Fullscreen HTML5Med Res (??MB)HTML4

APRIL 2026 ISSN 1030-2662 04 The BEST DIY Projects! 9 771030 266001 $ 00* NZ $14 90 14 INC GST INC GST Calliope Amplifier 100W Stepper Motor Driver DC & DCC control with adjustable speed response PicoSDR Software Defined Shortwave Receiver EXPLORE THE ELEGOO® RANGE (AU) TL4986 TL4976 TL4830 EXPLORE THE ELEGOO® RANGE (NZ) TL4842 NEW DIMENSIONS. NEW POSSIBILITIES. ELEGOO® 3D Printers and Materials - Stocked at Jaycar USE CASE FILAMENT PRINTERS USE CASE RESIN PRINTERS EVERYDAY PRINTS Neptune 4 Neptune 4 Pro Neptune 4 Plus TL4970 TL4972 TL4974 $399 $549 $649 DESKTOP RESIN PRECISION Mars 4 Mars 5 Mars 5 Ultra TL4824 TL4830 TL4832 $349 $399 $599 LARGE FORMAT BUILDS Neptune 4 Max OrangeStorm Giga TL4976 TL4982 $799 $4499 PROFESSIONAL RESIN OUTPUT Saturn 4 12K Saturn 4 Ultra 12K Saturn 4 Ultra 16K TL4840 TL4842 TL4844 $729 $899 $1049 Centauri Carbon Centauri Carbon 2 Combo TL4980 TL4986 $699 $999 PREMIUM HIGH-SPEED PRINTS SEE IN-STORE OR ONLINE FOR OUR EXTENSIVE RANGE OF FILAMENT AND RESIN AT GREAT VALUE Explore our great range of ELEGOO® 3D Printing gear, in stock on our website, or at over 140 stores or 130 resellers across Australia and New Zealand. jaycar.com.au 1800 022 888 | jaycar.co.nz 0800 452 922 Prices shown in $AUD, and correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. Contents Vol.39, No.04 April 2026 20 The History of Intel, Part 3 The final part in our series concentrates on Intel’s present and future. That includes their most recent desktop processors (Meteor Lake) and their current attempt at making dedicated GPUs with Intel Arc. By Dr David Maddison, VK3DSM Electronics feature 44 Power Electronics, Part 6 The History of Intel Part 3: page 20 Image source: Konstantin Lanzet https://w.wiki/GVqx In this series of articles, we explore the principles of power electronics. This month, we cover DC-AC converters and, for a practical example, we calculate the thermal losses in the switching elements of an IGBT bridge. By Andrew Levido Electronic design 56 Whole-house Thermal Logging Designing a home with many energy-efficient aspects was a big goal for me when building my own house. One way I did this was by incorporating multiple sensors (temperature, humidity etc) in various locations. By Julian Edgar Home temperature logging 92 Tektronix 2465B Oscilloscope The vintage 2465B is an analog oscilloscope with some problems that come with old age. It actually has a lot of the features that you would expect from a digital ‘scope, but without the sampling or aliasing concerns. By Dr Hugo Holden Vintage Electronics 35 PicoSDR Shortwave Receiver Supporting AM, AM-Sync, LSB, USB, FM & CW, this software-defined shortwave radio receiver has a tuning range from 3-30MHz. It does all this using a Raspberry Pi Pico or Pico 2. By Charles Kosina Radio project 50 DCC/DC Stepper Motor Driver This compact design drives stepper motors and can take its speed signal from either a DC voltage, or a Digital Command Control (DCC) system in a model railway. It supports bipolar stepper motors with adjustable speed. Part 6 by Tim Blythman Model train / motor control project 66 Calliope Amplifier The Calliope is an updated version of our old Hummingbird amplifier from 2021. We have used newer parts that are readily available (along with alternative parts) and made minor improvements to the design. By Phil Prosser Audio project 78 Micromite-based Music Player Using little more than a Micromite LCD BackPack and a DFPlayer Mini module, this project can play MP3 files from a microSD card. It is capable of driving a 4Ω loudspeaker. By Gianni Pallotti Audio project Page 56 Whole-House Environmental Logging Page 78 Micromite-based MUSIC PLAYER 2 Editorial Viewpoint 4 Mailbag 16 Circuit Notebook 65 Subscriptions 77 Kits 84 Serviceman’s Log 90 Online Shop 101 Ask Silicon Chip 103 Market Centre 104 Advertising Index 104 Notes & Errata 1. Digital vehicle compass 2. 44-pin Micromite adaptor 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): $72.50 12 issues (1 year): $135 24 issues (2 years): $255 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 Postal address: PO Box 194, Matraville, NSW 2036. Phone: (02) 9939 3295. ISSN: 1030-2662 Printing and Distribution: 1 Huntingwood Dr, Huntingwood NSW 2148 54 Park St, Sydney NSW 2000 2 Silicon Chip Editorial Viewpoint Intel’s new mobile chips look good The concluding article in our series on Intel this month covers both their relatively new discrete graphics products (Intel Arc/Xe) and their tile technology. Since that article was written, Intel has released its Panther Lake laptop/notebook processors, derived from the Meteor Lake designs described in our article. Now that reviews are appearing, it’s good to see that these new chips from Intel are quite competitive and offer excellent integrated graphics. It seems Intel is putting the Xe architecture to good use in this case. Like Meteor Lake, Panther Lake uses tiles, allowing CPU and GPU dies to be manufactured separately and then combined into a single package using Intel’s Foveros packaging technology. This approach is a key part of what allows such high performance from a single chip while maintaining good power efficiency. The ‘flagship’ model Intel has released is the Core Ultra X9 388H. It has four performance cores, eight efficiency cores and four low-power efficiency cores for a total of 16 CPU cores. There’s 18MB of cache in total and the cores can run at up to 5.1GHz. The all-important integrated graphics is the Intel Arc B390, with 12 Xe3 cores, 12 ray-tracing units and 96 vector/XMX AI engines, all running at up to about 2.5GHz. That gives performance comparable to a discrete NVIDIA RTX 3050 GPU. So it appears Intel may be staging something of a comeback, at least in the laptop/notebook processor market. Comparing Intel’s new offering with those from its main competitor, AMD, is a little challenging. That’s partly because it’s difficult to decide whether it’s most appropriate to compare Panther Lake with AMD’s Strix Point (AI 340-375) or Strix Halo (AI Max+ 380-395) series of chips. Let’s look at Strix Point first. These are broadly similar in that both chips are designed for relatively thin and light portable computers. In this comparison, the Intel chips have roughly 10% better single-core performance, while the AMD chips are about 50% faster in heavy multi-core workloads. This is largely because all 16 cores in the AMD design are high-performance types, compared with just four of 16 in the Intel chip. However, Intel’s integrated graphics is roughly twice as fast as the integrated Radeon graphics in Strix Point processors. Intel’s chips also appear to offer somewhat better overall power efficiency. Things change a bit if Panther Lake is compared with AMD’s Strix Halo processors. In this case, CPU performance is broadly similar, but the Strix Halo ‘integrated’ graphics is much faster than Intel’s. The quotation marks are because it’s closer to having a discrete GPU integrated into the same package as the CPU. As a result, these chips tend to appear in larger and more powerful systems. That is partly because Strix Halo uses a much wider memory interface, giving the GPU far more bandwidth than a typical integrated graphics system. So Intel’s offering seems to sit in a useful middle ground: good CPU performance, strong graphics capability and excellent power efficiency in a relatively compact package. To round out the picture, Apple’s higher-end chips offer more graphics power than Intel’s Panther Lake processors, although they are not quite as powerful as AMD’s Strix Halo designs. Apple chips can also provide very strong CPU performance for certain workloads, although AMD and Intel processors still tend to perform better in heavy multi-core workloads and intense numerical computation. It’s great to see strong competition in the CPU market – it keeps everyone on their toes. by Nicholas Vinen Cover background: https://unsplash.com/photos/an-abstract-blue-background-with-wavy-lines-VhG_oPx5CEY 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”. PicoMSA Logic Analyser Pico 2 upgrade Tim Blythman’s article on updating projects that use the original RP2040-based Pico board to the newer RP2350 Pico 2 board, in the March 2025 issue (siliconchip.au/Article/ 17796), prompted me to test the Mixed-Signal Logic Analyser (September 2024; siliconchip.au/Article/16575) with the updated processor board. While the re-compiled firmware worked well with a Pico 2, the speed benefits were marginal as the original project already overclocked the original Pico processor. While testing the revised configuration, I came across alternative firmware and software that, when coupled with a Pico 2 microcontroller, allows it to operate at 400MHz in ‘blast mode’ (see photo below). The software was developed by Augustin Bernad (aka El Dr Gusman). You can find it at https://github.com/gusmanb/logicanalyzer The firmware and software are fully compatible with the Mixed-Signal Logic Analyser hardware, with the exceptions that only 16 channels are supported and the new software does not have any analog capture capability. There is a substantial Wiki attached to the repository, plus compiled firmware and software to download at https:// mega.nz/folder/SGxDHAZL#afLGgQbJAaqOYXjhJBwokQ The software is available for Windows, Linux and macOS. To benefit from the latest features and ‘blast mode’ capture, download version 6.5 of the software and the ‘turbo’ firmware. The Windows software I tested was in the file 4 Silicon Chip “all-in-one_6.5.0.0-beta2-win-x64.zip”, with the firmware in “logicanalyzer_6.5-beta2_BOARD_PICO_2_Turbo.zip”. Richard Palmer, Murrumbeena, Vic. More on synchronising LED Stars I have finally tried the modification covered in Ask Silicon Chip, March 2026 (p100), under the heading “Synchron- ising two RGB LED Stars”. The idea was for one ‘master’ Star to drive several ‘slaves’. Sadly, it only worked for a while. It was running on the bench and after about 20 minutes I smelled something electrical that wasn’t right. Not quite burning, but... I rushed over to switch them off, but too late, the one driving them failed. The problem was the microprocessor burning out. It resembled a dodo – a fried one. Replacing that fixed it. My guess is that the load on that one master processor was too great. I have increased the four 330W resistors on pin 11 to 1kW (still not really enough) and it seems to be running OK. I have an additional 270W resistor in series with the master Star. What I would say is that four running together looks really great, as expected. So, I am going to be ordering a replacement soon... Also, regarding the Mains Power LED Indicator, are you aware that mains-powered LEDs are available? I buy them from LEDSales in Tasmania and find them a delight to work with. Brett Cupitt, Gympie, Qld. 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! 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. Creative Color Correction Editing, Color, Audio and Effects! Designed to Grow With You DaVinci Resolve is the world’s only solution that combines editing, color correction, visual effects, motion graphics and audio post production all in one software tool! You can work faster because you don’t have to learn multiple apps or switch software for different tasks. For example, just click the color page for color, or the edit page for editing! It’s so incredibly fast! DaVinci Resolve is designed for collaboration so as you work on larger jobs you can add users and all work on the same projects, at the same time. You can also expand DaVinci Resolve by adding a range of color control panels that let you create unique looks that are impossible with a mouse and keyboard. There’s also edit keyboards and Fairlight audio consoles for sound studios! Professional Editing 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 PowerWindows™, qualifiers, tracking, advanced HDR grading tools and more! DaVinci Resolve ......................................................................... Free DaVinci Resolve Micro Color Panel .............. Only $765 Learn the basics for free then get more creative control with our accessories! Download free on the DaVinci Resolve website Learn More! NO SUBSCRIPTIONS • NO ADS • NO USER TRACKING • NO AI TRAINING Comment: The WS2812B LED data sheet doesn’t have an input impedance figure (we assume it’s high) but it specifies an input capacitance of 15pF. Simulating driving a 3.3V square-wave at 1MHz (higher than the actual frequency) into a 330W resistor feeding a 15pF capacitor, the average current delivered is just 512μA. The microcontroller’s I/O pin current rating is ±25mA, so on that basis, you’d expect it to be able to drive roughly 50 Stars in parallel. However, the peak current, when it is charging the 15pF capacitor, is closer to 4.5mA. So we could reach the rating with just five Stars. Extra stray capacitance, for example, from wiring, would make the currents higher. The true limit is likely somewhere between 5 and 50 Stars. We wouldn’t expect four Stars to burn the chip out under those conditions, but perhaps the stray capacitance from the added wiring is much higher than estimated. If it’s approaching several hundred picofarads, that could be a problem. Increasing the series resistance would reduce the peak capacitor charging current, so we think your solution is fine. Another option would be to use something like a hex CMOS buffer IC to drive each Star so the load on the microcontroller doesn’t increase. RGB Xmas Star and SMD soldering guides Thank you for the RGB LED Christmas Star project in the December 2025 issue (siliconchip.au/Article/19372). It ended up working very well after my initial concerns about soldering the SMDs to the board, including the 8-lead AP5002 regulator chip. I read your January 2026 editorial on “Myths about SMD soldering” (siliconchip.au/Article/19550) and watched the video you linked to. Like many hobbyists, I fear dealing with SMDs, but the excellent YouTube video you linked to demonstrates drag soldering using liquid flux. I watched another video on SMD soldering using a flux pen after that (https://youtu.be/PUFCDh9BxQU). It is a great presentation and would reassure anyone reluctant to attempt SMD soldering. It should give them the confidence to give it a try. John Okey, Torquay, Qld. Comment: flux gel makes it even easier since it doesn’t vaporise so quickly (eg, Jaycar Cat NS3039 or Altronics Cat H1650A). It stays around long enough to allow the solder to reflow and form very smooth joints. The most important thing about soldering SMDs is to be gentle and patient. As long as you’re careful and don’t damage the PCB or bend any pins, you can always try again! A fascinating circuit from the Apollo spacecraft Vintage electronics is ever a popular subject for a great many electronics enthusiasts, especially the ‘oddball’ topics covered by authors like Dr Hugo Holden and Fred Lever. During my regular wander through YouTube land, I came across a fascinating yet totally obscure piece of ‘lost technology’ from the analog days. As I had seen several of the producer’s other excellent videos, I knew I wouldn’t be disappointed, and wow! What a fascinating circuit! You can view the video here: https:// youtu.be/I6lNQU7pchM Andre Rousseau, Auckland South, NZ. 6 Silicon Chip Australia's electronics magazine siliconchip.com.au Measuring tools for now and the future DIGITAL READOUT 7" Colour LCD Screen Programmable Up To 3 Axis Colour Multiple Pre-Set Colours ZERO One Touch Axis Zero Keys Display SCAN HERE For More Information Multi Language Menu 2-Year Warranty 352 (Q8500) $ IP-54 RATED PROTECTION AGAINST INGRESS OF DUST & WATER Rechargeable Digital Calipers Range Q170 • Magnetic charging in under 3 hours • Long battery life with low battery alert • Metric, Imperial and Fraction measuring modes • 4-Way measuring • Auto-off function Range $ Vernier Calipers - 32-1946 • 0-180mm/7” • Mono-block vernier • With fine adjustment $ 93.50 (Q1946) $ Digital Outside Micrometer 10-1245 Inside Micrometers Rod Type 23-148 Metric Outside Micrometers 6 Piece Set - 20-118 • 0-25mm/0-1” range • ±0.001mm accuracy • Large LCD for easy reading • Carbide measuring faces • 25-50mm capacity • The anvil and spindle are hardened & ground • Interchangeable rod is marked with the range • 150-300mm Range • Easy adjustment for recalibrating with ratchet spanner • Carbide tipped anvils, Flatness 0.0008mm • Micro-fine clear graduations on satin chrome finish PROTECTED TO IP65 SPECIFICATIONS 220 (Q1245) 242 (Q148) $ 869 (Q118) $ $ Digital Indicator 34-2205 Dial Test Indicator Metric - 34-218 Indicator - Long Range Dial - 34-510 Centering Dial Indicator - 34-515 • 12.5mm/0.5” range • Zero setting at any position • Metric/Imperial system • 55mm dial face • Data output interface • Large measuring range 1.6mm - +1.6mm • Measurement in both directions steel ball end • Gradient of 12 degrees on dial face • Mono enclosure for air tight seal • 0-50mm capacity • Steel Body with black & white steel bezel • Jeweled movement • Steel back with lug • Lifting screw and revolution counter • Locate center quickly and accurately • Centering internal & external • Includes 7 stylus probes and a restraining arm • Operates horizontal and vertical 132 (Q2205) $ 198 (Q218) $ $ Precision Steel Squares • BSS:939 Grade "B" • Hardened spring steel blade • True right angle inside and outside Size 27.50 (Q644) 38.50 (Q645) $ 150mm 44.00 (Q646) $ 225mm 66.00 (Q647) 75mm 100mm $ 209 (Q510) SHOCK PROOF MOVEMENT Measuring Box Set 70-605 • CNC machined for high accuracy • Ground measuring face • Black anodized coating for a protective anti rust coating • Precision laser engraved markings 99 (Q605) $ MACHINERYHOUSE.COM.AU/ SIC2603 INCLUDES 7 STYLUS PROBES AND A RESTRAINING ARM 220 (Q515) $ IP-65 Digital Protractor 35-2041 Dial Thickness Gauge 34-506 • Full 360° range (90° x 4) • 0.05° resolution • ±0.15° accuracy BACK • IP-65 waterproof rating LARGE LIGHT LCD • Magnetic base SCREEN • 0-10mm • Standard steel contact point & anvil Ø10mm diameter • Compact design • Ideally suited for quick inspection 165 (Q2041) $ $ FOR MORE PRODUCTS VISIT • Made of stainless steel • 4-Way measuring • Accuracy ±0.03mm IP67 Rated 129 (Q175) $ 200mm / 8" 139 (Q176) $ 300mm / 12" 149 (Q177) 150mm/6" Q177 IP-67 RATED WATERPROOF UP TO 1M FOR 30 MINUTES IP54 Rated 89 (Q170) $ 200mm / 8" 99 (Q171) $ 300mm / 12" 109 (Q172) 150mm/6" 121 (Q506) $ SYDNEY BRISBANE MELBOURNE PERTH ADELAIDE (02) 9890 9111 (07) 3715 2200 (03) 9212 4422 (08) 9373 9999 (08) 9373 9969 1/2 Windsor Rd, Northmead 625 Boundary Rd, Coopers Plains 4 Abbotts Rd, Dandenong 11 Valentine St, Kewdale 11/20 Cheltenham Pde, Woodville Specifications & prices are subject to change without notification 02_SIC_300326 NEW RELEASE Switching to Linux I was reading R. C.’s letter in Mailbag January 2026 about switching to Linux. My wife was using a Core i5 laptop with 8GB of RAM with Windows 10. It would regularly slow down and almost freeze; it was also constantly needing to restart for updates. In addition, it had Wi-Fi network connecting issues (a problem with Windows, not the hardware). I was getting sick of having to troubleshoot these problems. I decided to get my wife’s previous laptop, a Core i3 with 8GB of RAM with Windows 10 that she was using before, swap out the hard drive and install Lubuntu Linux on it. While there was a bit of a learning curve for my wife in finding folders when saving documents, she says it’s going well and it’s a lot faster than the Core i5 system running Windows 10. We also have another laptop with Lubuntu Linux, a Core i5 and 8GB of RAM that we use in the lounge room to connect to our TV, which is quite old. It has an analog tuner that gets used with a PVR. The TV reception here is hopeless, and a lot of the recordings are corrupted, so we use the Linux laptop to watch catch-up TV. I previously tried connecting Windows 7 and Windows 10 laptops to the TV via HDMI, but because the TV is so old, they could not determine the correct resolution and couldn’t be used. Lubuntu Linux connects straight up via HDMI, and we have no problems with it finding the correct resolution. For anyone who is sick and tired of Windows, there are two Linux distros that I would recommend: Lubuntu and Kubuntu. As the names imply, both are based on Ubuntu and therefore have very good support and a huge range of applications available, as R. C. mentioned. I agree with your comment that Ubuntu is not very userfriendly for beginners, but Lubuntu and Kubuntu are very similar to Windows XP and for anyone using Classic Shell (start menu) on later versions of Windows. With the Classic 8 Silicon Chip Shell start menu set like XP, they would be at home with Lubuntu or Kubuntu. There’s also good online support for anything that users may need help to do. R. C. mentioned using the terminal occasionally. I often use the terminal for updating and installing applications. There are over a hundred different Linux distros that I know of, and I have tried around 20 of them. According to the AI, there are over 600 distros that are actively maintained. I definitely recommend sticking with distros based on Ubuntu, as they are a lot easier to set up and use than those based on other distros like Arch. The accompanying screenshot shows the menu open and an update in progress in the terminal. Updates can also be done graphically. It shows how much like Windows XP the menu is and how easy it is to use Lubuntu compared to Ubuntu. Bruce Pierson, Dundathu, Qld. Comment: for the average person who just needs a web browser, email, a word processor, spreadsheet etc Linux is more than good enough and, as you say, it performs very well, even on ‘outdated’ hardware. It’s also pretty easy to install and set up these days. Hifi Headphone Amp connector problem Thanks for a great project and kit with the Compact Hifi Headphone Amplifier (December 2024; siliconchip.au/ Series/432). I found the winding of the inductors and the heatsinks on the transistors tricky, but otherwise it was a straightforward build. I managed to drill the holes sightly wonky on the case and a bit oversized, but the case all snapped together. With some high-quality headphones plugged into the 6.35mm jack socket, the sound is magnificent. I checked all the current draws and ripple voltages, performed the DC offset and bias adjustments, and it was all correct and perfect. I powered it with 12V AC. Australia's electronics magazine siliconchip.com.au I tested it by playing audio from a mobile phone and from a laptop headphone output socket using an adaptor to RCA plugs. There is no amplifier hiss; it goes very loud and has very high-quality sound. After I put together the case, out of curiosity, I tested the 3.5mm headphone socket. Using that socket, the sound was all weird. With some songs, I could hear the piano and guitars but no vocals. I figured out that CON4, the jack socket on the PCB, was faulty. Logically, it could only really have been the connector, as the amplifier was obviously working fine. To verify that, I measured the resistance between the contacts on my headphone plug and got readings of around 30W for both the left and right channels. Then I plugged it into the socket on the board and measured across the soldered pins. I got readings of nearly 1kW from the left and right channels to ground. I must have damaged it pushing it in or with heat soldering it. I do reckon the 3.5mm socket is likely to fail. The 6.35mm socket would be simpler inside I reckon, as well as being bigger. Anyway, after replacing the 3.5mm socket, it sounds great on both. I compared the specifications of this design to commercially available headphone amplifiers. It seems your design is quite high-fidelity and comparable to $300-800 products. I live in a small house with my family; I never thought about it before, but a headphone amplifier is good for serious music listening if you have high-quality stereo headphones. Edward Menzies, Kew, Vic. Comment: 3.5mm jack connectors are famously weak and can easily be damaged. That’s one reason we provided the 6.35mm socket, which is favoured by musicians for its robustness (although they still sometimes manage to break them). It’s possible the part we received to make the kit was already faulty, or perhaps it was damaged in transit. This design was a conscious effort to make the simplest possible headphone amplifier design that was still truly hifi (although the second input was a bit of an indulgence, albeit a useful one). We think the combination of low-noise op amps and current-boosting output stages has worked out very well and, as you say, the sound quality is excellent given the relatively simple circuit and use of low-cost parts. Improving the output stage in transistor radios Reading Ian Batty’s article on the Columbia TR-1000 portable transistor radio (February 2026; siliconchip.au/ 10 Silicon Chip Article/19669) prompted me to provide the following tip. One problem with old Class-B (or better put, Class-AB) audio amplifier output stages was the shared emitter resistor for both the audio output transistors. It was a money-­ saving thing. If those transistors are not exactly matched in their static gain (hfe) characteristics, the transistor with the higher gain and thus emitter current tends to pull the other transistor with the lower gain & emitter current further out of conduction, thereby aggravating the difference between the two transistors. So if one transistor has a higher current gain than the other, the problem of asymmetry in the output waveform is significantly magnified with a common emitter resistor. For special vintage large-body transistors like this, it is better to keep them for their historical significance. However, the output stage balance can be significantly improved simply by using two separate emitter resistors (one for each transistor). You can also tailor the values of each for a near-perfect balance, even if the two output transistors do not match each other in DC current gain. Dr Hugo Holden, Buddina, Qld. A VHF airband radio design On page 104 of the January 2026 issue (in Ask Silicon Chip), you have a request for a circuit diagram for a VHF Air Band radio. A suitable design was published in the British magazine Radio & Electronics World, September & October 1982. I was a regular buyer of that magazine, Electronics Australia etc. Having said that, I doubt if the RF chips used are still available. I built the radio some time ago. It sits in my kitchen to this day and has rarely been off; I even take it on holidays with me. It works exceptionally well. It worked the first time; there were a couple of minor published corrections. I removed the 10.7MHz filter; it resulted in too much signal loss. It is quite sensitive with a good signal-to-noise ratio (SNR), although I never measured it. Aircraft radios are audible 225nmi (>400km) from home. I tried several VHF preamps from various magazines but none improved the SNR, so I gave up on that. There were a couple of component failures over the years, each of which I diagnosed and fixed. There’s nothing like a failure to force a complete understanding of how a circuit works! SC Warren McTackett, Maitland, NSW. Australia's electronics magazine siliconchip.com.au Where Australia’s Electronics Future Comes to Life Explore breakthrough technologies, design solutions and manufacturing advances for electronic products. SMCBA CONFERENCE Engage with Australia’s industry leaders and experts at the SMCBA Electronics Design and Manufacture Conference. Details at www.smcba.asn.au In Association with Supporting Publication Organised by SERIOUS POWER, SERIOUSLY GOOD VALUE! $ INTEGRATED BLUETOOTH® FOR SMARTPHONE CONNECTIVITY ONLY 999 INTEGRATED CARRY HANDLES MB4102 IP21 RATED 12V CIGARETTE SOCKET & 2 X 12VDC OUTLETS USB-A WITH QUICK CHARGE 3.0 & USB-C WITH POWER DELIVERY PURE SINE WAVE OUTPUT FOR SENSITIVE 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 MB4102 HIGH POWER MODELS INCLUDE 12V 30A HIGH CURRENT OUTPUT 5 YEAR WARRANTY WHEELS & LUGGAGE STYLE HANDLE 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) 6 Mains Outputs 4 5 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 5 Years 5 Years 5 Years 5 Years Availability In-store and online In-store and online Order online or in-store Order online or in-store RRP RRP $999 RRP $1999 RRP $2999 RRP $3999 Explore our great range of 3D Printing gear, in stock on our website, or at over 140 stores or 130 resellers across Australia and New Zealand. jaycar.com.au 1800 022 888 | jaycar.co.nz 0800 452 922 Prices shown in $AUD and correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. 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 . QM3552 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 TS1328 VOLTAGE AND CURRENT DISPLAY $ ONLY 39 95 CONSTANT CURRENT & VOLTAGE IN A SLIMLINE FORM FACTOR . TH1827 CABLE MAKING ONE HANDED! Heavy Duty Wire Stripper • Cutter, crimper & wire guide • Strips 10-24 AWG/0.13-6.0mm • Single handed operation TH1827 $ 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 5995 . QM1323 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 PROVIDES THE PERFECT SOLUTION FOR YOUR SOLDERING & ASSEMBLY NEEDS MEET YOUR NEW RIGHT-HAND Third Hand PCB Holder • Four adjustable arms • Sturdy metal base • Anti-slip ONLY TH1981 $ 1495 . TH1981 Explore our great range of 3D Printing gear, in stock on our website, or at over 140 stores or 130 resellers across Australia and New Zealand. jaycar.com.au 1800 022 888 | jaycar.co.nz 0800 452 922 Prices shown in $AUD and correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. $ ONLY 219 MP3842 SOLDERING STATIONS Soldering made easy with our BEST RANGE of soldering stations at the BEST VALUE, to suit hobbyists and professionals alike. LIGHTWEIGHT, EXCEPTIONALLY DELICATE LIGHTWEIGHT IRON WITH ADJUSTABLE TEMPERATURE • 8 WATT • ROTARY TEMPERATURE CONTROL DIAL $ ONLY 49 95 • 48 WATT • SLIMLINE DESIGN IDEAL STARTER STATION . TS1610 $ ONLY 5995 . TS1620 IDEAL HOBBYIST ENTRY LEVEL STATION GREAT FOR EVERYDAY ELECTRONICS ENTHUSIASTS $ ONLY 149 TS1564 OUR MOST POPULAR STATION FOR HOBBYISTS • 48 WATT • ANALOGUE TEMP ADJUSTMENT GREAT FOR ENTHUSIAST'S WEEKEND PROJECTS ONLY 229 $ TS1640 RELIABLE OPERATION WITH EXCELLENT TEMPERATURE STABILITY • INCLUDES FULL SET OF SPARES INCLUDING REPLACEABLE PENCIL • 60 WATT • DIGITAL TEMP ADJUSTMENT • ESD SAFE Don't pay 2-3 times as much for similar brand name models when you don't have to. COMPLETE SOLDER/DESOLDER STATION $ • 60 WATT IRON • 300W HOT AIR PUMP • RAPID TEMP RECOVERY • DUAL DIGITAL DISPLAY • ADJUSTABLE TEMPERATURE • ESD SAFE ONLY 379 TS1648 SOLDER OR DESOLDER SURFACE MOUNT COMPONENTS ENTRY LEVEL MID LEVEL PROFESSIONAL TS1610 TS1620 TS1564 TS1640 TS1648 Key Feature Compact Design Slimline Ceramic Element Digital Display Soldering & Hot Air Power (Watts) 8W 48W 48W 60W 300W Temp. Range 100-450°C 150-450°C 150-450°C 160-480°C 50-480°C Soldering 100-500°C Hot Air Display Digital Digital ESD Safe • • $229 $379 Price $49.95 $59.95 $149 *Temperature rating is set by the soldering iron tip. ESD means Electro Static Discharge SHOP JAYCAR FOR YOUR SOLDERING ESSENTIALS: • Soldering stations • Electric handheld irons • Gas powered irons • Classic 60/40, lead-free, silver & paste solder options • Multiple desolder braid and tools • Wide range of stands, cleaners and PCB holders Explore our great range of soldering gear, in stock on our website, or at over 140 stores or 130 resellers across Australia and New Zealand. jaycar.com.au - 1800 022 888 jaycar.co.nz - 0800 452 922 Prices shown in $AUD and correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. 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. Digital Vehicle Compass This digital compass is based on a design from the July 2024 issue (siliconchip.au/Article/16330). Tim used an HMC5883L compass board. I couldn’t obtain that so I used a QMC5883L board with a GY271 compass chip. Although similar to the HMC5883L, it needs a different Arduino library. This compass has been made for vehicle dashboard mounting, with the compass board mounted on an Arduino Uno shield, along with some other circuitry. An alternative position for the compass board is in a small Jiffy box mounted elsewhere and connected to the main unit by a Cat5 cable. This may be necessary if unresolved magnetic interference or distortion is experienced with the Uno shieldmounted version. Included in this design is a temperature and humidity module. This can be mounted remotely, via a Cat5 cable if desired, similar to the optional external compass module. The unit includes a vehicle battery state monitor and automatically dims the LED display when the vehicle lights are on. To ensure accuracy and reduce interference, place the compass unit with the compass board in situ, as far from known magnetic sources (meters, motors, current-carrying wires, metal objects etc) as possible. The compass module used should be mounted horizontally, with the x,y label in line with the vehicle’s fore/aft axis. The battery state monitor measures the incoming 12V supply and indicates it on the LED display at startup and any time the reset (red) button is pressed. The display first gives the battery voltage, then the estimated charge percentage remaining (for either an SLA or FLA 12V battery, chosen in the Arduino sketch). If the engine is running, it will show the charging voltage. The temperature and humidity monitor uses an FHT20 sensor, which can be placed at any convenient position 16 Silicon Chip in the vehicle if connected via a Cat5 cable. The black and green buttons adjust the LED display brightness at any time the unit is powered, while the blue button switches between degrees and a cardinal (compass) point readout. If the vehicle lights are on, the brightness is reduced to a minimum value preset in the Arduino sketch. The current brightness level is saved in EEPROM and recovered at power-up. The compass starts when the auxiliary vehicle supply is switched on. It shows, in sequence, the battery voltage, battery % remaining, temperature and humidity. Pressing the red reset button will give these values any time they are required. If the battery voltage drops below 20%, the display will cycle through the voltage and the vehicle heading readings. If the battery charge remaining is 10% or below, the display will flash FLAT. Calibration The compass board as delivered is unlikely to give accurate readings. Two types of magnetic distortion influence compass accuracy: hard iron and soft iron. Hard iron distortion is caused by magnetic fields from devices like motors and speakers. This distortion will calibrate out provided it is constant and minimised by compass placement. Soft-iron distortion is caused by the presence of high-permeability materials that distort the Earth’s magnetic field. This distortion is hard to counteract. Distortion caused by vehicle wiring such as lights, starter motors etc that are used intermittently cannot be calibrated out. Calibration is normally done in all three axes (x, y & z). With this vehicle compass, for simplicity, calibration is only done in the x and y axes. Therefore, vehicle rocking and pitching may produce temporary errors. To re-calibrate the compass, remove Australia's electronics magazine the declination by setting it to 0°. Press and hold the blue button and momentarily press the red reset button. When CAL appears on the display, release the blue button and move the vehicle around covering all bearings until CAL goes away (maybe a few minutes). Now ‘swing’ the compass by driving slowly around a full circle, observing the vehicle heading compared to a compass held away from the vehicle (do this in a quiet parking lot or paddock, not on a public road!). If a mobile phone compass is used here with the local declination set in, set the vehicle compass declination to the local value first. When I tested the Compass on the dashboard of my hybrid car, calibration could not be achieved. A survey of the vehicle showed large magnetic deflections, so be warned. In this case, an external compass module would likely be required. After fitting the compass assembly (compass board in situ) in the dashboard of a four-wheel drive offroad vehicle, calibration was not good enough. The compass module was then fitted to the centre console between the front seats of the vehicle, and a very acceptable calibration was achieved (no more that a 5° error in a four-point check). Declination The Earth’s magnetic field is not lined up with geographic (true) north and varies around the globe. For this reason, the declination (horizontal magnetic angle away from true north) needs to ‘wound out’. For example, in Auckland, it is 20°E. Use Google to establish local declination. To alter the declination, press and hold the black button and use the green and blue buttons to set the local declination. The setting will be saved after releasing the black button. In time, the declination may change, so a reset to a different value may be necessary. Small errors in calibration in one siliconchip.com.au direction (clockwise or anti-clockwise) can be taken out by adjusting the declination. Offset The compass board can be orientated in one of four 90° positions relative to the fore and aft axis of the vehicle. To set the offset, press and hold the black button, then momentarily press reset (the red button), wait for the desired offset to show on the display and release the black button. The offset setting will be saved. Power supply The vehicle’s 12V supply will contain significant transients and noise. The 10W series resistor and TVS1 will help to suppress the worst of them. TVS1 conducts at about 18V. D2 is a reverse-polarity protection diode. siliconchip.com.au The buck regulator module efficiently derives the required 5V to run the rest of the circuit, while ZD2 protects the downstream components from overvoltage. Two resistive dividers allow the Arduino to monitor the battery voltage (A0) and lights on/off (A1) via software. ZD1 protects the Arduino from overvoltage on the A0 pin. The Arduino uses a 1.2V reference provided by REF1 for making accurate analog voltage measurements. When the headlamps are on, the A1 input rises to about 1V and the LED display is dimmed. Software There are some settings available in the sketch (siliconchip.au/ Shop/6/3611) to optimise the compass performance. In particular, the range Australia's electronics magazine can be set to 2G (0.2mT) or 8G (0.8mT). The range is set to 8G because initial road tests showed that the Arduino registers could overflow otherwise. If desired, this setting can be changed in the sketch. Murray Tricker, Auckland, NZ ($120). Circuit Ideas Wanted Got an interesting original circuit that you have cleverly devised? We will pay good money to feature it in Circuit Notebook. We can pay you by electronic funds transfer, credit or direct to your PayPal account. Or you can use the funds to purchase anything from the Silicon Chip Online Store. Email your circuit and descriptive text to editor<at> siliconchip.com.au April 2026  17 Jury-rigged 44-pin Micromite I needed a 44-pin Micromite module (August 2014; siliconchip.au/ Article/7960) but didn’t have a PCB handy. Instead, I built an equivalent device using a 44-pin QFP (0.8mm pitch) adaptor board I had, along with a USB/serial module. Because of the narrowness of this adaptor board, it doesn’t have throughholes for all the pins. However, it does have SMD pads on the underside for all 44 pins. My solution was to solder two right-angle headers to the underside of the adaptor board, spaced apart correctly to fit into a breadboard with a 0.7-inch (17.78mm) or 1.1-inch (27.94mm) separation. Once the SMD microcontroller has been soldered, you can add the 47μF SMA tantalum capacitor between pins 6 & 7 (striped [positive] end to pin 7) and a 10kW M2012/0805 SMD resistor between pins 17 & 18. Next, solder the two 22-pin right-­ angle headers on the underside of the adaptor module, as shown in the photo. To keep them the correct distance apart, use two female headers and insert the pins either 7 or 11 rows apart until a few pins have been fully soldered onto the adaptor module. Next, just solder a few thin wires on the underside of the module: red wires joining pins 17, 28 & 40 and grey/black wires joining pins 6, 16, 29 & 39. Attach the USB-to-serial module using double-sided adhesive tape, by placing it on the lower end of the adaptor board inline with pins 22-23. Then join its terminals to the pins on the modules, as shown in the accompanying diagram. If the chip has not already been programmed, you can download the Micromite Mk2 firmware (siliconchip. au/Shop/6/2907) and load it onto the chip using a PIC32 programmer by soldering wires to pins 18 (MCLR), 21 (PGC), 22 (PGC) plus +3.3V and GND. A Snap, PICkit or the Microbridge (May 2017; siliconchip.au/Article/ 10648) programmer can be used. Gianni Pallotti, North Rocks, NSW. ($70) The finished Micromite is shown above, with the CP2102 mounted using double-sided tape. The photo on the right shows the soldering jig that I used to align the right-angled headers. Editor’s note: it’s a good idea to solder 100nF 50V M2012/0805 SMD X7R ceramic capacitors between pin pairs 16/17, 28/29 & 39/40 for local bypassing. The circuit and overlay diagram for the modified 44-pin Micromite. Note the 47μF capacitor soldered between pins 6 & 7, and the 10kW resistor between pins 17 & 18. 