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MARCH 2026 ISSN 1030-2662 03 9 771030 266001 The VERY BEST DIY Projects! $14 00* NZ $14 90 INC GST INC GST Solar Panel Protector and Optimiser low-cost protection from lightning strikes DCC Booster and Reverse Loop Controller Graphing low-cost Thermometer THIS ISN’T A NORMAL 3D PRINTER $ JUST 999 CENTAURI CARBON 2 COMBO TL4986 FOUR COLOURS. ONE PRINT. ZERO FUSS. PRINTS WHAT OTHERS WON’T. FAST. QUIET. DIALED IN. CANVAS: AUTOMATIC COLOUR SWITCHING BUILT FOR ADVANCED MATERIALS SMART CALIBRATION. CONSISTENT PRINTS. SEE THE FULL HOME OF 3D PRINTING ONLINE 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.03 March 2026 16 The History of Intel, Part 2 Part two in our three-part series concentrates on Intel’s technological developments from the early 1990s to now. They were dominant from the 1990s until the 2010s, but have been struggling a little of late. By Dr David Maddison, VK3DSM Electronics feature 40 Power Electronics, Part 5 In this series of articles, we explore the principles of power electronics. This month, we cover the active techniques that help with power factor correction and electromagnetic interference (EMI) filtering. By Andrew Levido Electronic design 60 Self-powered Wireless Switches Also called ‘kinetic’ switches, these wireless switches do not need an external power supply, and are commonly found in doorbells and remotecontrolled light switches. By Tim Blythman Low-cost electronic modules 66 Wiring up a New Home Here are some helpful tips and tricks for when you’re building your own house, or are just interested in the process. There’s a lot to consider with the wiring, from mains, audio-video, internet and even temperature sensing. By Julian Edgar Domestic wiring 28 Solar Panel Protector This simple design reduces the chance of lightning-induced surge damage to your solar panels, and provides an ‘ideal’ diode function, so that you can still get power from the panels even when some are shaded. By Ian Ashford Solar power project 49 DCC Booster The capstone piece for our model train system is this functional DCC Booster, Reverse Loop Controller, and even a simple Base Station all-in-one. It functions over a standard voltage range of 8-22V and handles up to 10A. Part 5 by Tim Blythman Model train project 71 The Internet Radio, Part 2 Sporting a large touchscreen and running Linux, this Internet Radio uses your choice of media player software to play audio. Because it uses preassembled modules and 3D-printed parts, you can build it in one afternoon. By Phil Prosser Audio/radio project 78 Graphing Thermometer Taking just a temperature reading isn’t always enough; our low-cost Graphing Thermometer shows you how the temperature changes over time, and can take samples from once per second to once every 900 seconds. By Andrew Woodfield Measurement project The History of Intel Part 2: page 16 Image source: Konstantin Lanzet https://w.wiki/GVqx Power Electronics Part 5: Page 40 Tips & Tricks for Wiring New Homes Page 66 Page 78 Graphing Thermometer 2 Editorial Viewpoint 4 Mailbag 39 Circuit Notebook 59 Subscriptions 84 Serviceman’s Log 90 Online Shop 92 Vintage Radio 100 Ask Silicon Chip 103 Market Centre 104 Advertising Index 104 Notes & Errata 1. Converting a mousetrap into a helping hand for soldering SMDs RCA Radiola 17 (AR-927) by Jim Greig 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 Expect more Chinese-brand computer parts Thanks to the current AI boom (bubble, in my opinion) consuming vast quantities of DRAM and flash memory, computer memory and solid-state storage prices have been climbing sharply. At the same time, China has been pushing hard to become more globally competitive in higher-end semiconductors, including flash memory, DRAM and eventually CPUs and GPUs. Seeing how the price of DRAM has risen dramatically over the past year (in some cases several-fold) and with rumours that storage prices were set to follow suit, which they now appear to be doing, I decided to buy a bigger SSD to add to my computer. Adding a 2TB drive to my existing 1TB drive would have been enough for now, but I suspected I might regret that decision if I needed more space later and had to pay significantly more to upgrade. So I decided to go with a 4TB NVMe drive, at the upper end of what’s currently available at prices that could still be described as reasonable. Shopping around, I wasn’t particularly impressed. Even budget “mainstream” brand SSDs were around $550 for a 4TB model that wasn’t especially fast. Better-known brands clustered in the $650–700 range; for example, a Samsung 990 EVO Plus