Fullscreen HTML5Med Res (??MB)HTML4

MARCH 2025 ISSN 1030-2662 03 The VERY BEST DIY Projects! 9 771030 266001 $ 00* NZ $1390 13 INC GST INC GST Artificial Limbs Modern robotic and electronic prosthetics serve as replacements for lost limbs Power LCR Tester Measures inductance from 50μH to 1H at up to 30A to determine the saturation point, capacitance from 50nF to 1F and resistance from 1mΩ to 300Ω Waveform Generator Handy for audio equipment analysis, circuit development/demos and as a pulse source The Future of the Grid What will our energy grid be powered by in the future? What benefits & downsides do the current types of energy generation have? RPi Pico 2 Audio Analyser Including a built-in signal generator, oscilloscope and spectrum display in a handheld format ...and much more in this issue! MISS FLIPPING THROUGH OUR CATALOGUE? It’s Back—Digitally! The 596-page Engineering and Scientific Catalogue is back! Updated with the latest products and ready for you to browse online. View Online Now! Scan the QR Code or visit: catalogueflip.jaycar.com.au www.jaycar.com.au IT’S BACK! Contents Vol.38, No.03 March 2025 14 Prosthetic Limbs Page 28 Electronic replacement limbs can allow users to perform many of the same tasks as they could before, leading to a big increase in their quality of life. By Dr David Maddison, VK3DSM Medical technology 40 The Power Grid’s Future, Part 1 Australia generates the majority of its power from coal and gas but that could change. What is the future electricity grid likely to look like? By Brandon Speedie Electricity generation 48 Antenna Analysis, Part 2 Learn how antennas work and design matching circuits for them. We show you how to use Smith V4.1 software to tune antennas using Smith charts. By Roderick Wall, VK3YC Radio antennas POWER LCR METER Versatile Waveform Generator 76 Precision Electronics, Part 5 One major source of circuit errors to consider is from noise. So let’s look at what we can do to minimise the effects of noise on our circuits. By Andrew Levido Electronic design 88 Transitioning to the RPi Pico 2 We explain what you need to do to convert software for the Raspberry Pi Pico over to the Pico 2, and our progress on porting projects over. By Tim Blythman Microcontrollers 28 Power LCR Tester, Part 1 Our new and robust Tester can measure inductors from 50μH to over 1H, capacitors from 50nF to over 1F and resistors from 1mΩ to 300Ω. It can also measure inductance saturation from 10μH to 1H at up to 30A. By Phil Prosser Test equipment project 46 Audio Mixing & Shed Alarm your own audio mixing cables to add an extra input to an audio 72 Build amplifier, starting on page 46. And make your own workshop/shed alarm with a keyfob remote control; see page 72. By Julian Edgar Simple electronic projects 64 Versatile Waveform Generator This Waveform (function) Generator uses just three op amps to produce square, pulse, triangle, ramp and sine waves from 1Hz to 30kHz. By Randy Keenan Test equipment project 82 Pico 2 Audio Analyser Our Pico Audio Analyser from November 2023 has now been updated to use a Raspberry Pi Pico 2, improving its THD measurement floor to 0.2%. By Tim Blythman Audio project Page 64 transitioning to the page 88 Raspberry Pi Pico 2 2 Editorial Viewpoint 5 Mailbag 27 Subscriptions 59 Mini Projects 92 Circuit Notebook 94 Serviceman’s Log 100 Silicon Chip Kits 101 Vintage Radio 106 Online Shop 108 Ask Silicon Chip 111 Market Centre 112 Advertising Index 1. RF Remote Receiver 2. Continuity Tester 1. YouTube jukebox using a RPi Zero National R-70 Panapet by Ian Batty SILICON SILIC CHIP www.siliconchip.com.au Publisher/Editor Nicholas Vinen Technical Editor John Clarke – B.E.(Elec.) Technical Staff Bao Smith – B.Sc. Tim Blythman – B.E., B.Sc. Advertising Enquiries (02) 9939 3295 adverts<at>siliconchip.com.au Regular Contributors Allan Linton-Smith Dave Thompson David Maddison – B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Dr Hugo Holden – B.H.B, MB.ChB., FRANZCO Ian Batty – M.Ed. Phil Prosser – B.Sc., B.E.(Elec.) Cartoonist Louis Decrevel loueee.com Founding Editor (retired) Leo Simpson – B.Bus., FAICD Silicon Chip is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 626 922 870. ABN 20 880 526 923. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Subscription rates (Australia only) 6 issues (6 months): $70 12 issues (1 year): $130 24 issues (2 years): $245 Online subscription (Worldwide) 6 issues (6 months): $52.50 12 issues (1 year): $100 24 issues (2 years): $190 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 194, Matraville, NSW 2036. Phone: (02) 9939 3295. ISSN: 1030-2662 Printing and Distribution: Editorial Viewpoint Alipay & WeChat show us the way I have been to China a few times and went again late December last year. It’s quite a fascinating place to visit, especially megacities like Beijing. Beijing has basically as many people as live in all of Australia within its metropolitan area (and an incredible subway system that I am envious of). Something I’ve noticed before but haven’t really commented on is how good their payment and ordering systems are. This relates to one of the problems we have here, which is that every different business you deal with seems to want you to use their app these days. I don’t know about you but I already have a huge number of apps on my phone and I don’t want to install any more! Especially when so many of them are just glorified web browsers. In China, two apps that basically everyone has on their phone are Alipay (their equivalent to PayPal) and WeChat (their equivalent to, say, WhatsApp and Facetime). However, in many ways, they are far superior to what we have. Let’s start by looking at Alipay. This allows you to pay just about anyone, from your friend or family member to a street vendor or a large company, in seconds by scanning a QR code or via the phone interface. It’s fee-free for payments under ¥200 (about $44). PayPal lets you do something similar but, excluding the ‘friends and family’ option, they charge relatively high fees (around 3%). Visa or Mastercard transactions usually involve fees closer to 1–1.5%. Alipay also supports NFC, similar to ‘tap and go’. So imagine the convenience of ‘tap and go’ but without any of those pesky tacked-on fees. But it gets better. Just about any large vendor you will deal with in China (coffee shops, restaurants etc) will let you scan another QR code to quickly and easily install an add-on (or ‘mini app’) within Alipay that includes their menu. This mini app will let you browse the menu, choose what to order and pay. Importantly, the UI (user interface) for most of these mini apps is pretty consistent, so once you’ve used one, all the others are quick and easy to figure out. Plus, it’s all within Alipay, so you don’t ‘pollute’ your phone with dozens of specific apps. For example, from my hotel room, I could go into the Luckin Coffee app. It would automatically find the nearest store, just around the corner. I could order coffee in the morning, pay, go out of the hotel and walk into the shop, then pick up the coffee and walk out (after they scanned the code showing it was my order). It was super convenient. Sure, you can do that with some shops here, but it’s generally much more of a hassle. I tried using the McDonalds app once. I spent quite a bit of time putting together an order, then it wouldn’t let me pay, and I had to order in the restaurant. By contrast, Alipay just works. WeChat is similar; it provides communications facilities (text, video chat etc) and is widely used by Chinese people, including those living in Australia. It also has payment features similar to Alipay, and its own set of mini apps. In many cases, you can choose which one you prefer to use at a given shop (Alipay or WeChat/Weixin); they mostly work interchangeably. I hope we get something similar here one day. Perhaps these apps will eventually become popular in Australia and provide an alternative to the Visa & Mastercard duopoly. They will also provide a lot of convenience and keep our phones free of extraneous icons. by Nicholas Vinen 9 Kendall Street, Granville NSW 2142 2 Silicon Chip Australia's electronics magazine siliconchip.com.au MAILBAG your feedback Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd has the right to edit, reproduce in electronic form, and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman’s Log”. 3G network should not have been shut down I have just finished reading the January 2025 issue of Silicon Chip. It was very enjoyable – thank you. I noticed an error in the drawing on page 70. CON2 is marked as a “3.5mm JACK PLUG” but it should be a “2.5mm JACK PLUG”. Regarding your editorial, I am regularly appalled by the technical decisions made by our governments. Why shut down the 3G network and consign millions of perfectly good phones mostly to landfill? I think 3G should have been kept going as an alternative to 4G. Then there is the question of what are the total emissions to make replacement phones? Another point is that all these replacement phones will have to be paid for in foreign currency – not good when we are already in debt. I was not impressed when the domestic shortwave service was shut down. Guess what, the shortwave service would be the last method of communication available to the public in times of emergency, when everything else had failed. David Williams, Hornsby, NSW. Request for more information on authors It’s great to see work from new authors in Silicon Chip. New names that have appeared in recent times include Andrew Levido, Charles Kosina, and Brandon Speedie. Some of them seem to have become regular contributors. I, for one, am curious about their backgrounds. Have you considered adding an “About the Author” paragraph at the end of their contributions, or even introducing them in an editorial? Paul Howson, Warwick, Qld. Comment: we have put this to the authors with a mixed response. Some like the idea, while others prefer to let their articles speak for them. You may see some “About the Author” panels in upcoming articles, but it will depend ourPCB LOCAL SERVICE <at> OVERSEAS PRICES AUSTRALIA PCB Manufacturing Full Turnkey Assembly Wiring Harnesses Solder Paste Stencils small or large volume orders premium-grade wiring low cost PCB assembly laser-cut and electropolished Instant Online Buying of Prototype PCBs www.ourpcb.com.au siliconchip.com.au Australia's electronics magazine 0417 264 974 March 2025  5 Nut & Bolt Identification Set 70-608 • Metric - (ISO) Course and fine pitch • Imperial 60 Degree UNC & UNF • Withworth (BSW) imperial 55 degree Portable, Digital Hardness Tester - 50-520 • Large LCD display screen • Hardness scale: HL, HB, HRB, HRC, HRA, HV, HS • Displays scales for Leeb, Brinell, Rockwell • A,B,C, Vicker & Shore $ 40 (Q608) $ SAVE $9.50 SAVE $275 1,375 (Q520) Dial Calipers - 33-190 Imperial Outside Micrometer - 10-101 • 0 - 6” range • 0.001” graduations • Precision internal movement • Stainless steel slide, tinite coated edges • Four way measurement • 0-1” Range • Accuracy 0.0001” • Carbide measuring faces • Measuring face 6.5mm, Flatness 0.0008mm • Ratchet stop for exact repetitive readings • Resolution 0.0001” - Vernier scale $ 109 (Q190) $ $ SAVE $23 SAVE $10 SAVE $69 Digital Outside Micrometer - 10-124 Inside Micrometers - Rod Type 23-148 Metric Dial Indicator - 34-211 45 (Q101) • 0-25mm/0-1” range • ±0.001mm accuracy • Friction thimble design • Large LCD for easy reading • Carbide measuring faces • 25-50mm • Spindle thread is hardened and precision ground • Each interchangeable rod is marked with the range • Resolution: 0.01mm. Accuracy: Metric(6+L/50)µm Metric Outside Micrometers Interchangeable Anvils - 20-120 • 100-200mm Range • Interchangeable anvils fitted with adjusting collar to set the overall measurement • Carbide measuring faces, Flatness 0.0008mm • Micro-fine clear graduations on satin chrome finish 349 (Q120) • 0-10mm range • 0.01mm graduations • Smooth movement • Ø58mm Face $ 110 (Q124) $ $ SAVE $22 198 (Q148) SAVE $44 SAVE $13.50 Dial Bore Gauge - 34-226 HAIMER Universal 3D Tester EL-3D Straight Edge with Bevel - SE500 • 50-160mm range • 0.01mm accuracy • 150mm readable depth • Self aligning mechanism • 12 interchangeable anvils 176 (Q226) • X, Y, Z-Axis readings • 0.01mm accuracy • 4mm round probe • Ø20mm shank • 163mm overall length • Made in Germany 825 (M694) 69 (Q211) • 500 x 40 x 8mm • Straight edge & 35º bevelled edge • Precision ground finish on both sides and edges • Carbon tool steel 143 (M706) $ $ $ SAVE $33 SAVE $110 SAVE $22 View and purchase these items online: www.machineryhouse.com.au/SIC2502 MEGA DEMO DAY! Get in-store to see some of Australia’s best metal shapers, ask questions and learn a lot! Saturday 22ND only! AND FREE SAUSAGE SIZZLE D PM SAT.22N L 3:00 DING OPEN TIL RA EXTENDED TSTARTS FROM MARCH 10TH - 31ST Measuring Kit - 4 Piece - M012 • 0 - 25mm micrometer • 150mm / 6” rule • 150mm / 6” vernier • 100 x 70mm square Magnetic Base - Standard - M050 • 64 x 50mm V-base for placing on round surfaces • 60kg holding power • Dual lock type • Easy On/Off switch Digital Height Gauge - M704 • Dual imperial/metric scale • Fine adjustment • Pre-sets and memory • 12”/300mm capacity • Carbide-tipped scriber 165 (M704) $ $ $ SAVE $33 SAVE $9 SAVE $12 Dial Caliper - 505-741 Digital Caliper - M740 • 8" • Mitutoyo dial calipers • 3 Modes of measurement IP54 • Absolute & incremental functionality • 4-way measuring 35 (M050) 65 (M012) 330 (M103) $ Double Ended Scriber 70-630 Digital Angle Rule - M970 • 180mm blade length • 360° range • Stainless steel • Quick lock system • 190mm in length • Straight & 90° hardened steel tips • Precision manufactured • Knurled body for grip SAVE $33 Digital Calipers - 500-753 • 200mm / 8" • IP67 Rated 374 (M114) 35 (M740) 12 (Q630) 29 (M970) $ $ $ $ SAVE $22 SAVE $9 SAVE $3.40 SAVE $9.50 Digital Bevel Box - DB-180 Metric O-Ring Assortment • Mini digital protractor that provides digital readings of 4 x 90º • Ideal for measuring mitre and bevel angles on saw benches etc. • Auto shut off • Magnetic base • 0.1° resolution • Contains the most popular metric o-rings ranging from 2.8mm ID x 6.6mm OD to 47.7mm ID x 54.7mm OD • Resistant to heat, low/high temperature, air, water, petroleum products, mineral oil and hydraulic fluids, natural gases, kerosene, silicone fluids, non-aromatic fuels and solvents • Use in plumbing, hydraulics, air, gas, connections and many industrial applications $ 39 (M977) $ SAVE $10.50 SAVE $9.90 22 (K74150) Metric Nylon Lock Nut Assortment Metric Hex Cap Screw Assortment - K72024 • 150 Piece • 6 assorted nylon locknuts for use in high vibration applications! • Nylon insert works as a lock washer to keep fasteners secure • Zinc plated to resist rust and corrosion • Precision machined and heat treated • Black oxide finished carbon steel • Neatly organised in a convenient divided PVC storage case with chart inside box lid for easy selection 15 (K72450) $ $ SAVE $7 SAVE $7 15 (K72024) SAVE $7 COMPETITIVE FREIGHT RATES DELIVERED TO YOUR DOOR MORE THAN 4000 PRODUCTS ON SALE ONLINE, INSTORE OR CALL SYDNEY MELBOURNE BRISBANE PERTH ADELAIDE (02) 9890 9111 (03) 9212 4422 (07) 3715 2200 (08) 9373 9999 (08) 9373 9969 01_SIC_270225 Specifications & Prices are subject to change without notification. All prices include GST and valid until 31-03-25 on the particular author being willing to provide information on themselves. Watch out for asbestos in old radios The article in the September 2024 issue on Mains Earthing systems by Brandon Speedie concerns land-based power networks (siliconchip.au/Article/16574) was interesting. It almost demands a follow-up on Earthing systems for marine vessels with on-board mains supplies. Perhaps he could be persuaded to write a follow-on article. On a separate issue, the Vintage Radio articles are always intriguing. Because of the typical period from which they originate, many use Bakelite cabinets and insulating componentry. I thought readers will find this video on manufacturing Bakelite parts in 1936 compelling: https://youtu. be/umM21vFIc7Y In fact, for keen old-tech collectors, it may prove to be a bit more than just interesting because it contains an embedded warning. It explains how some Bakelite mouldings incorporated asbestos reinforcing fillers. This is no exaggeration of the potential danger. I currently have a friend, an avid vintage radio gear collector, slowly dying from cancer (Mesothelioma). There is no way to know for sure exactly where he became exposed to the asbestos that is killing him, but you’d have to put his hobby high on the list of potential candidates. Restorers be warned! Andre Rousseau, Auckland South, New Zealand. Beware fake power tool batteries! A friend recently asked me to look at a Makita power tool battery, purchased online, to see if it could be fixed. It was only a few months old, but the charger wouldn’t charge it, and the battery would not run the tool. I measured the terminal voltage, which was 5V, and tried it in my Makita charger. It immediately indicated a fault. I opened it up to see if it had a faulty cell or some other problem. The accompanying photo shows what I found. The case is identical to a genuine Makita one, and is labelled 18V 8Ah. It carries a Makita part number. The purple cells are connected in series and are wired directly to the charger and the output terminals, with no battery management system or BMS (a red flag!). The IC on the small board appears to tell the charger to operate as if it were a genuine battery. There was also no temperature sensor fitted to monitor the temperature when charging – that’s dangerous! The blue cells sat in the bottom of the case and have no connections at all. I measured these and they were all open-circuit. Opening up one of these revealed why: it was filled with sand! While the battery is labelled 8Ah, it only contains 2Ah of cells, so even when it was working it was a terrible product. Beware what you buy online. Bruce Boardman, VK4MQ, Highfields, Qld. Analysis of crystal resonator reliability On pages 8 & 9 of the January 2025 issue, there is a letter from Vincent Stok regarding an unexpected failure of a 20MHz crystal in an automotive ignition system. When referring to the electronic equipment reliability handbook MIL-HDBK-217F, in Section 19.1 it lists the baseline reliability of a 20MHz crystal as 26 FIT (26 failures in 1,000,000,000 operating hours). It also lists a quality factor weighting of 2.1 if it is not of military grade, and a further weighting of 10 if it is operating in a Ground-Mobile environment. With these weighting factors applied, the expected reliability becomes 546 FIT. Ground-Mobile means it is in an enclosure which is moving about (and hence subject to physical shock and vibration), and is not environmentally controlled (hence subject to high temperature and humidity extremes). This is a good summary description of the engine bay compartment of a car. From a very quick Google search, I found the typical temperature range of an engine compartment (when the engine has been running for some time) is 87-104°C, whereas the Ground-Mobile model only goes up to 65°C. After doing a bit of digging on crystal reliability versus temperature, the data appeared to suggest that the FIT value of crystals does not change significantly as temperature increases, so I decided not to examine any Arrhenius equation calculation to scale up from 65°C to 95°C. I then made an estimate of 25,000km travelled per year, and based on my own experience driving around Sydney, this equates to roughly 22 vehicle operating hours per week, or 1144 hours per year. So, (546 FIT x 1144 hours) ÷ 1,000,000,000 indicates an expected failure probability of 0.0624% per year, or 0.5% failure probability over eight years of service. Given the environment it is operating in, the crystal failure is not so amazingly unexpected. David Neville, Kogarah, NSW. More on extracting ROM data from 68705s I found the article in the January 2025 issue on Extracting ROM data from old microcontrollers very interesting (siliconchip.au/Article/17609). When I started my career developing products in the mid 1980s, I used the 68705P3 devices in my products. These are very similar to the G2s mentioned in the article and used a very similar programming process: we would program the software into an EPROM, then use a programmer board to transfer the data into the device. The P3 devices themselves were pretty simple, but they 8 Silicon Chip Australia's electronics magazine siliconchip.com.au FREE Download Now! Mac, Windows and Linux Edit and color correct using the same software used by Hollywood, for free! Creative Color Correction DaVinci Resolve is Hollywood’s most popular software! Now it’s easy to create feature film quality videos by using professional color correction, editing, audio and visual effects. Because DaVinci Resolve is free, you’re not locked into a cloud license so you won’t lose your work if you stop paying a monthly fee. There’s no monthly fee, no embedded ads and no user tracking. PowerWindows™, qualifiers, tracking, advanced HDR grading tools and more! Editing, Color, Audio and Effects! Designed to Grow With You DaVinci Resolve is the world’s only solution that combines editing, color DaVinci Resolve is designed for collaboration so as you work on larger jobs correction, visual effects, motion graphics and audio post production all in you can add users and all work on the same projects, at the same time. You can one software tool! You can work faster because you don’t have to learn multiple also expand DaVinci Resolve by adding a range of color control panels that apps or switch software for different tasks. For example, just click the color let you create unique looks that are impossible with a mouse and keyboard. page for color, or the edit page for editing! It’s so incredibly fast! There’s also edit keyboards and Fairlight audio consoles for sound studios! Professional Editing DaVinci Resolve 19 ............................................................... Free DaVinci Resolve Micro Color Panel .............Only $809 DaVinci Resolve is perfect for editing sales or training videos! The familiar track layout makes it easy to learn, while being powerful enough for professional editors. You also get a library full of hundreds of titles, transitions and effects that you can add and animate! Plus, DaVinci Resolve is used on high end work, so you are learning advanced skills used in TV and film. www.blackmagicdesign.com/au DaVinci Resolve’s color page is Hollywood’s most advanced color corrector and has been used on more feature films and television shows than any other system! It has exciting new features to make it easier to get amazing results, even while learning the more advanced color correction tools. There’s Learn the basics for free then get more creative control with our accessories! Learn More! NO SUBSCRIPTIONS • NO ADS • NO USER TRACKING • NO AI TRAINING were a big step up from previous CPUs that required separate RAM, ROM, peripheral ports and all the glue logic to make them work. We already had an EPROM programmer; the programming board I made was based on a schematic in the data sheet. Software development was a fairly long process – write some software, burn it to an EPROM, use the programming board to transfer to the EPROM to the device, put the device in your product and try it out. Repeat. Since there was no support for on-chip debugging, you had to be creative with output pins and have an oscilloscope. All in all, they were very useful for us, and we used a great many of them in multiple product lines, although mostly we used the functionally equivalent but non-­windowed P5 version because it was cheaper. I sometimes think back and wonder if any of those products still exist, and if so, what it’d take to get the software out of one and into another. I think Dr Holden’s solution is quite a good one and could probably be applied to the P3 as well. During my time using them, I found the mask ROM that contains the software that transfers the external EPROM data into the device while during programming was fully accessible at any time, not just while the device was in programming mode. Thinking this code might be useful to me, I wrote some software for the P3 that read and displayed the mask software byte by byte on one of the peripheral ports, which I then copied down and attempted to disassemble by hand. In the end, something more important came along and I gave up, but maybe Dr Holden may find it useful to know what’s going on inside the device during programming, if he wants to pursue his idea further. D. T., Sylvania, NSW. Running induction motors at reduced voltages I am replying to the letter to the Editor published in the January 2025 edition from Ian Thompson (on page 6), asking about running a 3kW motor on a mains-powered variable-­ frequency drive (VFD). The answer is that it can be done with the following caveats. The torque of a synchronous motor running at a constant excitation frequency is proportional to the applied voltage squared. In his case, the torque developed by his motor will be (240 ÷ 440)2, which will give about 30% of its rated torque. The motor will run near its nameplate speed, but will only produce 1kW (torque × speed = power). One should not exceed 30% of the motor nameplate current so as not to overheat the motor. An alternative strategy is to alter the applied volts per Hz (V/Hz). A VFD alters the V/Hz to maintain a constant flux in the motor under all speed conditions. By maintaining a constant flux, it allows the motor to develop its nameplate torque at all speeds. From the 3kW motor nameplate, the rated V/Hz is 8.8. If we are only able to apply 240V to the motor, the maximum frequency required to maintain a constant flux is 27.27Hz. After that, the flux starts to decrease as the VFD is unable to provide more than 240V. In this case, the motor speed is reduced to 54% of the nameplate rating AND the power of the motor is reduced to 1.63kW. In this manner, one can run the motor up to its nameplate current. 10 Silicon Chip Australia's electronics magazine siliconchip.com.au Some advanced VFDs allow one to change the V/Hz setting or, if you have access to the software of custom designed VFDs, you can change that parameter. As a side note, I worked with Andrew Levido in two different companies at both ends of our careers. I see he has not lost any of his engineering skills, even though he diverted to management many years ago. Robert Budniak, Denistone, NSW. Dealing with SSD degradation over time The ‘One Identity’ Factor A time machine would work on individual atoms, not on larger items like living bodies. When those atoms travel back in time each of them can only exist once; each atom with take up the identity it had before and proceed to exist in its previous role. This could have quite unexpected results for living bodies. The group of atoms that you called your body five years ago is significantly different from the group that you now own. The Loop You make a time machine and to test it out you set it to take you back one second. You press ‘start’ and it takes you back to where you were a second ago; you relive that second then the machine triggers again and you spend the rest of your life living that one second loop over and over again. Galactic Movement Astronomers tell us that the Milky Way galaxy is moving in relation to other galaxies at 580 kilometres per second. No-one knows where stationary actually is. If you set your time machine for one second forward it will take you to where your starting point will be in one second’s time. That could be a few hundred kilometres into outer space or underground. It is recommended that you time your first trial for when the constellation Virgo is just above the horizon, take a parachute and if there is water anywhere near have an EPIRB in your pocket. Get your copy for just $5.50: https://moonglowpublishing. com.au/store/p48/bewarethe-loop-jim-sinclair Beware! The Loop is available as an EPUB, MOBI & PDF RRP $5.50 | available as an EPUB, MOBI and PDF 12 Silicon Chip E-ISBN 9780645945669 You previously covered the problem of USB memory sticks not having the claimed storage. This has been a problem for a while and has been mentioned in several podcasts I listen to. One of the better ones is Security Now with Steve Gibson who has been doing it for 20 years. He runs Gibson Research Corporation and has produced many great utilities. One, which is free, is Validrive (www.grc.com/validrive. htm). This software will “Quickly spot-check any USB mass storage drive for fraudulent deliberately missing storage”. It writes and reads the entire USB drive, so it knows exactly how much is really there and should prevent anyone getting caught short (of storage). His main product, though, which he charges for is SpinRite (www.grc.com/sr/spinrite.htm). All storage media degrades over time and this is probably even more of a problem with SSDs. Storage that is read and rarely written becomes more difficult and slower to read over time. So if you think your computer is not as fast as it once was, this could be a significant reason why. SpinRite runs under FreeDOS, so you need to install it on a CD/DVD or USB memory stick and boot your computer from it. The cost is US$89 but you can use it on any machine you have as often as you like. Before you buy it, you can download his freeware that will test whether you will be able to boot up SpinRite. Unfortunately, I am unable to get my Dell Inspiron to do that, even though it will happily boot from Linux DVDs. I just thought I would pass this on. Michael Byrne, Woodford, Qld. Review of 0patch desired I am writing about your Editorial Viewpoint column titled “Staying on Windows 10” (February 2025) and your comments that you will be doing this and using the “0patch service”. I have my own set of reasons for not wanting to upgrade from Windows 10. I currently have it on my home desktop (tower) PC and on my laptop which I use (via WiFi) when I am in Sydney staying with family. I would not enjoy upgrading to Windows 11 and then possibly having software that has served me well on several previous versions of Windows not working on future releases. As such, are you considering, or would you consider, doing a review of this software package after you have been using it for a suitable time? Presumably, you will be able to provide readers with an objective review. Paul Myers, Karabar, NSW. Comment: thanks for your feedback. We will probably post some sort of update on the software, possibly in the Editorial Viewpoint of a future issue. We don’t know if we will have a lot to say about it other than whether it seems to be doing its job or not. SC Australia's electronics magazine siliconchip.com.au Discover New Technologies in Electronics and Hi-Tech Manufacturing See, test and compare the latest technology, products and explore turnkey solutions SMCBA CONFERENCE Hear from international experts presenting the latest design and assembly innovations at the Electronics Design and Manufacturing Conference Details at www.smcba.asn.au In Association with Supporting Publication Organised by Co-located with www.p exels.c om/ph oto/a-p erson-h olding -a-pro sth etic-arm -61533 45/ Artificial Limbs By Dr David Maddison VK3DSM Artificial limbs have been around since ancient times, but were typically just timber extensions attached to the stump of a remaining limb. Modern prosthetics are much better replacements for lost limbs and can even provide functional hands, capable of many tasks that a human hand can perform. M any people with ‘passive’ prosthetics (up to 44%) decide not to use their artificial limbs because of problems relating to weight, discomfort and lack of functionality, as described in the paper at https://pubmed.ncbi.nlm.nih. gov/33377803 Currently, no artificial limb can come close to emulating a natural one. Still, even a small increase of functionality for an amputee can lead to an enormous quality of life improvement. There have also been great advances in wearable ‘powered exoskeletons’, particularly to assist those with paralysis, muscle weakness or infirmity. They are also used for rehabilitation. New developments in materials science, 3D printing, electronics, batteries and artificial intelligence (AI) have made new, lighter-weight, more comfortable and more functional artificial limbs or exoskeletons possible. We will look at some of these, in particular those that involve the use of electronics rather than purely mechanical devices. A replacement limb should ideally appear natural, although it seems some users like the non-natural ‘cyborg’ look. The limbs should generally 14 Silicon Chip mimic nature as closely as possible, both for a natural appearance as well as intuitive and expected operation (degrees of freedom etc). Cost is also an important consideration, as the cost of a prosthetic limb can be significant. Connection to the body One of the most important concerns affecting patient comfort is the way the artificial limb is connected to the body. Rather than cumbersome belts, silicone rubber and gel materials are a much more comfortable fit of the prosthesis ‘socket’ to the limb stump. Comfort can be further enhanced with 3D scanning of the stump and corresponding 3D printing of the socket to get the best possible fit. Direct skeletal attachment of the prosthesis (‘osseointegration’) is another recent development, but is not suitable for all patients, as great care is needed for the area where the skin is penetrated. Control, sensing & feedback When the prosthesis is active, ie, it has some form of motor or motors built into it, there obviously must be a means to control it. This generally has to be simple and easy to learn or adapt to. Australia's electronics magazine Ideally, there should also be some means of sensing the position of the prosthesis in space and also to provide feedback to the user of limb activity such as grip force for a hand (proprioception). By having both control and sensing, an artificial limb can approach the utility of a real one. One of the most important aspects of controlling an artificial limb is to determine user intent. This is commonly done by attaching electrodes to the skin in the vicinity of the remaining nerves that would have been used to control the limb. The body still sends electrical impulses from the brain to those, as if the limb still existed. These can be interpreted to establish what the person wishes the limb to do. There are also other possible control methods, which we will discuss later. Beyond that, the next step is to interface directly to the nerves or even the brain, as in the case of Neuralink, a brain-computer interface. Proprioception Proprioception is the ability of a person to determine the location of parts of their body without having to look, as well as sensing the weight of siliconchip.com.au an object and forces exerted. While we are taught in primary school that there are five senses, we actually have between 22 and 33; proprioception is one of the more important ones, along with balance (via the inner ear), pain and temperature sensing. For more realistic prosthetic limb behaviour, it is important that proprioception is incorporated into the artificial limb. In the natural human body muscle spindles, Golgi tendon organs and skin receptors are all responsible for producing proprioception sensations. These allow us to sense changes in length, tension and deformation, as shown on the left in Fig.1. These same senses can be measured electronically by (for example) the number of revolutions of a rotary encoder, the amount of current a motor is drawing or the output of a strain gauge, as shown on the right in Fig.1. This information can then be fed back to the patient via various means, such as vibration (for example). In an electronically controlled prosthetic limb (Fig.2), proprioception information may be acquired as per the following example. 1. The prosthesis is activated by biological signals from the user, such as through surface electrodes to pick up nerve activity on the stump or a brain-computer interface such as Neuralink. 2. Proprioception information is acquired via sensors like strain gauges to measure deformation, rotary encoders to determine joint angle, limit switches and the amount of current drawn by a DC motor, which is related to its mechanical load. 3. This data is fed to a microprocessor and translated into information for position, movement, force and load. 4. This information is translated into a feedback signal for the user, such as (for example) some sort of amplitude or frequency modulated waveform that might represent angular position or torque. 5. The waveforms representing angular position and torque are sent to a ‘stimulator’ in the socket of the prosthetic device to create a sensation on the user’s skin or nerves. Devices to do this might cause skin stretch, vibration, electrical stimulation of nerves or the creation of a tendon-­vibration illusion (TVI), which generates a perception of joint motion. Sometimes, several proprioception siliconchip.com.au Fig.1: natural (left) and artificial (right) proprioception strategies. Source: www. researchgate.net/figure/fig1_373816713 Fig.2: artificial proprioception. Source: www.researchgate.net/figure/ fig2_373816713 methods can be used simultaneously to provide multi-channel feedback to the user. Prosthesis control Proprioception information and control of prosthetic devices may be Australia's electronics magazine achieved via the following means, which are either in use, under development or proposed. They involve either external sensors (such as capacitance measurement of the external environment) or sensing of residual muscle or nerve activity in a patient’s stump. March 2025  15 Servomotors Controlled prosthesis joint Agonist Channel 3 Reference Antagonist Residual limb Channel 1 Channel 2 Inductive powering system Wireless communication with both servomotors Channel 4 Fig.3: a proposed cineplastic procedure to sense forces on a muscle pair (agonist and antagonist) to control a prosthesis. Source: Control Methods for Transradial Prostheses Based on Remnant Muscle Activity and Its Relationship with Proprioceptive Feedback; siliconchip.au/link/ac3s Fig.4: a possible arrangement of EMG electrodes on a healthy forearm. A similar arrangement would be used in the case of a missing hand. Some of these methods are more accurate than others, while some are subject to noise. Both of these problems can be improved by a combination of approaches. Some may turn out to be impractical. Capacitance sensing is a method to measure the distance to nearby conductive objects using a pair of electrodes, with the electrodes excited by a sinewave at several hundred kilohertz (kHz). As a conductive object is moved closer to the electrodes, the amplitude of the excitation signal is modulated, indicating the distance. The closer the object, the greater the amplitude. Cineplasty (Fig.3) is an old surgical approach to altering residual limb muscle to enable a mechanical connection to control a prosthesis. It has several disadvantages, but a modern proposed conceptual approach involves connecting servomotors at ends of muscle pairs with wireless communication to and from a prosthesis. Electrical impedance tomography (EIT) involves wrapping a series of electrodes around a residual limb, like a forearm, and measuring the electrical impedance between electrodes. Information thus obtained can be used to infer user intent and a prosthetic device such as a hand can be controlled. Electromyography (EMG) is the most common method in use today to control prosthetic devices. It involves interpreting nervous system signals within residual muscles. An EMG signal has a voltage of around 1-10mV and a frequency up to 500Hz. Typically, EMG signals are measured on the skin surface, but electrodes can also be implanted for this purpose. Fig.4 shows a possible arrangement of multiple EMG electrodes on intention to operate a prosthesis, although this approach seems impractical for a variety of reasons. Phonomyography is a method of detecting muscle activity by its emission of low-frequency oscillations (5-100Hz) during contraction. They can be detected using acoustic means, such as by microphones or accelerometers placed in contact with the skin. Sonomyography uses ultrasound to monitor muscle movement in a stump. This can be used to interpret patient intention to control a prosthetic device. 16 Silicon Chip the skin surface of a healthy forearm. Force myography consists of attaching an array of force sensors on a residual stump to determine patient intention to move a prosthetic device by their activation of the remaining muscles. Magnetomyography is a method of measuring nerve system electrical signals in the stump by detecting extremely small magnetic fields using such devices as SQUIDs (superconducting quantum interference devices). Such methods are certainly impractical in a portable device at the moment. Myokinetics is a proposed procedure in which magnets are implanted in the residual muscles of a forearm. A three-axis magnetic field sensor is wrapped around the surface of the limb to control a prosthetic hand as the muscles are activated by the patient. Near-infrared spectroscopy using light at wavelengths of 760nm and 850nm can detect oxygenated and deoxygenated haemoglobin in the bloodstream. This can be used as a proxy to monitor muscular contractions. Human tissue is somewhat transparent to these wavelengths and so, as the amount of oxygenated blood changes in muscle as they relax or contract, it is possible to monitor muscle movement. If the residual muscles of a stump are monitored using a separate near-infrared transmitter and receiver in contact with the skin surface, it is possible to infer patient intention to control a prosthetic device. Optical myography is an approach whereby high-resolution imaging is used to look for changes in the shape of a stump due to skin deformation caused by underlying muscle activity. This can indicate the patient’s Australia's electronics magazine Commercial prostheses Some commercial electronically controlled prosthetic limb devices are as follows: Blatchford Intelligent Prosthesis The first commercially available microprocessor-controlled artificial limb was the Blatchford Intelligent Prosthesis, released in 1993 by UK company Blatchford Mobility. This was a leg with an articulated knee design, which was programmed to suit individual users and enabled a smooth, energy efficient gait pattern. It did this by determining walking speed and allowing the appropriate amount of swing phase extension. Unfortunately, we can’t find any good photos of the device. Bebionic Myoelectric Hand Bebionic (www.ottobock.com/ en-au/home) makes an artificial hand, shown in Fig.5, which is myoelectrically controlled by nerve signals picked up from skin electrodes on the residual limb. It can be coupled with arm components if the forearm or upper arm is also missing. siliconchip.com.au It is controlled by electrodes contained within a forearm enclosure, which pick up myoelectric signals from the residual forearm. This prosthesis uses Myo Plus pattern recognition and machine learning to interpret user intent. Luke Arm The Luke Arm (mobiusbionics.com/ luke-arm) is a prosthetic arm inspired by the prosthetic hand attached to Luke Skywalker from the movie Star Wars: A New Hope (1977) – see Fig.6. It is only available in the United States. It is of modular construction and is available in three lengths (transradial, transhumeral and shoulder disarticulation), depending on the extent of the arm or hand amputation. In the longest version, it has ten powered degrees of freedom, including a powered shoulder, humeral rotator and wrist flexor with ulnar/radial deviation. In addition, the hand component has multiple preprogrammed positions with grip force feedback. The company states that it is the only commercially available prosthesis with a powered shoulder. The transradial version weighs 1.4kg, transhumeral 3.4kg and shoulder disarticulation 4.7kg. The prosthesis has multiple control options, such as with pressure switches, rocker switches or myoelectric electrodes. It can also make use of inertial measurement units worn on the shoes to translate foot movement to a specific hand/arm action controlled by movement of the toe, heel, inside or outside of the foot. The forearm of the device has lights that indicate to the wearer hand or arm mode, current grip selection, battery levels, low battery icons and faults. There is also an optional feature called Tactor, which provides alerts and sensory feedback such as for grip force, via vibration. Open Bionics Open Bionics (https://openbionics. com, not to be confused with https:// openbionics.org) makes relatively inexpensive 3D printed arms and other prosthetics. The Hero Arm product, designed for those missing a forearm but who have a remaining elbow, has a hand with a gripping capability with six different grip types and is available in a variety of sizes, including one to suit children over eight years. siliconchip.com.au Fig.6: the longest version of the Luke Arm, inspired by Star Wars. Source: https:// mobiusbionics. com/luke-arm Fig.5: the Bebionic EQD hand. Each finger has individual motors and there are 14 different grips and hand positions available. Skin-coloured “gloves” are available to cover the hand. Source: www.ottobock.com/enus/product/8E70 Fig.7: the Open Bionics Hero Arm. Source: https://openbionics. com/hero-armoverview Fig.9: the Össur microprocessorcontrolled waterproof Proprio Foot. Source: www. ossur.com/enus/prosthetics/ feet/propriofoot Fig.8: the Össur i-Limb Quantum “multi-articulating myoelectric hand prosthesis” hand. This model has titanium digits for increased grip force and strength. Source: www. ossur.com/en-us/ prosthetics/arms/ilimb-quantum It is operated by picking up nerve signals from the stump. Interestingly, it can be customised with various different covers with different designs, including a Spider-Man design for children – see Fig.7. Several videos of it in action can be seen at https:// openbionics.com/how-to-use-a-heroarm showing operation of the arm for some common tasks. Össur i-Limb Quantum Hand & Proprio Foot Össur (www.ossur.com/en-us) makes various products including prosthetics, such as partial and full hands, feet and waterproof prosthetic legs, as well as others. Two products of note are a myoelectric controlled hand prosthesis (see Fig.8) and a microprocessor-controlled foot prosthesis (Fig.9). PSYONIC Ability Hand The PSYONIC Ability Hand (www. psyonic.io/ability-hand) promotes itself as the “world’s fastest, incredibly Australia's electronics magazine durable, and first ever touch-sensing bionic hand” (see Fig.10). It has sensors that detect grip pressure and provide user feedback via vibration. It is also designed to be strong and water resistant. Up to 32 different grip patterns are available. It is charged via a USB-C and a charge lasts about 6–8 hours of use. It is operated by myoelectric sensing of nerve system activity in the residual limb, as well as force-sensitive resistors and linear transducers from third parties. The Ability Hand can also be fitted to robots – see Fig.11. Utah Bionic Leg The Utah Bionic Leg (www. Fig.10: the PSYONIC Ability Hand. Source: PSYONIC user manual; siliconchip.au/link/ac3q March 2025  17 ◀ Fig.11: a NASA humanoid robot and a person both fitted with PSYONIC Ability Hands. Source: www.psyonic. io/robots Fig.12: the Utah Bionic Leg. Source: www.mech.utah.edu/utah-bionic-legin-science-robotics mech.utah.edu/utah-bionic-leg) is under development at the University of Utah – see Fig.12. It is designed for lower-­leg amputees. It is lightweight, using artificial intelligence and a variety of sensors for determining torque and acceleration and the prosthesis’ position in space. It can adapt to a variety of different walking activities. It does not use significant power for walking on level ground, so it can be used almost indefinitely on such terrain. During such activity, the battery is recharged upon limb deceleration, similar to regenerative charging in an electric vehicle (EV). Open-source prostheses There are several open source prosthetic limb projects as follows: OpenBionics OpenBionics (https://openbionics. org) describes itself as an open-source initiative that develops “affordable, light-weight, modular, adaptive robotic and bionic devices that can be easily reproduced using off-the-shelf materials”. It derives its original inspiration from the Yale Open Hand Project, described below. One of OpenBionics’ developments is shown in Fig.13. Open Source Leg The Open Source Leg (www.