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SEPTEMBER 2020 ISSN 1030-2662 09 The VERY BEST DIY Projects! 9 771030 266001 $995* NZ $1290 INC GST INC GST The Night Keeper Lighthouse It’s finally here! ‘Shirt-pocket’ The High Power Audio Oscillator Ultrasonic Cleaner HOW WORKS THE HISTORY OF THE AUSTRALIAN POWER OUTLET awesome projects by On sale 24 August 2020 to 23 September 2020 Our very own specialists have developed this fun and challenging Arduino® compatible project to keep you entertained this month with special prices exclusive to Club Members. BUILD YOUR OWN: Mailbox Notifier ‘You’ve Got Mail!’ Just like your e-mail inbox, your home mailbox now can alert you straight to your phone when letters arrived. A simple switch fits behind the door of your mailbox ready to trigger the ESP8266. Then, using the popular and simple IFTTT service, get an email or push notification straight to your phone. This all fits inside a simple HB enclosure and powered by 3 x AA batteries. SKILL LEVEL: Intermediate TOOLS REQUIRED: Soldering Iron WHAT YOU NEED: 1 x Wi-Fi Mini ESP8266 Main Board 1 x Light Duty Silicone Hook Up Wire Handy Pack 1 x SPDT 250V 5A Standard Micro Switch with Lever 1 x Jiffy Box - Black - 83 x 54 x 31mm 1 x AA Alkaline Batteries Pk4 1 x 3AA Side by Side Flat Battery Holder $24.95 $11.95 $3.75 $3.45 $3.25 $2.25 XC3802 WH3036 SM1039 HB6015 SB2425 PH9274 www.jaycar.com.au/mailbox-notifier See other projects at www.jaycar.com.au/arduino KIT VALUED AT $49.60 A BIG SHOUT OUT TO... BEN from Auckland, NZ who received a $100 gift card for sharing his brilliant project idea! Upgrade Your Project 148(L) X 74(W)MM ONLY 9 $ 3995 $ SAVE 15% SEE STEP-BY-STEP INSTRUCTIONS AT: ONLY CLUB OFFER BUNDLE DEAL 95 9 $ REPLACE BATTERY POWER WITH SOLAR Wire up a few of these Hobby Solar Modules in a series, to power the ESP replacing the batteries. ZM9012 RECORD A MESSAGE FOR THE POSTMAN Use this Record and Playback Module to give the postman a simple “thank you” message once he delivers the mail. XC4605 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. * ADD A REMOTE LOCKING MECHANISM ONLY 3995 $ 95 Use our Linear Servo Motor and make a locking mechanism to lock / unlock your mailbox remotely. YM2748 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.9 September 2020 SILICON CHIP www.siliconchip.com.au Features & Reviews 12 5G Mobile Networks 5G is the newest iteration in a long line of cellular network standards. Apart from the often-touted (large) speed and bandwidth increase, we look at what else is new and how it actually works – by Dr David Maddison 32 The History of the Australian General Purpose Outlet The ubiquitous three-pin power plug and socket as used in Australia, New Zealand and the South Pacific is a simple but effective design. In this article we look at how the design came about and where it came from – by John Hunter 72 Advanced Vehicle Diagnostics with OBD2 The OBD2 standard lets you easily troubleshoot the increasingly complex vehicles that are on the road today. This article details the various OBD2 dongles that are available and how to use them – by Nenad Stojadonovic It seems like nearly everyone’s been talking about 5G recently. So we thought we’d join in, by describing how it works and where it differs from its predecessors – Page 12 Constructional Projects 24 High Power Ultrasonic Cleaner This easy-to-build Ultrasonic Cleaner is ideal for cleaning large items like mechanical parts and fabrics. All you need is a suitable ‘bath’ made from stainless steel, aluminium or plastic and away you go – by John Clarke 42 A Shirt-pocket Sized Audio DDS Oscillator This compact little audio oscillator provides you with an accurate sinewave wherever you need it. It displays the output frequency on a 64x32 pixel OLED screen and is housed in a 3D-printed case – by Andrew Woodfield 68 The Night Keeper Lighthouse Finally, it’s actually here! Our High Power Ultrasonic Cleaner is ready just in time for spring – Page 24 This portable oscillator generates a sinewave from 1Hz all the way up to 9999Hz with 0.002% accuracy – Page 42 A perfect project for beginners. This small PCB uses fewer than 10 components and serves as a good introduction to basic electronics. It can also double as a night light for young kids once they’ve built it – by Andrew Woodfield 86 USB SuperCodec – part two This month we cover all the details on the circuit design of the SuperCodec. Since the SuperCodec can also be used as a signal analysis system, in addition to its recording and playback functions, there is a lot to explain in terms of how each section of the project works – by Phil Prosser Your Favourite Columns 49 Circuit Notebook As a nice, simple project, this lighthouse serves as a great introduction to electronics, in part due to how few components it uses – Page 68 (1) Low-power flashing LED thermometer (2) Adjustable power supply using a fixed voltage switchmode regulator (3) Giant 1024-pixel RGB LED clock 61 Serviceman’s Log Troubleshooting temperamental tea – by Dave Thompson 96 Vintage Radio US Marine Corps TBY-8 squad radio – by Ian Batty Everything Else 2 Editorial Viewpoint 4 Mailbag – Your Feedback siliconchip.com.au 85 Product Showcase 104 Silicon Chip Online Shop 106 Ask SILICON CHIP 111 Market Centre Australia’s magazine 112 Noteselectronics and Errata 112 Advertising Index Cover Image: www.jbsa.mil/News/Photos/igphoto/2002310276/ OBD2 dongles are great tools to help you maintain (or even modify) your vehicle. Here’s how to choose one and how to use it – Page 72 September 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 5G and the stupid Broadband Tax When I first heard about the upcoming 5G mobile technology and its touted high data speeds, my first thought was: isn’t 4G fast enough? 4G is capable of data delivery at close to 1Gbps, and that seems more than fast enough for most users’ mobile data needs. You could fill up the flash memory of a 256GB phone in less than half an hour at that speed. But the more I thought about it, the more I realised that it isn’t the maximum throughput that matters, it’s the aggregate bandwidth in a given area. It might be possible to get 1Gbps download if you’re the only person in your suburb who’s awake, but when thousands of other people are all trying to stream videos at the same time, each only gets a small slice of the pie. This became especially apparent to me when my NBN connection was down (as detailed in my June rant…). Many people were working from home due to COVID-19, so 4G data speeds in my area were miserable during the day. I was lucky to get more than 1Mbps most of the time. So having more spectrum space and more mobile ‘towers’ servicing smaller cells starts making a lot more sense. There are more and bigger ‘pies’, so even if the maximum size of a slice is similar, users can still get larger servings when demand is high. It still seems like it will be a vast job to roll out 5G across all urban areas in Australia, given how many millions of microcells that would require, but at least the rationale for doing so makes a certain amount of sense. The existing NBN infrastructure presumably will help with that. That brings me to the stupidity that is the recently-passed Broadband Tax (its implementation now delayed until January 2021). As David Maddison points out in his article starting on page 12, that doesn’t apply to 5G connections, only fixed line internet. But you have to wonder if that might change if lots of people ditch their NBN connections and hop onto 5G instead. Can you think of any other area in which a monopoly is funded by taxes placed on its competitors? I can’t. That the government has to funnel money to the NBN from private businesses to keep it going shows how poorly it was conceived and executed. Despite all this, I can’t imagine mobile broadband taking over from fixedline services. It would be a colossal waste of spectrum. Even if mobile data can burst to higher speeds than the NBN, the aggregate bandwidth available is much more limited. Perhaps the ideal would be a fixed-line connection for streaming video and so on, plus wireless technology used in parallel to speed up large downloads. Altronics catalog delay Astute readers may be aware that Altronics publishes a new catalog every 18 months and, as the last one was bundled with our March 2019 issue, you might have expected to get a copy of the new catalog with your copy of the September 2020 issue. However, COVID-19 has caused delays in sourcing products and, as a result, Altronics has decided to delay their new catalog. So if you live in Australia, you can expect to receive a copy of the next Altronics catalog with your copy of the March 2021 issue of Silicon Chip magazine. In the meantime, please see their website at www.altronics.com.au to see what they have on offer. Nicholas Vinen 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Australia’s electronics magazine siliconchip.com.au siliconchip.com.au Australia’s electronics magazine September 2020  3 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”. Nostalgic for old issues on USB under $4500 with monitor and key- ror and seeking to buy a replacement My USB drive with Silicon Chip board! That’s around $10,000 in to- part. They said they do not supply day’s dollars. Also, we just purchased parts for these machines, and that the PDFs arrived today – very professional a 16TB hard disk for under $800. best thing to do was to find an engineer and good quality; well done! I jumped into the first issue and did That’s an increase in megabytes-per- to manufacture a new part. Not only was I annoyed that this vithat bring back some memories... and dollar of more than 800,000 times, RAYMING even ignoring inflation! tal part was plastic and hence broke, also the realisation of how good we TECHNOLOGY but I was doubly annoyed when I have it nowadays, not only with the PCB Manufacturing and PCB Assembly Services Why use metal when found out that a replacement part quality of the magazine, Fuyong but the masBao'an Shenzhen China was unavailable. I was able to put two sive reduction in the price of goods. plastic is cheaper? 0086-0755-27348087 I agree with the sentiments of Dave stainless steel worm clamps around I’m glad the ads were kept in, as it Sales<at>raypcb.com shows this dramatically, especially Thompson completely in his “Well- the part to get it working. I’ll avoid when one considers the www.raypcb.com value of the designed thoughtlessness” Service- using it on 6mm rod, but maybe now Aussie dollar in those times compared man column (July 2020; siliconchip. it is strong enough to cope. com.au/Article/14502). I have worked Simon Miller, to the earned salary of the day. via email. I remember buying my first hard in electronic support at a university for disk, a full-height 5.25in 20MB unit nearly 40 years in both construction/ that I could squeeze to 30MB by us- design and repair and never cease to Hydrogen storage breakthrough I think you should consider an artiing an RLL controller for $800. Soon be amazed at the stupidity and unafter that, I bought a 387 co-processor helpfulness of many of the equipment cle on hydrogen storage developments MAU for almost the same price as a manufacturers and suppliers whose at UNSW. It was in the Herald yesterday, and it’s going to be a real gamefull 386 PC. We have become very equipment I have to repair. One example is a metal roller I re- changer for the world – let’s hope it conditioned nowadays to cheap electronics, and the throw-away attitude cently purchased. It looked sturdy; I stays Australian. You can see the aradmit that I used it slightly past its ticle at siliconchip.com.au/link/ab46 worries me greatly. Lee Bourgeois, A big thank you, and all the best to limit, rolling a piece of 6mm rod – I later realised that it is rated to 5mm. Mittagong, NSW. the Silicon Chip team. The central piece holding the rollers William Sherwood, is made of plastic, which I had not no- Early digital cartography in Australia Stirling, WA. In reference to your March 2020 Response: to highlight your point, ticed or imagined. It was black, like all there’s a review of a 16MHz 286-based the other metal parts. To my surprise, article on Digital Cartography (siliconchip.com.au/Article/12577), computer starting on page 16 of the this plastic cracked. I rang the supplier, admitting my er- I saw an interesting vehicle at the May 1989 issue. As tested, it was just 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 “Setting the standard for Quality & Value” ’ CHOICE! 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Keep up the good work. Chris Robertson, Sydney, NSW. I would like to express my admiration for Ken Kranz’s fine article on his restoration of a Velco 1937 radio (August 2020; siliconchip.com.au/ Article/14544). There are probably many old sets like his, sitting on the “too hard” shelf, that will not be seen as worth even listing when a collection is disposed of. I was especially interested to see his rebuilding of the IF transformer. I recently had an Astor Mickey Grand with a butchered first IFT – someone had simply “splatted” solder on to the primary winding (probably) in an attempt to repair an open circuit. The Mickey’s IF transformer coil sets and trimmers, while tuning to 455kHz, looked identical in construction to the Velco’s. My solution was to remove the damaged winding until I found a good connection point. I then needed to parallel the existing trimmer with around 68pF to make up for the loss of winding inductance. While the set worked OK, I recognise that the modified transformer probably has a different response from that which the manufacturer intended. I will certainly apply Ken’s fix if I ever see a similar problem. Ian Batty, Rosebud, Vic. been built, and they wanted a data line to the east coast of the USA from Alice Springs. The route was from Alice Springs to Adelaide, then Sydney, then via Compac Cable to San Francisco and across the USA. A single voice circuit was required on our 12-channel open wire system to Adelaide. As Adelaide was a major centre, its frequency stabilisation was done by a 4kHz master oscillator and its harmonics. At Alice Springs, we were using a remote end terminal with three crystal-controlled oscillators close to 500kHz to set the channel frequencies to send on the open wire system to Adelaide. When we were only using this for speech, we had no problems, but with the data line, we started to have problems with slight frequency drift. So we had Darwin send down their frequency meter. It arrived in a container about 1.5 x 1.5 x 0.5 metres and weighed what seemed like a ton. The air freight must have cost a bomb! It was a valve unit with Nixie tubes as a readout. Having adjusted the oscillators, we then had to send the unit back to Darwin. This had to be done several times as the frequency kept drifting. After a visit from a transmission inspector who was not very happy with the arrangements, next time when we asked for a frequency meter, we got a box about 400mm per side and weighing almost nothing. Inside was a new Racal frequency meter using all semiconductors; it was very different from the other unit and only about the size of a lunchbox. We eventually found out what was causing the drift. To make the adjustments, we had to take the rack covers off, then replace them afterwards and the temperature slowly increased until we took the covers off again. We ended up drilling holes in the rack cover so that we could make the adjustment with the covers on. That ended our problem. Brian Dunn, Old Noarlunga, SA. Frequency adjustments in the old days Comment on NBN hookup horrors An interesting radio restoration Reading the panel on direct-reading frequency meters on page 74 of the July 2020 issue (in the Tektronix Type 130 LC Meter article – siliconchip.com.au/ Series/346) jogged my memory. I was the officer in charge of the telephone exchange at Alice Springs in the late 1960s. The Pine Gap station had just 6 Silicon Chip Australia’s electronics magazine That was a horrifying piece you wrote for the June 2020 Editorial Viewpoint (siliconchip.com.au/Article/14454). I hope that NBNco and your ISP saw it and are contemplating their navels. I waited until February this year to get NBN in Willoughby. My ISP siliconchip.com.au is iiNet (now part of TPG), and they were excellent. My biggest concern was how to connect the phones; we have four phones on three levels. I eventually solved that problem by getting a Panasonic cordless with the base station plugged into the modem. It works very well. I have not had a single NBN dropout. The connection is FTTC and it works perfectly. So I have concluded that you used a dodgy ISP or the techs who served you were no good or somehow the fibre cable in your street is faulty. You may be interested in the following article in the Sydney Morning Herald titled “How to get the best deal on your NBN plan”: siliconchip.com. au/link/ab36 Response: I have no proof that any of my problems were the fault of my ISP. I am on FTTC (fibre to the curb) too, and it has been working well since they finally got all those problems sorted out. The initial connection problems were almost certainly the fault of the contractors who ran the fibre in our area. As for the unexpected disconnection, my ISP reps told me they did not request my line be disconnected, and they were mystified as to why it was done. Our property was divided into two about three years ago, and some companies get our address mixed up with our neighbours (even though they are clearly separate). I wonder if that had something to do with it. Still, that’s something that the NBN should be set up to deal with. Switchmode converter limitations I want a device that can generate a 12V output from a set of paralleled Li-ion cells at about 4A. I have experimented with switchmode supplies for almost 40 years, and I still have a lot of trouble with the magnetics, so I thought I would take the easy way out. I bought a “DC Voltage Boost Module with Display” from Jaycar, Cat XC4609. When I saw that the main inductor was rated at 4.7µH, I was sure that this module could not deliver what I wanted. With a 3V input, it was only able to supply 400mA at 12V; a little more with a 4V input. I then tried 12V in and 24V out. The power was limited by my power supply, and with 3A in, it delivered almost 1.5A out with greater than 90% 8 Silicon Chip efficiency. So, the device can provide a reasonable amount of power efficiently. It is just a pity that they do not supply a graph of Vin versus power output. Still, it will be useful to me as I sometimes need to run 24V motors from a 12V battery pack. I have experimented with the old MC34063A, but efficiencies of 60 to 70% do not impress me. I will keep looking for a solution. On a semi-related topic, I found some very useful Mosfets which can handle decent currents (1.5-4A) at 2040V that can be driven from a 3.3V device. The DMG2302UK(20V, 2.4A) is fully on with a gate-source voltage of just 1.2V, while the DMP3099L (30V, 4.5A) is entirely on at 3.0V. They both come in small SOT-23 SMD packages and cost just 22¢ each in quantities of 100 plus. George Ramsay, Holland Park, Qld. Comment: it is tough to design a switchmode circuit that will work well over a wide range of input and output voltages. It’s also challenging to boost low voltages at significant currents, as you want, although it can be done. Those universal modules typically give specifications under the best conditions, so at very low or high voltages or very high currents, their capabilities can be limited. Low-value inductors aren’t necessarily the problem; they can work well with very high switching frequencies, and this has the advantage that the inductors are small and can also have a very low DC resistance for lower losses. We think that you’re better off putting the Li-ion cells in series rather than trying to step up the voltage. Charging does become a bit more difficult then, as you need to balance the cells. Still, balance chargers are available at quite a modest cost, and we should be publishing a very capable standalone battery/cell balancer in the next few months. The MC34063 is very crude. We would not recommend it for new designs. It’s difficult to get it to operate in anything other than ‘bang-bang’ mode, which generally results in bad subharmonics. Yes, Mosfets with low gate drive voltages are very useful. Unfortunately, it’s tough to find good ones in throughhole packages these days. Virtually all of the newer Mosfets are SMD-only. Australia’s electronics magazine Diode sizes vary I am building the High-Performance Linear Power supply from the OctoberDecember 2019 issues (siliconchip. com.au/Series/339). The pad spacing and the hole diameters are wrong for the SB380 and 1N5404 3A diodes. To get these diodes to fit, you would need to drill out the holes, and also bend the leads on the diodes right next to the case, not a recognised good practice. Richard Blacksell, Bungendore, NSW. Response: you are right that the diode holes are too small, although we managed to fit them on our prototype (our samples must be on the small side!). We have produced a revised PCB with larger holes, and we will eventually replace our stock with the new ones. You can drill out the holes if necessary, just be sure to solder the diode leads top and bottom. It is also possible to surface-mount these diodes as they do not dissipate much except under fault conditions (which are hopefully brief). As for the hole spacing, that is odd since the part data sheets indicate a nominal body length of 7.6mm and the pads are 12.7mm apart. That should provide enough space to bend the leads without stressing them too much. Perhaps your diodes are at the upper limit of manufacturing tolerances in terms of size. To be safe, we’ve moved the pads further apart in the revised PCB design. Alternative fans for Bench Supply I am building your 45V 8A Linear Bench Power Supply as described in the October-December 2019 issues (siliconchip.com.au/Series/339). I have been unable to purchase the fans specified; they have been on backorder since November 2019 and Digi-Key do not know when they will come in. On looking at other possibilities, I came across an Altronics fan, Cat F0950. This is 80x80mm and rated at 53 CFM (1.7m3/hr), but it needs a 12V DC supply. So I added an extra winding to the toroidal power transformer to get a suitable supply. I found that by winding 22 turns around the core and using a bridge rectifier with a 1000µF 25V filter capacitor, I got close to 12V DC with the fans connected. There are some advantages to this approach: the fans are in stock locally, they are IP68-rated, and if one fan fails, the other will continue working 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 as they are connected in parallel rather than in series, as in the original design. I fitted a Pressphan insulating washer over the transformer (left over from making the shield, with a 50mm hole in it), to protect the outer winding layers of the transformer when it is clamped down. To add the windings, measure 5m of insulated cable or winding wire of at least 0.5mm diameter and wind it onto a bobbin made from sturdy cardboard. Tie one end to one of the secondary leads, then pass the bobbin through the centre of the toroidal transformer, keeping the wire tight. After 22 turns, tape the ends to the core and coat the wire with varnish to keep it in place. Make sure you don’t have any overlapping turns. John Chappell, Port Macquarie, NSW. Editor’s note: the specified fans (Cat P122256-ND) are back in stock at Digi-Key. Constructive comments on DAB+/FM/AM radio Thanks for publishing the DAB+ tuner project back in 2019 (January-March 2019; siliconchip.com.au/Series/330). During the COVID-19 lockdown, I was motivated to build the project as a hifi receiver to complement the Ultra-LD Mk.1, 2 & 3 amplifier and Studio Series Preamp that I’ve been thoroughly enjoying for fifteen or so years. I thought I’d let you know of some problems I ran into with the radio and my solutions, as I expect other readers may have encountered the same problems. Firstly, I’m from Canberra. One of the frequencies used for DAB+ in Canberra is 201.072MHz (block 8D), but the software default for the lowest Australian frequency in this project is set to 202.928 MHz. It was an easy fix to change this to 201.072 MHz by editing the crunched basic program at line 1970. The ACMA web site also lists a frequency of 199.36MHz at Mandurah, if you have readers near there. Secondly, my DAB+ radio failed to initialise correctly with the circuit constructed as-published. Although I had built it with the WM8804 S/PDIF transceiver, the software would fail to detect it and shortly afterwards, would generate errors with a “Waiting for CTS timeout” during the “Loading bootloader for Si4689” phase, with additional errors subsequently. 10 Silicon Chip While trying to diagnose the issue, I eventually discovered that the radio booted as expected if I gently touched the three 47W resistors adjacent to CON3 during poweron and boot. After the radio was up and running, I could remove my fingers and the radio continued to work asexpected thereafter. Over the course of an evening and morning debugging, I found (at different times) I could get the radio to boot when touching only one of the three resistors, and finally, touching just a multimeter probe carefully onto one of the three resistors. With the finger-touch and multimeter probe hint, I added three 3.3kW pull-up resistors between the 3.3V pin on CON8 and the DAB+ radio side of the three 47W resistors. The radio now boots perfectly every time and always recognises the WM8804 chip. I assumed the cause must have been a ringing issue on the SPI/Si4689 chip select lines but none-the-less, this fix was simple, and it worked. Thirdly, I and several online commenters have noticed unnerving loud cracks that occur every power-on boot, at every change of band, and when operating the DIG OUT feature. I found the critical hint when I traced the first crack sound to the “SETPIN 21, DOUT” statement. I realised the effect of pin 21 and this statement is to control the shutdown pin of the LM2663 regulator (REG4), and then recognised that shutting the regulator down cannot avoid causing a step change in any of the analog outputs (Line Out, Headphones or Speakers). I am uncertain of the original motivation for implementing this regulator shutdown and could not think of a good reason to keep the feature. Cutting the track connecting CON8 pin 35 and REG4 pin 1, and then grounding REG4 pin 1, resolved the loud cracks. I hope my experiences can help somebody else get their radio working. I should also comment that despite 35 years as an electronics engineer, some of this time spent working in factories doing SMD work, hand-soldering 0603 devices remains challenging for a DIY project. I appreciate that the components surrounding the Si4689 must be closely spaced for RF reasons. Still, perhaps one of the larger component series would improve the constructibility and maintainability of future projects involving SMD components. Stefan Keller-Tuberg, Fadden, ACT. Nicholas responds: thanks for your thoroughly-researched letter. We were not aware that blocks 8C and 8D were in use in Australia. Perhaps this is a recent development; last time we checked, the information we had was that all Australian DAB+ stations were on blocks 9A-9C. I also didn’t realise that REG4 was being shut down when changing band; that doesn’t make much sense. I designed much of the PCB but did not write the software. Perhaps there was a misunderstanding between Duraid and myself regarding the purpose of that signal. The original intention was to allow that regulator to be shut down when the radio was switched into standby mode. I realised that this would cause a transient but figured that it could be managed. I think the handling of REG4 shutdown could probably be fixed with some software changes. The fact that you needed to add pull-up resistors is interesting as we did not experience that problem with Australia’s electronics magazine siliconchip.com.au our prototype. Perhaps its operation is marginal. They shouldn’t do any harm. We almost always use SMD parts in 2012/0805 size or larger, but in this case, we couldn’t. I am somewhat used to working with 1608/0603 parts, so perhaps I am biased; if you think those are hard, try hand-soldering 1005/0402 parts. They are smaller than a grain of rice, and I have trouble seeing them clearly without magnification! Thanks for help with the Reflow Oven Controller I’d like to thank Phil Prosser for helping me to solve a problem with the DIY Reflow Oven Controller that I built (April & May 2020; siliconchip.com.au/Series/343). It all went together OK, but upon powering it up, the LCD showed a Silicon Chip splash screen, then a page displaying the version number; then it went blank. Very occasionally, it continued to the screen showing a target temperature. I could adjust that temperature using the rotary encoder. Press the EXIT button would momentarily show the screen to set the PID and other parameters, then the screen would go blank. As far as I could see, the processor was still running because the LED continued to flash, but the screen was blank until I cycled power. I checked everything but couldn’t find any faults. Phil kindly sent me a known-good LCD screen to try, and that fixed it. So I guess the screen I got was slightly out of spec, or possibly intermittently faulty. Having fixed that, I found that the thermocouple amp did not have the correct reference voltage even though it was the same colour as the article recommended (purple), but shorting pin 2 to GND solved that. With the TEMPCO set at the recommended level, it is spot on at 19°C but reads 6°C at 0° and 90°C at 98°C. I think lowering the TEMPCO a little would correct this, but I don’t think it is significant for the proposed task. I tried reflow soldering a board with a few passive components and an IC. The job was perfect; it worked like a dream. There were a small number of solder balls present, but they were only visible under fairly heavy magnification. Chris Minahan, Hallidays Point, NSW. Toyota Hybrid accessory battery charging I found the article regarding the Toyota hybrid system (December 2019; siliconchip.com.au/Article/12172) very interesting and informative, especially since I have just bought a new Camry hybrid. In light of some negative comments made about the charging system in some modern cars in your magazine, I decided to measure the output of the 12V power socket in the dashboard. By pure coincidence, this was on the day before my December subscription copy arrived. Imagine my surprise when, after I turned on the hybrid system, the voltage showed 14.4V, even though the petrol engine had not even started! I drove the car, and the petrol engine started after about 30 seconds. After a couple of minutes, the battery voltage dropped to 12.5V. I later pondered the situation, and concluded that the 12V battery is charged from the high-voltage battery (244.8V NiMH, which Toyota refer to as the “traction battery”). I think the whole system is quite brilliant. Roger Chapman, Shelly Beach, NSW. SC siliconchip.com.au Helping to put you in Control 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 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 September 2020  11 The latest 5G mobile data and voice communications technology promises to provide much higher data speeds and greater bandwidth than the existing 3G or 4G. But what exactly is new, what benefits can you expect from it and how does it work? Dr David Maddison explains: 5G Mobile Communications 5G band connections at home (in Australia, this would com(fifth generation) mobile technology has been pete with the NBN; see comments in this month’s editorial available in some parts of Australia since late about Australia’s “broadband tax” and the panel below). 2019. 5G is a package of technologies, not just Different carriers might focus on various aspects of the one, including smart antenna design, many more base stations than the typical mobile towers we are used to, a much technology. For example, one might concentrate on offerbroader frequency range (eventually) plus much higher fre- ing fixed internet at home via 5G, another might focus on mobile phone service, and others might focus on the Interquencies (millimetre waves, around 26GHz and up). The vision of 5G is that it will allow much greater connec- net of Things or the Internet of Everything. Or they might tivity between all manner of things (see Fig.1). Apart from become involved in all aspects of 5G. its obvious application in telephony, 5G will: • allow dramatically improved video streaming, for watch- The 5G radio access network (RAN) The RAN is that part of a telecommunications system that ing videos and videoconferencing; • enable communications with vehicles such as driverless connects devices to other parts of the network via radio. For cars and other machinery, and pilotless aircraft such as 5G, it consists of traditional base-station towers, small cells delivery drones in the city, connections to utility meters, to provide additional coverage, wireless systems in builda surgeon connected to a robotic surgical device hundreds ings and homes, and potentially large numbers of mmWave of kilometres away and innumerable other uses, many of (millimetre wave or EHF, 30-300GHz) antennas in suburban areas, on street lights or power poles. which have not yet even been conceived; Like its predecessors, 5G is a cellular system whereby • wirelessly connect “Internet of Things” (IoT) devices, specifically via wireless “machine-to-machine communica- each 5G device operates in a small geographic area called tion” or M2M. This will evolve into “massive Machine a “cell” at any given time. Cells are typically a few kilomeType Communication” (mMTC), where information will tres across in a suburban area and contain one or more fixed be generated, exchanged and acted upon by machines transceiver stations, on dedicated towers or a structure on with little or no intervention from humans. mMTC ap- top of a tall building or hill. Adjacent cells use different frequencies or other nonplications are being developed for healthcare, transport, interfering modulation schemes. These multiple cells and utilities, energy, agriculture and industrial monitoring; transceivers allow for many • achieve all of the above more mobile devices, as the due to high-speed, low- Crazy conspiracy theories frequencies can be reused in latency (delay) data comThere are innumerable conspiracy theories and claims of physiother non-adjacent cells. munications, while sup- cal and mental harm from 5G being promoted online and elsewhere. This scheme also reduces porting a much larger We consider these to be too ridiculous even to bother refuting them. the required transmit and renumber of connections The amount of power radiated from a 5G (or 4G) phone is in most ceiver power, allowing much than existing systems; cases so low that it is of no concern. smaller devices with less bat• and allow wireless broad12 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.1: a vision of the near future, with 5G connecting everything we use together. Source: ITU (International Telecommunications Union). tery drain. The cell scheme can also be extended virtually without limits, to cover an entire city or country as required. A key feature and requirement for cellular systems is the ability to reuse the limited number of available frequencies. This is because there might be millions of devices in a city and there simply is not sufficient radio spectrum to have a different frequency assigned to every single device, particularly with modern high-bandwidth service requirements such as streaming video. Frequencies can be reused by other cells as long as they are sufficiently far away to avoid interference. The reuse distance is the minimum spacing between towers before a frequency can be used again, avoiding so-called co-channel interference. Modulation schemes also exist which allow multiple users to share a single frequency. Since there is a limit to the number of available frequencies, as the number of users has grown, the cell size has shrunk. The smaller the cell size, the greater number of total users that are possible and the greater the number of antennas. This leads to a concept of variable cell sizes, which have been given names like macrocells, microcells, picocells and femtocells (Figs.2-6). A full-size (macro) cell usually has a tower at the centre, or antennas mounted on a building. They are generally Indoor: 10-100mW Outdoor: 0.2-1W Coverage radius: 10s of metres Indoor: 10-100mW Outdoor: 1-5W Coverage radius: 10s of metres Outdoor: 5-10W Coverage radius: 100s of metres Outdoor: >10W Coverage radius: kilometre(s) Fig.2: a description of various mobile cell sizes. Small cells allow an increase in the number of users in a particular geographic area. Smaller cells also allow for more frequency reuse than macrocells. “Backhaul” is how the cells connect to the core network, either by an existing wired or optical fibre connection or wireless connections. siliconchip.com.au Fig.3: a 4G microcell mounted on a tram power pole outside Melbourne’s Flinders St Station. These boost capacity in busy locations or improve reception in certain areas. Many more similar small cells will be needed for 5G. Source: Telstra. Australia’s electronics magazine September 2020  13 Before 1G, a Telecom Australia (later Telstra) “007” mobile phone. This is only half the story: there was also a large box mounted in the boot! Fig.4: a cellular pattern from US Patent 4,144,411, granted 1979. Each number represents a frequency. Notice how certain frequencies are used multiple times. Each tower radiates one of its three 120° beams into an adjacent cell, so each cell is served by three beams, one each from three towers. The shape of real cells depends on geography and the availability of antenna sites. directional, often having a radiation pattern covering 120 degrees from each array. So a typical tower has the antennas mounted in a triangular array. This enables more users to be simultaneously connected compared to having just one omnidirectional antenna. It is also possible to electronically ‘steer’ beams to a particular user, which we will discuss later. In all cellular communications, as a mobile user moves to the edge of a cell and signal strength diminishes, they are automatically and seamlessly connected to the next available cell. This is a core functionality in cellular systems. To do this, the base stations have to communicate with each other and the handset. The phone needs to find a station with available channels and sufficient signal strength. If the next nearest cell (the logical one to use) is at capacity, the handover might be to another base station that is further away but has available capacity. Previous mobile telephony (1G to 4G) Before discussing how 5G works, let’s go over the previous generations of mobile telephony. Before 1G, various mobile phone systems were in use in Fig.5: user-captured data of the location of Telstra 4G LTE base stations around the Melbourne CBD. They are placed in convenient locations and don’t necessarily conform to the idealised layout shown in Fig.4. This map was generated at www. cellmapper.net – you can use this website to show cellular base stations in any area or country. 14 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.6: the Telstra 5G coverage map around the greater Melbourne area at the time of publication. It is not nearly as complete at this stage as 4G. Australia and elsewhere. In 1950, the PMG (the predecessor of Telecom and then Telstra) introduced a manually-connected mobile telephone service using equipment manufactured by AWA. It only supported hundreds of connections, and there was a long waiting list for service. In 1981, Telecom launched the Public Automatic Mobile Telephone System or PAMTS (“007 service”). It operated at 500MHz in the mainland capitals until 1993, and could support up to 14,000 services on 80 base stations. It was very expensive for equipment and to use. For a US video about an early mobile telephone service see the video titled “1940s BELL EARLY CELL PHONE / MOBILE TELEPHONE SYSTEM 90884” at https://youtu.be/ xDy2tHCPdk8 1G was an analog system. AMPS (Advanced Mobile Phone System), or 1G as it is now also known, was developed throughout the 1970s and 1980s and was introduced into Australia in 1987, starting with just 14 base stations in Sydney and Melbourne. The maximum data throughput on 1G was 2.4kbps. AMPS was fully closed by 2000. 2G, the replacement for 1G, was a digital system, launched in 1993 in Australia. It was implemented by two different technologies depending on who the carrier was; either CDMA (Code Division Multiple Access) or GSM (formerly Groupe Spécial Mobile, now Global System for Mobile Communications). Australian authorities significantly delayed the introduction of these services as they wanted exchanges modified to make interception of the encrypted calls made possible (see siliconchip.com.au/link/ab3d). By 2018, all Australian carriers had shut down 2G service except on Christmas Island and Norfolk Island. 2G introduced many current features such as SMS (short message service) and MMS (multimedia message service), multiple users on a single radio channel via multiplexing, conference calls and roaming. The maximum data rate was 9.6kbps in the initial standard, with enhancements giving 40kbps for GSM GPRS (General Packet Radio Service) and 1Mbps for GSM EDGE. There were interim standards of 2.5G and 2.75G before 3G. Phones that used 2G were not typically in the format of the large touchscreen devices we have today, although an early example of a smartphone was the LG Prada from 2007, followed by the LG Prada II in 2008 that supported 3G. The Prada was announced before the iPhone, and the head of the LG Mobile Handset R&D Center claimed Apple took the idea of the iPhone from that device. 3G introduced better internet connectivity for web browsing, video streaming, email and video conferencing. These features were available on early popular smartphones such as the original iPhone launched in 2007, the LG Prada II from 2008 running on Flash UI and the first Android smartphone, the HTC Dream from 2008. The CPU power of these phones plus the available data bandwidth finally allowed them to upload photos and video to the internet. 3G is based on UMTS or Universal Mobile Telecommunications System, which itself is based on the IMT-2000 standard by the International Telecommunications Union. It combines some elements of 2G with other enhancements for better voice compression and faster data. It uses spreadspectrum technology, whereby the signal is spread across a range of frequencies. The minimum data rate for 3G is 200kbps, but the standard calls for stationary speeds of 2Mbps and mobile speeds Frequency domain Frequency domain The broadband tax Time domain Time domain Fig.7: the difference between two multiplexing methods, ODFM (left) and ODFMA (right). Source: GTA. siliconchip.com.au Unbeknown to many, Parliament introduced a “broadband tax” for users on fixed-line networks other than NBN, to make the NBN seem more competitive by artificially raising the prices of alternatives (see siliconchip.com.au/link/ab3e). Products such as Optus’ 5G Home product are not currently included in this tax, but that could change in the future. It is possible that 5G could become the preferred method of home broadband connections, so this tax could stifle the new technology. Do we need to explain why politicians shouldn’t be making engineering decisions? Australia’s electronics magazine September 2020  15 Fig.8: beamforming, beam tracking and MIMO using a smart antenna array. A beam can be steered by adjusting the phase and amplitude of multiple antennas. Multiple propagation paths due to reflections can be utilised to send one data stream via numerous different paths. Multiple data streams can also be sent on the same path using different signal polarisations. The signal of an interfering user on the same frequency can also be nulled out using this technique. Source: Ericsson of 384kbps. The maximum theoretical speed for the latest implementation of 3G, HSPA+ (evolved High-Speed Packet Access) is said to be 168Mbps download and 22Mbps upload. 3G was introduced in Australia in 2003. Later implementations of 3G were known as 3.5G, 3.75G, 3.9G and 3.95G. 3G LTE (Long Term Evolution) is similar to 4G, and sometimes called by that name, but it is really a “sub-4G” technology and is sometimes referred to as 3.95G. 4G is based on Internet Protocol communications (IP telephony) for voice, unlike previous generations which used traditional circuit-switched telephony (where a dedicated end-to-end communications channel is established for each call). It also allows conventional internet services such as multimedia, web browsing, email, gaming, video conferencing etc with high speed and security. Unlike 3G, it does not use spread spectrum. Instead, it uses the key technology of OFDMA (Orthogonal FrequencyDivision Multiple Access) on the downlink, which allows multiple users to share a single frequency. It also uses MIMO (Multiple Input Multiple Output), whereby multiple antennas in a ‘smart’ array communicate with multiple users via a single radio link by exploiting multipath signal propagation. ODFMA allows fast data communications despite multipath signal propagation. The relevant standard specifies peak data rates of 100Mbps for low-speed users and 1Gbps for high-speed users. Later versions of 4G include 4.5G and 4.9G. 4G LTE was introduced into Australia in 2011, although as mentioned above, LTE is really sub-4G or 3.95G. However, the ITU (International Telecommunications Union) has ruled that LTE can be called 4G while real 4G is called “True 4G” [as if it wasn’t confusing enough already! – Editor]. 5G frequencies If no 5G service is available, a 5G phone will fall back to an available 4G service. In Australia, current 4G networks use frequencies in certain bands from 700MHz to 2.6GHz. Due to government policy, the first phase of 5G is in the 3.6GHz frequency band, from 3575MHz to 3700MHz. Most modern WiFi routers operate at both 2.4GHz and Fig.9: beamforming and beam steering with multiple antennas in a line. They are indicated by blue dots, and all transmit the same signal; the more antennas, the more directional the beam. The beam can be steered by altering the phase and amplitude of each antenna, causing constructive or destructive interference and changing the lobe position. Beamsteering in three dimensions requires a two-dimensional antenna array. Source: siliconchip.com.au/link/ab3f 16 Silicon Chip MIMO Fig.10: multipath propagation of signals as used in WiFi, 4G and 5G. MIMO utilises multiple antennas and transmitters to send signals along numerous pathways to one or more receivers. Each receiver can receive multiple signals from various pathways. Source: Wikimedia user Claudeb. Australia’s electronics magazine siliconchip.com.au Fig.11: approximate existing and new spectrum allocation for 5G worldwide. 