at around $640, or a Lexar NM790 coming in at about $695. Then I came across a brand I’d never heard of: Fanxiang. They were offering drives with apparently better performance, a five-year warranty, and a price just over $400. I ended up paying $424 including delivery for their 4TB S880E PCIe 4.0 model. It uses TLC flash (generally preferable to QLC), promises around 7.3GB/s read and 6.6GB/s write speeds, and has a quoted endurance of about 3000TB written – more than adequate for my needs. Online reviews and benchmarks suggest it’s a solid and reliable performer, although, as always, time will tell. What struck me was that this may be part of a broader trend. Fanxiang is a brand of Shenzhen IDCEMS Technology Co Ltd, and it appears their drives use flash memory from Yangtze Memory Technologies Co (YMTC), China’s first large-scale commercial 3D NAND flash memory manufacturer. YMTC was established as part of China’s strategic push to build indigenous semiconductor capability. They are positioning themselves as a competitor to established flash manufacturers such as Samsung, SK Hynix, Kioxia, Micron and Western Digital, with technology that is increasingly competitive in the global marketplace. As with any SSD, overall reliability depends not just on the flash itself, but also on the controller, firmware and validation. I suspect we’ll start seeing something similar with Chinese-made DDR5 DIMMs as Western brands price themselves out of reach for many home users. It wouldn’t surprise me if we eventually see Chinese motherboards too. It will probably be some time before Chinese CPUs and GPUs are genuinely competitive with offerings from Intel, AMD and NVIDIA, but I wouldn’t rule it out. We’re already seeing many Chinese cars on our roads, and Chinese brand appliances in our stores. I don’t think computers will be any different. That means more competition and more affordable hardware, so it may not be a bad thing. Finally, if you need a new SSD, I suggest you get one sooner rather than later. by Nicholas Vinen Cover background: https://unsplash.com/photos/a-blurry-image-of-a-blue-sky-with-clouds-oKfcrzCM9og Cover solar panel: https://unsplash.com/photos/a-solar-panel-on-the-ground-HEu4G6tJ0Nw 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”. Finally got RGB LED Analog clock working In response to the letter from Paul Philbrook regarding his problems with the RGB LED Analog clock PIC in the October issue, I would like to add my tale of woe. I successfully assembled the kit, and the clock worked well to start with, but mysteriously stopped completely. I blamed myself and bought another PIC and fitted it, with the same result. Silicon Chip kindly sent another PIC at no cost, but this time the result was totally garbled LED operations. Frustrated, I shelved it for a while. The poor copper tracks for the PIC were getting very tired. I had arranged for a wood-turning friend to make up a very nice surround, so I decided to give it another try, and got yet another PIC, number four. The clock worked properly this time, and continues to do so – a very “cool” addition to my office, according to a friend. I’m still not sure if I was responsible for the failure of the previous three PICs, but I am very pleased with the results of my persistence. David Coggins, Beachmere, Qld. Comment: this is baffling; a few constructors have had similar problems, but in our experience, PICs are generally very robust. It’s unusual for them to be damaged by soldering or static discharge. Our guess is that one batch of chips we bought to make kits and programmed micros was somehow faulty, but not faulty enough to be picked up by factory testing or us during programming. SLA Battery Tester works well I built the SLA Battery Condition Checker (August 2009: siliconchip.au/Article/1535) that is available from Jaycar as a kit (KC5482) and it seems to work correctly first go. The soldering of the components was straightforward. I found getting the LED to the right height a little tricky; I didn’t get it perfect but it’s okay. Also, the knobs seem to have the white markings around the wrong side, so I will have to paint some white markings on the right side. I found the final stage, where you have to push 0.71mm tinned wire through the battery terminal connectors, very tricky. I got some Anaconda battery alligator clips with leads for $15 (if you join up as a member for free) and they can carry 50A: www.anacondastores.com/BP90238475-black I tested a 12V small SLA battery and my car battery, and they both hit the blue LED with the decay of lighting all the LEDs down to the red. I wonder whether