Fullscreen HTML5Med Res (??MB)HTML4

MAY 2021 ISSN 1030-2662 05 The VERY BEST DIY Projects! 9 771030 266001 $995* NZ $1290 INC GST INC GST Hybrid Bench Supply 24V <at> 0-3.5A or 0-18V <at> 0-5A ■ WiFi remote monitoring/control 100-240V AC, 50-60Hz supply ■ 10mv/10mA setting resolution Multiple units can be combined wirelessly to make a tracking supply Variac-based Mains Voltage Regulator PLUS THESE OTHER ARTICLES siliconchip.com.au Digital Radio Modes: Amateur Radio etc electronics magazine History of Australia’s Videotape: Digital FX Pedal Unit: Cassette Systems Creating New Effects May 2021  1 64-Key MIDI Matrix: Software and Android Want to build your own Music Beat Bar? Dance to the music with this beat bar! Get a visual display that bounces in tune with the music. Uses a new 8-bit-friendly Fast Fourier Transform library to detect different frequencies and pulses the bars for bass, midrange, and treble. Contained in a tidy little box so you can take it with you and hang it up at your next party. SKILL LEVEL: Intermediate TOOLS: Soldering Iron, Drill, Hot Glue Gun CLUB OFFER BUNDLE DEAL 7495 $ SAVE 40% KIT VALUED AT $127.95 What You Need: 1 × Arduino® Compatible Nano Board 1 × Monochrome OLED Display Module 1 × Black Enclosure Box 4 × RGB LED Strip Module 1 × Microphone Sound Sensor Module 1 × 150mm Socket to Socket Jumper Leads 1 × SPDT Miniature Toggle Switch 1 × PC Mount 9V Battery Holder 100W Large Glue Gun Easy and simple to use with trigger controlled glue feed. Mains powered. Supplied with 11mm dia. glue sticks. TH1999 JUST 19 $ 95 100 $ gift card Awesome projects by On Sale 24 April to 23 May, 2021 FREE 6pk Glue Sticks With purchase of TH1999 Large Glue Gun. TH1995 Valued at $4.95 XC4414 XC3728 HB6082 XC4380 XC4438 WC6026 ST0335 PH9235 $29.95 $24.95 $14.95 $9.95ea $7.95 $5.95 $2.95 $1.45 For step-by-step instructions scan the QR code. www.jaycar.com.au/music-beat-bar See other projects at www.jaycar.com.au/arduino 200g Duratech Solder 60% Tin / 40% Lead. Resin cored. 2 sizes available. 0.71MM NS3005 1.00MM NS3010 JUST 16 $ 95 EA. Got a great project or kit idea? JUST 8995 $ 15W 240V Soldering Iron High quality iron. Exceptional heat recovery. Up to 320°C temp range. High insulation, low current leakage. TS1430 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 Looking for your next build? Silicon Chip projects: jaycar.com.au/c/silicon-chip-kits Kit back catalogue: jaycar.com.au/kitbackcatalogue 1800 022 888 www.jaycar.com.au Shop online and enjoy 1 hour click & collect or free delivery on orders over $99* Exclusions apply - see website for full T&Cs. * Contents Vol.34, No.5 May 2021 SILICON CHIP www.siliconchip.com.au Features & Reviews 12 Digital Radio Modes – Part 2 Continuing on from last month, this article focuses mostly on transmission modes used by amateur radio enthusiasts, plus mesh networks, LoRa and offgrid communication – by Dr David Maddison 61 Review: EVOR04 Audio Analyser This $110 device incorporates a spectrum analyser, oscilloscope, VU meter and a frequency meter plus it’s controlled using a 3.5-inch touchscreen display – by Allan Linton-Smith 86 The History of Videotape – Cassette Systems Cassettes quickly became the most popular videotape format due to their size and ease-of-use, even commercially. This was led by one of the earliest format wars, between Betamax and VHS – by Ian Batty, Andrew Switzer & Rod Humphris This remote-controllable Lab Supply can even be set up as a group, making it possible to use it as a tracking supply. Each unit is compact, fitting into an ABS case measuring 260 x 190 x 80mm – Page 24 Constructional Projects 24 Programmable Hybrid Lab Supply with WiFi – Part 1 This Lab Supply can deliver up to 18V at 5A (and higher voltages at slightly lower currents) and allows you to remotely control it over WiFi. It has current limiting, soft-start and voltage/current monitoring. Since the supply is programmable, it could be used for automated testing etc – by Richard Palmer 38 Digital FX (Effects) Pedal – Part 2 This device has a real-time stereo audio analyser via 31band FFT analysis – a feature that was previously only available on specialist equipment – Page 61 This final article in the series covers how you can create and then install different effects into your unit’s EEPROM using SpinCAD Designer and SpinASM – by John Clarke 46 Arduino-based MIDI Soundboard – Part 2 We’ll show you how you can control the MIDI Soundboard using Androidbased smartphones and tablets, along with some software that can be used to further enhance it – by Tim Blythman 64 Variac-based Mains Voltage Regulation Using a motor to drive a Variac provides one of the easiest ways to supply a constant AC voltage for sensitive equipment. Building on this, we can make our own mains voltage regulator using a Variac – by Dr Hugo Holden Your Favourite Columns 83 Circuit Notebook (1) Revised GPS Analog Clock for NTP module (2) Simple DMM calibrator (3) Infrared remote control jammer Variacs provide a way to deliver a constant mains voltage. This means you can use one to build your own mains regulator – Page 64 96 Serviceman’s Log Some jobs are much harder than they should be – by Dave Thompson 103 Vintage Workbench 1972 BWD 141 audio generator – by Ian Batty Everything Else 2 Editorial Viewpoint 4 Mailbag – Your Feedback 37 Silicon Chip Online Shop siliconchip.com.au 102 Product Showcase 108 Ask Silicon Chip 111 Market Centre 112 Notes and Errata Australia’s electronicsIndex magazine 112 Advertising The introduction of cassettes was a big change to consumers and even professionals, eventually culminating in the incredibly popular VHS format – Page 86 May 2021  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. Nicolas Hannekum, Dip. Elec. Tech. Technical Contributor Duraid Madina, B.Sc, M.Sc, PhD Reader Services Rhonda Blythman, BSc, LLB, GDLP 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 Staff (retired) Ross Tester Ann Morris Greg Swain, B. Sc. (Hons.) 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 per year, post paid, in Australia. For overseas rates, see our website or email silicon<at>siliconchip.com.au Recommended & maximum price only. 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 Printing and Distribution: Editorial Viewpoint Farewell to Gary Johnston A Remarkable Australian Over the last 70 years or so, many exceptional people have made great contributions to Australia and our way of life. One of those people was Gary Johnston, the owner of Jaycar Electronics and Electus Distribution, and a great friend of mine for over 50 years. So I feel privileged to have been asked by Nicholas Vinen to write this editorial. Gary was diagnosed and died of mesothelioma in March this year, at the age of 71. When I first met Gary, he was working for Philips. He was friendly and outgoing, a keen sportsman and very interested in all aspects of electronics, but otherwise just another young bloke aspiring to the good life. A few years later, he joined Dick Smith and quickly became a key man in what was to become the most dynamic retailer in Australia in the 70s and 80s: Dick Smith Electronics. Then in 1981, just as Dick Smith Electronics was being sold to Woolworths, Gary made a great leap into the unknown; he bought a very small shop in Sussex Street, Sydney: John Carr & Co. Gary quickly changed this to Jaycar Electronics and immediately began applying everything he had learnt while at Dick Smith Electronics. He worked very closely with me at Electronics Australia magazine and was the instigator of quite a few innovative electronics projects. But despite working very hard at his business, he did not have an easy run and encountered difficulties early on. He eventually surmounted those and after a few years, he was going very well. Before we started Silicon Chip magazine in 1987, Gary was one of the key people I approached for advertising support, along with Dick Smith Electronics and Jack O’Donnell of Altronics in Perth. Without their support, Silicon Chip would never have seen the light of day. Jaycar and Altronics have remained as key supporters of Silicon Chip to this day. As well as advertising, Gary took a keen interest in the magazine’s content and we often cooperated closely in the development of new projects and sourcing of hard to get components, which Jaycar then supported by producing the kits; a vital aspect for readers who wanted to build them. Also, Gary was often instrumental in enabling us to produce some interesting feature articles. These would not have been possible without him providing introductions to people in organisations that would otherwise have been inaccessible to us. While all this was going on, in the late 80s, Gary found the time to take a Master of Letters degree, majoring in American Literature, at the University of New England, in Armidale NSW. That gives an insight into his keen intellect; his interests were very wide-ranging. While Gary was most important to Silicon Chip, his influence spread right across Australia and he contributed to the personal development of thousands of young people as well as employing over 1300 people in Jaycar and Road Tech Marine stores in Australia. The overwhelming success of Jaycar enabled Gary to do his greatest work, becoming a very generous benefactor to many diverse organisations around Australia. Perhaps the most well known would be his endowment of a Chair in Water Management at the University of New South Wales. Apart from that, most of his work as a benefactor has gone largely unheralded. That would be in keeping with his philosophy; try to do good without seeking the limelight. He was a generous and good friend. I miss him so much. Guest Editorial by Leo Simpson 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Australia’s electronics magazine siliconchip.com.au siliconchip.com.au Australia’s electronics magazine May 2021  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”. Grateful for donated test equipment A few months ago, I sent you an e-mail about a BWD instrument I wanted to repair, and expressed interest in buying other BWD products. Thank you for publishing this for me. I have been given two oscilloscopes by your readers, for which I am very grateful. When I am too old, I plan to give my collection to Wireless Hill Museum here in Perth. So thank you for all you have done for me. Trevor Collins, Bellevue, WA. Giving away console radios & chassis As a keen reader of your fine publication, I have been engaged in electronics for the last 60 years. I have repaired and restored many valve sets and military equipment. As a result, a lot of ‘to do’ items have heaped up. With advancing age and deteriorating eyesight, things have come to a halt. Having lost colour perception and fearing high voltages, I have decided to call it quits. I have about two cubic metres of console radios and chassis. This includes a Tasma, a Stromberg-Carlson, an unusual Sanyo, Radiola and other chassis for fixing or pillaging. I would like the whole lot to go to a keen restorer. Should any of your readers be interested, contact me by e-mail to discuss details. Most of this gear is untouched. W. Schaaij, Broken Hill, NSW. pimschaaij<at>gmail.com in the April issue identifying the Test Master was good feedback. I am prompted to see if your readers can identify another piece of test equipment. I was given a Transistor Test Set (see photo below) which has no identification as to its source. It also has laced cabling, so it might also be a Telecom training exercise. Does the name ACE on the meter face have any significance? Probably not. The test set has a professionally-made front panel, but the squarecased meter seems to be a substitute for what could have been a circular-cased original. Also, the ADJ.Vgs knob appears to be from an AWA radio, not original. In David’s article, he also mentions that 10% of NOS (new old stock) KT88s are gassy. There is a trick worth trying with KT88s (and KT66s) that test gassy; let them run for 24 hours with only 6.3V heater voltage applied. This can sometimes restore them to a usable state. Many years ago, I designed test amplifiers using KT66s for AWA’s loudspeaker factory test rooms. After the annual factory Christmas holiday shutdown, when switched on for the first morning, the fuses would blow; gassy valves! I eliminated this by running the amplifiers with the rectifier valve removed the day before the factory resumed production in subsequent years. That warmed the valves without HT applied and drove out the gas, solving the problem. Mind you, that was only after a few weeks, not many years. Also in the March issue, in your “All About Capacitors” article (page 75), I believe I have spotted the first use in Silicon Chip of the correct SI prefix for high-value electrolytic capacitors; 68mF, not 68,000µF! Why do all manufacturers persist with non-SI designations? I still remember the days when a 1nF capacitor was designated either 1,000pF, 1,000µµF or .001µF. At least they have got that right! Ross Stell, Kogarah, NSW. Comment: many hoarders refuse to admit as much; kudos to you for doing so! The main reason we do not use Letter from an admitted hoarder Dr David Maddison’s article, “Hoarding: Urban Electronic Archaeology” was very interesting (March 2021; siliconchip.com.au/Article/14773). It appealed to me because I too am a hoarder. The response from two former Telecom apprentices in Mailbag 4 Silicon Chip Australia’s electronics magazine siliconchip.com.au GME Australia mF very often is that many people incorrectly use mF when they mean µF, leading to confusion; possibly this is because they do not know how to generate a µ symbol. GME (www.gme.net.au) is a privately owned company that designs, develops, manufactures and distributes worldclass radio communication equipment right here in Australia. We are proud to be Australia’s only manufacturer of UHF CB radios, with our state-of-the-art engineering and manufacturing facility in Western Sydney. Geekcreit LCR-T4 and germanium transistors Hiring Senior RF and Firmware Engineers And we are Hiring! We are always on the lookout for Senior RF and Firmware Engineers. Our Senior RF Engineers: → Develop RF circuitry, create specifications, select components, design schematics, and layout PCBs → Evaluate and test designs against specifications and for industry standards compliance (we have a selection of environmental test chambers, 3D printers and more!) → Ensuring compliance with all communication legislation and liaise with certification test houses → Preparing assembly and test documentation for the production team Our Senior Firmware Engineers: → Develop real-time code, digital signal processing, user interfaces, and communication protocols; all on modern 32-bit microcontrollers → Testing designs against specifications and for compliance with industry standards and user requirements It would be a big plus if you have any of the experience above, or are currently working in the Defence Industry. We have recently started designing for the Defence Industry and are seeking to complement our workforce with Engineers who are skilled in military communications design. We’d love to hear from you if you’re interested in either or both of these roles and especially if you have a keen interest in all things radios (we know you’re out there!) Please email your resume to: HR<at>gme.net.au Or call us on (02) 8867 6029 17 Gibbon Road WINSTON HILLS NSW 2153 6 Silicon Chip I have a version of the LCR-T4 Mini Digital Multi Tester that you reviewed (February 2021; siliconchip.com.au/ Article/14755) and, as you say, it tests many devices quite well. While not a problem for most people, my unit fails with germanium transistors, though. James Greig, Spring Gully, Vic. Comment: you are right; it does not handle germanium devices well. That is likely because their base-emitter conduction voltages are considerably lower than silicon types, and below its detection or operating threshold. Capacitors article was informative I’m just writing a short note to say how much I appreciated the piece by Nicholas Vinen titled “All About Capacitors” (March 2021; siliconchip. com.au/Article/14786). With no formal training in electronics, I have always fallen back on my high school physics description of two metal plates separated by an insulator. I don’t think I will even look at another capacitor the same again. From now on, I shall ask myself “what would Nicholas say about that capacitor in that application?” Keep turning out the great magazine. I don’t build too many of the circuits anymore but enjoy reading about them and the other various articles each month. Cliff King, Oxley, Qld. Tantalum capacitors prone to failure Thanks for the informative article on capacitors in the March 2021 issue (siliconchip.com.au/Article/14786). I have a few comments regarding tantalum electrolytic types. I had a recent failure (smokey explosion) inside a piece of commercial test equipment which involved 10μF 16V miniature bead-type tantalum capacitors. I had never had a problem with these before, and assumed them to be safe and reliable. But then I ran a web search for “tantalum capacitor failures”. Australia’s electronics magazine It appears that these devices can have a catastrophic thermal runaway condition leading to destruction and damage to nearby components if there is sufficient power supply energy. Otherwise, they fail short-circuit. This often occurs a short time after the equipment is turned on. The consensus for use appears to be that they should never be allowed to receive even a momentary reverse polarity voltage; should not be connected directly across a low impedance/high current voltage rails; should always have some series resistance to limit current flow in the event of failure; be operated at no more than 50-60% of their rated voltage; and must not be overheated when soldering. In my case, one capacitor was across the 15V supply and self-destructed with noise, light and smoke. The second capacitor was connected as a transistor collector bypass and fed from the 15V rail via a 10W resistor – it had gone short-circuit and toasted the 10W resistor. Ashley Smith, Flagstaff Hill, SA. Comment: We have also found that older style tantalum capacitors are not reliable long-term. Modern types are used extensively in computer equipment and do not appear to be a significant source of failures, although that might change as they age. If your list of restrictions were accurate, that would make tantalum capacitors pretty much useless. The main reason to use them is their low ESR value; hence, they are suitable for high-frequency bulk bypassing, where regular electrolytics are not. We normally use multi-layer ceramic capacitors instead, as they are superior in virtually every way. Only in a few specific cases are tantalum capacitors worthwhile, and in those cases, you usually need to use the expensive solid types to make using them worthwhile. March issue enjoyed S ilicon C hip March 2021 is a ‘bumper issue’! Super! Regarding the History of Videotape (siliconchip.com. au/Series/359), I learned my TV Studio engineering in Germany, with an RCA TRT-1, full of valves. “Statistically, one is dead all the time”, commented our instructor. I even mastered the art of editing (physically cutting) tapes by hand; it often worked. siliconchip.com.au Ready for Tomorrow We are constantly investing in our services and product range to make sure you are ready for tomorrow! A global electronics distributor that provides you with x x x x Local support Dedicated account management Quotes on volume requirements Not in catalogue sourcing x x x Contract Pricing Flexible scheduled ordering Exclusive buffer stock arrangements Contact us now Phone: 1300 361 005 Sales: au-sales<at>element14.com Quotes: au-quotes<at>element14.com au.element14.com/ready4tomorrow Helping to put you in Control PID Temperature Controller 230VAC powered N1030-PR Compact sized PID Temperature Controller with auto tuning PID 230 VAC powered. Input accepts thermocouples J, K, T, E and Pt100 sensors. Pulse and Relay outputs. SKU: NOC-320 Price: $81.00 ea Digital 4-20mA Generator EPM-3790-N can be used as a Control Panel For VFD Speed Controller. It has a 4-20mA output and a direction output which can be set by the front panel keypad. SKU: EEI-401 Price: $129.95 ea Digital Voltmeter Round Waterproof 3 Digit Red LED Round Voltmeter measures 5 to 48VDC. SKU: HEI-001 Price: $11.95 ea RS-232/422/485(TB) Modbus Gateway Modbus TCP to Modbus ASCII/RTU converter allows Modbus TCP masters to communicate with serial Modbus slave devices. Is fitted with Terminal block not D9 connector. SKU: ATO-159 Price: $269.95 ea Isolated Load Cell 2mv/V 0-10V Transmitter with Display Converts a signal for a 2 mV/V load cell to a 0 to 10 V signal. Able to power 2 load cells in parallel. DIN-rail mount. SKU: ALT-415 Price: $249.95 ea LabJack T7 Data Acquisition Module LABJACK T7 Multifunction DAQ with Ethernet, wifi and USB. Features 14 analogue inputs, 2 analogue outputs and 23 digital I/O SKU: LAJ-045 Price: $739.30 ea Ultrasonic Wind Speed & Direction Sensor RK120-07-AAC Economical Ultrasonic Wind Speed & Direction Sensor with Modbus RTU RS485 output and 4 metre cable. 12~24VDC powered. SKU: RKS-028M Price: $499.95 ea For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Silicon Chip More details wanted on digital radio modes Thanks for the article on Digital Radio Modes in the April 2021 issue (siliconchip.com.au/Series/360). By the way, the correct spelling is Hellschreiber, not Hellshrieber. Despite that mistake, I found the article interesting. Perhaps you could also expand on HF radio data modes such as PACTOR and the more recent VARA (which works amazingly well with a PC soundcard). These modes offer quite high data rates on voice bandwidth radio channels. Horst Leykam, Dee Why, NSW. Comment: as you will see in part two this month, we mention PACTOR but not VARA. There are so many different encoding schemes that it is difficult to cover them all. Multi-amplifier module wanted Prices are subjected to change without notice. 8 Then the Bosch-Fernseh Quadruplex came along. It looked like a rebadged Ampex VR-1000A. The article explains things so well; I wish I had it 50 years ago! I’m looking forward to the follow-up parts. Then the Urban Electronic Archeology article by Dr David Maddison (siliconchip.com.au/Article/14773) reminds me of my outback electronic garage... And last but not least, Nicholas’ article about capacitors (all about – really!). That article must have taken years of research; a masterpiece (siliconchip.com.au/ Article/14786). I have several Sony shortwave radios, very nice ones at the time, but most of them died because of capacitor demise. The story goes that these radios (made in Japan) were made with capacitors from a container full of secondclass devices. It’s challenging to find the culprits, as desoldering the suspect caps is required. Strangely, other Sony gear (amplifiers, Betamax VCRs etc) didn’t suffer, only the radios – pity! My local radio repair shop refuses to repair those radios, but gave me an interesting hint. There is test gear (in kit form) that allows capacitors to be measured in-situ, without desoldering. How is that possible? Anyway, thanks for the great magazine. Hans Schaefer, Armidale, NSW. Comment: we’re glad you enjoyed that issue. The Videotape Recording series consists of four parts in total. Yes, in-circuit capacitor testers exist. They can be affected to some extent by other components in the circuit, but usually will give you good enough results to know if a capacitor has failed or not. We have reviewed some in the past, eg, the EDS-88A in our May 2013 issue (siliconchip. com.au/Article/3782). We aren’t sure if that device is still available, though. As for faulty capacitors, your story reminds us of the “capacitor plague”, which greatly affected computer motherboards and related gear in the early 2000s. We had an article on the subject in the May 2003 issue (siliconchip. com.au/Article/6644), or you can read more about it at https://w.wiki/39AD I sent you a question recently about the possibility of installing your SC200 amplifier modules (January & February 2017; siliconchip.com.au/Series/308) in place of Australia’s electronics magazine siliconchip.com.au the ETI series 5000 modules that blew up in my old amp. I’ve since been pondering changing my system over to an active crossover type, and was looking at your active crossover design from 2003. But building six separate power amplifier modules is a bit daunting, so I started looking around for a three amplifier mono module designed for active crossovers. I haven’t been able to find anything suitable. What I would like is a quality (stereo) amplifier like the SC200 for bass, a 50W or so for mid-range and perhaps a 20W amplifier for the tweeters, all on one board with a sub-board having the active crossover. The options that a multi amplifier/crossover like this would give to the DIY speaker builders worldwide would be enormous as the ‘black art’ of crossover design is eliminated. I know this can all be done with modules, but I’m not sure whether the lower power amp modules are of the same quality as the SC200, and I’m also not sure whether many would know how to lay out all the modules to minimise noise etc. Tony Brazzale, Bumberrah, Vic. Comments: low-power amplifiers aren’t much simpler to design or build than high-power amplifiers as they still need pretty much all the same ‘front end’ components. You could build SC200 modules but leave one pair of output devices off (and some of the associated components like the emitter resistors) to save a bit of time and money. Also, keep in mind that if you are building a system with a mix of low-power and high-power amplifier modules, you will probably need several different supply rails to achieve good efficiency. For example, ±57V or so for the 200W modules, and maybe around ±35V for lower power (50W) modules. That complicates the power supply and wiring. Another reason you wouldn’t want to run the low-power modules from the higher voltage rails is safety. If a lowimpedance load is connected (like a 4W speaker, or one with severe dips in its impedance curve), the current is no longer being spread between multiple output devices, leading to an increased chance of failure. Running those amps from lower voltage rails reduces the maximum current drawn. Another electricity saver scam I have just seen this advertisement for a “power saving” device called the Voltex. It is unbelievable. It’s even worse than electronic rust prevention. See https://getvoltex.com/ article4/au Bruce Pierson, Dundathu, Qld. Comment: it’s frustrating that this sort of scam is still around (see our previous debunkings of these devices, eg, in the November 2007 issue). There are only three ways to reduce what you pay for electricity: get a better rate, reduce your usage, or steal electricity. It is possible to reduce your usage by increasing efficiency (eg, getting a better-sealed fridge), but a box that plugs into the wall isn’t going to do that. They claim a 95% reduction in your electricity bill is possible, making the stealing electricity option the only viable answer as to how they achieve it... SC 10 Silicon Chip Australia’s electronics magazine siliconchip.com.au Our capabilities CNC Machining UV Colour Printing Enclosure Customisation Cable Assembly *** Box Build *** System Assembly Ampec Technologies Pty Ltd Australia’s electronics magazine siliconchip.com.au Tel: (02) 8741 5000 Email: sales<at>ampec.com.au Web: www.ampec.com.au FEBRUARY 2021 37 Digital Radio Modes In part one last month we looked at many of the varied types of digital radio in use today. But we couldn’t fit all of them in . . . so here we’ll continue our discussion of some more digital radio     Part Two . . . modes, including those used by and/or by Dr David Maddison available to radio amateurs. vi) Amateur radio digital modes 1) FreeDV for radio amateurs FreeDV (https://freedv.org/) is an amateur digital mode for HF (shortwave frequencies). It uses either a computer and soundcard for encoding/decoding or a dedicated device, and is shown in Fig.17. Many other digital modes, even though they have open-source software, use proprietary codecs. But FreeDV uses an open-source codec. It uses neural net speech coding called LPCNet (www.rowetel.com/?p=6639) Fig.17 (right): a screengrab of FreeDV in operation. Image courtesy Mark, VK5QI 12 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.18: an image received via FSQ. and is called Codec 2 (www.rowetel. com/?page_id=452). This enables a very low data rate transmission of voice, eg, using just 1.1kHz bandwidth. The modern implementation of Codec 2 was developed by Australian Ham Dr David Rowe VK5DGR and others. See the video titled “David Rowe interviewed about Codec2” at https://youtu.be/ Nzf4XCCwHoI 2) FSQ Fast Simple QSO (where QSO means contact in the radio Q Code) is a relatively new digital mode for amateur radio, released in 2015. It is like a chat program with each side typing messages to which the other responds, and it also supports the transfer of images (see Fig.18). It can be used on HF (shortwave) and has been adapted for VHF, using FM in both cases. Each party can transmit to the other at a different speed. There are agreed-on, dedicated frequencies for its use. FSQ uses an efficient alphabet coding whereby most common characters can be sent with just one symbol, or at most, two for less common characters – see Fig.19. A symbol is a pulse or tone in digital transmission systems, representing an item of information. It could be 0 or 1 in the simplest schemes (ie, binary coding), but more advanced siliconchip.com.au schemes use many more states. The typing rate can be as high as 60 words per minute (wpm) using 290Hz Symbol(s) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Char SPACE a b c d e f g h i j k l m n o p q r s t u v w x y z . CRLF Symbol(s) 0–29 1–29 2–29 3–29 4–29 5–29 6–29 7–29 8–29 9–29 10–29 11–29 12–29 13–29 14–29 15–29 16–29 17–29 18–29 19–29 20–29 21–29 22–29 23–29 24–29 25–29 26–29 27–29 28–29 Char <at> A B C D E F G H I J K L M N O P Q R S T U V W X Y Z , ? of bandwidth at 5.86 baud. This is the same typing rate as RTTY with only about 1/8th the baud rate, since RTTY uses just one bit per symbol, so a character needs 7.5 symbols, plus it uses additional data for synchronisation. Additional advantages of FSQ are: • no synchronisation is required between the two stations, making it more resistant to propagation delays, noise and avoiding time wasted synchronising • each party can transmit at their own speed of 2, 3, 4.5 or 6 baud, corresponding to around 20-60wpm; 4.5 baud being the most common rate used • messages can be sent to one station or a number at the same time. Pictures can be transmitted using an analog format with similar bandwidth, using Near Vertical Incidence Skywave (NVIS) for less noise (a technique where the radio transmission is bounced off the ionosphere with a near-vertical angle for transmission ranges up to 650km). A 320 x 240 pixel colour image would take just over three minutes. FSQ uses incremental frequencyshift keying (IFK+), a type of frequencyshift keying (FSK) which confers Symbol(s) 0–30 1–30 2–30 3–30 4–30 5–30 6–30 7–30 8–30 9–30 10–30 11–30 12–30 13–30 14–30 15–30 16–30 17–30 18–30 19–30 20–30 21–30 22–30 23–30 24–30 25–30 26–30 27–30 28–30 Char ~ 1 2 3 4 5 6 7 8 9 0 ! quote # $ % & ( ) * + − / : ; < > IDLE Symbol(s) 0–31 1–31 2–31 3–31 4–31 5–31 6–31 7–31 8–31 9–31 10–31 11–31 12–31 13–31 14–31 15–31 16–31 17–31 18–31 19–31 20–31 21–31 22–31 23–31 24–31 25–31 26–31 27–31 28–31 Char = [ \ ] ^ { } ` ± ÷ ° × £ BS DEL Fig.19: the FSQ symbol table. It is a type of “varicode”, where more common letters use one symbol and the less common ones use two. Australia’s electronics magazine May 2021  13 Fig.20 (left): a representation of FSK modulation showing an unmodulated carrier wave in the centre, the data to be transmitted at top and how that data is modulated onto the carrier wave at the bottom. Source: Wikimedia user Ktims. Fig.21 (above): phase-shift keying (PSK), where the change in carrier signal phase encodes data. resistance to multipath propagation errors and frequency drift. IFK was invented by an Australian, Steve Olney (VK2XV/VK2ZTO) and is implemented in several other digital modes such as JASON, DominoEX, Thor and Throb. For more details of that transmission scheme, see siliconchip.com.au/ link/ab6m 3) ASK (amplitude shift keying) represents data by variations in the carrier wave’s amplitude. OPERA is an example of a beacon system that operates with this modulation. 4) FSK (frequency-shift keying) is a modulation scheme whereby information is transmitted via frequency changes in the radio carrier wave (see Fig.20). FSKH105 is an example, while MSK144 is a variation of FSK designed for communication via meteor scatter. FST4 and FST4W are new digital modes that use Gaussian FSK. 5) MFSK (multiple frequency shift keying) and GFSK (Gaussian FSK) are variations of FSK. MFSK8 and MFSK16 are radio ham variations of FSK, designed explicitly for keyboard conversations via HF long-path DX (distant reception), and were the first amateur digital modes, introduced in 1999. Other MFSK modes are Olivia, Contestia, JT65, FSK441, JT6M, WSPR, FT4, JS8, FT8, FSQ, THROB, WSQ, WSQ2, Q65. MEPT_JT is a mode intended for propagation testing, not keyboard conversations. 6) IFK and IFK+ (incremental FSK) are variants of MFSK. DominoEX and 14 Silicon Chip Thor use this modulation scheme. EXChat is a variation of DominoEX. 7) PSK (phase-shift keying) is a modulation scheme in which the phase of a carrier wave is changed to convey information – see Fig.21. Examples include PSK31, PSK63, MT63, 2-PSK, 4-PSK and Q15X25. 8) ROS is an amateur radioteletype mode. According to www.sigidwiki. com/wiki/ROS it uses a “combination of FHSS (Frequency Hopping Spread Spectrum), DSSS (Direct Sequence Spread Spectrum) and 2G (Second Generation) CDMA (Code Division Multiple Access)”. RSID (Reed-Solomon identification) is a method to identify digital modes; see www.w1hkj.com/RSID_ description.html There is a demonstration of the JS8 mode by prominent Australian radio amateur in the video “JS8: My first contact” at https://youtu.be/ZAfb3x3b8xc vii) Non-amateur digital modes and shortwave applications 1) SailMail (https://sailmail.com/) is a non-profit association of yacht owners to enable them to send emails beyond line-of-sight. According to the website, email can be transferred via any form of internet access such as “Iridium, Inmarsat, VSAT, Globalstar, Thuraya, terrestrial WiFi, terrestrial cellular networks, or via SailMail’s own worldwide network of SSB-Pactor radio stations”. It is based on the Winlink software described later. Australia’s electronics magazine 2) PACTOR is a radio modulation mode used by amateurs, commercial, government and military operators alike. It is based on AMTOR and packet radio. AMTOR (amateur teleprinting over radio) is known commercially as SITOR (simplex teleprinting over radio). 3) CLOVER refers to a series of commercial radio modem modulation techniques used in HAL Communications Corp products. viii) Weak-signal modes WSJT (https://physics.princeton. edu/pulsar/k1jt/) and related programs are open-source software designed for weak-signal digital modes. WSJT supports the weak-signal modes of JTMS, FSK441, FSK315, ISCAT, JT6M, JT65, and JT4. WSJT-X (Fig.22) supports FT4, FT8, JT4, JT9, JT65, QRA64, ISCAT, MSK144, and WSPR, as well as one called Echo, designed for receiving your own signal via moon bounce propagation. See also the related section below on beacons and WSPRnet. ix) Beacons and reverse beacons Beacons and reverse beacons help radio operators, including hams, to assess radio propagation conditions on particular bands and between specific locations. Propagation conditions change because of changes in the ionosphere about 48km to 635km above the Earth, from which radio waves are reflected or refracted. These changes are due to time of day, season, weather and sunspot activity. siliconchip.com.au Fig.22: a screengrab of WSJT-X. Source: Amateur Radio Experimenters Group (AREG) in Adelaide (www.areg.org. au/wsjt-x). 1) The amateur NCDXF/IARU International Beacon Project (www.ncdxf. org/beacon/index.html) is a conventional beacon network – NCDXF is Northern California DX Foundation, and IARU is the International Amateur Radio Union. The beacon locations worldwide are shown in Fig.23, including VK6RBP in Perth (www. vk6uu.id.au/vk6rbp.html). Signals are sent out at various set times, frequencies and power levels and individual stations monitor them to determine propagation conditions between the beacon and themselves. In the aforementioned network, signals are sent out every three minutes at reducing power levels of 100W, then 10W, 1W and 0.1W and at different frequencies. You can listen to these beacons without a radio using the online receivers at http://ve3sun. com/KiwiSDR/ In a reverse beacon network such as WSPRnet, PSK Reporter or Reverse Beacon Network (RBN) (see below) a user listens for transmissions, just as in a conventional beacon network. But instead of the transaction finishing with a user just hearing the beacon, the RBN user then reports via the call sign, signal strength and other information back to a central database via the internet. Therefore, ‘openings’ on propagation conditions can be spotted. 2) WSPRnet (Weak Signal Propagation Reporter Network; http://wsprnet. org/drupal/), shown in Fig.24, is an RBN that only hears transmissions intended for WSPRnet ‘spotting’. It uses an extremely sensitive low-power digital mode called MEPT_JT (Manned Experimental Propagation Transmitter; JT are the inventor’s initials) to test propagation conditions and report to a database. The MEPT_JT protocol was developed in 2008 with the objective of creating a tool for ionospheric sounding that used very little power and bandwidth (6Hz), but with very high sensitivity. Each sounding station can send or receive signals, or both. It is used on LF, MF and HF frequency bands. MEPT_JT messages are tightlycoded to have as much information as possible, and contain forward error-correction and the signal. Current software can detect this at a -27dB signal-to-noise ratio in 2.4kHz of bandwidth. Like some other digital radio modes, such weak signals can be detected because of their extremely low bandwidth, with known timing of the data bits and error correction. Each message is 50 bits long and takes about two minutes to transmit. In addition to the message bits, there is a 162-bit pseudorandom noise sequence transmitted for synchronisation. The symbol rate is 1.466 baud (ie, the number of changed signal states per second) with two bits per symbol transmitted. It uses IFK modulation. For technical details of how the MEPT_JT mode works, see siliconchip. com.au/link/ab6o You don’t have to be a radio ham to become a WSPR listener and reporter, but you do have to be one to transmit signals. 3) PSK Reporter (https://pskreporter.info/) is a service whereby radio amateurs run client software and monitor the bands for amateur radio digital voice modes. The results are automatically relayed to a central server (see Fig.25). Nothing is transmitted; the system just listens and logs CQ calls (requests for a conversation) and a previously Fig.23: the beacon locations for the International Beacon Project siliconchip.com.au Australia’s electronics magazine May 2021  15 Fig.24: WSPRnet propagation reports plotted according to frequency band over a 24-hour period. Current maps can be viewed at http://wsprnet.org/drupal/wsprnet/map or see http://wsprd.vk7jj.com/ registered participant call sign (with location) via digital modes. As no transmission is involved, you can participate in PSK Reporter without being a radio ham. Watch the video titled “PSK Reporter: How You Can Be Part! AD #33” at https://youtu.be/ HwlpnQb6E6k One difference between WSPRnet and PSK Reporter is that WSPRnet runs fully automatically, and you can check who heard you and whom you heard whenever you want; it requires no interaction from the user. With PSK Reporter, you monitor existing conversations (QSOs) between stations and have to tune them in and respond etc. The signals are not deliberately sent to obtain propagation reports as with WSPRnet. The amateur radio Reverse Beacon Network (www.reversebeacon.net) is a system of volunteers who monitor the amateur bands with broadband software-defined radios (SDRs) and report back to a sender via the internet where in the world they have heard that sender’s signal. They run software listening for CQs or TEST messages followed by a callsign on Morse, RTTY or PSK31. In contrast to PSK Reporter and WSPRnet, this system, when used with CW Skimmer software (Fig.27; www.dxatlas.com/ cwskimmer/) and SDRs can be used to report activity across multiple frequen- Fig.25: a map from PSK Reporter showing propagation conditions on various bands. 16 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.26: the WIRES-X scheme. C4FM is a proprietary Yaesu digital mode for amateur radio to transmit voice and data implemented on certain radio models (siliconchip.com.au/link/ab6w). cies and bands simultaneously, due to the wide bandwidth of SDRs. For more information, see the video titled “The Ham Radio Reverse Beacon Network, AD#32” at https://youtu. be/4Y5ZHqfeJgo x) Radio over the Internet Apart from the fact that most commercial radio stations stream live over the internet, various amateur radio projects involve linking some part of a radio transmission via the internet. 1) WIRES-X (Wide-coverage internet repeater enhancement system) is a Yaesu-developed standard (siliconchip.com.au/link/ab6p) to enable equipped radios to connect to internet gateways and establish connections with other users – see Fig.26. The radio’s connection to the gateway is made via a digital voice and data modulation mode called C4FM, which is backward-compatible with analog FM. Australia has several C4FM compatible repeaters; see http:// siliconchip.com.au/link/ab6q 2) The Free Radio Network (www. freeradionetwork.eu) enables radios to connect to an internet gateway, transmit via voice over IP (VoIP), then reconnect to another gateway and another radio somewhere else. 3) EchoLink (www.echolink.org) is a free system for radio amateurs that enables them to communicate with other hams throughout the world, by routing part of the connection over the internet using VoIP – see Figs.28 & 29. A connection can be made as long as the initiating radio and the receiving radio are in wireless range of an EchoLink node. The software is available for all popular platforms and smartphones. 4) IRLP (The Internet Relay Linking Project; www.irlp.net) routes amateur calls from radio to the internet, then back to radio again at any location worldwide where there is an IRLP gateway (a “node”). The node contains both a transceiver and a computer with an internet connection. Radio amateurs within range of the node contact the node and enter DTMF tones to indicate the remote node they Fig.27: a screengrab of CW Skimmer (www.dxatlas.com/cwskimmer/). This software listens for CW (Morse code) signals, extracts the call signs, logs and transmits them if necessary, for monitoring applications such as the Reverse Beacon Network. Fig.28: how EchoLink works. siliconchip.com.au Australia’s electronics magazine May 2021  17 siliconchip.com.au/link/ab6t xi) Internet over radio Fig.29: the EchoLink software. want to connect to. Voice is carried by a VoIP protocol. There are 49 IRLP nodes in Australia and thousands worldwide. 5) DMR (Digital Mobile Radio) is an international standard for commercial, personal and amateur communications, ratified in 2005. A list of Australian DMR repeaters is at siliconchip.com. au/link/ab6r 6) D-Star (https://3fs.net.au/dmr-inaustralia/) is the first digital radio system designed specifically for amateur radio (see Fig.30). It was developed in the late 1990s by the Japan Amateur Radio League. It can be used for voice and data and over the air or via internetconnected gateways. It is suitable for HF, VHF, UHF and microwave amateur bands. There is a list of Australian D-Star repeaters at siliconchip.com.au/link/ab6s 7) QsoNet virtual ionosphere (www. qsonet.com) is amateur radio without the radio. The system simulates the ionosphere, and licensed amateurs speak to each other via the internet with VoIP. The modes allowed are voice, CW (Morse code), PSK and FSK on five bands. It is a paid service with a 30-day free trial then US$39 per year. See Fig.31 and the video titled “CQ100 VOIP Ham Radio Transceiver” at https://youtu.be/ YagTAAI4Yq4 There are many aids to assist visually impaired or disabled people with conventional radio equipment. QsoNet can also help such people because they don’t have to get on roofs to install or maintain antennas etc. It is also used by people who have living circumstances that prohibit them from installing appropriate antennas, 18 Silicon Chip or where radio propagation conditions are poor. 8) HamSphere (http://hamsphere. com/) is a subscription service for radio amateurs and others to use a smartphone or PC to simulate radio ham communications over the internet, complete with simulated propagation conditions. See the video titled “HamSphere – How it looks and sounds in action” at https:// youtu.be/zJNWSmsXjEU 9) Remote amateur transceiver control. Due to a radio-poor location or the inability to set up satisfactory antennas, such as for apartment-dwellers, many radio amateurs are choosing to operate their transceivers remotely over the internet. For an Australian example, see The internet can be accessed over HF radio links, but generally at a relatively low speed. 1) Automatic Link Establishment (ALE) is a protocol for establishing digital links on HF. ALE establishes a connection for voice and data exchange. ALE uses automatic channel selection, scanning receivers, selective calling, handshaking, and robust modems to find the best available operating frequencies for a link. If internet connectivity is required, High-Frequency Internet Protocol (HFIP) can be employed. STANAG 5066 is an example of an HFIP standard. There is an amateur radio HFIP network called HFLINK (see http:// hflink.com). 2) Barrett Communications (siliconchip.com.au/link/ab6u) is an Australian company that offers a commercial email and data transfer over HF system, the 2020 HF Email fax and data system. 