5G can use the existing mobile spectrum plus the mmWave spectrum of 26-86GHz. The higher the frequency, the higher the data rate, the smaller the cell size and the greater the number of users in a given geographical area. In Australia, only the 26GHz band is currently allocated for mmWave 5G. 5GHz. If you have one at home, you may have noticed that the 2.4GHz signal reaches more areas of the house, but it has a lower data rate than the 5GHz signal. The initial 5G frequency is almost exactly in the middle of those two frequencies. The very high speeds achievable with 5G require mmWave (~25-300GHz) frequencies to be used which are not yet commissioned. The Australian government will auction part of the 26GHz band for 5G use, 25.1-27.5GHz, in 2021. It is not clear what 5G frequency ranges Australia might use in future, apart from the two mentioned above. Naturally, the network operators will use a combination of frequencies, not just one. Overseas, some 5G operators use low-band frequencies 600-700MHz, mid-band of 2.5-3.7GHz and highband of 25-39GHz, with the possibility of higher frequencies in the future. It is likely that in the future, the spectra of legacy services such as 3G and 4G will be released for use by 5G, as well as mmWave frequencies up to 86GHz. Consider that if you are buying a new 5G phone, you may wish to make sure it supports both mmWave frequencies as well as the 3.6GHz band. It’s not clear what will happen in Australia, but in the USA, a Samsung Note 10+ was offered by two different carriers with each having their own version. Low frequency cells 700MHz Large scale events Thousands of users One version supported 5G on sub-6GHz only, and the other supported mmWave only. Key 5G technologies Apart from the use of certain technologies and features from earlier generations of mobile telephony, 5G introduces or enhances several techniques including but not limited to: 1) Multiple users on a single radio channel. ODFMA was mentioned above concerning the downlink for 4G LTE, and is used for both data uplink and downlink on 5G. To understand ODFMA, we first look at OFDM (Orthogonal Frequency Division Multiplexing) – see Fig.7. The bandwidth is divided into multiple subcarriers with a fixed spacing and transmitted in parallel. Each subcarrier can be individually modulated. In ODFM, users are allocated a specific timeslot in which they can use the entire range of frequencies. In ODFMA, users are allocated a timeslot and a frequency domain, and the subcarrier spacing can be variable and is flexible. So a channel could be given to a single user, or many. In ODFMA, multiple users can use a single channel by assigning subsets of subcarriers to particular users. 2) Smart antennas are antenna arrays that use a combination of hardware (antenna and radio system) and software, High frequency cells 3.2-3.8GHz Vehicle communications Transport Infrastructure Environmental monitoring & smart cities Millimetre wave cells 26GHz Transport & Infrastructure Improved residential connections, smart energy Fig.12: approximate frequency ranges for different cells sizes and possible applications. The smaller the cell size, the higher the frequency and the greater the number of users and data rate, but the shorter the range. The lower frequency cells cover the largest areas and provide the longest range but also the lowest data rate (purple shading). The medium size cells are indicated by blue shading and the smallest cells by the green beam pattern. siliconchip.com.au Australia’s electronics magazine September 2020  17 Peak data rate (Gbit/s) Enhanced Mobile Broadband User experienced data rate (Mbit/s) Area traffic capacity (Mbit/s/m2) Massive Machine-Type Communications Spectrum efficiency Ultra Reliable & Low Latency Fig.13: the original 5G vision. These are new or improved features over previous generations, on top of all existing 4G functions. Source: Samsung. including smart signal processing algorithms, to identify the direction of a received signal from a user. They then calculate the required transmission pattern to form a directional beam aimed at a mobile receiver, and track it as the receiver moves. They are also used to generate multiple beams on multiple independent pathways to one or multiple users. Smart antenna arrays are used for both beamforming and tracking, and simultaneously for MIMO or massive MIMO (see #4). 3) Beam-forming and beam tracking (see Figs.8 & 9). At 3.6GHz, building penetration is not as good as lower frequencies. These two technologies help to improve that. Instead of a base station transmitting a beam in a 120° radiation pattern, wasting transmission power and connection slots, the 5G antenna array tracks the user, and both directs (tracks) and focuses (forms) a pencil-like beam toward them. This results in much better building/foliage penetration than would otherwise be the case. Tests have shown that at 3.5GHz, 5G can get penetration as good as a unidirectional 1.8GHz beam as used by 4G. Due to poor building penetration at mmWave frequencies, 26GHz and above, it is particularly important to use Mobility (km/h) Network energy efficiency Connection density (devices/km2) Latency (ms) Fig.14: a spiderweb chart comparing 4G and 5G. The peak data rate goes from 1Gbps to 20Gbps. “User experienced data rate” refers to the minimum achievable data rate in a real-world environment and goes from 10Mbps to 100Mbps. Latency (delay time for a data packet) is improved from 10ms to 1ms. IMT-advanced is the International Mobile Telecommunications advanced standard for 4.5G, and IMT2020 is the standard for 5G. Source: ETSI. beamforming and tracking at these frequencies. When the base station is receiving from a specific user, the beamforming antenna works in reverse, to capture the signal from a particular user. 4) Massive MIMO (see Fig.10). Multiple-input multipleoutput is a method to increase the capacity of a radio link by exploiting multipath propagation to send and receive more than one data link over the same radio channel. Both 4G and Fig.15: an illustration showing the diverse nature of 5G communications. At the centre is an antenna with massive MIMO (multiple-input multiple-output), allowing radio beams to be directed toward particular users. D2D stands for “device to device” communications. Small cell transceiver 18 Silicon Chip User equipment (UE) Australia’s electronics magazine siliconchip.com.au 4G ANTENNA 5G ANTENNA Fig.16: the directional nature of massive MIMO antennas on 5G makes it possible to direct radio energy to a specific user rather than in all directions as with, say omnidirectional antennas (left). This helps, to some extent, to overcome the more limited building penetration possible for radio signals at higher frequencies. WiFi use this. Standard MIMO uses either two or four antennas, while massive MIMO uses many more. 5) 5G can perform full-duplex data transmissions, that is, data can be sent and received at the same time on the same frequencies, not on separate frequencies as was previously required. This saves radio spectrum. 6) mmWave for higher data rates and more users due to greater frequency availability, and shorter ranges mean a higher cell density is possible too. 7) 5G client communications are designed to minimise power to increase battery life. For example, better focused RF beams mean that less power is required to communicate over the same range. 8) The 5G network is based on virtualisation, using software rather than purpose-built network infrastructure. Functions like network routing, packet processing, security, and many others are performed in software rather than hardware. It is somewhat akin to the concept of a software-defined radio (SDR). 9) The 5G carrier network routes calls and data through the shortest paths, unlike 4G, where calls had to go through the core network. There is interoperability with other networks and connections such as 3G, 4G, WiFi and Bluetooth. Multiple protocols can be used simultaneously. 10) Device-to-device (D2D) communications. 5G devices can communicate directly with other 5G devices without using a carrier network. Usage examples include vehicleto-vehicle and vehicle-to-roadside device communications. 11) “Network slicing”, to create service-specific sub-networks for specific applications or customers. An example might be a network dedicated specifically to the Internet of Everything (see the video titled “what is internet of everything” at https://youtu.be/6Mm8pN6lSSQ), with a large number of low-data-rate devices, or another network dedicated to reading utility meters. Each network slice has specific characteristics optimised for an individual customer’s business requirements. This also relates to “multi-tenancy”, to created logical networks for independent service providers. Complicating the changeover to 5G Moving from 1G to 2G to 3G to 4G allowed essentially the same towers and other base stations to be used, with only the antennas and equipment needing to be changed. But because of the lesser range and penetration of 5G radio beams, many more base stations have to be built than now exist for 4G, especially to utilise the mmWave frequencies siliconchip.com.au when they become available. Bonding 4G and 5G As it will take some time to roll out 5G services fully, a 5G phone can fall back to a 4G service, or it is also possible to utilise 4G and 5G services simultaneously (if both are available) to get higher data throughput and network capacity. This also ensures that a connection is maintained to the greatest possible extent. This dual connectivity technology is also known as EUTRAN New Radio Dual Connectivity (EN-DC) or just Dual Connectivity EN-DC. E-UTRAN is another name for 4G LTE, and New Radio is 5G NR. This is a distinct approach from 2G, 3G or 4G when devices were connected only to one technology at a time, having to switch modes to fall back to an earlier one. Mobile phone cell sizes The ultimate objective is to cover an entire country with cellular coverage. This is easily achievable in smaller countries with a high population density, but it is very difficult and expensive with a low population density such as in Australia. In remote areas, a satellite phone is the preferred communications method (see our article in November 2017 at siliconchip.com.au/Article/10863). Nevertheless, the vast majority of Australians are rarely out of mobile phone connectivity. With current technology, cells can vary in overall size. Originally, cells were “macro” sized. Their size was and still is dictated by usage density and signal strength. The A world first for Australia During the Commonwealth Games in Brisbane in 2018, Telstra provided the world’s first 5G-powered WiFi hotspots. These were free WiFi hotspots with a 10GB download limit per day that people could connect to with the WiFi on their normal mobile phones. But the connection between the Telstra network and the Telstra WiFi hotspot was via 5G (see Fig.22). Connection speeds between the Telstra network and the WiFi hotspot (the “backhaul speed”) of 3Gbps could be obtained. Since 5G phones were not then available, it was a way of demonstrating some benefits of 5G. A speed of 3Gbps would allow 1000 HD-quality movies to be streamed simultaneously. At the same time, Telstra revealed its 5G-enabled “Connected Car” on the road using the Intel 5G Automotive Trial Platform, with a connection speed of 1Gbps and its own WiFi hotspot. Australia’s electronics magazine September 2020  19 more users, the smaller the cell was made due to capacity limitations. The maximum size is limited by the send and receive capability of a mobile handset, which depend on reception sensitivity, transmitter strength and antenna type. Apart from reducing cell size to cope with more users, with certain 5G frequencies, the cell size needs to be reduced to compensate for reduced range. 5G can utilise a variety of frequencies from just under 1GHz up to 86GHz. Frequencies above 30GHz are known as millimetre-wave as the wavelength at 30GHz is about 10mm, dropping to around 1mm at 300GHz. In 5G terminology, frequencies above 26GHz are referred to as millimetre wave or mmWave. As mentioned above, the ACMA (Australian Communications and Media Authority) will auction the mmWave spectrum to prospective telcos in the first quarter of 2021 (see Figs.11 & 12). While higher frequency signals can provide higher data speeds, they have less range and are more affected by fac- tors like fog, rain and tree foliage. Unlike the 4G signals we are used to which can propagate many kilometres, the maximum range of mmWaves in 5G is of the order of just 500m or so, assuming line of sight and no rain or tree foliage. However, 5G can achieve the same range as 4G when lower frequencies are used. Due to the lower range of mmWave signals, there needs to be many more base stations compared with 1-4G. It is anticipated that they will only be installed in high usage areas such as the CBDs of cities, train stations, sports stadiums, high-density urban areas and so on. Small 5G base stations similar in size to WiFi routers could also be installed in the suburbs, at locations such as on power poles, on apartment buildings or other existing structures. Optus is already using 5G to deliver wireless internet to home customers as a substitute for NBN. Future developments using mmWave 5G for home broadband could delivFig.17a (left): This tower in Melbourne, ACMA SITE ID 570447 is shared by Telstra (25m height), Optus (20m height) and Vodafone (19m height) and supports Telstra 3G, 4G & 5G, Optus 3G & 4G and Vodafone 2G, 3G & 4G. All of these services have 2x2 or 4x4 MIMO. Note the triangular pattern of antenna placement to give 120° per array. With MIMO, transmission environments with a large number of good scatterers such as buildings allow a higher data rate due to the multiple signal paths. Weak scatterers such as vegetation do not result in improved data rates. Fig.17b (below): The upper portion of the tower shown at left, which has the Telstra 3G, 4G and 5G antennas. At the moment no active mmWave antennas are installed on that tower, just 5G at 3605MHz with 2x2 MIMO. The small rectangular antenna is probably the one for 5G. 20 Silicon Chip Australia’s electronics magazine siliconchip.com.au 4G/Sub-6-GHz 5G Antenna mmWave 5G Antenna 1 3G/4G/ GPS/WiFi Antenna 3G/4G Antenna mmWave 5G Antenna 2 4G/Sub-6-GHz 5G Antenna Fig.18: this concept drawing shows how multiple antennas can be integrated into a mobile handset. These include 3G, 4G, 5G (both sub 6GHz and mmWave), GPS and WiFi. Note that there are multiple antennas for each of 3G, 4G and 5G. Source: Wonbin Hong via Semantic Scholar. er wireless broadband using an outdoor antenna at speeds ten times faster than a fibre NBN connection. How is 5G different from previous standards? Distinguishing new features for 5G as compared to previous generations include the three main aims of developers, in addition to all previous functionality from 4G (see Figs.13 & 14), which were: 1) Enhanced mobile broadband. This attempts to achieve significantly improved download speeds from 100Mbps siliconchip.com.au Fig.19: the Qualcomm Snapdragon X50 modem-RF system for use in mobile devices or to replace fibre-to-the-home (FTTH) installations with wireless 5G connections. The modem chip (X50, bottom left) can support up to four QTM052 mmWave antenna modules (top) and up to 5Gbps download speeds. It supports beamforming, beam steering and beam tracking and both the sub-6GHz band and mmWave band. It can be combined with a Snapdragon processor with an integrated 4G LTE modem to give 4G/5G dual connectivity. The Australian 5c coin for comparison is 19.4mm in diameter. (minimum) to 20Gbps per user for uses such as high definition (HD) video, virtual reality and augmented reality. Downloading a 15GB HD video takes 120 seconds at 1Gbps on 4G, but could be done in six seconds at 20Gbps on 5G under ideal conditions. Even with weak reception conditions such as at a cell edge, the aim is to achieve 100Mbps. All users in crowded areas such as sports stadiums and airports are expected to have full HD streaming capability. 2) Ultra-reliable and low-latency communications. Low Australia’s electronics magazine September 2020  21 A very interesting app Fig.20: a Taoglas Aurora CMM.100.A 5-6GHz C-Band Massive MIMO Phased Array antenna for a 5G base station. It employs massive MIMO and beamforming and has 64 individual antenna elements, each with two polarisations to give an effective 128 antenna elements. Multiple panels can be clicked together to make an even larger array. While writing this article, we came across an Android app called “Aus Phone Towers”. This plots mobile base stations on a map along with the frequencies, operator and technology used and also tells you which one you are connected to and the signal distribution. It uses the ACMA database for transmitter locations. You may be surprised just how many mobile base stations there are near you. Other apps to look at are OpenSignal and Network Cell Info. latency means short delays, while reliable communication is critical for tasks such as robot remote control; for example, a surgical robot or autonomous vehicle. It’s even more essential for couch potatoes who are “pwning n00bs” in Call of Duty or Fortnite. Err, we are referring to online gaming, of course. 4G latency is typically in the tens of milliseconds, but with 5G the aim is less than 1ms. Consider an autonomous vehicle remotely controlled via the mobile network. With the 10ms delay on 4G, a vehicle travelling at 70km/h (20m/s) will have travelled about 20cm (1/5 of a metre) before a command is received, but will have only travelled 2cm or 20mm after 1ms. Real-world latency for 4G can be much higher than 10ms according to some reports, so the difference will be even more stark. If the mobile network is also being used for sensor feedback from the vehicle, the delay (and thus travel distances) will be doubled due to the data ‘round trip’. Short delays are also crucial for online automated stock trading (so much so that stock trading companies move closer to stock exchange computers to minimise latency due to the speed of light, giving a competitive edge). In the future, these transactions might be made over 5G instead of a wired connection. 3) Massive machine-type communications. This refers to the Internet of Things (IoT) with numerous devices connected to the internet such as washing machines, refrigerators, agricultural machinery and irrigation systems, cars and autonomous vehicles and nearly anything else you can (or cannot yet) imagine. One million devices being connected in one square kilometre is an aim. That’s one device every square metre. Apart from this original vision, many other features have since been added to 5G. 5G or 5G NR? You may hear the term 5G NR (New Radio) instead of 5G. 5G is the overall technology, but 5G NR refers to the early first release of the standard. It is not “pure” 5G just as LTE is not pure 4G. The standard is written and maintained by the 3G Partnership Project or 3GPP (www.3gpp.org). It was named during the development of 3G, but the organisation has not changed its name despite also developing 5G. Mobile phone range In the days of analog mobile phones (AMPS or 1G), the distance between the phone and the cell tower was restricted only by signal strength and line-of-sight considerations. There is an online report of someone placing a call between the Telstra Black Mountain tower in Canberra and the tower in Cooma, 107km away. In the case of 2G or GSM, there was a definite distance limitation of 35km due to signal timing considerations. With 3G, there is no intrinsic distance limitation, and 100km is achievable with the correct antenna (with Tel- Fig.21: a 5G mmWave phased array base station antenna module from Gapwaves for integration into complete antenna systems. The assembly ready for integration is at left with its component parts shown on the right. 22 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.22: a Telstra 5G-connected WiFi hotspot as used in the Brisbane Commonwealth Games in 2018. stra and possibly other carriers there was an earlier 80km limit imposed by software). As reported in 2007, Telstra had several special 200kmrange towers in its Next G (3G) network (see www.zdnet. com/article/telstra-boosts-next-g-reach/). 4G also has no intrinsic distance limitation. There are reports that Telstra tested connections at 75km. Extreme distances are not likely to be achieved with a phone’s internal antenna; an appropriate external antenna such as a Yagi is required. As stated earlier, 5G can achieve similar ranges compared to 4G using the lower frequencies, but the higher frequencies required to achieve the lofty bandwidth goals have a much shorter range. It has been estimated that to provided 100Mbps download speeds to 72% of the US population and 1Gbps to 55% would require 13 million utility-polemounted 28GHz base stations at a cost of US$400 billion. Therefore, for maximum range and utility 5G, will need to continue to use lower frequencies when range is more important than speed. 5G antennas As 5G antennas must be capable of operating in the sub6GHz band, they are not dissimilar to 4G antennas. Separate mmWave antennas may be used for the mmWave frequencies 26GHz and up (see Figs.15-21). SC AUSTRALIA’S OWN MICROMITE TOUCHSCREEN Since its introduction in February 2016, Geoff Graham’s mighty Micromite BackPack has proved to be one of the most versatile, most economical and easiest-to-use systems available – not only here in Australia but around the world! Now there’s the V3 BackPack – it can be plugged straight into a computer USB for easy programming or re-programming – YES, you can use the Micromite over and over again, for published projects, or for you to develop your own masterpiece! The Micromite’s BackPack colour touchscreen can be programmed for any of the following SILICON CHIP projects: BACKPACK Many of the HARD-TO-GET PARTS for these projects are available from the SILICON CHIP Online Shop (siliconchip. com.au/shop) Poor Air Quality Monitor (Feb20 – siliconchip.com.au/Article/12337) GPS-Synched Frequency Reference (Oct18 – siliconchip.com.au/Series/326) FREE Tariff Super Clock (Jul18 – siliconchip.com.au/Article11137) P R O G R Altimeter & Weather Station (Dec17 – siliconchip.com.au/Article/10898) Buy either AMMING tell us whichV2 or V3 BackPack, Radio IF Alignment (Sep17– siliconchip.com.au/Article/10799) for and we’ll project you want it Deluxe eFuse (Jul17 – siliconchip.com.au/Series/315) program it fo r you, FREE OF C DDS Signal Generator (Apr17 – siliconchip.com.au/Article/10616) HARGE! Voltage/Current Reference (Oct16 – siliconchip.com.au/Series/305) Energy Meter (Aug16 – siliconchip.com.au/Series/302) Micromite Super Clock (Jul16 – siliconchip.com.au/Article/9887) Boat Computer (Apr16 – siliconchip.com.au/Article/9977) V3 BackPack: Ultrasonic Parking Assistant (Mar16 – siliconchip.com.au/Article/9848) $ 00* JUST 75 See August 2019 (Article 11764) P&P: Flat $10 PER ORDER (within Australia) *Price is for the Micromite BackPack only; not for the projects listed. siliconchip.com.au Australia’s electronics magazine September 2020  23 High Power Ultrasonic Cleaner Part 1 By John Clarke This large and powerful Ultrasonic Cleaner is ideal for cleaning bulky items such as mechanical parts and delicate fabrics. It’s also quite easy to build and is packed with features. Y ou’ve probably seen the small, low-cost ultrasonic cleaners available online. They are great for cleaning items like jewellery, glasses etc. But what if you want something a bit bigger and more powerful, to suit a wider variety of cleaning jobs? Cleaning fuel injectors or an old carburettor or any other intricate parts is a messy and time-consuming task, 24 Silicon Chip requiring soaking in harsh solvents such as petrol, kerosene or degreaser and scrubbing with various brushes to clean up the parts. It is a difficult and tedious task, and often does not reach the small apertures that are usually the essential areas to cleaned. Our Ultrasonic Cleaner makes this task so much easier. Just place the components in a solvent bath, press a button and then come back later to remove Australia’s electronics magazine the parts in sparkling clean condition. It will even clean internal areas! It uses a high-power piezoelectric transducer and an ultrasonic driver to release the dirt and grime with ultrasonic energy. For more delicate parts, the power can be reduced to prevent damage to the items being cleaned. How does it work? A metal container is filled with a solsiliconchip.com.au Features • Drives a nominal 40kHz, 50W or 60W-rated transducer • Adjustable power level • Power level display • Stop and Start buttons with run operation indication • Auto-off timer from 20 seconds to 90 minutes • Soft start • Over-current and startup error shutdown and indication • Power level diagnostics • Automatic or manual transducer calibration • Standing wave minimisation • Supports a resonance frequency of 34.88Hz to 45.45kHz vent, deionised water, or normal hot water and a detergent or wetting agent. The ultrasonic transducer agitates the contents of the bath; at higher power levels, the ultrasonic wavefront causes cavitation, creating bubbles which then collapse. This is shown in Fig.1. As the wavefront passes, normal pressure is restored, and the bubble collapses to produce a shockwave. This shockwave helps to loosen particles from the item being cleaned (Fig.2). The size of the bubbles is dependent upon the ultrasonic frequency; they are smaller with higher frequencies. We are using the commonly available bolt-clamped Langevin ultrasonic transducer, depicted in Fig.3. It comprises piezoelectric discs sandwiched between metal electrodes. The centre bolt not only holds the assembly together, but is critical in ensuring the piezo elements are not damaged when being driven. The bolt is torqued to a pre-determined tension and locked (glued) in place to prevent it loosening. The bolt tension ensures the piezo discs always remain in compression even while it is operating, preventing the discs from breaking apart. When a voltage is applied to the piezoelectric discs, forces are generated by the piezo elements that move the two metal ends closer together and then further apart at the ultrasonic drive rate. Our Ultrasonic Cleaner drives the piezo transducer at close to its nominal 40kHz resonant frequency. Fig.4 shows the power applied versus frequency for the particular ultrasiliconchip.com.au The “works” of our Ultrasonic Cleaner before the transducer is attached to the cleaning bath. Operation is pretty simple: turn on, set the timer and push the “start” button! sonic transducer we are using. It claims to have a resonant frequency of 40kHz with a 1kHz tolerance either side of this frequency. We found that the transducer resonates at 38.8kHz under load. The transducer drive frequency needs to be controlled to within a fine tolerance to maintain a consistent power level. A small change in frequency from the resonant point will reduce the power quite markedly. Additionally, their impedance Figs.1 & 2: the sound waves produced by the Ultrasonic Cleaner rapidly create and destroy bubbles in the liquid. When the bubbles collapse, they generate localised shockwaves. This ‘cavitation’ stirs up the solvent layer that’s in contact with the dirt, grease and grime, helping to break it up and more rapidly dissolve it away. You can do this by hand – it’s called scrubbing – but it’s a tedious job, and it’s hard to get into nooks, crannies and internal spaces in the parts being cleaned! Australia’s electronics magazine September 2020  25 Scope1: the gate drive to Q1 (top trace, yellow) and Q2 (bottom trace, cyan) measured at pins 5 and 6 of IC1. The vertical cursors show the dead time when both Mosfets are not driven as 2µs. That is for when Q1 switches off and Q2 switches on; the dead time is the same between Q2 switching off and Q1 switching on. varies depending on load. So when operating in free air, the impedance is much lower compared to when the transducer is driving a bath full of cleaning fluid. Circuit details The circuit of the Ultrasonic Cleaner is shown in Fig.5. It is based around a PIC16F1459 microcontroller (IC1). This controls the two Mosfets (Q1 and Q2) that drive the primary windings of transformer T1 in an alternating fashion. T1 produces a stepped-up voltage of 100V AC (RMS) to drive the ultrasonic transducer. IC1 also drives the power LED (LED1) and level LEDs (LED2-LED6); plus it monitors the timer potentiometer (VR1) and switches S2 and S3, used for starting and manually stopping the cleaner operation. IC1 also monitors the current flowing through Mosfets Q1 and Q2 at its AN11 analog input, at pin 12. And it controls the soft-start charging of the main bypass capacitor using transistor Q5 and Mosfet Q6. Transformer drive A complementary waveform generator within IC1 is used to drive Mosfets Q1 & Q2 in push-pull mode. The transformer is centre-tapped to allow this type of drive. IC1’s PWM generator includes an adjustable dead time, Fig.3: this shows the construction of the ultrasonic transducer that we’re using. Two piezoelectric (ceramic) discs are sandwiched between the two halves of the body, with electrodes to allow a voltage to be applied across the piezo elements. The compression of the piezoceramics due to the tension from the bolt holding the whole thing together is critical to preventing early failure from the ultrasonic vibrations. 26 Silicon Chip Scope2: the lower trace (cyan) shows the transformer output voltage when driving the ultrasonic transducer at 39.26kHz. The top trace shows the current measurement voltage at the AN11 input of IC1 (TP1). 4.18V represents a 2.98A current driving the transformer primary with a 12V supply. This equates to approximately 35.8W delivered to the transducer. so that there is time for one Mosfet to switch off before the other Mosfet is switched on (Scope1). This prevents ‘shoot-through’ which would otherwise cause the Mosfets to overheat. IC1’s RC5 and RC4 digital outputs provide the complementary gate drive signals for Mosfets Q1 & Q2. Since these outputs only swing from 0V to 5V, we are using logic-level Mosfets. Standard Mosfets require gate signals of at least 10V for full conduction, but logic-level Mosfets will typically conduct fully at 4.5V, or sometimes even lower voltages. With the STP60NF06L Mosfets we are using, the on-resistance (between drain and source) is 14mΩ at 30A with Fig.4: the frequency vs power curve for the transducer in our prototype. Most transducers with a nominal 40kHz resonance should be similar, but the exact frequency of the peak will vary, as will the steepness of the slopes. Hence, our Cleaner has an automatic calibration procedure to find this peak; the 100% power setting runs it at a frequency close to the peak, while lower power settings are at higher frequencies. Australia’s electronics magazine siliconchip.com.au                                SC  HIGH POWER ULTRASONIC CLEANER Fig.5: the complete Ultrasonic Cleaner circuit. IC1 produces complementary drive signals to the gates of Mosfets Q1 & Q2, which in turn drive the primary of transformer T1 in a push-pull manner. This results in around 100V AC at CON3. Current is monitored via two 0.1Ω Ω shunt resistors at the sources of Q1 and Q2, via amplifier IC2b into analog input AN11 of IC1; the power is computed from this and a voltage measurement at analog input AN8. a 5V gate voltage. They are rated at 60A continuous and include over-voltage transient protection that clamps the drain-to-source voltage at 60V. Q1 & Q2 are driven alternately and these, in turn, drive the separate halves of the transformer primary of T1, which has its centre tap connected to the +12V supply. When Mosfet Q1 is switched on, current flows in its secsiliconchip.com.au tion of the transformer primary winding. Q1 remains on for less than 25µs (assuming a 40kHz operating frequency) and is then switched off. Both Mosfets are off for two microseconds before Q2 is switched on. Q2 then draws current through its section of the T1 primary winding and remains on for the same duration as for Q1. Both Mosfets remain off again for two Australia’s electronics magazine microseconds before Q1 is switched on again. The gap when both Mosfets are off is the “dead time” and accounts for the fact that the Mosfet switch-off takes some time. Without dead time, the two Mosfets would both be switched on together for a short duration. This would cause massive short-circuit current spikes, not only resulting in overheating of the September 2020  27 Mosfets but also drawing large current spikes from the supply filter capacitor and DC power supply. The alternate switching action of the Mosfets generates an AC square wave in the secondary winding of transformer T1. With a turns ratio of 8.14:1 (57-turn secondary and 7-turn primary), and 12V AC at the primary, the secondary winding delivers about 98V AC to the piezoelectric transducer. ducer is switched off. This voltage represents an average of 350mV measured across each 0.1 resistor, or a 3.5A average current flow. That’s calculated as (4.9V÷14) ÷ 0.1. An over-current error is indicated by flashing LED2, LED4 and LED6 on the front-panel level display. When this happens, the power will need to be switched off and restarted to resume cleaning. If the problem persists, the cause will need to be found. Standing waves Running the Ultrasonic Cleaner at a constant frequency near resonance is efficient, since the impedance of the transducer is almost purely resistive under those conditions. However, this is not ideal for minimising standing waves within the cleaning bath. Standing waves can build up in strength while the frequency remains constant. These waves are caused by reflections from the parts being cleaned and the tank walls being in-phase. This can damage delicate parts. Our Ultrasonic Cleaner has the option of reducing the power for use with delicate parts, but even larger parts can have delicate sections within them, especially in thin-walled cavities. To avoid standing waves, the frequency can change over time to prevent the constant phase of the waveform, which would cause constructive interference at various locations in the bath. As the power versus frequency graph shows, changing the frequency even by a small amount will drastically alter the power. So it is not ideal if the frequency is varied continuously, as it reduces the cleaning power. Instead, we operate the transducer at a fixed frequency for 10 seconds at a time, then run it over a range of different frequencies for a short time before returning to the maximum power frequency for another 10-second burst. In the intervening time, the frequency varies in small 37.5Hz steps over a 2.4kHz range for around 400ms. That means that power is reduced only about 4% of the time. The cycling in frequency alters the phase of the ultrasonic vibrations in the bath, giving time for standing waves that occur during the fixed frequency period to die down, thus preventing them from building up to a damaging level. Over-current protection Over-current protection for the Mosfets is provided in two ways. Both rely 28 Silicon Chip Power control The 40kHz transducer is available both here in Australia and online. Note, though, that if you do buy online you need to make sure you get a 40kHz type – there are other frequencies available and they look pretty much identical. (See the panel on P31). on current detection via the voltage across the 0.1 between the sources of Q1 and Q2 and ground. The first method uses NPN transistors Q3 and Q4. These have their baseemitter junctions connected across those 0.1 current-sense resistors. Over-current starts when the voltage across the 0.1 resistor exceeds about 0.5V, ie, with more than 5A through either Q1 or Q2. The associated transistor Q3 or Q4 then begins to conduct. The current flowing from its collector to its emitter reduces the gate voltage to the associated Mosfet. This has the effect of increasing the Mosfet on-resistance, which then reduces the current. This protection is a fast-acting, cycleby-cycle protection measure. At the same time, the voltages across the two 0.1 current-sense resistors are averaged by a pair of 10k resistors and filtered by a 100nF capacitor. This averaged voltage is then applied to non-inverting input pin 5 of op amp IC2, which amplifies the signal 28 times (27k ÷ 1k + 1). The averaging effectively halves the sensed voltage, since only one of Q1 or Q2 is on at any given time. So this results in an overall amplification of 14 times. The output from pin 7 of IC2b is measured by the AN11 analog input of IC1 (pin 12) – see Scope2. This voltage is converted to a digital value and processed by IC1. Should this voltage stay at 4.9V or more over a 160ms period, the drive to the transAustralia’s electronics magazine The current measured at the AN11 input is also used for controlling the power applied to the ultrasonic transducer. The maximum power rating of the transducer is 50W, but this is not a continuous rating. The recommended continuous power is 43W. We limit power to a more conservative 36W. For a 12V supply, the current required for this power is 3A. During operating, the current is monitored via AN11 and the drive voltage is also sampled, via a resistive divider, at analog input AN8 (pin 8). This allows the micro to calculate the power flowing into the transformer as the frequency is adjusted, so that it can maintain the power at the required level. IC1’s instruction clock is derived from its internal oscillator, and thus the PWM output frequencies are derived from this as well. The internal oscillator can be adjusted in small steps using the OSCTUNE register. This can vary the internal oscillator frequency over a 12% range in 128 steps. For the 40kHz drive to the ultrasonic transducer, this allows a 4.8kHz control range in steps of 37.5Hz. The 37.5Hz step resolution is sufficiently small to drive the ultrasonic transducer at the desired power level. However, the OSCTUNE register does not have sufficient frequency range to ensure we can drive an ultrasonic transducer that is resonant outside the range of 37.6kHz to 42.4kHz. To widen the operating range, the unit calibrates itself automatically (it can also be initiated manually). This finds the approximate resonant frequency of the transducer using a coarser adjustment. Fine-tuning is then done via OSCTUNE; this allows a variety of different transducers to be used. This coarser calibration is performed using the PR2 register, which siliconchip.com.au Parts list – High Power Ultrasonic Cleaner 1 double-sided PCB coded 04105201, 103.5 x 79mm 1 double-sided PCB coded 04105202, 65 x 47mm 1 panel label, 115 x 90mm (see text) 1 diecast aluminium box, 115 x 90 x 55mm (Jaycar HB5042) 1 50/60W 40kHz ultrasonic horn transducer (resonance impedance 10-20) [see text] 1 12V DC 60W switchmode supply or similar [Jaycar GH1379, Altronics MB8939B] OR 1 12V battery (10Ah or greater) with 5A+ rated twin lead 1 EPCOS ETD29 13-pin transformer coil former, B66359W1013T001 (T1) [RS Components 125-3669, element14 1422746] 2 EPCOS ETD29 N97 ferrite cores, B66358G0000X197 (T1) [RS components125-3664, element14 1422745] 2 EPCOS ETD29 clips, B66359S2000X000 or equivalent (T1) [RS components 125-3668, element14 178507] 1 6A SPST mini rocker switch (S1) [Altronics S3210, Jaycar SK0984] 2 SPDT momentary push button switches (S2,S3) [Altronics S1393] 2 switch caps for S2 & S3 [Altronics S1403] 1 5A PCB-mount barrel socket, 2.5mm ID (CON1) [Jaycar PS0520, Altronics P0621A] 1 5A barrel plug, 5.5mm OD x 2.5mm ID [Jaycar PP0511, Altronics P0165] (optional) 1 vertical 2-pin pluggable header socket with screw terminals (CON2) [Jaycar HM3112+HM3122] 1 2-way PCB mount screw terminal with 5.08 spacing (CON3) [Jaycar HM3130, Altronics P2040A] 1 14 pin box header (CON4) [Altronics P5014] 1 14 pin IDC plug (for CON4) [Altronics P5314] 1 14-pin IDC transition plug (CON5) [Altronics P5162A] 2 3AG PCB-mounting fuse clips (F1) 1 4A 3AG fuse (F1) 1 10k 16mm linear potentiometer (VR1) 1 knob to suit potentiometer 1 20-pin DIL IC socket (for IC1) 1 8-pin DIL IC socket (for IC2) 3 TO-220 silicone washers and bushes 4 stick-on rubber feet Transducer housing parts 1 50mm length PVC DWV (Drain, Waste and Vent) fittings; end cap (Holman DWVF0192) and adaptor (Holman DWVF0022) or 1 40mm length of 50mm ID pipe 1 cable gland for 3-6.5mm cable Neutral cure silicone sealant (eg, roof and gutter) Epoxy resin (eg, JB Weld) Parts for testing 1 100mm length of 0.7mm tinned copper wire 4 9mm-long M3 tapped spacers 4 M3 x 6mm machine screws extra length of 0.63mm diameter enamelled copper wire sets the period and thus the frequency of the PWM drive waveform. For our circuit, this provides steps of approximately 540Hz. We restrict the coarse adjustment range to be from 34.88kHz to 45.45kHz. This range caters for all siliconchip.com.au Cables, wiring & hardware 1 M3 x 6mm machine screw (for REG1) 3 M3 x 9mm machine screws (for Q1, Q2 & Q6) 4 M3 hex nuts 1 cable gland for 3-6.5mm diameter cable 1 800mm length of 1mm diameter enamelled copper wire (T1 primary) 1 3.6m length of 0.63mm diameter enamelled copper wire (T1 secondary) 1 1m length of 0.75mm square area dual sheathed cable or figure-eight wire (for transducer connection) 1 160mm length of 5A (1mm2) hookup wire 1 200mm length of 14-way ribbon cable 8 PC stakes 1 30mm length of 5mm heatshrink tubing (for S1 connections) 1 roll of electrical insulating tape Semiconductors 1 PIC16F1459-I/P microcontroller programmed with 0410520A. hex (IC1) 1 LMC6482AIN CMOS dual op amp (IC2) 1 7805 5V 1A linear regulator (REG1) 2 STP60NF06L logic level N-Channel Mosfets (Q1,Q2) 3 BC547 NPN transistors (Q3-Q5) 1 SUP53P06-20 P-channel Mosfet (Q6) 1 13V 1W zener diode (ZD1) 1 1N5404 3A diode (D1) 1 1N4004 1A diode (D2) 6 3mm LEDs (red or green) (LED1-LED6) Capacitors 1 4700µF 16V low-ESR PC electrolytic 2 100µF 16V PC electrolytic 2 10µF 16V PC electrolytic 1 470nF MKT polyester 4 100nF MKT polyester Resistors (0.25W, 1% unless specified)        4-band code    5-band code 1 1M brown black green brown brown black black yellow brown 2 100k brown black yellow brown brown black black orange brown 1  27k red violet orange brown red violet black red brown 1  20k red black orange brown red black black red brown 8  10k brown black orange brown brown black black red brown 7   1k brown black red brown brown black black brown brown 2   47 yellow violet black brown yellow violet black gold brown 2   0.1 1W (SMD 6432/2512-size; Panasonic ERJL1WKF10CU or     similar) [RS Components 566-989] transducers that have a nominal 40kHz resonance. So the transducer’s resonance is found to within 540Hz by adjusting PR2, and this value is stored in nonvolatile flash memory. OSCTUNE can Australia’s electronics magazine then vary the frequency at least 1.8kHz above and 1.8kHz below the value initially set by the PR2 register (1.8kHz ≈ 2.4kHz - 540Hz). Different power levels are available by adjusting the drive frequency. The September 2020  29 10k pull-up resistors. A closed switch is detected when it is pressed as the input is pulled to 0V. Note that we are using pushbutton changeover switches that have common (C), normally closed (NC) and normally open (NO) contacts. The pins on the switch are in a line, with the common pin at one end, NO in the middle and NC at the other end. Usually, that means that you would need to orientate the switch correctly on the PCB for correct operation. However, we have designed the PCB pattern so that either orientation will work by wiring the C and NC connections together on the PCB. Power supply This shows what the completed Ultrasonic Cleaner will look like when we cover the construction and testing side next month. We’ll also show you how to set up your ultrasonic cleaning bath using cheap “cooking” containers. highest power is at the frequency closest to resonance, while lower power levels use a frequency above resonance that has the transducer producing a lower power. Nine power levels are available, ranging from 100% (36W) down to 10% (about 3.6W). Depending on the transducer characteristics, the lowest power level may not be available. LED indicators LEDs2-6 indicate which of the nine power levels is selected, with LED2 lit to indicate the lowest power level. The next step up is with LED2 and LED3 lit, then LED3 and so on until LED6 only is on, showing the highest power level. The power level is adjusted by holding down the Start switch. It will then cycle up through the nine possible levels to the maximum, then down again. The switch can then be released at the desired level setting. The transducer is not driven during power level adjustments. The On/Run LED (LED1) shows when power is applied to the circuit. This LED also acts as an operation indicator. The LED goes out during trans30 Silicon Chip ducer calibration and then lights when the required value for PR2 is found. This takes a few seconds, unless there is something wrong, such as when there is no transducer connected. Once running, LED1 only lights when the transducer is being driven at the required power setting; it acts an ‘in lock’ indicator. When the Stop switch is pressed, the drive to the transducer ceases, the level LEDs go off and the power LED turns on. LED1 then goes out when the main power source is switched off via S1, or if the supply itself is disconnected or switched off. Cleaning timer VR1 is the timer control. The voltage from its wiper is applied to the AN9 analog input of IC1 (pin 9), and it varies between 0V and 5V. This corresponds to a timer range from 20 seconds through to 90 minutes. The timer starts when the Start switch is pressed. After the selected period, the transducer drive stops. Switches S2 and S3 connect to the RA0 and RA1 inputs of IC1 respectively. The inputs are held high (at 5V) by Australia’s electronics magazine 12V DC power for the circuit is fed in via CON1. It needs 4A minimum. If using a 12V battery, it should be rated at 10Ah or more. Power is switched by S1, which is wired back to the PCB using a plug-in screw connector and socket (CON2). Power then passes to the 5V regulator (REG1) via reverse polarity protection diode D2. Linear regulator REG1 provides the 5V required by IC1 and IC2. 