the simple small carbon pile tester I bought from Bunnings (I/N: 0064863) is better, though, as it puts more of a load on the battery and would probably be better for a car battery. It is interesting; I thought with kits, the soldering would be the hardest part, but with my hand skills, I find the drilling, wire cutting, hooking up cables and attaching heatsinks a lot harder. Edward Menzies, Kew, Vic. Move over, Arduino? Some aspects of the February 2026 editorial, “Will Arduino survive?”, struck a chord with me. I am perhaps less worried that Qualcomm will preside over the demise of the Arduino, as I already see highly credible alternatives sitting in the wings. The cause of such demise, however, is two-pronged. Firstly, stemming from uncompromising license agreements, which reduce collaboration & sharing, and increase costs for companies such as Adafruit. The second is more insidious. Adding functionality such as AI and so on into an otherwise simple product makes it harder to use. I have historically been a Microchip ecosystem user. Not so much because it is the best; more that I have a history of projects in this ecosystem, and moving from one project to the next over generations has been easier than ‘jumping horses’ to another processor family. David Coggins’ finished RGB LED Star with a timber enclosure. The SLA Battery Condition Checker, which was built from a Jaycar kit. 4 Silicon Chip Australia's electronics magazine siliconchip.com.au FREE Download Now! Mac, Windows and Linux Edit and color correct using the same software used by Hollywood, for free! Creative Color Correction DaVinci Resolve is Hollywood’s most popular software! Now it’s easy to create feature film quality videos by using professional color correction, editing, audio and visual effects. Because DaVinci Resolve is free, you’re not locked into a cloud license so you won’t lose your work if you stop paying a monthly fee. There’s no monthly fee, no embedded ads and no user tracking. PowerWindows™, qualifiers, tracking, advanced HDR grading tools and more! Editing, Color, Audio and Effects! Designed to Grow With You DaVinci Resolve is the world’s only solution that combines editing, color DaVinci Resolve is designed for collaboration so as you work on larger jobs correction, visual effects, motion graphics and audio post production all in you can add users and all work on the same projects, at the same time. You can one software tool! You can work faster because you don’t have to learn multiple also expand DaVinci Resolve by adding a range of color control panels that apps or switch software for different tasks. 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There are multiple configurations required just to get a PIC to say “Hello World”. On the positive side of the ledger, once you have been through the pain, there is an amazingly rich suite of capabilities that your project can access. This complexity is quite challenging if you are learning or an occasional user, which leads to the point that I draw from your editorial. The Raspberry Pi family is well known for its larger Pi 3, 4 and 5, and its high-level OSes. The new Pico 2, as you reviewed recently, has been integrated into Visual Studio. Setting this up is incredibly simple and it just works. The downside is that it is less obvious how a program can get into the microcontroller and peripherals at the register level. The upsides I found recently were truly surprising: • There are drivers for most things you would want to do and they just work. • The environment integration to the Pico 2 is good at a high level. Connection is via USB with the simplicity this brings. (You want your Pi-based project to talk to the PC? It is right there to printf() straight to your serial port!) • The Visual Studio environment includes a range of AI agents that can assist with coding and debugging. While I see downsides with some of these, the positives far outweigh the problems. Just never allow the AI agents free rein to change slabs of code unless you check first! The upshot is that adding functions and complexity to a proven recipe will undermine the foundations of its success. However, the new version of the ‘old kid on the block’ has real potential to step in from left stage. The world is always changing, of course, and I see this confluence of development environment and hardware platform changes being a very positive one. Phil Prosser, Prospect, SA. Comment: we think you are right that Raspberry Pi Picos are the ‘new Arduino’. They are certainly cheap, flexible and powerful. You can also program them using the Arduino IDE. PICs