3) AMPRNet of The Amateur Packet Radio Network is used to transfer data between computer networks. A part of AMPRNet is the Europeanbased High-speed Amateur-radio Multimedia NETwork (HAMNET; https:// hamnet.eu/), covering 4000 nodes in central Europe. 4) HamWAN (http://hamwan.org/) is a multi-megabit, IP-based digital network for amateur radio use in the Fig.30: D-Star connectivity. Source: Dave VK3LDR. Australia’s electronics magazine siliconchip.com.au Silicon Chip Binders REAL VALUE AT $19.50 * PLUS P &P Fig.31: a virtual “CQ100” transceiver of QsoNet. United States. It is in western Washington state and expanding. 5) Winlink (www.winlink.org) is a volunteer-administered system to send emails worldwide via licensed radio amateurs – see Fig.32. It can operate on amateur HF and other bands, or if the internet is not available, through a mesh called Winlink Hybrid Network. See the two videos titled “What Is Winlink?” at https://youtu.be/ qGhUfW8pjY8 and “Email using Ham Radio! It’s FREE!” at https://youtu. be/1Gf1fJFfTok xii) Digital radio messages for ships and aircraft 1) NAVTEX or Navigational Telex is a digital radio mode for automated receive-only navigational messages and alerts for maritime operations. It is free and transmitted on 518KHz for international English service, and 490kHz in local languages (just below the AM broadcast band). There is also a Marine Safety Information broadcast on HF 4209.5kHz. It has a design range of 200 nautical miles (about 370km). If you are interested in receiving NAVTEX yourself with an SDR, see the video titled “Decoding NavTex with Software Defined Radio – SDRuno RSPdx” at https:// youtu.be/9b6w5Me6tpU 2) ACARS (Aircraft Communications Addressing and Reporting System) and AIS (Automatic Identification System) are for identifying and tracking aircraft and ships, using signals that are continuously transmitted. You can monitor these fairly easily with various decoding programs and with a regular receiver that can receive 129-137MHz, or an SDR. We published detailed articles on AIS and how to receive AIS transmissions in the August 2009 (siliconchip.com. au/Article/1528) and January 2010 (siliconchip.com.au/Article/41) issues. xiii) PICO balloons We first looked at PICO balloons in Are your copies of SILICON CHIP getting damaged or dog-eared just lying around in a cupboard or on a shelf? Can you quickly find a particular issue that you need to refer to? 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. H 80mm internal width H SILICON CHIP logo printed in gold-coloured lettering on spine & cover Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Fig.32: a screenshot of Winlink. Source: Denver Amateur Radio Emergency Service. siliconchip.com.au Australia’s electronics magazine Order online from www.siliconchip.com.au/Shop/4 or call (02) 9939 3295 and quote your credit card number. *See website for delivery prices. May 2021  19 Fig.33: this small balloon circumnavigated the world six times. Source: www.qrp-labs.com/images/circumnavigators/hirf6.jpg our February 2015 issue (siliconchip. com.au/Series/281), describing the work of Australian Andy Nguyen VK3YT. PICO balloons are Mylar party balloons like you would get from a party supply shop. Balloonists attach a tiny transmitter package to them weighing as little as 10.5 grams. Their location is tracked by GPS, and sensors measure temperature and pressure. This data is transmitted to and recorded by ground stations – see Fig.33. Power comes from batteries or supercapacitors which can be recharged by tiny solar panels. The transmissions are on VHF or UHF with a range of approximately 380km, or HF with a range of up to 16000km at just 25mW. How is such an incredible range achieved with such a tiny amount of power? PICO Balloons may use APRS (Automatic Packet Reporting System) with amateur radio digital modes such as Olivia or THOR on VHF or UHF, or on HF they may use JT9, JT65 or WSPR (Fig.34). The signals are received and uploaded to a tracking site, or propagation reports are sent to WSPRnet. For information on Australian PICO balloon releases, see siliconchip.com. au/link/ab6v and http://picospace.net/ You can track a variety of balloons worldwide at https://tracker.habhub. org/ equivalent to the time light or radio waves take to travel ~3000km. Signals might not just be delayed; they can suddenly appear to become advanced as a shorter signal path is established, so observing a static data bit being repetitively sent, it would seem to move back and forth with respect to any particular time reference. Any digital mode relying on ionospheric propagation, either through it such as with GPS satellites and other digital modes from satellites, or via reflection such as from one location on Earth to another, must be able to take account of and compensate for these significant timing differences. Even at the very slow speed of radioteletypes, which operated at 45bps, each bit took 22ms to transmit. So a delay of 10ms could introduce significant errors into the received data bits. With faster modern modes, the problem is far worse. These effects are apparent with the Hellschreiber, as shown by the distortion of the text, or can be heard if you listen to a shortwave radio station. xv) Mesh networks Mesh networks are a type of computer network architecture that is nonhierarchical, self-configuring and selforganising. The functions of routers, switches, bridges etc are performed within each device, or node, within the mesh (see Fig.35). As conditions change, such as a node being removed from the network, the mesh network can dynamically reconfigure itself using adaptive or dynamic routing technology to automatically choose the shortest and best route to send and receive data. It is said to be ‘self-healing’. Mesh networks have applications where a large number of similar devices need to be part of a network. Examples include: • smart electricity or other utility meters xiv) Ionospheric problems HF signals reflected from the ionosphere can have propagation delays and multiple paths due to changing conditions. Signal delays can be as much as 10ms and the signal can be Doppler shifted in frequency. 10ms is 20 Silicon Chip Fig.34: a commercially-available WSPR transmitter for a PICO balloon from ZachTek (www.zachtek.com/product-page/wspr-tx-pico-transmitter). It weighs 10.5g without an HF antenna and balloon harness, and can have an output power of 20mW on the 20m and 30m amateur bands. It is Arduino-based and uses open-source software. Some PICO balloon operators make their own. Australia’s electronics magazine siliconchip.com.au Fig.35: the architecture of a wireless mesh network with multiple types of devices connecting into it. Source: J. Rejina Parvin DOI: 10.5772/intechopen.83414. • environmental sensor networks • battlefield surveillance and soldierto-soldier communications (the technology was originally developed for the military) • tunnel surveillance • security surveillance cameras • mobile video such as sports/racing cameras • emergency services communications • home and commercial building monitoring and automation (eg, with ZigBee) • industrial monitoring and control • medical monitoring • connection of consumer electronic audiovisual equipment • automotive • broadband wireless connections within homes or commercial buildings • environmental monitoring • Iridium satellites • security systems The modulation schemes used in wireless mesh networks are the same as WiFi and governed by standards such as IEEE 802.11a through to 802.11ax, 802.11s and 802.21. xvi) LoRa and LoRaWAN LoRa and LoRaWAN (Long Range Wide Area Network) are fascinating relatively new digital radio transmission technologies offering the advantages of low cost, low power consumption and long range (see Fig.36 & Table1). They use a technology called Chirp Spread Spectrum in which a ‘chirp’ signal is transmitted over a broad bandwidth, making it resistant to noise and fading. siliconchip.com.au Fig.36: typical throughputs and ranges for some common digital wireless technologies. Higher throughput means a greater data bit rate, but also requires high powers to get good coverage. Greater ranges can be obtained with low power but also at a lower bit rate. Source: DOI: 10.1088/1755-1315/195/1/012066. A chirp signal is an FM sinewave signal that increases or decreases in frequency over time, often with a particular mathematical pattern (see Fig.37). There is always a trade-off in radio, so even though LoRa is long-range and lowpower, it also has a relatively low bit rate, so cannot be used for voice or video. LoRa is one of the core technologies of the Internet of Things (IoT) – see www.thethingsnetwork.org and SILICON CHIP, November 2016 (siliconchip. com.au/Article/10425). LoRa transmits on license-free radio bands. In Australia and North America, it uses 915MHz; in Europe, 868MHz; and in New Zealand, both. LoRaWAN is a form of LPWAN (Low-Power WideArea Network). LoRa’s features include: • standardised protocol • up to 50km range under ideal conditions • low-power operation • encryption • geolocation data available due to built-in GPS • low-cost • base stations have a high capacity for messages from connected devices It has numerous applications, such as: • monitoring agricultural or environmental sensors • • • • smart buildings and cities utility metering emergency service industrial control Its low cost enables the roll-out of devices in huge numbers. LoRa can achieve a data rate of up to 50kbps with channel aggregation, but for something like a sensor, it might just need to send a few bytes, such as its location and temperature. The modulation technique used is proprietary to the LoRa Alliance (https://lora-alliance.org/) and not open-source. LoRa devices can also be tracked without GPS using differential time-of-arrival (DTA) techniques. The current world record distance for LoRaWAN communication is 702km, but it is usually 2-3km in urban areas and 5-7km in rural areas. LoRa can also be used as part of a mesh network. See the video titled “#337 LoRa Mesh Communication without Infrastructure: The Meshtastic Project (ESP32, BLE, GPS)” at https:// youtu.be/TY6m6fS8bxU xvii) Off-grid communications Several communications systems are being developed based on fully self-contained mesh networks, and require no existing infrastructure. 802.11n (WiFi) 4G mobile LoRaWAN Throughput <300Mb/s 100Mb/s+ <1Mb/s Range 100-200m 2-10km 20km+ Battery life Days Days Years Table1: typical performance of WiFi, 4G and LoRaWAN devices. Australia’s electronics magazine May 2021  21 Fig.37: the frequency variation of a LoRa signal with time. Fc is the centre frequency and BW is the bandwidth. Source: DOI: 10.3390/s16091466. These include: 1) Locha Mesh (https://locha.io/), to transfer Bitcoin and Monero cryptocurrencies and chat without the internet. 2) Project OWL (www.project-owl. com), to establish off-grid networks with open-source software for a variety of purposes such as natural disasters, government for C4ISR (Command, Control, Communications, Computers, Intelligence, Surveillance, and Reconnaissance), mass networking at major public events such as sport, and industry to support large scale sensor networks. Project OWL uses the ClusterDuck Protocol (http://clusterduckprotocol. org/), which is open-source firmware for mesh network IoT devices based on LoRa radio. 3) Lantern Works (www.lantern. works) is another mesh-based disaster recovery network. 4) Disaster.radio (https://disaster. radio/), as the name implies, is an offgrid, self-contained communications network to provide communications during natural disasters when all other infrastructure may have failed – see the video titled “What is disaster.radio?” at https://youtu.be/uZkGudvjNzw It uses many low-cost, solar-powered nodes to create a mesh network. Each of these nodes acts as a WiFi access point that can be communicated with via smartphones. The smartphones do not need to be connected to any network, but they do need the disaster.radio App installed before the disaster. The network is based on free, open-source software and inexpensive open-source hardware. 5) The PT01 Power Talkie (www. ptalkie.com) is a walkie-talkie type device that lets you use your smartphone to send messages when no mobile connection exists. It operates by creating a mesh network with other uses. It operates at UHF frequencies of 462MHz (USA) and has a range of about 1.5km in urban areas and 5km in the country. See the video titled “PowerTalkie Mesh Network – Maintain Smartphone Communication Off Grid!” at https:// youtu.be/aPKKmzRbSp0 6) Meshtastic (www.meshtastic.org) is an open-source community project. The devices establish a mesh network to communicate. xviii) Off-grid Internet Othernet (https://othernet.is/) is a company that sells an inexpensive satellite receiver (shown in Fig.38). It can receive free broadcasts from its satellite of various internet-based digital content such as news, information, education materials, radio programs, emergency information, weather data, the entire contents of Wikipedia and any type of data file. It is also possible to make one yourself with an SDR. The data is broadcast only from its satellite, with no consumer uplink, so all the information on offer is contin- Fig.38: an Othernet satellite “Dreamcatcher 3.05” transceiver with a range of 85-6000MHz. It is suitable for various forms of communication apart from satellite reception of Othernet broadcasts. It is now obsolete and will be replaced with a device that can only receive on 2400MHz. If you are interested in Othernet, check there is satellite reception in your area. uously transmitted and downloaded into a data cache. Other devices can be connected to the receiving device by WiFi to access the information. See the video titled “Othernet Dreamcatcher: Free Internet content” at https://youtu. be/0F57ARpZFig xix) Other digital radio technologies 1) Digital mobile phones The latest digital mobile telephony technology was discussed in the article on 5G, in the September 2020 issue (siliconchip.com.au/Article/14572). 2) Timekeeping signals Digital radio signals are also broadcast in many countries for timekeeping services. See my article on that topic in the February 2020 issue (siliconchip. com.au/Article/14736). 3) Satellite navigation We discussed digital radio signals for satellite navigation in detail in the October 2020 (siliconchip.com. au/Article/14597), November 2019 (siliconchip.com.au/Article/12083) and September 2018 (siliconchip.com. au/Article/11222) issues. SC Online SDRs If you don’t have any receiving equipment, you can still listen to various online SDR radios. This one is in Melbourne at http:// sdr-amradioantennas.com:8073/ and there is a worldwide list of online SDRs at www.websdr.org Even if you do have receiving equipment, you won’t necessarily be able to hear distant signals, but you can connect to an SDR closer to your area of interest. 22 Silicon Chip Here is one in Araluen, NSW: http://tecsunkiwisdr.access. ly:8073/ There is also a list of a certain brand of online SDR hardware called KiwiSDR at http://kiwisdr.com/public/ KiwiSDR is a type of commercially-made receiver that you can place online to run a streaming SDR feed by connecting it to a tiny BeagleBone Black open hardware Linux PC (see https://beagleboard.org/black). Australia’s electronics magazine siliconchip.com.au “Setting the standard for Quality & Value” Established 1930 ’ CHOICE! THE INDUSTRY S Metal Working Sheet Metal Fabrication • • • • • 22 litre tank • 113L/hr, 240V pump • 398 x 298 x 210mm ID LE FLU FLEXIBZZLE NO 76 litre tank 180L/hr, 240V pump Safety fusible lid 700 x 480 x 250mm 88 HEAVY DUTY Order Code: A006 406mm seat height 3 x drawers with ball bearing slides 420 x 235mm padded seat 2 x magnetic side trays 360º swivel wheels 99 RR-5G Manual Section Rolling Machine • • • • 25 x 3mm flat bar cap. Ø5mm round bar cap. Hardened & knurled rolls Weighs 6kg 132 $ cs-55 - Circular Plunge & Mitre Cut Saw PACKAGE DEEAL BL • 160mm saw blade AVAILAW874) ( • 55mm cut depth <at> 90º E IN L ON • 45º tilt saw head • 1.2kW/1.6hp, 240V $ ALL & THIS E R MO & TORE IN S INE ONL CAMERON HD12 - Dust Collector 680cfm LPHV system Large collection area 3/4hp, 240V motor Includes 4 in 1 reducer & 2M hose Order Code: W886 ONLINE OR INSTORE! siliconchip.com.au T-13B Bench Mount Thicknesser 1/2", 3/4", 1", 1-1/2", 2" & 3" 370 x 290mm cast iron table Rotating & oscillating 450W / 240V motor • • • • 275 330 x 152mm capacity 2 x HSS blades Anti-kick back fingers 2hp, 240V motor 517 319 UB-100 Workshop Bar Bender Flat: 100 x 5mm Square: 16 x 16mm Round: Ø18mm dia. Includes additional bending plates $ VIPER™ 182 MKII Multi-Function Inverter Welder-MIG-MMA • 30 - 180 Amps • Inverter technology • 10% <at> 180A duty cycle • 240V / 10amp SUPER 16 Air Compressor • • • • S GASLES GAS / Order Code: W2441 $70 FREE 453l/min. W-triple pump 60 litre tank 120psi pressure 3hp, 240V motor Order Code: C342 675 1,210 $ www.machineryhouse.com.au/signup $ COMPETITIVE *DELIVERED Simple & Quick Online Freight Rate Check! FREIGHT RATES! TO YOUR DOOR *Remote areas may require depot collection in your town DISCOUNT VOUCHERS VIEW AND PURCHASE THESE ITEMS ONLINE AT NEW E RELEAS Order Code: W812 $ 363 SC0521 462 Order Code: W843 $ DES INCLU E TABL AT RM RUBBE $ OS-58 - Vertical Oscillating Bench Bobbin Sander • • • • 360kg load capacity 820 x 520mm table 240-775mm table height 2 fixed & 2 swivel wheels with brakes Order Code: J051 141.90 $ UNIQUE PROMO CODE • • • • $ Order Code: B043 Staff Member LT-360 - Hydraulic Lifter Trolley Order Code: W1004 126.50 • • • • 198 $ • Huge 100kg load capacity • 760 x 510mm table • 790~925mm table height • 2 x sturdy casters • Folds flat Order Code: D102 253 125mm jaw width 150mm max. opening Swivel head & base Includes anvil & pipe jaws Order Code: V075 WT-01 Welding Table - Fold-Up $ Order Code: W875 • • • • 165 • 11 piece set • M42 Bi-Metal high speed steel • 19, 22, 25, 32, 35, 38, 44, 51, 57, 64, 76mm • Includes 3/8" & 1/2" arbor shank & pilot drill 495 MPV-12 - Cast Iron Multi Purpose Bench Vice $ Metric HSS Hole Saw Set • • • • $ Order Code: V090 121 Order Code: S680 Order Code: A337 • 152mm jaw width • 190mm max. opening • Fitted width serrated jaws $ 450kg load capacity 360º geared rotating head Six swivel caster wheels Fold-up legs for storing P FOLD U LEGS No. 6 Cast Iron Bench Vice Order Code: A001 $ • • • • $ TCS-3 - Mobile Tool Storage Cabinet Seat • • • • • ESR-450 Engine Stand 352 176 Measuring Equipment Machine Tool Accessories Order Code: S289 $ MCW-47C - 2 in 1 Mechanics Creeper & Seat Combination Cutting Tools • Heavy-duty steel cabinet • 835 x 510 x 360-550mm blast area • Includes LED light, tempered glass screen, gloves, gun & ceramic nozzle Order Code: A368 $ Lifting Handling SB-200 - Workshop Sandblasting Cabinet ID LE FLU FLEXIBZZLE NO Order Code: A370 1200 x 450 x 130mm Fabricated steel frame Quick & easy conversion 150kg weight capacity 6 swivel wheels Workshop & Automotive APW-76 Auto Parts Washer APW-22 Auto Parts Washer • • • • • Wood Working Australia’s electronics magazine www.machineryhouse.com.au/SC0521 NSW (02) 9890 9111 QLD M (07) 3715 2200 2021  23 1/2 Windsor Rd, Northmead 625 Boundary Rd, Coopers Plains ay VIC (03) 9212 4422 4 Abbotts Rd, Dandenong WA (08) 9373 9999 11 Valentine Street Kewdale Specifications & Prices are subject to change without notification. All prices include GST and valid until 27-05-21 02_SC_290421 CNC Machinery Programmable Hybrid Lab Power Supply with by Richard Palmer This Lab Supply has inbuilt wireless control over WiFi or via a colour touchscreen and rotary encoder, with the ability for several supplies to be synchronised wirelessly. It is compact and inexpensive for its performance, delivering 0-27V, with 0-5A up to 18V and slightly lower currents above that. It has current limiting and voltage/current monitoring, soft-starting, and its final regulation stage is linear for a well-controlled and smooth DC output. T his design avoids bulky power transformers and substantial heat generation by using a switchmode AC/DC converter and switchmode pre-regulator. The final regulation stage is linear for improved line and load regulation, plus lower ripple and noise. With its modest heat generation, the Supply fits into a compact plastic 24 Silicon Chip instrument case, and the whole unit weighs just 1.5kg – less than the power transformer in a conventional design. The Supply is programmable, making it very useful as part of a suite of lab instruments. For example, you could use it for automated testing. Its WiFi interface enables remote monitoring via a web interface, and remote control using the industry-standard SCPI Australia’s electronics magazine (Standard Commands for Programmable Instruments) protocol. Voltage and current are set in increments of 10mV and 10mA, and voltage is controlled to millivolt accuracy. Settings are stored in the unit’s onboard flash memory for retention between sessions. Current limiting, short-circuit and thermal protection are software-controlled. siliconchip.com.au Safe operating area constraints for the output devices are enforced by software, providing an extra layer of protection against overtaxing the Supply, in addition to the inbuilt protections of the three regulators. Fig.1 provides an overview of how the Lab Supply works. It is based on three modules: the control module at top, the regulator module at bottom, and a commercially-made switching AC-to-DC converter which provides the DC supply to run all the circuitry. The control module is powered from lower voltage supply rails that are derived within the regulator module. More features Traditionally, lab supplies ‘crash start’ when the output is connected via a switch or relay, unlike the behaviour of most inbuilt power supplies, where the voltage builds over tens of milliseconds. This lab supply has a soft start feature which raises the voltage from zero to the set value at a rate of 100V per second when the output is switched on. The remote control includes adjusting output voltage and maximum current via WiFi (TCP) and isolated USB. It can readily execute scripted sequences such as step voltage changes and ramps. For example, you can write SCPI scripts in EEZ Studio (a free download from https://github.com/eez-open/ studio) to set the output voltage alternately to two different values, to test a device’s load regulation or response to a step-change in its input voltage. Direct-connected USB serial communication is not recommended once the instrument is commissioned. The local USB ground is directly connected to the power supply’s negative terminal, which is usually floating. Therefore, connecting the output negative terminal to a voltage source could damage your computer. It’s much safer to use WiFi control or a USB isolator. Rather than connecting the instrument to an existing WiFi LAN, you can also configure it to provide its own password-protected network with the SSID ESPINST. When powered on, the Supply first tries to connect to an existing WiFi network if credentials have been previously provided via the on-screen menu. If this does not succeed, it tries to connect to an existing ESPINST WiFi network. If this fails, it sets up siliconchip.com.au Features & specifications • • • • • • • • • • • • • • Hybrid bench supply with SMPS pre-regulation and final linear regulator Remote monitoring and control via WiFi Compact, lightweight and low heat dissipation Multiple units can coordinate for flexible stacking and tracking options High-efficiency design with low ripple and noise at the output Delivers up to 24V <at> 0-3.5A, 0-18V <at> 0-5A. Setting resolution: 10mV and 10mA Coarse and fine adjustment of output voltage and current Control resolution better than 1mV and 1mA Current limiting, over-voltage and over-current protection Excellent line and load regulation and good transient response with no overshoot Soft-start when output is switched on, avoiding ‘crash’ starts HTTP, telnet (TCP) and isolated USB serial control supported using universal SCPI commands Universal AC input (100-240V AC, 50-60Hz) the ESPINST WiFi network itself. Where an existing WiFi network is used, the Supply can be accessed by its IP address or by instrument_name. local (defaulting to MYPSU.local) using the mDNS protocol. The instrument provides a web page which displays the settings and measured values, along with a ‘big red button’ to turn off the output remotely. No other controls are provided on the web page, as it not secured. Several programmable supplies may be set up as a group, communicating over WiFi, making it possible to provide the normal functions of tracking supplies, ie, linked voltage settings and synchronised current limiting without needing a host computer. As each Supply is fully floating, they may also be stacked in series to provide higher output voltages, or paralleled for higher current. While limited space precludes a full run-down on all the instrument’s features and how to use them, full Fig.1: the Lab Supply is built from three modules: an AC-DC mains supply, a hybrid switchmode/linear regulator and measurement module, and a WiFi control board based on a prebuilt ESP-32 microcontroller module and a colour touchscreen. Australia’s electronics magazine May 2021  25 Scope1: there is no detectable mains ripple in the output. A small amount (35mV RMS) of switching noise is present, predominantly synchronised with the pre-regulator’s switching. descriptions are contained in the manual provided as part of the downloads for this project at siliconchip.com.au/ link/ab72 Operational overview The output voltage and maximum current can be set via the touchscreen, using a combination of right-hand touch screen buttons (V & A) that select the setting to be altered, two momentary switches selecting which digit is being changed, and a rotary encoder to change the actual value. This provides a smooth transition from coarse to fine control. Current-limiting can be enabled with an on-screen button (L), as can tracking functions (T) when more than one lab supply is available. The actual output voltage, current and power are displayed on the left side of the main screen. Along the top edge of the screen, the input voltage, heatsink temperature, fan and WiFi status are also shown along with an [E] (for EEPROM) indicator that shows when a flash memory parameter save is pending. There is a 30-40 second delay on saving to flash memory after the last setting was changed, as the memory has a guaranteed lifetime of fewer than 100,000 erase/write cycles. Sub-menus for setting communication parameters (COM) calibration functions (CAL) and tracking (TRA) are accessed via the buttons arranged across the bottom of the screen. Once the Supply is commissioned, the submenus will rarely need to be accessed. 26 Silicon Chip Scope2: under a full 5A load, the ripple at the 260kHz switching frequency is more pronounced, but still less than 100mV peak-to-peak (orange trace). The yellow trace is before the output toroidal inductor, to indicate the effectiveness of even a few turns in reducing spikes. Two dedicated momentary switches at the panel’s left-hand side turn the output relay on and off. These control panel switches are hard-wired to the power supply board, to ensure that the output can be disconnected even in the unlikely event of the CPU going on vacation. The supply output is floating, so a third GND terminal is provided for situations where mains Earthing is required. Performance The AC-to-DC conversion is handled by a commercial switchmode unit rated at 24V, 4.5A (nominally 108W). But as long as we don’t exceed the overall power envelope, we can sneak a little more current at lower voltages and a little more voltage at the top end. With the trimmer on the converter at full rotation, the prototype’s AC-DC supply provides just under 30V. At light to moderate loads, the pre-regulator and final regulator each have dropout voltages of under 2V, bringing the theoretical maximum output voltage to 27V from the 30V Supply. As the load increases and current booster transistor pair Q1/Q2 begins to conduct (described in more detail below), the voltage drop rises to limit the maximum output voltage to just under 24V at full power. This characteristic compares favourably with the voltage sag experienced under heavy load with transformer-based designs. Several factors constrain the Supply’s maximum output current: the total power envelope of the AC-DC Australia’s electronics magazine converter, its 4.5A rating at full power, and the 5A current rating of the pre-regulator stage. The red line in Fig.2, the safe operating area (SOA) curve of the Supply, shows its limits. The pre-regulator can handle 5A, defining the top line. The cut-off corner corresponds to an output power of 90W, as 18W of the ACDC converter’s 108W capacity is converted to heat by the linear stage at full current. The right-hand line is the 27V maximum output voltage. The power stage can deliver slightly less than the absolute maximum power at higher voltages, and the red line indicates its measured performance. The SOA current limits are enforced by software: even if you set 5A as a current limit point at 20V, limiting will begin at around 4.5A, to ensure that the maximum power of the converter is not exceeded. Ripple and noise Output ripple is small, and the most significant components are at the pre-regulator’s switching frequency of 260kHz (see Scope1). Scope2’s output (orange) trace indicates that the 37mV RMS (150mV peak-to-peak) of unwanted output components comprises 100mV peak-to-peak ripple, superimposed with 50mV switching transients. The yellow trace, showing the linear regulator output, is almost identical to that at its input, confirming that its ripple rejection ability is not strong at high frequencies. The improvement in RF noise is due to a choke between the siliconchip.com.au Scope3: the output behaviour (yellow trace) when a 2A load is rapidly switching in and out (orange trace) using Mosfets driven by a square wave. PCB and output terminal. Increasing its inductance would further reduce the unwanted signal, though possibly making the output unstable with some capacitive loads. Load control Scope3 shows that a step-change in load from 0 to 2A causes almost no measurable change in the output voltage. The brief spikes are caused by very short rise and fall times of the current, as the load was controlled by a square wave driving switching Mosfets. After the spike, there is a small positive bump at the drop to zero current (about 100mV), caused by the software’s response to the transient. This Scope4: the transients in Scope 3 are eliminated when the load change has a slower rise time, due to the Mosfets being driven by a triangle wave instead. has settled within 10ms. As the load comes back on, the voltage overshoots by a similar amount, and stabilises in less than 5ms. In Scope4, the load Mosfets are driven by a triangle wave producing a current pulse (green trace) with a 1ms rise time. There is no discernable switching spike or voltage variation in the yellow output voltage waveform. Voltage control While the Supply is capable of finer voltage regulation, a hysteresis of 1mV has been introduced into the voltage control algorithm to prevent hunting. In almost all practical situations, the Supply’s output stability is far more Fig.2: the Safe Operating Area (SOA) for the Lab Supply. It can provide 5A up to 18V. Above that, the 108W limit of the AC-DC converter and the 18W dissipation in the linear stage causes the maximum current to taper until reaching the maximum voltage that can be produced, taking into account the dropout voltage of the linear regulator. siliconchip.com.au Australia’s electronics magazine critical than the actual voltage value. After all, this is a lab supply rather than a voltage reference instrument. With a knob-driven design, the main criterion is that it can vary the voltage as quickly as you can turn the knob. But with digital control, particularly remote digital control, it becomes practical to use the Supply to provide step-changes in voltage, and even generate ramps or square waves. The settling time is more crucial under these conditions. The ability of the Supply to handle changes in output voltage under load is quite substantial. Scope5 shows the response of the bare regulator to a short rise-time voltage step of 1V to 10V into a 20Ω load. It shows overshoot after a 35ms rise time, with the voltage settling in less than 100ms. As it is undesirable to have voltage overshoot, rising voltages are intentionally rate-limited in software to 100V/s (Scope6), with no significant remaining overshoot. With a falling voltage (Scope7), the output has settled within 25ms with minimal undershoot. The rate of voltage fall is not rate-limited by software, and mostly depends on the time constant of the load resistance and the 10µF output capacitor. Rate limiting of rising voltages, when coupled with the output voltage rising from 0V when the output is turned on, forms the core of the softstart feature. Hardware design The basic design of the Lab Supply is shown in the simplified circuit May 2021  27 Scope5: with a substantial 9V step with a 20Ω Ω load, the untreated output shows undesirable overshoot, despite a short settling time of around 75ms. diagram, Fig.3. AC power is converted to 28-30V DC using a commercial 100W switch-mode module. This has been chosen to reduce the size, cost, and weight. Next, an LM2679-based DC-DC buck regulator reduces the DC voltage to 3.6V more than the required output. Finally, a boosted linear regulator, based on an LM317, brings the voltage down to the correct output value. The output current is converted to a voltage using an INA282 high-side current-to-voltage converter measuring the voltage drop across a 0.01Ω shunt resistor. The output voltage and current are then measured using a 16bit analog-to-digital converter (ADC). Scope6: limiting the voltage rise time to 100V/second almost eliminates the overshoot. The LM317’s output voltage is controlled by a digital pot, IC3, and trimmed using the digital-to-analog converter’s output (DAC). All digital control functions use an I2C serial bus, and two modules can share a single controller, by altering one bit of each device’s I2C address via a jumper. While a three-stage approach to voltage regulation may seem complicated, it provides the best balance of performance and simplicity of several configurations tested. One of the key design challenges in any switch-mode design is controlling switching noise at the output. Careful attention has been paid at each regu- lator stage to minimise its generation and transmission. The Supply is built using two PCBs: one which carries all the regulation componentry, and a second control board which has the microcontroller module with WiFi, a touchscreen, buttons and a rotary knob. They are joined together by a ribbon cable. As several vital chips on the power supply board are only available as SMD parts, we have opted for fully SMD layouts. We’ve kept the part sizes to 2.0 x 1.2mm (0805 imperial) or larger, to aid with manual assembly. For those who have not ventured into SMD construction yet, you could consider building our DIY SMD Reflow Fig.3: a simplified circuit diagram demonstrating the Lab Supply’s operation. The AC-DC converter is followed by a preregulator based on the LM2679 5A switching regulator, then a linear stage comprising an LM317 with a pair of currentboosting transistors. The micro monitors the output voltage and current and drives the ADJ terminal on the LM317 with a mixture of varying resistance (via the digital pot) and a small voltage, provided by the DAC for fine control. 28 Silicon Chip Australia’s electronics magazine siliconchip.com.au It’s a versatile design . . . Scope7: there is almost no overshoot with falling output (10V, 20Ω Ω), so fall-time limiting is not required. Oven (April & May 2020; siliconchip. com.au/Series/343) to build this project. However, you can also assemble it by hand if you want to; in that case, a syringe of flux paste, some braided solder wick and fine-tipped tweezers are all you need in addition to a temperature-controlled iron. Heat management Most of the waste heat is generated by one transistor, Q2. The preregulator maintains it at a steady 3.6V higher at its collector than its emitter, so its heat output is directly proportional to the load current. At full current, Q2 will generate 18W of waste heat. The LM317 regulator is operating at low current and with a lower voltage differential. The pre-regulator is specified with a minimum 84% efficiency across its voltage and current range. At full load and rated efficiency, 18W could be generated, shared between the regulator IC, schottky diode and inductor. In practice, the heat generated in this section of the prototype is substantially less than that of Q2. With a potential maximum of 36W heat to be dissipated, this hybrid design is a substantial improvement on the 108W that would be generated by a fully linear design delivering full current near zero volts. The modest heat output allows a moderately-sized heatsink to be fitted into a compact plastic instrument, with a small fan to keep air moving when the heatsink temperature rises. If the heatsink temperature rises too far, the load will be switched off by the control software. In extreme cirsiliconchip.com.au While the control board described in these articles was designed primarily to control this Supply, it it is essentially a style of Arduinocompatible ‘BackPack’ with two powerful 32-bit microcontrollers, lots of flash plus RAM and WiFi and Bluetooth support. So it could be used for a wide range of different projects and tasks, and it has been designed with that in mind. The sections at either side where the pushbuttons and rotary encoder mount can be cut off if they aren’t required for a given design. They can also be wired back to the main portion of the control board if their functions are desired, but placement needs to be changed. Alternatively, headers can be fitted at those locations to provide for more I/O pins than are available at 20-pin box header CON2. Its power supply arrangement is flexible, too. It can be powered from around 7-15V DC applied to the barrel socket, via the USB socket on the ESP-32 module or via the pins of CON2. And we must not forget about the optional onboard micro SD card socket. In summary, it is a very powerful and flexible control module and deserves to be used in other applications! cumstances, the LM317 and LM2679 will trigger their internal thermal shutdown circuits, providing a final layer of protection. There are two heatsink options for this project: a commercial heatsink can be used (Cincon M-B012), or one can be folded up from two pieces of 1.6mm-thick aluminium. As the power dissipation is not that high, either will perform adequately. Plans for the DIY heatsink will be given later. Control board The controller features a powerful ESP32 WiFi system-on-a-chip (SoC), the big brother to the ESP8266 module featured in our D1 Mini BackPack (October 2020; siliconchip.com.au/ Article/14599). It has two CPUs onboard, allowing one to be dedicated to communication functions. While this might seem unimportant, as a 180MHz 32-bit processor has far more capacity than is needed for any but the most ambitious projects, WiFi functions preempt user code in a single-processor design, sometimes creating unacceptable processing delays for real-time applications like this. The ESP32 has 520kB RAM, compared with 80kB in the ESP8266. This is particularly important when overthe-air (OTA) reprogramming is employed, as both the original and the new program need to fit in memory simultaneously. The controller communicates via WiFi, either connecting to a local LAN or setting up its own. Bluetooth communication, both traditional and low-energy (BLE), is also supported, as is serial over USB. Australia’s electronics magazine The ESP32 module plugs into a socket on the control PCB. The DevKit C module we have selected has substantial expansion capabilities (32 pins compared with 16 on the D1). It is an Espressif reference design that has been implemented by multiple board manufacturers, ensuring wide availability and competitive pricing. A 2.8in or 3.5in LCD touchscreen is mounted on the front of the control PCB, along with two momentary switches and a rotary encoder. In this project, they are used (along with an on-screen touch menu) to set the instrument’s configuration and control values. On the left are two more switches and one LED, used as on/off buttons and indicator for the output. The controller’s expansion capabilities are provided on a 20-pin header and include I2C, SPI, serial, GPIO, ADC, DAC and power (3.3V and 5V) pins. It can be powered via a USB cable, an external 5-12V plugpack or via the pin header. The PSU board will power the controller in the finished project, while USB power is used for commissioning. The full range of the control board features are included in a PDF manual which you can get via the following link: siliconchip.com.au/link/ab72 Regulator circuit The full circuit of the regulator board is shown in Fig.4. The incoming DC from the AC-DC switchmode Supply is fed in at upper left, and the output terminals are at upper right. This feeds into the LM2679 preregulator stage (based around REG1), which is controlled by op amp IC3b. May 2021  29 Fig.4: the regulator board includes the switchmode pre-regulator, based around REG1, the final linear regulator stage (REG2, Q1 & Q2) plus control and monitoring circuitry. Digital pot IC2, DAC IC4 and op amp IC3a are used to control the output voltage, while the pre-regulator tracks 3.6V higher due to the operation of the differential 30 Silicon Chip Australia’s electronics magazine siliconchip.com.au amplifier built around IC3b, which drives REG1’s feedback pin. Shunt monitor IC5 feeds a voltage proportional to the output current to the ADC, IC1, which also monitors the input and output voltages and heatsink temperature via 10kΩ Ω NTC thermistor TH1. siliconchip.com.au Australia’s electronics magazine May 2021  31 The final output and the pre-regulator voltages are divided by a factor of 15 (68k/4.7kΩ for VO_SENSE and 6.8kΩ/470Ω for VPRE_SENSE) before being subtracted by IC3b, acting as a differential amplifier. The difference is fed into the feedback (FDBK) terminal of the LM2979. The pre-regulator’s voltage must be 3.6V higher than the output voltage, to allow for the maximum dropout of the final linear regulation stage. So zener diode ZD1 is inserted at the top of the VPRE_SENSE divider. The op amp has moderate DC gain, to ensure accurate tracking despite the FDBK input of REG1 having a 1.2V operating point. The op amp is heavily damped by the 100nF capacitor across its feedback resistor, so its AC gain is close to unity, ensuring that the configuration is stable. Schottky diode (D2) at the FDBK input ensures that the voltage doesn’t swing too far negative at start-up, potentially damaging the regulator. The LM2679’s soft-start and current limiting functions are both enabled, with the 5.6kΩ resistor from its CL_ADJ pin to GND chosen to limit the switching Mosfet’s maximum current to 6.3A. The selection of 3.6V for zener diode ZD1 was a key design decision. Raising the voltage drop across the linear stage increases the waste heat. But if the voltage differential across the LM317 becomes too small, it ceases to regulate and could oscillate in conjunction with the current-boost transistors. Setting the pre-regulator to 3.6V above the output voltage provides a few hundred millivolts headroom for the LM317 at full load, ensuring stability while limiting heat. As the switching frequency is 260kHz, small value output capacitors for the pre-regulator stage adequately control ripple; however, the 47µF electrolytic capacitor must a low-ESR type. RF noise is reduced by adding a 10µF multilayer ceramic capacitor in parallel, which needs to be an X7R or X5R type to ensure a good high-frequency response. The ground plane for the switching pre-regulator is divided off from the rest of the circuit, only meeting at the common ground point. L2 is a toroidal choke, to minimise radiation, as their magnetic field is mostly contained within the device. Eagle-eyed readers will notice that the linear output stage bears a strik32 Silicon Chip ing resemblance to Tim Blythman’s 45V/8A Linear Bench Supply design (October-December 2019; siliconchip. com.au/Series/339). The main difference is that the output voltage is computer-controlled via a 5kΩ digital pot (IC2) and DAC (IC4), using values measured by a 4-channel, 16 bit ADC (IC1). This allows significant software flexibility for current-limiting, circuit protection, remote control and even allows several separate units to operate as a single entity via WiFi connections. The LM317’s coarse output voltage is set by the ratio of the 220Ω resistor between its out and ADJ pins, and the digital pot, IC2. The output voltage will stabilise when the voltage between the LM317’s output (OUT) and adjust (ADJ) pins is 1.25V. The digital pot’s maximum resistance is 5kΩ, providing a maximum output voltage of 30V. The digital pot’s resolution is eight bits, providing control steps of approximately 120mV. This is not sufficiently fine control for our purposes, so the 12-bit DAC and op amp IC3a provide the dual function of fine control and providing a negative offset for the bottom of the digital pot, so the LM317’s output can go down to 0V. The inverting input of IC3a is at 0.7V, set by diode D4. With the op amp gain set to -3.9, this translates to around -2.8V at its output. The DAC delivers an output voltage of 0-3.3V which is divided by the 68kΩ and 1kΩ resistors to give around 47.8mV full-scale, and 186.5mV when amplified. With the DAC set at its midpoint, op amp IC2a delivers around -2.35V, which is the voltage required to bring the LM317’s output voltage down to zero. A negative voltage larger than -1.25V is needed because the digital pot has a finite minimum (wiper) resistance of around 200Ω. Each of the DAC’s 4096 steps corresponds to a 45.5µV change in the output – more than sufficient resolution. When a new output voltage is set, the software calculates the most likely setting for the pot and DAC in one of two ways. If the change is small, only the DAC’s value needs to be changed to accommodate the difference. The