12V DC also goes to Mosfet Q6 via fuse F1. This Mosfet is used as a softstart switch to charge the large 4700µF low-ESR bypass capacitor slowly. Without soft starting, charging the 4700µF capacitor would cause a substantial surge current. This can blow the fuse or cause a 12V switchmode supply to shut down. When power is first applied, Q6 is off and the 4700µF capacitor is not charged. When the Start switch is pressed, the RC3 output of IC1 goes to 5V and this switches on transistor Q5. The gate voltage of P-channel Mosfet Q6 then begins to drop towards 0V as the 10µF capacitor charges via the 100k resistor to the collector of Q5). As the Mosfet begins to conduct, it slowly charges the 4700µF capacitor. After half a second, the gate charging is stopped by switching off Q5 and after a 250ms delay. The voltage across the 4700µF capacitor is then measured using the AN8 analog input of IC1. If the voltage across the capacitor is under 9V (3V at AN8), all the level LEDs flash twice per second. This indicates that either the 4700µF capacitor is leaky, or there is a short circuit causing the capacitor to discharge. Power can then be switched off, and the fault investigated. siliconchip.com.au If there is no error, Q5 is switched back on, to continue charging the gate of Q6. It takes one second for the gate to drop 7.5V below the source, at which time Q6 is almost fully on. After a few more seconds, the gate voltage will be very close to 0V, leaving the full 12V between the gate and source. Zener diode ZD1 protects the gate from overvoltage by limiting the gate-source voltage to -13V. Reverse polarity protection for the power section of the circuit is via a 4A fuse F1, diode, D1 and the integral reverse diodes within Mosfets Q1 and Q2. These diodes conduct current, effectively clamping the supply voltage at -0.7V and protecting the 4700μF electrolytic capacitor from excessive reverse voltage. This current will quickly blow the fuse and cut power. The bath The ultrasonic transducer needs to be attached to the outside of a suitable container. This can be made from stainless steel, aluminium or plastic so that the ultrasonic vibration is efficiently coupled to the fluid. Stiffer materials couple the ultrasonic waves with fewer losses. Ideally, the bath should have a flat side or base where the transducer can be attached. The material also needs to be compatible with the epoxy resin used to glue the transducer to the bath. Metals are the most compatible material. We found a series of “gastronorms” at a kitchen supply shop that are ideal. These are the types of food containers you often see at buffets. They slot into steam tables that keep the food warm, and they are available in various shapes and sizes, with several good options at or near the ideal 4L volume. You can get them made from stainless steel, polycarbonate or polypropylene with the first two options being the best. We got ours (pictured) from www. nisbets.com.au (they have shops in NSW, Vic, Qld & ACT). We recommend either the 150mmdeep ¼ gastronorm tray (capacity 4L), the 100mm-deep 1/3 gastronorm tray (capacity 3.7L) or the 100mm-deep ¼ gastronorm tray (capacity 2.5L). The 150mm-deep ¼ tray is tall and rectangular while the 100-mm deep 1/3 tray is more square and shallow. The other tray is in-between the other two. You can also get stainless steel or siliconchip.com.au If I knew you were comin’ I’d’ve baked a cake . . . these are some of the stainless steel containers we found at a kitchen supply shop which would be ideal for this project. Choose the size and depth which best suits your application. clear or black polycarbonate lids to suit all these, which would be a good idea if you’re cleaning with a strongsmelling solvent (especially if you plan to leave the solvent in the bath when you aren’t using it). Larger sized baths with more liquid will have a lesser cleaning effect than smaller containers with less fluid. The fluid used in the bath can be tap water with a few drops of detergent as a wetting agent. Other fluids that can be used include deionised water, alcohol (methylated spirits, isopropyl alcohol etc), acetone or similar solvents. Cleaning effectiveness is greatly enhanced when the fluid is warmed. Filling with around four litres is ideal for the power available from the ultrasonic transducer. With deeper containers, it might be possible to fill them with less liquid for cleaning smaller items. However, you would need to recalibrate the unit after each fluid lev- el change, and you might find that it would shut down with less liquid in the tank due to the transducer impedance dropping, and the power delivery going above 40W. This approach would require some experimentation for successful use. The recalibration procedure will be described later. Note also that you would need to mount the transducer quite low on the container (or on the base) to allow different fluid levels to be used. Conclusion Next month, we will present the construction details including how to wind transformer T1, the PCB assembly steps, wiring it up, encapsulating the transducer, case preparation and final assembly. We’ll also describe the testing and calibration procedures, plus give some hints on how to use the Ultrasonic SC Cleaner most effectively. Obtaining the parts for your Ultrasonic Cleaner . . . As usual, you can order the two PCBs and the programmed microcontroller for this project from the SILICON CHIP ONLINE SHOP – see pages 104 & 105 for details. We have also decided to stock the ultrasonic transducer, as it isn’t all that easy to find locally. Jaycar did sell a 50W rated transducer (Cat AU5556), but according to their website, it has been discontinued. Our transducers are rated at 50W and are designed for 40kHz operation. They should be in stock by the time the second and final part of this article appears next month (Cat SC5629 <at> $54.90). Australia’s electronics magazine You can get the remaining parts for this project from the usual suspects: ie, Jaycar and/or Altronics; or element14 or RS Components for the more specialised bits. You could also get almost all of the parts from Digi-Key overseas; they offer free express delivery to Australia or New Zealand for orders over AU $60. The PVC parts for the transducer housing are available at hardware stores like Bunnings, while containers for the bath are available from Nisbets, as described above. September 2020  31 The Aussie electrical plug and socket: Where did it come from? By John Hunter Most people never give it any thought, but have you considered where the design of the three-pin plug and socket used in Australia, NZ, and the South Pacific came from? Did you know it was actually an American design? B eing part of the British Empire, it was natural that Australasia would choose British wiring methods. So, it was hardly surprising that 200-250V AC mains supplies were adopted, with what was initially called the “Swan” base for light bulbs. This was named after the British inventor of the incandescent lamp, Joseph Swan. This soon became known as the bayonet base, which is still used today. But what about plugs and sockets for other appliances? Electricity to homes was initially for lighting only, so the ubiquitous socket on the wall, known as a power point (or “GPO” – General Purpose Outlet, in electrical parlance) did not exist yet. At the beginning of the 20th century, there were few domestic appliances as we know them today; just carbon filament lightbulbs. Refrigeration was not yet in a form suitable for domestic use; there was 32 Silicon Chip no radio or TV, and heating or cooking appliances were run from combustible fuel. However, this being a time of creative invention, other uses were Fig.1: typical of early appliances, this toaster is connected to the mains with a bayonet plug. Australia’s electronics magazine found for this electric supply. Soon came an explosion of all kinds of appliances running from “clean” and “labour saving” electricity. Such appliances were invariably based around motors and/or heating elements. Table fans, toasters, irons etc started to appear. Having acquired such an appliance, the next thing to consider was where to plug it in. The only place, of course, was into a light socket. Thus, appliances came fitted with bayonet plugs (or Edison screw plugs in the USA) – see Fig.1. To use such an appliance and not be in the dark at the same time, bayonet double-adaptors were available, with one socket for the light bulb and the other for the appliance (Fig.2). While this worked, it was a pain having to climb up to the light socket every time to connect or disconnect the appliance. Also, the light sockets could only supply up to about 5A; no good for a 2.4kW radiator! siliconchip.com.au The origins of this fea Fig.2: before wall-mounted sockets, appliances were connected to light sockets with bayonet adaptors. Also, no Earth connection was available. Nevertheless, this method of connecting low-power appliances was still common into the 1950s. It is not uncommon to see advertisements for appliances from that time still with a bayonet plug. For most appliances, wall-mounted sockets are clearly far more practical. In the USA, a plug and socket were developed by Harvey Hubbell with two flat parallel blades, to take the place of the wall-mounted Edison screw socket. Hubbell remains one of the largest manufacturers of electrical accessories in the USA to this day. Flat blades were chosen to mimic a knife switch, with its inherently reliable contacts. Britain and Europe used various cylindrical pin configurations. Although Continental Europe has persisted with a multitude of incompatible plug designs, the two-pin “Europlug” goes a long way to solve this problem, for double-insulated appliances at least (Fig.3). The UK replaced their multitude of round pin plugs and sockets with the square-pin BS1363 plug in 1949. Fig.3: the two-pin “Europlug” fits most Continental sockets, where different methods of Earth connection prevent full compatibility of three-pin plugs. siliconchip.com.au Way back in the Jan uary 2002 issue, we published a letter from some bloke with the un likely name of “Dick Smith” which read (in part): “By the way, how ab out doing some interesting invest igation. 3-pin mains plugs like those we have in Australia seem to be the same as used in parts of China , New Zealand and Argentina. Where did our 3-pin plug and socket design come fro m and why are they the same as used in those other countries?” Since his name was cle arly made ture . . . up, we had no choice but to ignore him. But then we got an other e-mail earlier this year from, you guessed it, a Mr D. Smith sugge sting the very same thing. That lead to a little discussion over some aspects of the Aussie GPO, so we did a bit of Googling. Then we discovered that John Hunter (who’s written for us in the past) is apparently a bit of an expert on the subject. Well, Mr Smith (if that is your real name!) – we hope tha t this article lives up to your expe ctations. Australia By the 1920s, Australia was using the British cylindrical pin plug and socket, but the two-flat-pin American plug was also in use. Sometimes one still sees ancient examples of these two-pin fittings in second-hand building material centres, still on their timber mounting blocks. Clipsal still makes the parallel twopin plug (Cat 492) and socket, which is approved for 250V where an Earth connection is not required, although these days it’s usually used with imported 120V equipment. However, the polarised version of this plug which appeared in the USA later, with a wider Neutral pin, was never used here (Fig.4). This can be a problem with some step-down transformers, fitted with the locally-made socket, if modern US appliances are to be plugged into them. While electrical safety wasn’t given the attention that it gets these days, it was realised that Earthing appliances was necessary, thus requiring three pins. Both the British and Americans had a three-pin plug which was being used here (Fig.5). The British plug was, of course, a cylindrical pin design, while the American one used flat pins. It was not, however, their three-pin plug of today (known as NEMA 5-15), but had two angled pins for the supply, and another flat pin beneath for the earth. It was imported by General Electric, and was what most would recognise today as the “Australian” plug (see Figs.6-12). Americans know it as the “crowfoot”. This early three-pin plug design was not popular in the USA because of incompatibility with their existing two-pin plug. Nevertheless, there are plenty of surviving examples. It was considered obsolete before the NEMA (National Electrical Manufacturers Association) standards came into being, and was never allocated a type number. Around 1930, an attempt was made by Clipsal and Ring Grip (the predominant electrical accessory manufacturers at the time), along with the State Electricity Commission of Victoria, to adopt the American design as the Australian standard. It was chosen over the Fig.4: these plugs and the NEMA 5-15 sockets were introduced to North America after Australia had adopted their old two- and three-flat-pin configurations, and were not used here. The wider Neutral pin ensures consistent connection polarity. Fig.5: a selection of old American and English two- and three-pin plugs and sockets. These were commonly used in Australia prior to the American 3-pin type (at right) being standardised in Australia and New Zealand. Australia’s electronics magazine September 2020  33 Fig.6: three flat-pin fittings from a Canadian GE catalog, from 1915 (left) and 1920 (right). This three-pin American plug was patented in 1916 by G.P. Knapp of the Hubbell Company. British design because it was easier for local manufacturers to make flat pins. An article published at that time (see Fig.14) states “Efforts now being made by the Electrical Association of N.S.W. to standardise the types of power plugs in use will receive enthusiastic endorsement from many consumers.” “The necessity for improvement along this line is indicated by the results of the association’s investigations. In reviewing the existing position, a collection was made of every plug on the market. The amazing result was an array of 71 distinct versions.” “... After examining and testing every variety, the association decided that the ‘three-pin flat pin’ type of 10 ampere capacity was most suitable. Its advantages are positive contact, giving consistent efficiency and a high degree of safety (the third pin being an earth connection).” “Accordingly, this plug has been recommended to the Standards Association of Australia by the New South Wales trade body. The electrical traders of Victoria and South Australia are also in agreement, and have endorsed the recommendations.” The US design (Fig.15) was officially adopted in 1938 by the Australian Standards, with the only modification being to shorten the pins by about 2mm. Fig.16 shows the difference in pin length before and after the standard was officially adopted. In “Radio & Hobbies in Australia”, the “Serviceman Who Tells” article for December 1951 stated that mains sockets for the service bench should include a bayonet socket, a two-flat- Fig.7: the original Hubbell patent. It shows the common use of an Edison screw lamp socket to provide power to appliances. Fig.8: examples of US-made sockets in the author’s collection. These fit the modern Australian plug perfectly, and are rated at 125V/15A or 250V/10A. 34 Silicon Chip Australia’s electronics magazine pin socket and various cylindricalpin sockets. This indicates that a significant number of these fittings were still in use then. Safety features Some power points in Australia have had shutters, but they are not compulsory. A particularly problematic type of shutter arrangement was used in some sockets from the 1950s. It is actuated by the Earth pin of the plug being inserted, which then uncovers the Active and Neutral connections. This became a problem when twopin plugs started to appear in the 1960s. One would have to insert something into the Earth pin receptacle before inserting the plug, or plug in via a three-pin double adaptor, or simply dismantle the power point and remove the shutters. Soon after, power points with shutters relied only on the Neutral pin being inserted, solving this problem. Fig.9: examples such as these sometimes appear on the USA eBay website. siliconchip.com.au Fig.10: this Hubbell adaptor converts NEMA 5-15 to ‘crowfoot’. While one could still insert something into the Neutral socket, the polarity had been standardised, so there was minimal shock hazard. Power points for portable applications, such as caravans, are required to have double-pole switching since they may be used with extension cords with unknown wiring polarity. A further attempt at improving safety came in the late 1990s, when proposals were made to recess sockets, as is common in Europe. This was unpopular because of the multitude of existing plugs and plugpack transformers, which would not fit into recessed sockets. However, extension cord sockets fitted with a shroud did appear. In 2005, an alternative safety measure was introduced where plug pins were required to be insulated at the plug body end. Use elsewhere Fig.11: unless one knew that Hubbell is a US manufacturer, the assumption would be that this socket was made in Australia. Like Australia, NZ also imported electrical equipment and accessories from the USA, so it is perhaps not coincidental that both countries were using the same fittings. However, it is interesting to note that one wiring manual from the 1970s stated that British sockets were still permitted. Despite this, it does not appear that they were used then to any extent. For some years, NZ and Australian wiring rules have been the same (AS/ NZS 3000), allowing for a few local exceptions. Because of the Australian and NZ influence in the region, the three-flat- New Zealand also adopted the American design with apparently greater initial enthusiasm than Australia. There, another US design, the two-pin polarised “T” plug had also been used for 230V, along with the three-pin and two-parallel pin designs (see Fig.17). Fig.12: they are not particularly rare in the USA either. Here’s one in a collection of plugs seen on eBay. siliconchip.com.au Fig.13: this surviving example of a US-made (General Electric) power point is located in an old house in the Central West of NSW. Although still connected, it is doubtful anything has been plugged in for many years. Australia’s electronics magazine Fig.14: one of several newspaper articles from 1929-30 explaining the problem of having around 70 different types of mains plug and socket in use, and the need to standardise. September 2020  35 Fig.15: from Popular Science, April 1942, this shows the three-flat-pin plug still in use in the USA. Note that Active and Neutral are swapped compared to the Australian standard. pin plug design is standard throughout Commonwealth areas of the South Pacific. Argentina also adopted the threeflat-pin American plug, but the Active and Neutral connections are reversed to that used elsewhere, following the original US configuration (Fig.18). The plug design is classified under the IRAM 2073 standard. Because of the polarity difference, Fig.16: the plug at left is a very early HPM, while the modern plug on the right has shorter pins, as specified by the 1938 standard. The slight difference does not cause any compatibility problems. power leads and accessories for the Argentine market cannot be sold in Australasia and vice versa. But in reality, someone travelling between South Pacific countries and Argentina wouldn’t have any problems. Properly designed appliances accommodate the possibility of transposed Active and Neutral connections. China is a late adopter of this plug design (see Fig.19). It is difficult to find Fig.17: this advertisement from 1939 mentions the three types of American plug in common use in New Zealand. 36 Silicon Chip Australia’s electronics magazine any information on when and why it was adopted. However, Chinese power points also allow the insertion of two-pin American and two-pin European plugs, usually via a separate socket on the same plate but sometimes with extra holes in the same socket (a bit like a multisystem travel adaptor). Unlike Australia and NZ, they are not switched, and the socket appears upside-down to the usual convention. This is apparently a safety measure, so that if something conductive falls across a partially inserted plug, it’s less likely to form a short-circuit between Active and Neutral (in the modern Australian plug, the pin base insulation provides a similar benefit). The Active/Neutral polarity in China is the same as Australasia. Papua New Guinea was a territory of Australia until 1975 and naturally adopted Australian wiring practices. Other Pacific islands such as Pitcairn Island, Fiji, Vanuatu, Tonga etc use Australian/NZ wiring practices, since accessories are imported from these countries. Polarity was not originally standardised There was no official Active/Neutral polarity convention initially. After all, AC has no polarity, so an appliance will work connected either way round. In fact, until the 1960s most plugs were not even labelled as to which pin was Active (sometimes known as “live”, “line”, “hot”, or “phase”); only the Earth pin was designated. There was even a common doubleadaptor design which reversed the polarity of one socket, since it was easier to make that way (see Fig.20). Appliances from the 1950s wired in the factory with the red (Active) and black (Neutral) wires transposed in the plug are not uncommon. With a history of using bayonet light sockets and two-pin plugs, it was assumed that appliances could be connected either way round (see Fig.23). This approach continued even into the 1970s. For this reason, where a switch was provided for a portable appliance, it was usually a double-pole type. Switched light sockets, as used with desk or standard lamps, are a common example of this. This was not as unsafe as it seems. The first generation of power points used separate switches and sockets. siliconchip.com.au Fig.18: an Argentine power point. Although this one is switched, that is not mandatory, unlike in Australia. They were not a complete assembly, with switch integral to the socket (known as “combinations”) – see Fig.21. It was mandatory that Active was switched, but how the socket was connected after the switch was not critical. So, if the switch was off, the appliance was dead with either connection. However, there was a “recommended” standard which eventually became official, apparently during the late 1960s. This stated that, looking at the socket, the pin at upper left was Active. An easy way to remember this is that a modern single GPO has the switch on the left and is thus closest to the Active pin. Australia & NZ probably adopted this convention for that very reason. With most people being right-handed, it is natural to insert the plug with the right hand, leaving the left to operate the switch. In the USA, where sockets are not usually switched, this was irrelevant. As to why Australian sockets are always switched, early documentation from the 1920s explains this. At the time, it was noted that flexible cords were a somewhat common cause of fires and other faults. Therefore, it was safer to switch off the appliance before the flexible cord, rather than leaving it live when not in use. Not always Earthed Many years ago, I took the cover off an ancient porcelain socket in a house that must have been wired in the late 1920s, and was rather surprised to see no Earth wire connection. siliconchip.com.au Fig.19: Chinese socket also allows the insertion of non-polarised two-pin US and European plugs. It was a typical power point of the era, with the switch and socket mounted on a 6in x 3in timber block. It was probably the first generation of the three-flat-pin socket used in Australia. As I later learned, this lack of Earth connection was permitted in the wiring rules. The condition was that the socket had to be Earthed if there were other Earthed objects within a certain distance of the power point. Hence, a power point in a bedroom might not be Earthed, but one in a kitchen would be. This is not as dangerous as it may seem. Providing there are no other Earthed objects within reach, and the appliance becomes live, it’s unlikely to get a shock from it. Timber floors and walls make good insulators. To get a shock from a ‘floating’ appliance requires you to be part of a complete circuit to Earth. It appears this was allowed at least into the 1950s, and possibly later, but eventually it became compulsory to Earth all sockets. It was also in the 1970s that an Earth connection became required for all light fittings, even if out-of-reach of an Earthed object. Fig.20: a common older doubleadaptor design shows that the Active and Neutral polarity was not initially standardised as the adaptor swapped Active and Neutral top to bottom. points and switches were mounted on timber blocks. This, along with split seam steel conduit, was a legacy of British methods. While surfacemounted fittings and timber mounting blocks were still being installed later than this, flush-mount switches and power points were preferred for their modern appearance. These, like their US counterparts, sometimes had the switch and socket with separate cover plates, although single-unit “combinations” had appeared. Where the switch and socket Wall box dimensions It may also surprise some that it wasn’t just the three-pin socket we adopted from the USA, but also their wall box dimensions. Not only are the switch plate dimensions the same, but the screws used to secure the switch or socket have the same 6-32 thread. Australian fittings fit into a US wall box perfectly well, and vice versa. Until the late 1940s, most power Australia’s electronics magazine Fig.21: with separate switches and sockets, the socket polarity could be either way. The only requirement was that Active was switched. September 2020  37 Fig.23: the 1960s HPM plug on the left shows Live and Neutral polarity identification, but the older Ring Grip only shows the Earth connection. GPO plate orientation Fig.22: this assortment of power points shows the different pin orientations which have been used. Present standards require the Earth pin at the bottom. were still separate behind a standard cover plate, the polarity of the socket was still not guaranteed. By the 1960s, power points were being made with the mechanisms being part of one unit, with an integral switch plate. MEN system The MEN (Multiple Earth Neutral) system of earthing is another Americanism we adopted. In it, the Neutral is connected to Earth at the switchboard. The reasoning is that if the Earth connection to the water pipe (no longer recommended) or Earth stake has a high resistance, the fuse will still blow under fault conditions. The downside is that if the Neutral connection fails and the Earth connection is high resistance or non-existent, then the Earth wire, and all that is connected to it, could be at mains potential. What we did not adopt was the American colour code, instead sticking to the British scheme of red for Active and black for Neutral. This later changed to the current scheme of brown for Active, blue for Neutral and Green/Yellow for Earth in appliances and leads, although the old scheme is still allowed for fixed wiring. 38 Silicon Chip Even though Australia adopted the US-style wall plate, one area of departure was that unlike in the USA, power points were mounted horizontally. Horizontal mounting of power points was not common in New Zealand. Instead, they kept to US practice and most power points there were mounted vertically. Whether the Earth pin was up or down was another variable. It’s normally down, but some manufacturers such as Clipsal for a while had it at the top. HPM during the 50s and 60s even had the socket rotated by 90° from the usual orientation (see Fig.22). For some time now, the official orientation has the Earth pin at the bottom. The reasoning behind this is that if a plug should be partially withdrawn from a socket, hanging down, the Earth pin will still make contact, with Active and Neutral disengaging first. There is an opposing point of view as implemented in some other countries, notably the UK. This is that the Earth should be uppermost because if the plug is partially withdrawn and a conductive object falls into the gap (Venetian blinds are one recorded example), it will not become live. As mentioned above, this also possibly explains the Chinese orientation. Mains voltage There are many different mains voltages in use around the world, for reasons of development and politics. The first reticulated power system, implemented by Edison from the Pearl Street (New York) power station in 1882, was 110V DC. Given the prevalence of arc lamps at the time, this voltage suited two in series. Also, lamp-making technology, being as primitive as it was at the time, Australia’s electronics magazine Fig.24: one common plug and socket (shown without wall plate), used for 240V in North America. had difficulty making reliable lamps for higher voltages. However, as is well documented, a simple 110V reticulation system was very limited. For any given power, the current is doubled if the voltage is halved. But line losses quadruple due to the I2R rule. An improvement can be made by implementing a three-wire system where two 110V supplies are in series, giving 220V, with the common connection being Neutral. Provided the current drawn on both 110V supplies is close to equal, little current flows through the Neutral wire, and transmission losses are reduced. This scheme has been in used in the USA for a very long time now, except that the supply voltage has since been standardised at 240/120V, 60Hz. It does not seem to be widely known outside the USA, but most residences there do have a 240V supply. This is from a 240V centre-tapped winding on the pole transformer, the centre tap being the Earthed Neutral. However, the current per 120V branch of the circuit is still limited. This leads to the situation where domestic appliances that draw more than 1800W (15A <at> 120V) require a special 240V socket (Fig.24). There is a growing trend for American travellers to bring back kitchen appliances from Europe. After experiencing the faster heating time of 220-240V kettles and coffee machines, compared to the 120V version, they are keen to have a 240V socket installed at home. Europe In Europe, there was a mixture of 110V, 127V and 220V at 50Hz AC, or in a few instances, DC. If 127V seems siliconchip.com.au a little odd, it’s the phase-to-Neutral voltage of a 220V three-phase supply. However, 220V single-phase/380V three-phase was adopted as the standard, and the lower voltage systems replaced by the early 1980s. Siemens in Germany actively promoted 220/380V, with its advantages over the lower voltage systems. In Britain, with a very localised power generation and distribution system, there was little standard. Anything from 100V DC to 250V AC could be found, and the AC wasn’t always 50Hz! It depended on who built the generating equipment as to what the voltage and frequency would be. This all changed with the commencement of the National Grid in 1926. Its completion resulted in a nationwide frequency of 50Hz and a standard residential voltage of 230V. It was intended that not only would the UK use 230V, but so would the rest of the British Empire. That didn’t quite happen, with each country going their own way. In 1946, the UK standard was changed to 240V AC. Australian mains voltage Australia followed British practice and chose 200-250V for the single-phase residential supply, thereby avoiding the disadvantages of the 110120V system. Two- or three-phase supply (400/415V between phases) to homes is common in Australia. Apart from providing increased efficiency for all appliances, it is also used domestically for high-power loads, such as instantaneous water heaters, large air conditioners and some workshop equipment. Australian-made electric ranges allow for a two-phase supply where this is available. But the mains voltage in Australia wasn’t always standardised – see Fig.25. At one point, New South Wales, Tasmania and Queensland standardised on 240V 50Hz, with Victoria on 230V 50Hz. Heading west, 210V 50Hz was used in South Australia, and 250V at both 40Hz and 50Hz in Western Australia. There were once two large towns using 110V: Launceston (50Hz), and Broken Hill (100Hz). Away from the capital cities, there was more variation, with 220-250V DC being used in some towns. siliconchip.com.au Fig.25: from the Radio Trade Annual, 1937, this shows the variation in Australian mains supplies at the time. The reason W.A. was the odd-oneout with regards to frequency is that the 40Hz generating plant had been imported from South Africa. DC mains were also used in a small part of the CBD of some capital cities. In Sydney, the DC supply existed in the northern part of the CBD until the end of 1985, but by that time remaining only for lift motors. DC mains was reticulated using the three-wire system, which meant that depending on what side of the mains the consumer was connected to, the supply could be either positive or negative with respect to Earth. By the 1950s, plans were afoot to standardise Australia on 230V 50Hz in line with the Empire, and many localities, especially those using DC, went through the conversion process. Australia’s electronics magazine 240V areas were to be left as-is, being within 10% of 230V. Presumably because the 240V areas outnumbered the others, this became the standard instead (although it has since changed back to 230V). Victoria changed to 240V in the early 1960s. Adelaide started to move away from its 210V supply in the 1950s, and Western Australia dropped to 240V in 1985. If it seems like a huge exercise to convert to a new supply system, it must be remembered that at the time, houses had few appliances. In the 1950s, apart from incandescent lamps in each room, there would be a toaster, jug, cooking range, and a radio. The more affluent would also have a refrigerator, washing machine and maybe a vacuum cleaner. September 2020  39 Fig.26: the T-socket used for Extra Low Voltage supplies (up to 32V) at up to 15A. It is recommended that where the supply is referenced to Earth, the bottom pin should be used for this. All the heating appliances and lamps previously operating on DC worked the same on AC. Similarly, universal type brushed motors work on either type of supply. Should the new voltage be markedly different, eg, converting from 110V to 240V, it was a simple matter to replace the lamps and elements, which were all standard types. In the case of 110V appliances not easily converted, a step-down transformer could be used. Where the voltage change was minor, appliances like radios could be switched to a different tap on the power transformer. If it was part of a radiogram, the pulley on the turntable motor would have to be replaced when changing from 40Hz to 50Hz. The few AC/DC radios usually needed no modification, since most included a barretter to stabilise the valve heater current, and could accommodate a wide range of voltage. New Zealand voltages New Zealand had standardised nationwide on 230V 50Hz right from the start, although in Wellington there was Where do you get those HARD-TO-GET PARTS? Where possible, the SILICON CHIP On-Line Shop stocks hard-to-get project parts, along with PCBs, programmed micros, panels and all the other bits and pieces to enable you to complete your SILICON CHIP project. SILICON CHIP On-Line SHOP www.siliconchip.com.au/shop 40 Silicon Chip Above, a special plug and receptacle will maintain the polarity of a cord-connected appliance. Such a plug can be inserted in only one way. Fig.27: we can see here the American origin of the Australian ELV socket. However, in the USA it was intended for 120V use. NZ used it for 230V. an unusual 105V 80Hz supply from a steam-driven power station. With the disadvantages of the low voltage supply becoming apparent, it was decided in the mid-1920s to change to the 230V standard. This was completed in the early 1930s, by which time the power source was hydroelectric. Australia and the new 230V standard Since 2000, the “official” standard for Australian mains voltage is 230V. In a sense, this is déjà vu for those living in Victoria. However, this was really a case of being politically correct, because the actual voltage was not changed from the nominal 240V. The same situation occurred in the UK, although a few years earlier. In the 1980s, the IEC proposed to standardise on two world voltages: 120V and 230V. This was to assist manufacturers in making electrical products for a global market. The idea was that 240V and 220V countries would “harmonise” their mains voltage. Thus, the UK and Australia, for example, would drop their mains supply by 10V, and Continental Europe would increase theirs by the same amount. In Australia, a “230V Committee” was established in 1994 to oversee this transition locally. The perfect bureaucratic situation could be imagined here, with much paper shuffling but nothing else. In effect, nothing actually changed as far as the consumer was concerned; all that was done was to reduce the lower mains voltage limit to -6% instead of the previous -10%. The nominal 240V still falls well within that. One will note that incandescent lamps (including halogen types) sold in Australia are still rated at 240V, to reflect Australia’s electronics magazine Fig.28: cylindrical Earth pin connectors originally intended for lighting circuits. the truth of the situation. As summed up in one letter to the UK magazine “Practical Electronics” some years ago the change was “...only on paper”. Extra Low Voltage and the “T” plug & socket Rural homes not connected to any public supply usually used 32V DC, but sometimes 12V, 48V, or 110V DC, from a set of generator-charged batteries. These would be charged from a stationary engine or a wind generator. Another American socket had been adopted for these extra-low voltages known as a “T” socket (Figs.26 & 27), but unfortunately, many simply used the three-pin 240V type instead. Disastrous results awaited appliances so fitted with a three-pin plug, when taken to another location and plugged into a 240V power point. The two-pin parallel blade plug and socket has also been used for non-polarised ELV applications, particularly for 32V lead lamps. Although not ideal, it does prevent accidental connection to 240V. In the modern day, 32V DC systems only exist in the hands of vintage technology enthusiasts, since appliances have not been made for this voltage since the 1960s. Rural off-grid electrical systems today tend to be solarpowered and use 12V DC for small systems. Large systems are usually 240V AC, inverter-powered from a 24V or 48V battery bank. The “T” socket (Clipsal 402/32) is nowadays mainly used for 12V applications, such as in a solar-powered house, or for caravan, boat, and 4WD use. It’s also commonly used for portable lead lights powered from 32V AC isolating transformers. As mentioned previously, the “T” siliconchip.com.au DEAD OR DYING BATTERIES IN YOUR EBIKE? Fig.29: the American parallel flat pin non-polarised plug has the same pin dimensions and spacing as the Australian plug. So it is possible (but not recommended!) to simply twist the pins to enable insertion into an Australian socket. plug and socket was used in NZ for 230V. At that time, Australia and NZ had their own independent wiring regulations. The present-day status of this connector in NZ is not entirely clear. It is conceivable there might be very old installations where sockets of this kind are still connected to 230V. That would obviously be unacceptable if it was also used for ELV. Cylindrical Earth pins This was initially introduced for use on lighting circuits. A typical situation would be in a commercial building with a false ceiling. Here, the luminaires are usually connected by flexible cable to fixed sockets (see Fig.28). However, it never became popular for that purpose, with the conventional three-flat-pin sockets usually preferred. Instead, the cylindrical Earth pin configuration became used for all kinds of “special” applications. For example, it has been used to differentiate between circuits supplied by uninterruptable power supplies or isolating transformers, and the ordinary public supply. Other uses include connecting remote switches (eg, a switch for a room light mounted in a bedside table). Sometimes it is used for low voltages, despite the existence of the “T” plug and socket. Essentially, it is used where compatibility with the standard mains connector is undesirable. With the increase in appliances fitted with two-pin plugs, the design is no longer as incompatible as it once was. Therefore, the socket should not be fed with a voltage or frequency that could siliconchip.com.au damage a normal mains appliance. Once upon a time Until the 1980s, it wasn’t uncommon to see two-pin US plugs being used in Australian power points, as shown in Fig.29. This came about mainly from Japanese electronic equipment being sold in Australia from the 1960s onwards. Overseas travellers would also bring back appliances from foreign dutyfree stores. Because the pin dimensions and spacing are the same, a simple twist with a pair of pliers will enable the plug to fit into an Australian socket. There is, however, a shock hazard where the twisted pins prevent the plug from being fully inserted, and the plug has too narrow a body. There is also evidence that this weakens the pins and/or the connection to the cables. It is also handy to know that European plugs will fit into a standard appliance cord as used with old electric jugs and toasters. However, this should not be done where an Earth connection is required. As regulations were tightened, all appliances sold in Australia must now be compliant with Australian Standards. References • Practical Electrical Engineering, Vol. 2, Newnes. • Radio Trade Annual, 1937. • Electronics Australia, January 1986. • Amateur Radio Action, Vol.9, Issue 12. • Evening News, Sydney, January 21st, 1930, p15. SC • Popular Science, April 1942. Australia’s electronics magazine SEGWAY? MOBILity BUGGY? GOLF CART? ESCOOTER? Premier Batteries can recell and/or custom manufacture Lithium Ion batteries for Segways, Ebikes, Electric Golf Carts, Scooters and Mobility Buggies – often with increased capacity and range etc. Quality cells are used and batteries are Fully Guaranteed PREMIER BATTERIES High quality batteries for all professional applications SUPPLIERS OF QUALITY BATTERIES FOR OVER 30 YEARS Unit 9, 15 Childs Road Chipping Norton NSW 2170 Tel: 02 9755 1845 email: info.premierbatteries.com.au Web: www.premierbatteries.com.au September 2020  41 by Andrew Woodfield Using fewer than twenty inexpensive parts, this compact little audio oscillator can fit into your shirt pocket, yet it delivers a super-accurate sinewave when and where you need it. It even fits into a snazzy 3D-printed case! A Shirt-Pocket Crystal-locked Audio DDS Oscillator C ing tested. That can be handy in some ler, a rotary encoder with integrated ompact, battery-powered test audio test setups. push switch for output frequency segear is really useful if you have lection, a compact I2C OLED display to travel a lot. It can be invaluCircuit description to show the selected frequency, and a able for some professional tasks in reThe complete circuit of the audio crystal for accurate timing. mote places, or you can use it to work oscillator is shown in Fig.1. It uses an A few other passive components on your own projects while out and Atmel ATtiny85 8-pin microcontrolcomplete the design. about, should the opportunity arise. The ATtiny85 micro (IC1) forms This equipment must be small, the heart of the design. Its main clock light, and inexpensive. It’s all too is generated using a standard 8MHz easy for equipment to be damcrystal with two 15pF ceramic load aged or lost. capacitors, and its internal oscillaThis oscillator is equally usetor amplifier. ful around the workbench. It deThe small 64x32 pixel OLED dislivers very accurate audio tones, play is used to show the selected just like much larger and more audio output frequency. A customexpensive equipment. designed font provides excellent disBeing battery-powered and in a play clarity. It connects to the small plastic case, it’s easy to Actual size of the case (including knobs) is 75 x 30 x isolate it from the circuit be- 50mm so it will easily fit in your pocket (as shown above). ATtiny85 via a two-wire I2C 42 Silicon Chip Australia’s electronics magazine siliconchip.com.au bus (SDA for data and SCL for clock). Two I2C bus pull-up resistors are typically connected to each of these I2C bus lines. Here, these resistors are inside the OLED display module, reducing the parts count. Compatible OLED screens are made by several vendors; most data sheets give 3.3V as the maximum supply voltage. A few suppliers suggest they can run off 5V, but we’re keeping it under 3.3V for wider compatibility. A standard ATtiny85 chip will operate from 2.7V to 5.5V, according to the Atmel/Microchip data sheet, with a maximum clock speed of 4MHz at 2.7V. However, I bench tested more than 30 devices from multiple batches and found that they will cheerfully operate down to 1.65V using either the internal or external 8MHz clock. Therefore, I thought it reasonable to power the device directly from a battery of two regular AAA cells in series. It’s a simple solution supplying a nominal 3V for the modest load current of 10mA. The battery life will vary depending on specific requirements. The oscillator, including display, will successfully operate down to the typical end-of-life voltage of the pair of AAA batteries, around 1.8V. Given this, you can expect about six months of intermittent use, ie, an hour or so of use every couple of days. Rotary encoder The rotary encoder selects the re- Features & specifications • Frequency range: 1-9999Hz in 1, 10, 100 or 1000Hz steps (user selectable) • Frequency accuracy: crystal-locked to within 0.002% at 1kHz • Output level: 0 – 1.5V peak-to-peak (0 - 530mV RMS) sinewave (3V supply) • Total harmonic distortion (THD): less than 3% • Display: 0.49in (12.5mm) 64x32 pixel OLED • Power supply: 2 x AAA cells <at> 10mA typical • Battery life: estimated six months of intermittent use • Enclosure: 3D-printed compact clip-together PLA clamshell or standard Jiffy box • Size (in clamshell case): 75 x 30 x 34mm (excluding 3D-printed knobs)    75 x 30 x 50mm (including knobs) • Weight: 75 grams (with battery) quired output frequency and the tuning step size. The photo overleaf shows what a typical quadrature rotary encoder with pushbutton looks like. The circuit arrangement used here is unusual, detecting rotary encoder rotation and button pressing with a single I/O pin on the microcontroller! Usually, the two quadrature outputs of a rotary encoder are connected to separate pins on the microcontroller. The integrated pushbutton switch on the encoder then often demands an additional pin. That would result in the need for at least 10 pins total on the microcontroller in this application. Instead, I have used a basic threeresistor analog-to-digital converter (ADC) along with a noise-reducing 10nF capacitor to connect all three switches internal to the rotary encoder to one micro I/O pin. The component values used are important. They ensure that the closing of any of the internal three rotary encoder switches will generate a logic high-to-low ‘pin-change’ interrupt on the microcontroller. This allows the use of an event-driven interrupt handler routine to quickly and efficiently update the audio oscillator frequency within the very fast ‘direct digital synthesis’ (DDS) software loop. This DDS software method prevents the use of the commonly used periodic timer interrupt, which would introduce a regular and unacceptable pause in the sinewave output. The pinchange interrupt method also delivers an improved encoder response; there is no need to wait for a periodic timer to detect rotation or switch closure. The response to rotating the knob is immediate.     