are complex enough to do a lot of things well without being so complex they are cumbersome. One thing they do very well is ease of flashing (eg, no fuse bits to program separately). Power Electronics series is covering Active PFC A big thank-you to Andrew Levido. Like Paul Howson (Mailbag, February 2026, page 6), I too am thoroughly enjoying his engineering theory articles (the “Power Electronics” series; siliconchip.au/Series/452), with the different ways of looking at switch-mode power supply (SMPS) circuit operation. A few years ago, I became determined to repair a computer SMPS, expecting to find a bridge rectifier input circuit with a 220-240V/110-120V AC switch, followed by a couple of 470μF filter capacitors needed to provide about 340V DC for the main switching circuit. Instead, there was a bridge rectifier and boost converter followed by a single 270μF/450V electrolytic cap charged to a regulated 380V DC for the main switching circuit. The boost converter seemed to be controlled to provide a steady load to the mains input (over the full mains cycle), while at the same time regulating its output to 380V DC. 8 Silicon Chip Australia's electronics magazine siliconchip.com.au A 230V/115V switch is no longer needed because of the now wider input voltage range. I’m guessing this meant that the design presented a good power factor and neatly reduced production cost because the same energy could now be stored in a smaller electrolytic capacitor running at a fixed 380V DC instead of being limited to approximately 340V DC in the older design by the bridge rectifier output. Dave McIntosh, Eastwood, NSW. Comment: this type of active power factor correction (Active PFC) is covered in Power Electronics part 5, starting on page 40 of this issue. The end of free to air television? When digital television first started, we had good reception on our original combination UHF/VHF aerial and cabling. When it was time to upgrade, I bought a cheap digital aerial on eBay and installed new cables. That was alright for several years, but then the reception got worse. Early last year, I did some research and bought a good-quality digital aerial that was specifically matched to the transmission frequencies we have here. At first, we had good reception on all channels, but with occasional slight corruption on Channel 7. Still, it was quite watchable. Late last year, things got a lot worse. ABC went off the air completely, then Channel 10 went off the air through the day, but usually came good at night. Then Channel 7 was corrupted through the day, but sometimes came good at night. SBS was on air sometimes through the day and sometimes good at night. Just recently, Channel 10, Channel 7 and SBS have gone off the air completely. Through all this mess, Channel 9 is still on the air almost all the time, but has occasional slight corruption. This time last year, we had 40 TV channels, including some duplicates. As of now, we have six TV channels, including one duplicate. All the channels we can currently get are related to Channel 9. On checking the tuner information, Channel 9 has 99% signal strength and 99% signal quality. The other channels have 99% signal strength and 0% signal quality. I don’t know what these TV stations are doing, but clearly, they have major problems with their transmission. A friend in a nearby town said that they no longer have any free-toair television reception at all. I have been asking around the neighbourhood here, and I get the same answer from everyone: that they only watch TV online and not on air due to all the reception problems. It is not only here, either. Recently, I was talking to someone from Melbourne who stayed at a motel in Nambour, and he said that all the channels were corrupted there. Early last year, we were at our daughter’s place in Brisbane and I noticed that Channel 9 was corrupted. She said Channel 7 was often a lot worse. A friend in town now has no TV reception at all. They are a little further from the transmitter than we are. For the last couple of months, we’ve been watching our regular shows through online catch-up TV streaming. It’s the only way we get to watch them. I use a Linux laptop through HDMI to our old TV and it works well. If Channel 9 can be on the air almost all the time with infrequent corruption on most days, what are the other channels doing that they can’t keep up with Channel 9, and have gone off the air completely? SC Bruce Pierson, Dundathu, Qld. 10 Silicon Chip Australia's electronics magazine siliconchip.com.au FROM FIRST LAYER TO FINISHED MASTERPIECE. Explore the full range of ELEGOO® Filament Printers now at Jaycar. 