initial jump is slightly conservative to avoid overshoot, and a final setting is reached within 4-5 cycles by repeating the process. Australia’s electronics magazine If the change is large, the correct setting for the digital pot is calculated and set, the DAC is set to mid-value, and the fine control algorithm is invoked. As each control iteration takes only 4ms, the settling time is of the order of 20ms. The 100nF capacitor from REG2’s ADJ pin to ground improves regulation by stabilising the voltage on that pin, without increasing the response time. The DAC’s control range is intentionally set at around four digital pot increments, to avoid invoking the coarse adjustment mechanism for small voltage changes, and the consequent disturbance to the output voltage. Current limiting is accomplished in a similar manner, using the ratio of the desired and actual output currents to control the digital pot and DAC settings. While current limiting can be disengaged on the control panel, the software still monitors the output current to provide over-current and short-circuit protection, and keeps the Supply operating within its safe operating area (SOA). The output current of REG2 is boosted by transistors Q1/Q2 acting as a Sziklai pair. When the current through the LM317 exceeds 100mA, the voltage across the 68Ω resistor rises above 0.7V, causing Q1 to conduct and switch on Q2, which passes most of the output current. The combination of Q1 and Q2 has a potential current gain of more than 10,000, so careful attention is needed to ensure stability. A 1µF capacitor provides AC feedback to the base of Q1, and Q1’s 1.5kΩ base resistor is chosen so that the maximum current through Q2 is just above 5A. The 22Ω base resistor for Q2 ensures the current through Q1 is limited to a few hundred milliamps. The 10µF output capacitor is a type chosen for effectiveness at high frequencies, reducing RF noise. An offboard toroidal choke, L3 (not shown in Fig.4), further reduces HF noise. The input and output voltages, output current and the heatsink temperature are monitored by an ADS1115 16-bit analog-to-digital convert (ADC). Each input signal is conditioned to be in the range it can handle, which is 0-2.048V. Simple voltage dividers are adequate for bringing the voltage and temperature values within the ADC’s range. However, the current readings proved unreliable at no load, so siliconchip.com.au the INA282 current sensor’s output is offset by schottky diode D5 to bias its pin 7 REF1 input (a schottky diode has about half the voltage drop of a silicon diode), before being divided by the 4.7kΩ/3.3kΩ resistor pair. With a current shunt of 0.01Ω (10mΩ) and 50V/V gain, this corresponds to 2.5V deflection at the output of the INA282 at 5A output current, and 0.35 – 1.38V to the ADC. This equates to a resolution of 150µA. Q2’s temperature is measured by a thermistor voltage divider, and linearisation is taken care of in software. Q4 turns the fan on when Q2 reaches 35°C. The fan is small and quiet, so simple on/off control is adequate. The output is relay-switched, controlled by a latch built from logic gates (IC6a & IC6b) and NPN transistor Q3. Q3 also drives the LED1 indicator. IC6 ensures that the output is always off at start-up, no matter the state of the microcontroller. The 74C02 dual NOR gate is configured as an SR latch, with the 100nF capacitor providing a brief positive pulse when power is applied, resetting it. IC6 is directly controlled by the on/ off switches on the control board, as well as the microcontroller, ensuring that pressing the off button will always turn off the output immediately, even if the microcontroller is busy with other tasks. Auxiliary ±5V supplies provide power for the logic and op amp, as well as the controller board. Both of these rails are supplied by 3-terminal DC/DC converter modules which have the same pinout as standard linear regulators. We published similar designs in our August 2020 issue (siliconchip.com.au/ Article/14533), but their maximum input voltage of 30V is (just) insufficient here. So we have specified commercial modules which have higher ratings. The 500mA component chosen for the -5V regulator (VR4) has a 31V maximum input voltage for negative output configurations. It cannot be substituted with the 1A version used for the +5V regulator (VR3) which can only handle 27V in this mode. The regulator board connects to the control/display board via CON1, a 20pin box header and a matching ribbon cable with IDC plugs at either end. The 3.3V rail powering IC1, IC2 and IC4 comes from a regulator on the control board via CON1. Power for the control board is fed from the 5V rail on this board, via pins 18 & 20 of CON1. Control circuit The control board circuit is shown in Fig.5, with the ribbon cable from CON1 on the regulator board terminating at matching header CON2. The two main components on this board are the ESP-32 microcontroller and WiFi module and the 2.8in or 3.5in touchscreen. They are connected via an SPI bus and a few digital control lines in the usual manner, allowing the micro to update the screen’s contents and sense touch events. There’s also an optional onboard SD card socket sharing the same SPI bus, although it’s unnecessary for this project. It’s mainly provided as the control board could be used for other purposes, where having onboard storage could be useful. The connections between the ESP-32 and CON2 include the shared SPI bus, two I2C buses, serial, plus several digital I/O pins. Note that many of these are not connected at the other end, and are provided for future expansion. The functions that are used are the first I2C bus (SDA/SCL), to control the Radio, Television & Hobbies: the COMPLETE archive on DVD YES! NA MORE THA URY T N E C QUARTER ICS N O R OF ELECT ! Y R HISTO This remarkable collection of PDFs covers every issue of R & H, as it was known from the beginning (April 1939 – price sixpence!) right through to the final edition of R, TV & H in March 1965, before it disappeared forever with the change of name to EA. For the first time ever, complete and in one handy DVD, every article and every issue is covered. If you’re an old timer (or even young timer!) into vintage radio, it doesn’t get much more vintage than this. If you’re a student of history, this archive gives an extraordinary insight into the amazing breakthroughs made in radio and electronics technology following the war years. And speaking of the war years, R & H had some of the best propaganda imaginable! Even if you’re just an electronics dabbler, there’s something here to interest you. • Every issue individually archived, by month and year • Complete with index for each year • A must-have for everyone interested in electronics Exclusive to: SILICON CHIP siliconchip.com.au ONLY 62 $ 00 +$10.00 P&P Order now from www.siliconchip.com.au/Shop/3 or call (02) 9939 3295 and quote your credit card number. Australia’s electronics magazine May 2021  33 Fig.5: as mentioned earlier, the control panel is designed to be flexible enough that it could be used for other purposes, but it is well-suited to the task of controlling this supply. The main part of this circuit is the ESP-32 module and its connections to the touchscreen and CON2, which connects it to the regulator board. It also carries four pushbuttons switches, a rotary encoder and an LED for enhanced user control. The onboard regulator is not required for this project. USB provides power for setting up; after that, it’s powered from the other board. 34 Silicon Chip Australia’s electronics magazine siliconchip.com.au ADC (IC1), digital pot (IC2) and DAC (IC4) plus four digital I/O lines. These are pin 9, which is the DRDY interrupt signal from the ADC which indicates that a conversion is complete, the on & off switch sense lines at pins 12 & 16, and the fan control line at pin 14. The module can be powered by USB for tethered applications and commissioning. A barrel jack and 5V regulator have been included for projects where external power is required. 5V power can also be supplied via the 20-pin expansion header (CON2), which is the approach used in this project. The ESP module consumes 225mA when delivering its full WiFi output power. The module can provide up to 50mA of 3.3V power for additional logic from the ESP-32’s onboard regulator, and as mentioned earlier, this is taken advantage of by the regulator board. Switches S1 & S2 have pull-down resistors, debounce capacitors and are configured as active-high. While the debounce and pull-down functions can be provided by port configuration and software, adding them in hardware adds little complexity or cost. SW_ON and SW_OFF switch the power supply output in this project. As well as leading to GPIO pins, they are also hard-wired to the expansion connector. The arrangement is slightly unusual in that SW_ON is an input when the power supply’s output is off, but becomes an output (high) after being clicked. It is re-configured to become an input by SW_OFF being depressed. This ensures that LED1 remains lit after SW_ON is released. SW_L and SW_R work with the rotary encoder to allow easy setting of numeric values. The rotary encoder changes the value by one ‘unit’ up (clockwise) or down (anticlockwise) per click. SW_L and SW_R select the magnitude of this unit, which is also highlighted on the screen. SW_L moves the digit being controlled by the rotary encoder to the next digit to the left. This increases the magnitude of the amount added or subtracted for each encoder click by a factor of ten. SW_R has the opposite effect. This arrangement is common on digital instruments, as it allows quick and accurate value adjustments, and is readily mastered. The rotary encoder and its switch are active-low. The microcontroller provides pull-ups for the encoder. The encoder’s push-switch is not used in this project. If required, it can be connected to IO26 on the ESP-32 module via JP3. The current software does not use the touch screen interrupt; however, it can be jumpered to IO2 via JP1. Care should be taken when using IO2 for other purposes, as its state at power-on (along with IO0) determines how the ESP-32 boots up. Next month In our June issue, we will have the full construction details for the Programmable Hybrid Lab Supply plus more information on how to set it up and use it. To whet your appetites, here’s a sneak peak of the completed Programmable Power Supply. We’ll cover complete construction details and setup next month. siliconchip.com.au Australia’s electronics magazine May 2021  35 Parts list – Programmable Hybrid Lab Power Supply 1 ABS instrument case, 260mm x 190 x 80mm [Altronics H0482, Jaycar HB5910, Pro’skit 203-115B] 1 front panel label 1 MeanWell LRS-100-24 switchmode AC-DC converter [Mouser, RS] 1 regulator module (see below) 1 control panel module (see below) 1 IEC mains power socket [Jaycar PP4005] 1 red binding post 1 black binding post 1 green binding post 1 40-60mm 5V DC low-current fan [eg, Altronics F1110] 16 M3 x 15mm panhead screws & hex nuts (for fan, heatsink and front panel) 2 M3 x 15mm countersunk head screws & hex nuts (for IEC connector) 3 M3 x 25mm countersunk head screws (for MeanWell supply and heatsink) 3 4G x 8mm self-tapping screws (for PCB and AC-DC converter) 1 6mm M3 spacer (for MeanWell supply mounting) 1 IEC mains cord with 3-pin moulded plug 1 10cm+ 20-way ribbon cable fitted with IDC plugs 1 1m length of mains-rated hookup wire 1 1m length of 5A DC rated hookup wire 1 50mm length of 6mm diameter heatshrink tubing (for mains connections) 3 3mm ID crimp eyelet lugs for binding posts (optional) 3 TO-220 insulation kits (mica or silicone rubber) 1 TO-3P insulation kit (mica or silicone rubber) 1 small tube of thermal paste (only required if using mica insulating washers) 1 15mm diameter (or larger) ferrite toroid [Jaycar LO1242] 1 2-pin plug & matching socket (for fan) 1 mains socket shroud Parts list – regulator module 1 double-sided PCB coded 18104212, 136 x 44.5mm 1 20-pin IDC box header (CON1) 1 2-pin polarised header & matching plug (CON3) 1 10µH 1A SMD inductor, 4x4mm (L1) [eg, Taiyo Yuden NRS4012T100MDGJ] 1 47µH 5A toroidal inductor (L2) [Altronics L6617] 1 5V DC coil 10A SPDT G5LE relay [eg, Omron G5LE-1-DC5] 1 small heatsink [CINCON M-B012 or cut & bent from 1.6mm aluminium sheet] 1 10k NTC thermistor, eyelet mounting with flying leads [Altronics R4112] Semiconductors 1 ADS1115DGSR ADC, MSOP-10 (IC1) 1 MCP45HV51-502 5k 8-bit I2C digital potentiometer, TSSOP-14 (IC2) 1 LM358D dual single-supply op amp, SOIC-8 (IC3) 1 MCP4725A0T-E/CH 12-bit DAC, SOT-23-6 (IC4) 1 INA282AIDR bidirectional current sensor, SOIC-8 (IC5) 1 SN74LVC2G02DCTR dual 2-input NOR gate, SSOP-8 (IC6; 0.65mm pin spacing) 1 LM2679T-ADJ switchmode regulator, TO-220-7 (REG1) 1 LM317 linear regulator, TO-220-3 (REG2) 1 CUI VXO7805-1000 5V 1A switching regulator module, TO-220-3 (REG3) 36 Silicon Chip 1 CUI VXO7805-500 5V 500mA switching regulator module, TO-220-3 (REG4) 1 BD140 80V 1.5A PNP transistor, TO-126 (Q1) 1 FJA4313 250V 17A NPN power transistor, TO-3P (Q2) 2 BC817 or equivalent 45V, 500mA NPN transistors, SOT-23 (Q3,Q4) 1 SMD LED, M2012/0805 size (LED1) 3 V2F22HM3_H 1A 20V schottky diodes, DO219-AB-2 (D1,D2,D5) 1 STPS1045SF 15A 60V schottky diode, TO-227A (D3) 3 BAS21 or equivalent small signal diodes, SOD-123 (D4,D6,D7) 1 BZV55 3.6V zener diode, SOD-323/mini-MELF (ZD1) Capacitors (all SMD M3226/1210 size unless otherwise stated) 1 270µF 50V low-ESR electrolytic (3.5mm lead pitch, maximum 8mm diameter) 1 47µF 50V low-ESR electrolytic (3.5mm lead pitch, maximum 8mm diameter) 2 10µF 50V X7R SMD M3226/1210 size 3 10µF 35V X7R SMD M3216/1206 size 2 1µF 50V X7R SMD M2012/0805 size 13 100nF 50V X7R SMD M2012/0805 size 1 10nF 50V X7R SMD M2012/0805 size 1 1nF 50V NP0/C0G SMD M2012/0805 size Resistors (all 1% SMD M2012/0805 size unless otherwise specified) 1 820k 2 100k 3 68k 1 39k 3 10k 1 6.8k 1 5.6k 3 4.7k 1 3.3kΩ 1 1.5k 4 1k 4 470 1 220 1 150 1 68 1/2W 1% through-hole axial 1 22 1/2W 1% SMD M3216/1206 size 1 10m 1W 1% wirewound through-hole axial Parts list – control panel module 1 double-sided PCB coded 18104211, 167.5mm x 56mm 1 Espressif ESP32-DEVKITC-compatible WROOM-32 WiFi MCU module [Altronics Z6385A, Jaycar XC3800, NodeMCU-32S] 1 2.8in SPI LCD touchscreen with ILI9341 controller [eg, SILICON CHIP Cat SC3410] 1 2.1mm PCB-mount DC barrel socket (CON1; optional) [Altronics P0620, Jaycar PS0519] 1 20-pin box header (CON2) [WURTH 61202021621 or similar] 1 40-pin female header (cut into two strips of 19) 1 SMD micro SD card socket (optional) [Hirose DM3D-SF] 1 rotary encoder (RE1) [Alps EC12E, eg, Jaycar Cat SR1230] 1 knob for rotary encoder [eg, Altronics H6514 (23mm) or Adafruit 2055 (35mm)] 4 12mm SPST PCB-mount tactile switches with square actuators (S1-S4) [Altronics S1135, Jaycar SP0608] 2 black, white or grey switch caps [Altronics S1138] 1 red switch cap 1 green switch cap Semiconductors 1 7805T 5V 1A linear regulator (REG1; optional) 1 5mm red or green LED (LED1) Capacitors 1 47µF 10V X5R/X7R SMD (M3226/1210 size) 1 10µF 25V X5R/X7R SMD (M3226/1210 size) 9 100nF 50V X7R SD (M2012/0805 size) Resistors (all SMD 1% 1/10W M2012/0805 size) 3 10k 2 1.8k 1 1k Australia’s electronics magazine SC siliconchip.com.au SILICON CHIP .com.au/shop ONLINESHOP PCBs, CASE PIECES AND PANELS USB SUPERCODEC ↳ BALANCED ATTENUATOR SWITCHMODE 78XX REPLACEMENT ULTRASONIC CLEANER MAIN PCB ↳ FRONT PANEL NIGHT KEEPER LIGHTHOUSE SHIRT POCKET AUDIO OSCILLATOR ↳ 8-PIN ATtiny PROGRAMMING ADAPTOR D1 MINI LCD WIFI BACKPACK FLEXIBLE DIGITAL LIGHTING CONTROLLER SLAVE ↳ FRONT PANEL (BLACK) LED XMAS ORNAMENTS 30 LED STACKABLE STAR ↳ RGB VERSION (BLACK) DIGITAL LIGHTING MICROMITE MASTER ↳ CP2102 ADAPTOR BATTERY VINTAGE RADIO POWER SUPPLY DUAL BATTERY LIFESAVER AUG20 NOV20 AUG20 SEP20 SEP20 SEP20 SEP20 SEP20 OCT20 OCT20 OCT20 NOV20 NOV20 NOV20 NOV20 NOV20 DEC20 DEC20 01106201 01106202 18105201 04105201 04105202 08110201 01110201 01110202 24106121 16110202 16110203 16111191-9 16109201 16109202 16110201 16110204 11111201 11111202 $12.50 $7.50 $2.50 $7.50 $5.00 $5.00 $2.50 $1.50 $5.00 $20.00 $20.00 $3.00 $12.50 $12.50 $5.00 $2.50 $7.50 $2.50 Subscribers get a 10% discount on all orders for parts DIGITAL LIGHTING CONTROLLER LED SLAVE AM/FM/SW RADIO MINIHEART HEARTBEAT SIMULATOR I’M BUSY GO AWAY (DOOR WARNING) BATTERY MULTI LOGGER ELECTRONIC WIND CHIMES ARDUINO 0-14V POWER SUPPLY SHIELD HIGH-CURRENT BATTERY BALANCER (4-LAYERS) MINI ISOLATED SERIAL LINK REFINED FULL-WAVE MOTOR SPEED CONTROLLER DIGITAL FX UNIT PCB (POTENTIOMETER-BASED) ↳ SWITCH-BASED ARDUINO MIDI SHIELD ↳ 8X8 TACTILE PUSHBUTTON SWITCH MATRIX DEC20 JAN21 JAN21 JAN21 FEB21 FEB21 FEB21 MAR21 MAR21 APR21 APR21 APR21 APR21 APR21 16110205 CSE200902A 01109201 16112201 11106201 23011201 18106201 14102211 24102211 10102211 01102211 01102212 23101211 23101212 $5.00 $10.00 $5.00 $2.50 $5.00 $10.00 $5.00 $12.50 $2.50 $7.50 $7.50 $7.50 $5.00 $10.00 HYBRID LAB POWER SUPPLY CONTROL PCB ↳ REGULATOR PCB VARIAC MAINS VOLTAGE REGULATION MAY21 MAY21 MAY21 18104211 18104212 10103211 $10.00 $7.50 $7.50 NEW PCBs PRE-PROGRAMMED MICROS & ICs As a service to readers, Silicon Chip Online Shop stocks microcontrollers and microprocessors used in new projects (from 2012 on) and some selected older projects – pre-programmed and ready to fly! Some micros from copyrighted and/or contributed projects may not be available. $10 MICROS 24LC32A-I/SN ATmega328P-PU ATmega328P-AUR ATtiny85V-10PU PIC10F202-E/OT PIC12F1572-I/SN PIC12F617-I/P PIC12F675-I/SN PIC16F1455-I/P PIC16F1455-I/SL PIC16F1459-I/P PIC16F1705-I/P PIC16F88-I/P $15 MICROS EEPROM for Digital FX Unit (Apr21) RF Signal Generator (Jun19) RGB Stackable LED Christmas Star (Nov20) Shirt Pocket Audio Oscillator (Sep20) Ultrabrite LED Driver (with free TC6502P095VCT IC, Sep19) LED Christmas Ornaments (Nov20; specify variant) Car Radio Dimmer Adaptor (Aug19), MiniHeart (Jan21) Refined Full-Wave Universal Motor Speed Controller (Apr21) Tiny LED Xmas Tree (Nov19) Digital Interface Module (Nov18), GPS Finesaver (Jun19) Digital Lighting Controller LED Slave (Dec20) Ol’ Timer II (Jul20), Battery Multi Logger (Feb21) 5-Way LCD Panel Meter (Nov19), IR Remote Control Assistant (Jul20) Ultrasonic Cleaner (Sep20), Electronic Wind Chime (Feb21) Flexible Digital Lighting Controller Slave (Oct20) UHF Repeater (May19), Six Input Audio Selector (Sept19) Universal Battery Charge Controller (Dec19) ATSAML10E16A-AUT High-Current Battery Balancer (Mar21) PIC16F1459-I/SO Four-Channel DC Fan & Pump Controller (Dec18) PIC32MM0256GPM028-I/SS Super Digital Sound Effects (Aug18) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sept19) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) RCL Box (Jun20), Digital Lighting Controller Micromite Master (Nov20) PIC32MX170F256B-I/SO Battery Multi Logger (Feb21) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) $20 MICROS PIC32MX470F512H-I/PT Stereo Echo/Reverb (Feb 14), Digital Effects Unit (Oct14) PIC32MX470F512H-120/PT Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) PIC32MX470F512L-120/PT Micromite Explore 100 (Sept16) $30 MICROS PIC32MX695F512L-80I/PF PIC32MZ2048EFH064-I/PT Colour MaxiMite (Sept12) DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20) KITS & SPECIALISED COMPONENTS VARIOUS MODULES & PARTS LED CHRISTMAS ORNAMENTS (CAT SC5579) - 2.8-inch touchscreen LCD module (Hybrid Lab Power Supply, May21) - Spin FV-1 IC (Digital FX Unit, Apr21) - 15mW 3W SMD resistor (Battery Multi Logger / Arduino Power Supply, Feb21) - DS3231 or DS3231M real-time clock SMD IC (Battery Multi Logger, Feb21) - MCP4251-502E/P (Arduino Power Supply, Feb21) - Pair of CSD18534 (Electronic Wind Chimes, Feb21) - IPP80P03P4L04 (Dual Battery Lifesaver / Vintage Radio Supply, Dec20) - 16x2 I2C LCD (Digital RF Power Meter, Aug20) - WS2812 8x8 RGB LED matrix module (Ol’ Timer II, Jul20) - MAX038 function generator IC (H-Field Transanalyser, May20) - MC1496P double-balanced mixer (H-Field Transanalyser, May20) - AD8495 thermocouple interface (DIY Reflow Oven Controller, Apr20) - I/O expander modules (Nov19): PCA9685 – $6.00 ¦ PCF8574 – $3.00 ¦ MCP23017 – $3.00 MINI ISOLATED SERIAL LINK COMPLETE KIT (CAT SC5750) $22.50 $40.00 $2.50 $3.00 $3.00 $6.00 $5.00 $7.50 $15.00 $25.00 $2.50 $10.00 MINIHEART HEARTBEAT SIMULATOR (CAT SC5732) $10.00 (JAN 21) All SMD parts, including IC2 – does not include PCB AM/FM/SW RADIO - PCB-mount right-angle SMA socket (SC4918) - Pulse-type rotary encoder with integral pushbutton (SC5601) - 16x2 LCD module (does not use I2C module) (SC4198) RGB STACKABLE LED CHRISTMAS STAR (CAT SC5525) $14.00 (NOV 20) $38.50 Complete kit including PCB, micro, diffused RGB LEDs and other parts D1 MINI LCD WIFI BACKPACK KIT (OCT 20) $70.00 Complete kit including 3.5-inch touchscreen, PCB and ESP8266-based module COLOUR MAXIMITE 2 in stock now Short form kit: includes everything except the case, CPU module, power supply, optional parts and cables (Cat SC5478) Short Form kit (with CPU module): includes the programmed Waveshare CPU modue and everything included in the short form kit above (Cat SC5508) (JUL 20) $80.00 $140.00 MICROMITE LCD BACKPACK V3 KIT (CAT SC5082) (MAR 21) All parts required to build the project including the PCB (NOV 20) Complete kit including micro but no coin cell (specify PCB shape & colour) $5.00 (JAN 21) $2.50 $3.00 $7.50 (AUG 19) Includes PCB, programmed micros, 3.5in touchscreen LCD, UB3 lid, mounting hardware, Mosfets for PWM backlight control and all other mandatory on-board parts $75.00 Separate/Optional Components: - 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 $10 flat rate for postage within Australia. Overseas? Place an order via our website for a quote. All items subect to availability. Prices valid for month of magazine issue only. All prices in Australian dollars and included GST where applicable. PAYPAL (24/7) INTERNET (24/7) MAIL (24/7) PHONE – (9-5:00, Mon-Fri) eMAIL (24/7) To Use your PayPal account siliconchip.com.au/Shop Your order to PO Box 139 Call (02) 9939 3295 with silicon<at>siliconchip.com.au Place siliconchip.com.au Australia’s electronics magazine Morder ay 2021  37 silicon<at>siliconchip.com.au Collaroy NSW 2097 with & credit card details Your You can also order and pay by cheque/money order (Orders by mail only). Make cheques payable to Silicon Chip Publications. Order: 05/21 Digital FX Unit Our new DFX unit, introduced last month, can produce 15 different effects for musicians or recording technicians to customise their instruments and sounds. You can customise eight of those effects – and this article describes how to create and install different effects patches into the unit’s EEPROM. Part two – by John Clarke W hile we have included a great variety of pre- 1, 2 and 3 in the program listings. programmed effects in the EEPROM supplied for The assembler program for the selected effects patch can our new Digital FX Unit (adding to those already be downloaded from the site by choosing the cyan “Downpresent within the SPIN FV-1 chip), you might want to load SpinAsm” link at the bottom of the effect patch detail change some of these effects patches. area (see Screen1 opposite). That will ensure that the Digital FX unit has the effects If you want more programs, these are available directly you want. from the SPIN semiconductor website at www.spinsemi. Numerous effects patches can be freely downloaded. If com/programs.php you are an avid programmer, free software is available with graphical proPatch Effect Adjustment C Adjustment B Adjustment A gramming to write your own effects 1 Chorus-reverb Chorus mix Chorus rate Reverb mix patches. More on that later. 2 Flange-reverb Flange mix Flange rate Reverb mix To program the Digital FX unit’s 3 Tremolo-reverb Tremolo mix Tremolo rate Reverb mix EEPROM, you need an EEPROM programmer suitable for the 24LC32A. 4 Pitch shift ±4 semitones We will describe how you can do 5 Pitch echo Echo mix Echo delay Pitch shift this with a Microchip PICkit 2 or PICk6 Test it 3 programmer. Available effects patches But first, let’s look at the pre-made effects that are freely available. There is a reasonably comprehensive list at https://mstratman.github. io/fv1-programs/ In that set of listings, you can see details for each by selecting the “MORE” box. This additional information often includes details on the functions of VR7 (A control), VR6 (B control) and VR5 (C control) on the Digital FX unit. These are labelled as 38 Silicon Chip 7 8 Reverb 1 Reverb 2 Low filter Low filter 9 10 Octaver Pitch shift glider Down octave level Up octave level Glide Depth High filter High filter 11 Oil can delay Feedback Chorus width 12 Soft clip overdrive Tone Volume 13 Bass distortion Dry/wet mix Tone 14 Aliaser 15 Wah Filter Q Sensitivity 16 Faux phase shifter Feedback level Time Table 1: preprogrammed effects patches (9-16 can be changed) Australia’s electronics magazine Reverb time Reverb time Dry mix Rate Time rate Gain threshold Gain Sampling rate Reverb Speed width siliconchip.com.au ICSP header pin 24LC Function EEPROM pin 1 - MCLR / Vpp 2 8 Vdd (positive supply) 3 4 GND / Vss (0V) 4 - PGD (Data) 5 6 PGC/SCL (Clock) 6 5 SDA (Data) Table 2: ICSP header pin mapping From last month, where we had all the construction details for the Digital FX unit – here it is ready to mount in its diecast case. Inset above right is the ICSP header pin mapping, Table 2. You can download these files to any folder you like, as long as you remember where you put them. Collation Once you have all your selected effects patches, these will need to be collated in a form suitable for programming into the EEPROM. Each effects patch is placed into a separate 512 x 8-bit memory block, and there are eight such memory blocks in the 32kbit EEPROM. To generate the required data, you will need to use the Spin Semiconductor assembler called SpinAsm (Windows-only). SpinAsm can be downloaded from the Spin Semiconductor website linked above; it is called “SpinAsm assembler for the SPN1001 V1.1.31 (Windows executable)”. If you need more information regarding installing this program, see the installation guide later in this article. Once installed, move the saved effects patch files (.spn extension) to the “C:\Program Files (x86)\SpinAsm IDE\ spinsrc” folder. To open the SpinAsm program, right-click on the SpinAsm icon and select “Run as Administrator”. If you do not run as Administrator, your work will be not be saved. You will be asked whether you want this app to make Screen1: you can download a range of pre-made effects patches from the Spin Semi website as “SpinASM” files. These can then be compiled and uploaded to the EEPROM on the Digital FX Pedal. siliconchip.com.au changes to your computer. After clicking Yes, the program opens. Left-click on the “Open Project Dialog” icon just to the right of the Spin icon (see Screen2). This opens up a table of PROG0 to PROG7, where you can place the required effects patches, as shown in Screen3. To select the first effects patch, right-click on the PROG0 box in the (UNCHANGED-NO OVERWRITE) area and select Load File Entry from the project dialog box (Screen4). Select the required file from the “C:\Program Files (x86)\ SpinAsm IDE\spinsrc\” folder. Note that you can change the directories for file locations by selecting the tree icon just to the right of the project dialog icon (Screen5). However, we will describe the setup using the default directory locations, as shown. With the first patch selected (Screen6), use the same technique to load the patches for PROG1 to 7. You do not need to load all PROG locations if you don’t need all eight effects used. But the programs you wish to load need to start at PROG0 and continue with successive PROG locations. It is OK to have the UNCHANGED-NO OVERWRITE comment after the last program entry if you do not fill up all the possible programs. Screen2: use the Open Project Dialog button in SpinASM to load one of the effects patch ASM files you have downloaded. Australia’s electronics magazine May 2021  39 Screen3: when loading a SpinASM file, you will be prompted to select which of the eight available EEPROM slots it should go into. See our comments in the text about large (512-byte) patches needing to go into the last slot (PROG 7). Screen4: after right-clicking on one of the slots, you are presented with a menu. Select the “Load File Entry” option, and you will be prompted to choose a file to load into that slot. This is meant for use with the SPIN development board. It allows single-location programming without affecting the other programmed locations in EEPROM. We don’t use that feature, however. Once all the required programs are loaded, select the Save button and save the project under a suitable name. We named ours “SC Patches.spj” – see Screen7. Once saved, select the “Intel Hex” checkbox in the lowerleft portion of the project dialog box and then press the “Build” button. The HEX file will be saved to the “C:\ Program Files (x86)\SpinAsm IDE\hexout” folder. It will be named the same as the project saved, but with a .hex extension. In our example, it is “SC Patches.hex”. This is the file you need to program into the EEPROM. If the hex file and project file were not saved, that probably means that SpinAsm was not run as an Administrator. have an EEPROM programmer suitable for the 24LC32A, that would be the easiest way to do it. If you have a Microchip PICkit 2 or PICkit 3, you can program the EEPROM using free software that you can download from Microchip’s website. We are not using MPLAB X IPE, as we would for PICs, as it does not support this EEPROM. For PICkit 2 download the software. PICkit 2 Firmware V2.32 and user’s guide PICkit 2 Microcontroller Programmer User’s Guide Both can be found at: siliconchip.com.au/link/ab7w This is very similar to the PICkit 3 programming software that we now describe. The PICkit 3 is the successor to the PICkit 2, and while PICkit 2 is suitable for directly programming the 24LC32A EEPROM, the PICkit 3 requires some modifications. It also needs to be loaded with a PICkit 2 emulator to work. In this article, we describe how to program the EEPROM using the Microchip PICkit 3 programmer, as that is the one we think readers are most likely to have. We tested Programming the EEPROM There are several ways to program the EEPROM. If you Screen5: you can change the default folders where files are loaded and stored by the SpinASM, although we decided to stick with the defaults. 40 Silicon Chip Screen6: the SpinASM files have an extension of .spn, and here we have loaded the new octaver effect into the first slot, PROG 0. Australia’s electronics magazine siliconchip.com.au Screen7: a standard file dialog is presented when you opt to save your project (.spj file). Note that we have loaded all eight slots with different effects. Choose a memorable file name. Fig.1: we temporarily removed two components from the PICkit 3: diode TR3 at far left, and resistor R50 just above the programming socket. These interfere with EEPROM programming. Keep the parts as you can reinstall them later if you want to turn the PICKit 3 back into a PIC programmer. Note the original orientation of TR3 (cathode stripe towards PTC4). one clone version of PICkit 3, and found it would not connect correctly. Different clone versions might work, but we cannot recommend using anything but the genuine Microchip PICkit 3. The Digital FX unit includes an in-circuit serial programming connection (ICSP) suitable for programming the EEPROM. The PICkit 2 or PICkit 3 plugs directly onto the ICSP header. You might need to use jumper wires to make suitable connections to the ICSP header for other programmers. Table 2 shows the connections from the ICSP header pins to the EEPROM on the Digital FX Pedal PCB. EEPROM pin 7 is disabled and connected to GND. Pins 1, 2, 3 are the address pins and are connected to Vcc or Vdd, depending on the application. Screen8: this version of the PICkit 3 programming software can program EEPROMs. Note the message in the yellow shaded box indicating that it has detected the hardware. Screen9: use this menu option to load firmware into the PICkit 3 to emulate a PICkit 2. This is required to program the type of EEPROM we are using. siliconchip.com.au Modifying the PICkit 3 To enable the PICkit 3 to program the 24LC series of EEPROMs, TR3 (a diode) and R50 (a resistor) need to be removed from inside the PICkit 3. Crack open the case and locate the components. These are labelled on the PCB screen printing, as shown in Fig.1. Desolder these, taking note of TR3’s orientation and keep the parts in a safe place for replacing later on. The easiest way to do this is with a hot air rework station, gently heating the components while holding them with tweezers. Australia’s electronics magazine May 2021  41 Screen10: having selected the option shown in Screen9, the next step is to find the file shown here, This file is included with the software download and should be on your computer in the location described in the text. Screen11: with the PICkit 2 emulator loaded, select the 24LC EEPROM device from the Device Family menu. Screen13: with the programmer connected to the powered Digital FX Pedal, the Device selected and the HEX file loaded, click the Write button to program the effects into the EEPROM chip. You should be greeted with the Programming Successful message on a green background. Unplug the programmer and test all the effects to check that they are working as expected. However, you can also do it with a regular iron, by alternately heating the joints while holding it with tweezers, until the part comes loose. PICkit 2 programmer emulator Screen12: you can now select 24LC32A from the Device dropdown at upper left, then use the File menu to open the EEPROM HEX file you generated earlier. 42 Silicon Chip The software required to use the PICkit 3 to program the EEPROM can be downloaded here: siliconchip.com. au/link/ab7t If you aren’t sure how to install this software package, see the separate section below. Before starting the PICkit 3 programmer, you need to connect the PICkit 3 to the computer. This so that the program will run correctly at startup. Having installed the software linked above, navigate to C:\Program Files (x86)\Microchip\PICkit 3 v3\ and start the PICkit 3 application, or place a shortcut on your desktop and use that. The programming software will open, and state that the PICkit is connected (Screen8). Under the Tools menu, select “Download PICkit Operating System” (see Screen9). This is the PICkit 2 emulator. Select the file “C:\Program Files (x86)\Microchip\PICkit 3 v3\PK3OSV020005.hex” (installed with the software; see Screen10) and the PICkit 3 will be loaded with the required firmware. Then, in the Device Family menu, select EEPROMS and 24LC (Screen11). Next, find the 24LC32A entry under the Device dropbox (Screen12). Next, using the File menu, load the Spin.hex file locat- Australia’s electronics magazine siliconchip.com.au Screen15: do not be surprised if you get this error message upon closing the programming software. Click Quit. You might need to launch Task Manager (eg, by pressing Ctrl+Alt+Del) to kill the process if it lingers. Screen14 (left): after you have finished your EEPROM programming, if you want to revert the PICkit 3 to normal operation, in addition to refitting the two components removed earlier, you will have to select this menu option to re-load its original firmware. ed at “C:\Program Files (x86)\SpinAsm IDE\hexout\SC patches.hex” (or whatever name you saved it under). Once this file has been loaded, the EEPROM can be programmed. First, make sure one of the first eight effects is selected so the FV-1 chip will not access the EEPROM during programming. Then connect the PICkit 3 to the ICSP header, with its triangle to pin 1, and switch on power to the Digital FX Pedal. Do not select the option of target power via the PICkit. Then click the “Write” button to program the EEPROM – see Screen13. Before closing the program, in the Tools menu, select the “Revert to MPLAB mode” option to restore the PICkit 3 to normal operation, suitable for use with MPLAB (see Screen14). When closing this program, it is not unusual to see an “unhandled exception” dialog box appear, as shown in Screen15. Click “Quit” to close it. The program may take a while to close; you might have to force close it using Windows Task Manager. If you are finished programming, you can reinstall TR3 and R50 on the PICkit 3 board, to restore its full PIC programming function. Catch 22 If an effects patch fills the entire 512 x 8-bit memory block, it must be placed in the last used PROG position. Otherwise, that effect will not work, as its data will be corrupted. The catch is that you will not know as the corrupted file will have similar ending values to the other patches. The hex files are easily viewed in the PICkit 3 Programmer siliconchip.com.au software. Typical effects patches do not fill the entire 512 bytes, and the unused memory is filled with 00s and 11 at every 4th location. So a corrupted file will not be evident until it is tested and found not to work. Swapping the non-working patch to the end of the list by reordering the PROG selections should solve this. It also means that you can only use one effects patch that fills the entire allocated memory section. We found that the “Faux-phaser-2” patch did not work when it was placed in PROG6 position. Moving it to the PROG7 (last) position made it work. We then realised that the code for this patch filled the full 512 bytes. When this patch was in PROG6, the 512 bytes were not completely filled with code, showing that it was corrupted. Note that each PROG entry has its own address range. These are: • PROG0: 000 to 1FF • PROG1: 200 to 3FF • PROG2: 400 to 5FF • PROG3: 600 to 7FF • PROG4: 800 to 9FF • PROG5: A00 to BFF • PROG6: C00 to DFF • PROG7: E00 to FFF Home-grown effects Writing your own effects, or modifying existing effects patches, can be done using SpinAsm, or you can use a graphical programming package called SpinCAD Designer. You will need to do some reading to be conversant with how to write the required code. You can also load some of the already-written effects patches to use as examples. The SPIN Semiconductor website has much of the required information. It is recommended that you read the knowledge base section: siliconchip.com.au/link/ab7q This has information on the FV-1 architecture, instruction set, DSP basics and coding examples to list a few. You would also benefit from reading the data sheet and the user manual. These are found at siliconchip.com.au/link/ab7r and siliconchip.com.au/link/ab7s SpinCAD Designer SpinCAD Designer is an open-source Java project which allows the creation of patches for the Spin FV-1 audio DSP chip using graphical instead of text coding. SpinCAD is available from https://github.com/ HolyCityAudio/SpinCAD-Designer Australia’s electronics magazine May 2021  43 Installing SpinCAD Designer You can download SpinCAD from https://github.com/ HolyCityAudio/SpinCAD-Designer Click the green ‘download code’ button towards the upper righthand corner of the page (see Screen18), then select “Download ZIP”. Having downloaded the file, extract its contents to a suitable directory such as “C:\Program Files\SpinCad Designer”. Screen16: SpinCAD Designer allows you to design effects patches without having to write assembly language code. The graphical designer is easy to use, and once you know what you are doing, you can create an effect very quickly indeed. If you need help installing this, see the separate section on installation. Navigate to the SpinCAD Designer folder and open the Spin CAD-designer-1027 jar file. This will start SpinCAD Designer. Note that the patches folder for SpinCAD Designer includes many effects patch files that have already been written, in a compressed format. These are included as SpinCAD files as well, as SpinAsm files. These can be used as examples to get you started. The example shown in Screen16 is a test patch written for a ring modulator in Patch0. It includes a 6-band equaliser and ring modulator adjusted with Pot 0. It took me only a few minutes to create, and probably is not a very good effect, but it does show that the graphical program is very useful and effective for developing an effects patch. Once you have created a patch, it can be saved as an assembler file and then loaded into SpinAsm and converted to the Intel hex format using the “Save Patch as ASM” option in the File menu (see Screen17). Screen18: you need to extract the SpinCAD Designer software zip before you can use it. You can accept the default destination, as shown here, or alter it before continuing. To run SpinCAD, you will need the Java Runtime Environment JRE/JDK 1.8 or later installed. You can get this from www.java. com/en/download/ After downloading Java, run the executable file and agree to allow it to make changes to your device. Click through the following steps to install the Java runtime environment. Now you can navigate to the folder where you extracted SpinCAD Designer earlier, and launch the Spin CAD-designer-1027 jar file. Installing SpinAsm When you click on (or type in) the link to download SpinAsm, you might get a dialog box like the one shown in Screen 19. Screen17: once you have created your effect in SpinCAD Designer, select the “Save Patch as ASM” option to get a file that you can program into the Digital FX Pedal using the procedure described in this article. It’s also a good idea to use the “Save Patch” option to save it in a format that will allow you to make changes in future! 44 Silicon Chip Screen19: when you click the link to download Spin, depending on what web browser you are using, you will probably be faced with a save dialog something like this. You will need to click “Save File” and allow it to download before launching the installer. Australia’s electronics magazine siliconchip.com.au Select “Save File”, then once it has downloaded, open it. It might ask you whether you want this app (from an unknown source) to make changes to your computer. Select Yes; then, you can agree to the terms and conditions and select the standard setup option (Screen20). Screen20: the default options to install SpinAsm IDE will suit most users. Click Next to continue, then click Install (Screen21). Screen23: after SpinASM itself is installed, the driver installer will launch. Click Next to complete the setup. Installing the PICkit 3 Programmer software The software zip file (the link is under “PICkit 2 programmer emulator” in the main body of this article) is in a compressed format, often described as an archive. Open the file and select ‘extract all’, accepting the default folder (C:\ Users\<username>\Downloads\PICkit3 Programmer Application v3.10), as shown in Screen24. You can change the default extraction path if you like; it doesn’t matter since, once installation is complete, you can delete the folder entirely. Screen21: you can change the SpinAsm IDE installation folder, but we left it at the default. When you are prompted to install the driver (Screen22), click Next, then Finish (Screen23) and installation is complete. Screen24: now that it has been installed, you can click Finish and launch the software. Screen22: as part of the SpinAsm installation, you will also need to install the SpinAsm drivers, which will require you to click through some more permission dialogs. siliconchip.com.au With the box at the bottom ticked, the folder should appear as soon as the extraction process has finished. When that happens, launch the setup executable (normally done by double-clicking on the file). Use the default settings and file locations and agree to the conditions. The installer will ask permission to install the software. Upon clicking Yes, the installation will begin. When completed, close the installer. To save disk space and reduce clutter, after the installation has completed, you can delete the extracted installation folder, as the SC files will have been copied elsewhere on your system. Australia’s electronics magazine May 2021  45 64-KEY Last issue we described low-cost hardware that you can build to work with MIDI, including a comprehensive MIDI Encoder Shield and a MIDI Key Matrix to drive it. We have developed some more software to make even better use of this hardware, and we’ll show you how you can even use it with Android smartphones and tablets. T he first part of this series showed how to build a simple MIDI Key Matrix, consisting of a grid of 64 tactile switches. These are scanned by an Arduino-compatible Leonardo board, which acts as a MIDI Encoder. It uses its USB peripheral to generate MIDI messages which can be received on a personal computer running synthesiser or digital audio workstation (DAW) software. It’s also fitted with a pair of MIDI-standard 5-pin DIN sockets. These are configured as MIDI-out and MIDI-in ports. MIDI-out ports generate ‘hardware’ MIDI messages which can be fed to the MIDI-in port on a device such as a MIDI synthesiser. Thus, the MIDI Key Matrix and MIDI Encoder together form a generic MIDI output device, suitable for triggering sounds and notes on any number of MIDI-capable devices that have either a USB or 5-pin DIN MIDI-in connection. It also has a very basic onboard synthesiser which delivers notes to a small 1W speaker as key events occur. On its own, it forms a very simple musical instrument. 