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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 had the right to edit, reproduce in electronic form, and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman’s Log”. Important information about the Tele-com (OzPLAR) In the Tele-com article on page 38 of the October issue, one of the alternative transformers for the ringer section in the parts list is shown as Triad FS24-100-C2 (Mouser Cat 553-FS24100-C2). This should instead be Triad FS24-100 (Mouser Cat 553-FS24-100). Note that the Altronics M7024A is a good performer, and about the same price as the Triad FS24-100. The FS24-100-C2 version (while cheaper) is designed to be short circuit proof, and as a result, it just doesn’t perform well in the ringer circuit. I purchased quite a few and was disappointed to discover this. Another recommendation that isn’t covered in the article is the type of self-tapping screw used to mount the board in the Pac-Tec LH96-200 case. I initially used some 8mm-long 4G self tappers and found that one of the mounting stand-offs in the case split down the side. The PT (Plas-tite) screws WN1411KB30X6Z available from PSM Fasteners in Marrickville, NSW can be used to avoid this happening. Editor’s note: we usually find 4G/3mm screws to be fine for this sort of job, but perhaps 8mm is a bit long; 6mm screws are less likely to split the posts. Note that both feed bridge designs were tested using a power supply similar to those in the parts list, and we could not notice any audible switching artifacts in the telephones. However, some constructors may not use the recommended PSU and instead elect to use a small plugpack such as the Altronics M8968B (superseded by 4 Silicon Chip M8968C) because they are considerably cheaper. Testing with the M8968B after the article went to press showed that when the LB1011AB feed bridge was used, switching artefacts were audible in the telephones as an annoying ‘digital squeal’. It is not noticeable when the M1000 inductor feed bridge is used with the M8968B. Fitting the M8968B with an 820μH inline inductor using adhesive heatshrink and decoupling pin 8 of both LB1011ABs with 4.7μF 50V capacitors effectively eliminated the noise. Still, the likelihood of constructors opting for the LB1011AB feed bridge is minimal, although we can supply them if needed. The 820μH inductor tested was Mouser Cat 815-AIAP03821K. I used 6mm adhesive heatshrink (Altronics W0994A) to increase the diameter of the cable on the M8968B and sheathed the inductor with 19mm adhesive heatshrink (shown below; Altronics W0997A). I haven’t checked the switching frequency of the Altronics M8968B, but I suspect it is around 500kHz. I also tested a plug pack that operated at 50kHz, and the modified inductor/ capacitor filter arrangement effectively suppressed the noise from that as well. Ross Herbert, Carine, WA. Silicon Chip magazines to give away I have many Silicon Chip magazines that I wish to give away. If you are interested, please e-mail silicon<at> siliconchip.com.au and they will pass your message on to me. John Maarssen, Thornlie, WA. Australia’s electronics magazine SMD Test Tweezers – more than just something to build This is just a note to let you know how much I enjoyed the October article by Tim Blythman on the SMD Test Tweezers. I went right ahead and purchased the kit but never built it! My interest started because I was curious about how to use the OLED display, how the sleep mode worked and anything else I could learn from it. It is great that you make the source code available, so I immediately downloaded the C source code from your website. I’m by no means a ‘crack’ C programmer. Still, on opening the code in MPLABX, it just looked very neat and concise with its separate includes for the I2C communications, the OLED operation and convenient utility routines such as getDigit for displaying on the OLED. I mapped the font.h file onto a spreadsheet with “x”s to see how the fonts were made. It was a real learning experience. For example, I discovered the term “include guard” when exploring the #defines. I always had a vague idea what that was about, but there it is, nice and simple. It inspires one to try to write neat code. I’ve decided to get familiar with the PIC16F1459, so as an exercise, I set the circuit up on a breadboard, using different pins (because the processor is different). I created a new MPLAB X project with your code and began porting it across. All this meant getting familiar with MPLAB X again, fiddling around with the PICkit programmer and using different pins for wake up on interrupt. In the end, I now have a nice little siliconchip.com.au test jig (which behaves as a pair of test tweezers) for practising with I2C driven OLED displays and a whole lot of new ideas as to how to format the code. The reason I’ve written is to thank you for your efforts and to let you know a different angle from which some of your readers might derive enjoyment from such projects. Dave McIntosh, Eastwood, NSW. Backwards compatibility nightmares My reading list is far and wide, and I always read (or at least flip through) your magazine with interest because I never know what I will find. April’s edition was no exception, and I wanted to add to your editorial comments (“Adobe making our lives difficult”), which are not exclusive to