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Up to 100°C LEARN MORE: (AU) jaycar.com.au/p/TL4982 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 LEARN MORE: (NZ) jaycar.co.nz/p/TL4982 SEE IN-STORE OR ONLINE FOR OUR EXTENSIVE RANGE OF FILAMENT AND ACCESSORIES AT GREAT VALUE 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. 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 2 b y D r D avid Mad K3D V , n o d is SM The second in a three-part series on Intel, this article concentrates on its projects, manufacturing and events from the early 1990s to the present. Last month’s article gave an overview of the company and its background, plus a detailed history from its early days to the late 1980s. T his article will end with the events of the last few years from Intel’s perspective; the third and final part in this series next month will then look at the technologies they are currently pursuing and what the future may hold. 1990s: PC market dominance In the 1990s, Intel became a household name, partly because of the popularisation of the PC and the “Intel Inside” marketing campaign that started in 1991. This led it to become the most valuable semiconductor company in the world by 1995. “Intel Inside” brought, for the first time, brand recognition of computer components such as CPUs in consumer devices. It also brought billions of dollars of licensing revenue to Intel; Intel co-marketed their CPUs with manufacturers, leading to advantages for both parties. This strategy was quite different from competitors AMD and Cyrix, whose combined market share was around 10-15%, while Intel held The rise and fall of Intel’s value Intel became the most valuable semiconductor company in the world around 1995, a position it held until around 2011. After that, it experienced a period of decline, and was surpassed in sales by Samsung by 2017. It has since been surpassed in market capitalisation by companies like TSMC and NVIDIA. By 2022, AMD surpassed Intel’s market capitalisation. Presently, Intel has just under half of the desktop CPU market, with the other half being AMD CPUs. AMD has been gaining significant market share of late and has made major inroads in the server market, currently capturing around 25% of the highly profitable server CPU market. So Intel remains dominant for the moment, but AMD is now undoubtedly a serious competitive threat to them. 16 Silicon Chip Australia's electronics magazine around 90% of the market. Nowadays Intel doesn’t have as much of a hold on the market (see the panel below). The Pentium The original Pentium processor was released in 1993 as a successor to the 80486 and remained the brand name for Intel’s premium processors until the Core lineup was introduced in 2006. After that, it became the brand for a more affordable line of processors than the Core series. These later Pentiums were discontinued in 2023 and had little commonality with the original except for using the x86 instruction set. The original 1993-2001 Pentium contained 3.1-4.5 million transistors depending on the variant. It was the first Intel processor to use a ‘superscalar architecture’, a form of processor parallelism in which more than one instruction can be executed per clock cycle – see Figs.24 & 25. This is done by simultaneously sending instructions to more than one execution unit within the processor. siliconchip.com.au Intel Pentium Microarchitecture Branch Target Buffer Prefetch Address TLB Fig.24: the Intel Pentium architecture. Source: https://w.wiki/ GZY5 (CC BY-SA 3.0) Code Cache 8 KBytes Branch Verif. & Target Addr. 256 64 Bit Data Bus 32 Bit Address Bus Instruction Pointer Control ROM Instruction Decode Control Unit Address Generate (U Pipeline) Page Unit Bus Unit Prefetch Buffers Floating Point Unit Address Generate (Y Pipeline) Control Register File Control Integer Register File ALU (U Pipeline) 64 64 Bit Data Bus Barrel Shifter 32 32 Bit Address Bus Superscalar vs pipelining Early processors handled instructions one at a time. Each instruction went through a sequence of steps: fetch the instruction from memory, decode it, fetch any required data, execute the operation and write the result back to registers or memory. The CPU could not begin the next siliconchip.com.au Divide 32 32 32 32 This is different from the ‘pipelining’ of the 80386 and 80486, which split instructions up into stages so that they could be executed sequentially without interruption. A later variant of the Pentium added the MMX (Multimedia eXtensions) instruction set, which introduced SIMD (single instruction, multiple data) operations on packed