SC  SHIRT POCKET AUDIO OSCILLATOR Fig.1: the complete Audio Oscillator circuit. It is based around microcontroller IC1, an OLED display, a rotary encoder and an output filter/level control. The filter converts the 62.5kHz PWM signal from pin 6 of IC1 (which has a varying duty cycle) into a smooth sinewave by removing the higher frequency components. siliconchip.com.au  Australia’s electronics magazine  September 2020  43 Scope1: the waveform at pin 1 of IC1 when rotary encoder RE1 is rotated one step clockwise. Oscilloscope screen grabs Scope1 & Scope2 show the resulting waveforms at pin 1 of the micro, for clockwise and anticlockwise rotation respectively. The sharply falling leading edge triggers the interrupt. The two different waveforms which follow this leading edge for each direction of rotation are then detected by the software by sampling the analog voltage on that pin. The tuning step size is changed using the encoder’s integrated pushbutton. Pressing this pulls pin 1 of IC1 directly to ground, below the voltages produced by encoder rotation. This allows the micro to detect the button press and switch to the next step size (1, 10, 100 or 1000Hz). The 10nF capacitor prevents switch bounce from interfering with the process of detecting encoder rotation. Sinewave generation The audio output tone is generated using pulse-width modulation (PWM) from one of the ATtiny85’s internal counter-timers, which is fed to its dig- Fig.2: potentiometer VR1 allows the output level to be adjusted over the full range of 0-530mV RMS. However, if you want switchable ranges, they could easily be incorporated using a scheme like this. 44 Silicon Chip Scope2: the waveform at pin 1 of IC1 when rotary encoder RE1 is rotated one step anticlockwise. It is almost a mirror image of Scope1. ital output pin 6. Its 62.5kHz modulated carrier is higher than usual with an 8MHz crystal; a tradeoff resulting in 1% higher distortion. A simple passive 3-pole elliptical low pass filter comprising three capacitors and one inductor, after the 1kΩ resistor from pin 6, filters out the carrier from the wanted sinewave. This filter has a 40dB notch around 60kHz. This filter method reduces current consumption and the component count. The PWM output is matched to the filter using that 1kΩ resistor. Otherwise, the low output impedance of the microprocessor pin would cause increased waveform distortion, particularly below about 1.5kHz. The filtered sinewave output voltage level of about 1.5V peak-to-peak can be adjusted using the front panel level control potentiometer, VR1. Resistor RX is optional. It may be a simple wire link if the output range is suitable for your applications, or an extra resistor can be added to reduce the maximum level. Alternatively, a two- or three-way switch and additional resistors could be added in series with the output potentiometer to provide a range of output levels, if space permits. Fig.2 shows one possible arrangement using a three-way switch. Space has been provided for wiring this into the PCB using the connections for RX. The version described here does not implement this optional feature, making the finished oscillator as small as possible. The output does not include any DC blocking capacitor. Most equipAustralia’s electronics magazine ment you would feed the sinewave into will have an input capacitor. But if required, a suitable capacitor could be squeezed into the remaining space around VR1. Software The software is written using a mix of assembly code and BASCOM, the BASIC-like compiled language for the Atmel/Microchip AVR family. Assembly code is used for the core tone generating routine which must be very fast. Other sections, such as the interrupt handler code and the I2C and OLED routines, are written in BASIC as they are not so speed-critical. The DDS lookup table contains 256 bytes of data defining the amplitude of the sinewave over time. The frequency is precisely determined by the value of the 24-bit word used to increment the DDS cycle accumulator. One byte (eight bits) of this word is used as a pointer into the sinewave amplitude data, with the other two bytes (16 bits) represent the fractional position. The 24-bit wide accumulator ensures excellent frequency precision, along with the accurate and stable crystal-controlled processor clock. A fast interrupt subroutine handles the rotary encoder and tuning step size selection. It looks for specific voltage changes to determine the direction of rotation, the number of turns, and the selection of tuning steps. The interrupt routine unavoidably disrupts the output waveform briefly while the frequency change is being made. But the waveform is never going to be pure when the frequency is siliconchip.com.au being adjusted anyway. Screen updates for the ultra-compact 64 x 32-pixel OLED display are sent via the I2C serial bus. The display’s integrated SSD1306 controller requires careful initialisation to deliver correct operation. Its parameter settings differ significantly from those needed for the larger and more common 128x32 or 128x64 OLED displays, despite using an identical controller. The display software also makes use of a purpose-designed character font for this display, shown in Screen1. It aims to maximise character clarity and visibility despite its size. The resulting four-digit display largely determines the frequency range of the oscillator. Displaying frequencies of 10kHz or above accurately would require five digits. That would reduce display clarity beyond acceptable levels, particularly for those of us with reduced visual ability. Note that smaller 0.42in (diagonal) 72x40 pixel OLED displays are available but oddly, they are built on a larger PCB than the 0.49” 64x32 pixel OLED display I chose! So there is little benefit in using one, but if you have one, it will work. The software is also compatible with some, but not all, 0.96in 128x64 OLED displays using SSD1306 controllers. A few of these have extremely slow (faulty) I2C reset performance and will not operate correctly with this software. The software will not work with any OLED displays fitted with an alternative “compatible” SH1106 controller. Rotary encoder selection The rotary encoder used in this design is critical. It must be a pulse-type rotary encoder. Unfortunately, these are visually indistinguishable from level-type encoders; worse, most suppliers will not tell you which type they are selling! Electrically, however, they are quite different. The two outputs on leveltype encoders change at the ‘click’ or detent as the shaft is rotated, with the two encoder output pins remain fixed in one of the encoder’s four quadrature output states when the shaft is stationary. In contrast, pulse-type rotary encoders produce a pair of short quadrature pulses mid-click, with both encoder output pins resting open circuit. These encoders are the most commonly supsiliconchip.com.au Parts list – Audio DDS Oscillator 1 PCB coded 01110201, 65.5 x 24.25mm 1 8MHz low-profile crystal (X1) [Altronics V1249A] 1 ATtiny85 8-bit microcontroller, DIP-8, programmed with 0111020A.hex [Jaycar ZZ8721 or Altronics Z5105] 1 8-pin DIL IC socket 1 pulse-type rotary encoder with integrated pushbutton switch (RE1) [see text] 1 DPDT slide switch (S1) [Jaycar SS0852, Altronics S2010] 1 0.49in 64 x 32 I2C OLED display module [eBay, AliExpress etc] 1 15mH molded radial choke (L1) [eg, Murata 17156C (Digi-Key) or Murata 22R156C (RS)] 2 2-pin headers and matching sockets (CON1 & CON2; optional) 1 4-pin SIL header socket, ideally a low-profile type (CON3) 1 4-pin header (plugs into CON3; may come with OLED screen) 2 knobs to suit RE1 & VR1 [3D printed or Altronics H6016] 1 2 x AAA side-by-side cell holder (optional; see text) [Jaycar PH9226, Altronics S5052] 1 pair of small alligator clips [Jaycar HM3020, Altronics P0101+P0102] 1 3D-printed plastic enclosure, assembled size 75 x 30m x 34mm (or a UB5 Jiffy box – see text) 1 300mm length of light- or medium-duty two-core cable 1 100mm length of red light-duty hookup wire 1 100mm length of black light-duty hookup wire 1 20mm length of insulated solid-core wire (eg, bell wire or breadboard jumper wire) Capacitors 1 4.7µF 50V electrolytic 1 100nF ceramic 2 33nF MKT or greencap 1 10nF MKT or greencap 1 470pF ceramic 2 15pF ceramic Resistors (all 1/4W 1% metal film) 1 10k 1 3.9k 1 1.8k 1 1k 1 1k linear 9mm potentiometer (VR1) [Jaycar RP8504, Altronics R1986] Programming Adaptor Board (optional) 1 PCB coded 01110202, 25.5 x 22mm 1 8-pin DIL IC socket 1 3x2 pin header (CON4) 1 3mm red LED (LED1) 1 100nF ceramic capacitor 1 1k 1/4W resistor plied at low cost from Asian sources. This open-circuit condition at the rest position is critical for generating the desired encoder interrupt waveforms A mugshot of the troublesome rotary encoder. Unfortunately, level-type encoders are externally indistinguishable from the pulse-type encoders that we need. You just have to take an educated guess about which one to order, then test it when it arrives, using the procedure described in the text. Australia’s electronics magazine used in this design. These two encoder types can be quickly and easily distinguished with a continuity tester. An encoder can be tested using an ohm-meter or even an arrangement as simple as a series LED, resistor and battery as follows: 1. Connect one lead of the continuity meter to the centre pin of the three (ignore the two on the opposite side). 2. Connect the other lead to one pin on either side of the centre pin; it doesn’t matter which. 3. Rotate the shaft one click. 4. Measure the continuity while the encoder is at rest. 5. Repeat steps 3 and 4 several times. September 2020  45 Fig.3: the components mounted on the PCB, with matching photos to assist assembly. Don’t fit CON1 & CON2 when using the printed case. The wire link (shown in red) is not needed on  commercially-made double-sided boards. The OLED screen     (not shown in the photo at right)       plugs into CON3 after the other components have If the encoder is a pulse type, the been fitted. meter should show an open circuit     (very high resistance) at all rest positions. You should see a brief period of continuity (low resistance) while rotating the encoder. If the encoder is a level type, the meter will show continuity on every second detent position and an open circuit on the other detent positions. So my suggestion is to order an encoder from a website like ebay, AliExpress or Banggood and then verify that it is the pulse type using the above method before proceeding with construction. Construction The Pocket Crystal Audio Oscillator is built on a PCB coded 01110201 which measures 65.5 x 24.25mm. I etched mine at home, but the commercially-made version available in the SILICON CHIP ONLINE SHOP only costs a couple of dollars. Refer to the PCB overlay diagram, Fig.3, to see which parts go where. For those making this single-sided PCB at home, the board may be left square if it will be fitted into a Jiffy box, or trimmed carefully along the curved PCB outline if using the 3Dprinted enclosure. Construction should begin by fitting the resistors and then the capacitors. The single electrolytic capacitor is the only polarised one; its longer lead goes into the pad nearest the edge of the board, marked with a + symbol. Also, space the 4.7µF electro off the board by about 1.5mm to allow it to be bent over when inserted later into the 3D printed case. Next, solder the crystal onto the PCB, followed by the 8-pin IC socket. Ensure that the pin 1 notch on the socket faces in the direction shown. If you’ve etched the board yourself, you need to fit one insulated wire link, shown in red on Fig.3. The commercial board should have a top layer track joining these points, so you won’t need to install a link. Next, mount the four-way header socket for the display (CON3), then the 15mH moulded inductor. Follow with the rotary encoder and potentiometer. Depending on the type of 9mm potentiometer you purchase, it may either mount directly onto the PCB or use component lead off-cuts to extend its leads to allow vertical mounting. If doing that, it would also be a good idea to glue the pot body to the board (eg, using neutral-cure silicone) as horizontal pots lack the mounting tabs of the vertical types. Next, fit a pair of thin, 50mmlong red and black insulated stranded wires to CON1 for power. You can use a header and socket or, as I did, simply solder the wires to the PCB pads. Similarly, connect the 300mm output twin lead to CON2. If you don’t have twin lead, you could use heatshrink tubing on a pair of individual light- or medium-duty hookup wires. Do not fit anything to the other end of these wires just yet. Programming IC1 If you have a blank micro, program it as per the box labelled “Programming the ATtiny85”. After programming (or if you purchased a preprogrammed micro), plug it into the socket, ensuring that its pin 1 dot lines up with the notch on the socket. You may need to straighten its leads to fit into the socket. Be careful not to allow any of the leads to fold up under the chip body during insertion. Next, plug the OLED display into its socket on the PCB. The screen is usually supplied with a four-way 0.1inpitch header. If it has not already been fitted to the display PCB, solder it now. Next, if you’re using a standardheight header socket for CON3, use Audio DDS Oscillator Hz TUNE LEVEL Fig.4: this artwork can be printed, laminated, cut out and attached to the front panel of the unit using glue or double-sided tape. You can also download this as a PDF from the SILICON CHIP website. 46 Silicon Chip Fig.5: renderings of the 3D printed front and rear panels that form the custom case, along with the 3Dprinted knobs. The associated STL files can be downloaded from our website, or you can purchase these pre-made. The back panel has an integrated battery holder, but you need to fabricate or acquire the spring terminals and clips (eg, as part of the SILICON CHIP kit), as described in the text. Australia’s electronics magazine siliconchip.com.au Programming the ATtiny85 If you haven’t purchased a preprogrammed ATtiny85, you will need to program your blank chip before you can use it. You can use an AVR ISP programmer such as the USBasp (See www.fischl.de/usbasp/). It can be purchased online from many suppliers, often for less than $3, including delivery! Such programmers are used with a PC or laptop; suitable software is available for Windows, Linux and macOS. This description will focus on the Windows platform. The drivers for the chosen programmer must be installed before using it. The drivers for the USBasp can be obtained from the link above. Programming software is also required. (Freeware) software for Windows includes eXtreme Burner (siliconchip.com.au/link/ ab3m), AVRDUDESS (siliconchip.com.au/link/ab3n) and Khazama (http://khazama.com/project/programmer/). There are many websites and YouTube videos describing the setup and use of these programs. Here is a summary of the procedure required to program the ATtiny85 for this project: 1) Load the USBasp drivers. 2) Plug in and complete the installation of the USBasp programmer. If the option is present on the USBasp programmer, and some boards support this feature, select 5V operation rather than 3.3V for programming the ATtiny85. 3) Download the programming software and install it. 4) Open the programming software and select ATtiny85 as the target device. 5) Download the HEX file for the audio DDS generator and select it as the file to be used to program the ATtiny85. 6) Plug the six-pin connector from the USBasp programmer into CON4 on the Programming Adaptor Board (more on this below). 7) Select “Write FLASH buffer to chip” or “Write – Flash” to program the ATtiny85 with the HEX file. The LEDs on the USBasp will blink furiously for about a minute while the HEX file is being   The ATtiny85 Programming Adaptor circuit just connects the micro pins to the 6-pin programming header, with a small power supply bypass capacitor. a spudger or a sharp-edged blade to carefully slide off the plastic pin separator from the pin header. Then trim the four pins shorter by about 2mm. This allows the display to fit as closely as possible to the top of the ATtiny85 chip. See the side view photo for an idea of how it plugs together. If you were able to get a low-profile header socket for CON3, that should not be necessary. It should just plug straight in, although you may still have to trim the header pins a little. The PCB can now be tested. Before you connect the 3V supply, carefully siliconchip.com.au programmed. A bar graph may be displayed to show progress. 8) Program the ATtiny85’s internal ‘fuses’. These memory locations configure the operating characteristics of the ATtiny85 to suit the software being run on the device. To do this, type in the following settings into the relevant Fuse page/section of the programming software, then click on “Write” to send the data to the fuses: Low: 0xEF High: 0x5F Extended: 0xFF (unchanged) Lock: 0xFF (unchanged) 8) Assuming the programmer reports the programming has been successful, remove the programming cable from the adapter board and transfer the ATtiny85 from the programming adapter board to its socket on the audio DDS oscillator PCB. Programming Adaptor Board There is no programming connector for the ATtiny85 on the oscillator PCB. I program my ATtiny85 chips using a separate adaptor built from a scrap of prototyping board with an 8-pin IC socket, the Atmel-standard 6-pin programming pin header and a couple of supporting components. The circuit diagram for my adaptor and the equivalent PCB are shown below. For those wanting to make a little PCB for this programming adaptor, if you don’t want to make it on veroboard, you can order this board when you order your main PCB (and possibly case), for just a couple of dollars more. The resistor and LED are optional. They show when power is applied to the Programming Adaptor Board from the USBasp programmer. The ATtiny85 to be programmed is plugged into the 8-pin IC socket; make sure it is orientated correctly, with its pin 1 dot near the notch. The USBasp programmer plugs into CON4, with its pin 1 towards the IC socket. Power for the programming adapter board comes from the USBasp. If your USBasp or similar programmer has a selection of programming voltages available, it’s best to select ‘5V’ for reliable programming of the ATtiny85. Fit the components as shown here; the two wire links can be made from component lead off-cuts. Pins 1 of both the IC and CON4 are at upper left. check all of your soldering for shorts or missed connections. If it looks OK, connect up a 3V supply (important: no more than 3.3V!) and check that the Oscillator operates as expected. Making the enclosure The enclosure should now be prepared and assembled with the battery holder and power switch. You can purchase a small Jiffy box enclosure from the usual suppliers if you wish. Alternately, you can get the 3D printed custom enclosure parts from the SILICON CHIP ONLINE SHOP, or Australia’s electronics magazine make them yourself if you have a 3D printer – see Fig.5. There are two files required to print the enclosure; the first is for the front panel half of the enclosure, the second is for the rear half with its integrated battery holder. These are available for download in the standard STL format. These can be 3D printed using standard PLA filament in any colour. The prototype enclosure was printed using grey filament with 50% fill and a 0.2mm layer thickness, although these parameters are not critical. Each half requires about 2g of filament. If you September 2020  47 One half of the custom case houses the PCB while the batteries fit neatly into the other half. The alternative would be to build the Audio Oscillator into a small jiffy box (or similar) but you probably won’t be able to fit it into your pocket! do not have your own 3D printer, it is also possible to go to a Jaycar maker hub and do it there. The two halves of the enclosure clip together firmly without the need for additional screws. The rear section’s integrated battery holder is dimensioned for two AAA cells. It requires the addition of battery contacts, wiring, and a battery joiner. The battery contacts can be made by cutting 4mm and 3mm diameter circles from thin tinplate. A scrap piece of 0.2mm-thick tinplate was used for the prototype. It is possible to recycle a domestic tin can; Milo tin lids are nice and flat. These handmade battery contacts should approximately match the divots provided inside the battery holder at the switch end. Solder a 10mm length of thin red multi-stranded insulated wire to the centre of the smaller circle and a similar length of black wire towards one edge of the larger circle. The wire should then be fed through the switch end of the battery holder, and the metal circles glued in place using epoxy. Once the glue has set, test-fit a pair of AAA batteries. These should clip firmly into place side-by-side, but they will likely slide back and forth in the holder by about 1-1.5mm. Bend the battery joiner to take up that space. There is a slot provided for this foldScreen1: despite being quite tiny (at around 12mm diagonal – it’s shown here about twice life size), the currently selected frequency is clear due to the bold font, with its four digits occupying the entire width of the screen. 48 Silicon Chip ed joiner to be inserted into one end of the battery compartment. To make this, cut a 60mm x 8mm strip of tinplate. Trim and bend it approximately into a flattened C shape to fit the available space. When folded correctly, the batteries will fit snuggly into the battery holder. Along with the PLA plastic of the case, the arrangement will also provide a little tension to maintain good battery contact. A useful accessory during this process is a voltmeter clipped to the black and red wire. This allows all of the connections to be checked for reliability during final assembly. Completing construction The wiring to the slide power switch can now be completed. Begin by connecting the short red and black wires from the PCB to the switch. They should be about 50mm long. Make sure the power switch is off and the batteries are removed from the holder before soldering the power wiring in place. The switch can now be mounted on the rear panel using a little hot melt glue or neutral-cure silicone sealant. If your slide switch has mounting tabs, trim these off first using a pair of side-cutters. Mount the PCB in the front half of the enclosure, first feeding the output wires through the hole provided. The PCB assembly is mounted using the nuts and washers supplied with the rotary encoder and potentiometer. Vertical-mount potentiometers may not have nuts; in this case, it will just be the rotary encoder boss and nut holding in the board. The small alligator clips may now be fitted to the output wires. Alternately, if you are using a Jiffy box, you may prefer to use a small output connector mounted on one end of the box. Options include a panel mounted RCA socket (eg, Jaycar Cat PS0270 or Altronics Cat P0161 etc), or a 3.5mm audio socket (eg, Altronics Cat P0093 or Jaycar Cat PS0122 etc). Print the front panel artwork (Fig.4) and attach it to the front of the enclosure. The artwork can be printed using a colour laser or inkjet printer. Trim the artwork to size and cover it with self-adhesive transparent film. This panel artwork can then be glued Australia’s electronics magazine to the front of the enclosure. Doublesided adhesive tape can be used quite successfully. If using glue, it is desirable to cover the rear of the artwork first with another piece of self-adhesive film to prevent the glue bleeding through the printed artwork. The two knobs can now be fitted to the control shafts. The prototype used two knobs specifically designed for the unit which were 3D-printed (see Fig.5). These STL files are also available for downloading, or if you purchase the 3D printed case, it will come with the knobs. These slide firmly onto the respective control shafts. Alternately, see the parts list for commercially-made alternatives. The final step is to install the battery. Then clip the case together, and the oscillator is ready for use. Operation It couldn’t be easier. Switch it on, select the frequency you want with the tuning knob, set the desired output level with the level control, and you are in business. Press the tuning knob to step through the various frequency step options: 1Hz, 10Hz, 100Hz, 1kHz and then back to 1Hz again. Despite its simplicity, this compact little audio oscillator is surprisingly useful. I hope one of these finds a home in your shirt pocket too. SC OBTAINING THE PARTS Because of the difficulty in sourcing the pulse-type rotary encoders used in this project with any certainty, the SILICON CHIP ONLINE SHOP will be stocking and selling them (Cat SC5601). We will check each batch to make sure they are the right type! This part can also be used in some of our previous projects, such as the AM/FM/CW Scanning HF/VHF RF Signal Generator and the DIY Solder Reflow Oven. We have also decided to offer an (almost) complete kit for this project, Cat SC5622. It will include the programmed micro, PCB, all onboard parts, and 3D-printed case. The case has been tweaked to accommodate pre-made AAA battery clips, which will also come in the kit. We’ll be supplying standard knobs with the case (not 3D printed). The only parts not included are the wires and battery. See our Online Shop on pages 104 & 105 for more details. siliconchip.com.au 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. Low-power flashing LED thermometer This circuit shows how a simple green LED can be used both as a temperature sensor and also to read out the temperature! As with a standard silicon diode, the LED’s forward voltage has a temperature coefficient of about -3mV/°C (usually within the range of -1.5mV/°C to -3mV/°C), as per Vektrex application note AN051608A. This means that with a 10-bit analog-to-digital converter (ADC) and a reference voltage of around 3.072V, we can measure the ambient temperature with a resolution of about 1°C. I wanted to use a tiny 6-pin PIC10 microcontroller which only has an 8-bit ADC. I found that by averaging multiple readings (specifically, 16), I was able to approximate the precision of a 10-bit ADC to get the desired 1°C resolution. As the PIC10F222 doesn’t have a reference voltage pin, I am instead running it with a supply voltage of 3.072V, and this also forms the ADC reference voltage. Before making temperature meas- siliconchip.com.au urements, LED1’s diode junction is forward-biased by bringing the GP1 output (pin 3) of IC1 high, to +3.072V. The 10kW resistor value limits the current to a low level, preventing LED1 from lighting and also minimising self-heating. It then makes the 16 ADC readings, averages them and computes the temperature. Digital output GP0 (pin 1) is then pulsed high, flashing LED1 to indicate the temperature. First, the temperature (in °C) is divided by ten and the remainder computed. This many short (25ms) pulses are emitted at one-second intervals. Then, the result of dividing the temperature value by ten is flashed out in longer (256ms) pulses, also at 1Hz. So by counting the number of short and long pulses, you can tell the temperature. In the example shown here, with four short and two longer pulses, the temperature reading is 24°C. The circuit then sleeps for four seconds, and the whole process repeats as Australia’s electronics magazine long as the circuit has power. When power is first applied, LED1 lights for ten seconds. Measure the ambient temperature with another thermometer, then press calibration button S2 once for each 1°C above freezing (eg, if it’s 20°C, press it 20 times). LED1 blinks off briefly each time S2 is pressed. The value is stored in RAM as the micro lacks EEPROM, but the battery lasts a long time, so you don’t have to recalibrate it frequency So that the battery lasts a long time, the 3.072V supply for IC1 comes from low quiescent current, low dropout regulator REG1. This is also a Microchip product. It’s an adjustable regulator so we can set its output pretty close to 3.072V via the string of three resistors between Vout, ADJ and GND. It is fitted with the required input bypass and output filter capacitors, plus a 10nF capacitor to improve ripple rejection, bypassing pin 4 (ADJ). The regulator can be powered from a Liion cell or similar, via slide switch S1. In case you can’t easily get the TC1187, you can build a more-orless equivalent low-dropout regulator September 2020  49 circuit from discrete parts, as shown below the main circuit. All you need is one standard NPN transistor, one PNP transistor, a common TLV431 voltage reference and a handful of passives. Adjust VR1 to get the output as close to 3.072V as possible. Transistors Q1 and Q2 are arranged in a complementary or Sziklai pair, acting similarly to an NPN transistor but with more current gain (beta). The TLV431 (VREF1) sinks more current via its cathode as the voltage at its REF pin exceeds 1.2V, so when the output voltage rises, it diverts current from the 120µA flowing to the base of the transistor pair via the 12kW resistor from the input supply. This switches Q1 and Q2 off, lowering the output voltage. Similarly, if the output voltage drops, VREF1 switches Q1 and Q2 on harder, bringing the output voltage back up. It is this negative feedback action which regulates the output voltage to the desired value, and under steady- state conditions, the whole circuit only draws 157µA (120µA + 37µA) more than the load current. The 1µF capacitor across VREF1 helps to stabilise the circuit, preventing high-frequency oscillation and overshoot, as does the 1µF output filter capacitor. The PIC10 firmware was written in assembly language. The source code (OneLED.asm) is available from siliconchip.com.au/Shop/6/5627 Benabadji Mohammed Salim, Oran, Algeria. ($80) Adjustable power supply using a fixed voltage switchmode regulator This power supply circuit efficiently provides one of eight possible voltages over the range of 3.3-18V, one of which can be customised. It does this using a single regulator intended to be used in a fixed-voltage application; specifically, delivering 3.3V. The power source is a common laptop charger ‘brick’. It works by inserting a series resistance between the output terminal and the feedback pin (pin 1) of step-down (‘buck’) switchmode regulator chip REG1. This adds to REG1’s internal resistance at the top of its internal feedback divider, thus influencing its target output voltage. With rotary or slide switch S1 in the 3.3V position, the output voltage is fed back directly to pin 1 of REG1, and it operates as intended. In one of the higher voltage positions, different value resistors are inserted in series. REG1 has an internal 1.7kW/1.0kW 50 Silicon Chip divider between pins 1 & 4 (power ground), resulting in a nominal 1.23V going to its internal error amplifier for a 3.3V output voltage. The resistors added via switch S1 increase the division ratio, so a higher output voltage is required to produce the same internal 1.23V feedback. Hence, rotating S1 increases the output voltage in steps. There are seven standard fixed voltage selections available. In the eighth position, potentiometer VR1 is connected in series with the feedback pin, so you can adjust VR1 to get any output between 3.3V and 16V. Inductor L3 and the following 100nF and 220µF capacitors form the buck regulator LC filter, while schottky diode D2 is the freewheeling diode that prevents switch pin 7 of REG1 (OUT) from going too far negative during its internal switch off-time. The buck regulator output is fed to one pin on Australia’s electronics magazine the three-way terminal block, with a pi filter providing a secondary, lowernoise (but worse regulated) output rail. LED2 lights up to indicate that the circuit has power while LED3 lights up to show when there is a voltage at the output, and will get brighter as the output voltage increases. As red LED1 is wired up in reverse across LED2, it will only light up if the input supply polarity is wrong. In this case, fuse F1 will blow due to high current conduction via protection diode D1. Several capacitors plus a common mode choke between the DC input and regulator REG1 prevent switchmode noise from being radiated back along the supply wiring, and the 100µF, 100nF and 1nF capacitors at pin 5 of REG1 (Vin) also act as its supply bypass capacitors. Petre Petrov, Sofia, Bulgaria. ($70) siliconchip.com.au Giant 1024-pixel RGB LED clock An 8x8 RGB LED ‘Neopixel’ display module was described back in the January 2020 issue (siliconchip.com. au/Article/12228), and one was used in the Ol’ Timer II clock (July 2020; siliconchip.com.au/Article/14493). But did you know that 16x16 LED versions are also available? When I saw that they only cost about $20 each, I decided that I had to build a giant 32x32 (1024-pixel) LED clock using four of those modules and a few other bits and pieces. As each 16x16 module measures 160x160mm, the finished clock is 320x320mm and it looks fantastic hanging on the wall. The total cost for the project was just over $100. The only disadvantage of using LED arrays to create a wall clock is the power consumption. I decided to limit the maximum brightness to 40% (not just to save power but also my eyes!), but that still means you need a 4A 5V supply to drive it. That’s despite only about one in five LEDs being lit at any given time. My design includes a GPS module for accurate timekeeping, but since it is based on an ESP8266 microcontroller module with WiFi, you could leave off the GPS module and use internet (NTP) time instead. The software would need a few changes to accomplish this. See my previous submission, the NTP OLED clock from February 2018 (siliconchip.com.au/ Article/10975). Having received the 16x16 LED matrices I ordered, I discovered that they are effectively four 8x8 matrices glued and wired together. Hence, they are shown on the circuit that way. Note that the physical layout of the modules shown on the circuit doesn’t match the actual layout of the displays, since each 16x16 module is square but is shown running across the page for clarity. As you can see from the diagram overleaf, besides the GPS modules, D1 Mini micro board and the LED displays, there isn’t much else involved. An optional 128x64 mono OLED screen shows the received GPS data; the clock will work fine without it. The 5V supply that runs the LEDs is regulated down to 3.3V for the D1 Mini, GPS receiver and OLED by an AMS1117 low-dropout linear regulator. As described in the January 2020 article, the WS2812B RGB ‘pixels’ are siliconchip.com.au updated using a special type of serial data stream, and this snakes its way through all 1024 devices in the display from the D4 digital output of the ESP8266 module. If using the GPS receiver, it will need to be near a window to find the signal from the GPS satellites. The GM-22U7 is extremely fast to acquire the satellite signals, so apart from the first power-on when it has to get the almanac data, the time and date appears within a few seconds. Australia’s electronics magazine The clock display colour changes every minute. The colour scheme is defined in an array in the file colors.h, which is in the same directory as the main sketch file (the code itself). The main sketch (neopixel-gps-clock6), a sketch to test whether the 1024-pixel array has been wired up correctly (led-matrix-test) plus the required third-party libraries are available from siliconchip.com.au/Shop/6/5628 Bera Somnath, Vindhyanagar, India. ($150) September 2020  51 1024-pixel RGB LED clock circuit diagram 52 Silicon Chip Australia’s electronics magazine siliconchip.com.au young maker electronics by PROJECTS FOR YOUNG MAKERS! $ TOBBIE II ROBOT KIT FOR MICRO:BIT FUN & EASY LEARNING FOR CODING Build-it-yourself hexapod robot with a 360° free-rotation body. Pair it with micro:bit board (XC4320 sold separately) to create the coolest projects you can program. 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XC4334 WAS $14.95 Build your own Retro Pi Arcade Console PLAY 000'S OF CLASSIC RETRO GAMES! 95 BREAKOUT BOARD WITH 2 X AA BATTERY HOLDER FOR MICRO:BIT Provides an independent 3V power supply to your micro:bit project and enables you to interface to other hardware. XC4330 WAS $19.95 995 $ RETRO NES CASE RETRO ARCADE GAME CONSOLE • Connects to your TV, computer or projector with HDMI or VGA cable • 2 Player console XC9062 $169 10" SCREEN RETRO ARCADE GAME CONSOLE • Includes a joystick and 6 buttons. • Built-in speaker XC9064 $249 WITH PURCHASE OF XC9001 AND EITHER XC9062 OR XC9064 54 click & collect Supplied with 400-hole breadboard, designed to break out all IO pins on your micro:bit for you to create additional circuits and hardware. XC4332 WAS $23.95 JUST See website for detailed install instructions. (VALUED AT $24.95) SAVE 15% PROTOTYPE BOARD WITH 400 PIN BREAKOUT BOARD FOR MICRO:BIT SNES layout. Features A/B/X/Y buttons, start, select, and direction controls. Easily configurable, USB powered. XC4404 Let the games begin with these exciting retro arcade consoles. Simply install a Raspberry Pi 3B+ (XC9001 $89.95 Sold Separately), into the console, insert a Retropie installed micro SD card (XC9031 $24.95 Sold Separately), copy over some games and you are ready to play. BONUS GIFT: FREE RETROPIE OS ON SD CARD 1995 $ RETRO NES STYLE CONTROLLER ONLY 249 $ NOW ONLY 169 Perfect for building a Raspberry Pi 3/3B+ based emulator. • HDMI, 3.5mm, and micro USB (power) access • USB Ports: 4 (Standard, Type –A) XC4403 $ + OR Buy online & collect in store = FREE ONLY 3995 $ ON SALE 24.08.2020 - 23.09.2020 ARDUINO® COMPATIBLE DUINOTECH LEARNING KIT 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! XC3900 BUILD A Snake GAME FINISHED PROJECT FROM XC3900. NO ADDITIONAL PARTS NEEDED. Once you have successfully performed some of the online tutorials, you can build this fun old ‘Snake’ game (Reminiscent of the old Nokia phone and Atari days – showing our age?). All of the necessary components are already included in the XC3900 kit to the left. JUST 7995 $ SEE PARTS & STEP-BY-STEP INSTRUCTIONS AT: www.jaycar.com.au/snake-game ® I P & O N I U D R MICRO:BIT, A NOW ONLY JUST 9 $ 95 12 $ ARDUINO® COMPATIBLE KEYPAD MODULE Compact 16-key touch interface for your project, based on the TTP229 capacitative touch sensor IC. Works on 2.4-5.5V. Onboard power indicator. • Two wire serial data interface • 65(L) x 50(W) x 12(H)mm XC4602 JUST $ 49 $ 95 ALSO AVAILABLE: 2 x AA Batteries SB2424 $1.95 In the Trade? 37-PCE DELUXE MODULES PACKAGE Includes commonly used sensors and modules for Duinotech and Arduino®: joystick, magnetic, temperature, IR, LED and more. Packaged in a clear plastic organiser. XC4288 WAS $99 See website for full list of included modules. Build your own Arcade Joystick PT4631 An Arduino-based 8-bit handheld game console that you can code or upload your favourite games. Driven by an Arduino® Leonardo and features a 1.3” OLED screen and volume control. USB powered or from 2 x AA batteries (not included). XC3752 SAVE $20 Large, colourful touch display shield which piggybacks straight onto your UNO or MEGA boards. Fast parallel interface. • MicroSD card slot • Resistive touch interface • 77(L) x 52(W) x 19(H)mm XC4630 NON-INSULATED SPADE CONNECTORS Packet of 10. 6.3mm size. 10A max. Socket PT4630 Plug PT4631 BUILD-A-GAME LEARNING KIT 95 240 x 320 LCD TOUCH SCREEN FOR ARDUINO® Build your very own customised Arduino® compatible projects. Comes with Uno bootloader and 16MHz crystal oscillator. ZZ8727 SEE WEBSITE ON HOW TO PROGRAM AND MODIFY YOUR OWN GAMES! ONLY 29 95 ATMEGA328P MCU IC DIY Game console 79 $ USB INTERFACE FOR JOYSTICK AND BUTTONS PT4630 JUST 375 $ ILLUMINATED ARCADE BUTTON SWITCHES EA Suitable for arcade games, flight simulators or anything that works with a USB joystick. XC9046 Brightly coloured pushbutton switches ideal for creating a custom arcade machine. Suits 25mm mounting hole. Red, yellow, green, blue & white colours available. • Microswitch for reliable operation • 6.3mm spade connections SP0662-SP0669 JUST 9 $ 95 EA ARCADE JOYSTICK WITH MICROSWITCHES JUST 1995 $ Ideal for arcade games and emulators. 2/4/8-way options NOW restrictor plate. • Metal mounting plate and main shaft • Removable knob SAVE SM1052 WAS $24.95 1995 $ SEALED POLYCARBONATE ENCLOSURES 5-WAY CRIMPING TOOL FROM JUST Moulded in light grey. IP65 rated. • Lid fixing screws are M4 stainless steel (non-magnetic) into threaded brass inserts 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 14 $ 95 HB6230 JUST $5 Cuts and strips wire. Can also cut bolts with diameter M2.6, M3.0, M3.5, M4.0 & M5.0. TH1828 995 $ 55 INTRODUCE YOUR LOVE OF ELECTRONICS TO YOUR KIDS MAKEY MAKEY LEARNING KIT Have fun using everyday objects to create innovative projects e.g make a piano using bananas. Ages 8+. • Supplied with six coloured leads with alligator clips, USB cable and jumper wires to provide even more output. XC3750 WAS $49.95 NOW 698-IN-1 SNAP ON ELECTRONIC PROJECT KIT Build up to 698 different experiments. Easy snap together no tools required. Ages 8+. KJ8985 39 $ 95 SAVE $10 Uses conductive and insulating play dough to teach the basics of electrical circuits. Comes with more items and plenty of pre-made doughs so you can start circuit building right away! Ages 8+. KJ9352 JUST 89 129 $ $ ENHANCE THEIR CREATIVITY 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 See website for details For kids captivated by colours and craft, nurture their creativity with these kits and readily available supplies in your household. JUST 79 $ VALUED AT OVER $125 PLANETARIUM EDUCATIONAL KIT POTATO CLOCK Build your own planetarium model. Snap to build, no glue required. Age 8+. KJ8994 Educational project kit for constructing a clock powered from a potato. Ages 10+. KJ8937 free Download your : BOOK COLOURING k /colouring-boo au www.jaycar.com. 6-IN-1 SOLAR ROBOT Build robots out of a can, water bottle or wasted CDs! 6 robots to build. Ages 10+. KJ8939 JUST 1295 9 $ 95 Learn about solar power and hydraulics. 12 easy to build models including crocodile, T-Rex, elephant, monkey, ostrich, scorpion, and excavator. Ages 8+. KJ9030 SALT WATER FUEL CELL ENGINE CAR KIT Demonstrate the concept of a salt powered automotive engine. Assemble, add salt water, and off the car goes! 120mm long. Ages 8+. KJ8960 JUST 39 $ click & collect 95 JUST 26 $ 95 SOLAR EDUCATIONAL KIT Experiment with solar energy the energy source of the future. See website for inclusion. Ages 8+. KJ6690 JUST 18 $ Buy online & collect in store 95 JUST 1995 $ SEE STEP-BY-STEP INSTRUCTIONS AT: www.jaycar.com.au/ make-a-potato-clock 12-IN-1 SOLAR HYDRAULIC ROBOT KIT 56 6995 SQUISHY CIRCUITS DELUXE KIT Kids can draw the circuits with the conductive pen and then watch them come to life. Each kit includes a detailed sketchbook with JUST examples and templates to work through. Ages 8+. KJ9310 $ JUST $ DRAW CIRCUITS 17-PCE MAKER KIT JUST Electronics is a fun, educational and satisfying hobby. But SOLDERING stops many people from entering this world. Today we have a range of electronic construction kits that require no soldering and can be as simple as joining two bits of playdough together! 6-IN-1 SOLAR EDUCATIONAL KIT Build any one of six different projects: windmill, car, dog, plane, airboat, revolving plane. Power from the sun or household 50W halogen light. Ages 10+. KJ8926 JUST 1695 $ ON SALE 24.08.2020 - 23.09.2020 TEACH THEM ABOUT ! H C T A R SC MBOT BLUETOOTH® ROBOT KIT Easy to aeemble, entry level robot that can avoid obstacles, follow lines, play soccer, and more. Control from your Smartphone or Tablet via app or program using simple drag-and-drop programming blocks or Arduino® IDE. Ages 12+. KR9200 JUST 199 $ Kids can learn coding and AI while they play. Comes in two parts: Codey (detachable mainboard) equipped with more than 10 electronics modules that can be controlled via code. Rocky (car) that lets you take Codey anywhere you want. Support AI and IoT. Cloud storage. Ages 6+. KR9230 Limited stock. Store only. MINI ELECTRIC MOTOR EXPERIMENT KIT Demonstrates the basics of how the magnets, armature and commutator work together. Ages 8+. KJ9032 JUST 19 $ 95 More ways to pay: JUST 99 $ 3MP USB PORTABLE DIGITAL MICROSCOPE 400+ pieces of blocks that kids can build more than 18 cool multifunctional models. Allows kids to do coding with their creations by graphical programming language. Compatible with major building block brands. Ages 8+. KJ9354 CHECK OUT THE VIDEO ONLINE! 119 SAVE $10 219 $ Use the 6 terrestrial tracks/ crawlers to create a working gripper, rover or forklift. Electric motors and detailed instructions included. Requires 4 x AA batteries. Ages 13+. KJ8918 ALSO AVAILABLE: 4 x AA Batteries SB2425 $3.25 WAS $99.95 6995 $ JUST 5995 $ SPACE RAIL CONSTRUCTION KIT SAVE $30 GLOW IN THE DARK Build your own marble rollercoaster with unlimited track possibilities. 488pce. Multi-fit baseboard. Requires 1 x C battery. Ages 15+. KJ9001 ALSO AVAILABLE: C Size Battery Pk2 SB2416 $4.50 JUST 4995 $ CHECK OUT THE VIDEO ONLINE! CARDBOARD RADIO CONSTRUCTION KIT 12-IN-1 ELECTRICAL EXPERIMENT KIT JUST JUST Make your own AM/ FM radio. No soldering needed. Requires 3 x AA batteries. Ages 8+. KJ9021 24 $ WAS $129 $ Perfect introduction to robotics and programming. Support STEM learning and can be used at home or school. Clear scratch resistant shell. Completely waterproof! JUST • Gyroscope • Accelerometer KJ9200 ALL TERRAIN MULTIFUNCTION TRACKED ROBOT KIT Excellent for educational purposes and a myriad of practical applications. Up to 600X magnification. • 640 x 480 Resolution QC3191 They'll be challenged and required to spend hours or the weekend creating their 'engineering masterpiece'. Each contains full instructions so no previous experience or tools are required except maybe a screwdriver and a pair of pliers. APITOR SUPERBOT ROBOT KIT SPHERO SPRK+ PROGRAMMABLE ROBOT IN A BALL CODEY ROCKY ROBOT KIT TAKE THEIR CONSTRUCTION SKILLS TO THE NEXT LEVEL Scratch and similar block-based programming applications represent the perfect entry point for learning to code. It’s free, easy to use, and it lets people of all ages quickly design and program their own interactive animations, stories, games, and even program robots built on core computer components such as Arduino® or Raspberry Pi. All this without writing a single line of code. 95 ALSO AVAILABLE: 4 x AA Batteries SB2425 $3.25 12 different experiments to construct that demonstrate various electronic principles. Requires 2 x AA batteries. Ages 8+. KJ8919 2995 $ ALSO AVAILABLE: 2 x AA Batteries SB2424 $1.95 AIR POWER ENGINE CAR KIT Operates entirely using air and travels up to 80m on one single tank. No batteries or motor required. Ages 10+. KJ8967 JUST 3995 $ 57 THE BEST REWARDS & PERKS! SHOP In store & online EARN POINTS For dollars spent 1 point = $1 GET REWARDS eCoupons for future shops in store +offers, PERKS event invitations, 200 points = $10 eCoupon account profile and more... exclusive CLUB offers: 6-PCE INSULATED SCREWDRIVER SET Ergonomic handles with excellent non-slip grips. Fully insulated shafts rated for 1000V. TÜV and GS approved. TD2026 REG $24.95 1850 CLUB OFFER $ 25W SOLDERING IRON STARTER KIT Includes all soldering essentials for various projects. TS1652 REG $44.95 SAVE 25% 3295 CLUB OFFER $ SAVE 25% 30-PCE TOOL KIT Includes most common tool for minor DIY repairs and held securely in a zip-up case. TD2166 REG $29.95 See website for contents. 2195 $ CLUB OFFER SAVE 25% CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE GREENCAP CAPACITOR PACK MOISTURE LEVEL METER 75 OHM RG59 COAX CABLE GAFFER TAPE IN HI-VIZ CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE 20M CCD CAMERA EXTENSION CABLE 12V 1A SLA BATTERY CHARGER TELEPHONE EXTENSION RINGER 12V SOLID LED STRIP LIGHT 3 joined cables: BNC, RCA and DC power cables. WQ7278 RRP $64.95 CLUB $54.95 Interchangeable DC plug and alligator clip. 2m cable. MB3619 RRP $21.95 CLUB $17.95 CLUB OFFER SAVE 120MM LONG-LIFE LOW-NOISE MAGLEV BEARING CASE FAN 30% 25% Values range from 0.001μF - 0.22μF, all 100V. 60 pieces. RG5199 RRP $14.95 CLUB $9.95 Measure water content in wood and building materials QP2310 RRP $39.95 CLUB $29.95 15% 15% 20% IP54 dust, waterproof. 12VDC. YX2584 RRP $36.95 CLUB $28.95 30% White or black colour available. 30m roll. WB2001 OR WB2005 RRP $22.95ea. CLUB $14.95ea. 25% 20% 11mm strips fitted with 5050 tri-chip SMD LEDs. 500mA. ZD0552 RRP $24.95 CLUB $19.95 CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE VGA TO HDMI CONVERTER & UPSCALER UNIVERSAL DRILL PRESS STAND 240V TO 24VAC 150VA Up to 60mm drilling depth. LIGHTING TRANSFORMER 20% HDMI Upscaling up to 1080p. AC1718 RRP $89.95 CLUB $69.95 20% 15% 497(H) x 350(W) x 160(D)mm. TD2463 RRP $49.95 CLUB $37.95 20% OFF SEALED ABS ENCLOSURES* *See T&Cs for details. click & collect Fluoro green or hot pink available. 10m. Waterproof. NM2813 OR NM2815 RRP $14.95ea. CLUB $12.95ea. Wall mountable. Multiple tone and pitch. YT6068 RRP $34.95 CLUB $24.95 EXCLUSIVE CLUB OFFER 58 10% Buy online & collect in store Output 6.25A via screw terminals. MP3045 RRP $64.95 CLUB $54.95 YOUR CLUB, YOUR PERKS KEEP UP TO DATE WITH THE LATEST OFFERS & WHAT'S ON! Visit www.jaycar.com.au/makerhub ON SALE 24.08.2020 - 23.09.2020 ! H C N E WORKB rers! e k in t g n u o y e h t r o f Essentials 1. DESKTOP PCB HOLDER • Hold PCBs of up to 200 x 140mm • Adjustable angle • 300(L) x 165(W) x 125(H)mm TH1980 WAS $19.95 2. 10W 240VAC SOLDERING STATION • Compact and lightweight • 100-450°C temperature range • Rotary temperature control dial • Integrated soldering pencil holder TS1610 WAS $34.95 3. SILICONE BENCHTOP WORK MAT • Heat resistant • Suitable for soldering applications • Magnetic areas to hold metal parts. • 398(W) x 269(D) x 10(H)mm. HM8102 NOW 2995 $ 4. LOW COST DIGITAL MULTIMETER • 500V, 2000 count • AC voltages up to 750V • DC voltages up to 1000V • DC current up to 10A • Includes test leads QM1500 5 JUST 4 5. 7-PCE INSULATED SCREWDRIVER SET • Quality set for electrical work. • Slotted sizes 2.5mm, 4mm,5.5mm & 6.5mm • Phillips sizes #0, #1, and #2 • 1kV insulation rating TD2022 WAS $34.95 6 6. MINI GLUE GUN • Fast, easy and simple to use • 30W Mains powered • Supplied with 2 x 7mm dia. glue sticks. TH1997 WAS $12.95 NOW 3 995 $ SAVE $3 14 $ 95 95 • 99.3% Tin / 0.7% copper lead free. • 1.00 & 0.71mm (dia.) available. • Rosin cored. 200g rolls. 