18 Silicon Chip Australia's electronics magazine siliconchip.com.au Image source: https://pixabay.com/photos/intel-8008-cpu-old-processor-3259173/ T o r y of t s i h he intel Pa rt 3 b y D r D avid Mad K3D V , n o d is SM Over the last two issues, we have traced Intel’s history from its beginnings in 1968 until recently. That included a lot of information on the primary product that Intel is known for: computer CPUs. Now that we’ve caught up to the present, we’ll investigate their current and future technologies. W e finished part two last month with information on Intel’s hybrid CPUs with high-performance P-cores and high-efficiency E-cores. They were introduced in their mainstream products starting with the 12th generation Core CPUs launched in 2021, but those cores were still part of a single, monolithic die. That’s in stark contrast to their direct competitor, AMD, which launched its Ryzen 2 series processors in 2019. They used a different approach, combining multiple silicon die “tiles” (or “chiplets”) to form a complete CPU. Intel started doing something similar in 2023, although with some important differences. New interconnection techniques Microprocessors and AI chips are now so complex and contain so many components that the silicon area required exceeds that which can be produced by a single lithography reticle field. That is, the area that a design can be projected onto, currently 20 Silicon Chip around 858mm2 or a rectangle of about 26 × 33mm. This means that multiple chips are required to fulfil the latest designs. Also, even if it’s possible to make a 26 × 33mm chip, yield (ie, the percentage of chips that are usable) drops with increasing die size, so it’s more economical to make multiple smaller dies than one large one. These smaller chips are called (generically) chiplets, and processor designs may comprise a variety of different chiplets such as CPU, GPU, AI accelerators, memory, I/O etc, as described last month for Meteor Lake (siliconchip.au/Article/19823). Intel’s preferred name for the generic chiplet is “tile”; this describes their specific implementation of the chiplet approach, but in their literature and in industry, both terms are used. The chiplet approach was popularised by AMD with its Ryzen 2 and EPYC processors, the first high-­ volume products to use this approach. AMD chiplets are mounted side-byside (with some exceptions, eg, 3D V-Cache), while Intel’s tile approach using Foveros technology can vertically stack tiles, allowing for higher overall chip density – see Table 6. Each chiplet or tile is specialised and optimised, and can be “mixed and matched”, including (critically) using different process nodes in the one package. The chiplets are connected by a variety of 2D (side-by-side) and 3D (stacked) methods as part of a modular design. Meteor Lake Meteor Lake, released in late 2023, was Intel’s first consumer CPU to adopt Feature size measurements 1 micron or 1µm: 0.001mm, 0.000001m (1 × 10-6m) 1 nanometre or 1nm: 0.000001mm, 0.000000001m (1 × 10-9m) 1 ångström or 1Å: 0.1nm, 0.0000001mm, 0.0000000001m (1 × 10-10m) Australia's electronics magazine siliconchip.com.au Fig.41: a die shot of the compute tile of Meteor Lake, one of the four active tiles (see Fig.42). This version contains two P-cores and eight E-cores. Source: https://x.com/Locuza_/status/1524465856167792640/photo/1 Fig.42: the function of the four tiles in a Meteor Lake processor’s base tile. Source: Intel – siliconchip.au/link/ac9v siliconchip.com.au the NPU (Neural Processing Unit) for AI workloads. Importantly, it also contains a separate cluster of low-power Crestmont “LP E-cores”. These ultra-efficient cores form a ‘low-power island’ capable of handling light background and OS tasks while the compute tile is powered down, significantly improving idle and low-load power consumption. This is why the SoC tile occupies such a large proportion of the total area. ● I/O tile: provides high-speed I/O such as PCIe, USB4/Thunderbolt, display PHYs (physical layers) and memory PHYs. It is built on a mature TSMC process (N6), well suited to mixed-­ signal and I/O circuitry. Underneath all these is the base tile, which mechanically supports the active tiles and provides the high-­ density interconnect between them. Intel uses technologies described overleaf, such as Foveros 3D stacking, EMIB (Embedded Multi-Die Interconnect Bridge) and TSVs (Through-­ Silicon Vias) to bond the tiles together. Australia's electronics magazine Graphics Tile SOC Tile IOE Tile a tile (chiplet) architecture (Figs.41 & 42). Instead of a single monolithic die, the processor is built from multiple specialised tiles, each manufactured on the most appropriate process node for its function. The design includes four active tiles plus a passive base tile: ● Compute tile: contains the high-performance Redwood Cove P-cores, the main cluster of Crestmont E-cores, their associated L2/L3 caches, and the core interconnect fabric. This tile is manufactured on Intel 4, Intel’s first EUV-enabled (extreme ultraviolet) process, chosen because the CPU cores benefit most from cutting-edge lithography. As a result, it isn’t the largest tile on the chip. ● Graphics tile: includes the Intel Arc integrated GPU, based on Xe-LPG architecture. It is manufactured by TSMC (N5/N6 process). ● SoC (System-on-Chip) tile: the largest tile, made using Intel 6 process. It contains a wide range of system-level functions: the media engine, display engine, power management, memory fabric, connectivity controllers and Compute Tile April 2026  21 Fig.43: a better look at the die, and tile structure, of Meteor Lake. Compare it to Fig.42. Source: https://wccftech.com/intelcore-ultra-meteor-lake-cpu-die-shots-closer-look-at-various-cpu-gpu-io-chiplets/ Fig.43 provides further information on Meteor Lake die, illustrating the arrangement of tiles and interconnect structures. Meteor Lake’s modular design allows Intel to update or replace tiles independently, mix process nodes, and reduce wafer costs while improving yields. It also represents a major architectural shift: by moving media, display, AI acceleration and low-power processing to the SoC tile, the compute tile can power down completely, delivering better efficiency than previous Intel laptop processors. Foveros Direct 3D Foveros Direct 3D is an Intel chiplet (tile) connection technology for the direct attachment of a tile to an active base die. The second generation of this technology uses copper vias in the tiles with a pitch of 3 microns (3μm). Attachment can be by thermocompression bonding, using heat and pressure to join individual tiles to the underlying die. Foveros replaces the earlier solder-based microbumps and provides a much higher (10100×) interconnect density, plus better power and thermal performance – see Fig.44. EMIB Intel Embedded Multi-die Interconnect Bridge is a silicon ‘bridge’ embedded in a substrate to connect between tiles – see Fig.46. Intel Foundry FCBGA 2D+ Intel’s Flip Chip Ball Grid Array 2D+ is a type of processor packaging used in laptops, which replaces traditional pin grid arrays. A grid of solder balls on the bottom mates with corresponding lands on the motherboard; the chip is heated to solder it in place – see Fig.45. The processors are not removable, replaceable or upgradeable except by replacement of the motherboard. Processors designed for desktop platforms use traditional LGA (land grid array) pins and are removable. PowerVia In Intel’s earlier technology, all external connections, for both power delivery and signal I/O, were made to the top layer of the chip. There was no connection beneath the chip, which provided only structural support and heat transfer. From the 18A process node, Intel decoupled the connections for power and signals, calling the method Power­ Via. Thus, power is provided from beneath the die, and signal connections are made on the top side – see Fig.47. This means that the power and signal connections and routing can be independently optimised, giving 90% more efficient area utilisation, lower power consumption and lower voltage drop Figs.44 & 45: the tiles (labelled “die”) are connected to an active base die using Foveros Direct 3D (left). Intel’s FCBGA 2D+ method for mounting processors on motherboards in laptops (right). Source: www.intel.com/content/dam/www/centrallibraries/us/en/documents/2024-02/intel-tech-clearwater-wp.pdf 22 Silicon Chip Australia's electronics magazine siliconchip.com.au Table 6 – Intel vs AMD chiplet technology Foveros 3D stacking of tiles Chiplets mounted and EMIB for connection horizontally on an between tiles. An active or organic substrate. passive base die or “interposer” allows vertical stacking. The interposer contains TSVs (through-silicon vias). Interconnects High-bandwidth, low-latency links between tiles; no need for a full bus as they collectively act like a single chip. Infinity Fabric serial bus for inter-chiplet communications. Simpler, but can increase latency. Scalability Optimised for low power consumption (eg, laptops). Tiles can be swapped for different applications. Optimised for desktops and servers with large numbers of cores, eg, 128+ in EPYC. Complexity and cost Complex and expensive to assemble. Variants require new base dies. Simpler and cheaper. Power efficiency Almost no power overhead. A small amount of extra power is consumed by interconnects. RibbonFET With Intel’s present 18A process node, adverse quantum mechanical and other effects are a significant concern. Hence, Intel developed the gateall-around (GAA) transistor architecture known as RibbonFET (Fig.49) to mitigate effects like electron tunnelling, leakage currents and to provide improved electrostatic control compared to the earlier FinFET (Fig.48). While Samsung and AMD also have GAA technology, Intel’s nanosheets are engineered to be extremely uniform and scalable for their PowerVia backside power delivery. Intel intends RibbonFET + PowerVia to be a tightly integrated technology pair. Moore’s Law is over From the 1960s until roughly 2016, Intel largely followed, and was driven by, Moore’s Law, doubling transistor density every couple of years. But physical and practical limits have now been reached: quantum effects, heat dissipation and lithography challenges mean that simple geometric scaling is no longer providing the historical gains. Clock speeds have also plateaued. To improve performance, the industry has shifted focus. Instead of shrinking transistors indefinitely, manufacturers now rely on advanced packaging technologies: stacking multiple chips vertically (3D packaging, such as that seen in AMD’s X3D series of CPUs), using chiplets or tiles placed side-byside, and high-bandwidth interconnects such as EMIB to combine multiple dies in a single package. New transistor architectures, like Intel’s RibbonFET gate-all-around design, increase performance and efficiency even when further shrinking is impractical. Power Packaging technology (a 30% reduction) as well as an overall 6% performance improvement. AMD chiplet Signal Intel tile Power & Signal Feature Transistors Fig.47: the old die connection technology (left) compared to the new PowerVia technology (right). Source: www.intel.com/content/ dam/www/central-libraries/us/ en/documents/2024-02/intel-techclearwater-wp.pdf Software and algorithms are also evolving. Specialised architectures – particularly GPUs and AI accelerators, which contain many parallel processing units – enable significant performance gains despite the slowdown in raw transistor density improvements. Artificial Intelligence (AI) Intel and its chips have a long history of involvement in AI. In the 1980s, Intel collaborated in the development of the Connection Machine, a massive supercomputer built for AI research, which influenced early neural computing. It was said to have provided i860 RISC processors and custom chips for the project. In 1997, they launched the MMX instruction set, which accelerated multimedia and early machine learning tasks like image processing. In 2013, Intel acquired Indisys, a Spanish company specialising in Fig.46: an illustration of various Intel interconnect technologies for tiles. Figs.48 & 49: the older FinFET technology (left) and the new RibbonFET technology (right). Source: same as Fig.47 siliconchip.com.au Australia's electronics magazine April 2026  23 natural language processing and AI. In the same year, they acquired Israeli company Omek Interactive, which had technology that enabled users to interact with devices via hand and body gestures with 3D cameras. RealSense makes 3D cameras, vision processors and AI vision systems. It was ‘incubated’ by Intel internally from 2014 and spun off in 2025 as an independent company. In 2016, the AVX-512 x86 instruction set extension was released. It can accelerate AI workloads by processing in parallel using wide 512-bit registers, speeding up machine learning, image and speech processing and large language models (LLM). In 2017, Intel acquired US company Nervana Systems for its expertise in deep learning software, which was later integrated into Intel processors as the Nervana Neural Processor (NNP). However, that was discontinued, to be replaced with Habana Labs’ technology, an Israeli company Intel acquired in 2019 for their Gaudi2 and Gaudi3 AI accelerator technology. In 2016, Intel purchased Movidius for its vision processing chips. Also in 2016, Intel established the Nervana AI Academy to train AI developers. In 2017, Intel purchased Mobileye, which specialised in autonomous driving and related technologies. In 2019, Intel released the oneAPI suite of tools, libraries and a programming model for developing and optimising AI applications across all Intel hardware such as CPUs, GPUs and FPGAs. During 2019-2024, Intel produced the Ponte Vecchio AI accelerator with over 100 billion transistors and 47 tiles (chiplets) using five different process nodes. It is to be replaced by Gaudi2/3. In 2022, Intel released the Gaudi2 AI accelerator. The Gaudi3 was released in 2023. It is claimed to be capable of 50% faster training than the NVIDIA H100 at half the cost. Also in 2023, the Meteor Lake series of processors was released with integrated NPUs (Neural Processing Units) for on-device AI. In mid-2026, Intel plans to release the Jaguar Shores AI accelerator designed for data centres. It will use the 18A process node. Graphics Processing Units Intel has included integrated graphics in its CPUs since the mid-2000s 24 Silicon Chip Fig.50: an Intel Arc A770 graphics processing unit. Source: https://w.wiki/GdyA and considering this, by unit volume, has long been the world’s largest GPU (Graphics Processing Units) vendor. However, these integrated solutions were designed mainly for desktop display output and light graphics use. Intel left the performance GPU market to AMD and NVIDIA for decades. The rise of AI changed that. GPUs, originally designed for massively parallel graphics workloads, proved far better suited to machine-learning tasks than traditional CPUs. Recognising that GPUs would become strategically important across consumer, workstation and data centre markets, Intel entered the discrete GPU space in 2022 with the launch of the Intel Arc family. Arc is based on the Xe architecture, which scales from integrated laptop GPUs through to high-performance compute accelerators. The first generation (Arc A-series, “Alchemist”) included six desktop cards (from the A310 4GB to the A770 16GB) and seven mobile variants (A350M to A770M – see Fig.50). A second generation of Arc products (B-series, “Battlemage”) began arriving in late 2024/early 2025 with models such as the B570 10GB, B580 16GB and B50 24GB – see Figs.51 & 52. Although Intel lacks a competitor for ultra-high-end GPUs like AMD’s Radeon RX 7900 XTX or NVIDIA’s RTX 5090, Arc performs well in the low to midrange when compared at similar price points. Arc also offers industry-­leading AV1 video encoding and strong efficiency, making it attractive for media, gaming and general-­ purpose GPU workloads. Driver maturity was initially a weakness, but Intel has significantly improved support, especially for older DirectX 9, 10 & 11 games. Intel’s long-term commitment has occasionally been questioned, but Australia's electronics magazine multiple factors suggest Arc is here to stay. Intel has already announced future generations (“Celestial” and “Druid”), and its Xe graphics architecture is now embedded in its laptop CPUs, data-centre accelerators and AI platforms. With AMD and NVIDIA struggling to meet global AI-related demand, a third major competitor is beneficial for the industry and consumers. It therefore seems likely that Intel will continue to refine Arc, with “C-series” products expected to arrive sometime in 2026, quite possibly in the first half of the year if development stays on track. More details on Intel’s CEOs Last month we provided a list of Intel CEOs but with only a very brief description of each person. Here is some more detailed information on some of the key figures who became CEOs at Intel and their major contributions to the company. Robert Noyce, 1968-1975 Visionary founder, and inventor of the first monolithic IC. Gordon Moore, 1975-1987 He defined Moore’s Law, which gave Intel an objective to strive for: increased chip density and performance each year. Fig.53: Andrew Grove, Robert Noyce & Gordon Moore in 1978; from part one. Source: www.flickr. com/photos/ 8267616249 siliconchip.com.au Figs.51 & 52: a render showing the parts breakdown for an Intel Arc B580 card and the die. Source: https://newsroom.intel.com/client-computing/intel-launches-arc-b-series-graphics-cards Andrew Grove, 1987-1998 A strict management disciplinarian, driven by results, and the author of the book “Only the Paranoid Survive”. Craig Barrett, 1998-2005 He was a materials scientist and focused on high-volume, reliable fabrication of microprocessors and the “Copy Exactly” system, which standardised equipment, processes and even minor details like the colours each fabrication plant was to be painted. This approach was responsible for the explosive growth of Intel during the 1980s and 1990s. As CEO, he brought the company through the dotcom boom and bust. Paul Otellini, 2005-2013 He was the first non-engineer CEO at Intel, bringing a sales and marketing mindset to a company built by technical visionaries. In 1993, he oversaw the rollout of the Pentium processor and the “Intel Inside” campaign. As CEO, he generated more revenue in 2012 (US$53 billion) than Intel had seen in its entire prior history. On the downside, he admitted to missing the shift to mobile computing and turned down a deal for the ARM processor for the iPhone. Brian Krzanich, 2013-2018 Brian Krzanich came from the manufacturing side of Intel, with experience in semiconductor process engineering and supply-chain operations. As CEO, he pushed Intel to diversify beyond the declining PC market toward what he called data-centric computing. This strategy included major acquisitions such as Nervana Systems (AI accelerators) and Mobileye (autonomous driving technology). He also promoted internal cultural and workplace reforms, some of which were praised and some criticised, particularly around restructuring and workforce reductions. By 2018, Krzanich’s strategy had succeeded in changing Intel’s revenue mix: approximately half of Intel’s revenue now came from data-centric businesses rather than PCs, which was a significant shift. However, his tenure is strongly associated with the 10nm process delay, arguably the most damaging manufacturing slip in Intel’s history. Under his leadership, Intel attempted to make too many major process innovations simultaneously. This opened the door for TSMC and Samsung to establish leadership in advanced process nodes and allowed AMD to regain CPU market share. Krzanich resigned in 2018 due to a personal misconduct policy violation unrelated to business performance. Robert Holmes Swan, 2019-2021 He was a finance executive and an external appointment from outside Intel, and was Intel’s shortest tenure CEO. He contributed financial stewardship, “cultural overhaul” and “organisational unity” to the company. Like Krzanich, he was also criticised for delays related to the 10nm process node. Patrick Gelsinger, 2021-2024 He was Intel’s chief technology officer (CTO) from 2001 to 2009. He managed the development of USB, WiFi integration and was the architect of the 80486 processor, oversaw the development of the Pentium 4, Core, Xeon and 64-bit computing. Figs.54-59 (left-to-right): Craig Barrett, Paul Otellini, Brian Krzanich, Robert Swan, Patrick Gelsinger & Lip-Bu Tan. Source: Craig Barrett’s photo – https://w.wiki/GkEz; all the other photos are from Intel Corporation siliconchip.com.au Australia's electronics magazine April 2026  25 Table 7 – major Intel fabs Years active Location Wafer size and process node Notes 1968-1983 Mountain View, California 2-inch (50.8mm), 10µm from 1972. Mainly for research and to produce the 4004. 1984-1990s Santa Clara, California, 3-inch (76.2mm), 8µm from 1974, 6µm from 1976. Fabs 1-5. Produced the 8080. 1980-present Chandler, Arizona 4-inch (101.6mm), 3µm from 1982, 0.13µm from 2001. Produced 300mm wafers from 2000. Switched to 65nm in 2006, 45nm in 2008, 22nm in 2012, Intel 3 and 20A (cancelled) in 2024. Fabs 12, 22, 32, 42, 52, & 62. Produced the 80386. Core 2, 1st Gen. Core i7 and 4th Gen Core. Fab 62 will start Intel 18A production in 2026. 1996-present Hillsboro, Oregon 200mm, 0.25µm in 1998. 300mm, 130nm, in 2002. Supports Intel 4 and 3 as of 2023. Fabs D1A-D & D1X. Mainly for research and development (R&D). 1996-present Kirygat, Israel 300mm, 45nm in 1996, 22nm in 2011, Fab 28, Intel 7 in 2023. 2002-present Leixlip, Ireland 300mm, 130nm in 2004, Intel 4 in 2023, Intel 18A in 2026. Fabs 10, 14, 24 & 34. 2030-2032? Licking County, Ohio Intel 14A. Fab 27, expected production dates 2030-2032. He became CEO with a vision to reclaim Intel’s manufacturing and technology leadership and “bet” US$100 billion plus on “IDM 2.0” (Integrated Device Manufacturer) to make Intel the world’s leading foundry, and restore American chip making dominance. He wanted Intel to be a foundry that designs, makes and sells chips both for itself and others. Despite his bold strategy, he was “ousted” by the board that lost confidence in him due to failure to reduce process nodes fast enough, poor financial performance, and poor response to the market such as missing the AI boom that needed (NVIDIA) GPUs, which Intel had failed to adequately develop. During this time, Intel lost market share to AMD. Lip-Bu Tan, 2025-present Ex-CEO of Cadence, a company that provides software to design integrated circuits (ICs) and PCBs (one of the ‘big three’ EDA vendors that dominate the global semiconductor design tooling industry). He has BS in Physics, Master’s in Nuclear Engineering and Master of Business Administration. He is attempting a turnaround of Intel by slashing bureaucracy, doing foundry deals and becoming more customer-­focused. Intel’s development models Until 2006, Intel had no formally named development model, but 26 Silicon Chip improvements were a continuing cycle of: 1. develop a new microarchitecture; 2. release it; 3. shrink the process size once or more with incremental improvements (eg, the P6 microarchitecture of the Pentium Pro was shrunk three times); 4. repeat at irregular intervals as technological improvements allowed. After problems with the NetBurst microarchitecture of the Pentium 4, Intel management decided they wanted a more formal and disciplined development model. The process-architecture-optimisation (PAO) model was introduced in 2016 and remained in use until 2021 to address the limitations of the ticktock model (see our panel on p24 last month). It operated on a three-year cycle comprising three stages: 1. Process: a die shrink to the next manufacturing node to give a higher density of transistors, but typically using an existing microarchitecture. 2. Architecture: a major redesign of the microarchitecture for improved performance. 3. Optimisation: iterative improvements to the architecture. This model allowed Intel to introduce new processor generations every 12-18 months while spreading the risk and cost of new process nodes over a range of products. Intel phased out the PAO model around 2021-2023 as it was becoming Australia's electronics magazine increasingly difficult to develop new process nodes on a three-year schedule. That’s similar to how the tick-tock model was abandoned when further feature shrinkage was no longer economically feasible. The “process leadership” roadmap was adopted around 2023 to emphasise node advancements such as Intel 3, 20A, 18A with less emphasis on strict two- and three-year cycles, but with a focus on “five nodes in four years”. Note that the 20A process was cancelled in 2024, and they skipped from Intel 3 straight to 18A. Taiwan Semiconductors was instead contracted to make parts planned for the 20A node, such as Arrow Lake. Intel’s fabrication facilities Some significant Intel past, present and future fabrication facilities (fabs) include those shown in Table 7. Other Intel developments and inventions Apart from CPUs, GPUs, the x86 instruction set, memory chips and related chipsets, Intel has also been involved in inventing, innovating or contributing in the following areas: 3D XPoint This was a form of non-volatile storage media technology developed jointly between Intel and Micron. It was introduced to the market in 2017 and discontinued 2022. siliconchip.com.au It was designed to fit in the speed gap between faster traditional non-­ volatile NAND flash and slower volatile DRAM. It was marketed under the brand name Optane (see Figs.60 & 61), Intel’s commercial implementation of 3D XPoint memory. Optane could act as extremely fast cache storage for hard drives, improving performance, but its more significant role was in early high-performance SSDs and in the persistent-memory DIMMs designed for data centres. Optane was not made obsolete by normal SSDs; rather, Intel discontinued the product line in 20222023 after its manufacturing partner Micron exited 3D XPoint production and demand failed to meet expectations. Technically, Optane was exceptional: it offered dramatically lower latency than NAND SSDs and extremely high endurance. Because of this, some users still prefer Optane drives for specialised workloads. XPoint was not based on traditional charge storage in cells, but on a change in some other physical property, generally thought to be a material phase change, although Intel never confirmed this. The structure of the memory chip had multiple layers in a 3D stack. The first generation of XPoint had two layers, and the second generation four layers, allowing up to 256GB per die – see Fig.62. Accelerated Graphics Port (AGP) The Accelerated Graphics Port was introduced in 1996. It was a dedicated graphics port intended as an improvement in speed over the PCI slots used for other accessory cards. It provided faster data transfer rates with a dedicated connection to the CPU, and dedicated memory bandwidth, which was necessary because of the development of 3D graphics and gaming. AGP cards had their own memory and could also access system RAM. The first chipset to support AGP was Intel’s legendary Celeron 440 series of CPUs from 1997/1998. In 1998, Intel also introduced the i740 dedicated AGP graphics chip to help promote AGP as a standard (see Fig.63). AGP was superseded by the PCI Express (PCIe) standard introduced in 2003. siliconchip.com.au Fig.60: Optane storage in an SSD (M.2) format. Source: https://hothardware.com/photo-gallery/ article/2720?image=big_intel-optane800p-pair.jpg Fig.61: Optane is non-volatile but fast enough to use like system RAM! Source: www.forbes. com/sites/tomcoughlin/2022/08/08/gifts-fromintels-optane-memory (from Intel) Memory cell Wire Positive charge Selector Negative charge Voltage affects selector, causing it to read/write the memory cell Fig.62: the 3D XPoint technology used in Optane memory. The memory cells are light grey and green, and the address lines (bit lines and word lines) are a darker grey. Source: www.bbc.com/news/technology-33675734 Fig.63: the Intel i740 was their first AGP-slot graphics card. It was one of Intel’s ealiest ventures into the dedicated GPU market. It wasn’t very successful, compared to the NVIDIA GeForce 256 or 3dfx Banshee, which used a PCI slot. Australia's electronics magazine April 2026  27 One of the people at Intel who worked on AGP was Ajay Bhatt – this won’t be the last you hear of him. ATX power supplies These widely used PC power supplies and their compatible motherboards conform to a standard developed by Intel and released in 1995. It replaced the AT form factor, which originated with the IBM PC in 1981. Flash memory Intel introduced the first commercial NOR flash chip in 1988, marking a major advance in non-volatile memory technology. Intel later co-­developed 3D NAND flash, with the first generation announced in 2015. By 2020, Intel’s 3D NAND products had reached 144 layers and triple-level cell (TLC) technology (three bits per cell). In late 2020, Intel sold its entire NAND and 3D NAND flash business, including its Dalian fab, to SK Hynix (now operating as Solidigm). Ethernet Ethernet was originally developed at Xerox PARC (Palo Alto Research Center) in the early 1970s by Robert Metcalfe and colleagues. In 1980, Xerox partnered with DEC and Intel to create the DIX Ethernet specification (also called Ethernet v1.0 and later 2.0). This work formed the basis for the IEEE 802.3 standard, published in 1983. Integrated graphics (iGPU) on motherboards This was introduced by Intel in 1982, in the form of the 82720 Graphics Display Controller. In 2010, Intel integrated a graphics chip into the CPU itself. Nowadays, most Intel desktop and laptop CPUs include an integrated GPU, the exceptions being those with an “F” or “KF” suffix. In those cases, the onboard graphics circuitry is disabled. As always, for niche or OEMonly variants, it pays to check the specification sheet rather than rely solely on naming. Even if the CPU has onboard graphics, dedicated graphics cards can still be added. In fact, it is usually possible to use both simultaneously. An external card will generally have better 3D performance. Movidius Vision Processing Units VPUs are specialised chips designed specifically for accelerating computer vision and related AI tasks. They allow the processing to be offloaded from the CPU and GPU, and can be used in applications such as drones, robots, smart security systems (to recognise targets), real-time AI powered video processing, machine vision, virtual reality, augmented reality headsets and smart cameras. Such chips include dedicated hardware for deep learning, such as a Neural Compute Engine in the Myriad X chip. They are designed for energy efficiency. Intel acquired Movidius in 2016. The DJI Phantom 4 (see Fig.64), released in 2016, was the world’s first consumer drone with autonomous flight capabilities thanks to a Movidius Myriad 2 VPU chip with functions such as forward-facing obstacle avoidance and subject tracking. It can also hover at a fixed location using object tracking alone, without the need for satellite navigation signals. PCI Peripheral Component Interconnect was introduced by Intel in 1992 as a modern, processor-agnostic expansion bus to replace ISA and EISA. It quickly became the industry standard throughout the 1990s and early 2000s – see Fig.65. Ajay Bhatt – whom readers may recognise from several other entries – played a key role in its design. PCI Express The PCI Express expansion standard that’s widely used today was invented by a consortium of companies including Dell, IBM and HP, although Intel was the dominant player. It was introduced in 2003. Ajay Bhatt made a major contribution to the development of the specification. Platform power management PPM was co-invented by Ajay Bhatt at Intel. It is a series of technologies that dynamically adjust the CPU clock speed and voltage to reduce power consumption dependent upon processor load. PresentMon PresentMon is software used to track performance primarily for games. It’s mostly maintained by Intel (https:// game.intel.com/us/intel-presentmon), and is useful for benchmarking. Fig.64: the DJI Phantom 4 drone uses the Movidius Myrid 2 vision processing unit (VPU). Movidius was acquired by Intel in 2016, although they haven’t released any new products in the last few years. Source: www.pexels.com/ photo/a-drone-camera-across-the-blue-sky-4355183/ Thunderbolt Thunderbolt is a high-speed interface developed by Intel in collaboration with Apple. It allows data, video and power to be transferred through a single cable, supporting devices such as monitors, external storage, docks and high-performance peripherals. A Thunderbolt-supported USB-C port is typically marked with a lightning-bolt icon (see Fig.66). Thunderbolt 5 is the latest standard, offering up to 120Gbps of Australia's electronics magazine siliconchip.com.au 28 Silicon Chip bi-directional bandwidth using its “Bandwidth Boost” mode when driving high-resolution displays, with a base bandwidth of 80Gbps. Although Thunderbolt was once most strongly associated with Apple systems, it is now widely available across Windows laptops and desktops. Modern versions of Thunderbolt use the USB-C connector, meaning the same physical port may support USB, Thunderbolt, DisplayPort and power delivery. In recent years, many Thunderbolt capabilities have been incorporated into the USB standard, particularly with USB4 and USB4 v2, which are based on Intel’s Thunderbolt 3 specification, contributed to the USB-IF (USB Implementer’s Form). USB The USB interface was invented by Intel’s Ajay Bhatt (him again!). He and his team at Intel developed the first USB standard, which was released in 1996. Wi-Fi Intel has been a major force behind Wi-Fi adoption since the early 2000s. Their Centrino platform (2003) effectively made Wi-Fi standard in laptops, pushing the entire PC industry toward wireless networking. Intel played significant roles in the IEEE committees for 802.11n, 802.11ac, Wi-Fi 6 (802.11ax), and Wi-Fi 7 (802.11be), contributing reference designs, test silicon, and architectural proposals. Today, Intel is one of the largest suppliers of Wi-Fi chipsets for PCs, and its engineering teams continue to help shape future Wi-Fi standards. Fig.65: Intel developed both PCI (lower) and the more modern and faster PCI Express (upper) expansion slots. PCI Express slots come in different lengths, from a single lane to 16 lanes, and in different generations, from Gen1 to Gen6. Source: https://w.wiki/GdyB (CC BY-SA 2.0) Fig.66: while Thunderbolt 1 & 2 used unique connectors, Thunderbolt 3, 4 & 5 use USB-C connectors. That means the same ports can be compatible with USB and Thunderbolt. Source: https://w.wiki/GdyC (CC BY-SA 4.0) Figs.67 & 68: Intel’s quantum computer chip; bare die (above) and in packaging (below). Source: https://newsroom.intel.com/newtechnologies/quantum-computingchip-to-advance-research Quantum computing Intel is developing Tunnel Falls (see Figs.67 & 68), an experimental 12-qubit quantum computer chip, which is being made available to researchers at universities and the US military. A qubit is a basic element of quantum information. Whereas a transistor can have two bit states, a 0 or 1, a qubit can be a 0, a 1 or both simultaneously. It has an infinite amount of superposition states, but when measured, it will still be a 0 or 1. This ability can enable it to solve many types of problems that are insoluble or very slow to solve on conventional computers, including siliconchip.com.au Australia's electronics magazine April 2026  29 decryption. Intel’s silicon spin qubits are up to 1 million times smaller than other qubit types, and the Tunnel Falls qubit chip is highly scalable. Intel aims to sell both the computing hardware and software as a complete solution. Past Intel failures Intel, like any company, has had its fair share of failures: ● The NetBurst architecture used for the Pentium 4 was supposed to be the way of the future, but it was a dead end, never reaching the clock speeds they were aiming for. ● Delays in the 10nm process node, at least partly due to the failure to adopt new technology such as EUV lithography. ● Defects in large numbers of 13th& 14th-generation processors, leading to an extended warranty and a large number of warranty replacements. ● A failure to develop discrete GPUs at the appropriate time. ● A failure to recognise the mobile market. ● Turning down an offer from Apple to make chips for the iPhone, along with no longer supplying Intel CPUs for Apple computers. ● The acquisition of McAfee, which had little to do with Intel’s core business. ● Intel declined to invest in Open­AI in 2017. ● Losing its dominant position in the CPU market to AMD after spending many years making minimal gains. Intel processor model differentiation Intel produces or recently produced the Core, Xeon, Pentium, Celeron and “Intel Processor” models of microprocessors. They are differentiated as follows: Core: Intel’s main CPU product line Xeon: The enterprise and workstation product line Pentium: Once the mainline product, later becoming the entry-level processor line. Retired in 2023. Celeron: The even more entry-level processor line. Retired in 2023. Intel Processor: the replacement for the Pentium and Celeron models. ▪ ▪ ▪ ▪ ▪ From left-to-right: the original Pentium logo from 1993, the Celeron logo used during 2008, and the current Xeon and Core logos. ● Failure to take the lead in providing hardware for AI. ● In 1972, they purchased the Microma watch company to produce complete digital watches, but struggled in the market and sold the company in 1977. ● Intel purchased Basic Science in 2014 to enter the fitness tracker market, but the product was discontinued after Intel acquired it. Intel also had a series of CEOs that stifled innovation and even got involved in social politics and moved the focus away from its core mission of being a chip company. There were also inappropriate share sales by a CEO before bad news was announced Fig.69: Intel’s Gaudi3 chip costs about US$16,000, has 128GB of HBM (highbandwidth memory), and is meant for AI applications. Source: https:// newsroom.intel.com/artificial-intelligence/next-generation-ai-solutions-xeon-6gaudi-3 30 Silicon Chip Australia's electronics magazine regarding the discovery of a chip security vulnerability. Conclusion In this series, we have covered the founding of Intel and how it “accidentally” became a microprocessor company after being asked to produce a calculator chipset. We examined Intel’s early focus on memory chips, its loss of the DRAM market to Japanese competitors, and its subsequent shift to becoming an almost exclusively microprocessor-focused company. We then detailed the 8008’s adoption by hobbyists, the selection of the 8088 for the IBM PC and how that decision fuelled the explosive growth of personal computing. From there, we followed Intel’s development of the 80286, 80386 and 80486, and later the Pentium and Core series, charting how Intel maintained a leadership position for decades. Intel made a big mistake around 2005/2006 when it declined a request from Apple to make iPhone chips and was mind-bogglingly overambitious when it came to the NetBurst design. From the 2010s, Intel further stumbled, failing to develop the 10nm node in a timely manner (again, because of overambition) and failing to recognise many market opportunities, including the mobile market, which allowed competitors to take hold. It is now trying to remake itself with new, better processors, new foundries, new management, job cuts and a commitment to re-establish itself as a SC market leader. siliconchip.com.au Build It Yourself Electronics Centre® It’s a new catalogue Celebration ! Latest release deals & great value savings. HOT SELLER! X 0438 X 4300B T 1345 NEW! 89 $ NEW! SAVE $30 99 $ vacuum accessory valued at $14.95 Ultra High Speed Mini Jet Blower Vac This high power rechargeable fan/vacuum is great for servicing computer equipment, cleaning keyboards even inflating air mattresses for camping. High speed jet fan with up to 1.5 hours use per charge. USB C rechargeable. All metal design. If you use a few cans of air duster a year, it pays for itself in no time! SAVE $20 79 C 9040R SAVE 12% 34 $ $ .95 D 2201 Magnetic Phone Charger Magsafe compatible. Provides 25W wireless charging to keep your phone juiced up on the road. Best paired with a QC3.0 charger. 28 Portable Digital Microscope Camera Completely portable perfect for schools! A compact digital microscope with a 4.3” colour screen, ideal for classrooms, hobbyists, and PCB inspection. Offers adjustable focus, zoom, LED lighting, USB connectivity, photo storage, and portable rechargeable operation. C 9040G NEW! 39.95 $ NEW! $ FREE Handheld LCD Magnifier Camera Completely portable magnifier camera with 3” display with live view. It offers high levels of magnification with LED illumination and auto focus for a crisp, clear view. Record photos or video to internal SD card (sold separately). Recharge via USB C. 119 T1346 $ C 9040B T 2197 C 9040W A 2798A AM/FM Pocket Radio Features easy-to-use digital tuning, a bright LCD display, and a built-in speaker with headphone jack. Requires 2xAAA batteries. FlyBuds ANC Ear Buds Available in 4 colours! These true wireless earbuds offer high performance noise cancelling and up to 9 hours of listening time. Your electronics supplier since 1976. Visit one of our 11 store locations around Australia: WA » PERTH » JOONDALUP » CANNINGTON » MIDLAND » MYAREE » BALCATTA VIC » SPRINGVALE » AIRPORT WEST QLD » VIRGINIA NSW » AUBURN SA » PROSPECT 1000V Screwdriver/Bit Set Includes both a driver handle and rotating ferrule top to convert any driver bit into a screwdriver! Fully insulated 100mm shafts with 1000V IEC 60900 rating. Shop in store or online at altronics.com.au Sale ends April 30th 2026. Gadget Upgrades! NEW! 29.95 $ X 7019* A handy benchtop cleaner! SAVE $20 109 $ X 3265 W/White X 3266 RGB 3 in 1 Camping & String Lights Two Roasts, One App. It’s a lamp, its a torch, it’s 10m of string lights! This compact multiuse gadget is great for camping, or just adding instant atmosphere for parties and more. Monitor your roast or BBQ with ease using this smart Bluetooth meat thermometer—track temps, set targets, and get real-time updates right from your phone. Easy USB recharging. Includes battery. SAVE $10 G-Sensor Wi-Fi Dash Camera 39 $ NEW! 99 $ Capture every moment of your travels with this compact dashcam with 1296P recording. Easy wi-fi recording management. 32Gb SD card to suit DA0365 $41.25 109 $ Blast away grime! X 0103A Great for glasses jewellery and small parts. This 60W ultrasonic cleaner uses water and household detergent, coupled with ultrasonic waves to clean jewellery, small parts, DVDs etc, without damage - no solvents required. 180x80x60mm tank. Freestanding Device Mounts X 0436 S 9431A SAVE $30 10x Mini LED UV Magnifier Ultra compact magnifier loupe for close up inspection. Offers standard and UV modes, plus easy USB C recharging. Handy all metal desktop stands for your phone or tablet. Use as a second screen while you work. D2221 suits devices 4.7”13”. D2220 max device size 10”. D 2221 SAVE 15% 42 $ SAVE 25% 22 $ D 2220 4K video or 20MP still shot ! SAVE $26 99 $ A 1107A M 8070B SAVE $19 50 $ 240V from your vehicle cup holder. Simply plugs into a 12V cigarette lighter socket & provides mains power! 