­ opensourceleg.org) project has a mission to develop standardised hardware and software platforms for prosthetic legs and to encourage worldwide cooperation from researchers in the field. In particular, it is to help develop appropriate control strategies to operate the legs (see Fig.14). It is not specifically intended as a user leg, but rather it is for researchers. The platform runs a Raspberry Pi computer. The website contains all the information necessary to enable researchers (or even Silicon Chip readers!) to build their own prosthetic leg. The cost is estimated at US$900019000, which is much cheaper than commercial devices. You can see the detailed costings at www.opensourceleg.org/build/make and a video on it at https://youtu.be/ xFliFk65l3Q The Yale OpenHand project The purpose of the Yale OpenHand Project (www.eng.yale.edu/grablab/ openhand) is to make low-cost, opensource robotic hands (see Fig.15). It is mentioned that a purpose of the project is to “make prosthetic hands more widely available through the lowering of costs” (siliconchip.au/ link/ac3r). We see no reason that these hands could not be incorporated into prosthetic limbs. Fig.13: the OpenBionics hand model. Source: https://openbionics.org/ affordableprosthetichands 18 Silicon Chip Australia's electronics magazine siliconchip.com.au Exoskeletons A powered exoskeleton is a wearable machine that covers all or part of a wearer’s body and interprets their intended motion and moves accordingly. They have a variety of uses in the military and industry, to assist the carrying of heavy loads or to relieve users of possible repetitive strain injuries. They can also be used to assist the paralysed, or those with muscle weakness or infirmity, to walk. They have uses in rehabilitation too. We will look at some powered exoskeleton devices that assist people who have trouble walking. Cyberdyne Hybrid Assistive Limb The Hybrid Assistive Limb (www. cyberdyne.jp/english/products/HAL) is a joint development between Japan’s Tsukuba University and the robotics company Cyberdyne. The lower body version is shown in Fig.16 and helps the partially paralysed (where some residual nerve function still exists in the legs) or infirm to walk. The device has sensors that are attached to a patient’s flexor and extensor muscles that detect and interpret electrical signals from nerves. There are four motorised joints, one for each hip and knee. It is available as a single- or dual-leg model, weighing 9kg or 14kg respectively, with an operating time of about one hour. EksoNR by Esko Bionics The EksoNR (Fig.17) is an exoskeleton device designed to assist in the rehabilitation of patients in a clinical setting with physical therapists. It is suitable for conditions such as acquired brain injury, stroke, multiple sclerosis (MS) and spinal cord injury, and is designed to re-teach the brain and muscles how to walk again. Figs.16-18 (left-to-right): the Cyberdyne Hybrid Assistive Limb; EksoNR exoskeleton; and the HANK lower limb exoskeleton. Sources: www.cyberdyne. eu/en/products/medical-device/hal-limb & https://eksobionics.com/eksonr & www.gogoa.eu/en/exoesqueletos-medicos-hank It can work with software called GaitCoach, which alerts therapists to any aspect of the patient’s gait that needs correction and further training. The device weighs about 27kg. See https://youtu.be/RtBaQEKcguk HANK by Gogoa Mobility H A N K ( w w w. g o g o a . e u / e n / exoesqueletos-medicos-hank) is a lower limb exoskeleton intended for rehabilitation of patients with spinal cord injuries, neurodegenerative disorders and who have had brain injuries (see Fig.18). WalkON Suit F1 exoskeleton Korea Advanced Institute of Science and Technology (KAIST, www.kaist. ac.kr) of South Korea makes the WalkON Suit F1, developed jointly with Angel Robotics (https://angel-robotics.­ com/en). It is described as a wearable robot for paraplegics. The F1 can walk independently up to a user sitting in a wheelchair, after which the user attaches the device. The F1 learns an optimal walking strategy for each user based on weight and balance considerations using a neural network. See Fig.19 and the video at https://youtu.be/ kQ2fSap1E2I This suit and its research team won a gold medal at the 2024 Cybathlon (described later in text). Fig.14: the Open Source Leg. It is designed for researchers to develop control software for prosthetic legs. Source: www.opensourceleg.org/ build/make Fig.15: an open-source robotic hand at the end of a robotic arm, from the Yale OpenHand project, which could be incorporated into a prosthesis. Source: www.eng.yale.edu/grablab/ openhand siliconchip.com.au Australia's electronics magazine March 2025  19 ReWalk exoskeleton ReWalk is a “personal robotic exoskeleton” from Israel (https:// golifeward.com) that allows paralysed patients to walk again (see Fig.20). Patients strap themselves into the device and it provides powered hip and knee motion to walk, turn, negotiate curbs and climb stairs. It uses a computer-based control system and motion sensors to mimic walking. Fig.19: the WalkON Suit F1 for paraplegics. Source: https://angelrobotics.com/en/products/suit/ walkon-suit.php Walking Assist Device by Honda Although it doesn’t appear to be currently on the market, the Walking Assist Device by Honda (the car company) was designed to help patients with impaired walking function who are unable to walk unassisted, for example, stroke victims or those with muscular weakness. It consists of an exoskeleton-type device with attachments via straps at the hip and thighs and it weighs only 2.7kg (see Fig.21). It is, or was, an offshoot of Honda’s walking robot research. Wandercraft Wandercraft (en.wandercraft.eu) makes the Atalante X exoskeleton device to assist paraplegics to become uprightly mobile again. Unlike most other exoskeleton devices, it does not need handheld poles, and is thus hands-free – see Fig.22. Brain interfaces Fig.20: the ReWalk Personal Exoskeleton allows paralysed patients with spinal cord injuries to walk again. Source: https://golifeward. com/products/rewalkpersonalexoskeleton Fig.21: Honda’s Walking Assist Device. Source: https://assets. blackxperience.com/content/ blackauto/autonews/walk-assist-back-view-3.jpg 20 Silicon Chip Fig.22: the Wandercraft Atalante X hands-free exoskeleton for paraplegic patients. This patient is being trained, hence the overhead support strap. Source: https://en.wandercraft.eu An alternative strategy to sensing myoelectric impulses on the skin surface or other methods is to control prosthetic limbs via a direct brain-computer interface. A complete system (Fig.23) consists of the electrode array, a neural signal processor and software. A video of a patient using the device to move robotic arm can be seen at https:// youtu.be/QRt8QCx3BCo BrainGate BrainGate’s by-line is “turning thought into action” (www.braingate.­ org). This research organisation has developed an experimental brain-­ computer interface implant to interpret electrical activity at specific brain locations to assist patients with conditions such as amyotrophic lateral sclerosis (ALS) or spinal cord injury. This allows them to control artificial limbs or operate computers. It uses an electrode system known as the Utah Array, also called the NeuroPort Electrode, which is commercially available for experimental purposes from Blackrock Neurotech (https:// blackrockneurotech.com/products/ utah-array). Neuralink Elon Musk’s company Neuralink (https://neuralink.com) is developing a brain-computer interface (BCI) device to transform a person’s thoughts into actions by a computer or other device – see Fig.24. Neuralink can potentially control wheelchairs, robotic exoskeletons and artificial limbs by thought alone. The amazing potential for Neuralink to control external devices is shown in the following video, in which a monkey with two Neuralink devices installed plays “MindPong” using its thoughts alone: https://youtu.be/­ rsCul1sp4hQ Neuralink is running a clinical trial called “Precise Robotically Implanted Australia's electronics magazine siliconchip.com.au Fig.23: the Blackrock brain-computer interface system with the Utah Array (Neuroport Electrode array) shown insert. Source: https://blackrockneurotech. com/our-tech Fig.24: an exploded diagram of Neuralink. Source: https:// drkaushikram.com/wp-content/ uploads/2023/07/Neuralink.jpeg Brain-Computer Interface (PRIME) study”. It “aims to evaluate the safety and effectiveness of its BCI implant, the N1, along with the surgical robot R1 and the N1 User App”. The implant will have 1024 electrodes. The first human with a Neuralink chip installed has used it to move a cursor to play chess. You can see this in the video at https://youtu.be/­ 5SrpYZum4Nk load-bearing prosthetic limbs is called osseointegration. In both cases, the body interprets them as foreign bodies and mounts an aggressive immune system attack to isolate or expel them. It is thus vitally important to use the most biocompatible materials possible, such as titanium, certain ceramics such as zirconia, and silicone. Still, even these materials are recognised as foreign by the immune system. When such penetrations are made, they can be prone to infection and sometimes have to be removed. Nevertheless, advances in these techniques have been made. Note that osseointegration of prosthetic components such as hip and knee joints is already done routinely and effectively. The difference with prosthetic limbs is the externalisation of the implant through the skin, which creates many additional challenges. Tooth implants with the support structure externalised through the gum are generally successful, although the mouth is more resistant to infection than the skin. Fig.26: a patient with a prosthetic leg attached to their body using the OPRA osseointegration system. Source: https://integrum.se/about-us/ourtechnology/opra-implant-system Fig.27: a patient with an experimental e-OPRA prosthetic limb who can complete challenging tasks as a truck driver. Source: https://integrum.se/ about-us/our-technology/e-opra Transcutaneous penetrations and skeletal attachments Two of the most challenging and related areas of prosthetic devices are the transcutaneous (through-skin) penetrations of tubes and wires, and direct skeletal attachment of prosthetic limbs. Direct skeletal attachment of The OPRA implant system Integrum (https://integrum.se) is a Swedish company that has developed the OPRA implant system for osseointegration of prosthetic limbs. There are two different versions of OPRA: one is commercially available, while another, called e-OPRA, is experimental. Fig.25 shows the method by which the OPRA implant is attached to bone and externalised through the skin. A patient with a prosthesis attached via the OPRA system is shown in Fig.26. Bone Fixture Skin Abutment Abutment Screw Fig.25: details of the OPRA implant system. Source: https://integrum. se/about-us/our-technology/opraimplant-system/transfemoral-aboveknee-amputations siliconchip.com.au Australia's electronics magazine March 2025  21 The experimental e-OPRA system is connected directly to the body’s nervous system rather than sensing electrodes on the skin, as shown in Figs.27-29. Cybathlon Cybathlon (https://cybathlon.com/ en) is a competitive event for teams from all over the world that develop assistive technologies – see Fig.30. There is a video of highlights from the 2024 Cybathlon viewable at https:// youtu.be/WbhvEbVW1-I Such events encourage the development and use of new prosthetic technologies. Limb regeneration or transplanting Though not the main topic of discussion here, there are alternatives to prosthetic limbs. Rather than having an artificial limb, the ultimate solution would be to regrow an entire new body part. This process already occurs with some animals like salamanders, so it is at least possible in principle. If their leg is cut off, they will regrow it. It is believed that limb regrowth is at least theoretically possible in humans. It is a matter of activating the right biological pathways to enable it to happen, and many researchers are investigating this. An Australian scientist, Dr James Godwin, discovered that in humans, the scarring that occurs due to a significant wound actually prevents limb regeneration. If scarring could be prevented, perhaps limb regeneration would occur. There is also a substance called ‘extracellular matrix’, one variety of which has been called “pixie dust”, that has been shown to produce tissue regeneration in humans with some success. With advances in management of tissue rejection and surgical techniques, limb transplants, such as hands, arms and legs have been performed. Another approach is the ‘biolimb’. A biolimb is created when a donor limb has its cells removed, leaving behind just the collagen supporting matrix. This is then repopulated with cells from the intended recipient such as nerves, muscles, blood vessels and skin tissues. These are placed into the appropriate areas. 22 Silicon Chip This has been done for more simple body parts, such as windpipes, with varying levels of success. With a limb, there are numerous tissue types to populate, so the process is much more complicated. As no tissue remains of the donor that could be recognised as foreign by the recipient, there are no problems with rejection or having to take lifelong immunosuppressive drugs. Further reading Enabling the Future (https://­ enablingthefuture.org) is a global network of citizen volunteers who use their 3D printers to make opensource upper limb designs to assist Fig.28: an e-OPRA osseointegration system. The abutment is where the prosthetic limb is attached, and there are connections to nerves and muscle tissue. Source: https://integrum.se/ about-us/our-technology/e-opra children and adults in need. They are mainly for those born without fingers or hands, or who have lost them due to war, natural disasters, illness or accidents. Instructions on how to get involved are at https://enablingthefuture.org/ learn-more-get-involved Some companies are partnered with a wide range of prosthetic manufacturers and also perform customisation to help formulate a solution for most types of amputees. One US company we saw was A Step Ahead Prosthetics (www.weareastepahead. com). You can watch a YouTube video about them at: https://youtu. SC be/KDMbJOTXNrw Fig.29: with the e-OPRA system, control and sensory information is transmitted by nerves from (blue line) and to (green line) the brain. Sensory information from the prosthesis provides a sense of feel. Source: https://integrum.se/about-us/ourtechnology/e-opra Fig.30: a competitor with a prosthetic leg completes a task at Cybathlon 2024. Source: https://cybathlon.com/en/events/edition/cybathlon-202 Australia's electronics magazine siliconchip.com.au Maker March altronics.com.au K 8600A 369 $ Deals to get you creating. Arduino UNO R4 Compatible Boards BONUS! 1kg roll of black filament valued at $39.95 (K8397A) Z 6240A UNO R4 30 $ Get designing on the latest UNO R4 compatible development boards - same form factor as earlier Arduinos for maximum shield compatability, but with expanded memory and faster clock speed. Available in standard and ESP32-S3 WiFi versions. 49 $ .95 ZW6240A UNO R4 WiFi Creality® Ender 3 V3 SE 3D Printer 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. 68W Compact Soldering Station T 2555 T 2480 SAVE 22% 40 $ All heat & no flame! Iroda® Pocket thermo-gun. Great for removing adhesives & heatshrinking. 650°C max. Refillable. Add butane gas for $9.50 (T2451). SAVE 15% 30 $ GREAT Hands free, VALUE! head worn magnifier. Offers convenience and plenty of power for the enthusiast with precise dial control and temperature lock. In-built sleeper stand shuts down the unit when not in use saving on power costs. Includes a fine 1.2mm chisel tip, solder reel holder and tip sponge. Thousands sold! Offers 1.5, 2.6 and 5.8x magnification with LED lamp. Requires 2xAAA batteries. Hot seller! Over 1000 sold. SAVE $26 99 $ T 2040 Ultimate Helping Hands SAVE 22% T 2183 SAVE 24% 27 $ 15 $ 106 Pc Precision Driver Set An affordable do-it-all servicing set with 92 4mm chrome vanadium bits, flexible extension bar, tweezers & magnetiser ring. For repairing phones, laptops & more! T 2356 Handy Rotating PCB Holder Work on boards up to 200 x 140mm. Metal base provides a sturdy work platform. This space efficient work station packs in loads of features, including 4 flexible T 1462 clamp arms, solder SAVE $5.95 reel holder, dry tip cleaner, container $ of flux. 29 Your electronics supplier since 1976. Shop in-store at one of our 11 locations around Australia: WA » PERTH » JOONDALUP » CANNINGTON » MIDLAND » MYAREE » BALCATTA VIC » SPRINGVALE » AIRPORT WEST QLD » VIRGINIA NSW » AUBURN SA » PROSPECT Sale ends March 31st 2025. Build It Yourself Electronics Centre® DIY Maker Parts. Great for CNC projects Z 6491 NEW! NEW! NEW! 19.95 19 $ .95 $ $ Motor Speed Controller. 5-22A PWM MOSFET control board for wide range of DC motor control projects. Z 6490 Arduino CNC Shield NEW! 9 .95 24.95 $ Z 6496 Stepper Motor Driver A4988 DMOS microstepping driver carrier with soldered header pins & heatsink. Up to A4988 stepper motor carriers can be plugged into this shield for control of engravers and cutters etc. Z 6493 16 Channel PWM Servo Controller. Allows you to control up to 16 servos using only 2 pins via I2C communication. 6 $ .80 NEW! Z 6489 9 NEW! $ .95 Turn a USB charger into a power supply. Allows you to connect to a USB PD power supply and output 5, 9, 12, 15 or 20 Volts. Z 6492 STM32 F103 Dev Board 19.95 $ Ideal platform for learners and developers looking to explore and master the STM32 microcontroller based on the ARM Cortex-M3 32-bit core. Includes headers. Z 6434 RP2040-Zero Dev Board A low-cost, high-performance Pico-like MCU board based on Raspberry Pi RP2040 microcontroller. Compact & feature rich! SAVE 24% 25 Z 6387 $ ESP32 Camera Board An ultra compact ESP32 based module with on-board camera, BT BLE & 802.11n Wi-Fi. 5V input. NEW! Z 6427 11 $ Z 6497 NEW! Z 6317 9 12V input with single 10A relay for on/off control. -30 to +110°C range with 0.1°C accuracy SAVE 22% 19 $ 14 .95 $ $ .95 Precision Temp Controller NEW! Temperature & Humidity Controller A 2 channel board which activates a connected load at preset temperature (-20 to 60°C) or humidity (0-100%). Runs off 12V DC with 10A relay outputs. Wi-Fi ESP8266 Relay Module J 0085 Water Flow Sensor A handy Wi-Fi activated 3A relay module for wireless switching applications. 3.3V input. Connects to 1/2” pipe connectors to provide water flow sensor readings using a hall effect sensor. 5-18V DC working voltage. J 0080 NEW! Z 6316 27.95 $ Bluetooth Relay Board Dual 12V 10A relay and control board with the ability to switch on and off loads using eWeLink app on your phone. Z 6319 NEW! SAVE $10 29.95 $ Digital Temperature Controller The STC-1000 controller is a 12V DC heating/ cooling controller allowing you to activate or deactivate loads up to 10A. Includes 1m sensor. SCAN TO FOLLOW US! Stay up to date on latest releases, exclusive specials and news on our socials. 29 $ Twilight Switch NEW! 19.95 $ A 0724 Allows you to automatically activate lighting at night. 12VDC input. 24V 3A max load. Liquid Dosing Pump 12V peristaltic type pump for delivering up to 100ml/min. Great for automated irrigration and more! Like our service? Review your store on Google. Every review helps us serve you better. Workspace Buys. SAVE $26 99 $ T 2690A 30W SAVE $40 Includes bench stand and tip cleaner! 159 $ T 2418A Upgrade your old clunker iron! This excellent multi purpose 80W soldering iron is ideal for service technicians, schools, engineers, R&D, production work etc. Fitted with Japanese long life ceramic element. 200°-480°C. 0.8mm tip. 2 year warranty. Go Anywhere Lithium USB Soldering Iron 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 - or USB battery bank. Includes replaceable 18650 battery. Goodbye eye strain! LED Magnifier for micro tasks Why pay $300 for a MaggyLamp? The inspect-a-gadget illuminated desk magnifier is an absolute bargain at under $70, we believe ours is every bit as useful. An incredible visual aid for detailed inspection and work on fine items with full clarity through the quality glass lens. Tackle complex miniature tasks with confidence! $15 OFF THIS MONTH! 60 $ X 4204 3+12 Dioptre 65 $ X 4205 5 Dioptre T 2125 T 2128B SAVE $30 SAVE 20% Workshop essential. 99 $ 55 $ T 2306 SAVE 25% 20 $ Great for crafts and hobbies too! Repair faster with a lithium screwdriver. This Jakemy® USB rechargeable screwdriver has a fully adjustable torque drive for fast and accurate driving of precision screws found in modern high tech devices. Two way direction control. 4mm driver bits (21 included). 4 hrs use per charge. See web for full contents list. Pro 72 Piece Servicing Kit Premium HSS-R Drill Bit Set 19pcs between 1-10mm for plastic, wood & metal. Metal storage case. SAVE 10% T 2164A A premium quality driver set with a huge variety of driver 4x28mm driver bits, opening tools, spudger, curved tip tweezers and flexi extension. Includes bit types for latest phones & laptops. 20 $ Micron® USB Lithium Rotary Tool Set Drills, cuts, sharpens, cleans, polishes and engraves most surfaces, this rotary tool is ideal for enthusiasts, hobby makers, or just odd jobs around the house. 5 speeds from 5000 to 25000RPM. USB C recharge with 60 mins operation. 42 accessories included. T 2188 T 4021 SAVE $15 40 $ SAVE 20% 40 $ 1000V Screwdriver Set Smaller sizes than most 1000V driver sets. 3 flat blade (2.0, 2.5 & 3mm) & 3 phillips (#000, #00, #0). Jumbo Anti-Static Bench Mat This ESD safe matting is a workbench essential! Generous 1mx0.5m size with anti-static wrist strap. NO STRESS 30 DAY RETURNS! GOT A QUESTION? Not satisfied or not suitable? No worries! Return it in original condition within 30 days and get a refund. Ask us! Email us any time at: customerservice<at>altronics.com.au Conditions apply - see website. Light Savers. Rechargeable USB Sensor Light SAVE $10 Adjustable LED panels 39.95 Three colour & dimmable! A handy 40cm sensor light with in-built USB rechargeable battery. Great for wardrobes & cabinetry. 30 second on time. Detaches for recharging. $ X 2384 SAVE 25% 22 $ X 2386 4W 500 Lumen X 2387 7W 800 Lumen LED Solar Sensor Lights Add instant security to your place with these weather resistant solar lights! Shed some light on pathways, driveways, gardens and patios. Require no wiring and are IP54 rated for use outdoors - plus stainless steel rust resistant hardware. 3 dusk activated lighting modes. Great night light for kids! 39.95 $ Lights up to 80sq/m with this powerful multi panel 600 lumen LED light which requires no wiring and is powered by the sun! IP65 rated. 30 $ SAVE $10 Super Bright Cable Free Solar Security Light SAVE 24% X 2396 X 2388 44.95 $ 40 25 SAVE 26% X 2385 SAVE 30% 39 SAVE $9.95 $ 2 for $ X 2390 $ X 0213 SAVE 26% Wall Mountable 6W Solar Outdoor Light This powerful solar light needs no wiring. Ground spike or wall mount. Flood/spot modes. 6-7hr run time. IP67 rated. 2 for $ 29.95 22 $ X 2391 X 2389 Caravan Oyster Lights Outdoor Solar Lights Weather resistant 12V input LED lights. Pure white 5500K. X2390: 180mm. X2391: 125mm with switch. Handy 3 in 1 Torch & USB Battery Bank Ideal for camping, roadside emergencies and a variety of uses around the home. It can be used as an LED lantern, torch, emergency light and USB battery bank for keeping devices charged when camping. 4800mAh internal battery. Provides low level lighting for steps, paths and decks. Turns on automatically at night. X2388: 109Øx22mm. X2389: 100x88x50mm. 20% OFF Neon Flex Rope Lighting. Use it in long lengths for stunning coloured lighting effects or cut and shape into your own custom “neon” signs. Super flex design for tight radius bends, IP65 weather resistant. See web for full range and pricing. SAVE 24% SAVE 15% 15 25 $ X 0203 $ X 0204 X 3229 X 0212A SAVE 15% SAVE 20% 2 for $ 33 USB Dual LED Head Torch Weather resistant, USB rechargeable, & 120 lumens for JUST $15! Why pay $50 or more? 29 $ Wardrobe Sensor Light Kit Aluminium USB Torch Genlamp® Pro Head Torch At less than $20 you can afford to put these 4xAAA battery powered sensor lights in every cupboard! 1m length. Durable all metal 5 Watt USB rechargeable torch. Can be used as an emergency power battery bank. 182mm long. A camping essential! 280 lumen spot + 220 lumen flood beam. USB C recharging. Sale Ends March 31st 2025 Shop in-store at one of our 11 locations around Australia: WA » PERTH » JOONDALUP » CANNINGTON » MIDLAND » MYAREE » BALCATTA VIC » SPRINGVALE » AIRPORT WEST QLD » VIRGINIA NSW » AUBURN SA » PROSPECT Or find a local reseller at: altronics.com.au/storelocations/dealers/ Shop online 24/7 <at> altronics.com.au © Altronics 2025. 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. B 0003 Subscribe to FEBRUARY 2025 ISSN 1030-2662 02 The VERY BEST DIY Projects ! These plus more in this month’s 9 771030 266001 $13 00* NZ $13 90 INC GST INC GST magazine: Programmable Frequency DIVIDER COUNTER 300Hz – 77MHz input freque ncy range | 85,000 division ratios | USB programmabl e High-Bandwidth Differential Probe Battery-powered, ideal for use with oscilloscopes Measure signals up to ±400V from Earth 100:1 or 10:1 ranges 30MHz/25MHz bandwidth IR Remote Control Australia’s top electronics magazine with NFC programmaing Keyfob Compact keyfob case which can attach to a keyring Sends up to three IR commands in NEC, Sony or Philips RC5/RC6 formats. Commands can be changed via NFC. Silicon Chip is one of the best DIY electronics magazines in the world. Each month is filled with a variety of projects that you can build yourself, along with features on a wide range of topics from in-depth electronics articles to general tech overviews. Published in Silicon Chip If you have an active subscription you receive 10% OFF orders from our Online Shop (siliconchip.com.au/Shop/)* Rest of World New Zealand Australia * does not include the cost of postage Length Print Combined Online 6 months $70 $80 $52.50 1 year $130 $150 $100 2 years $245 $280 $190 6 months $82.50 $92.50 1 year $155 $175 2 years $290 $325 6 months $100 $110 1 year $195 $215 All prices are in Australian dollars (AUD). Combined subscriptions include both the printed magazine and online access. 2 years $380 $415 Prices are valid for month of issue. Try our Online Subscription – now with PDF downloads! High-Bandwidth Differential Probe; February 2025 40A 5MHz Current Probe; January 2025 HiFi Headphone Amp; Dec 2024 & Jan 2025 An online issue is perfect for those who don’t want too much clutter around the house and is the same price worldwide. Issues can be viewed online, or downloaded as a PDF. To start your subscription go to siliconchip.com.au/Shop/Subscribe Part 1 by Phil Prosser POWER LCR METER While we have published plenty of LC and LCR meters over the years, this one is quite different. It can deliver up to 30A to inductors to determine their properties at higher power levels. That makes it particularly useful for determining when and how an inductor saturates. It can also measure very low resistances and very high capacitances. I nductors are the easiest of the basic components to make yourself. This is typically done by winding enamelled copper wire around a core or former. For air-cored inductors, you’re generally only worried about the inductance (which can be measured with an LC meter) and DC resistance (measured with a low-ohms meter). It’s quite a bit more complicated for inductors with a core, though. Cores are typically made of ferrite, compressed powdered iron or mu metal, and they all behave quite differently at higher current levels. As the current through the inductor increases, eventually the core saturates and the inductance drops. This meter will let you determine at which current the inductance starts to drop off and how fast it drops off. It isn’t just handy for self-wound inductors; any that you recover from a piece of equipment will likely have unknown properties – this device can erase that mystery. It can also measure very high capacitances and low DC resistances, which is handy for characterising the series resistance of any inductor, including air-cored types. As an example of when this device might come in handy, if you use a ferrite or iron-cored inductor in a loudspeaker crossover, its inductance will fall as the current through it increases Power LCR Meter Features & Specifications » Measures capacitance from 50nF to more than 1F » Measures resistance from 1mΩ to 300Ω » Measures inductance from 50μH to 1H+ » Measures inductance saturation from 10μH to 1H at up to 30A (limited by internal resistance) » Optional Kelvin probes for measuring low resistances » Power supply: 12-20V DC at 1A 28 Silicon Chip Australia's electronics magazine past its saturation point. The result of this is non-linear behaviour that will be heard as distortion. High-quality speakers use air cored inductors because they do not suffer this problem. However, large inductors in speakers still often have ferrite or iron cores to manage cost, and the bulk and high resistance of a large coil of wire. Another common application of power inductors is in switch-mode power supplies. At high currents, saturation in the core can reduce the inductance and degrade the performance of the power supply. While this tester will not characterise inductors at high frequencies, it is unusual in that it allows characterisation of inductors at very high currents, up to about 30A. Our Power LCR Meter measures inductance, resistance and capacitance for larger power devices. For measuring low resistances, it will push up to 1A through the resistor, although only for a very short time. This is not a general-purpose meter; it is for those chunky passives you are considering for your switch mode power supply, Class-D amplifier siliconchip.com.au output or loudspeaker crossover. It will give you insight into your parts that you won’t find in many other testers. Operating principles Rod Elliot describes a circuit that can be used to manually measure the saturation of power inductors on his website at https://sound-au.com/ project250.htm (we’ve seen it elsewhere but his description of how it works is pretty thorough). The problem with that approach is that you need an oscilloscope to make the measurements. This circuit uses an interesting technique to make that measurement, and in the deal we are forced to measure capacitance and resistance as part of the overall system, which makes for an unusual and capable device. The concept is to monitor the transient behaviour after we apply a voltage step across the inductor, analysing the current through and voltage across the device under test (DUT) over time. Pretty much all the similar circuits on the internet that we found use a variation of the simple circuit shown in Fig.1. We will avoid lots of maths here, but the following principles are used in this project. Most of us are familiar with the resistance equation (Ohm’s law): V = IR. The capacitor equivalent to this is C = q/v and its differential is C = (dq/ dt) ÷ (dv/dt). Realising that dq/dt is simply current, we have C = I ÷ (dv/ dt). For inductors, the equivalent formula is L = V ÷ (di/dt). This circuit uses the property that if we turn that driving Mosfet on and apply 1V across a 1H inductor, we can expect to see the current increase at 1A per second. Similarly, if the inductor is 100μH and the rail voltage is a 10V or so, then we get the formula 10-4H = 10V ÷ (di/dt), so we can expect di/ dt to be 105A/s or 100mA/μs. For a 10μH inductor with 10V applied, we can expect a rather lively 1A/μs rate of increase in current. This means that we will have to switch the Mosfet off pretty quickly after it turns on, or be ready to handle some very high currents after a few millionths of a second! By measuring the rate of change of current through the inductor, we can measure its inductance. If we measure that repeatedly at a series of points on siliconchip.com.au that current curve, we can monitor how the inductor behaves at different currents. Neat! Rod Elliot makes a case that running this manually with a programmable pulse generator makes sense. We found ourselves in a situation somewhat akin to the serviceman looking at a broken widget that probably ought to be thrown in the bin. The temptation to ‘have a go’ at automating the measurements was irresistible. Challenges this presents include: 1. Inductors have resistance, which really messes up the measurements if you ignore it. 2. The precise voltage across the DUT is important; if it droops during the measurement, you need to know by how much, or your results will be inaccurate. 3. It has to work over a wide range of inductor values and sizes. 4. We should ideally make sure that if someone connects an unexpected component, it won’t explode. 5. How do we make measurements of a process that can be over in 50 millionths of a second, and even get multiple results in that short a time? 6. If we have an inductor being tested with 30A flowing through it, we have the potential for a massive backEMF spike with significant energy once the test finishes. Those first three challenges mean that this meter needs to be able to Fig.1: the basic principle of measuring inductance at various currents. A brief pulse applied to the Mosfet gate results in the voltage source being applied across the DUT, resulting in a current ramp through Rshunt that can be measured. The inductance can be calculated from its slope. accurately measure the resistance of the DUT and also the test voltage applied, as this is essential to get a good measurement of the inductance. This meter needs to be able to tell whether the DUT is a capacitor or not. Only after determining these things can the meter then run the saturation current test. To measure resistance and capacitance, we can use a current sink in a fairly conventional way, which involves driving a constant current through the device under test, not a constant voltage. Dealing with the back-EMF that will be created when we switch off There are a few parts on the PCB but it isn’t overly complex. The second large capacitor is optional and zener diode ZD13 is not required on the final board. Australia's electronics magazine March 2025  29 the Mosfet drive after an inductance test requires a reverse diode across the DUT. As it turns out, our circuit needs a Mosfet there to discharge capacitors while testing them, so we can use a P-channel Mosfet to deal with this. With a bit of head scratching, we arrived at an arrangement that allows us to parallel the high-current saturation drive Mosfet with a constant current sink that’s used for resistance and capacitance tests. Since we have a system to measure resistance and inductance, and also to sense whether the DUT is a capacitor or not, we might as well measure what the capacitor value actually is. In Fig.1, the Mosfet basically shorts the DUT across the 10V supply rail. If we leave it inactive, we can dial up a current on a programmable current sink to make those other measurements. This leads to the arrangement shown in the block diagram, Fig.2. The key system components are: • A power supply capable of delivering 10V at up to 30A for brief periods • The DUT • A Mosfet that can connect the DUT between the power supply rail and the current sense circuitry. This includes a hardware-based current limiter. • A discharging Mosfet that can apply a load across the DUT. • A programmable current sink. • Differential current and voltage sensing circuits for the DUT. • The PIC32MK0128MCA048 microcontroller to manage all this (in a 48-pin TQFP package). The PCB includes headers allowing the trigger timing and DUT current to be monitored on an oscilloscope so you can look at those waveforms, but the microcontroller samples all relevant signals and provides measured results. To see the waveforms on an oscilloscope, you need to set it on single shot and run a measurement, as we describe later. The power supply operates from a DC plug pack. This is nominally 12-20V at 1A. The average current draw is not great, but tests will demand up to 1A from time to time. The software implements four distinct algorithms, for measuring resistance, capacitance inductance and the saturation of an inductor (plus low inductances). Measuring resistance In this mode, the Mosfets are left off and the constant current sink is switched on at ~10mA. We have two channels that can monitor the voltage across the DUT, one with a gain of 20 and one with unity gain. We can measure up to 3.3V across the DUT, which is a maximum of 330W at 10mA. The software looks at the value determined by the voltage, and if the resistance is less than about 30W, it increases the current to 100mA. If the resistance is below about 15W, the high gain channel is used with a current of 10mA, and so on through to Fig.2: in addition to the Mosfet to switch voltage across the DUT, a second one can be used to discharge it (in case it is a capacitor). The programmable current sink allows for lower-current testing, with a DAC controlling the current level. Two differential amplifiers are used to monitor the voltage across the DUT and the current through it (via the voltage across the shunt). 30 Silicon Chip Australia's electronics magazine the meter driving 1A with a high gain. At 1A drive with high gain, the maximum value is 0.165W (165mW) and with the 12 bits of analog-to-digital converter (ADC) resolution, we should be able to resolve under 1mW. You will need to be using the Kelvin probes to measure resistances down at this level. The precision of these measurements is a result of the current sink and its calibration, the differential amplifier, the Kelvin probes and the ADC itself. If you are reasonably careful with your current calibrations and use 1% resistors, you will see accuracy in the region of a few percent. Measuring capacitance The software can use the same constant current sink along with the discharging Mosfet to determine if there is a capacitor on the DUT terminals. It does this by discharging the DUT by shorting the terminals, then feeding current to the DUT for a short period, then monitoring the voltage across the DUT after this current is removed. If the DUT is a resistor or inductor, the voltage will rapidly fall to 0V. In fact, for an inductor, the back-EMF will generate a negative voltage across the DUT. If the DUT is a capacitor, it will hold charge and the software will see this positive voltage. We can control the magnitude and duration of the current applied to the DUT, and we have a pretty decent ADC that can measure the voltage across it. So the software can also read the capacitance. To achieve this, the positive terminal of the DUT is connected to the positive rail and the current sink draws 10mA from the negative terminal. At the same time, the software switches the Mosfet across the DUT switches on. This discharges the capacitor we are measuring and also provides a path for the 10mA to flow. After the current sink has stabilised, the software clears its measurement buffer and starts sampling at the maximum sampling rate of 3.75Msa/s. The software then switches the DUT discharge FET Mosfet off, allowing the DUT to start charging. If the capacitor exceeds a predefined voltage, the software stops sampling, switches the current off and discharges the DUT. The data in the measurement buffer is similar to an oscilloscope trace of the capacitor (DUT) voltage. As shown in Fig.3, the software looks for two points siliconchip.com.au on this charging trace, V1 & V2. It also counts the number of samples between them (T1 & T2). From this, we can calculate dv/dt = (V2 − V1) ÷ (T2 − T1) and, knowing the current applied, we can calculate the capacitance from C = I ÷ (dv/dt). This technique is a bit limited because, with 10mA flowing, a capacitance of 50nF will have a dv/dt of 10-2A ÷ 5 × 10-8, which is 0.2V/μs. Our ADC has a full-scale voltage of 3.3V, which means that the total charging time is about 16μs. Our dv is actually 2.2V if you dig into the software, which means dt is 11μs. At 3.75Msa/s, this is only 41 samples. Further, the power devices in the circuit have some pretty substantial self-capacitances that we have to calibrate out in software. So we have settled on 50nF as a practical lower capacitance limit. What happens if a big capacitor is connected? Our software data buffer is 12,800 samples long, which means we can measure a capacitance with dv = 2.2V and dt = 12,800sa ÷ 3,750,000sa/s or 3.4ms. This gives a maximum capacitance of 15μF or so. Luckily, our software can look at the measurement buffer and see that we have not achieved our preferred V2 threshold, then reduce the sampling rate and rerun the test. Sampling rates of 3.75Msa/s, 375ksa/s and 37.5ksa/s are used. If a big capacitor is being tested, we can then increase the test current to 100mA and then 1A. This gives us an upper measurement limit of 1.5F. Discharging a huge capacitor from 2.2V down to 0V requires a little caution. The software does this by pulsing on the Mosfet across the DUT, starting with 1μs pulses and increasing them until the Mosfet is fully on. This is intended to discharge large capacitors without creating massive current spikes. Similar to the resistance measurement system, the resolutions of these measurements are good. Parasitic capacitance, slew rate limitations and suchlike limit the precision below about 100nF. From there up, the meter will provide a measurement accuracy of a few percent. Measuring inductance The meter has two approaches to measuring inductance. Both use the property of applying a voltage to the siliconchip.com.au Fig.3: measuring a capacitor value involves first discharging it, then applying a fixed current and measuring the rate of voltage rise. Fig.4: measuring inductance is similar to capacitance, except that we are applying a fixed voltage and measuring the rate of current rise. DUT and measuring the rate of change of current. The simple inductance measurement uses the constant current sink. As shown in Fig.4, it is similar to how we measure capacitance in that we start by setting up the constant current sink with the DUT discharge FET switched on. Then, when we are ready, we switch it off and monitor the voltage across the inductor (DUT) and also the current flowing through it. Keep in mind that the “constant current sink” is really a current-limited constant voltage. That means the current sink is saturated and switched on hard right until the end of the test. We have chosen this approach for initial inductance measurement as we know that the current will be controlled to the limit set by the constant current sink. If a user attempts to test an extremely low inductance, or a short circuit, the DUT will be subjected to a brief current pulse that grows to 1A and runs for no more than 12,800 samples at 3.75Msa/s, or 3.4ms. An inductor’s key property is that it ‘resists’ changes to the current flowing through it, hence that di/dt = V/L property. So what happens if we switch a constant current sink on across an inductor? The current starts at zero, then immediately after the shorting Mosfet is switched off, the current is still zero. The constant current sink is on hard, applying the full 10V across the inductor, with no current (yet) flowing. Remember that equation, di/dt = V/L? Now V = 10V, and the current through the inductor grows at a rate set by the inductance. This increase in current continues linearly. Once the current through the inductor reaches the current sink’s set point, it starts throttling back to maintain the current at a constant value. So di/dt goes to zero, and the inductor current is constant, with notionally 0V across the inductor. Our software in this test captures a series of readings of both the voltage across the inductor and the current being through it. The software switches the current measurement ADC to high-gain mode, which uses a 1W shunt. We start with the maximum sampling rate, which allows us to measure the smallest inductors. On this test, the minimum practical measurement is about 50μH, which results from the 1A test current; di/dt = 10V ÷ (50 × 10-6H), which is 0.2A/μs. Our cutoff current is 1A, so we get 5μs of data before the current limit is reached. The op amp takes a while to respond and the current overshoots quite a lot, so we actually get somewhat more than this to work with. If you have a smaller inductor, the saturation test mode (see below) will measure down to about 10μH. We capture two sets of data: the voltage across the inductor and the current through it. Similar to the capacitance test, when the voltage across the inductor transitions from close to 0V to full-scale on our ADC, we know the pulse has started. When this voltage falls again, we know the maximum current has been achieved. If the software does not find the voltage falling before the end of the buffer, we know we need to reduce the sampling rate. The minimum sampling rate is 37.5ksa/s, which allows a minimum di/dt of 0.29A/s (0.1A ÷ [12800sa ÷ 37500sa/s]). This allows Australia's electronics magazine March 2025  31 the measurement of very high inductances, in the Henries range. The software uses only the mid-­ section of the current vs time curve to calculate the inductance, between 25% and 75% of the buffer. This means this inductance test result is at about 0.5A. The voltage across the inductor might not fall right down to 0V once the current through the inductor reaches the limit because real inductors have resistance. If there is a DC resistance of say 1W, once we reach 1A, there is 1V across the inductor. We can easily get around this in software by changing our detection threshold voltages. However, the voltage drop across that internal resistance affects the measured inductance. We need to consider the internal resistance of a component like an inductor as a property of the device. We can represent a real inductor as several ideal components, as shown in Fig.5. We ignore R2 in our meter, as this is the equivalent of a resistance ‘shorting’ your windings. In real-world circuits, especially tuned LC filters, such a resistance may be intentionally added to dampen the circuit, but it is generally not significant in normal devices. Fig.5: even ignoring core saturation, a real inductor can be modelled as four ideal components. It’s the selfcapacitance that is most troublesome. Fig.6: the current can rise higher than would be expected based on a lowcurrent test due to core saturation. The software takes this into account. 