46 Silicon Chip While it’s possible to wire up the matrix of 64 keys by hand, we also showed how to build a PCB-based Switch Matrix, which simplifies this greatly. The Switch Matrix has support for several differently-sized tactile switches. We expect some people will think of new and interesting ways to use this hardware. This might include custom programming of the MIDI Encoder to perform a specific role in a MIDI setup. Or it Australia’s electronics magazine might involve using the Switch Matrix to simplify interfacing to hardware in an unrelated project. If you want to know more about MIDI’s background and workings, see the “What is MIDI?” panel on page 51. LED Matrix While we intended to create a cheap and useful MIDI input device, we’ve used the ample space on the Switch Matrix PCB to add extra features. In particular, there are pads to allow illuminated switches to be fitted. These are also connected in matrix fashion back to a pair of 8-way connectors (CON3 and CON4), with a series resistor for LED current limiting on each row. We showed some basic code to drive the LEDs in the first part, but the original hardware couldn’t sense keypresses and drive the LEDs at the same time. We will now address that. Leonardo limitations The problem is that there aren’t many pins spare on the Arduino Leonsiliconchip.com.au MATRIX Part 2 – by Tim Blythman Here’s the full rig, with an Android phone hooked up to the MIDI Encloder and Matrix. A second Leonardo drives the LEDs on the Switch Matrix. ardo; certainly not enough to drive the LEDs and scan the switches simultaneously. Indeed, there aren’t many Arduino compatible boards around that would allow that and still provide a USB peripheral. The Arduino Mega has enough pins, but unfortunately, its USB support is limited to serial data through a separate USB-serial IC. In the last issue, we noted that if you just want to light up all the LEDs, you can simply connect power rails to CON3 and CON4 on the Switch Matrix PCB. But if you want independent control of the LEDs, the simplest approach is to add a second microcontroller board. You might want to light up each key as a prompt to indicate which one should be pressed next. This could be handy as a learning tool, helping to learn a musical piece by rote. Another example would be to light up the LEDs in time with the keys that are being pressed. This is what we’ve done with our example code. A tale of two micros To light up the keys in time with the siliconchip.com.au keypresses requires communication between the two micros, even though we’ve already established that one of them doesn’t have many pins to spare. Our trick is to borrow one that’s already being used. The MIDI specification supports so-called SYSEX (System Exclusive) messages. These messages are intended to allow manufacturers of MIDI equipment to send custom data that doesn’t fit into the standard messages. They can be used (for example) to send audio sample data between devices. Many manufacturers have specific identifiers, but the 0x7D identifier can be used for development purposes, and that’s what we’re doing here. Using this identifier means our data won’t be confused with another manufacturer’s signals. The System Exclusive message that we send consists of a status byte 0xF0, identifier 0x7D, followed by the ASCII codes for ‘SC’. These extra characters reduce the chance that the data could be misunderstood by other equipment. We follow this with any number of data bytes in the range 0x00 to 0x7F, which gives us 128 codes. Codes 0-63 turn off LEDs 0 to 63 respectiveAustralia’s electronics magazine ly, while codes 64-127 turn on one of them. Any data byte greater than 0x7F (ie, with the most significant bit set) ends the SYSEX message, although we send 0xF7 as this is the defined ‘End SYSEX’ command. All MIDI equipment understands this, and thus everything remains in sync, ignoring data inside these packets. We send this data out on the MIDIout port. Most MIDI equipment will ignore these bytes, so it won’t interfere with our note messages. It’s then a simple case of receiving that data and displaying it on the LEDs. We’re using a second Leonardo board to do this. Because MIDI data is no more than a serial bitstream at 31,250 baud, we set up a state machine to monitor the incoming data. Once it has received the bytes 0xF0, 0x7D, ‘S’ and ‘C’, it assumes that any following data bytes are commands to turn the LEDs off and on as described above, until it receives a byte above 0x7F, which resets the state machine to wait for the sequence again. The LEDs are multiplexed by a timer interrupt, which ensures that each May 2021  47 Fig.5: this wiring bypasses the MIDI connectors and allows the MIDI Encoder to both power and communicate directly with the LED Driver. Naturally, there is no isolation in this case! Although two wires are shown for data (green and orange), only one is needed as the pins at each end are connected by PCB traces. column receives an equal amount of time and thus the LEDs are driven with even brightness. The code scans through each column in turn, lighting up the LEDs according to the previously received commands. LED driving hardware Since our LED Driver uses standard MIDI packets, the deluxe way to assemble this is to use two Leonardo boards, each topped with a fully kitted-out MIDI Encoder. A standard MIDI cable from the MIDI-out port of the unit programmed as the MIDI Encoder is connected to the MIDI-in port of the unit programmed as the LED Driver; each unit is supplied with power via its USB port. The LED connections on CON3 and CON4 of the Switch Matrix are connected to CON2 and CON1 on the MIDI Shield, as described in part one. So the MIDI Encoder Shield only needs the MIDI-in, CON1 and CON2 headers to act as the LED Driver. In line with our cheap and cheerful philosophy for this project, we have a simpler solution. Fig.5 shows the minimal wiring needed, with the MIDI Encoder Shield at left and the LED Driver board (using the same PCB) on the right. Our photos show this minimal arrangement too. We have soldered a 2-way female header to each PCB at the 5V/GND connections, and these are connected by a pair of jumper wires (red and blue). The LED Driver PCB is simply our shield PCB from part one fitted with headers to break out the connections. There are also headers underneath to connect to the Leonardo. The easiest way to solder these is to insert the headers into the Leonardo’s sockets, slot the PCB onto the headers and then solder them. The pins are thus square and aligned. We used socket headers for CON1 and CON2 to allow simple plug-plug jumper wires to be used, although these could even be soldered in place. Make sure to wire pin 1 of CON2 (shield) to pin 1 of CON3 (Matrix) Parts list – additional parts for LED Driver 1 double-sided PCB coded 23101211, 69 x 54mm 1 Arduino Leonardo module 1 10-way pin header (shield headers to Leonardo) 1 8-way pin header (shield headers to Leonardo) 2 6-way pin headers (shield headers to Leonardo) 2 8-way pin headers or sockets (to connect to Matrix PCB) 2 8-way jumper wires (to connect to Matrix PCB) 3 jumper wires (to connect to MIDI Encoder) 48 Silicon Chip The Switch Matrix fitted out with a full complement of 3D-printed key caps. Australia’s electronics magazine siliconchip.com.au Here’s the front and rear PCB photographs which match the overlay diagrams at left. Obviously, there’s not much on the rear side of the PCB except sockets, as shown. These plug directly into the “sandwiched” Leonardo board. and pin 1 of CON1 (shield) to pin1 of CON4 (Matrix). The data line is connected at the MIDI Encoder end by piggy-backing it onto the TX jumper at JP1, while the LED Driver is connected to the RX header at JP1. If you have a bare Leonardo at either end, you could wire from the TX pin (pin 1) of the MIDI Encoder Leonardo to the RX pin (pin 0) of the LED Driver Leonardo. Of course, you will need the Switch Matrix variant with illuminated switches fitted; they should have their anodes towards the top of the PCB. Software We’ve updated the MIDI Encoder software also to output the SYSEX LED data, so upload the “MIDI_ENCODER_ LED_SERIAL_OUT” to the Leonardo which is acting as the MIDI Encoder. The LED Driver Leonardo should Screen1: the FluidSynth MIDI Synthesiser App has few controls, but that is part of what makes it easy to use. Once the MIDI Encoder (or other MIDI device) is plugged in, it becomes available from the top of the screen. siliconchip.com.au similarly be programmed with the “MATRIX_LED_DRIVER_SERIAL” sketch. Once that is done, and both boards are powered up, pressing any key should cause the corresponding LED to light up. If they don’t match up, try swapping or rotating the connections to CON3 or CON4 of the Switch Matrix. If you wanted to do something fancy, like have the LEDs “radiate out” from each key pressed, you just need to make modifications to the MATRIX_ LED_DRIVER_SERIAL sketch. The 16mm spacing on the Switch Matrix is a good compromise between compactness and usability. If the keys were much closer, there’d be a higher chance of pressing more than one key, while a wider spacing would quickly cause the PCB to blow up in size. We made the off-hand comment last issue that 3D-printed keycaps would be an economical way to add finishing touches to an illuminated matrix. While 12mm tactile switches can be found with large buttons which are easy on the fingers, there are fewer options for the smaller illuminated parts. Unfortunately, many small, illuminated switches only support small keycaps (around 10mm), which would look very odd on the 16mm spacing we have used. So we designed a 3D-printed keycap to suit the ILS series switches that we used. We printed some of these in a translucent PLA filament (Jaycar’s Cat TL4274), and it helped diffuse the light from the LEDs, although as they are so small, they were a fussy fit. So we’ve made the 3D files available for download if you want to 3D Screen2: the MIDI Encoder appears as an Arduino Leonardo device when selected. The number shown is different every time the Encoder is reconnected, but this doesn’t seem to cause any problems. Screen3: we’ve only used the Settings option from the menu. Recordings are a paid premium feature that we did not test as we figured it would be easy enough to connect a 3.5mm stereo aux lead to the phone’s jack to record audio. 3D printed keycaps Australia’s electronics magazine May 2021  49 Apple devices (such as iPhones), but it’s not something we’ve delved into. Note also that there are many different types of Android phones, and we can’t claim that this will work with all of them. If you can check that your phone supports USB OTG (on-the-go) and has a fairly recent Android version, then you have a decent chance of success. Android is not restricted to mobile phones; some tablets run Android, plus some other devices (eg, smart TVs). What you need Screen4: it’s only necessary to download the SoundFont file during initial setup. After this, you will just need to check that the MIDI Encoder is selected on the main screen before using it. print your own keycaps and try them for yourself. The accompanying photos show what the result looks like. MIDI on Android While testing our different MIDI hardware variants, including the MIDI Encoder PCB and the Switch Matrix PCB, we wondered if there was a way to connect the MIDI Encoder to a smartphone. With many people possibly having an old mobile phone around that could be repurposed, such an arrangement would be a quick, cheap and easy way to create a useful musical instrument. We only looked at Android devices because that is what most of us (at SILICON CHIP) use. Our minimal research suggests that this might be possible on One thing that you’ll almost certainly need is a USB on-the-go (OTG) adapter. This allows the USB socket on your phone to behave as a host device instead of a peripheral device. Not all phones support OTG, but it’s quite common these days. The OTG adapter will have a plug that suits the USB socket on your phone (micro-USB or USB-C) and a USB-A socket (such as you might find on a computer). Jaycar Cat WC7725 (micro-USB lead) or Cat WC7709 (USB-C lead) should work. Or use Altronics Cat P1921 for micro-USB or Cat P1924 for USB-C. Smaller adaptors are available which do not have any leads; they connect the devices directly. We like them because they’re small enough to carry around in your pocket or bag. You can see one of these in our Android phone photo. Indeed, an OTG adapter is a handy thing to have these days, with many phones having support for USB keyboards, mice and flash drives. We’ve even seen an app that lets you use one to program Arduino boards! Having said that, writing Arduino sketches on such a small screen isn’t the easiest thing in the world. Note that your phone and apps need to have support for the devices you want to attach. Fortunately, MIDI is supported as a Device Class Definition by the USB standard, meaning that any compliant USB MIDI device should work, without needing specialised drivers. MIDI Apps We don’t have any affiliation to the following Android MIDI Apps; we found them by searching the Google Play Store. The first one we tried was called MIDI Keyboard, which was able to recognise the attached Leonardo, but was limited to a single piano instrument. So we kept looking to see what other options were available. The second App, called FluidSynth MIDI Synthesizer, gave a few more options. At the time of writing, it generally had positive reviews, and it also appeared to support downloadable SoundFont (.SF2) files. There is a paid upgrade available to allow recording on your device, but we were well entertained by simply playing sounds back through our phone speaker. A connection using a 3.5mm stereo aux cable should be sufficient to connect the audio to other equipment for amplification or recording. Installing the App was quite simple. It works with Android 6 and later. We found that it needed permission to access device storage; this is required to access the downloaded SF2 files. Screen1 shows its initial screen. When a MIDI device (like the MIDI Encoder) is plugged in via an OTG adapter, it appears in the dropdown menu at the top of the screen. Screen2 is shown when such a device is selected, giving control over the MIDI device. From the menu icon at top left, select Settings (Screen3) and choose “Download a SoundFont”. The Chaos V20 option (Screen4) is the Fig.6: the arrangement of a typical ‘Note-on’ message. The first byte has its most significant bit set to flag that it is the start of the message. The high nybble of 9 means that this is a Note-on message (8 would mean Note-off), with the low nybble containing the channel number. The following bytes carry 7-bit values for note number and velocity. 50 Silicon Chip Australia’s electronics magazine siliconchip.com.au What is MIDI? MIDI stands for Musical Instrument Digital Interface. It’s a standardised system for communicating between electronic musical instruments, keyboards, controllers and sequencers (including PC-based sequencers). The original MIDI standard was agreed on by a group of musical instrument makers in 1983, and has been used and extended since then. The last time we looked at MIDI was before the Arduino phenomenon had fully developed. Arduino has made it very easy to interface electronics to MIDI equipment. People have created an assortment of controllers, instruments and even synthesisers with a variety of sounds using Arduino. A MIDI 2.0 standard was released in January 2020, and is intended to be backwards-compatible with the original MIDI specification. The new standard is not yet in widespread use and is still undergoing testing. Electrical protocol The standard specifies events that occur (such as the start or end of notes being played), which are encapsulated in messages that are transmitted between devices. The ‘original’ MIDI relies on serial data communication at 31.25kb/s using asynchronous 5mA current-loop signalling, with the current provided by the transmitting end. This means that each byte of a MIDI message takes only 320µs to be transmitted (counting start and stop bits). Since MIDI messages are either one, two or three bytes in length, this means that over 1000 such messages can be sent each second via a single MIDI cable. Each MIDI cable carries only one signal, so for bidirectional communication, two cables must be used. The cables themselves use shielded two-conductor wire. All MIDI cables are fitted with standard 180° 5-pin DIN plugs at both ends. However, only pins 4 and 5 are used for the actual current loop signalling (wired 4-4 and 5-5). Pins 1 and 3 are left unconnected, while the shield braid is connected to pin 2 at each plug. Inside MIDI equipment, pin 2 is connected to Earth only on MIDI OUT sockets. This provides shielding via Earthed cable shield braids without creating Earth loop problems. Unlike most other current-loop signalling protocols, current only flows in a MIDI link when data is being transmitted. This allows MIDI cables to be ‘hot’ plugged and unplugged without any problems, as long as they are not in active use. All MIDI inputs are provided with 3kV of galvanic and electrostatic isolation via an optocoupler to prevent equipment damage due to wiring errors or component faults. For proper MIDI communication between equipment, a MIDI OUT or MIDI THRU socket at one end must be connected to a MIDI IN socket at the other. That is what we call the ‘hardware’ MIDI implementation. There also exists a USB implementation that allows for much faster communication. This is not merely a USB-serial type of translation (although software exists to use USB-serial converters for this purpose). Jaycar’s Cat XC4934 USB MIDI Interface is one example of available hardware for translating between these two protocols for device interconnection. Since MIDI is not much more than a series of data bytes, various other ‘hardware transports’ have been used. These include FireWire, LAN and even wireless transmission methods. Logical protocol Each message starts with a byte that has its most significant bit set, and the remaining bytes (for practically all messages) has the most significant bit cleared. This means it is very easy to serialise and siliconchip.com.au packetise the data for conversion over other transports. There is a single main controller or sequencer in most MIDI systems from which most of the MIDI messages originate (often the computer, or perhaps a keyboard or DAW). When these messages must be sent to more than one instrument, they can be distributed in either ‘star’ or ‘daisy-chain’ manner as desired. It’s possible to combine two MIDI streams. However, a device to do that is not trivial to implement, as it must handle the case when two messages arrive at the same time and queue them for consecutive output without delaying them excessively. There’s no need to worry much about the actual code messages sent over the MIDI links. Nowadays, that is handled by sequencer or other software running in the PC and by firmware running in the other instruments and keyboards. It’s probably enough to know that most MIDI messages are short commands to allocate a particular instrument to a specific channel, to tell it to start or stop playing a particular note, to change the instrument’s attack/decay or other performance parameters, and so on. As mentioned earlier, these commands are generally in the form of three-byte messages (see Fig.6). However, some configuration and/ or system management messages are only one or two bytes long. Longer, equipment specific configuration messages also exist, for example, to load digital audio samples into a sampler. File format Using a PC-based music editing and sequencer program, and perhaps with a MIDI music keyboard to feed in the actual notes, you can assemble a complete sequence of MIDI commands to play a piece of music – eg, on the ‘instruments’ in a synthesiser. The synthesiser can then be made to ‘perform’ that piece of music by merely sending the sequence to it, via the MIDI link. When you’re happy with the result, you can save the sequence on disk as a MIDI music file. These have a standardised format and are identified with a “.MID” extension. The .MID file format is essentially a series of MIDI messages after a header, stored in chunks (in a similar fashion to .WAV file chunks) and intermingled with timing data to ensure that the messages can be played back correctly. It’s important to realise that although a MIDI music file may look superficially similar to a .WAV file of a digital sound recording, it’s really quite different. It’s more like an electronic equivalent of sheet music – simply a sequence of detailed instructions describing how to play the music. In this case, they are instructions for electronic instruments rather than for human players. And depending on the instrument that is providing playback, the sound that is output can vary substantially. Software The advent of Arduino-compatible boards with an integrated USB peripheral such as the Leonardo (based on the ATmega32u4 microcontroller) makes it easy to implement a USB MIDI interface. And there is much PC software around that can work with USB MIDI devices. While testing our design, we experimented with MuseScore (https:// musescore.org/en), an open-source score-writing program and Anvil Studio (www.anvilstudio.com), a digital audio workstation program. Both can act as a synthesiser, producing sounds based on incoming MIDI messages. If you want to delve more into the technicalities of MIDI, take a look at the MIDI Manufacturers Association website at www.midi.org/ specifications Australia’s electronics magazine May 2021  51 A pair of 2-pin header sockets soldered back to back and with their pins bridged can be used as a jumper that provides extra sockets to tap into. We used this arrangement to break out the MIDI signal from the MIDI Encoder board from JP1, with an extra jumper wire leading to the LED Driver board. PROGRAM” button to activate it. By default, the MIDI Encoder only delivers data on channel 1, but we have created a software variant that outputs on four channels instead. The Arduino sketch is named “MIDI_ENCODER_4_ CHANNEL”, and when uploaded to the MIDI Encoder and Switch Matrix hardware, will generate events on channel 1 when S1-S16 are pressed, channel 2 for S17-S32, channel 3 for S33-S48 and channel 4 for S49-S64. You might find that this combination works very well for triggering sound effects. Look near the bottom of the instrument list, among the percussion instruments. Conclusion Our basic setup allows access to myriad options through musical instrument choices and SoundFont files. The Encoder PCB here is only fitted with headers to connect to the Switch Matrix. smallest of the download options, and gave many different sounds. Returning to the main screen (Screen2) then allows the various channels and instruments to be configured. Having done that, you can use the MIDI Encoder to play through the phone’s speaker. The Channel and Instrument dropdowns allow specific instruments to be allocated to different channels. Once each channel/instrument combination is set, press the “SEND With the addition of a second Leonardo board and not much else, we can add controllable LEDs to our MIDI Encoder and Matrix. And since our system uses the existing MIDI hardware, our software could be modified to give MIDI control over other things too. Using our MIDI Encoder and Switch Matrix with an old Android phone is a very economical way to access a full range of playable sounds. Of course, you’re not limited to using our MIDI Encoder with this App. You might want to modify the Arduino sketch to provide your own interface, or even plug in another USB MIDI device. Links SoundFont files: https://musescore.org/en/handbook/soundfontsand-sfz-files FluidSynth MIDI Synthesizer App https://play.google.com/store/apps/details?id=net. volcanomobile.fluidsynthmidi SC Glossary Channel: Each MIDI message can specify one of 16 channels, allowing data to be routed to or from different instruments while maintaining its source or identifying that it should be played back on a particular instrument. Our software uses a single, fixed channel which can be changed in the code. Message: The smallest unit of MIDI data is a message and corresponds to a single event (like a piano key being pressed or released) or a setting that is to be changed. Note number: Each musical note is associated with a number in the range 0-127. Middle C is assigned to number 60. Our design implements 64 of these (in an 8x8 matrix), with the range start and end defined in the code. Note-on and Note-off messages: The Note-on and Note-off mes52 Silicon Chip sages correspond to events that occur during music playback and are the only messages that the Encoder generates. They include information about the channel, velocity (see below) and note number. Status: The first byte of a message is called the status byte and is marked as such by having its most significant bit set. Typically, the lower nybble (four bits) of the status byte contains a four-bit value indicating the channel number. Velocity: Velocity is how fast the key on a musical instrument is pressed, but is usually manifested as how loud a note sounds (which is related to how fast, for example, a piano key is pressed). Our software uses velocity 64, which is the default for devices that can’t detect key velocity. Like Note number, it can have the value 0-127, with 0 also corresponding to Note-off for some devices. Australia’s electronics magazine siliconchip.com.au r u o y For ojects r p Y I D 4 ale 2 On S to April 021 ay, 2 23 M Flashforge 3-Way Desk Adventurer 3 Powerboard 3D Printer new Brushed aluminium pop-up power board that flush mounts into a desk. Equipped with 2 x USB Type A sockets, HDMI & ethernet RJ45 sockets. 240V mains powered, terminated with mains plug. 112Wx94Dmm. MS4106 BUILT-IN CAMERA Control print jobs via the cloud. Removable print bed, detachable nozzle, & automatic filament feeding. Prints up to 150Lx150Wx150Hmm. TL4256 JUST 139 $ JUST 899 $ LOTS OF FILAMENT COLOURS & STYLES AVAILABLE FROM $19.95 best seller Arduino® Compatible UNO R3 Board 37 Piece Deluxe ONLY Module $ 95 Package 29 Stackable design makes adding expansion shields easy. Powered by DC or a USB. ATMega16u2 USB-Serial chipset. 53Lx75Wx13Hmm. XC4410 Includes commonly used sensors & modules for Arduino® projects. Joystick, magnetic, temperature, IR, LED and more. Clear plastic organiser. XC4288 NOW 79 $ SAVE $20 RUNS UP TO 2 MAINS APPLIANCES PERFECT FOR COMPACT WORKSPACES SPIRIT LEVEL Desktop Magnifier with LEDs 100mm 3-dioptre glass lens provides powerful magnification. Adjustable stand. Changeable lens. QM3552 4" 5-Dioptre Lens To Suit QM3553 $12.95 POWERS SENSITIVE DEVICES 2000W Pure Sine Wave Inverter NOW 49 $ 95 12VDC to 230VAC inverter to power devices such as power tools, laptops, battery chargers etc. Dual AC output. USB port. MI5740 See website for full range. SAVE $10 Shop the catalogue online! JUST 499 $ Free delivery on online orders over $99* Exclusions apply - see website for full T&Cs. * NOW FROM 6995 $ Wall Mount TV Brackets with 180° Swivel UP SAVE TO $15 Safely hold flat panel TVs. Ultra-thin design. Built-in spirit level. VESA compliant. 23-55" CW2868 NOW $69.95 SAVE $10 32-70" CW2869 NOW $84.95 SAVE $15 See website for full range. www.jaycar.com.au 1800 022 888 Make it visual IP65 RATED 8x5 RGB LED Shield ONLY 2995 $ RGB LED Strip Light Flexible and waterproof LED strip light with 120 (60 LEDs/m) addressable WS2812B RGB LEDs to create amazing lighting displays. 5V. 2m long. XC4390 INDIVIDUALLY ADDRESSABLE LEDS NOW 14 $ 95 15% OFF RGB LED Ring Module Add dazzling circular-shaped LED patterns to your next project or costume. 72mm in diameter and 24 x RGB LEDs with 256 brightness levels. XC4385 14 95 RGB LED Module Ideal for electronic prototyping and Arduino® projects. Labelled rows and columns. Adhesive back for mounting. PB8815 ONLY 11 $ 95 Logic Level Converter Module Includes 70-pcs of single core wire. 5-pieces each of 14 different lengths. PB8850 Provides two bi-directional channels to safely marry 3.3V with 5.0V. Drops straight into solder-less breadboard. 12-pin DIL package. XC4486 NOW 3 $ 95 20% OFF Breadboard Power Module More ways to pay: 95 20% OFF Breadboard Jumper Kit Adds a compact power supply to your breadboard. Power from a USB socket or DC. 3.3V or 5V switchable. XC4606 NOW 3 $ ONLY 995 $ AVR ISP 10pin to 6pin Adaptor Use with an ISP programmer to update bootloaders or reflash bricked boards. 10 pin plug to 6 pin socket. XC4613 NOW 7 $ 95 20% OFF NOW 395 $ 4 pin header. Can be interfaced with a variety of microcontrollers. 3.3-5VDC. XC4428 20% OFF NOW 1695 $ 15% OFF SEND & RECEIVE INDICATORS Breadboard with 830 Tie Points 25% OFF Strip of eight RGB LEDs which can be controlled by a single Arduino® pin. Daisy chain up to 1000 LEDs run from one pin. 256 brightness levels. 5V. 54mm long. XC4380 A mini-USB to 6-pin serial port module used to communicate with Arduino® boards and modules. Uses the original FT232 chip with power, send and receive indicators. 3.3V-5VDC. XC4464 ONLY $ 14 95 RGB LED Strip Module USB to Serial Adaptor Module NOW $ Plugs directly onto your UNO compatible board to create a dazzling LED display. 40 x RGB LEDs. Stackable design. Built-in driver IC circuit. 12VDC. XC3730 NOW 7 $ 95 20% OFF RS-232 to TTL UART Converter Module Connect a legacy device (or computer) to your existing Arduino® board to directly communicate with a huge variety of serial peripherals. Supports TX and RX signals. XC3724 NOW 395 $ 20% OFF 5V DC to DC Converter Module Capable of providing a stable 5V, from a single Li-Po or two Alkaline cells. Input: two solder pads. Output: female USB socket. 2.5-5VDC. XC4512 Spend $50 on any Arduino® compatible boards and get magazines* Make it wireless Wi-Fi Mini ESP8266 Main Board HALF PRICE Arduino® compatible. Perfect compact solution to your IoT sensor node problem. 80MHz microcontroller with Wi-Fi into a board. 4MB flash memory. 11 digital IO pins. 3.3V. XC3802 *Choice of BE5025 or BE5030 ONLY 24 95 $ ESP32 Main Board with Wi-Fi and Bluetooth® Arduino® compatible. Dual core microcontroller equipped with Wi-Fi and Bluetooth® connectivity. 512kB of RAM, 4MB of flash memory and heaps of IO pins. 3.3V. XC3800 95 59 MEGA Board with Wi-Fi $ Arduino® compatible. Stackable design and features more I/O pins, memory, PWM outputs and serial ports than the standard UNO board. Integrated ESP8266 chip connects your projects to the cloud without the need for additional shields. Powered by DC or USB. XC4421 JUST 3995 $ ONLY 1595 $ This stackable shield makes semi-permanent prototyping simple. Provides solder-pad access to all of the Arduino's pins, and a large area of isolated pads. Includes reset button. XC4482 ONLY 9 Compact 16 key touch interface for your Arduino® compatible project. Works on 2.4-5.5V. Onboard power indicator. Two wire serial data interface. XC4602 2 FOR 2 FOR 25% OFF 20% OFF 8 5V Relay Board Operates directly from 5V. SPDT relays. 10A rated. XC4419 RRP $5.45EA. ARDUINO® COMPATIBLE This icon indicates that the product will work in your Arduino® based project. UNO Board with Wi-Fi Arduino® compatible. Stackable design. Includes integrated ESP8266 chip to connect your projects to the cloud without the need for additional shields. Powered by DC or USB. XC4411 JUST 4995 $ 240x320 LCD Touch Screen Large, colourful touch display shield which piggybacks straight onto your UNO or MEGA. Fast parallel interface. microSD card slot. Resistive touch interface. 77Lx52Wx19Hmm. XC4630 $ 16 Key Touch Keypad Module $ 3995 ONLY 3.5" Touchscreen LCD with Stylus and Enclosure for Raspberry Pi ONLY 14 95 95 JUST $ 2995 $ Prototyping Board Shield $ JUST Quad 14 Segment Alphanumeric Display Module Displays numbers, alphabet & special characters. Amber colour backlight. XC3715 Perfect for prototyping or to set up a portable device with your Raspberry Pi 3B+. Minimal set-up. XC4631 Raspberry Pi 3B+ sold separately. 2 FOR 9 2 FOR 10 $ 35 $ $ 35% OFF PIR Motion Detector Module Add motion detection to your project. 0.3-18s adjustable delay. 5-20VDC. XC4444 RRP $5.95EA. 25% OFF DC Voltage Regulator Accepts voltage from 4.5- 35VDC, and outputs any higher voltage from 3-34VDC. Output adjusted via a multi-turn potentiometer. 2.5A max output current. XC4514 RRP $7.95EA. RASPBERRY PI COMPATIBLE This icon indicates that the product will work in your Raspberry Pi project. 1.3" 128 x 64 OLED Monochrome Display Module For projects that don't require full colour. Wide viewing angle to eliminate eye strain. XC3728 RRP $24.95EA. Not sure what to build next? Here's some inspiration: jaycar.com.au/projects Turn ideas into reality BUY BOTH FOR 699 $ CAPTURES GEOMETRY IN AS FAST AS 1 MINUTE! SAVE $49 Anycubic 2-In-1 Wash & Cure Machine VALUED AT $748 Rotating curing platform. Touch button. TL4424 $249 EA. Liquid resin makes for much higher resolution 3D models. It is the latest in 3D printing technology. Anycubic 500ml Resin Wide range of resin available in various colours. Black TL4425 Grey TL4426 Clear TL4427 Blue TL4428 Green TL4429 IDEAL FOR FINE DETAIL COMPARED TO FILAMENT 3D PRINTERS Anycubic Resin 3D Printer The latest in 3D printing technology. Uses liquid resin to create more highly detailed prints compared to filament-type printers. Prints up to 165Hx130Lx80Wmm. Photon Mono UV. Resin in multiple colours sold separately. TL4422 $499 EA. See website for details. 0.01G ACCURACY Desktop SAVE $100 3D Scanner Watch real life objects become digitised before your eyes. Scans up to 250Hx180Dmm. Folds for easy storage. Supplied with MFStudio software with +Quickscan. TL4420 See website for details. JUST 3995 $ EA 5MP USB Digital Microscope IP67 True RMS Autoranging Cat IV DMM Excellent for educational purposes and a myriad of practical applications such as technicians, jewellers, laboratory work and more. 10x to 300x magnification. LED illumination. QC3199 Suitable for most electrical works. 600V, 4000 count. AC/DC voltages up to 1000V. AC/DC currents up to 10A. Data hold and relative function. QM1549 NOW 169 $ SAVE $30 JUST 199 $ 1kg Digital Bench Scale Precision scale with resolution of 0.01g. Weighs in grams, ounces, pounds, grains, carats, troy ounces. Supplied with a wind shield and a built-in bubble level. Mains powered or 4 x AA batteries (SB2425 $3.25 sold separately). QM7264 FROM 3 $ $ Jiffy Boxes UB5 HB6015 $3.45 UB3 HB6013 $4.50 UB2 HB6012 $7.95 UB1 HB6011 $5.25 NOW 149 $ SAVE $10 ONLY Mixed Hook and Loop Cable Ties Keep your cables neat and tidy. Assorted sizes from 125 to 180mm. Pack of 16. HP1232 NOW 8995 $ SAVE $10 Non Contact IR Thermometer Get fast and accurate temperature readouts via the infrared sensor without needing to come in contact with the source. Dual mode: Body (34°C – 43°C temperature range) & Surface (0°C – 100°C temperature range). Fever alarm. Accurate to +/-0.2°C. Requires 2 x AAA batteries (SB2426 $1.95 sold separately). QM7422 Powerful 60W heating element. 160-480°C temperature range. °C or °F temp display. Comes with vented soldering iron stand with integrated sponge and tray. TS1640 13 45 Manufactured from ABS plastic. Various sizes from 83x54x31mm to 197x113x63mm available. 60W ESD Safe Soldering Station NOW 1399 $ JUST 6995 $ ONLY 19 95 $ JST Connectors Kit 95 Includes the popular JST XHP 2.54mm and PH 2.0mm housings & headers. Used for prototyping, repairs, and hobby applications. PT4457 NEW LOW PRICE JUST 2995 $ Large Rare Earth Magnets Exceptionally strong (SCARY!). Made from NdFeB (Neodymium Iron Boron). Nickel plated. LM1652 Set up your workbench ONLY 109 $ Bonus Gift JUST 369 $ Bonus Gift Bonus Gift Regulated 0-15VDC 0-40A Power 13.8V electronics & comms equipment in your home, office, garage or lab. Fixed output voltage. Short circuit protection. MP3096 ALSO AVAILABLE: 10A MP3097 $149 20A MP3098 $199 + FREE DMM QM1517 Valued at $16.95 Highly efficient & reliable for testing and servicing applications. 0-15VDC variable output voltage. 0-40A variable current limiting. Overload and over temperature protected. MP3091 + FREE DMM QM1551 Valued at $69.95 Variable 2 x 0-32VDC 3A Dual output, dual tracking power supply in one case. The two outputs can be operated independently, connected in parallel, or series for multiple output currents and voltages. Large backlit display. MP3087 + FREE Clampmeter QM1632 Valued at $89.95 IDEAL FOR INTRICATE HOBBY WORK FREE 6 Pack Glue Sticks Mini Glue Gun JUST 12 $ Handy tool around the house. Easy and simple to use with trigger controlled glue feed. 30W mains powered. TH1997 95 Workshop Handtools Slotted 1.0, 1.2 & 1.6mm and Phillips #00, #0 & #1 housed in a handy storage case. TD2023 JUST 9 $ 95 $ 210 Piece Rotary Tool Kit Drill, saw, sand, polish, carve, engrave & grind in your workshop. Flexible shaft. 240V <at> 32,000RPM. TD2459 See website for inclusions. JUST 5995 $ Mini Bench Vice Essential tools for any workshop. Artwork Knife HG9955 NOW $3.95 Automatic Centre Punch TH1770 NOW $7.95 Micro Engraver TD2468 NOW $23.95 NOW FROM 3 $ 95 20% OFF Clamp to surfaces up to 1" thick and hold material up to 2" thick. 50mm opening jaw. TH1764 6 Piece Precision Tamperproof Torx Set Consists of T7, T8, T9, T10, T15 and T20 drivers presented in felt-lined plastic case. 145mm long. TD2021 JUST 19 $ 95 Looking for more product information? Visit your local store or our website jaycar.com.au NOW 14 95 $ 15% OFF 15 Piece Micro Driver Set Slotted, Phillips, Torx, Hex of different sizes. Colour-coded handles. 105mm long. TD2069 JUST 27 $ JUST 5495 TH1991 Valued at $3.95 6 Piece Jeweller's Screwdriver Set 439 $ Fixed 13.8VDC 5A JUST 95 Heavy Duty Terminal Crimper Used for crimping lug/eye terminals. Built-in rotating die. Hex crimper. 450mm long. TH1849 22 Piece Long Bit Screwdriver Set with Case Includes popular Slotted, Phillips,Star and TRI bits of different sizes house in a handy storage case. TD2114 JUST 34 95 $ We reward our industry professionals Maximise your network coverage ONLY 895 $ Cat-5 Punch-Down Tool / Stripper JUST 3995 $ 99 $ AC600 USB Dual Band Wi-Fi Dongle Equip your old PC or laptop with ultra fast Wi-Fi. Combined speed of up to 600Mbps (5GHz 433Mbps + 2.4GHz 150Mbps). Compact size. YN8334 SAVE $50 N300 Wi-Fi Ethernet Over Power Kit Extend wireless network using your existing mains wiring. Integrated power socket. Fast 300Mbps data speed. YN8357 AC2100 Dual Band Wi-Fi Router • 10X FASTER THAN CONVENTIONAL FAST ETHERNET • 5 X GIGABIT PORTS • CONNECT MULTIPLE DEVICES Incredibly fast with a combined Wi-Fi speed of up to 2100Mbps (5GHz 1733Mbps + 2.4GHz 300Mbps). 2.4GHz/5GHZ dual-band mode avoids signal congestion. 6 antennas to help boost signal. YN8394 ALSO AVAILABLE: Tri-Band Wi-Fi Router YN8396 NOW $199 SAVE $30 NOW 149 $ NOW SAVE $20 Strip wire up to 5-6mm, and doubles as a punch-down tool for 110/88-type terminals with blade. TH1738 Extra Long Cat5e Cables RJ45 to RJ45. 10m YN8205 15m YN8206 20m YN8207 30m YN8208 $15.95 $22.95 $26.95 $39.95 FROM 1595 $ Network Cable Tracer Easily trace cables even when cables are in a bundle or hidden in NOW punchdown blocks or wall plates. Single/ multi tone SAVE $20 signal. XC5083 7995 $ 1080p Wi-Fi IP Cameras 3995 $ 24 Piece Lock Picking Kit JUST Supplied with a transparent practice padlock so you can see how the various mechanisms operate. 20 Different picks. 3 Torsion wrenches. Automatic tension tool. TH2200 Jaycar will not accept responsibility for any unlawful use of this item. It is intended for private (personal security) and hobby (locksport) use only. JUST 1995 $ PR 2 Piece Cylinder Practice Locks A great complement to the lock picking set (TH2200). 2 Different types of cylinders. See-through design. 2 keys for each lock. TH2202 IDEAL FOR HOME UNIT BLOCK MANAGERS NOW 249 $ Inspection Camera with Record and LED Illumination Outdoor use. 1080p HD recording. Bullet type. With IR LEDs QC3864 NOW $99 SAVE $30 With LED Spotlights QC3857 NOW $129 SAVE $40 (Shown) NOW FROM 99 $ UP SAVE TO $40 Security on a budget SAVE $50 View live footage on a Smartphone. Pocket-size endoscope with camera and LED illumination on a 1m semi-flexible 5.5mm tube to inspect hard to reach areas. 3" display. Records to microSD card (sold separately). HD 720P resolution. Drop resistant. QC8716 32GB microSD card XC4992 $36.95 Smartphone not included. + 1080P Wi-Fi Camera with Security Alarm SECURITY BUNDLE DEAL* Dummy Cameras FROM 16 $ Simple and effective visual deterrent. Bullet or dome with CCTV sticker. Dome LA5332 $16.95 Bullet LA5325 $24.95 95 Surveillance Warning Sign ONLY 16 $ Visual deterrent to warn thieves off. Lightweight and durable. 300L x 300Wmm. LA5115 95 149 $ SAVE $49.85 VALUED AT $198.85 * Package includes QC3870 + QC3876 + QC3874 + QC3872 Use as a stand-alone camera to record audio and video or expand it with sensors (sold separately) to turn it into a security system. QC3870 RRP $129 + PIR Sensor 12m detection range. 1yr battery life. QC3876 RRP $29.95 + Reed Sensor Protects against intrusion. QC3874 RRP $19.95 + Panic Button Trigger security system in duress. QC3872 RRP $19.95 Let's get loud! FROM 14 95 $ Speaker Cable 30m Rolls Light Duty 14/0.14mm WB1703 $14.95 Heavy Duty 24/0.2mm WB1709 $35.95 Extra Heavy Duty 79/0.2mm WB1713 $89.95 2 FOR 30 $ 20% OFF 25mm Titanium Dome Tweeter Produces very crisp and clear high frequencies. 50WRMS. 8Ω. CT2007 $19.95 EA. JUST 19 $ 95 NOW 99 NOW 34 $ $ 95 SAVE $10 IDEAL FOR WORKSHOPS, PA IN HALLS ETC. 2 x 18WRMS Stereo Amplifier Simple, fairly bullet-proof transistor amp and surprisingly loud! 160dB signal to noise ratio. 240V powered. 170Lx77Wx157Hmm. AA0472 Phono Stereo Amplifier Provides frequency equalisation of turntable output and increases the signal level so that it can be fed to your line-level amplifier. AUX input. Volume control. AC1591 FROM 8 $ 95 2 x 15WRMS Stereo Amplifier with Bluetooth® Stream music via Bluetooth® with this compact stereo amplifier. 102dB signal to noise ratio. RCA line input. Extruded aluminium enclosure. 12V powered. 150Lx86Wx51Hmm. AA0522 Front NOW 4995 $ SAVE $10 Back ONLY 5995 $ Stainless Steel Wire Stripper, Cutter, Pliers Strips wire up to 2.6mm and cut steel wires up to 3.0mm. TH1841 4 Way Stereo Speaker Switch Allows up to four pairs of speakers to be connected to a single entertainment unit or amplifier with each pair individually turned on/off. AC1618 NOW 24 95 $ IEC Leads IEC Male to 3pin Female 150mm long PS4100 $9.95 IEC Female to IEC Male 1800mm long PS4108 $8.95 ONLY 3995 $ 65W Laptop Power Supply with USB Spare or replacement power supply for your laptop, notebook, or ultrabook. Slim design. Lightweight. Regulated output. MP3342 AC OUTPUT SAVE $8 NBN/UFB Replacement Power Supply BUY 2 FROM 35 $ UP SAVE TO 25% Plug-in for direct connection into your NBN or UFB connection box. No wiring required. Input: 100 240VAC 50/60Hz. Output: 12VDC 2.5A. MP3538 ALSO AVAILABLE: POWER CONNECTOR WITH BARE ENDS TO SUIT PP2028 $4.95 Excellent for replacement or for new speaker design construction. Clean bass output.Strong steel frame basket. High power magnet and voice coils. 4" 27WRMS CW2190 $24.95 OR 2 FOR $35 5" 50WRMS CW2192 $29.95 OR 2 FOR $45 6.5" 60WRMS CW2194 $34.95 OR 2 FOR $55 8" 90WRMS CW2196 $39.95 OR 2 FOR $65 10" 225WRMS CW2198 $69.95 OR 2 FOR $120 12" 225WRMS CW2199 $89.95 OR 2 FOR $150 FROM 2695 $ Unregulated Power Supplies Supplied with seven different plugs which suit most applications. Single voltage. SAA approved. 9VAC MP3027 $26.95 12VAC MP3026 $29.95 24VAC MP3032 $26.95 FROM Woofer Speakers 6 $ ONLY 12 $ 95 10A Cigarette Lighter Extension Cable 3m long. PP1992 SUITABLE FOR USE IN A VEHICLE OR BOAT SAVE $20 Merit Plugs & Sockets 95 Commonly used in automotive power connections. Smaller in size, extremely rugged and provides higher reliability and current ratings than regular cigarette lighter adaptors. PP2090-PS2096 SLIM & LIGHTWEIGHT JUST 95 49 High Powered $ EA Mains Power Supplies Slim mains power adaptors designed with low energy consumption. Regulated output voltage. Supplied with 7 changeable DC tips. 12VDC 5A 65W MP3560 24VDC 2.5A 65W MP3562 48VDC 1.25A 65W MP3564 FROM 7 $ 95 Waterproof Deutsch Connector Sets Male and female set with housings, wedges, seals and crimp pins. 2 Way PP2150 $7.95 4 Way PP2149 $9.95 6 Way PP2148 $11.95 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 3: Spend $50 on any Arduino compatible boards and get Silicon Chip (BE5025) or Diyode (BE5030) magazines of your choice HALF PRICE. Diyode (BE5030) not available in NZ. Arduino boards apply to XC3802, XC3800, XC4411, XC4421, XC3940, XC4431, XC4414, XC4430, XC3812, & XC4420. Page 4: 3D Printer Bundle includes 1 x TL4422 + 1 x TL4424 for $699. Page 5: Lab Power Supplies deal: Buy 1 x MP3096, MP3097 or MP3098 and get 1 x DMM (QM1517) FREE. Buy 1 x MP3091 and get 1 x DMM (QM1551) FREE. Buy MP3087 and get 1 x Clampmeter (QM1632) FREE. Buy 1 x TH1997 and get 1 x 6pk Glue Stick (TH1991) FREE. Page 6: Security Bundle applies to 1 x QC3870 + 1 x QC3876 + 1 x QC3874 + 1x QC3872 for $149. SUPPLY CHAIN DISRUPTION. We apologise for factors out of control which may result in some items may not being available on the advertised on-sale date of the catalogue. n o e Sav rance clea nes li Y BE S MA OCK Y! ST URR 9" High Resolution Colour LCD Monitor Ideal for car or truck. Equipped with anti-glare shield to improve visibility. RCA & HDMI inputs. 12/24VDC. QM3874 ! TED LIMI H IDEAL MONITOR SOLUTION FOR SECURITY, REVERSING OR MULTIMEDIA ENTERTAINMENT DISPLAY 3-in-1 Jump Starter Jump starter, USB charger & LED worklight in one unit. Huge 300A power. Portable with heavy duty battery clamps. MB3734 Limited stock. Available only in-store & online via Click & Collect. 2.4" LCD NOW NOW 99 99 $ $ SAVE $50 SAVE $40 NOW 1995 $ SAVE $10 2 FOR 60 $ SAVE $39.90 16-Bin Benchtop Storage Organiser Keep your workbench neat and tidy! Provides various methods for storage. Assorted bin sizes. Magnetic strip for tools. HB6341 $49.95 EA. 95 SAVE $15 Front Converts a VGA output to standard RCA composite video, VGA and S-Video outputs simultaneously. Simultaneous PC & TV display. USB powered. XC4907 $ SAVE $30 NOW 5995 $ NOW 189 1080P HD NOW 34 VGA To Composite & S-Video Converter MAGNETIC TOOL HOLDER SAVE $50 Back $ Monitor local wildlife or use as an outdoor security camera. 10sec-10min motion detection recording onto microSD card up to 32GB (sold separately). Water resistant housing. Time lapse recording. Requires 8 x AA batteries (sold separately). QC8041 32GB microSD Card XC4992 $36.95 12 Pack AA Batteries SB2333 $7.95 Provides more uniform heat transfer and can melt all solder pads at once. 240V powered. Temp range: 100-450°C. Pushbutton / digital display. TS1645 Limited stock. Available only in-store & online via Click & Collect. Includes cutters, pliers, knife, tape measure and folding Allen keys held securely in a zip-up case. TD2166 Limited stock. Available only in-store & online via Click & Collect. 720p Outdoor Trail Camera NOW 300W Hot Air Rework Station 30 Piece Tool Kit with Case SAVE $50 109 $ NOW 169 $ SAVE $20 TOSLINK & Coax Audio Cat5e/6 Extender with Infrared Perfect for running ultra-long digital audio connections up to 200m with no loss in quality! Includes 2-way infrared emitter, infrared receiver and mains power adaptor. AC1733 150m 1080p HDMI Cat5e/6 Extender with Infrared Allows full HD 1080p HDMI, bi-directional IR remote signals, RS232 and DC power to be sent over one CAT6 straight through network cable to a distance of up to 150m. AC1746 Limited stock. Available only in-store & online via Click & Collect. LEARN, BE INSPIRED, PROJECTS, WORKSHOPS & MORE! 24/7. 