0.71mm NS3088 1.00mm NS3094 JUST 2595 $ EA More ways to pay: INSULATION TAPE - 6 ROLLS MAGNET BARS JUST JUST • Designed to remove dangerous solder fumes from the work area • Suitable for workbenches or the hobbyist TS1580 WAS $74.95 SOLDERING IRON STANDS General purpose stand. Large, tip cleaning sponge & pressed metal base. Economy TS1502 $9.95 Deluxe TS1507 $16.95 995 $ EA for kids 25W 240V SOLDERING IRON SAVE $15 FROM $ 95 SOLDERING NOW 5995 • Educational magnets • Ideal for hobbyists & children to learn more about magnetism. U Shaped 30 x 30 x 6mm TH1873 Bar Magnet 70 x 12 x 5mm TH1874 1 $ 240V SOLDER FUME EXTRACTOR LEAD-FREE SOLDER 1 395 ONLY 1995 $ NOW One roll each of green, black, yellow, white, blue and red. Each 5m in length x 19mm wide. NM2806 $ 19 $ ONLY 995 $ electronics. Complete with comprehensive assembly instructions and detailed descriptions of how each component works. Volume 1 BJ8502 WAS $10.95 NOW $9.50 SAVE $1.45 Volume 2 BJ8504 WAS $12.95 NOW $11.50 SAVE $1.45 Volume 3 BJ8505 WAS $14.95 NOW $13.00 SAVE $1.95 Set of 3. Measures angled & duckbill 120mm, superfine 135mm. ESD safe. TH1760 SAVE $5 SAVE $5 SHORT CIRCUITS A great way to teach kids about STAINLESS STEEL TWEEZER SET 2995 $ 2 SAVE $5 10% OFF NOW TS 0 15 2 Ideal for the hobbyist and handy person. Stainless steel barrel and orange cool grip impact resistant handle. Fully electrically safety approved. TS1465 ONLY 1495 $ 59 W E N S ’ T WHA 2 x Thunderbolt™ Pins 4K HDMI Port Rear 2000W 240V ADJUSTABLE TEMPERATURE HEAT GUN Remove paint, shrink heatshrink, soften adhesives and many other applications. Mains powered with 2 heat settings. Includes 4 nozzle attachments. • Low Power: 400°C, 250L/min • High Power: 600°C, 500L/min TH1609 COVID FEVER NON-CONTACT THERMOMETER Due early September Measure from -50°C up to 600°C. Includes a 12 point laser to indicate the measured area. • 12:1 Distance to Spot Ratio • Adjustable emissivity • Large colour LCD display • Powered from 2 x AAA Batteries (included) QM7424 JUST ONLY 2995 USB Type-C 2 x USB3.0 Ports USB Type-C with Power Delivery 9995 JUST $ 9995 $ $ USB POWERED BATTERY CHARGERS SINGLE CHANNEL QUAD CHANNEL DUAL CHANNEL Charges Li-ion battery cell from a USB power source. • Supported batteries include: 26650, 26500, 22650, 18650, 18490, 17670, 17335, 16340 (RCR123A), 14500, JUST & 10440. MB3705 Charges up to 2 x Li-ion, Ni-MH or Ni-Cd battery cells at the same. • Supported batteries include: AAAA, AAA, AA, A, Sub-C, C, 26650, 22650, 21700, 18650, 14500 & more. MB3707 1495 $ A compact Arduino® compatible board with an integrated W600 Wi-Fi module. Ideal for compact and low power projects. USB C port for power (5VDC) and provision to run from and charge a 3.5-4.2V Li-po battery. • 2.4GHz Wi-Fi • 6 Analogue and 14 Digital Pins • UART, I2C, and ICSP Port ONLY XC3812 69 $ 95 JUST 1995 $ DUINOTECH SAMD21 WIRELESS DEVELOPMENT BOARD SD & MicroSD Card Readers Front Uni-directional, suitable for podcasting and audio recordings. Solid construction with an adjustable desk tripod for optimum positioning. Mac® and Windows compatible. 24-Bit resolution. 5VDC USB powered. AM4136 JUST 7995 $ 4995 $ 1800 LUMEN 3" 20W LED WORK LIGHT 21.5" 6500 LUMEN 21.5" SINGLE ROW SOLID LED LIGHT BAR JUST 49 $ number of ports on your MacBook™. Includes a HDMI port that can mirror or extend your display. Suitable for later version of MacBooks. Plug and play. See website for details. XC4938 USB STREAMING MICROPHONE Charges up to 4 x Ni-MH, Ni-Cd, Li-ion, or LiFePO4 battery cells using Pulse Width Modulation (PWM) at the same time. • Supported batteries include: AAA, AA, Sub-C, C, 26650, 22650, 21700, 18650, 14500 & more. MB3703 JUST Waterproof, dustproof and shockproof to suit 4WD and marine applications. Wide input voltage to suit 12 and 24 volt systems. • 5 x 5W OSRAM LEDs • 5500 - 6500K Colour Temperature • IP68 Ingress Protection • 87(W) x 102(H) x 73(D)mm ST3252 MACBOOK™ PORTABLE DOCK This Thunderbolt™ 3 Dock expands the 95 PR Features 16 x 5W OSRAM LEDs, IP68 water and dustproof rating, and suits 12V and 24V systems. Supplied with a steel bracket and mounting hardware. For off-road use only. • 6000K colour temperature JUST • 70W LED output power • 547(L) x 54(H) x 74(D)mm • 1.3kg Weight SL4020 ALSO AVAILABLE: Wiring Harness To Suit SL4022 $49.95 9995 $ 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 1 BUNDLE DEALS: Micro:bit Tobbie 2 Bundle includes 1 x KR9260 + 1 x XC4320 + 1 x SB2413 for $87.95. Micro:bit Robot Kit Bundle includes 1 x KR9262 + 1 x XC4320 + 1 x SB2298 for $134. Page 2: BONUS GIFT: Free RetroPie OS (XC9031) with purchase of 1 x XC9001 + 1 x XC9062 or 1 x XC9001 + 1 x XC9064. Page 6: Club Offer: 20% OFF Sealed ABS Enclosures applies to Jaycar 230F: ABS Boxes – Sealed product category. LONE PI AUTO BARN SPOTLIGHT N WY LL H CHE MIT NE AVE HARVEY NORMAN BCF P HEA ERC SUP AUTO NEW STORE Orange Orange Homemaker Centre 4/168 Lone Pine Ave Orange, NSW 2800 PH: 1800 022 888 For your nearest store & opening hours: 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 24.08.2020 - 23.09.2020 SERVICEMAN'S LOG Troubleshooting Temperamental Tea Dave Thompson It’s hard to do much work before you’ve had your morning tea (or coffee), especially when brainpower is required. But when it’s your kettle that’s acting up, you don’t have much choice! Despite shelling out much moola for what I thought was a carefully crafted coffee kettle – a jolly good jug – it utterly failed to boil any water. So I had to take my sleeping cap off and put my thinking cap on... If you want to insult an engineer, you refer to them as a “wheelbarrow mechanic”. This implies that the most advanced device they are capable of working on is a bucket with handlebars and a wheel attached. There was a similar term in the electronics world, “valve jockey”, but that has been obsolete for many years now. It referred to people whose sole troubleshooting capability was to swap out the valves in a radio or TV set, in the hope that one of them was bad and replacing it would fix the set. Given how out-of-date that term is, it’s tempting to come up with a new insult for electronic engineers. One possibility is to call them a “kettle technician”. After all, you can’t make a much simpler device than your standard kettle or jug; it’s basically just a big resistor connected to the mains with a combined on/off switch and a thermal cut-out. Your bog-standard toaster is just slightly more complicated, replacing the thermal cut-out with a simple timer. But if you haven’t been into a department store recently (do they even still exist?), you might be surprised how sophisticated modern jugs and toasters have become. Some toasters are motorised now! Talk about gilding the lily… And jugs aren’t that far behind. Some models, very popular these days in Asian countries, don’t just boil water but also will cook food like eggs and noodles. In some cases, they have a dozen modes or more. So I guess that takes some of the sting out of the “kettle technician” insult! As I’ve mentioned on several occasions in the past, part of being a serviceman (or servicewoman) is that we are genetically predisposed to have a go at whatever needs fixing. If that happens to be a kettle (or a wheelbarrow), we will usually rise to the challenge without prejudice. No broken object is so simple that fixing it is beneath us! A fool for tools And simple though most kettles are, some require odd tooling to get them apart. It could be those awful ‘safety fasteners’ modern manufacturers seem to love using, or some other odd-ball instrument required to pop plastic clips or unseat gaskets. So if we want to service even basic appliances like this, we have to accumulate all the necessary tools. This isn’t usually a problem; like Items Covered This Month • • • • Troubleshooting in the cold Dremel rotary tool repair PA system repair Hyundai coil diagnostics *Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz siliconchip.com.au Australia’s electronics magazine September 2020  61 many servicemen, I’m ‘into’ tools and test gear. I’m perhaps a bit too enthusiastic about tools; the subject of several of my missives! So I will usually jump at the chance to add something new to the toolbox if the opportunity arises. Whether I will use any of these more esoteric tools more than once is immaterial; the point is that I have them in my toolbox, and am therefore able to cope with any future repair situations that may arise. However, it is clear to anyone that going out and buying one of every tool in the shop just in case we might need it one day is madness, or at least reserved for those who have far more dollars than sense (and we probably all know someone like this!). Having said that, I think that many servicemen would jump at the chance to buy, borrow or hire a new tool, especially if we have a particular job for it. There is a fine line between capa- 62 Silicon Chip bility and hoarding, though, and I’ve long come to accept that I can’t be prepared hardware-wise for every job that comes my way. One recent example is when I needed to crimp several large terminals to some really heavy-gauge wiring; I had to borrow the crimping tool I needed from a sparky friend, but was sad to see it go once the job was done. I could see many possibilities and advantages to owning such a tool, though knowing how much use it would actually get precluded me from shelling out a not-inconsiderable amount of money to buy my own set. But sometimes, it is worth buying the right tool for the job. A while ago, I needed to work on a telephone line that was buried amongst a loom of dozens of other similarly-sized and coloured wires. Sorting out which ones were the active phone line was going to be a mission, especially without any Australia’s electronics magazine kind of schematic or wiring diagram. While I initially considered trying to find one of those tracer type tools, where a signal is sent down the wire and picked up by a separate receiver, I thought something like a hand-held telephone test handset would be better. You’ve probably seen them. They’re traditionally used by Post Office techs and linesmen types (or, in the olden days, eavesdroppers or cheapskates without a fear of heights!). Usually, they are an industrial-style handset featuring a rotary dial, a belt clip and a curly cord with a couple of crocodile clips so anyone can just tap into the telephone grid and get connected. I went so far as to go out and look for one, asking around some ex-Post Office/Telecom guys I know and anyone else who might have been able to loan me one. Sadly, I couldn’t find one of these handsets. However, I did eventually siliconchip.com.au locate and buy an inexpensive ‘ersatz’ version, which is essentially just a small touch-tone handset with a simple digital display and a set of assorted leads and telephone-style connectors (including crocodile clips). I got it for just a few dollars. It was ideal for the task, and made the job so much easier than it would have been if I didn’t have the right tool. I thanked my lucky stars (and AliExpress!) that I could find one for such a little outlay, which made it a perfect tool/test equipment purchase. While it is true I may never use it again in anger, I at least have it in my toolkit, and that gives me a warm, fuzzy feeling inside. I’m sure most of us accumulate our tools the same way. I know that my dad did; when he needed something specific, he either made it or sourced it from somewhere, and over the years, those acquisitions mounted up. Looking through the stuff I inherited, there is plenty of tooling I don’t recognise and have no idea what it was used for. As I’m not planning on taking up precision machining any time soon, I will likely never use it. At least I have it though, just in case! Penny wise, pound foolish This raises a dilemma though; if we’re only going to use any given tool for one or two jobs, and we can’t borrow or hire it, do we shell out for a really good quality version or buy something cheap and nasty, and take the risk it might break or get thrown away? For me, it usually comes down to my budget, but as a tool snob, I consider buying junk tools to be a false economy. However, I am also realistic, and given that my wife also has a say in it, I usually end up going for the best value, rather than the most expensive (which one would hope means ‘the best’, but doesn’t always). Luckily, these days there are increasingly middle-ground options such as that telephone tester I purchased; it isn’t junk, but it isn’t super-high quality either, yet it does its job perfectly. This buying philosophy isn’t just for tools. I’m sure we’ve all been there; do we buy a cheaper appliance, even though it might only last a season or two before throwing it away or replacing it, or do we stump up and buy that higher-end model which will (hopefully) last much longer? While we usually siliconchip.com.au pay a suitably higher price for the privilege, I tend to go for the latter option. As an example (this is going somewhere, I promise), I like my wristwatches, and over the years owned many very cool examples. The majority of these were purchased at overseas markets for little money, but perhaps unsurprisingly, none lasted very long. I am reasonably tough on watches, because I only take them off when safety determines I do so. Otherwise, I wear one 24/7. Usually, the cheap bracelets would give out, but occasionally I would crack a screen or body by whacking the watch into an engine component while fixing a car or similar. I got sick of replacing my watches just because they couldn’t take the dayto-day use, and eventually resolved the issue by purchasing a ‘proper’ Tag Heuer watch in the early 90s, which I still wear today. It certainly wasn’t a cheapo like those other watches, but as I have not needed to buy another watch for 30 years, in the greater scheme of things, it was the most sensible option. And so when we were renovating our kitchen a few years back, with the same philosophy in mind, we shelled out a relatively tidy sum for a matching Dualit kettle and toaster package. We haven’t been disappointed, as these traditional and very well-made appliances have easily stood the test of time. Like most people, I’ve purchased many jugs and toasters over the years, most of which simply die or become so grotty after a while that we ended up replacing them. Not so with these Dualit models; they are built to last and are made to be repairable, with readily-available (though relatively expensive) spare parts. Like many brands, some of the cheaper models are made in the farflung corners of the East. Our appliances were “assembled” in the USA, which today is meant to imply a level of quality. Increasingly, this ‘made in so-andso’ designation is fluid; I remember as a kid when something was stamped with “Made in Japan”, it was considered junk. These days, the opposite is true; “Made in Japan” usually indicates the highest quality available. Also, given that parts and subassemblies these days are made all over the world, you have to wonder what that ‘assembly’ actually involves. Australia’s electronics magazine September 2020  63 The appliance could be made in two halves overseas and then screwed together locally, and it would still be “assembled in so-and-so”. At the end of the day, you have to evaluate quality based on the fit and finish of the device itself, as well as reviews by other owners. Just because something is made in China doesn’t mean it’s junk (a lot of high-end stuff is made there), and similarly, there are plenty of goods made in Australia or the USA that leave much to be desired! But I digress. An interruption to my morning routine The other morning I got up and went to boil the jug. Usually, I check the water level and just hit the switch below the handle to get everything started while I go about other mundane morning tasks, such as waking up. When I came back to the jug to pour out some water, it was cold. I hadn’t even noticed the lack of the sound of boiling water (one of the selling points of this jug is the ‘quiet boil’ feature), but even so, I can still usually hear it. I made sure the toggle switch was engaged, and it was, but the jug was dead, and even the neon ‘idiot lights’ mounted in the base of the kettle didn’t come on when I flicked the switch. Now fully awake, I automatically went into troubleshooting mode. The first thing I checked was the mains socket the jug was connected to, ensuring that the plug was firmly in and the power switched on. Many a serviceman (and by that, I mean me) has been flummoxed by somebody turning off a usually-left-on wall socket switch. Unfortunately, this one was still on, and as the toaster sitting next to the jug was plugged into the same (dual) wall socket and happily fired up when the lever was pulled down, I knew that power was getting to it. This jug is a ‘cordless’ model, which means that it gets power via a socket in the base, which disconnects when it is lifted up to dispense water. The close tolerances between the base’s plug and the corresponding socket built into the bottom of the jug rely on a sound physical and electrical connection for power to flow. Any foreign object sitting on the jug base will prevent the plug and socket from making proper contact, and this could be as small as a crumb of toast. In this case, the base was clear of de64 Silicon Chip bris, and the jug seated properly, so that wasn’t the problem. For further troubleshooting, I needed a multimeter, and I was soon armed with my trusty analog unit and ready to measure. There was 240V AC (or thereabouts) across the contacts in the base, though measuring it was tricky because the socket has pressure-actuated covers which pop into place when the jug is removed, to prevent anything being purposely or accidentally contacting the inside of the socket. Yet no power was reaching the jug’s element. At this point, I hit the internet to search for a service manual. This may sound a ridiculous step to take, but given the price and quality of the jug, I did expect to find one. As it turned out, I couldn’t find a service manual (and thus any part numbers for spare parts), but I did find a user’s manual, which included a handy troubleshooting chart. It didn’t need much technical nous to follow the manual and determine what the possible causes for non-operation were. According to the book, a blown element or an activated or faulty thermal switch (installed in the jug circuit to prevent dry boiling) were the most likely culprits. As with any troubleshooting process, the symptoms ultimately determine what the problem is. In this case, the troubleshooting chart suggested that if the neon lamps don’t light up and the jug doesn’t boil, the likely culprit is the boil-dry switch. If the neons do show, but the jug doesn’t boil, a blown element is likely to be the problem. The fact the jug remained totally dark pointed to the thermal switch, but there were problems with this diagnosis. To begin with, I knew we hadn’t boiled the jug dry. I have done that before; I killed the first kettle I ever bought, and I’ve been extra-cautious since. It was a bitter lesson. I loved that modernistic plastic-fantastic kettle, but one day I neglected to load it with water, and it ended up a very funny shape, about half as tall and twice as wide as it started. I learned my lesson, and I’ve never dry-boiled another jug. However, I think there is another component in play here. I noticed the first few times we used this jug that a few minutes after it has boiled, I hear a very distinctive and metallic ‘ping’ sound. I think this is a thermal switch Australia’s electronics magazine resetting. It can’t be a boil-dry switch, as that shouldn’t be activated at all in normal use. While there is no mention of a thermostat in the troubleshooting guide, common sense tells me there must be one, as any so-called automatic kettle will have a device that cuts power to the element when the water reaches 100°C (boiling point). If this switch fails, the jug will either boil itself to death (if it failed short-circuit) or no longer switch on at all (if it failed open-circuit). In the latter case, I’d expect no idiot lights either, which was what was happening here. A quick internet search for kettle schematics (yes, really) confirmed that there are typically two thermal switches in most decent kettles. One is for automatically switching the jug off when it boils, usually via a ‘steam tube’ arrangement, and the other triggers only if the jug is dry-boiled. I also found a very informative, nontechnical consumer article comparing our kettle to inexpensive ‘big-box store’ models, arguing that both are as good as each other. I didn’t particularly care about the product comparisons or the conclusions drawn. Still, this article had several good-quality photographs and descriptions of the components inside our appliance, which was very useful. From this, I learned that the “neon” indicators inside our kettle are in fact LEDs, even though they are still referred to as “neons” in the user manual. I also discovered that the ‘guts’ of the jug is a large, single assembly mounted inside the bottom. This includes the two thermal switches, two power sockets and the element connections. This part is manufactured by a UK company named Otter Controls, and spares are readily available, though eye-wateringly expensive due to the whole package usually being replaced if anything in it goes wrong. I gathered my tools to take the jug apart and turned it over to work on it, when I heard that distinctive ‘ping’ again. On a hunch, I put the jug onto the base and it powered up. I boiled it through a couple of cycles and heard the thermal switch pinging/resetting normally each time after boiling. Regardless, I opened the base, cleaned everything out and descaled the jug as per the user manual. It is still siliconchip.com.au working well today, so I didn’t find a “smoking gun”, but I at least know what I’m dealing with and what to do should it fall over again. Jug technician indeed! Dremel 8000 rotary tool repair G. C., of Salamander Bay, NSW, decided to upgrade his rotary cutting tool, but he didn’t quite get what he bargained for. It needed a few repairs, but he did manage to get it going in the end, despite a few pitfalls... Around a year ago I purchased a second-hand Dremel which I got cheap because the battery wouldn’t hold a charge. My battery-powered Dremel 1100 was getting old and was underpowered even when new, so I jumped at the chance to purchase this newer, bigger and hopefully more powerful Dremel. From the (tiny) picture and the “near-new” description, I had assumed it was a current model Dremel 8200 with dodgy batteries. But when I opened the package, I found a 15-yearold Dremel 8000 with a totally dead lithium-ion battery pack. Giving my new/old Dremel a thorough external check, the good news was that it appeared in remarkably good condition mechanically. Its plastic housing was covered in paint flecks and some unknown gunk, but a spray of Nifty and some elbow grease fixed this. Mechanically, it was good, and the shaft spun freely with zero bearing slop, so it was worth seeing if I could fix the battery problem. I unclipped the battery pack from the Dremel body and separated the two halves. This proved to be a bit tricky and was only accomplished after wedging two spudgers under the release clips. Inside I found three standard 18650 lithium-ion cells, spot welded together in an oddly shaped assembly to fit inside the plastic case. As expected, each cell was dead beyond repair. Luckily I have lots of 18650 cells, mostly salvaged from old laptop battery packs (I test them all and only keep the ones which show a capacity of at least 1Ah). So I saved the two power connection clips from the original cells and soldered three good 18650 cells into a (nearly) identical battery pack (with some added insulation for the bottom cell). I then noticed a glaring error in the original design. Rather dangerously, Dremel only provided external connections to the 0V and +10.8V points in the battery pack, so there was no way to balance the voltages across the three cells. This could allow an imbalance to build up over time, and I think this could be what caused the pack to go kaput. This wasn’t a hard problem to fix, as I have several BC-4S15D Li-ion balance chargers and dozens of two-, three-, and four-cell balance charging leads for my radio-controlled models. 18650 cells were taped to the base of the Dremel, with an external lead fitted to allow for balance charging. siliconchip.com.au So I just had to solder the balance lead wires in the correct order and make a small exit slot for the wires, a method I have also used extensively with other DIY 18650 Li-ion packs. I could then use my balance charger periodically to both charge the pack and ensure that the voltage is evenly distributed between the cells, so none are over-charged or over-discharged during use. Happily, when everything was plugged together, the Dremel worked perfectly – I just give it a top-up charge every few weeks with the BC-4S15D. It worked perfectly until a couple of months ago. It then developed a new fault: it was either off or running at full speed, with the speed adjustment wheel having no effect. From Balance charging the Dremel with a BC-4S15D periodically helps to ensure all cells are charged evenly. Australia’s electronics magazine September 2020  65 many years’ experience, I suspected the problem was a dead power Mosfet, so I unscrewed the Dremel body, got out a DVM and checked. As I suspected, the Mosfet had a short circuit between its source and drain pins. A quick Google search didn’t help with a replacement Mosfet, but I knew that it must be an Nchannel type due to its source being connected to battery ground. So I took a punt and used an IRF3205 Mosfet, which is rated at 110A with a low onresistance of just eight milliohms. This was overkill, but cheap enough and the low Rds(on) would minimise heating at full power. Removing the original Mosfet was tedious, as it was riveted in place, but not exceedingly tricky after I used my old Dremel with a 20mm diamond cutoff wheel. It worked fine for another 10 days, and then the same problem happened again. So, with many four-letter words being uttered, I repeated the repair, this time replacing the Mosfet with an HY3403D, having an even lower Rds(on) of just 4mW. You can imagine how pleased I was, and the nature of my mutterings, when it too failed after only a few days. This was getting ridiculous, and I was determined to find out why these overpowered Mosfets were being repeatedly killed. My first thought was that the design might be a just a simple analog speed control rather than a PWM (pulsewidth modulation) digital controller, as the Mosfet was running hot enough to burn me when I checked with a finger. So I fired up my Tektronix CRO and looked at the voltage at the Mosfet drain. Immediately, the reason for the failures became glaringly obvious. Yes, it was receiving PWM drive, but the back-EMF spikes were extremely high at 70V, when they should be clamped around 12V. It appears that the Mosfets were going into avalanche breakdown, and this was what was killing them after just a few days. The most likely cause was a faultyback EMF protection diode. Looking at the Dremel PCB, the diode was easy to spot, but its type was unreadable. It was obviously a high-current dual Schottky diode in an SMD D2PAK (TO-263) package, but strangely, only one half of the dual diode appeared to be wired up. 66 Silicon Chip I didn’t have any D2PAK diodes on hand, but as only half was used anyway, I didn’t need one. I just soldered in the highest-current SMD schottky diode I had, a 3A 40V SS34, across its pads. After fitting the diode, I powered up the Dremel and found the voltage spikes were being clamped to less than 15V, and the Mosfet wasn’t even getting slightly warm. I’m happy to say my new(ish) Dremel has been running flawlessly for many weeks now. In hindsight, I would have saved a lot of time and a few Mosfets if I had used the CRO at the beginning, or even thought to check the Mosfet operating temperature after low-speed use. Church PA system repair B. C., of Dungog, NSW was called in when someone plugged a keyboard into the PA amplifier at his church, and all of the loudspeakers stopped working. What he found was an unholy mess; since cleanliness is next to godliness, he had to do something about it... Taking a closer look at the church’s sound system, I found a Realistic MPA95 PA amplifier with a TEAC stereo amplifier slaved to it. The TEAC’s internal fuses had blown. I replaced them, but then only the indoor loudspeakers worked. I thought that this was probably due to internal damage to the STK amplifier IC inside the TEAC amplifier. A few days later, I walked around the outside and inside of the church building and made a quick sketch showing the four microphones and seven speaker positions, plus their cabling. In addition to the MPA95 and TEAC amps, there was also a more modern Power Dynamics PD572 Radio Microphone Dual Diversity Receiver. Beneath this lot was a veritable rat’s nest of unbalanced microphone cables and figure-8 low voltage power cables. There were also six black zippy boxes scattered around the church containing preamplifiers, power supplies, toggle switches and sockets. I was given the go-ahead to upgrade the microphone cabling and to repair/ upgrade the MPA95. I disconnected the MPA95, carefully labelling of all the connections. I was told that this amplifier had blown up about twenty years ago. It had been looked at by a third party, who had returned it unrepaired. He Australia’s electronics magazine had suggested to instead slave a stereo amplifier to the preamp out socket (ie, the TEAC). The balance control was used to fade in or out the outdoor loudspeakers. Back in my workshop, I removed the top of the MPA95 to find that Q506, Q507, Q508 and Q509 (the driver and output transistors) were missing. I tried a Google search to find out more about this amplifier but was unsuccessful. So I decided to try to keep the unit but fit two new amplifier modules internally, to drive each set of speakers, with independent volume controls. The MPA95 had a 30-0-30V AC power transformer, so I took to eBay to look for suitable amplifier modules. I found a prebuilt mono amplifier with a TDA72934 IC. This device’s data sheet indicates that it can handle supply rails up to ±50V and delivers up to 100W into an 8W load.That seemed like a good match. This module can be mounted to a heatsink with a single screw, and all the necessary connections are available via three terminal blocks on the PCB. I ordered two of these, and while I was waiting for them to arrive, turned my attention to the wiring. The church now only needed two fixed microphones, one at the lectern and one at the altar; the 2-channel radio microphone would cover other scenarios. So I removed all the old microphone cables, the figure-8 low voltage cables and the six black zippy boxes. Then I ran new shielded microphone cables and fitted XLR connectors at each end. The two Realistic 600W Highball Omnidirectional unbalanced microphones still worked quite well. I rewired them internally and fitted them with balanced cables and XLR plugs. That left the loudspeaker wiring to be sorted out. Fortunately, I have a loudspeaker impedance meter. There was a bundle of figure-8 loudspeakers cables coming down the wall near the MPA95. Two of these were for the four indoor church speakers. I measured about 9W, indicating that the speakers were in series. Two more cables went to old-style Bakelite tumbler switches on a timber mounting block, labelled “south” and “north & west”. With both switches on, the impedance dropped down to about 2W. No wonder there had been amplifier reliability problems! I rearranged the siliconchip.com.au wiring to place them in series instead, and the impedance went up to about 9W. There might be a slight difference in sound levels between the three outdoor loudspeakers, but I didn’t think that would be a real problem. After the two amplifier modules arrived in the post, I prepared the MPA95 for a transplant. First, I removed the old line matching transformer. The large vertical heatsink assembly had enough space for mounting the two modules side-by-side. After the marking out and drilling of the two holes required, I tapped them with an M3 thread, then mounted the modules using silicone rubber insulating kits. Since the bridge rectifier was also mounted on the heatsink, it provided a convenient point to pick up the two 30V AC rails required by the modules. Each module has its own bridge rectifier and filter electrolytics. I then ran the speaker output wires from each module to the terminals at the rear of the chassis. For their input connections, I cut the wire to the centre terminal of the main volume control pot and ran this via shielded cable to the input of the amp module that would feed the indoor speakers. Then I fitted a 50kW log potentiometer to a free area on the front panel and connected this, also with a shielded cable, to be in parallel with the main volume control. Its wiper signal then went to the other amp module input. I decided it would be wise to check all of the original soldering on the MPA95 main PCB. This was a good thing because I found dry joints around the two voltage regulating transistors which supply the ±12V rails to run the preamp IC. I also found more dry joints in areas of the main PCB, so I resoldered them too. A couple of highESR electrolytic capacitors next to the regulators also had to be replaced. I checked everything, connected a test loudspeaker to each of the outputs, plugged in a microphone and switched it on. Everything appeared to be working properly. I left the MPA95 to soak test, with a CD playing music through the AUX input, for the rest of the afternoon. The next morning I took the MPA95 back to the church and set it up. I set up a suitable music CD playing and walked around to set the correct speaker levels. I then adjusted all the microphone levels so they all siliconchip.com.au matched. However, there was some audible hum present. If the radio mic levels were set to minimum, the hum disappeared! So I removed the PD752 radio mic receiver and took off the top cover. DMM tests revealed that the internal PCB ground and the mains Earth connection were joined together via the metal chassis. There was an Earth loop being created by this internal connection. Fortunately, there was also a 12V DC power input socket on the back. I found that by powering it from a plugpack, the hum disappeared. The handheld and lapel radio microphones had both previously tested OK. However, I now found that the headset mic had an internal wire break. I ordered a replacement from eBay. Upon receipt, I removed the mini-XLR plug from the old headset and soldered it onto the new headset lead. I then tested it and found it to work well. I must admit, the wearing of this type of microphone does give one a sense of freedom compared to a handheld microphone. Hyundai coil diagnostics N. S., of Lismore, NSW was able to use an OBD2 scanner and a little bit of logic to easily diagnose and fix his engine misfire problem. While OBD2 scanners don’t always point you straight to the source of a problem, often they do and can save you a lot of effort (and in some cases, cursing)... I have spent (all too) many years pondering lifeless, defunct or deceased electronic circuits in every setting I can conceivably imagine. As our venerable columnist Dave has often noted, when you can do this stuff, you can’t leave well enough alone. The idea of throwing something away because it doesn’t work never enters my head. This is especially true of cars, and I’ve recently been presented with several cars that are showing the dreaded “check engine” light. Many people solve this by merely taping over the light, but not me! The latest incident was with a recently purchased 2006 Hyundai Accent. It ran fine for a few days after we drove it home, then started to miss. The check engine light shone steadily until it warmed up and then started to flash ominously. A flashing light is said to be particularly serious because it indicates a misfire that can result in large quanAustralia’s electronics magazine tities of raw fuel going through the exhaust system. This can overheat the catalytic converter, and they’re pretty expensive to replace and in extreme cases, can start fires. As it was a recent acquisition, I did a routine service and detailed visual inspection. This model has one coil per spark plug. They are sunk into wells in the valve cover, above the plugs. One was swimming in spilled oil from the nearby oil filler while another was swimming in rusty water from parts unknown. Pulling the plugs showed that they were a long time past replacement and fitting a set of new ones brought back the snarl – it’s a pretty decent little engine! All was fine for a thousand kms, but then the same symptoms came back. The Accent has an OBDII port, so I bought myself a scan tool from OBD2Australia. I chose this one because they provide a complete list of vehicles it supports, and it is covered by a warranty that covers both the tool and the vehicle it is used on. A scan quickly brought up cylinder one as missing, which is useful information. (I had a look, oddly, all the cylinders were still there…). The scan tool display also provided a link to a YouTube of a mechanic progressively testing the ignition coils of the same model car, which is a very smart feature. You can see it for yourself here: https://youtu.be/aQWgp4e0T68 The testing procedure was to simply disconnect and reconnect the control input from one coil after another, and observe the response from the engine. No response to a disconnected coil means a suspect coil unit. To check that the fault was with the coil and not, say, an injector, the suspect coil is swapped to another cylinder and the process repeated. Sure enough, using this process, I determined that my cylinder one coil was a dud and a replacement was both quick and cheap. This showed me that new cars are fast becoming a peripheral to their central computer, but that computer is not the be-all and end-all. There is still a need to peer at the car’s wiring diagram and for systematic testing of faults – something that the readers of this magazine will appreciate! Editor’s note: N. S. wrote a comprehensive article about OBD2 starting on page 72 of this issue. SC September 2020  67 The Night Keeper Lighthouse By Andrew Woodfield The Night Keeper Lighthouse briefly lights up the darkness, to keep children’s dreams from running aground on dangerous shores. This is an excellent project for beginners; it’s easy to build, and you will learn several important aspects of electronic circuit theory. M any readers will have children or grandchildren who from time to time peer enquiringly at electronic parts and gizmos you’re working with on the bench. At moments like these, it’s useful to have a simple project available to encourage the next generation to take up the hobby. When my grandchildren were planning a visit recently, I was asked if I could help the 8-year-old build ‘something electronic’. Does this sound familiar? Searching for a suitable circuit suitable for children, it’s essential that they can build it reasonably quickly, before they lose interest. Equally, it should be useful enough to gain parental approval. I have had a blinking light circuit running on the shelf above my workbench for several years. I built it while testing some ideas for discrete high-efficiency boost power supplies. The “rat’s nest” of parts was built on a scrap of prototype board. These days, I use it for the occasional end-of-life 1.5V cell. It’s a simple way to use up the very last whiff of energy from such near-dead batteries. Rather than just building a blinking light, I thought I could make it a little more useful and exciting with a few simple improvements. First, I designed a printed circuit board (PCB) to make it easier for children (and parents, grandparents or caregivers) to build. That PCB allowed me to mimic a widely recognisable object, and make it more attractive and interesting. It also suggested a few other applications, 68 Silicon Chip which will be noted later. This, then, is the “Night Keeper”. Building it is well within the capabilities of a bright 10to 12-year-old, or perhaps even younger with some adult assistance. Since a soldering iron is required, they will need close adult supervision and a well-ventilated workspace. A kitchen table with a similar clear workspace of about one square metre is perfect; cover it with a cloth or some cardboard to protect the surface. Circuit description This simple and well-known oscillator circuit (shown in Fig.1) consists of two transistors, a white LED, and a few passive components. It brightly flashes the LED once every second for many months from a single 1.5V cell. Even a near-exhausted battery can power the LED for a month or two. The two transistors forming the heart of the device operate as a highly efficient regenerative oscillator. When power is first applied, the voltage on the base of Q1 (Va) begins to rise slowly as the 10MΩ resistor charges the 330nF capacitor from the battery. When Va reaches about 0.6V, the base-emitter junction of Q1, which acts much like a silicon diode, becomes forward-biased and begins to conduct. Meanwhile, the 10kΩ resistor has quickly charged the 100µF capacitor to close to the battery voltage. That’s about 1.5V for a new cell. This produces a voltage across LED1 (Vc) very close to 1.5V. However, LED1 cannot light up yet, because white LEDs need more than 2.5V to operate. Australia’s electronics magazine siliconchip.com.au      3.5V 6.3mA 2.8V 5.4mA 2.1V   4.5mA 1.4V 3.6mA 0.7V 2.7mA 0V SC  NIGHT KEEPER 1.8mA -0.7V Fig.1: the Night Keeper uses a two-transistor oscillator to drive a charge pump based on the 100µ µF electrolytic capacitor and the diode junction of white LED1. Once per second or so, the point labelled “Vc” will shoot up to around twice the battery voltage (about 3V), providing enough voltage to light the LED brightly for a few tens of milliseconds. 0.9mA -1.4V 0mA -2.1V -0.9mA -2.8V -1.8mA -3.5V -4.2V 4.8s 5.1s 5.4s 5.7s 6.0s 6.3s 6.6s 6.9s 7.2s 7.5s -2.7mA 7.8s As soon as Q1 begins to turn on, its increasing base- Fig.2: this simulation shows how the voltages at Va (cyan), Vb emitter current causes its collector current to rise still (green) and Vc (red) in Fig.1 change over time. Va ramps up, and faster due to the transistor’s current gain (beta or hFE) then all three voltages suddenly shoot up, at which point the being greater than unity. In turn, this results in Q2’s current through LED1 (blue) spikes, until the voltages drop and base-emitter junction starting to conduct too. The the process begins again. instant Q2 begins to conduct, voltage Vb starts to rise due to the current passing from Q2’s emitter to its collector. This causes Q2 to abruptly turn off too. The result is Vb Q2 amplifies Q1’s collector current still further, as a result suddenly falls from 1.5V to 0V. Va, via the 330nF capacitor, of its own current gain. The increasing voltage Vb causes then drops from 0.5V to -1V. Va to rise in ‘lock-step’ as the rise is coupled through the It goes negative because, just before Q1 and Q2 switch 330nF capacitor. This triggers a swift ‘avalanche’ effect off, Va is at around 0.5V while Vb is about 1.5V. So when through Q1 and Q2, causing them to both switch on fully Vb drops to 0V, that is coupled through the capacitor and as a result of their combined current gain. 0.5V – 1.5V = -1V. Consequently, the voltage at Vb rises suddenly and At this point, the entire cycle begins again. The result is abruptly up to the full battery voltage, around 1.5V with a very efficient regenerative oscillator which produces a a new cell. Since Vb is now suddenly at 1.5V, Vc rises in brief, but bright flash from the white LED about once every ‘lock-step’ via the 100µF capacitor to give about 3V at Vc. second or two. This is largely determined by the time the This is enough to forward-bias LED1, lighting it up. The 330nF capacitor takes to charge from -1V to about 0.6V via charge stored in the 100µF capacitor is then dumped into the 10MΩ resistor. LED1, giving a brief bright flash of light. Note that while the parts list suggests BC54x and BC55x This process is demonstrated in the simulation traces types, you could also use a 2N3904, 2N2222 or 2SC1815 shown in Fig.2. Va is shown in cyan, Vb in green and Vc in for the NPN transistor; and a 2N3906, 2N2907 or 2SA1015 red. The current through LED1 is in blue. You can see that for the PNP. Almost any pair of NPN and PNP transistors all three voltages rise rapidly at the same time, coinciding will work, but keep in mind that pinouts can vary. with the spike in LED1’s current. While LED1 is lit, the 330nF capacitor keeps Q1 switched Construction on and in doing so, discharges through its base-emitter If all of the parts are ready to hand, the Night Keeper junction. It manages to keep Q1 on for about 30ms. How- should take about an hour or so to build. Expect younger ever, as soon as Va falls below 0.6V, Q1 begins to turn off. children to take longer. Splitting the build into two parts, Parts list – Night Keeper Lighthouse 1 PCB, code 08110201, 64 x 91mm 1 BC547, BC548 or BC549 NPN transistor [Jaycar ZT2154 or Altronics Z1042] 1 BC557, BC558 or BC559 PNP transistor [Jaycar ZT2164 or Altronics Z1055] 1 5mm white high-brightness LED [Altronics Z0876E or Jaycar ZD0190] 1 100µF 16V electrolytic capacitor [Jaycar RE6130 or Altronics R5123] siliconchip.com.au 1 330nF MKT, ceramic or greencap capacitor (code 0.33, 330n or 334) 1 PCB-mount AA or AAA cell holder [AA: Altronics S5029 or Jaycar PH9203; AAA: Altronics S5051; Jaycar PH9261] Glue or double-sided foam tape to fix cell holder to back of main PCB Resistors (all 1/4W, 1% or 5%) (see overleaf for colour codes) 1 10MΩ Australia’s electronics magazine 1 10kΩ 2 1kΩ September 2020  69     +   Fig.3: the PCB is made of two parts, the lighthouse itself and its round base, complete with dangerous rocks! Snap or cut them apart before fitting the components where shown here.  Ratherthan attaching the cell holder via wire leads (as shown here, which you could do), we instead recommend mounting the holder on the back of the board. fitting the resistors and capacitors in one brief session and the remaining parts in a second, makes construction easier and suits the shorter attention spans of young children much better. Completing the project with the addition of the battery holder and base could be managed in a brief third session. The Night Keeper Lighthouse is built on a PCB coded 08110201, which measures 64 x 91mm. Before starting, snap or cut off the circular base from the side of the lighthouse, and file or sand both edges smooth. It’s a good idea to score along the cut line before snapping it. To do that, run a sharp knife along the line joining the small ‘mouse bite’ holes several times. Set the base aside for now, then refer to the PCB overlay diagram (Fig.3) and construction guide (Fig.4) to see which parts need to go where. All of the parts, except for the battery holder, mount on the top side (the side with the component outlines and part numbers), with their leads soldered on the opposite side. The battery holder is mounted the other way around, and that should be done last. Begin by fitting the four resistors, which can be identified by the coloured bands as shown. 1% resistors usually have five bands, while 5% resistors typically have four. Both possibilities are shown. Bend the legs of each resistor in turn with a pair of fine needle-nose pliers or a bending jig, so they neatly fit through the holes for each component in the PCB. Insert them, one by one, in turn, spreading the wire leads apart slightly to hold them in place. They can be fitted either way around. Turn the PCB over and solder both leads to the pads. Then trim off the leads flush with the solder joint using a pair of sharp side-cutters. 