32 Silicon Chip C1 is a ‘lumped parallel capacitance’. This is most commonly the result of capacitance between the windings in a coil; an iron-cored inductor can also have capacitance between the windings and the core. Our meter does not seek to correct for this in the measurement, as the errors resulting from it are not significant. However, we see the impact of this when we apply a voltage across large coils, as the parallel combination of C1 and L1 causes visible ringing in the current in some cases. If you look at the data sheet for a commercial inductor, you will often see a ‘self resonant frequency’ figure; this capacitance plays in that characteristic. You can see some of this ringing in Scope 1, right at the start. This plays havoc with inductance estimation! R1 in Fig.5 is significant. This is the internal resistance we are concerned about. Our equation for di/dt = V ÷ L applies to only L1 in the figure; the voltage dropped across R1 is excluded from this. As the current flowing in the coil creates a voltage drop across the internal resistance, the effective voltage across L1 decreases. For a real coil, di/dt reduces as the current increases. This is clearly visible for a large air-cored inductor, which has a DC resistance of 0.46W, shown in Scope 2. When measuring inductance, the first thing our software does is to measure the DC resistance of the DUT. When calculating the inductance of the DUT, the software uses this as a correction factor; with some inductors, this correction is very significant. Measuring inductor saturation The saturation test will give you insight into the inductance’s behaviour as a function of current. This test uses the same principal as above, but this time we are not using a constant current sink. Instead, we will be connecting the DUT directly across the two 47,000μF capacitors using the main switching Mosfet, with our hardware current detector switching the Mosfet off when our pre-­programmed limit is reached. Again, the first thing the software does is to measure the DC resistance of the DUT. This is crucial, as the DC resistance tells us the maximum current that can flow through the DUT with our 10V across it. The software selects the current limit as 50% of Australia's electronics magazine the theoretical maximum, as for highvalue inductors, we expect the 47mF capacitors to discharge significantly during the test. The software then measures the inductance of the DUT using the constant current technique. This gives us a pretty optimistic value of inductance at high currents for all but air-cored inductors. The software uses this to calculate the time required for this inductor to reach the peak test current, and the sampling rate is adjusted to fit this into our sample buffer. Fig.6 shows what is happening here. The software then checks to see if the user has a capacitor on the DUT terminals. While we never managed to damage anything during development, it isn’t a great idea to suddenly apply 10V to a potentially large capacitor. The ADC inputs are set to monitor the high-current (low gain) measurement, which can measure up to 33A, while the second ADC channel monitors the 10V rail, which we know will droop throughout the test. From a first run, the software looks to see if the sampling rate was OK. If the DUT has saturated early, we increase the sampling rate to get a closer look at the saturation curve. So a second set of samples is taken with an optimised sampling rate, which fills our buffer with usable data. Once we have this data, the software splits this into 10 sections and calculates the inductance for each of the 10 regions. This set of results is stored to allow the user to scroll through. Our ADC has 12 bits of resolution, which gives a maximum of 4095 discrete current measurement values. If we had more than about 10 time slices, our current measurements would introduce quantisation errors and any noise on the measurements would become more significant. On the other hand, with fewer slices, we wouldn’t get as good an idea of the inductor’s behaviour. We decided that 10 readings is the best compromise. We initially intended for the software to estimate the saturation current from this data. If you take a look at some of the sample curves we provide later on, you might get a sense of the challenge this presents. The shape, rate of collapse of inductance and all sorts of ‘interesting’ effects would need to be considered. We were concerned that if the software throws up a guess, it will take siliconchip.com.au on a credibility it does not deserve. A human can scroll through the numbers and easily see where the inductance rolls off and how fast it falls. The software sets the second measurement to “100%” as it is normally the cleanest data point, and all others are relative to this. 11.2A. This shows the inductance starts somewhat above the rating and falls relatively slowly. That glitch on the initial application of the test voltage is from inter-winding capacitance, and demonstrates why we do not try to measure inductance from the start of the sample set. Real measurement examples Circuit details Let’s look at why saturation matters in inductors. We will include some plots of the inductors we used in testing this device, as the behaviours illustrate not only why this parameter is important, but also why it is hard for the meter to give a simple answer to this value. In each of the following oscilloscope plots, the blue/cyan curve is the current, which is at a scale of 100mV per amp. So 3.3V is the full scale of the ADC at 33A. The yellow trace is the trigger signal. The duration of these sweeps all vary, as that is a function of the DC resistance of the coil, and thus the inductance and the sampling rate the software selects. Scope 1 and Table 1 are for a Bourns 2200LL-470-V-RC rated for 20.9μH <at> 10.3A. It starts with an inductance somewhat above its rating and falls relatively slowly. Scope 2 and Table 2 are for a 1.8μH air-cored inductor. This shows current curving downwards as a result of the DC resistance of the inductor. Scope 3 and Table 3 show the values for a 550μH air-cored inductor. There is some variation in the measured inductance; given this is an air cored inductor, this is due to measurement errors in the meter. Scope 4 and Table 4 are for the secondary of a Dick Smith M-2156 transformer. This is typical of the saturation in a soft-iron-cored device. The measured values show the remarkable collapse in inductance past saturation. Scope 5 and Table 5 are for an Altronics L6630 470μH 5A inductor. This shows that this device behaves as specified at the rated current, but the initial inductance is substantially higher, and the inductance rolls off in a reasonably controlled manner. That step at the start of the curve is the INA181 differential amplifier slewing to ‘keep up’ with the rate of change; this forms a real limitation on the lower inductance we can measure. Scope 6 and Table 6 are for a Bourns 2200HT-100-V-RC rated for 7.9μH <at> Now that we know how the device works, let’s look at the full circuit. siliconchip.com.au We have broken it up into three separate diagrams that perform logically distinct functions: the test circuitry (Fig.7), the control circuitry (Fig.8) and the power supply (Fig.9). We’ll start by examining the test circuitry, which is where most of the complexity lies. The DUT connects between CON5 and CON6, to the left of centre in Fig.7. This places it between the +10V_FILT high-current supply rail and Q4 & Q5. Current Inductance 2.2A 44μH 3.4A 41μH 4.7A 35μH 6.2A 32μH 7.9A 27μH 9.9A 22μH 12.4A 18μH 15.4A 14.2μH 19.3A 10.4μH 24.4A 7.7μH Scope 1: testing a Bourns 2200LL-470-V-RC inductor rated for 20.9μH <at> 10.3A. Current Inductance 1.0A 1.8mH 1.9A 1.8mH 2.8A 1.8mH 3.7A 1.8mH 4.5A 1.8mH 5.2A 1.8mH 6.0A 1.8mH 6.6A 1.9mH 7.2A 1.8mH 7.8A 1.8mH Scope 2: testing a 1.8μH air-cored inductor with a relatively high DC resistance of 0.55W. Current Inductance 1.2A 555μH 2.4A 559μH 3.6A 570μH 4.7A 566μH 5.7A 559μH 6.6A 575μH 7.5A 544μH 8.4A 512μH 9.2A 582μH 10A 564μH Scope 3; testing a 550μH air-cored inductor with a 0.44W DC resistance. Australia's electronics magazine March 2025  33 Fig.7: the blue text here refers to connections from this circuit to pins on microcontroller IC1, shown in Fig.8. Q4 applies the full +10V_FILT across the DUT when on; if the current gets too high, IC4b causes IC3b to reset, switching Q4 off. Q5 sinks a fixed current determined by DAC IC2. The voltage across the DUT is monitored by IC6 or IC7a and fed to the micro, while IC8 monitors the current (the 1W shunt voltage is also fed directly to microcontroller pin 12). Q4 is the main switch that connects the bottom end of the DUT to ground via the low-value 5mW shunt, while Q5 is the constant current sink, in combination with an extra 1W shunt and op amp IC7b. Q4 is an Infineon IPP013N04NF2SAKMA1. These are relatively inexpensive but only have 1.3mW of on-­ resistance and can carry up to 197A continuously. We don’t suggest you substitute this part, but if you must, most Mosfets with under 10mW of on-resistance and a continuous current rating of at least 50A should be OK. The gate drive for Q4 comes from transistors Q9/Q10, which form a totem pole drive. This buffers the very high gate capacitance of the Mosfet, speeding up the switch-on and switch-off times. Q9 & Q10 are controlled by a 4013 D-type flip-flop (IC3b). 34 Silicon Chip This enables us to switch off the Mosfet rapidly once the current through it exceeds a programmed threshold. To achieve this, we drive the reset pin of our flip-flop from a dedicated comparator (IC4b) which compares the current reading to a programmed threshold. IC2 is an MCP4822 12-bit DAC. One of its outputs (output A, pin 8) drives the negative input of this LM393 comparator, while the current sense line from IC8 (INA281) drives the positive input. The INA281 has a 5% settling time of 1μs, the LM393 has a response time of 1μs, and the 4013 reset-to-Q time is 130ns (0.13μs). The Q output of IC3b controls the Mosfet, so we have an overall delay from sensing the current to switching the Mosfet drive off in less than 5μs. We can program the MCP4822 to produce voltages from 0 to 2V, allowing us to set a current limit from 0 to 30A. Australia's electronics magazine The microcontroller sets flip-flop IC3b using control signals from its RC11 and RC10 pins that are level-­ shifted by transistors Q6 & Q7 and applied to the CLK and D inputs of IC3b, respectively. This allows the micro to set the flip-flop and enable Mosfet Q4, but the reset signal from the over-current detection circuitry can always override this and switch the Mosfet off. Mosfet Q2 is used to discharge the DUT. This is a Vishay SUP70101EL P-channel Mosfet. It is included to allow capacitors to be discharged before testing. It also provides a reverse current path for an inductive DUT at the end of tests. If the voltage across the DUT reverses, up to 30A can flow through the body diode in Q2. This device needs to be able to handle the maximum saturation current, as at the end of a saturation test, Q2 is switched on, and it will carry the full siliconchip.com.au Current Inductance 1.1A 15.9μH 1.5A 10.1μH 2.1A 6.8μH 3.0A 4μH 4.4A 2.7μH 6.3A 2.0μH 8.4A 1.7μH 10.8A 1.5μH 13.1A 1.3μH 15.5A 1.1μH Scope 4: testing the secondary of a Dick Smith M-2156 transformer with a soft iron core (DC resistance of 0.28W). Current Inductance 1.9A 718μH 2.6A 604μH 3.5A 476μH 4.7A 342μH 6.2A 255μH 8.4A 176μH 11.3A 131μH 15A 98μH 19.8A 73μH 25.5A 57.1μH Scope 5: testing an Altronics L6630 470μH 5A toroidal inductor with a powdered iron core. Current Inductance current through its body diode until it decays. This will result in energy being dissipated in Q2. The SUP70101EL is rated at 100A, with an Rds(on) of 10mW. If substituting, we would stick to similar ratings, but this is not an expensive part for what it does. As Q2 is a P-channel device, its gate drive is relative to its positive source terminal, which connects to the +10V_FILT rail. Thus, there is a level-shifter based around transistors Q3 and Q8 that allows us to drive it from a 0-3.3V microcontroller output pin (RD8). Diode D8 speeds up its switch-off. The programmable current sink is included to allow us to measure the resistance of the DUT. We generally want to run this at 10mA, 100mA or 1A. The actual current is programmed by the other DAC channel, output B (pin 6) of IC2. siliconchip.com.au 3.2A 11.8μH * 5.4A 13.6μH 7.5A 13.0μH 9.6A 12.0μH 11.9A 11.5μH 14.3A 10.9μH 16.9A 9.5μH 19.6A 9.3μH 22.4A 8.6μH 25.5A 7.8μH Scope 6: testing a Bourns 2200HT-100-V-RC inductor rated for 7.9μH <at> 11.2A (with a DC resistance of 0.01W). * this low measurement is likely due to inter-winding capacitance The current sink is fairly conventional, with IC7 amplifying the difference between the voltage from IC2 on its positive input with the voltage sensed across the 1W and 0.005W shunt resistors. Running a wide-bandwidth current sink with various inductances as a load is a challenge with stability. The 33nF Australia's electronics magazine feedback capacitor across IC7b helps to keep it stable. The differential current and voltage sense circuits are implemented with INA281B1 instrumentation amplifiers (when a higher gain is required) and TLC072 op amp for low-gain (unity) differential voltage measurements. These differential amplifiers all have March 2025  35 their ground references tied to the VREF− pin used by the ADC. The TLC072 was chosen in preference to the more common TL072 due to its lower DC offset. Using differential amplifiers allows us to remove common-mode signals on the +10V_FILT rail, which we know will droop during measurements, and also remove the DC offset on the DUT voltage. This allows us to make best use of the 0-3.3V input voltage range of the ADC. CON1 provides a way to improve measurement accuracy by removing the voltage drop in the connectors and leads to the DUT from the equation. If CON1 is not used, IC6 measures the voltage across the DUT directly from CON5 & CON6 via 10W resistors. If instead separate wires connect from pin 1 of CON1 to the DUT’s negative lead and pin 2 to the positive lead, any voltage drop between the PCB connectors to CON5/CON6 and the DUT itself will not affect the measurements. The extra test leads will effectively short out the 10W resistors, providing a voltage measurement right at the DUT terminals. Schottky diodes D6, D7, D9 & D10, in combination with 470W series Fig.8: microcontroller IC1 dominates the control circuitry. Results are displayed on an LCD screen connected to CON2, while pushbuttons S1-S4 allow the user to select modes. EEPROM IC5 stores calibration data, while crystal X1 provides accurate timing. 36 Silicon Chip Australia's electronics magazine resistors, protect the microcontroller’s analog inputs from voltages outside the range of 0-3.3V that it can handle. At the same time, zener diodes ZD11 & ZD12 protect the Mosfets from voltage spikes at their gates that could damage them. Half of IC3 (IC3a) and IC4 (IC4a) are not used, so their inputs are terminated to avoid them floating and possibly causing extra noise. Microcontroller circuitry The control circuit is shown in Fig.8. All the lower pins of microcontroller IC1 with arrows and blue labels connect to points in Fig.7. Those points in Fig.7 also have arrows and blue writing showing which microcontroller pin they connect to. In Fig.8, besides the 48-pin microcontroller, we have an alphanumeric LCD screen connected via 16-pin header CON2, four pushbuttons (S1S4) with associated pull-up resistors, an EEPROM (IC5) that’s controlled by IC1 over an SPI serial bus, an 8MHz crystal for accurate timing, an in-­ circuit programming header (CON3) and numerous bypass capacitors. We chose the PIC32MK0128­ MCA048 because it incorporates two 3.75Msa/s, 12-bit ADCs that we can operate synchronously. Well, it has three, but we only use two. These can sample voltages at various pins; we are using five inputs in this project (AN0, AN1, AN3, AN6 & AN13). This microcontroller includes a direct memory access (DMA) subsystem that allows the ADC data to be moved into RAM quickly by hardware inside the microcontroller. This means the PIC32 is only interrupted after 128 samples are captured on each channel, allowing the PIC32 to capture a large buffer of samples at this full sampling rate for us to analyse. This PIC has 32kiB of RAM and 128kiB of flash program memory. We use the majority of the RAM for a large data buffer. In inductor tests, this includes synchronised 10V rail voltages and current measurements. This processor runs at 120MHz and includes an amazing array of peripherals for a chip that costs less than $7. The only thing that is more amazing is how complicated some of these modern processors can be to set up and write software for! The 25AA256 EEPROM is used to store calibration data; just about any siliconchip.com.au Fig.9: the power supply generates five rails from the 12-20V DC input: +3.3VD, +3.3VA, -3.3V, +10V_FILT and +10V. The +10V and -3.3V rails power devices like op amps, +3.3VD powers the micro, +3.3VA is the ADC reference voltage and +10V_FILT supplies current to the DUT. pin-compatible SPI EEPROM will do, as we only use a handful of locations at the bottom of the address range. The three pushbuttons (ENTER/UP/ DOWN) are mounted on the rear of the PCB so they project through the case, near the standard 16×2 character LCD screen. We have stuck to a text display as these are commonly available, and aside from the power and LED connections being inconsistent between suppliers, they are interchangeable. While a graphical display might be nice, it is not essential and would add cost and complexity. It would also complicate sourcing, as there are many similar but incompatible graphical displays available. The support circuitry around the PIC microcontroller is mostly per application notes. There are separate 3.3V digital (+3.3VD) and analog (+3.3VA) rails. The analog rail forms the reference for the ADC, so keeping it clean is important. Power supply Turning now to Fig.9, the 10V rail is generated with an LM2576 switchmode buck regulator (REG5) for reasonable efficiency. Its switching output is filtered by inductor L1 and the 1000μF capacitor on its output to efficiently produce a smooth 10V rail. The output current from the LM2576 siliconchip.com.au is limited to about 1.5A by PNP transistor Q1 and the 0.39W resistor, which together pull the feedback pin of REG5 high if the current limit is exceeded. This is included to ensure that for extended high current pulses, the LM2576’s internal over-current protection is not activated. There are two 10V rails. The one labelled +10V drives the op amps. This is isolated by diode D3 and a 100μF filter capacitor to minimise disturbances on this rail during high-current pulses on the +10V_FILT rail. The +10V_FILT high-current rail is filtered by a 330μH inductor which feeds two 47,000μF 16V capacitors (they are in Fig.7). This very substantial filter has been selected to ensure that even when testing large inductors, the +10V_FILT rail does not droop too much. Diodes D1 & D2 form a charge pump with the two 10μF capacitors to generate a negative voltage from REG5’s switching node, which is regulated down to -3.3V by REG3 (LM337). This allows our op amps to handle signals right down to 0V. The +3.3VA and +3.3VD rails are generated from the 12-20V input by identically configured linear regulators REG1 & REG2. We can get away with this since there isn’t a huge demand for current on those rails. Australia's electronics magazine During calibration, we measure the 3.3VA rail voltage. This is important as any error in this voltage will translate to the measurement errors. The LP2950 regulators have an inherent accuracy of about ±1%. We recommended using the LP2950ACZ-3.3G but the non-AC version is available from local stores with only slightly reduced specs. Calibration will take care of that. Bulk capacitance Using two 47,000μF capacitors seems pretty generous but if we want to test a 10mH inductor at 20A, these capacitors need to deliver ½LI2J of energy, which is 2J (0.5 × 0.01H × 202A). This energy can only come from the capacitors, as the LM2576 can only deliver an amp or so. At 10V, our two capacitors store ½CV2J = 4.7J (0.5 × 0.047F × 2 × 102V). If we take 2J from these capacitors and put it in the inductor, the voltage rail will drop from 10V down to 7.6V or so. We can test much larger inductors than 10mH, but our design assumes that they will be tested at lower currents, which we think is reasonable as such a large inductor will have a fairly high DC resistance. This DC resistance will limit the maximum current. By the way, 2J is quite a lot of energy. Do not touch the DUT during testing, March 2025  37 and do not disconnect it while the test is running, as the back-EMF from such a large amount of energy will generate a very high voltage if it is disconnected while current is flowing. The substantial P-channel Mosfet on the board handles this back-EMF at the end of each test. If you disconnect the DUT from the tester during operation, this current path for back-EMF will be removed, which will result in a very high voltage spike. This could deliver a serious shock if you are touching the DUT terminals. An industrial electric fence delivers 2-5J, which is sufficient to dissuade the most stubborn animals. You really do not want to experience that! So much software The real functionality in this meter is all in the software. While we’ll discuss it in broad strokes, you can download the complete source code from our website. So if you are inclined, you can take a deeper look, or perhaps could write your own functions or display routines. The code is written in the relatively low-level C language, as the software needs to run very quickly during testing. C is not too hard to learn, but it does leave a lot of responsibility for the user to get things right. I am a hardware engineer, and the code does kind of reflect this. Still, you will find a structured state machine controlling the meter, drivers for various hardware subsystems, and an effort to implement code in functions to improve its readability. A brief look at the PIC32MK0128 data sheet is also enough to turn your hair grey. It is 562 pages of joy, and a lot of it directs you to sub-data-sheets for specific functions. This project uses multiple timers, ADC channels, direct memory access, SPI modules and general purpose I/Os. For different measurements and component values, the software changes the settings on many of these. Microchip provides a development environment that integrates the compiler, code editor, programmer and debugger. There is also a “Code Configurator tool”, which helps configure the bewildering array of modules in the microcontroller. This is a mix of graphical representation of how parts of the microcontroller interconnect with text boxes that allow you to, for example, program 38 Silicon Chip Parts List – Power LCR Meter 1 double-sided PCB coded 04103251, 156 × 118mm 1 Ritec RP1285 186 × 146 × 75mm IP65 sealed ABS enclosure [Altronics H0310] 1 12-20V DC 1A+ power supply 1 3D-printed LCD bezel (see text next month) 2 PCB-mount M205 fuse clips (F1) 1 1A fast-blow M205 fuse (F1) 1 16 × 22mm TO-220 PCB-mounting heatsink (HS1) [Altronics H0650] 2 330μH 3A toroidal inductors (L1, L2) [Altronics L6527] 3 vertical PCB-mount SPDT momentary pushbuttons plus small button caps (S1-S3) [Altronics S1493 + S1481] 1 vertical PCB-mount SPDT mini toggle switch (S5) [Altronics S1315] 1 8MHz low-profile crystal resonator, HC-49S (X1) 1 20kW top-adjust single-turn trimpot (VR1) 1 16 × 2 wide blue LED-backlight alphanumeric LCD [Altronics Z7018] Cable/wire/tubing 2 200mm lengths of red/black heavy-duty hookup wire 2 200mm lengths of red/black medium-duty hookup wire 1 500mm length of light-duty figure-8 wire 1 200mm length of 16-way ribbon cable 1 100mm length of 3mm diameter black heatshrink tubing Hardware 1 TO-220 silicone insulating washer and bush 4 M3 × 10mm tapped spacers 1 M3 × 10mm panhead machine screw 8 M3 × 6mm panhead machine screws 1 M3 hex nut 9 M3 flat washers Connectors 3 2-pin vertical polarised headers, 2.54mm pitch, with matching plugs and pins (CON1, CON7, CON11) 1 2×8-pin vertical header, 2.54mm pitch (CON2) 1 5-pin vertical header, 2.54mm pitch (CON3) 1 2-way mini terminal block, 5/5.08mm pitch (CON4) 2 6.3mm PCB-mount vertical spade lugs (CON5, CON6) 3 2-pin vertical headers, 2.54mm pitch (JP8-JP10) 3 jumper shunts 1 16-way IDC inline socket 2 panel-mount binding posts, red & black 2 panel-mount banana sockets, red & black 2 chassis-mount BNC sockets 1 panel-mount DC socket (to suit power supply) Integrated circuits 1 PIC32MK0128MCA048 32-bit microcontroller programmed with 0410325A.HEX, TQFP-48 (IC1) 1 MCP4822-E/P 12-bit SPI DAC, DIP-8 (IC2) 1 4013B dual D-type flip-flop CMOS IC, DIP-14 (IC3) 1 LM393 dual single-supply comparator, DIP-8 (IC4) 1 25AA256-I/SN 32kiB EEPROM, SOIC-8 (IC5) [Mouser 579-25AA256-I/SN] 2 INA281B1 20V/V 1.3MHz current sense amplifiers, SOT-23-5 (IC6, IC8) 1 TLC072AIP dual low-noise JFET-input op amp, DIP-8 (IC7) 2 LP2950-3.3 3.3V 100mA low-dropout linear regulators, TO-92 (REG1, REG2) 1 LM337 1A adjustable negative linear regulator, TO-220 (REG3) 1 LM2576 3A integrated buck switch-mode DC/DC converter, TO-220-5 (REG5) Other semiconductors 2 BC558 30V 100mA PNP transistors, TO-92 (Q1, Q10) 1 SUP70101EL 100V 120A P-channel Mosfet, TO-220 (Q2) [Mouser 78-SUP70101EL-GE3] 5 BC548 30V 100mA NPN transistors, TO-92 (Q3, Q6-Q9) Australia's electronics magazine siliconchip.com.au 1 IPP013N04NF2SAKMA1 40V 197A N-channel Mosfets, TO-220 (Q4) [Mouser 726-IPP013N04NF2SAKM] 1 TIP121 NPN Darlington transistor with integral diode, TO-220 (Q5) 2 12V 400mW/1W zener diodes, DO-35/DO-41 (ZD11, ZD12) 4 1N4148 75V 200mA signal diodes, DO-35 (D1-D3, D8) 1 1N5822 40V 3A schottky diode, DO-201AD (D4) 5 BAT85 30V 200mA schottky diodes, DO-34 (D5-D7, D9, D10) Through-hole capacitors 2 47,000μF 16V snap-in electrolytic [Mouser 598-81LX473M016A452] 3 1000μF 25V low-ESR radial electrolytic 5 100μF 25V low-ESR radial electrolytic 6 10μF 50V low-ESR radial electrolytic 16 100nF 63/100V MKT 1 33nF 63/100V MKT 1 220pF 50V ceramic SMD capacitors (all X7R ceramic SMD M2012/0805 unless noted) 2 10μF 10V 3 1μF 50V 8 100nF 50V SMD M2012/0805 2 18pF 50V NP0/C0G ceramic SMD M2012/0805 TH resistors (all ¼W 1% axial unless noted) 2 47kW 23 4.7kW 1 560W 1 330W 1 1W 1W 5% 1 33kW 1 2.7kW 4 470W 4 100W 1 0.39W 5W 5% 1 10kW 2 1kW 1 330W 1W 5% 1 100W 1W 5% 1 0.005W open-air [Welwyn OAR1-R005FI or similar] SMD resistors (all ⅛W 1% SMD M2012/0805 unless noted) 1 10kW 1 1kW 1 470W 2 10W timer periods. This code configurator generates device driver code for each subsystem that you can use in your program. This forms the device driver layer for the microcontroller, making our life much easier. For the external parts like the SPI EEPROM, DAC and 16×2 LCD, we don’t have the luxury of a code configurator, but we can use libraries that we or other people have developed in the past. For control of things like the Mosfets, we wrote simple ‘drivers’ to allow the main program to perform common functions without the complication of directly interfacing to hardware. A good example is the “CORETIMER_DelayMs(X)” function call, which lets our program ask for a delay of X milliseconds. The driver looks after things like clock frequencies and suchlike. Similarly, HDByteWriteSPI() is a function that allows us to write a byte to the SPI EEPROM at a defined location. We don’t care what specific EEPROM it is, as long as we can save data to it and read data from it. By using these high-level drivers in our program, the code is much easier to read and also, once we have tested them, we can treat them as ‘black boxes’. Our top-level algorithm can command the hardware to perform functions such as “Pulse_Start()” without needing to bother with any of the hardware details. You will have noticed there are actually four fairly independent measurement modes. We won’t go into detail here, but from a high level, the main program file “Inductor_Tester.c” performs the main functions: 1. Configures the hardware 2. Loads and saves calibration data 3. Allow the operator to: a. Calibrate the meter b. Measure resistance, inductance, capacitance and inductor saturation c. Display results. These functions all live in a simple state machine that allows the user to select the measurement desired and review the measurements. Next month The PCB mounts on the rear of the lid. Except for the power input, the terminals on the side are optional. siliconchip.com.au Australia's electronics magazine This article has already become quite long, and we haven’t gotten up to the construction, calibration or testing steps yet. We’ll have all that next month, along with some hints on using the device effectively. SC March 2025  39 The Future of our Power Grid Humanity has used fossil fuels as our dominant source of energy since the Industrial Revolution. We are now in the throes of change as we transition to other energy sources. Electrification is increasing, but how will we generate all this power? A ustralia generates the majority of its electricity from coal, as explained in my article in the August 2023 issue on the Australian electrical grid and its generation mix (siliconchip. au/Article/15900). Coal has been a cheap and reliable source of power for a century, but many coal-fired power stations are approaching the end of their designed life and will be decommissioned in the coming years (see the panel). These coal-fired power stations will need to be replaced with new generators. Additional capacity will also need to be built to meet increasing demand from population growth, transport electrification, industry and domestic consumption. Fortunately, Australia can take a pick of the best technologies, as we have some of the world’s most plentiful fuels. This article will consider ‘best’ to be the cheapest generation that meets the Australian Energy Market Operator’s (AEMO) reliability standard: 99.998% or better uptime, or less than 11 minutes per year of blackout on average per person. These costs must include not just the generator itself, but also any required network augmentation, storage, waste disposal, etc. Deliberately excluded are any discussions of indirect costs of generation, such as ecological impacts, population health issues, noise pollution and so on as while they are real, they are difficult to quantify. Coal power stations The most obvious solution to replacing our existing coal power stations is simply to build new ones. In many ways, this makes sense; Australia has some of the world’s largest coal reserves. We also have established mines to extract it, transmission infrastructure already built to carry this power to where it is needed, and an experienced workforce well versed at running this type of plant. It is an approach that has served us well thus far, so why change now? The problem is that coal is an increasingly uncompetitive way to Part 1 by Brandon Speedie generate electricity, driven largely by two factors. Firstly, cheaper variable sources of generation are entering the market. As coal power stations are designed to run all the time with only gradual changes to their output power, it’s challenging to match them to an increasingly dynamic grid. Second, the price of coal is rising. In a little over two years from August 2020 to September 2022, prices increased from $50 per tonne to $430 a tonne (see Fig.1). Prices have since fallen to around $150 per tonne, but that is still high by historical standards. It is for these financial reasons that many coal power stations are facing an early closure, despite still having usable life left. Nuclear power stations At first glance, nuclear fission looks promising as a drop-in replacement for coal. Nuclear power stations operate similarly to coal plants, with large turbines spinning all the time and only slow changes to output power. The Fig.1: the Australian coal price in USD ($) per metric tonne over the last five years. Source: https://ycharts.com/indicators/ australia_coal_price 40 Silicon Chip Australia's electronics magazine siliconchip.com.au power stations could be built nearby or in place of the existing coal fleet, reusing the transmission infrastructure and (with some training) redeploying the skilled workforce. The grid would hardly notice a difference. Australia is also well-suited geologically to nuclear fission-based power. This country has by far the biggest uranium reserves in the world, much of which is served by established mines. Also, the landmass sits in the centre of a tectonic plate, mitigating the risk of a meltdown from a natural disaster. The main problem is inflexibility. Fission power stations typically operate above 90% capacity factor, meaning that they run close to the full rated output power at all times. Much like coal, they are slow to ramp their power up and down, and very slow to restart if stopped completely. This makes them increasingly difficult to match to the grid. Nuclear power is also expensive; assuming a high-capacity factor, it is the most costly generation type of the established technologies. If required to run flexibly (that is, at a lower capacity factor), costs increase further. irradiance of any country, which makes photovoltaics our cheapest way to generate electricity. But solar is highly variable, so it needs to be combined with more expensive technologies to provide stability to the grid. Rooftop solar is being built rapidly, with over 3.4 million homes, businesses and industrial facilities now boasting a solar system. This represents over 20GW of capacity across the eastern states. Grid-scale solar is even cheaper than rooftop due to economies of scale, and also its more favourable yield and generation profile. Grid-scale farms are designed to avoid shading between panels and from nearby structures, which is often not possible on rooftop systems. Most grid-scale farms also have motorised pivots to track the sun. This results in superior energy production per panel, but also a more favourable generation profile (see Figs.2 & 3). The grid is typically shorter on supply at dawn and dusk than during the middle of the day, so grid-scale solar earns better financial returns by tracking the sun and maximising output at these times. Natural gas Wind power Given the trends in fossil fuel prices, natural gas is an increasingly expensive way to generate electricity. However, gas has an advantage over many other generation types, which will likely see it remain part of our energy mix well into the future. That advantage is speed; gas ‘peakers’ can ramp their output power up and down rapidly. This makes them good for ‘firming’: shoring up supply when there is a critical shortfall, or when other generation types can’t respond fast enough. Australia has the world’s 13th largest natural gas reserves, and is the world’s largest exporter, so it is a well-­supplied industry. While natural gas is currently the dominant fuel in this segment, it is possible other types will enter the market. Waste methane from industrial processes, such as waste water treatment and agricultural processing, is increasingly being captured and combusted for generation. Alternative fuels such as hydrogen may also have a future role to play. Australia’s southern states have some of the best wind resources in the world given their proximity to the “Roaring Forties”. Onshore wind has a higher capital cost than solar, but due to its more favourable generation shape and capacity factor, it is able to earn higher revenues. Thus, its overall energy cost levels out to only slightly higher than solar. It is our second-cheapest source of electricity. While wind is less variable than solar, it will also need to be combined with more expensive technologies to ensure grid stability. The economics of offshore wind are much more uncertain. Globally, there are some offshore projects in construction or operation, but they compare poorly to onshore developments due to their high capital cost and maintenance difficulties. Solar power Australia has the highest solar siliconchip.com.au Hydroelectricity Hydroelectricity has a long history in this country; projects like the Snowy Mountains Hydroelectric Scheme are a source of great national pride. Unfortunately, rain is one of the few natural resources Australia doesn’t have much of, being the driest inhabited continent Australia's electronics magazine Coal power plants in Aus. A list of coal power plants in Australia that are either still operating or have been decommissioned recently. Victoria Hazelwood (1600MW): built in 1964, decommissioned in 2017 Yallourn W (1480MW): built in 1975, due for closure in 2028 Loy Yang A (2200MW): built in 1984, due for closure in 2035 Loy Yang B (1050MW): built in 1993, due for closure in 2047 New South Wales Liddell (2051MW): built in 1971, decommissioned in 2023 Eraring (2880MW): built in 1982, due for closure in 2027 Vales Point B (1320MW): built in 1978, due for closure in 2029 Bayswater (2640MW): built in 1982, due for closure in 2033 Mt Piper (1400MW): built in 1993, due for closure in 2040 Queensland Callide B (700MW): built in 1988, due for closure in 2028 Gladstone (1680MW): built in 1976, due for closure in 2035 Tarong (1400MW): built in 1984, due for closure in 2037 Stanwell (1445MW): built in 1993, due for closure in 2046 Kogan Creek (744MW): built in 2007, no scheduled closure date Callide C (810MW): built in 2001, no scheduled closure date but hasn’t operated since 2021 Millmerran (852MW): built in 2002, no scheduled closure date South Australia Northern (520MW): decommissioned in 2016 Playford B (240MW): decommissioned in 2016 Western Australia Collie (340MW): built in 1999, due for closure in 2027 Muja (854MW): built in 1981, staged for decommissioning in 2022, 2024 & 2029 Bluewaters (416MW): built in 2009, no scheduled closure date March 2025  41 Fig.2: the power output (red) of a real-world solar farm with fixed tilt panels. Irradiance is shown in pink. Fig.3: similar to Fig.2 but the solar farm has panels that track the sun. Horizontal irradiance is shown in purple, with panel irradiance shown in pink. Note the increased output at the start and end of the day compared to the fixed system. on Earth. Of the rain that we do get, much is already captured in existing hydro systems. The opportunities that exist are not cost-competitive from the perspective of electricity generation. In fact, many of Australia’s existing hydro projects serve the main purpose of irrigation for agriculture, with electricity as a secondary benefit. For this reason, Hydro is unlikely to see any meaningful expansion in this country. There are several Pumped Hydro projects in construction and development and that sector is expected to continue strong growth. See the later section on storage. The generation mix Looking at generation types in isolation is useful to understand the relative merits and drawbacks of each technology, but the optimum fleet will feature a diverse mix. By combining different fuels, the limitations of some types can be compensated for by others. A good example of this is our historical fossil fuel system, which used coal as the workhorse and gas for load matching. It would be difficult to run 42 Silicon Chip a grid on just coal, and expensive on just gas; a combination of the two gives a more optimal solution. Fig.4 shows a forecast of how the eastern seaboard grid (the NEM) is likely to change from now until 2050. Three scenarios are modelled: “step change”, which forecasts changes to the industry at current rates; “progressive change”, which is a more conservative view of the speed of the energy transition; and “green energy exports”, which is a bullish view that considers Australia becoming an exporter of energy to other nations (mainly through derivatives such as hydrogen or metals smelting). This modelling has some interesting takeaways. Most striking is the sheer increase in capacity. The entire fleet expands six-fold, from the current level of 50GW to just under 300GW. This is driven by increased electricity demand and a shift away from high-capacity factor generation (coal, mid-merit gas) towards low capacity factor generators: wind, solar, flexible gas and storage. Unsurprisingly, rooftop solar is projected to continue its rapid expansion. Australia's electronics magazine From now until 2050, capacity is expected to increase from 20GW to a monumental 100GW. A similar but slightly smaller growth is seen in gridscale solar and onshore wind. Interestingly, this modelling shows a small amount of offshore wind, which is the direct result of a taxpayer funded scheme to build a farm off the Gippsland coast and/or in Bass Strait. If the Victorian government changes their policy in future, this capacity will disappear in the modelling, as the private sector deems it uneconomic. The combination of wind and solar makes up a mammoth 220GW of capacity and will be the workhorse of the future power grid. These two generation types work favourably together because their supply is driven by opposing weather patterns; high pressure is generally good for solar, while low pressure accompanies increased wind. Despite this correlation, there are times when both solar and wind output is low. During these periods, other generation will need to be called upon, so-called ‘dispatchable capacity’, which can be run on demand. The black line in the modelling shows the required dispatchable capacity increasing from the current 40GW to around 75GW by 2050. While the amount of this capacity only increases modestly, its composition changes quite dramatically. Currently, dispatchable capacity is predominantly coal, with smaller contributions from hydro and mid-merit gas (otherwise known as load following gas; not as versatile as flexible gas, but faster than coal). Hydro aside, this composition is projected to entirely change by 2050. Firstly, coal and mid-merit gas reach their end of life and are not replaced by new power stations. Instead, utility storage takes its place, mostly made up of pumped hydro and batteries. There is also a modest increase in flexible gas that can start up rapidly. From around 2030 onwards, an interesting trend emerges. The modelling shows a large increase in ‘coordinated CER storage’. CER stands for consumer energy resources, which are small-scale storage assets like home batteries or electric vehicles with V2G capability (see the July 2023 article for a detailed look at EV charging, including Vehicle to Grid – siliconchip.au/ Article/15857). siliconchip.com.au These assets would be directly controlled to respond to the needs of the grid, typically as a member of a ‘virtual power plant’ (VPP). Most remarkably, AEMO is projecting CER storage will overtake grid-scale storage in overall capacity by around 2045. A smaller amount of ‘passive CER’ is also modelled. These are home batteries and EVs that aren’t directly orchestrated in a VPP, but are still incentivised to respond to grid demands through indirect means like a price signal. While the AEMO doesn’t consider this ‘dispatchable’ by their definitions, it will still support the grid in the same way. Remaining dispatchable capacity is made up of a very small amount of biomass (combustible organics), and ‘demand side participation’, which will be covered in the later section on Demand Response. I believe AEMO is being conservative with their estimates of demand-side participation, and actual dispatchable capacity will be higher. the Electric Grid from August 2023 – siliconchip.au/Article/15900). They are increasingly also being deployed in network support roles, easing transmission constraints (Fig.5) and deferring costly line upgrades. Batteries are also used in voltage control applications, which will be discussed in the later section on reactive power. Given their flexibility to perform in multiple applications and their freedom to be installed basically anywhere, lithium-ion batteries are currently being constructed at a rapid rate. They have recently overtaken pumped hydro as the largest storage in the NEM. Fig.6 shows how one of the major inputs for building lithium-ion batteries has become a lot cheaper over time. There are also some less mature technologies that are worth mentioning. Some early generation ‘flow batteries’ such as vanadium and zinc bromine types are currently operating in the grid. They don’t degrade through charge and discharge cycles like a Energy storage The largest change in dispatchable capacity is a trend away from fossil fuels towards utility and CER storage. While it could be argued that fossil fuels are a form of storage (chemical energy held in carbon bonds, and released when burnt), the phrase ‘storage’ is reserved for technologies that consume electricity and later release it. Historically, this has mainly been pumped hydro, but more recently lithium-­ion batteries have shown enormous growth. In the same way as the generation mix, storage technologies work best when used together. The main advantage of Pumped Hydro is its long duration. While this capacity is often constrained by competing factors such as environmental limits or water supply security, it is cheaper than lithium-ion batteries in this role. By contrast, lithium-ion batteries are cheaper than pumped hydro for short duration storage, and also offer a higher round trip efficiency (90% batteries vs 75% for pumped hydro). Lithium-ion batteries have other benefits that are making them increasingly popular. As they are extremely fast responding, they are being employed in grid stability services such as FCAS (Frequency Control Ancillary Services; see my article on siliconchip.com.au Fig.4: generation mix changes from now until 2050. Three scenarios are modelled, the most bullish being “green energy exports”, the most conservative “progressive change” and the central scenario shown as “step change”. Dispatchable capacity is indicated by the black line. Source: AEMO ISP 2024, p48 Fig.5: using a battery for ‘peak shaving’. As the transmission line reaches its thermal limit, the battery discharges to prevent an overload. Overall throughput is improved, as the line can be operated closer to its rating for longer periods. Source: www.mdpi.com/1996-1073/15/6/2278 Australia's electronics magazine March 2025  43 Fig.6: the mined lithium carbonate price in the last year. Lithium-ion batteries have subsequently shown a sharp reduction in cost over the last few months. Source: https://tradingeconomics.com/commodity/lithium lithium-ion battery does, but they have much lower energy density and poor round-trip efficiency. Mechanical energy storage methods, such as compressed air or gravity storage, are also used in very niche scenarios. One notable example is using decommissioned mine shafts to suspend weights. It has poor economics from an electricity storage perspective, but there are other benefits in mine shaft upkeep and rehabilitation. See the April 2020 article on GridScale Energy Storage for a more detailed look at grid storage, including gravity systems (siliconchip.au/ Article/13801). Demand Response While dispatchable capacity is largely thought of from a supply perspective, it can also be created from demand side solutions. Demand Response (DR) refers to deliberately switching off a load to meet a generation shortfall, network constraint or grid stability requirement. While this is not technically storage, it helps the grid in the same way. At its crudest, this can be the deliberate load shedding network operators employ in an emergency scenario. Historically, this has been during summer heatwaves when the grid exceeds its rated capacity, and substation feeders are deliberately switched off on a scheduled rotation. This type of DR is extremely unpopular in Australia, as electricity customers have no control over when the outage occurs. Fortunately, there are less impactful ways to shed load that can have the same positive outcomes. Any process that has some flexibility in when it needs to run is a good target for DR. An example might be a cool room used for frozen food storage. Given the vast size of the fridge, it might take three days to defrost, but only needs compressors to run eight hours a day to maintain temperature. By automating the pumps to turn on during periods of high supply and turn off when the grid is supply constrained, the thermal mass of the refrigerator is effectively used as storage. Diesel backup generators are another example gaining popularity. Many commercial or industrial facilities already have diesel backup for blackouts, or for operation/maintenance reasons. While most of these generators are not allowed to export energy into the grid, they do effectively work as demand response by removing a grid connected load. It is common for these assets to run for a minimum of 20 hours per year for preventative maintenance reasons. Simply aligning those mandatory hours with periods of high electricity demand increases dispatchable capacity. Cost comparisons It is common in industry to compare generators by their LCOE (Levelised Cost Of Energy/Electricity), which considers revenues and costs over the Fig.7: Levelised Cost of Electricity (LCOE) estimates for 2023 marked in cyan. Projected costs for 2050 are shown in red and are based on current trends. VRE is a combination of wind and solar, with storage and transmission costs included. Source: Gencost 2023/24, p72 & p75 44 Silicon Chip Australia's electronics magazine siliconchip.com.au entire life of the asset. Simply put, the LCOE of a generator is how much revenue it would need to earn per MWh of energy generated to pay for its construction and operating expenses. While this metric isn’t without its flaws, it does give a reasonable indication of how cheaply different generation types can be built. Still, there can be large variation in returns over different timescales, regions, and economic conditions, so we are listing an upper and lower range for a given fuel type. Fig.7 shows the current range of prices for 2023 in cyan, while in red shows a projection of the same costs at 2050, using current trends. The cheapest generator is solar, currently being built for between $47 and $79 per MWh, followed by onshore wind for $66 to $109 per MWh. This is the price for the individual generators, but given their variability, they will need to be combined with other technologies. This modelling considers a separate generator, VRE (variable renewable energy), which is a combination of solar and wind along with firming via storage and associated transmission upgrades. The price for a 90% VRE share is currently assumed at between $100 and $143 per MWh, projected to reduce to between $89 and $128 in 2030 (see Figs.8 & 9). The next cheapest are the fossil fuel generators; black coal at between $107 and $211 per MWh, followed by brown coal at $118 to $199. Midmerit gas is broadly similar at $124 to $183 per MWh. Gas peakers are classified separately; they operate at a low capacity factor, so are more expensive per unit of energy. Depending on the technology, they can currently be built for between $204 and $296 per MWh. Nuclear is estimated at between $155 and $252 per MWh, reducing to $133 to $221 by 2050. Without firming, offshore wind is estimated at between $146 to $190. Figs.8 & 9: the VRE cost breakdown for 2023 (top) and 2030 (bottom). Spillage is curtailed energy, a deliberate reduction in generation to ease an oversupply problem. It is cheaper to overbuild wind and solar generation and spill energy, rather than investing in additional storage. Source: Gencost 2023/24, p70 Grid stability The operation of a grid is not just about meeting supply with demand, but also ensuring the system is robust. Historically, this has been achieved mainly through ‘spinning reserve’; large rotating turbines. The energy transition is seeing a trend away from these alternators towards Inverter Based Resources (IBR), which replace these electromechanical systems with electronics. siliconchip.com.au Fig.10: global trends in LCOE from 2009 to 2023. Source: https://w.wiki/BnN IBRs have different strengths and weaknesses to spinning reserve, and will need to be operated differently to achieve the same stability outcomes. In the follow-up article next month, we will look at how the different types of Australia's electronics magazine IBRs work, and how they are used to provide grid stability. That article will also include plenty of detail on the electronics used in modern electrical generators and the electricity distribution grid. SC March 2025  45 Audio Mixing Cables Simple Electronic Projects with Julian Edgar Add an extra input to an audio amplifier or mix the sounds from two sources with these easy do-ityourself mixing cables. I have installed two large subwoofers in my roof space, powered by a dedicated two-channel amplifier, that need to work with two different audio systems. One is my home hifi system, while the second is a home theatre system. I could use a line-level switch to connect the subwoofer amplifier to either the home theatre or hifi system, one at a time. However, since the subwoofer amplifier is located in the roof space, that would have made things a bit difficult without adding very long leads. But why not permanently connect both inputs to the amplifier via twointo-one Y cables? Well, I tried that and found it won’t work! The hifi and home theatre system outputs end up ‘fighting’ each other. John Clarke suggested a very simple solution: put together a couple of Y mixing cables. Here’s how I made them; it only takes a short time and costs little. To make a two-channel system for stereo, you will need (see Photo 1): • Some good-quality RCA leads (don’t use cheap ones – the conductors aren’t thick enough to work with). • Four 1kW ½W resistors. • A small piece of plain punched board (laminate). • Two small plastic boxes. Depending on how you mount the boards and cables, you may also need some PCB stakes, standoffs and grommets. Buy sufficient RCA cables to give you the correct number of plugs and sockets for your application. In my case, I needed two mixing cables, each with a male output and one male and one female input. We will now look at making one cable – each assembly is identical. Cut the leads so that you have three connectors and their associated cables. Once you have done this, carefully strip the outer insulation sheath from the end of each cable and then twist the braid (the outer copper sheath) strands together. With some cables, you will need to use a thin pointer to separate the strands of the braid first. When you are twisting the braid into a single wire, be very careful that every tiny strand of copper is twisted together, with no loose strands remaining that could cause short circuits. This twisted conductor is the ground Photo 1: these are all the parts required to build the Audio Mixing Cables for a two-channel amplifier system. Photo 2: the RCA leads should be cut as shown with the wires stripped. 