Adobe. I published some books on lighting design, for which a few of the fonts have since been ‘updated’. This means that I need to change the whole contents because the new fonts are not only ghastly and inappropriate, but they completely scramble all of my work, including paragraph endings, tables and the like. To overcome this problem without re-doing the layouts, I check with the printers to ensure that the fonts I’ve typed are still in their system. That is the best I can do under the circumstances, though I now have three publications requiring the same method for printing. But it doesn’t stop there! When I was forced to upgrade to a new computer and Windows 10, I was assured that every piece of technology would work on the new system. However, my brilliant Epson 1260 scanner, which also does 35mm colour slides and negatives, would not work. After wasting so much time, I contacted Epson directly only to be told that the scanner was too old and I needed to purchase another item which is superior (probably because it was also a printer – whoopty-doo). This is what it’s all about – getting us to upgrade all of our equipment whenever a newer model is produced. Thank goodness the medical professional doesn’t value our lives in the same manner! Then a few months ago, I thought I’d watch a quick DVD on Windows 10, only to discover that I now need to purchase and download an app 6 Silicon Chip that will allow my DVD player to run. This is absolute nonsense in its highest form. The new regime has allowed third parties to piggyback and make more money by stealth, not only in the computer industry but with most bookings or purchases done online. As a result of all this, I have had to go back to using Windows Vista on my laptop so that I can use my preferred software. But I have to keep it offline to ensure that there are no ‘updates’ that break its operation. Some of us try desperately to uncomplicate our lives. I look forward to your next edition of Silicon Chip. Karen Wardell, Nelson, New Zealand. Comment: perhaps the most frustrating aspect of this culture of providing updates that break backwards compatibility is how little these companies, to whom we pay a considerable amount of money to use their software, seem to value our time or effort. They are quite happy to cause us hundreds of hours of work and frustration, then act as though they are doing us a favour. More feedback and a suggestion A quick note to let you know I really enjoyed the October issue; it is packed with many interesting projects and reviews! I was also wondering if you’d consider publishing an updated electronic load circuit. This is a very handy device on the bench, and the last Silicon Chip design is from 2006. Olivier Aubertin, Singapore. Comment: we have a contributor working on an electronic load design, and it sounds like it will be finished soon. Getting competitive about vintage gear I expect another older reader will top this, but I can beat Greig Sheridan’s venerable EA power supply (mentioned in his letter you published in the October issue) by some decades. That magazine’s predecessor, Radio, Television & Hobbies, published an FM tuner circuit in January 1957, presented by its avuncular editor, John Moyle. The one I built was in almost everyday use until the advent of stereo FM in the mid-seventies and supplied my LP disc cutter with high-quality ABC orchestral concerts. It is still working perfectly (mono only, of course) with its original four 6AM6 valves. Today, Australia’s electronics magazine it sits under my bench, and I listen to it now and again simply for the sentimental satisfaction of keeping it alive. Brian Wallace, Dora Creek, NSW. Windows updates and DMM AC calibration In your July editorial, I noticed that you pinged Microsoft for their dodgy fix that didn’t fix. Shock horror. You’re surely not suggesting that Microsoft sells software of dubious quality. Let’s not forget that one of the first, if not the first, vulnerabilities exposed in Windows XP was inherited from Windows NT, and Microsoft knew about it for years but did nothing to fix it. I think you need to keep in mind that the primary aim of almost every company is to make profits, and manufacturing something or supplying goods or services is just the process they use to achieve that end. Providing superior products, services etc comes at an extra cost which has to be passed onto customers or taken out of profits. Some companies have successfully managed to provide quality as well as make a profit, although many more have delivered quality and gone bust. So to stay up with the competition, flashy new thingamabobs are often the more cost-effective route to staying in business. Henry Ford is reputed to have said that “There is one rule for the industrialist and that is: Make the best quality goods possible at the lowest cost possible, paying the highest wages possible.” Modern manufacturers have pretty much ditched the last part and are concentrating on the second at the expense of the first. It is a cut-throat game. Having said all that, I must add that my observation is that most goods I use these days are of higher quality and provide greater utility than they ever have in the past 60 years, and they are relatively cheap. Smartphones and computer systems would be the most glaring exceptions to that. Fortunately, although life