70 Silicon Chip Next, fit the 330nF capacitor. It may be either a mylar, MKT or ceramic type. Then install the electrolytic capacitor, and solder and trim the leads in the same manner. Make sure that the longer lead of the electro goes into the pad marked + on the PCB. The striped side of the can should be opposite the + symbol. Now it’s time to fit the two transistors. Q1 is an NPN transistor while Q2 is a PNP transistor. Each transistor must be fitted in the correct location. They are generally not pushed right down on the PCB, but rather, left with leads sticking out by about 5-10mm. This distance is not critical. You will probably find it helpful to spread the three leads of each transistor slightly apart before inserting them into the PCB, making sure the flat face is orientated as shown. Once you have pushed the leads through the PCB, spread them apart a little more on that side to hold them in place before inverting the PCB to solder them to the PCB. Again, trim the leads once soldering is completed. Now mount the white LED at the top of the board. It has a slight flat edge on one side. The LED should be inserted so this matches the shape printed on the PCB overlay for the LED. The longer anode lead will be on the opposite side to the flat. Carefully check that all of the parts are correctly located, and that all of the component leads have been soldered and trimmed. Check also that there are no solder splashes which would cause short circuits. The battery holder can then be mounted on the back of the PCB. A standard AA cell holder is sufficiently large that the end of the battery holder allows the lighthouse to sit it on the edge of a shelf or a book, as shown in the photo. The battery provides an ideal weight to hold the lighthouse vertical, useful for tight corners of a bedroom or office. The wire tails of some battery holders will fit precisely into the holes provided on the PCB. The positive (+) lead should go into the hole nearest the top of the PCB, adjacent to the LED. Other battery holder leads may need to be bent slightly to fit. Use a pair of needle-nosed pliers to bend the wires gently into the appropriate shape to fit neatly. Ideally, space the battery holder off the conductor-side of the PCB by about 3mm. This provides enough space to solder the two wire connections of the battery holder to the correct pads on the rear of the PCB. Attaching the base Alternatively, the circular base PCB can be added. This features a ‘rock-like’ overlay to add to the overall effect, and allows the Night Keeper to be placed on a flat surface. This part of the build may require additional adult assistance to complete – two hands to hold everything in the right place, the other two to apply solder and the soldering iron. Begin by briefly soldering two small ‘blobs’ of solder at each end of the lower tinned edge of the lighthouse PCB. Place this on the tinned strip located on the upper surface To join the two PCBs together, first “tack” them with solder and then run a bead of solder along the tinned copper tracks on the PCB. It won’t let go in a hurry! Australia’s electronics magazine siliconchip.com.au And here’s a side-on view showing the two boards soldered together and the battery holder in position. OK, we cheated a bit: we found that the stiff tinned wire was sufficient to hold it in place without glue or tape. You don’t have to solder the main PCB to the base: the weight of the AA battery holder will ensure it stays in place “hanging” over the edge of a bookshelf. of the circular base PCB. The main PCB should be approximately central and vertical on top of the base. Touch the soldering iron to the two ‘blobs’ of solder to ‘tack’ the two boards together. Repeat this if necessary, reapplying the soldering iron briefly to each tacking point while adjusting the main PCB slightly, until the main board is precisely vertical and centred on the base. Then apply further blobs of solder with the iron along the join, keeping the two boards in their final position. Finally, run the soldering iron down the tack seam to smooth the join and tidy its appearance. instead of the AA type. In that case, you can expect the cell to last closer to six months. The battery life you achieve will vary depending on the battery type (heavy-duty, alkaline etc) and on its condition when first inserted (new, slightly used, near-exhausted etc). Using the Lighthouse The Night Keeper makes a useful bright night-light for children. But keep in mind that flashing lights can disturb sleep, especially if they’re aimed at one’s face. Also, because of the brightness of some high-efficiency white LEDs, the Night Keeper should not be placed where the LED will shine directly into any young and especially sensitive eyes. It’s preferable to locate the Night Keeper lighthouse so that the LED light shines slightly upwards or at right-angles, perhaps onto an adjacent wall. Such arrangements are generally more effective for use as a night light anyway. Older constructors may find, as I did, that the Night Keeper can be useful for locating things in the night, for children and adults alike. Suitably mounted near a door, a light switch or placed on a shelf, it can help guide your way to a location or around furniture in the depths of the darkest of nights. SC Just like a real lighthouse! Operation Have you noticed that there’s no power switch? The circuit uses such a tiny current, a switch is unnecessary. The battery life in use is similar to that of the shelf-life of the battery. A new non-alkaline AA battery can run the Night Keeper for over a year. Hopefully, the faces of the new builders will light up as brightly as the Night Keeper just as soon as they insert the battery. As soon as the battery is inserted, the circuit will start to blink. Note that you could use a AAA battery holder and cell LED1 White LED Align flat on LED with PCB overlay 10k resistor, 5% or 1% Brown - Black - Orange - Gold or Brown - Black - Black - Red - Brown 10M resistor, 5% or 1% Brown - Black - Blue - Gold or Brown - Blk - Blk - Green - Brown BATT+ 100F electrolytic ‘can’ capacitor Align longer lead with PCB + (Stripe on opposite side from +) 1k resistor, 5% or 1% Brown - Black - Red - Gold or Brown - Black - Black - Brown - Brown + Q2 BC557 (PNP) Align shape with PCB overlay 557 330nF MKT capacitor Fit this capacitor either way Q1 BC547 (NPN) Align shape with PCB overlay 1k resistor, 5% or 1% Brown - Black - Red - Gold or Brown - Black - Black - Brown - Brown BATT- 547 Fig.4: in case it isn’t clear from Fig.3 which part goes where on the board, here is what each component looks like. Just follow the arrow to see where it goes. You can match up the part orientations to the drawings, too; the five components where orientation matters are LED1, Q1, Q2, the electrolytic (can-shaped) capacitor and the battery holder. The rest don’t care which way around they go. siliconchip.com.au Australia’s electronics magazine AA or AAA Cell Holder Glue or double-sided tape to the OTHER (copper) side of the PCB + (red) lead goes near LED1 - (black) lead goes to ‘Batt-’ September 2020  71 You too can – advanced vehicle diagnostics Modern vehicles deliver impressive performance and many extra functions like semi-autonomous driving, live maps, streaming audio, motorised doors and hatches etc. This all relies on many computer control modules throughout the vehicle. What do you do when something goes wrong; how do you even know where to start? Luckily, most vehicles will tell you what they think is wrong – as long as you have the right diagnostic tool! A nyone who has driven a modern car cannot fail to be impressed by their many electronic systems. The engine and transmission are under computer control these days, but you might be surprised at how many other electronic modules are involved and all communicating with each other to deliver a seamless experience For folks raised on carburetted cast-iron engines, this level of sophistication was something that could only be dreamed of, but like so many things, the fabulous developments are a double-edged sword. The sheer complexity of onboard systems has resulted in a matching increase in the diagnostic and repair skills required to keep them running, to the point where even seasoned mechanics are struggling to keep up. On the other hand, all these computers also give us advanced diagnostic tools that are continually monitoring operating conditions, and they can be interrogated to ‘spill the beans’ and tell us not only what they think is wrong, but also give live data on the operating conditions and even information on what might go wrong in the future. The more advanced tools (often vehicle manufacturer-specific) used to cost thousands of dollars. Now they have come down in price significantly, and are accessible to even the most impoverished mechanic or tinkerer. dread that comes with knowing that a costly repair could be in your immediate future. But don’t panic; there are many simple and cheap repairs for faults that trigger this light. The key is in using the onboard diagnostics system to pinpoint the faulty component. In some cases, the path back to a fully functioning car can be long and expensive, and the temptation to do it yourself can be powerful. For anyone contemplating this, it’s important to understand just what this OBD technology has to offer. Before the 90s, most vehicles with digital engine computers already had some form of onboard diagnostics, but it was a hodge-podge of different plugs and protocols. Work to change that started in California in 1988, in an effort to provide a consistent diagnostic interface to ensure that vehicle emissions equipment was functioning correctly. This resulted in a mandate for all US passenger vehicles to implement the new OBD1 standard by 1991. Enter OBD For many people, the OBD (OnBoard Diagnostic) system is the onramp into the world of automotive electronics. When the dreaded “Check Engine” light (also known as the malfunction indicator lamp [MIL] or, to your mechanic, the “cha-ching” light!) comes on, many experience the existential 72 Silicon Chip OBD2 systems use a standardised 16-pin connector. While the pinout is standard, the communications protocols can vary. Australia’s electronics magazine siliconchip.com.au OBD2 By Nenad Stojadonovic Limitations surfaced soon after release. OBD1 monitored only limited systems and was consequently unable to detect common but important problems, such as misfires or malfunctions in the evaporative emissions systems. There was also a requirement for only one O2 sensor, meaning that the function of the catalytic converter was not monitored – owners looking for higher performance could (and did) remove the catalytic converter without triggering any trouble codes from the system. (By the way, in many cases it’s still possible to remove the cats and fudge the system to avoid a check engine light. This is stupid, in our opinion, as modern cats have little impedance on exhaust flow and thus minimal effects on performance. They do, however, reduce pollution dramatically). The OBD1 system further suffered from the disadvantage that the diagnostic tools were often proprietary and expensive, thus keeping the average owner from taking advantage of the system. Some manufacturers allowed access to basic malfunction codes by blinking the Check Engine light or an auto test lamp in Morse code fashion. This is triggered by actuating certain dashboard controls in a particular order, or by shorting pins of the OBD1 port together. While this was a crude system, having any access to a relatively sophisticated onboard computer was a boon to the home mechanic, who up to that point had been diagnosing problems by examining spark plugs under a magnifying glass or sniffing the exhaust pipe. OBDII In 1994, the OBD2 (or OBDII) standard was developed by the Society of Automotive Engineers (SAE) and mandated for all US cars from 1996 onwards. Australian-made cars adopted this same standard starting in 2006, although by then, most imported cars already used the system so that they could be sold in the USA. We reported on the emergence of this standard in several siliconchip.com.au past issues of the magazine, mainly in December 2003 (“A Self-Diagnostics Plug For Your Car”; siliconchip.com.au/ Article/4793) and then in February 2010 (“A Look At Automotive On-Board Diagnostics”; siliconchip.com.au/Article/6). The February 2010 issue also had a project to build your own OBDII-computer interface (“An OBDII Interface For A Laptop Computer”; siliconchip.com.au/Article/9). Back then, commercial devices cost hundreds of dollars. Nowadays, you can get a Bluetooth module using an ELM137 clone chip for just a few dollars! Those articles are still relevant, but many developments have occurred in vehicle diagnostics in the past ten years (even though the same OBDII interface is still used). Hence, we decided it was time for this update. OBDII history and details The history of this development makes fascinating reading, with massive input and negotiation from the various stakeholders which is beyond the scope of this article. But the outcome was the standardisation of data held by the onboard computer(s), together with the format and location of the diagnostic port, as outlined in Standard J1979 and J1962. These standards have slowly been introduced to the world’s passenger vehicles and light trucks – heavy vehicles comply with the substantially different J1939 standard, which is optimised to take into account the sophisticated hydraulic, pneumatic and other specialised systems that these vehicles often carry. A good place to find the data standardised under J1979 is contained in a Wikipedia page that can be found at https://en.wikipedia.org/wiki/OBD-II_PIDs Australia’s electronics magazine September 2020  73 The OBD2 port is mandated to be located close to the steering wheel – and is usually found behind a panel between the wheel and the driver’s door. It looks bewildering, but basically, it says that each chunk of data produced by a vehicle’s onboard computer is stored under a parameter ID (PID) in the same way as any processor stores values in memory – or like file folders in a filing cabinet, for the older readers. For example, PID 04 is the calculated engine load, and PID 05 is the engine coolant temperature. The PID numbers are often stated in hexadecimal so, for example, the engine RPM value PID 0C (hex) translates to 12 in decimal. For maximum flexibility, the PIDs are grouped into what used to be called ‘modes’ but are now officially called ‘services’. There are ten standard modes/services in all, and the above PIDs came from Service 1, which is the ‘Show Current Data’ service/mode. Refer to Tables 1 & 2 for more details; note that Table 2 shows a tiny subset of the available PIDs. Trouble codes problem somewhere in the vehicle. A DTC will automatically turn on the ‘Check Engine’ light, also known as the ‘Malfunction Indicator Light’ (MIL) or ‘Check Wallet’ light. Technically, the trouble codes are read out by a scan tool via a Service/Mode 3 (read stored DTCs) and follow the format of a letter followed by four numbers, eg, P0301. There are four letters available to indicate the broad subgroup that the problem belongs to, where P is Powertrain, B is body, C is Chassis and U is Network. The numbers indicate the nature of the problem – in this case, the 3 indicates a misfire and 01 indicates the misfire is in the no.1 cylinder. Finally, the zero after the P indicates that this code is generic. Codes can be generic or manufacturer-specific, and there is no easy way to tell which is which just by looking. For example, P2004 is a generic code that indicates an intake runner is stuck, but P3000 is manufacturer-specific while Service/ Description Mode No 01 Show current data 02 Show freeze frame data 03 Show stored Diagnostic Trouble Codes (DTCs) 04 Clear DTCs and stored values 05 Test results, oxygen sensor monitoring (non-CAN only) 06 Test results, other component/system monitoring (CAN-only) 07 Show pending DTCs (current or last driving cycle) 08 Control operation of on-board component/system 09 Request vehicle information 10 (0A hex) Permanent DTCs (Cleared DTCs) PID decimal (hex) 0 (00) 1 (01) 2 (02) 3 (03) 4 (04) 5 (05) 6 (06) 7 (07) 8 (08) 9 (09) 10 (0A) 11 (0B) 12 (0C) 13 (0D) 14 (0E) Table 1 – OBDII services/modes Table 2 – Abbreviated list of PIDs for Show current data (service 01) PIDs are separate from trouble codes. The correct name for these is Diagnostic Trouble Code (DTC), and they are stored in memory when an onboard computer detects a 74 Silicon Chip Description PIDs Supported Monitor status since DTCs cleared Freeze DTC Fuel system status Calculated engine load Engine coolant temperature Short term fuel trim, Bank 1 Long term fuel trim, Bank 1 Short term fuel trim, Bank 2 Long term fuel trim, Bank 2 Fuel gauge pressure Intake manifold absolute pressure Engine RPM Vehicle speed Ignition timing advance Australia’s electronics magazine siliconchip.com.au P3405 is a generic code that relates to an exhaust valve. Fortunately, the internet is as ever ready to come to our rescue; a quick search for the trouble code will typically find detailed explanations of the meaning, and quite often a good video or two regarding a repair related to that code. An excellent source of the various trouble codes, including some manufacturer-specifics, is at www.obd-codes.com/ trouble_codes/ So where does this get us? It doesn’t take much perusal of the standard PIDs to realise that the main thrust of the standard OBD2 system is engine performance, fuel use and emissions. Given that it was the clean-air regulations that provided the initial impetus for its development, this makes good sense – and it was perfectly adequate for the cars available when it was initially developed. After all, most of them only had a single computer that was devoted entirely to engine management (and maybe one or two others, eg, for transmission control and miscellaneous functions like the instrument cluster and trip meter). As time went on, vehicles of all kinds became more and more computerised, and the modern car can have anything up to 100 individual computers operating via the vehicle’s own onboard internet. Even unexpected things like car radios can be connected and talking to everything else – I had the experience of a radio that had a data feed from the speedometer and wouldn’t allow itself to be programmed while the car was moving! To do this, manufacturers have gone far beyond the standard codes. As mentioned above, they have put in specialised PIDs and diagnostic codes relating to the features of a particular car or series of cars – such as data for sunroofs, security features, specialised entertainment options etc. See the panel reviewing the Forscan tool for a list of real computers in a few different, relatively modern vehicles. Fig.1: some DTCs found by Car Scanner and an ELM327based Bluetooth OBD2 dongle on a 2004 Peugeot. Hierarchy of scan tools Discovering and cataloging these many codes is expensive and time-consuming, and what this means for us is that the cheaper OBD2 scan tools tend to focus on the engine and transmission, and stick to the standard codes. The next step up from the cheap scan tools gives the ability to diagnose and clear faults in other systems such as the ABS (anti-skid brakes), tyre pressure and airbag computers. From there, the next step is the start of the sophisticated scan tools that are intended for workshops and repair facilities. To access the correct data files relating to the vehicle to be tested, these tools will ask questions relating to the make, model, transmission type, engine type and configuration, the type of central computer etc. Once they know this, they can interrogate everything down to such esoteric modules as touch-sensitive door handles, collision-avoidance radar etc. Finally, there are the top-of-the-line tools that will do all of the above, but can also inject data into the OBD2 port to command the actuation of various functions in the car (Service/Mode 8). These tools can, for example, turn the fuel pump on and off, actuate the transmission solenoids, change various engine parameters etc. There is even a function which will detonate the airbags siliconchip.com.au Fig.2: a live data plot of the output of two narrowband oxygen sensors on that same Peugeot, indicating failure of the catalytic converter. Australia’s electronics magazine September 2020  75 in the car to make them safe when they reach the end of their service life! (We hope that one asks if you really, really, really are extra sure that you want to go ahead…) The good news is that with the steady advance of technology and the intensity of competition, the price of scan tools is coming down, and the list of available functions is getting longer. It is worth noting that the functions available in any scan tool are mainly the result of the software that the tool is running. Many of the cheaper tools use a ‘dongle’ that plugs into the OBD2 port and communicates with a phone (or tablet) via Bluetooth or WiFi. One such device is shown in the lead photo. It is the App that does the work; the dongle is simply there to pass messages between the OBD2 port and the App. Thus, the functions available from a dongle type scan tool are somewhat dependent on the App that you download to your phone to drive the dongle (some features require extra hardware in the dongle, so the software can’t unlock those). I use an iPad, and my dongle is compatible with Car Scanner, which I downloaded from the app store. More info on this App can be found at www.carscanner.info For those with an Android phone, my dongle works with Torque Pro or Torque Lite (screengrab in the panel below). Numerous forums discuss this App, and you can have a look at the developer’s description of it on Google Play at siliconchip.com.au/link/ab2r What to look for There are countless scan tools available on the market, especially from overseas. I needed to work on several engine control systems, so I bought a dongle from OBD2Australia. I could have bought the tool from overseas for perhaps $15 or even less, but I paid the Australian dealer $39 for several reasons. The main one is compatibility. Many of the cheap OBD2 dongles use ELM327 clone chips, which are not fully compatible with the genuine ELM327. This limits what you can do with it, and will cause problems if you attempt anything other than the most basic scans. Secondly, compatibility has been a thorny subject in the way that data is delivered to and from the OBD2 port. The content is always the same, but the different manufacturers have encoded it in different ways. They have furthermore changed and evolved these over the years. Wikipedia discusses the different encoding or ‘signalling’ protocols that have been used over the years at and, given the fiercely individualistic nature of the car manufacturers, they are entirely incompatible with each other. So if your scan tool doesn’t understand that particular vehicle’s communications protocol, you won’t get the full details. A subtle ‘gotcha’ here is that Australian vehicles often have different specs from the same overseas model. I have found the reputable retailers either publish lists of vehicles that any particular scan tool is compatible with, or else have someone to ask – and remember that warranty issues for an expensive machine from overseas can be a nightmare. The ELM327 You can’t go far without seeing the ELM327 logo. Elm of Canada produces a range of chips that communicate with 76 Silicon Chip an OBD2 interface, and the ‘327 is a very capable chip that can handle most of the protocols that have been used over the years. Their web site gives an excellent rundown of these and the chips that work with them at siliconchip.com. au/link/ab2s But be warned that to get the full functionality of an ELM327 chip, you must have a genuine ELM327 chip, which is probably not what you will find inside any of the cheaper devices! What can I do with it? Good OBD2 dongles can do lots of things, including changing vehicle settings, running tests, resetting modules and so on. But the single most important feature for most people is scanning for DTCs, ie, trouble codes. These are set when one of the vehicle’s computers has detected a fault and turned on the Check Engine Light, and that there will be a corresponding trouble code available that can be read via the OBD2 port. In some cases, preliminary DTCs are generated even with the Check Engine Light off, only illuminating the light once the problem repeats frequently enough. This is especially true when using one of the better and/ or manufacturer-specific scan tools. You might find dozens of DTC ‘warnings’, which may give you a clue as to incipient or intermittent faults, even if the “check wallet” light is still off. When scanning for DTCs with most dongles, the operation couldn’t be simpler. Just plug in the tool, open the App (if it doesn’t have its own display) and wait while it downloads the appropriate data from the OBD2 port. Fig.1 shows my Car Scanner App displaying four codes thrown by a 2004 Peugeot, indicating a problem with the pollution control system. One of them says it is “pending”, so you wouldn’t necessarily know there was a problem without a scan tool. If you look carefully, you can see that the App has a function that will look up web pages relating to the particular trouble code, up to and including for the specific vehicle that is being tested. Genius! In this case, the P0410 test is incomplete but strongly indicates a problem with the secondary air injection pump, which turned out to be correct – the air hose from the pump had given up the ghost. Once the hose was repaired, I could have left the car asis and the OBD2 system would have automatically cleared the trouble code by itself after a certain number of drive cycles. But I wanted more data, so I hit the “Clear DTC” button and reran the scan. Sure enough, the P0410 code was gone, but the P0420 was still there. The P0420 codes indicate a problem with the catalytic converter. The internet link took me to a YouTube showing how to diagnose the trouble code using the live data function. Live data This is a function that most mechanics of yesterday would have sold their grandmother for. It lets you see, in real time, the data collected by all the sensors available to the particular scan tool, on the screen as a continuous flow of data. Australia’s electronics magazine siliconchip.com.au At a glance, you can see things like fuel mixture (air:fuel ratio), turbo boost pressures, engine torque and power output, fuel pressures, engine load and RPM, various temperatures etc. All of which are worth gold when troubleshooting. In this case, I investigated the P0420 fault by displaying the data from the two oxygen sensors, as shown in Fig.2. Modern cars have at least one O2 sensor close to the cylinder head (typically two in the case of V-engines with two heads), which produce a signal directly related to the richness of the fuel mixture. Most modern vehicles also have a second O2 sensor downstream of the catalytic converter, which monitors the efficiency of the chemical reactions inside the cat. As it is typically a narrowband sensor, which only works across a narrow range of air:fuel mixtures around the stoichiometric point, the first sensor can be expected to swing back and forth across its full range at idle. The top graph in Fig.2 shows this to be happening. The second sensor is expected to remain steady at somewhere around 0.5V once the cat is warmed up and doing its job, because it should be catalysing the reaction between the excess fuel at one extreme, and oxygen at the other, in order to burn all the fuel completely. Alas, this was not happening, as can be seen in the bottom graph of Fig.2. There are a few reasons why this could be, including simple things like exhaust air leaks. Still, a few gentle taps with a rubber mallet resulted in a loud rattle from inside the cat, which strongly supported the theory that it was an ex-catalytic converter. Freeze frame (Service/Mode 2) If that’s not enough, vehicles will take a snapshot of all PID data when a fault occurs and the corresponding DTC is set, and many scan tools can download that data for analysis. For those of us who have struggled to find elusive intermittent problems, having the operating conditions under which a fault occurs is a huge leg up. Note that not all scan tools will support this function. If you need it, check that it is available in the scan tool you’re ordering. Service/Mode 6 diagnostics Not all faults are serious, and not all faults have an eas- ily defined point at which they become a fault. Better scan tools will allow you to investigate problems which may be brewing before they trigger a trouble code, both to see them and also to see how close they are to a predefined threshold which will set the relevant trouble code. A good example of this comes in the form of misfires. Most cars will have the occasional misfire, especially when idling where the engine operates under the leanest fuelling conditions. To avoid every misfire setting a trouble code, the engine control computer counts misfires in each cylinder, then runs the tally through a statistical analysis algorithm that compares it to an upper limit. Screen1: some of the live In other words, the odd data parameters that can misfire is ignored, but be shown with the free App when they start to mount Torque Lite and almost any up to an unacceptable lev- OBD2 dongle. el, the computer will trigger the P03xx trouble code. Mode 6 is invaluable in this instance, as the raw count can be investigated and it can show patterns that facilitate diagnosis and repair. I looked at a car recently that would misfire noticeably under load, but didn’t trigger a fault code. I found a particular cylinder had a high count that turned out to be caused by a coil pack that was on its way out (a very common problem, unfortunately). Magic Hopefully, this brief guide will provide you with a good idea of where to go when the dreaded Check Wallet light comes on. OBD2 is not magic, and there will be no arrow floating in the air pointing at the offending component, but with the appropriate workshop manual and bit of practice, there will be few problems that will cause you much angst. At the very least, you will not be peering at spark plugs and sniffing the exhaust pipe like your grandfather had to do. Even if you have zero mechanical skills, being able to scan for faults before they become serious can be very helpful. And if you do have a serious fault, doing a scan immediately might tell you something that could be lost before you get the vehicle to a mechanic. It may also save you from unnecessary repairs, as we’ve heard of some unscrupulous mechanics who will quote for a lot of unnecessary work in addition to fixing the real problem, just to make more money. If you have a good idea going in what’s wrong, you may be able to head that off at the pass… siliconchip.com.au Australia’s electronics magazine September 2020  77 Forscan, Torque and other OBD2 software . . .         I purchased the Forscan dongles pictured here for $45 (Bluetooth version) and $39 (USB version), including postage, from www.obd2australia.com.au (believe it or not, I ordered them before Nenad sent in his article and I saw where he got his…). These can be used as generic OBD2 dongles, but they are designed to give full access to modern Ford and Mazda vehicles (hence the name). They will probably work well with other makes too, as they use genuine ELM327 chips. Why Ford and Mazda? Ford owned a stake in Mazda from 1979 to 2015, and they shared a lot of engineering, including engines and engine computers. In fact, many four-cylinder Ford engines today are derivatives of Mazda designs. And both companies appear to be still using compatible electronic protocols for their vehicle electronics. This is ideal for me because, in my immediate family, we own one Australian Ford, one European Ford and one Japanese-built Mazda. So this one cheap dongle gives us Screen2: page one of many of the vehicle info given by Forscan Lite for a 2015 Ford Kuga (which has since been renamed “Escape”). 78 78  S Silicon Chip dealer-level diagnostics and configuration support for all our vehicles! The accompanying screengrabs from an Android phone show this dongle being used by three different apps to communicate with my wife’s Ford Kuga (the latest model is called the Escape). Screen1 is from Torque Lite, mentioned in the main text of the article. You can configure the screen to show just about any combination of parameters, including running graphs. Here I have just selected some of the more useful parameters and taken the Screen3: page two of the Kuga module information. The car has over a dozen separate electronic modules. Australia’s Australia’s electronics electronics magazine magazine screengrab with the engine idling. Torque can also read DTCs, but doesn’t show anything much if none are found. I selected the option and simply got a message indicating that no codes were found. As Torque doesn’t seem to be geared towards reading DTCs, I had a quick look and found Car Scanner (the Android version this time). Its main screen is shown in Screen8. It appears to be pretty capable, but unfortunately contains ads (how does it know I need new boots?). Screen4: page three of the Kuga module information. The vehicle has two buses, so you need a dongle with a switch to scan them all. siliconchip.com.au by Nicholas Vinen Interestingly, as shown in Screen9, this software did find two DTCs logged in the vehicle. These appear to be communication errors between various modules in the vehicle. It wouldn’t show me any more information than this, though; pressing on these errors did however helpfully redirect me to a website indicating what might cause these codes. Then I fired up the Forscan Lite software, for which I paid less than $10. The full Forscan software runs under Windows and is free, except for its advanced features; more on that below. After connecting to the dongle, it spent some time querying data, with a series of LEDs pulsating on the dongle. I then pressed on the Vehicle Information menu item, and the result is shown in Screens2-4. This gives you an idea not only of how comprehensive this software is, but how many different modules are in the car! Interestingly, as well as listing the modules and their hardware and software revisions, it shows the odometer readings which are stored in several different modules. This gives you a way of checking whether the odometer reading is accurate, or if it has been messed with; they should all agree. I then went into the “Errors” menu item to read the DTCs (Screen5). While Torque Lite showed zero errors and Car Scanner showed two, Forscan found three, and also gave more detailed information in each case. So this shows you the value of having a manufacturer-specific or dealer-type diagnostic system for troubleshooting. Forscan Lite also lets you run vehicle self-tests (only some of which are shown in Screen6) and perform service tasks such as resetting or calibrating certain modules (see Screen7; again, this is a small subset of the available options). I plugged the same dongle into the Mazda CX-9, and I was surprised to find that even more modules were available! I suppose I should not have been so surprised, as it is an even newer vehicle. Rather than take up a lot of space with screen grabs, I’ll simply list what it found. It found the Engine Control Unit (ECU), Transmission Control Module (TCM), Powertrain Control Module (PCM), OBDII interface, Head Up Display (HUD_ MZ), Amplifier Module (AM), Connectivity Master Unit (CMU), Power Liftgate (PLG_MZ), Smart Brake Support/Mazda Radar Cruise Control (SBS/MRCC), 4X4 Control Module (4X4M), Antilock braking system (ABS), Electric Parking Brake (EPB), DC to DC Converter Control Module (DCDC), Driver’s Seat Module (DSM), Restraint Control Module (RCM), Adaptive Front Lighting System / Auto Levelling Module (AFS/ALM), Start Stop Unit (SSU), Electronic-Controlled Power Steering (EPS), Front Body Control Module (F_BCM), Instrument Cluster (IC), Forward Sensing Camera (FSC), Blind Spot Monitoring, Left and Right (BSML, BSMR), View Monitor Camera (VMC_MZ), Rear Body Control Module (R_BCM), Parking Sensor Module (PSM_MZ) and Electronic Automatic Temperature Control (EATC). Phew! I’m glad to report that those are all working, and there were no DTCs to be found. Screen5: some of the DTCs that Forscan Lite found in the vehicle. It’s handy that it shows which module has thrown them. Screen6: some of the procedures that Forscan Lite allows you to carry out, such as resetting various modules or running calibration procedures. Screen7: you can also use Forscan Lite to run some vehicle self-test routines, some of which are shown here. siliconchip.com.au Australia’s electronics electronics magazine magazine Australia’s USB, Bluetooth and WiFi Those are the three available communications options for the Forscan dongles. September eptember 2020  79 Screen8: I also tried Car Scanner with my Forscan dongle. It worked, but didn’t give as comprehensive results as Forscan Lite. Screen9: Car Scanner found some but not all of the DTCs that Forscan Lite reported. 80 80  S Silicon Chip I originally purchased the Bluetooth version as it’s the most convenient for use with a smartphone. Presumably, the WiFi version will work with a phone too; I haven’t tried it. But one of the main reasons I bought it was to turn on the auto-door-locking feature in my wife’s car. This is a feature that all our other cars had, but for some reason, the Kuga doesn’t. This is despite the “anti-carjacking” feature being mandatory in North America, where the same car is sold (in left-hand drive form, obviously). To turn this on, I needed to go into the vehicle’s “Central Configuration” mode. This involves uploading a small ‘bootloader’ to the body computer and rebooting it into a mode that lets you change the configuration. You need the full (paid) version of the Forscan PC software to do this, but it isn’t expensive – around $100 for a lifetime license, and less for a few years. However, when I tried this, I got several error messages and a warning that if something went wrong, it could ‘brick’ the car! Having failed on the first attempt, I decided that Bluetooth wireless comms was not reliable enough for this type of operation, so I ordered the USB version instead. It did seem to work much more reliably; I still got some error messages, but this time, I was able to get into the configuration and turn on that feature. We’ve been waiting to enable it for years, so I was very pleased when I went for a short test drive afterwards, and the doors locked and unlocked themselves. That alone was worth the total of under $200 for both scan tools and the software. The screens at right show some of the other settings which were available for me to change. I would say that these little units are excellent investments if you own any newer Ford or Mazda model (say, made in the last ten years). The Bluetooth version is great if you just want to read DTCs or run basic tests, but if you want to change the configuration, get the USB version. See www. forscan.org for extensive documentation and forums. By the way, one major advantage of the Forscan PC software compared to phone Apps like Forscan Lite is that the much larger laptop screen is that you can more easily display and log the dizzying array of data and parameters availSC able to scan. Australia’s Australia’s electronics electronics magazine magazine Above: the four pages of configuration settings I can change in the Kuga’s Central Configuration. siliconchip.com.au Gear UP! Build It Yourself Electronics Centres® Bluetooth® 5.0 True Wireless Earbuds Bluetooth 5.0 offers superior range (up to 10m) & audio quality - plus automatic connection. Sweat resistant and light weight design makes these buds great for exercise. 3-4hrs of listening time. Includes charging case (provides 2 recharges), replacement earbuds and USB C 9037B charging cable. All the gear you need to keep building & creating. 49.95 $ ber 30th. Sale ends Septem 9999 Count True RMS DMM With in-built AC mains detection. 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SAVE 28% 35 $ P 1012A 1660 Hole SAVE 26% 40 $ P 1015A 2309 Hole Must have for the electronics maker! Joondalup Store NOW OPEN 2/182 WINTON RD JOONDALUP, WA. OPEN 7 DAYS. Western Australia Build It Yourself Electronics Centres Sale Ends September 30th 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 0092 ‘Due’ Development Board Z 6387 SAVE 20% PRODUCT SHOWCASE The smallest automotive maXTouch controllers from Microchip To help enhance today’s driving experience, automotive manufacturers are adding multiple touch displays. Supporting these secondary displays with advanced features, Microchip Technology announced the extension of its market-leading maXTouch portfolio with the new MXT288UD touch controller family – the industry’s smallest automotive grade packaged touch screen controllers. The MXT288UD-AM & MXT144UDAM devices offer a low-power mode, weatherproof operation and glove touch detection in multi-function displays, touch pad and smart surfaces for vehicles, motorcycles, e-bikes and car-sharing services. These touch surfaces can be placed in both the interior and exterior of a motor vehicle, such as handlebars, doors, electronic mirrors, steering wheel, between seats etc. With the MXT288UD’s small 7x7mm VQFN56 package, tier one suppliers can now reduce board space by 75% and greatly minimise the overall Bill of Materials (BoM) – all while exceeding the requirements for excellent and reliable touch performance. The family’s low-power wait-for- touch mode consumes less than 50µA, remaining responsive for the user, even if the display switches off to save power or to avoid disturbing the driver at night – a touch event anywhere on the touch surface will wake the system up. In addition, the MXT288UD-AM & MXT144UD-AM enable detection and tracking of gloves through a wide variety of overlay materials and thicknesses, like leather, wood or across uneven surfaces – even in the presence of moisture. For example, in car sharing applications, this functionality helps users access a car from the outside by tracking touch coordinates on an exterior display in any environment, from rain to snow or extreme heat. As a turnkey solution, the MXT288UD family provides proven firmware, developed according to Automotive SPICE processes and is AECQ100 qualified. This makes it easy for automotive manufacturers to integrate into existing systems at a lower risk and faster time to market. Microchip Technology Inc. Unit 32, 41 Rawson Street Epping 2121 NSW Tel: (02) 9868 6733 www.microchip.com Staying safe in the workplace using FLIR Thermal Imagers Thermal imaging cameras cannot detect or diagnose an infection. However, FLIR thermal cameras are an effective tool to measure skin temperature and identify individuals with Elevated Body Temperature (EBT). FLIR thermal cameras enable the screening of people with EBT that might indicate illness. People who are suspected of an EBT must then be screened by professionals for diagnosis of any medical condition. FLIR thermal cameras detect heat radiation and can be used to identify the surface temperature of objects and people. With this capability, FLIR thermal cameras are commonly used as a non-contact screening tool to detect differences in skin surface temperatures and pattern changes. The IEC states that the inner eye is the best area for body temperature siliconchip.com.au readings due to it being over an important artery. FLIR’s cameras “see” or detect the temperature differences with temperature measurements between -20°C to +2000°C across their range of Thermal Imaging Cameras. Some FLIR cameras include a screening mode (below) that provides an alarm when a person is detected to have an elevated temperature. Activating the screening mode will turn on a measurement box and screening data on the camera’s screen: 1) Sampled average temperature 2) Alarm temperature 3) Measured temperature The alarm will trigger when the measurement box measures a temperature higher than the provided alarm temperature. In order to obtain a good temperature reading, it is recommended that the intended target be as close to the camera as possible. Therefore, distance to the target is an important consideration, as is focus. Rapid Tech Equipment is a FLIR Premium Sales Channel Partner. Rapid-Tech Equipment Pty Ltd Tel: 1800 358 531 Website: www.rapid-tech.com.au/flir/ Australia’s electronics magazine September 2020  85 USB By Phil Prosser Part II: Circuit Description Last month, we introduced our new USB Sound Card design which boasts unimpeachable recording and playback performance. It isn’t only useful for recording and playback either; with some inexpensive software, it can make a very advanced audio signal analysis system. Now it’s time to describe the details of the circuitry behind its phenomenal performance. W e covered the basic operating principles of the SuperCodec in last month’s introductory article, but we ran out of space to fit the full circuit details. As you will see from this article, that’s mainly due to the number and size of the circuit diagrams. As the circuit of the SuperCodec is too large to fit across two pages, we have broken it up into five sections: the computer interface with galvanic isolation (Fig.12), local clock generation and asynchronous sampling rate conver- sion (Fig.13), the ADC section (Fig.14), the DAC section (Fig.15) and the power supply (Fig.16). Galvanic isolation The galvanic isolation is provided by IC12, a Maxim MAX22345 (see Fig.12). This is a fast, low-power, fourchannel galvanic isolator chip. We are using the 200Mbps version as we wanted to be able to transfer clock signals at more than 12MHz (the bit clock [BCLK]) and 24MHz (the USB3.3V I2S data OUT Ch1&2 J1 26 51 1 2 1 J2 10 I S data IN Ch1&2 2 VDDA DEFA 3 IN1 4 DVDD3.3V 100nF IC12 MAX22345 20 7 VDDB DEFB 14 OUT1 18 MINIDSP I2S_DAC IN2 OUT2 17 MINIDSP B CLK 5 IN3 OUT3 16 MINIDSP LRCLK 6 OUT4 IN4 15 MINIDSP I2S_ADC1 USB BCLK 8 USB LRCLK 9 OPTICAL OUTPUT 1 J3 2 (VIA CON2) (VIA CON3) 1 2 12 1 76 100nF OPTICAL INPUT MINIDSP MCHSTREAMER MODULE USB TYPE B DVDD3.3V 2 ENA ENB NC NC GNDB GNDB GNDA GNDA 10 13 12 19 RESET_L 11 10k USB GND 3 USB3.3V BC549 VCC DS1233 USB3.3V B E 1k 2 C 2 OPTO1 4N28 6 1  5 4 C B Q1 BC549 RESET IC13 DS1233 GND 1 E 3 2 1 SC  2020 SUPERCODEC (USB SOUND CARD) MiniDSP MCH Streamer & Galvanic Isolation Circuitry Fig.12: this section of the full circuit connects the MCHStreamer to a MAX22345 high-speed isolator and a bogstandard 4N28 optocoupler. The latter releases the ADC & DAC reset lines 350ms after plugging in USB. 86 Silicon Chip Australia’s electronics magazine siliconchip.com.au ally bulkier). Maxim does not explicitly state which, but it master clock [MCLK]). appears to be capacitive. The version that we are We’re also using an ordinary old 4N28 optocoupler. This using provides three “left to tells the audio side whether there is power being received right” and one “right to left” from the computer. channels. This is ideal for isoIf there is no power, the ADC and DAC are held in reset. lating the I2S output from the Once there is 3.3V power from the USBStreamer, the MCHStreamer. When we had the computer ground electrically connected to the USB Sound Card ground in a real-world system, we found it impossible to get rid of residual 50Hz related noise and a bunch of “spurs” in the noise floor. While these were low enough to be inaudible, putting the galvanic isolation into the system saw these drop significantly. Indeed, even allowing the USB earth to connect to the case of the USB SuperCodec increased the 50Hz hum by 10-20dB! This chip is not that expensive, but the benefit of using it as part of a measurement system is huge. We must make it clear that while this device provides a high degree of isolation, we have not designed the circuit board to handle significant voltage differences between the two domains. Do not, in any circumstances, rely on this design to provide safety isolation between the PC and the sound interface! It is purely intended to improve the performance, and allow a few volts of difference between your computer and audio grounds, as can sometimes occur. The data rates from the USB interface are quite high. The MCLK signal is at 24.576MHz for the 192kHz sampling rate, and the BCLK is half this, at 12.288MHz. Design and layout of a board for reliable operation at 25MHz requires attention to detail, careful grounding and termination for long traces. We have used series termination on the 25MHz clock signal, and managed to keep high-speed traces tidy and with a minimum of vias. They all run over a solid ground plane for their entire length. Where we have had to route across these signals, we made the aperture in the ground plane as small as possible. We came close to utilising a four-layer PCB for this design, but by constraining the digital signals to a limited area, and with careful layout, we have avoided the cost this would incur. In the final version of the design, we are using a local clock oscillator for the 24.576/25MHz clock, so while we can access the master clock from the MiniDSP MCHStreamer, it is not used, as we can do better with a local clock source. Hence, Fig.12 does not show any connection to the MCLK pin of the MCHStreamer module. In case you are wondering how the MAX22345 works, isolators like this generally get the signal across the isolation barrier We’ll get onto the construction next month, after we’ve finished with using either magnetic or capacitive coupling the rather involved description. To whet your appetites, here’s the (high-speed optical isolators exist but are usucompleted PCB mounted on the input/output socket, shown life size. siliconchip.com.au Australia’s electronics magazine September 2020  87 Fig.13: the ASRC circuitry sits in between the galvanic isolation section and the ADC and DAC chips. Its job is to pass digital audio data between two clock domains: that of the USB MCHStreamer, with a nominal 24.576MHz master clock, and the ADC and DAC, clocked by 25MHz crystal oscillator module XO1. The relative drift of these two clocks is taken care of by the digital filters in IC6 & IC7. ADC and DAC are taken out of reset after 350ms. The DS1233 provides this delay; the signals from the USB Streamer should have stabilised after 350ms. From a users perspective, this means that when you plug the USB SuperCodec in, it looks after its own reset and “just works”. Local Clock Generation and ASRC This section has been the subject of a lot of work. It would be possible to drive the ADC and DAC directly from the miniDSP MCHStreamer, as isolated by the MAX22345. But what if the user wants to operate the card at 44.1kHz, 48kHz, 96kHz, 192kHz or some other rate? How do the ADC and DAC get set up for this? The CS4398 and CS5381 chips both have mode pins that must be set depending on the sampling rate at which we 88 Silicon Chip want to operate. In the prototype, we used jumpers to set the sampling rate for the ADC and DAC. We quickly decided that users will want to plug the card in and have it sort this out for itself. It would be possible to, say, use a microcontroller to sense the sampling rate and set the chips up accordingly. But there is a better way – using a device called an asynchronous sampling rate converter (ASRC). ASRCs are found in professional recording studios and also consumer equipment which has digital audio to digital audio interfaces. Imagine you have two digital audio devices, say an amplifier and a CD player. Each is a standalone device with its own clocks and generally looks after itself. When you plug these together, if you want to have the CD player pro- Australia’s electronics magazine siliconchip.com.au vide digital data to the amplifier, what happens if (as is inevitable), the CD player’s clock is just slightly different in frequency to the clock in the amplifier? Eventually, the CD player will provide either too much or too little data to the amplifier. In serious situations (eg, professional mixing rigs), you can have a master clock distribution system. But most devices don’t have provision for that. Alternatively, you can use an ASRC. Instead of locking the clocks of different chips together, the ASRC flips the problem on its head. It allows our ADC and DAC to have their own clocks, and does a bunch of maths to pass the correct digital values to and from the computer at whatever sampling rate it happens to be running at. This involves the ASRC monitoring the different sampling rates, then implementing digital filters to deliver the exact digital value needed at every sample interval. The upshot of this is that we can use a local 25MHz clock source to drive both the ADC and DAC. The clock we have chosen is good without getting silly. Its typical RMS jitter is less than 1ps (one million millionth of a second!). You could go for a better unit, but our analysis suggests that the difference would be essentially unmeasurable. Indeed using a “better” clock is a tweak that some serious audiophiles do. We have used a sample rate converter in each of the ADC and DAC lines, as we need to perform this translation for both recording and playback. The devices we’re using are both Cirrus Logic CS8421s. If you are worried about what these things may do to the sound, fear not. These are rated for 175dB dynamic range and -140dB (0.00001%) THD+N! So the impact of these devices is so low that it is not at all detectable, let alone audible. (We have donned our asbestos underwear as we await the flame throwers of the anti-ASRC audiophile crowd!) The actual implementation of these chips is not complex, as shown in Fig.13. The digital audio signals go into pins 7, 8 & 9 at one particular sampling rate and emerge from pins 12, 13 & 14 at a different rate, to match up with the clock signal applied to pins 2. Using an ASRC has a couple of implications on how the ADC and DAC are set up and driven. Firstly, we must provide a low-noise clock. This is from XO1, a 25MHz clock oscillator module. Secondly, we need the local left/right clock (ie, sampling rate) at a higher rate than the 192kHz that the MiniDSP USBStreamer uses, to ensure no degradation of the digital signal. 