46 Silicon Chip Australia's electronics magazine siliconchip.com.au connection. Strip a short length from the other wire – the signal connection – and then tin each conductor with solder (Photo 2). Next, solder the signal leads of each input cable to the resistors that then feed the single output. To give attachment points on the perforated board, push short lengths of stiff copper wire through the holes to form pins. You could use PCB stakes instead. Let’s now look at the board more closely (Photos 3 & 5). All the connections are visible – there is no wiring under the board. Solder the braided ground connection of each cable to a stake to physically secure it. The two signal inputs each connect to one end of a resistor, with the other ends of the resistors joined to the output signal. The ground connection between the joined input grounds and the output ground is made by the insulated black wire visible in the photos. Once the soldering is complete, the board can be mounted in a box. I already had these salvaged boxes; all I needed to add were some cable grommets through the existing U-shaped holes (Photo 4). You could use a lowcost Jiffy box or similar. Before you close the box up, do some testing with your multimeter. Every plug’s outer (ground) connection should have continuity (near zero resistance) to every other plug’s ground connection. The two input plugs should have 2kW resistance between their inner (signal) connections, and there should be 1kW resistance between each of the input signal connections and the signal connection of the output. Finally, there should not be continuity between any signal and ground connection. In addition to allowing two different inputs to operate a two-channel amplifier, as the name suggests, the cables also allow the two signals to be mixed (both input signals being heard simultaneously) if that is desired. For example, you could play music while watching TV and hear both if you used such a cable to merge the outputs of a CD/DVD/Blu-ray player and television. The signal level is reduced by half in the mixing cable. The resulting disadvantage is that the signal-to-noise ratio of the signal is a little poorer, but that is not so important for my subwoofer use case. And now, I don’t have to climb into the roof space to swap the inputs of the subwoofer amplifier! SC siliconchip.com.au Photo 3: the layout of the Audio Mixing Cables is very simple, so you can either wire it up as shown or choose your own way. Note that we don’t have any connections on the underside of the laminate. Photos 4 & 5: the finished project mounts neatly in a small plastic box. These boxes are around 5 × 7.5cm. Australia's electronics magazine March 2025  47 Antenna Analysis and Optimisation Last month, we introduced a range of concepts related to antennas, such as resonance, reactance, complex impedance, Smith charts and dipoles. We will now look at using software to tune antennas. It can save a lot of time compared to manual calculations and experimentation. Part 2 by Roderick Wall, VK3YC A fter reading the article last month, you should understand how the complex impedance of an antenna can be plotted on a Smith chart. You should also realise why it is important to use an antenna at its resonant point and with a VSWR as close to 1:1. The question then becomes, if you have a real-world antenna and can measure its complex impedance, how do you know how to make it resonant? And how do you improve the VSWR if it’s significantly worse than 1:1? Luckily, free computer software makes doing all that relatively straightforward. The “Smith V4.1” software I use can be downloaded from www.fritz. dellsperger.net There is a free version and a paid version that has extra features; the free version is suitable for our purposes. Fritz also has examples and a very good introduction to the Smith chart that can be downloaded. Before using this software, it needs to be set up correctly. After starting Smith, left-click on the “Tools” menu and select “Settings”. Under the “Smith chart” heading, make sure “Z-plane (on/off)” is selected and “Y-plane (on/off)” is not selected. This displays the results on a Z-Smith chart. Also make sure that under the “General” heading, the Default Zo = 50W, then click “OK”. Refer to Fig.8, an antenna impedance vs wavelength plot reproduced from last month. If the driven element length is increased from 0.25 of the wavelength at point (b) to 0.2654 of the wavelength at point (c), the real resistance increases from 36W to 50W, which is required to obtain a VSWR Screen 1: using the Smith V4.1 software, click the Keyboard button shown to be brought to Screen 2. Fig.8: reproduced from last month, this plot of the complex impedance of a Marconi antenna versus wavelength provides some useful examples for designing matching networks. 48 Silicon Chip Australia's electronics magazine Screen 2: for the first example, fill in this menu with the values as shown. siliconchip.com.au Screen 3: this toolbar lets you insert different elements into the circuit you want to test. It is located at the upper right of the main window as shown in Screen 4. of 1:1 for a 50W system. However, the antenna is no longer resonant; its reactance is +j65.65W (inductive). A series capacitor can be added to make the antenna resonate. Let’s use the Smith software to plot a Smith chart for the antenna at point (c) in Fig.8, with a length of 0.2654λ and a complex impedance of (50.1 + 65.65j)W. Example #1 To enter the antenna’s complex impedance, click the “Keyboard” button in the toolbar (see Screen 1). Select Cartesian and enter real resistance (Re) and imaginary/reactance (Im) values as shown in Screen 2. Also change the frequency to 28.3972MHz and click “OK”. On the Smith chart, you will see that DP 1 is sitting on the unity constant impedance (real resistance 50W) circle, between the +j50W and +j100W lines, indicating an inductive reactance of +j65.65W. In the “Schematic” window, the antenna is shown as Zl. To show what the VSWR would be if this antenna were connected to the transmitter without a matching circuit, leftclick “Tools” and select “Circles”, then select the VSWR Tab. Under the “Defined” heading, select both “3” and “5” then click OK. The Smith chart shows that the antenna VSWR will be between 3:1 and 5:1, then go back to the VSWR tab. Now click “Clear all” and type “3.5” under the “Select other” heading, then click “Insert” and click OK. This shows the VSWR to be 3.5:1. We want a VSWR of 1:1. To see where we want to move to, add a constant VSWR circle at 1.05 and click OK. For the best VSWR, we need to end up in the middle of the constant VSWR 1.05 circle. Click the insert Series Inductor “L” button, second from left in Screen 3. The cursor moves in the wrong direction as it moves further away from where the best VSWR is. The inductor is making it more inductive than it already is. To move the VSWR in the correct direction, a capacitive reactance of 65.65W is required to cancel the inductive reactance, making the antenna resonant at (50 + j0)W. Right click to remove the inductor and click the Insert Series Capacitor “C” button (on the left in Screen 3). Move the cursor and click in the middle of the VSWR 1.05 circle. Using maths, we see that a capacitance of 85.4pF gives a capacitive reactance of 65.65W at 28.4MHz. Xc = 1 ÷ (2πfC) and C = 1 ÷ (2πfƒXc). The Smith chart should now look as shown in Screen 4. The “Datapoints” window shows complex impedances for DP 1 and TP 2, while the Schematic window shows the equivalent circuit. We have just designed our first matching circuit by adding a series capacitor between the driven element and the antenna terminals. The capacitor cancels the inductive reactance, making the impedance (50 + j0)W. Screen 4: our initial example circuit (incorporating just a series capacitor) produces this Smith chart. siliconchip.com.au Australia's electronics magazine March 2025  49 The antenna can now be connected to any length of 50W coaxial cable to the transmitter, and the VSWR will be close to 1:1. The maximum possible power will be transferred to the antenna. There will be some losses in the transmission line and matching components; they should be kept as low as possible. Another method to determine capacitor value without using a Smith chart is to adjust the driven element length until the real resistance is 50W. Then add a series-connected variable capacitor and adjust it until a VSWR of 1:1 is obtained. You can then use a capacitance meter to measure the capacitance, allowing you to replace the variable capacitor with a fixed one of a similar value. You can also calculate the required capacitance, use the formula C = 1 ÷ (2πfƒXc). We know the necessary capacitive reactance (Xc) is 65.65W because the antenna inductive reactance is 65.65W, and the frequency (ƒ) in this case is 28.3972MHz. You can also use an online capacitor calculator. Example #2 (5/8-wavelength antenna) The next example is a 5/8-wavelength antenna, shown at point (e) in Fig.8. A 5/8 antenna is often used instead of a 1/4-wave Marconi antenna because it has a lower radiation angle. Select File → New, then enter the complex impedance (49.95 – j232)W and 28.3972MHz into the Smith chart software. The real resistance of 50W is already sitting on the unity resistance circle we call the Z-matching circle, the road to where VSWR is 1:1. This time, insert a series inductor, move the cursor and click on the middle of the Smith chart where the VSWR is 1:1, ie, (50 + j0)W. Screen 5 shows the results. Using maths, we see that a 1.3μH inductor gives an inductive reactance of 232W at 28.4MHz (XL = 2πƒL and L = XL ÷ 2πƒ). This time, an inductor is needed to cancel out the capacitive reactance to make the antenna resonant. There is a method to adjust a 5/8 antenna without using a Smith chart. Adjust the element length to obtain a real resistance of 50W, then use a series variable inductor to obtain a VSWR of 1:1. Mathematics can be used to calculate the required inductor value, L = XL ÷ 2πƒ. We know the required inductive reactance, XL, is 232W because the antenna’s capacitance reactance is 232W. In the above two examples, the real resistance part of the complex impedance was 50W, so it already sat on the unity constant resistance circle. The usual procedure to obtain a VSWR of 1:1 is to first get the point onto the unity resistance circle and then move it around to (50 + j0)W. For the above two examples, the matching capacitor or inductor was connected in series with the driven element at the antenna. Example #3 (parallel components) Another method of making an antenna resonant is with hairpin inductors. The hairpin matching component is connected in parallel with the antenna terminals. When parallel matching components are used, the admittance Y-plane must be used. To set this up, click File→ New and then Screen 5: the Smith chart for our second example using the complex impedance of (49.95 − j232)W. Screens 4-6 are measured with a fixed frequency of 28.3972MHz. 50 Silicon Chip Australia's electronics magazine siliconchip.com.au “Tools” menu and select “Settings”, then enable the Y-plane. Make sure the Z-plane is not selected. This will display results on a Y-Smith chart. Enter a complex impedance of (32.15 – j24.55)W and a frequency of 28.3972MHz into the Smith software. As the real resistive part is 32.15W and not 50W this time, it sits on the blue unity conductance circle at 20mS (millisiemens). This is what we also call the Y matching circle, another road to where the VSWR is 1:1. Click the “Insert Parallel Inductor” button and move the cursor to click in the middle of the Smith chart at the (50 + j0)W point. The parallel inductor value will be close to 374nH – see Screen 6. The curved lines on this chart are called constant susceptance circles. This example shows that a Marconi antenna shorter than a 1/4-wavelength can be made resonant with a parallel inductor. This may be suitable for a short (160m) vertical Marconi antenna if its capacitive reactance is high enough to get onto the Y-matching circle. If its capacitive reactance is not Fig.12: hairpin inductors formed from simple metal rods are often used to create a basic matching network for Yagi antennas, which are typically on the capacitive end of resonance. high enough, a capacitor can be added to get it there. Other possible solutions will be discussed overleaf. This example can also be used to show hairpin matching for a 1/2-­wavelength centre feed dipole. The 374.6nH inductor is half of the hairpin matching inductor. Hairpin inductors are often used on Yagi antennas where the driven element is a centre-­ feed dipole. When using two Marconi antennas to make a Hertz dipole antenna, as described last month, the antenna impedance is doubled: 50W × 2 = 100W. The other side element of the dipole also needs a parallel 374.6nH inductor, as shown in Fig.12. A 2:1 balun transforms the 100W impedance to match the transmitter’s 50W. The driven dipole element length is shorter than half the wavelength (1/4-wavelength per side), giving the complex impedance capacitive reactance and making it sit on the Ymatching circle. Each side of the dipole is similar to an LC matching circuit. The hairpin is the inductor, while the antenna complex impedance supplies the capacitive reactance without using a discrete capacitor. Screen 6: the Smith chart for example #3 with a complex impedance of (32.15 − j24.55)W. This one requires an inductor to be added in parallel with the antenna to achieve a VSWR of 1:1. siliconchip.com.au Australia's electronics magazine March 2025  51 Screens 7 & 8: two example solutions and Smith charts for example #4 with complex impedance (36.32 + j0)W. 52 Silicon Chip Australia's electronics magazine siliconchip.com.au Our example is a dipole antenna in free space with no directors or reflector elements. Suppose directors or reflector elements are added and placed above ground. In that case, the coupled complex impedance for the driven dipole element before matching will be different than for a self-impedance naked (uncoupled) element. The balun impedance ratio may also be different to this example. A 4:1 balun is used when the centre-feed dipole antenna impedance is 200W with the parallel inductors. Example #4 Let’s consider a 1/4-wavelength 36W resonant antenna. The VSWR is 1.4:1, below what might be acceptable. Two matching components can be used to fix this. The complex impedance is (36.32 + j0)W and is not sitting on the blue Y-matching circle or the red Zmatching circle. In this example, we can use a 251pF series capacitor to get it onto a matching circle. Then a parallel inductor brings us to the centre, (50 + j0)W – see Screen 7. Screen 8 shows another possible solution, with a series inductor and parallel capacitor forming a low-pass filter as in Screen 8 rather than a highpass filter. It also achieves a VSWR of 1:1. Fig.13: we want to get the antenna’s complex impedance onto one of these red circles, as we then only need to add one more component to achieve a VSWR close to 1:1. This diagram provides guidance on what component to add and how to add it to get the antenna onto one of those circles. General rules for achieving resonance The following rules can be used when designing matching circuits. Fig.13 provides guidance on whether to use a series or parallel capacitor or inductor, depending on where your antenna falls on the Smith chart. Similarly, Fig.14 shows the ‘forbidden areas’ and suggests the first component to add to get onto a matching circle. There may be two or more possible solutions to a matching requirement. Fig.15 shows another way of determining what components to use. To move from Capacitive (-j) to Inductive (+j), add an inductor in series or parallel, as shown. To move from Inductive (+j) to Capacitive (-j), add a capacitor, either in series or parallel, as shown. When selecting components for matching circuits, ensure their voltage and current ratings are sufficient for the power being transferred to the Fig.14: most antennas can be brought to a VSWR of 1:1 using one of these eight types of two-component matching networks. siliconchip.com.au Australia's electronics magazine March 2025  53 Silicon Chip Binders REAL VALUE AT $21.50* PLUS P&P 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 S ilicon C hip . They feature heavy-board covers, hold 12 issues & will look great on your bookshelf. H 80mm internal width H Silicon Chip logo printed in goldcoloured lettering on spine & cover Silicon Chip Publications PO Box 194 Matraville NSW 2036 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. 54 Silicon Chip Fig.15: here’s another way to visualise what type of component needs to be added in which manner to achieve resonance in your antenna. antenna. They must also be suitable for radio-frequency use, at the frequency they will be used at. For inductors, that means either aircored inductors (which can operate at virtually any frequency) or those with core materials specifically designed for use up to the radio frequency range you will be using. For capacitors, you will generally need to use low-inductance, low-loss ceramic or plastic film types, depending on how high a frequency they will operate at. Many large parts suppliers have specific RF inductor and capacitor categories or search tags. Check the data sheets of the devices you plan to use to verify that they can operate at the required frequencies. When designing matching circuits for a band of frequencies: 1. Measure the complex impedance of the antenna at the lowest frequency. 2. Measure the complex impedance of the antenna at the highest frequency. 3. Measure the complex impedance of the antenna at the centre frequency. 4. Design the matching circuit for the centre frequency. Australia's electronics magazine 5. Enter one of the antenna band edge complex impedances and frequencies (lowest or highest) into Smith. 6. Insert the matching circuit components with the values determined for the centre frequency. 7. Add constant VSWR circles to determine the VSWR at the band edge. 8. Repeat for the other band edge (lowest or highest). Component values can be edited by clicking on a component in the schematic window, altering their values in the window that appears, then clicking “OK.” We still need to address the bandwidth of the matching components; that is the topic of the third and final instalment of this series, which will be published next month. In the meantime, you can perform an exercise to check that you have understood the information in this article. There are four ways to achieve resonance for an antenna with a complex impedance of (25 + j43)W in a 50W system. See if you can figure out all four possible matching networks. SC siliconchip.com.au Multi-coloured prints, uninterrupted Meet the K2 Plus CFS* Combo, the ultimate game-changer for 3D printing enthusiasts. Handle multi-coloured prints seamlessly — no more pausing to swap colours mid-print. *Creality Filament System INTELLIGENT MULTI-COLOUR CREALITY FILAMENT SYSTEM^ • AUTO FILAMENT SELECTION • AIRTIGHT FILAMENT STORAGE • PRINT UP TO 16 COLOURS ^Offered as part of Combo with 4 rolls of filament BACK IN STOC K GET YO U RS NOW STOP-SERVO MOTOR SYSTEM DUAL AI CAMERAS MONITOR FLOW RATES & FAILURE DETECTION 32,678 MICROSTEPS FOR ULTRA PRECISE POSITIONING NEXT-GEN EXTRUDER KIT • REDUCED CLOGGING • EASY TO MAINTAIN • 40MM/S FLOW RATE ACTIVELY HEATED CHAMBER UP TO 60°C STURDY MATRIX FRAME HELPS AVOID LAYER SHIFTS FLAWLESS PRINT QUALITY WITH ACCURACY DOWN TO 0.05MM ULTRA LARGE BUILD VOLUME 350W X 350D X 350HMM Just $2569 • Includes four 500g rolls of filament • Available online only • Limited stock. Don't miss out. Scan QR Code to learn more or visit: jaycar.com.au/creality-k2-plus TL4856 Shop with confidence at Jaycar Backed by a trusted local team, nationwide stores for all your 3D printing needs, and expert support you can count on. Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. While Stock Lasts. Looking to refresh your workbench? We’ve got the essentials to power up your next project, at the best value. PERFECT FOR COMPACT WORKSPACES ADJUSTABLE ARM IDEAL FOR SOLDERING, PLASTIC CUTTING, HEAT SHRINKING, ETC. ONLY 5995 $ FOR A BETTER VIEW Illuminated Desktop Magnifier • 100mm 3-dioptre glass lens • 30 bright LEDs • Mains powered QM3552 SOLDER ANYTHING, ANYWHERE! SuperPro Gas Soldering Tool Kit • Up to 580°C temp range • Up to 120 min run time • Durable case with extra tip storage TS1328 ONLY 209 $ VOLTAGE AND CURRENT DISPLAY ONLY 3995 $ CABLE MAKING ONE HANDED! Heavy Duty Wire Stripper • Cutter, crimper & wire guide • Strips 10-24 AWG/0.13-6.0mm • Single handed operation TH1827 ONLY 4995 $ CONSTANT CURRENT & VOLTAGE IN A SLIMLINE FORM FACTOR SLIM IN SIZE, BIG IN OUTPUT Slimline Lab Power Supply • 0-16VDC <at> 0-5A (max.) 0-27VDC <at> 0-3A (max.) 0-36VDC <at> 0-2.2A (max.) • Up to 80W max. • Just 300L x 138H x 53Wmm MP3842 ONLY 219 $ 2 CHANNELS ALL THE REGULAR OSCILLOSCOPE FUNCTIONS IN A SMALL FORM FACTOR MEASUREMENTS MADE EASY! Autoranging Digital Multimeter with Temperature • Cat III 600V • 10A AC or DC current • 40MΩ resistance • 100µF capacitance • 760°C temperature • K-type probe & case incl. QM1323 TURN YOUR COMPUTER INTO AN OSCILLOSCOPE 20MHz USB Oscilloscope • High accuracy interface • Spectrum analyser (FFT) • 48M Sa/Sec sampling rate • 20mV/div sensitivity QC1929 Explore our great range of Tools and Test Equipment, in stock on our website, or at over 121 stores or 134 resellers nationwide. ONLY 249 $ www.jaycar.com.au 1800 022 888 Prices listed in Australian dollars and correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. SERIOUS POWER, SERIOUSLY GOOD VALUE! INTRO OFFER NOW FROM $ INTEGRATED BLUETOOTH® FOR SMARTPHONE CONNECTIVITY NEW 999 INTEGRATED CARRY HANDLES SAVE<at>$1000 IP21 RATED ON SALE: 26TH FEB TO 7TH MARCH, 2025 12V CIGARETTE SOCKET & 2 X 12VDC OUTLETS USB-A WITH QUICK CHARGE 3.0 & USB-C WITH POWER DELIVERY PURE SINE WAVE OUTPUT FOR SENSIVITE ELECTRONICS CHARGE VIA 12V, MAINS POWER OR VIA SOLAR PANEL BUILT-IN HIGH CAPACITY LIFEP04 BATTERY WITH ADVANCED BATTERY MANAGEMENT SYSTEM INTEGRATED MPPT SOLAR CHARGER UPS FUNCTION TO KEEP DEVICES RUNNING DURING POWER BLACKOUTS WHEELS & LUGGAGE STYLE HANDLE MB4102 3 YEAR WARRANTY HIGH POWER MODELS INCLUDE 12V 30A HIGH CURRENT OUTPUT INTRO OFFER 2999 1999 $ INTRO OFFER 999 $ INTRO OFFER 4999 $ INTRO OFFER $ SAVE $800 SAVE $1000 SAVE $400 SAVE $200 SCAN QR CODE TO LEARN MORE MB4102 (S1) MB4104 (S2) MB4106 (S3) MB4108 (S5) Output Power (Total) 2000W Continuous 4500W Peak 2500W Continuous 5400W Peak 3600W Continuous 7000W Peak 5000W Continuous 7000W Peak Capacity 1024Wh (12.8V 40Ah) 2048Wh (51.2V 40Ah) 3072Wh (51.2V 60Ah) 5040Wh (48V 105Ah) Mains Outputs 4 5 6 6 Pure Sine Wave Output • • • • USB-C Output 2 (100W max.) 2 (100W max.) 2 (100W max.) 2 (60W max.) USB-A Output 4 x QC3.0 (18W max.) 4 x QC3.0 (18W max.) 3 x QC3.0 (18W max.) & 1 x 10W 3 x QC3.0 (18W max.) & 1 x 10W 12V Outputs 1 x Cig. Lighter Socket & 2 x DC Sockets (10A max.) 1 x Cig. Lighter Socket & 2 x DC Sockets (10A max.) 1 x Cig. Lighter Socket & 2 x DC Sockets (10A max.) 1 x Cig. Lighter Socket & 2 x DC Sockets (10A max.) 12V 30A Output - • • • PV Solar Input 14A / 800W max. 15A / 2100W max. 15A / 2100W max. 15A / 2100W max. Dimensions (W x D x H) 384 x 232 x 295mm 460 x 270 x 305mm 641.5 x 304.5 x 437.5mm 641.5 x 304.5 x 437.5mm Warranty 3 Years 3 Years 3 Years 3 Years Availability In-store and online In-store and online Order online or in-store Order online or in-store RRP RRP $1199 RRP $2399 RRP $3799 RRP $5999 Explore our NEW range of portable power solutions, in stock on our website or at stores and resellers nationwide. www.jaycar.com.au 1800 022 888 Prices listed in Australian dollars and correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. $ ONLY 329 $ QM1493 Specialty meters combined with multimeter functions. $ 119 TAKE EASY ENVIRONMENTAL MEASUREMENTS • MULTIMETER FUNCTIONS • SOUND LEVEL • LIGHT LEVEL • INDOOR TEMP • HUMIDITY TEST ALMOST ANYTHING! TEST WIRING INSULATION QM1632 CONTACTLESS HIGH CURRENT MEASUREMENTS • MULTIMETER FUNCTIONS • TRUE RMS • AUTORANGING • CAPACITANCE • NON-CONTACT VOLTAGE 179 QM1594 HIGH VOLTAGE INSULATION TESTING "MEGGER" • MULTIMETER FUNCTIONS • DIGITAL DISPLAY • ANALOGUE BARGRAPH • DATAHOLD ONLY ONLY MEASURE HIGH CURRENT $ ALL MODELS FEATURE: • AUTORANGING • AUDIBLE CONTINUITY • MAX / DATA HOLD ONLY 119 XC5078 DETECT OPEN, SHORT OR MISS-WIRED LAN CABLES • MULTIMETER FUNCTIONS • PINOUT INDICATOR GREAT FOR I.T. TECHNICIANS SIMPLIFY YOUR TOOLBOX, NOT YOUR RESULTS Save money and enjoy the convenience of carrying just one tester in your toolbox. Specialty Function QM1632 QM1493 XC5078 QM1594 Clamp Meter up to 600A AC/DC Insulation Test up to 4000MΩ LAN Cable Test with pinout indicator Sound, Light, Humidity & Temp Display (Count) 4000 4000 2000 4000 Security Category Cat III 600V Cat III 1000V Cat III 600V/Cat II 1000V Cat IV 600V/Cat III 1000V 600V AC / 600V DC 600V AC / 600V DC 200mA AC/DC 10A AC/DC True RMS • • Voltage 600V AC/DC 750V AC / 1000V DC Current 600A AC/DC Resistance 40MΩ Capacitance 100mF 100µF 10MHz 4000MΩ 20MΩ 40MΩ Frequency 10MHz Temperature 1000°C Relative Measurement • • • Non Contact Voltage • • • 750°C Explore our great range of multimeters, in stock on our website, or at over 121 stores or 134 resellers nationwide. www.jaycar.com.au 1800 022 888 Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. SILICON CHIP Mini Projects #022 – by Tim Blythman RF Remote Receiver Jaycar’s MS6147 Remote Controlled Mains Outlet lets you control mainspowered devices without having to deal with mains wiring. It can be operated by the included RF remote control or another device equipped with a 433MHz transmitter (like we used in Mini Project #006, June 2024). That handy RF remote control can be used to control other devices too! T he MS6147 Remote Controlled Mains Outlet Controller bundle includes three switched outlet receivers and a handheld remote radio frequency (RF) transmitter. The transmitter has four channels, so there is an unused channel that could control something else. You can get extra mains outlet receivers, such as MS6149, to use with that extra channel. But that isn’t all you can do with it. For example, imagine a USB-powered lamp. While you could control it from one of these outlets by having a mains-powered USB power supply plugged into it, that would be unnecessarily complex. You could switch USB power to the lamp with a low-voltage relay or even a transistor, as we did in the Gesture-controlled Lamp Mini Project from January 2025 (siliconchip.au/ Article/17601). Or use this RF Remote Receiver to control the relay or transistor instead. It can receive signals from any of five different RF transmitters and then control something attached to the Arduino Uno board. Our project uses four LEDs to show the status of the four channels, making it easy to test the operation of these systems. The basic operation can be seen in our video at siliconchip.au/ Videos/RF+Remote We also wired up a relay module to demonstrate how to switch just about any low-voltage device. The Arduino ecosystem makes it very easy to customise the operation of the Receiver; you could add the USB-switching circuitry from the Gesture-controlled Lamp to add a switched USB outlet, for example. Alternatively, you could add some logic to the Arduino sketch to control some other low-voltage device. You could even program it to send a command (using a different medium, such as infrared) to another device, unifying control to a single transmitter. Circuit details Our circuit is quite simple, and we have laid it out on a prototyping shield attached to the Uno as per Fig.1. We expect many constructors will want to add their own hardware, so you might consider what else you want to control before commencing assembly. The 433MHz receiver module gets its power from the Uno via the shield to its Vcc and GND pins. A simple wire antenna is connected to the ANT pin of the receiver, while its DATA output goes to digital pin 2 (D2) of the Uno. Fig.1: the circuit is simple enough to wire up on a breadboard, but we laid it out on a prototyping board to make it more robust. Ensure that the necessary pads are connected underneath the board. To switch something with the relay, connect the C (centre, common) and NO (normally open) contacts as though they are a switch’s contacts. siliconchip.com.au Australia's electronics magazine March 2025  59 We are using this type of RF transmitter for this project. It can be purchased as part of a bundle (along with one or more Mains Outlets) from Jaycar with catalog codes MS6147 or MS6148. Kits like Jaycar MS6148 allow up to three mains devices to be controlled by a handheld remote, leaving a channel free on the transmitter for us to use. The Mains Outlets can be paired with up to three transmitters, but our Receiver can work with up to five! Four LEDs are driven by digital pins 7, 9, 11 and 13 (designated A, B, C and D, respectively). These have been chosen to allow a bit of space between them as they are laid out on the shield. Their anodes connect to the Uno’s pins via 470W resistors, while their cathodes are all connected to circuit ground. A 5V relay module is driven from digital pin 7 (connected directly to the relay module’s S pin). The module’s + and – pins are also wired to 5V and GND, respectively. About the only thing that should not be changed is the receiver’s DATA pin connecting to D2. The library we are using depends on the interrupt feature on this pin. Software We are using the RF433any library to decode the RF signals in this project. It can work with encodings from various protocols, including that used explore these a bit later, but each of the four LEDs behaves much the same as one of the four mains outlets would. For example, the ‘A’ LED will light up when either the A ON or ALL ON button is pressed. It will go out when either the A OFF or ALL OFF button is pressed. This keeps the operation straightforward and intuitive. The button codes are decoded independently, so there is no reason they can’t be allocated to ten independent and distinct functions by changing the way the software responds to the codes. In other words, there’s no reason the ON button has to switch an output on, or the OFF button switch it off. They are just buttons, including ALL ON and ALL OFF. This is left as an exercise for the reader! Construction by the Remote Controlled Mains Outlet Controller. More information can be found at https://github.com/sebmillet/­ RF433any As noted, this library uses the pin change interrupt feature of the ATmega328, so this project will only work with boards like the Uno or Nano and can only receive data on digital pins 2 or 3. It might work on other boards, but that has not been tested. The library waits for a transmission to be received and the 32-bit code is extracted. In the code used by the Outlet Controller, 20 bits are assigned to the address and four bits to the data or command, with another eight bits forming a checksum. The software compares the address to those stored and, if it matches, the output state is changed. There are mechanisms to learn an address and save it in EEPROM for later use. We’ll Have a look at our photos and Fig.1 to see how we assembled the parts for our prototype. The circuit is simple enough to be laid out on a breadboard, but we figured many constructors would want something robust. Fit the receiver module to the shield, watching the orientation. Solder it in place and then run insulated wires to the necessary pins on the shield. Note that some of the connections are made between adjacent pads on the underside of the shield. Next, fit the resistors and the LEDs. Make sure the LED anodes (the longer leads) connect to the resistors. Then connect all the LED cathodes together and to circuit ground. The relay module is wired up with plugsocket jumper wires; you could easily allocate it to a different button by connecting its S pin to a different digital pin on the shield. We also added a short length (~17cm) of coiled insulated wire to form the antenna; naturally, it connects to Parts List – RF Remote Receiver (JMP022) 1+ Transmitter from a Remote Controlled Mains Outlet Controller [Jaycar MS6147 or MS6148] 1 Arduino Uno R3 [Jaycar XC4410] 1 Prototyping shield [Jaycar XC4482] 1 5V single relay module [Jaycar XC4419] 1 433MHz wireless receiver module [Jaycar ZW3102] 4 yellow 3mm LEDs [Jaycar ZD0110] 4 470W ½W axial resistors [Jaycar RR0564] 1 USB cable to suit the Uno assorted hookup and jumper wires 60 Silicon Chip Australia's electronics magazine The 433MHz receiver module (Jaycar ZW3102; above) and 5V relay module (Jaycar XC4419, left). siliconchip.com.au the receiver module’s ANT pin. This length makes it a quarter-wave antenna at 433MHz, but we’ve generally found that these receivers work fine with just about any sort of antenna, or sometimes none at all! Programming Plug the shield into the Uno and connect it to your computer for programming. If you don’t already have the Arduino IDE installed, get it from www.arduino.cc/en/software Now install the RF433any library. Open the Library Manager in the IDE, search for “RF433any” and install the library with that name. We included a ZIP file of the version we used in the software download package (get it from siliconchip.au/Shop/6/1820). Assuming you have built the hardware as presented, select the Uno board and its serial port, then upload the RF_RECEIVER sketch. Open the serial monitor at 115,200 baud to interact with the Receiver. You should see something like Screen 1 appear when it starts up. The serial port is used for programming new codes and testing but it is not needed for normal operation (ie, receiving and responding to codes). The status report can also be triggered by sending a ‘~’ character (tilde) to the terminal. You will probably need to press Enter after that in the Serial Monitor, but other terminal programs may not require that. Pressing a button on a transmitter should result in a 32-bit code (eight hexadecimal nybbles) being printed to the serial monitor, like at the top of Screen 2. You can then enter “s” to save the address; it will be saved to the first free spot. The new code is seen in the updated status report. Subsequent presses of that button will also report that the Receiver is responding to that command, and you should see the corresponding LED switch on or off. Sending “0” on the serial monitor will delete the code allocated to the first slot; 1-4 will delete the others. So if you have multiple transmitters, you should press a button on each, then save it to the Receiver. After that, you can check the saved addresses with the “s” command. Each change to the address list is implemented immediately and also saved to EEPROM, so it will be available when the processor is restarted. Once it is all set up, it does not need to be connected to a computer and can be powered from a USB power supply instead. If you are interested in adding your own hardware to the Receiver, you can change the output pins near the start of the sketch with the likes of the RF_A_OUTPUT #define. The actions caused by each command can be customised further in the code­ Action() function. Summary The compact handheld transmitters of the Outlet Controller can now be used to control things other than mains outlets. With the Arduino IDE, you can add your own hardware and SC functions to our simple design. This is the finished RF Remote Receiver. You can change how the Arduino software responds to different commands. siliconchip.com.au Australia's electronics magazine SCREEN 1 ________________________________ A: OFF B: OFF C: OFF D: OFF 0 CODE: 0x----1 CODE: 0x----2 CODE: 0x----3 CODE: 0x----4 CODE: 0x----Last code: 0x0 ~ for debug data s to save last code to a slot 0-4 to clear a slot ∎ When first powered on, the Receiver will deliver the status report shown here to the serial port at 115,200 baud. You can also trigger the report by sending a tilde character (“~”). SCREEN 2 ________________________________ 903E0FAE Added to slot 0 Saved A: OFF B: OFF C: OFF D: OFF 0 CODE: 0x903E0 1 CODE: 0x----2 CODE: 0x----3 CODE: 0x----4 CODE: 0x----Last code: 0x903E0 903E0FAE 0: A ON 903E0FAE 0: A ON 903E0FAE 0: A ON 903E0FAE 0: A ON 903E0FAE 0: A ON 903E0FAE 0: A ON 903E0FAE 0: A ON Slot 0 cleared. A: ON B: OFF C: OFF D: OFF 0 CODE: 0x----1 CODE: 0x----2 CODE: 0x----3 CODE: 0x----4 CODE: 0x----Last code: 0x903E0 ∎ To add a code, press a button on your transmitter and see that the Receiver acknowledges it, then send “s” on the serial port. After that, you should see the Receiver respond to that transmitter. If you get an error that all the slots are full, free up a slot by sending a digit from 0 to 4. March 2025  61 SILICON CHIP Mini Projects #023 – by Tim Blythman Continuity Tester A Continuity Tester is one of the simplest pieces of test gear out there. Still, it can perform functional tests on numerous devices such as fuses, globes, resistors and even diodes. Its simplicity means it can be assembled on a breadboard. C ontinuity Testers check for the presence of a low-resistance circuit, as found in a functional fuse or light globe. Most multimeters have a continuity mode and will make a sound when a circuit with a low enough resistance is probed. A typical threshold (based on the multimeter in front of me) is 150W. Many readers will have a multimeter, but for those who do not, you can simply assemble a handful of components on a breadboard. Even if you have a multimeter with a continuity function, you might still be interested in this circuit and how it works. For example, you could create a continuity tester that operates with a different resistance threshold. You can also use this circuit to trigger near a particular current value. It uses a Darlington transistor arrangement, which is also a handy configuration to know about. Circuit details Fig.1 shows a very basic continuity tester circuit. The LED and its ballast resistor are in a standard configuration. You can imagine that connecting a 150W (or lower) resistance would cause the LED to light up, which is what we want. However, the LED will still light up if a 1kW resistor was connected, even though the LED current is lower. It would be hard to tell the difference in brightness, and thus to tell if we truly have continuity or not. Fig.2 is an improved version. It still has the LED and resistor, but the test points are displaced by some other circuitry. The two PNP bipolar transistors 62 Silicon Chip are arranged in what is called a Darlington configuration (named after Sidney Darlington). This is not restricted to PNP transistors and will work much the same with NPN types. The two collectors are connected together, while the base of one transistor (Q2) is connected to the emitter of Q1. This effectively gives a single device with three leads, similar in function to a regular transistor. Components are even manufactured as such, with two transistors in one package, still with three external leads. This arrangement has the advantage that the gain of the transistor pair is much higher than the gain of the individual transistors. For most scenarios, multiplying the individual gains is a good approximation. There are some downsides. For example, the base current must pass through two PN junctions, so the effective base-emitter voltage drop is doubled compared to a typical single device. We’ll assume with a value of 1.2V (or about two 0.6V diode drops) for our circuit. The arrangement also means that the saturation voltage (between the collector and emitter when the transistor is on) must also be higher, by one diode-drop. If this were not the case, there would not be enough voltage to keep both transistors biased on. In the Continuity Tester, the benefit of the high gain of the Darlington pair is a sharper threshold transition. We can set a threshold current by means of the 470W resistor connected to Q1’s base. Consider a current flowing through the device under test. It will flow through the 1.5kW resistor and then can either pass through the upper 470kW resistor or from the base of Q1 and through the Darlington pair. Below about 2.5mA (1.2V ÷ 470W), all the current flows through the resistor, since there is not enough voltage developed to overcome the forward voltage of the two PN junctions. But soon, there is enough current to cause Fig.1: you might think that a circuit like this could do the job of testing for continuity, but the LED will light up even if a relatively high resistance is probed. Fig.2: this improved circuit adds two transistors in a Darlington configuration. Note the cyan rectangle outlining the two transistors; it has three wires crossing its border. They can be treated as the base, emitter and electronics collector of magazine the pair. Australia's siliconchip.com.au 3mA 2mA 1mA 0mA 100W 200W 300W 400W 500W Scope 1: the vertical axis is the LED current, while the horizontal axis is the resistance between the test probes. The green trace shows the very soft response offered by the circuit in Fig.1. The blue trace of the Fig.2 circuit has a much sharper transition. some to flow through the base of the Darlington pair. With a 5V supply and a red or yellow LED, about 6mA will flow through the LED when the pair is switched on fully. Parts like the BC557 have a gain well above 100, meaning the Darlington pair has a gain of over 10,000. For 6mA to flow through our LED, we need no more than 0.6µA to flow into the base of Q1. To turn this threshold current into a resistance, we choose the value of the second resistor to supply just over 2.5mA when a 150W resistance is placed across the test points. The resistance between the 5V rail and the base of Q1 should be about 1.5kW (3.8V ÷ 2.5mA). Just like a regular diode or transistor, the actual voltage across the PN junction is not always exactly the same, so the actual transition will not be perfectly sharp, but it will be much sharper than for the circuit shown in Fig.1. Scope 1 shows the results of a simulation comparing these two circuits, with the horizontal axis being the resistance between the test points. The Fig.1 circuit produces the green trace, while the Fig.2 circuit is the blue trace. Note that the Fig.2 circuit transitions much more sharply. It still is not a ‘brick-wall’ cutoff, but it is good enough for our purposes. Assembly We have used two of the same type of transistor in our Darlington pair, which works out neatly since they have the same pinout and we can use the layout shown in Fig.3. Note that a Darlington pair will often use a smaller transistor for Q1 and a power transistor for Q2, so that will not always be the case. The purple wires are the test leads, while the power rails on the breadboard should be connected to a suitable power supply. We’ve used a regulated 5V supply from an Arduino board, which is necessary because the supply voltage figures into the threshold calculations. A 9V supply should work just as well, although the value of the 1.5kW resistor will need to change. The threshold current (2.5mA) does not depend on the supply voltage, but the LED current does (due to the 470W resistor). Using it The first test you can do (once you have connected power) is to touch the two probes together. The LED should light up when they touch and stay off when they are not touching. If this is not the case, check your wiring before continuing. You can test out the Continuity Tester on some resistors, fuses or globes. Be sure to only use it on parts that are out of circuit, since it will interact with and possibly cause damage to other powered circuits. Touch one probe to each terminal or lead of the device. The LED will light if the fuse or globe has a low resistance. If the LED Parts List – Continuity Tester (JMP023) 1 small breadboard [Jaycar PB8820] 2 BC557 45V 100mA PNP transistors [Jaycar ZT2164] 1 yellow or red 3mm LED [Jaycar ZD0110] 2 470W ¼W axial resistors [Jaycar RR0564] 1 1.5kW ¼W axial resistor [Jaycar RR0576] 1 5V DC power supply Hookup wire or jumper wires siliconchip.com.au Australia's electronics magazine Fig.3: we laid out our circuit on a breadboard like this, since it is easy to do and you might want to assemble it in a hurry (eg, if your multimeter has a flat battery). is off or dim, then the resistance is higher and the fuse or globe is probably faulty. It is not foolproof, since it only applies a very small current. It’s not uncommon for a fuse to test OK with a continuity tester but then fail in circuit where it has to handle a higher current. On the other hand, a continuity test failure is usually definitive. Other applications A transistor circuit like this is wellsuited to driving heavier loads than just LEDs. The BC557 can handle up to 100mA through its collector, so is well-suited to driving small globes, buzzers and relays if you need a different sort of indication. The relay simply replaces the LED and its resistor. You can use such a circuit to detect a current or voltage. Keep in mind that the relay should be equipped with a diode to catch the inductive spike when it switches off. Also remember that the Darlington configuration will drop almost a volt, even when fully switched on, so your supply should have enough headroom to drive the relay with the reduced voltage. You can imagine that our original Fig.1 circuit would be quite hopeless at driving a relay and that the Darlington transistor is handy at providing the extra current needed. SC This simple circuit can be used to test if things like fuses and globes have continuity, ie, they have a low resistance and are probably operational. March 2025  63 Project by Randy Keenan Versatile Waveform Generator This versatile waveform generator (also known as a function generator) is handy for a variety of uses, including audio equipment analysis, circuit development, displays and demonstrations and as a pulse source for developing switching and motor controls. It uses three op amps to deliver square, pulse, triangle, ramp and sine waves from 1Hz to 30kHz. W aveform generators are often built around specialised ICs, such as the Exar XR2206, Intersil 8038 or the Maxim MAX038. However, I wanted to make a waveform generator using only generic components, like op amps, with these features: ∎ Output frequencies covering the audio range and more, from 1Hz to 30kHz. ∎ Waveform outputs of: a. square/pulse, variable from 5% to 95% duty cycle, or wider b. triangle/ramp/sawtooth, variable from positive to negative ramps c. sinewave with a total harmonic distortion (THD) of around 1% ∎ Duty cycle/symmetry adjustments do not alter the frequency or amplitude appreciably ∎ Output amplitudes of the three waveforms can be matched, peak or RMS, from 0V to 6V peak-to-peak. ∎ An output impedance less than 200W. ∎ Battery-powered for portability and isolation. ∎ Compact size. The design presented here is the result. It uses three op amps, two voltage regulators, six diodes, plus passive components. If any of the specified ICs become scarce, others of the same or better specifications could be substituted. Operating principle The circuit needs to generate the three basic types of waveform: square/pulse, triangle/ramp and sine. Since producing triangle/ramps and sinewaves from a pulse is complicated, the design begins with an op amp integrator producing a repeating triangle/ ramp waveform. Referring to the block diagram, Fig.1, the integrator at left produces the triangle/ramp waveform, with its frequency range set by switching in one of nine different integrator capacitor values. The triangle/ramp waveform is fed to a comparator that turns it into a square/pulse waveform, which is then fed back via the frequency adjustment pot to ensure oscillation. This gives us the triangle and ramp waveforms. The two diodes and symmetry adjustment pot allow the positive and negative ramp rates to be varied to give square/pulse output waveforms. Modifying (shaping) the triangular waveform by a separate circuit section converts it into a sine shape. While the result is not a perfect sinewave, it’s pretty close, as demonstrated by its relatively low distortion/THD figure of about 1%. The waveforms are selected by the middle switch, buffered and level-­ adjusted by IC3, and then fed to the outputs. Circuit details Fig.1: the Waveform Generator is designed around three op amps. IC1 is configured as an integrator and its output feeds into IC2, acting as a comparator, which feeds back into IC1. This feedback loop causes both to oscillate, with IC1 generating a triangular or sawtooth waveform and IC2 producing a square or pulse wave. A triangle-to-sinewave shaper produces the third waveform option. 