could be better, it could also be much worse. I’ll finish this diatribe with an observation from the late, great Douglas Adams: “The idea that Bill Gates has appeared like a knight in shining armour to lead all customers out of a mire of technological chaos neatly ignores the fact that it was he … [who] led them into it in the first place ...” siliconchip.com.au Can you deliver reallife technology solutions? Is the answer automated smart grids that connect industry and households to renewable energy? Could you engineer robotic systems that improve safety and increase efficiency in manufacturing and farms? Work alongside USQ’s world-class lecturers and help solve current industry problems with a USQ engineering degree. Study 100% online, on campus or a mix of both. #1 uni in Australia for graduate starting salary in engineering.^ Experience more opportunities and personalised support with our small class sizes. Join this in-demand industry and study electrical, mechatronic, computer systems engineering and more. USQ Engineering ^ Good Universities Guide, 2022 CRICOS: QLD 00244B, NSW 02225M | TEQSA: PRV12081 Helping to put you in Control Spectrally Flat Class C Pyranometer DeltaOHM PPYRA03AC – Spectrally Flat Class C Pyranometers according to ISO 9060:2018. Complete with levelling device and calibration report. SKU: OHM-001 Price: $1545.50 ea UC100 USB Motion Controller Directly replaces the traditional Parallel port with modern USB. Can control up to 6-axis with Mach3, Mach4 or UCCNC software. Up to 100kHz step frequency operation, Fast communication with data buffer for robust and stabile operation. SKU: CND-001 Price: $198.00 ea M18 Shielded Inductive Proximity Sensor NPN, NO+NC IPSI/L-18NOC5B Shielded (flush) M18, 4-wire NPN-style output with NO+NC contact type. It has a sensing distance of ~5 mm. Screw on connector. Choose 2m cable with straight or 90 degree 4 wire M12 connector. SKU: IBS-0280 Price: $30.25 ea Programmable Range Pressure Sensor Novus Automation’s NP620 Programmable Range pressure sensor with input range of 0 to 10 Bar. 2-wire 4 to 20 mA output, 0.25% accuracy and 1/2” BSPP process connection. SKU: NOS-206 Price: $259.60 ea 604 Differential Pressure Switch Huba 604 is used as a DP flow switch in ventilation ducts for the control of filters and fans, and in control systems for the control of dampers. Pressure range 0.2-3mbar option 1-10, 0.5-5, 10-50. SKU: NOS-2600 Price: $307.95 ea Thermostat Controller with NTC Sensor and Buzzer Panel mount thermostat with included NTC sensor on 2 m lead. Configurable for a huge range of heating and cooling applications. Fitted with Buzzer for alarm. 100 to 240 VAC powered. SKU: CET-0012 Price: $121.00 ea 2.0 N·m NEMA 23 Integrated Stepper Motor iST-2320 2.0 N·m NEMA 23 stepper motor with integrated driver. Standard pulse and direction (or CW/CCW) input. Advanced antiresonance DSP driver. Comments on component shortages SKU: SMC-126 Price: $241.95 ea For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Prices are subjected to change without notice. 8 Silicon Chip Also, I thought about R.M.’s problem of measuring AC for calibration purposes (Ask Silicon Chip, July 2021, page 110). Most DMMs do not have very high accuracy on the AC ranges, usually much poorer than the specified DC accuracy. For example, Keysight U123x meters have specified DC accuracy of 0.5%, AC accuracy of 1% for the low voltage ranges, and frequency accuracy of 0.1%. I used to own one, and I thought it was a great general-purpose instrument. The corresponding figures for the U1282A are 0.025%, 0.3% and 0.005%. I own one now but rarely use it because it’s expensive, and I don’t want to damage it. 1% is a pretty typical accuracy for the AC ranges on DMMs. You recommend that R. M. use a “low-distortion sinewave oscillator”, but consider how much distortion contributes to the RMS value of a (nominal) sinewave. Because you have to use the root-of-sum-of-squares method to add distortion and fundamental the distortion has to exceed 14% before the RMS value increases by 1%. A 1V RMS sinewave with 1% distortion has an RMS value of 1.00005V RMS, which is well within the accuracy of even five- or six-digit DMMs. I realise that “low-distortion” is a relative term, but even a cheap function generator should deliver acceptable performance. Besides, if you are using the LTC1966 as a reference, it should be irrelevant what the waveform is so long as it is within the meter’s crest factor capabilities. The exercise is complicated by the LTC1966 working over a fairly small range, up to 500mV max, so it cannot be used reliably to calibrate higher voltage ranges without also calibrating the gain circuit. Also, strict attention must be paid to the effects of loading, both resistive and capacitive. If the multimeter is not a ‘True RMS’ meter, the need is less. Phil Denniss, Darlington, NSW. Nicholas comments: You are right; a pretty basic sinewave generator should be fine for calibrating most DMMs on AC voltage ranges. The main requirement is that sinewave amplitude must be more precisely known than the DMM’s measurement tolerance. Also, some of the blame for how buggy computer software has become must lie with consumers. The reason software companies prioritise adding bells and whistles over fixing bugs or improving performance is that they’ve figured out that is why people