150W rated (300W surge). Boost your o wireless audi range to 80m! X 7014 SAVE $20 NEW! 34.95 79 $ $ Keep an eye on the weather This handy indoor/outdoor weather monitor provides temperature, humidity, clock & calendar in one handy jumbo readout. Includes wireless sensor. SCAN TO FOLLOW US! Stay up to date on latest releases, exclusive specials and news on our socials. Long Range Bluetooth® Audio Transceiver Transmit or receive Bluetooth 5.0 audio across distances up to 80m! Fitted with digital S/PDIF input and output for connection to the latest hi-fi equipment. Uses low latency technology so theres no lip sync issues! Includes 3.5mm, S/PDIF, USB & RCA cables. S 9446E 4K video surveillance anywhere you need it! Great for monitoring in remote locations, temporary CCTV etc. Footage review screen inside. Requires SD card, DA0366 64GB $28.95 & 4xAA batteries. Like our service? Review your store on Google. Every review helps us serve you better. A must have reference for your projects in the year ahead. 2026-27 Catalogue OUT NOW! FREE with any order or download your copy at www.altronics.com.au/catalogue/ 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. Great value power ups! 100Ah SAVE $90 509 $ SL4576BT Recharge anywhere you go! Introducing our new global travel power banks. Available in either 20W or 65W power delivery with in-built mag safe compatible wireless charging they come with travel adaptors (US inbuilt + 3 adaptors) for travel all over the world. All supplied in a handy zip up case. A0319A 20W 10000mAH A0323 65W 15000mAH SAVE $20 SAVE $30 79 $ 120Ah SAVE $90 659 $ With magnetic wireless charging. SL4578BT Get powered up for the open road! Power up your campsite with premium lithium batteries. Bluetooth wireless monitoring in-built. LiFePO4 batteries offer longer service life & weigh HALF as much as SLA batteries. LiFePO4 also provide more usable life per cycle, allowing for longer run times. All have high discharge battery management system on board for safe and reliable use. 5 year warranty. 129 $ N 0704A 10W Powertran® USB-C Charging Stations SAVE 25% 44 $ High-power USB charging designed for education, libraries, corporates and training labs. SAVE 24% 60 $ N 0706A 15W SAVE $200 995 $ SAVE $354 M 8886 16 Bay Station 1885 $ Powertran® Solar Battery Charger/Maintainers M 8887 32 Bay Trolley Featuring Power Delivery 3.0 for fast and efficient device charging, these solutions minimise downtime while keeping devices secure and organised. Each unit includes a full set of USB-C to USB-C cables and offers smart power management and scheduling through the InnovateCharger app. These compact solar panels are designed for keeping your vehicle batteries topped up when parked. Easy croc clip or car accessory plug connection. Can even be permanently installed outdoors. SAVE $20 SAVE 22% 79 19 $ $ S 2752 SW3244 Each 16 bay module outputs a massive 1000W for fast charging all devices at once. M 8883 16 Bay Rack Mount SAVE $100 499 $ Anderson & 4 Way Switch Panel Handy power control plate for cars, caravans and 4WDs. 4 x rocker switches, dual USB charger, cig socket and dual 50A Anderson style sockets. Size: 150 x 120 x 100mm. Sealed In-line Switch Box IP65 weatherproof rated DPST rocker. 16A <at> 250V AC rated. Sale Ends April 30th 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 B 0004 © Altronics 2026. E&OE. Prices stated here in 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. *Devices for illustration pursposes only. PicoSDR Shortwave Receiver by Charles Kosina, VK3BAR My SSB Shortwave Receiver, published in June & July last year, is a classic superheterodyne receiver (siliconchip.au/Series/441). This one is quite different – it uses a Raspberry Pi Pico to implement a software-defined radio (SDR). This is the first standalone SDR published in Silicon Chip. Tuning range: 3-30MHz Minimum tuning step: 10Hz Modulation support: AM, AM-Sync, LSB, USB, FM, CW AGC: adjustable speed & gain Power supply: 7-9V DC from plugpack or internal battery SNR/sensitivity: 10dB for 1μV input over 3-10MHz; 5μV <at> 30MHz Display: OLED with optional external TFT LCD screen T here is nothing wrong with the classic superhet design, but with advances in digital technology, you won’t find too many radio receivers built that way anymore. The various analog circuits have been largely displaced by programs running on high-speed processors. As a result, this receiver is quite a bit simpler and easier to build while being more capable. About three years ago, I bought a couple of Raspberry Pi Pico modules with the intention of doing ‘something’ with them. After some half-hearted siliconchip.com.au Bandwidth: adjustable Audio output: internal speaker or headphones Squelch: optional & adjustable attempts at designing something with them, I put them back in their box. Recently, though, I came across a GitHub project using the Pico as the basis of an SDR (siliconchip.au/link/ ac9m). This was the first of what turned out to be a four-part series written by Jon Dawson. To quote Jon: The receiver covers frequencies up to 30MHz, including commercial broadcasts on Longwave, Medium Wave, Shortwave, and the HF amateur radio bands. What’s great about this design is that it’s completely Australia's electronics magazine Antenna connector: BNC standalone—it doesn’t need a PC or sound card and can run for hours on just three AAA batteries. I decided to design a receiver based on his articles, but with some enhancements. I recommend that you read all the articles as the design is quite complex. The mathematics written to decode all the modes is extremely advanced. Jon does describe everything in the articles, but to fully understand what he’s doing, you need a good knowledge of communications theory at an advanced tertiary level, and C++ April 2026  35 programming. My electronics engineering degree was of some help, but goes back many years and predated many of the current techniques. I will not attempt to reproduce the mathematics in those articles; it makes for interesting reading, but a full understanding is not required to build this Receiver. The starting point of SDR designs is producing the in-phase (I) and quadrature (Q) signals from the input signal. This is achieved by multiplying the signal by local oscillators 90° out of phase. It is important that the amplitudes and phases of the signals are accurate. The traditional way in the past was to use double-balanced diode mixers, like the circuit shown in Fig.2. However, this requires close matching of all components and is an expensive way of doing things. Dan Tayloe published a paper titled “Quadrature Sampling Detector”, where the same multiplication is performed with an analog switch: www. norcalqrp.org/files/Tayloe_mixer_ x3a.pdf The incoming signal is mixed with a two-phase local oscillator, with 90° phase shift between them. We get 36 Silicon Chip four outputs, each containing the sum and difference between the input frequency and the local oscillator, but with phase differences of 0°, 90°, 180° and 270°. We are only interested in the difference frequency; a simple RC lowpass filter eliminates the sum. If the local oscillator and input frequencies are the same, we recover the two baseband signals with different phase shifts. Following the quadrature detector, we have two low-noise, highgain op amps that give us the amplified I and Q signals, 90° out of phase. As it is described below, the local oscillator signal does not have to be at the same frequency as the incoming signal; instead, it is offset to give an intermediate frequency (IF) output. Now that we have the I and Q signals, digital processing takes over. They are sampled with analog-to-­ digital converters (ADC) at a very high sampling rate. The Nyquist criterion means the sampling rate needs to be at least double the required bandwidth. Two-phase local oscillator In many designs, the two-phase local oscillator is generated using the Silicon Labs Si5351A clock-­generator chip. This is extremely cheap and Australia's electronics magazine is ubiquitous in lots of commercial radios, signal generators and spectrum analysers. But the RP2040 chip on the Pico module is extremely powerful and fast, so it is possible to use it to generate the quadrature signals. It has a somewhat novel feature: a programmable state machine that can offload IO functions from the software and generate the quadrature outputs on two I/O pins (I write “somewhat” because some newer PICs have similar hardware). Once this is configured, it runs autonomously without software intervention. But it isn’t quite that simple. Because this is a digital oscillator that’s timed using the chip’s global phase-locked loop (PLL), the output resolution is not nearly enough, and as the frequency increases, so does the step size. The step size is as large as 8kHz. To achieve a step size of 1Hz, the software implements a second, very high-resolution numerically controlled oscillator (NCO) that shifts our IF to baseband. The IF is typically 4.5kHz, but it is varied slightly in conjunction with the NCO and gives a theoretical resolution of 0.0001Hz, far more than required for a 1Hz step size. siliconchip.com.au Fig.1: the RF board for this radio bears some similarity to the SSB Shortwave Receiver published last year, but it’s considerably simpler since most of the processing after the tuning and RF gain stage is performed digitally. IC2 is a digitally controlled analog multiplexer chip that, under the Pico’s control, mixes the RF signal with a local oscillator and produces the I/Q signals to feed back to the Pico for audio extraction. If this sounds complicated, that’s because it is, and requires very clever coding to generate our local oscillator. Processing the I and Q signals Processing of the signals to decode amplitude modulation (AM), frequency modulation (FM) and single sideband (SSB) is beyond the scope of this article. If you’re interested in how it works, I recommend you read the articles written by Jon Dawson at the link above. Choosing a Pico module The Pico 2 module using the RP2350A processor is considerably more powerful than the original Pico module that uses the RP2040 chip. The RP2350A also fixed a bug in the analog-­ to-digital converter (ADC) module within the chip, although the amount of averaging applied and noise present in this circuit means that bug does not currently affect its performance. So both modules can be used in this radio, with no real difference in the user experience. The advantage of using the Pico 2, which costs a couple of dollars more, is future-proofing it. While the Pico can handle the processing load at the moment, features may siliconchip.com.au be added in the future that require the Pico 2 to work, or at least to work well. So, we suggest you spend the extra couple of dollars and get the Pico 2 module, but there will be no immediate benefit. You need to load the right firmware – there are separate files for the Pico and Pico 2. For more details on this subject, see siliconchip.au/link/ac9n We recommend that you purchase a genuine, original Pico or Pico 2. There are clones in existence, and they work, but our testing shows that they are not directly compatible and will not work in this project without significant modifications to the board. So stick with the original. RF board circuit Like my SSB Receiver design, this receiver uses two circuit boards, a control board and an RF board. The circuit of the RF board is shown in Fig.1. The left-hand side is very similar to the July/August 2025 SSB Shortwave Receiver front-end (siliconchip.au/ Series/441), but it has some improvements incorporated. Two schottky diodes on the antenna input limit the input voltage to a safe level. Australia's electronics magazine Fig.2: an old-fashioned doublebalanced mixer uses two transformers and four diodes as shown here to mix the local oscillator (LO) and tuned antenna (RF) signals. The signal at the IF OUT terminal includes several new signals, one of which is the desired intermediate frequency (IF) signal. To control the tuning, there are three digital lines from the Pico: BAND0, BAND1 and BAND2. They go to a three-to-eight decoder IC (IC1) that selects filters on the antenna input. They could be fixed bandpass filters, but that would require numerous components. I opted for a similar technique to my SSB receiver and used two high-Q toroidal inductors. The 74HC238 chip selects different-­ value capacitors to roughly tune the radio to the centre of eight different bands. A BB201 dual varicap diode is then used to make the antenna circuit resonate at the input frequency; only half of it is used. This has a capacitance of 118pF at 0.5V and 27pF at 8V. The minimum capacitance, including stray/parasitic capacitance, is about 35pF. This requires an inductor value of 0.8µH at 30MHz. At 10MHz, we need 7µH. See Table 1 overleaf for the frequencies of the eight different ranges. These are chosen so that they are within range of the varicap tuning and the fixed capacitors across the input inductors. The changeover between the two toroids is 10.2-10.3MHz; you will hear the relay click on this transition. There are no capacitors switched in for Band 8, so there is no setting. Seven NPN transistors are used to select the capacitors (not eight, as the highest frequency uses just the varicap). These are BFR92P devices chosen for their very low collector-to-base and emitter capacitances. The relay is switched by the BAND2 signal, buffered by two N-Channel Mosfets, April 2026  37 The top and bottom of the Control Board for the PicoSDR Receiver. Q8 and Q9. A diode across the relay absorbs the switch-off transient. The BF998 dual-gate Mosfet (Q10) gives about 20dB of RF gain and also improves the noise figure. The gain is varied by a front-panel potentiometer that adjusts the gate 2 voltage, avoiding overload on strong signals. A wide-bandwidth Coilcraft transformer (T3) is used in the drain circuit. This has a 4:1 turns ratio, which gives a 16:1 impedance ratio. One problem with receiver design is the rejection of strong signals at other frequencies that may overload the front end. There is no easy solution to this, and various filters are used to reduce such interference. The Tayloe mixer uses half of a 74CBTLV3253 dual 4-way analog multiplexer chip. The input is DC-biased half the supply voltage of 3.3V, which gives midpoint bias to the following op amps. The requirements for the op amps are low noise, wide bandwidth and rail-to-rail operation with a 3.3V supply. The combination of this multiplexer (mux), the two op amps and the way the mux is controlled via the LOI and LOQ digital lines results in the extraction of the I/Q signals (RXI & RXQ) from the tuned RF signal. These are fed to the control board via CON2 for processing. Table 1 – tuning bands Toroid Band Centre frequency Low 1 3625kHz Low 2 4375kHz Low 3 5625kHz Low 4 10250kHz High 5 10625kHz High 6 11250kHz High 7 14500kHz 38 Silicon Chip The MCP6022 op amp is recommended for IC3, having a gain-bandwidth (GBW) of 10MHz and 8.7nV/√Hz of noise while running from 2.5-5.5V. With the resistor values used, the voltage gain is 683 times (57dB), giving a -3dB bandwidth of 14.6kHz (10MHz ÷ 683). A two-pole low-pass filter is provided using 56nF capacitors on the output of the ‘3253 and 220pF capacitors across the 56kW resistors. Control board circuit The control board sits behind the front panel. Its circuit is shown in Fig.3; it is based around a Raspberry Pi Pico or Pico 2 module (MOD1). There is not much connected to the Pico. A standard rotary shaft encoder is used for tuning and selecting items in the menu, with two extra pushbutton switches for display options and choosing menu items. The OLED screen is a standard SSD1306 module, with a resolution of 128×64 pixels. The Pico handles RF signal demodulation and produces an audio output generated by filtering a pulse-width modulated (PWM) signal from digital output pin GP16. The 100W/470nF low-pass filter removes most of the high-frequency switching components of the signal, and potentiometer VR1 provides volume control. The menu system does include a digital volume control, but this requires several pushbutton presses and encoder rotations, which is not very convenient. The original design fed headphones and could, in a pinch, drive a small speaker. In the final version, I have included an LM386 audio amplifier. The external 8W loudspeaker is connected via a headphone jack, so it is automatically disconnected when the ‘phones are plugged in. A resistor in series with the headphone connection Australia's electronics magazine limits the power to a safe level. The two-phase local oscillator required by the RF board is produced at the GP0 and GP1 pins of the Pico. The I & Q signals coming back from the RF board go to the GP26 and GP27 pins via anti-aliasing low-pass filters made of 5.6kW resistors and 2.2nF capacitors. It is from these signals that the modulated audio is recovered by software in MOD1. There are three connectors on the control board; CON4 & CON6 connect to the RF board, while CON8 goes to an external socket for an optional TFT LCD screen. A 16-pin connector is used for an IDC cable to the RF board, siliconchip.com.au On the left side of the RF board are the antenna tuning components: two transformers, the relay and a series of tuning capacitors. The mux is in the centre and dual op amp on the right. plus a 4-pin connector for selecting the input tuning and a 6-pin connector for the optional LCD screen. Power comes from a 9V DC source to CON9, which can be a plugpack. At least 8V is required to give sufficient range for the varicap fine-tuning. While a plugpack can be used, the best performance is with a battery supply, so that is what I’ve shown. Two lithium-ion rechargeable cells connected in series provide up to 8.4V when fully charged. A two-cell AA holder is adequate, but I opted for a three-AA battery holder and added a 1.2V NiMH rechargeable cell, which has a capacity of 1500mAh and results in a total supply voltage of up to 9.6V. 14500 (AA-size) Li-ion cells have a capacity of about 1200mAh, and with a total current drain of 100mA, will last up to 12 hours. Make sure to buy good-quality cells as cheap Li-ion cells carry a fire risk (see Mailbag, January 2026). The Pico requires a supply voltage of about 5V, so an LM1117 low-­dropout regulator is used. The Pico module has an on-chip 3.3V supply, available on one of its pins, which is used by the RF board. The 3.3V supply could also be used to power the OLED screen, but it is an I2C device and there is switching noise when it is being accessed. Coupling of this noise into the main supply is reduced by running it off the 5V supply instead, through a diode and using a 100µF filter capacitor. The series diode is not strictly necessary, but is included as a precaution and helps to isolate its supply from the other components. Construction Start by assembling the control board, which is coded CSE251101 and measures 96.5 × 53.5mm. Begin by soldering all the SMD components – refer to the overlay diagram, Fig.4. There are no fine-pitch devices on the board, and only one SOIC-8 chip, the LM386. Next, solder the connectors on the back of the board, including the two 20-pin socket strips for the Pico module. This module is plugged in rather than soldered; otherwise, replacing a faulty Pico module would be very difficult. Make sure that the 16-pin box header has its notch orientated correctly. There is provision for an Si5351A module socket on the back of the board. This was added as it is supported by the firmware as an option. You may experiment with it if you Fig.3: the control board is built around MOD1, a Raspberry Pi Pico or Pico 2. It produces the local oscillator signal, performs audio demodulation, controls the tuning circuitry, updates the screen(s) and feeds the audio signal to amplifier chip IC4. The user controls are volume (VR1), RF gain (VR2), fine tuning (VR3) plus the rotary encoder and three pushbuttons to drive the menu system. siliconchip.com.au Australia's electronics magazine April 2026  39 Fig.4: the control board has the Pico and connectors on the back (plus the electrolytic capacitor) and the user controls and other parts on the front. The Pico is plugged into a pair of header strips so it can be removed if necessary. When finished, D1 and the 100μF capacitor are hidden under the OLED screen. wish, but it is not required. The male header should be installed with the pins pointing up from the top side. If you are not using that module, you don’t need to fit JP1 or JP2. The front side of the board has the on/off toggle switch, three potentiometers, the rotary shaft encoder, two pushbutton switches and the socket for the OLED screen. To ensure that the components are aligned correctly, slip the front panel over the controls before soldering. Don’t forget the two components that will be hidden under the OLED screen (D1 & the 100μF ceramic capacitor). Once all the components are mounted on the front, flip the board over and add the five connectors on the back (CON4CON6, CON8 & CON9), orientated as shown, plus the two 20-way header sockets for the Pico module. Finally, add the electrolytic capacitor, with its longer + lead towards the closest edge of the board. Once the board has been cleaned, inspect it for any short circuits or dry joints. Use an ohmmeter (eg, a DMM) to check that the 5V and 3.3V lines are not shorted to ground. Before plugging in the Pico module, connect the power supply and measure the voltage on the output of the voltage regulator (REG1) to ensure that it is close to +5V. 40 Silicon Chip At this stage, it is worthwhile programming the Pico and checking the operation of the program. Programming is very simple – use a USB cable to connect to a PC. Hold the BOOTSEL button down when plugging the cable in. It will then appear as a removable disk drive. For the original Pico, the file to be programmed is “picorx.uf2”, or for the Pico 2, it is “pico2rx.uf2” (you can download both from siliconchip.au/ Shop/6/3579). Just transfer this file to the Pico’s “drive” and it will be written to its flash memory. Do not press the button again. Unplug the Pico module from your computer and connect it to the control board, with the USB connector at the top. Connect your power supply or battery and switch it on. You should immediately see a PicoRX splash screen followed by a picture on the OLED, which is a schematic of a crystal set! This stays up for a couple of seconds. This is followed by a complex menu system, to be described later. RF board construction The RF board is coded CSE251102 and measures 82.5 × 53mm; its overlay diagram is shown in Fig.5. All the components on this board mount on the same side. There are three integrated Australia's electronics magazine circuits, which you should solder first. All three must be orientated with the pin 1 locator placed as shown in the diagram. The 16-pin 74CBTLV3253 comes in a fine-pitch package and needs great care. Position it very carefully so that it is accurately on all the pads, then apply a small blob of solder on opposite corners. Run some flux paste on both sides and, using a fine-tip soldering iron, move it slowly across the pins. Editor’s note: I prefer a medium conical or chisel tip for better heat transfer; when using good flux paste, you don’t need a very fine tip. You may end up with shorted (bridged) pins, in which case the excess solder can be removed with some copper braid. It may take a couple of attempts with extra flux to get clean joints with no shorts between them. Note that the 74HC238 is mounted in the opposite orientation to the other chips. This was done to make the layout easier. Make sure orientation is correct; the circuit will definitely not work if any IC is reversed. While fixing them after soldering is possible, it is a real pain, especially if you don’t have a hot air rework station! All the transistors except the BF998 have SOT-23 footprints (the BF998 is in a similar package but with an extra, wider pin, which must be placed as shown). This also applies to the BB201 dual varicap diode, so ensure you don’t confuse it for a transistor. The wideband Coilcraft RF transformer (T3) is also fitted ‘upside down’, in the same orientation as the 74HC328. The remaining resistors and capacitors can be fitted now. They are all in M2012/0805 SMD packages (2.0 × 1.2mm) and are not polarised. The resistors will be marked with codes indicating their values, but the capacitors won’t, so solder them in place as soon as you remove them from their packaging to avoid confusion. Winding toroidal transformers can be tedious, but take your time and keep them neat and wound in the correct direction so they correspond to the termination pads on the PCB. The low-band toroid (T1) requires 37 turns of 0.3mm diameter enamelled copper wire, closely spaced (connected between points C & D on the PCB). This leaves enough room for the siliconchip.com.au four-turn primary winding, also using 0.3mm diameter wire, connected between points A & B. The high-band toroid (T2) uses 13 turns of 0.6mm diameter wire, which should be spread out around the toroid to connect between points G & H, again leaving room for the two-turn primary (also using 0.6mm diameter wire), connected between points E & F. There are only a few through-hole components remaining to be mounted: the relay (RLY1) and connectors CON1-CON3. Make sure the notch on the 16-pin box header is aligned as shown in Fig.5. Fig.5: the RF board is considerably smaller and easier to build than the one for the SSB Shortwave Receiver thanks to the digital processing. The only tricky part to solder if IC2, as it is a finepitch IC, but it isn’t too difficult if you have decent light, good flux paste and a magnifier. Preparing the cables The main connection between the control and RF boards is a 16-wire flat ribbon cable with 16-way IDC connectors at either end. Cut a piece about 80mm long and use a vice or IDC crimping tool to clamp the cable on the connectors. Make sure the cable is exactly square onto the connector and that the pin 1 notches are facing the same way at each end before clamping them. The other cable required is 120mm long with four wires. Crimp pins on each end for the four-way polarised connectors and push them into the blocks, ensuring that the wire order is the same at each end. You could strip out a length of 4-wire ribbon cable to make this, or use individual wires twisted together or held within tubing for neatness. If you want to use the optional external TFT LCD screen, this requires a 6-way shielded cable. The ground wire and shield wire should be crimped onto the same pin. A round 6-pin connector on the back panel is used to connect this screen, as per Fig.6. The shield is needed to reduce RF radiation that would induce noise into the RF board. Keep this cable away from the RF section. Even with the best arrangement, there will still be a pulsating noise at low signal levels. The external screen can be switched off in the HW Config → TFT Settings menu to remove this source of noise. Two-way connectors are used for the input DC power and speaker connections. As there is no room for the headphone socket on the front panel, it is on the back panel. Wire it in such a way that the speaker is disconnected with headphones plugged in (if in siliconchip.com.au The wiring is straightforward, as shown here. Ensure pin 1 on both connections between the boards are the same at each end. doubt, refer to Fig.3). A 100W ¼W resistor mounted on the headphone socket (also shown in that diagram) limits the headphone power to avoid hearing damage. Case assembly Attach the 50mm speaker to the front panel using four 10mm-long M3 machine screws, washers and nuts. The control board is attached to the front panel by M2.5 × 16mm threaded spacers and M2.5 × 6mm screws. I used black screws on the front panel for the best appearance. The RF board should be mounted on the bottom plate to line up the 16-pin headers. Use the board as a template for the holes in the base. The RF board is attached by four M2.5 × 10mm threaded spacers and eight M2.5 × 6mm screws. Next, mount the connectors on the back panel. The antenna connector is a 15cm-long coax cable with an SMA plug on one end and a panel-­mounting BNC socket on the other. This is a Australia's electronics magazine ready-made item available from AliExpress (see the parts list). If an external DC supply is used, include a suitable connector (eg, a chassis-mounting barrel type). As mentioned above, the headphone jack socket is also on the back panel. See the photos for a suggested layout. The two pushbuttons pass through 3mm holes on the front panel. If you have access to a 3D printer, their appearance and ease of use can be improved by making caps to fit over the buttons. The caps are a push-fit on the switch. This will require drilling out Fig.6: if using the optional larger external LCD screen, wire it up to the circular plug like this. April 2026  41 Parts List – PicoSDR Reciever 1 assembled control board (see below) 1 assembled RF board (see below) 1 black front panel PCB coded CSE251103, 159 x 64.5mm 1 170 × 75 × 130mm vented metal enclosure [AliExpress 1005007496723103] 1 50mm 4W or 8W 10W loudspeaker [AliExpress 1005006957225238] 1 100mm length of 16-way flat ribbon cable 2 16-way IDC line sockets [Jaycar PS0985] 1 3.5mm jack socket, 5-pin type (CON7) [AliExpress 1005006501723152] 1 6-pin circular connector with matching plug (optional; for external TFT LCD screen) [AliExpress 1005004645761532] 1 150mm-long SMA male to panel-mount BNC female coaxial cable [AliExpress 1005001385620859] 1 2-cell or 3-cell AA battery holder with flying leads (see text) 2 AA-size (14500) Li-ion rechargeable cells 1 AA-size (14500) NiMH rechargeable cell (optional; see text) 4 M3 × 16mm black panhead machine screws 4 M3 flat washers 4 M3 hex nuts 16 M2.5 × 6mm black panhead or countersunk head machine screws 4 M2.5 × 16mm tapped spacers 4 M2.5 × 10mm tapped spacers Control Board 1 double-sided PCB coded CSE251101, 96.5 × 53.5mm 1 Raspberry Pi Pico or Pico 2 module (MOD1) 1 128×64-pixel 0.96in 4-pin OLED screen with SSD1306 controller (OLED1) [Silicon Chip SC6176] 1 3.5in LCD module with ILI9488 controller (optional) [Silicon Chip SC5062] 1 SPDT solder tag toggle switch (S1) 2 PCB-mounting 4-pin tactile pushbuttons with 15mm-long actuators (18mm total height) (S2, S3) [AliExpress 1005001629305461] 1 rotary encoder with integrated pushbutton and 20mm-long D-shaped shaft (RE1) [AliExpress 1005006690469571] 1 10kW 9mm logarithmic taper vertical potentiometer with 20mm-long D-shaped shaft (VR1) [AliExpress 1005008648801832] 2 10kW 9mm linear taper vertical potentiometers with 20mmlong D-shaped shafts (VR2-VR3) [AliExpress 1005006029199652] 1 medium/large knob to suit RE1 3 small knobs to suit VR1-VR3 [AliExpress 1005006637211404] 1 4-pin vertical polarised header (CON4) 2 2-pin vertical polarised headers (CON5, CON9) 1 2×8-pin keyed box header (CON6) 1 6-pin vertical polarised header (CON8) 2 20-pin header strips (for mounting MOD1) 2 20-pin female headers (for mounting MOD1) 1 4-pin female header (for mounting OLED1) 2 11mm-long untapped (or tapped) spacers, 2.5mm inner diameter (for mounting OLED1) 2 M2 × 16mm panhead machine screws (for mounting OLED1) 2 M2 hex nuts (for mounting OLED1) 42 Silicon Chip Semiconductors 1 LM386M audio amplifier IC, SOIC-8 (IC4) 1 LM1117(I)MP(X)-5.0 5V LDO linear regulator, SOT-223 (REG1) 1 LL4148 100V 200mA signal diode, SOD-80 (D1) Capacitors (all SMD M2012/0805 size 50V X7R unless noted) 1 470μF 16V electrolytic 1 100μF M3216/1206 size 10V X7R 6 10μF 16V 1 470nF 1 100nF 1 47nF 2 2.2nF Resistors (all SMD M2012/0805 1% unless noted) 1 6.8kW 1 220W 1 100W ¼W axial resistor 2 5.6kW 1 100W 1 47W 1 680W RF Board 1 double-sided PCB coded CSE251102, 82.5 × 53mm 1 vertical PCB-mounting female SMA connector (CON1) 1 2×8-pin keyed box header (CON2) 1 4-pin vertical polarised header (CON3) 1 HFD4-5 DPDT 5V DC coil telecom relay (RLY1) 2 Micrometals T50-6 Carbonyl toroidal cores, 12.8 × 7.5 × 4.95mm (T1, T2) [www.minikits.com.au/T50-6] 1 200mm length of 0.3mm diameter enamelled copper wire (T1) 1 50mm length of 0.6mm diameter enamelled copper wire (T2) 1 Coilcraft PWB-16-ALC 80MHz 1:16 SMD signal transformer (T3) [Mouser 994-PWB-16-ALC] Semiconductors 1 74HC238D/74HC238M 3-to-8 decoder IC, narrow SOIC-16 (IC1) 1 74CBTLV3253PW dual 4-way analog multiplexer, TSSOP-16 (IC2) 1 MCP6022(T)-I/SN or MCP6022(T)-E/SN dual 2.7V low-noise 10MHz op amp, SOIC-8 (IC3) 7 BFR92P low-noise 15V 5GHz NPN transistors, SOT-23 (Q1-Q7) 2 2N7002 60V 115mA N-channel logic-level Mosfets, SOT-23 (Q8, Q9) 1 BF998 12V 1GHz dual-gate Mosfet, SOT-143 (Q10) 1 BB201 dual varicap diode, SOT-23 (VD1) 1 LL4148 100V 200mA signal diode, SOD-80 (D2) 2 1N5711 70V 15mA axial schottky diodes (D3, D4) Capacitors (all SMD M2012/0805 size 50V X7R unless noted) 2 10μF 16V 9 100nF 4 56nF 1 1nF 1 330pF NP0/C0G 3 220pF NP0/C0G 2 180pF NP0/C0G 1 100pF NP0/C0G 1 68pF NP0/C0G 1 4.7pF NP0/C0G Resistors (all SMD M2012/0805 1%) 1 470kW 8 12kW 1 220W 1 100kW 2 10kW 4 82W 2 56kW 1 1kW Australia's electronics magazine siliconchip.com.au the front panel holes to 5mm. The file for this is “button_caps_V02_CK.stl”. Thanks to Andrew Woodfield for the design of these caps. Initial setup The menu system is quite overwhelming, and it reminds me somewhat of menus in digital cameras. It has a branching tree system to adjust many different parameters and settings. The menu items are chosen using the two pushbutton switches, plus the rotary encoder with its integrated pushbutton switch. As with digital cameras, some of the settings are of little importance and are best left alone. But there are some initial setup parameters that are important. The first of these is Encoder Direction. Press the ▲ button and the display will show Menu on the top line and Frequency on the second line. Rotate the encoder knob one click right or left and, depending on the shaft encoder direction, it will show HW Config. If HW Config comes up with a clockwise rotation, you need to change the direction of the tuning knob. With HW Config on the second line, Press the ▲ button and the display will show HW Config on the top line and Tuning Options below. Rotate the encoder knob to navigate to Reverse Encoder. Press the ▲ button and the display will show Reverse on the top line and Encoder on the second line. Rotate the encoder knob to select On. Finally, press the ▲ button and the display will go back to Menu on the top line and Frequency on the second line. Press the ▲ button to return to the opening screen, then press the ▼ button several times to select Viewing Option. There are about 25 different parameters that can be set by first pressing the ▲ button and then rotating the knob to select different options. One of them is Volume, which can be adjusted from 0 to 9. This is why I have added the volume control on the front panel, to avoid going through several steps to get to such a basic control. The following are some of the more important parameters: • Mode: AM, AM-Sync, LSB, USB, FM, CW • AGC: Manual, Fast, Normal, Slow, Very Slow • AGC Gain: with maximum gain, the background noise is high. Changing this to 30dB reduces it significantly, siliconchip.com.au An external display can be added to the PicoSDR if you need a bigger screen with more information. without affecting the sensitivity. • Squelch: this silences the receiver until a signal is strong enough. I found that S5 will completely silence it, but a 1μV signal will open up the receiver on most frequencies. Experiment with this setting to find the optimum value. • Bandwidth: Normal, Wide, Very Wide, Very Narrow, Narrow • Freq Step: 10Hz, 50Hz, 100Hz, 500Hz, 1kHz, 5kHz, 6.25kHz, 9kHz, 10kHz, 12.5kHz, 25kHz, 50kHz or 100kHz. In the HW Config menu, there are 22 different hardware parameters that can be adjusted! Many of them can be safely ignored. I won’t go through all the possible menu settings; you can look through them if you want to. The ▼ button selects what appears on the OLED. The photos show some of the possible displays. Australia's electronics magazine As with all receivers, there are some spurious signals and ‘birdies’ due to harmonic mixing. If they happen to be on a frequency that you are tuned to, there is a simple way of removing them. Navigate to IF Frequency and change it from the nominal 4.5kHz slightly. The received frequency is identical, but the birdie has moved. Conclusion This receiver is an example of what can be done with a software approach to design. Jon Dawson has done an incredible job in writing the highly complex code to make it possible. It could not be classed as a first-class ‘communications receiver’, but it does have creditable performance. There are regular updates to the software on his site, so it’s worthwhile SC looking at it from time to time. April 2026  43 By Andrew Levido Power Electronics Part 6: DC-to-AC Converters Having covered DC-DC and AC-DC converters in earlier articles in this series, we will now move on to DC-AC converters. They have been around for a long time, but their usage has become widespread over the last couple of decades. T here was a time when the applications for DC-to-AC converters were limited to industrial motor drives and commercial UPS systems. However, the widespread adoption of domestic solar power systems and electric/ hybrid vehicles means that DC-AC converters have become extremely common. As has become the custom for this series, we will start by analysing the simplest possible converter and build from there. Fig.1 shows four switches arranged in a H-bridge, fed from a DC voltage source. If we close S1 and S4 for a period equal to a half-cycle of the desired output frequency and S2 and S3 for the other half cycle, we can synthesise a square wave with amplitude Vsrc and frequency ω, shown in red. Recall that ω (omega) is just a frequency expressed in radians per second; 2π radians is one cycle, so 2π radians per second is the same as 1Hz. There are a couple of important things to note about this circuit. First, energy passes from the DC side to the AC side, so this is an inverter; in a rectifier, it goes the other way. Secondly, the switches create an AC voltage source at the output terminals, so this is a voltage-source inverter. The need for these seemingly obvious observations will become apparent soon. The RMS value of the output voltage is just Vsrc, so the only way to change vload, or the power delivered to the load, is to adjust Vsrc. We can change this by introducing a third switching state into the cycle, one where all switches are off and the output is zero, as shown in the blue trace. Here, the switches are off for a phase angle of δ (delta) at the beginning and end of each half-cycle. We can now use δ to adjust the RMS output voltage, and hence the power delivered to the load, according to the expression vload(rms) = Vsrc √1–2δ ÷ π. This kind of inverter is sometimes known as a tri-state inverter because each output terminal can be connected to +Vsrc, –Vsrc or zero (another term you might see referring to similar systems is ‘modified sinewave inverter’). Fig.1: the simplest single-phase voltage-source DC-AC converter uses four switches to create a square wave output. By leaving all switches open for a phase angle of δ at the beginning and end of each half-cycle, we can control the output voltage and power. 