64 Silicon Chip Australia's electronics magazine The full circuit is shown in Fig.2. The heart of the circuit is the integrator composed of op amp IC1. It uses capacitors as the timing element and switched frequency range switch S1. siliconchip.com.au Fig.2: the complete Waveform Generator circuit. S1 selects between nine possible frequency ranges by switching a different amount of capacitance across the integrator (IC1). Switch S2 is used to choose the desired waveform; its level is adjusted using VR5, then it is buffered by IC3 and fed to two pairs of outputs, one set DC-coupled and the other AC-coupled. The capacitor is charged and discharged via pot VR8, trimpots VR9 & VR10 and diodes D5 and D6. It works as follows. Assume that initially the timing capacitor is discharged, and it is being charged by a current to pin 4 of IC1 through D6. IC1’s output will be a linear negative-going ramp to counteract the increasing charge of the capacitor. The integration needs to be stopped at some point, so the op amp output is fed to a second op amp, IC2, configured as a comparator with hysteresis. When IC1’s output reaches the lower hysteresis voltage, set by trimpot VR7 and associated components, the comparator is triggered and its output goes negative, which is fed back to IC1’s input via potentiometers VR10, VR9, VR8 and D5, which is now forward-­ biased. This causes the timing capacitor to start discharging, resulting in siliconchip.com.au a positive-going linear output ramp from IC1. This continues until IC1’s output reaches the upper hysteresis voltage of the comparator, and the output of IC2 switches again, producing a negative-going ramp from IC1. Thus, the process of charging and discharging of the timing capacitor and switching of IC2’s output continues indefinitely to produce an upward and downward ramp, plus a coincident square wave from the output of IC2. Varying the duty cycle/ symmetry The upward and downward slopes of the triangle or ramp are determined by the charging and discharging currents through the two arms of VR8. If VR8 is at its midpoint, the slopes are equal and a triangular wave is produced. If VR8 is off-centre, the currents through D5 and D6 are Australia's electronics magazine unequal, and a sawtooth waveform is produced. Since the sum of the resistances to D5 and D6 and to IC1 is the same at any setting of VR8—equal to the total resistance of VR8—the period of the ramp, or triangle, will be constant regardless of its shape. (This is not quite true because of the non-ideal schottky diode characteristics and non-ideal characteristics of VR8, but it’s pretty close.) The setting of VR8 also determines the duty-cycle of the square wave/ pulse from IC2, since it depends on the periods of the upward and downward triangle wave ramps. To vary the frequency, the square/ pulse output voltages from IC2 are adjusted by VR10 over a range of approximately 3:1. I chose this range to allow for precise setting of the frequency and to reduce non-ideal effects of the components. March 2025  65 To cover a wide range of frequencies, a series of nine charging/timing capacitors can be selected by rotary switch S1, as shown in Table 1. Note that there is a 330pF capacitor always connected between pins 1 & 4 of IC1, and this is the only timing capacitor that is used on the highest (10-30kHz) range. It also adds to the switched-in capacitances on the 3-10kHz and 1-3kHz ranges, but for lower frequency ranges, its value is too small to have any real effect. To obtain a precisely symmetric triangle or 50% duty-cycle square wave, the potentiometer’s centre detent has to be pretty close to the point where the resistance from the wiper to each end of the track is identical. I have found that for a typical pot, the resistances of the two arms are not equal when set at the detent; furthermore, the detent generally has some ‘wobble’. Also, PCB-mounting potentiometers with a centre detent are not readily available. So, to ensure a symmetric waveform, the S3 “Symmetry” switch can be switched to its “50%” position, engaging VR11 and its 43kW series resistor for equal charging and discharging currents, and thus a fixed 50% symmetry. In the other position, S3 enables variable symmetry, as described earlier. Table 1 – Timing capacitors S1 Freq. range Capacitance 1 1-3Hz 3.3μF 2 3-10Hz 1μF 3 10-30Hz 330nF 4 30-100Hz 100nF 5 100-300Hz 33nF 6 300Hz-1kHz 10nF 7 1-3kHz 3nF or 3.3nF * 8 3-10kHz 2 × 330pF 9 10-30kHz 330pF * 3.3nF might make the 1-3kHz band too low in frequency Table 2 – Li-ion battery options Type & size Voltage Capacity 6F22, “9V” ~8V (use two) 6001300mAh 10440 ~3.7V 350(use four) 1000mAh 14200/ 14250 ~3.7V ~300mAh (use four) 14500 ~3.7V 800(use four) 2500mAh 66 Silicon Chip The final task is to produce a sinewave, and the method must work over the entire frequency range of the generator. In other words, it must be frequency-­independent from 1Hz to 30kHz. This requires some non-­linear circuit elements. There are various methods, but I chose a simple one. Feeding the triangle wave to four diodes—two for positive and two for negative, plus a couple resistors— can reasonably approximate a sinewave. These diodes (D1-D4) should be closely matched, ideally from a single order and adjacent on a tape. This technique will never achieve a perfect sinewave, but it can come close (see Scope 3). The waveforms square/pulse, triangle/ramp, and sine are selected by S2 and then buffered by op amp IC3 before being sent to the output terminals. Both direct and capacitor-­isolated outputs are provided. S2 is arranged with a pattern of square, off, triangle, off, sine for two reasons. Firstly, it provides some isolation among the waveforms, and secondly, having an off position or positions can be handy during use. Because the sinewave from the shaper has the lowest amplitude of the three waves, the output op amp gain is adjusted, via trimpot VR2 (“Sine”), to accommodate the sinewave. Then the square/pulse and triangle/ramp amplitudes can then be adjusted via trimpots VR3 (“Tri”) and VR6 (“Sq”). The wave amplitudes may be adjusted to either have equal peak amplitudes or equal RMS amplitudes, as desired. One reason for choosing equal RMS (root-mean-square) voltages is that each of the waveforms would deliver the same power to the load at the same setting. difficult to fit those into the specified enclosure. Compared to 78L05 & 79L05 voltage regulators, the ADP3300-5.0s have a much lower dropout voltage and lower quiescent current use for lower battery drain. They also have the ability to drive dropout LED indicators (LED1 and LED2 in this circuit) and provide a more accurate regulated voltage. The specified LEDs are high-­ brightness types for operation at low current and thus lower battery drain. The more accurate voltages, coupled with low-input-offset voltage op amps, reduces the need for compensation-­ adjustment circuitry. The ADP33005.0 is used for both the positive (IC4) and negative (IC5) voltage regulation. Thus, the batteries do not have a common connection. If you use USB-rechargeable batteries with a double charging cable, be sure to remove the USB cables from the batteries before switching on the Waveform Generator as the circuit does not have a common battery connection, whereas the USB charging cables do have a common battery connection. The current drawn from each battery is about 18mA each polarity, depending slightly on the frequency and waveform. Thus, the “9V” 600mAh batteries should provide about 20 hours (or more) of operation per charge, as confirmed by my trials, or twice as long for 1200mAh batteries. A 220W load increases the current up to 26mA for a square wave output at 6V peak-to-peak, or several milliamperes lower for the other waveforms. Part choices/variations Two different parts are specified in the parts list for VR8, the SymmePower supply try adjustment potentiometer. The I wanted the waveform generator to P0915N version is better as it results be battery-powered for easy portability in smaller frequency shifts at the as well as electrical isolation. extremes of symmetry/duty cycle, on The two batteries need sufficient the order of about 1-2%. Using the voltage for the 5V voltage regulators PTV09 version will probably result in (REG1 and REG2), meaning about larger frequency shifts. 5.5V minimum, and preferably 7-8V. However, if using the (better) The specified batteries are “9V” (actu- P0915N version, its terminals will ally about 8V) lithium-ion recharge- need to be reformed or trimmed and able types. the two projections on the bottom— Alternative rechargeable lithium-­ not the mounting tabs—will need to ion batteries are listed in Table 2, but be removed so the pot will sit directly check the capacity. I don’t recommend on the PCB. Since its shaft is smooth, using 14500 (AA-size) cells, as four you can drill out a knurled knob for are required, in two holders, and it’s a clean fit. Australia's electronics magazine siliconchip.com.au Photos 1 & 2: this PCB was assembled with the five SMDs on adaptor boards. Note how the miniature banana sockets on the right are soldered to the pads on the top of the PCB. I glued the 9V rechargeable batteries to the bottom of the enclosure and connected them to the PCB using standard battery snaps. Unfortunately, potentiometers typically have a resistance tolerance of ±20%. Consequently, the values of some resistors may need to change depending on the actual resistance of the pots you get. 1. VR8’s nominal value is 100kW. If yours measures above 100kW or below 92kW, you should ideally change the value of the 43kW resistor. Halve the measured value of VR8 and subtract 5kW, then pick the closest available value to use in place of the 43kW resistor. 2. VR10’s nominal value is 1kW. If its value is below 935W or above 1.03kW, you should ideally change the value of the 390W resistor. Multiply VR10’s actual resistance by 0.4 and then pick the closest available value to use in place of the 390W resistor. A good alternative combination of op amps is AD8065 for IC1, either AD8051 or AD8091 for IC2, and AD8033 or AD8065 for IC3 (the AD8033 comes in a smaller package than the others, so will be more tricky to solder). For the five surface-mount ICs, there are two mounting techniques: (a) directly on the PCB as surface mount, or (b) using adaptor boards with pins and receptacles. The main advantage of using adaptor boards is that you can unplug the ICs for testing and it’s easy to replace them later (eg, for experimentation). If you decide to use the adaptor boards, you can prepare them by first inserting five pins, long end down, in the appropriate pattern into a stably mounted DIL socket – see Photo 3. Then place an adaptor board, with the surface-mount pads upward, onto the pins and solder each pin (Photo 4). With the pins attached, solder the IC to the pads using your preferred technique. There are a few ways to do it, either with a regular iron or hot air; the construction procedure below goes over our preferred method. Make sure that the orientation of the IC is correct (see Photo 5). For the op amp ICs, finding the correct orientation is straightforward— they only have five leads. For the regulators, it’s a bit more tricky as they are rotationally symmetrical; refer to the construction procedure below for instructions. Inspect with a magnifying glass to verify that all leads have been soldered correctly. Pin sockets need to be inserted into the PCB to receive the adaptor board pins. It’s best to temporarily attach the adaptor board, solder those socket pins to the main board, Photo 3: using a DIP socket as a jig to hold the PCB pins. Photo 4: soldering the PCB pins to the SMD adaptor board. Photo 5: soldering the SMD IC to the adaptor board. siliconchip.com.au IC mounting Australia's electronics magazine March 2025  67 then unplug it before you power it up. Construction The Waveform Generator is built on a double-sided PCB coded 04104251 that measures 101.5 × 73.5mm. The following instructions assume you will be soldering the three op amp and two regulator ICs directly to the PCB pads. If you want to use adaptors instead, the procedure is not terribly different except that you will be soldering those parts to the adaptors, then fitting the adaptors with pins and soldering matching sockets to the sets of five through-hole pads arranged around each chip location. Start by soldering the five SMDs. In each case, spread a thin layer of flux paste over the PCB pads first. The op amps, IC1-IC3, each have five pins with two on one side and three on the other, so the correct orientation of each should be obvious. Place the part on the board, tack-­solder one pin and check that the device is flat on the board and each lead is centred over its pad. If not, remelt the initial solder joint and gently nudge the part into place. Repeat if necessary until it is nicely aligned, then solder the remaining pins. Add a small amount of flux paste to the first pin and touch it with a clean soldering iron tip to reflow the joint. Given that these leads are quite close together, you may have accidentally bridged two or more pins. Use a magnifier to check. If you have, it’s quite easy to correct: simply add a small amount of flux paste to those pins, put the end of some solder-wicking braid on top and press it down onto the board and pins with your soldering iron. Wait for a few seconds until the solder melts, then drag the wick away from the pins and lift it and the iron off the board. That should leave behind just the right amount of solder. REG1 and REG2 are similar to IC1-IC3, but they’re a bit more tricky because they have three pins on each side. That means you’ll have to figure out which of the two possible orientations is correct. The PCB is missing a pad on one side because pin 2 of these devices is not used. Examine the chip under magnification and find the pin 1 indicator in one corner. Rotate it so that corner is next to the missing central pad, then tack-solder one pin. Proceed with soldering as for IC1-IC3 but of course you can skip the pin which has no corresponding pad. You should still check for bridges to pin 2 (however unlikely they are) and fix them if present. If you manage to solder them in the wrong orientation, simply remove the middle pin and resolder it on the other side of the adaptor. Now move on to fit the throughhole resistors and diodes. The orientations of the resistors do not matter but the diodes do, so make sure their cathode stripes face as shown in the overlay diagram (Fig.3). Also, don’t get the similar-looking 1N4148 (standard silicon, D1-D4) and BAT41 (schottky, D5 & D6) diodes mixed up. Note that the resistors used are smaller than the standard 1/4W or 1/2W types generally used in our projects. As 1/4W resistors won’t fit in the specified case, we recommend you use 1/6W or 1/8W miniature body resistors. There are many resistor values used, so refer to the colour code table in the parts list or use a DMM set to measure ohms to ensure they go in the right locations. Follow with the capacitors, none of which are polarised except for the two larger electrolytics. Their longer (positive) leads face each other, as shown by the + marks on Fig.3. While many of the ceramic capacitors are 1μF types, there are quite a few different values, so don’t get them mixed up. The two larger 1μF 250V caps go near the output terminals as shown, laid over as otherwise they will be too tall to fit in the enclosure later. Next, fit the trimpots. There are eight in four different values, so again, make sure the right ones go in the right locations. Note that the footprints for the trimpots on the PCB have four pads, while the trimpots have three pins. This is to allow you to use either the common 3362P types or the less-­ common 3362R reversed version. Fig.3 shows the correct orientations for 3362P trimpots, and the PCB also has “P” and “R” labels on the two possible locations for the central pin. If using 3362R trimpots, rotate them 180° compared to what’s shown in Fig.3, so the central pin goes into the pads marked “R” on the PCB. Testing If you are using adaptors for the op amps, you can test the board before connecting any of the expensive op amps to the circuit. Connect the batteries, plug in the two regulators Fig.3: the three ICs and two regulators are shown soldered directly to the PCB here, but they can also be attached via SMD-to-DIL adaptors, using the rows of holes above and below each of those devices. Watch the orientations of the ICs, diodes, electrolytic capacitors, trimpots and rotary switches. The two LEDs indicate both when it is switched on and also whether the 9V batteries are still OK. Also note the way the batteries are wired – there is no reverse polarity protection! 68 Silicon Chip Australia's electronics magazine siliconchip.com.au and switch the power on; both LEDs should light up. When connecting the batteries, it is best to have the power switch off; otherwise, accidentally touching a connector with the wrong polarity could damage a voltage regulator. Using the output ground (“COM.”) as a reference, measure the voltages at pins 2 & 5 of IC1 (you can use the larger through-hole pads or sockets rather than trying to probe the SMD pads). Pin 2 is at top centre and should measure -4.98V to -5.02V, while pin 5 is at lower-right and should measure +4.98V to +5.02V. If not, switch off and check for faults. If you’ve soldered these ICs directly to the board, you can still perform this test, but there is a risk of damaging the ICs if something is wrong with the regulators. So check the orientation of REG1 & REG2 carefully before switching on, as well as the polarity of the batteries and their wiring (you can do this by probing the battery terminals on the PCB with a multimeter). If everything checks out, and you have socketed the ICs, switch the power off and plug in IC1, IC2 and IC3. Make sure they’re all orientated correctly, with the sides with two pins facing towards the bottom of the PCB. Set the Amplitude control (VR5) to maximum and the Waveform switch (S2) to square wave. Set Symmetry (S3) to the 50% position, and all trimpots to around midrange. When power is switched back on, there should be a square waveform—or nearly so—at the output, centred at 0V. Troubleshooting Are both LEDs on? If not, the batteries, voltage regulators and associated circuitry need attention. If they’re on but there’s no output, check that the Waveform switch (S2) is not at one of the off positions and that the Amplitude control (VR5) is not at or near minimum. Try adjusting trimpot VR7 (“Hyst”). As usual, if you run into any problems, check that the ICs and diodes are all in the correct orientations. Remove the ICs, if using adaptor boards, and verify the supply voltages again. Check that the resistors and capacitors are all the correct values. Look for unsoldered pins or wires, and for solder bridges on both sides of the PCB. If you’re still stuck, check the output of IC1 at pin 1 (upper right). If siliconchip.com.au Parts List – Waveform Generator 1 double-sided PCB coded 04104251, 101.5 × 73.5mm 1 Serpac 131,BK plastic enclosure [Mouser 635-131-B] 1 panel label, 104 × 74mm 2 9-position vertical rotary switches, 18t split shafts (S1, S2) [Taiwan Alpha SR1712F-0109-15K0A-N9-N-027] 2 miniature PCB-mount vertical DPDT toggle switches (S3, S4) [Nidec ATE2D-2M3-10-Z] 4 miniature 2mm banana sockets [Amazon B096DD21SP] 5 SOT-23-6 to DIL breakout boards (optional) [SparkFun BOB-00717] 25 0.51mm diameter PCB pins (optional) [DigiKey ED90325-ND, Mouser 575-90810001508] 25 0.51mm diameter PCB pin sockets (optional) [Mouser 575-3016015152127] 2 9V rechargeable batteries [eg, 600mAh EBL6F22] (BAT1, BAT2) 2 9V battery snaps with flying leads (BAT1, BAT2) 5 knobs to suit the 18t spline shafts of S1, S2, VR5, VR8 & VR10 4 3mm inner diameter, 1mm-thick plastic or fibre flat washers 4 No.4 × 8mm self-tapping screws 4 stick-on rubber feet Semiconductors 2 AD8065ART op amps, SOT-23-5 (IC1, IC3; see text for other options) 1 AD8091ART op amp, SOT-23-5 (IC2; see text for other options) 2 ADP3300ARTZ-5 low-dropout 5V linear regulators, SOT-23-6 (REG1, REG2) 1 high-brightness 3mm red LED (LED1) [Kingbright WP710A10SRD/J4] 1 high-brightness 3mm green LED (LED2) [Kingbright WP710A10ZGDK] 4 1N4148 or equivalent 75V 200mA signal diodes (D1-D4) 2 BAT41 or equivalent 70V 15mA schottky diodes (D5, D6) Capacitors (all 50V radial multi-layer ceramic, 2.5mm pitch unless noted) 2 330μF 6.3V low-profile (5mm tall) radial electrolytic [Panasonic ECE-A0JKS331] 1 3.3μF 25/50V X7R ±10% [Murata RCER71E335K2DBH03A] 2 1μF 250V X7R ±10% [Murata RDER72E105K5B1H03B] 12 1μF 25/50V X7R ±10% [Murata RDER71H105K2M1H03A] 1 330nF 25/50V X7R ±5% [Kemet C333C334J5R5TA] 1 100nF 25/50V NP0/C0G ±5% [Murata RCE5C1H104J2A2H03B] 1 33nF 25/50V NP0/C0G ±5% [TDK FA14C0G1H333JNU00] 1 10nF 25/50V NP0/C0G ±5% [Kemet C315C103J3G5TA] 1 3.3nF NP0/C0G ±5% [Murata RCER5C1H332J0DBH03A] 1 1nF NP0/C0G ±5% 3 330pF NP0/C0G ±5% [Kemet C315C331J3G5TA] 1 100pF NP0/C0G ±5% [Vishay K101J15C0GH53L2] 1 47pF ±5% [TDK FG18C0G1H470JNT00] 1 33pF NP0/C0G ±5% [Vishay K330J15C0GF53L2] Potentiometers (all 9mm vertical plastic pcb-mount 18t spline shaft types) 1 5kW linear B-type (VR5) [Bourns PTV09A-4030U-B502-ND] 1 100kW linear B-type (VR8) [DigiKey 987-1708-ND – see text] 1 1kW linear B-type (VR10) [DigiKey PTV09A-4020U-B102-ND] Trimpots (all 3362P-style miniature top-adjust) 3 2kW (VR1, VR2, VR6) 3 5kW (VR3, VR7, VR9) 1 1kW (VR4) 1 10kW (VR11) Resistors (all ⅛W miniature axial 1%) 2 470kW 1 3.3kW 1 100kW 2 2.2kW 1 43kW 1 1kW 1 27kW 1 470W 2 22kW 1 390W 1 3.9kW 1 330W Australia's electronics magazine March 2025  69 Fig.4: a pure sinewave shaped like this will have a low distortion figure, well under 1% THD. Try to get the output of your unit to match this as closely as possible. there is a triangle waveform, then IC1 & IC2 are working and IC3 may need attention. If you’re getting strange waveforms, verify that the schottky and regular diodes have the correct orientations. Check the values of the following components: the filter capacitors across VR3 and series diode pair D1 & D3, IC3’s feedback capacitor, and compensation capacitor across the 2.2kW resistor from IC1’s output to VR7. Set-up and calibration Calibration requires the following steps in sequence. 1. Set the Frequency Band switch (S1) to the 1-3kHz position. Set the Frequency pot (VR10) and all trimpots at approximately midrange. 2. Connect an oscilloscope to the lowest lead of a capacitor below S1, using the output common terminal as the reference. 3. Set the S3 Symmetry switch to the 50% position and apply power. A triangle wave should be displayed on the oscilloscope. Adjust trimpot VR7 (Hyst) so you get exactly 4V peak-topeak. The triangle may be slightly asymmetrical; that will be fixed in step 5. 4. Connect the oscilloscope to the direct output terminal, set the Waveform switch (S2) to square wave mode and adjust VR5 for maximum amplitude. A square wave should be displayed on the oscilloscope. 5. Adjust trimpot VR4 (Balance) for an exactly symmetrical square wave. A multimeter with a duty-cycle measurement option would be useful here, or use a similar oscilloscope measurement. Adjust VR10 (Frequency) if necessary. 6. Set S3 to its alternative Vary position. Adjust trimpot VR9 (“Sym”) so you get slightly less than 5% duty cycle with VR8 fully anti-­clockwise and slightly more than 95% duty cycle with VR8 fully clockwise. The duty cycle can be pushed from 2% to 98%, but frequency shift may increase. 7. With S3 still in the Vary position, adjust VR9 (Sym) for an exactly symmetrical waveform. Note the frequency. Set S3 back to the 50% position and achieve exactly the same frequency by adjusting VR11 (50% Freq). 8. Set S3 back to the 50% position and S2 to sinewave. An approximate sinewave should be displayed. Sinewave adjustment 9. Adjust trimpot VR1 (THD) to achieve the cleanest possible sinewave. You can trace Fig.4 onto tracing paper, baking paper or clear plastic and place it over the oscilloscope screen as a guide. Alternatively, if your ‘scope has a spectrum analyser mode (or you have a spectrum analyser) adjust VR1 for minimum harmonics. If you are not fussy, forming an approximation to a sinewave on a ‘scope screen may be good enough. If using a spectrum analyser, I suggest setting the Wave Generator frequency to 1kHz and the analyser frequency span to cover the audio range. Momentarily switch to triangle wave mode and adjust trimpot VR4 (“Bal”) to minimise the second (2kHz) and all other even harmonics. This should only require a slight readjustment. Switch back to sinewave mode and adjust VR1 (“THD”) to minimise the odd harmonics. Then adjust trimpot VR1 (THD) to minimise the odd harmonics. VR7 (Hyst) may also be adjusted a slight amount, but this will also alter the frequency bands. When you’ve finished, all even harmonics should be approximately 60dB lower than the fundamental and all odd harmonics (starting at 3kHz) should be at least 45dB lower than the fundamental. Adjust the amplitude setting as necessary to avoid overloading the spectrum analyser. A sinewave THD close to 1% should be achievable. Wave amplitudes 10. Leaving the ‘scope connected to the direct output and S2 in the sinewave position, set VR5 (Amplitude) to maximum. Now you have a choice of equal peak voltages or equal RMS voltages for the three waveforms. For equal peak voltages, decide on what maximum you want and adjust VR2 (Sine) to that maximum. I do not recommend greater than 6V peak-topeak. Next, set S2 to square wave mode and adjust VR6 to achieve the chosen maximum output level. Switch S2 to triangle wave mode and adjust trimpot VR3 (Tri) to achieve the same maximum level. Alternatively, to set the waveforms to equal RMS voltages, use Table 3 or an RMS-reading device (multimeter or oscilloscope). 11. Check that VR10 (Frequency) varies the frequency over a range of at least 3:1 and check the minimum Fig.5: the controls are quite complicated so you’ll need this panel label to understand what they all do. It will also help you locate the holes for the switch and potentiometer shafts, LEDs and banana sockets. You can download it as a PDF from our website and print it at actual size (1:1). 70 Silicon Chip Australia's electronics magazine siliconchip.com.au and maximum frequency for each band. The bands should overlap. If the minimums are not low enough, decrease the value of the 390W resistor. If the maximums are not high enough, adjust VR7 (Hyst) slightly and return to step 8. The frequency bands will likely not track by exact factors because of the typical variations in capacitance of the timing capacitors. That’s why these capacitors (all the ones that connect to pin 1 of IC1) should have a ±5% or better tolerance, if possible. In the worst case, you may need to replace one or two caps or parallel them with lower-value capacitors. 12. With S2 (Waveform) set to triangle wave and S3 (Symmetry) at the Vary setting, rotate VR8 (Symmetry) to both extremes to check that the triangle wave becomes a clean downward or upward ramp/sawtooth, and recheck that, on the square wave setting, the output becomes a pulse that varies in duty cycle between 5% and 95%. Enclosure preparation Fig.5 is a front panel label that can also be used as a drilling guide. You can download it from siliconchip.au/ Shop/11/1823 We have instructions on preparing and attaching panel labels online, see: siliconchip.au/Help/FrontPanels With the panel label attached, the holes can then be drilled through carefully. The final hole sizes are 3mm for the LEDs, 8mm for the potentiometers, 10mm for the rotary switches, 4mm for the toggle switches and 2.5mm for the banana sockets. If possible, I suggest punching the small holes. I also suggest countersinking the small holes on the inside of the enclosure for easier insertion of the LEDs, switches and banana receptacles. The mounting post on the top part of the enclosure that is near rotary switch S2 needs to be trimmed back a bit to allow room for the switch. The anti-rotation tabs on the tops of the rotary switches and pots need to be removed. Insert the LEDs and banana sockets into the PCB with the LEDs in the correct orientations, but do not solder them yet. Temporarily fit the PCB into the enclosure using a 1mm-thick non-­ conductive (eg, plastic or fibre) spacer or washer on each mounting post. Top tip: use super glue to stick the washers in place temporarily (either to the enclosure or top of the PCB) so they don’t slide out as you’re trying to assemble everything. Adjust the LEDs and banana receptacles as desired, then solder the LEDs, and tack-solder the sockets quickly to avoid melting the plastic. Remove the PCB and solder the sockets to the upper surface of the PCB, being careful to maintain their position. You can now screw the PCB into place in the enclosure on the 1mm spacers. Do not use panel-mount hardware on the rotary switches or VR8. After considering several mounting methods for the batteries, I simply used a little epoxy to attach them to the lower part of the enclosure, with a piece of thick paper in between should I ever want to remove them. You could also consider foam-cored double-sided tape, although it may not be strong enough to hold them long-term. Usage notes The square wave or pulse rise and fall times are approximately 90ns (see Scopes 1 & 2). There is a barely noticeable non-linearity in the triangle waves at the three lowest frequency bands. I attribute this to the capacitors, which are X7R for these bands. The higher-frequency bands use C0G/NP0 capacitors and look perfectly linear to my eye. Using C0G or film capacitors for the higher-value timing capacitors would eliminate the slight non-linearity, but they are too large to realistically fit. For an explanation of capacitor types, see our detailed March 2021 article on capacitors (siliconchip. au/Article/14786). Scope 3 compares the Waveform Generator’s quasi-sinewave (mauve) to a pure sinewave (yellow) at 1kHz; the pure sinewave was generated by sending the Waveform Generator quasi-­sinewave through a three-stage RC filter. Table 3 – peak vs RMS voltages Waveform RMS formula Peak for 1V RMS Peak for 2V RMS Square/pulse Vrms = Vpeak 1V 2V 1.73V 3.46V 1.41V 2.83V Triangle/ramp Sine siliconchip.com.au Vrms = Vpeak ÷ √3 Vrms = Vpeak ÷ √2 Australia's electronics magazine Scope 1: a 30kHz pulse with a duty cycle of 2%, from setting “Waveform” to square/pulse and the “Symmetry” control fully anti-clockwise. Scope 2: a 30kHz ramp, from setting Waveform to triangle/ramp and Symmetry control fully anti-clockwise. Scope 3: a pure sinewave (yellow) with the generator’s output overlaid (mauve) at 1kHz. The total harmonic distortion (THD) is around 1% if it’s properly adjusted. There is a slight phase shift between the two waveforms. There is a frequency shift, up to 1-2%, as the symmetry/duty cycle is varied between 5% and 95%. This appears to be a peculiarity of the potentiometers; in particular, carbon-­ element potentiometers. Cermet pots have much less shift, but they are considerably more expensive. A likely additional contributor is the nonideal characteristics of the schottky diodes. SC March 2025  71 Workshop/Shed Alarm Simple Electronic Projects with Julian Edgar This remote-control alarm uses a two-stage siren and can optionally switch on inside and outside lights when triggered. The design uses commonly available prebuilt modules and relays. M Photo 1: I built my alarm into a plastic utility box. Two terminal strips provide the external connections. y new home workshop was recently completed. It’s built on the block of land next to where we currently live (one day, we will build a house on the new block as well) and is a few hundred metres away from our existing house. I decided to install an alarm in the workshop – but then the fun started. Or didn’t, actually. I thought what I wanted was very simple. I wanted an alarm that could be armed/disarmed by a keyfob remote control that I’d carry on my workshop keys. When the alarm was armed, I wanted LEDs flashing at each door. If the alarm was triggered by unauthorised entry through the opening of any door, I wanted a siren to sound, quietly at first (in case I forget to deactivate the alarm), then subsequently at full volume for a set period. When the alarm was triggered, I also wanted interior and exterior LED floodlights to switch on. Finally, I wanted the LED lights, system controller and siren to run off 12V provided by a rechargeable battery. I couldn’t find anything even close to these specifications! Instead, I found very complex systems that would send me emails or text messages, ones that used single motion sensors that could never cover the interior area of the workshop, or others that were so expensive I just couldn’t believe it. Cheap car alarms came closest, but they tended to have very poor instructions that would take hours to sort out (I know, I bought one) – and that’s before adapting the system to these unique requirements. So I decided to build my own alarm. If you break the above requirements down, all that is needed to achieve the above list is: • An off-the-shelf remote control module and fob. • Door switches. • A latching system so that the alarm continues to sound even if a door is shut again. • Two timers – one for giving the ‘quiet siren’ period and the other the ‘total siren’ period. • Flashing door LEDs. • Switched power for the floodlights. • A siren, battery etc. Photo 2: note how I extended the curly antenna of the remote-control module. Behind the remote-control module is the latching relay that keeps the alarm sounding even if an opened door is later closed. Photo 3: the two red boards are the timers. One switches off the siren after a pre-set time and the other causes the siren to switch to full loudness after a short period. The relay at the back switches on 12V floodlights if the alarm is triggered. Photo 4: any 12V-powered siren can be used. This one was originally supplied in a car alarm kit and cycles between different sounds – very attention-getting! 72 Silicon Chip Australia's electronics magazine siliconchip.com.au Rather than taking an Arduino or similar approach, I decided that the controller would primarily consist of relays – yes, old-fashioned relays! One relay could drive the 12V lighting, while another could provide the latching function. The timers could be provided by some low-cost eBay modules, again with relay outputs. The system could be activated when the remote control module’s output relay closed, feeding power to the rest of the system. That left only the flashing LEDs – easily sourced, complete with dropping resistors for the 12V supply – and a battery and plugpack charger. Fig.1: when the alarm is armed via the remote control, power is fed to the flashing door LEDs and a latching relay. The latter stays dormant until a door is opened. Opening a door sends power to Timer 1, which feeds Timer 2, resulting in a quiet sound from the siren, followed by a loud one if the unit is not quickly disarmed. Design Fig.1 shows a block diagram of the system, while Photo 1 shows the completed unit. When the alarm is armed via the remote control, power is fed to the flashing door LEDs. Power is also then available to the latching relay, but it stays dormant until a door is opened. Door opening causes the relay’s coil to be powered, its contacts to close and then stay latched via one of its two sets of contacts. This feeds power to Timer 1, which starts counting. The timer output that is used is the Normally Closed one – so when this timer’s relay activates after about a minute, the output is switched off, silencing the siren. Timer 1 feeds Timer 2, which supplies only a low voltage to the siren for the first seven seconds before switching to full voltage. The latching relay also switches on the lighting relay, activating interior and exterior LED floodlights. 12V floodlights (eg, those sold for ancillary car lighting) are suitable and, these days, are quite cheap. These lights stay on until the system is reset by the keyfob (or by removing battery power). Alternatively, you could feed the LED floodlight relay following Timer 1, so the lights would go off when the siren stops. If you use high-power lights, taking this latter approach will help to stop the battery from going flat. Fig.2 shows the circuit. There are a few things to note: 1. Both external relays are double-­ pole, single-throw designs (DPST). Only an SPST relay is needed for the lights, but for the sake of convenience, I used the same type of relay for both latching and lighting functions. 2. The door switches carry only the current needed to operate the latching siliconchip.com.au Fig.2: each of the five main parts – the remote-control module, latching relay, lighting relay and two timers – can be wired and then tested before proceeding to the next stage. Timer 1 switches its output off when the timed period is activated, while Timer 2 bypasses the series resistor feeding the siren when the timed period has elapsed. relay’s coil, which is very little. The switches, in the circuit configuration shown here, need to close when the door is opened. 3. I used 6-core cable to connect the door switches and also to power the flashing LED at each door. Only 4-core cable is needed, but I had a large roll of 6-core cable that I’d acquired cheaply. The workshop has six doors (five roller doors and one personal access door) and the cable runs are long. However, there are no problems with voltage drops as the currents are so low. Components Here’s what you will need to build this alarm (also see the Parts List). • A 12V remote control module with relay output. Almost any 12V relay output remote module that has a latching function will be suitable. Australia's electronics magazine Latching means that the output relay stays engaged after you have taken your finger off the fob’s button. Some remotes require you the press the button again to unlatch, and others have separate ‘on’ and ‘off’ buttons – either approach is suitable. • A DPST (or DPDT) 12V-coil relay with 5A-rated contacts. This relay acts as the latch and also supplies all current to the rest of the circuit. • An SPST 12V-coil relay rated to drive the LED floodlights. This relay drives the lighting circuit. You could also use a DPST or DPDT relay. • Two variable delay modules (Photo 3). Almost any cheap delay module that has a relay output will work. However, the modules must operate from 12V, and they also need to have at least a single pole, double throw (SPDT) relay output. This means they will have Common, Normally March 2025  73 Open and Normally Closed relay connections. • A 12V siren (Photo 4). I used the one from the car alarm I bought. It draws about 800mA at 12.5V and is quite loud. It also cycles through different sounds, which is attention-­ getting. A variety of 12V sirens is available from about $12. • A resistor to reduce the siren’s output for the quiet period. I found an appropriate value resistor through some quick testing. In my case, with the siren being fed 12V, 180W gave the required reduction in siren volume, and the ½W resistor did not get warm. Different sirens will require different values. Start with values around 200W Photo 5: the alarm is triggered by door switches that must close when the door is opened. Here, an industrial roller switch has been used, activated by the folded aluminium bracket screwed to the door frame. Smaller, less expensive door switches are available. and increase it if the siren is still too loud. Ensure the resistor does not get warm – if it does, increase its wattage. Going too high in wattage is no problem. • Flashing LEDs, pre-wired for 12V use. These are cheap and commonly available. Choose whatever colour you want! (See Photo 7.) • A 12V battery. See the discussion below on options. • A means of charging the battery (eg, a solar panel or plugpack charger). • 12V LED floodlights. Using car accessory lights is cheapest, but ensure you do not select very powerful lights. Otherwise, you’ll need to upgrade the relay and battery. Photo 6: the opening of roller doors can be tricky to detect, but this is achieved here using another industrial roller switch, with this one equipped with a long lever. The switch has been protected by being mounted inside galvanised brackets. • Door switches. A wide variety of switches is suitable, including microswitches and reed switches. I used industrial roller switches (Photos 5 & 6). These are normally quite expensive, but I found a supplier that had them on sale for about $5 each. They are splashproof and durable over many cycles. Their large rollers are also easy to trigger from door movement. You can use as many switches as you like – just wire them in parallel. Remember, the switch needs to close when the door is opened. • A box to house the alarm, terminal blocks, standoffs, screws and nuts, cable etc. Battery choice Literally any 12V rechargeable battery can be used. If you charge the battery from a float charger, the battery needs to supply power to the system only during a mains power failure. Thus, the battery doesn’t need to do a lot, and it’s likely a salvaged ex-car lead acid battery will be fine. Your local car mechanic is likely to have half a dozen waiting to go to the recycler. They’ll be free or only at nominal cost. If you are using a solar panel to charge the battery, the battery will need to power the system for perhaps up to a week in rainy weather. Current consumption will depend on the specific remote module, relays and LEDs you use. As a guide, my system had a current consumption of 12mA (unarmed) and 41mA (armed), plus an average consumption of each flashing LED of 13mA. When activated (relays engaged, siren running) the current consumption was about 1A. Building it Photo 7: the flashing LED (circled in green) is inconspicuous in the daytime but very obvious at night. It is bright and flashes at 1Hz. It is mounted in an aluminium bezel and sealed with silicone. 74 Silicon Chip Australia's electronics magazine I built my alarm into a plastic box that measured 190 × 110 × 80mm. This is a little bigger than required, but it gives room for the remote module’s normally coiled antenna to be stretched upwards – something that gives noticeably better range (see Photo 2). I suggest you build the Alarm stepby-step on the bench, testing it at each step. Start by connecting power to the remote control module. Check that the output relay clicks appropriately when the remote fob button is pressed (Photo 8). The relay should switch on and stay pulled in, then with another button press, switch off. siliconchip.com.au Next, add one of the flashing LEDs. Check that the LED flashes when the alarm is armed via the remote and turns off when the alarm is disarmed. As with the switches, you can use as many LEDs as required, again wired in parallel. Wire in the latching relay next. Do this in two steps. The first step is to ensure that when the alarm is armed via the remote and a door switch is closed, this relay pulls in. Then add the relay’s ‘latching’ wiring and repeat the test. This time, the relay should stay pulled in, even when the ‘door’ is again closed (ie, the door switch is opened). Disarming via the remote should cause this relay to unlatch and the flashing LED to switch off. Wire in the lighting relay next and check it operates when the alarm is triggered. The two delay modules are next. Note that the Normally Closed relay output connection is used for the main timer – that is, the output is energised until the timed period elapses, whereupon the output is switched off as the relay contacts are pulled in. Wire in this module and check its relay activates at the end of the period that you want the siren to sound for. These timers typically have an onboard pot that allows the period to be adjusted. In the case of the timers shown here, the maximum period was a bit short (10 seconds). I extended it by soldering a 470μF 16V capacitor in parallel with the main timing capacitor, giving a one-minute maximum period. This sounds like a short time for the siren to sound, but in the quiet location where I live, it’s plenty. The second timer, that allows the siren to sound only quietly at first, uses both relay outputs. The Normally Closed output (that is energised when the timed period has not yet elapsed) feeds the siren through the resistor. When the timed period has finished, the relay switches and the Normally Open contact is energised. This feeds the siren directly, so bypassing the resistor and causing the siren to sound at full loudness. Wire this relay in next. The complete system can now be bench-tested, with the siren suitably muffled with a towel or similar. Check that: 1. The alarm can be armed and disarmed by the remote, with the flashing LED indicating the status. siliconchip.com.au Parts List – USB Solar Charging System 1 12V remote control module with relay output and latching function [eBay 155694654180] 2 DPST (or DPDT) 12V DC coil relays [Jaycar SY4065] 2 variable delay modules [eBay 235710400707] 1 12V siren [Jaycar LA8908] 1 12V rechargeable battery [Jaycar SB2484] 1 12V battery charger [Jaycar MB3619] flashing LEDs, pre-wired for 12V use [Jaycar LA5082] door switches [Jaycar LE8777] 12V LED floodlights [eBay 235086391538] 1 plastic case, large enough to house the parts (I used 190 × 110 × 80mm) 1 chassis-mount fuse holder & fuse rated to suit maximum total draw cabling and wire to suit installation various machine screws, nuts, standoffs and terminal strips as required 2. When the alarm is armed, closing a door switch (opening a door) causes the lighting relay to pull in and the siren to start operating, quietly at first before then switching to full volume. 3. The quiet siren period is as you have set it (eg, seven seconds) and the full siren period is also as set (eg, one minute). 