pay for their products. Consider that Microsoft and Apple essentially form a duopoly, and by refusing to license macOS to be run on hardware they do not sell, Apple allows Microsoft to act as a monopoly. Monopolies rarely lead to good outcomes for consumers. Linux is making inroads into the desktop market, but only slowly. Concerning your October Editorial Viewpoint, I am not surprised that components are also in short supply. This suggests that the situation will be quite bad for Silicon Chip and hobbyists because we are at the bottom of the pecking order. The inability of hobbyists to play with electronics simply does not rate against manufacturers who need to keep their production operational. Australia’s electronics magazine siliconchip.com.au Design Contest Win $500+ Dick Smith challenges you Win $500 by designing a noughts-and-crosses machine that can beat 14-year old me! Dick Smith has described in his new autobiography how one of the turning points in his life, at age 14, was succesfully building a ‘noughts-and-crosses machine’ (also known as tic-tac-toe) that could play the game as well as anyone. Keep in mind that this was in 1958, when nobody had computers; it was a purely electromechanical device. Email Design to Enter Design your own noughts-andcrosses circuit and send your submission to compo<at>siliconchip. com.au including: a) Your name and address b) Phone number or email address (ideally both) c) A circuit or wiring diagram which clearly shows how the device works d) The display can be anything as long as it’s understandable e) Evidence that your device can always play a perfect game (it never loses) f) A video and/or supply images and text describing it g) Entries requiring software must include source code The deadline for submissions is the 31st of January 2022. ➠ ➠ Win $500 + Signed Copy of Dick Smith's Autobiography ➠ Four winners to be decided, one each for the following categories: ➊ The simplest noughts-andcrosses playing machine most ingenious noughts➋ The and-crosses playing machine youngest constructor to ➌ The build a working noughts-and- DICK SMITH crosses playing machine most clever noughts-and➍ The crosses playing machine not using any kind of integrated processor The entry we judge overall to be the best will also be featured in our Circuit Notebook column and receive an additional $200. ‘Businessman, adventurer, philanthropist…Di ck Smith is a true Australian legend.’ JOE CITIZEN Conditions of entry Dick Smith writes 1) You must be a resident of Australia or New Zealand 2) One entry per family (Silicon Chip staff and their families are not eligible) 3) Submissions will be confirmed within 7 days. If you do not receive a confirmation of your submission, contact us to verify that we have received it 4) Chance plays no part in determining the winner 5) The judges’ decision is final 6) The winners will be decided by the 3rd of February 2022 and will be notified immediately By 1958 I’d advanced from building crystal radio sets to designing and building what I called a noughts and crosses machine. It really was an early computer. I used second-hand parts from a telephone exchange to build it. It would play noughts and crosses against anyone and no one could beat it. This was a great boost to me, because while I was no good at rote learning and theory, I was fine at practical things. The fact that my mind was capable of working out how to build this complex machine gave me confidence as I left school. Now I just had to find a job. Because this was such a turning point in his life and he’s so enthusiastic about youngsters learning electronics, he’s putting up $2000 of his own money to award to people who can come up with a modern version of his noughts-and-crosses machine. Silicon Chip will judge the entries. Winners will be announced in the March 2022 issue of Silicon Chip magazine and will also be contacted directly for payment information. siliconchip.com.au Australia’s electronics magazine December 2021  9 POWER SUPPLIES PTY LTD ELECTRONICS SPECIALISTS TO DEFENCE AVIATION MINING MEDICAL RAIL INDUSTRIAL Our Core Ser vices: Electronic DLM Workshop Repair NATA ISO17025 Calibration 37 Years Repair Specialisation Power Supply Repair to 50KVA Convenient Local Support SWITCHMODE POWER SUPPLIES Pty Ltd ABN 54 003 958 030 Unit 1 /37 Leighton Place Hornsby NSW 2077 (PO Box 606 Hornsby NSW 1630) Tel: 02 9476 0300 Email: service<at>switchmode.com.au Website: www.switchmode.com.au 10 Silicon Chip But hobbyists have one advantage; we can use recovered components, whereas manufacturers cannot afford the risk. For many years, I bought old equipment and PCBs to get expensive and rare components, and in doing so, I collected a lot of common parts. The result is that the shortage is not a hindrance to my experimentation. I realise that I am in a unique position, but there will still be old equipment with components that can be retrieved. One just needs a good hot air gun to make for easy removal. If you don’t already know, Wiltronics are still advertising surplus components. They are: BAS16 SOT-23, BC848C SOT-23, BC849C SOT-23, all in 3K reels <at> $30 per reel; TIP32B TO-220 as 500 pack <at> 73¢ each; 1SMB5941 47V diode 1.5W in 2K reel <at> $40; and 16V 5W Zener diode in pack of 1000 for $50. You can find these online at: www.wiltronics.com.au/ product-category/semiconductors-surplus/ The Dick Smith noughts & crosses competition intrigues me. I have no intention of entering it, but it is interesting that noughts & crosses is being revisited when it has been researched to death. The creation of an unbeatable machine is a trivial exercise. I will be very interested to see the winning entries. Regarding Mr Smith himself, I am impressed that he created an unbeatable machine at age 14, especially back in 1958. He was very fortunate to have access to telephone exchange parts as such things were almost impossible to obtain in the early 1960s, when I was his age. As I age (now 70) and suffer more and more from knotted neurons, I have become interested in technical people who have achieved something remarkable. Their stories are far more interesting than those from other areas of endeavour. The microprocessor used in the USB Cable Tester project of the October Silicon Chip edition is a new one to me, and I was curious to look at its specs. Since the COVID-19 pandemic has caused a shortage of microcontrollers, it has occurred to me that Microchip and other manufacturers may use the pandemic to rationalise their products. In particular, older ICs that use more silicon real estate than current products would undoubtedly be targets for phasing out. Since Microchip has a vast range of microcontrollers, I would expect them to take advantage of the situation. The PIC16F18877 looks like a drop-in replacement for many earlier microcontrollers, including some very popular ones that have been around for some time and are in short supply. Microchip has been very good at maintaining common pinouts on many of their microcontrollers, which is to their credit. However, the move to the ‘swiss army’ microcontroller does leave a bit to be desired because that increased complexity also leads to microcontrollers which are much harder to understand. George Ramsay, Holland Park, Qld. Comments: we reckon most people who’d be interested in entering the competition would already know how to win the game. The real challenge is coming up with a clever circuit that uses minimal components, especially if no microcontroller is involved. Australia’s electronics magazine siliconchip.com.au By the way, while the situation has stabilised somewhat, we can’t see the shortages going away until late 2022 at the earliest, and more likely 2023-2024. As far as we are aware, Microchip has never phased out a product, and we don’t think they will start any time soon. However, their older products become more expensive over time, making switching to newer devices attractive. They generally perform better and have more features at a lower price, so it makes a lot of sense to migrate code where possible. We are sure you are right about other manufacturers taking this opportunity to cull their ranges, though. Yes, Microchip does a great job of maintaining pin compatibility. For example, the PIC16F1887x family looks like a drop-in replacement for the venerable PIC16F877. We don’t think the new micros having more features is a problem. You don’t have to use all the features; many of them do nothing unless enabled, but it’s nice to have them present in case you need them. The processor cores are still pretty easy to understand and work with, although Microchip’s stablemate AVR processors are significantly easier to understand at a low level than the PIC series. A familiar tale of woe I read with particular interest your column in the October 2021 issue with respect to the global silicon chip shortage. Your Mosfet lead time quote is the worst one I have heard so far (2.5 years!), but for all the other MCUs I use at RICTECH, the lead-time is usually quoted as November 2022 at the earliest, so at least a full year of waiting at this stage. I sell the Colour Maximite 2 units on my website, and I have one left and no chips to get any more made for at least a full year, probably longer at the rate things are going. I will continue to offer it once I can get the chips again, but who will remember or even want one in a year? I was also interested in your Tele-com project starting on page 30 of the same issue. It’s a clever idea, and I remember my older brother building something similar back when I was just a nipper, although it was 9V battery-based and used the handsets only, not the whole phone. Graeme Rixon, RICTECH(NZ) Ltd. Notes about connecting to Micromite via Bluetooth I have been doing some more work with my Micromite project that you published in the September 2021 issue, and thought it would be a good idea to pass on some additional advice. When using the Bluetooth terminal on your Android phone, you can often connect OK, but the screen is blank. This is because the program auto-starts and is out of sync with the terminal. Powering the Micromite on and off a few times will sometimes get things back in sync, but the best way is to send Ctrl-C to the Micromite from the terminal. That will halt the auto-running BASIC program and return you a cursor input prompt. You then just type in RUN, and things will start at the beginning for you. The Bluetooth Terminal App recommended in the article has the facility to program a macro key. I have programmed my M1 key to send Hex 03, which is Ctrl-C. Tom Hartley, Allens Rivulet, Tas. SC siliconchip.com.au Australia’s electronics magazine December 2021  11