integers – see Fig.26. While not capable of accelerating floating-point workloads, MMX significantly improved performance in multimedia and DSP tasks such as image filtering, video decoding (DCT/ IDCT), audio processing and colour space conversion. Add ALU (Y Pipeline) TLB Data Cache 32 8 KBytes 32 instruction until this entire sequence finished. Any delay – for example, waiting for a value to arrive from memory – stalled the whole processor. Pipelining improves this by dividing the instruction cycle into separate stages. Different instructions can occupy different pipeline stages at the same time; while one instruction is being decoded, another can be fetched, another executed and so on. A non-pipelined CPU must wait for one stage to finish before the next can start, so it can’t take advantage of hardware parallelism like a pipelined CPU can. Once the pipeline is full, the processor can complete one instruction per clock cycle, improving throughput dramatically. A stall in one stage (eg, waiting for memory) still prevents earlier stages from progressing, so the pipeline as a whole does pause. However, stages ahead of the stall continue to finish their in-flight instructions, and the pipeline quickly resumes once the data arrives. Australia's electronics magazine 80 80 Multiply Fig.25: an original Intel Pentium die. Source: https://w.wiki/GZY3 (CC BYSA 3.0) Fig.26: a 166MHz Pentium MMX CPU de-lidded. Source: https://w.wiki/GZY6 March 2026  17 The more advanced ‘superscalar architecture’ allows multiple instructions (or parts of different instructions) to be issued and executed in parallel in the same clock cycle using multiple execution units. A superscalar CPU usually has multiple ALUs (arithmetic logic units) and FPUs (floating point units). In more advanced CPUs with out-oforder execution, independent instructions can continue to execute while the pipeline waits for data, allowing multiple kinds of delays to overlap. Pentium Pro The Pentium Pro was introduced in 1995 and discontinued in 1998. It was the first processor with Intel’s P6 microarchitecture. It had “Dynamic Execution”, which permitted outof-order execution of instructions to improve efficiency, and an integrated L2 cache on a separate die within the processor module connected via a dedicated 64-bit bus so it could operate at the same speed as the processor. L1 cache is the fastest memory available to the process other than registers. It is usually small, integrated into the die (starting with the 80486) and mainly holds instruction code for frequently executed routines and data that’s frequently accessed. L2 cache is a slower, larger memory that’s still significantly faster than main memory and is used to hold instructions and data that still need to be accessed frequently, but will not fit within the smaller L1 cache. Later processors introduced another layer, L3 cache, again larger and slower (but still faster than accessing main memory). The Pentium Pro/P6 also allowed speculative execution, allowing it to predict the result of instructions ahead of time, to keep the processor pipeline full. It was mainly aimed at servers and high-end workstations. It had 5.5 million transistors and was made on a 500nm process, later reduced to 350nm. Pentium II The Pentium II was introduced in 1997. It kept the P6 microarchitecture introduced on the Pentium Pro but added the MMX instruction set that was missing from the Pentium Pro. It had 7.5 million transistors, except for the Dixon variant with a large amount of cache, which had 27.4 million. It was built on a 350nm process, reduced to 180nm for later variants. Its distinguishing features were its availability in a Slot 1 cartridge format, with L2 cache on a separate circuit board within the cartridge – see Fig.27. Unlike the Pentium Pro, that cache only ran at half the speed of the CPU to reduce cost (and because the Pentium II was generally clocked higher than the Pentium Pro). StrongARM As mentioned last month, Intel acquired the rights to DEC’s Strong­ ARM processor design as part of a legal settlement. They produced it from 1997 until 2004. It was the predecessor to Intel’s XScale chip (2002-2006). Celeron As with many Intel product names, Celeron can be confusing. It was originally introduced in 1998 as a lower-­ cost Pentium II with no L2 cache (early variants were famously overclockable as it was usually the L2 cache that limited the processor speed). It was discontinued in 2002. After that, there was a variety of different Celerons, unrelated to the original and ultimately discontinued in 2023. There are too many versions of Celerons to