4. You can switch the operating siren and lights off by deactivating the system via the remote. Installation How you install the system is largely up to your individual requirements. As my main workshop wiring was being done simultaneously with the alarm installation, I used the same approach for the alarm wiring as for the normal mains wiring – that is, placing the cables in plastic conduit. This protects and conceals the alarm wiring. I placed the siren high in the workshop (out of reach!). The door switches are triggered by small aluminium brackets that I bent to the required shape. The alarm controller and the sealed lead-acid (SLA) battery are concealed in a timber enclosure within shelves – it’s not obvious where they are. In my application, the battery is charged by a solar panel working through a small solar charge regulator. Conclusion There’s something to be said for working with electronics where you can see components (like relays and switches) actually working. Also, apart from the door switches and siren, every other component was already SC in my parts drawers! Photo 8: the alarm is activated and deactivated with this remote control. Australia's electronics magazine March 2025  75 Precision Electronics Part 5: Noise So far, this series has mostly been concerned with errors arising from component matching and unwanted currents and fixed voltages. There is another type of unwanted signal that can cause all sorts of problems that we refer to as noise. So, how can we quantify its effects on our circuits and reduce the resulting errors? By Andrew Levido I n electronics, the term “noise” can refer to any form of unwanted signal that masks a signal of interest. This includes noise that is imposed upon a circuit from external sources such as radio-frequency interference or mains hum, which can be reduced or eliminated by filtering, shielding or other design techniques. However, there are sources of noise that are intrinsic to the components themselves. They come from within the circuit, not outside, so they cannot be reduced by shielding. In this article, we will look at this type of truly random noise that is caused by various physical phenomena within the components we use. As we have discussed in earlier articles, precision electronics design is all about understanding and quantifying the sources of uncertainty, and noise is another error source that we cannot always ignore. To understand noise, we will have to start with a bit of theory, but I will try to keep it to a minimum. We will then get into the practical side with a full noise analysis of a simple audio amplifier. Let’s begin by looking at the main types of noise of concern to electronics designers. Johnson noise Johnson noise, sometimes also called Nyquist or thermal noise, is essentially the electrical signal produced in lossy components by the random movement of charge carriers (usually electrons) due to temperature. Remember that temperature relates to the motion of atoms and other elements of a material; they are only still when the material is at absolute zero. For example, a 10kW resistor at room temperature will develop a noise voltage across its terminals of 76 Silicon Chip around 1.3µV RMS if measured with a high-impedance AC voltmeter with a 10kHz bandwidth. If we were to short-circuit the resistor, we would measure a noise current of about 130pA (1.3µV ÷ 10kW) over the same bandwidth. This phenomenon was first described by John Bertrand Johnson in 1927 and characterised by Harry Nyquist in 1928. Nyquist showed that the noise voltage density in a resistor is given by the equation Vrms = √4kTRfb, where k is Boltzmann’s constant (1.38 × 10-23), T is the absolute temperature in Kelvin, R is the resistance and fb is the bandwidth in hertz (Hz). This highlights the first important thing to keep in mind when discussing noise: we can only quantify a noise voltage or current if we also specify a bandwidth over which to measure it. If we don’t know the bandwidth of concern, we can only describe noise in terms of a voltage or current per unit frequency, called the voltage or current noise density. The units of voltage noise density are V/√Hz and those for current noise density are A/√Hz. You have to be careful to distinguish between an absolute value of noise (an RMS [root-mean-squared] voltage or current) and its density. The relationship between them is analogous to the relationship between the mass and density of a material. Density is a property intrinsic to the material, but the mass of an object made of the material depends on the amount of it we are dealing with in a specific case. The noise voltage density of a resistor, for example, is a property of the resistor at a given temperature, but the noise voltage developed across it depends on the bandwidth we use to measure it (or over which it has an effect). In the case of Johnson noise Australia's electronics magazine (and any white noise, as we will see below), the relationship between noise density and voltage is the square root of the bandwidth. Johnson noise is an inescapable result of the thermal agitation of electrons that occurs anywhere that charges are free to move. Fortunately, you can normally ignore the Johnson noise generated in conductors like wires, since their resistance is so low that any noise that they may contribute is negligible. In fact, mostly lossless devices like capacitors and inductors (up to a point) do not contribute to the overall noise in a circuit. They can, however, impact bandwidth and therefore can influence the noise voltage or current. Shot noise Johnson noise occurs even when no current is flowing. On the other hand, shot noise occurs because a flowing current is made up of discrete ‘chunks’ of charge (electrons or holes). If the moving charges act independently of each other, the resulting randomness of the current flow causes noise. This phenomenon does not occur in metallic conductors, where the moving electrons influence each other and therefore don’t act randomly. It does occur in semiconductors, though; for example, when charge carriers are diffusing across a semiconductor junction. The shot noise density is given by the formula in = √2qIdc and is expressed in units of A/√Hz. Here, q is the charge on an electron (1.6 × 10-19C) and Idc is the average current. The RMS value of shot noise is therefore irms = √2qIdcfb . This means that a steady 1A current passing through a semiconductor junction will see a random variation of 57nA RMS when measured over a siliconchip.com.au 10kHz bandwidth. That corresponds to about 0.057ppm (parts per million) – small enough to be immaterial in most situations. Shot noise gets relatively larger as the current reduces because there are fewer moving charge carriers. For example, a 1µA current will have a superimposed shot noise of 57pA RMS, which corresponds with 57ppm; it is becoming more significant. 1 ∕f noise Shot and Johnson noise are both types of ‘white noise’, ie, they carry equal power per unit of frequency (hertz) across the spectrum. This is why we can simply multiply the noise density by the square root of the bandwidth to calculate the noise voltage or current. 1∕ noise (sometimes called flicker f noise) differs from Johnson or shot noise, which are the result of atomic-­ level physical phenomena. 1∕f noise is created by a variety of mechanisms (not all well understood) relating to materials and construction techniques. 1∕ noise has the defining characf teristic of having an equal energy per decade of spectrum. In other words, it has the same power in the 1-10Hz range as it does in the 10-100Hz and 1-10kHz ranges. This means the power per hertz is inversely proportional to frequency – hence the 1∕f name. Noise with this power spectrum is known as ‘pink noise’ and it occurs in a wide variety of places, including the flow of traffic, ocean currents and the loudness profile of classical music! From an electronics perspective, 1∕ noise does occur in some resistors f depending on their construction (carbon composition resistors were notoriously bad for this) but it can usually be safely ignored in modern resistors. It can become significant in op amp circuits, which is why we need to know about it. Burst and avalanche noise There are two other sources of noise in electronics that are worth mentioning: burst noise and avalanche noise. Burst noise, also known as popcorn noise, is a low frequency (<100Hz) ‘popping’ phenomenon caused by manufacturing imperfections in semiconductor materials. It used to be a problem in the early days of integrated circuits, but improved manufacturing processes have all but eliminated it. Avalanche noise is similar to shot noise but occurs during the reverse breakdown of semiconductor junctions. Its amplitude can be very high, so it is often used when we want to deliberately to create an analog white noise source. We don’t usually operate our circuits with semiconductor junctions in reverse breakdown, so we can ignore avalanche noise most of the time. There is one major exception: zener diodes with voltage ratings above about 5.5V operate in a controlled avalanche breakdown mode. Those rated below 5.5V use the Zener effect, which is a different phenomenon altogether (interestingly, a 5.6V zener diode uses a mixture of both!). If you have these in your circuits, you may have to take avalanche noise into account. Now we have covered the sources of noise, we have to consider one more important point that will allow us to analyse noise in practical circuits. Gaussian distributions Johnson, shot and 1∕f noise are all considered Gaussian, which means the amplitude of instantaneous voltage is distributed according to a Gaussian, sometimes called ‘normal’, curve as shown on the left of Fig.1. The average amplitude of noise is zero, but the peak value at any given instant will be a matter of probability. Higher-amplitude excursions are less likely than those close to the mean due to the ‘bell’ shape of the Gaussian distribution. The probability that the instantaneous voltage will be between any two values is given by the area under the curve between those values. Statisticians love these curves, but I don’t find them a particularly intuitive way to look at amplitude. I prefer the relative occurrence chart on the righthand side of Fig.1. The vertical scale is the fraction of time the instantaneous voltage will exceed some multiple of the RMS voltage. For example, the instantaneous amplitude will exceed twice the RMS voltage approximately 4.6% of the time, but will exceed four times the RMS voltage only 0.006% of the time. You can also see from the occurrence chart that the instantaneous noise voltage will be below the RMS value approximately 2/3 of the time. This, plus the fact that the different sources of noise in a given circuit will be uncorrelated (they behave completely Fig.1: the probability of a given instantaneous voltage occurring in white noise is distributed according to a Gaussian curve (left). The relative occurrence curve on the right instead shows the fraction of time that the peak voltage will exceed a specific amplitude, which I find easier to understand. siliconchip.com.au Australia's electronics magazine March 2025  77 Fig.3: the noise equivalent circuit for a parallel RC circuit. The resistor and capacitor form a low-pass filter for the resistor’s Johnson noise source. The resulting noise voltage depends only on the temperature and the capacitor value. Fig.2: the noise equivalent circuit of a resistor is a noiseless resistor in series with a voltage source with a value given by the Johnson noise equation. independently), means that adding the RMS values of different noise sources will over-estimate the resulting noise. So, instead of adding noise in the normal arithmetic way, we add noise as the root sum of squares. This means we square the values, add them together, then take the square root to arrive at a value that is statistically equivalent to the sum. If we are adding more than two noise sources, we just extend the sum by adding more squared values before taking the square root. The root sum of squares method leads to a shortcut that can help simplify noise calculations significantly. If one of the quantities being added is smaller than another by a factor of 10 or more, you can ignore it altogether with very little resulting error. For example, a 10µV and 1µV source sum to 10.05µV using root-sum-of-squares, so we could simply ignore the 1µV source in that case. A simple example Noise calculations in circuits can get quite complex since almost every component contributes to or shapes noise. For this reason, it is important to take a step-by-step approach, breaking the circuit down into manageable chunks. For each ‘chunk’ of circuit, we need to analyse the ‘noise equivalent circuit’ to calculate the total noise. We must understand the noise equivalent circuits of the components to accomplish this. The noise equivalent circuit of a resistor (Fig.2) is a good place to start. We have already seen that a resistor will exhibit Johnson noise with a voltage of √4kTRfb so it can be modelled by a noiseless resistor in series with a voltage source of that value. Resistors in parallel or series can be reduced to a single equivalent resistor, then converted to the noise equivalent circuit. We mentioned above the capacitors 78 Silicon Chip don’t themselves contribute noise, but Fig.3 shows the noise equivalent circuit of a capacitor in parallel with a resistor. If we replace the resistor with its noise equivalent circuit from Fig.2, we have a noise source feeding a simple single-pole RC low-pass filter. This filter will reduce the noise bandwidth and thus the noise voltage seen at the terminals of the RC pair. The -3dB bandwidth of the RC filter will be 1 ÷ (2πRC), but we can’t just use this in noise calculations since such a filter lets through frequencies higher than the corner frequency, albeit in an attenuated form. We therefore need to convert the -3dB bandwidth to an ‘equivalent noise bandwidth’ (ENBW), which is the bandwidth of a perfect ‘brick wall’ filter that lets through the same amount of noise. The scale factor for a single-pole filter turns out to be π ÷ 2, so the ENBW for a single-pole RC filter is 1 ÷ (4RC). Substituting this into the equation for Johnson noise gives an expression for the resulting noise voltage: Vrms = √kT ÷ C. A parallel RC circuit therefore has the noise equivalent circuit shown on the right in Fig.3. Notice that the noise voltage is dependent only on the temperature and the capacitor value – the resistor value is irrelevant! Noise can be weird sometimes. Op amp noise equivalent circuit A typical op amp exhibits Johnson and shot noise with a flat power spectrum, as well as 1∕f noise, which has a power spectrum biased towards lower frequencies as shown in Fig.4. At low frequencies, the 1∕f noise dominates, while at high frequencies, the Johnson and shot noise dominate. At some frequency, fc, the amplitudes of these two noise components will cross over. When specifying op amp noise, manufacturers condense everything down to three things: a figure or graph for fc, an input noise voltage density (en) referred to the non-­ inverting input, and an input noise current density (in) at each input. Fig.5 shows the noise equivalent circuit of an op amp. It consists of a noiseless op amp with noise sources at its inputs. These current sources Fig.4: op amps exhibit both pink (1∕f ) noise, which dominates at low frequencies, and white (Johnson and shot) noise, which dominates at high frequencies. The frequency at which they cross over is the noise corner frequency, fc. This figure is usually specified in the data sheet. Australia's electronics magazine siliconchip.com.au Fig.5: the noise equivalent circuit of an op amp includes noise current sources associated with each input of a noiseless op amp, plus a noise voltage source in series with its non-inverting input. Fig.6: a simple audio amplifier stage circuit we will analyse for noise performance. produce noise voltages across the source resistances at the op amp’s inputs. The noise crossover frequency is used together with these sources to calculate the overall op amp noise. shown in row 1 of the noise budget table (Table 1). Next, we have the op amp’s noise voltage, shown in Fig.7(c), which is given by the voltage noise density (11nV/√Hz) and the bandwidth. We have seen that for white noise, we simply multiply the noise density by the square root of the circuit bandwidth to get the voltage. However, we know that the op amp produces pink 1∕f noise up to 150Hz – well within our 1Hz to 25kHz bandwidth. We take this into account by applying a modification factor to the bandwidth, a bit like we did to determine the ENBW from the -3dB bandwidth. When the bandwidth of interest straddles fc, we have to use the formula fb + fcloge(fh ÷ fl) to calculate an equivalent bandwidth. In this equation, fb is the nominal bandwidth, fc is the noise corner frequency, fh is the upper bandwidth limit and fl is the lower limit of bandwidth. So the op amp noise bandwidth evaluates to 26.5kHz instead of 25kHz. Plugging this into the op amp’s input noise density gives us a noise voltage at 1.79µV. We can now consider the noise voltage generated by the op amp’s current noise. This is a bit trickier. Fig.7(d) shows the superposition circuit for this source. We have a current source in parallel with a resistor A practical example Let’s apply this to a real-world example. Consider a simple op-amp based audio amplifier circuit, as per Fig.6. The input signal is AC-­coupled to the op amp via C1. This forms a high-pass filter with R1, which has a -3dB cutoff frequency of about 1.6Hz. The op amp is configured as a non-inverting amplifier with a signal gain of 11. C2 rolls off the amplifier’s frequency response at around 16kHz. The example circuit uses a TLV2460 general-­ purpose rail-to-rail input/output (RRIO) op amp with en = 11nV/√Hz, in = 0.13pA/√Hz and fc = 150Hz. We will analyse the noise in this amplifier in a step-by-step manner, using the principle of superposition. This analysis technique allows us to analyse linear circuits with multiple sources by calculating the effect of each one in isolation and adding the results. We replace any voltage sources we are ignoring with short circuits, and any current sources we are ignoring with open circuits. We will build up a noise budget table (Table 1) as we go. Before we start, we need to define the nominal bandwidth over which we will calculate the noise. Since our circuit has a single-pole 1.6Hz highpass filter at the input and a single-pole 16kHz low-pass filter around the op amp, our overall bandwidth is well defined. However, just like the parallel RC case above, we have to calculate the equivalent noise bandwidth, since the roll-offs are far from abrupt. Recalling that the ENBW scale factor for a single pole filter is π ÷ 2, the lower ENBW limit becomes 1Hz and the upper one becomes 25kHz. So, the overall noise bandwidth of the circuit is 25kHz – 1Hz ≈ 25kHz. We start our analysis at the non-­ inverting input of the op amp. Since the source voltage is short-circuited, R1 and C1 are in parallel as far as noise is concerned. Fig.7(a) shows the noise equivalent circuit of this part of the circuit. There are three noise sources: the R1/ C1 parallel noise voltage, the op amp’s voltage noise source and the current noise source, both at the non-­inverting input of the op amp. We will look at each in turn and use the superposition principle. Fig.7(b) shows the R1/C1 source. We have already seen that the noise voltage in this case is √kT ÷ C. Plugging in a temperature of 300K (26.85°C) and the 1µF value of C1 gives a noise voltage of 64.3nV. This calculation is Raspberry Pi Pico W BackPack The new Raspberry Pi Pico W provides WiFi functionality, adding to the long list of features. This easy-to-build device includes a 3.5-inch touchscreen LCD and is programmable in BASIC, C or MicroPython, making it a good general-purpose controller. This kit comes with everything needed to build a Pico W BackPack module, including components for the optional microSD card, IR receiver and stereo audio output. $85 + Postage ∎ Complete Kit (SC6625) siliconchip.com.au/Shop/20/6625 siliconchip.com.au Australia's electronics magazine March 2025  79 Fig.7: the process of analysing the input stage noise equivalent circuit for Fig.6(a) shows all the noise sources together and the subsequent circuits show how the noise contribution of the individual sources are evaluated. 80 Silicon Chip Fig.8: the process for analysing the noise sources at the op amp’s output is similar to that for the input. This time, there are four noise sources, including the input noise multiplied by the op amp’s noise gain. Australia's electronics magazine (and a capacitor, but let’s park that for a moment), so we can replace these with the Thévenin equivalent voltage source in series with the resistor, as shown in Fig.7(e). In case you are not aware of Thévenin’s theorem, it states, “Any linear electrical network containing only voltage sources, current sources and resistances can be replaced by a voltage source in series with a resistance.” It is a powerful tool for simplifying circuits and well worth reading about if you don’t understand it (see https://w.wiki/9XaJ). The current noise density is 0.13pA/√Hz and the resistance is 100kW, so the Thévenin noise voltage density is 13nV/√Hz. Now let’s bring the capacitor back into the picture. This forms a low-pass filter with R1, which will impact the bandwidth we should use to calculate the RMS voltage at the op amp’s input. The filter’s ENBW is given by 1 ÷ (4RC), as we saw above, so we use this figure (2.5Hz) in the calculation. The resulting voltage will be 20.6nV (line 3 of the Table 1). To complete the superposition process, we just have to add all three voltages together using root-sum-ofsquares to get a single equivalent noise voltage at the non-inverting input of the op amp. Since the op amp’s input noise voltage is more than an order of magnitude higher than either of the other two, we can safely ignore the others. This leaves us with a total voltage noise voltage at the op amp input of 1.79µV RMS. Now we turn to the op amp output. Fig.8(a) shows the equivalent circuit. This time, there are four sources of noise voltage: the output noise of the op amp due to the amplified input noise we just calculated, two resistor noise voltages (R2 and R3) and the current noise at the op amp’s inverting input. We use superposition again to calculate each contributing part of the noise voltage individually. Fig.8(b) shows that the first of these is easy; it is just the 1.79µV input noise voltage multiplied by a gain of 11, giving 19.7µV. For a non-inverting amplifier, the noise gain is the same as the signal gain, since the noise source is on the same input as the signal. This isn’t necessarily true for all op amp configurations, so you will need to scrutinise each circuit for noise sources. For example, for a standard inverting siliconchip.com.au amplifier configuration, the noise gain equals the signal gain plus one. Remember that the op amp’s voltage noise equivalent is always referred to the non-inverting input. The noise due to R2/C2, as shown in Fig.8(c), is also easy to calculate since this is just another RC parallel circuit that we are already familiar with. The noise voltage here is 2.03µV. The noise due to resistor R3, shown in Fig.8(d), is also easy using the formula for Johnson noise on page 76. This works out to be about 643nV. The noise voltage due to the op amp’s current noise can be calculated using the Thévenin equivalent circuit shown in Figs.8(e) & 8(f). In this case, the noise voltage works out to be 20.6nV. The only trick here is to use the 26.5kHz augmented bandwidth to account for the 1∕f noise. The total noise at the output of the circuit is calculated by root-sum-ofsquares of the voltages. It turns out to be 19.8µV RMS. Since the circuit was designed to deliver signals at 1V RMS, the signal-to-noise ratio (SNR) is 20log10(1V ÷ 19.8µV) ≈ 94dB. Power supply noise This analysis so far ignores power supply noise. Power supply noise will be coupled into the op amp’s output to some degree, although op amp designers try hard to maximise the rejection of such noise. The op amp’s power supply rejection ratio (PSRR) defines the degree to which a disturbance on the power supply rail reaches the output. The TLV2460 has a power supply rejection ratio (at 25°C) of >80dB up to 20kHz. This means any power supply noise will be attenuated by a factor of 10,000 over the frequencies we care about. To calculate the power supply noise contribution, you reduce the RMS noise present on the power supply by the PSRR and add the result as you would for any other noise voltage source on the op amp’s output. Put another way, if we can keep the power supply noise in our example circuit under 20mV RMS, the op amp’s PSRR will reduce this to 2µV at the op amp output. This is one tenth of the ~20µV of noise we just calculated, so will make no meaningful contribution to the overall circuit noise. Minimising noise We have seen that noise is an inescapable phenomenon, with causes linked to the fundamentals of physics. There is nothing we can do to eliminate it, short of cooling our circuit down to absolute zero. However, you can minimise the noise in any circuit using a few techniques. They may not all be possible or relevant in your application, but the following ideas are worth considering. 1. Reduce bandwidth: we have seen that noise voltage depends highly on bandwidth and that reducing bandwidth reduces noise amplitude. You may not be able to reduce the overall bandwidth of the circuit, but even limiting bandwidth in parts of the circuit may help. 2. Use oversampling: this is a kind of bandwidth reduction. If you are measuring a noisy quantity with an ADC, you can take multiple samples and average the results. Since noise is Gaussian with zero mean, the average of several samples tends toward zero as the number of samples increases. 3. Minimise gain: the gain elements in your circuit amplify input-side noise voltages. Use the minimum gain necessary to amplify your signal. 4. Use lower value resistors where possible. A 1kW resistor has a noise voltage density of ~4nV/√Hz, compared to ~40nV/√Hz for a 100kW resistor. A 100W resistor is even better at ~1.3nV/√Hz. 5. Choose the right op amps. There is a huge range of ‘low noise’ op amps and their headline specifications don’t always tell the full story. Low voltage noise density does not always mean low 1∕f noise and vice versa. Depending on your bandwidth, you might need to balance one parameter with another. 6. Pay attention to power supplies. Power supply noise can be coupled into your signal path in all sorts of ways. Linear regulators are generally quieter than switch-mode ones (or you could use a switch-mode regulator with a linear post-regulator). 7. Pay attention to power supply and ground routing, especially where high current circuits are present on the same board. Use decoupling capacitors thoughtfully and consider using LC filters or capacitance multipliers to create a low noise supply to particularly sensitive portions of the circuit. Keep high-current ground networks separate from signal grounds. As a concrete example, refer to our circuit shown in Fig.6. We calculated its SNR as being close to 94dB. If we intended to use it to process an audio signal, we probably want to reduce the noise a bit, for an SNR of at least 100dB. That could most effectively be achieved by using a lower noise op amp. An op amp like the NE5534, for example, with a voltage noise density of 3.5nV√Hz, a current noise density of 1.5pA√Hz and an fc of about 1kHz might be a better choice. A quick estimate using these figures gives an op amp voltage noise (line 2 of the table) of 0.66µV compared to 1.79µV, and the overall circuit noise figure reduces to about 7.5µV giving SC an SNR of just over 102dB. Table 1 – a noise budget for our example audio amplifier circuit Line Noise Source Figure Notes Result (RMS) 1 R1/C1 (100kW, 1μF) 7(b) Parallel RC: Vn = √kT ÷ C 64.3nV 2 Op amp voltage noise (11nV/√Hz, 150Hz) 7(c) 3 Op amp current noise (0.13pA/√Hz) 7(d)(e)(f) Thévenin equivalent and LPF: en = inR1, fb = 1 ÷ (4RC) 20.6nV 4 Total input noise (Lines 1-3) − Root sum of squares, Line 2 dominates 1.79µV 5 Output noise due to input noise 8(b) Line 4 times noise gain of 11 19.7µV 6 R2/C2 (10kW, 1nF) 8(c) Parallel RC: Vn = √kT ÷ C 2.03µV 7 R3 (1kW) 8(d) Resistor: Vn = √4kTRfb 643nV 8 Op amp current noise (0.13pA/√Hz) 8(e)(f) Thévenin equivalent: Vn = inR3√fb + fc loge(fh ÷ fl) 21.2nV 9 Total output noise (Lines 5-8) − Root sum of squares, Line 5 & 6 dominate 19.8µV siliconchip.com.au Bandwidth straddles fc so use Vn = en√fb + fc loge(fh ÷ fl) 1.79µV Australia's electronics magazine March 2025  81 Project by Tim Blythman We have updated the Pico Audio Analyser design from November 2023 to use the Pico 2, which has improved its performance in some areas. A followup article also examines how the Pico 2 would work in some of our other Pico projects and some other hints for using the Pico 2. 2 PICO Audio Analyser T he Pico Analyser project from November 2023 (siliconchip. au/Article/16011) is a compact handheld device that offers many useful features for analysing audio frequency signals. It includes a signal generator, oscilloscope and spectrum displays and can perform harmonic and sweep frequency response analyses. The Pico Analyser is by no means a high-end device, but it was let down somewhat by a defect in the RP2040 chip used on the original Pico. We discussed this in detail in a panel in that earlier article. To sum it up, the 12-bit ADC (analog-to-­digital converter) on the RP2040 chip has errors in the tiny capacitors used to perform the conversion. This means that the ENOB (effective number of bits) of the ADC is only eight; less than the nine or so that would be expected. This affects the accuracy of measurements and in particular limits the THD (total harmonic distortion) measurements to no better than around 0.4%. We were able to apply some Features & Specifications > Audio signal generator (up to 3V peak-to-peak/1.06V RMS) with selectable frequency > Sine, square, triangle, sawtooth and white noise waveforms > Audio signal input with switchable 3.6V and 34V peak-to-peak ranges (1.27/12V RMS) > Oscilloscope and spectrum displays > Harmonic analysis with THD measured down to 0.2% (1.2V RMS, 1.2kHz) > Can measure and monitor mains distortion with a suitable plugpack > Sweep analysis with frequency response display > RCA sockets for input and output > Runs from USB power or an internal rechargeable battery > Uses 128×64 OLED display and pushbutton controls > Compact and portable > Controllable from a virtual USB serial port > Typical current draw around 50mA > Operates for around 12 hours with a fully charged 600mAh battery 82 Silicon Chip Australia's electronics magazine compensation to the ADC readings, improving it to 0.3%. The Pico 2 uses an RP2350 microcontroller instead of the RP2040, and the RP2350 data sheet notes that the spikes in differential nonlinearity should not be present in the newer part. It claims an ENOB of 9.2, which should theoretically allow total harmonic distortion (THD) to be measured below 0.2%. So it’s clearly worthwhile to update the Pico Audio Analyser with the Pico 2. We’ll also look at whether the Pico 2’s increased flash memory, increased RAM or faster processor clock will provide any other opportunities for improvement. A straightforward update The Pico Analyser was intended to be simple and inexpensive, so we have not made any radical changes to the circuit. In fact, the only change in the Pico 2 Audio Analyser hardware is substituting a Pico 2 for the Pico. Fig.1 is the circuit for the Pico Analyser with this small change. To briefly recap, the Pico 2 generates a PWM (pulse-width modulated) audio signal on GP16 that has its higher frequency components attenuated by a pair of 2.2kW/1nF low-pass filters. The signal is then buffered by the op amp, AC-coupled and biased to circuit ground before being delivered to CON2. siliconchip.com.au Fig.1: the circuit for the Pico 2 Analyser has not changed much from the original Analyser, with the exception of a Pico 2 now being used for MOD1. The other half of the op amp is arranged to provide a mid-rail 1.65V reference. The audio input at CON1 is filtered to remove ultrasonic components before being AC-coupled and biased to the 1.65V rail to centre it within the ADC’s input range. The processed input voltage is sampled at the Pico 2’s GP26 pin. The 510W resistor switched in by S6 can be used to attenuate the incoming signal, allowing for input voltages up to 34V peak-to-peak. That’s ideal for using something like an isolated 9V AC (RMS) mains transformer to check mains power distortion. IC2 and its associated components form a charging circuit for a rechargeable lithium battery, with LED1 providing a status display. The Pico 2 is powered either from its USB socket or the battery if S5 is closed. The Pico 2 connects to four tactile switches (S1-S4) for user input and MOD2, an I2C OLED display. The 22kW/22kW voltage divider allows siliconchip.com.au the Pico 2 to also monitor the battery’s voltage at its GP28 analog input. Software features The software has numerous modes and means to set some calibration parameters. Much of the calibration is done automatically once a multimeter is connected externally to set the output level correctly. A WAVE OUTPUT screen allows the frequency, amplitude and waveform (eg sine, square, triangle, sawtooth or white noise) to be set. Most of the remaining screens provide analysis of the input signal. SCOPE and SPECTRUM screens provide displays of the input waveform. A HARMONIC ANALYSIS screen determines the fundamental frequency of the input and the amplitude of the fundamental and its harmonics, as well as reporting a THD figure. Finally, a SWEEP page drives the output with a sinewave at varying frequencies and measures the received response back at the input. These last three screens make use of a fast Fourier transform (FFT) to extract frequency information about the waveform at the input connector. There was no need to update the Analyser PCB, so it looks the same as the original. Australia's electronics magazine March 2025  83 The fully assembled PCB of the Pico 2 Analyser looks much the same as its predecessor, with the Pico 2 silkscreen on MOD1 being the only visible difference. Note the unusual mounting arrangements for the LED and OLED. If you’d like to read about the circuit and software operation in greater depth, we recommend reading the original Pico Analyser article from November 2023. That article also contains the detailed construction notes for the Pico Analyser. The construction of the Pico 2 Analyser is the same, with the proviso that a new binary file (0410723B.UF2) is needed to program the RP2350 processor on the Pico 2. In any case, the Pico 2 should ignore a binary file for a different processor (such as one prepared for the Pico), so there is little chance of damage, even if the wrong file is inadvertently used. If you’re more interested in simply building the Pico 2 Analyser, you can follow the instructions in the older article with those two minor amendments to the build process. Hardware differences The Pico 2 offers slightly different hardware features to the Pico, so we have investigated what can be improved by using these. The ADC is the first of these to address. While the Pico 2’s RP2350 corrects the erratum present in the Pico’s RP2040, there is otherwise not much difference in the peripherals that are used in the Analyser. Both parts are capable of 500kS/s ADC operation at 12 bits of sampling depth and can use the DMA (direct memory access) peripheral to capture samples without bogging down the processor. In the Pico Analyser, the ADC is run at 490kS/s, taking 12-bit samples using DMA, and we have done the same for the Pico 2 Analyser. So both parts are run very close to their respective limits in that regard; we cannot do much to improve the effective sampling rate. The software binary for the Pico Analyser required less than 10% of the Pico’s flash memory, so the extra flash memory doesn’t help here. The ARM Cortex M33 processor on the Pico 2 can run at up to 150MHz, about 10% faster than the 133MHz of the Pico’s ARM Cortex M0+. While the Pico Analyser was not constrained by processing speed, this provides one advantage in that the processor on the Pico 2 can generate the audio samples at a higher rate. The PWM outputs now run at around 73kHz instead of 64kHz, so there is an improvement in the attenuation of higher-frequency PWM artefacts by the low-pass filters. This shaves about 0.05% from the final THD reading when the signal is looped back into the Analyser. It’s a small but tangible improvement. To test the impact of the different ADC, we fed in a sinewave from an Audio Precision System One Audio Analyser. It typically deals with THD levels below 0.001%, so its output can be considered close enough to pure for the purposes of testing the Pico 2 Analyser. Under the same conditions as our tests on the Pico Analyser (a 1.2V sinewave at 1.2kHz), the Pico 2 Analyser reported a THD of 0.20%, better than the 0.30% that we saw with the Pico Here are the internals from the Pico 2 Analyser, just before the case is closed up. Note the mounting of the LED and OLED. You should apply some glue or sealant wherever the wires meet the PCB; this will help to prevent them from coming loose if a solder joint breaks. 84 Silicon Chip Australia's electronics magazine siliconchip.com.au Analyser. Note that this is almost, but not quite, what we expected based on the figures provided in the data sheet and is a definite improvement. Of course, our tests on the Pico 2 Analyser required disabling the code we added that corrects the Pico’s ADC readings for the error in the RP2040 silicon. We’ve also changed the initial splash screen to help tell the two apart. Porting the code Our Pico 2 Review in the December issue (siliconchip.au/Article/17316) noted that much of our existing code for projects based on the Pico required little more than recompiling to work with the Pico 2. The RP2350 in the Pico 2 is from a different family of ARM processors, so the two are not ‘binary compatible’. We found that the same was true for the Pico Analyser code. We used the Arduino IDE and the arduino-pico board profile (https://github.com/ earlephilhower/arduino-pico) to compile the code for the Analyser. Since the Pico and Pico 2 are easy to program using their USB flash drive bootloader, if you just want to use the compiled UF2 binary file, then you don’t need to worry about the steps involved in compiling the software, and you can jump to the next section. The first step in porting the code is to update the board profile. We are using version 4.1.1 of the arduino-pico board profile, which is the latest at the time of writing. v4.1.0 version was the first to provide the option to compile the code to use the RISC-V processor cores. If you have not installed the board profile previously, the process is to add the appropriate Additional Boards Manager URL (noted in the We have changed the splash screen for the Pico Audio Analyser Mk2, so that you can tell it apart from the older version. GitHub repository above) to the Preferences menu of the Arduino IDE and use the Boards Manager to install the package. The external libraries can be installed from the versions we included with the software download or via the Library Manager. We found that the existing code compiled without changes, but as we noted above, we needed to disable the ADC corrections needed for the RP2040, and we also took the opportunity to increase the PWM frequency for audio generation. Since writing the original Pico Analyser article, it has become clear that the RP2040 chip used in the Pico is capable of being overclocked, that is, operated at a frequency above its specified maximum. There are reports that the Pico 2 is similarly overclockable. We tried compiling the code at higher processor speeds to see if this could improve the output audio further, but the gains were negligible. So we opted to run the Pico 2 Analyser at its maximum design speed of 150MHz for the sake of stability; it is much newer and so has not been as thoroughly tested as its predecessor. Some parameters were tied to the 133MHz processor clock, so they needed adjusting to work at 150MHz. However, running the Pico 2 at 133MHz was sufficient to get the same code working without changes. We also tracked down a minor bug that was giving odd readings when no signal was applied to the Pico 2 Analyser. It was present in the Pico Analyser, but for reasons we could not determine, did not result in spurious readings. We suspect it is due to differences in the underlying library code. We’ve also updated the splash screen graphic shown when the Pico 2 Analyser starts up. While it might appear purely decorative, it also gives time for the internal biases to settle. Construction Construction of the Pico 2 Analyser is much the same as for the Pico Analyser. While we won’t give the full details here for brevity, experienced constructors should be able to work from the overlay diagram reproduced here as Fig.2. As well as using a Pico 2 instead of a Pico, the firmware image is different. Otherwise, assembly and operation are much the same. First, fit the surface-mounting parts (excluding the six switches) to the PCB in the usual fashion. Before fitting the switches, clean off any excess flux. Note that the reverse-mount tactile switches can benefit from having their leads splayed slightly before soldering. The Pico 2 (MOD1) and OLED (MOD2) modules are each fitted in a non-standard way. MOD2 is attached first, with its front side visible through the large hole in the front of the PCB. Don’t forget to remove the screen’s protective film! Four wires are used to connect the GND, VCC, SDA and SCL Fig.2: this overlay diagram shows the locations of the parts on the Pico 2 Analyser PCB. If you need detailed assembly instructions, refer to the original Pico Analyser article. siliconchip.com.au Australia's electronics magazine March 2025  85 Silicon Chip PDFs on USB ¯ A treasure trove of Silicon Chip magazines on a 32GB custom-made USB. ¯ Each USB is filled with a set of issues as PDFs – fully searchable and with a separate index – you just need a PDF viewer. ¯ Ordering the USB also provides you with download access for the relevant PDFs, once your order has been processed ¯ 10% off your order (not including postage cost) if you are currently subscribed to the magazine. ¯ Receive an extra discount If you already own digital copies of the magazine (in the block you are ordering). EACH BLOCK OF ISSUES COSTS $100 NOVEMBER 1987 – DECEMBER 1994 JANUARY 1995 – DECEMBER 1999 Parts List – Pico 2 Audio Analyser 1 double-sided PCB coded 04107231, 83 × 50mm, with black solder mask 1 UB5 Jiffy box (83 × 53 × 30mm) 2 chassis-mount RCA sockets (CON1, CON2) [Altronics P0161] 1 single AA cell holder with flying leads 1 14500 (AA-sized) Li-ion rechargeable cell with nipple 1 Raspberry Pi Pico 2 board, programmed with 0410723B.UF2 (MOD1) 1 1.3-inch (33mm) OLED module (MOD2) [Silicon Chip SC5026] 4 reverse-mount SMD tactile switches (S1-S4) [Adafruit 5410] 2 SPDT SMD slide switches (S5-S6) 4 M3 washers, 1.5mm thick 2 20cm lengths of hookup wire (eg, white and black) 1 4cm length of fine bare wire (eg, lead offcuts from LED1) 1 small tube of neutral-cure silicone sealant 1 short RCA-RCA cable (for testing & calibration) Semiconductors 1 MCP6002 or MCP6L2 rail-to-rail dual op amp, SOIC-8 (IC1) 1 MCP73831-2ACI/OT Li-ion charge regulator, SOT-23-5 (IC2) 1 bi-colour red/green 3mm LED (LED1) 1 SS34 40V 3A schottky diode, DO-214 (D1) Capacitors (all M3216/1206 size, X7R ceramic) 6 10μF 16V+ 3 1nF 50V Resistors (all M3216/1206 size, 1% 1/8W) 4 100kW 2 2.2kW 2 22kW 2 1kW Use this photo as a 3 10kW 1 510W guide to fitting the 3 4.7kW smaller components. This stage of assembly is a good point to clean off any excess flux in preparation for adding the final components like the switches, LED, Pico 2 and OLED. Pico 2 Audio Analyser Kit SC6772 ($50): includes the PCB and everything that mounts directly on it. The Pico 2 is supplied blank and will need to be programmed using a computer and USB cable. A loopback cable like this can be used to test and calibrate the Pico 2 Analyser. JANUARY 2000 – DECEMBER 2004 JANUARY 2005 – DECEMBER 2009 JANUARY 2010 – DECEMBER 2014 JANUARY 2015 – DECEMBER 2019 OUR NEWEST BLOCK COSTS $150 JANUARY 2020 – DECEMBER 2024 OR PAY $650 FOR THEM ALL (+ POST) WWW.SILICONCHIP.COM. AU/SHOP/DIGITAL_PDFS 86 Silicon Chip Fig.3: the UB5 case needs holes for the USB socket and RCA sockets, as well as notches for the slide switches. Australia's electronics magazine siliconchip.com.au pads, with two extra wires providing mechanical support. Fig.3 shows the case cutting diagram. We recommend you prepare the case before fitting the Pico 2, since it will allow you to check the switch slots and also that the Pico 2 is aligned correctly with the hole for its USB socket. MOD1 is mounted on its edge, using only pins 21-40. At this stage, you can program the Pico 2 using the 0410723B.UF2 file, and you should see a display on the OLED screen if all is working well. You can refer to the earlier photo to see the state of the board after these steps. The LED has its leads bent 180° to allow it to point downwards at the hole in the PCB solder mask, while the battery holder and RCA sockets are soldered to the PCB via flying leads. Use glue to help secure the battery wires to the PCB and affix the battery holder to the case. Once the glue has cured, the cell can be fitted to the holder. The Analyser should start up when S5 is closed. If all is well, close up the case using the Nylon washers to space the lid off the pillars slightly. Ideal Bridge Rectifiers Choose from six Ideal Diode Bridge Rectifier kits to build: siliconchip. com.au/Shop/?article=16043 28mm spade (SC6850, $30) Screen 1: pressing OK on the WAVE OUTPUT screen cycles between the parameters, while UP and DOWN modifies them. The USB serial port can also control the output waveform. 