44 Silicon Chip Australia's electronics magazine Most of the interesting loads we want to drive are not purely resistive, so we should see what happens if we add an inductor to the load (Fig.2). We will assume that the L/R time constant is large compared to the output frequency so that the AC current can be approximated by its fundamental component. There is a phase shift between the voltage and current of Ø radians, as we would expect with an inductive load. This angle is fixed by the relationship between the load inductance and resistance, so it does not help us to change the power delivered to the load. Things are different if the load includes an AC voltage source, as shown in Fig.3. This scenario is pretty common; for example, in a solar inverter feeding the power grid or an inverter driving a synchronous motor with its sinusoidal back-EMF. This circuit gives us another variable to play with, as we can control the phase angle between vload and vac. With this circuit, you can even dictate the direction of power flow – from source to load (inversion) or load to source (rectification). We effectively have two AC sources: the inverter output vload, and the AC source, vac, with an inductor between them. The inductor acts as a ‘buffer’ between the two, absorbing the instantaneous voltage difference. The greater this difference is, and the longer it has to be sustained, the larger the inductor required. Still, a large inductor reduces the power factor, limiting the real power that can be transferred. The solution is to move the inductor to the DC side of the H-bridge, where it won’t impact the power factor, no matter how large it is. This arrangement (Fig.4) means that the output of the H-bridge is an AC current, so this is now a current-source inverter. The siliconchip.com.au DC voltage source and inductor are equivalent to the current source Isrc. We can’t use the same switching strategy to achieve the ‘zero-state’ output as we did in the voltage-source inverter. If we turned all the switches off, the source current would have nowhere to go and the voltage across the H-bridge would rise uncontrollably. Instead, we achieve the zero state by turning both S1 and S2 or S3 and S4 on at the same time, diverting the current away from the load. I have shown the current-source inverter switching pattern in the figure. This ‘shoot-through’ would be catastrophic in a voltage-sourced inverter, as would a short on the output, because the source would be short-circuited and the resulting current uncontrolled. Current-source inverters are inherently current-limited, making them very robust compared to their voltage-source counterparts, which require additional circuitry to protect against short circuits. I won’t go through the maths, but it is possible to show that the power delivered to the load by this current-­ source converter is given by the equation P = (2vac Isrc ÷ π)cos(δ)cos(Ø). We can control the power flowing to or from the load by changing either δ (the time spent in the zero state) or Ø (the phase angle between the inverter output and vac), or both. These are dictated by switch timing, so they can be nicely varied by a microcontroller-based implementation. Full control of Ø requires true bidirectional switches – switches that can conduct or block in both directions. This is somewhat difficult to implement, since Mosfets and IGBTs both normally have an anti-parallel diode that means they can never block reverse current. In the case of Mosfets, this is the inherent body diode, and in the case of IGBTs, it is usually a separate diode integrated into the package. Typical applications therefore tend to leave Ø at or very near zero and manipulate δ to control power. We have used single-phase DC-AC converters so far, but everything we have covered is equally applicable to three-phase converters. Fig.5 shows that these are just a single-phase converter with an extra pair of switches. Each phase-to-phase voltage is created by manipulating the switches just like siliconchip.com.au Fig.2: with an inductive load, there will be a phase angle difference between the voltage output and load current that is determined by the load inductance and resistance. Fig.3: if there is an AC voltage source associated with the load, such as a photovoltaic inverter feeding the grid, we can control the phase angle between it and the inverter output, allowing us to control the power flow in either direction. Fig.4: if the inductor in Fig.3 is moved to the DC side, it results in a currentsource inverter. The zero-state output occurs when switches S1 and S2 or S3 and S4 are on. Fig.5: a three-phase DC-AC converter is just like its single-phase counterpart with an extra pair of switches. The phase shift between switching is 2π/3 radians (120°) instead of the π radians (180°) in the single-phase case. Australia's electronics magazine April 2026  45 the single-phase example, but shifted by 2π/3 radians (120°) instead of π radians (180°) in the single-­phase case. You could, in theory, build an n-phase converter with n switch pairs (or two pairs for single-phase) with a phase shift of 2π ÷ n between them. However, diminishing returns means we rarely deal with more than three phases in reality. The exception is primarily in aircraft and ship motor drive systems, plus some large-scale mining equipment, where more phases (eg, six or 12) can result in lower torque ripple, a lower current per phase, reduced harmonics and EMI, plus better fault tolerance. Pulse-width modulation The examples we have seen so far have all produced more-or-less squarewave outputs, which we know have a terrible power factor, so are not very efficient at transferring power. Practical DC-AC converters therefore employ some kind of modulation scheme to reduce the level of harmonics in the output, or at least push them up to high frequencies where they are easier to filter. One common method used for small to medium power converters (up to a few hundred kilowatts) is sinusoidal pulse-width modulation. The switch drive is modulated at a carrier frequency (fpwm) much higher than the desired output frequency. The on-time in each modulation period is proportional to the instantaneous amplitude of the desired sinusoidal output waveform, as in Fig.6(a). I have shown only one half-cycle for clarity; the other is identical but reflected in the horizontal axis. In that diagram, the carrier frequency is an integral multiple of the output frequency, but this does not have to be the case if the carrier frequency is high enough – say a couple of hundred times higher than the maximum output frequency. This means the carrier frequency can be fixed, making synthesis a lot simpler. Textbooks generally show the switching signals derived from analog circuits that compare a triangle-shaped carrier wave to a sinusoidal reference, but in reality these days, they will almost certainly be produced by software running in a microcontroller. Pre-computed sine values are typically stored in a lookup table, and each carrier period, the appropriate one is extracted, multiplied by a scaling factor (the modulation depth) to set the amplitude, and loaded into a timer configured as a PWM generator. In the case of three-phase inverters, you have to add some third harmonic to the reference sinusoid or the output amplitude will be limited. For a fuller explanation, see the “Variable Speed Drive for Induction Motors” article we published in the November 2024 issue (siliconchip.au/Series/430). It provides a good overview of how this type of modulation can be implemented in a microcontroller. Current control In the case of current-source converters, such as in photovoltaic systems, it is preferable to control the inverter’s output current rather than its voltage. There are a couple of ways to do this, both shown in Figs.6(c) & (d). Both of these assume there is a current transducer measuring iload. The compensator-based current Fig.6: this figure shows four different modulation schemes for DC-AC converters. (a) & (b) are suitable for voltage-source converters, while (c) & (d) are for current-source converters. 46 Silicon Chip Australia's electronics magazine controller shown in Fig.6(c) uses a PWM modulator identical to the one discussed above, except that the reference input is not a fixed sinusoid. Instead, the PWM modulator is ‘wrapped’ in a current control loop that compares the load current to a sinusoidal reference and drives the modulator via a loop compensator to reduce the current error to zero. This control method has the advantage of a fixed switching frequency, but the current ripple can vary widely. You can also use hysteretic modulation, like in Fig.6(d), analogous to current-mode control in DC-DC converters. The switches are controlled in such a way that the load current always remains within a hysteresis band ±ih around the reference. This control method provides fixed current ripple and built-in current limiting, but it does mean that the switching frequency is variable. This might not be a problem for solar inverters, for example, which operate over a very narrow range of output frequencies. Harmonic elimination Really large (multi-megawatt) or high-voltage DC-AC converters generally don’t use Mosfet or IGBT switches. Instead, they use gate-turnoff (GTO) thyristors, which come with voltage ratings up to 4.5kV and can handle currents up to 4kA or more. Their switching frequency is limited to something less than 1kHz, so pulsewidth modulation is not generally practical. Instead, a technique known as harmonic elimination is used. The ‘tri-state’ waveform shown in blue in Fig.1, like all of the waveforms we have seen, is ‘half-wave symmetric’. This just means that the second halfwave looks like the first reflected in the horizontal axis. This type of waveform only has odd harmonics, so the largest amplitude harmonic after the fundamental is the third. Its amplitude will be vload(3) = (4Vsrc ÷ 3π)cos(3δ). If we set δ to π/6, the amplitude of the third harmonic drops to zero. In fact, all multiple-of-three harmonics (n = 3, 9, 15...) become zero. Furthermore, you can add additional zerostate pairs of specific length at specific angles to eliminate other harmonics and their multiples. With three such sets of zero-state ‘notches’ in the right places, you can eliminate the 3rd, 5th, 7th and 9th siliconchip.com.au Fig.7: space vector modulation maps a set of three-phase sinusoidal waveforms to a single rotating vector in the αβ plane. You can synthesise a threephase voltage set by determining how much time to spend in each state. harmonics with a switching frequency just five times the fundamental. The largest harmonic present in the output will be the 11th. This is shown graphically for one half-cycle in Fig.6(b). We already know that in a balanced three-phase system, the 3rd harmonic and its multiples are already zero, making the 5th harmonic the highest one present in the waveforms shown in Fig.5. In this case, the first harmonic elimination zero-state pair is therefore placed to eliminate the 5th harmonic and its multiples. Three pairs of zero-state notches can eliminate all harmonics below the 13th in three-phase systems. The main downside of harmonic elimination is that by fixing the zerostate angles, you can’t use δ to control the output voltage. Converters in the multi-megawatt range are normally driven from a dedicated transformer and use tap changers to regulate voltage. Space vector modulation The science-fiction sounding space vector modulation (SVM) is a modulation technique used in balanced threephase inverters, especially in motor drives. It takes advantage of the symmetry in these systems to simplify the calculations necessary to synthesise a desired set of sinusoidal waveforms. While it may simplify the modulator, understanding it can be a bit of a mind-bender, so we are going to need some background. It is possible to represent any set of three variables, like three-phase voltages at some instant in time, as a point in 3D space. Each of the variables defines a length along one of the three orthogonal axes. This set of three values is called a vector because it describes a point in 3D space that is some specific direction and distance from the origin. For physical space, we usually label siliconchip.com.au the coordinates x, y and z, but for our three-phase system, we will name the axes a, b and c, representing each phase. Three values (va, vb, vc) define a vector vabc that represents all threephase voltages at any instant in time. We use a bolded v to indicate that this is a vector. In the case of balanced three-phase systems, we have a further constraint. At any moment in time, the sum of the phase voltages must be zero. This severely limits the range of values that the vector describing those variables can take. In fact, vabc must lie on a plane passing through the origin and tilted such that its normal vector (a vector standing perpendicular to the plane) passes through the point (1, 1, 1). Don’t worry if this is hard to picture; we are about to simplify matters. With quantities confined to this plane, it is natural to assign a new pair of orthogonal axes as if ‘looking down’ the normal vector. These axes are traditionally labelled α and β, and the plane is unsurprisingly called the alpha-beta plane. On this plane, we can describe a three-value three-phase vector as a point with coordinates (xα, xβ). The transformation between the two systems is known as a Clarke transform. This is named for its inventor, Edith Clarke, who among her many distinctions was the first female American professor of electrical engineering when she joined the University of Texas in 1947. If we take a set of three-phase sinusoids and map them to the αβ plane, they correspond to a point rotating in a circle around the origin. The speed of rotation is related to the frequency, and the radius is related to the amplitude. We now have all the tools we need to explore space-vector modulation. A three-phase inverter like that shown in Fig.7(a) can produce eight possible switch states, which produce the three-phase voltages shown in the Australia's electronics magazine adjacent table. The phase voltages are referenced to an imaginary ‘Neutral’ point at half of the source voltage and shown in the table normalised to Vsrc. The last two columns in the table show how each of these switch states maps onto the αβ plane using the Clarke transformation. Don’t worry too much about the weird √6 values. What is important is that if you plot these points on the αβ plane, you get the result shown in Fig.7(b). Each non-zero state maps to a vertex of a hexagon, and the two zero states map to the origin. Any point inside the hexagon represents a set of balanced phase voltages that we could synthesise. Fig.7(c) shows how, using an example from the triangle with vertices x1, x2 and x0x7. To synthesise the voltage represented by the red vector, we need to be in each of these three states for an April 2026  47 appropriate proportion of time, so the result ‘averages out’ to the desired voltage set. The length of the blue vector relative to x1 defines the proportion of time we need to spend in state x1, while the length of the green vector relative to x2 defines it for the x2 state. The remaining time is spent in one or the other of the zero-states. In the example, the fraction of x1 is around 0.3 and the fraction in x2 is around 0.4, leaving 0.3 of the time spent in the zero states. If we want to synthesise a set of three-phase sinusoidal voltages, we just rotate the vector around the origin, tracing out the red circle/arc. Over each switching period (Tsw), the red vector advances by some angle proportional to the output frequency. Typical implementations start and end each switching period in a zero-state to minimise output harmonics. There will therefore be three transitions per switching period: zero to state A, state A to state B and state B to zero. Each transition only requires one switch to be changed if you select the right zero-states. The sequence of states is always the same as you rotate around the circle, so it can be programmed in advance. Only the time spent in each state has to be calculated (or looked up in a table) in real-time. This is more efficient code-wise than threephase sinusoidal PWM, although the speed and capability of today’s microprocessors makes this advantage less important than it once was. Like every modulation technique, space vector modulation has plenty of variations and options. It’s a pretty deep rabbit-hole if you want to go exploring. Getting practical I thought it would be interesting to dig into the design of a real DC-AC converter by looking at an aspect of converter design that is often overlooked: calculating the thermal losses in the switching elements. This is far from simple in the case of DC-AC converters with pulse-width modulation and inductive loads, as you will see. I will use the IGBT bridge from the Variable Speed Drive Induction Motors article mentioned earlier as an example. This three-phase converter uses DGTD65T15H2TF 650V 30A IGBTs with integral freewheeling diodes, switching at 15.625kHz. There are two kinds of losses that we have to consider: conduction losses that occur when the IGBT or diode is on, and switching losses that occur in the IGBT as it switches on and off. Conduction losses are the product of the current through, and the voltage across, the IGBT and diode when turned on. The manufacturer provides graphs to show how these quantities are related, reproduced in Fig.8. These characteristics are not linear, and in the case of the IGBT, vary with gate drive voltage. Conduction losses get worse with higher temperature, so I have assumed the maximum 175°C junction temperature to be safe. Superimposed on the charts is a dotted piecewise linear approximation that we will use to calculate conduction losses. We will assume that the IGBTs’ Vce is a combination of a fixed drop, Vto, plus a voltage that increases linearly with current – effectively an on-resistance, Rce. This converter uses a 15V gate drive, so I have set this resistance to match the appropriate curve. In this case, we can read off Vto ≈ 1V and Rce ≈ 90mW. We can do a similar thing with the diode characteristic, giving Vfo ≈ 1.2V and Rak ≈ 40mW. If the current through the IGBT and diode is ic, the instantaneous conduction losses will be Pi(cond) = Vto ic + Rce ic2 and Pd(cond) = Vfo if + Rak if 2. The current is an AC quantity, so we have to find the average power over one cycle. This requires us to integrate these expressions over one cycle and divide by 2π. Since the switching frequency is high and the load is inductive, the inverter current will be sinusoidal, given by the equation i = Ipk cos(θ – Ø), where Ø is the phase angle between voltage and current. This current will flow in the IGBT when the switch is on, and in the diode when the switch is off. The proportion flowing in the IGBT is determined by the duty cycle, which is in turn defined by the phase angle and the modulation depth m, Fig.8: calculating the conduction losses in an inverter bridge is not a simple undertaking. It starts with a piece-wise linear approximation of the forward characteristics and ends with the expressions below the graphs. 48 Silicon Chip Australia's electronics magazine siliconchip.com.au according to the expression D = ½(1 + mcos[θ]). The proportion flowing in the diode is determined by 1 – D. Plugging all this together makes for a pretty nasty integral, but I have shown the results below the graphs in Fig.8. The total conduction loss for one IGBT/diode is the sum of these two equations. The terms involving the modulation depth m and load power factor cos(Ø) are interesting. Both can vary from zero to one, and the effect of reducing either of them is to move losses between the IGBT and the diode, while the total stays roughly constant. This makes intuitive sense because in each case, there is less IGBT on-time and more diode freewheeling time Switching losses are (thankfully) a little easier to calculate. Switching loss depends mainly on capacitance, so the energy expended each transition is related to the square of the voltage. The data sheet provides the switching energies for each transition, helpfully at 175°C, and at 400V, a little above the maximum we can expect, so comfortably conservative. These energies are Eon = 342µJ and Eoff = 288µJ. With sinusoidal PWM, you can show the switching losses will be Pi(sw) = (Eon + Eoff) fsw ÷ π. Using values from the variable speed drive in single-phase mode (Ipk = 10A, PF = 0.95, m = 1, fsw = 15.625kHz) gives conduction losses of 4.8W for the IGBT and 0.6W for the diode, and switching losses of 3.1W, for a total worst-case loss of 8.5W per device. There are four active devices, so the total is 34W. For the three-phase case (Ipk = 6A, PF = 0.85, m = 1, fsw = 15.625kHz), the power dissipation works out to be 5.8W per device and, coincidentally, 34W for the six active devices. That’s close to 98% efficiency for the DC-AC converter part (there are additional losses in the rectifier). You will notice that the IGBT switching losses are approaching the conduction losses in magnitude at a switching frequency of just over 15kHz. In many applications, we want switching frequencies much higher than this, so switching losses can become a huge concern in high-power converters. The next instalment RP2350B Computer A Fully-assembled general-use computer The RP2350B Computer runs BASIC and is excellent for creating your own programs, games, tinkering with external circuits and more. And we are selling it pre-assembled, with little to no soldering required to have it up and running. It supports a keyboard, mouse or even a SNES controller. Video output: DVI via an HDMI connector <at> 640 × 480, 720 × 400, 800 × 600, 848 × 480, 1280 × 720 or 1024 × 768 pixels Removable file storage: microSD Card, FAT16/FAT32, up to 32GiB Clock Speed: 252-375MHz Non-volatile program memory: 184kiB General usage RAM: 220kiB (expandable to over 6MiB) Internal File Storage: 14MiB Audio formats: single-frequency tones, stereo WAV, FLAC, MP3 & MOD USB ports: four Type-A for peripherals, one Type-C for power/console and one micro Type-B for firmware loading Clock: battery-backed real-time clock & calendar External console: serial over USB <at> 115,200 baud via the USB Type-C socket External I/O connector: 30 pins with 22 GPIOs, including 7 with analog input ability, plus ground, 3.3V and 5V outputs Power supply: 5V <at> 220mA RP2350B Computer Assembled Module [ SC7531 | $90.00 + post ] fully-assembled PCB, except for the optional components (instrument case, mounting screws, 3-pin header for serial wire debugging and APS6404L PSRAM IC [SC7530 | $5]) Front & Rear Panels [ SC7532 | $7.50 + postage ] pre-cut panels, white silkscreen and black solder mask; not included with the kit above In part seven, we will take a look at resonant or soft-switching converters, which can minimise or even eliminate SC switching losses. For all the details on how to build it, check out the article in the November 2025 issue of Silicon Chip (siliconchip.au/Article/19220). siliconchip.com.au Australia's electronics magazine April 2026  49 By Tim Blythman Remote Controller DCC Booster Stepper Motor Driver μDCC Decoder Stepper Motor Driver and Decoder Stepper motors are capable of remarkably precise movement but are more difficult to control than a brushed DC motor. This compact board drives stepper motors with ease and can be configured to work with different control inputs, including direct current and Digital Command Control (DCC). Image source: https://unsplash.com/photos/miniature-train-set-with-detailed-landscape-rNOwodoejTc Y ou might have seen that tiny stepper motors are available quite cheaply from online marketplaces like eBay and AliExpress. A typical example is the assembly used to move the laser head on a DVD drive (see the photo below). This one is fitted with a helical shaft for linear control of the head assembly position. I have been curious about whether it would be possible to use such a motor to drive a model locomotive. Tiny DC motors are available, but are known for high speed and low torque, which is not a good match for the wheels on a model locomotive. Compact coreless DC motors are often used in This stepper motor is 15mm in diameter and works well with our Driver. The assembly is similar to the type used in CD/DVD/Blu-ray drives to position the laser head. 50 Silicon Chip quadcopters, where they only operate at high speed. Adding a gearbox can provide appropriate speed and torque, but also adds complexity and uses up valuable space. Many stepper motors can be driven slowly and still provide useful torque directly from their output shaft. Stepper motors require different control circuitry; they typically have two or more windings that are energised in sequence to control the speed and direction of the motor. It’s not possible to apply a DC voltage as can be done for a simple brushed motor. In this context, DC means a relatively steady voltage of either polarity, or perhaps a PWM (pulse-width modulated) voltage. We’ve published articles about stepper motors and the hardware needed to drive them by Jim Rowe in the past. The Quick Primer on Stepper Motors (January 2019; siliconchip.au/ Article/11370) is a good place to start if you aren’t familiar with how stepper motors work. He also wrote about some stepper motor driver modules in Part 22 of the Cheap Modules series (February 2019; siliconchip.au/Article/11405). This type of module makes it easy to control a stepper motor using a microcontroller, but I thought it would be handy to drive a stepper by applying a DC voltage in the same way you might power a brushed motor. I realised that our recent DCC Decoder (December 2025; siliconchip. au/Article/19377) already has most of This tiny board (shown at actual size in the lead image and on the right) can run a small stepper motor as though it were a DC motor. It can also operate in DCC mode (with some parts left off), using a stepper motor to power a model locomotive. Some of the stepper motors and assemblies that we were able to control with the Driver are also shown in the lead; the largest is 15mm in diameter. The smaller two motors are only about 5mm in diameter and ran quite hot, so we recommend using a lower current limit if driving such motors. siliconchip.com.au Features & Specifications 🛤 Four motor connections to suit bipolar stepper motors 🛤 Two additional current-limited opendrain Mosfet outputs 🛤 Adjustable speed response 🛤 Selectable drive current limit 🛤 Can be configured for DC or DCC operation 🛤 Maximum peak input voltage: 17V 🛤 Motor drive current: up to 500mA 🛤 Accessory outputs: up to 100mA 🛤 Module size: 24 × 13 × 4mm the components needed for driving a stepper motor. The firmware that provides the DCC decoding function would just need to be adapted to drive a stepper motor instead of a DC motor. So this Stepper Motor Driver and Decoder (we’ll call it the Driver for short) has two operating modes. It can accept a DC voltage and generate a waveform to drive a stepper motor as if it were a DC motor. In other words, the polarity of the applied voltage determines the direction of rotation, and the magnitude determines the speed. The other mode is to behave as a DCC decoder. Instead of a brushed DC motor, it has outputs that can be used to drive a small stepper motor. Since it has much in common with the earlier Decoder design, we recommend that you read the DCC Decoder article if you have not already done so. The Driver also has two open-drain outputs that can sink current. In DCC mode, these work in the usual fashion as DCC function outputs (for lights or similar accessories). In DC mode, one switches on for one input polarity and the other for the reverse polarity, providing a similar directional lighting function. DCC PROJECT KITS DCC Decoder, December 2025 (SC7524, $25) includes everything in the parts list DCC Base Station, January 2026 (SC7539, $90) includes everything in the parts list, except for the case, power supply, glue and the CON4 & CON5 headers DCC Remote Controller, February 2026 (SC7552, $35) includes all required parts, except for the UB5 case and wire/cable DCC Booster, March 2026 (SC7579, $45) includes all required parts, except for the Jiffy box, OLED screen, power supply and front panel. The OLED screen (SC7484, $7.50) and front panel (SC7578, $5.00) are available separately. DCC Stepper Motor Driver & Decoder, April 2026 (SC7601, $30) includes all required parts for DC or DCC mode. A with a positive voltage, then coil B with a positive voltage. The next phase is to drive coil A with a negative voltage, followed by coil B with a negative voltage. The cycle then repeats. These four phases correspond to the four steps of the stepper motor’s rotation. To drive the motor in reverse, the sequence is reversed. Note that reversing the polarity of one coil will have the same effect as reversing the sequence. Most stepper motor drivers employ micro-stepping, which effectively interpolates the output between each phase to create more, smaller steps. Our Driver implements 256 microsteps, where the four phases noted above correspond to microsteps 0, 64, 128 and 192. We use PWM (pulsewidth modulation) to interpolate between the steps. Scope 1 (with filtering applied for clarity) shows the voltage at the four stepper motor connections as the Driver progresses through its cycle. A+ 6V B+ A− For example, microstep 32 (between microstep 0 and microstep 64) drives both coils A & B with a 50% duty cycle in the positive direction. Internally, the microcontroller has a counter that dictates the current microstep. Having 256 microsteps means it is simple to loop around when the counter overflows; we can just ignore all but the lowest eight bits of the counter. The counter is incremented every 200μs (at 5kHz) and the increment determines the rate at which the cycle advances and thus how fast the motor turns. Applying a negative increment reverses the cycle and thus the direction of the motor. It isn’t expected that the motor will be precisely positioned to within 1/64th of a step, but the choice of that many divisions allows the speed to be set with a reasonable resolution while keeping the arithmetic simple for the 8-bit processor. B− A+ 4V Driving a stepper motor The distinguishing feature of the Stepper Motor Driver and Decoder is that it can drive a stepper motor, so let’s look at how that works in the firmware. The two H-bridge outputs are intended to connect to the two coils of the stepper motor, which are often denoted as A and B. The outputs are driven in a specific sequence to rotate the motor’s shaft. A typical waveform might drive coil siliconchip.com.au 2V 0V Microstep 0 Microstep 64 Microstep 128 Microstep 192 -2V 0.0ms 20.0ms 40.0ms 60.0ms 80.0ms Scope 1: this shows a typical waveform for driving a stepper motor from the unit. The shape of the waveforms means that the power draw is quite steady, regardless of the current motor drive phase. Australia's electronics magazine April 2026  51 The PWM is applied in a complementary fashion, so that at any instant, exactly one output is being driven, which keeps the load relatively constant. This also ensures that the current limit is applied uniformly at all times. Circuit details Fig.1 shows the circuit diagram for the Stepper Motor Driver and Decoder; it has a striking similarity to the DCC Decoder noted earlier. The main difference is that this circuit boasts two motor driver ICs to provide the fourwire connection needed by bipolar stepper motors. Since it is so similar to the Decoder, we’ll focus mainly on the differences. The incoming power supply connects to bridge rectifier BR1, which provides a voltage that we’ve labelled as a nominal 12V. In practice, the incoming supply can vary from 0V up to around 17V. The 17V limit is set by REG1’s maximum input voltage of 16V (allowing for a 1V drop across the bridge). REG1 provides a 3.3V rail – both rails have 10μF bypass capacitors. IC1 is a 14-pin, 8-bit PIC16F18124 (or -5 or -6) microcontroller that is powered from 3.3V, while IC2 and IC3 are DRV8231 motor driver ICs that are powered from the 12V rail. Their four outputs (available as motor connections A and B) require four control signals from the microcontroller. The keep-alive circuitry comprises diode D1, a 100W resistor and an optional capacitor. IC1 has a 100nF bypass capacitor and a 10kW resistor on its MCLR pin. This is exactly the same as the corresponding circuitry on the DCC Decoder. Similarly, the ICSP connections to pins 1, 4, 12, 13 and 14 allow IC1 to be programmed if needed. The two Mosfets, Q1 & Q2, are driven from a further two digital outputs of IC1. In the Decoder article, we described the current-limiting circuitry on the Mosfets (enforced by the 100W source resistors) and how the 0.68W resistors on the ISEN pins of the DRV8231 ICs set a 500mA limit on their outputs. The connections to sense the incoming voltage are different from the Decoder, since we need to measure the amplitude of that voltage. 100kW/10kW dividers bring both voltages down to a safe range for IC1’s ADC (analog-todigital converter) to measure, while the 10μF capacitor between the middle of the dividers low-pass filters the signal. This filter means that it is possible to apply a PWM drive signal to the inputs, and the filter will provide the average input voltage to the microcontroller for measurement. This chip has a differential ADC, so we can directly measure the difference between the two voltages, giving us the polarity and amplitude of the applied voltage. When configured for DCC operation, the low-side resistors and the 10μF capacitor are left off, providing the same sensing configuration as used in the Decoder circuit. The 10kW/10kW divider across the +3.3V rail, connected to pin 8 of IC1 (CONFIG) is used to configure the adjustable speed response, as mentioned earlier. Using different values here will provide different speed responses. Leaving the upper resistor off will force CONFIG to 0V, and the Stepper Motor Driver and Decoder will then operate as a DCC decoder instead of responding to the applied DC voltage. Firmware In DC mode, we can expect a varying input (supply) voltage. Below 5V Fig.1: the circuit of the Driver is similar to that of the DCC Decoder published previously. Since we need to control four motor outputs, there are only enough spare I/O pins to provide two open-drain function outputs. 52 Silicon Chip Australia's electronics magazine siliconchip.com.au at the bridge rectifier inputs, there is about 3.5V on the input to the regulator, and it is barely able to maintain its 3.3V output. When it starts up, the microcontroller samples the voltage on its pin 8 input (the “CONFIG” signal), to set its speed and mode. The microcontroller repeatedly measures the input voltage, but does not drive any of the outputs. With less than 4.5V on their supply pins, IC2 and IC3 stay in under-voltage lockout. Above 5V at the input, the micro enables Q1 or Q2, depending on the supply polarity. In a model railway application, these would be used to drive directional lights, with current sourced from the 12V rail. At 6V, IC2 and IC3 are now receiving 4.5V and will enable their outputs if commanded to do so. The micro subtracts 6V from the input voltage and uses that value, combined with the speed setting and input polarity, to generate an output waveform to drive the stepper motor. The 6V offset means that it is possible to easily achieve low-speed control. It also means that, for example, applying 12V to the input will drive the motor at double the speed compared to a 9V input. The analog reading of the CONFIG input is transformed into a ratio that reflects the ratio of the resistors used to set the voltage. Using ratios makes it easier to calculate the values needed to achieve a specific speed. For example, if the default 10kW: 10kW divider gives a certain speed, then changing it to a 20kW:10kW divider will give double that. The upper ratio limit is 10:1 (ten times the default speed), while the lower limit is about 1:100 (1% of the default speed). If the upper resistor is a very high value or left off (giving a lower ratio than 1:100), the Driver starts up in DCC mode instead. In DCC mode, the Driver operates like a DCC Decoder described in the earlier article, except that its motor outputs are arranged to drive a stepper motor. Since a DCC Decoder has configuration variables (CVs) for setting the speed response, we don’t need the CONFIG divider for this purpose. Notes In DC mode, the default speed (with the 10kW:10kW divider fitted) at 7V (1V above the 6V threshold) is 30 steps per second, or 7.5 full cycles of the output siliconchip.com.au waveform per second. This becomes 300 steps per second at 16V (10V above the 6V threshold). Of course, you can change this by changing the divider. In DCC mode, CV5 is used to set the speed ratio. CV2 and CV6 are not implemented, since the low-speed behaviour of stepper motors does not require the compensation that these CVs offer. The default value of CV5 is 64, implying that the speed can be increased approximately fourfold by setting CV5 to 255. A value of 64 for CV5 corresponds to 155 steps per second at speed step 127. This also means that a value of 52 for CV5 gives 127 steps per second at speed step 127; this value might be easier to use as a base for calculations. There is a very wide variety of stepper motors available, with different numbers of steps per revolution, winding resistances, output torque and shaft arrangements. So we recommend doing your research before connecting a stepper motor to ensure it works as best it can and doesn’t burn out or get damaged. We tested various stepper motors, ranging from a tiny unit measuring just 4mm across up to a so-called NEMA-8 unit. The NEMA-8 stepper motor looks similar to the NEMA-17 motors used in 3D printers, but is about half the diameter. The smallest motors worked well enough but got quite hot. So we recommend changing the 0.68W resistors to a higher value to reduce the current limit with such motors. The current limiting is based on a 0.33V threshold, so the formula is 0.33V ÷ I, where I is the target current in amps. For example, a limit of 100mA (0.1A) would require the 0.68W resistors to be replaced with 3.3W resistors. Don’t go any lower than 0.68W for the current sensing resistors, since that could result in the bridge rectifier exceeding its 1A limit. The NEMA-8 motor struggled to generate torque and would stall easily. These have a very low winding resistance and normally operate with a much higher current than the 500mA that is available from the Driver. Motors in between these sizes, around 8mm to 15mm in diameter, seemed to work quite well and typically had coil resistances of around 20-30W. The motor shown at the bottom of page 50 has a 15mm diameter. Motors with gearboxes will generally Australia's electronics magazine provide more torque; we found that even the cheap and common 28BYJ-48 type motors worked well. These have five wires, since they are arranged for unipolar operation, but if the common (typically red) wire is left disconnected, the Driver can power them. There are many varieties of stepper motor around, and we cannot characterise all of them. Still, the above should give you some idea about what motors will work best and how to adjust the Driver for the best operation. You should also check the stepping rate that your motor can support and ensure that you are operating within that range. Operating above the maximum stepping rate will cause the stepper motor to lose torque and possibly stall. Like the Decoder, connections to the board are made by soldering directly to surface-mount (holeless) pads. During our testing, we soldered headers to the various pads to easily try out different connections. Most connections are close to 0.1in pitch (2.54mm), so standard headers and sockets should work if you want to experiment. The firmware has been compiled to fit in the smaller flash memory of the PIC16F18124 (7kiB), but since the register maps are the same, the firmware should work without issue on the PIC16F18125 (14kiB) and PIC16F18126 (28kiB). Construction Being effectively set by a resistor, the firmware operating mode is fixed once construction is complete. To set the Driver to work in DC mode, all the parts listed should be fitted to the PCB. This is seen in the overlay diagrams, Figs.2 & 3. The resistors in the green The DCC version of the Driver leaves off three resistors and one capacitor to allow the firmware to switch to DCC mode and to properly sense the incoming DCC signal. April 2026  53 box are the CONFIG divider that can be used to alter the motor speed. To work in DCC mode, the high-side resistor (10kW) of the CONFIG divider is left off, as are the lower (10kW) resistors of the sense divider and the 10μF capacitor that provides filtering on the sense lines. These are labelled in red in Figs.2 & 3. If these were left on, they would interfere with sensing the DCC signal. We’ll describe fitting all the parts, so be mindful of which parts to leave off, depending on your intended use. Like other SMD projects, we recommend that you have flux paste, solder wicking braid, a magnifier, tweezers and some sort of fume extraction on hand. Working outside can help with avoiding smoke and fumes if you don’t have an extraction fan. Start assembly with the side shown in Fig.2, including REG1. Apply flux to all the pads on that side. Start with REG1, being careful not to mix it up with the similarly packaged Q1 and Q2. Rest it in place with the tweezers, tack one lead and adjust as needed. Then, solder the remaining leads. Install the two 0.68W resistors (or your other chosen value). These will be tricky to get to if they are soldered after IC2 and IC3. Next, fit the bridge rectifier, observing its polarity, and follow with the two 10μF capacitors on this side. Next solder IC2 and IC3, being sure to locate their pins 1 correctly. When the board is orientated as in Fig.2, the chip markings are upright, with the pin 1 dot at lower left. Then solder D1, making sure that its cathode stripe faces to the left, towards the bridge rectifier. Complete this side with the three resistors near D1. Note that it is only the 10kW resistor below the SC marking that is omitted for DCC operation on this side. Turn the board over and apply flux to the pads on this side of the board. Following Fig.3, solder IC1, noting that its pin 1 dot is at top right. Follow with the two SOT-23 transistors at upper right. That just leaves the passives. The CONFIG resistors are at upper left on this side, with the high-side resistor in the divider being the one closest to IC1; this is left off for DCC operation. The other two parts to be left off for DCC are at lower left, below IC1. Take care with the values of the remaining passives and note that the sole 100nF capacitor sits to the right of IC1. Clean the board using an appropriate flux cleaner and allow the board to dry. Inspect it for bridges and poor solder joints; repair any before attempting to power up the Driver. Testing and programming A weak power source, such as a 9V battery or current-limited supply set to around 12V and 100mA, can be applied to the T connections shown in Fig.2. You should see regulated 3.3V (3.2V to 3.4V) between the 3.3V and GND pins on the ICSP header. If that Figs.2 & 3: pay close attention to the components in the overlay diagrams and be sure to leave off the components marked in red if you are building the version for DCC. At a minimum, you should make connections to the T, A and B pad pairs to drive a motor; the other connections are not mandatory. 54 Silicon Chip Australia's electronics magazine The DC version is populated with all the components. The CONFIG divider has been set to its default of two 10kW resistors; these values can be changed to alter the speed response of the Driver. siliconchip.com.au is not right, or your power supply goes into current limiting, check your construction again. Further testing will require the chip to be programmed. If you have bought a programmed chip or kit from the Silicon Chip Shop, then this should not be required. Otherwise, solder a fiveway pin header to the ICSP header and connect it to a programmer such as a Snap, PICkit 4, PICkit 5 or PICkit Basic. The power supply noted above should be adequate if your programmer cannot supply power. Program the 0911124S.HEX file and check that the programming and verification complete successfully. Connections Figs.2 & 3 also show the connections that can be made. Note that the two pads marked A must connect to opposite ends of the same winding on the stepper motor, while the pads marked B connect to the two ends of the other winding. The easiest way to check the windings is to test for continuity, although this may not apply to five-wire motors. Just like the DCC Decoder, you can connect a capacitor to the + and – keep-alive connections to store and later provide energy if the supply is intermittent. While this was intended to handle dirty tracks in a model railway, it can also be helpful if you are trying to power the Driver with a PWM power source. The pad marked 12V is simply rectified DC from the bridge, so could vary over a wide range, especially if the Driver is being used in the DC configuration. If you want to use the Q1 and Q2 outputs with a varying supply, you Table 1 – supported configuration variables CV# Notes Default value 1 7-bit short address 3 3 Acceleration rate 0 4 Deceleration rate 0 5 Speed scaling: the default value of 64 results in 155 steps per second at speed step 127. Other values scale proportionally; for example, a value of 52 gives 127 steps per second at speed step 127. 