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 confirmed at the time of print. Call your local store to check stock. Occasionally discontinued items advertised on a special / lower price in this flyer have limited to nil stock in certain stores, including Jaycar Authorised Resellers, and cannot be ordered or transferred. Savings off Original RRP. Prices and special offers are valid from 24.04.2021 - 23.05.2021. Review by Allan Linton-Smith EVOR04 real-time Audio Spectrum Analyser This device cost $110 on eBay. It incorporates a spectrum analyser, oscilloscope, VU meter and frequency meter plus more. But is it a tool or a toy? A udio analysers are usually a rare breed, and are generally not anywhere near the budget of DIYers. But they are getting cheaper, smaller and better, and this is a great example of such a device! So is it a tool, or just a toy with a colourful screen? We put it to the test and found that it is remarkably accurate and easy to use. This little gadget combines a spectrum analyser, an oscilloscope, a VU meter and a frequency meter. It also has a few extra bells and whistles, such as a goniometer (which generates Lissajous figures on the X/Y oscilloscope setting). The EVOR04 gives you a stereo audio spectrum in real-time via a 31-band FFT analysis (1/3rd octave). This feature was previously only available on very specialised and expensive devices, such as the Keysight 35670A. Using it Connecting up the analyser is very simple. You can feed in audio signals via shielded cable to a set of screw terminals. If you wish, you can wire up a second set of signals; you can then switch between them. It will run from 5-24V DC, again wired to screw terminals. USB power (5V) is suitable. Once it has been wired up and powered on, simply tap the screen to bring up the main menu and select your preferred mode: spectrum, VU, oscilloscope etc. You can check out the instructions on YouTube for more detail, at https:// youtu.be/vQxXD6dpaCo This device is sensitive down to siliconchip.com.au 2.2mV RMS (AC), but should not be fed with more than 2V RMS. That means it will accept some ‘line-level’ signals, but if you’re taking the output from a CD player, DVD player, Blu-ray player or DAC, you might need to add series resistors to attenuate the signals to a safe level, in combination with the device’s internal input impedance. You could also feed in larger amplitude signals, such as the outputs of power amplifiers. In that case, you would need to add resistive dividers with appropriate power ratings and division ratios to both reduce the signals to safe levels, and prevent them from clipping when the EVOR04 samples them. Viewing modes Screens 1-7 show examples of some of the viewing modes. Note that many of these have adjustable parameters. These are, in order: frequency counter, real-time stereo audio spectrum, VU meter (analog-style), VU meter (bargraph style), goniometer, dual spectrum analyser and oscilloscope waterfall. USB interface The module is equipped with a USB communication interface. With the VuRemote Windows software, it is possible to access all configurable options. This software has the following features: Features ● 3.5in colour TFT LCD touchscreen ● runs from 5-24V DC including USB ● seven modes: VU meter, 31-band real-time spectrum analyser, oscilloscope, envelope, goniometer (X/Y plot), VU meter, frequency meter ● two displayed channels, individually selectable from four inputs ● 167 adjustable parameters ● 48 programmable presets ● 127 image slots for background and skins ● 8Hz to 22kHz bandwidth ● USB communication with a PC Specifications ● ● ● ● ● ● ● ● Supply voltage: 4.8-5.2V DC (USB), 4.2-24.2V (PWR) Operating current: 165-180mA <at> 5V; 38-45mA <at> 24V Input signal range: -2.7V DC to +2.7V DC Adjustable 0dB reference: 2.2mV RMS (-53dBv, -50.8dBu) to 2V RMS (+6dBv, +8.2dBu) Noise level: -85dB with respect to 2V RMS Input impedance: 33-38kW Regulated output voltage: 3.3V (3.1-3.4V), max 50mA draw Input signal levels: 0-0.6V (low), 2.2V to V+ (high) Australia’s electronics magazine May 2021  61 1 • • • • adjust effect and input parameters change images store and load presets store and load the configuration to/from a file • backup and restore • take a snapshot of the screen 2 Applications 3 4 5 6 7 Screens 1-7: some of the viewing modes include a frequency counter, real-time stereo audio spectrum, VU meter (analog), VU meter (bargraph), goniometer (an instrument for measuring angles), dual spectrum analyser, and oscilloscope waterfall. Below: the bottom side of the EVOR04 audio analyser, which measures 108 x 84 x 30mm. 62 Silicon Chip Australia’s electronics magazine So, is it a real instrument or just a nice toy to attach to your amplifier or speaker system? The answer will pretty much be determined by your needs. To try to solve this conundrum, we ran the unit through several tests. To measure signal amplitude, you first have to set up the EVOR at 0dBv or 1V RMS, by adjusting the input amplitude for both channels using the attenuators. Once you are confident that 0dBV is exactly 1V RMS, all the subsequent VU measurements you make can be quantified. We found that the results it gave were generally accurate after this calibration. Screen 8 shows the oscilloscope display when applying a 441Hz square wave to the unit’s inputs. This shows minimal overshoot, and it automatically triggered to give a stable trace. Screen 9 shows the unit in frequency counter mode, measuring a 441Hz signal from an accurate Audio Precision generator. It is accurate to 1Hz as long as the resolution is set at 1Hz. This mode can be very useful for tuning instruments using a microphone and amplifier, or you could use it to calibrate other instruments. Screen 10 is a goniometer trace (Lissajous figure / Bowditch curve) created by the oscilloscope mode on the X/Y setting. The horizontal axis is fed by signals from the left channel input, while the right channel input signal feeds the vertical axis. In this case, the signals were oscillators set at 2kHz and 4kHz, respectively. Screen 11 shows an intermodulation distortion (IMD) test signal being applied in oscilloscope mode. This is a combination of 250Hz and 8kHz sinewaves. It is not synchronised, but this signal fools most benchtop scopes! Screen 12 is a spectral analysis of the same IMD signal, and accurately shows the two signals at a 4:1 amplitude. Further testing showed that the unit can measure harmonic distortion down to -85dB or 0.005%, providing the input amplitude is close to the maximum permitted (6dBv). siliconchip.com.au 8 9 10 11 12 13 Screens 8-13: osilloscope with a 441Hz square wave, frequency counter mode, goniometer trace, intermodulation distortion test signal, spectral analysis of the previous distortion test signal, and one of the VU meter displays. Screen 13 shows one of the VU meter displays which, as mentioned earlier, is accurate as long as the input levels are correctly calibrated. Conclusion This is an interesting and accurate analytical tool. It would be handy for anyone who dabbles in audio for checking amplitude, frequency and distortion in amplifiers, preamplifiers and speakers (with a suitable microphone & preamp). It could also be useful for checking or calibrating other audio instruments such as oscillators, oscilloscopes and multimeters. Every audio experimenter should probably have one of these in their kit. It could be mounted in a Jiffy box or similar; consider that the module is ‘bare bones’ and could be damaged if it is placed on a metal surface or obsiliconchip.com.au ject, or a wire or component comes in contact with it. But probably its best use is mounting it in the front panel of an amplifier to provide some interesting displays while using it! In addition to the ‘nuts and bolts’ functions, it has a fun quality and would look really smart integrated with audio equipment. You could then ‘watch’ your music and monitor it for any clipping, amplitude or balance problems. Or you can just look at the pretty display! The EVOR04 can be purchased at: http://sch-remote.com/index.php www.ebay.com/itm/171765947707 And check out these videos: “EVOR Color VU meter, Real Time Analyzer Demo” – https://youtu.be/ vQxXD6dpaCo “Modern HIFI Oscilloscope & Waveform & Spectrometer” – https://youtu. be/CfbP-7xE1Oo SC Australia’s electronics magazine May 2021  63 Regulating Mains Voltage with a Variac by Dr Hugo Holden The idea of using a motor to drive a Variac to maintain a constant mains voltage has been around for a while. It’s a simple solution to a difficult problem, and for the most part, works very well. This article describes how you can build your own mains regulator. T his device was built to obtain a 115V AC stabilised power source to run a vintage computer. Still, it can easily be adapted to provide a stabilised 230-240V AC supply for running any manner of mains equipment including radios, amplifiers etc. Using a motor to drive a Variac for mains regulation is the easiest way to get a constant AC voltage for voltagesensitive equipment. Of course, it can’t respond on a cycle-by-cycle basis, but it does an excellent job of accounting for the longer-term changes. Mains voltage shifts are widespread these days due to solar and wind power, which can significantly increase the supply voltage at times of high insolation/wind. Of course, it will then drop back again later, so you can’t merely account for it with a step-down transformer. Demand changes during the day can also cause fairly significant shifts, as can large loads (eg, in nearby factories) switching on and off Most modern devices will operate just fine from below 220V AC right up to the typical maximum of 253V AC (230V AC + 10%), although some areas can see voltages higher than this from time to time. It’s especially bad in rural areas where you might be at the end of a long supply line, and there might also be renewable energy generators in the area. But what if you have sensitive equipment? These very high voltages can 64 Silicon Chip damage some equipment, while devices which are not damaged by it can still malfunction. So it’s desirable to have a way to stabilise the voltage being fed to them. In the case of my retro SOL-20 computer, as was common with many S-100 bus computers of the 1970s, it has a transformer-based (analog) power supply. After the transformer is a fullwave rectifier and very high-value filter capacitors. It uses linear regulators to produce its 5V rail, so the higher the mains input voltage, the more those regulators dissipate heat. By regulating its supply voltage to the lowest value that gives enough headroom for the linear regulators to operate, I reduce its internal dissipation and lengthen its lifespan. My design therefore has an adjustable output voltage, which I set to around 94V AC. That’s sufficient to keep the computer stable and its 5V rail nicely regulated, while minimising dissipation. The voltage set knob on the front panel has a mechanical locking ring, so it cannot get accidentally bumped out of position. I harvested that from a defunct laboratory amplifier. By the way, it would be possible to do something similar to using a Variac by feeding the output of a beefy switchmode AC-to-DC converter into the input of a pure sinewave inverter. The inverter’s output voltage would thus be decoupled from variations in the mains Australia’s electronics magazine voltages, which presumably would not bother the step-down circuitry. However, this results in a significantly noisier output with a lot more EMI due to having two high-current switching converters in the device. I also think that this configuration is more prone to failures, some of which could damage connected equipment. That approach could also be quite expensive and probably inefficient. So I went ahead with the Variac-based design. Despite the ‘vintage’ nature of a Variac, the sinewave amplitude (output voltage) is very well and smoothly controlled, and efficiently too. Importantly, it’s also quite easy for me to set up the Variac-based design to physically limit the maximum possible output voltage to a safe level. This way, even if there is a complete electronic failure, it can’t damage the load device(s). Design concept The basic operation of the Mains Voltage Regulator is shown in the block diagram, Fig.1. The incoming mains voltage is applied to the input side of the Variac via a fuse, and the output of the Variac drives the load. It also powers a secondary supply to run the control circuitry. Part of this supply generates a DC voltage related to the AC voltage from the Variac output. That is then fed to the non-inverting input of an op amp based differential siliconchip.com.au amplifier, with the inverting input connected to a fixed +8V reference. The output of this amplifier indicates how much the Variac output voltage deviates from the reference point. That voltage is fed to the inverting input of the second op amp. Its non-inverting input voltage is controlled by the output voltage set pot on the front panel. So its output will be negative when the output voltage is higher than the setpoint, and positive when the output voltage is lower. This then controls the motor driver, which drives the Variac in the correct direction to maintain the desired voltage. Importantly, a dead band is implemented in this drive to prevent the motor from hunting due to minimal mains voltage variations. We don’t want it doing anything Fig.1: the basic concept of the AC voltage regulator. The output of the variable autotransformer is fed to an 8V DC power supply made using a small transformer, so that its DC output varies with the AC voltage. This is compared against a fixed 8V DC reference, and if it differs sufficiently, the motor is driven to rotate the Variac shaft and return the output to the desired AC voltage. siliconchip.com.au Australia’s electronics magazine May 2021  65 With the Earthed cage removed, this photo clearly shows the clutch which prevents damage if the motor tries to drive the Variac beyond its end stops. unless the output voltage has drifted by more than, say, one volt from the set point. In my case, the device is powered from the output of a step-down transformer so its input is ~115V AC and the output is below 100V AC. Still, most Variacs can deliver an output voltage from close to 0V up to a higher voltage than the incoming mains, so the design is just as suitable for when you need an output in the 220-240V AC range. Design specifics The closed-loop gain of the servo is around 23.5:1. The programmed dead band is around ±1.2V, and it takes another 1.2-1.3V to get the motor rotating. So the input voltage offset has to be around ±100mV. Since this voltage is derived from the mains AC output 66 Silicon Chip by a step-down transformer with a ratio of around 10:1 (in this case), the Variac’s output will vary by around ±1V from nominal. In applications where the output voltage is closer to 230V AC, the stepdown ratio of the transformer powering the control electronics is closer to 20:1, so the output will vary by around ±2V. This is generally not going to worry any equipment which it’s likely to drive, and will reduce the possibility of hunting due to mains-borne noise. With a sudden step in the mains line voltage of say 5V, the motor is forced to near full speed, and makes a more rapid correction. Since my unit uses a 2 RPM motor (via a gearbox), it takes a few seconds to make the correction. There are small 100Hz ripple voltages in the control circuit voltage that Australia’s electronics magazine is being monitored. With the specified filtering, these have a magnitude of about ±215mV. This falls inside the ±1.2V dead band. While more filtering would lower the ripple, it would also lengthen the unit’s response time to mains voltage changes. The Variac is merely a toroidal autotransformer where a carbon brush taps off the winding. On account of being a toroidal autotransformer, it is highly efficient. I chose a high-quality vintage General Electric Variac with gold plated copper where the carbon brush contacts the winding turns, rated to supply around 240W. A 240-300W Variac is quite compact, at about 76mm (three inches) in diameter and 50mm (two inches) deep. The Variac shaft is coupled via a Huco Clutch and combined Oldham coupler siliconchip.com.au SC Ó VOLTAGE STABILISER SERVO CONTROLLER Fig.2: the control circuit is relatively simple, being based on just two op amps, a zener diode as a voltage reference and a pair of Darlington transistors to drive the motor in either direction. The Darlington base-emitter voltages of around 1.4V each result in a dead band which prevents the motor from hunting due to small mains variations. to a 2 RPM output 12V DC motor. The purpose of the clutch is to slip when the Variac reaches its maximum or minimum voltage mechanical stop points. I crafted the minimum mechanical stop point so that the lowest output voltage is about 85V, while I set the maximum voltage stop point to 115V AC. But you could set it much higher, to say 240V AC. Electronics A pair of medium-power Darlington transistors drive the motor. These Darlington devices very conveniently provide the ±1.2V dead-band due to their base-emitter junction voltages. If less than 1.2V is applied across their junctions, they do not conduct, so nothing happens. Also, they have enough current gain to allow their bases to be fed directly from an op amp output. I have several mil-spec 741 op amps (type 10101) on hand, which I tend to use in critical applications, as I figure they are better made than many modsiliconchip.com.au ern ‘jelly bean’ op amps in plastic cases. One great thing about the 741 is that it is utterly deaf at radio frequencies, and not much use above 20kHz either, where it is intrinsically slew-rate limited. That makes it perfect for low-speed servo applications. The 741 is obsolete by modern standards, but for this particular application, it is all that is required. In many electronic feedback motor servo control systems, such as the rotating head drum in a VCR, the loop filtering is designed to prevent hunting and correction overshoots. The loop filter components are often similar to those seen in a typical PLL (Phase Locked Loop) circuit, with a main loop filter capacitor and anti-hunt RC network. Also, the op amps’ high-frequency responses are often rolled off to make the system interference immune, especially if it is a low-frequency application. However, in an electromechanical servo feedback system, where it is not Australia’s electronics magazine a continuously rotating machine, one does not want constant activity of the motor. Hence the dead band, which solves the hunting issue; the anti-hunt RC network is not required. Once the motor shaft has moved to the correct output position, the motor current ceases. Only when the output variable (voltage in this case) steps significantly away from its set target value does the motor rotate to correct the Variac’s shaft angle. Circuit details The full circuit is shown in Fig.2, and as the block diagram implies, it is based around two op amps. It is powered from the mains using two Jaycar Cat MP3296 integrated open-frame switchmode supplies with 12V, 1.3A outputs. These are stacked to provide ±12V rails. A ~10V reference voltage is produced by zener diode ZD1, supplied with around 23.5mA from the +12V rail via 10Ω and 75Ω current-limiting May 2021  67 resistors. This is then reduced to a calibrated +8V via trimpot VR1, and this is fed to the inverting input of the first differential amplifier based on op amp IC1, via a 51kΩ resistor. The feedback voltage is applied to the primary side of transformer T1, a Jaycar Cat MM2018 mains transformer with an output of around 9-10V AC at the desired mains voltage. In my case, as I was aiming for an output below 100V AC, I used a nominal 240V to 24V 150mA transformer, giving a 10:1 stepdown ratio. For a voltage nearer to 230V AC, you would use a 240V AC to 9V AC transformer instead. This transformer’s output is rectified by a W04M silicon bridge rectifier and then applied across a 180Ω 2W load resistor, giving a transfer characteristic similar to my SOL computer power supply. A portion of the voltage across this load resistor appears at the wiper of potentiometer VR2, which provides trimming of this part of the circuit. Its wiper voltage then goes through a 2.7kΩ ÷ 1µF RC low-pass filter and is applied to the non-inverting input of IC1 via a second 51kΩ resistor. As all four divider/feedback resistors in the differential amplifier around IC1 are 51kΩ, it has unity gain. So the voltage at its output pin 6 is the feedback voltage minus the 8V reference. Thus, it will be above 0V if the feedback voltage is above 8V or below 0V if it is below 8V. This difference voltage then goes to the inverting input of op amp IC2 via a 5.1kΩ resistor. The 120kΩ feedback resistor sets the gain of this stage to 120kΩ ÷ 5.1kΩ = 23.5 times. The noninverting input is held at a constant voltage between +2V and -2V as set by output adjustment potentiometer VR3. Both ends of VR3 are connected to the junction of 2.2kΩ/510Ω resistive dividers across the +12V and -12V supply rails, providing the correct adjustment range. This allows a maximum adjustment of around 25% of the nominal mains voltage, which is plenty. A 100nF capacitor lowers the frequency response enough to make it unresponsive to noise. Output pin 6 of IC2 then drives a pair of Darlington emitter-followers that drive the motor from the ±12V rails, with 1.5Ω 5W emitter resistors limiting the peak motor current to around 5A. A 680nF capacitor across the motor 68 Silicon Chip Fig.3: PCB assembly is straightforward. Simply start with the lowest-profile components and work your way up. Be careful to orientate the ICs, diode, bridge rectifier and Darlington transistors correctly. You can mount the Darlingtons on top of the board, and bolt them to the side of your case, or underneath (as shown in our photos) and bolt them to the base. reduces radiated motor commutation hash. 10Ω resistors in the ±12V supply lines isolate motor supply noise from the rest of the circuit. DC load sampling You might be wondering about the purpose of the 8V DC input at CON1. This is so that if you have a DC rail in one of the devices you’re powering that varies based on its mains input voltage, you can regulate that DC rail directly, rather than relying on the onboard transformer, rectifier and load resistor. In this case, you connect your device’s DC supply across pins 4 & 5 of CON1, and this dominates the other feedback mechanism, providing (theoretically) better regulation of your device’s internal voltages. I tested by connecting the voltage rail feeding the input of the 5V regulator on my vintage computer, but found that it didn’t improve regulation very much. So in the end, I stuck with the internal feedback, but I left this option in the design in case it came in handy in other use cases. PCB assembly I etched a PCB and assembled it using a selection of high-quality components I had on hand, as shown in the photos above. But as you are unlikely to have these same components (and probably can’t easily get them either), Australia’s electronics magazine SILICON CHIP has designed an equivalent PCB to accept more standard components, shown in Fig.3 and the adjacent photos. Assembly is straightforward. Start by fitting all the resistors where shown in the overlay diagram, followed by the zener diode (correctly orientated) and the IC sockets. If you are not using IC sockets, you can solder the op amps straight to the board, but either way, make sure their pin 1 dots/notches are aligned correctly. Install the bridge rectifier next, with its longer + lead to the pad so marked. Follow with the trimpots (both 1kΩ and likely coded 103), then the smaller capacitors, then the terminal blocks, with their wire entry holes towards the board edges. Next, mount the sole electrolytic capacitor, ensuring its longer lead goes to the pad marked + on the PCB. With that in place, fit four tapped spacers to the board’s underside using short machine screws through the four mounting holes. That just leaves the two Darlington transistors. These must be isolated from any heatsink using the insulating washers and bushes, as shown in Fig.5. You can mount them vertically at the edge of the board, so they can be bolted to a vertical heatsink or the side of the metal case. Alternatively, you can bend their leads so that they mount under the board, with the leads going siliconchip.com.au Two views of the assembled SILICON CHIP PCB, the one on the right mainly to show the method of mounting Darlingtons Q1 and Q2 – they’re inserted from under the double-sided board with the legs first bent up 90°, then soldered on the top side. (If you mount them vertically, make sure they’re the right way around – emitters are closest to the shrouded socket.) Otherwise assembly is quite straightforward – as usual, watch the polarity of ICs, semiconductors and electrolytic capacitors. up through the pads and then being soldered on top. That will allow you to bolt them to the same panel that the board is on. If you are going to have the Darlingtons underneath like that, make sure they are installed at sufficient distance to rest on top of insulating pads sandwiched between their tabs and the bottom of the case. Mechanical construction I built my electronics into a Hammond pre-painted steel chassis with a ventilated top cover, then created an insulated structure on top of the case which holds the Variac, the DC motor and the clutch. If you are going to leave the Variac exposed, you need to make the connections fully insulated, unlike mine, which has exposed spade terminals at dangerous potentials. I mounted the Variac, clutch and motor on brackets made from 10mmthick phenolic electrical panel (an excellent insulator). The phenolic insulating material can be tapped, which simplifies construction. You will need to come up with a similar construction to suit your Variac, clutch and motor. It would be possible to use 10mm thick epoxy fibreglass sheet. The easiest (and probably safest) way to cut an extension cord in half and run the cable ends of both halves into the metal case via a cord grip grommets or cable glands. You can then connect the plug end into the Variac’s output and use that to power the internal circuitry, with the socket end being internally wired to the plug to provide an external connection for the load(s). In my case, the Variac has exposed mains terminals (spade lugs), so I had to enclose that whole section in an Earthed metal mesh box. You could do that too, but if you use the plug and socket approach and keep all the mains wiring inside the control box, it won’t be necessary. (Left): phenolic (thermosetting plastic) is an excellent insulator and is also easily machined. (Right): the three phenolic panels screwed together form brackets to hold the Variac, motor and clutch assembly together. siliconchip.com.au Australia’s electronics magazine May 2021  69 Fig.4: this wiring diagram shows the general arrangement of the overall device and the wiring specifics. All exposed nonEarthed metal is covered with heatshrink tubing, and all the Earth wires are terminated to a single star Earth point on the chassis. It’s a good idea to use two nuts for this connection, and don’t use the bolt for any other purposes. Ensure there is 70 Silicon Chip Australia’s electronics magazine siliconchip.com.au no paint or other insulating material where the Earth lugs contact the chassis. siliconchip.com.au Australia’s electronics magazine Fig.5: whether you mount the darlington transistors horizontally or vertically, you need to use a washer between the tab and case plus an insulating bush between the tab and screw head/nut. This prevents the tab from shorting out on the Earthed chassis. Check for high resistances between the tabs and case before powering the device up. May 2021  71 (Above): I used TO-66 package Darlington transistors in my unit with the flat metal flange acting as their heatsink. However, the SILICON CHIP PCB is designed to suit the more modern TO-220 package. (Right): the small extra piece of plastic acts as a stop on the wiper arm rotation and prevents the output going below a certain voltage like 85V, but the control system worked so well, it was removed in the final design. With a steel chassis, it is vital after cutting to smooth the hole edges with 1000 grade dry paper, and paint these edges to prevent rusting. I also add stainless steel captive nuts, rather than using self-tapping screws into the chassis metal they are supplied with. It pays to use metal spacers when fitting rubber feet so that the rubber is not excessively compressed, and the screws can be tightened up so that they don’t come loose later. Stick-on rubber feet are a waste of time as the glue fails and they fall off, so don’t be tempted to use them, even though it appears to save you time. It is essential to have a solid main Earth stud for reliable chassis Earthing. The head of the screw must not be accessible, and should be tightened up with a socket wrench and lock washers, and at least two nuts. Make sure to clean the paint off the chassis where it makes contact. For the mains wiring, I used silicone rubber covered “harsh environment” wire (sourced from RS components). It is extremely temperature-resistant insulation and does not retract on sol72 Silicon Chip dering, and is far superior to PVC covered appliance wire in every way (but more expensive). Wiring Wire the unit up as shown in Fig.4. Your mains input (whether via a chassis-mounting IEC socket or captive cord) needs to go to the two switchmode modules’ inputs and the Variac input. The Earth wire needs to be connected to all of those via the chassis Earth lug. The Variac output is applied to the small 9-10V transformer (for a ~230V AC output). For the Variac wiring, cut a short extension lead in half and wire the socket end to the input terminals on the 12V switchmode supplies. Connect the plug end to the Variac output and terminate it to the surface-mount screw terminal. Run mains-rated wire from these to the 9V AC transformer and mains outlet GPO on the side of the case. The wiring diagram shows the mains cord entering the chassis via a cable gland. If a gland is used, the securing Australia’s electronics magazine nut that tightens the cord in place must be secured with some super glue to ensure the cord cannot be loosened easily. All mains wiring must be insulated using heatshrink tubing over soldered joints or using insulated crimp connectors. Also add cable ties to the mains wiring near connection points to prevent wires from coming free and possibly causing an electrocution risk. A common Earth point secures all Earths together using an M4 screw, star washer and nut. Crimp eyelets are used to make the connection to the Earth point. The outputs of one 12V DC switchmode modules goes between the +12V and 0V terminals of CON2, and the second is wired between 0V (+ output) and -12V (- output). The motor connects between the middle two terminals of CON2 (ie, one end will be common with the two switchmode supply leads). After chassis-mounting potentiometer VR3, wire its terminal back to pins 1-3 of CON1, as shown. The output of the small transformer (between the 9V and 0V taps, if it is a tapped type) siliconchip.com.au Parts list – Voltage Stabiliser Servo Controller 1 control module (see below) 1 variable autotransformer (“Variac”), to suit your application 1 geared DC motor, approximately 2 RPM (eg 35mm Spur Geared Motor [980D Series]) [RS Components 834-7666] 1 small clutch assembly (to connect motor to Variac shaft) (eg, Huco Friction Clutch, 6mm bore 53Ncm) [RS Components 890-3036] 1 Oldham clutch coupler adaptor for Variac-to-clutch connection 2 230V AC to 12V DC 1.3A open-frame switchmode supplies [eg, Jaycar MP3296] 1 small 230V AC to 9-10V AC transformer [eg, Jaycar MM2017] 1 panel-mount M205 safety fuse holder [Jaycar SZ2028] 1 M205 fast-blow fuse, to suit Variac rating 1 DPST 240V AC Neon illuminated rocker switch [Jaycar SK0995] 1 2-way surface-mount screw terminal strip [Jaycar HM3167] 1 cord grip grommet or cable gland to suit mains lead 1 panel-mount mains socket (GPO) 1 M4 x 15mm screw 1 4mm star washer 1 M4 nut 6 M3 x 15-16mm machine screws 10 flat washers to suit M3 screws 6 M3 hex nuts 1 short extension lead (cut in half to give plug lead and socket lead) 1 mains lead with 3-pin moulded plug 1 metal box large enough to fit switchmode supplies, controller PCB etc Insulating material (phenolic, MDF etc) to make brackets for Variac, motor, clutch etc Screws, washers, nuts, crimp eyelet lugs, crimp spade connectors, cord grip grommets, mains-rated wire etc Control module parts 1 double-sided PCB coded 10103211, 102 x 65mm 1 3-way 5.08mm screw terminal (CON1) 2 2-way 5.08mm screw terminals (CON1) 1 PCB-mounting 4-way terminal barrier with two mounting holes (CON2) [Jaycar HM3162] 1 pair of M205 fuse clips (F1) 1 3A fast-blow fuse (F1) 2 TO-220 insulating kits (washers & bushes) 4 9mm-long M3 tapped Nylon spacers 8 M3 x 5mm machine screws Semiconductors 2 LM741 op amps or equivalent (IC1,IC2) 1 TIP121/BD649/BDX53C 8A 80V NPN Darlington (Q1) [Jaycar ZT2198] 1 TIP126/BD650/BDX54C 8A 80V PNP Darlington (Q2) [Jaycar ZT2199] 1 W02M/W04M 1.5A bridge rectifier (BR1) 1 10V 0.6W/1W zener diode (ZD1) Capacitors 1 1000µF 25V radial electrolytic 2 4.7µF 50V radial electrolytic 1 1µF 63V MKT 1 680nF 63V MKT (mounted on motor terminals) 7 100nF 63V MKT Resistors (all 1/4W 1% metal film unless otherwise stated) 1 120k (Code brown red yellow brown or brown red black orange brown) 4 51k (Code green brown orange brown or green brown black red brown) 1 5.1k (Code green brown red brown or green brown black brown brown) 1 3.3k (Code orange orange red brown or orange orange black brown brown) 1 2.7k (Code red violet red brown or red violet black brown brown) 2 2.2k (Code red red red brown or red red black brown brown) 1 1.5k (Code brown green red brown or brown green black brown brown) 2 510 (Code green brown brown brown or green brown black black brown) 1 270 (Code red violet brown brown or red violet black black brown) 1 180 10% 5W (No code – value printed on body) 1 75 (Code violet green black brown or violet green black black brown) 1 47 (Code yellow violet black brown or yellow violet black gold brown) 2 10 (Code brown black black brown or brown black black gold brown) 2 1.5 10% 5W (No code – value printed on body) 2 1k mini horizontal trimpots (VR1,VR2) (Code 102) 1 10k 16mm linear potentiometer (VR3) (Code B103) siliconchip.com.au Australia’s electronics magazine May 2021  73 Holes drilled through the phenolic base and lower case lid allow the wiring to pass between the two plus provide some airflow to the box below. The finished unit; the holes in the upper mesh section allow cooling air to circulate. The unit is very efficient, but still dissipates a few watts at full load. connects to pins 6 & 7 of CON1, either way around. Setup There are three adjustments to be 74 Silicon Chip made: adjusting VR1 to get very close to 8V between TP1 and TPG, adjusting VR2 to get 8V between TP2 and TPG, and setting VR3 to get the desired output voltage. Australia’s electronics magazine Leave fuse F1 off the board initially, so the motor will not receive power. The safest way to adjust VR1 is by using a 12V bench supply or small battery to power the circuit, with no mains connection at all. Simply connect this between the +12V and 0V terminals and then adjust VR1 while monitoring TP1. If you don’t have a suitable supply, you can use the 12V switchmode module(s) you will use to power the final device. In this case, make sure that all the mains wiring is fully insulated before you power it up and connect your DMM and screwdriver to make the adjustments. To adjust VR2, you will need to apply mains power, so double-check your insulation and use a plastic adjustment tool. Be careful when probing TP2 and TPG to stay away from all mains connections. Once again, turn the pot until you get a reading very close to 8V. You can then fit the fuse, close the whole thing up, power it up and monitor the Variac output voltage (using a mains-rated DMM) while adjusting VR3 to get exactly 230V AC (or whatever your target voltage is). Make sure there is no load connected until you are sure that the unit is working correctly and the output voltage is set correctly, as some Variacs can produce high enough maximum voltages to damage sensitive equipment. If the motor runs continually and the Variac is stuck at one of its end stops, you might have to swap the motor wires over to get negative feedback instead of positive feedback. Note that you could add mechanical stops to the Variac to set a hard upper and lower limit on its output voltage with a nominal mains input. If you think about what will happen in a brownout, that is a very good idea. If the mains voltage is unusually low, the controller board will wind the Variac right up to maximum. When the mains voltage returns to normal, that could lead to a very high output voltage for a few seconds until it can return close to the 1:1 position. Another way to protect against that happening would be to combine this unit with a Brownout Protector, such as the one we published in the July 2016 issue (siliconchip.com.au/ SC Article/10000). siliconchip.com.au The Jumbo Build It Yourself Electronics Centres® TECH SALE! With outdoor sensors & smartphone app! X 7063 NEW! 269 $ Get live, local weather at home. Fire the weather man! This fantastic home weather station displays all your local weather data - great for boaties & gardeners. Bright & clear base station provides readings for indoor/outdoor temperature, humidity, air pressure, rainfall, wind speed and direction. Plus handy weather trends. You can even connect it to your home wi-fi to monitor readings & data with your smartphone. 100m sensor range. als on the latest 8 big pages with top de ces end May 31st. in electronics. Sale pri Magnetic ‘edge to edge’ grilles. 219 27 26 $ .95 $ T 2306 SAVE $50 $ SAVE 22% NEW! here! With internal battery - use it anyw S 8864 14” Portable Digital TV Perfect for the car or caravan! HD digital tuner, plus external magnetic antenna. Powered off internal rechargeable battery, your vehicle battery or mains plugpack. It’s also fitted with USB connection for recording TV shows. Bluetooth FM Audio Player Transmits bluetooth audio from your phone (music, routes phone calls etc) to your cars FM radio. Plus it’s also a QC3.0 & USB C charger. With stylish RGB light! SAVE 24% X 0604B 30 $ 379 /pr $ C 0876A Opus One® 2x30W Bluetooth® Wireless Ceiling Speakers Built to stream the best content from your favourite music streaming service, app or podcast player. Bluetooth 5.0 technology offers superb audio performance and range. In-built high performance 2x30W RMS amplifier. The ideal way to add permanent wireless sound to any room in the house. A modern, low profile finish is provided by frameless magnetic fit grilles. Includes power supply. Sold in pairs. Premium HSS-R Drill Bit Set 19pcs between 1mm and 10mm for plastic, wood and metals. Metal storage case. 99 The ultimate game console style case for any Retro Pi gaming project! Easy access to ports with internal fan to keep everything running cool while you game. SNES style USB controllers S 1146 ($9.95). 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, replacement earbuds & charge cable. C 9037B Handy kit to get started in online content creation! $ H 8953 Retro Raspberry Pi 4 Game Case X 0705 SAVE 20% 40 $ Case can be used as a battery bank! 240V power from a lithium battery! Pro grade condenser mic for a clear, crisp sound Great for uni students! Take high quality audio notes with ease! Record CD quality audio with excellent audio pick up for taking audio notes during lectures & recording interviews. 8GB on board memory with Micro SD slot. USB rechargeable. siliconchip.com.au D 0980 SAVE $40 SAVE $30 199 $ 119 $ Maono USB Podcast Microphone ® A premium finish USB microphone with all metal case, stand and protective grille. Adds high clarity sound to your desktop for live streams & podcasts. SAVE $90 D 0990 All-In-One Mini Audio Studio For Creators The MaonoCaster Lite provides everything you need to get started in podcasting, live streaming, YouTube & Twitch. Get top quality audio from the included XLR cardioid pick up condenser mic, control all your device levels, effects and music using the mixer buttons. Includes mic, mixer console, USB C cable, tripod, windsock, 3 x TRRS jack cables and monitor earphones. Australia’s electronics magazine 209 $ M 8199A Carry 240V Power Anywhere! This portable solar generator is fitted with 14Ah battery bank & 240V mains inverter. Allowing you cable free power for both AC and DC appliances anywhere! Plus 2.1mm DC power & USB charging. 40W solar panel (N0040F) to suit $115. May 2021  75 Order online <at> altronics.com.au | Sale pricing ends May 31st 2021. Great audio savings. Opus One® 140W Soundbar Wireless Subwoofer SAVE $40 199 $ Our new premium finish soundbar offers rich, clear sound from it’s 6 high performance speaker drivers, plus a 8” subwoofer which can be placed anywhere in your lounge room thanks to wireless connectivity. Offers bluetooth audio streaming from your favourite devices, plus S/PDIF digital audio input for connection to your TV (cable included). C 5064 Demo in store! 299 $ SAVE $90 Soundbar: 97 x 8 x 7.5cm, Subwoofer: 30 x 25 x 30cm C 5059 Opus One® Bluetooth Bookshelf System Want top notch sound for your games, hi-fi listening or home theatre? These new active bookshelf speakers need no amplifier, just plug them in and connect via Bluetooth, digital S/PDIF or stereo RCA. Amazing sound for their price with a sleek oak grain finish - looks great with grilles on or off! Size: 146 x 164 x 240mm. Dynalink® F2 Pro Gaming Headset Includes easy to mount ball joint bracket 50 SAVE $40 99 $ Premium sound in a tiny package Redback® 2.75” Mini Satellite Speakers. Deliver full and rich sound you’d hardly believe these speakers are only 10cm tall! They’re the perfect home and small commercial sound solution - especially when paired with our C 5210 subwoofer and A 4860 bluetooth amplifier. 8Ω 10W rated. C 9042 39 D 0981 NEW! 69.95 $ A 1112 Experience wireless sound while you game. Also works with laptops! This tiny USB type C adaptor provides wireless audio streaming for two pairs of headphones for two player gaming on Switch, PS4 or watching media on PC & Mac. *Accessories for illustration purposes. D 0984 SAVE 28% SAVE 25% 22 35 $ 109 $ $ USB Gooseneck Mic Great for gaming, YouTube and livestreaming. Quality omnidirectional mic insert. Mic gain and mute control knob with LED lighting. With muting button D 0985 NEW! 75 $ D 0982 3.5mm Lapel Mic Ideal for audio recording on smartphones, laptops, vlogging cameras. 3.5mm TRRS or TRS connection. 2m lead. Condenser type. Need to record high quality audio for YouTube or live demos? This 6m electret mic offers excellent audio clarity and 3.5mm TRRS or 6.35mm TS connections. 69 A 3195A 30 X 0604B Infra-Red Extender Package Transmits bluetooth audio from your phone (music, routes phone calls etc) to your cars FM radio. Plus it’s also a QC3.0 & USB C charger. Silicon Chip Top deal to transform your work space! 45 $ A 0930 $ Top quality audio for group communications or one-on-one meetings. USB C connection. Rugged diecast case with rubber feet for excellent noise isolation. Includes 2m USB cable. SAVE 24% $ SAVE 24% USB Conference Microphone Electret Lapel Mic SAVE $50 With stylish RGB light! 76 SAVE $20 $ SAVE $30 Want to get into recording podcasts, voice overs or making your own audio samples? This mini USB mixer connects directly to your PC or Mac and is powered directly from USB. Includes 3 band EQ and effects. A 2548 Bluetooth FM Audio Player LED base light shows when your mic is on $ Multi-platform ready! Suits PC, Playstation, Xbox and Switch with included TRRS adaptor. Offers excellent comfort for long gaming sessions with RGB lighting effects (when USB is plugged in). 2m cable. C 5285 4 Channel USB Mixer With Equaliser & FX SAVE 27% Got your AV gear in a cabinet or rack? This handy bi-directional IR extender kit will relay IR signals between two locations. Powered by USB port on your TV/amp. Includes emitter & target. DAC & Headphone Amp Boosts audio output & converts digital signals. Optical and coaxial inputs and 3.5mm/RCA outputs. Supports PCM audio <at> 192KHz (24-bit). USB powered. Australia’s electronics magazine See last page for store locations or visit altronics.com.au Desk Monitor Mounts Regain precious desk space! • Single or dual models with easy adjust arms • USB ports for easy peripheral connection • Monitors up to 30” • Desk clamp installation. • Max 6kg (per monitor). H 8230A Single SAVE $30 79 $ SAVE $70 109 $ H 8232A Dual siliconchip.com.au Upgrade the workbench. No gas required! Recharges in 3.5hrs SAVE $30 95 $ T 2690A High Output Blow Torch 30W Lithium ‘Go Anywhere’ Soldering Iron Super hot 1350°C flame with high output nozzle. Handheld or self standing design for tasks such as heatshrinking, model making, silver soldering! Easy to refill. Add butane gas for $9.35 45 minute run time. 600°C max. Ideal for occasional soldering jobs or light duty repairs and field servicing. Recharge by USB power adaptor in your car or at home - also recharges from a battery bank. Includes replaceable 18650 battery. Hands free, head worn magnifier. SAVE 15% 30 $ SAVE 24% Offers 1.5, 2.6 and 5.8x magnification with LED lamp. Requires 2xAAA batteries. SAVE $60 Micron® 60W Digital Soldering Station T 2417 An excellent multi purpose soldering iron for service technicians, schools, engineers, R&D, production work etc. Japanese long life ceramic element. 150°-480°C. 0.8mm tip. 2 year warranty. (T 2451) 60 $ T 2555 109 $ T 2496 STOCK UP AND SA VE THIS MONTH ONLY ! . 12.50ea $ 25% OFF 60/40 Leaded Solder Reels 250 gram rolls. T 1100, T 1110, T 1122 18 $ SAVE $22 screw heads! Torque adjustment prevents chewed out 88 T 5049 174x108x45 Was $22.95 $ SAVE $40 84 99 $ $ T 5051 302x206x162 Was $105. T 2128A 99 $ T 2098 300W Adjustable Solder Pot Repair faster with a lithium screwdriver. This USB rechargeable screwdriver features a fully adjustable torque drive for fast and accurate driving of precision screws found in modern high tech devices. Two way direction control. Standard 4mm driver bits (40 included). 