list. However, throughout their history, virtually all Celeron-branded processors have been lower-­ c ost, performance-­ reduced derivatives of existing Core or Pentium chips. The reduced performance was typically achieved through some combination of smaller caches, disabled cores or core modules, locked multipliers, lower clock speeds, missing features (hyperthreading, Turbo Boost, AVX instructions), or the use of partially defective dies that could not meet the speed of the full-specification parts. Hyperthreading is a now-common technique where one CPU core can execute two different instruction streams, sharing the same execution units but with separate pipelines. Its main benefit is that if one hyperthread pipeline stalls due to something like a memory access, the other can continue running, meaning the execution units don’t sit idle. It was introduced with the Pentium 4. Fig.27: a Pentium II CPU installed on a motherboard. Note how it’s plugged in vertically to an edge connector, similar to the RAM sticks near it, and how the heatsink and fan are integrated into the package. Source: https://w.wiki/GZXv (CC BY 4.0) Xeon Xeon processors were introduced in 1998, intended for high-end non-­ consumer workstation, server and embedded applications. They are based on the same cores as desktop CPUs, but have added specialised features such as support for ECC (error correction code) memory, higher numbers of cores, more PCI Express I/O lanes, support for larger amounts of RAM and larger cache memory. Australia's electronics magazine siliconchip.com.au 18 Silicon Chip They may also have extra RAS (reliability, availability and serviceability) features, enabling them to continue to execute code when a normal processor cannot. Xeon motherboards were also usually available with more sockets than regular desktop CPU boards. They are not generally suitable for desktop or consumer use as they have lower clock rates (due to an emphasis on parallel tasking); they usually lack an onboard GPU (graphics processing unit); and earlier Xeon models lacked support for overclocking. Nevertheless, they were used by some desktop users for some specialised tasks such as video editing. Just as Celerons are lower-tier versions of standard processors, Xeons are almost the opposite, being more-or-less higher-­tier versions of the standard processors. Xeons are still in production using the latest cores. Like Celerons, there are too many models to list here. Fig.28: a Pentium III without its heatsink; this generation of processor came on a plug-in card with separate cache SRAM chips (on the right of the core die). Source: https://w.wiki/GZXt (CC BY-SA 3.0) Pentium III The Pentium III was introduced in 1999 and discontinued in 2004 – see Figs.28 & 29. It introduced Streaming SIMD Extensions (SSE), similar to MMX but supporting parallel floating-point operations, leading to a major boost in multimedia performance. A controversial feature that was introduced was a processor serial number, which raised privacy concerns. There were several Pentium III variants with significant differences between them, such as cache size, manufacturing process and clock speed. Katmai used a 250nm process node with 9.5 million transistors; Coppermine, 180nm with 28 million transistors; and Tualatin, 130nm with 47 million transistors. 2000s: Higher clock speeds, challenges, diversification During the 2000s, Intel had an obsession with improving performance via higher and higher clock speeds. This led to the “NetBurst” microarchitecture, which proved challenging and was ultimately unsuccessful, giving way to the entirely new Core microarchitecture. During the early 2000s, the Pentium 4 dominated in PCs, but there was strong price and performance competition from the AMD Athlon series. The Intel Core 2 Duo was introduced in 2006, becoming a performance leader. However, in 2005, AMD introduced siliconchip.com.au Fig.29: a die photo of the Pentium III showing the significantly increased complexity you’d expect with around 40 million transistors. Source: https://w. wiki/GZXu the Athlon 64 X2 dual-core processor, which provided significant competition. Intel faced several major challenges during the 2000s: ● a series of antitrust actions alleging anti-competitive behaviour toward Australia's electronics magazine AMD, including a US lawsuit and fine (active from 2005 to 2010), and similar cases in Japan (2005), South Korea (2008) and the EU (2009, which was partly annulled much later) ● the need to abandon the failing March 2026  19 Table 4: Intel CEOs over the years CEO Years as CEO Background Robert Noyce 1968-1975 