25MHz divided by 32 (bits each in the L and R samples) divided by 2 then 2 again is 195.3125kHz. So that suits us fine. We need to set the ASRC for the CS4398 DAC as a master output so that it generates the 195.3125kHz left/right THIS . . . OR THIS: Every article in every issue of SILICON CHIP Can now be yours forever in digital (PDF) format! Nov 1987 Dec 2019 n n n * Some early articles may be scans High-res printable PDFs* Fully searchable files - with index Viewable on 99.9% of personal computers & tablets Software capable of reading PDFs required (freely available) Digital edition PDFs are supplied as five-year+ blocks, covering at least 60 issues. They’re copied onto quality metal 32GB USB flash drives. Just order the block(s) that you want! siliconchip.com.au n n n n Nov 87 - Dec 94 Jan 95 - Dec 99 Jan 00 - Dec 04 Jan 05 - Dec 09 Jan 10 - Dec 14 Jan 15 - Dec 19 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) and the USB Flash Drives are high quality metal USB3.0, so if you save the files to your PC hard disk, the USB Flash Drives can be used over and over! Subscriptions to SILICON CHIP remain the same Of course, so you won’t miss out on a current issue you can still subscribe to SILICON CHIP . . . and you’ll $ave money over the newsstand price. Your SILICON CHIP will be delivered every month right to your mail box . . . no waiting! n n Some of the components for this project are rather specialised so might be difficult to track down. To assist you in this endeavour, we have produced a spreadsheet which gives catalog codes for each part needed, from six different sources: • Altronics • Jaycar • Digi-Key • Mouser • element14 • RS. You’ll find this spreadsheet at siliconchip.com.au/ Shop/6/5597 n Each five-year block is priced at just $100, and yes, current subscribers receive the normal 10% discount. n SOURCING THE COMPONENTS n Subscribe to the printed edition Subscribe to the digital edition Subscribe to the combo printed/digital edition Want to know more? Full details at siliconchip.com.au/ shop/digital_pdfs Australia’s electronics magazine September 2020  89 clock (LRCK) and control signals for this ADC on its output – ie, the ASRC drives the DAC at this rate at all times. We need the ASRC for the CS5381 ADC as a master input so that it generates the 195.3152kHz clock and control signals for the MCHStreamer on its input. Pin 6, BYPASS, allow the ASRC action to be disabled, but since we always want it active, we have tied this to GND. Similarly, we are not using the Time Domain Multiplexing (multi-channel) feature, so pins 11 are tied low. The MS_SEL pin of IC6 is pulled down via a 2kΩ resistor, which sets the device to slave mode on its input side (clocks are inputs), and master mode on its output side (clocks are outputs). The 1kΩ resistor from pins 19 (SAIF) to ground sets the inputs of both devices to 32-bit I2S mode; one of six different digital audio protocols this chip supports. This matches the data format from the MCHStreamer. Similarly, the 4kΩ total resistance from pins 18 (SAOF) to ground sets the output side to I2S mode with 24-bit data, to suit our ADC and DAC chips. This is one of 16 possible formats the chip supports. Once set up as above, this forms a neat interface between parts of a system that may have differing clocks. Is there a downside? They are not cheap devices, at $17 each from Mouser. But we think that’s worth it for the flexibility they provide. Analog-to-digital conversion We’re using the CS5381-KZZ chip. Cirrus Logic make two similar devices, the CS5361 and CS5381. They are pincompatible, but the CS5381 has better distortion performance. We have specified the better of the two. You could drop in the CS5361                          SC  90   SUPERCODEC (USB SOUND CARD) Silicon Chip Australia’s electronics magazine siliconchip.com.au instead, and will lose a bit of performance on the input channels. The circuitry surrounding this chip, shown in Fig.14, is close to what is recommended by the Cirrus Logic application note. However, we have gone to extra lengths to ensure very symmetrical drive of the input, and to make sure that the sound card has a high-impedance input. Ferrite beads FB3 & FB4, with the following 100pF capacitors to ground, form RF filters at the inputs. Bipolar electrolytic capacitors block DC voltages, with a -3dB cutoff well below 1Hz. Schottky diodes D5, D10, D15 & D16 protect the op amp inputs against spikes and excess voltage. In normal operation, these do not affect the signal. IC2a/IC4a operate as unity-gain buffers. They provide a low-impedance drive for the following two stages without affecting the input. IC2b/IC4b operate as inverters. We have used 1.2k feedback resistors, as low as practical, to keep noise down while allowing the operational amplifier to drive the following stage without any concern of increasing distortion by overloading the output. We could have gone a touch lower           Fig.14: the stereo analog audio signals applied to RCA sockets CON6a & CON6b are buffered and pass through a series of RF filters before being converted to balanced (differential) signals, which are then fed to the pairs of ADC inputs at pins 16/17 and 20/21 of IC1. The 2.7nF filter capacitors are critical to getting good results, while numerous schottky diodes protect the various ICs from signal overload. siliconchip.com.au Australia’s electronics magazine in resistance, but feel this is a good compromise on performance and power use. IC3a/IC5a and IC3b/IC5b drive the differential inputs of the ADC, and all four stages are configured in a very similar manner. There are a couple of things going on here. The non-inverting inputs are held at a 2.5V bias via 10kΩ resistors from IC1’s VQ (quiescent voltage) pin, pin 22. These resistors have 10nF local bypass capacitors to ensure the op amps see a very low source impedance. The inverting inputs of these op amps are driven by the in-phase and inverted signals from the previous stage, which are capacitively-coupled to support the DC offset. You might be concerned that the input signal could affect the 2.5V, but these signals are balanced, so their effects on the reference voltage essentially cancel out. The 470pF feedback capacitors form low-pass filters in combination with the 680Ω and 91Ω resistors. This has a cutoff way above the audio band, at around 500kHz, to ensure stability and get rid of any RF noise which makes it past the input filter. At audio frequencies, these four stages form unity gain buffers. The fact that the output is taken from the junction of the resistors reduces transient loading on the operational amplifier. Some low-pass filtering is provided by the combination of these resistors and the 2.7nF capacitors across the pairs of differential ADC input pins. These capacitors are mounted very close to the input pins. Our testing showed that these capacitors are critical to the performance of the ADC. Do not use any old capacitor. Do not use an “audiophile” capacitor. Do use a ceramic NP0 or C0G type capacitor, surface mounting, of known provenance. We built a prototype with a film capacitor here, and the distortion went up by a factor of ten. We also tried silver mica caps, and they were no better. Clearly, it isn’t just the linearity of this capacitor that is critical; the oversampling ADC draws pulses of current from these caps at a high frequency, so we need caps with a low ESR at several megahertz, as well as linearity. Only NP0/C0G ceramics provide both. The ADC input pins have BAT85 diodes to each rail for protection. Reviewing the data sheet, it seems that the ADC should survive the maximum output current of a NE5532, but it might not September 2020  91 survive the maximum output current of an LM4562. Because some people might try different op amps – and since IC1 costs around $45 (!) – it’s worthwhile protection. The VA analog supply to IC1 is nominally 5V, and we have a local low-dropout linear regulator (REG5) to provide a 3.3V digital logic supply rail for IC1. We have done this locally as it draws little current and made the layout so much easier. Pin 15 of the ADC provides an overflow indication. This drives the LED on the front of the unit. Should this flash during operation, you are driving the ADC into clipping, and need to lower the input level. Generally, you should be running the input substantially lower than this. The noise and distortion are optimal at a decibel or so below clipping, and even if you run this 10dB lower, the impact on performance will be minimal. The ADC pins at upper right are tied either to VL or GND to set it up in ‘hardware mode’ (ie, not being controlled by a microcontroller), with the correct audio format selected. The dig- itised audio signals appear at pin 9 of IC1 and goes onto ASRC IC7, as shown in Fig.13. That same ASRC chip and XO1 provide the clock signals at pins 3, 4 & 5 of IC1. Digital-to-analog conversion The CS4398 DAC is configured in a fairly conventional manner – see Fig.15. Discussing the right channel, IC9’s differential outputs drive two low-pass filters formed by IC8a and IC8b. The filter on each pin is set up to present the same load to the two outputs. The impedances have been kept low to minimise noise. This filter is the same as used in the DSP Crossover last year and limits the output of supersonic signals. We have specified C0G ceramic capacitors (or NP0; same thing) where ceramic types are used. This is very important as other dielectrics will introduce more distortion. For the 1.5nF, 10nF and 22nF capacitors we used MKT capacitors. The self-resonance of low-value MKTs is typically in the 10MHz region, so the filter behaved well and provided ex- cellent performance. They are easier to obtain than NP0/C0G ceramics with those same values, so you might as well stick with the MKTs. But if you use very high-speed op amps in place of the NE5532s, things could change. IC10b forms a differential-to-singleended signal converter. The 1.2kΩ resistor values are low enough to minimise noise while not overloading the op amp, and leave headroom for it to drive a load. The 470pF capacitors in this stage form the final stage of the low-pass filter. The DC output level of the DAC is 2.5V. This runs through the filters formed by IC8a & IC8b. Rather than AC-coupling the signal to the differential to single-ended converter, we have used the converter to remove the bulk of the DC offset itself. The AC-coupling capacitor at its output removes any residual DC – though in our prototype, this was a very low level. The power supply The power supply, shown in Fig.16, may look over the top. This design makes no apology for taking power sup-                 SC  92  SUPERCODEC (USB SOUND CARD) Silicon Chip Australia’s electronics magazine siliconchip.com.au Still using NE5532s – really? We have specified NE5532 op amps for this project. This may be a point of contention with some readers. We built eight of the DAC modules as used in the DSP Active Crossover, allowing a comparison of NE5532 and LM4562 devices, and were unable to conclusively measure one as better than the other. We expect that we were measuring the actual ADC and DAC performance. Given that the LM4562 costs more than the NE5532 and consumes more power there seemed to be no good reason to use them. We have also used LM833 op amps; they work too, but not as plies and grounding to something of an extreme as we aim to deliver solid ADC and DAC performance, at the parts-permillion level. In particular, any noise on the +5VA rail is a very bad thing, and we want the +5VL and ±9V rails to be clean of noise and clocking artefacts. The first version of this unit used a toroidal transformer mounted on the opposite side of the case from the sensitive analog parts. It even included a copper shorting ring to reduce radiated noise. Even so, we could still see the 50Hz leaking into the plots down around the -110 to -130dB levels. well; they can’t drive as low impedances as NE5532s, so require more of a distortion/noise tradeoff. If you have a favourite op amp you want to use, we recommend you install high quality machined sockets, as desoldering op amps from a double-sided PCB generally kills the op amp, and may damage the PCB. Suitable sockets are the Altronics P0530. Things you would need to check if you do this include oscillation, ringing and leakage of HF products from the DAC to the output. We also suspect that you will, in the best case, get equivalent performance, and quite possibly worse. If you want to get the rated performance, it’s best to stick with the devices that we tested! So we changed it to run off a single +12V DC plugpack. It uses two LM2575 buck regulators (REG1 & REG2) to generate a +6.5V DC rail and -12V DC rail. This choice might raise a few eyebrows as switchmode converters are not famous for low levels of radiation. And you may wonder how the same chip is used to generate both positive and negative rails. Let’s start with that negative rail. In essence, we are turning REG2 on its head; its positive output connects to GND (after the LC filter), while its GND pin is actually ‘floating’ on the                Fig.15: IC9 converts the digital audio signals from the ASRC stage to balanced analog outputs at pin pairs 19/20 and 23/24. These are then filtered to remove digital artefacts and converted to single-ended audio, to be fed to RCA output sockets CON7a & CON7b. siliconchip.com.au Australia’s electronics magazine negative rail! It may seem strange, but if you analyse the circuit carefully, you will see that this will work. But there are a few things you need to be aware of when using a buck regulator this way. On startup, it tends to draw a lot of current for a short period. The Texas Instruments data sheet warns of this, and they were right to! The peak startup current is about 2A, so be sure to use the recommended plugpack, or check that yours works OK. Altronics and Jaycar also sell the LM2576, which is a beefier version of the LM2575. This draws closer to 4.5A on startup. It works, but watch that startup current. So how does this work? Here’s a brief explanation: REG2 ‘tries’ to keep the feedback voltage at pin 4 about 1.25V above its ground pin, pin 3. As the -12V rail is initially at 0V, so is pin 4, so the output switches on hard. This means that current can pass from the 12V input, through inductor L3 and to ground. The regulator switches its output in pulses at about 50kHz. When it switches off, the inductor’s magnetic field causes current to continue to flow. This can no longer come from the LM2575, so the voltage at pin 2 drops and the current flows from the negative pin of the output capacitor, through D3. As a result, the voltage across the output capacitor increases, meaning its negative end gets more negative. This cycle continues, with the capacitor charging further, resulting in the ground pin falling negative relative to the output. As the voltage across the feedback divider is increasing, the voltage at feedback pin 4 relative to pin 3 also increases. Eventually, the capacitor is charged to 12V, and the ground pin is now 12V below the feedback pin. Pin 4 is then at around -10.75V, ie, 1.25V above pin 3. The regulator then operates normally, September 2020  93                                            SC  SUPERCODEC (USB SOUND CARD) Fig.16: the power supply circuitry efficiently produces five very clean supply rails from the possibly noisy 12V DC input. These are ±9V for the op amps, +5V for the ADC and DAC chips, +3.3V for the digital section of the DAC chip and the two ASRC chips (IC6 & IC7) plus the isolator (IC12) and +2.5V for DC-biasing the analog signals fed to the ADC. The ADC also has a local regulator (REG5) to produce its 3.3V digital rail from the +5V rail, as it was easier to lay out the board that way. varying its mark to space ratio to keep this voltage as required. The regulator is essentially driving a short-circuit at startup, hence the fairly impressive but brief initial current demand. To keep radiated noise from the 94 Silicon Chip switchmode supplies low, we have been rather careful with the layout, making sure current loops are small. We have also used low-ESR capacitors throughout, as well as oversized toroidal inductors. This contains the Australia’s electronics magazine magnetic field inside the inductors and avoids saturation, which would lead to increased radiation. The switchmode supplies are also located as far from the low-level analog electronics as we can manage. On our siliconchip.com.au Tweaking the SuperCodec’s performance Phil Prosser delivered a prototype to us with excellent performance. But upon measuring it, we detected an anomaly. The DAC THD+N figure increased for test frequencies below 200Hz, rising from 0.00054% at 1kHz to around 0.00085% at 20Hz. This was not what we expected, as performance usually improves as the test signal frequency drops. At first, we suspected that the 22µF bipolar output coupling capacitors could be the culprits, as rising distortion with decreasing frequency is a signature of coupling capacitor induced distortion. However, replacing these with 100µF high-quality units (which you may have noticed in our photos) yielded no improvement. This led us to suspect that the low-frequency signal was modulating a voltage rail, so we turned our attention to the capacitors surrounding the CS4398 DAC, IC9. The most critical capacitors are the electrolytic filter capacitor on pin 26, VQ, which stabilises the half supply rail (quiescent output voltage, hence VQ); the 33µF filter capacitor at pin 17 (VREF), which also helps to smooth the VA (analog supply voltage) 5V rail that it’s connected to; and the electrolytic catest plots, there is a tiny bit of noise visible around the 50kHz operating frequency, but it’s so low that it doesn’t matter. Also, that’s above the range of our hearing, a fact that is no coincidence. We have used a large output capacitor of 2200µF to minimise noise. Then we have added a 47µH/100µF LC lowpass filter to reduce noise at the output further. At this point, the ripple on the supply rail is only a few millivolts. The +6.5V supply is provided by a conventional implementation of a buck regulator, using REG1. Again, we have put in a 2200µF filter capacitor and 47µH/100µF post regulator filter. This also uses low-ESR capacitors. Why 6.5V? One problem you find with high-speed logic is that it can draw a fair current from low voltage rails. We do not want to use a linear regulator to generate a 2.5V or 3.3V rail that might have to deliver 100-200mA. We would need to dissipate 1.7W (12V – 3.3V) x 0.2A. This is possible, but is a real nuisance to dissipate in a small enclosure. So instead, we are using switchmode regulators to generate +6.5V and -12V rails, and then feeding these into four linear regulators to produce very clean +5V, +3.3V, +2.5V, +9V and -9V supplies for the ICs. The input of each linear regulator is fed through a ferrite bead, to minimise the chance of any RF type signals passing through the regulator. The +12V and -12V ‘noisy’ rails siliconchip.com.au pacitor at pin 15 (FILT+). The capacitor from pin 26 to ground was originally 3.3µF. After soldering a 47µF capacitor across it, we re-tested the unit and found two things. One, it took a lot longer to reach normal operating conditions (presumably the larger capacitor takes longer to charge). And two, while the THD+N figures did drop around 25% at lower frequencies (and a bit across the board), there was still a rise in distortion below 200Hz. Adding a 470µF capacitor from pin 17 (VREF) to ground did nothing, indicating that this rail was sufficiently noise-free. But moving that capacitor to go from pin 15 (FILT+) to ground, which originally had a 100µF in parallel with the 100nF, totally eliminated the rise in distortion at lower frequencies and also slightly lowered distortion across the board. So we decided to compromise with the VQ filter capacitor at 10µF; higher than the original 3.3µF for improved overall performance, but not so high that the unit takes ages to stabilise when powered on. And we definitely upgraded the 100µF capacitor at the FILT+ pin to a high-quality 470µF unit, which just fits, as this was the ‘cherry on top’ in terms of obtaining the ultimate performance. are regulated to +9V and -9V using LM317 and LM337 adjustable regulators. These have especially good ripple and noise rejection. The ±9V rails power the op amps for the ADC and DAC sections. Note that there is a further RC filter in the ADC and DAC domains, formed by 10Ω resistors and 47µF capacitors, to ensure isolation between the ADC and DAC supply rails. A low-dropout AZ1117H regulator is used to generate the +5V VA rail. This is a low-noise rail, and if you analyse the PCB, you will find that it is routed away from the digital section. The DVDD +3.3V and VD +2.5V rails are for digital purposes, and use ordinary old LM317 devices. PCB layout trick We’ll be presenting the PCB design next month, along with the PCB assembly, testing and wiring instructions. But there are a few performance-related things to consider about the PCB, which we’ll briefly mention before signing off. With the power supply at the bottom, all the digital signals and power supplies run up the left-hand side of the board, and the low noise and analog signals up the right-hand side. This is intentional, to maintain isolation between these domains. The switchmode section that generates the -12V and -6.5V rails has a separate ground plane. At the output of this are the final 47µH/100µF filters. After that, there is a wire jumper from Australia’s electronics magazine the ‘noisy ground’ at the input to the larger ground plane for the linear regulators. The aim here is to avoid allowing currents in the ‘noisy ground’ injecting noise into the remainder of the circuit. There is also a vertical cut on the lefthand side of the ground plane which isolates the digital section from the power supplies. This ensures that the digital circuitry is operating in a ground plane largely separated from the analog section, with the ‘connection’ being around the DVDD +3.3V output. The aim is to avoid the digital circuitry injecting noise onto the analog ground plane. There is a ground plane across almost the entirety of the top of the board (bottom under the digital section), and ground fills everywhere practical. So here we have a range of low-noise, carefully isolated power supplies that are distributed in a manner to minimise contamination of the analog parts with any switching or digital noise. SC Next month . . . Once again, unfortunately, we have run out of space. In the third and final article next month we’ll have all the construction details, plus the test procedures after each stage of construction, to ensure that everything is working correctly before you proceed to the next step. We’ll then cover a final set of tests; how to download, install and set up the USB drivers, and some useful information on using the finished product. September 2020  95 Vintage Radio US US Marine Marine Corps Corps TBY-8 TBY-8 Squad Squad Radio Radio By Ian Batty Military equipment can be state-of-the-art, or just plain ancient. This radio is a bit of both; it’s seemingly an obsolete design at the time it was fielded, but there are good reasons for the choices made, and it turns out to be an outstanding performer. It’s also a bit different from your usual vintage radio fare. 96 Silicon Chip Australia’s electronics magazine Consider the US Air Force, which fields some of the latest and greatest aviation technology, like the F-35 Lightning II multi-role stealth fighter, and some positively ancient technology, like the B-52 Stratofortress. Some B-52s still in service today were built in the early 1960s! The RAAF is not much different; they also field the thoroughly modern F-35 alongside the positively ancient C-130 Hercules, which first took flight in 1956, over 60 years ago. The common thread here is fitness for purpose. It takes billions of dollars and decades to design new military equipment, so if the old equipment does the job, and can be kept going, it’s often the way to go. Consider the modulated oscillator transmitter and the super-regenerative receiver. These were well-proven if somewhat ‘old hat’ even in the 1930s. That’s when the United States Navy contracted for a new radio set. It was to be “ultra-portable” for use by Marines on foot, to operate well above the commonly-used lower frequencies of the HF band, and to offer Wireless Telegraphy (W/T) for Morse code transmission and Radio Telephony (R/T) for voice transmission. It’s part of the T (transmitters) series, B (portable) subseries, letter Y in order of registration. This class of equipment is now known as a squad radio. As well as being carried on foot, TBYs were also commonly used as ship-to-ship links in convoys and battle groups. The TBY was famously used by specially-recruited Navajo-speaking “Codetalkers”, as the Navajo language had never been documented. Its purely oral tradition, unusual syntax and highly inflected, tonal pronunciation made it unlikely that, even if intercepted, any “codetalked” message could ever be decrypted. It’s one of the few examples of “clear speech” being anything but clear to the enemy. siliconchip.com.au This was the inspiration for the 2002 movie “Windtalkers”. Technical details Condensed Specifications The full height of the antenna is approximately 9ft. Squad radios commonly use battery or generator power, since they need to be able to go where the troops do. As most use directly-heated valves, cathode biasing for each stage is impractical. The most common designs use multi-voltage batteries that include the bias supply. It’s not unusual to see one or two filament and HT supplies along with the negative bias supply. The TBY uses this design, with 1.5V and 3V LT rails, 150V HT and a -7.5V bias battery. Its full circuit is shown in Fig.1. Multi-channel transceiver designs would either use a bank of quartz crystals (rare, bulky and expensive in the 1930s), with one per channel, or a much simpler Variable Frequency Oscillator (VFO) design. If the transmitter were crystal controlled, it would have been possible to use the same crystal for receive and transmit (with a bit of magic between), but it would still have been an intricate design. With no crystal control in the transmitter, however, the receiver would have to be continuously-tuned. The TBY uses a modulated oscillator transmitter, which has the great advantage of simplicity; it only requires one RF stage. But that simple design leads to frequency instability, producing frequency modulation along with the intended amplitude modulation (AM). For receiver performance, nothing could beat Edwin Armstrong’s super-regenerative design in its day, and that’s still true today. So long as a valve can be made to oscillate, it can be used as a super-regenerative demodulator, right up to its maximum operating frequency. While the super-regenerator was good enough in the 1930s, even ham radio operators were abandoning it by the 1950s, gradually pushing the design to higher and higher VHF/UHF bands until finally giving up on it. Its versatility and simplicity, though, did see the use of super-regenerating klystrons in simple radar receivers. If it can oscillate, it can super-regenerate. So we have two mostly deprecated systems from the late 1930s/early 1940s: an unstable, messy modulation transmitter and a primitive, cranky siliconchip.com.au Operating frequency: 28~80MHz in four bands; 131 channels at 400kHz spacing. Transmission/reception: A2 (tonemodulated continuous wave – MCW), A3 (AM – double-sideband full carrier – R/T). Transmit power/operating range: MCW 0.75W, R/T 0.5W. Range up to 3 miles (~5km). Receiver sensitivity: 5µV on bands 1, 2 and 3; better than 15µV on band 4, all for 1mW output at 6dB SNR. Power supply and duration: combined battery, 1.5V “A” supply (RF section), 3V “A” supply (audio section), 150V “B” supply, -7.5V “C” supply. 25 hours operation when new, minimum of 15 hours. Versions: TBY-1 and -2 used fixed antenna mounts of Westinghouse manufacture. TBY-3 not issued. TBY-4 to -8 featured rotatable antenna mount and SO-239 socket for antennas other than the nine-section rod, Colonial Radio manufacture. Metering: indicating meter switchable to RF filament voltage, audio filament voltage, transmitter anode current (loading) indications. Operator-useable rheostats to control audio and RF valve filament voltages. Interfaces: R/T provision for two headsets, Morse key for MCW operation. Channel selection: channels set according to the attached individual calibration chart. Able to be set accurately on any channel an exact multiple of 5MHz. On any other channel, dependent on equipment tuning chart and antenna coupling. One report shows transmitter frequency varying by as much as 100kHz with coupling adjustment. Accessories: Carbon microphone/ dynamic earphones combination, Morse key, dry battery, ten-section rod antenna, 4V accumulator and vibrator power pack, 115V DC/AC mains power pack, canvas carry backpack, 72.5MHz fixed ground plane antenna, timber transit case. Australia’s electronics magazine September 2020  97 receiver. Given the poor opinion most authors have of this combination, I want to find out just how bad (or good!) they can be. The TBY squad radio The TBY (version 1 released in 1938) is a seven-valve, battery-powered squad radio transceiver which can be carried by one person in a backpack. It provides four switched, manually-tuned bands from 28~80MHz and uses a nine-section whip antenna whose length is adjusted (by add- ing or removing sections) to always be roughly one quarter-wavelength at the chosen operating frequency. Completely assembled, the antenna just tops 2.6m! (The red ribbon at the top is not recommended for combat conditions). Tuning is indicated by graduated wheels behind viewing windows. No frequency calibration is provided; operators use reference charts attached to the top cover to select any one of 131 operating channels at 400kHz spacings. The internal 5MHz crystal calibrator’s “marker” signals allow receiver and transmitter calibration at intervals of 12-½ channels. I acquired this one in the 60s at ACE Radio, a disposals company long gone. I was actually not sure what it was, but its design was too good to pass up. Transmitter circuit The transmitter uses Acorn 958A valves (V3 and V4) in a push-pull Hartley circuit. Unlike Class-B audio circuits, this operates in Class-C, Fig.1: circuit diagram for the TBY-8 radio. There is no capacitor C23 shown (but there is a C24), and C23 does not appear in the parts list. Presumably, this was a late change during manufacturing, or a change from a previous version. 98 Silicon Chip Australia’s electronics magazine siliconchip.com.au where the conduction angle is considerably less than 180°, and the control grids are driven sufficiently positive to rectify and create grid current during part of the operating cycle. You’d expect such a brief conduction cycle to create massive distortion, and it does. Class-C can only work with tuned loads (“tank” circuits) that ‘force’ the output to form a sinewave. You can think of the tank circuit as acting like a flywheel, pushed along by anode current pulses; or, as a conventional tuned circuit that only responds to the desired frequency, attenuating the ‘crossover distortion’ harmonics. Class-C operation can give efficiencies exceeding 70%. Simply put, during conduction, the valve operates in heavy saturation with little voltage drop across it and little power wastage. This high efficiency is a boon in battery-powered sets, but it also allows valves to give substantial outputs exceeding three times their anode dissipation limits. The basic Hartley circuit uses a tapped inductor to provide feedback. The TBY’s push-pull transmitter’s anode tuned circuit uses centre-tapped coils to both combine valve currents and provide ‘cross-connected’ feedback. Feedback is provided by 50pF capacitors C15/C16 to the grids of V3/V4, with centre-tapped choke L10 isolating the grids from the RF ground provided by 500pF capacitor C17, which bypasses 5kW grid bias resistor R4. The transmit stage is matched to the antenna via the secondary of the selected tank coil, in combination with matching variable capacitor C13. In operation, meter M1 is switched to the Plate Current position, and C13 adjusted for a centre reading on M1. The intimate coupling between oscillator and antenna makes the TBY’s frequency stability vulnerable to antenna length and capacitive effects between the antenna and other objects. For R/T (voice) transmission, modulation begins with the carbon microphone, powered from the -7.5V bias supply. The microphone current is stepped up by transformer T2 to drive V7, a 1E7 dual pentode. T2’s grid drive to V7 is in anti-phase, so the modulation amplifier works in Class-B push-pull mode, with T3 combining the anode currents of V3 and coupling modulation (via its secondsiliconchip.com.au ary) to the transmitter. V7 receives the full -7.5V grid bias via the driver winding (secondary) of T2. For Morse transition, pushbutton key S101 switches the tertiary winding of T1 to ground, as well as activating transmit/receive relay K1 and keying the transmitter. Grounding T1’s tertiary activates V6’s feedback loop (C25/R12/R13), which is inactive until pin 5 on T1 is connected to ground. V6 oscillates at around 500Hz, feeding the tone to modulator V7, which in turn modulates the transmitter. Receiver circuitry The receiver begins with 959 Acorn pentode V1, operating as a commoncathode RF amplifier. This provides the usual gain and selectivity, but also helps reduce radiation from the oscillating demodulator. Without adequate demodulator isolation, this set would radiate enough energy in receive mode to allow hostile interception and direction-finding. It’s the military version of a flashing “kick me” sign on your back. The antenna circuit uses one of four turret-switched coils (L1-3 & L15), with its secondary tuned by the C1 section of the receiver’s ganged tuning capacitor. Antenna trimmer C2 compensates for antenna capacitance and/ or nearby objects. The amplifier gets grid bias from the bias battery via the antenna coil secondary, from resistive divider R21/R22. V1’s anode load, the primary of L4-6 Australia’s electronics magazine The side of the TBY radio showing where the antenna mount is attached. & L16, couples to its tuned secondary. This secondary forms the Hartley oscillator circuit for V2, the super-regenerative demodulator. The super-regenerator, one of Edwin Armstrong’s four industry-defining patents (regeneration, super-regeneration, the superhet and frequency modulation) achieves astounding sensitivity. How does a single-stage voltage gain approaching a million sound? Heavy feedback, aided by 1MW grid bias resistor R2’s return to V2’s positive anode connection puts V2 into powerful oscillation. The rectified grid current develops a negative voltage across 100pF coupling capacitor C7, counteracting the positive September 2020  99 voltage that would otherwise be present on the grid. This counteraction continues until the negative bias is so strong that the valve cuts off. With no oscillation to maintain it, the cut-off bias across C7 will be discharged according to the time constant of grid resistor R2, coupling capacitor C7 and the positive supply voltage. As the cut-off bias leaks away, V2 will come back into conduction and will again oscillate, re-initiating negative bias across C7. This cycle will repeat at the quenching frequency (22~40kHz in the TBY, depending on the Regen setting). I’ll use 30kHz as my example. You might expect this to simply produce a self-modulated RF output. Indeed, such ‘squegging’ oscillators were used in ultra-simple lifeboat transmitters. But the average anode current of this circuit is very noisy. The quenching frequency exhibits a large amount of phase noise (jitter). It’s related to the conditions at the instant when oscillation is re-initiated. As this exact instant is strongly influenced by valve noise, the average anode current which forms the quench frequency is also noisy as shown in Fig.2. So far, all we have is either a jittery oscillator or a circuit greatly magnifying its own inherent noise. But what if an external, unmodulated signal is fed to the super-regenerator? It will ‘lock’ to the incoming signal and, although the quench frequency will remain at around 30kHz, it will now be very stable. Each new burst of oscillation will be initiated as the incoming signal brings the grid out of cut-off and into active operation, rather than by valve noise. Fig.3 shows that, if the anode current jitter is quieted, the anode current assumes a constant, noiseless DC value. Fig.2 100 Silicon Chip The left-hand side of the TBY radio showing the transmitter section. You can also see one of the 958 Acorn valves (V4) at upper left. Applied signal synchronisation Now, if we supply a modulated signal, the initiation of each oscillatory period is determined by the varying instantaneous input signal amplitude. The incoming modulated signal will influence the quench frequency’s phase. The simplest modern paradigm is that of pulse-width modulation (PWM). But PWM is, in context, a ‘modern’ concept, postdating Armstrong’s invention by over thirty years. It’s why you’ll find incomplete, confusing and elaborate descriptions of the super-regen, including its “strong AVC action”. Fig.4 shows how the modulated input signal is translated into an audiovarying anode current that is amplified and delivered to the headphones. The dotted line is a notional bias voltage that the input signal’s amplitude must exceed to provoke oscillation as the circuit’s highly negative bias ‘leaks off’. Eagle-eyed readers may interpret the input signal’s modulation as suffering from non-linearity. You’d be correct, but the illustration does show that the super-regen can successfully demodulate an AM signal. More on this later. The demodulator circuit connects Fig.3 Fig.4 Australia’s electronics magazine siliconchip.com.au To reduce lead inductance, conventional basing methods were eliminated, and the shortest possible connections made to the external circuit. RCA’s all-glass Acorn valves (named for their envelope shape) set the stage for the next thirty years of valve design: baseless all-glass construction, connecting pins penetrating the envelope, and electrode connections welded directly to the connecting pins. The Acorn base demanded a spacehogging peripheral socket, so the final B7G development had the pins exit the envelope in a circle around a glass button base, with the socket not much larger than the valve’s envelope. How good is it? The right-hand side of the TBY-8 which showcases the receiver section. to the supply via the primary of audio transformer T1 and 500kW potentiometer R8, the regeneration control. In operation, R8 is adjusted so that the receiver just comes into reliable super-regeneration. That gives maximum sensitivity. T1’s secondary feeds audio to 500kW volume control pot R7, and then to preamplifier valve V6. Like V7, this gets a -7.5V grid bias from the battery. V6’s anode drives output valve V7 via audio transformer T2. Transmit/receive switching is managed by relay K1, which responds to the press-to-talk (PTT) switch on the microphone. K1 gets current from the +3V filament supply. Transmit/receive changeover is managed by switching filament power (K1d). HT to the transmitter is also switched (K1e), as early versions of the 968A would continue to oscillate with no filament power applied – anode current alone was sufficient to sustain emission. The circuit contains a lot of RF bypassing not generally seen in AM radios. This is needed for predictable siliconchip.com.au operation in the low VHF band, and – especially in the receiver – to reduce possible radiation from the oscillating demodulator. Acorn valves The 1930s saw an explosion of research into higher and higher radio frequencies. Governments, along with commercial and scientific organisations, joined the race to exploit the revolution. But experimenters quickly discovered the thermionic valve’s limitations. Even ‘modern’ octal-based types, universally preferred for MF (medium frequencies) to low VHF (very high frequencies), struggled to work much past 100MHz. This was due to three principal problems: transit time from cathode to anode, internal capacitance, and lead inductances. Much smaller constructions could reduce transit time and capacitances, and lead inductances by much shorter leads. This was pretty simple to achieve; just reduce the valve’s elements down to the limits of hand assembly. Australia’s electronics magazine I get 1mW in 600W output (775mV) from a 30%-modulated 3µV signal. Given that such a signal carries around 1µV of modulated audio, this set has a voltage gain of about 775,000 from the antenna to headphones. Beat that! In decibels, 1µV into 50W is around 2 × 10-14 watts. We have one milliwatt output, making the power gain around 113dB. Not bad for just four valves. For the demodulator itself, I get around 70mV of audio for a measured input of 3µV (implying 1µV of audio modulation), so the demodulator voltage gain is about 70,000. Like I wrote earlier, in its day, nothing gave more gain than the super-regen, and nothing can today. Note that I’m not quoting a dB figure for the demodulator, as I can’t state the demodulator’s input and output impedances, and dBs should only be calculated with known impedances. A close-up of a 955 Acorn triode valve. Source: https://en.wikipedia. org/wiki/File:955ACORN.jpg September 2020  101 I’m guessing this set has not been used since it was decommissioned, so I wondered how well it had retained its calibration. So I set my HP signal generator to Channel 1 (28MHz) and tuned it in. It came in at 27.85MHz, a calibration error of around 0.5%. That’s excellent long-term stability. Following the instructions, its internal calibrator allowed me to set Channel 6 (30MHz) to correct this error to within 6kHz. That isn’t bad for a calibrator that’s over 70 years old, with no temperature control or adjustment. It sits at 5.000750 MHz, an accuracy of 150 parts per million, and certainly adequate for the application. The receiver still meets specifications, with a sensitivity of 3µV bettering the quoted 5µV for a signal-to-noise ratio (SNR) of 6dB on Bands 1~3, and 10µV or better on Band 4. The receiver -3dB bandwidth varies from ±100kHz at 28MHz to ±200kHz at 80MHz. For -60dB, it’s ±500kHz and 700kHz respectively. That bandwidth sounds woeful compared to a superhet, but remember that superhet designers can specify an IF bandwidth as low as a few 102 Silicon Chip kilohertz, regardless of the incoming signal frequency. Essentially a TRF design, the super-regen must rely on high-Q RF coils to give usefully narrow bandwidths. Since Q = F ÷ df, where Q is the quality factor, F the operating frequency and df the -3dB bandwidth, at 28MHz Q = 140 and at 80MHz, it’s 200. That’s very good for just two tuned circuits, one of which is heavily loaded by the oscillating demodulator. Although the RF amp’s gain is small, its lack of loading allows the antenna circuit to contribute most of the circuit’s selectivity. Signal output is determined by the maximum possible change in anode current pulse width, and it reaches this limit at quite low signal levels. In this way, it’s similar to an FM receiver’s limiter. Starting with a 3µV signal at 28MHz, it needed around 200mV to get a 3dB audio output increase, a range of more than 90dB. For the accepted 20dB SNR, it needed over 10µV, and never achieved much better. You may know of FM’s capture effect, where a signal that’s only a few times stronger than another will ‘blanAustralia’s electronics magazine ket’ the weaker signal. The TBY exhibits significant capture effect with a signal ratio of three times or more. It does produce heterodyning ‘birdies’ if there is any large frequency difference, and this seems to be due to interaction with the 30kHz quench frequency. The circuit is naturally noisy and exhibits poor linearity. A 25µV signal (30% modulation at 400Hz) produced 15% total harmonic distortion (THD). Audio response from the antenna to headphones of 160~600Hz, as determined by the demodulator; from the primary of T1 to the headphones it’s 160~6500Hz. For the microphone input, it exceeds 80Hz to 10kHz. It is capable of demodulating FM, but needs a stronger signal to exploit slope demodulation: at 28MHz, a 25µV signal with ±60kHz deviation produced 1mW output. So while it would receive FM broadcasts with some rebuilding of the Band 4 coils, given the audio top end of under 1kHz you’d be pretty disappointed with the results. Transmitter output exceeded the specifications on all bands, delivering upwards of 1W on some frequencies. And yes, it does produce substantial siliconchip.com.au frequency modulation. Fig.5 shows the carrier and many side frequencies. A pure amplitude-modulated signal will produce the carrier and only two side frequencies: upper and lower. Multiple side frequencies are a frequency modulation signature. Although the TBY’s receiver will demodulate an FM signal, this isn’t much help in demodulating the FMrich signal from another TBY, as you would have to detune your own set to go into slope demodulation with the penalty of lower sensitivity. I was concerned about demodulator radiation, but it appears well-con- Fig.5: shown in greyscale for clarity. siliconchip.com.au trolled. I tried an FM Walkman that tunes down to 76MHz, and could just pick up the radiation with the two sets next to each other. The demodulator’s anode voltage varies with the Regen setting, and the circuit shows typical values. The set under test was powered by an inverter bought off eBay. It works well, but does give a high bias output, as shown in the circuit readings. Usability For equipment designed to be used under the extreme conditions of warfare, the TBY’s simplicity of operation is excellent. Once tuned, all one needs to do is listen or talk, for up to 25 hours. But re-tuning is another matter. Band changing is simple, but actual channel tuning is difficult to the point of being almost impossible. The tuning knobs are small and difficult to operate, and the dials can only be read by looking directly into the windows. Perhaps the original luminous markings would have helped, however, in their now-degraded state they are visible but not readily legible. Australia’s electronics magazine Originally-described as “radio-active”, a Geiger counter registered emissions at the lower end of concern. References • Instruction book for Navy Model TBY-8 Ultra-Portable Very High Frequency Transmitting-Receiving Equipment, 1943, Colonial Radio Corporation, Buffalo NY • Catalog for the models TBY, TBY1 & 2: siliconchip.com.au/link/ab3x • VMARS has heaps of military manuals, including the TBY-8, at siliconchip.com.au/link/ab3u • An extensive description of the radio: siliconchip.com.au/link/ab3v • Complete description and analysis of super-regeneration: Microwave Receivers, Van Voorhis, S. N. Ed., McGraw-Hill, 1948, Chapter 20, Superregenerative Receivers, Hall, G. O. pp 545-578. (MIT Rad. Lab. Vol 23) • Armstrong’s patent, US1424065: https://patents.google.com/patent/ US1424065A • Armstrong’s paper: Some Recent Developments Of Regenerative Circuits, Armstrong, E.H. siliconchip. com.au/link/ab3w SC September 2020  103 SILICON CHIP .com.au/shop ONLINESHOP HOW TO ORDER INTERNET (24/7) PAYPAL (24/7) eMAIL (24/7) MAIL (24/7) PHONE – (9-5:00 AET, Mon-Fri) siliconchip.com.au/Shop silicon<at>siliconchip.com.au silicon<at>siliconchip.com.au PO Box 139, COLLAROY, NSW 2097 (02) 9939 3295, +612 for international You can also pay by cheque/money order (Orders by mail only) or bank transfer. Make cheques payable to Silicon Chip. 09/20 YES! You can also order or renew your Silicon Chip subscription via any of these methods as well! The best benefit, apart from the magazine? Subscribers get a 10% discount on all orders for parts. 