3 hours use per charge. See web for full contents list. Tin multiple stranded hookup wires or removing multipin connectors from boards quickly and easily. Takes up to 1350g of solder. Stable temperature control: 200-480°C. Suitable for lead free and leaded work. 1kg leaded solder bar $64.95 (T 1140A). 300W. T 5053 352x242x172 Was $125. 135 $ SAVE 20% T 5055 412x302x182 Was $170. 164 $ T 5056 452x352x192 Was $205. 29.95 $ 209 $ T 5066 521x292x183 Was $265. 19 $ T 1461 T 2758A 45 $ .95 .95 5pc Plier & Cutter Set A must have for any electronics enthusiast. Includes: • Side cutters. • Flat long needle nose pliers. • Flat bent needle nose pliers. • Long nose pliers/cutters. • Bull nose pliers Ultimate Flexible Helping Hands Upgrade to the ultimate in soldering helper hands. Includes magnifier to assist with those fiddly jobs. Arm length ≈30cm. 6pc Soldering Helper Tool Kit A 6 piece set of tools for reworking solder joints, cleaning pad surfaces and removing debris. 19.95 16 $ 10 Pack of PCB Drills T 2329 A 10 piece set of PCB drill bits in a handy plastic carry case. Includes 10 sizes: 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2mm. siliconchip.com.au 15 $ .95 T 1489 A handy 4” stainless steel bowl with magnetic base to keep screws from straying while you work Precision Knife Set T 1489 Includes aluminium handle with 13 blades to suit different cutting jobs. Includes plastic carry case. Australia’s electronics magazine d FREE BONUS Drawer dividers value SAVE 40% SAVE 40% 36 $ at $4.95. H 0237 H 0239 60 $ See-Through Parts Storage Drawers T 4018 Magnetic Bowl Top quality sealed IP67 rated cases for storing test gear, tools, cameras, drones - anything important that needs protection! Padlockable latches with perforated foam for easy customisation. Measurements are internal size. T 2351 $ .95 Jellyfish® Equipment Cases Great way to tidy up your work bench - with room for all your parts, test leads, nicknacks & doohickeys! H 0237: 347W x 142D x 187Hmm. Pack of 20 dividers free. H 0239: 447W x 180D x 246Hmm. Pack of 10 dividers free. May 2021  77 Order online <at> altronics.com.au | Sale pricing ends May 31st 2021. Gear for the open road. NEW! Powerhouse® Portable Power Battery Box Packages include internal & external antennas plus cabling. Fits a standard 90-120Ah automotive battery for powering appliances at your camp site - a totally self contained power unit! Fitted with 2.4A USB charger, dual Anderson sockets, volt meter, car acc. socket & battery terminals. CEL-Fi 4G Boosters For Vehicles TM The best solution on the market for addressing the universal challenge of poor cellular coverage on the road in Australia. Simply install Ce-Fi GO inside your vehicle and enjoy having great 3G or 4G mobile reception. No longer will you need to stop or drive to a particular spot to be able to make and receive phone calls. Available in truck/4WD, caravan and marine packages to suit your needs. Easy self install can be completed in just a couple of hours. Convenient top mount connections, breaker & voltmeter. Fitted with secure lid clips unlike most others on the market! T 5098 139 $ Powerhouse® Watt Meter 130A D 4400 Truck/4WD • 3.5dBi Adhesive • 6-8dBi External 1070mm (5m cable) D 4415 Marine • 3.5dBi Adhesive • 5-7dBi Wall Mount • 7-10dBi Marine External (10m cable) D 4405 Caravan • 3.5dBi Adhesive • 5-7dBi Wall Mount Internal • 10-11dBi Wideband External (10m cable) 1278 1357 $ 1587 $ $ 39.95 P 7812 $ 14.95 $ are Includes 10m cable & mounting hardw Pins Part ONLY Caravan/Boat TV Antenna 2 Pin P 7892 $8.95 $11.95 $17.95 $19.95 IP67 Dust & Water Proof DC Conectors 3 Pin P 7893 4 Pin P 7894 6 Pin P 7896 Great for automotive wiring - requires no special crimpers to terminate! Use a standard automotive crimper, pliers or solder terminate. 14A rated. 49.95 $ Q 0592 A comprehensive power monitor panel for solar and remote power systems. Huge selection of on screen power stats. Supplied with a 200A shunt for easy connection. Cut out size: 87 x 47mm. $ P 7810 89 $ Digital Power Meter M 8636A Don’t get a h caught wit y! flat batterwer Know your po usage. SAVE $10 39.95 NEW! L 2003 Get crystal clear TV reception wherever you travel! Omnidirectional 360° design requires no adjustment when you park up. Easy DIY install. Perfect for measuring input and output currents and wattage from solar panels or batteries. This digital wattmeter accurately measures DC power usage. Display measures volts, watts and amps in real-time. Peak current 200A. 34.95 $ M 8656 Anderson/USB/Car Acc. Panel Anderson Style Panel Socket Easy connection for solar panels and auxiliary batteries. Mounting hole: 40x21mm Handy power connection panel for flush mounting power connections into cabinets or bodywork. Mounting hole size: 126x30mm Handy Power Panels For Cars, Boats & Caravans These panels can be easily .95 surface mounted to custom $ panels to provide power to your P 0698 Car Acc devices & portable appliances. + USB + Volt. Both have 15A DC breaker. P 0697: 50x130x70mm. P 0697 Car Acc + USB P 0698: 50x187x70mm. 49 36.95 $ 42.95 $ Fused Anderson Cable Easy way to add fused protection to any external equipment connected to your vehicle battery. M8 ring terminals. 50A maxi fuse. NEW! 68.95 P 8073 Corner Mounts $ T 1539 NEW! 59.95 $ 29 .95 $ Battery Capacity Meter Q 0587 A handy (and colourful!) meter for keeping an eye on your battery usage. Cut out size: 87 x 47mm. 12V batteries only. 78 Silicon Chip M 8655 26 $ Anderson Style To USB Charger Cable .95 P 8067 Side Mounts ABS ‘No Drill’ Solar Panel Mounts A 2m Anderson style cable fitted with USB type C Power Delivery Charger (18W) & USB QC 3.0 port for keeping devices charged. These tough surface mount brackets offer a way to mount solar panels without penetrating the roof of the caravan or boat. They can be attached using a silastic or similar adhesive. Australia’s electronics magazine See last page for store locations or visit altronics.com.au Ideal for DIY DC power wiring Ratchet Lug Crimper Quick and easy crimping for Anderson SB50 connectors and other uninsulated lugs between 20AWG & 8AWG. siliconchip.com.au Power solutions for car & home. Automate your home appliances Ultimate family charging station! NEW! SAVE $45 130 $ LiFePO4 Lithium Rechargeable Batteries The latest generation in maintenance free batteries is here! LiFePO4 batteries offer longer service life than traditional lead acid batteries, plus weigh less than HALF as much as SLA batteries. LiFePO4 also provide more usable life per cycle, allowing for longer run times by holding a higher voltage until capacity is almost exhausted. These batteries will also maintain 80-90% charge when in storage - far higher than their lead acid counterparts. All are 12.8V output with battery management system on board for safe and reliable use. 3 year warranty. Model Type (Connection) SL4541A 8Ah (4.8mm Spade) SL4547A 12Ah (4.8mm Spade) SL4551A 20Ah (M5 bolt) SL4557A 30Ah (M5 bolt) SL4576A 100Ah (M8 bolt) SL4578A 120Ah (M8 bolt) RRP Benefits of LiFePO4: $79 $145 $199 $299 $749 $999 ✔ Half the weight of lead acid batteries. ✔ Less discharge when in storage. ✔ Longer service life. ✔ Longer run time. M 8882A* Charge 10 USB devices at once! Switch any connected appliance on or off remotely from anywhere in the world. Set schedules, monitor and control via your using the Tuya Android/iOS app. Maximum 10A 2400W. Works with Google Home and Alexa P 8149 23.95 $ • Great for families, classrooms & business. • Massive 19A charge output • Rapid charging on each port • Includes adjustable dividers & power supply. *Devices & charging leads not included SAVE 30% SAVE 20% 20 $ 63 $ D 0511B D 2326* Say goodbye to charging cables! 10W ultra-slim charging pad for wireless charging equipped iPhone & Android devices. Requires USB wall charger, such as M8862A $13.95. Includes USB cable. Jumbo QC3.0/USB C Power Bank Offering both the latest QuickCharge 3.0 charging and 18W USB-C PD output, this enormous 20,000mAh power bank will keep your devices charged away from mains power. 136x70x25mm 179 $ 90W output charges any M 8539 SAVE $20 49 $ SAVE 25% ADD ON DEAL: SAVE 10% 70 $ USB QC 3.0 wall charger for $10 (M 8863) D 2320 M 8994* Wireless Charger Alarm Clock Powerhouse® 12V Auto Battery Charger Offers support for batteries up to 300Ah with an output current up to 12A. 7 stage charging delivers the appropriate charge current to maintain best performance & battery life. Can also recover deeply discharged cells. Suits permanent connection, making it great for seldom used vehicles. Auto reconnect starts charging again as soon as you connect the unit to mains! NEW! 16 $ Need an extra laptop charger? A stylish USB powered clock with in-built 10W wireless charging for your phone & 8 colour night light. Clock auto dims at night time. Dual alarms so you’ll always wake up on time! USB output also lets you charge your watch. This 90W USB-C power delivery (PD) charger offers fast recharging for MacBooks, Nintendo Switch and other type “C” devices. Plus a standard 2.4A USB charger output. 39.95 NEW! .95 $ D 2324* Q 3001A Sheath Piercing 15W fast charging! 13 $ .95 22.95 12.95 $ 12V Alternator Tester Provides quick and easy way to test alternator/charging system function in 12V vehicles. Provides instantly whether your alternator output is the problem or your battery is in poor condition. SAVE $26 $ Q 3000A Standard Q 3004 USB-C laptop Q 3203 NEW! Handy Automotive Voltage Probes Universal Battery Tester A handy tool for troubleshooting wiring faults in vehicles and other wiring looms. 6-24VDC range. Available in standard probe or sheath piercing versions. Still got a bit of juice left in those batteries? Know for sure with this handy tester for AAA, AA, C, D, 9V, CR cells and button batteries. Keep it in the desk drawer for quick battery checks. P 8146 89 $ The handy pop-up power board. Fits into a standard 60mm desk hole cutout to provide appliance power. Instant pop up design. 3 outlets plus dual USB port charging. Great for any work space. See notifications while you recharge. Handy upright 15W wireless charging stand allows you to read incoming notifications at a glance without having to stop charging. Requires QC3.0 USB wall charger (such as our M8863) *Devices shown on this page are for illustration purposes and not included with the product. siliconchip.com.au Australia’s electronics magazine May 2021  79 Order online <at> altronics.com.au | Sale pricing ends May 31st 2021. Save on 3D Printing. Need help with 3D printing? SAVE $50 419 $ Ask our friendly staff in store for guidance on how to start, recommended software, tips & tricks! K 8600 30 x 30 x 40cm build volume for larger prints The worlds best selling 3D printer! Over 800,000 sold worldwide. K 8606 SAVE $106 989 $ Print bigger with the Creality® CR-10 V2 3D Printer Creality® ‘Ender 3’ 3D Printer The CR-10 offers reliable large volume printing up to 30Wx30Dx40Hcm! The dual port fan cooled hot end offers reliable and precise print quality whilst the triangular design provides excellent stability. Heated print bed reduces warping, ensuring great prints every time. This printer is great for anyone who needs to print larger designs such as cosplay parts, architectural models & replacement parts. Creality’s top selling 3D printer is here! The Ender 3 is a compact 3D printer offering excellent print quality with a build volume of 22Wx22Dx25Hcm and is compatible with ABS, PLA and TPU filaments. Supplied mostly assembled and can be up and running within an hour. Creality® Premium PLA Filament NEW! $70 * *Mixed colours ok n K 8387A Silver n K 8388A Gold n K 8389A Pink n K 8391A Orange n K 8392A Green n K 8393A Yellow n K 8394A Purple n K 8395A Blue n K 8396A Red n K 8397A Black n K 8398A Grey n K 8399A White $ .50 T 1489 Deburring Hand Tool 16 Pc Precision Knife Set Remove rough edges and neaten up prints with this comfort grip external chamfer tool. Ideal for trimming plastic supports from prints. SAVE 24% T 1296 SAVE 12% 15 $ 5 Piece Needle File Set T 2352 Fine edge files for smoothing 3D prints. 80 Silicon Chip SAVE 15% Blow Brush 16 $ T 1480 Remove fine debris from prints when smoothing or reworking. Printing with ABS instead of PLA. We’ve also added to the range Creality ABS. 1kg rolls. 44.95 n K 8383A White n K 8384A Black $ Fluoro Filament A translucent fluoro yellow coloured PLA for brightly coloured prints! 1kg roll. 57 $ .95 K 8390A Cut, Polish, Grind, Sand & Carve. 19.95 T 2370 18 $ We’re now stocking Creality’s premium 1.75mm PLA designed for use in many brands of 3D printer on the market. Creality have focused on making top quality non toxic filaments with a tolerance of just 0.02mm. Each filament is 100% bubble free and offers excellent tensile strength & fluidity. This all adds up to more reliable prints and less waste! 1kg rolls. 2 for Made from high quality materials for less brittle filament breakages. ABS Filament 60 $ Fume Extractor & Fan Whisk away solder/print fumes from your workspace! Also works as a fan. Adjustable speed. Great for finishing and smoothing your 3D prints! Perfect for odd jobs and hobbies. Powerful 130W motor with variable speed between 8000 and 33000 RPM. Included is a 172pc accessory kit of grinding wheels, drills, cutters, sanding discs, polishing pads and more. Australia’s electronics magazine See last page for store locations or visit altronics.com.au T 2120 SAVE 18% 69 $ siliconchip.com.au Make, Invent & Design. Raspberry Pi Pico is here! NEW! The new Pi Pico is a tiny, fast and versatile board using RP2040 - a brand new microcontroller! Programmable in C and MicroPython this handy board can be used to integrate into any project of your own making! Z 6309A Turns your Pi 4 into a high resolution network music player for MP3, FLAC, ALAC, WAV, AAC, FLAC, DSD, Audio CD and many more file types. On-board DAC for very high quality audio output. 124 $ Raspberry Pi USB C Power Supply Create all-in-one, integrated projects such as tablets, infotainment systems and gaming consoles. Connects via DSI port on your Pi. 800x480 resolution. 10 finger capacitive touch. Screen dimensions 192x111mm (inc. bezel). 11 $ Argon® ONE Nanosound Case 7” Touchscreen to suit Raspberry Pi® .95 169 $ H 8932 SAVE $20 Z 6421 SAVE $20 sic player Build a network mu with top notch sound! 19.95 $ Official 3A power supply to power your Raspberry Pi 4. M 8821 13.95 $ NEW! Z 6481 15cm 14.50 $ SAVE 17% SAVE 17% 19 $ Z 6483 46cm 14.95 $ H 8967 Z 6486 60cm Micro SD Card Extender Cables Allows easier access to SD card slots in custom enclosures for Pi’s, 3D printers and IoT boards. 39.95 $ 19 $ H 8951 H 8959 Mount Your Pi To Your Monitor! Vented Aluminium Pi 4 Case Vented Aluminium Fan Pi Case A standard 100mm VESA mount compatible acrylic case with cooling fan for your Raspberry Pi 4. Note: GPIO not accessible once assembled. A simple screw together design with perforated vents top and bottom for plenty of cooling. Dual fan cooled case. Provides protection and thermal dissipation for your Pi 4. Note: GPIO not accessible once assembled. *Pi not included. Need a new Pi for a project? Z 6302G 4GB RAM $109 Z 6302H 8GB RAM $144 Educational Smart Turtle Robot 29 $ .95 SAVE $10 4WD! Includes motors. Z 6480 Free Z 0977 8x8 RGB LED matrix valued at $9.95. BONUS! 8x8 RGB Matrix Shield A UNO compatible shield for easy connection to Z 0977 RGB LED matrix. 5V input. 39 $ K 1094 Mecanum Wheel Robotics Base Kit Build your own omnidirectional robot! Mecanum wheels allow sideways movement in tight spaces. Aluminium pre-drilled base for easy construction. Size: 260L x 162Wmm. Easy to program 2 wheel, Arduino based, obstacle avoidance and line tracking robot. The front of the robot features a 5x5 LED panel which can display icons, text and symbols (or display the direction of travel). It is controlled via Bluetooth on your tablet + IR remote. Requires 2x18650 lithium cells. CAN-BUS Arduino Shield Relays Normally NOW Z 6325 1 $4.95 Z 6422 2 $7.95 Z 6327 4 $12.95 Z 6328 8 $19.95 $4 $5 $10 $15 NEW! Z 6426 siliconchip.com.au 19.95 $ ESP32 Camera Board SAVE 24% Z 6387 HALF PRICE! 99 $ SAVE $19 10A rated relays with 5V DC coil. Can be controlled directly by Raspberry Pi, Arduino, 8051, AVR, PIC & more! Model Z 6453 Z 6454 Allows you to interface Arduino’s with CAN-BUS control systems found in automotive electronics. Use an Arduino to build your own vehicle monitors. Relays For Automation Arduino based. Program it your way! 25 $ An ultra compact ESP32 based module with onboard camera, Bluetooth BLE & 802.11n Wi-Fi. Ideal for building your own IoT smart device projects. 5V input. Australia’s electronics magazine 70 $ Build & code your own robot. STEM bot is an easy to program 2 wheel obstacle avoidance and line tracking robot. Coding your program is easy using the standard BBC Micro:bit software. Construction has been designed to be as simple as possible with easy to folow instructions. Can also be controlled via Bluetooth. Runs from 18650 rechargeable lithium cells (S 4736 $18.50). Ages 8+ Requires Z 6440A micro:bit board. Add one for $30. May 2021  81 Order online <at> altronics.com.au | Sale pricing ends May 31st 2021. Lighting 75 .95 $ Music sensor triggers lights to the beat! Home Security Wi-Fi RGB Strip Lighting Kit This kit includes 5m of RGB strip lighting, power supply, controller unit and IR remote control allowing you to create colourful lighting effects around your home. Controller features a music sensor input allowing the lighting to trigger to music being played in the room. Great for home entertaining. Works with Alexa and Google Assistant. 60 LEDs per metre. X 3227* SAVE $100 399 $ S 9901J IS PRICE! 20 SYSTEMS ONLY AT TH Affordable 5 Megapixel CCTV Surveillance System. Simple to install with instructions supplied. Cameras can be remote viewed on iOS/Android. Each pack includes: • Hybrid digital video recorder (IP camera ready!) • Pro grade 5MP resolution weatherproof cameras • 20m connection leads • Power supply • HARD DRIVES TO SUIT: 1TB $104 (D 5514), 2TB $130 (D 5516). IP65 weatherproof casing with stainless steel brackets and hardware. 139 $ HOT PRICE! Standard Genlamp® Security LED Floodlights Great for added security around the house, back shed or garage. PIR models activate when motion is detected & have adjustable sensitivity, on time and dusk settings. Fitted with 240V 3 pin mains plug. Fully approved. Natural white. Rust free stainless steel brackets and hardware. 89 $ .95 X 2318C 50W PIR 99 X 2317C 50W 56.95 $79.95 X 2315C 20W 39.95 $59.95 $ X 2312C 10W X 2340C 10W Great for caravans, 4WDs and utes. Direct connection to your car via bare end cable. Natural white. Rust free stainless steel brackets and hardware. 36 .95 X 2310C 10W 56 $ Cable Free Wi-Fi Surveillance 1080p HD! This handy 1080p camera can be installed just about anywhere indoors or out and has an in-built battery so you don’t need to run any cables! Offers 4-6 months of motion detect recording. When it’s flat, just take it off the wall & recharge via USB. iOS and Android app monitoring via Tuya Smart Home app. NEW! 199 $ S 9843B $ $ X 2316C 20W S 9455A S 9850 Answer the door when you’re not home! Wi-Fi Video Doorbell with Tuya smartphone app control and 2 way audio. This stylish doorbell connects to your wi-fi and notifies your mobile phone when a person arrives at your doorstep. Great for telling the postie where to put packages. • Security camera mode • Motion detect notification • Includes power supply and indoor doorbell ringer unit. Low Voltage Floodlights $ Why settle for just HD? This system features 2K detail and clarity. .95 X 2316C 20W Sale Ends May 31st 2021 Phone: 1300 797 007 Fax: 1300 789 777 Mail Orders: mailorder<at>altronics.com.au *Note: We encourage this item be used responsibly for legitimate CCTV use. Covert Wi-Fi HD Camera Clock Looks like an alarm clock but has a 1080p camera capable of streaming direct to your iOS and Android device via Tuya Smart Home app. Motion detect recording. USB or battery powered. S 5315 NEW! SAVE 25% 15 $ 56.95 $ S 5327 Window/Door Open Alert Alerts you when a door or window opens with an alarm or chime. Adhesive backed, installs in seconds! » Perth: 174 Roe St » Joondalup: 2/182 Winton Rd » Balcatta: 7/58 Erindale Rd » Cannington: 5/1326 Albany Hwy » Midland: 1/212 Gt Eastern Hwy » Myaree: 5A/116 N Lake Rd SAVE 44% 360° Mini PIR Detector Provides 8m of conical detection coverage when mounted in 2.4m ceiling. 12V DC. Mounting hole size: 31mm. Western Australia Build It Yourself Electronics Centres 169 $ NEW! 25 $ S 5320 Motion Door Alarm A nifty motion detect doorbell/minder and alarm all in one! 9V battery operated. Victoria 08 9428 2188 08 9428 2166 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 08 8164 3466 Find a local reseller at: altronics.com.au/storelocations/dealers/ 82 Silicon Chip Australia’s electronics magazine siliconchip.com.au © Altronics 2021. 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. *All smartphone devices pictured in this catalogue are for illustration purposes only. Not included with product. B 0091 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. 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. Revised “GPS” Analog Clock for NTP module I built the GPS-synchronised Analog Clock Driver (February 2017; siliconchip.com.au/Article/10527), but instead of a GPS module, I used the Clayton’s “GPS” time source (April 2018; siliconchip.com.au/Article/ 11039), which gets its time from the internet using the NTP protocol. The problem I ran into is that the ESP8266 microcontroller with WiFi draws considerably higher peak currents than a GPS module. With spikes above 200mA, the power supply in the Analog Clock Driver was not up to the task. Circuit Ideas Wanted siliconchip.com.au So I modified the Analog Clock Driver circuit as shown here, substituting the MAX756-based boost regulator with a MAX1760-based circuit, shown in the red box. The MAX1760 can supply up to 800mA; more than enough to power the ESP8266 module. Besides changing the chip, the inductor value is significantly lower as the MAX1760 operates at a higher frequency, and it requires a few extra passive components. As the MAX1760 only comes in SMD packages, I chose the 10-pin MSOP version and soldered it to a commonly available MSOP-to-DIL adaptor. I then mounted most of its external components immediately at the adaptor connection points. Five points need to be wired back to the Analog Clock Driver board. I purchased the 3.3µH inductor and the output electrolytic filter capacitor from Mouser. They are both very small, minimising conductor path lengths. This resulted in a unit that synchronises with NTP time reliably. Graeme Dennes, Bunyip, Vic. ($100) Got an interesting original circuit that you have cleverly devised? We will pay good money to feature it in Circuit Notebook. We can pay you by electronic funds transfer, cheque or direct to your PayPal account. Or you can use the funds to purchase anything from the SILICON CHIP Online Store, including PCBs and components, back issues, subscriptions or whatever. Email your circuit and descriptive text to editor<at>siliconchip.com.au Australia’s electronics magazine May 2021  83 Simple DMM calibrator Low-cost digital multimeters (DMM) can be excellent value for money. They can provide many features, and some have 4-digit readouts. Such precision is terrific, but only if it’s accurate. The 1-3% deviation (or more, in some cases) makes four digits pointless. You need a way to adjust them to provide the accuracy that their readouts suggest. This demonstration circuit provides multiple points for the accurate measurement of different DC volts and amps, and the concept can be customised to your needs. It uses low-cost, commonly available parts that you might already have. It is not intended to be an ultimate calibration standard; more as a way to adjust/align multiple DMMs easily. It allows calibration at 100mV, 1.0V, 5.0V, 10.0V, 100mA and 1.0A, all within commonly-used DMM ranges. Meter scale linearity is not addressed, but it appears to be generally good in modern DMMs. An accurate voltage reference is needed to start with. My gold standard is Jim Rowe’s 10.000V Precision Voltage Reference (August 2014; siliconchip.com.au/Article/7954). It uses the Analog Devices AD587KNZ IC (RS Cat. 523-7415). This is used as part of my circuit. S1 is a standard two-pole, six-position switch that selects accurate voltages determined from the reference input via a voltage divider network. They are applied sequentially 84 to non-inverting input pins 3 and 5 of an LM358 op amp, acting as a simple voltage follower. IC1b buffers 5V or 10V at its output pin 7 from the same voltage at input pin 5, as selected using S1. These two voltage values can be measured directly from pin 7, the advantage of the buffer being its ability to source or sink around 30mA while maintaining an accurate voltage. The AD587 IC specifications limit the output current to about 10mA. IC1a operates a little differently. Mosfet Q1 is inserted into the feedback loop, and IC1a adjusts its gate voltage to maintain the selected voltage at its source terminal. This voltage is applied to a 1W, 2W resistor load. So if 1V or 100mV is selected using S1, as long as the HI and LO terminals are bridged, there will be very close to 1V or 100mV at the output labelled 1.000V/100.0mV. Alternatively, if a meter is connected between the HI and LO terminals, as the 1.000V/100mV is placed across a 1W resistor, the meter will have either 1A or 100mA flowing through it. You can even use both modes simultaneously, measuring a current through one DMM and the voltage across the 1W resistor with another. To fine-tune the device, it helps to have an accurate voltmeter (borrow one if you have to!). Temporarily connect a multi-turn 1MW trimpot in place of RT2 or RT4 and adjust it until you get exactly 1V at the output with S1 set appropriately. Then remove the trimpot, measure its resistance and solder in a fixed resistor of a similar value. Repeat for the other trim resistors RT1-RT6 until the 5V, 1V and 100mV references are all accurate. RT5 is a bit more tricky, as it depends on whether the 1W resistor value is high or low. Ideally, you should find one that’s a bit on the high side, measure its value and then use the formula RT5 = 1 ÷ (1 – 1 ÷ R) where R is the measured value of the 1W resistor. It is better to use a low-tempco 4-pin precision resistor instead of the 1W resistor. A Vishay 1W 0.02% 8W resistor is available for $40 (Mouser Cat. 71-VPR221T1R00000Q9L). With the 1A load through the shunt resistor it will dissipate 1W, but note that the Mosfet requires good heatsinking, as it dissipates around 10-11W in this condition. The warming of the shunt resistor and the Mosfet at a 1A current flow will cause minor variations in the voltage across this resistor, so leave it for about 20 seconds to stabilise before taking the measurement. The 12V supply is necessary for adequate headroom (approximately 2V) for the LM358 to accurately provide the 10.00V output when selected. As a bonus, on the 1.00A setting, low-value unknown load resistors (less than 10W) can be connected across the upper pair of test pints, and the voltage generated across them accurately measured and read directly as ohms. Accurate low-ohms direct measurement is difficult with the average DMM. Colin O’Donnell, Adelaide, SA. ($80) Infrared remote control jammer This device was developed to preserve our sanity when our grandson or younger family members come to visit. They love watching childrens TV channels at high volume levels, resulting in an amazing amount of highly irritating sounds. The result is continuous cries of “turn it down”, only to have the volume slowly turned up again over the course of a few minutes. This device sends out a 15-second burst of infrared at around 38kHz whenever the volume up button is pressed on the remote control. This swamps the IR receiver in the television, stopping the volume increasing. To successfully turn the volume up, two buttons on the remote must be pressed first (in either order), then the volume up button. I chose the yellow and red buttons on my TCL brand remote. Note that as soon as another button is pressed, for example to change channels, the device reverts to jamming mode. I also had to disable the manual volume up button on our TV as our grandson soon worked out that he could turn the volume up that way! The circuit is simple – the infrared receiver and IR LED are both powered from the Arduino’s 5V supply. The receiver feeds remote control codes into digital input D11 while digital output pin D8 drives the IR LED via NPN transistor Q1, with a 270W base current limiting resistor and a 10W LED current limiting resistor. I built my device inside a plastic box and powered it from a USB power supply that goes to the same socket as the television, so the circuit has power whenever the TV is plugged in. The infrared LED needs to be reasonably close to the TV, and ideally hidden to avoid sabotage. The software code is commented to show where to enter the required infrared codes to suit other TVs. You will need to use the included IR decoder sketch (which I did not write) to determine the codes produced by your remote control. Both sketches are available for download from siliconchip.com.au/Shop/6/5821 Geoff Coppa, Toormina, NSW. ($75) 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 May 2021  85 The History of Videotape – part 3 Cassette Systems By Ian Batty, Andre Switzer & Rod Humphris The Bulletin, Volume 96, Number 4903, April 27 1974, pages 72-73: http://nla.gov.au/nla.obj-1617182059 The previous two articles described the electronic and tape interface systems for video recording and playback, up to the development of VHS & Betamax. While professional/broadcast systems overwhelmingly used reel-to-reel tape, for domestic use, cassettes are much easier to handle. And even at a TV station, when dealing with hundreds of thousands of tapes, cassettes made life a whole lot easier. R eel-to-reel videotape recorders used similar tape speeds to audio recorders. The popular Electronics Industry Association of Japan (EIAJ) standard accepted the audiotape speed of 19.05cm/s (7.5 inches/s [ips]) for NTSC and 16.32cm/s (6.426ips) for CCIR/PAL. Standard 7-inch reels could therefore hold an hour of standard tape or 90 minutes of long play tape, with 5-inch reels offering only 30/45 minutes of play time. While these high speeds gave good audio response, the audio industry’s previous adoption of the compact cassette showed the way forward. 86 Silicon Chip Try as they might, designers of reelto-reel were limited in how far they could miniaturise their offerings. Using smaller tape reels allowed for a smaller deck, but even Akai’s standout VT-100, overlapping its reels to save space, was limited to 30 minutes due to its high tape speed of 21.8cm/s (8.6ips). Sony’s AV-3400, running at 19.05cm/s, also managed only 30 minutes. Nobody was going to consider a home VTR with these running times – you’d need more than four reels to watch the 1956 version of War and Peace, and you would only get it in black and white. As with the final developments of Australia’s electronics magazine portable quadruplex VTRs, machine electronics were shrinking to the point where the tape reels, video head drum and the transport dictated the final size of the design. U-matic Already prominent in the open-reel video recorder market, Sony took the plunge and led the development of VCR systems. Needing a cassette of acceptable size, Sony designers settled on dimensions of 219 x 136 x 38mm. The width and depth were dictated by the sizes of the two reels; the thickness, by the use of 3/4-inch (19.05mm) tape. siliconchip.com.au Fig.33: the U-loading principle used by the Sony U-matic system. It is elegant but mechanically very complex. It was the resulting unreliability that led it to fall from favour. A 60-minute record/play time demanded a slower tape speed for the reel size and length of tape available, and the audio speed of 3.75ips or 9.5cm/s was chosen. While the EIAJ system had been developed for colour recording/playback, a half-inch/12.5mm tape width lacked sufficient head-to-tape speed for acceptable performance at the reduced speed dictated by the smaller reel size in the proposed video cassette housings. The 19mm tape width gave longer video tracks. Run at a tape speed of 9.5cm/s around a 110mm head drum, the U-matic achieved a head-to-tape speed 853cm/s (336ips). The U-matic’s electronic and head drum design was an evolution, but tape handling would need a revolution. The tape would somehow need to be drawn out of the cassette shell, wrapped 180° around the head drum, engage with the stationary erase, consiliconchip.com.au trol track and audio heads, and be sandwiched between the transport capstan and pinch roller. This mechanism would be the precedent for all subsequent VCR systems. The solution was the loading ring (see Fig.33). The U-matic cassette was loaded by pushing it into the carrier, then dropping it over the loading mechanism. A cutout in the cassette shell allowed the main extraction guide to sit behind the tape inside the cassette. At the same time, the cassette door flipped open. On loading, the loading ring rotated clockwise, with the main extraction guide pulling the tape out of the cassette and drawing the capstan and up to six path guide pins behind it. The tape presents its oxide surface outwards, so the loading mechanism wraps the tape oxide against the erase head, video head drum and heads, audio and control heads and the capstan. Australia’s electronics magazine The pinch roller contacts the back of the tape (unlike in audio compact cassettes), so the likelihood of the tape sticking to the pinch roller is greatly reduced. Once the tape is fully loaded, the capstan and head drum both spin up to operating speed. On playback, a solenoid closes the pinch roller against the capstan (you can see a video of this at https://youtu.be/AFu7FhBDCrA). Contact with all heads (erase, video, control and audio) is by tape tension alone. There are no pressure pads. Three adjustable guides (master entry, video entry, video exit) position the tape precisely; it must be aligned vertically to micrometre accuracy so that video tracks on the tape will exactly match the path of the video heads. All non-video heads are aligned manually to match the positioning determined by the three adjustable guides. The audio exit guide is a simple pin with no vertical adjustment. Audio alignment relies on the video exit/audio entry guide, perfect alignment of the capstan spindle and vertical/azimuth adjustment screws for the audio and control track head mounting platform. The cassette reels rotate in opposite directions. While this seems odd, it means that the inner circumferences are going in the same direction, and this allows the tape from the fuller reel to intrude into the space vacated by the emptier reel, it also helped keep the tape tensioned. There is not enough space inside the cassette for two full reels! It’s an engineering marvel. The head of U-matic development, Sony’s Nobutoshi Kihara, urged his principal engineers Akinao Horiuchi and Yoshimi Watanabe to produce “Nothing too complex, try to find a simple and reasonable design. Remember that it must be easy for people to use.” Horiuchi and Watanabe did produce a machine that was a snap to use: insert a cassette, wait a few seconds, hit play. Internally, it’s a mechanical jungle. Fig.34 shows an exploded view of just the loading ring, giving some idea of the mechanism’s complexity. The initial design only extracted and threaded the tape in play or record, with fast forward or rewind seeing the tape withdrawn into the cassette. This reduced tape wear, but could only rely on an inaccurate, uncalibrated mechanical tape counter. May 2021  87 But the control track contained a highly accurate 25 pulse-per-second signal, one ‘pip’ for each recorded television signal frame. A revised tape mechanism used two arms to draw the tape part-way out of the cassette and engage it over the control track head as soon as the cassette was inserted. This ‘half-load’ allowed the control track circuitry to pick up the control track signals and to drive an electronic tape counter in rewind and fast forward. Play and record would still need full tape loading, and the tape counter would work in both these modes as well. Each end of the tape was spliced to a short length of transparent leader. Optical sensors were triggered by the change in opacity to signal the end of the tape and to stop any current play, record, rewind or fast forward. Some models also offered an auto-rewind feature. Recording format Aside from housing the tape in a cassette, U-matic is pretty similar to formats that preceded it. The slanted video tracks occupy almost 80% of the tape’s width, with the linear control track at the top edge, and two linear audio tracks at the bottom edge. Each linear track has an unrecorded strip on either side (a guard band) to prevent pickup from adjacent tracks. Stereo audio recorders do the same thing to provide separation between the left and right channels. The video tracks also use guard bands. Being only 85µm wide, severe demands are placed on the mechanical and electronic alignment of the VCR’s mechanism and transport. So U-matic’s designers allowed a 52µm guard band between the video tracks. This works just fine in practice, but it’s giving up almost 40% of the total tape real estate. Guard bands would become a target for the next generation of VCR designs, as engineers tried to pack as much signal information as possible on smaller, and slower, tape systems. The width of all tracks, and their spacings, have been exaggerated for clarity in Fig.35. In reality, there are some 110-plus video tracks across the width of the almost 15mm allowed for video recording. Notice that the head gaps are perpendicular to the video tracks. This is unremarkable, as it’s how audio and video systems commonly work. Indeed, any off-perpendicular azimuth error causes significant loss of high-frequency playback both in audio and video systems. Fig.34: and here you can see just how complicated the U-matic loading ring was. We would hate to have to pull it apart to replace worn components! 88 Silicon Chip Australia’s electronics magazine siliconchip.com.au Sony’s initial release Sony’s 1971 release of the VO-1600 model U-matic (Fig.36) offered a builtin tuner and TV signal output, and was aimed at low-cost markets, including domestic consumers. While it succeeded in education and industry, its cost, size and one-hour runtime saw it fail to take off in the domestic market. The VO-1600 also lacked a timer. Although Sony offered an external timer/ tuner at extra cost, the VO-1600 failed to meet all the criteria for a home VCR that anyone could just put in the stereo shelves and use with no ‘sidecar’ equipment. Readers are probably more familiar with the VO-1800, which lacked the inbuilt tuner, and the VP-1000, which was a player only. Meanwhile, in Europe… Philips released the 1-inch EL3400 in 1964, and entered the domestic Fig.35: the layout of the tracks on U-matic tape. The guard bands were necessary to prevent cross-track interference but took up quite a bit of space. open-reel market with half-inch VTRs beginning with their 1969 release of the desktop LDL-1000. Although easy to use, it lacked a tuner, forcing users to have existing TV receivers modified to supply video and audio signals for the VTR. Such modified sets were known as receiver monitors. The LDL-1000 achieved some success, but recalling the success of their audio Compact Cassette system (July 2018; siliconchip.com.au/ Article/11136), Philips began devel- Fig.36: a Sony VO-1600 VTR which used the U-matic system. It also had a built-in TV tuner and TV signal output. Source: www.ebay.com/itm/163608576903 siliconchip.com.au Australia’s electronics magazine opment of a cassette system for video recording. Their N1500 (Fig.37), released in 1972 (just one year after Sony’s U-matic), offered an integrated design. Containing a tuner and a timer and able to supply a standard television signal output, the N1500 hit the spot with consumers, except for the problem of tape length. The N1500 can claim to be the world’s first domestic VCR (video cassette recorder). Philips’ VCR system mechanism, like their compact cassette mechanism, was offered royalty-free to manufacturers who agreed to maintain the design standard and use the VCR logo. You can see a video of a VCR tape loading at https://youtu.be/9-Bw8m65mVY The VCR cassette stacked the supply and reels above each other in a coaxial design. At only 125 x 145 x 40mm, it was much more compact than the standard U-matic cassette. Its width (under 60% that of U-matic) helped moderate the size of the entire tape drive mechanism. While this elegant solution offered a genuinely compact medium, the complexity of its threading mechanism meant that its reliability was only fair. Using a half-inch tape with a conventional 180° degree omega wrap (Fig.38), the Philips VCR was able to offer 60-minute record/play times May 2021  89 Fig.37: the Philips N1500 VCR had an integrated tuner and timer, making it the first VTR suitable for use in the home. But the maximum recording length of one hour meant that as soon as Betamax and VHS came along, it was obsolete. Courtesy of Greatbear Audio & Video Digitising: www.thegreatbear.net/ project/philips-n1500-n1700/ at the CCIR/PAL speed of 14.29cm/s (5.63ips). Philips attempted to market to the United States in mid-1977, but NTSC’s higher field rate (60Hz vs CCIR/PAL’s 50Hz) forced an increase in tape speed to around 17.2cm/s (6.8ips), giving only 50 minutes for a cassette. A thinner tape, offering the full 60 minutes for NTSC, proved unreliable in use. Other compromises finally made their VCR unsuitable for the American and other NTSC markets, while the introduction of VHS in 1977 convinced Philips to abandon the US market. As a result, their VCR was only market- ed to the UK, Europe, Australia and South Africa. Philips tape loading is simpler than that of the U-matic (see Fig.39). Sony had put every interaction (transport, heads and guides) in the external tape path. Philips cleverly used two cassette doors: an upwards-hinging one at the front for tape extraction, and a sliding one at the right, allowing the audio/control track head and the pinch roller to intrude into the cassette. Video entry and exit guides, and the capstan, also intruded vertically into the cassette as it was loaded downwards, giving a much more compact tape transport than that of U-matic. The pinch roller and audio/control heads, mounted on a pivoted arm, were swung into place for playback and recording. Where the U-matic head drum was designed with slip-ring contacts from the heads to the VCR electronics, Philips used a rotary transformer design that had already been used in Ampex 1-inch open-reel VTRs. Although more difficult to design and manufacture, the rotary transformer overcame noise and signal loss caused by slip-ring corrosion or misalignment. It would become the design of choice in Beta, VHS and following formats. The N1500 was developed as far as the N1520 production model. Dispensing with the inbuilt tuner, the N1520 offered recording/playback and full electronic assembly/insert video and audio editing. Released in 1973, it beat Sony’s VO-2850 workalike U-matic editor to market by a full year. Fig.38 (below): the tape loading mechanism of the Philips VCR. It used a 180° omega-wrap which, combined with the half-inch tape, made it significantly more compact than the Sony U-matic system. Fig.39 (above): a direct size comparison between the Philips VCR system and Sony U-matic. 