21mm square pin (SC6851, $30) Screen 2: the SPECTRUM display uses UP and DOWN to change the horizontal scaling, while OK toggles the vertical scale between peak and total energy. siliconchip.com.au 5mm pitch SIL (SC6852, $30) mini SOT-23 (SC6853, $25) Screen 3: the SCOPE display also uses UP and DOWN to change the horizontal scaling. The OK button changes between dot and line displays. Width of W02/W04 2A continuous, 40V Connectors: solder pins 5mm apart at either end IC1 package: MSOP-12 Mosfets: SI2318DS-GE3 (SOT-23) D2PAK standalone (SC6854, $35) Screen 4: HARMONIC ANALYSIS provides information about the harmonic content of a waveform. Connecting the input to the output is a good way to check this feature. Conclusion The Audio Analyser wasn’t the only Pico-based project we had a go at updating. In fact, we tested all our Pico code on the Pico 2 and also decided to look into taking advantage of some of the Pico 2’s new features, like the RISC-V cores. The following article explains what we found and gives a few hints to those keen to use the Pico 2. SC Compatible with PB1004 10A continuous (20A peak), 72V Connectors: solder pins on a 14mm grid (can be bent to a 13mm grid) IC1 package: MSOP-12 Mosfets: TK6R9P08QM,RQ Compatible with KBL604 10A continuous (20A peak), 72V Connectors: solder pins at 5mm pitch IC1 package: MSOP-12 Mosfets: TK6R9P08QM,RQ Calibration and use Cycle through the screens using the MODE button and press OK to enter calibration mode. Follow the instructions on the screen to complete the calibration. For the OUTPUT LEVEL, you will need a true RMS voltmeter to trim the output from CON2. You will also need an RCA-RCA cable (connected between CON1 and CON2) to complete the INPUT LEVEL calibrations, since the Analyser reads back its own output to establish that its input is correct. Ensure that the calibration values are saved before using the Analyser. You can check its operation by running a SWEEP with the RCA-RCA cable connected; it should be flat at 0dB with slight dips at each end. Compatible with KBPC3504 10A continuous (20A peak), 72V Connectors: 6.3mm spade lugs, 18mm tall IC1 package: MSOP-12 (SMD) Mosfets: TK6R9P08QM,RQ (DPAK) Screen 5: in this display, the UP and DOWN buttons change the vertical scaling; the unlabelled horizontal line is the -3dB point compared to the set level at the output. Australia's electronics magazine 20A continuous, 72V Connectors: 5mm screw terminals at each end IC1 package: MSOP-12 Mosfets: IPB057N06NATMA1 (D2PAK) TO-220 standalone (SC6855, $45) 40A continuous, 72V Connectors: 6.3mm spade lugs, 18mm tall IC1 package: DIP-8 Mosfets: TK5R3E08QM,S1X (TO-220) See our article in the December 2023 issue for more details: siliconchip.au/Article/16043 March 2025  87 transitioning to the by tim blythman Raspberry Pi Pico 2 This article explains what you need to do to convert software written for the Raspberry Pi Pico over to the Pico 2. We also take a look at how to use some of its new features. W hile the Pico 2 contains two ARM cores, like the original Pico, they are not the same types (Cortex-M33 rather than Cortex M0), so a UF2 file for the Pico will not work on the Pico 2. However, generally, code written for the Pico can be recompiled to a new UF2 file that will usually work on the Pico 2 without needing further changes. Still, there are a few things to look out for that might trip you up in the process. Generally, the software and tools you use will need to be updated to gain support for the Pico 2. Once you do that, the transition is pretty seamless. Pico 2 challenges Our review of the Pico 2 also highlighted one serious erratum in the RP2350. According to the data sheet, erratum RP2350-E9 applies to the A2 stepping of that processor. As far as we know, this includes the vast majority of RP2350 chips in circulation. It is a fault with the internal pulldown on the GPIO pins, and it can manifest as excessive current being sourced when the pin’s voltage level is between valid high and low levels. The sourced current will oppose the pull-down and can cause the pin to get stuck in the invalid state. The recommended workarounds include not using the pull-downs or to use an external pull-down resistor. We are fortunate in this regard that we have not used this feature in any of our Pico projects, so the RP2350-E9 erratum does not affect our ability to port any of our Pico projects to the Pico 2. If you are using PicoMite BASIC, it provides the option to set the pull-ups and pull-downs from the BASIC interface. So MMBasic projects on the Pico could run afoul of this error if they use the pull-down feature. Table 1 provides a brief overview of our experience in porting our projects to the Pico 2. Note that this doesn’t include contributed projects or those using the Pico W. At the time of writing, the Pico 2 W is not yet available, although we expect it will be shortly. As you can see, most projects simply need recompiling to work with the new processor. So we’ll focus on the changes that have occurred to the individual platforms. Some of these platforms are still under development and might change; we also expect to see more changes when the Pico 2 W is released. C SDK update The C SDK (software development kit) has been updated to version 2.0.0 to coincide with the release of the Pico 2. We have also seen substantial changes to the various tools that accompany the C SDK and these are worth noting. We’ve written about this in more detail in a separate panel, which will be of interest to those readers who wish to set up and use the bare C SDK for programming both the Pico and Pico 2. Table 1 – notes on porting projects to the Pico 2 Besides the silkscreened label, there aren’t many obvious differences from the original Pico. 88 Silicon Chip Project Issue Platform Notes PicoMite Jan 2022 BASIC PicoMite 2 firmware available. Pico BackPack Mar 2022 Multiple PicoMite 2 firmware available. Arduino, C SDK and MicroPython code working without any code changes. VGA PicoMite Jul 2022 BASIC PicoMite 2 firmware available. Pico Analyser Nov 2023 Arduino Minor code changes as noted. Digital Video Mar and Apr Terminal 2024 Arduino MOD1: no code changes, set processor speed to 250MHz. MOD2: no code changes, set processor speed to 120MHz. MOD3: no code changes, set processor speed to 120MHz. Pico Gamer Apr 2024 BASIC PicoMite 2 firmware available. Pico Computer Dec 2024 Multiple PicoMite 2 firmware available. Arduino working without any code changes, although some libraries needed updating. Australia's electronics magazine siliconchip.com.au Arduino support Not long after the original Pico was released, there was an ‘official’ Arduino board profile for the Pico. This also supported the Arduino Nano RP2040 Connect, a WiFi-equipped RP2040 board, although that board profile is now deprecated. A separate project known as ‘arduino-­pico’ was produced not long after. The arduino-pico board profile now appears to be the preferred option for many people, and we have used it for all our Arduino IDE-based Pico projects. The release notes (https://github. com/earlephilhower/arduino-pico/ releases) indicate that version 4.0.0 was the first to support the RP2350 and thus the Pico 2. At the time of writing, version 4.1.1 is current and is what we have been using for testing. So porting an existing arduino-pico project to use the Pico 2 should involve little more than updating the board profile to the most recent version, which can be done from the Boards Manager. The profile defaults to a processor speed of 150MHz for the Pico 2. You might need to try 133MHz, as we have done, in case anything in your code depends on the CPU speed. You’ll see from our notes in Table 1 that some of our projects require other specific processor speeds to work. These and other options are accessible from the Tools menu of the Arduino IDE (see Screen 1). That screen grab shows the option to choose the Board (Pico 2) and the CPU architecture (currently selected as ARM), as well as the greater flash memory capacity (4MB) and CPU speed (150MHz). We have not come across any ‘breaking changes’ so far. We also found that some libraries required an update to work with the Pico 2. Like the arduino-pico board profile, these typically note that the version change is to align with the Pico C SDK versions that support the RP2350 and Pico 2. For many of our Arduino-based projects, we have provided compiled versions (UF2 files) of the projects so you can easily try them out yourself and see that everything still works much the same. At the time of writing, we would say that there is little benefit to switching to the Pico 2 for our existing projects, apart from the Pico 2 Analyser, for the reasons we’ve mentioned. It is more siliconchip.com.au Screen 1: the arduino-pico board profile provides all these options under the Tools menu. The latest versions add the option to compile using the RISC-V architecture, under the CPU Architecture option. expensive and, currently, less widely available. Pico BackPack users would likely benefit from better performance if they use the BackPack for their own custom projects. We may consider updating some projects to add more features or to see if we can improve their performance. For example, MOD1 of the Digital Video Terminal (which produces the video signal) might be able to support higher display resolutions and colour depths. This would potentially use the RP2350’s new HSTX peripheral and would definitely rely on its larger RAM (almost double the size). MicroPython With the Raspberry Pi Foundation directly involved in MicroPython development for the Pico 2, it is not surprising that a very complete MicroPython port was available at around the time of the Pico 2’s release. We haven’t made much use of MicroPython, but had no trouble getting the original Python code from the Pico BackPack to run on a Pico 2 fitted to a BackPack instead of a Pico. Of course, we needed the new Pico 2 MicroPython firmware image to do this. For the software downloads, we have created a firmware image (UF2 file) containing a working copy of MicroPython and the BackPack demo. It can be loaded onto a Pico 2 fitted to a Pico BackPack. More information on MicroPython for the Pico 2 can be found at: https://micropython.org/ download/RPI_PICO2/ PicoMite BASIC We previously noted that development of PicoMite firmware for RP2350based boards (such as the Pico 2) was being documented on The Back Shed Forum (https://thebackshed.com/ forum/ViewTopic.php?TID=17173). This has seen the PicoMite firmware stepping up to version 6.0.0 and includes features like support for Australia's electronics magazine HDMI-compatible video and USB host support for devices like game pads and keyboards, as well as versions supporting VGA. Our February 2025 issue saw the release of the PicoMite 2 firmware (siliconchip.au/Article/17729) and a jump to version 6.00.01 of the Picomite firmware. All these features are now available on the Pico 2, as well as many other boards which use the RP2350 chip. There are six Picomite firmware variants for the Pico 2 as well as four updated variants for the Pico. There are also two WebMite variants, one for the Pico W and one for the Pico 2 W. The firmware can be downloaded from https://geoffg.net/picomite.html Other changes Another interesting feature to note is the update of the “flash_nuke.uf2” file, which completely erases the flash memory of a Pico or Pico 2. There is now a ‘unified’ file which works on both boards, and presumably, other RP2040- and RP2350-based boards. This works because the blocks in a UF2 file format can each contain a processor identification code and the processor can choose to ignore blocks that are not intended for it. In practical terms, the new “flash_ nuke.uf2” consists of individual UF2 March 2025  89 Using the latest C SDK (software development kit) The C SDK consists of headers, libraries and a build (code compilation) system, although other software is needed for a complete development environment. The GitHub repository for the C SDK can be found at https://github.com/ raspberrypi/pico-sdk In our original review of the Pico (December 2021 issue; siliconchip. au/Article/15125), we noted that the instructions for the C SDK were firmly focused on those using a Raspberry Pi computer as their development machine. We tried it out using a Raspberry Pi and found it very easy to use. For setting up a development environment on Windows computers, we also tried the Pico Setup for Windows project at https://github.com/ndabas/ pico-setup-windows Since then, this project has been taken over by the Raspberry Pi Foundation and further development has appeared to cease. Pico Setup for Windows, as the name suggests, was only intended for use with Windows operating systems. It included the cross-platform Visual Studio Code IDE (integrated development environment), also known as VS Code, as well as compilers and other tools. The C SDK has now been made available as an extension for VS Code and now works on Windows, Linux and macOS, so it provides broad, uniform support. This means that setting up the C SDK on just about any computer now involves installing VS Code and then installing the extension for the Pico C SDK. Once installed, the extension can create projects, then compile and upload them to the Pico or Pico 2. It is much more configurable, although we wouldn’t be surprised if our readers found the number of menus and options excessive! It also seems that the files associated with the extension (and their dependencies) add up to several gigabytes. Screen 2: the Pi Pico extension can be installed from this menu within VS Code. The extension requires downloading many files, so it could take a while. Screen 3: the extension adds a new Raspberry Pi Pico Project item to VS Code; it can be found on the sidebar. The options to build & run the project are found there. Screen 4: creating a new project is much the same as in previous versions of the C SDK, except that it can be done from within VS Code. Clicking the Example button creates a new project based on one of the included examples. Setting it up VS Code can be downloaded from https://code.visualstudio.com Interestingly, there are installer options for ARM64 processors running Windows. Run the installer and open VS Code. Screen 2 shows how to install the Extensions; the Ctrl-Shift-X shortcut 90 Silicon Chip Australia's electronics magazine siliconchip.com.au will also open this panel. Search for “pico” and install the Raspberry Pi Pico extension. This will also install dependencies such as C/C++, Python language support and a serial port monitor. After this, you will see a new “Raspberry Pi Pico Project” item down the left side of the VS Code window. Screen 3 shows this along with the options that are now available. You’ll see that there are options for both C/C++ and Python projects. Clicking the “New C/C++ Project” option opens the panel shown in Screen 4. This interface is similar to Project Generator, which was present in older versions of the C SDK. There is also the option to use one of the Example programs as a template for a new project. There is an option to choose either a Pico, Pico W or Pico 2 board and the Pico 2 option allows the code to be compiled to use the RISC-V processor. If you haven’t worked with the C SDK before, we suggest creating a project from one of the examples, such as blink. This simply flashes the Pico 2’s onboard LED; you can modify the delay (LED_DELAY_MS) to check that the changes in the code are having an effect. We also recommend that you use the File → Save Workspace As… option. That will allow you to easily reopen the project’s workspace for later use. Screen 5 shows the workspace for a blink-derived project. At left are the files, including “Cmakelists.txt”. We found that in some of our projects, we have had to manually add references here to hardware libraries (eg, hardware_pwm) in the “target_link_libraries” section for the project to compile correctly. Running the code The Compile Project item in the Pico Project Extension creates a binary file if it succeeds. These files (including the UF2 file for uploading) can be found in the project’s “build” subfolder. The Run Project button will compile and upload the binary file to a Pico device in bootloader mode. The Terminal in the lower half of the screen reports the results of running these commands. You will also find the likes of a Serial Monitor here too. Summary Using VS Code presents a different environment to what we have used for previous versions of the C SDK. Nevertheless, it was easy to set up and use once we became familiar with it. files for the RP2040 and RP2350 that are simply concatenated (joined) together. Theoretically, this system can be used to create UF2 binary files that can be used with numerous processor and board types. To tell them apart, the newer file is around 96kB in size, while the older file is around 25kB. The new file can be downloaded from https://datasheets. raspberrypi.com/soft/flash_nuke.uf2 Picotool We have made good use of the picotool utility for working with Pico boards. It is a command-line program that can interact with a Pico (or other RP2xxx boards) during debugging and development. Its repository is at: https://github.com/raspberrypi/ picotool In particular, it has the ability to extract the flash memory contents and write it to a UF2 file for distribution. This is handy for platforms using PicoMite BASIC, allowing a snapshot of the flash memory including saved BASIC programs, libraries and options. Like much of the other software, these tools have been updated to allow them to work with the RP2350 as well as the RP2040. Extra commands have been added to version 2.0.0 of picotool, allowing access to the OTP (one-time programming) and security features of the newer part. While there are instructions for compiling picotool (and some other software tools), this can require extra tools to be installed. We have found and used a separate project that provides compiled binaries at https:// github.com/raspberrypi/pico-sdktools/releases Summary Screen 5: a new project should be saved as a workspace to assist navigation. All the important files are found in the left-hand pane. siliconchip.com.au Australia's electronics magazine The Pico 2 appears to be better than the Pico in almost every way and is only slightly more expensive. As it also corrects the ADC erratum in the Pico, it is satisfying to be able to update the Pico Analyser to make use of this new part, although we don’t have any plans to update any other projects immediately. We have found the transition to the new board to be just about seamless, and look forward to using it in future projects. In recent news, the Pico 2 W has been released and we expect that using it should be similarly straightforward. SC March 2025  91 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. YouTube jukebox using a Raspberry Pi Zero A couple of years back, I purchased an Amazon Alexa, but I wasn’t happy that I had to continue paying for an Amazon Music membership to keep using it. I decided that I would rather pay for YouTube Music, so I created this device to allow me to use it similarly to Alexa, with voice prompts. If you have seen any of my other circuits involving a Raspberry Pi Zero, you will see that this circuit is similar. LED1 blinks to indicate that the Pi Zero is currently processing a request. The LCD screen (which can be either a 240×320 pixel or 128×128 pixel type) can show text notifications like “Processing…”, “Playing…”, or “Error” to keep you informed about the status. 92 Silicon Chip I am powering a PAM8403 stereo amplifier from the 5V pin of the Pi Zero, although it’s better to power it directly from the main 5V supply if possible. In addition to pushbutton S1 to start or stop the program, you can use voice commands. Pressing S1 is equivalent to the “daisy on” command. The commands are: • daisy on: start the device and wait for a video/audio description • daisy off: if playing or paused, this will terminate the program and go to standby mode • daisy pause: if playing, this will pause the program and wait • daisy resume: if paused, it will resume playing Australia's electronics magazine • daisy stop: stop everything and power off. • daisy set alarm: sets an audio alarm at a given time today/tomorrow/ next Monday/some date You can see videos of the Jukebox in operation at: Playing a song: https://youtu. be/3A1QBgAEcgU Setting an alarm: https://youtu.be/ UwGiKDawCrA There is no sound output on the Pi Zero board. To avoid having to connect an HDMI device for audio output, we are using two of the PWM-­ capable GPIOs (GP13 & GP19) to produce audio. To do this, we need to add just one line to the /boot/config.txt file: siliconchip.com.au The finished YouTube Jukebox prototype in use. The software to run this can be downloaded from: siliconchip. com.au/ Shop/6/1828 dtoverlay=audremap,pins_19_13 To add this, access the Pi’s console and type “sudo nano /boot/config.txt”. Use the nano editor to add that line, save the file and reboot. The PAM8403 is available as an inexpensive module; there’s also the PAM8406, which has a better Class-D amplifier with 5W+5W output from a 12V supply. For the voice input, I settled for a cheap USB microphone; the beautiful thing is that it just works out-ofthe-box. Once inserted into the only USB port of Pi-zero, run the “lsusb” command to determine the hardware device number. You may need an OTG cable to interface between the micro USB socket on the Pi Zero and the USB microphone. To verify that the microphone is working, run the command “arecord -f S16_LE -r 33100 -d 10 -c 1 output. wav” in a terminal. It will record audio at a sampling rate of 33.1kHz for 10 seconds and save it to the output.wav file in the current directory. Adjust the options (-d for duration, output file name etc) to your requirements. To play the audio file, run “aplay output.wav”. Adjust the microphone to get clear audio recordings and keep the speakers away from it to avoid feedback. For speech synthesis, since our device needs to be online to work, we will tap Google speech-to-text and text-to-speech to interpret our voice commands and provide updates, respectively. The software is written in Python, so you will need to install several Python modules for it to work. To achieve that, check the import sections at the start of the code, then use the “pip install modulename” command in a terminal to install each one. “pip list” will provide you with a detailed list of pip modules installed on the system. Another thing you must do before you can run the code is to create a YouTube API key and add it into the code (explained in the section below). The file named “vi_youtubeLED5.py” is for use with a 128×128 pixel display, while “vi_youtubeLED67.py” is for the 240×320 pixel TFT display. Ensure that the Pi Zero board logs automatically into your network. To start the program on every boot, we have to include it in the “.profile” file of the user login. To suppress the program displaying any non-critical siliconchip.com.au error messages, we also need to redirect errors to /dev/null. To do this, we run “nano .profile” from a terminal (in your home directory) and add the following single line at the end: python vi_youtubeLED5.py 2 > /dev/null & Change the file name to vi_youtubeLED67.py if you are using the larger screen. After boot-up, the program will wait for the “wake” command, and it will indicate this on the screen. On hearing “daisy on”, it will ask you for a follow-up command. It will ask you or repeat for confirmation. In case of a problem, it will go back to the previous command mode. Besides playing music for you, it can read news/podcasts, tune to live TV and more. “Daisy” stands out and avoids Australia's electronics magazine misinterpretation with similar sounding words, making it a reliable choice as a wake word, but you can change it in the software if you want. YouTube API key For text-to-speech & speech-to-text, we use the Google GTTS & speech_recognition module for Python. Google speech recognition is pretty fast and can understand the nuances of human voice. It is also free for use. You need to get a YouTube API key for your Google account from https://console.cloud. google.com/ Log in there, go to security and generate your YouTube API key. Copy the key and paste it into the Python code. That’s all! If you need help, here’s a YouTube video on the subject: https:// youtu.be/F5yQ1BgDIDQ Bera Somnath, Kolkata, India. ($100) March 2025  93 SERVICEMAN’S LOG The dishwasher that wouldn’t Dave Thompson It’s that time of year again when everyone seems to go a little mad. I know I do! Unfortunately, our dishwasher decided to go a little mad as well, leading to me calling in the big guns. It has been playing up for a while and we’ve been doing the usual things, running commercial cleaners through it and putting in bowls of vinegar, the sort of fixes suggested by the internet. The filters are always a good place to start; this stainless-steel German-branded model we have now has quite a good system for ease of access and cleaning the filters. They were all clean, but I could hear a faint grumbling sometimes while the machine was doing its thing. Suggestions were made that something had gotten through to the pump and it was causing problems, but I just couldn’t see how that was possible given the filter system. It is, of course, possible we lost an impellor blade or something else had come loose beyond the filters and was fouling the pump. Still, I couldn’t see anything in it, and surely it would be making a much more noticeable noise if that were the case. We put up with still having dirty dishes in the morning on the odd wash cycle, but it got progressively worse over time. This unit is around five years old, and it isn’t the original dishwasher we put in when we renovated this house. That was a Samsung model, using a different type of technology to the rest of the pack (I’m a sucker for trying 94 Silicon Chip new things!), yet it really never worked properly. It would fault often, and I wrote about it at the time, because at under two years old, it should have performed way better than it did. I sold that appliance cheaply to a local repair guy who said he knew what was likely wrong with it and waved goodbye as he drove away with it on his trailer. Of course, we took quite a financial hit, but we simply wanted a machine that worked and cleaned the dishes without faulting or stopping half-way through a cycle. This new fancy German one was far better in every respect, from the clever folding dish-retaining system to the almost silent operation. Stealthy silverware scouring The latter isn’t a huge selling point for me, as we put it on downstairs overnight, but it is amazing how quiet it is. The only noise from it usually is the odd water-draining gurgle – which is, of course, not the dishwasher per se, but our drainage system, and the beeping when it finishes a cycle. We’ve been very happy with it, and it does a fantastic job of washing dishes. Until recently. As I mentioned, I’d heard the odd grumble from it, which was all the more obvious as it is usually so quiet. It didn’t seem to make much difference to the operation, though, and there were no error codes thrown up or any other sign that something was amiss. The dishes still washed OK, and everything seemed tickety-boo. But then it wasn’t. We started noticing that the cutlery, which sits in a sliding tray at the top of the machine, was often not washed properly. There is no dedicated rotating arm for this tray; instead, the one under the middle glasses tray must spray this cutlery tray as well, and it just wasn’t doing it. We would often also find the pellet undissolved sitting in the middle tray. It is designed to pop out of the dispenser and sit in a soap-dish-type tray that doubles as the handle for pulling the basket out of the machine. Those rotating arms come off relatively easily, so I disassembled them and washed them in the sink with detergent, ensuring all the water holes were clear, and they were. They seemed very clean and unimpeded, so if it isn’t them, it must be the pump not delivering the water properly. I checked the input water line to make sure it was clear and flowing properly, which it was. And that’s about the extent of what I could do. I visited the product’s web page and downloaded the usual manuals and documentation. The suggestions for this sort of concern were mostly what I’d already done. Australia's electronics magazine siliconchip.com.au Items Covered This Month • Dishwasher repair • Closing the case on a roller shutter • Repairing an off-grid water heater • A faulty leaf blower charger Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz Cartoonist – Louis Decrevel Website: loueee.com I wasn’t about to drag it out and take the sides off – that is beyond my pay grade. I’ve done it before on an older model dishwasher, but this one is much more intimidating. There was nothing for it but to book one of their techs to come out and have a look, something we could do easily through the web page. This is a great feature as it would be a serviceman very familiar with the brand. I gave a detailed description of the problem in the web form and all our other details and hit the ‘send message’ button. Time to call in the experts Within a day, a guy called, and we made an appointment for him to visit just a few days later. I initially thought I might have to wait for several weeks, so this was a pleasant surprise. He said he knew what the problem likely was and would bring some parts. Excellent service so far! As is usual for this type of serviceman, he could only give us an approximate time between 1pm and 5pm. This is fine for us because we work from home, but it would be pretty annoying if I had to take half a day off work just to wait around for him. I guess that’s just the way it works; many of the jobs they do, they don’t really know how long it will take. This reminds me of that Soviet man who decided he wanted to buy a Lada. He was told that the waiting list for the car was long and he would get it exactly three years from today. He asks, “will it be ready in the morning or the afternoon?” The salesman is shocked and responds, “It’s in three years. What difference will it make?” He responds, “well, the plumber is coming that morning”. Anyway, to be fair, I get asked this all the time when someone drops a machine in to me to troubleshoot: how long will it take? I always ask them, how long is a piece of string? Unless I know exactly what the problem is (often I do), I can’t give an accurate time-frame until I get well into it. If I don’t know what I’m dealing with, I don’t know how long it will take. All I can do is call the customer and tell them once I find the problem, which I usually do anyway, especially if it is going to cost more. I’ve always operated with a ‘no surprises’ policy. I don’t just spend hundreds, then present them with a bill, giving them the option of what to do and which way to go. That is, unless I can fix it quickly and inexpensively, in which case I call them and tell them it is ready. I suppose people are worried about mounting costs if it is going to take a while. As it turned out, he arrived at around 1:30pm after calling siliconchip.com.au ahead 30 minutes before to let us know he’d be there then. Again, good service. Operating on the patient When he arrived, he put down some protective blankets on the floor and tried a few cycles on the washer, which he could cancel at any time, and he confirmed the pump was the likely culprit. Of course, he did what I’d done, checking the inflow and outflow and filters. He then pulled the washer out from under the bench and onto the groundsheet, and whipped the covers off with well-practised ease. It was obvious he knew exactly what he was doing, and all the while, he kept up informational patter as he went through it. Just looking at the insides, I was glad I didn’t try this. It looked hugely complex compared to the one I pulled apart years ago, with tubes and wires and valves everywhere. It was also stuffed with sound-deadening material, with wires and tubes buried in it, so I really wouldn’t be comfortable tackling a job like that. I guess now we know why it’s so quiet! He sat on the floor on the side away from where I was standing so I couldn’t really see what he was doing, but he passed me the pump assembly he’d just removed like a surgeon handing a nurse a freshly removed organ. The manufacturing quality of this component was unlike anything I’ve seen in a long time. It looked like a turbocharger from a car and boasted a hard plastic body and water connections, but the quality of the plastic and the moulding was amazing, and I marvelled at the compactness of it. The guy said it was quite rare for a pump on this particular model to fail after such a relatively short time, so the company would be replacing all the parts he used on this repair under warranty, even though technically it was out Australia's electronics magazine March 2025  95 access some such fasteners, so I completely understood this guy making his own custom tools. Anyway, he finally finished installing the bits and bobs he’d brought with him and plugged the washer back into the power socket. Everything else was still connected, so he ran a quick cycle through it and seemed satisfied it was all working properly. It certainly was much quieter, even with the sides off; we must have gotten gradually used to the noisy pump. He soon had the sides back on and, after a quick clean over with a rag, had it all looking perfect. He slid it back into the gap under the sink, ensuring all the hoses and cables were in the right place and not crimped or kinked. We had some dishes in the sink, so I loaded it up and put a pellet in it and set it to do a 60-minute cycle, the usual setting we use it on. It worked perfectly and I couldn’t hear it at all now! I guess when something starts grumbling we don’t hear it after a while and until the problem is resolved, we just consider it ‘normal’. But of course, it isn’t normal. It’s like a loudly ticking clock – after a while, we don’t hear it because our brains just negate the sensory input. Manufacturer support is worth paying for the other side of our warranty period. We would only be liable for this guy’s fee. He also replaced a couple of sensors and valves while he had it apart. The pump assembly retails for about $500, so I’m glad they were covering it! I’m not sure what the sensors and valves would cost, but he said it would be a good idea to replace them while he had it apart, and they were paying anyway! Another big tick in the good service box. It seemed like a relatively tricky job putting it all back together, if the time taken was anything to go by. As I wrote, I couldn’t see what he was doing, but he was elbow-deep in the guts of this machine for quite a while. Our galley-style kitchen is quite narrow and, with the machine in the middle of the floor, there was no getting past it. I could have gone around and come up from the other way, but I really don’t like people hovering over me while I work, so I extend the same courtesy to other servicemen. I was interested in his tools, though, and had a discussion with him about that while he worked. He was quite happy to chat. He had what looked like a pretty comprehensive toolkit, and I could see a few special tools he’d accumulated over the years, likely for all the different models he’d encountered. While some were supplied by the various manufacturers, others he’d made himself from existing tools. Dad and I did this for various cars I’ve owned and ended up doing my own repairs on. British cars especially had some bolts and nuts in crazy places, as if they suddenly thought, where is this Fitzer valve going to fit? I know, we’ll put it behind and under the engine next to the firewall and make the nuts and bolts impossible to get to! We fabricated many special spanners and wrenches to 96 Silicon Chip We are lucky in that we bought a known, branded appliance, and we did so because the last one had let us down so thoroughly. The old adage that you get what you pay for is especially true these days. That said, some of the cheaper appliances work just as well, but it is always a risk to buy them given they often have no official after-sales technical support. Instead, you have to rely on some random service guy who might be able to fix it when it breaks. Or perhaps not. I imagine some of the parts for those cheap, big-box store models would be nigh on impossible to get, unless of course they use the same parts as some other brand, like some TVs sold here under other names. Many use the same PCBs as big-name overseas brands, but finding out which parts are compatible can take a lot of time and research. I’ve found online forums very handy for this, as many service people post in them and I’ve had many questions answered by the people who frequent those forums. They tend to share their knowledge freely. At the end of the day, buying the best we can afford is usually a good practice, and this appliance illustrates that, with the company standing behind their gear and supplying parts for them because they know they will wear out one day. The pump went pretty early, I suppose, but we run it every night and it has done a lot of work in the time we’ve had it. 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. Australia's electronics magazine siliconchip.com.au Nothing lasts forever, and with built-in obsolescence increasing, it is only going to get worse for consumers. That’s even before you factor in totally unexpected events like the pandemic, which shut factories down all over the world and created a huge parts vacuum that has still not been filled. It is increasingly difficult for me to get computer parts, for example, with my traditional suppliers only stocking a fraction of what I could get from them pre-pandemic. This has a knock-on effect on customers who might be looking for a new machine. While it appears that some stores seem to have an abundance of parts, they could have either bought a container-­ load before the pandemic, or have some pretty good contacts in Taiwan and China where they can snap them up before any of the more traditional suppliers can get their hands on them. Either way, it makes my business difficult. Thank goodness for the guy who fixed our dishwasher, though. He was prompt, professional and claimed that all parts were available for it. For a 5-year-old appliance, that’s not bad these days. It has been going flawlessly since he swapped the pump out, so that was obviously the problem. He took the old one away, but I wished I’d taken a photo; it really is a beautifully made item – classic German engineering! I guess it could be a different story if something goes wrong with the electronics or the touch-activated control panel, but I guess we’ll cross that bridge if we come to it. dropped on the bench top with a noticeable ‘clunk’ noise. Looking at the top of the PCB, the remote had obviously been dropped from a fair height, producing enough force to separate the inductor body from its mounting pins. This is another example of poor design, with the inductor’s ferrite body being much too heavy for the support provided around its mounting pins, which just disintegrated when it was dropped. Could I fix the inductor, would I need to rewind it, or bite the bullet and source a replacement? Luckily, it was at least labelled, so at least I knew its value was 470µH. After a careful (magnified) look, I saw that, luckily, there were two enamelled copper wire pigtails sticking slightly out of the bottom of the inductor. So it looked like repairing it was at least theoretically possible. The repair turned out to be relatively easy. I tinned both pigtail ends, then carefully positioned the longest pigtail over its PCB pin and soldered it in place. To minimise the chance of future separation, I used superglue to hold the inductor body in place. I considered using silicone sealant, but it takes a several hours to provide sufficient mechanical support, whereas superglue (aided by Zip Kicker for instantaneous hardening) dries immediately, with high mechanical strength. I then soldered the other pigtail in place and added enough superglue to provide a really strong mount. Thinking about what else I could do to stop the inductor separating from the PCB again, I temporarily reassembled the case and realised there was no mechanical support on top of this heavy inductor, so I also glued some high density sponge rubber to the case, which provides the necessary extra mechanical support. Apart from the unfortunate synergy of poor inductor design combined with the lack of any support above the inductor, this remote appears well made. However, these two design flaws would have been sufficient to have consigned this expensive remote control to being ewaste; just another example of an expensive item ($140) ruined by the manufacturer saving 50¢. I was also surprised at the large capacity of the batteries in this remote control. They are much larger than usual, with a four-cell pack of 14500 AA-size lithium-ion rechargeable cells. That’s quite a massive increase over the single tiny Repairing a roller shutter remote control My daughter runs a local primary school canteen. Yesterday, she dropped a largish remote control in my hot little hand and said that the battery won’t charge and it doesn’t work. I decided, as I usually do, to remove the four Pozi­ driv self-tappers and have a look inside. Fault diagnosis turned out to be super easy because, as I prised the two plastic covers apart, a small ferrite inductor siliconchip.com.au The opened-up remote control for the school canteen roller shutter door. Australia's electronics magazine March 2025  97 coin cell used in car and garage door RF remote controls, or the two AAA cells in IR remotes. Happily, my daughter reported the next day that, after charging the battery, everything was working again, with no problems feeding her ravenous horde of school kids. G. C., Cameron Park, NSW. Joolca HOTTAP V2 repair My daughter rang and asked if I would help her partner fix their portable off-grid water heater, which had stopped working. It connects to a water source and an LPG gas bottle. There was a digital temperature gauge and controls to set the water and gas flow to adjust the temperature of the hot water outlet. It is powered by two D cells in a battery box. We decided to check the batteries and battery box to make sure the heater had power. The battery box simply unscrews from the unit, providing access to two terminals that feed the heater. I measured the voltage at 3.2V, which is fine. Next, we took off the cover to check for any obvious damage. The heater has an ignition coil, a solenoid to control the gas flow, a Klixon thermal switch connected to the outlet pipe, a microswitch that looked like it operated when water flowed through the system and various other components. Nothing seemed to be damaged or loose. We decided to connect the heater to the garden tap and see if anything happened. The display did not show any indication, and nothing else seemed to be working. Overnight, I visited the Joolca website and found that the most common fault was flat batteries. I also discovered that if the Joolca logo on the temperature gauge was pressed, a fault indication should be displayed. The next morning, I had another look at the battery box. I pressed the Joolca logo and there was no indication on the display, so maybe no power was reaching it. I then removed the battery holder and measured the voltage as I had on the previous evening; I got a reading of 1.6V. Obviously, something was wrong with the power. I checked both batteries, which were about 1.5V each. The batteries are connected in series by a metal strip in the battery box lid. When I examined the holder under my magnifying light, the spring on which the negative of one cell sat seemed to be loose. I found that if I wriggled the battery, I could get a voltage reading. So it looked like the fault was a high resistance in the battery caused by the loose spring. I had to cut two plastic tabs to remove the metal strip from the plastic lid, then clean and re-attach the spring. When I put it all back together, with the metal strip glued in place, I measured 3.2V at the terminals and get the display to show a fault code, indicating no flame. So my initial measurement of the voltage the night before was obviously a fluke, with momentary good spring contact. I reinstalled the cover and connected the system to the garden tap and my LPG bottle. When I allowed water to flow, I heard the ignition sparking and the gas solenoid operating. The temperature gauge showed water temperature The top three photos show the Joolca HOTTAP V2 unit and its faulty battery connector. ► The bottom-most photo shows the charger used in the leaf blower, which had the wires shorting each other due to damaged insulation. 98 Silicon Chip Australia's electronics magazine siliconchip.com.au increasing, so the heater was working. My daughter was happy to have hot water when next they go camping. J. W., Hillarys, WA. Leaf blower charger repair I bought a Black Eagle leaf blower many years ago on eBay. Over time, I have repacked both batteries with new 18650 cells, as documented in the Serviceman column of the June 2024 issue (p92; siliconchip.com.au/Article/16294). I also repaired the charger after the wire broke at the plug end. I later had to re-solder a wire on the leaf blower’s power switch, as one of the wires had come off. The leaf blower is still working well but this morning, my wife told me that the original charger was not working and the LED was not lighting. First, I plugged it in to a different outlet to verify that it didn’t work, which was confirmed by the fact that the LED did not light up. On closer inspection, I found that the insulation on the wires next to the cable strain relief was broken and the bare wires were touching each other. I wondered if the charger would still work after the output had been short-circuited. I removed the charging cable, separated the remaining bits of wire and plugged it in again. The LED lit up green, indicating that it probably still worked. The next problem was to separate the two case halves; they were glued together, rather than being screwed. This is very annoying and makes repair difficult. I took the charger out to my workshop and got a wood chisel and hammer. I carefully went along the seam with light blows, working my way around the entire charger. This worked without breaking the charger case, and the two halves separated. Next, I pulled the remaining cable out of the cable strain relief and fortunately, it came out without too much trouble. I turned my attention to the circuit board, which had something that looked like contact adhesive over the wires where they entered it. Scraping this off with the point of a knife was successful, so I could desolder the wires from the board. I shortened the cable and tried to get it back through the strain relief, but this proved to be quite difficult. In the end, I bared around 30mm of the cable end and tinned it. I was still having problems getting the cable through, but found that I could do it by separating the wires and feeding them through one at a time. I have used superglue to secure the cable to the strain relief in the past, but I decided not to use it for this repair in case I needed to fix it again later. So I tied a knot in the cable to prevent it from pulling out. This might not be ideal, but I have found quite a few devices with this done from new, so I did the same. The circuit board had terminals labelled B+ and B−, which made it easy to know which was positive and which was negative. I knew that the plug was wired centre positive, but I double-checked the output of the new charger just to verify this. Then I used my multimeter on the ohms range to verify that both wires of the cable were intact and to identify which was which. I soldered the wires to the PCB and tested the charger before gluing the case back together with superglue and clamping it in the vise until the glue dried. Another successful repair and another item saved from the scrap pile. B. P., Dundathu, Qld. SC siliconchip.com.au Australia's electronics magazine March 2025  99 SOnline ilicon Chip Shop Kits, parts and much more www.siliconchip.com.au/Shop/ Compact OLED Clock & Timer September 2024 Short-Form Kit SC6979: $45 siliconchip.au/Article/16570 This kit includes everything needed to build the OLED clock, except the UB5 Jiffy box and Li-ion cell. Dual Mini LED Dice August 2024 Micromite-Explore 40 October 2024 Complete Kit SC6991: $35 SMD LED Complete Kit SC6961: $17.50 TH LED Complete Kit SC6849: $17.50 siliconchip.au/Article/16418 siliconchip.au/Article/16677 Includes either 3mm through-hole or 1206sized SMD LEDs. Choice of either white or black PCB. CR2032 coin cell not included. Includes the PCB and all onboard parts. Audio Breakout board and Pico BackPack are sold separately. Compact HiFi Headphone Amplifier Complete Kit SC6885: $70 Capacitor Discharger December 2024 December 2024 & January 2025 siliconchip.au/Series/432 This kit includes everything required to build the Compact HiFi Headphone Amplifier. The case is included, but you will need your own power supply. Programmable Frequency Divider Complete Kit SC6959: $60 Feb25: siliconchip.au/Article/17733 Includes all onboard components, except for a power supply and the optional programming header. Short-Form Kit SC7404: $30 siliconchip.au/Article/17310 Includes the PCB, resistors, semis, mounting hardware and banana sockets. Case, heatsink, thermal switch and wiring are not supplied. → Subscribers receive a 10% discount on all purchases, except for subscriptions (postage is not discounted). → Prices listed do not include postage. Postage rates within Australia start at $12, rates are calculated at the checkout. Vintage Radio The National R-70 Panapet AM Radio By Ian Batty That’s no moon... The National (Panasonic) R-70 Panapet is a sixtransistor superhet shaped into a unique spherical case (pictured at the centre). We even have a “blue moon” immediately to its right. I reckon I know how not to sell a radio: “This offering is a boring old six-transistor superhet with an autodyne converter, two intermediate frequency amplifiers which are necessitated by the limited stage gain of around 30dB per stage, blah, blah, blah…” By the time the Panapet was released, anything apart from the ‘standard six’ was unusual and would need extra investment to make it work. So Panasonic used the combination of a highly unusual design and a special occasion to sell the Panapet. It looks remarkable – maybe siliconchip.com.au nobody trusted the chain well enough to snap the key ring over a belt loop and let the radio swing about on the end of the chain, but it must have been tempting! The recessed tuning dial, added to the two silvered control knobs, really do make it look like some kind of weird ‘pet’ just begging to be given a home. It was released in the early 1970s; if they had only waited a few years, they could have called it the Death Star and the shelves would have been emptied pronto! It was released in bold colours: red, blue, green, yellow and white. There Australia's electronics magazine was also an elusive purple version, which is pretty rare. So why not maximise its impact by showing it off at an international occasion? How about the 1970 World Expo (https://w.wiki/Ay$K) in Osaka, Japan? With visitors from across the world coming to a six-month-long festival promising “Progress and Harmony for Mankind”, what better time and place to present this cheeky offering, and showcase Japanese design? A review from Future Forms states, “First exhibited at the World Expo in Osaka, the Panapet perfectly captured the playful pop spirit of the early March 2025  101 1970s. With its boldly futuristic spherical design and space age styling, it was an instant hit with the young and youthful-at-heart when it burst onto the scene” (siliconchip.au/link/ac1t). Circuit description This radio follows the design that had stabilised by the mid-1960s. As shown in Fig.1, it’s the familiar six transistor superhet. Although the R-70 uses PNP transistors throughout, ground connects to battery negative. While this does not affect the set’s operation, all emitters go to the supply and all collectors go to ground. Where we’d usually find emitter voltages of up to 2V and collector voltages close to supply, the R-70 upends that idea. Converter TR1, a 2SA102, is a drift type developed from the successful alloyed-junction design (as detailed in my article on transistors in the April 2022 issue – siliconchip.au/ Article/15272). Drift transistors used graded doping across the base area, giving improved high-frequency performance. The 2SA102 offers a minimum transition frequency of 20MHz, compared to the OC44’s 7.5MHz. This circuit uses collector-to-base feedback. It’s pretty much a signature non-European design. I’m making that distinction as most Australian, European and US designs continue the plan used in the first transistor radio, the Regency TR-1, which used feedback to the emitter. 