64 7 Manufacturer version number (read-only) 0x5D 8 Manufacturer identification number (read-only) 13 11 Packet timeout 0 17 Most significant bits of long address 192 18 Least significant bits of long address 0 19 Consist address and direction 0 29 Configuration 2 33 Function mapping 1 34 Function mapping 2 35 Function mapping 0 36 Function mapping 0 37 Function mapping 0 49 Function effect bitmap for forward light output 255 50 Function effect bitmap for reverse light output 255 could use a constant current-circuit instead of the resistors shown in Fig.3. An alternative would be to feed the LEDs from 3.3V on the ICSP header, although this will offer much less headroom. You shouldn’t draw more than about 10mA from the 3.3V supply due to dissipation in REG1. DC use If you have a stepper motor connected, you can test out the Driver by applying a voltage at the T input to the bridge rectifier. We used a 9V battery for much of our testing; it went flat fairly quickly, but it was able to rotate Parts List – DC/DCC Stepper Motor Driver 1 double-sided 13 × 24mm PCB coded 09111242, 0.8mm thick 1 PIC16F18124-I/SL (or 18125 or 18126) 8-bit microcontroller programmed with 0911124S.HEX, SOIC-14 (IC1) 2 DRV8231DDAR motor driver ICs, SOIC-8 (IC2, IC3) 1 MCP1703A-3302E/CB 3.3V low-dropout linear regulator, SOT-23 (REG1) 2 2N7002 SOT-23 N-channel Mosfets (Q1, Q2) 1 1A SMD bridge rectifier (BR1) [MBS4 or CD-MMBL110S] 1 1N5819WS SOD-323 schottky diode (D1) 1 3cm length of 20mm diam. heatshrink tubing (to protect & insulate Driver) Capacitors (all SMD M2012/0805 size MLCC) 3 2 10μF 25V X5R 1 100nF 50V X7R Resistors (all SMD 1%, M2012/0805 size, ⅛W unless noted) 2 100kW 7 4 10kW 1 100W 2 10W 2 0.68W ¼W n values are to suit DCC mode. The values of two of the 10kW resistors can also be adjusted to change the speed response in DC mode. siliconchip.com.au Australia's electronics magazine all the stepper motors that we tested. DCC operation You will need a DCC signal to test out the Driver in DCC mode. The earlier parts of this series (siliconchip.au/ Series/455) describe a few options for Base Station Hardware. Table 1 lists the configuration variables (CVs) that are implemented on the Driver when it is operating in DCC mode. Apart from CV5, the other CVs will work in much the same fashion as those described in the Decoder article (December 2025). Thus, the remaining CVs have only brief descriptions of their characteristics. Note that we have used a different version ID (CV7) so that you can tell these Decoders apart. Otherwise, the DCC code is much the same, and the Driver should operate much like the earlier Decoder in all other respects. Conclusion We don’t expect that all stepper motor types will work well with this Driver. It is something of an experimental device; it originally began as a DCC Decoder that could be used to drive stepper motors. Still, we think that the ability to accept a DC voltage for power and control will be adopted for cases where basic operation of a SC stepper motor is needed. April 2026  55 Whole-House Environmental Logging By Julian Edgar In the March 2026 issue, Julian Edgar gave some tips about wiring up a newly built home. Now we look at the electronic logging and display system he has built to oversee the thermal behaviour of his house. Image: the active/passive solar house uses largely conventional current Australian construction. Here it’s shown with AI-added landscaping – the landscaping won’t be finished for several years. But the house and rainbow are real! M any Australian houses are constructed with insufficient regard to the climate, especially in the use of low-cost passive solar design approaches such as orientation, shading and use of internal thermal mass. After over 45 years of being interested in passive solar house design, I could finally incorporate as many energy-efficient aspects as my wife and I could think of, get planning permission for, and afford! In addition to obvious aspects such as insulation in the walls and ceilings and double-glazed thermally broken windows, the house uses a thick, steel-reinforced concrete slab floor supported on deep concrete pillars into the earth. Don’t many houses have concrete slab floors? Well, in our case, that floor acts as an earth-bonded heat stabiliser, keeping the house cooler in summer (it acts as a heatsink) and warmer in winter (it acts as a heat source). In passive solar house design, this temperature-­ stabilising function is often called ‘thermal mass’. 56 Silicon Chip To enhance its winter performance, the house faces north and has extensive window area on this face. Winter sunshine falls on the slab, warming it during the daytime and so providing heat at night. To prevent warming of the slab in summer, the width of the northern eaves has been carefully calculated to block the summer sun, which is higher in the sky, from entering the house. But it gets a little more complicated than that, especially in summer. On a hot summer day, the house is closed up, with the slab keeping the interior cool as it acts as a heatsink. Inevitably, the slab temperature will rise as heat passes from the house interior into the slab, so we need a way of getting rid of that heat. This is typically done when the temperature drops at night, at which time the house windows and doors are opened for cooling breezes. But what if the night is still – there’s no wind? That happens occasionally here, about 100km north of Canberra. In that case, another aspect of the Australia's electronics magazine house comes into operation. A large (600mm diameter) roof ventilator can be powered by its brushless DC motor, drawing air out of the roof space. Connecting the house interior to this roof space are ceiling vents, opened by electric actuators. Aided by the convectional flow (hot air rises), the house and the slab are cooled by this airflow. In winter, there’s another twist. Software modelling of the house design showed that, especially during a cloudy week in winter, the slab would get too cold to adequately warm the house. To cater for that, we have a modern wood stove. In this rural area, firewood is free, and the stove has low particulate emissions and high efficiency. However, the wood stove is in the lounge room and so would heat only that room. To circulate the heat more widely, a duct connects the lounge to the other end of the house, with an automatically controlled fan moving warm air through the duct. I described that system, with its custom controller, siliconchip.com.au in the August & September 2025 issues (siliconchip.au/Series/446). Now, I am sure you’re thinking, that’s all very nice – but what does it have to do with electronic logging and display? If you think about it, the occupants must control this scheme. We need to know when to close the windows and doors, and when to open them. We need to know when to open the ceiling vents, and when conventional and wind-induced airflow through the roof ventilator is insufficient and the ventilator should be powered up. Because it is automatic, we don’t need to know when it would be beneficial to switch on the ducted heat transfer fan, but we need to adjust the controller’s temperature difference and hysteresis settings for the best results. Many of these ‘house operating’ decisions need to be made in the context of temperatures – temperatures of the different rooms, of the concrete slab, of the outside air. Other decisions need to be made in the context of the season, the predicted weather over the next few days, and what weather has occurred in the previous days. What the occupants are doing also matters, eg, cooking over a hot stove, sitting at a home office typing, or sleeping. Initially, I thought of automating all these decisions – that is, having windows and ceiling vents that opened themselves, automatically switchingon the roof ventilator, and so on. Then I realised that such a system would rapidly become complicated, expensive and hard to maintain over the life of the house. So, manual control it is – but with a lot of information at our fingertips. That’s where the logging and display system comes in. Showing 25 sensed and calculated parameters, both numerically and via trend line graphs, the system allows us to see, at a glance, what the house is doing, and what we should do (if anything). If the house needs to be opened up for summer night cooling, the time to do it is when the falling outside temperature graph line crosses the interior temperature line. If, during winter, the slab temperature is getting low, lighting the wood stove early will help ‘recharge’ it with heat. The logging and display system will also show how well the house design siliconchip.com.au House passive solar design features » R5 roof and R2.7 wall insulation; periphery of concrete slab insulated to R2.3 » Thermally broken, double-glazed windows » 150mm-thick concrete slab floor with two layers of steel mesh reinforcement, multiple deep cast-in pillars » Rectangular plan-form house with extensive northern glazing, limited eastern glazing shaded by a 5m deck overhang, very limited western glazing (a door) shaded by a porch, southern glazing limited in area and illuminated in winter by a freestanding southern reflector panel (yet to be built) » Increased interior thermal mass provided by brick feature walls and two internal 2000L steel water tanks, one at each end of the house, plus a further 375L tank in the home office » 600mm wind powered roof ventilator working in conjunction with electrically opened ceiling vents The 2000L water tank in the lounge provides thermal mass, reducing indoor temperature fluctuations. The main thermal mass is provided by the concrete floor slab, insulated around its edges. The slab was strengthened to bear the two-tonne weight of the tank. The tiling wasn’t complete at the time of this photograph – it was added using AI. actually works. How hot and cold does the interior get over a year? How long does it take for heat to migrate from the northern, sunshine-exposed side of the slab to the southern side? I have many books with descriptions of a home designed with passive-­ solar optimisation principles, but invariably when it comes time to describe how effective they are, the analysis gets quite vague! For this house, I wanted hard data. So, finally, Australia's electronics magazine what does the logging and display system comprise? Logging and display The logging and display system comprises the following: • A wall-mounted, 24-inch (61cm) LCD touchscreen panel shows realtime data, such as room temperatures • A logging system records data and displays it numerically and in trend graphs April 2026  57 Two Picolog model 1012 10-bit analog loggers are used. Each logger has 12 single-ended input channels. Off-the-shelf software allows the use of lookup tables and displayed values calculated from multiple inputs. The main display is a touchscreen PC in a wall nook located centrally in the house. The PC allows easy control over the scaling and data to be displayed. Two USB cables link the PC to the Picolog loggers in the loft directly above. There is a repeater display in the home office. This wall-mounted sensor detects radiant heat. It uses a thermistor mounted inside a metal hemisphere. 58 Silicon Chip The outside sensors for the logging and display system include wind speed and UV intensity (bottom sensors). The top sensors are for a Davis Vantage Vue weather station used for calibration and redundancy. Australia's electronics magazine • Warnings/indicators are shown when certain actions are suggested The LCD touchscreen is an HP 24-cr1000a all-in-one desktop computer. This is located in a wall recess that is easily accessible from all parts of the house. A repeating LCD screen, linked by a fibre optic HDMI cable, is mounted in my home office. Data is collected and logged by two Picolog model 1012 10-bit analog loggers. Each logger has 12 input channels and two digital outputs, giving the system 24 input channels and 4 software-­ switchable outputs. The Picolog units are in a storage loft, directly above the PC, and are connected to it by two USB cables. These cables power the Picologs, and provide data transfer to the PC. I selected Picologs because the UK-based Pico company provides free logging and display software and has good technical support. The software allows quite complex treatments of input data for calibration (eg, the use of equations or lookup tables) and has easily programmable maths functions to display calculated data. The lookup tables allow non-­linear or linear sensors to be used, and maths functions can be used for functions like averaging the readings from multiple sensors. In addition, data from each individual input can be averaged over pre-selected time periods, eg, temperature readings can be averaged over 10-minute periods. The Picologs use 0-2.5V single-­ ended sensor inputs – that is, the input signal for each channel needs to be an analog voltage in this range. A regulated 2.5V output is available for powering sensors. The amount of data logged is limited only by the storage available on the PC or, if desired, the ‘cloud’ – so in practical terms, it is unlimited. In my system, nine different environmental factors are displayed: • indoor temperatures • indoor relative humidity • indoor dew point temperature • indoor carbon dioxide (CO2) level • indoor radiant temperature • outdoor temperatures • outdoor wind speed • outdoor UV intensity • the flow volume through the roof ventilator Let’s look at each in turn. Most of the logger inputs are for temperature sensors. Temperatures are sensed: siliconchip.com.au The flow through the roof-mounted ventilator is measured by a pitot tube (circled) and differential pressure sensor. The logging software shows this flow in m3/min, calculated from the velocity and crosssectional area. Electrically opening ceiling hatches allow convectional or forced air ventilation through the house. • Within the concrete slab • 1150mm above the floor in multiple rooms • Near the peaks of the cathedral ceilings in the two main end rooms • In the two internal water storage tanks (more on these later) • Outside in the shade • In the roof space near the ventilator In total, 18 temperatures are currently sensed. Not all are displayed by trend graphs on the PC screen – sometimes, an average of multiple sensors is calculated and this average then shown on the graph. Temperature sensors A lot of thought was given to using temperature sensors that would have a very long life – this ruled out IC-based sensors, for example (they would be more susceptible to lightning damage, especially on the end of long cables). Should they fail, the in-slab sensors are not easily replaceable – although, unfortunately, that has already happened. The chosen temperature sensor is a thermistor, a device that changes resistance with temperature. I used the Ametherm ACW-016 precision thermistor exclusively; this has a 50kW resistance at 25°C and an accuracy of ±0.5°C. In use, I have found them to be more accurate than their specification suggests. This sensor is also provided with a table of resistance versus temperature readings, and this table, when converted to voltages, can be input directly into the Picolog software to give a readout in °C (the change in resistance is not linear with respect to temperature). To allow the thermistor to give a variable voltage output, a precision 50kW resistor is used to form half of a voltage divider, with the thermistor forming the other half. The ACW-016 thermistor is tiny – its body is only 1.8mm in diameter, and its connecting wires are equally small – just 0.2mm thick! This means the sensors and their wiring need to be connected so that no physical stress is placed on them. The slab sensors were soldered directly across the splayed ends of the cabling conductors, with the connections and thermistors then wrapped in electrical tape before being placed in the flexible plastic conduit (truck siliconchip.com.au Before the concrete slab was poured, plastic tubes containing thermistors and their associated cabling were put into place. One of the orange tubes can be seen here. Unfortunately, nearly every tube allowed water in, wrecking the thermistors! It happened twice – I nearly cried. Australia's electronics magazine April 2026  59 air brake hose) that was buried within the slab. As events proved, taking this approach was a mistake – more on that soon. The room thermistors were wired in the same way, with these assemblies then mounted in small, ventilated enclosures that attach to standard Clipsal Classic wall plates, which visually match the rest of the wallmounted switches. The thermistors sensing the temperature of water in the internal heat storage tanks were attached to the outside of the tanks, then insulated from the room air with polystyrene blocks shaped to match the tank corrugations. All temperature sensing connections were made with 1.5mm2 shielded instrumentation cable – physically strong, with a very low resistance. Hundreds of metres of cable were used, all installed during the house construction. The Picologs are optionally provided with plug-in PCBs that have connecting terminal blocks. However, these terminal blocks were too small to take the sensor cable conductors, and physically not strong enough to resist the pull of 12 cables on each Picolog. To cater for these aspects, the Picologs were mounted in a 19-inch rack mount case with the sensor cable terminations on heavy-duty terminal strips mounted on standoffs. The required voltage divider resistors were easily installed between the sensor inputs and another terminal strip fed from the 2.5V reference supply. Other sensors Indoor relative humidity is detected by a commercial sensor that has a linear analog output. However, after monitoring the relative humidity for a while, I found it rather useless in assessing comfort. This is because, if the temperature is low, one doesn’t even notice high relative humidity – it feels ‘muggy’ only when the temperature is also rather high. I therefore added a calculated dew point to the display. Dew point is the temperature at which condensation would occur at a given combination of relative humidity and air temperature. Because it takes into account both of these factors, it is a very good guide to human comfort. If you live in a temperate climate, dew points above about 15°C start to feel uncomfortable. As with all human 60 Silicon Chip comfort parameters, it also depends on what you’re used to. The dew point calculation can get very complex; a simplified equation is (dew point) = (air temperature) – (100% – relative humidity) ÷ 5%/°C, but note that this is more like a ruleof-thumb than a rigorous equation. For more details on this calculation, including its loss of accuracy at low relative humidities, refer to “The relationship between relative humidity and the dew point temperature in moist air: A simple conversion and applications” by Mark G. Lawrence in the Bulletin of the American Meteorological Society, February 2005 (see siliconchip.au/link/ac9l). Carbon dioxide is measured with a commercial sensor. This parameter is a good proxy for general ventilation flow – CO2 levels should be kept below about 1000ppm. The normal atmospheric CO2 level is about 400ppm. I found that a correction was needed – when calibrated with outside air, the sensor tended to read too high. This offset was added in the Picolog software. Radiant temperature is measured in one room. Much heat gain in a house is via radiation through the windows – direct radiation (sunshine) and indirect radiation (reflected light). Radiant heat is measured by sensing the temperature inside a small black metal ball or hemisphere. I used a Sontay TT-BB radiant heat sensor, with the assembly disassembled and the standard thermistor replaced with an Ametherm ACW-016 thermistor to give directly comparable readings to the other temperature sensors. The difference between radiant and normal temperatures can be very small, so an offset was added to the radiant thermistor’s output until, in conditions of no radiant heat gain or loss, it was precisely the same as air temperature measured at the same location. Outside wind speed is detected by a rotating cup anemometer that has a 0-5V output. This is reduced to 0-2.5V by a voltage divider. The anemometer output was calibrated in km/h by comparison with the output of a Davis Vantage Vue weather station anemometer mounted on the same mast. The table of wind speed versus output voltage was then fed into the Picolog software. UV intensity is detected by a Sonbest SM9568V5 sensor. Sonbest makes a variety of sunlight sensors, Australia's electronics magazine including total irradiance and light level. I decided a UV sensor was the most practically useful in terms of the likelihood of getting sunburn; I also expect this sensor’s output to roughly correspond with sunlight intensity. The sensor has a 0-5V output (converted to 0-2.5V using a voltage divider); however, the manufacturer’s data sheet doesn’t relate the output voltage to UV Index. The sensor was calibrated by comparing its output voltage to the Bureau of Meteorology’s locally published UV Index daily data. This relationship was then converted to a lookup table in the Picolog software. This conversion probably needs further work – the sensor output doesn’t seem linear with respect to published UV levels. In the meantime, I use this sensor primarily to determine whether the sun has been out. The anemometer and UV sensor are mounted on a 1.4m-tall mast above the roof at the eastern end of the house. This end of the house is highest above the ground, so it is the most exposed to the wind. The mast is mounted to the fascia; during construction of the house frame, this area was strengthened with added pieces of timber. In addition, the mast carries the sensors for the standalone Davis weather station, which shows temperature, wind speed and direction, relative humidity and rainfall. The volume of air passing through the rooftop ventilator is measured by a pitot tube working with a Dwyer Magnesense II pressure-measuring transmitter. Good-quality aluminium pitot tubes are now available quite cheaply from China; these are sold for measuring the airspeed in model aircraft. The Magnesense transmitter was bought cheaply in a job lot – an alternative would be to use the pressure-­ sensing electronic modules also sold for model aircraft use. A pitot tube measures airflow speed by comparing two pressures sensed by the pitot. One is the atmospheric pressure, sensed by several tangential ports around the periphery of the tube. The other pressure is atmospheric plus the ‘impact’ pressure, sensed at the end of the pitot that faces into the airflow direction. The greater the pressure difference between the ports, the higher the airflow speed. By measuring airflow speed and knowing the cross-sectional area of siliconchip.com.au House modelling Many people are unaware that the heating and cooling energy consumption of a house can be modelled before the house is built. Or, in the case of an existing house, before any improvements are made. The software, developed under the umbrella of the Australian Government’s NatHERS (Nationwide House Energy Rating Scheme; www.nathers.gov.au) program, provides the energy star ratings that all new houses must meet. However, rather than being used just to provide an energy rating, the software can also be used to develop a house design to give reduced energy usage. Different NatHERS software packages are available, including one that is free. I initially had my house design NatHERS-modelled by an architect, and then when I saw how fascinating the results were, I took the course myself in one of the software packages. It is not something you could easily pick up just by trial and error. The software allows house design changes to be made and then the annual energy usage modelled. For example, in your climate, what difference occurs from fitting R6 rather than R5 ceiling insulation? What about adding more windows on the south wall? Changing the northern eave width? A different house orientation? And so on. Not only will the software show the annual energy consumption for heating and cooling, it can also be configured to show the modelled interior room temperatures for every hour of every day of a typical year, in every room! This is another reason I wanted a logging system – to see how well the actual house performance matches the modelled performance. At the time of writing, the performance of the house has been close to the software predictions – if anything, it is doing better than the software predicted. Finally, the CSIRO has released predicted climate data that can be used in the software, so the house design can be modelled for future climates – a good idea since the life of a house is likely to be 50+ years. The modelled temperature of my home office (blue) and the outside temperature (red) for a year, with no heating or cooling systems operating. The modelled temperatures for each room at 3pm on July 31st in a typical year. The outside temperature is only 11°C but most rooms are around 20°C. The lower temperatures are in the rooms with exhaust fans – even when closed by dampers, lots of heat is still lost through these openings. This is with no heating or cooling systems operating. These two images were made using the software FirstRate5 (www.fr5.com.au). siliconchip.com.au Australia's electronics magazine April 2026  61 Climate 80km north of Canberra These values shown in the table below are averages – the extremes are 43°C and -8°C. Note the high diurnal (night/day) temperature range in summer, allowing a passive solar home to work very effectively in this climate. Initial results indicate the house will likely not need cooling or heating more than 90% of the time. Mar Apr May Mean max. 27.9°C 26.4°C 24°C Month Jan 20°C 15.8°C 12.3°C 11.5°C 13.3°C 16.6°C 19.9°C 22.9°C 26°C Mean min. 14°C Feb 13.7°C 11.5°C 7.9°C the ventilator’s throat, airflow volume can be calculated and displayed by the logging system. I use units of cubic metres per minute. I made a lookup table to display the data in this form, with a check of the system’s accuracy made with a handheld flow meter positioned temporarily in the throat of the ventilator. Thermistor problems Unfortunately, the in-slab thermistors gave a lot of trouble. As described, the thermistors were soldered to the cables, then wrapped in tape and slid into hard plastic hoses, with the assemblies placed before the concrete slab was cast. Well before the house construction was finished, the logging system was up 4.6°C Jun 2.6°C Jul 1.7°C Aug 2.4°C and running – and this soon showed a problem. One by one, the in-slab sensors started to give incorrect readings. The readings progressively worsened until, typically, they were showing either extremely high or low temperatures. Reluctantly, because I didn’t think they could be replaced, I pulled out each cable, complete with sensor, from its plastic tube. This invariably revealed that the sensor was wet. Either the plastic hose had been holed during the concrete pour, water had entered the ‘house’ end of the plastic hose (despite it being sealed with tape) before the roof was on, or condensation was occurring. Even a small amount of moisture was enough to cause problems. Sep 4.7°C Oct 7.2°C Nov 9.8°C Dec 12°C Furthermore, even when the thermistors were dried, they still gave incorrect readings. Clearly, new sensors needed to be installed – and they needed to be waterproofed. A new thermistor was soldered across each cable’s conductors, as had been done previously. But this time, rather than wrap the sensor in tape, I slipped a 50mm length of vinyl tubing over the sensor, with about 10mm of the tubing then pushed over the full diameter of the cable, where it was a tight fit. I then used Selleys MarineFlex sealant to fill the open end of the tubing, completely enveloping the sensor and its wiring, while adding some more of the sealant around the vinyl tubing/ cable join. Screen 1: about three weeks of temperature data in November with no heating or cooling. The outside temperature (green) varied from 2-32°C, while the indoor temperature (blue) varied from 18-24°C. The concrete slab varied in temperature by only 1.5°C (red). Four of the slab temperatures (right-hand column) show the fault discussed in the article. The gap in the recording is due to an electrical storm. 62 Silicon Chip Australia's electronics magazine siliconchip.com.au With some effort, each sensor could then be pushed into the plastic hose sufficiently far that the sensors were returned to the original positions, deep inside the concrete slab and in about the middle of the respective rooms. Incredibly, this did not fix the problem! Months later, when the house walls were complete and so access to the cables and thermistors was near-impossible, one by one, the thermistors began to give the same trouble. I can only assume that again water was the culprit – and that it could infiltrate through the cable insulation. Luckily, a single thermistor cable could still be accessed – it was behind the plasterboard wall inside a linen cupboard. I was able to cut a hole in the plasterboard and fish out the cable. I then drilled a hole in the concrete slab inside the cupboard and put in a new sensor. I covered the wiring junction with a wall blanking plate. Should further problems occur, this sensor is easily replaceable. While it is not as good as having multiple slab sensors in different parts of the house, the sensor is at least located centrally and so provides a good average slab temperature. At the time of writing, three of the eight original slab sensors remain working – but I am not hopeful that will continue! Trend graphs The most useful aspect of the logging and display system is the trend graphs. Three different vertical axes can be shown on the one screen, and typically the following approach is used: • Top axis: inside temperature, concrete slab temperature, outside temperature • Middle axis: wind speed and roof ventilator flow • Bottom axis: UV index Using the touchscreen, the number of axes shown (one, two or all three) can be changed, with the graphs automatically resizing to fill the screen. The horizontal and vertical axes of each graph are also easily rescaled by two-finger pinching and expanding on the touchscreen. This approach allows many parameters to be shown in a way that allows understanding at just a glance. It’s easy to use the touchscreen to draw horizontal lines that show the maximum and minimum of each graph. The system then calculates and displays the numerical difference. For example, seeing the range over which the slab temperature has varied in the past month is quick and easy. Screens 1-5 show some of the logged data. Conclusion Apart from those darned slab thermistors, the system has worked flawlessly. The ability of the system to work with any analog sensor with an output range of at least 0-2.5V means that sensors for most environmental parameters are readily available and can be easily connected. The touchscreen PC and Picolog software give intuitive and quick interaction – selecting data, changing scales and allowing measurements to be made. Hard-wiring of the sensors avoids the need for periodic sensor battery replacement, and is more immune to interference. The system wasn’t cheap, but my major goals of ease of use, accuracy and clarity have been achieved. Plus, my wife and I find the results fascinating – while many of the measurements are as we expected, significantly, some are not. So it’s been a great learning experience – on a scale the size of a house! SC See overleaf for Screens 3-5 Screen 2: all three axes are visible: the top graph of temperature, middle graph of outside wind speed and roof ventilator flow, and bottom graph of sunshine intensity. The abrupt dips in the sunshine graph indicate passing clouds. siliconchip.com.au Australia's electronics magazine April 2026  63 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). Screen 3: the red line shows the temperature at shoulder height, and the green line the temperature at about 5m, near the ceiling. Note how the temperature at height is greater than normal room temperature during the day, but this reverses at night due to heat loss into the roof space through the upper walls and ceiling. Screen 4: logging over two days shows how slowly the internal temperature of the concrete slab (red) varies. Here, its greatest rate of change is about 0.5°C per day. The black line is the temperature of one of the 2000L internal water tanks that provides quicker-response thermal mass. The tank changes in temperature a little more rapidly than the concrete slab and is about 1°C warmer. EACH BLOCK OF ISSUES COSTS $100 NOVEMBER 1987 – DECEMBER 1994 JANUARY 1995 – DECEMBER 1999 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 64 Silicon Chip Screen 5: the air temperature of different rooms in the house over two days. Even with all the internal doors open, the northern rooms, exposed to spring sunshine, are 1-3°C warmer than the southern rooms. siliconchip.com.au Subscribe to MARCH 2026 ISSN 1030-2662 03 The VERY BEST DIY Projects ! 9 771030 266001 $14 00* NZ $14 90 Solar Panel Protector and Optimiser INC GST INC GST low-cost protection from lightn ing strikes DCC Booster and Reverse Loop Controller Graphing low-cost Australia’s top electronics magazine Thermometer 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 $72.50 $82.50 $52.50 1 year $135 $155 $100 2 years $255 $290 $190 6 months $85 $95 1 year $160 $180 2 years $300 $335 6 months $105 $115 1 year $200 $220 All prices are in Australian dollars (AUD). Combined subscriptions include both the printed magazine and online access. 2 years $390 $425 Prices are valid for the month of issue. Try our Online Subscription – now with PDF downloads! The History of Intel; Feb 2026 – Apr 2026 Wiring up a new Home; March 2026 Mains Hum Notch Filter; February 2026 Designing PCBs; Dec 2025 – Feb 2026 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 The miniature 100W Hummingbird Amplifier from December 2021 has been popular, but some of the parts used in that design are now obsolete. This improved version features several minor improvements, plus the ability to use a wide range of transistors in several roles. 100W Calliope Amplifier by Phil Prosser T his amplifier is founded on a classic design made famous by Douglas Self as the ‘blameless amplifier’, and is reliable and powerful, especially for its size. As with many things in the electronics field, parts change and go obsolete. Since it is useful and popular, we thought it was worth updating to use currently available devices, with as many alternatives as possible; in case something else becomes hard to get... While at it, we have made a few optimisations to the layout, which at least technically improves the performance of this amplifier. Still, the performance of the original amplifier was very good, so we consider these minor upgrades. Part of the popularity of the Hummingbird amplifier module is that it that packs a surprising punch for its size, while keeping the low-­distortion characteristics of the Ultra-LD Amplifiers from which it takes inspiration. It can achieve up to 60W into 8W or 100W into 4W with distortion below 0.0005% at 1kHz, and less than 0.004% all the way up to 20kHz. That’s way better than “CD quality”. This project is more about the process of dealing with obsolescence, validating the changes and some discussion on the measurements we made. For an in-depth explanation of the design itself, refer to the original article (siliconchip.au/Article/15126). If you are in for a truly deep dive into amplifier design, look up Douglas Self’s books, especially the Power Amplifier Design Handbook that we reviewed in the March 2010 issue (siliconchip.au/Article/89). It is still very much relevant more than 15 years later. Maintaining and supporting this design is a balancing act between making necessary changes and adding improvements while maintaining both physical and performance compatibility with the original design. The part that triggered this update is the KSC3503 transistor (Q14) used in the voltage amplification stage (VAS), between the input differential pair and Scopes 1 & 2: a Calliope amplifier driven into clipping with a KSC3503 transistor as the VAS compared to another Calliope board with an MJE340 for the VAS (right). With the MJE340, it spends quite a long time ‘stuck’ to the negative rail. For high-frequency signals, this can get very ugly. 66 Silicon Chip Australia's electronics magazine siliconchip.com.au the output stage. This does not look that critical, but it provides the bulk of the voltage gain in the amplifier. How this transistor behaves as it enters and leaves saturation, which occurs when the amplifier clips, is an important but unusual requirement. For a transistor to do well as a VAS device, it needs to handle high voltages, and its Cob (output capacitance) needs to be extremely low, ideally only a couple of picofarads. In the old days, this was an easy thing to find, as the video stage in cathode ray tube (CRT) television sets demanded similar specifications. These are broadly: ● Output capacitance (Cob): very low, ideally < 3pF ● Collector-emitter voltage (BVceo): >150V ● Current gain bandwidth product (Ft): ideally in the 50-100MHz region ● Collector current (DC): >50mA ● Power dissipation: >1W When we saw the KSC3503 was marked as ‘end of life’, we went looking for an alternative part. With the passing of the days of CRT monitors, there is little reason for manufacturers to produce this type of device. We knew this would not be a simple change, as we looked for good VAS transistors during the original design. After days of searching suppliers and audio forums, it started looking like the only option was a surface-­ mounting device. Were we being silly? Should we care that much? What happens if we just throw a bog standard MJE340 into the board instead? Well, the amplifier will work, but you take a serious hit on how it behaves around clipping, and in general performance and stability, as shown in Scopes 1 & 2. Less critical but also important for the future, the range of output devices and drivers has changed. We bought a selection of different parts and validated them, so you can confidently build this with one of numerous parts options. Of particular interest to us are new output device options (see Table 1 overleaf) and driver transistor options (Table 2). As can be seen in Table 3, ideal options for the VAS are pretty limited, and there is no ideal part that is readily available in a through-hole package. There are some decent choices in SOT-223 (a fairly large SMD package), though. So we had to bite the bullet and make board changes to accommodate SMD parts for the VAS. To test the VAS devices, we set up a Calliope on our test jig (Photo 1), set the input to 0.9V RMS and connected a 3W load. We then tested each VAS device, one after another, without changing any settings or moving cables. This setup might look agricultural, but has a fair bit of thought in it and allows an objective comparison between modules. The test jig allows rapid changeover between modules and allows us to change components in situ, as the base is narrow enough to access the rear of the boards. It includes enough local filtering to let us run it from a bench DC supply, so there are no mains voltages involved, and we have a 6A current limit on our power supply. Despite that, it is beefy enough to allow us to run the amplifiers hard. The heatsink is undersized, and gets very hot on long tests, but this is handy, as we want to know how the various versions behave when abused. Amplifier Features Accepts a wide range of easy-toget parts (especially transistors) Low distortion and noise Extremely compact PCB Fits vertically on a 75mm heatsink, and can be stacked in a 2RU case Produces the specified output continuously with passive cooling Uses all through-hole parts (or optionally, one SMD for the VAS transistor) Low in cost and simple to build Onboard DC fuses Output over-current and shortcircuit protection Clean overload recovery with minimal ringing Improved tolerance of hum and EMI fields through small size and improved layout Quiescent current adjustment with temperature compensation Amplifier Specifications Output Power (with ±34V DC rails): 100W RMS into 4Ω, 60W RMS into 8Ω Frequency response (-3dB): 1Hz to 150kHz Signal-to-noise ratio (SNR): 118dB with respect to 50W into 4Ω Input Sensitivity: 1.2V RMS for 60W into 8Ω, 1.04V RMS for 100W into 4Ω Input impedance: 22kΩ || 1nF Total harmonic distortion (THD) (32W into 8Ω, ±32V DC): < 0.005%, 20Hz to 20kHz, 50kHz bandwidth Photo 1: our test rig made it really easy to measure the difference in performance as we changed various transistors on the board. You can see the difference between the correct wiring on the right (cyan curve in Fig.2) and the incorrect wiring on the left (mauve curve). siliconchip.com.au Stability: unconditional with any normal speaker load ≥4Ω Power Supply: ±20-40V DC; ideally ±34V DC from a 25-0-25V AC transformer Quiescent current: 53mA nominal Quiescent power: 4W nominal Output offset: typically <20mV (measured) Australia's electronics magazine April 2026  67 Table 1 – output transistor options (available from Mouser, DigiKey & element14) Device Key characteristics Comment MJW21193G/ MJW21194G High gain, optimised for linearity A new version of a ‘bulletproof’ favourite MJW21195G/ MJW21196G High gain, optimised for linearity A new, higher-voltage version of a ‘bulletproof’ favourite MJL21195G/ MJL21196G Same as above but in a slightly different package TTA1943Q/TTC5200Q Targets audio or 2SA1943/2SC5200 applications – linear gain A cost-effective version of another old favourite – higher Hfe and Ft NJW0281G/ NJW0302G Lower power versions of a ‘standard’ Optimised for match and linearity – lower power MJL21193G/ MJL21194G Known good MJL3281A/ MJL1302A Known good NJW21193G/ NJW21194G Known good 2SC5242/2SA1962 Known good Table 2 – driver transistor options (available from Mouser, DigiKey & element14) Device Key characteristics Comment MJF15030G/MJF15031G Insulated-tab versions of standard output drivers Known good MJE15030G/MJE15031G Known good MJE15032G/MJE15033G Known good Table 3 – VAS transistor options (most available from Mouser, DigiKey & element14) Device Package Key characteristics Comment KSC2690A TO-126 A higher Cob than preferred Works, but with some sticking on clipping KSC1845FTA TO-92 On the edge with power Do not use at high handling voltages KSC3503 TO-126 Obsolete/hard to find Known good, if you can get them 2N6517TA TO-92 Higher Cob than preferred Works fine but do not use at elevated voltages BSP19-115 SOT-223 70MHz Ft Prefer BF720/722 BF720 SOT-223 60MHz Ft Works fine BF722 SOT-223 60MHz Ft Works fine (preferred) PZTA42-TP SOT-223 50MHz Ft Assumed OK given DZTA tests DZTA42-13 SOT-223 50MHz Ft Works fine (almost surprisingly well) 2SC2911 TO-126 Obsolete/hard to find A good choice if you can get them 2SC3416 TO-126 Obsolete/hard to find A good choice if you can get them BF469 TO-126 Obsolete/hard to find An outstanding part if you can get them 68 Silicon Chip Australia's electronics magazine We found a handful of BF469 transistors that had been gathering dust. We don’t use obsolete parts in projects, so they are not specified here, but it is an old-school legendary VAS driver. Since we had the test jig up and running, we dropped one in to compare to all the other choices. It did very well, so if you have a few BF469s and are building this amplifier, we suggest you use them. Load line curves, which show the safety margins for the various output transistor options with 4W & 8W reactive loads (simulating typical loudspeakers) are shown in Figs.1(a) & 1(b). You can see that all the options are more than good enough for 8W loads, apart from the venerable TIP35/36, which are marginal but work if you limit the supply rail voltages. The recommended devices for 4W loudspeakers are shown in Fig.1(b) and they are all suitable. Fig.1(c) shows how the single-slope load line protection curves compare to the SOA curves for a selection of output devices. The circuit is designed to limit the devices to stay under the dashed lines, which are fully within the respective SOA curves, providing complete protection. There is no need to actually change the general design, as the ‘blameless’ configuration is known to be good and in use in many amplifiers around the world. However, while we were at the computer shuffling parts around, it gave us the opportunity to make some changes that have been on our ‘to-do list’ for some time. The changes we have made to the PCB layout are: ● Moving the driver transistors from the middle of the board to right next to the output devices, and moving the bias setting potentiometer and associated parts. This reduces routing complexity and provides better thermal coupling of the driver transistors to the output stage, which will improve thermal stability. The better routing should improve high-­ frequency performance, although this is not something we could measure. ● We made room for a VAS transistor in an SMD SOT-223 package, with a modest PCB heatsink area, while keeping the option to use a TO-126 through-hole device. We also tried a few different VAS compensation schemes, in particular, two-pole compensation as used on the Ultra-LD Mk.3 & Mk.4 Amplifiers. siliconchip.com.au Photo 2: the Calliope (Hummingbird Mk2) Amplifier module. We could measure a difference, but with this amplifier being so squished, we saw more effect from wiring layout changes than the compensation change delivered. So we used the KISS principle on this and went back to single-pole compensation. The final board is shown in Photo 2. Performance Fig.2 shows total harmonic distortion plus noise (THD+N) measurements for the new amplifier into a 9W resistive load at 32W. This is what we could generate using our bench supply, but it is representative of what will be achieved at higher supply voltages into normal loudspeaker loads. The performance is essentially the same as the original Hummingbird. If you are comparing this to what we published in the December 2021 issue, it’s important to realise that this plot includes noise, whereas the earlier one was THD only, so that plot showed lower figures. As with the original design, we have tested the distortion of a range of output devices, VAS transistors and output drivers to ensure it behaves well with all of them. An important test for an audio amplifier is how it behaves coming out of clipping, especially with low impedance loads. If you have the wrong VAS device, it will ‘stick’ to the negative rail, and if the output stage has very high-frequency devices, you can find bursts of oscillation near negative rail clipping. Scope 3 shows the behaviour when driving a worst-case 3W load. Figs.1(a)-(c): SOA curves and load lines for the various output device options with 4W & 8W reactive (loudspeakerlike) loads. The dashed lines in Fig.1(c) show the protection lines that the circuit prevents the devices from exceeding, which remain within their safe operating areas (SOA). siliconchip.com.au Australia's electronics magazine April 2026  69 We also have checked the squarewave behaviour. The Calliope is very well behaved with what is essentially a band-limited square wave output. We tested the harmonics generated by the Calliope using a high-quality audio spectrum analyser and found they are very low in level. All harmonics are in the region of -110dBc (0.000316%) to -115dBc (0.000177%). Circuit details Scope 3: clipping with the recommended BF722 VAS. The slight sticking to the rails is normal; the amplifier recovers from saturation at a high output current without ringing or oscillation. Fig.2: three THD+N plots for the Calliope amplifier module at a reasonably high operating power into a resistive dummy load. The cyan curve shows what you can expect if you follow our instructions, while the mauve curve is what you get if you don’t route the output wire as suggested. The red curve shows the result of all the transistors being mismatched. We will not go into a detailed description of the circuit, as the one in the December 2021 issue still applies. This article focuses on building the updated amplifier. You can download or purchase this article from our website if you don’t have a copy and want the detailed design description. The Hummingbird and Calliope amplifiers are physically much smaller than those in the Ultra-LD series, but a review of the circuit (shown in Fig.3) reveals that it is very similar, with the major difference being that Hummingbird/Calliope uses only one pair of output devices (to handle up to 100W) instead of two (up to 200W), and is optimised for operation at the lower voltages that implies. There are three main stages in a ‘blameless amplifier’. These are all described in detail in the original article: 1. The input stage, which uses Q7 & Q8 as a differential pair having a constant-current source (Q3) and a current-­mirror load (Q15 & Q16). 