90 Silicon Chip Australia’s electronics magazine siliconchip.com.au Regrettably, the Philips VCR format suffered from unreliable tape loading/ handling, and that dreaded one-hour time limit. Philips did develop a long-play VCR, the N1700 series, by halving the tape speed. Not released until 1977, when the Sony-JVC/Beta-VHS melee was well underway, the Philips VCR lapsed into obscurity. The follow-on Video 2000 suffered a similar fate (see https://youtu.be/SeSz6MoX00Q). Panasonic Video Cartridge Wanting to join the race, National/Panasonic came out with the NV5120 video cartridge (Fig.40). Based on their reel-to-reel half-inch EIAJ colour VTRs, these machines used a video cartridge containing a single tape reel of 30 or 60 minutes duration. The format was properly known as EIAJ2 or EIAJ-M. For loading, the tape was driven out with a stiff transparent leader. This was captured by the transport and driven along a slot that encircled the head drum. The leader would catch onto the internal takeup reel, and normal playback/recording would be available once the leader had been taken up, and the videotape proper followed. The tape was permanently engaged, so fast-forward and rewind offered picture search. While convenient (about the same size as a Philips VCR cassette), the Video Cartridge could not be developed beyond a 60-minute playing time. Also, you were forced to completely rewind the tape before ejection. Panasonic’s Video Cartridge had one unique ability: it was possible to do high-speed copying. Conventional tape mechanisms had to pass the tape over the video head drum for recording, and it was impossible to do this at any higher than standard play speed, as the video tracks would not be laid down correctly. But the tape from a Video Cartridge could be extracted and laid oxide-to-oxide against a master tape, and wound onto a takeup reel. The master/copy tape pack was then subjected to an intense, high-frequency magnetic field that transferred the magnetisation from master to copy. While this would usually erase a tape, the master’s formulation had such high coercivity that its recorded patterns were unaffected. Copying a 60-minute tape took around three minutes. Ironically, this was mostly the time taken to transfer the audio track using conventional high-speed techniques. Betamax vs VHS Leveraging off the success of U-matic, Sony’s Betamax, released in Japan in 1975, should have dominated the domestic marketplace. It had an all-in-one design, inbuilt tuner, RF output for direct connection to a standard TV set, conveniently-sized cassette and colour recording and playback. The second ‘format war’ saw Sony’s Beta face off against JVC’s Video Home System (VHS). Betamax was not just named after the second letter of the Greek alphabet. Rather, it’s an Anglicised version of the Japanese term used to describe the way signals were recorded onto tape and the letter β resembled the tape path through the loading system. The cassette size (155 x 95 x 25mm) appears to follow Masaru Ibuka’s declaration that it should be “the size of a Sony diary”. One wonders whether any brave individual thought of saying “I am most sorry, Ibuka-san, but you just can’t get enough tape into that size for a decent playing time”. It seems no-one did, and, and so the seeds of Beta’s downfall were sown. Sony retained the proven “U” loading principle, reversing the loading direction (see Fig.41 and https://youtu. be/1i_xirpJ550). Some describe this as the “B” loading system. Like U-matic, Beta suffered from slow loading/unloading times. Apart from size, Beta’s mechanism differed from U-matic in several ways. First, the tape was left fully threaded for all modes: play, record, fast-forward, rewind and pause. This allowed users to step between modes much more rapidly than with U-matic, which either wholly or partly unloaded for rewind and fast-forward. Beta also used two extraction guides rather than U-matic’s initial single guide. The master entry guide is mounted on a swing arm and draws tape to the left over the erase head. The main extraction guide is mounted on the loading ring with the pinch roller and other guides. Rotating anti-clockwise, it loads the tape to the right and wraps tape around the head drum and over the control/audio heads. Beta also swapped the positions of supply and takeup reels within the cassette, with both reels rotating in the same direction. Some later models reversed the loading direction, reverting to that of U-matic (see https:// youtu.be/1aFtDRtzKA0). Third, Beta used conventional sideby-side reels, rather than the overlapping design of U-matic. Finally, Beta used metallic leaders on each end of the tape. Pickup coils at each end of the tape path are driven by oscillator circuits. When a metallic leader passes by, the oscillator’s Fig.40: a Panasonic “Video Cartridge” VTR. As with the U-matic and Philips systems, its maximum onehour recording time was the final nail in its coffin. Source: www. labguysworld. com siliconchip.com.au Australia’s electronics magazine May 2021  91 Fig.41: the Betamax tape path. While Beta video quality was somewhat superior to VHS, once again, it was the maximum recording duration (initially one hour) that doomed it. VHS was also arguably a more elegant mechanical solution. Fig.42: when the playback azimuth differs from the recording azimuth by just a few degrees, high-frequency signals are severely attenuated. This was taken advantage of to prevent track-to-track crosstalk, by recording adjacent tracks using heads set at different azimuths. activity changes sufficiently to signal the end of the tape to the VCR’s system control circuitry and the tape is stopped. Azimuth recording U-matic was an oddball format, us92 Silicon Chip ing ¾-inch tape in a cassette that allowed one reel’s tape pack to overlap the other reel’s vacated area for both to fit in. Beta went back to the proven tape width of half-inch, with conventional side-by-side tape spools. Due to the low tape speed necessitated by Australia’s electronics magazine the small cartridge, steps had to be taken to pack the video in as much as possible. The first economy was to dump the guard bands used all the way from Quadruplex to U-matic, reclaiming up to 40% of the available tape area. But now, it would be impossible to prevent a video head from picking up some signal from the tracks adjacent to its intended track signal. Sony’s solution was azimuth recording. As noted above, tape recording formats (of all kinds) commonly align the head gap to be precisely perpendicular to the tape. Fig.42 shows the effect of azimuth errors. In the top diagram, a perfectly vertical tape head gap scans identicallymagnetised areas across the width of the tape, and a unique signal (the originally recorded one) is recovered perfectly. The lower diagram shows that if the head gap is off-vertical, the gap will scan differently-magnetised areas across the tape. Multiple signals are recovered, and the effect is to ‘smudge’ the amplitude of high-frequency signals. So if a playback tape head is off-azimuth to the original recording, there’s a severe loss of high frequencies during replay. This effect is exploited in azimuth recording. Each head’s gap is offset from the other; Beta uses angles of +6° and -6°. Beta’s FM luminance signal uses frequencies between 3.8MHz and 5.2MHz, and the 12° difference between the even field track and the odd field track pretty well eliminates crosstalk. This means that, even if the odd field track’s head happens to overlap onto the even field track, it cannot detect the even field signal due to its azimuth error. Minor tracking errors will not affect FM luminance playback. Betamax release The SL-7200 (Fig.43) was released in 1976. It featured inbuilt VHF/UHF tuners, but needed an external clock for timer recording, and you couldn’t automatically record more than one show at a time. But Beta’s biggest problem was the short recording/playback time of only 60 minutes. Sony seems not to have learned from their own experience with U-matic’s limited tape time, or to have noticed the same issue with Philips’ VCR format. siliconchip.com.au Fig.43: a Sony SL-7200 Betamax VCR. Source: http://takizawa.gr.jp/uk9o-tkzw/tv/SL-6300.pdf While U-matic’s one-hour duration had been acceptable for industry and education, how was anyone expected to record, for example, an American Football game that would often run for three hours? Yes, you could pause the tape every time there was a stoppage of play or a commercial break. But then you might as well just watch the game. And what about your favourite movies? Hardly anything is going to fit on just one cassette. Video rental shops would get behind a format that could put an entire movie on just one handy cassette: VHS. And why, oh, why, use a cassette top that only showed the supply reel (Fig.44)? Yes, you could tell when a tape was fully played/fast-forwarded, but how do you know much you’ve used once you start? Some two-window cassettes were made (Fig.45), seemingly trying to catch up with the more informative design of VHS cassettes. JVC’s Video Home System VHS seems a bit of a Betamax copycat. Sony had consulted with JVC and Matsushita (National) in the early 1970s, aiming to unify a new design based on the U-loading format. Sony engineers were dismayed to find that JVC’s advertising of a ‘new’ video format used elements of Beta’s design: azimuth recording and rotating-phase heterodyne colour (described in more detail below). The success of VHS follows from such a simple idea that you wonder how Sony missed it: enough tape to Fig.45: a later Betamax cassette which added the much-needed second window. But it was too late; VHS was already winning the format war. Fig.44: a standard Betamax cassette. The single window was also a strange design decision as it made it difficult to judge just how much of the tape you had used up. siliconchip.com.au run for two hours without needing long play and its compromises. VHS’s longer tape length, and consequently larger tape reels, required a cassette 187 x 108 x 25mm in size (Fig.46). But VHS is not a simple copycat. JVC probably considered the “U” loading system, but adopted the quicker, simpler “M” load. This uses two arms that extract the tape and draw it out to either side of the head drum (see Fig.47 and https://youtu.be/MPYrKtmuQ41). There are arguments that M loading increases tape tension and wear, but its loading speed, more compact size and its lack of tape-hanging-in-mid-air paths combined to make it the technology of choice for VCRs. However, note that there was an oddball Grundig VS-340 that used B-loading. Given that all the loading mechanism has to do is get the tape onto the drum, it obviously worked well enough, and the user would never know the difference. VHS cassettes used transparent tape leaders. A small lamp on a post intruded into the cassette, and two optical sensors (one on the supply side, one on the takeup side) viewed the lamp via small ‘tunnels’ in the cassette body. Normally, the opaque tape would block the sensors’ view of the lamp, but the leader would allow light through and signal start/end-of-tape. This lamp was vital to proper tape handling, so the VCR’s control system would test the lamp for continuity before allowing operation. Service techs were frequently reminded, for a VHS set with “no operation”, to check the tape sensor lamp first. Following JVC’s release of the HR3300 in 1976 (Fig.48), National Panasonic came on board. Video hire companies endorsed the much longer playing time that VHS offered in standard play and VHS would come to dominate home video recording. Track layout Fig.46: the now-familiar (to anyone over 35, anyway) VHS cassette. The track layout for VHS is shown in Fig.49. VHS uses ±7° azimuth offsets between the video heads/tracks, but otherwise works just like Betamax. While the offset azimuth works fine for luminance frequencies above 3MHz, it is ineffective for the down-converted ~627kHz (626.953kHz) chroma signal. Lower frequencies are less affected by azimuth errors, so some other means of eliminating chroma crosstalk was needed. Australia’s electronics magazine May 2021  93 Fig.47: the VHS tape path. It uses M-loading, where the tape is pulled onto the head drum by two sets of moving guide wheels. This makes for a more compact mechanism. The solution was to take the chroma signal and progressively rotate one track’s phase by 90° for each scan (let’s call it the B track). The other (A) track was recorded ‘as is’. On playback, a two-line delay would give cancellation of the undesired chroma signal. It’s a bit complicated, so let’s just leave it at that – you can check the references below if you’d like to delve more deeply. Sound quality With a tape speed less than that of the Compact Cassette, audio qual- ity was going to suffer. It had only been just adequate with the Philips VCR system, with a bandwidth of 100Hz~12kHz. Beta managed to get 50Hz~10kHz at standard play and 50Hz~7kHz for long play. VHS managed 50Hz~10kHz standard play, but, depending on the model, only up to 4kHz for long play; barely better than telephone quality. Engineers had already packed a good part of the video signal’s bandwidth onto half-inch tape with an ingenious combination of FM and AM recording. Given that FM broadcast Fig.48: an early JVC HR-3300 VHS VCR from around 1976. Source: https://en.wikipedia.org/wiki/File:JVC-HR-3300U.jpg 94 Silicon Chip Australia’s electronics magazine radio could give a high-quality stereo performance, why not employ FM for the audio channel? That would also provide the option of stereo audio. And that’s what they did. Hifi audio recording fed program audio to frequency modulators and then onto the tape. While the electronic design was already available (FM transmitters, FM receivers), the problem was where to put the signal within the available tape bandwidth. Colour Betamax VTRs split off their luminance and chrominance signals, using frequency modulation for the luminance at frequencies above 3MHz. This had left a band centred around 620~650kHz for the amplitudemodulated chrominance signal, and it only extended to around 1MHz. So why not put the FM sound in at about 1.5MHz? Going to 1.5MHz FM audio meant that the audio signal would be recorded in the video section of the tape, and would have to be recorded by the rotating video heads along with the video signal. That’s where the available spectrum existed, and it would have been quite impossible to record any frequency higher than about 10kHz on a linear track, let alone the approximately 1.5MHz FM audio signal. Sony shifted the luminance signal up the spectrum by 400kHz to make extra space available, then used four FM signals: Head A 1.38MHz (left) and 1.68MHz (right), and head B at 1.53MHz (left) and 1.83MHz (right). This allowed Sony to continue using just two video heads, and, in some models, to provide for an external hifi audio processor. For VHS, though, there wasn’t enough spare spectrum, so VHS hifi used depth multiplexing (Fig.50 shows the complete VHS hifi recording spectrum). The FM signal would penetrate the tape’s oxide layer to a depth of around 1µm, while the higher-frequency video signal would only penetrate some 0.3µm. This saw the VHS audio FM signal recorded by a separate pair of record heads, placed some 60° in front of the video heads. The audio heads needed to record first, as the audio signal’s greater depth penetration of around 1µm would have erased the shallower 0.3µm video, had the video been laid down first. While the existing audio signal was partly erased by the following video, the erasure was only shallow. The siliconchip.com.au remaining audio magnetisation was strong enough to be successfully recovered, with the benefit that, being frequency-modulated, any minor tape imperfections would not affect sound quality. Unlike Beta, VHS hifi could not be added to existing two-head VCRs. VHS used either two-head linear audio or four-head hifi/two-head linear. In common with broadcast FM, Beta/VHS hifi used preemphasis at the upper end of the audio band to improve signal-to-noise ratios. This preemphasis was removed by a deemphasis circuit during replay. Also, a companding (compressing-expanding) system compressed the dynamic range during recording from 80dB to 40dB. Left uncorrected, such compression would sound most unnatural, with quiet sounds made unnaturally loud. On playback, the off-tape 40dB dynamic range was expanded back to the original 80dB. With a few other tricks, VCR hifi audio managed a signal-to-noise ratio of 80dB, frequency response of 20Hz~20kHz, with wow and flutter (speed variation) of just 0.005%. And it met these specs at standard, long and triple play. The resulting audio quality was pretty much indistinguishable from Compact Disc. There were even some hardy souls who used hifi VCRs as high-quality audio recorders. Fig.49: unlike U-matic tape (shown in Fig.35), VHS has no guard bands between the video tracks, allowing for higher density and thus longer playback/ recording times. To prevent crosstalk between tracks, they are recorded with alternating azimuth offsets of ±7°. rior colour performance. A side-by-side replay of standard colour bars shows better definition and less noise/artifacts in the colour signal than for VHS. A pity about the one-hour cassette. We’ll look at Super-Beta and S-VHS in the next (and final) article in this series. Part four will also describe how manufacturers responded to the demand for ever smaller and lighter VCRs. We’ll also have a short bit on LaserDisc for those who thought we had forgotten about it. References • Video Cassette Recorders, Humphris, Rod, 1998, TAFE Course Notes • U-matic development by Sony: www. sony.net/SonyInfo/CorporateInfo/ History/SonyHistory/2-01.html • The Impossible Feat inside Your VCR, from Technology Connections: youtu.be/KfuARMCyTvg • The VHS cassette was more clever than Beta: youtu.be/hWl9Wux7iVY • Also check out the rest of his YouTube channel: youtube.com/channel/ UCy0tKL1T7wFoYcxCe0xjN6Q • The history of VTRs before Beta and VHS: www.labguysworld.com • An extensive picture gallery of Philips VCR, Beta and VHS: www. oldtechnology.net • Special thanks to Rewind Museum for the use of various images: www. SC rewindmuseum.com Was Beta Better? Arguably, yes. Beta’s wider FM bandwidth offers somewhat superior luminance definition. Specifications put Beta (luminance resolution 260 lines) a little ahead of VHS (240 lines) at standard play. Beta’s use of a high-amplitude pilot burst for colour correction gives supesiliconchip.com.au Fig.50: the spectrum of hifi VHS recorded onto tape. It’s essentially the same as standard VHS but with the addition of two audio channels frequency-modulated onto 1.4MHz and 1.8MHz carriers. Australia’s electronics magazine May 2021  95 SERVICEMAN'S LOG Some jobs are much harder than they should be Dave Thompson It is often the way of the serviceman that some of the small jobs turn out to be the most testing. My progressing age doesn’t help, but nor do modern manufacturing techniques which cram so many tiny components into a tight space. One reason for my increasing difficulty effecting these repairs could be that I’m getting on a bit now, and my once-dexterous hands don’t feel quite as capable as they once did. Nor do my eyes seem as sharp as when I was 20 years old. A good magnifier with a bright light (or better still, a high-resolution USB microscope with a decent-sized screen) will help with the fading eyesight. But there isn’t a lot I can do to keep my motor skills young. It isn’t as if I can’t pick up a cup or walk up the stairs without my bones creaking and groaning, like many of my martial-artist friends who practised the striking arts. They spent their careers punching and kicking each other and breaking bits of wood and bricks, and many are now feeling the effects of doing such a sport. I spent 25 years practising Aikido; one of the skills involved is learning to fall over without getting hurt, so that’ll 96 Silicon Chip set me in good stead for the future! But I am noticing a slow but inevitable decline. It’s the same when people suddenly find they can no longer run 100 meters without a rest break, or throw or kick a ball nearly as far as they used to. Obviously, this is all part of getting older, but it still affects what we servicemen do. I’ve been lucky enough to have steady hands and good tools to help with some of the trickier jobs I’ve done over the years. While good tools help, it’s the skill behind them that makes all the difference. Dad taught me to solder about the time I started talking, and I gained further valuable skills in this area working at the airline. However, much of this knowledge is deprecated now, given the massive increase in the usage of SMDs over through-hole components. Many of those SMDs are almost invisible to my old eyes. As a result, some projects and device repairs are beyond the scope of even skilled servicemen, and repairs increasingly require specialist (read: expensive) kit that many of us don’t see the value in acquiring. I recently had a quite challenging small-form job through the workshop: a Logitech mouse. Before you all jump up and down and query the wisdom of repairing something like this, it isn’t one of those 10-dollar corded jobs you buy at the checkouts at a supermarket. This 7-button wireless mouse was quite costly, and the owner thought it prudent to try to have it repaired before shelling out for a new one. The problem was the left click button; for some reason, it started douAustralia’s electronics magazine Items Covered This Month • Of mice and men • Volume control issues with an • • electric guitar kit The lab and the variac Clenergy SPH15 1.5kW solar inverter repair *Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz ble-clicking, no matter how gently or firmly one manipulated the flexible plastic actuator. Thinking it could be a software problem, even though the owner had tested an old mouse and found it free of this defect, I plugged it into my machine. Sure enough, a single click of the left button resulted in a double-click action. The right button was fine, a­nd if you listened and felt the tactile difference between the two button clicks, you could sense something was up with the left one. It felt and sounded worn out. This mouse hadn’t been used all that much, so it was unusual that the button had ‘worn out’ in such a short time. Micro-switches typically have a stipulated lifetime, measured in actuations, but I have mice that are decades old and have literally travelled many hundreds of kilometres with millions of clicks. I know this because, for many years, I had a piece of software installed that enhanced my mouse’s capabilities, which also measured how far my mouse had travelled and how many of the various button clicks I’d performed. It is astonishing how quickly siliconchip.com.au the kilometres and clicks add up! Sadly, this software won’t run on Windows 10 and is now abandon-ware. Returning to the mouse in question My semi-educated guess is that the switch was just one of the small percentage of the many millions mass-produced every year that fail early. This so-called acceptable failure rate happens with everything from ovens to soldering irons and cars to hard disks; it is just part of modern manufacturing. A famous case (to computer nerds at least) is a hard drive that came out in the 90s called the Quantum Bigfoot (https://w.wiki/3AmL). For about a year, most PCs purchased came with one of these drives. My first PC had a 2.1GB Bigfoot; a massive amount of disk space at the time. The Bigfoot got its name from the large form factor it had compared to other hard drives, which were physically smaller, known as 3.5-inch drives (referring to the diameter of the platters inside). The Bigfoot was much larger, being the same width and taking up the same bay space as one of those ancient 5.25-inch floppy drives, or a slightly more modern CD-ROM drive. It had one flaw, though: it was rubbish! Most hard disk manufacturers have an acceptable failure rate for their products in the region of 2.5% or so, meaning that out of every 40 manufactured, one will fail within the first 12 months of use. That sounds pretty good, unless you are one of those who experience that failure and the data loss that ensues. The Bigfoot had a failure rate of close to 50%, which was previously unheard of. I found out about it because the Bigfoot in my desktop PC failed within a couple of months, taking all my data with it. I replaced it with another make siliconchip.com.au and model of drive, at my expense, because the company I’d bought it from had gone under. That was a common occurrence in the early days of pop-up stores selling computers in the mid-90s boom. This did teach me some very valuable lessons, though. The first: always assume a computer will fail. It is almost inevitable. If you haven’t backed up your data, how much trouble would you be in if it went ‘bang’ when you next fire it up and you lost everything? The second: computer repair guys back then were often sharks and rip-off merchants, playing on the ignorance of the average owner. Being a beginner at the time, I got burned. A little later, when I unexpectedly lost a gig working at a local TV studio, I looked into fixing computers for a living and realised that it was something I could probably do. I understood the basic principles and systems well enough, and with the arrogance of youth, I figured that I could do it. That was 27 years ago, and for the record, I probably wouldn’t have the nous to make that same decision today. But I’m glad that I did at the time. Back to the mouse again If you’ve ever had the pleasure of opening one up to see what’s inside, you were probably surprised at how little lives inside them. The bulk of your basic twoor three-button corded mouse is likely taken up with the laser Australia’s electronics magazine and (optional) scroll-wheel assembly, with their associated switches mounted to a small PCB on the bottom of the chassis, which also has the USB or PS/2 interface circuitry. It’s pretty simple stuff, and certainly not worth fixing given the ultra-low cost of them these days. That’s not to say I haven’t re-terminated cables or cleaned balls and optical wheel sensors out in my time; I have, many times. But these days, unless someone really loves their mouse and is prepared to pay to have it fixed, it will end up in the bin. This particular customer likes his mouse a lot, and since this type costs a lot more than your garden variety mouse, he was keen to have the errant microswitch swapped out. He’d had a look inside and baulked at the many PCBs stuffed with SMDs and the complex internal construction, concluding that the fitting of a new switch was beyond his pay grade. And so he brought it all to me. It turned out that I have an identical mouse stored away in my, erm, mouse storage place. This could be a stroke of luck, as it is always nice to have an identical model to refer back to, especially if the breadcrumbs I leave or photos I take along the way don’t lead me back to an easy reassembly! To be honest, I felt pretty much the same way as my client when I took the case off. It looked like a Mars Rover without the wheels, stacked with electronics on layered PCBs. Fortunately, the customer had already opened up the case; he’d done the hard work of finding the four hidden screws and plastic clips that were holding it all together. This is a classic case of manufacturers making things difficult to repair. I guess it could be worse; they could have used deeply-buried anti-tamper fasteners. Despite that, the unwary or inexperienced might just conclude that because there aren’t any visible screws holding it together, there mustn’t be any, and begin by trying to pry the case apart. Of course, this will end in tears (or at the very least, a mouse with a mangled case that won’t come apart). The two front screws are hidden behind a couple of those stuck-on Teflon bumpers many computer mice have these days. These are to help it slide more smoothly over a desktop or mouse pad. May 2021  97 You might assume the two rear screws were hidden under the back bumper, but no. Those back screws were cunningly hidden inside the battery compartment, underneath the stickers that denote battery type and polarity. The ends of the stickers had to be carefully peeled back to find and access the screw holes. The cowboy in me might have been tempted to just punch straight through the stickers with my screwdriver if this was my own mouse, but for a client, one has to maintain certain standards and decorum. So it was fortunate that he’d already done the hard work, peeling back those stickers and removing the screws. I could see the offending microswitch as plain as day at the bottom of the heap, but getting to it was going to involve removing a lot of tiny screws, most of which were different sizes and threads. The photos I took periodically during disassembly would definitely help with putting it all back together. My memory of what part went where would also be a valuable tool; thank goodness that hasn’t gone south on me yet... A challenging repair job The various boards inside the mouse were connected with a mix of those really stiff, hard-soldered flying leads and thin, flexible ribbon cables terminating into ‘backflip’ edge connectors. These connectors are very similar to what I find in laptops, phones and tablets to connect PCBs together. One problem I’ve found with this type of connector is that they are often limited-use items. If I toggle them open and closed too many times, many break, give out or won’t 98 Silicon Chip connect properly anymore. Replacing them is also very difficult for mere mortals like me. Long story short, I had to disassemble the whole mouse just to gain access to the switch in question. Replacement switches are available all over the usual auction sites online, but as I had a good collection of NOS (new old stock) microswitches, I was sure one of them would be fit-for-purpose. The bigger problem for me was removing the old one, given the small form-factor and tight spaces. Sometimes it is easier to cut the component off with the likes of a Dremel/rotary tool with a cut-off disc attachment, but there was no room for that rather ham-fisted approach here. I could just get my soldering iron’s finest tip to the contacts, but even though I could melt the solder, removing the switch was not easy. It appeared to be stuck down, likely to ensure it stayed in place for the reflow soldering process. While I had the legs unsoldered and clear of the board, the switch would just not let go. I tried soaking it with isopropyl alcohol and various contact cleaners in the hope it would loosen up; it didn’t. I had to resort to using my dental picks to try to break the bond, being very careful not to damage anything on the PCB underneath, all to no avail. It was stuck fast. I ended up breaking the switch off the board as gently as I could, but was horrified to see several of the tiny copper tracks coming with it. That pretty much ended the repair job right there. While I could see where the three tracks had been torn from, re-joining them, especially on a double-sided PCB, was not going to be feasible. While I might have been able to do it, the time involved would push the repair into loss-making territory for me. Fortunately, I had that identical mouse. After installing batteries and using the Unifying software to associate my mouse with the customer’s dongle, I figured it would be much easier to just sell him this one as a second-hand device rather than persevere with the now-damaged one. He was grateful for this option, so we all went home happy. This was one of those jobs that, if it went well, it was worthwhile doing, but as soon as something went awry, it became a non-feasible repair. As a serviceman, I have to try the former option, but I also need to know when to pull the pin on a dead-end job. Having a suitable replacement mouse in this case was just good luck. If I didn’t have one, the client would likely have had to shell out for a new one. Such is life. And I have to say that gluing components to the board might be convenient for manufacturers, but it certainly makes those parts hard to replace if they fail! Ideally they should use a type of glue that loses its strength over time or with heat, or that is just tacky enough to hold the components down for soldering but still allows the possibility of pulling it off later, should it need to be replaced. That might even help the manufacturers if they have to ‘rework’ any of their products before sending them out to be sold. An electric guitar kit with volume control issues J. N. of Mt Maunganui in New Zealand recently built an electric guitar from a kit. He had a bit of a problem with some of the electronics, and the solution was a bit unusual… Australia’s electronics magazine siliconchip.com.au All went well with my guitar build until I began playing the guitar via an amplifier. I started having intermittent faults with the volume control to one of the two Humbucker single-coil pickups. Naturally, I re-checked all my wiring to find nothing amiss. Then the volume control started working again, but not for long! So the problem must either be in the pickup or its associated volume control. However, both checked out fine. The pot measured 500kW and a normal 10kW+ for the pickup. But as soon as I reinstalled everything, it happened again. This repeated several times, with me checking and re-checking until the penny dropped. The volume control worked when removed, but as soon as I remounted it, it would not function. So it had to be an installation problem. Sure enough, on very close inspection, I noticed that this particular pot (unlike the other three), was mounted on a slightly curved part of the guitar soundboard. Consequently, when the fixing nut and washer were tightened, the pot became warped and would not function. I replaced the steel washers with rubber washers and had no more problems after that. The lab, the questionable students and the variacs D. D. of Coogee, NSW, wrote in to say that he loved the story about the Old TV Repair in Serviceman’s Log, April 2020. It reminded him of when he was a young serviceman in the 1960s, which prompted him to write the following story... Back in the 60s, I worked in the chemistry department of a university in the UK, where I was in charge of the electronics workshop. One winter morning, soon after I arrived for work, I had a call from the glassblower. He was a lovely chap and a real glass craftsman but had no real understanding of “electrics”, and I realised he was a bit scared of it. I grabbed my trusty Avometer and set off for his workshop. When I arrived, he showed me a machine and said: “the green light is on, but I haven’t turned the power on yet, what do you think could be going on?” The machine was an induction heater in a large metal case mounted on the wall, about 60cm above the bench, so he could feed glass tubes into the induction coil to heat them up. It had various controls and an on/off switch on the front panel as well as a large green indicator light. This was glowing brightly and was freaking him out. He was very worried about this and asked if I thought we should call the university electrician in case some weird power fault had occurred. I was initially puzzled because I didn’t think it was likely that the machine could be on without being switched on. I pointed out that the switch was still in the off position, but he was not convinced. I then said, “Well, I can’t see the light glowing from here.” He pulled me back over to the door and said: “look, you can see it from here.” It was only then I realised that where the machine was mounted on the wall, the sunlight from a window behind it could enter through the perforated metal back of the cabinet and make the light appear to be on! Needless to say, he was a bit embarrassed, but we had a good laugh about it and became firm friends afterwards. In fact, he became a bit of a mentor to me and helped me in lots of ways. siliconchip.com.au Australia’s electronics magazine May 2021  99 Another problem I had to solve concerned variacs. They were used in constant-temperature water baths in the teaching and research laboratories. These were magnificent brass tanks about 1m square and 0.5m deep. They had a pyrotenax heating element in the bottom, a slowly-rotating paddle wheel to circulate the water and a mercury-in-glass thermostat. They were made in-house; Ron, in the main workshop, made the tank and the paddle wheel. “Big wheels turning slow, mate” he said to me one day with a knowing tap of his nose. (I had no idea what he meant but pretended I did!) My mate the glassblower made the thermostat, which was basically a mercury thermometer with one fixed platinum wire contact and another mounted on an adjustment screw to allow the temperature to be set to the desired level. Ron wired these contacts through a relay to switch power on and off to the heater. The variac was needed because the heater had a resistance of about 10W and needed about 4A to heat the water to the required temperature. The system worked really well and could control the water temperature to a small fraction of a degree at a much lower cost than commercially-available units. The problem, however, was the users; mainly research students, who while they were very good at chemistry, could not do a simple Ohm’s Law calculation and so tended to overload the variacs. When they put a flask of chemicals into a water bath, it took a long time to warm up the contents before they could start their experiments. With the Professor breathing down their necks for results, and the fact that they often had late starts due to too much social life, there was a great temptation to wind the variac up a bit to speed up the heating process. They had a current rating of 4A, and despite being warned not to exceed 40V, the users did not seem to realise that exceeding this could cause a problem. Of course, the carbon brushes overheated and eventually failed. Each time a brush failed, damage was caused to the copper winding of the variac, and before long, the inevitable happened – a winding burned out. This proved to be the case one day when I was called to “Derek’s” lab. He had been copping a bit of flak lately from his Professor about various blunders and delays, so he was in a right panic when I told him his variac was “cactus”. To try to help him out, I offered to go to the main store and get a new one for him. I didn’t stock variacs; they were far too expensive, but there were a couple in the storeroom. It didn’t occur to me that maybe I shouldn’t just walk in; after all, I was a staff member, not a student; so in I went. I was chatting to the stores girls whose main occupation seemed to be filling beautiful old glass-topped reagent bottles engraved with the Latin names of chemicals. They were filling them from large tubs of chemicals and putting them on the shelves to be issued later (a cost-cutting measure). The manager strode up to me and drew himself to his full height. “Can I help you?” he asked. He was what I suppose you would call a dapper little man, impeccably dressed (unlike the rest of us) in a striped white shirt, tie, neatly ironed trousers and his white lab coat starched to within an inch of its life. He carried a plastic wallet in his breast pocket with black, blue and red biros and a propelling pencil. “Yes, please” I said, “I’d like a variac; I see you’ve got two left.” The girls later told me they could see the steam coming out of his ears! When he had finally regained his composure, he rushed me into his office and shut the door. “Dave I know you’re new and that, but that’s not how things are done Servicing Stories Wanted Do you have any good servicing stories that you would like to share in The Serviceman column in SILICON CHIP? If so, why not send those stories in to us? It doesn’t matter what the story is about as long as it’s in some way related to the electronics or electrical industries, to computers or even to cars and similar. We pay for all contributions published but please note that your material must be original. Send your contribution by email to: editor<at>siliconchip.com.au Please be sure to include your full name and address details. 100 Silicon Chip Australia’s electronics magazine you know!” He proceeded to explain his “stores system” to me. He gave me a stores requisition book and a stock list and explained that four carbon copies were needed. “You fill it in, with your name, department, extension number and the details of what you want, referenced from my stock list. Then you sign it, hand it in at the stable door and we will bring your items out to you. Don’t forget to put the carbon paper in; the white copy is for my records, red for the office to charge to your account, yellow goes into storage, and you keep the green copy in your book. Understand?” Feeling somewhat chastised by all this, and as it was nearly hometime, I withdrew back to my workshop and went home, forgetting all about poor Derek waiting upstairs! The next day I returned to the stores with a neatly filled out requisition and rang the bell at the half-stable door. One of the girls came up, and I handed her the requisition. She went off with it, and after a little while, the manager came over to the door. “Sorry Dave, I can’t let you have one” he said, much to my surprise. “Why not?” I asked, “Have I filled out the requisition wrong somehow?” “Oh no, that’s OK” he said, “It’s just that I haven’t got enough stock.” This was a bit puzzling because I knew he had two yesterday and didn’t think he could have issued both of them already. Eventually, I blurted out, “But you had two yesterday.” “Yes,” he replied in an irritated tone. “So why can’t I have one?” I said. Imagine my amazement when he explained that one was needed in case “someone” wants one and the other was a pattern for re-ordering! “But I’m someone” I tried. He wouldn’t budge, however, and I felt like I had been sent off or sin-binned! Later, I found out that the only way I could get one was to get Derek’s Professor to ring down for one. Jim explained the Professor was the “someone” – his secretary would fill out the requisition, which would be sent to the stores in the internal mail and a girl would deliver the item to Derek’s lab. This was duly done, and I installed the new variac, telling Derek to more careful in future not to turn the “herbs” up too much. That should have probably been the end of the story, but I couldn’t resist siliconchip.com.au getting my own back on the manager. I had just bought a huge Circuits Manual from the USA, and as I was browsing through it, I saw something exciting. It was billed as a solid-state variac replacement; just what I needed, I thought! The circuit showed a power controller consisting of a UJT firing circuit and an SCR. It was said to be capable of controlling resistive loads of any current, limited only by the SCR rating. I soon had the parts and shortly after, had a breadboard version working. Of course, it was much smaller and cheaper than a variac, and I soon had a few prototypes out in some of the labs. The guys seemed to like them, but they had a few teething problems. They had terrible hysteresis, which meant that as you reduced the power level, they would suddenly turn off and to get them to fire again, you had to turn up the power way past the point where you were before. The guys naturally didn’t like this, especially as they weren’t sure what was happening. Later versions used a quadrac, which was a new device consisting of a Triac with an integrated Diac. The manufacturers even helpfully included a low-hysteresis firing circuit and RFI filter on the data sheet. It wasn’t long before we had the device perfected, and the researchers were all ordering them to replace their variacs. All went well for about six months until one day, the stores manager bailed me up after morning tea and said: “If you still want that variac, I have just received an order of a dozen so you can have one!” siliconchip.com.au The look on his face was priceless when I said: “Oh, we don’t use those any more. They’re old hat now. I’ve replaced them all with solid-state power controllers!” At least he would not have stock problems any more! Clenergy 1.5kW solar inverter repair R. S., of Fig Tree Pocket, Qld, got sick of having to get his solar inverter replaced under warranty. So he decided to try to fix it himself, with some success... The Clenergy SPH15 1.5kW solar inverter was supplied by Origin Energy as part of their low-cost solar power system. These inverters started giving an “Output Relay Failure” message after a few years. Mine was replaced twice due to this fault. I can see that the inverter boards now have external diodes placed across the relay coils, so it appears that the relay drivers were being destroyed by back-EMF from the coils. This must have been costly, with so many units replaced. A new problem is now occurring, with messages such as “GFCI Fault”, indicating leakage current to ground from the solar panels. However, megger testing of the panels shows no leakage. It seems that the currents on the DC inputs (from the solar panel) are being compared and the error is displayed if an imbalance is detected. There are two current transformers on the main board, one on the positive input and one on the negative input. There is a buck-boost converter immediately after the input, with two IGBTs Australia’s electronics magazine in parallel and a large rectifier. The IGBTs are driven by an ICC2818 controller, optically coupled via a TLP350 Mosfet/IGBT driver for isolation (see photo directly below). As current transformers need current pulses to produce an output, I thought that the buck-boost converter might not be operating. I have had problems with optically coupled isolators in the past gradually failing due to either low output from the internal LED and/or low sensitivity of the optical receiver. So I replaced the TLP350, and the inverter started working again. The GFCI fault disappeared. I am wondering how many of these inverters have been scrapped due to these problems. Be careful when working on these inverters, as the large high voltage capacitors take a long time to discharge. The low voltages are also supplied from these capacitors, so be sure that these are not present when working on the control section. I notice that to reset the display board, it is sometimes necessary to disconnect and then reconnect the ribbon cable. This is because the supply voltages persist, as described above. Since I repaired my inverter, a new error message is now showing: “Ground I Fault”. This has stopped the inverter working again. I will investigate this, but it will take some time as there are no circuit diagrams available. The only hope I have is to compare the operation of a working unit with the faulty one. It seems to be a fault on the main board, as swapping display boards does not make the error go away. SC May 2021  101 PRODUCT SHOWCASE Weller introduces a new range of soldering irons The leader in soldering equipment worldwide, Weller, has announced the launch of the Weller Red range of soldering irons. These are designed for passionate DIYers and craft creators, who need precision tools to make their visions come to life. Whether repairing RC aircraft or cars, general electronics, drone modifications and more, Weller soldering irons finish jobs quickly and safely. Weller’s latest sol­der­ing tech­nol­ogy, with its ergonomic handles, lighting ability and precision design, en­ables working better over longer periods. The Weller Red range comes in 25W, 40W and 80W versions, ensuring you have the perfect tool for your project, no matter the complexity. The new range also features the lat- est heat-resistant LED technology, delivering unparalleled lighting while working. An aesthetically pleasing, slimline triangular front housing captures the light and focuses it on your work area. Once the tip position is determined, the hand naturally gravitates to the triangular area, providing a stable and effective way to control the tip. Weller high-performance consumer soldering irons deliver comfort and flexibility. A round, soft grip, nonslip handle design helps relax the hand during extended use. The round handle provides a mechanism to roll and position the tip as required. The heat-resistant housing ensures a long life, and the high-performance stainless steel heaters ensure quality soldering for years to come. The Weller Red range features temperature control up to 470°C (model dependent), allowing soldering for myriad DIY and craft applications. Weller soldering irons can be purchased from Bunnings Warehouse; see siliconchip.com.au/link/ab81 Weller Tools www.weller-tools.com Mouser now stocking ams AS7038xB and AS7030B vital sign sensors Mouser is now stocking AS7038xB vital sign sensors and the AS7030B sensor module from ams. These small sensors are suitable for medical wearables and remote diagnostic equipment, such as disposable patches used for blood oxygen saturation (SpO2) and electrocardiogram (ECG) measurements. The ams AS7038RB/GB sensors and AS7030B sensor module are based on photoplethysmography (PPG) and ECG. The AS7038RB sensor is the industry’s thinnest dedicated sensor for SpO2 measurement, at just 3.7 × 3.1 × 0.65mm. Mouser Electronics Inc. Phone: (852) 3756 4700 Web: www.mouser.com The sensor enables designers to incorporate vital monitoring capability into small consumer products such as earbuds, smart watches and wristbands, as well as in medical devices such as oximeters. The sensor’s on-wafer interference filter technology developed by ams enables it to capture optical signals in the 590nm-710nm and near infrared (800nm-1050nm) wavelength bands for SpO2 measurement, while blocking interference from ambient light at other wavelengths. The AS7038GB version features peak sensitivity at the 525nm (green) wavelength for use in heart rate and heart rate variability measurement, while the AS7030B HRM/HRV sensor module integrates two 535nm LEDs in a single 3.55 × 6.2 × 1mm package. To learn more, visit: w w w. m o u s e r. c o m / n e w / a m s / ams-as703x-biosensors/ www.mouser.com/new/ams/amsas7030b-vital-sign-sensors/ New MCP356xR ADC family from Microchip The MCP356xR family offers high precision at much faster data rates, making the devices ideal for a variety of precision applications that require precision at both low and high data rates, including industrial process control, factory automation and sensor transducers and transmitters. These ADCs reduce the overall cost of a system by eliminating the need for external components. 