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64x32 pixel white OLED (0.49-inch/12.5mm diagonal) $10.00 - Pulse-type rotary encoder with integral pushbutton $3.00 Includes PCB and all onboard parts (3.3V, 5V, 8V, 9V, 12V & 15V versions) $12.50 Short form kit: includes everything except the case, CPU module, power supply, optional parts and cables (Cat SC5478) $80.00 Short Form kit (with CPU module): includes the programmed Waveshare CPU modue and everything included in the short form kit above (Cat SC5508) $140.00 Two BTN8962TA motor driver ICs & one 6N137 opto-isolator 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) $30.00 $3.00 $5.00 $7.50 $6.00ea Complete kit – includes PCB plus programmed micros and all onboard parts Programmed micros – PIC32MX170F256B-50I/SO + PIC16F1455-I/SL $30.00 $20.00 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: - 3.5-inch TFT LCD touchscreen (Cat SC5062) $30.00 - DHT22 temp/humidity sensor (Cat SC4150) $7.50 - BMP180 (Cat SC4343) OR BMP280 (Cat SC4595) temp/pressure sensor $5.00 - BME280 temperature/pressure/humidity sensor (Cat SC4608) $10.00 - DS3231 real-time clock SOIC-16 IC (Cat SC5103) $3.00 - 23LC1024 1MB RAM (SOIC-8) (Cat SC5104) $5.00 - AT25SF041 512KB flash (SOIC-8) (Cat SC5105) $1.50 - 10µF 16V X7R through-hole capacitor (Cat SC5106) $2.00 siliconchip.com.au/Shop/ ULTRASONIC CLEANER (SEP 20) 40kHz 50W ultrasonic transducer (Cat SC5629) ETD29 transformer components + three Mosfets (Q1-2,Q6) (Cat SC5632) $54.90 $35.00 VARIOUS MODULES & PARTS - 16x2 I2C LCD (Digital RF Power Meter, Aug20) $7.50 - DS3231 real-time clock SMD IC (Ol’ Timer II, Jul20) $3.00 - WS2812 8x8 RGB LED matrix module (Ol’ Timer II, Jul20) $15.00 - MAX038 function generator IC (H-Field Transanalyser, May20) $25.00 - MC1496P double-balanced mixer (H-Field Transanalyser, May20) $2.50 - AD8495 thermocouple interface (DIY Reflow Oven Controller, Apr20) $10.00 - Si8751AB 2.5kV isolated Mosfet driver IC (Charge Controller, Dec19) $5.00 - 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) $4.00 - 23LCV1024-I/P SRAM & MCP73831T (UHF Repeater, May19) $11.50 - MCP1700 3.3V LDO regulator (suitable for USB M&K Adapator, Feb19) $1.50 - LM4865MX amplifier & LF50CV regulator (Tinnitus/Insomnia Killer, Nov18) $10.00 - 2.8-inch touchscreen LCD module with SD card socket (Tide Clock, Jul18) $22.50 - ESP-01 WiFi Module (El Cheapo Modules, Apr18) $5.00 - WiFi Antennas with U.FL/IPX connectors (Water Tank Level Meter with WiFi, Feb18): 5dBi – $12.50 ¦ 2dBi (omnidirectional) – $10.00 - NRF24L01+PA+NA transceiver, SNA connector & antenna (El Cheapo, Jan18) $5.00 - WeMos D1 Arduino-compatible boards with WiFi (Sep17, Feb18): ThingSpeak data logger – $10.00 | D1 R2 with external antenna socket – $15.00 - ERA-2SM+ MMIC & ADCH-80A+ choke (6GHz+ Frequency Counter, Oct17) $15.00 - VS1053 Geeetech Arduino MP3 shield (Arduino Music Player, Jul17) $20.00 - 1nF 1% MKP (5mm) or ceramic capacitor (LC Meter, Jun18) $2.50 - MAX7219 red LED controller boards (El Cheapo Modules, Jun17): 8x8 SMD/DIP matrix display – $5.00 ¦ 8-digit 7-segment display – $7.50 - AD9833 DDS modules (Apr17): gain control (DDS Signal Generator) – $25.00 ¦ no gain control – $15.00 - CP2102 USB-UART bridge $5.00 - microSD card adaptor (El Cheapo Modules, Jan17) $2.50 - DS3231 real-time clock module with mounting hardware (El Cheapo, Oct16) $5.00 *Prices valid for month of magazine issue only. All prices in Australian dollars and include GST where applicable. # P&P prices are within Australia. Overseas? Place an order on our website for a quote. PRINTED CIRCUIT BOARDS & CASE PIECES For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT DATE PCB CODE Price PRINTED CIRCUIT BOARD TO SUIT PROJECT DATE PCB CODE Price EFUSE SPRING REVERB 6GHz+ 1000:1 PRESCALER MICROBRIDGE MICROMITE LCD BACKPACK V2 10-OCTAVE STEREO GRAPHIC EQUALISER ↳ FRONT PANEL ↳ CASE PIECES RAPIDBRAKE DELUXE EFUSE ↳ UB1 LID VALVE RADIO MAINS SUPPLY (INC. PANELS) 3-WAY ADJUSTABLE ACTIVE CROSSOVER ↳ FRONT/REAR PANELS ↳ CASE PIECES (BLACK) 6GHz+ TOUCHSCREEN FREQUENCY COUNTER ↳ CASE PIECES (CLEAR) KELVIN THE CRICKET SUPER-7 SUPERHET AM RADIO PCB ↳ CASE PIECES & DIAL THEREMIN PROPORTIONAL FAN SPEED CONTROLLER WATER TANK LEVEL METER (INC. HEADERS) 10-LED BARAGRAPH ↳ SIGNAL PROCESSING FULL-WAVE MOTOR SPEED CONTROLLER VINTAGE TV A/V MODULATOR AM RADIO TRANSMITTER HEATER CONTROLLER DELUXE FREQUENCY SWITCH USB PORT PROTECTOR 2 x 12V BATTERY BALANCER USB FLEXITIMER WIDE-RANGE LC METER (INC. HEADERS) ↳ WITHOUT HEADERS ↳ CASE PIECES (CLEAR) TEMPERATURE SWITCH MK2 LiFePO4 UPS CONTROL SHIELD RASPBERRY PI TOUCHSCREEN ADAPTOR RECURRING EVENT REMINDER BRAINWAVE MONITOR (EEG) SUPER DIGITAL SOUND EFFECTS DOOR ALARM STEAM WHISTLE / DIESEL HORN DCC PROGRAMMER (INC. HEADERS) ↳ WITHOUT HEADERS OPTO-ISOLATED RELAY (INC. EXT. BOARDS) GPS-SYNCHED FREQUENCY REFERENCE LED CHRISTMAS TREE DIGITAL INTERFACE MODULE TINNITUS/INSOMNIA KILLER (JAYCAR VERSION) ↳ ALTRONICS VERSION HIGH-SENSITIVITY MAGNETOMETER USELESS BOX FOUR-CHANNEL DC FAN & PUMP CONTROLLER ATtiny816 DEVELOPMENT/BREAKOUT PCB ISOLATED SERIAL LINK DAB+/FM/AM RADIO ↳ CASE PIECES (CLEAR) REMOTE CONTROL DIMMER MAIN PCB ↳ MOUNTING PLATE ↳ EXTENSION PCB MOTION SENSING SWITCH (SMD) PCB USB MOUSE AND KEYBOARD ADAPTOR PCB LOW-NOISE STEREO PREAMP MAIN PCB ↳ INPUT SELECTOR PCB ↳ PUSHBUTTON PCB DIODE CURVE PLOTTER ↳ UB3 LID (MATTE BLACK) FLIP-DOT (SET OF ALL FOUR PCBs) ↳ COIL PCB ↳ PIXEL PCB (16 PIXELS) ↳ FRAME PCB (8 FRAMES) APR17 APR17 MAY17 MAY17 MAY17 JUN17 JUN17 JUN17 JUL17 AUG17 AUG17 AUG17 SEP17 SEP17 SEP17 OCT17 OCT17 OCT17 DEC17 DEC17 JAN18 JAN18 FEB18 FEB18 FEB18 MAR18 MAR18 MAR18 APR18 MAY18 MAY18 MAY18 JUN18 JUN18 JUN18 JUN18 JUN18 JUN18 JUL18 JUL18 AUG18 AUG18 AUG18 SEP18 OCT18 OCT18 OCT18 NOV18 NOV18 NOV18 NOV18 NOV18 DEC18 DEC18 DEC18 JAN19 JAN19 JAN19 JAN19 FEB19 FEB19 FEB19 FEB19 FEB19 MAR19 MAR19 MAR19 MAR19 MAR19 APR19 APR19 APR19 APR19 04102171 01104171 04112162 24104171 07104171 01105171 01105172 SC4281 05105171 18106171 SC4316 18108171-4 01108171 01108172/3 SC4403 04110171 SC4444 08109171 06111171 SC4464 23112171 05111171 21110171 04101181 04101182 10102181 02104181 06101181 10104181 05104181 07105181 14106181 19106181 SC4618 04106181 SC4609 05105181 11106181 24108181 19107181 25107181 01107181 03107181 09106181 SC4716 09107181 10107181/2 04107181 16107181 16107182 01110181 01110182 04101011 08111181 05108181 24110181 24107181 06112181 SC4849 10111191 10111192 10111193 05102191 24311181 01111119 01111112 01111113 04112181 SC4927 SC4950 19111181 19111182 19111183 $7.50 $12.50 $7.50 $2.50 $7.50 $12.50 $15.00 $15.00 $10.00 $15.00 $5.00 $25.00 $20.00 $20.00 $10.00 $10.00 $15.00 $10.00 $25.00 $25.00 $12.50 $2.50 $7.50 $7.50 $5.00 $10.00 $7.50 $7.50 $10.00 $7.50 $2.50 $2.50 $7.50 $7.50 $7.50 $7.50 $7.50 $5.00 $5.00 $5.00 $10.00 $2.50 $5.00 $5.00 $7.50 $5.00 $7.50 $7.50 $5.00 $2.50 $5.00 $5.00 $12.50 $7.50 $5.00 $5.00 $5.00 $15.00 $.00 $10.00 $10.00 $10.00 $2.50 $5.00 $25.00 $15.00 $5.00 $7.50 $5.00 $17.50 $5.00 $5.00 $5.00 ↳ DRIVER PCB iCESTICK VGA ADAPTOR UHF DATA REPEATER AMPLIFIER BRIDGE ADAPTOR 3.5-INCH LCD ADAPTOR FOR ARDUINO DSP CROSSOVER (ALL PCBs – TWO DACs) ↳ ADC PCB ↳ DAC PCB ↳ CPU PCB ↳ PSU PCB ↳ CONTROL PCB ↳ LCD ADAPTOR STEERING WHEEL CONTROL IR ADAPTOR GPS SPEEDO/CLOCK/VOLUME CONTROL ↳ CASE PIECES (MATTE BLACK) RF SIGNAL GENERATOR RASPBERRY PI SPEECH SYNTHESIS/AUDIO BATTERY ISOLATOR CONTROL PCB ↳ MOSFET PCB (2oz) MICROMITE LCD BACKPACK V3 CAR RADIO DIMMER ADAPTOR PSEUDO-RANDOM NUMBER GENERATOR 4DoF SIMULATION SEAT CONTROLLER PCB ↳ HIGH-CURRENT H-BRIDGE MOTOR DRIVER MICROMITE EXPLORE-28 (4-LAYERS) SIX INPUT AUDIO SELECTOR MAIN PCB ↳ PUSHBUTTON PCB ULTRABRITE LED DRIVER HIGH RESOLUTION AUDIO MILLIVOLTMETER PRECISION AUDIO SIGNAL AMPLIFIER SUPER-9 FM RADIO PCB SET ↳ CASE PIECES & DIAL TINY LED XMAS TREE (GREEN/RED/WHITE) 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 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 USB SUPERCODEC SWITCHMODE 78XX REPLACEMENT WIDEBAND DIGITAL RF POWER METER APR19 APR19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 JUN19 JUN19 JUN19 JUN19 JUL19 JUL19 JUL19 AUG19 AUG19 AUG19 SEP19 SEP19 SEP19 SEP19 SEP19 SEP19 OCT19 OCT19 NOV19 NOV19 NOV19 NOV19 NOV19 NOV19 NOV19 DEC19 JAN20 JAN20 JAN20 JAN20 JAN20 FEB20 FEB20 MAR20 MAR20 MAR20 APR20 APR20 APR20 APR20 MAY20 MAY20 JUN20 JUN20 JUN20 JUN20 JUL20 JUL20 JUL20 JUL20 JUL20 JUL20 AUG20 AUG20 AUG20 19111184 02103191 15004191 01105191 24111181 SC5023 01106191 01106192 01106193 01106194 01106195 01106196 05105191 01104191 SC4987 04106191 01106191 05106191 05106192 07106191 05107191 16106191 11109191 11109192 07108191 01110191 01110192 16109191 04108191 04107191 06109181-5 SC5166 16111191 18111181 SC5168 18111182 SC5167 14107191 01101201 01101202 09207181 01112191 06110191 27111191 01106192-6 01102201 21109181 21109182 01106193/5/6 01104201 01104202 CSE200103 06102201 05105201 04104201 04104202 01005201 01005202 07107201 SC5500 19104201 SC5448 15005201 15005202 01106201 18105201 04106201 $5.00 $2.50 $10.00 $5.00 $5.00 $40.00 $7.50 $7.50 $5.00 $7.50 $5.00 $2.50 $5.00 $7.50 $10.00 $15.00 $5.00 $7.50 $10.00 $7.50 $5.00 $5.00 $7.50 $2.50 $5.00 $7.50 $5.00 $2.50 $10.00 $5.00 $25.00 $25.00 $2.50 $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 $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 $12.50 $2.50 $5.00 ULTRASONIC CLEANER MAIN PCB ↳ FRONT PANEL NIGHT KEEPER LIGHTHOUSE SHIRT POCKET AUDIO OSCILLATOR ↳ 8-PIN ATtiny PROGRAMMING ADAPTOR SEP20 SEP20 SEP20 SEP20 SEP20 04105201 04105202 08110201 01110201 01110202 $7.50 $5.00 $5.00 $2.50 $1.50 NEW PCBs We also sell an A2 Reactance Wallchart, RTV&H DVD, Vintage Radio DVD plus various books at siliconchip.com.au/Shop/3 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 Colour Maximite 2 complete kit wanted I am interested in buying a kit for the Colour Maximite 2 (July & August 2020; siliconchip.com.au/Series/348), but I want one with as many of the optional parts as possible, especially the labelled front and rear panels with cut-outs. Do you know who can supply such a kit? (A. F., Salamander Bay, NSW) • We aren’t sure exactly what is in the kits from other suppliers. You can check their websites via the links in the parts list on page 38 of the July 2020 issue. Our Cat SC5508 kit (siliconchip. com.au/Shop/20/5508) comes with pretty much everything you need except the plastic case, including the front and rear panels with white labels and pre-cut holes. The reason we don’t include the case is that you can easily get it from Jaycar or Altronics at a price that would be tough for us to match. The only other parts we don’t include are the infrared receiver and DS18B20 temperature sensor. The IR receiver is also available from Jaycar (Cat ZD1952) or Altronics (Cat Z1611A). If you want the exact TSOP4838 part specified by Geoff Graham, you would have to go somewhere else like element14 (Cat 491319001), but we believe all of these parts are suitable. As for the DS18B20, Altronics has it (Cat Z7280), as does element14 (Cat 2515553). Jaycar has the XC3700 module with a DS18B20 sensor onboard; you should be able to solder that to the CMM2 PCB, or else desolder the DS18B20 sensor from it and transplant it into the CMM2. Substituting Reflow Oven Controller reg. I am gathering the parts list for the Reflow Oven Controller (April & May 2020; siliconchip.com.au/Series/343), and when I went into Altronics and searched for the LD1117V adjustable 106 Silicon Chip voltage regulator, I was directed to the “LD1117V33 - 3.3V 800mA TO220 Low Drop Out Voltage Regulator” (Cat Z2695). I assume I can use this instead by replacing the 560W resistor with a 0W resistor and omitting the 10µF capacitor and 330W resistor. (R. S., Huntly, Vic) • Yes, that should work. Interfacing JRMI with DCC Controller I built the Arduino DCC Decoder Programmer (October 2018; siliconchip. com.au/Article/11261) & Arduino DCC Controller (January 2020; siliconchip. com.au/Article/12220); both stacked on an Arduino Uno. I have this connected to the rail inputs of a DCC Concepts Zen Black Decoder Z218. I am using a 15V DC power pack without MOD1 & JP1 is in the “VIN” position. After loading the “DCC_Single_ Loco_Control.ino” sketch, I can turn on the power on and off (P/p), run the motor both forwards or backward and turn the lights on and off (A/a), both front and rear as per the motor direction. I then loaded the DCC++ Base Station sketch (“DCCpp_Uno.ino”) and applied the advised settings and restarts as per page 50 in the January 2020 issue. However, on running DecoderPro (V4.20), I cannot get the JRMI red power button to change to green. I’ve tried installing “new loco” (using the DCC Concepts Zen Z218) without any response, although this is not suggested in the article. Can you help? (K. R., Arundel, Qld) • It seems that you are using a newer version of JMRI (DecoderPro) than we did. We found that setting up DecoderPro was fiddly; the required settings were discovered by trial and error. As the hardware works fine with our test sketch, it sounds like a software problem. Since our projects are intended to replace the DCC++ hardware, the DCC++ site might have some information on the settings required to get the Australia’s electronics magazine software to talk to our hardware. See github.com/DccPlusPlus/BaseStation/ wiki/What-is-DCC--Plus-Plus Arduino compilation warnings I have finally built the Diode Curve Plotter (March 2019; siliconchip.com. au/Article/11447), and after uploading the sketch, I was presented with an all-white screen. During the compilation process, I get multiple warnings: “warning: ISO C++ forbids converting a string constant to ‘char*’ [-Wwrite-strings]” (amongst others). Are these warnings of concern? (P. W., Perth, WA) • The message at the end of the list of warnings you supplied reads: Sketch uses 56986 bytes (22%) of program storage space. Maximum is 253952 bytes. Global variables use 1683 bytes (20%) of dynamic memory, leaving 6509 bytes for local variables. Maximum is 8192 bytes. This means that the compilation has completed successfully. None of these warnings affect the initialisation of the display, so we don’t think they are your problem. The Arduino language takes a few shortcuts, so some warnings are not unusual. You wouldn’t usually see them unless you have them turned on, though, which must be done manually. Mini SMD steam whistle wanted Thank you for the Steam Train Whistle project (September 2018; siliconchip.com.au/Article/11226). I built one for a friend, for his new layout. We were delighted with the result, especially the doppler effect. Is it feasible to produce a PCB using SMD components so it can be mounted in a train? With some rail pickups and a 12V-to-5V converter, the unit could be triggered by DCC or a track sensiliconchip.com.au sor on a DC layout. A train-mounted unit could also generate a chuff-chuff sound using the white noise generator and a speed sensor from the line voltage or the DCC decoder. (R. M., Paynesville, Vic) • Thanks for your comments on the Steam Train Whistle. A smaller surface-mount version would be possible. We may do this at some point, depending on other commitments. HDMI Pattern Generator wanted How about an HDMI pattern generator project? It would be a handy tool for troubleshooting all sorts of video equipment. It could be based on the Raspberry Pi or similar device. Including an audio tone would be helpful too. (J. O. S., Revesby, NSW) • It’s quite simple to turn a Raspberry Pi into an HDMI pattern generator, and it seems that others have beaten us to the punch. For example, see github. com/LeipeLeon/PiPatternGenerator Direct speed feedback for motor controller I need to drive a 10A DC motor (from a treadmill) at precise speed under a cyclically varying load. Would it be possible to modify your Full Wave Universal Motor Speed Controller from March 2018 (siliconchip.com. au/Article/10998) with the addition a feedback input from a light chopper? As many people are using these motors to drive small lathes and other devices that would benefit from more precise control, it might make a good supplement to the original project. (G. C., via email) • The Full Wave 10A Universal Motor Speed Controller published in March 2018 is not suited for DC motors. It is only for mains-operated universal motors. They may be similar in appearance, as both types have brushes, but the DC motor on the treadmill can’t be run from AC. Even if the output of the AC Motor Speed Controller was rectified, the peak applied voltage of up to 350V or more could break down the insulation in the 180V-rated DC motor and that could lead to motor damage and would also make it a shock hazard. We have carefully considered producing a speed controller for this type of motor, but there are several probsiliconchip.com.au lems with doing so. One is that DC motors have varying voltage and current requirements, so it would be difficult to come up with a ‘one size fits all’ approach. Our design would also be quite large and complex, and not price competitive with off-the-shelf DC motor speed controllers, which are available. The commercial controllers are switchmode designs, which are considerably more compact and efficient, but would be hard to do as a DIY project. Problems with Mk3 Theremin I am building your newest Mk3 Theremin (January 2018; siliconchip. com.au/Article/10931) from a kit my folks purchased from Jaycar Electronics some time ago. Long story short, I can’t get it to work. I have power running through it, the LED lights up, and I can hear static coming weakly from the speaker. Most of the test points come back with voltages that vary from the expected values; most of them are 1-5V below the expected values. Three specific test points have odd voltages. TP5 and TP6 both measure 1.26V while TP9V is a little high at 9.82V. I have gone over all my soldering and can see no faults. I have had two other competent sparkies look at it as well, and both cannot see any obvious mistakes, with one painstakingly going over all of my resistors and capacitors. It is a pretty safe bet that all of the components are in the right place, and the soldering is good. Our last guess is that I might have blown a component during installation, or when I ran the wrong power supply through it. I used a 60W iron at an average of 400°C for soldering, and originally was given a 12V DC power supply instead of 9V AC. One of the sparkies had a good look at the circuit diagram but couldn’t be certain where an issue would arise when I used the wrong power supply. (N. S., via email) • Accidentally applying 12V DC will not damage anything. It does seem strange that TP9V is 9.82V as the regulator output should be no more than 9.25V according to the device data sheet. The only apparent way to fix that is to replace REG1. The voltages at TP5 and TP6 concern us more, though. TP6 should Australia’s electronics magazine measure about 0.6V less than TP5. We think either Q4 has a short between its base and emitter, or there is a short on the PCB between these points. Circuit to drive slave clocks Have you ever done a project to drive old-school slave clocks? I have one that works on a 1/60Hz, 24V pulse to move the minute and hour hands via a coil (draws 100mA each activation). I’m looking for something that’s reasonably accurate to drive it. (D. V., Newcastle, NSW) • We haven’t published a suitable project. In theory, you would just need to take something like a GPS module that has a 1PPS (one pulse per second) output and then add a divide-by-sixty circuit after that. But it isn’t quite that simple as there are a variety of requirements. Some clocks require a reverse polarity alternating pulse, some require hour forward/hour back and pulse forward signals to set the clock. Elliott Sound Products has a fair amount of detail on driving this type of clock at https://sound-au.com/clocks/ arduino.html Help aligning Super-7 AM Radio In my dotage, I have completed the Super-7 Radio (November & December 2017; siliconchip.com.au/Series/321) but am having difficulty aligning it. The DC supply is 9.2V, and the test point readings are 8.78V, 1.56V, 8.79V, 1.15V, 8.78V, 1.73V, 8.91V, 4.50V, 4.33V, 3.67V and 4.15V. The current drain is 5mA. My new DDS IF Alignment unit (September 2017; siliconchip.com.au/ Article/10799) provides a nice curve to encourage me that my second-hand CRO is giving the correct readings. Applying 455kHz with the small wire loop with various signal levels from the DDS, with the CRO on TP6 and my DMM on TP3 (1.15V) and using my mother’s knitting needle to adjust the three IF transformers, I get no change on the DMM reading and I get nothing on the CRO. I am not sure about the level on the DDS. The text says 1mV RMS and 800mV RMS for the other methods. I have noted there is minimal movement on the transformer slugs. I have unsoldered the tiny wires on September 2020  107 the tuning coil, and there is no short circuit. Also on the tuning coil, the clear wire is not at the far end of the coil, as mentioned in the text. (P. M., Hadfield Vic) • Your test readings are all good. The problem could be with the tuning coil connection, as there are two windings. The main winding connects between the two terminals marked “clr” and “blu”, and the tapping winding connects between the terminals marked “grn” and “red”. Check that the far end of the main winding connects to the “clr” terminal and the other end of that winding is to the terminal marked “blu”. You can check which winding is which by measuring resistance. There should be a low ohms reading between the wires that go to the “clr” and “blu” terminal. This wire must be disconnected to measure the winding itself, so it is isolated from the connections on the PCB. Similarly, you should measure a low ohms value between the “grn” and “red” terminals while the wire that goes to the “blu” terminal is still disconnected. It might help us to figure out what’s wrong with your unit if you send us a photo of the board (ideally top and bottom, as sharp and well-lit as possible). Help driving an I2C LCD with a PICAXE I am trying to use an I2C LCD with a PICAXE20M2 without any success. I have sorted out some address problems and learned a lot about the I2C protocol. I have confirmed that the I2C LCD works with an Arduino, with full display features. I then programmed an Arduino as an I2C slave with the PICAXE as the master and confirmed the PICAXE was sending the codes correctly on the I2C bus. The LCD seems to be receiving something, as the display flashes, but the simple text “Hello World” refuses to appear. Can you please have a look at my code and see whether you can figure out why it doesn’t work. (W. S., Wellington, NSW) • It appears you are sending raw strings to the display over the I2C bus, eg: hi2cout (“Hello World”) The Arduino library translates text 108 Silicon Chip into a series of commands and data to send to the LCD. In other words, the display will not work with the data you are sending it. It does not expect to receive one byte to display at a time, but instead receives four bits at a time (half a byte). The remaining four bits in the I2C data packet are control codes which tell the display whether a command or data is being sent and provide the clock to tell it when to receive data. Sending a single ASCII character to the LCD involves at least four bytes being sent on the I2C bus. If you have a spare Arduino, you use your I2C slave code to monitor what is being sent by the working Arduino code. You can then try sending that data from the PICAXE. Our article on I2C LCDs (March 2017; siliconchip.com.au/Article/10584) is a handy resource, and it is worthwhile reading the LCD controller data sheet too (eg, see siliconchip.com.au/link/ ab4a). Stationmaster 5V rail measures very low I have built the Stationmaster PWM train controller (March 2017; siliconchip.com.au/Article/10575). When I apply power, LED3 lights up, but I get very little voltage at the output. I measured 0.3V at the Vcc test point and half that at Vcc ÷ 2. I expected 4.55.5V. What might be causing this? (T. G., Tauranga, NZ) • There are many reasons why the supply voltage could be low. Check that the bridge rectifier, BR1, is orientated correctly and that you can measure the input supply voltage (approximately) at pin 5 of IC3. The 5V supply rail could be low due to a short circuit or an incorrectly orientated electrolytic capacitor or IC (IC1 or IC2). Check your construction carefully. If the input to REG1 is OK but the output is just 0.3V, that suggests there is a problem with a component that runs off the 5V rail (most likely IC1 or IC2). If the input to REG1 is also low, then we suspect a problem with either BR1 or one of the three 1000µF electrolytic capacitors. If you still can’t figure it out, send us photos of the top and underside of the printed circuit boards. We may be able to spot the problem from those photos. Australia’s electronics magazine High power DC motor speed controller Have you published any 12V or 24V DC motor speed controllers recently capable of currents up to 70A? I am looking for a 24V version, preferably at up to 70A. (P. H., Gunnedah, NSW) • We haven’t published a 70A-rated DC motor speed controller, but the High Power DC Motor Speed Controller from February & March 2017 (siliconchip.com.au/Series/309) can handle up to 40A. It is available as a kit from Jaycar (Cat KC5534), and is currently on sale. But we suspect that means it will soon be discontinued, so if you want one you had better act fast. It may be possible to use two Mosfet boards in parallel to achieve 70A, but you would need some serious wiring, and we haven’t actually tried that. Using PV panels for heating water I was just reading issue 152 of Renew magazine, and there is an article starting on page 56 about DIY PV water heating. If I recall correctly, Silicon Chip magazine has already explored the direct connection of the output of a PV panel to an electric water heater utilising a new element. From that discussion, I gleaned that the devil was in the detail, and corrosion would be a serious problem with a DC supply. A proposed solution being to alternate polarity at a regular interval via a relay, though this created a new problem with likely arcing of the contacts from repetitive switching under load. I want to write to Renew magazine so their readers can be alerted to the potential problems. However, I would like to refresh my understanding so I was looking for the article, but can’t find it. I’m hoping that your internal search engine is better than Google, so you can provide me with the details. Then I will also be able to recommend interested Renew readers read the Silicon Chip article for themselves. (T. H., Canberra, ACT) • We found references to this topic in the following issues: • September 2013, Ask Silicon Chip, pp98-99. • September 2014, Ask Silicon Chip, pp98-99 • November 2014, Mailbag, p9 siliconchip.com.au • October 2017, Ask Silicon Chip, p96 • December 2017, Mailbag, p5 Reconfiguring Micromite touchscreen I have successfully constructed and programmed the Micromite LCD BackPack (February 2016; siliconchip. com.au/Article/9812). I got the display working in landscape mode. How can I reconfigure the display? I want to invert it. But when I enter “OPTION LCDPANEL ILI9341,RL,2,23,6”, it says it is already configured. Even if I reprogram the Micromite, the display configuration is retained. (A. D., Erskine, WA) • Use the OPTION LCDPANEL DISABLE command first, then try reconfiguring the display. This is explained on page 18 of the Micromite manual (siliconchip.com.au/link/aaxu). The OPTION LIST command is a handy way to tell what the currently set options are. Preamp for 2 x 5W Class-D amplifier Thanks for all your help when I was building the Currawong valve amp. It is now working well. I have just completed the One-Chip 2 x 5W Mini Stereo Amplifier from November 2014 (siliconchip.com.au/Article/8064), and it’s working (something to do while “staying at home”). Which pre-amp would be best suited for this amp, so that I can operate a mic and a guitar? The Pre-Champion kit looks OK; or is there a better one for this amp? I am an old bloke, just turned 90. (R. W., Menora, WA) • The Pre-champion is cheap and easy to build and should suit your application, so give that a try. It is very basic though, and it may not give you enough gain, depending on the sensitivity of your microphone and guitar. If you require a balanced input for the microphone, then consider our September 2010 High Performance Microphone Preamplifier (siliconchip.com. au/Article/283). Modifying a drill for motor speed controller I built your 230V/10A Speed Controller for Universal Motors (February & March 2014; siliconchip.com.au/Sesiliconchip.com.au ries/195) shortly after you published it, and it transformed what I could do with a Unimat 3 lathe. It gives amazing performance to this day. Recently, I made up an attachment to drill out the threaded stud holes on two Mk1 Escort rear axles, in a larger lathe, to take larger and longer threaded wheel studs. This involves locking the lathe chuck in a fixed position and offering the drilling machine up to the stud holes to enlarge them with the lathe saddle. The problem is that the drill runs far too fast, even on slow speed, and as you mentioned in your February 2014 article, the trigger “speed controller” cuts out at anything below 50% speed. I thought to use my KC5526 controller on the drill, but remembered your article point that it couldn’t be used on any power tool with an inbuilt speed controller. Is there any way I can cut the drill speed controller out and replace it with an on/off trigger so that I can use my Speed Controller with it? (R. K., Auckland, NZ) • You shouldn’t need to rewire the drill. Just press in the switch at the full speed setting and lock it in place (usually, these drills have a switch lock to hold the drill switch in). This will bypass the internal speed controller. Then use the one you built to control the drill. Substituting amplifier output transistors I discovered your magazine a decade ago and have built multiple projects from it. Recently, I bought your PDFs on USB magazine package all the way back to the first issue (siliconchip. com.au/Shop/digital_pdfs), and I’ve only covered a tiny fraction of it so far. It has been enjoyable reading. I have been looking at your amplifier designs and am intrigued by the way they have evolved over time. I am interested in building the Class-A Amplifier from May-September 2007 (and potentially the Studio 350 from Janaury-Febraury 2004) and was hoping to understand better why MJL21193/94s transistors were specified. Looking around, there are other cheaper transistors with very similar names available such as the FJA4213/4313 (used in the SC200), 2SA1962/2SC5242; FJL4215/4315, Australia’s electronics magazine 2 S A 1 9 4 3 / 2 S C 5 2 0 0 , T TA 1 9 4 3 / TTC5200, MJL3281/1302 (used in the Ultra-LD Mk.1), MJW3281/1302, NJW0281/0302, NJW3281/1302 and NJW21193/94. My electronics knowledge is basic, so selecting parts, understanding their function and designing circuits is beyond my ability. My first preference for replacing the MJL21193/94 would be FJA4213/4313 (or variants), as these are the cheapest parts. Would these, or what looks like its bigger brother, the FJL4215/4315s (or variants) be suitable? Second preference, with slightly higher cost would be the MJL3281/1302. The April 1996 amplifier used MJL21193/94s, which were successfully replaced in what I understand to be its successor, the original Ultra-LD, with MJL3281/1302s. Would I be able to do the same with the ClassA Amplifier and use MJL3281/1302 (or variant) parts, as they are available cheaper? I am led to believe from Silicon Chip’s use of the five-legged ThermalTrak variants in later Ultra-LD designs that transistors with 281/302 in their name have excellent performance. As my third preference, would I be able to use NJW21193/94s instead, which have almost the same name, seem to be the same product but are still slightly cheaper? (E. B., Viewbank, Vic) • While the MJL21193/94 transistors from ON Semiconductor are the ones we recommend, you could use the ON Semiconductor NJW21193/94 transistors instead. We don’t recommend the other alternatives you have mentioned, as the performance is likely to be compromised. The low distortion design assumes the use of the specified transistors. To understand why output transistor selection matters so much, you should read Chapter 6 of Douglas Self’s Audio Power Amplifier Design Handbook (“The output stage”). To achieve excellent performance, the output transistors must be very linear, well-matched and have other desirable properties. Two transistors with very similar specifications may perform very differently in this respect. The “ThermalTrak” NJL3281/ NJL1302 five-lead transistors used in the Ultra-LD Mk.2, Mk.3 and Mk.4 amplifiers are virtually identical to the MJL3281/MJL1302 three-lead September 2020  109 transistors used in the Ultra-LD Mk.1 except for the addition of the thermally tracking diode junction. They are all excellent performers. The FJA4313/FJA4213 used in the SC200 were chosen because they are excellent value and the SC200 was supposed to be cheap and easy to build rather than offering ultimate performance (although, it turned out to be a decent performer). We usually find that changing the output transistors in a power amplifier requires other changes throughout the amplifier such as varying the VAS current, the compensation capacitor/ scheme, the biasing scheme and possibly other aspects. Otherwise, you can end up with an oscillator rather than an amplifier, or just inferior performance. We do a lot of testing and tweaking with our specified components, so it’s a good idea to stick with them if at all possible. Instructions for Digital Pulse Adjuster kit I need the build instructions for the Digital Pulse Adjuster kit. I have the actual kit but no instructions. (P. H., Metford, NSW) • The article describing that project was published in our Performance Electronics for Cars book. We have sold out of printed copies, but it is available as a digital edition at siliconchip. com.au/Shop/3/3023 PIC-TOC construction is difficult I built the old PIC-TOC clock from the July 2001 issue (siliconchip.com. au/Article/4169) but am having problems making it go. Was any errata published for this project? Its assembly was a nightmare, with components on both sides of a single-sided circuit board. It is running (it starts and says “1 2 3”), but not making noise and I can’t set it up. Probably those darn switches on the underside aren’t connected properly. (B. M., Shenton Park, WA) • You can check the Notes & Errata on our website (siliconchip.com.au/ Articles/Errata), although we haven’t published any errata for the PIC-TOC. We certainly avoid designs like that these days. Try checking the function of each pushbutton with a DMM set 110 Silicon Chip in continuity mode. You will need to identify which tracks connect to which buttons, which can be seen in Fig.2. They appear to be chained, so a bad solder joint on any one would prevent them all from working. Substitute for obsolete thermistor I recently found myself with a lot of time on my hands. I came across an article in an old copy of Electronics Australia (January 1985). Page A20 of the Holiday Projects section of the magazine has a “Sine and Squarewave Oscillator” by David Edwards. The oscillator uses easy-to-get components like BC549s and 559s for the sinewave portion and a 555 for the square wave part. However, the RA53 thermistor is no longer available, which really puts a damper on things. Is it possible to substitute a different thermistor to give new life to this design? (K. W., Hamilton, NZ) • Unfortunately, the RA53 thermistor had certain properties that are not matched in more modern thermistors. These made it very suitable for amplitude stabilisation in an oscillator circuit. We are not aware of any substitutes or old stock. Elliott Sound Products has a web page discussing this problem and some possible alternative devices at https://sound-au. com/project22.htm Help using hobby CNC machine Firstly, let me congratulate you all on an excellent and wonderful publication. I find myself watching for my postman in anticipation of the next month’s edition. A little while ago, I asked for advice regarding a hot air rework station. I ended up getting a Horusdy dual soldering station with a temperaturecontrolled soldering iron and a hot air rework station, all in one. With the money I saved, I also bought a Micron T2065 vacuum desoldering station. The total cost came in well under my $400 budget (which pleased my wife immensely). I now think to myself all the time: how did I ever work without them? Instead of spending a lot of time slowly desoldering SMD components and ICs, then more time cleaning the pads etc before I can fit the replacement IC, I Australia’s electronics magazine just fire up the hot air, and the job is complete in minutes instead of hours. I would like some more advice because I have acquired a Woodpecker CNC milling machine. It is a hobby machine, readily available online from eBay etc at a very reasonable cost. However, it uses G-code, and the software supplied with this unit is dismal at best. Could you please advise me on the best (and maybe free) design software that will produce a G-code file. I also need control software to send the Gcode to the machine. (D. S., Maryborough, Qld) • Tim Blythman responds: we haven’t used that style of CNC machine very much, but it does look a lot like a machine I tried out about four years ago at my previous job. The Woodpecker looks the same as the LinkSprite CNC machine, which you can see at siliconchip.com.au/link/ab47 There is a link to the control software at the bottom of the page, which at the time of writing this goes to the following ZIP file: siliconchip.com. au/link/ab48 I was able to run some engraving jobs using that software, but did not try to do anything complicated. It seemed to work fine. Since your machine requires Gcode, you probably need a three-step workflow, the details of which will depend on what you are making with your mill. For example, milling 3D shapes will be different than engraving 2D shapes onto a flat object. The first step will involve some sort of CAD/design software. This will create files which (theoretically) can be used with any mill or perhaps other types of CNC machine. Simple milling/engraving outline designs would probably be similar to what we do for laser cutting acrylic case pieces. We use various pieces of 2D design software (some people use CorelDraw, some use OpenScad), but they all generate a DXF file. We then load that into the laser cutter software and go through a few steps to produce the file that controls the cutter. The LinkSprite page mentions ArtCam and InkScape as software alternatives. I have dabbled with InkScape and know that it can produce DXF files. The second step is to turn the file you produce into G-code for your 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 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 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 Silicon Chip Binders REAL VALUE AT $19.50 * PLUS P & 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 – condition varies. All books can be viewed at: siliconchip.com.au/link/aawx Email for a postage quote: Silicon Chip silicon<at>siliconchip.com.au PCB PRODUCTION 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 P Keep your copies safe, secure and always available with these handy binders These binders will protect your copies of SILICON CHIP. They feature heavy-board covers, hold 12 issues & will look great on your bookshelf. Silicon Chip Publications Order online from www. siliconchip.com.au/Shop/4 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 September 2020  111 Coming up in Silicon Chip Balanced Inputs & Attenuator for the USB SuperCodec Rather than resting on his laurels, Phil Prosser has produced an add-on board for his SuperCodec USB Sound Card which adds two balanced inputs and selectable attenuation settings of 0dB, 10dB, 20dB or 40dB. It fits in the same case as the SuperCodec and provides professional balanced audio recording, plus makes it an even more potent audio measurement system. MicroElectroMechanical Systems (MEMS) Advertising Index Altronics...............................81-84 Ampec Technologies................... 9 Dave Thompson...................... 111 Digi-Key Electronics.................... 3 Emona Instruments................. IBC We’ve used MEMS devices before but haven’t described how they work in detail. Dr David Maddison’s article explains what they are, how they are made and shows the many different types of MEMS available. The article includes electron microscope images showing the amazing precision of these tiny devices. Hare & Forbes............................. 5 Mini WiFi LCD BackPack Keith Rippon Kit Assembly...... 111 All of our “BackPack” projects which combine a microcontroller with a colour touchscreen have been popular with constructors; some incredibly so. But one thing they have generally lacked is WiFi connectivity. This one not only provides WiFi but also contains a powerful 32-bit processor and is surprisingly inexpensive! Jaycar............................ IFC,53-60 LD Electronics......................... 111 LEDsales................................. 111 Ten LED Christmas Ornaments Microchip Technology......... 7,OBC We will have multiple Christmas projects in our October & November issues, including two different, impressive LED Stars that you can fit atop your Christmas tree (or just put on display). Plus, we will describe eight mini LED Ornaments which are cheap and easy to build, and look great. They come in a variety of different colours, and you can also mix and match LED colours to your heart’s content. Ocean Controls......................... 11 The First Computer Graphics Cards Silicon Chip Binders............... 111 Dr Hugo Holden describes, in detail, the Matrox ALT-256 and ALT-512 graphics cards. These were two very early expansion boards (the ALT-256 almost certainly being the very first) which allowed computers with an S-100 bus to display video graphics on a monitor. You can even gang up three ALT-256s to display in colour. Silicon Chip PDFs on USB....... 89 Note: these features are planned or are in preparation and should appear within the next few issues of Silicon Chip. The October 2020 issue is due on sale in newsagents by Thursday, September 24th. Expect postal delivery of subscription copies in Australia between September 22nd and October 9th. Premier Batteries...................... 41 RayMing PCB & Assembly.......... 4 Silicon Chip Shop...........104-105 The Loudspeaker Kit.com......... 63 Tronixlabs................................ 111 Vintage Radio Repairs............ 111 Wagner Electronics..................... 6 Notes & Errata Arduino-based Digital RF Power Meter, August 2020: in Fig.5, IC1 is labelled IC4. Also, the capacitor referred to in the text as Cobp is actually Clpf. GPS-Synchronised Analog Clock Driver, February 2017: on page 39, the text states “For either type of clock, the clock pulse width can be changed in steps of 1ms…”. This is incorrect; only the sweep hand firmware offers 1ms steps. For clocks with stepping hands, the pulse width can only be set from 16ms to 96ms in 8ms steps. One reader found that a 56ms pulse width gave reliable drive with a battery voltage as low as 2V with his clock. 230V 10A Universal Motor Speed Controller, February & March 2014: the STGW40N120KD IGBT used in this project is no longer available. Several suitable alternatives are available; the best option is the IGW40N120H3FKSA1 (1200V, 80A). specific machine. I don’t remember what I used to produce the G-code; I suggest Googling for “dxf to gcode grbl”. DXF2GCODE looks like it is worth trying (see http://grauonline. de/wordpress/?page_id=3211), but I can’t vouch for it. 112 Silicon Chip Many 3D printers use G-code too, so 3D printer ‘slicing’ software might create workable G-code. Finally, the Linksprite Control Software can be used to send this to the machine. I would definitely have my finger on the power switch while tryAustralia’s electronics magazine ing this for the first time; something as simple as a units mismatch could cause your mill to do something unanticipated. Since the Linksprite CNC runs the ‘grbl’ software, you can use that as a keyword in searches for tools. 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! 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