102 Silicon Chip Operating the local oscillator (LO) in grounded-base ensured that the grown-junction converter, with its limited high-frequency specification, would operate reliably over the broadcast band. Base-injected circuits have stopped working in the past when I’ve dropped my signal injector onto the converter base, so I’ve developed a workaround. This set’s LO tuning capacitor section uses the cut-plate design. As this naturally forces the LO to track 455kHz above the incoming signal frequency, no padder capacitor is needed. Transistor TR1 appears to work with almost zero bias, but that implies that it’s working close to Class B, as we’d expect with an autodyne (self-­ oscillating) converter stage. The component side of the R-70; note the two output transistors sandwiched between the two transformers at the bottom of the PCB. Australia's electronics magazine siliconchip.com.au Fig.1: the R-70 Panapet circuit diagram with suggested test points and expected voltages. It’s ‘upside-down’ with ground at the top and the positive supply at the bottom, because that’s how the original was drawn. Slug Colour Function Red Local oscillator Yellow First IF White Second IF Black TR1 feeds the tuned, tapped primary of first intermediate frequency (IF) transformer T1, in the familiar ‘silver can’. It is permeability tuned by an adjustable ferrite slug. T1’s secondary feeds the base of first IF amplifier transistor TR2. As this has automatic gain control (AGC) applied, its base resistor (R4) has a relatively high value of 100kW. This allows the AGC control voltage to significantly reduce TR2’s bias on strong signals, thus reducing the stage gain and helping to keep the audio output constant across a range of station strengths, from weak to strong. TR2 feeds the tuned, tapped primary of second IF transformer T2. Like T1, it’s the familiar silver can type. T2’s untuned, untapped secondary feeds The R-70 uses a simple design for the dial. siliconchip.com.au Australia's electronics magazine Third (final) IF the base of second IF amplifier transistor TR3. TR3 gets its bias from the same source as TR2. This is unusual, as most designs only apply automatic gain control to the first IF amplifier. We’ll soon find out whether this improves the AGC performance over other, more conventional designs. TR3 feeds the primary of the tuned, tapped third IF transformer, T3. Its secondary feeds demodulator diode D1, and the demodulated audio goes to IF filter M1. This is an integrated device, comprising two capacitors and a series resistor. It’s a simplified version of the Couplate used in the Emerson 838 hybrid radio (described in the October 2018 issue – siliconchip.au/ Article/11276). The audio signal from M1 goes to the volume control potentiometer, R8. This also develops the positive-going AGC voltage that is fed back to TR2/ TR3 after being low-pass filtered by 10kW resistor R6 and 33μF capacitor C7. Audio from the volume control goes to the base circuit of audio driver transistor TR4, which uses combination bias. TR4 feeds the primary of phase-­splitter transformer T4. The output transistor pair, TR5/TR6, operates in the usual Class-B mode. Bias is derived from resistive divider R13/R14, with temperature compensation by thermistor RRT. Its notation of “251” is probably a type number rather than its resistance at 25°C. Top-cut is applied by 1.5nF feedback capacitors March 2025  103 testament to this set, it can just pick up 774 ABC Melbourne inside my screened room – no easy feat. The converter’s 455kHz sensitivity of 9μV for 50mW output backs up the air interface figures. As this converter uses base injection, it wasn’t possible to inject test signals to the base, so I used my standard workaround of coupling to the ferrite rod’s tuned primary via a 10pF capacitor. This has the advantage of minimal detuning of the circuit and giving a repeatable indication for testing. The injected signal levels were 2.5mV at 600kHz and 550μV at 1400kHz. The IF bandwidth is ±1.7kHz for -3dB and ±26kHz for -60dB. The AGC allows some 6dB rise for a 40dB signal increase. The audio response from antenna to speaker is 600Hz to 2700Hz for -3dB. From the volume control to the speaker, it’s around 700Hz to a bit over 5kHz. At 50mW, total harmonic distortion (THD) was around 5.5% with clipping at 120mW for a total harmonic distortion (THD) of 10%. At 10mW output, THD was 7%. The low battery performance was good; with a 4.7V supply, it managed a useful 35mW at clipping, albeit with visible crossover distortion due to the voltage-divider bias circuit. Audio response The tuning gang trimmer and volume control pot are mounted on the plastic chassis. The earphone jack can also be seen in the lower half of the case. C14/C15, while some local feedback is provided by common 12W emitter resistor R15. TR5/TR6 drive the output transformer, T5, and its secondary drives the internal speaker, or an earphone plugged in to the earphone socket. The circuit and service notes are available online. As the Panapet uses PNP transistors with a positive supply, their circuit voltages are shown as negative with respect to the positive supply. I have used the conventional method and taken all voltage measurements with reference to ground. Restoration The review set was in good cosmetic condition, so a light clean had it looking just fine. Initially, it seemed deaf, only giving a signal in the low 104 Silicon Chip milliwatts with a strong input signal. The problem was light oxidation on the earphone socket. With that fixed, it responded well to my radiating ferrite rod test setup. How good is it? It’s better than its specifications state. National quote 150μV/m for 5mW output, but I was able to get 50mW output from a signal of 120μV/m at 600kHz, some four times the specification. At the upper end of the broadcast band, 1400kHz, it needed 190μV/m for 50mW output. The signal+noise to noise (S+N/N) figures were 13dB at 600kHz and 15dB at 1400kHz. For the more standard 20dB S+N/N, 300μV/m is required at both 600kHz and 1400kHz for 50mW output. In Australia's electronics magazine So, the audio frequency response is not very good, as shown in Fig.2, but why? Could my test set have a driedout electrolytic capacitor? Usually, a dried-out cap affects gain across the audio spectrum, but it was worth checking. On the basis that ‘if it’s worth doing, it’s worth over-doing’, I replaced emitter bypass C12 (10μF) with a 100μF type, and coupling capacitor C11 (330nF) with a 4.7μF type. However, there was virtually no improvement. Then I performed a frequency sweep and recorded the signal voltage at the collector of TR4. If there was some weird low-frequency deficiency, it should have been evident at the primary of driver transformer T4. Despite the constant input signal of 8mV, the voltage developed at the primary of T4 ranged from only 280mV at 200Hz (where the audio output was only 1.1mW, 17dB down) to a substantially constant 1.3V (giving 50-60mW) from 1kHz to 5kHz. T4’s primary inductance is clearly siliconchip.com.au inadequate, as shown by the falloff in developed voltage below 1kHz. The problem is worsened by TR4 having a high output impedance of around 30kW. I connected the low-impedance output of my audio generator to T4’s primary and drove it directly with a 1.3V signal across the audio band. This improved the 200Hz output to 22mW, just a little worse than 3dB down. My audio oscillator’s low impedance (as a voltage source) partly overcame T4’s low impedance at low frequencies, giving a much better bass response. It may seem counterintuitive that the driver transformer should need a higher primary inductance than the output transformer. However, this is needed to give a sufficiently high impedance to get a useful signal current through the transformer at lower audio frequencies. While the driver and output transformers are roughly the same size, it’s mainly the driver transformer that causes the poor low-frequency response observed here. Yes, it’s a charming, must-have gadget, but considering that the human voice’s fundamental frequencies lie between 95Hz and 230Hz, don’t expect the dulcet tones of your favourite actor to come through at all well. And the bass fiddles in the Choral Symphony? Pardon? Transistor coding The Japanese Industrial Standard (JIS) semiconductor coding is a little more helpful than the chaotic RETMA system. We can at least distinguish polarities, technologies and Fig.2: the measured audio response peaks at 2kHz and is down by over 20dB in the critical voice range of 80-250Hz. As a result, voices tend to sound rather tinny. applications based on part codes, although chemistry (germanium/silicon) and power ratings are not coded for. The prefixes are: 2SA: high-frequency PNP bipolar junction transistors (BJTs) 2SB: audio-frequency PNP BJTs 2SC: high-frequency NPN BJTs 2SD: audio-frequency NPN BJTs 2SJ: P-channel FETs (both JFETs and Mosfets) 2SK: N-channel FETs (both JFETs and Mosfets) Special handling The Panapet is easily dismantled for servicing. Be aware that, depending on the serial number, the circuit board may be secured by one or two screws. My white one (serial #40322) used two, while the blue (serial #50593) used just one. It uses a dial cord mechanism. Both of mine were still OK, but you would need the service notes for re-stringing. Would I buy another? Having two now, it’s tempting to collect the entire set. That would mean finding the very rare purple version, as well as the French Radiola RA010, which tunes the long-wave band of 150~250kHz. It’s an oddity, given that long-wave would have been in its final years of broadcast usage by the mid-1960s. Further Reading • R-70 service manual: siliconchip. au/link/ac21 • Radiomuseum Panasonic R-70: siliconchip.au/link/ac22 • Radiomuseum Radiola RA010: SC siliconchip.au/link/ac23 The R-70 has a striking appearance and was available in a variety of colours (red, blue, green, yellow, white and purple). Readers should also look at the service manual (siliconchip. au/link/ac21), as it has a very good quality drawing of the circuit and PCB wiring diagrams. March 2025  105 SILICON CHIP .com.au/shop ONLINESHOP HOW TO ORDER INTERNET (24/7) PAYPAL (24/7) eMAIL (24/7) MAIL (24/7) PHONE – (9-5:00 AET, Mon-Fri) siliconchip.com.au/Shop silicon<at>siliconchip.com.au silicon<at>siliconchip.com.au PO Box 194, MATRAVILLE, NSW 2036 (02) 9939 3295, +612 for international You can also pay by cheque/money order (Orders by mail only) or bank transfer. Make cheques payable to Silicon Chip. 03/25 YES! You can also order or renew your Silicon Chip subscription via any of these methods as well! The best benefit, apart from the magazine? Subscribers get a 10% discount on all orders for parts. PRE-PROGRAMMED MICROS For a complete list, go to siliconchip.com.au/Shop/9 $10 MICROS $15 MICROS ATmega328P ATtiny45-20PU PIC10LF322-I/OT PIC12F617-I/P 110dB RF Attenuator (Jul22), Basic RF Signal Generator (Jun23) ATSAML10E16A-AUT High-Current Battery Balancer (Mar21) 2m VHF CW/FM Test Generator (Oct23) PIC16F1847-I/P Digital Capacitance Meter (Jan25) Range Extender IR-to-UHF (Jan22) PIC16F18877-I/P USB Cable Tester (Nov21) Active Mains Soft Starter (Feb23), Model Railway Uncoupler (Jul23) PIC16F18877-I/PT Dual-Channel Breadboard PSU Display Adaptor (Dec22) Battery-Powered Model Railway Transmitter (Jan25) Wideband Fuel Mixture Display (WFMD; Apr23) PIC12F617-I/SN Model Railway Carriage Lights (Nov21) PIC16F88-I/P Battery Charge Controller (Jun22), Railway Semaphore (Apr22) PIC12F675-I/P Train Chuff Sound Generator (Oct22) PIC24FJ256GA702-I/SS Ohmmeter (Aug22), Advanced SMD Test Tweezers (Feb23) ESR Test Tweezers (Jun24) PIC16F1455-I/P Auto Train Controller (Oct22), GPS Disciplined Oscillator (May23) Railway Points Controller Transmitter / Receiver (2 versions; Feb24) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sep19) Battery-Powered Model Railway TH Receiver (Jan25) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) PIC16F1455-I/SL Battery Multi Logger (Feb21), USB-C Serial Adaptor (Jun24) Advanced GPS Computer (Jun21), Touchscreen Digital Preamp (Sep21) Battery-Powered Model Railway SMD Receiver (Jan25) PIC32MX170F256B-I/SO Battery Multi Logger (Feb21), Battery Manager BackPack (Aug21) USB Programmable Frequency Divider (Feb25) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) PIC16LF1455-I/P New GPS-Synchronised Analog Clock (Sep22) $20 MICROS PIC16F1459-I/P K-Type Thermostat (Nov23), Secure Remote Switch (RX, Dec23) ATmega32U4 Wii Nunchuk RGB Light Driver (Mar24) Mains Power-Up Sequencer (Feb24 | repurposed firmware Jul24) ATmega644PA-AU AM-FM DDS Signal Generator (May22) 8-Channel Learning IR Remote (Oct24) PIC32MK0128MCA048 Power LCR Meter (Mar25) PIC16F1459-I/SO Multimeter Calibrator (Jul22), Buck/Boost Charger Adaptor (Oct22) PIC16F15214-I/SN Digital Volume Control Pot (SMD; Mar23), Silicon Chirp Cricket (Apr23) $25 MICROS PIC16F15214-I/P Digital Volume Control Pot (TH; Mar23), Filament Dryer (Oct24) PIC32MX170F256B-50I/SO + PIC16F1455-I/SL Micromite Explore-40 (SC5157, Oct24) PIC16F15224-I/SL Multi-Channel Volume Control (OLED Module; Dec23) PIC32MX470F512H-120/PT Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) NFC IR Keyfob Transmitter (Feb25) PIC32MX470F512L-120/PT Micromite Explore 100 (Sep16) PIC16F18146-I/SO Volume Control (Control Module, Dec23), Coin Cell Emulator (Dec23) $30 MICROS Compact OLED Clock & Timer (Sep24), Flexidice (Nov24) PIC16LF15323-I/SL Remote Mains Switch (TX, Jul22), Secure Remote Switch (TX, Dec23) PIC32MX695F512H-80I/PT Touchscreen Audio Recorder (Jun14) PIC32MZ2048EFH064-I/PT DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) STM32G030K6T6 Variable Speed Drive Mk2 (Nov24) DIY Reflow Oven Controller (Apr20), Dual Hybrid Supply (Feb22) W27C020 Noughts & Crosses Computer (Jan23) KITS, SPECIALISED COMPONENTS ETC PICO 2 AUDIO ANALYSER SHORT-FORM KIT (SC6772) (MAR 25) USB PROGRAMMABLE FREQUENCY DIVIDER (SC6959) (FEB 25) NFC PROGRAMMABLE IR KEYFOB (SC7421) (FEB 25) COMPACT HIFI HEADPHONE AMP (SC6885) (DEC 24) CAPACITOR DISCHARGER KIT (SC7404) (DEC 24) The Pico Audio Analyser kit from Nov23, but with an unprogrammed Pico 2 Complete kit: includes all components (see p85, Feb25) Complete kit: includes all required items, except the cell (see p67, Feb25) Complete kit: includes everything except the power supply (see p47, Dec24) Includes the PCB and all components that mount on it, the mounting hardware (without heatsink) and banana sockets (see p36, Dec24) PICO COMPUTER $50.00 $60.00 $25.00 $70.00 $30.00 (DEC 24) For full functionality both the Pico Computer Board and Digital Video Terminal kits are required, see page 71 in the December 2024 issue for more details. - Pico Computer Board kit (SC7374) $40.00 - Pico Digital Video Terminal kit (SC6917) $65.00 Separate/Optional Components: - PWM Audio Module kit (SC7376) $10.00 - ESP-PSRAM64H 64Mb SPI PSRAM chip (SC7377) $5.00 - DS3231 real-time clock SOIC-16 IC (SC5103) $7.50 - DS3231MZ real-time clock SOIC-8 IC (SC5779) $10.00 FLEXIDICE COMPLETE KIT (SC7361) (NOV 24) MICROMITE EXPLORE-40 KIT (SC6991) (OCT 24) DUAL-RAIL LOAD PROTECTOR (SC7366) (OCT 24) PicoMSA PARTS (SC7323) (SEP 24) Includes all required parts except the coin cell (see p71, Nov24) Includes all required parts (see p83, Oct24) Hard-to-get parts: includes the PCB and all semiconductors except the optional/variable diodes (see p73, Oct24) Hard-to-get parts: includes the PCB, Raspberry Pi Pico (unprogrammed), plus all semiconductors, capacitors and resistors (see p63, Sep24) $30.00 $35.00 $35.00 $50.00 siliconchip.com.au/Shop/ COMPACT OLED CLOCK & TIMER KIT (SC6979) (SEP 24) DISCRETE IDEAL BRIDGE RECTIFIER (SEP 24) DUAL MINI LED DICE (AUG 24) AUTOMATIC LQ METER KIT (SC6939) (JUL 24) ESR TEST TWEEZERS COMPLETE KIT (SC6952) (JUN 24) DC SUPPLY PROTECTOR (JUN 24) Includes everything except the case & Li-ion cell (see p34, Sep24) $45.00 Both kits include the PCB and everything that mounts to it (see page 83, Sep24) - All through-hole (TH) kit (SC6987) $30.00 - SMD kit (SC6988) $27.50 Complete kit: choice of white or black PCB solder mask (see page 50, August 2024) - Through-hole LEDs kit (SC6849) $17.50 - SMD LEDs kit (SC6961) $17.50 Includes everything except the case & debugging interface (see p33, July24) - Rotary encoder with integral pushbutton (available separately, SC5601) Includes all parts and OLED, except the coin cell and optional header - 0.96in white OLED with SSD1306 controller (also sold separately, SC6936) All kits come with the PCB and all onboard components (see page 81, June24) - Adjustable SMD kit (SC6948) - Adjustable TH kit (SC6949) - Fixed TH kit – ZD3 & R1-R7 vary so are not included (SC6950) USB-C SERIAL ADAPTOR COMPLETE KIT (SC6652) (JUN 24) WIFI DDS FUNCTION GENERATOR (MAY 24) Includes the PCB, programmed micro and all other required parts Short-form kit: includes everything except the case, USB cable, power supply, labels and optional stand. The included Pico W is not programmed (SC6942) - Optional laser-cut acrylic stand pieces (SC6932) - 3.5in LCD touchscreen: also available separately (SC5062) 10MHz to 1MHz / 1Hz FREQUENCY DIVIDER (SC6881) Complete kit: Includes the PCB and everything that mounts to it, including the 49.9Ω and 75Ω resistors (see page 38, May24) *Prices valid for month of magazine issue only. All prices in Australian dollars and include GST where applicable. # Overseas? Place an order on our website for a quote. $100.00 $3.00 $50.00 $10.00 $17.50 $22.50 $20.00 $20.00 $95.00 $7.50 $35.00 (MAY 24) $40.00 PRINTED CIRCUIT BOARDS & CASE PIECES PRINTED CIRCUIT BOARD TO SUIT PROJECT WiFi PROGRAMMABLE DC LOAD MAIN PCB ↳ DAUGHTER BOARD ↳ CONTROL BOARD NEW GPS-SYNCHRONISED ANALOG CLOCK BUCK/BOOST CHARGER ADAPTOR AUTO TRAIN CONTROLLER ↳ TRAIN CHUFF SOUND GENERATOR PIC16F18xxx BREAKOUT BOARD (DIP-VERSION) ↳ SOIC-VERSION AVR64DD32 BREAKOUT BOARD LC METER MK3 ↳ ADAPTOR BOARD DC TRANSIENT SUPPLY FILTER TINY LED ICICLE (WHITE) DUAL-CHANNEL BREADBOARD PSU ↳ DISPLAY BOARD DIGITAL BOOST REGULATOR ACTIVE MONITOR SPEAKERS POWER SUPPLY PICO W BACKPACK Q METER MAIN PCB ↳ FRONT PANEL (BLACK) NOUGHTS & CROSSES COMPUTER GAME BOARD ↳ COMPUTE BOARD ACTIVE MAINS SOFT STARTER ADVANCED SMD TEST TWEEZERS SET DIGITAL VOLUME CONTROL POT (SMD VERSION) ↳ THROUGH-HOLE VERSION MODEL RAILWAY TURNTABLE CONTROL PCB ↳ CONTACT PCB (GOLD-PLATED) WIDEBAND FUEL MIXTURE DISPLAY (BLUE) TEST BENCH SWISS ARMY KNIFE (BLUE) SILICON CHIRP CRICKET GPS DISCIPLINED OSCILLATOR SONGBIRD (RED, GREEN, PURPLE or YELLOW) DUAL RF AMPLIFIER (GREEN or BLUE) LOUDSPEAKER TESTING JIG BASIC RF SIGNAL GENERATOR (AD9834) ↳ FRONT PANEL V6295 VIBRATOR REPLACEMENT PCB SET DYNAMIC RFID / NFC TAG (SMALL, PURPLE) ↳ NFC TAG (LARGE, BLACK) RECIPROCAL FREQUENCY COUNTER MAIN PCB ↳ FRONT PANEL (BLACK) PI PICO-BASED THERMAL CAMERA MODEL RAILWAY UNCOUPLER MOSFET VIBRATOR REPLACEMENT ARDUINO ESR METER (STANDALONE VERSION) ↳ COMBINED VERSION WITH LC METER WATERING SYSTEM CONTROLLER CALIBRATED MEASUREMENT MICROPHONE (SMD) ↳ THROUGH-HOLE VERSION SALAD BOWL SPEAKER CROSSOVER PIC PROGRAMMING ADAPTOR REVISED 30V 2A BENCH SUPPLY MAIN PCB ↳ FRONT PANEL CONTROL PCB ↳ VOLTAGE INVERTER / DOUBLER 2M VHF CW/FM TEST GENERATOR TQFP-32 PROGRAMMING ADAPTOR ↳ TQFP-44 ↳ TQFP-48 ↳ TQFP-64 K-TYPE THERMOMETER / THERMOSTAT (SET; RED) MODEM / ROUTER WATCHDOG (BLUE) DISCRETE MICROAMP LED FLASHER MAGNETIC LEVITATION DEMONSTRATION MULTI-CHANNEL VOLUME CONTROL: VOLUME PCB ↳ CONTROL PCB ↳ OLED PCB SECURE REMOTE SWITCH RECEIVER ↳ TRANSMITTER (MODULE VERSION) ↳ TRANSMITTER (DISCRETE VERSION COIN CELL EMULATOR (BLACK) IDEAL BRIDGE RECTIFIER, 28mm SQUARE SPADE DATE SEP22 SEP22 SEP22 SEP22 OCT22 OCT22 OCT22 OCT22 OCT22 OCT22 NOV22 NOV22 NOV22 NOV22 DEC22 DEC22 DEC22 DEC22 JAN23 JAN23 JAN23 JAN23 JAN23 FEB23 FEB23 MAR23 MAR23 MAR23 MAR23 APR23 APR23 APR23 MAY23 MAY23 MAY23 JUN23 JUN23 JUN23 JUN23 JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 AUG23 AUG23 AUG23 AUG23 AUG23 SEP23 SEP23 SEP23 OCT22 SEP23 OCT23 OCT23 OCT23 OCT23 OCT23 NOV23 NOV23 NOV23 NOV23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 PCB CODE 04108221 04108222 18104212 19109221 14108221 09109221 09109222 24110222 24110225 24110223 CSE220503C CSE200603 08108221 16111192 04112221 04112222 24110224 01112221 07101221 CSE220701 CSE220704 08111221 08111222 10110221 SC6658 01101231 01101232 09103231 09103232 05104231 04110221 08101231 04103231 08103231 CSE220602A 04106231 CSE221001 CSE220902B 18105231/2 06101231 06101232 CSE230101C CSE230102 04105231 09105231 18106231 04106181 04106182 15110231 01108231 01108232 01109231 24105231 04105223 04105222 04107222 06107231 24108231 24108232 24108233 24108234 04108231/2 10111231 SC6868 SC6866 01111221 01111222 01111223 10109231 10109232 10109233 18101231 18101241 Price $7.50 $5.00 $10.00 $5.00 $5.00 $2.50 $2.50 $2.50 $2.50 $2.50 $7.50 $2.50 $5.00 $2.50 $5.00 $5.00 $5.00 $10.00 $5.00 $5.00 $5.00 $12.50 $12.50 $10.00 $10.00 $2.50 $5.00 $5.00 $10.00 $10.00 $10.00 $5.00 $5.00 $4.00 $2.50 $12.50 $5.00 $5.00 $5.00 $1.50 $4.00 $5.00 $5.00 $5.00 $2.50 $2.50 $5.00 $7.50 $12.50 $2.50 $2.50 $10.00 $5.00 $10.00 $2.50 $2.50 $5.00 $5.00 $5.00 $5.00 $5.00 $10.00 $2.50 $2.50 $5.00 $5.00 $5.00 $3.00 $5.00 $2.50 $2.50 $5.00 $2.00 For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT ↳ 21mm SQUARE PIN ↳ 5mm PITCH SIL ↳ MINI SOT-23 ↳ STANDALONE D2PAK SMD ↳ STANDALONE TO-220 (70μm COPPER) RASPBERRY PI CLOCK RADIO MAIN PCB ↳ DISPLAY PCB KEYBOARD ADAPTOR (VGA PICOMITE) ↳ PS2X2PICO VERSION MICROPHONE PREAMPLIFIER ↳ EMBEDDED VERSION RAILWAY POINTS CONTROLLER TRANSMITTER ↳ RECEIVER LASER COMMUNICATOR TRANSMITTER ↳ RECEIVER PICO DIGITAL VIDEO TERMINAL ↳ FRONT PANEL FOR ALTRONICS H0190 (BLACK) ↳ FRONT PANEL FOR ALTRONICS H0191 (BLACK) WII NUNCHUK RGB LIGHT DRIVER (BLACK) ARDUINO FOR ARDUINIANS (PACK OF SIX PCBS) ↳ PROJECT 27 PCB SKILL TESTER 9000 PICO GAMER ESP32-CAM BACKPACK WIFI DDS FUNCTION GENERATOR 10MHz to 1MHz / 1Hz FREQUENCY DIVIDER (BLUE) FAN SPEED CONTROLLER MK2 ESR TEST TWEEZERS (SET OF FOUR, WHITE) DC SUPPLY PROTECTOR (ADJUSTABLE SMD) ↳ ADJUSTABLE THROUGH-HOLE ↳ FIXED THROUGH-HOLE USB-C SERIAL ADAPTOR (BLACK) AUTOMATIC LQ METER MAIN AUTOMATIC LQ METER FRONT PANEL (BLACK) 180-230V DC MOTOR SPEED CONTROLLER STYLOCLONE (CASE VERSION) ↳ STANDALONE VERSION DUAL MINI LED DICE (THROUGH-HOLE LEDs) ↳ SMD LEDs GUITAR PICKGUARD (FENDER JAZZ BASS) ↳ J&D T-STYLE BASS ↳ MUSIC MAN STINGRAY BASS ↳ FENDER TELECASTER COMPACT OLED CLOCK & TIMER USB MIXED-SIGNAL LOGIC ANALYSER (PicoMSA) DISCRETE IDEAL BRIDGE RECTIFIER (TH) ↳ SMD VERSION MICROMITE EXPLORE-40 (BLUE) PICO BACKPACK AUDIO BREAKOUT (with conns.) 8-CHANNEL LEARNING IR REMOTE (BLUE) 3D PRINTER FILAMENT DRYER DUAL-RAIL LOAD PROTECTOR VARIABLE SPEED DRIVE Mk2 (BLACK) FLEXIDICE (RED, PAIR OF PCBs) SURF SOUND SIMULATOR (BLUE) COMPACT HIFI HEADPHONE AMP (BLUE) CAPACITOR DISCHARGER PICO COMPUTER ↳ FRONT PANEL (BLACK) ↳ PWM AUDIO MODULE DIGITAL CAPACITANCE METER BATTERY MODEL RAILWAY TRANSMITTER ↳ THROUGH-HOLE (TH) RECEIVER ↳ SMD RECEIVER ↳ CHARGER 5MHZ 40A CURRENT PROBE (BLACK) USB PROGRAMMABLE FREQUENCY DIVIDER HIGH-BANDWIDTH DIFFERENTIAL PROBE NFC IR KEYFOB TRANSMITTER DATE DEC23 DEC23 DEC23 DEC23 DEC23 JAN24 JAN24 JAN24 JAN24 FEB24 FEB24 FEB24 FEB24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 APR24 APR24 APR24 MAY24 MAY24 MAY24 JUN24 JUN24 JUN24 JUN24 JUN24 JUL24 JUL24 JUL24 AUG24 AUG24 AUG24 AUG24 SEP24 SEP24 SEP24 SEP24 SEP24 SEP24 SEP24 SEP24 OCT24 OCT24 OCT24 OCT24 OCT24 NOV24 NOV24 NOV24 DEC24 DEC24 DEC24 DEC24 DEC24 JAN25 JAN25 JAN25 JAN25 JAN25 JAN25 FEB25 FEB25 FEB25 PCB CODE 18101242 18101243 18101244 18101245 18101246 19101241 19101242 07111231 07111232 01110231 01110232 09101241 09101242 16102241 16102242 07112231 07112232 07112233 16103241 SC6903 SC6904 08101241 08104241 07102241 04104241 04112231 10104241 SC6963 08106241 08106242 08106243 24106241 CSE240203A CSE240204A 11104241 23106241 23106242 08103241 08103242 23109241 23109242 23109243 23109244 19101231 04109241 18108241 18108242 07106241 07101222 15108241 28110241 18109241 11111241 08107241/2 01111241 01103241 9047-01 07112234 07112235 07112238 04111241 09110241 09110242 09110243 09110244 9049-01 04108241 9015-D 15109231 Price $2.00 $2.00 $1.00 $3.00 $5.00 $12.50 $7.50 $2.50 $2.50 $7.50 $7.50 $5.00 $2.50 $5.00 $2.50 $5.00 $2.50 $2.50 $20.00 $20.00 $7.50 $15.00 $10.00 $5.00 $10.00 $2.50 $5.00 $10.00 $2.50 $2.50 $2.50 $2.50 $5.00 $5.00 $15.00 $10.00 $12.50 $2.50 $2.50 $10.00 $10.00 $10.00 $5.00 $5.00 $7.50 $5.00 $2.50 $2.50 $2.50 $7.50 $7.50 $5.00 $15.00 $5.00 $10.00 $7.50 $5.00 $5.00 $2.50 $2.50 $5.00 $2.50 $2.50 $2.50 $2.50 $5.00 $5.00 $5.00 $2.50 POWER LCR METER WAVEFORM GENERATOR PICO 2 AUDIO ANALYSER (BLACK) MAR25 MAR25 MAR25 04103251 04104251 04107231 $10.00 $5.00 $5.00 NEW PCBs We also sell the Silicon Chip PDFs on USB, RTV&H USB, Vintage Radio USB and more at siliconchip.com.au/Shop/3 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Send your email to silicon<at>siliconchip.com.au Increasing Headphone Amp output power I’m wondering if it’s possible and easy to increase the output of the Compact HiFi Headphone Amplifier to 2W or 5W into 4W or 8W (December 2024 & January 2025; siliconchip. au/Series/432). As a coincidence, the bar speaker I use for my PC failed about the same time as the December 2024 issue of Silicon Chip was published. I attempted a repair, but am unable to identify the amplifier chips installed. So, in order to still use the bar speaker arrangement due to its low profile I’m after a small external amp to drive it. I do have a fallback option being the Mini-D Stereo 10W Class-D Amplifier from the September 2014 issue (siliconchip.au/Article/7996). I’ve also built and use the Compact High-­ Performance 12V Stereo Amp from the May 2010 issue, but it’s overkill, power-wise and physically. (R. L., Gumdale, Qld) ● The September 2014 project you mentioned would be a good choice, or the Tiny Tim amplifier published in the October 2013, December 2013 & January 2014 issues (based on the headphone amplifier in the September & October 2011 issues). It isn’t really possible to increase the power output of the more recent design to the level you want. It was purposefully ‘cut down’ compared to the 2011 Headphone Amplifier to make it smaller, simpler and less expensive to build. Consequently, the maximum power it can achieve safely is lower. Using Headphone Amp for mixer monitoring I am enquiring about the Compact HiFi Headphone Amplifier project. I want to build this into a larger circuit. Basically, I want to use this specific unit’s whole stereo setup as an in-ear duo band monitoring system utilising two separate units (in one case). The combined vocal/musical instrument 108 Silicon Chip signal source output would be coming from the main desk (channel 1) with a separate, personal musical instrument signal (channel 2). This would enable volume control for each channel. I would also like to run the two units from the same plugpack power supply if possible. Would this design be suitable for my requirements, or am I aiming too high? Would the level of desk, line signal, outputs be too high for its inputs? I would like to use it with both analog and digital mixers. (D. W., Alexandra Hills, Qld) ● If we understand correctly, you want to feed one headphone amplifier with a signal from a sound mixer that has the whole music band sound (similar to front of house sound), and the second with the individual musical instrument sound (keyboard, guitar etc). We think that would work. The headphone amplifier can cope with typical mixer sends signal levels at around 1V RMS. The headphone amplifiers can cope with higher-level inputs, as long as the volume controls are reduced accordingly. You could power two from the same plugpack as long as it can supply the power demands. A 1A plugpack would be fine to drive two units to reasonable levels, as headphones are typically pretty efficient. The supply must be wired identically to both boards. In fact, such a supply would probably drive several headphone amps as long as the output volume levels were kept modest. Alternatively, you could use a single Compact Hifi Headphone Amp and connect its two inputs separately to the main and personal foldback signals, then use the separate volume controls to select between them. Using the VSD with a 120V AC 60Hz supply I live in the United States where 220V AC is available but inconvenient, and most motors are only rated Australia's electronics magazine for 120V AC. Will your 1.5kW Variable Speed Drive (November & December 2024; siliconchip.au/Series/430) work at 120V AC <at> 60Hz, with the understanding that I won’t get the full 1.5kW? I only need to about half a horsepower from a single-phase supply for applications like a drill press and belt sander. Thanks for your consideration. (S. G., Boise, Idaho, USA) ● The 1.5kW Speed Controller should work OK at 120V AC with a couple of caveats. First, as you observe, the power output will be reduced by about half since the output current will still be limited to 9A for single-phase operation. On top of this, the published firmware limits the output frequency to 50Hz and provides the full motor voltage at this frequency. This will have two effects on a 120V 60Hz motor: the top speed will be limited to 83% of the rated speed, and the motor may experience magnetic saturation since a 120V 60Hz motor expects around 100V at 50Hz. You could fix the latter problem by modifying the firmware. The only change needed is to alter the PWM_ FMAX #define in the “pwm.h” header file. Changing the value (currently 50.0) to 60.0 should allow it to work as expected. We have not tested the Speed Controller at 120V or 60Hz, so we suggest you proceed carefully in case something unexpected occurs. Query and feedback on Silicon Chip kits Do you have any plans to offer a parts set for the Digital Capacitance Meter (January 2025; siliconchip.au/ Article/17595)? Or should I just buy the preprogrammed PIC, an OLED screen and a PCB from your shop and start hunting around for the other components? The convenience of a kit from one source is very great. The most recent Silicon Chip project I built was the Compact OLED Clock & Timer (September 2024 issue; siliconchip.au/Article/16570). To my siliconchip.com.au intense surprise, after assembling it, it fired up right away and has kept accurate time ever since. The surprise was because my ageing eyes and fingers struggle with handling tiny SMD parts. However, a bright workbench light, a good soldering iron, fine solder, liquid flux and good tweezers of several kinds go a long way towards success. I thought that using a single sided PCB as the front panel with the copper and components on the back was a brilliant idea. (P. H., Slade Point, Qld) ● While we would like to, we don’t have the resources to create a kit for every project. In this case, there aren’t too many parts and they are mostly standard and easy enough to get. All our kits are listed on our website at siliconchip.au/Shop/20 and they are usually mentioned in the article and shop page in the magazine, so if you don’t find a project there, we haven’t created a kit for it. In this case, as you suggest, you can get the PCB, programmed microcontroller and OLED from us and you should be able to get the rest from Altronics and/or Jaycar. We’re glad to hear the Clock build went well for you. As you say, if you have a magnifier and a little patience, most SMDs are not too hard to solder. Pico Computer case is discontinued I’m building the Pico Computer (December 2024 issue; siliconchip.au/ Article/17317) from your kit and the recommended case, Altronics H0192, does not appear to be available any more. Can you suggest a suitable alternative, or another source for this case? (J. H., Nathan, Qld) ● It is frustrating that it was discontinued so soon after publishing the article (it was in stock at the time of publication). The article gives two alternatives to the Altronics Ritec case: Hammond RM2005LTBK and Multicomp MP004809. A Google search reveals that the Hammond case is available from DigiKey and Mouser: Mouser 546-RM2005LTBK DigiKey 23063056 While the photo on the Mouser website shows it as beige, the TBK suffix indicates it is actually the translucent black version. The Multicomp case is not currently in stock, but here is the link to order it from element14: 3497848 siliconchip.com.au Why does Compact Headphone Amp use air cored inductors? I bought the kit for the Compact HiFi Headphone Amplifier (December 2024 & January 2025; siliconchip.au/Series/432). I’m in the process of building it and have a query. Is there any reason why I can’t solder in a 4.7μH choke like Altronics L7018 instead of winding copper wire around the 10W resistors? (C. P., Lyndoch, SA) ● We have not tested the effect on audio quality that an inductor with a core would have. Cored inductors can be very non-linear and so are generally not used in hifi audio devices. That is why air-cored inductors are preferred instead. It may be that you can get away with using such a device when driving headphones but we haven’t tested it. We suggest you take a few minutes to wind the inductor that guarantees a good result, rather than spending more money and gambling on the resulting sound quality being good. We definitely don’t recommend using cored inductors in high-power hifi audio amplifiers. Air-cored inductors are used in that application almost exclusively, at least for linear amplifiers. Class-D amplifiers often used cored inductors in their output filters, but those have more stringent filtering requirements and the resulting sound quality is usually nowhere near as good. Further research reveals that RS Pro sells a version of the Ritec case, Cat 1981379 It is currently in stock, cheaper than the one at element14 and looks pretty good. It is semi-translucent, so it could be good for other projects where internal LEDs need to be visible. Making a photo slideshow on a TV I require a device to display slideshows on a television. I want to display a series of JPEG images from a USB stick onto a normal TV screen with a suitable delay between each, looping around on auto-repeat endlessly. Could the Pico Computer from December 2024 do that, or do you have a more practical solution? (I. M., Scoresby, Vic) ● The Pico Computer could probably do this using the HDMI output on the Pico Terminal PCB. However, you would have to write custom code to do it. The easiest way would be to use the Arduino IDE, due to the large number of available libraries. PicoMite BASIC does not (as far as we know) support the USB host port for USB sticks. If you were happy to use the microSD card slot instead of a USB drive, PicoMite BASIC should be able to do this as well. However, a Raspberry Pi computer would be a simpler choice. Once set up, one of the Pi Zero models would need little more than a power supply, an OTG adaptor (since they only have micro-USB ports), HDMI cable and power supply. You would probably need a keyboard and mouse for the initial setup. Australia's electronics magazine We have seen the Pi Zero models selling for around $30, and an online search for “raspberry pi slideshow” finds several solutions using simple scripts or installable programs. Software called FEH (https://feh.­ finalrewind.org) was mentioned in several of those solutions. Many TVs have a USB socket and can display a slideshow too. Check yours, as that would be a much simpler option if your TV supports it. Piezo transducer polarity I have a question relating to the piezo buzzer supplied with the Compact OLED Clock & Timer kit (SC6979). Your diagram on page 36 of the September 2024 issue implies this buzzer has positive and negative pins. The piezo buzzer supplied with the kit does not appear to have any polarity indication. There is a circular indentation near one of the leads – is this anything to do with polarity? The DigiKey website has a data sheet for this device, but I cannot find any reference to polarity markings. I also have a question about the software. I’m having difficulty in making the display show the time for Brisbane. No matter what I do, I seem to be stuck with Sydney DST. I changed the CUST TZ screen to show: HOME TIMEZONEBRISBANEUTC+10:00 NO DST If I then press MODE and go to the EXIT screen, then press OK to exit settings, I am returned to the home screen, which still shows Sydney time and not Brisbane time. March 2025  109 If I return to the CUST TZ screen, which is still showing Brisbane as the home timezone, then press OK TO SELECT, I get to the screen to change the STD OFFSET. Pressing OK advances to the USE DST screen and continuing to press OK takes me through screens to set DST times, finally ending up back at the HOME TIMEZONE screen, which still shows Brisbane. So again I press MODE to get to the EXIT screen. Upon exiting, I am returned to the clock showing Sydney time and not Brisbane. What am I missing here? How do I get my clock to show Brisbane time? (J. H., Nathan, Qld) ● Passive piezo buzzers are not normally polarised since they are mostly driven by an AC signal. The circuitry in active buzzers is polarised, and many electromagnetic buzzers are polarised too. The wiring shows polarity in case someone wishes to use a polarised device. The piezo supplied in the kit is not polarised, so you can solder it in either of the possible orientations. You can cycle between the time zones by using the UP and DOWN buttons on the CLOCK screen (see Screen 9 caption on p36 of the article). The Brisbane time zone is included, so you can use the custom time zone 110 Silicon Chip for another location. The CUST TZ page sets the time zone that is used to check the alarms, so leave it set for Brisbane. Origin of Silicon Chip capacitor symbols I noticed the symbol you use for electrolytic capacitors differs from the US standard (IEEE/ANSI 315, straight line with + symbol for the positive terminal and a curved line for the negative) and the UK/European standard (solid rectangle for the positive terminal, hollow rectangle/outline for the negative). Do you know where your symbol comes from and why it doesn’t match the two kinds of symbols that are used widely today? (J. R., Wales, UK) ● We searched back through our archives and found our electrolytic symbol (two solid rectangles with + and – markings) being used for electrolytic capacitors as far back as Wireless Weekly, 3rd of January 1936 – see the accompanying scan of that magazine. It may have been used earlier than that as Wireless Weekly started in 1922, but electrolytic capacitors were not as commonly used back then and manually searching the old magazines is time consuming. It’s even possible that our symbol Australia's electronics magazine predates 1922; the electrolytic capacitor was invented in 1896, so they may have been commercially available before 1922. However, it would be hard to verify that without access to very early circuit diagrams. We believe it was a local style that developed before the European or American standards, and it has stuck with us for the last century or so. It certainly predates the IEC 60617, IEEE 315, DIN EN 60617, BS EN 60617, JIS C 0617 and ISO 14617 standards that define the circuit symbols used elsewhere. This style was also very common in the AORSM (Australian Official Radio Service Manual) series of books. How does GPS Clock know the hand position? The GPS Clock I made from the Silicon Chip kit has been running like a champion since 2017. I have never really understood how it starts; do the GPS satellites send a starting pulse every 30 minutes? The electronics have no idea where the hands are on the clock face. (G. S., Eaton, WA) ● You set the hands to a known time (like 12 o’clock, or the next hour or half hour). When it has satellite lock, the GPS module continually sends the current UTC time. The clock applies your time zone offset to determine local time and compares that to the position of the hands. If the hands are pointing to the wrong time (ie, different from the GPS module), it either advances them quickly until they catch up to the current time or pauses them until the time catches up with the hand position. The microcontroller keeps track of where they’re pointing by their initial position and how many pulses it has sent to the motor. Once the hands are pointing at the correct time, it sends pulses to the motor at an appropriate rate to keep time. If the hands fall behind or ahead, it either sends extra pulses or skips pulses to keep the time correct. The trick is setting the hands to a position the microcontroller can expect them to be in initially. Once it knows the initial position and the number of pulses sent, it knows where the hands are pointing. That’s assuming the motor doesn’t skip any pulses, but if it does, the clock would rapidly continued on page 112 siliconchip.com.au MARKET CENTRE Advertise your product or services here in Silicon Chip FOR SALE FOR SALE USED ITEMS FOR SALE Retired Silicon Chip staff member Jim Rowe is trying to find good homes for the following items: 1. A Sony VPL-CSI LCD data and SVGA video projector ($100). 2. A Teac PC-10 portable stereo cassette recorder with ‘Dolby System’ and AC power pack ($75). 3. A Chinon 506-SM-XL Super-8 sound camera ($50). 4. A Pioneer VSX-D506 5-channel amplifier with a Dolby Digital decoder, and 100W output from each channel ($100). 5. An AKG D19C dynamic wideband cardioid microphone ($50). 6. An LG BP125 Blu-Ray player ($75). 7. A Toshiba SD-2500 DVD player ($40). 8. A Hantek DSO-2250 USB PC oscilloscope, with two 100MHz channels, plus an operating manual and a small software CD ($50). All of the above are available to be picked up from my home in Arncliffe, Sydney. Also available are quite a few mini file drawers with electronic components such as capacitors, resistors, transistors, ICs, LEDs and diodes, etc. These I’d be happy to give away if someone would be prepared to call and take them away. Please contact me by email to jimrowe<at>optusnet.com.au if any of the above is of interest. LEDsales KIT ASSEMBLY & REPAIR LEDS, BRAND NAME AND GENERIC LEDs, filament LEDs, LED drivers, heatsinks, power supplies, kits and modules, components, breadboards, hardware, magnets. Please visit www.ledsales.com.au DAVE THOMPSON (the Serviceman from Silicon Chip) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, New Zealand, but service available Australia/NZ wide. Email dave<at>davethompson.co.nz PMD WAY offers (almost) everything for the electronics enthusiast – with full warranty, technical support and free delivery worldwide. Visit pmdway.com to get started. KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com Lazer Security PCB PRODUCTION WE OFFER KITS, LEDs, LED assemblies and all sorts of quality electronic components, through-hole and SMD, at very competitive prices. Check out the latest deals at www.lazer.com.au PCB MANUFACTURE: single to multilayer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au FOR SALE: Fluke 760 Meter Calibrator (not tested) – $130 Military Analog Computer made by Sperry ca. 1955 (no info available) – $130 Email: Dieter Dauner, VK2EDD ddauner<at>bigpond.net.au Advertising in Market Centre Classified Ad Rates: $32.00 for up to 20 words plus $1.20 for each additional word. Display ads in Market Centre start at $82.50 per column centimetre per insertion. All prices include GST. Booking: email silicon<at>siliconchip.com.au and include your text, name, address & credit card details, or phone (02) 9939 3295. 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 March 2025  111 lose time with a regular quartz movement. SemTest not generating a high enough voltage I built the SemTest Semiconductor Tester (February, March & May 2012; siliconchip.au/Series/26) but it does not reach the maximum test voltage of 600V. I followed the instruction in the magazine to build it, but it only reaches 350V. Thank you. (Anon., Philippines) ● We suspect there is nothing wrong with the flyback transformer. It will Advertising Index Altronics.................................23-26 Beware! The Loop....................... 12 Blackmagic Design....................... 9 Dave Thompson........................ 111 DigiKey Electronics....................... 3 Electronex................................... 13 Emona Instruments.................. IBC Hare & Forbes............................ 6-7 Jaycar............................. IFC, 55-58 Keith Rippon Kit Assembly....... 111 Lazer Security........................... 111 LD Electronics........................... 111 LEDsales................................... 111 Microchip Technology.............OBC Mouser Electronics....................... 4 OurPCB Australia.......................... 5 PCBWay....................................... 11 PMD Way................................... 111 SC Pi Pico W BackPack.............. 79 Silicon Chip Binders.................. 54 Silicon Chip Bridge Rectifiers... 87 Silicon Chip PDFs on USB......... 86 Silicon Chip Shop.... 100, 106-107 Silicon Chip Subscriptions........ 27 The Loudspeaker Kit.com.......... 10 Used Gear - Dieter Dauner........ 111 Used Gear - Jim Rowe.............. 111 Wagner Electronics..................... 99 Next Issue: the April 2025 issue is due on sale in newsagents by Thursday, March 27th. Expect postal delivery of subscription copies in Australia between March 26th and April 11th. 112 Silicon Chip only develop 600V if relay 2a is operating, and that is when its coil is being driven via the pin 12 output of IC6. There could be a dry solder joint at one of the connections or an incorrect 680W resistor value at the normally-­ open contact of relay 2a. Check the PCB for correct placement of components and correct resistor values. Change in Jaycar LCD shield supplier I have run into a problem with the “Arduino RFID Keypad” project on the Jaycar website (www.jaycar.com. au/rfid-keypad). The current version of the LCD shield that Jaycar is selling (XC4630) is no longer compatible with the code for that project. Since the Jaycar website is undergoing some changes, the full details of this project are at https://github.com/ Jaycar-Electronics/RFID-Keypad-­ Relay Over time, the LCD shield suppliers to Jaycar have changed and consequently the code has three different configuration defines in the XC4630d.c file to cater for the different LCD shields. Unfortunately, none of these define options bring the current version of the LCD shield to life. A white screen is always the result. After doing some research and installing the MCUFRIEND_kbv-­ master library, I found that running the “diagnose_TFT_support” sketch with the included “MCUFRIEND_kbv. cpp” file having the “#define SUPPORT_8347D” line brought the LCD shield to life. The tft.readID() function returns a value of 0x7575, indicating that the LCD shield is using a HX8347G chipset. While I am comfortable turning on or off existing, pre-coded #defines, I don’t have the knowledge required to change the code to bring the LCD shield to life, hence my request for help. (T. G., Smiths Lake, NSW) ● We came across this same problem while designing our Symbol Keyboard project that was published in the May 2024 issue (siliconchip.au/ Article/16250). You have followed the same path as us, using the MCUFRIEND library to identify the LCD controller chip. For that project, we updated the XC4630d.c file to add support for the Australia's electronics magazine HX8347 controller. You can download the updated software files from: siliconchip.au/Shop/6/378 Use our newer version of the XC4630d.c file and make sure that XC4630_v4 is uncommented. Since you have already identified the controller, we see no reason why this should not work. We also recommend powering off the Arduino board after changing these configurations and uploading the sketch. This will ensure that it forgets any incorrect commands that were previously sent to the LCD controller when the Arduino board tries to configure it. That shouldn’t be necessary in theory, since a reset signal is sent, but we have needed to power cycle the board on occasion. Component values for Cartridge Preamp I have a query regarding the Magnetic Cartridge Preamp project (August 2006; siliconchip.au/Article/2740). I am wondering about Table 4 on page 51, especially the values for R1. R1 for the Westrex curve is listed as an 18nF capacitor. I am guessing this should be a 220kW resistor. Related to that, should the 220kW value for R1 for ffrr78 response curve be some other value? If 220kW gives a flat response, it will not suit a treble turnover frequency of 6.36kHz. Is it supposed to be an 18nF capacitor? Finally, what value of R1 will give me a treble turnover freq of 5.5kHz? (D. M., Hughesdale, Vic) ● R1 = 18nF for the Westrex curve is correct. This sets a stepped response at approximately 200Hz with the 33nF capacitor for C1 in parallel with 18nF (R1) that is then in series with resistor R2 (18kW). Note also that a capacitor is also used in the R1 position for the NARTB curve in Table 2. For the ffrr78 curve, the 220kW resistance seems correct. For a 5.5kHz turnover, change C2 to 1.8nF. We have created LTspice simulation files for the Westrex and ffrr curves that you can download from siliconchip. au/Shop/6/1826 You can change the values and run the frequency response for these to see the response to changes. If you don’t have LTspice, it is a free download from siliconchip.au/ link/ac2p SC siliconchip.com.au “Rigol Offer Australia’s Best Value Test Instruments” New 2024 Products Oscilloscopes New 12Bit Scopes RIGOL DS-1000Z/E - FREE OPTIONS RIGOL DHO Series RIGOL MSO-5000 Series 450MHz to 200MHz, 2/4 Ch 41GS/s Real Time Sampling 424Mpts Standard Memory Depth 470MHz to 800MHz, 2/4 Ch 412Bit Vertical Resolution 4Ultra Low Noise Floor 470MHz to 350MHz, 2 Ch & 4Ch 48GS/s Real Time Sampling 4Up to 200Mpts Memory Depth FROM $ 499 FROM $ ex GST 659 FROM $ ex GST 1,489 Multimeters Function/Arbitrary Function Generators New Product New Product RIGOL DG-800/900 Pro Series RIGOL DG-1000Z Series RIGOL DM-858/E 425MHz to 200MHz, 1/2 Ch 416Bit, Up to 1.25GS/s 47” Colour Touch Screen 425MHz, 30MHz & 60MHz 42 Output Channels 4160 In-Built Waveforms 45 1/2 Digits 47” Colour Touch Screen 4USB & LAN FROM $ 713 FROM $ ex GST Power Supplies ex GST 725 FROM $ ex GST Spectrum Analysers 689 ex GST Real-Time Analysers New Product RIGOL DP-932E RIGOL DSA Series RIGOL RSA Series 4Triple Output 2 x 32V/3A & 6V/3A 43 Electrically Isolated Channels 4Internal Series/Parallel Operation 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 $ 849 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