102 Silicon Chip Features include: • 24-bit resolution • 1/2/4 differential input channels or 2/4/8 single-ended channels • programmable data rate up to 153.6 kilosamples/sec • programmable gain: 0.33x to 64x • internal 2.4V reference • effective RMS bits: up to 23.3 • internal oscillator or external clock selection Australia’s electronics magazine • internal temperature sensor • 20MHz SPI-compatible interface with mode 0.0 and 1.1 • comes in 3 x 3mm 20-lead UQFN or 6.4 x 6.4 x 1mm 20-lead TSSOP • temp. range of -40°C to +125°C Microchip Technology Inc. Unit 32, 41 Rawson Street Epping 2121 NSW www.microchip.com siliconchip.com.au Vintage WORKBENCH 1972 1972 BWD BWD Model Model 141 141 Audio Audio Generator Generator By Ian Batty The BWD 141 is an Australian-made sine and square wave generator, produced around the early 70s. It has an output frequency range of 1Hz to 1MHz, and is powered by mains or two 9V batteries, boasting a respectable 600 hours of battery life. BWD, established in 1955 in Hawthorn, Victoria by John Beesley, Peter Wingate and Bob Dewey produced well-engineered and affordable test equipment for several decades. They eventually became McVan Instruments and currently work out of Mulgrave as Observator Instruments. BWD’s versatile and innovative 216A 0~400V power supply was described in the February 2019 issue of Silicon Chip (siliconchip.com.au/ Article/11419). This article describes a simpler piece of test gear, but one with a much longer history in electronics. You may be fortunate enough to have AWA’s R7077 Beat Frequency Oscillator in your collection. Released in 1940, it used two ultrasonic oscillators: one fixed, and the other adjusted by the frequency control. The oscillator signals were mixed, and the frequency difference was delivered as the audio output signal. This had the great advantage of a single-span dial covering the audio band from 30Hz to 13kHz. However, the siliconchip.com.au need to zero it before use and its lessthan-perfect sinewave output made it unsuitable for testing high-performance audio equipment. Modern function generators do offer sinewave output, but they generally are modified square waves of indifferent purity. I recall a TAFE colleague who was teaching audio and hifi discovering this. With a few choice words, he returned the class set of function generators to storage and ferreted out every ‘old-tech’ BWD audio generator and MiniLab he could find. Early signal generators Frederick Emmons Terman is one of the giants of electronics. He was born in 1900 and gained his Doctorate of Science in 1924. His supervisor was another giant of American science, the man who would lead the Manhattan Project: Vannevar Bush. Working at Stanford University, Terman designed a course of study and research in electronics, focusing on vacuum tubes. Terman’s Radio Engineering was first published in 1934, Australia’s electronics magazine and would become one of the most important reference works in the science of electronics. It remains an authority to this day. The saying goes that “if you were doing radio or electronics engineering anywhere from the ‘forties to the ‘sixties, and you weren’t reading Terman, you weren’t doing engineering.” Terman’s Stanford University students included Oswald Garrision Villard Jr. (ionospheric research and overthe-horizon radar), Russell and Sigurd Varian (inventors of the klystron), William Hewlett, and David Packard. Those last two would founded one of the world’s top makers of electronic instruments, and created the HP Way, a corporate model that has led innovation within the industry. From thesis to product Bill Hewlett’s Master’s thesis described a wide-range, low distortion audio signal generator. His supervisor was Frederick Terman, of course. Using the Wien Bridge filter, the HP 200A set aside tuned-circuit and other May 2021  103 Fig.1: the circuit diagram from Bill Hewlett's patent for a Variable Frequency Oscillation Generator. complex techniques and used a simple resistance-capacitance bridge that could easily deliver a 10:1 frequency ratio in each range. It was named the 200A for marketing reasons. It gave the appearance of being one-of-a-number of products, rather than the very first. The Wien Bridge (invented in 1891 by Max Wien) uses two resistors and two capacitors (R1, R2 and C1, C2 in Hewlett’s diagram). For equal-value resistors and capacitors, there is a frequency (f = 1 ÷ [2π × R × C]), where the phase shift from input to output is zero. This is one part of the Barkhausen Criterion for oscillation, the other part being an overall loop gain of +1.0. Notice that there are no exponents in the formula; frequency varies directly as the inverse of resistance or capacitance, so a 10:1 change in either R or C gives a 1:10 change in frequency. This decade span allows just three switched ranges to cover the three-decade audio band of 20Hz to 20kHz. It’s another advantage of the Wien Bridge principle. Tuned-circuit oscillators see frequency vary as the square root of L or C, so a 10:1 change in L or C gives only a 1:3.16 change in frequency. This three-to-one ratio is characteristic of L-C tuned oscillators. An oscillator circuit can be built by putting the Wien Bridge filter in the positive feedback path between the output and input of an amplifier. The amplifier only needs moderate gain to make up for the small losses in the filter circuit; a gain of about three is adequate. The single-sided PCB is mounted on the underside of the chassis. Interestingly the thermistor (TH1) is mounted in a glass tube with blackened top, and can be seen around the bottom centre of the PCB. 104 Silicon Chip Australia’s electronics magazine In practice, the circuit (shown in Fig.1) uses two feedback paths: the positive feedback circuit that contains the frequency-determining filter, and an adaptive negative feedback circuit that regulates the oscillator’s output and produces a sinewave of low distortion. Hewlett used a low-power light bulb, R3 in the circuit. More on this below. Hewlett opted to vary the capacitances in his filter circuit. This had the great advantage of reliability, using a four-gang capacitor. Variable resistors rely on sliding contacts with their attendant noise and possible interruption due to wear or corrosion. But the only moving contacts in a variable capacitor are the ball-bearing supports for the shaft, which ground the shaft on which the moving plates are mounted. A variable capacitance system, though, struggles to exceed a frequency range of six decades, and more commonly offers only four or five. With the HP 200A’s maximum capacitance of 1.05nF (1050pF) for each two paralleled sections of a practical four-gang 525pF capacitor, they needed 8.24MW resistors to get down to 20Hz. That’s approaching the point where a valve’s contact potential and other input phenomena affect circuit operation. The high-frequency end can use low-value resistors, but now we find that the minimum capacitance of the gang itself, combined with circuit capacitances, conspire to limit the highest practical frequency of operation. Variable capacitors, however, can have their plates cut to a non-linear capacitance-versus-rotation profile, giving a linear frequency dial. It’s more difficult to build the non-linear high-precision variable resistors that would be needed for a linear scale. HP’s 200A offered three ranges: 35~350Hz, 350~3500Hz and 3500~35,000Hz. The successor HP200B shifted the ranges down to 20~200, 200~2000 and 2000~20,000Hz while output power was 1W into 500W, with distortion less than 1%. Using ordinary ‘radio’ components, and weighing in at just over 8kg (18lb), it really could be built by two young men in a garage. Against this, General Radio’s much more complex beat-frequency oscillator weighed in at over 42kg (93lb). It’s not hard to guess which instrument the average technician preferred. siliconchip.com.au William Hewlett said that “…an oscillator of this type can be laid out and constructed on the same basis as a commercial broadcast receiver, but with fewer adjustments to make. It thus combines quality of performance with cheapness of cost to give an ideal laboratory oscillator.” BWD’s design rework The BWD 141 updates the classic HP design. It’s all solid-state, and works economically from two 9V batteries or a regulated mains supply. It also changes the variable element, using a two-gang potentiometer. Reliability is ensured by using a wirewound type, much less likely to suffer contact degradation and noise than a carbon pot. This change gave a six-decade range: 1Hz to 1MHz. The third change is to replace Hewlett’s low-power incandescent lamp with a negative temperature coefficient (NTC) thermistor, the venerable R54. If you’ve built yourself a Wien Bridge oscillator, you probably used the R54 (or its R53 cousin) as well. A square wave output was added. This was useful for testing the transient response of high-performance audio circuitry. BWD 141 outline The 141’s Wien Bridge circuit comprises three functions: a frequency-determining filter, a positive feedback amplifier and negative feedback stabilisation. Positive feedback is vital; without positive feedback, there will be no oscillation. The filter’s purpose The large black device at upper right is the rotary adjustment knob used to adjust frequency (RV1A/B). The knob at upper left is the amplitude range selector (RV3/6). The big metallic container at the bottom is the AC power pack, since the BWD 141 could be operated using two 9V batteries (type 216P). is also clear; it controls the oscillator’s frequency. The positive feedback must be sufficient to ensure reliable starting and operation for all settings of the filter’s controls (range and frequency), and to handle reasonable variations in load, temperature and supply voltage. It also needs to make up the filter’s loss. A sufficient amount of positive feedback will ensure fast, reliable starting, and the 141’s gain is around 70 times. This ensures startup, but it also drives the amplifier into clipping, giving a square wave output. Many tunedcircuit oscillators do just this, relying on their inductance-capacitance tuned circuits to reject the square wave’s harmonics and produce something approaching a pure sinewave. If you check out the specs for lowcost RF signal generators, you’ll discover that many of them have a top range that relies on the second harmonic from the oscillator, which is evidence that their sinewaves are not totally pure. It’s the negative feedback circuit that gives the Wien A side view gives a better look at the wiring for the front panel controls. You might be able to see that the cables from the power pack connect to the underside of the single-sided PCB. siliconchip.com.au Australia’s electronics magazine May 2021  105 Fig.2: the BWD 141 circuit shown here is for the mains-powered version. The battery-powered circuit can be found on Kevin Chant’s website along with the rest of the service manual: siliconchip.com.au/link/ab64 Bridge its pure sinewave output. The BWD 141 significantly betters the HP200A in terms of distortion too, delivering less than 0.1% total harmonic distortion (THD) over the audio spectrum. Circuit description The BWD 141 circuit is shown in Fig.2. NPN transistors Q1 and Q2 form the gain block, with complementary emitter-followers Q3 (NPN) and Q4 (PNP) forming a buffer to drive the load and supply the positive feedback path (via R1/RV1A/C3) and the negative feedback path (via RV3 and thermistor R54). DC conditions are set by negative DC feedback from Q2’s emitter, via RV2 and RV1B, to the base of Q1. This feedback sets the output emitters to about half-supply. The output stage operates in Class-B, with biasing set by the forward conduction voltages of series diodes D1/ D2. On startup, the output from the emitters of Q3 & Q4 rises rapidly to half-supply. This rise is conveyed back, via R5-RV1A and the range capacitor (C1, C3, etc – let’s take C3) to the base of Q1. C3 (and its companion C4) will be charging, and its charging current is what draws Q1’s base positive from its ‘resting’ DC position. Q1’s base will be more strongly forward-biased by this positive feedback action, so its collector voltage will fall, allowing Q2’s collector voltage 106 Silicon Chip to rise, pushing the emitters of Q3 & Q4 even higher. The circuit will eventually saturate as Q3 turns on fully. At this point, the voltage at the emitters of Q3 & Q4 can rise no further, and C3/C4 cannot charge any more. C3’s charging current into Q1’s base will fall, so Q1’s collector voltage will rise. Now, Q2’s base current will rise, as will Q2’s collector current, and Q2’s collector voltage will drop. This will bring the emitters of Q3 & Q4 towards ground, along with the top end of C3, reducing Q1’s base current. Once these voltages drop low enough, Q1’s bias circuit can begin to charge C3/C4 again, pulling Q1’s base positive and allowing base current to flow again. The cycle will continue at a rate determined mainly by the values of RV1A/C3 and RV1B/C4. The output will be pretty much a square wave due to the high gain of the circuit. Negative feedback Now, let’s consider the feedback path via the thermistor, and let’s just consider AC conditions. Any signal passing from the output (emitters of Q3 & Q4) back to Q1’s emitter will reduce the circuit’s gain. The thermistor has a negative temperature coefficient, with a ‘cold’ resistance of around 40kW and a ‘hot’ resistance (with only 3mW applied) as low as 500W. So any applied power will increase the circuit’s negative feedback and reduce its overall gain. Australia’s electronics magazine Since the output signal is applied to the thermistor, a high output signal will force its resistance to fall. And that’s what happens. As soon as the circuit goes into oscillation, the output signal will cause the thermistor’s resistance to fall, and negative feedback will increase. The combination of thermistor characteristics and the value of Q1’s unbypassed emitter resistor will cause the oscillator to settle at an output voltage of around 8V peak-to-peak, ie, 2.5V RMS. It’s important that the time constant of the negative feedback path is significantly slower than the rate of oscillation, due to the thermal inertia of the thermistor. Otherwise, it would modulate the signal and thus introduce significant distortion. As the entire circuit operates in the linear mode, distortion is low; no harmonics (ideally) are generated, and the output sinewave is of high purity. A recent advanced laboratory design of a similar circuit yielded a THD level of –140 dB (0.00001%)! Notice that the circuit diagram shows almost identical voltages indicated at Q1’s emitter and base for a 1kHz signal (marked with asterisks*). It’s working as a differential amplifier, and the amplifier’s open-loop gain of 70 times means that, for an output signal of 2.5V RMS, the difference between the two input signals only needs to be about 36mV (2.5V ÷ 70). Such a small difference was not apparent on the oscilloscope screen, siliconchip.com.au How good is it? hence the two identical voltage readings on the circuit. The square wave section uses a schmitt trigger driven by the sinewave, and this is the preferred method for generating square waves from pretty much any waveform. Its hysteresis allows the output square wave to have very rapid rise and fall times, regardless of the slopes and frequency of the input. It’s one of those simple circuits with a complicated description. If you’re interested in exploring it further, see the “further reading” section at the end of this article. Cleaning it up Upon receiving this BWD 141 signal generator, I found that it had no output signal. I jiggled a few controls and got something, but it still didn’t seem quite right. Cleaning the output attenuator pot and the range switches brought it back to life. I didn’t bother to clean the dual-gang frequency pot, as it worked just fine. It was a bit off calibration, but a few minutes with a frequency counter and a DVM had it back in spec. A quick clean of the cabinet, and it was ready for the photo session. siliconchip.com.au For a simple, cheap and cheerful instrument, it does the job. The frequency setting is accurate to the dial, but the output attenuator’s rudimentary scale could have been made more precise. Be aware that the thermistor loop does take a little while to stabilise after switch-on, and after changing frequency or ranges. THD across the audio band from 20Hz to 20kHz (at 1V RMS output) was less than 0.1%, agreeing with the BWD specifications. Square wave rise time (10% to 90%) was 200ns, fall time (90% to 10%) was 150ns at 100kHz and 1MHz. Frequency drift seemed absent in my workshop at 20ºC. It started at 19.448kHz cold, and that’s what I got for the next ten minutes. So I got out the hot air gun and cheekily warmed things up to around 35ºC, getting a frequency shift from 19.448kHz to 19.469kHz (about 0.1%). It’s a bit academic, as this kind of signal generator is not expected to give extreme frequency stability. Frequency accuracy is within dial setting, bettering 1% in each case. The output voltages varied a little with range. Selecting full sinewave output (2.5V/250mV/25mV/2.5mV) gave 2.4V, 260mV, 26mV and 2.5mV. The 1.5V, 150mV, 15mV & 1.5mV settings were similar, but the 0.5V, 50mV, 5mV & 0.5mV settings gave only about half their indicated values. Any selected output voltage was constant within specification across any one band. It benefits from the mains supply, as distortion rises rapidly with low voltage. With a 16.5V supply (ie, 8.25V Australia’s electronics magazine x 2), distortion increases to around 0.9%, with visible flattening of the negative sinewave peak. If using batteries, it would be sensible to check them before taking measurements needing a low-distortion signal. Would I buy one? I already have a very nice Kikusui 433 that includes an output voltage meter. It has served me well for ten years, so I’ll be returning this fine Aussie product to its generous owner to enjoy. The review set was Serial No. 26125, so I reckon there are still plenty around if you need a piece of test gear that combines Australia’s tech history with decent performance. Special handling The power supply is wholly contained in a separate section within the case, so there are no hazardous voltages in the case when you open it up for basic maintenance. While the circuit board is not too cramped, be careful when using an oscilloscope probe with a grounding ring behind the tip. A bit of tape or heatshrink over the ground ring is good insurance against accidental shorts to ground. Further reading • The HP200 (including manual!): siliconchip.com.au/link/ab3z • Thermistor data (look for R series): siliconchip.com.au/link/ab40 • Low distortion (-140dB) Wien Bridge design by Vojtěch Janásek: siliconchip.com.au/link/ab41 • Schmitt trigger: https://w.wiki/3AEH SC May 2021  107 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 Sourcing the AX-1000 current transformer I’m gathering the components to build the new Refined Full-Wave Motor Speed Controller (April 2021; siliconchip.com.au/Article/14814). I have run into a problem sourcing the Talema AX-1000 current transformer. Digi-Key has a minimum order quantity of 2,500 with none in stock and an 18-week lead time (probably closer to 26 weeks with the Suez Canal currently blocked). Do you know anyone else that has it? I can’t find it anywhere. Great magazine this month. Well done. (W. M., Sunnybank Hills, Qld) • At the time of writing this reply, the AX-1000 is in stock with RS Online (https://au.rs-online.com/web/p/ current-transformers/7754928/) at nearly $7 each, plus postage, with a minimum order quantity of one. They currently list 18 in stock in Australia, with another 239 overseas. How to obtain capacitors for projects I would appreciate help explaining the capacitors needed for the Arduinobased Adjustable Power Supply in the February 2021 issue (siliconchip.com. au/Article/14741). It lists the codes for the capacitors as 100nF (code 104, 100n or 0.1) and 1nF (code 101, 1n or .001), but I can’t find these at Mouser, Jaycar or Altronics. Can you point me to the right components to buy via online links or Jaycar/Altronics catalog codes? (M. W., Preston West, Vic) • The 100nF MKT capacitors are available from Jaycar (Cat RM7125) or Altronics (Cat R3025B), and the 1nF MKT capacitors are also available from Jaycar (Cat RM7010) or Altronics (Cat R3001B). The easiest way to find these on the supplier websites is to go to the search box and type in either “100nF MKT” or “1nF MKT”. The codes we list in the magazine are the short codes 108 Silicon Chip printed on the parts themselves, rather than any supplier part number. They are necessarily brief due to the parts’ small size and don’t give the full part type code. Mouser (one of your listed suppliers) also have plenty of suitable capacitors, for example, au.mouser.com/ Search/Refine?Keyword=810-FK26X7R1C106K For the 10μF ceramic part, the text in brackets refers to the capacitor’s size (metric 3216 [3.2 x 1.6mm] or imperial 1206 [0.12 x 0.06in]). Searching the website of a supplier like Mouser or Digi-Key for “10uF 16V X7R 1206” (if you want the SMD type) or “10uF 16V X7R radial” (through-hole version) should give several relevant results. Questions about Four Battery/Cell Balancer I’m planning on building the High-Current Four Battery Balancer (March-April 2021; siliconchip.com. au/Series/358) project and am ordering the parts. This Balancer circuit is controlled by a PIC micro, but neither the software nor the pre-programmed controller is currently available on your website. The option that is eventually made available will affect what parts I order from SC and what I order from elsewhere. My current hypothesis is that you haven’t released the software because it is still being optimised, and you don’t want to let it into the wild until it is stable. What’s your intention? Also, I had been looking at various active balance topologies before this timely project. So armed with a bit of background reading, I have two further questions about your design. Only one transformer is active at any time, so the switching could be arranged so that a single transformer is shared. Is the reason you’ve elected to use one transformer per cell that it cuts down the parasitic inductance, or is there some other reason? Finally, I’m not sure what voltage Australia’s electronics magazine should appear on Vstack. Fig.11 hints that it is the series voltage across all cells, consistent with ZD5 having a higher voltage than the corresponding per-cell zeners. On the other hand, the 1:1 ratio of each cell transformer suggests that the stack voltage is close to that of a single cell. I am quite looking forward to the next instalment, showing how this circuit is configured. (M. J., St Lucia, Qld) • It’s actually an ARM-based Atmel micro (ATSAML10E16A-AUT), but it can be programmed using a PICkit 4. We have the programmed chips for sale on our website now; when you wrote in, the second (constructional) article had not been published, and we had not yet received the software from the designer. Regarding only one transformer being active, the firmware currently acts in this way, but a future version could have multiple channels active simultaneously. The hardware certainly supports that. Duraid considered ‘shared primary’ type transformers, but there aren’t many appropriate (high coupling, low DCR resistance, low parasitic inductance) parts on the market. That is the same reason he didn’t use 1:2 transformers; they are more common, but still scarce compared to 1:1 types. This reduces efficiency somewhat, but it vastly increases flexibility in the parts choice. Many different 1:1 transformers will fit on the Battery Balancer board without modification. Also consider that the cost of the additional Mosfets involved in switching a single transformer between the cells would probably be higher than the cost of the extra transformers (highperformance Mosfets are not cheap!). The board layout would also be complicated considerably, as the current from all the cells would have to be brought to a single part, rather than there being separate sections for each cell. Concerning the stack voltage, in the typical battery balancing case, this will be the series voltage across siliconchip.com.au all cells in the battery, because that’s what it will be tied to. Again, the 1:1 winding choice comes with some efficiency cost, but it doesn’t preclude charge being transferred across these different voltages. However, the board has other potential use cases, such as shuffling charge out of a solar panel into cells, charging a battery from a DC bench supply, or even discharging cells into an electronic load. In all of these cases, the Vstack voltage will generally be different from the sum of the cell voltages. BK1198 single-chip radio antenna queries I am building the AM/FM/SW Single-Chip Digital Radio published in your January 2021 issue (siliconchip. com.au/Article/14704), and I have a question about the antenna coil. I went with the ‘coil transplant’ method and found that the inductance value exceeds the nominated 400μH value before the coil is entirely on the ferrite rod. When the coil is flush with the end of the rod, it measures 720μH, almost twice the nominal value. A little bit further on, and it is 2.5 times the nominal value. On another note, there is a discrepancy between the schematic on page 22 and the PCB. The 18pF capacitor C22 is connected in parallel with wirewound inductor L8 near the FM antenna connection on the PCB, whereas the schematic shows C22 shunting to GND. I am assuming the PCB is correct. (S. S., Zillmere, Qld) • The author, Charles Kosina, replies: The BK1198 chip automatically tunes the antenna coil, so the actual inductance is not that important. Because of the ferrite characteristics, the permeability varies a lot with frequency, so the inductance measured by the meter may not be a true indication. It depends on the inductance meter and what frequency it tests at. I measured the original ferrite rod purchased from Jaycar using a Q meter. At 500kHz, it resonates with 175pF (Q=80), which means the inductance is 579μH. At 1MHz, it resonates with 30pF (Q=50), which gives an inductance of 844μH! So the nominal value of 400μH is way off at either frequency. As for 18pF capacitor C22, from an RF point of view, it makes no difference whether it goes to ground or the other end of L8. The 100nF capacitor siliconchip.com.au at the DC input to the coil is a virtual RF earth due to its low reactance at that frequency. Yes, it is a minor schematic error that does not affect the performance of the radio. Advice wanted on CNC machines & laser cutters I read your article in the December 2020 issue about using CNC milling machines to make PCBs (siliconchip. com.au/Article/14672). I am teaching year 9 and 10 electronics at Casino High School in NSW. After much R&D, we were able to produce pretty good PCBs using a laminator and acid etching. However, after reading your article, I wish to purchase a milling machine. Unfortunately, your article did not mention any brand names. Is it possible for you to give me some idea as to which makes are better than others to give me an idea as to what to buy? Thank you very much for a great magazine, keep up the good work. (R. M., Casino, NSW) • The December 2020 article was contributed by Andrew Woodfield. While we have not tried any of these techniques ourselves, we make frequent use of a laser cutter similar to the unit shown on p38 of that issue. Since the article was focused on laser engraving, we did not look too deeply into CNC milling machines. If you want to mill PCBs, we understand the Bantam PCB Desktop Mill is the device to consider, as it is one of the few milling machines designed with PCBs in mind. Core Electronics used to carry these, but they are not available at the time of writing this (see https://core-electronics.com.au/ brands/bantam-tools-australia). In regards to laser engraving, many machines are imports of various degrees of quality, so a specific brand name is unlikely to be helpful. There are several Australian laser cutter/engraver sellers. We suggest that you look up and contact one or more of these, as they will be able to provide you with more detailed information, demonstrate their units and provide better peace of mind (eg, warranty) than obtaining one from overseas. As Andrew mentions, you will need at least 5W of laser power, and naturally, a working area large enough to accommodate the largest PCB you want to make. Australia’s electronics magazine How does wireless charging work? I purchased a new electric razor some time ago, and it came with a wireless charger which took about an hour to charge it. I was wondering how they worked. PS, please bring back the computer articles. (R. M., Melville, WA) • Wireless chargers use inductive coupling, much like an air-cored transformer. The principle is simple; the devil is in the details, such as using resonant energy transfer for better efficiency, and switching off the field when the razor is not ‘docked’. For more details, see the Wikipedia page at https://w.wiki/399W Breaking out Maximite DIL I/O header Has anyone come up with a breakout box for the 26-pin I/O connector on the back of the Maximite (March-May 2011; siliconchip.com.au/Series/30)? I believe this would be very useful. I have a Colour Maximite (September & October 2012; siliconchip.com. au/Series/22), but I have not had a chance to use it. I intend to start soon. I am very interested in electronics (I used to work in the industry) and astronomy. There is a warning in the Colour Maximite kit instructions about the current that can be drawn from the 5V and 3.3V rails (total of 150mA). Should the breakout box have its own power supplies? I am in awe of the Colour Maximite 2 (July & August 2020; siliconchip. com.au/Series/348). Does anyone sell one already built and tested? (R. M., Melville, WA) • It’s a bit difficult to make a “breakout box” for the Maximites because we don’t know what people will be using it for. It’s easy to plug DuPont cables into the connector and plug the other ends into a breadboard or other modules. It’s also possible to plug in a ribbon cable with an IDC header, then connect the ribbon cable to a header on a breadboard or similar. Our DSP Crossover LCD Adaptor PCB (code 01106196) converts a 20pin DIL plug or socket into a 20-pin SIL plug or socket, which could then be connected to a breadboard. You’d be left with six pins unused, but that would still be an easy and cheap way May 2021  109 to connect a Maximite or Colour Maximite to a breadboard. Some breadboards also have their own power supplies, or you can build one of the many 3.3V/5V/adjustable regulators we’ve published over the years to supply extra current. Rictech has a CMM2 board with all the SMDs pre-soldered, but there is still some assembly to be done. See www.rictech.nz/micromite-products Lead-acid vs silvercalcium batteries I was recently stranded with a flat battery in my 1995 Ford Falcon. My local motoring association patrolman arrived promptly, pronounced the battery “dead”, and fitted a new one. He got me to turn the headlights on to high beam and rev the engine while he measured the battery voltage. He told me he got 13.8V, so he said everything was fine, and departed. The next day, I had a good look at the new battery, and noticed that it was a “calcium battery”. Knowing nothing about these batteries, I did some online searching. I learned that these are fairly conventional lead-acid batteries, but with calcium instead of antimony as an additive. This is said to produce several performance advantages, including less gassing, so they are usually made sealed and ‘maintenance free’. However, they require a higher charging voltage than standard lead-antimony batteries (14.8V vs 13.8V). This being the case, I wondered whether my (older) car’s electrical system would be capable of ever charging the new battery fully, and whether this would lead to sulfation of the plates and an early demise of the battery. I contacted the motoring association that had sold me the battery and asked for some advice. Basically, what I got was: “She’ll be right mate, don’t worry about it. You’ve got a 2-year warranty anyway.” This was hardly satisfactory. More online searching produced a confusing array of contradictory information: calcium batteries are not suitable for older vehicles; calcium batteries are suitable for older vehicles etc. Can you shed some (sensible) light on the subject? Will a standard car charging system fully charge a calcium battery? Given that these batteries are sealed and cannot be checked with a hy110 Silicon Chip drometer, I assume that measuring the terminal voltage would be the only way to tell if the battery is fully charged. If so, what should the terminal voltage be, and under what conditions? What should the terminal voltage be of a fully charged calcium battery at rest, with no load? (D. P., Faulconbridge, NSW) • There is some confusion on various web sites between calcium/calcium and silver/calcium lead-acid batteries. Just about every car battery available now is a calcium/calcium lead-acid type. These are sealed and so do not require topping up with distilled water. The older type lead-acid batteries, which had antimony, tin and arsenic added to the lead, are no longer being sold as those heavy metals are toxic. (Of course, lead is too, but it is not generally as troublesome.) Calcium/silver lead-acid batteries are different again and have higher self-discharge rates, and require higher charging voltages. They are not suitable as drop-in replacements for standard lead-acid batteries unless the charging voltage(s) can be adjusted. Typically a car electrical system will charge to 14.4-14.8V. Your 13.8V charge voltage is very low and is generally the float charge value for a lead-acid battery, not the end-of-charge voltage. The alternator’s charge voltage is temperature-dependent, so the measured voltage could be lower than usual under high-temperature conditions. Old Silicon Chip PCB code decoded Greetings to all at Silicon Chip. I have a PCB with the code SC0611287. If this is one of your projects, please advise me of its date of publication. I can then look it up in my library. Many thanks, and please pass on my best wishes to Ann, who has been most helpful in the past. (B. G., Glen Iris, Vic) • You have the Subcarrier Adaptor for FM Tuners (January 1988; siliconchip. com.au/Article/7830). We found this using our Contents Search page (www.siliconchip.com. au/Articles/ContentsSearch). You need to leave off the “SC” from the front of the board number. You can tell it’s an early project since we only used PCB codes with a dash from November 1987 to about October 1988 (ie, the first year or so). Australia’s electronics magazine Recent board numbers are eight digits long and start with a two-digit category code, followed by a disambiguating number (usually 1), then the two-digit month and year codes of intended publication (which could be slightly different from the actual publication date), finished with a single-digit board number within the project, starting with 1. So, for example, the April 2021 Digital FX Pedal PCBs are coded 01102211 and 01102212, with the difference being that one uses a rotary switch to select the effect while the other uses a potentiometer. The project category code is 01 (audio), the disambiguating number is 1, and the month/year code is 0221 (February 2021; delayed due to lack of space). PCB wanted for old ETI project For nearly 50 years, I have been intending to build the ETI 309 Battery Charger. Can you supply a PCB for this project? What are the alternatives to the transistors and diodes listed? I have a suitable transformer and an SCR (although it’s a C220D), and a chassis that I could use. If no to everything, do you have a simple battery charger like this one with similar attributes, for which components might be easier to obtain? (I. S., Glenhaven, NSW) • Sorry, we don’t stock any EA or ETI boards. It would be very difficult to get them made. We don’t have any of the artwork, so all we could do is scan the magazine pages, and the result would not be good enough to manufacture without a lot of extra work (many hours’ worth). In fact, if we did need to get one of these boards made, it would probably be easier to redesign it from scratch on a computer. Generally, we will have published a design much more recently, making the EA or ETI project obsolete. Your best option is to build the newer project for which a PCB is available. In this case, we suggest that you build our Clever Battery Charger Controller (December 2019; siliconchip. com.au/Article/12159). You only need to add a basic charger, which is really just the transformer and full-wave rectifier. Many automotive shops sell these; eg, see www.arlec.com.au/ wp-content/files/BC228.pdf continued on page 112 siliconchip.com.au MARKET CENTRE Advertise your product or services here in Silicon Chip FOR SALE FOR SALE KIT ASSEMBLY & REPAIR LEDsales 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 LEDs and accessories for the DIY enthusiast PMD WAY offers (almost) everything for the electronics enthusiast – with full warranty, technical support and free delivery worldwide. Visit pmdway.com to get started. SILICON CHIP ASSORTED BOOKS FOR $5 EACH Selling assorted books on electronics and other related subjects – condition varies. Some of the books may have already been sold, but most are still available. Bulk discount available; post or pickup. All books can be viewed at: siliconchip.com.au/link/aawx Email for a postage quote, quote the number directly below the photo when referring to a book: silicon<at>siliconchip.com.au LEDs, BRAND NAME AND GENERIC LEDs. Heatsinks, LED drivers, power supplies, LED ribbon, kits, components, hardware – www.ledsales.com.au TRONIXLABS PTY LTD would like to thank all of our customers for their support and feedback. For any enquiries or customer technical support, please email support<at>tronixlabs.com 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 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 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 May 2021  111 If you decide to go ahead with the ETI 309, the BC177 and BC178 transistors could be replaced with BC327 types. The 2N3642 could be replaced with a BC337, and the C20D SCR could be replaced with the C122E (Jaycar ZX7012), although new-old-stock items are still available (siliconchip. com.au/link/ab7x). The bridge rectifier can be the MB354 30A 400V type. For D3 and D4, use 1N4004s. The enclosure needed is similar to the Jaycar HB5046 but is only 55mm tall instead of 100mm. The transformer might need to be specially wound. Is my Barking Dog Blaster working? Some years ago, you helped me build the Ultrasonic Cleaner, and it still works perfectly. In January of this year, I bought the September 2012 issue of your magazine for the Barking Dog Blaster project (siliconchip.com. au/Series/28). I built it, but I have a problem. It works, but it seems like it is too weak. You said it would consume about 1.4A with four piezo tweeters, but I measured a maximum of 250mA. I also have a question about the voltage on the drain terminal of the Mosfet. During operation, I measured only about 2V. On the secondary side of the transformer, I measured around 0.5V, but according to the article, it should be around 40V peak. Do you have any idea what the problem is? How can I increase the power? (Simon, Slovenia) • The current drain at 350mA per tweeter adds up to 1.4A; however, be aware that this is peak current and not the current that would be measured us- ing a multimeter. A meter would average out the peak current, so a measurement of 250mA is correct. The exact multimeter reading is dependent on the particular multimeter model and its frequency response. Similarly, a drain voltage of 40V peak will not measure as 40V using a multimeter; it would average it out to a much smaller value. The frequency response of the multimeter would be severely limited at ultrasonic frequencies. An oscilloscope is needed to measure the voltage accurately. We do show how to test the output by using the audible frequency test. This is described under the Testing cross-heading section. Note that the volume level is reduced for this test, as it would otherwise be very loud. So your unit is probably working correctly; the voltages and current you are measuring are likely due to the way the meter measures them, taking into account the difference between peak and averaged values as measured with a multimeter. Where to get a Barking Dog Blaster kit? Do you know where I can buy the Barking Dog Blaster kit? I know Altronics do not have it any more. (J. H., Queenstown, New Zealand) • You are right that the Altronics Cat K4500 kit has been discontinued. That was the only kit for this project. As usual, you can still get the programmed PIC microcontroller and the printed circuit board (PCB) from our online shop; see siliconchip.com.au/ Shop/?article=529 The remaining parts are available from Altronics or Jaycar. SC Advertising Index Altronics...............................75-82 Ampec Technologies................. 11 Dave Thompson...................... 111 Digi-Key Electronics.................... 3 element14................................... 7 Emona Instruments................. IBC GME Australia............................. 6 Hare & Forbes........................... 23 Jaycar............................ IFC,53-60 Keith Rippon Kit Assembly...... 111 LD Electronics......................... 111 LEDsales................................. 111 Microchip Technology.................. 5 Mouser Electronics...................... 9 Ocean Controls........................... 8 PMD Way................................ 111 Silicon Chip Binders................. 19 Silicon Chip RTV&H DVD........ 33 Silicon Chip Shop.................... 37 Silicon Chip Wallchart.............. 63 Switchmode Power Supplies..... 85 The Loudspeaker Kit.com......... 10 Tronixlabs................................ 111 Vintage Radio Repairs............ 111 Wagner Electronics................... 99 Weller Soldering Iron............. OBC Notes & Errata ESR Meter with LCD readout, Circuit Notebook, May 2016: there are some errors in this circuit diagram. Two capacitors were left out: one 470μF electrolytic and one 100nF ceramic or MKT type. They should connect between pins 3 & 5 of IC3, with the electrolytic capacitor’s negative terminal to pin 5 (the -5V rail) and positive terminal to pin 3 (GND). Also, the two 10MW resistors’ connections to pins 2 & 3 of IC4a are swapped. The resistor from the output should go to pin 2 (the inverting input), while the resistor from the wiper of VR2 goes to pin 3 (the non-inverting input). Barking Dog Blaster, September 2012: The initial timer duration differs to that set by the trimpot due to a software bug. Subsequent timer runs after the first are correct. The revised firmware, supplied by reader AJB, is named 2510812B and is available for download from our website. The June 2021 issue is due on sale in newsagents by Thursday, May 27th. Expect postal delivery of subscription copies in Australia between May 25th and June 11th. 112 Silicon Chip Australia’s electronics magazine siliconchip.com.au “Rigol Offer Australia’s Best Value Test Instruments” Oscilloscopes NEW 200MHz $649! New Product! Ex GST RIGOL DS-1000E Series RIGOL DS-1000Z/E - FREE OPTIONS RIGOL MSO-5000 Series 450MHz & 100MHz, 2 Ch 41GS/s Real Time Sampling 4USB Device, USB Host & PictBridge 450MHz to 100MHz, 4 Ch; 200MHz, 2CH 41GS/s Real Time Sampling 424Mpts Standard Memory Depth 470MHz to 350MHz, 2 Ch & 4Ch 48GS/s Real Time Sampling 4Up to 200Mpts Memory Depth FROM $ 429 FROM $ ex GST 649 FROM $ ex GST 1,569 ex GST Multimeters Function/Arbitrary Function Generators New Product! RIGOL DG-800 Series RIGOL DG-1000Z Series RIGOL DM-3058E 410MHz to 35MHz 41 & 2 Output Channels 416Bit, 125MS/s, 2M Memory Depth 425MHz, 30MHz & 60MHz 42 Output Channels 4160 In-Built Waveforms 45 1/2 Digit 49 Functions 4USB & RS232 FROM $ 479 FROM $ ex GST Power Supplies 725 ONLY $ ex GST Spectrum Analysers 789 ex GST Real-Time Analysers New Product! RIGOL DP-832 RIGOL DSA Series RIGOL RSA Series 4Triple Output 30V/3A & 5V/3A 4Large 3.5 inch TFT Display 4USB Device, USB Host, LAN & RS232 4500MHz to 7.5GHz 4RBW settable down to 10 Hz 4Optional Tracking Generator 41.5GHz to 6.5GHz 4Modes: Real Time, Swept, VSA & EMI 4Optional Tracking Generator ONLY $ 749 FROM $ ex GST 1,321 FROM $ ex GST 3,210 ex GST Buy on-line at www.emona.com.au/rigol Sydney Tel 02 9519 3933 Fax 02 9550 1378 Melbourne Tel 03 9889 0427 Fax 03 9889 0715 email testinst<at>emona.com.au Brisbane Tel 07 3392 7170 Fax 07 3848 9046 Adelaide Tel 08 8363 5733 Fax 08 83635799 Perth Tel 08 9361 4200 Fax 08 9361 4300 web www.emona.com.au EMONA