2. The voltage amplifier stage (VAS), comprising Q14 driven by emitter-­ follower Q13 and loaded by constant-­ current source Q2. 3. The output stage, which comprises transistors Q4/Q5 & Q11/Q12, plus protection devices Q6/Q10. This is a conventional complementary output stage. While the Hummingbird Mk1 and Calliope circuits are very similar, if Table 4 – protection resistor values for various output devices NPN device PNP device 22kW W 560W W 220W W Comments MJW21194G MJW21193G 22kW 560W 220W Performs as presented NJW21194G NJW21193G 22kW 560W 220W Performs as presented MJL21194 MJL21193 22kW 560W 220W Performs as presented 2SC5242 2SA1962 15kW 470W 220W Limit to 25V AC transformer if driving difficult 4W loads 2SC5200 2SA1943 12kW 560W 180W Performs as presented TTC5200Q TTA1943Q 12kW 560W 180W Essentially the same performance MJL3281A MJL1302A 15kW 560W 180W Essentially the same performance TIP35B/C TIP36B/C 10kW 680W 180W Limit to 25V AC transformer, prefer 8W load; good performance TIP3055 70 Silicon CTIP2955 hip 12kW 680W Australia's 270W Limit to 25V AC transformer & 8W loads; not verified electronics magazine siliconchip.com.au you compare Figs.4 & 5, you will see how much the layout has changed. Note how the new PCB accommodates either a through-hole or SMD package transistor Q14. We have thoroughly tested the various output transistor, driver transistor and VAS options. We have stuck to the MJE150XX family of driver transistors because they are available, robust and perform well. Any of the devices in this series will do as long as you use the complementary NPN and PNP types. The layout changes have shifted the drivers and resulted in a new layout for the whole top half of the board. This provides better thermal coupling of the drivers to the output devices, and reduces the length of traces with the relatively high base drive current for the output devices, improving stability. Should you be using this amplifier in a very demanding application, there is still room to mount small heatsinks to the output driver transistors. We have kept all mechanical features the same between versions, so if you need to mix and match or replace Hummingbird and Calliope amplifier modules, everything will drop in. We have kept the over-current/safe operating area (SOA) protection for the output devices. This provides protection if you connect a really horrible load or somebody abuses the amplifier. The Hummingbird amplifier delivers the measured performance with the parts specified, but we have checked that it works properly with a range of other parts. For different output devices, change the protection resistor values as per Table 4. An amplifier using a dual 25-30V AC output transformer, diode bridge and capacitor bank will have ±35-42V DC rails, which is safe operating into 4W, 6W and 8W loads. This will deliver 60W into an 8W load and 100W into a 4W load. Component matching Part selection for the Calliope amplifier should be fairly straightforward. We have provided tables of tested parts. Provided you use complementary pairs for the output devices and drivers, and select matched pairs for the input differential amplifier and current mirror, you will be fine. The output pair; for example, NJW21193/NJW21194, and the siliconchip.com.au Challenges with measuring low distortion levels Measuring very low levels of distortion is a lot harder than it might seem. There are a few reasons for this, including: 1. Generating a sinewave test signal that is pure enough to measure distortion at levels below 0.001% reliably is hard, especially if you want to vary the frequency. 2. Knowing if what you are measuring is your measurement system or the device under test is also tricky. 3. Even a tiny bit of EMI pickup can make huge differences in the measurements (simply rotating or moving the DUT can make the readings change massively). 4. Depending on how you Earth the DUT, you can measure voltages induced across ground wires if you are not very careful. For #1, we ended up using a Stanford Research Systems DS360 Ultra Low Distortion Function Generator. To measure the Calliope amplifier’s output harmonics, we are using a high-quality sound card/ADC that requires a line level signal, so we use a 2.2kW/120W resistive divider across the amplifier’s output, in parallel with our dummy load. If we feed the test signal back into the ADC directly, we get a THD reading of 0.00017%, so anything higher than that means we are measuring the amplifier’s distortion. While making amplifier measurements, we got a distortion reading of 0.0018%. While that is still not very high, it’s an order of magnitude higher than we were expecting. After a lot of fiddling, we realised that it depends on which of the two screw terminals of CON4 we make the measurement at! Connecting our measurement system to the unused terminal of the output connector gave a lower distortion reading than the one that is carrying the current (Photo 3). The only differences we see between these two points are: 1. We had to move the measurement probe and cabling slightly, which will pick up different magnetic fields. 2. The output current is going through the PCB-to-connector junction and the connector-to-output wire junction (this is probably the reason, as dissimilar metal junctions can be non-linear). The point of mentioning this is that, when you are aiming for very low distortion, all sorts of second order things start to matter, such as: 1. Earthing and where currents flow (probably the most significant concern) 2. Wiring layout, the magnetic fields the wires produce, and what they can couple into 3. The linearity of loads; we have seen wound Nichrome resistors cause significant problems 4. The types of connector used; our terminals are made of steel, which we think may be a factor 5. The actual ability of measurement equipment Now you know why, in the wiring section, we recommend running the output wire up past inductor L1 and trimpot VR1 to join the supply wires running across the top of the board. Simply running this wire on the other side of L1 has a measurable impact on performance, shown by the difference between the cyan and red plots in Fig.2. The effect is real and repeatable; moving the wire increases the size of the positive rail current loop to the output, which is coupling the positive rail current into the input and VAS stages. This makes the distortion worse across most of the audible frequency range. Photo 3: the two screw terminals on the output connector are both soldered to the output track; the left one is carrying the output current, the right none. We measured 0.0018% distortion on the left, 0.0007% on the right. Australia's electronics magazine April 2026  71 Fig.3: the Calliope circuit is intentionally similar to the original Hummingbird; there are a few subtle tweaks, but most of the improvements are in the PCB layout and expanded transistor choices. While we have nominated NJL21193/4, any of the MJL, MJL, NJL or NJW prefix series with the same numbers will work pretty much identically. Photo 4: the FrankenAmp in all its glory! The input transistors are all different parts, as are the drivers and output pair. Do not do this in your build unless you are truly desperate. drivers, MJE15032/MJE15033 are manufactured to have characteristics such that the NPN and PNP characteristics reflect one another. This reduces distortion when used in an amplifier of this type. The input differential pair, Q7/Q8, does the heavy lifting in making sure that the error in the amplifier output (ie, distortion) is minimised. It also plays a very important role in making sure there is no DC offset. These transistors should be the same as best we can match them, and ideally, thermally coupled. The current mirror, Q15/Q16, keeps the input differential pair in balance and provides gain. These transistors should also ideally be matched and thermally coupled. Feel free to choose pretty much any pairs from the table; match those input transistors and you will be good. At this point, a question arose in my mind: what if you get it really wrong? I couldn’t resist the temptation, so out of my fervid imagination comes the FrankenAmp (Photo 4). In this unit, every single part that can be mismatched was mismatched. It isn’t just a matter of using BC556s from different batches, either; in the FrankenAmp, the input differential pair is a BC558 and a BC556B, the current mirror uses a BC549 and a BC546, and so on. The drivers and output devices are from completely different families. How bad could it be? Fig.4: the original Hummingbird Amplifier PCB layout, shown for comparison to Fig.5. 72 Silicon Chip Australia's electronics magazine Unsurprisingly, the DC offset was terrible, at 140mV. This is because the gain of the input devices is grossly mismatched. Despite this, the amplifier is totally stable and even behaves OK on clipping. The distortion performance is even quite reasonable, as shown in Fig.2! (BD139s are notoriously different between manufacturers; it is likely I used an old Philips one, better than most). So even if you get it really wrong, as long as the DC offset is acceptable, the amp will work quite well. Construction Construction of the Calliope amplifier is pretty easy. It is built on a 63 × 86.5mm double-sided PCB that’s coded 01111212 – see Fig.5. First, based on the output devices you will be using, select the required resistor values from Table 4. These components are shown in red in Fig.5. If you read those same values off Table 4, build it as per our diagrams. siliconchip.com.au Otherwise, substitute the resistors with values shown in red for the different values in the table. After fitting those, install all the other small (¼W resistors). Follow with the 1N4148/1N914 diodes, making sure they are orientated as per Fig.5. Follow by fitting all the capacitors, soldering the smaller ceramic and MKT types first, then the electrolytics. Make sure that the electrolytic capacitors go in the right way around, with the longer (positive) leads to the pads marked +. If you are using an SMD VAS transistor, as recommended, fit it now, as there will be more room. Follow with all remaining transistors, except those that mount to the heatsink. Ensure that driver transistors Q4 and Q12 are installed with their metal tabs facing towards the amplifier input (ie, away from the output transistors). We want transistor pairs Q7/Q8 and Q15/Q16 to be thermally coupled with one another. Our approach is to superglue these face-to-back, then siliconchip.com.au put heatshrink tubing over them. You could glue them together after mounting them, as long as you mount their bodies reasonably close. If you can, select pairs for these devices with similar Hfe by measuring a handful of devices and choosing two that are similar. This can minimise the DC offset of the final amplifier. Now solder the fuse clips, making sure they go in the right way around, with the retention tabs on the outside. After that, solder all the connectors. The wire entries for the power terminal blocks go towards the edges of the board, while the output connector should have its wire entries facing towards nearby diodes D1 & D3. After that, you can mount the larger resistors (0.22W × 2, 4.7W & 15W) and the multi-turn potentiometer, VR1. We need to make sure the potentiometer starts at maximum resistance, so fit it with the screw located as shown, Fig.5: the new Calliope PCB layout moves the driver transistors (Q4 & Q12) closer to the output transistors (Q5 & Q11) and makes room for Q14 to be either in a vertically mounted through-hole (TO-126) package or an SMD (SOT-223) package. Australia's electronics magazine April 2026  73 Parts List – Calliope 100W Amplifier (per module) 1 double-sided PCB coded 01111212, 63 × 86.5mm 1 split rail power supply delivering ±20V to ±40V DC (15-28V AC mains transformer, bridge rectifier, filter capacitors, mains socket, mains-rated wiring, heatshrink etc) 3 2-way 5/5.08mm pitch mini terminal blocks (CON1, CON3, CON4) 1 2-way polarised/locking pin header (CON2) 4 M205 fuse clips (F1, F2) 2 5A M205 fast-blow ceramic fuses (F1, F2) [Altronics S5931] 1 1m length of 0.8mm diameter enamelled copper wire (L1) 1 500W vertical or side-adjust multi-turn trimpot (VR1) 2 TO-3P insulating kits (washers and bushes) 1 TO-126 insulating kit (washer and bush) 3 M3 × 25mm panhead machine screws 3 flat washers to suit M3 screws 3 crinkle washers to suit M3 screws 3 M3 hex nuts 2 blown M205 fuses (for testing, or purposefully blow 100mA fuses) 1 heatsink (we used one Altronics H0545 for six modules) 1 small tube of superglue 1 5cm length of masking tape Semiconductors 5 BC556 65V 100mA PNP transistors, TO-92 (Q1, Q3, Q7, Q8, Q10) 1 MJE350 300V 500mA PNP transistor, TO-126 (Q2) [Altronics Z1127, Jaycar ZT2260] 1 MJE15032G or MJE15034G 250V/350V 8A NPN transistor, TO-220 (Q4) [element14 9556621, DigiKey MJE15034GOS-ND, Mouser 863-MJE15032G] 1 NJW21194G or MJL21194 250V 16A NPN transistor, TO-3P (Q5) [Jaycar ZT2228, element14 2535656, DigiKey NJW21194GOS-ND, Mouser 863-NJW21194G] 3 BC546 65V 100mA NPN transistors, TO-92 (Q6, Q13, Q17) 1 BD139 80V 1A NPN transistor, TO-126 (Q9) [Altronics Z1068, Jaycar ZT2189] 1 NJW21193G or MJL21193 250V 16A PNP transistor, TO-3P (Q11) [Jaycar ZT2227, element14 9555781, DigiKey NJW21193GOS-ND, Mouser 863-NJW21193G] 1 MJE15033G or MJE15035G 250V/350V 8A PNP transistor, TO-220 (Q12) [element14 9556630, DigiKey MJE15035GOS-ND, Mouser 863-MJE15033G] 1 BF722 250V 100mA NPN transistor, SOT-223 (Q14) [element14 1757916, DigiKey BF722,115, Mouser 771-BF722-T/R] 2 BC549 30V 100mA NPN transistors (Q15, Q16) 3 1N4148/1N914 75V 250mA small signal diodes (D1-D3) Capacitors 1 220μF 25V electrolytic [Altronics R5144, Jaycar RE6324] 4 100μF 50V 105°C electrolytic [Altronics R4827, Jaycar RE6346] 1 47μF 50V low-ESR electrolytic [Altronics R6107, Jaycar RE6344] 1 10μF 50V non-polarised electrolytic [Altronics R6560, Jaycar RY6810] 1 220nF 63V MKT [Altronics R3029B, Jaycar RM7145] 5 100nF 63V MKT [Altronics R3025B, Jaycar RM7125] 1 22nF 63V MKT [Altronics R3017B, Jaycar RM7085] 1 1nF 63V MKT [Altronics R3001B, Jaycar RM7010] 1 220pF 100V NP0/C0G ceramic [element14 1600858, DigiKey 56-K221J10C0GH5UH5CT-ND, Mouser 594-K221J15C0GH5TH5] Resistors (all ¼W+ 1% metal film axial unless otherwise stated) 1 220kW 1 82W 4 22kW ♦ 2 68W 2 3.9kW 2 47W ♦ 3 2.2kW 1 39W 1 1.2kW 1 15W 1W 5% 2 560W ♦ 1 10W 1 390W 2 10W 5W 10% (for testing) 4 220W ♦ 1 4.7W 1W 5% 6 100W ♦ 2 0.22W 5W 5% ♦ ♦ two of each may need to change in value depending on the output transistors used ♦ ½W or 0.6W 1% metal film ♦ element14 1735119, DigiKey BC3440CT-ND, Mouser 594-AC050002207JAC00 then rotate the screw anti-clockwise until it clicks. Verify with a multimeter that the resistance between its two outside terminals is below 25W. By the way, side-adjustment pots are better if you’re going to be mounting the amplifiers vertically on the heatsink, while a top-adjustment pot makes most sense if it will be mounted horizontally. Next, make the inductor using 0.8mm diameter enamelled copper wire (ECW) as follows: 1. Find a mandrel that is about 10mm diameter and has a slight chamfer to it so that, once complete, you will be able to slide the inductor off. We chose a large Sharpie marker. 2. Put masking tape around the mandrel with the sticky side faced outwards. 3. Placed a bend in the ECW 30-40mm from the end and wind nine turns onto the tape. 4. Put a few drops of superglue on the ECW; don’t worry if it gets on the masking tape. You do need to be careful not to get glue on your mandrel, though! 5. Give this a minute to set, then wind another layer on top of the first nine turns. You might only be able to get eight in; that is OK. Add more super glue and again, allow it to set. 6. Add a final winding layer and glue it. 7. Push the inductor off the mandrel. 8. Tease the masking tape from inside the inductor; we used needle-­ nosed pliers to do this. 9. Scrape the enamel off the leads and mount it to the PCB above the 4.7W resistor. At this point, the board should be complete bar Q5, Q9 and Q11. From here, you need to mount the output devices to their final heatsink using insulating kits. Then bend the legs of the transistors to match the PCB, as shown in the photos. Slip them into their respective holes on the PCB. The aim here is that these transistors fit reasonably well. Once the three transistors are properly inserted into the PCB, solder them in place. This way, we know that the transistors are mounted with minimal tension on the soldered connections, ensuring a long life of the solder joints (a solder joint under stress has a tendency to crack and go dry). At this point, you should have all Australia's electronics magazine siliconchip.com.au 74 Silicon Chip Photos 5 & 6: The finished Calliope Amplifier, and the test jig used for measurements. The output wire (brown in this case) should be pushed back to run next to the emitter resistor, like it does here. parts mounted to the board, and are ready to test it. Testing & adjustment Your amplifier is probably mounted to the heatsink, but the initial test can be done without it – just make sure that the bias current is set to minimum. This test will check the amplifier is operational: 1. Remove the normal 5A fuses from the board and install blown M205 fuses with 10W 5W resistors soldered across them (‘safety resistors’). 2. Connect a voltmeter between the output and ground, set to a 200V range or similar. 3. Connect a voltmeter across one of the 10W safety resistors, set on a 20V range or similar. If you only have one meter, run an initial check monitoring the output voltage only. 4. With the input to the module disconnected, apply power. Anything over about ±15V is fine. If you can, set the current limit on the power supply to about 100mA. 5. Check that the output voltage settles to 0V ±50mV. We built 14 test units, and all were well within this range. 6. Check that the voltage across the 10W resistor is less than 1V (ie, it’s drawing under 100mA). If either test fails, you need to check for the cause. Do you have VR1 set at Songbird An easy-to-build project that is perfect as a gift. SC6633 ($30 plus postage): Songbird Kit Choose from one of four colours for the PCB (purple, green, yellow or red). The kit includes nearly all parts, plus the piezo buzzer, 3D-printed piezo mount and switched battery box (base/stand not included). See the May 2023 issue for details: siliconchip.au/Article/15785 siliconchip.com.au Australia's electronics magazine April 2026  75 the right end of its travel? Are all the electrolytic capacitors in the right way around? Do you have the input connected? If so, disconnect it. Are all the transistors in the right places and the right way around? Check those output devices are in the right spot! Is your power supply delivering both positive and negative rails, and do you have the ground connected? Assuming it passes the test, it’s time to adjust the quiescent current and run a full operational test. This requires the amplifier to be mounted to a heatsink with appropriate insulators for the output devices and thermal sense transistor. Before powering it up, verify a high resistance between both power supply rails and the heatsink. Apply power and adjust the bias by turning the potentiometer clockwise while watching the voltage across the 10W resistor. Nothing will happen for quite a few turns, then the bias current will rapidly increase. Adjust it to achieve 500mV across the 10W resistor. Allow this to settle and readjust. It can take a while to settle, and should be set with the full rail voltage applied. Power it off, re-install the 5A fuses and you are ready to connect a loudspeaker and run it with an audio signal. You can check the bias (quiescent current) later by measuring the voltage across the 0.22W resistors; you should see close to 10mV across each. Installation Our earlier discussion on measurement pointed out the criticality of Fig.6: when finalising the amplifier wiring in your case, run the supply and output wire to each module like this to get the best performance. layout to get the most of the amplifier. Careful attention to layout and the power supply is required. The power wiring from the main supply capacitors should be delivered on twisted sets of positive, negative and ground wires. The output should fold back toward the output devices, and run parallel to the 0.22W resistors, then follow the power wires – see Fig.6. The output wire should follow the power wires back past the power supply and pick up a ground wire, minimising the loop area created, then run as a pair from there to the speaker terminals. Ensure that the power supply has a ‘star Earth point’ from which you connect to the input ground, the amplifier ground and the speaker output ground, as shown in Fig.7. Also make sure that the way you connect the rectifier and its ground to the capacitors does not inject noise onto your star Earth point. The input cable shields/screens should also be connected to the star Earth point. Make sure all connections are secure and low resistance; poor connections can easily more than double the distortion level. We found this measuring a batch of modules we built to verify our results, having to tighten the connections to achieve consistent results. Is it worth upgrading a Hummingbird to the Calliope? Not really. While the layout is improved, and we provide options for some more recent and ‘optimised’ parts, the Hummingbird performs pretty well. While the Calliope is an improvement overall, its main advantage is that it is more future-proof and easier to source parts for. We have a mix of both in use and are quite comSC fortable with this. Boosting the output power Fig.7: configure your amplifier power supply like this to keep the ripple currents from recharging the capacitor bank out of the amplifier ground lines. 76 Silicon Chip Australia's electronics magazine If you add extra output devices, you can within reason. But watch the ratings of your capacitors and input devices. If you want serious power, you should consider the SC200 (January-March 2017; siliconchip. au/Series/308), which gives roughly double the output power. Otherwise, the Ultra-LD Mk.3/4 Amplifiers (July-September 2011 & August-October 2015) will give you roughly the same power as the SC200 but with lower distortion. siliconchip.com.au SOnline ilicon Chip Shop Kits, parts and much more www.siliconchip.com.au/Shop/ Rotating Lights April 2025 SMD LED Complete Kit SC7462: $20 TH LED Complete Kit SC7463: $20 USB-C Power Monitor August-September 2025 Short-Form Kit SC7489: $60 USB Power Adaptors May 2025 Complete Kit with choice of USB socket SC7433: $10 siliconchip.au/Article/17930 siliconchip.au/Series/445 siliconchip.au/Article/18112 This kit includes everything needed to build the Rotating Light for Models, except for a power supply and wire. This kit includes all non-optional parts, except the case, lithium-ion cell and glue. It does include the FFC (flat flexible cable) PCB. You can choose from one of four USB sockets (USB-C power only, USB-C power+data, mini-B or micro-B). The kit includes all other parts. Compact HiFi Headphone Amplifier Complete Kit SC6885: $70 PICKit Basic Power Breakout Board September 2025 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. Mic the Mouse Complete Kit SC7508: $37.50 August 2025 siliconchip.au/Article/18637 It includes everything needed to build one Mic the Mouse, except for solder, glue and a CR2032 cell. Complete Kit SC7512: $20 siliconchip.au/Article/18850 Includes the PCB, all onboard parts and a length of clear heatshrink tubing. Jumper wire and glue is 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. Project by Gianni Pallotti These days most mobile phones can play audio files (in formats like MP3 and WAV) but sometimes you just want something simple to play some music or sounds. This circuit uses little other than a Micromite LCD BackPack and a DFPlayer Mini module, and it can play such files from a microSD card. Micromite-based MUSIC PLAYER S ome potential uses for this design include playing sounds or white noise to drown out a noisy environment (such as construction noise), or playing calming music before bedtime, which can benefit some children or those with insomnia or tinnitus. Depending on personal preferences, options like coloured noise, soothing music or natural sounds such as running water, animal sounds or rain can help you to relax and fall asleep easily. A consistent sound, like running water or waves crashing, can help to mask background noises without being intrusive. I have succumbed to tinnitus (commonly known as ringing in the ears) and, after trying some possible solutions, I have found the best one is listening to soft sounds during the silent part of the day and night. Although there are various ways to listen to such sounds, including apps, websites and dedicated devices, I liked the idea of building my own player. I am using it to play the calming patter of rain on a window, soft rustling leaves, birds chirping, plus wind and ocean wave noises. They also help to focus our attention outward rather than on our own anxiety or obsessive thoughts. This project could also function as a digital MP3 music player, capable of storing and playing plenty of songs. The DFPlayer Mini MP3 player module (data sheet: siliconchip.au/ link/ac83) used in this design was described in detail in the article titled “A stamp sized digital audio player” (December 2018; siliconchip. au/­Article/11341). I also used it in a previous design, the Slot Machine project (May 2022; siliconchip.au/ Article/15310). microcontroller and LCD, effectively turning it into an ‘audio BackPack’. For the first two options, most components used are obtainable from the Silicon Chip Online Shop, such as the Micromite LCD BackPack kit (see siliconchip.au/Shop/20/3321) and DFPlayer Mini (siliconchip.au/ Shop/7/4789). The only other required Fig.1: very little needs to be added to a Micromite LCD BackPack to turn it into an audio player. The audio files are stored in MP3 format or similar on a microSD card plugged into the DFPlayer Mini module. Assembly options An enlarged view of the DFPlayer Mini’s underside. The module is shown at actual size in the lead photo. 78 Silicon Chip The circuit is quite basic, as shown in Fig.1. There are three ways to build the Music Player: 1. You can wire up the DFPlayer Mini module and other parts (there are just a few) to a Micromite LCD BackPack using jumper leads or by soldering wires. 2. You can build my small add-on board that hosts the DFPlayer Mini and other parts, and plugs into the LCD BackPack. 3. I have also designed a board that has everything onboard, including the Australia's electronics magazine siliconchip.com.au An empty cotton bud container is an inexpensive way to house the finished project. The add-on board for the Music Player. It’s a simple design due to most of the work being done by the Micromite BackPack. There is a single 1kW resistor on the underside. component is an adaptor for linking the DFPlayer to the BackPack. The optional PCB coded 01110251 (38.5 × 30.5mm) plugs into the BackPack and hosts the DFPlayer Mini plus a handful of other components, making both the construction and wiring easy. The optional all-in-one board, which uses a 2.4-inch touchscreen rather than the 2.8-inch one used on the BackPack, is coded 01110252 and measures 87 × 52mm. Besides connecting the audio player module to the BackPack, both boards also facilitate connections to a loudspeaker and the input power supply. The whole assembly will easily fit inside a small container measuring 110 × 80 × 55mm or so. I have found it very economical to use an empty cotton bud container for this. It costs just $2.99, and you get 200 cotton buds as a bonus! I painted the inside of the clear box to minimise any light from the LEDs on the DFPlayer Mini module showing through it, but you might like that effect. The cutouts required for the LCD panel, speaker, USB power input and on/off switch when using this container are shown in Fig.2. I used a 2.8-inch Micromite LCD BackPack V1 as it’s the simplest and cheapest of the BackPacks that use the 2.8-inch TFT touchscreen. You can use the V2 (with onboard USB interface and PWM backlight dimming) or the V3 (with even more features, although we don’t need any of them here). In the following description, I will assume you are going to use the V1 like I did. As there is no PWM option to reduce Fig.2: these are the cut-outs required in the specified 110 × 80 × 55mm box. You could use a larger box, but will need to adjust the hole positions. the LCD panel backlight on the V1 Micromite LCD BackPack, the unit can simply be placed face-down if you don’t want bright light from the screen. This will have the added advantage of better dispersion from the speaker hole in the rear of the case. If you use the larger all-in-one board, you don’t need to assemble a BackPack; it’s integrated into that design, as shown in the Fig.3 circuit. If you are using the separate BackPack, build the BackPack first, then assemble the add-on board as per Fig.4. 80 Silicon Chip It’s pretty straightforward. If building the all-in-one version, mount the components as per Fig.5 now. For the all-in-one version, either fit the 13W resistor and omit Q1 & Q2 for fixed touchscreen backlight brightness, or omit the 13W resistor and fit Q1 & Q2 for PWM backlight brightness control. Importantly, if your touchscreen has yellow plastic on the 16-pin connectors, it will run at full brightness regardless of the value of the 13W resistor, unless you opt for PWM backlight control. Australia's electronics magazine Note that if you are using Micromite LCD BackPack V3, or the all-in-one PCB with PWM backlight brightness control, by default, the backlight will be driven with a 50% duty cycle. It’s possible to have touchscreen controls to adjust the brightness, but they are not part of the supplied software. So if you want such controls, you will need to add them. Once the board(s) have been assembled, wire them up and mount the components in the case as shown in Fig.6 (overleaf). This shows the wiring siliconchip.com.au Fig.3: this is the simplified circuit of the larger all-in-one PCB that uses the 2.4-inch touchscreen. The other difference is the BUSY signal from the DFPlayer Mini module goes to pin 6 of IC1 instead of pin 24. Fig.4: it’s easy to build the add-on board; it basically exists just to connect the DFPlayer Mini module (via two header sockets) to the BackPack and loudspeaker. Fig.5: this board has all parts onboard so doesn’t require the BackPack, although it’s sized for the 2.4-inch touchscreen rather than 2.8-inch (they have the same pixel resolution). The screen plugs into CON4 & CON5 and mounts on the three tapped spacers. for the add-on board version. Note that the speaker wiring polarity is unimportant. Keep in mind that, if you use a USB-C socket like I did, and it doesn’t have any onboard resistors (most don’t), it isn’t guaranteed to work if you use a Type-C to Type-C cable. It will work with Type-C to Type-A cables, though. If you’ve built the all-in-one version, the USB socket is onboard, so position it to be accessible through the hole in the case. There is no power switch in siliconchip.com.au this case; you unplug it to switch it off. The speaker wiring is the only external wiring required. Software Once the board(s) have been built, assuming the PIC32 chip is programmed with the Micromite firmware, you just need to load the BASIC code onto it. You can do this by using a USB/Serial adaptor or, if your BackPack has a USB socket, via that socket. Refer to the Micromite and BackPack articles for detailed instructions on Australia's electronics magazine doing this. The basic procedure is as follows. You will need a serial terminal program, such as TeraTerm on the Windows operating systems. The AUTOSAVE command is probably the simplest way to load the BASIC code. You will also need to configure the Micromite OPTIONs to enable the LCD panel and touch sensor, then calibrate the touch sensor. If you haven’t used a Micromite processor before, Geoff Graham’s Micromite webpage includes all the April 2026  81 information you might need on the Micromite (see https://geoffg.net/ micromite.html). The Micromite manual, which you can download from that page, includes instructions for configuring LCD touch panels. The BASIC files list the OPTIONs in comments near the start. There are two different files. “Sound Player.bas” is used with the Micromite BackPack PCB, while “Sound Player2.bas” is used with the All-In-One PCB. Parts List – Micromite-based Audio Player Common to all versions 1 plastic box, 110 × 80 × 55mm 1 DFPlayer Mini audio player module [Silicon Chip SC4789] 1 4W 3W miniature loudspeaker [Adafruit 3351] 1 microSD card 1 2-pin right-angle female header socket, 2.54mm pitch 4 10G × 10mm self-tapping screws 4 M3 × 25mm panhead machine screws 4 M3 × 12mm tapped nylon spacers 4 M3 × 3mm untapped nylon spacers 2 M1.6 × 6mm machine screws and nuts 1 50cm length of twin medium-duty red & black cable Operating the Player Add-on PCB version The Micromite program is controlled through touch commands on the LCD screen. All-in-one version These include the following main buttons (see Screen 1): PLAY: start playing a track PAUSE: pause playback of the current track <PREV: play the previous track in the same folder NEXT>: play the following track in the same folder FOLD: change to the next available folder and play the first track −VOL: decrease the volume, from a maximum of 30 down to 0 +VOL: increase the volume, from a minimum of 0 up to 30 1 2.8-inch Micromite LCD BackPack programmed with MMBasic V5.05.05 [SC3321] 1 single-sided PCB coded 01110251, 38.5 × 30.5mm 1 SPST panel-mount switch (toggle or slide) 1 1kW SMD resistor, M2012/0805 size Connectors 1 panel-mount USB socket with breakout board 1 14-pin female header socket, 2.54mm pitch 1 2-pin right-angle header, 2.54mm pitch 1 double-sided PCB coded 01110252, 87 × 52mm 1 2.4-inch ILI9341-based LCD touchscreen module 1 PIC32MX170F256B-50I/SP microcontroller, DIP-28, MMBasic V5.05.05 (IC1) 1 28-pin DIL IC socket (optional; for IC1) 1 MCP1703AT-3302E/MB 3.3V LDO voltage regulator, SOT-89 (REG1) 1 2N7002 N-channel Mosfet, SOT-23 (Q1) 1 AO3401(A) P-channel Mosfet, SOT-23 (Q2) 4 10µF 50V X5R SMD ceramic capacitors, M3216/1206 size 2 100nF 50V X7R SMD ceramic capacitors, M3216/1206 size 1 10kW SMD resistor, M2012/0805 size 3 1kW SMD resistors, M2012/0805 size 1 13W SMD resistor, M2012/0805 size (optional; fixed backlighting; omit Q1 & Q2) Connectors 1 PCB-mounting 4-pin USB mini Type-B miniature socket (CON1) 1 4-pin female header socket, 2.54mm pitch (CON4) 1 14-pin female header socket, 2.54mm pitch (CON5) Screen 1: the default screen of the Audio Player in use. The round buttons provide the following options: PLAY ONCE: play the selected track once only REPLAY: continuous looping of the selected track 2HRS: stop playback after two hours SAVE: saves the current folder, track selection, play mode and volume The SAVE button changes to yellow each time a setting is changed, then reverts to white when the button is touched, confirming that the new settings have been saved. This is a reminder to save the changes. At startup, the stored data (if saved) is loaded and the MP3 is set accordingly. Otherwise, it uses the defaults: volume = 15, folder #1, track #1, no repeat (play once). The list of folders is hard-coded in the Micromite MMBasic program. For example, by default the line is: DIM FolderName(4) As String = (“1-Nature”, ”2-Rain”,”3-Water”, ”4-Wind”,”5-Sounds”) 82 Silicon Chip Australia's electronics magazine siliconchip.com.au The finished Music Player fits neatly in the painted plastic box that the cotton buds came in. Only the red (+) and black (-) wires need to be connected. This is the 3W speaker I used. It works well and I recommend it, but there are plenty of other options. The reason it’s (4) instead of (5) is that there is an index zero, so with a maximum index of 4, up to five strings can be stored. You can change that number, but make sure it’s always one less than the number of folders listed. Each folder can contain as many as 3000 tracks, assuming the SD card has sufficient capacity. If the next folder or previous/next track is not found, the program will revert to the first folder saved on the microSD card, or to the first track in the pre-selected folder. The name of the folder and the track