>emona.com.au Brisbane Tel 07 3392 7170 Fax 07 3848 9046 Adelaide Tel 08 8363 5733 Fax 08 83635799 Perth Tel 08 9361 4200 Fax 08 9361 4300 web www.emona.com.au EMONA