number within the selected folder will show on the LCD panel. The volume setting is shown as a bargraph and as a number next to the graph. Micromite pins 9 & 10 (COM2) are used for the 9600 baud bidirectional serial communications port with the DFPlayer Mini module. The commands sent to the module have been reduced to only the strict requirements, each consisting of three strings: Initiate$ + Function$ + End$. The Function$ string is the main command SC component. Fig.6: how to wire up the add-on module to the BackPack (V1 shown here), speaker, switch and power socket. The wiring for the full board shown in Fig.5 is much simpler, as only the speaker needs to be connected. siliconchip.com.au Australia's electronics magazine April 2026  83 SERVICEMAN’S LOG Going straight for the jug-ular Dave Thompson Home appliances – I love them! So much, in fact, that I have plenty languishing unused in cupboards and often have to have a clear out to make room for more. They make life so much easier for most of us. While the rock stars of the appliance world, such as ovens, refrigerators, dishwashers, washing machines and dryers, all make our usual chores faster and more efficient, it is the unsung heroes that can really make a difference. That’s the backing band of kettles, juicers, mixers and vacuum cleaners. These guys all get a thorough thrashing in the typical household, and are equally stars of the show. We all know that appliances are not made to last anymore; it seems nothing is made for a long service life these days. Still, so many of them are inexpensive and just ‘do the job’. For example, I can buy an electric jug from the local ‘mart’ (insert shop name here) for less than $20. These plastic fantastic models work well and do what they say on the tin – they boil water. Once the plastic taste is boiled out of them, they will give years of service, until they have boiled dry one too many times, or simply get too manky to clean anymore. When that happens – and it will – it’s no big deal to just go and buy another one. Rinse, wash and repeat ad nauseum (and ad infinitum?). These cheap jugs are perfect for a student doss, a worksite, or down in the shed; there is nothing wrong with these ‘consumable’ products. Back in my day, when I walked to school in the snow, bare-footed (and uphill both ways!), my parents ‘invested’ in appliances like a kettle or a bench mixer. Yes, they were more expensive than they are now, and it is true we had limited choices, but these things were well made and built to last (for a lifetime in some cases). The business model was similar to that of a car. By that I mean that you bought the appliance once as they had been made solidly and with longterm use and eventual repairs in mind. There was a backup network of agents, dealers, repair guys and (more importantly) lots of spare parts available, with the intention that their product would provide householders many 84 Silicon Chip years of service and last as long as it was still sensible and viable to repair them. And when you realised that company made good products, presumably you went back and bought more of them, since you wanted your stuff to last. Alas, that effect must not be too strong, because even legendary companies like Toyota seem to be giving up on quality being a selling point (or at least are struggling to maintain consistently high quality these days). My mother had a benchtop mixer made by a well-known brand. She had it for more than 30 years, and Dad kept it going with a bearing here and a motor armature there. Things wear out, especially if they are being used. The point is that he just got onto the agent and bought the parts for it; it was relatively easily repaired. We can still get parts for that mixer even now! But I digress. We’d been through many cheaper electric jugs and decided to splash out on the latest one. It’s a known brand, and while pricey, it is designed, built and supported according to the principles I mentioned above: aesthetically pleasing (and very retro), can be fully disassembled and the parts replaced, and those parts are available worldwide (more on this later!). The company has been around since the early 1900s, so they’ve obviously worked out how to do it well and in keeping with the old-style business model of building things to last. So if it does fail, we can simply repair it. I’ve actually written about this particular jug before (a while ago), where sometimes it wouldn’t ‘reset’ after it had boiled, in the September 2020 issue, starting on page 64 (siliconchip.au/Article/ 14575). Anyway, it eventually settled down and never did that again. However, a short while ago, it started not switching off when the water boiled. While it does seem to take a little longer than some kettles and jugs I’ve had, usually after about 10 seconds of boiling, it used to switch off and Australia's electronics magazine siliconchip.com.au Items Covered This Month • A juggling act • The heat gun that got too hot • Repairing an electric cooktop • An electric fence repair 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 the heating button would click back to its default ‘off’ position. As a test, I let this one boil for a good two or three minutes at a full, rolling boil and it still didn’t stop, so it was time to look into it. The first thing was to get more information. The user manual that comes with it is comprehensive, but doesn’t have much of a troubleshooting section because, well, there’s not a lot to troubleshoot! That section consists of just the basics: Jug doesn’t turn on? Check the power connection and that the jug is seated properly in the cradle, that sort of thing. Obviously, this isn’t much chop at all, so I went looking further afield into forums and user groups in the hope of a service manual. I didn’t find anything, to be honest. The best suggestion, which seems to have worked for some, is to de-scale the appliance. This seemed to me like too simple a resolution. I mean, yes, we all usually need to de-scale appliances, and I’ll admit, in the eight years we’d had it, we had never de-scaled it. Still, I didn’t think we had to if we couldn’t see any obvious signs of scale in the jug. It looked to me to be almost as-new inside. But this is what people were suggesting, so maybe that’s all it was? Perhaps it had clogged up with scale somehow. Of course, I had to then go and buy a de-scaling agent, and there are a surprising number to choose from. There are specialist types for dishwashers, coffee machines, water filters and others, but I only found one supposedly meant for kettles, so that would have to do . I wasn’t about to deep dive into the differences between them all (my hunch is they are likely all the same), so I stuck with that one and got down to de-scaling the jug. Editor’s note: you can also use white vinegar mixed 50/50% with water. Don’t boil it for long; switch it off and let it sit for 30 minutes before emptying, then rinse it thoroughly. Citric acid solution is even better. This highly technical process involves adding the contents of a sachet to the jug, pouring in half a litre of water and boiling it. I let it cool, then tipped out the solution and repeated. This is supposed to break down any limescale or other residues that might clog up the element or thermostat mechanism. This is fine in jugs and kettles that have an exposed element or a sensor inside the boil chamber, but if the element or thermal switch is on the underside of the chamber, it will never get scaly, anyway. To be honest, I didn’t see any difference to the boiling chamber after descaling, and in true fashion, it still didn’t switch off when the water boiled. So, no simple fix for me then! siliconchip.com.au There was no other option but to tear the thing apart and have a look. However, as we were dead in the water without a jug, we ordered another identical one, which was delivered a few days later. I was just hedging our bets; if I could repair the old one (at this point I had no idea if I could), at worst we’d end up with two jugs. Most people would never use two jugs, and I didn’t need two either, so if I did get it working, it would become a spare. It could sit in the cupboard with the other unused machines. But first, I’d have to find out exactly how this one worked. I mean, it’s not complex, but while manufacturers use various methods to control the automatic cut-off, all the ‘cordless’ type kettles appear to use a very similar system. It is simple, efficient and easy to repair, with ready access to whatever element (har!) needs replacing. Of course, different kettles will come apart differently. Some aren’t repairable at all; they are designed to be thrown away, not repaired, and are typically cheap and made of plastic. Luckily, this one is held together like an old aeroplane, with obvious and exposed PK/panhead-style Phillips screws that are all easily accessible. Most hold on the removable bottom cover. Revealing the gubbins is as easy as removing eight screws (some with fibre washers) and involves minimal fettling. I had to remove the on-switch button but then the whole bottom end opened up and this exposed everything I needed to check. As you no doubt already suspect, there isn’t a lot to it. An element, moulded into the metal base of the boil chamber, some fibreglass-coated wiring and a large plastic power socket and switch actuator assembly, which takes up much of the space in the jug base (see the photo overleaf). Of course, all the magic happens in that switch assembly. It is straightforward, meat and three veg technology, but don’t let the apparent simplicity fool you. There’s actually a lot going on in these very clever (and usually reliable) mechanisms. For those who just fill a kettle and switch it on, and don’t know what’s happening in there, here’s a brief kettle primer. In the old days, a metal kettle was put on the gas or electric stove t o Australia's electronics magazine April 2026  85 to heat water, and it whistled when the water boiled and steam started coming out of the small hole in the spout cap. If you left it, it would simply burn dry and be ruined (although that whistle is hard to ignore!). Then someone had the idea of putting an electric element in a kettle body and boiling the water that way – no stove needed. Those old appliances (many still exist) were corded, mains-powered and pretty efficient. However, the exposed elements they used presented problems, especially with scaling, where water impurities harden over time with heat, coating exposed metal surfaces with a hard, white residue. That made the kettle increasingly inefficient over time, not to mention tainting any water boiled in it. Then some bright spark came up with the idea of mounting the element underneath the bottom of the boil chamber, keeping it out of the water and essentially eliminating element scaling. Evolution in action. The next big leap was kettles that switched off by themselves when the water was vigorously boiling. If you forget about it, or get caught up doing something else, your jug wouldn’t boil dry. Otherwise, that would almost certainly burn out the element or even damage the kettle. While some electric kettles had thermostats to help prevent that from happening, the next big thing was already in the works. Soon, along came ‘cordless’ kettles. The term cordless these days usually implies something battery-powered, but in the high-octane world of kettles, this just means the kettle could be picked up from the base that had the mains cord attached, and used without the hassle of a cable dragging behind it as you pour. Despite the sheer number of styles and brands available, the majority of cordless kettles and jugs work in a very similar way. In this one, a thermostat senses the boiling water Most of the space in the base of the kettle is taken up by the switch actuator. 86 Silicon Chip temperature (technically 100°C, though this can change with altitude and water quality), and the power is disconnected automatically while the manually operated switch automatically drops back to the off position. Simple, effective and usually very reliable This jug sits on a circular base unit, which is connected to the mains. When switched on, the switching mechanism connects mains power to the element, which initiates the boiling cycle. When the water boils, steam makes its way down a silicone tube, hidden in the jug’s handle, to the switching mechanism. When it hits the right temperature, it ‘trips’ the switch, disconnects the elements and switches if off. The idea of descaling the jug aims to clear that silicone tube of any scale, which in rare cases can stop it from powering off. Sadly, not in this case. After removing the bottom, I could see a little of the south end of the tube and it looked totally clear. There was really only one possibility left: the thermal switch. This is where the clever bit comes in. Pushing the ‘on’ button sets a plastic swing-arm into a detent (as long as power is applied) and, after connecting the element (and any indicator lights that may be present), it stays that way until it trips off. When setting the mechanism, a bimetal convex (or concave) disc with a hole in the centre for a mounting pin, about the size of a (CR)2032 coin cell, is ‘puckered’ into its non-natural ‘active’ state. When the jug boils, steam is applied to the disc via the silicone tube, and as the disc heats, it simply pops back into its resting state and mechanically resets everything to ‘off’. Simple, yet very effective. Until that disc wears out, which apparently they do. I can ‘set’ the disc and the jug works, and of course I can manually stop it by lifting the switch or taking the jug from the cradle, but it seems that disc won’t return to its default state, no matter how hot it gets. The obvious solution here is to replace that bimetal disc. Unfortunately, that part isn’t available to buy separately. I Australia's electronics magazine siliconchip.com.au mean, they are in general, but I can’t find one specifically for this jug. The only way to buy it is as part of the main switch housing, with the disc already moulded into it. While I imagine there are ways of drilling the plastic centre pin out and replacing the thermostat disc with another, that would require modifying the housing, and there’s no guarantee that would work. There is nothing for it but to buy a whole new housing. My next step was to find a parts supplier in town. I couldn’t find any – although one guy I called said he could order one in, and it would be around $100. That sounded quite steep to me, so I hit the interwebs to see if I could find one elsewhere. Surprisingly, after me talking up the repairability of these appliances, I can only find filters. No elements or switches from their parts outlets anywhere. So, I searched for thirdparty suppliers and found dozens of thermostat assemblies, but nothing that looks anything like this one. Well, that was frustrating. This is a $400 jug, so while $100 plus shipping and tax is likely not too bad for a repair, I still thought I’d be able to get a new switch assembly for less than several times the cost of a whole new cheap jug that includes one! I ended up doing a Google image search and discovered that this looks like a standard Philips part, and I can get one from AliExpress for 20 dollarbucks, including delivery. On closer inspection, it looks identical; all the mounting measurements check out, so I think that’ll do me! It is on its way, and I’m confident it will solve the problem. In the meantime, the old housing is out and on closer inspection, the plastic centre pin is quite worn – I guess the edges of the disc chew away at it each time it is used. Anyway, now we’ll have two jugs! Anyone want a refurbished one for ‘cheap’? Taurus Heat Gun repair Many years ago, I bought a Taurus heat gun from ALDI Special Buys. I’ve used it many times over the years and it has been quite reliable. Just once I had to shorten the power cable slightly after one of the wires broke near the body. Recently, I had just switched it off and put it on the ground when I accidentally bumped it. That somehow switched it back on. I was about to pick it up to turn it off when there was a sudden fireworks display, a heap of smoke and the heat gun stopped. The switch was in the low-speed, low-heat position. I could move it to off, but not to high-speed, high-heat, so it seemed that the switch was damaged. The cheapest replacement heat gun I found was $40, but it had many one-star reviews saying that the case had melted in use. I also ruled out a $50 heat gun that had a lot of one-star reviews saying that it did not even get as hot as a hair dryer; that was useless! So the cheapest decent replacement I could find was $55, and it wasn’t even available locally. Thus, I decided to open up the Taurus heat gun to see what had happened to it. I expected to find everything burnt out, but the damage appeared to be confined to the switch, which was toast. I identified the Active wire coming into the switch, and the low-speed and high-speed wires going to the motor and element. I decided to test the motor and element to see if they still worked. I set things up in a safe way, including a ‘safety switch’ in the mains socket, and plugged the power cord into power Luckily only the switch was damaged when my heat gun stopped working. siliconchip.com.au Australia's electronics magazine April 2026  87 so I could use a jumper wire to connect the Active wire to the low-speed wire. The heat gun burst into life. I did the same with the high-speed wire, and once again, it worked. So it just needed a new switch. I couldn’t find a similar PCB-mounting switch on eBay in Australia, but widening my search to include other countries, I found one for about $8 from China. Further searching using the part number from that result and I found two PCB-mounting switches for $3.99. It took one month for the new switches to arrive. I compared one of the new switches with the old switch, finding that the actuating lever was quite a bit longer and the slider would not sit on the switch correctly. I got my mini hacksaw and, while holding the actuating lever with pliers, cut the excess length off and used a file to smooth the top and chamfer the edges. The slider then sat on top of the switch correctly. But first, I would need to remove the old switch and clean up the circuit board. I de-soldered the old switch and cleaned the soot from the circuit board. I then used a knife to scrape away all the burnt material, leaving a good-sized hole in the circuit board. I soldered on the new switch and used some copper wire to repair the circuit board tracks. With the new switch installed, I reconnected the power cable, reassembled the heat gun and tested it. It was back in working order. So I saved $53 and saved another item from ending up in landfill. Looking further at the destroyed switch, I figured out why it failed. When it was bumped, it was not fully on, with the contacts barely touching, causing them to overheat and arc. Bruce Pierson, Dundathu, Qld. The “Power & Control Relay” board had an IC that looked to have heat stress (the more orange area of the PCB). Electric cooktop repair I was asked to have a quick look at an electric cooktop with ceramic plate heating that wouldn’t switch on. The circuit breaker had been reset a couple of times with no benefit. I volunteered to call in and have a quick look. I checked the cooktop circuit breaker and it was OK. I found the range’s power junction box and determined that mains voltage was getting there. I surmised that the problem was within the touch controls under the glass top. I had to remove the glass sheet to see what was going on, and I discovered two separate PCBs underneath it: the “Touch Control Board” was mounted on top of the “Power and Control Relay Board”. I then discovered a blown 2A fuse on the “Power & Control Relay Board”. Removing the board, I found an IC that had obvious signs 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. 88 Silicon Chip The application circuit for the TinySwitch III (TNY274280) switch-mode IC. of heat stress around it on the PCB, which you can see in the accompanying photo. In desperation, I tried a temporary fuse replacement, which immediately failed. I thought I would simply go ahead and order a new “Power & Relay Board” but no; there were no spares for this 10-year-old cooktop in Australia on any of the sites I checked on the internet! I then took the cooktop home to start further investigations and unfortunately, the IC that was my suspect had its designations lacquered over. Luckily, I could read a few characters in strong light with a magnifying glass and started a search for a data sheet because this circuit was obviously designed to reduce the mains to 12V DC & 5V DC. It was using an IC that I hadn’t come across before; it turned out to be a TinySwitch III coded TNY274-280. I was able to obtain a new one and replace it. I also replaced the 10μF 450V DC capacitor at the input to this IC that sits across the mains bridge rectifier. While buying the replacement parts, I also happened to find a replacement board on AliExpress, so I ordered one. The cooktop is now working again with a new board, but I kept the old board as a spare. On powering it up after the Australia's electronics magazine siliconchip.com.au repair, I found that its 5V DC & 12V DC rails were present and correct. I don’t know what caused the IC to fail, but I suspect the closed space within the cooktop’s metal housing trapping heat contributed. Paul James, Kanwal, NSW. Electric fence repair (Xstop EL500LEDS) Like my dad, I’m scared of high voltages. I was horrified one day when we walked beneath a transmission line and a spark flew between us when we briefly touched. I think his fears were born from being an electrical operator at a terminal station. Scary things happened when possums tried to walk along a multi-hundred-kV bus! I grew up playing with Kettering ignition, but now as a farmer, high voltages are all around me in the form of electric fences. So you can imagine my dread when my electric fence energiser died. The neon voltage indicators stopped working a while ago, but as long as the shed kept emitting “tac… tac… tac”, I knew it was working. Now, however it was going “tic… tic… tic”, which to my experienced ear meant that either there was a dead short in the fence somewhere (usually a 5km round-trip walk to find out), or that it had carked it. The other indicator of fence failure was half of the cow herd in the house paddock. I’ve always wanted a directional fence tester, and I had hoped that one day a circuit would appear in Silicon Chip. I know testers have been published in the past, but I have long made do with a length of three-core mains cord that had been chewed by my Maremma dog. She chewed in linear fashion from the end, so I had a visual gradation in spark through the insulation when I touched the wire to the fence with the safe end grounded. Sadly, on this occasion, no spark. At least the oscillator was working. So the most likely culprits were the 40μF capacitor or the transformer. I needed to have a spare capacitor in stock in case that was it, so I ordered a couple. After swapping it out, there was still no spark. I had a great deal of trouble finding a suitable transformer; I ended up ordering one from Pakton Technologies, who know a bit about electric fences. The transformer wasn’t a direct swap and required some plastic case reshaping. The primary was easily identified by the heavy copper wires. It was a while ago that I learned higher voltage, lower current, so my secondary had lighter gauge. But there were three wires. I chose the pair with the highest resistance. After a bit of cable extending and connector soldering, I shoehorned it into the case. The neon indicator board had a blown 47kW 1W resistor, so I replaced it with a 3W equivalent I had on hand. In doing so, one of the neons disintegrated, so I had to replace that too. I set up a suitable spark gap and stood at arm’s length from the mains power switch. Upon flicking it, I was rewarded with a satisfying, yet strangely disturbing crack... crack... crack sound. A $150 unit was repaired for $80. Also, it provided some entertainment. My neighbour discovered the fence working after testing at my gate with his gluteus maximus… three times! I don’t think I can count on him testing it again in the near future, and I’m still scared of high voltages! SC Ian Oldman, Budgeree, Vic. siliconchip.com.au Australia's electronics magazine April 2026  89 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. 04/26 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 ATtiny85-20PU PIC12F617-I/P 110dB RF Attenuator (Jul22), Basic RF Signal Generator (Jun23) 2m VHF CW/FM Test Generator (Oct23) Graphing Thermometer (Mar26) Active Mains Soft Starter (Feb23), Model Railway Uncoupler (Jul23) Battery-Powered Model Railway Transmitter (Jan25) PIC16F1455-I/P Battery-Powered Model Railway TH Receiver (Jan25) Dual Train Controller (Transmitter / TH Receiver, Oct25) PIC16F1455-I/SL Battery Multi Logger (Feb21), USB-C Serial Adaptor (Jun24) Battery-Powered Model Railway SMD Receiver (Jan25) USB Programmable Frequency Divider (Feb25) Dual Train Controller (SMD Receiver, Oct25) PIC16LF1455-I/P New GPS-Synchronised Analog Clock (Sep22) PIC16F1459-I/P K-Type Thermostat (Nov23), Secure Remote Switch (RX, Dec23) Mains Power-Up Sequencer (Feb24 | repurposed firmware Jul24) 8CH Learning IR Remote (Oct24), Heat Transfer Controller (Aug25) Vacuum Controller (Oct25) PIC16F15214-I/SN Silicon Chirp Cricket (Apr23), Mic The Mouse (Aug25) PIC16F15214-I/P Filament Dryer (Oct24), Tool Safety Timer (May25) PIC16F15224-I/SL Multi-Channel Volume Control (OLED Module; Dec23) NFC IR Keyfob Transmitter (Feb25), Rotating Light (Apr25) PIC16F18126-I/SL DCC Decoder (Dec25), RGB LED Star (Dec25) DCC/DC Stepper Motor Driver (Apr26) PIC16F18146-I/SO Versatile Battery Checker (May25), RGB LED ‘Analog’ Clock (May25) USB-C Power Monitor (Aug25), DCC Remote Controller (Feb26) DCC Booster & Reverse Loop Controller (Mar26) PIC16LF15323-I/SL Remote Mains Switch (TX, Jul22), Secure Remote Switch (TX, Dec23) STM32G030K6T6 Variable Speed Drive Mk2 (Nov24) PIC16F1847-I/P PIC16F18877-I/PT Digital Capacitance Meter (Jan25) Dual-Channel Breadboard PSU Display Adaptor (Dec22) Wideband Fuel Mixture Display (WFMD; Apr23) PIC16F88-I/P Battery Charge Controller (Jun22), Railway Semaphore (Apr22) PIC24FJ256GA702-I/SS Ohmmeter (Aug22), Advanced SMD Test Tweezers (Feb23) ESR Test Tweezers (Jun24) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sep19) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) Advanced GPS Computer (Jun21), Touchscreen Digital Preamp (Sep21) PIC32MX170F256B-I/SO Battery Multi Logger (Feb21), Battery Manager BackPack (Aug21) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) STM32L031F6P6 SmartProbe (Jul25) $20 MICROS ATmega32U4 ATmega644PA-AU PIC32MK0128MCA048 PIC32MX270F256D-50I/PT Wii Nunchuk RGB Light Driver (Mar24) AM-FM DDS Signal Generator (May22) Power LCR Meter (Mar25) Digital Preamplifier (Oct25) $25 MICROS PIC32MX170F256B-50I/SO + PIC16F1455-I/SL Micromite Explore-40 (SC5157, Oct24) PIC32MX470F512H-120/PT Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) PIC32MX470F512L-120/PT Micromite Explore 100 (Sep16) $30 MICROS PIC32MX695F512H-80I/PT Touchscreen Audio Recorder (Jun14) PIC32MZ2048EFH064-I/PT DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20), Dual Hybrid Supply (Feb22) KITS, SPECIALISED COMPONENTS ETC PICOSDR SHORTWAVE RECEIVER (APR 26) STEPPER MOTOR DRIVER KIT (SC7601) (APR 26) CALLIOPE AMPLIFIER PARTS (SC6021) (APR 26) MICROMITE MUSIC PLAYER (APR 26) - 128×64-pixel 0.96in OLED screen with SSD1306 controller (SC6176) - 3.5in LCD module with ILI9488 controller (SC5062) Includes all required parts for DCC or DC mode (see p55, Apr26) Includes some of the harder-to-get transistors, resistors and a capacitor Micromite BackPack V2 Kit (SC4237): ready to load the BASIC code, 3mm acrylic lid is included but isn’t required for the project - DFPlayer Mini module (SC4789) DCC BOOSTER / REVERSE LOOP CONTROLLER KIT (SC7579) $10.00 $35.00 $35.00 $15.00 $70.00 $6.00 (MAR 26) Includes all required parts, except for the Jiffy box, OLED screen (see below), power supply and front panel (see p58, Mar26) - 0.91-inch OLED screen (SC7484) siliconchip.com.au/Shop/ RP2350B COMPUTER (NOV 25) Assembled Board: a fully-assembled PCB with all non-optional components, front and rear panels are sold separately below (SC7531; see p28, Nov25) - front & rear panels (SC7532) - 8MiB APS6404L-3SQR-SN PSRAM SOIC-8 IC (SC7530) DUAL TRAIN CONTROLLER MICROCONTROLLERS (OCT 25) PICKIT BASIC POWER BREAKOUT KIT (SC7512) (SEP 25) RP2350B DEVELOPMENT BOARD (AUG 25) - PIC16F1455-I/P programmed with 0911024D.HEX (Transmitter) - PIC16F1455-I/P programmed with 0911024S(or T).HEX (Receiver, TH) - PIC16F1455-I/SL programmed with 0911024S(or T).HEX (Receiver, SMD) firmware ending with “S.HEX” is for train 1, while “T.HEX” is for train 2 Includes all parts except the jumper wire and glue (see p39, Sep25) DCC REMOTE CONTROLLER KIT (SC7552) (FEB 26) Assembled Board: a pre-assembled PCB with all mandatory parts fitted, optional components are sold separately below (SC7514; see p49, Aug25) - 40-pin header (two are required, SC3189) - 8MiB APS6404L-3SQR-SN PSRAM SOIC-8 IC (SC7530) MAINS HUM NOTCH FILTER (SC7598) (FEB 26) Includes all parts except a CR2032 cell (see p64, Aug25) $45.00 $7.50 Includes all required parts, except for the case and wire/cable (see p63, Feb26) $35.00 MIC THE MOUSE KIT (SC7508) (AUG 25) USB-C POWER MONITOR KIT (SC7489) (AUG 25) Includes everything but the plastic case, power supply and some optional parts. The Pico 2 is supplied but not programmed (see p39, Jan26) $90.00 433MHz RECEIVER KIT (SC7447) (JUN 25) RGB LED STAR KIT (SC7535) (DEC 25) VERSATILE BATTERY CHECKER KIT (SC7465) (MAY 25) EARTH RADIO KIT (SC7582) (DEC 25) RGB LED ‘ANALOG’ CLOCK KIT (SC7416) (MAY 25) USB POWER ADAPTOR COMPLETE KIT (SC7433) (MAY 25) Includes everything except for the case and power supply (see p53, Feb26) DCC BASE STATION KIT (SC7539) Includes the mostly-assembled board and all non-optional components except the power supply (see p43, Dec25) Includes everything to build the radio itself except the case and battery, plus the plug for the antenna (see p65, Dec25) DCC DECODER KIT (SC7524) Includes everything in the parts list (see p73, Dec25) $50.00 Includes all non-optional parts except the case, cell & glue (see p39, Aug25) (JAN 26) $80.00 $55.00 (DEC 25) $25.00 Includes the PCB and all onboard parts (see p66, Jun25) Includes everything in the parts list (including the case), except the optional components, batteries and glue (see p30, May25) $90.00 $7.50 $5.00 $10.00 $10.00 $10.00 $20.00 $30.00 $1.00ea $5.00 $37.50 $60.00 $20.00 $65.00 Includes all the parts except the power supply. When buying the kit select either a BZ-121 GPS module or Pico W (unprogrammed) for the time source (see p66, May25) $65.00 Includes everything in the parts list and a choice of one USB socket: USB-C power only; USB-C power+data; Type-B mini; or Type-B micro (see p80, May25) $10.00 *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. PRINTED CIRCUIT BOARDS & CASE PIECES PRINTED CIRCUIT BOARD TO SUIT PROJECT WATERING SYSTEM CONTROLLER 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 ↳ 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) ARDUINO FOR ARDUINIANS (PACK OF SIX PCBS) ↳ PROJECT 27 PCB WII NUNCHUK RGB LIGHT DRIVER (BLACK) 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) DATE AUG23 SEP23 SEP23 SEP23 OCT22 SEP23 OCT23 OCT23 OCT23 OCT23 OCT23 NOV23 NOV23 NOV23 NOV23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 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 PCB CODE 15110231 01109231 24105231 04105223 04105222 04107222 06107231 24108231 24108232 24108233 24108234 04108231/2 10111231 SC6868 SC6866 01111221 01111222 01111223 10109231 10109232 10109233 18101231 18101241 18101242 18101243 18101244 18101245 18101246 19101241 19101242 07111231 07111232 01110231 01110232 09101241 09101242 16102241 16102242 07112231 07112232 07112233 SC6903 SC6904 16103241 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 Price $12.50 $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 $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 $7.50 $20.00 $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 For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT 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 5MHZ 40A CURRENT PROBE (BLACK) BATTERY MODEL RAILWAY TRANSMITTER ↳ THROUGH-HOLE (TH) RECEIVER ↳ SMD RECEIVER ↳ CHARGER USB PROGRAMMABLE FREQUENCY DIVIDER HIGH-BANDWIDTH DIFFERENTIAL PROBE NFC IR KEYFOB TRANSMITTER POWER LCR METER WAVEFORM GENERATOR PICO 2 AUDIO ANALYSER (BLACK) PICO/2/COMPUTER ↳ FRONT & REAR PANELS (BLACK) ROTATING LIGHT (BLACK) 433MHZ TRANSMITTER VERSATILE BATTERY CHECKER ↳ FRONT PANEL (BLACK, 0.8mm) TOOL SAFETY TIMER RGB LED ANALOG CLOCK (BLACK) USB POWER ADAPTOR (BLACK, 1mm) HWS SOLAR DIVERTER PCB & INSULATING PANELS SSB SHORTWAVE RECEIVER PCB SET ↳ FRONT PANEL (BLACK) 433MHz RECEIVER SMARTPROBE ↳ SWD PROGRAMMING ADAPTOR DUCTED HEAT TRANSFER CONTROLLER ↳ TEMPERATURE SENSOR ADAPTOR ↳ CONTROL PANEL MIC THE MOUSE (PCB SET, WHITE) USB-C POWER MONITOR (PCB SET, INCLUDES FFC) HOME AUTOMATION SATELLITE PICKIT BASIC POWER BREAKOUT DUAL TRAIN CONTROLLER TRANSMITTER DIGITAL PREAMPLIFIER MAIN PCB (4 LAYERS) ↳ FRONT PANEL CONTROL ↳ POWER SUPPLY VACUUM CONTROLLER MAIN PCB ↳ BLAST GATE ADAPTOR POWER RAIL PROBE RGB LED STAR EARTH RADIO DCC DECODER DCC BASE STATION MAIN PCB ↳ FRONT PANEL REMOTE SPEAKER SWITCH ↳ CONTROL PANEL DCC REMOTE CONTROLLER MAINS HUM NOTCH FILTER MAINS LED INDICATOR DCC BOOSTER / REVERSE LOOP CONTROLLER ↳ FRONT PANEL SOLAR PANEL PROTECTOR (WHITE) GRAPHING THERMOMETER DATE OCT24 OCT24 NOV24 NOV24 NOV24 DEC24 DEC24 DEC24 DEC24 DEC24 JAN25 JAN25 JAN25 JAN25 JAN25 JAN25 FEB25 FEB25 FEB25 MAR25 MAR25 MAR25 APR25 APR25 APR25 APR25 MAY25 MAY25 MAY25 MAY25 MAY25 JUN25 JUN25 JUN25 JUN25 JUL25 JUL25 AUG25 AUG25 AUG25 AUG25 AUG25 SEP25 SEP25 OCT25 OCT25 OCT25 OCT25 OCT25 OCT25 NOV25 DEC25 DEC25 DEC25 JAN26 JAN26 JAN26 JAN26 FEB26 FEB26 FEB26 MAR26 MAR26 MAR26 MAR26 PCB CODE Price 28110241 $7.50 18109241 $5.00 11111241 $15.00 08107241/2 $5.00 01111241 $10.00 01103241 $7.50 9047-01 $5.00 07112234 $5.00 07112235 $2.50 07112238 $2.50 04111241 $5.00 9049-01 $5.00 09110241 $2.50 09110242 $2.50 09110243 $2.50 09110244 $2.50 04108241 $5.00 9015-D $5.00 15109231 $2.50 04103251 $10.00 04104251 $5.00 04107231 $5.00 07104251 $5.00 07104252/3 $10.00 09101251 $2.50 15103251 $2.50 11104251 $5.00 11104252 $7.50 10104251 $5.00 19101251 $15.00 18101251 $2.50 18110241 $20.00 CSE250202-3 $15.00 CSE250204 $7.50 15103252 $2.50 P9054-04 $5.00 P9045-A $2.50 17101251 $10.00 17101252 $2.50 17101253 $2.50 SC7528 $7.50 SC7527 $7.50 15104251 $3.50 18106251 $2.00 09110245 $3.00 01107251 $30.00 01107252 $2.50 01107253 $7.50 10109251 $10.00 10109252 $2.50 P9058-1-C $5.00 16112251 $12.50 06110251 $5.00 09111241 $2.50 09111243 $5.00 09111244 $5.00 01106251 $5.00 01106252 $2.50 09111245 $5.00 01003261 $7.50 10111251 $2.50 09111248 $5.00 09111249 $5.00 17112251 $7.50 04102261 $3.00 PICOSDR CONTROL PCB ↳ RF PCB ↳ FRONT PANEL (BLACK) DCC/DC STEPPER MOTOR DRIVER CALLIOPE AMPLIFIER MICROMITE AUDIO PLAYER ADD-ON ↳ ALL-IN-ONE APR26 APR26 APR26 APR26 APR26 APR26 APR26 CSE251101 CSE251102 CSE251103 09111242 01111212 01110251 01110252 NEW PCBs $5.00 $5.00 $7.50 $2.00 $5.00 $2.50 $5.00 We also sell the Silicon Chip PDFs on USB, RTV&H USB, Vintage Radio USB and more at siliconchip.com.au/Shop/3 Vintage Electronics The Tektronix 2465B Oscilloscope and electrolytic capacitor ageing The 2465B is an analog oscilloscope but with digital supporting infrastructure. Because of this, it has many features of a digital ‘scope, but without any sampling or aliasing concerns. By Dr Hugo Holden I t has calibrated frequency, time and voltage cursors and a memory for the scope’s panel settings. There is also an on-screen digital display, but otherwise, it behaves like an analog oscilloscope. It was rated for a bandwidth of 400MHz, but testing with a levelled sinewave generator and 50W termination shows that it is flat to 400MHz and only 3dB down by about 600-650MHz. Its trigger circuits are so good that you can visualise and lock a 900MHz waveform. Of course, at that frequency, the amplitude calibration is meaningless. I used it to diagnose and repair UHF TV tuners. It can also be configured for four-channel use, which comes in very handy fault-finding logic circuits. The scope is a masterpiece of application-­specific ICs (ASIC). Tektronix called them ‘hybrids’. They optimised every stage and function with dedicated ASICs and other ICs they designed themselves. The main multi-layer board is nothing short of awe-inspiring (Photo 1). Tektronix also designed and manufactured the CRT, a highly complex process. It is a shame that no company in the world now manufactures or 92 Silicon Chip repairs CRTs. This CRT is an extravaganza of precision metallurgy, glasswork and phosphor coating, all created by complex industrial processes. This article focuses on the oscilloscope’s power supply unit (PSU). It is a mixed switching and linear power supply. For a scope made in the late 1980s, the question is: do all the electrolytic capacitors in the power supply need changing now that they are 35 years old? It is an interesting question, especially for a product where the designers sought in the first instance to use the highest-quality parts. The oldest 2465B I have was made in 1989. The last time I powered it on, about a year ago, it was 100% functional. This time, it was totally dead. I performed the usual initial checks and found that power was being applied, and none of the fuses were blown. What could have caused it to fail? A2A1 Board A3 Inverter Board Photo 2: the power supply boards inside the chassis. Australia's electronics magazine siliconchip.com.au Photo 1: this is what you’re greeted with when you first open the case of the 2465B. The PSU is buried inside the scope. Once the chassis is slid out of its outer shell, you are greeted with a top screening cover. With the cover removed, there is some access to the PSU. Two boards are sandwiched together with a series of long goldplated plug-pins that connect the two PCBs. The lower A3 inverter PCB largely processes the mains voltage (Photo 2). There are some line input filter circuit components on the upper A2A1 board, where the power on/off switch, NTC surge suppressor and X2 EMI filter capacitors are located. However, the A2A1 board primarily handles the low-voltage side of things. With the PSU unit mounted in the scope, the access to the A3 inverter board is very poor. An aluminium shield partially covers it too. It is not practical to gain access to most of the PCB’s components initially. Photo 3: the A2A1 board removed from the chassis. Its construction, particularly the components used, changed somewhat over time. siliconchip.com.au Australia's electronics magazine One solution is to remove the whole assembly, attach flying leads to various test points and re-fit the PSU to the scope. In many cases (not all), it is better, if possible, to diagnose the PSU with it connected to its standard loads in the scope. This is the case with most SMPS repairs, unless specific dummy loads are substituted. Another method is extension leads for the supply’s output connectors, if you have them on hand. Notice the green-jacket 100μF/25V electrolytic capacitors in Photos 2 & 3. These are high-quality 105°C Nichicon parts. There are three on the A3 board and five on the A2A1 board. A year or two later, Tektronix moved to 100μF/50V Nichicon types with a brown jacket. Clearly, they had a lot of confidence in these Japanese capacitors. The blue-jacket capacitors (which sometimes have a clear jacket) are American made 180μF/40V and 250μF/20V 105°C types. The two brown-jacket electrolytic capacitors on this board are 10μF/100V parts, which seldom if ever give any trouble. The smaller electrolytic capacitors with black jackets are April 2026  93 Fig.1: part of the 2465B’s power supply circuit. 94 Silicon Chip Australia's electronics magazine siliconchip.com.au Photo 4: note the two large 200V capacitors inside the black insulating box on the right. C1025 1μF/50V bipolar types, which appear very reliable. If they require replacement, I recommend using 1μF/63V MKT capacitors instead. The two small dark-blue-jacket capacitors are 47μF/25V Nichicon types that, in my scopes at least, are still OK. On the right-hand side, where the mains power is initially processed and rectified, is a pair of Rifa 0.068μF X2 capacitors; more on those later. The A3 inverter board shown in Photo 5 is a 1990 vintage specimen, when they had moved to 100μF/50V brown jacket Nichicon capacitors. This board also contains some Rifa Y capacitors. On the right in Photo 4, there two large blue radial capacitors in a black plastic carrier. These are the main filter capacitors on the bridge rectifier outputs. In every 2465B scope I have assessed, these 290μF/200V parts have been perfectly normal, with an ESR of about 0.04-0.06W, no electrical or electrolyte leakage and replacement was not required. Along with other high-voltage electrolytic capacitors in the 2465B scope, these appear, for reasons unknown, to have much better longevity than the lower-voltage-rated electrolytics. It likely relates to the lower ripple currents that higher voltage parts experience. In terms of capacitor failures in the 2465B, the surface-mount electrolytics, if present, fail first on the A5 computer board (due to electrolyte leakage), followed by a similar problem with the 100μF/25V green-jacket Nichicon parts. Some A5 boards were fitted with tantalum capacitors, and while they can fail short-circuit, they don’t usually leak corrosive liquid. The horizontally mounted radial capacitor under the plastic carrier on the right-hand side of Photo 4 is designated C1025 and relates to the power supply’s initial start-up function. This capacitor was stopping my oldest 1989 vintage 2465B scope from powering up (although the one in that scope had a green jacket, rather than blue). The 0.068μF X2 Rifa capacitors had failed on the A2A1 board on this scope in the past, evolving smoke, and had been replaced. This is a common problem because the plastic casings crack and they absorb moisture as they are a metallised paper type. They swell up, opening the cracks further until they become conductive and burn. The partial PSU circuit is shown in Fig.1. The area shaded in blue is what we are concerned about. The incoming mains voltage was normal and the two large filter capacitors charged up. However, the prer­ egulator buck converter based on Photos 5 & 6: a later inverter board, from around 1990 (left). A close-up of some of the troublesome capacitors (right). siliconchip.com.au Australia's electronics magazine April 2026  95 Photo 7: this one had clearly been leaking through its rubber bung. Fig.2: a litmus strip changes colour depending on the pH of the solution it’s soaked in. Comparing it to this chart gives the reading. Q1050 (an IRF820 Mosfet) and the TL494 driver IC was not running. I connected extension wires to the gate and drain of Q1050 and, using a Tektronix 222PS scope (with isolated inputs), I found that there were no gate drive pulses. This buck converter supplies the pre-regulated potential to the primary windings of the main inverter transformer, T1060. The power supply system is moderately elaborate in that the switching drive pulses to Q1050 are modulated in their duty cycle at power-up to give a soft start and avoid current surges. Like many mains-powered switchmode supplies, this circuitry needs a way to get started. In this case, current sourced from the main bridge rectifier flows via 270kW resistor R1020 and a start-up circuit to get the driver IC (U1030) running. Once oscillations are established, the power for the start-up circuit and U1030 is derived instead from pins 7 & 6 of the buck converter’s own transformer, T1020. However, when the power is initially applied, capacitor C1025 (100μF/25V) is charged toward the rectified mains voltage via R1020. The voltage at the base of Q1022 follows at a level determined by the voltage divider composed of R1022 (100kW), R1024 (47kW) and the load provided by IC U1030, which is likely significantly lower than 47kW. This forms about a 1/3 voltage divider. When the voltage across C1025 reaches about 21.5V, Q1022’s base gets to around 6.9V (21.5V ÷ 3). This overcomes the 6.2V zener voltage and Q1022’s base-emitter voltage, and Q1022 switches on, biasing on Q1021, and then both transistors then remain 96 Silicon Chip Photo 8: at a certain angle, a small amount of fluid could be seen under some components. saturated. This effectively places R1024 in parallel with R1022, which reinforces the initial base drive current to Q1022. One job of R1024 appears to be to add some hysteresis to the switch-on function of Q1022 and Q1021. The initial positive voltage supply to the pre-regulator IC U1030 is then established via CR1023. If the pre-regulator IC (U1030) starts and runs, capacitor C1025 is recharged via CR1022 and the buck transformer, and it stays at 13.2V However, after this start-up process, the pre-regulator IC draws current from capacitor C1025 and its terminal voltage drops. If the pre-regulator IC and buck converter circuit didn’t run, for any reason, the voltage across CR1025 diode drops to about 8V. This causes Q1022 and Q1021 to switch off. Under a fault condition, this start cycle repeats. In other words, the start circuit becomes a relaxation oscillator in the event of a failure. My initial tests showed that this was not happening either; there was no activity of any kind in the power-up circuit. The likely culprit was the 100μF/25V electrolytic capacitor, C1025 (see Photo 7). A quick check showed its ESR was a little high compared to a new part. Initially, I had not noticed a couple of telltale signs on the PCB in the area of the start-up circuit. However, while manipulating the PCB at a certain angle to the light, there appeared to be a fluid meniscus under several components below C1025, R1025, R1024 and R1023, along with CR1023, VR1020, Q1021 and Q1022 (see Photo 8). In essence, the whole area shaded mauve in Fig.1 had become a Australia's electronics magazine conductive blanket from leaked electrolyte from C1025. To get Q1022 into conduction, its base voltage has to initially exceed around 6.9V. A leakage with a resistance no higher than 25kW across the 47kW resistor would prevent that. It was either that, or the leaked electrolyte was shunting current from the base of Q1022 to ground. In addition to leakage, the electrolyte had caused component lead corrosion. Leaking electrolyte from the base of capacitor C1025 was easy to see after it was removed for inspection. Despite this, the capacitor measured normally, at close to 100μF on my capacitance meter. The rubber bung in the base was softened, swollen and electrically conductive. I tore the corner off a piece of A4 paper to soak up the fluid under the components. It was yellow and a quick test with my meter probes indicated it was quite electrically conductive. The resistance measured in the order of 100kW across a small section of the soaked paper. Inside the capacitor, the electrical leakage effect of the electrolyte is greatly reduced by the fact that one of the foils is covered in aluminium oxide, which is an insulator. The other 100μF/25V green Nichicon capacitors I had removed, on testing with 20V applied via a 560kW resistor for 15 minutes, had a leakage of only 1.5μA, corresponding to a leakage resistance of about 13.3MW. Further investigations I tested the pH of electrolyte from inside another of the green 100μF/25V Nichicon capacitors and it had a pH siliconchip.com.au very close to 6-7. This is similar to other new capacitors I have tested; I see 7-8 with some brands, so there is variation in electrolyte formulations. I then tested the paper soaked in the leaked electrolyte. It was quite alkaline, with a pH around 9 (see Fig.2). I also put a sample of the A4 paper I had used in another bag and it was neutral (pH = 7). Not only is an alkaline solution corrosive, it is much more electrically conductive than a neutral solution, explaining the relatively low resistance I measured. I presume this is due to the electrolyte sitting on the PCB for a while, in contact with lead, tin (solder) and copper (leads, PCB tracks). This is not unexpected because, when metals are dissolved by weak acids, the result is an alkaline solution. When an acid and a metal react, the metal gives electrons to the H+ protons to form hydrogen gas. The oxidised metal (now positively charged) combines with the acid’s negatively charged anions to form a salt. Most soluble salts derived from weak acids form alkaline solutions. This is because the anions in the salt accept H+ protons from water. This leaves hydroxide ions (OH−) in the water. For example, a lead borate solution has a pH of 8.6 and a tin borate solution a similar value. There was little copper corrosion yet, in this case, but copper borate has a pH of about 9. These may seem like small differences from a neutral pH of 7 but remember that it’s a logarithmic scale; if you add or subtract one from the pH value, you are changing the ion concentration by a factor of 10! So a solution with a pH of 9 has 100 times as many OH− ions available as a neutral solution. Pure water (pH = 7) has the lowest electrical conductivity compared to alkaline (pH > 7) or acidic (pH < 7) solutions. As a solution becomes more acidic below pH = 7, it becomes more electrically conductive because of the higher number of aqueous H+ protons. Similarly, as it becomes more basic above pH = 7, there are more hydroxide OH− anions, again making it more conductive. Manufacturers of electrolyte solutions generally have tried to keep the pH of the electrolyte as close to neutral as possible, although most are a little acidic. Ageing effects inside the capacitors, especially where H+ has siliconchip.com.au reacted with the aluminium to evolve hydrogen gas, result in a shift toward a higher pH, so the electrolyte becomes more alkaline. Loss of hydrogen by way of gas evolution is obviously bad for the capacitor’s chemistry; a domed top is a sign of it. If the electrolyte leaks out of a capacitor, there are four main concerns: 1. The electrical effects of the electrolyte on the circuit. 2. Short- and long-term damage to components. 3. Short- and long-term damage to the PCB. 4. How to safely remove the electrolyte and avoid further failures. Electrical effects on circuits In this case, the circuitry involved was relatively ‘high resistance’ in that the resistor primarily dependent for raising the base voltage of the transistor Q1022 has a value of 100kW and the source resistance charging the capacitor is also high at 270kW. However, low-resistance circuitry, below say 10kW, could have electrolyte leaked all over it with possibly no apparent fault until the resulting corrosion becomes severe. In many ways, the fact this start-up circuit failed relatively early after the electrolyte leaked was a blessing, because significant corrosion damage was yet to occur. It must have been relatively recent leakage because most of it was still wet. Damage to components This must be considered in a cleanup operation. Corrosion can occur where tin-plated copper leads enter a resistor’s body, which is often made of ceramic with a metallised coating. As this continues, it expands, increasing its physical volume. This can result in the component failing at a later date. In extreme cases, the expansion can crack the entire resistor or component body. Electrolyte leaked from capacitors can also eat through the conductive films on surface-mount resistors, rendering them open-circuit. In my case, corrosion had already entered the ends of the resistor bodies. Although the 3kW, 1.2kW and 47kW resistors tested OK, I replaced them to be safe. The 100kW resistor also had one leg affected. I also replaced both diodes, the zener with a 1N4735A and the plain diode with a 1N4148 (see Photo 9). PCB damage Unfortunately, the PCB’s conformal coating (typically green) is not a total barrier to a contaminated electrolyte and its corrosive effects. The coating breaks down after a period of exposure to the electrolyte, and the copper under it beginning to corrode. With voltages applied to copper tracks, the copper corrosion is accelerated by electrolysis, and fine tracks can be eaten completely away. If you find tracks that are fully corroded through, likely the electrolyte leak occurred many months beforehand and the instrument remained powered after that for a considerable time. After the electrolyte has been in contact with solder for a while, the Mild conformal coating and track damage Photo 9: the leaked electrolyte had already corroded some tracks and component leads. Australia's electronics magazine April 2026  97 solder loses its shiny metallic surface and acquires a grey oxide like coating. The coating is a thermal insulator and can sometimes make the component difficult to desolder unless its surface is scraped down and fresh solder is added. PCB cleanup methods While a PCB can be cleaned with contact cleaner, this does not help the green conformal coating where the electrolyte has absorbed into the full thickness, with moisture and ionic species filling microscopic voids in the coating. If two adjacent tracks are disconnected from any components and the coating between them has previously been in contact with electrolyte, testing will show electrical leakage between the tracks. This is evident even after the surface of the coating has been thoroughly cleaned with contact cleaner. While the coating might look normal, it is no longer an electrical insulator. One remedy some have tried is to remove the coating by scraping it off or dissolving it with methylene chloride, but this ruins the appearance of the board. Also, methylene chloride is toxic and difficult to get in some localities, and restricted for public use. I prefer to use a leaching method to remove the electrolyte but it requires some patience. It involves letting a thin stream of warm-to-hot water run over the affected area of the board for at least a half an hour (ideally an hour). The retained ions migrate from the coating into the water and are washed away. If deionised water is available, it is superior to tap water for this. After that, standard contact cleaners (IPA etc) can be used to clean the water off the board. Ideally, the stream of water runs off the nearest corner of the board, with the board held a 45° angle. The whole board is not dunked in water. Although that can leach out ions, there are components than can absorb water and they will be very difficult to dry out. You could damage them that way. Some people have put PCBs in dishwashers to clean them, but it can damage parts, especially items such as trimcaps, some transformers, DIP switches, IC sockets etc. Thus, I never do it. In this case, because the plastic carrier was screwed to the PCB in the area being washed, I had to release the nuts from the carrier, to lift it away from the board surface a little, or water could have become trapped in that area around the stud’s threads. Component replacement I removed all five 100μF/25V green Nichicon capacitors from the A2A1 board and the three from the A3 board for inspection and testing. Some of the capacitors had visible electrolyte leakage. Others had conductive bungs, as revealed by a DVM on its ohms range. This is something not all technicians are aware of. If an electrolytic capacitor has leaked electrolyte in the past, it renders the surface of the rubber bung in the capacitor’s base electrically conductive, which is easily picked up with a DVM. The removed green-jacket 100μF/ 25V Nichicon capacitors all had higher ESR values than a range of new parts with similar ratings, and two of them had an ESR higher than the worst-case figure of 0.5W suggested by the ESR meter’s guidelines. The damage on the A2A1 board indicated that one capacitor had probably been leaking for longer than the one that caused the failure preventing the scope from powering up. There was damage to the board’s conformal coating, and the electrolyte had started to attack the copper traces. Also, where the electrolyte had dried out, there were white crystalline deposits. Failure or degradation of the rubber seal is one of the reasons why electrolytic capacitors leak. The leakage can also be encouraged by hydrogen gas evolution, pressurising the contents, and in many cases, doming the top of the capacitor. However, for these particular Nichicon capacitors, all their tops were perfectly flat. Thus I think they are failing due to drying out. In another instrument, a 1000μF capacitor dried out completely and failed. There was no evidence of any electrolyte leakage; it had lost nearly all capacitance and went to a very high ESR. I opened it up for inspection and found that it was as dry as parchment paper inside. As an experiment, I placed it in a container of deionised water for a few hours. It returned to a normal capacitance value and a normal ESR. It appears that the seals can partially fail to the extent that water vapour can escape in some cases, but not fluid. Comparison to another scope Photo 10: a close-up of some of the corroded tracks (circled in red). The solder mask helps, but it doesn’t stop the damage! I stripped down another PSU unit from a low-power-on-hours Tektronix scope for examination. This time, the green Nichicon capacitors had a date code of 8930. Their rubber bungs were in good order, without softening, and they were not electrically conductive. Their ESRs were a little above the normal range compared to new parts tested, but within the 0.5W guideline, and there was no significant electrical leakage. So they were probably OK. Likely, in the next five years or so, they will also leak and damage components and the PCB, so I elected to replace them anyway. So apart from the date of manufacture, the amount of running time is Australia's electronics magazine siliconchip.com.au 98 Silicon Chip Photo 11: the repaired inverter board, after I replaced all the troublesome capacitors with new ones from Nichicon. the other main factor that determines when the capacitor spills out its electrolyte. Indicators of a failed electrolytic capacitor include: 1. Visible electrolyte around the capacitor or corrosion of tracks and adjacent components. Loss of a metallic shine on nearby solder. 2. Damage to the conformal coating and tracks directly under the capacitor. 3. Visible fluid leakage on capacitor’s rubber bung. 4. The rubber bung has become conductive. 5. Softening or disintegration of the rubber bung. 6. ESR above the normal range for similar new parts. 7. If a capacitor of exactly same type has leaked elsewhere. 8. A very old device or a unit with long running hours Less reliable indicators are: 1. Measured capacitance outside of the normal range. 2. High electrical leakage. 3. Capacitor has a domed top. Returning to the 2465B I decided that the other capacitors on the A3 board should also be replaced. The manufacturer had attempted to ‘leak proof’ them by gluing resin over the rubber bungs. This appeared to have worked, except that in one case, some electrolyte had passed through the bung and around the sides of the leads as they exited through the section of resin. For that capacitor, again the ESR was a little on the high side compared to new parts. I removed the red-brown siliconchip.com.au resin from one of the blue capacitors to inspect the rubber bung and test its electrolyte. On the capacitance meter, the 250μF 20V part read 330μF, or abut 1.32 times its marked value. The 180μF capacitor also measured about 1.45 times its marked value. I opened one for pH testing and found it had an alkaline electrolyte, with a pH of 8. Interestingly, an increase in capacitance can be a marker of increased hydroxides in the capacitor. I performed an electrical leakage test on one of the 250μF/20V parts and found that its leakage current was low, at less than 2μA with 20V applied after 30 minutes, which is acceptable. However, a new part’s leakage current tested at 0.2μA, an order of magnitude lower. Rather than buying different values, I decided it would be reasonable to replace all of these with new 330μF/50V 125°C-rated Nichicon BT series capacitors, which have a rated ESR of 0.02W. These are similar to milspec parts. They can be recognised by their pale blue jackets. I replaced the original 100μF/25V parts with the 100μF/50V capacitors, as Tektronix did in their later model 2465B scopes. Photo 11 shows one board recapped with the new capacitors, including replacement ceramic Y-type capacitors. Should any electrolytic caps be left unchanged on the A2A1 or A3 boards? There are a few 10μF high-­ voltage electrolytic capacitors on these boards. The main filter caps in these scopes don’t appear to have any Australia's electronics magazine problems in the four scopes I own. For now, I have left these ones in place for observation. There are also some small electrolytic capacitors elsewhere in the PSU. They are elevated a little off the PCB on their leads and are easy to inspect and not prone to physical leaking or other failure modes, yet. To inspect these, apart from ESR testing, look closely at the solder on their tracks. The X2 & Y capacitor dilemma The 35+ year old Rifa capacitors should always be replaced because their outer plastic casings crack. They absorb moisture and swell up widening the cracks. The positive feedback continues until the X2 capacitors become electrically conductive, heat up and burn, evolving copious smoke and making a mess on the PCB. The internet is awash with stories about smoking Rifa X2 capacitors. When they were new, they were good performers. 30 years down the line, though, trouble can start. It may simply be that they were not designed for long service. So I don’t judge the Rifa parts too harshly. I previously replaced the two 68nF Rifa X2 capacitors in the mains voltage input area on the A2A1 board on all my scopes. It is better to move away from a metallised paper film product and use plastic film X2-rated parts. I fitted Wima MKP (polypropylene film) or other plastic film 100nF types instead. However, there are three other Rifa capacitors on the A3 board that now have surface cracking and swelling in April 2026  99 Photo 12: the rear of the Tektronix 2465B oscilloscope. connector. You can generally trust the X and Y capacitors inside that unit; being sealed in a metal enclosure, there is no risk of smoke or fire. In summary, for replacing the X2 capacitor, I prefer Wima X2-class film parts, and for the Y-class, capacitors I use Y2-class (labelled) ceramic types, which have similar proportions to 3-5kV rated ceramic capacitors. Battery-backed SRAM all of my 2465B scopes. Two are 2.2nF Y-class capacitors (C1020 & C1051). The usage in the 2465B is to bypass both the positive and negative outputs of the bridge rectifier to Earth. The customary use for Y-class capacitors is to bypass the incoming Active and Neutral AC lines to Earth; however, the application in the 2465B similarly relies on them not shorting out. Hence the use of Y-class capacitors. There is also a 10nF capacitor, C1052, that couples the negative side of the bridge rectifier output to an electrostatic screen behind the power switching Mosfets on the A3 board. I found visible horizontal cracks in the bodies of the two 2.2nF Y-class capacitors. The 10nF capacitor’s body was starting to swell up on one side, too. Generally, X2-class capacitors are designed for applications directly across Active & Neutral, while Y-class capacitors are designed to connect from Active or Neutral to Earth. Both types are often used to aid in the suppression of high-frequency interference either entering or exiting the instrument via the mains wires. Often, they are combined with inductors to improve the filtering. Before the Rifa-style metallised paper film ‘safety capacitors’ were invented, many manufacturers used waxed paper, oil-filled or ceramic types for Y-class capacitors. They got around the reliability problems and mitigated the risk of failure by using capacitors with a substantially higher voltage ratings than were required, and seldom had any troubles. Some products were encased in metal housings to mitigate the fire risk. 100 Silicon Chip The Y-class capacitor must be able to support sustained voltages over 1kV. Some manufacturers specify a 4kV DC rating for a Y-class capacitor to give a wider safety margin. This is because, on occasion, high-voltage transients can ride on the Active line. So capacitor failure can be made less likely by increasing the insulation withstand voltage. Tektronix also added some gas-­discharge voltage arrestors in the mains power input circuitry. They act as a negative resistance and a voltage clamp once they activate. In any event, the X2- and Y-class capacitors in the 2465B’s power supply should be replaced, and they need to be suitably rated X and Y parts for the task. Ceramic capacitors generally don’t burn much, except for their outer coating; they are a minimal fuel source compared to a plastic part. I prefer them for this reason. Y-class ceramic capacitors usually have a flame-proof coating and are designed to fail open-circuit. X2 capacitors frequently fail short-circuit, which is why they burn up. Fortunately, in the 2465B, the mains input is protected by fusing prior to the Y- and X2-class capacitors. Tektronix were also clever with the X2 capacitors, in that not only were they placed after the fuse, but they added small low-value resistors in series with them. If the capacitor shorts, the high current vaporises the resistor if the fuse does not blow immediately. That happened in one of my scopes when the X2 capacitor went low-­ resistance. Tektronix relied on a Japanese-made metal-cased commercial line power filter as part of the panel-mount IEC Australia's electronics magazine The PSU’s electrolytic capacitors determine the speed that most of the voltage rails collapse when the scope is switched off. The 2465B uses a Dallas DS1225 battery-backed non-­volatile SRAM with an internal lithium battery to store the scope’s calibration data and control settings. The DS1225 incorporates either the DS1210 or DS1218 control IC. When the 5V power rail drops below a specific level, this chip disables the SRAM and prevents any writes that could corrupt its contents. It works extremely well; I have been unable to corrupt the SRAM’s contents even by switching it on and off rapidly. I previously replaced the DS1225 with Ramtron FM16W08 FRAM because the DS1225’s battery was flat. This worked very well, and many people did this later with very little trouble. However, I noticed that power cycling could occasionally alter the FRAM contents. Fortunately, it did not affect the calibration constants, as those addresses are not active at the time of power cycling, but did affect the last panel control settings. In one case, I was able to ameliorate it with a 330W resistor from the WE line to +5V. Additional information I have written many other articles about repairing different sections of the 2465B oscilloscope. A list of them can be found below: • siliconchip.au/link/ac7b • siliconchip.au/link/ac7c • siliconchip.au/link/ac7d • siliconchip.au/link/ac7e • siliconchip.au/link/ac7f • siliconchip.au/link/ac7g SC siliconchip.com.au 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 Identifying SMD parts I have three Panasonic TH-49LF80W LCDs with blown devices at their HDMI inputs. I believe they are in SOT23-6 packages labelled “APOR 16” and “APOH 16”. The blown ones are shorted between pins 6 and 2 (pin 2 is connected to GND). The result of this is they don’t seem to perform the EDID handshake with the source device and require an EDID emulator/reclocker. Does anyone know what this device is? (R. T., Northmead, NSW) system on an old slasher to make it work and checking its timing with a ‘squarker’ buzz box (p92, siliconchip. au/Article/19570). I got interested in the buzz box and was wondering if the Moisture Tester in Short Circuits Volume 1 (Project 9b, multivibrator circuit) would produce a tone that changes when points open. (E. M., Kew, Vic) ● Yes, you can use the Moisture Tester to perform the same function as the squarker. It is a very similar circuit, just used for a different application. Digital Preamp not using crystal ● Identifying SMDs can be tricky because usually only the first two or three letters of the printed code are meaningful and often, there are several or even dozens of devices that use the same code. A good website to narrow it down based on the code and package type is https://smd.yooneed.one/ code4150.html We can see several possibilities, including the Avago HSMS-280P bridge quad schottky diode, Ricoh RP500N synchronous buck regulator, 74AUP1G18 1-of-2 demultiplexer or Richtek RT9011 dual LDO linear regulator. All come in an SOT-23-6 package or similar and have markings that start with AP, usually followed by a batch code. All things considered, in this case, we think it is most likely the RT9011 regulator, although if it’s near the HDMI connector and involved with EDID handshaking, it’s possible it’s a logic device like the 74AUP1G18. I have started construction of your Digital Preamp (October-December 2025; siliconchip.au/Series/449). I have just installed the PIC chip (which I purchased programmed from the Silicon Chip Online Shop). However, the 8MHz oscillator does not run. It appears to try to start based on my probing with an oscilloscope, but cuts out almost immediately. I have changed the two 18pF capacitors, checked the 470W resistor and even changed the crystal. All to no avail. I have checked the signal continuity to pins 30 and 31. Everything looks OK. I have re-flashed the PIC with 0110725A. HEX using my PICkit 5. This worked fine, leading me to believe that the PIC is OK. What am I missing? (M. F., Brassall, Qld) ● You aren’t missing anything – it turns out that the configuration file in the software became corrupted during development, resulting in the distributed HEX file running the PIC32 from its internal 8MHz oscillator rather than the external 8MHz crystal. The software still works, but there will be little external oscillator activity as that oscillator is shut down shortly after booting. We now have a revised version of the software on our website (v1.1). The only change is that it does utilise the external 8MHz crystal as was the design intent (and as described in the magazine). Op amps need negative feedback Can you connect a balanced microphone to the non-inverting and inverting inputs of an op amp and then connect the output to an amplifier? (R. M., Melville, Qld) ● Such an amplifier would be in an open-loop high-gain configuration and would surely produce severe output clipping. Instead, use a differential amplifier arrangement with a set Why not use a transformer to power the LED? The January 2026 issue has a servicing story about changing the magneto Instead of the Mains LED Indicator circuit in the February 2026 issue (siliconchip. au/Article/19655), how about using a mains transformer such as Altronics M7012A 3VA 6+6V AC, rectifier, filter capacitor and resistor to power the LED? At least then the circuit is isolated from the mains. I’d like to have an LED light up my front door keyhole at night so I can see where to put the key, not necessarily powered directly from the mains. (I. H., Essendon, Vic) ● Yes you could use a transformer, rectifier and filter to drive the LED. The Mains LED Indicator project intended to show a method of driving a light-emitting diode directly from the mains as a replacement for neon indicators. Keep in mind that when using a transformer, the magnetising current and thus idle power of the transformer will likely be many times higher than the power actually delivered to the LED, making such a circuit very inefficient. The one we presented doesn’t draw much more real power from the mains than is delivered to the LED. In the long term, that could add up to quite a lot of extra electricity used to power the LED, especially if it’s on most of the time. siliconchip.com.au Australia's electronics magazine Converting moisture sensor to buzz box April 2026  101 gain that prevents excessive output swing. For more, see: siliconchip.au/ link/acb6 Versatile Battery Checker doesn’t work I just finished building the Versatile Battery Checker (May 2025 issue; siliconchip.au/Article/18121) today. It powered up OK, and then I connected a brand-new 1.5V AA cell. It fails to calibrate and test. It shows: TEST BAT 9.0V BATTERY 1.6V MAX CURR 1A —————————— CALIBRATE 8.8V Run Auto SET 3200mv After pressing Enter, I get “Running” and then “Scan Failed Battery Check”. I tried a few more new cells with the same result. I also randomly get “V too Low” and “I too High” messages. I did a reset and tried again with similar results. (K. H., Castle Hill, NSW) ● It seems like the unit’s calibration in EEPROM is corrupt for some reason. Try the “reset to defaults” option. Final adjustments for Differential Probe I’ve completed all but the last step of setting up my High Bandwidth Differential Probe (Feb 2025; siliconchip. au/Article/17721), trimming the frequency compensation. I can’t guarantee that the CMRR was below ±20μV in previous steps because my meter only has a millivolt scale with two digits after the decimal point. Shown from left-to-right are screenshots of the input, positive divider output and negative divider output on my 50MHz oscilloscope. The positive divider output has significant overshoot, while the negative 102 Silicon Chip divider setup output has significant undershoot. Adjusting the compensation trimmers doesn’t change the shape of the output waveforms at all. I have checked that adjusting the trimmers changes the parallel capacitance (C5 || C6 || VC1) by approximately 12-60pF. Do you have any suggestions? (D. H., Sorrento, WA) ● Andrew Levido responds: It’s odd that adjusting the trimcaps makes no difference at all to the waveform. It also strikes me that the positive side is over-compensated and the negative side is under-compensated. Assuming correct component placement, this suggests a measurement setup error to me. It’s hard to tell what the problem might be without seeing the exact configuration, but my first thoughts are that to check the following: • The input waveform must be applied between each input (positive or negative) and the large ground test point on the board. We only want to exercise half of the input divider at a time. • The connection to the scope should be a BNC-BNC cable, not an oscilloscope probe, which will have its own compensation network. • The divider compensation should be performed on the ×100 range. We are only trimming the input divider frequency compensation. The fixed compensation on the ×10 gain stage will muddy the waters. Shunt reference and heatsink questions For the June 2024 DC Supply Protector (siliconchip.au/Article/16292), I noticed the surface-mount version of TL431 layout on the PCB has 6 pins. I am assuming mounting of the TL431 is to use the overlay Fig 6. How do you know if you have the mirror version of the TL431? I need to use the surface-­ mounting TL431 because I want to protect a 5V supply. Australia's electronics magazine Also, what size heatsink do you need for an LM317T to handle 1.5A? I will be using an 18V DC 2.3A plugpack from Altronics. (R. M., Melville, WA) ● The TL431 pinout for the mirrored version will have a MFDT or MSDT type number ending. The heatsink requirements for the LM317T depend on the output voltage you set it at. So for a 12V output for example, there will be 6V (18V − 12V) across it. Multiplied by 1.5A that gives 9W of dissipation. So a <3°C/W heatsink will keep it no more than 27°C (9W × 3°C/W) above ambient. Porting the Arduino Seismograph to a Pico I am looking into porting the Arduino Seismograph from the April 2018 issue (siliconchip.au/Series/334) to a Raspberry Pi Pico, specifically the newer RP2350 version. Amazingly, when I select the RP2350 as the target in the Arduino IDE, the sketch compiles with no errors. Of course, to make it work on the real hardware, I will need to go through the sketch and make sure all the pin assignments make sense for the changed microcontroller. Do you have any suggestions about this? For example, the Pi Pico has two independent SPI channels; does it matter which one I use? Would it be worth separating certain software routines onto different cores of the RP2350? This is probably overkill; the massive speed increase of the RP2350 over the Arduino Uno will probably make the question moot. Were there other features of the Seismograph that you wanted to add but didn’t fit on the Arduino Uno version? (N. W., Canberra, ACT) ● You are right that the pin assignments will need to be checked, both for SPI and I2C. We would aim to use pins attached to SPI0 and I2C0 on the continued on page 104 siliconchip.com.au MARKET CENTRE Advertise your product or services here in Silicon Chip KIT ASSEMBLY & REPAIR FOR SALE 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 LEDsales KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com LEDS, BRAND NAME AND GENERIC LEDs, filament LEDs, LED drivers, heatsinks, power supplies, kits and modules, components, breadboards, hardware, magnets. Please visit www. ledsales.com.au PMD WAY offers (almost) everything for the electronics enthusiast – with full warranty, technical support and free delivery worldwide. Visit pmdway.com to get started. Lazer.Security PCB PRODUCTION 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 Dual Mini LED Dice August 2024 SMD LED Complete Kit SC6961: $17.50 TH LED Complete Kit SC6849: $17.50 siliconchip.au/Article/16418 Includes either 3mm through-hole or 1206sized SMD LEDs. Choice of either white or black PCB. CR2032 coin cell not included. WE HAVE QUALITY LED’S on sale, Driver sub-assemblies, new kits and all sorts of electronic components, both through hole and SMD at very competitive prices. check out the latest deals at www.lazer.com.au ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus $1.20 for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone (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 April 2026  103 Pico, since these should align to the default I2C and SPI peripherals used on the Uno (and thus the Seismograph libraries and sketch). This should minimise the code changes that might be needed. Assuming you are using the arduinopico package, this will involve using the likes of Wire.setSDA() and Wire.setSCL() for I2C and SPI.setSCK(), Advertising Index Altronics.................................31-34 Blackmagic Design....................... 5 Dave Thompson........................ 103 DigiKey Electronics..................OBC Electronex................................... 11 Emona Instruments.................. IBC Hare & Forbes............................... 7 Jaycar............................. IFC, 12-15 Keith Rippon Kit Assembly....... 103 Lazer Security........................... 103 LD Electronics........................... 103 LEDsales................................... 103 Microchip Technology.................. 9 Mouser Electronics....................... 3 PCBWay....................................... 19 PMD Way................................... 103 SC Dual Mini LED Dice.............. 103 SC RP2350B Computer.............. 49 Silicon Chip PDFs on USB......... 64 Silicon Chip Shop...........77, 90-91 Silicon Chip Songbird................ 75 Silicon Chip Subscriptions........ 65 The Loudspeaker Kit.com............ 6 Wagner Electronics..................... 89 Errata and on-sale date Watering System Controller, August 2023: the optional 24V transformer is incorrectly specified as Jaycar MT2112. It should be Jaycar MT2084 instead. Next Issue: the May 2026 issue is due on sale in newsagents by Monday, April 27th. Expect postal delivery of subscription copies in Australia between April 27th and May 12th. 104 Silicon Chip SPI.setRX() and SPI.setTX() for SPI. We’d probably put them right at the start of setup(), so they are set before any of the peripherals start up. As you say, the Pico or Pico 2 will be much more capable than the Uno, so we wouldn’t bother with splitting routines over cores. We wouldn’t be surprised if there are some other subtle changes that cause things not to work. We’ve had some odd issues with different versions of the SD card libraries, although the fact that it is compiling is a good sign. We updated that project in April 2019 (siliconchip.au/Article/11532) to use a geophone sensor (still using the Uno). The geophone is a purely analog device, so shouldn’t present any difficulties in interfacing, although we did use the Uno’s ATmega328 1.1V analog reference, which the Pico lacks. So there might need to be changes to get this version functional, but they should not be difficult. One thought that comes to mind is to use a Pico W and make the contents of the SD card available on a web server so the card doesn’t need to be removed for reading. This would be a similar concept to that used in the WiFi Weather Logger from December 2024 (siliconchip.au/Article/17315). Battery bank inverter efficiency Some years ago, I assembled the Appliance Energy Meter (July & August 2004; siliconchip.au/ Series/96) from an Altronics K4600 kit. I’ve been using it around the house to measure the energy use of various things. I recently purchased a Bluetti AC70P battery bank and am testing it using my car fridge. I’m using the AC power brick that came with the fridge, which has an input power rating of 220-240V AC 0.6A. The output of this (transformer-­ based) AC-to-DC converter is 12V DC at 5A (60W). When the fridge compressor is running, the energy meter shows a draw of about 56W; however, the Bluetti AC draw is showing about 96W, a factor of 1.7 higher. I would appreciate if you could comment on the accuracy of the Energy Meter. I’ve never had any reason to doubt it in the past. To explain this difference, I suspect that the energy figure shown by the power station is the actual draw Australia's electronics magazine from the battery, and the AC inverter is very inefficient at this low power draw. I would appreciate your comments on this line of thinking. 58% efficiency is low, but the AC inverter is rated at 1000W, so I guess that would be reasonable. I will investigate using the 12V 10A supply on the AC70P. This may be a more efficient use of the available battery watt-hours. (B. P., Jeir, NSW) ● That Energy Meter design should be accurate to <0.5% when calibrated. You certainly should expect the battery to be supplying more power at the inverter input than the appliance is drawing at the output. If you have something like an incandescent desk or floor lamp (or perhaps halogen) that you can use as a test load, run it from the inverter and make the same measurements. See if you find a similar amount of lost power (40W). That is enough to make something pretty warm. If left running for a while, does the inverter case temperature go up noticeably? An inverter can be expected to consume at least 10W internally, even with a light load. The lost power will probably be some fixed amount (say around 10W), plus a percentage of the load current (perhaps 10%). That implies it would be less efficient with a light load. Still, 40W seems like quite a lot of wasted power. It is possible that the battery bank power meter is not 100% accurate. Visual doorbell alert wanted for the deaf I have enjoyed your articles for many years. I am deaf and need some help to design/build myself a doorbell button to trigger several flashing lights simultaneously in several rooms in my apartment as I cannot hear audio door chimes commonly installed in homes. Jaycar sells 433MHz receiver and transmitter modules. I don’t know what decoder/encoder I need for this project. I am open to suggestions. (Anthony, via email) ● We have published a suitable project in the January 2009 issue, titled “433MHz UHF Remote Switch” (siliconchip.au/Article/1284). That back issue is still available to order, and programmed microcontrollers for this project are available from our Online Shop at siliconchip.au/ SC Shop/?article=1284 siliconchip.com.au “Rigol Offer Australia’s Best Value Test Instruments” New 2026 Products Oscilloscopes New 12Bit Scopes New Up To 13GHz RIGOL DS-1000Z/E - FREE OPTIONS RIGOL DHO/MHO Series RIGOL DSO-8000/A 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 4600MHz to 13GHz, 4Ch 410GS/s to 40GS/s Real Time Sampling 4Up to 4Gpts Memory Depth FROM $ 649 FROM $ ex GST 684 FROM $ ex GST 13,191 Multimeters Function/Arbitrary Function Generators 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 604 FROM $ ex GST Spectrum Analysers 632 ex GST Real-Time Analysers New Up To 26.5GHz 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 26.5Hz 4Modes: Real Time, Swept, VSA, EMI, VNA 4Optional Tracking Generator ONLY $ 799 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