Co-founder of Intel; one of the pioneers of the IC. Gordon Moore 1975-1987 Co-founder of Intel and author of “Moore’s Law”; steered Intel during its early growth and increasing focus on microprocessors. Andrew Grove 1987-1998 An early employee (3rd at Intel), previously company president; he led Intel through a transition away from memory (DRAM) toward microprocessors. Craig R. Barrett 1998-2005 Under his leadership, Intel invested heavily in manufacturing and scaling production, maintaining its manufacturing lead. Paul Otellini 2005-2013 First Intel CEO without an engineering background (he held an MBA). Oversaw an era of diversification, cloud and data-centre growth, and global expansion. Brian Krzanich 2013-2018 Long-time Intel engineer who rose through the ranks; became CEO to steer Intel through manufacturing and product-strategy challenges. Bob Swan 2019-2021 Former CFO (and interim CEO) of Intel. Led the company during a turbulent transitional period, trying to stabilise finances amid increasing competition and industry shifts. Pat Gelsinger 2021-2024 Veteran of Intel (early engineer and later CTO), returning to lead an attempted turnaround. Focused on reviving manufacturing strength, launching new fabs, and repositioning Intel for cloud, AI, and foundry services. Lip-Bu Tan 2025-present BSc in Physics, Master’s in Nuclear Engineering and an MBA. Former CEO of Cadence. Faces major challenges after Intel has lost significant market share and market cap. NetBurst architecture (described below) and replace it with the new Core architecture ● the impact of the 2008 global financial crisis Intel made some attempts at diversification during this period, such as the development of XScale ARM processors and the Atom processor. However, Intel misjudged the mobile market in the 2000s and failed in these areas. They saw low profit margins on mobile processors and chose to focus on x86 processors instead. They also sold XScale just before the mobile device boom – a critical error. Intel even declined Apple’s invitation to manufacture iPhone chips (around 2005/2006), as then-CEO Paul Otellini did not believe the iPhone would be a very high-volume business (oops!). ARM, which was specifically designed for low power consumption, became the dominant architecture for mobile devices, and Intel missed the opportunity. chips available at the time were also more integrated than XScale. Intel went on to focus on its own line of x86-based Atom low-power processors for mobile applications. For hardware vendors already partnered with Intel or using its reference designs, there was no need for another chip in their ecosystem. Since the sale of XScale, Intel’s acquisitions have been mostly in the area of software, not hardware; they have remained focused on a more limited ecosystem. Pentium 4 The Pentium 4, introduced in November 2000 and discontinued in August 2008, was based on the Fig.30: an early (Northwood) Pentium 4 CPU die. Source: https://w.wiki/GZXr XScale XScale was a range of ARM-based processors for mobile and other lower-­ power applications developed by Intel and released in 2002. They sold the chip division that produced them to Marvell Technology Group in 2006. According to a former Intel engineer commenting on Quora Digest, Intel saw itself as an x86 company and was not interested in selling other chips for the mobile market. Other mobile 20 Silicon Chip entirely new NetBurst microarchitecture (internal codename P68) – see Fig.30. NetBurst succeeded the longlived P6 microarchitecture used in the Pentium Pro, Pentium II, Pentium III and early Xeon processors. NetBurst was explicitly designed for extremely high clock speeds through a 20-stage (later 31-stage) hyper-pipeline, a double-pumped (running at twice processor speed) ALU, hyperthreading, an Execution Trace Cache that stored decoded micro-operations instead of re-fetching and re-decoding instructions, and a replay system to recover from mispredicted branches. Despite these innovations, Intel never reached its internal target of Fig.31: a Pentium 4 (Prescott) CPU. This is the final version of the Pentium 4, with x86-64 support, before they were discontinued in favour of the Core series of processors. Source: https://w.wiki/GZX$ (CC BY-SA 4.0) Australia's electronics magazine siliconchip.com.au 10GHz; the fastest shipping Pentium 4 topped out at 3.8GHz (with a brief 4.0GHz Extreme Edition), limited primarily by power consumption and heat dissipation. As a result, Intel abandoned NetBurst in 2006 and introduced the power-efficient Core microarchitecture, which formed the basis of all subsequent mainstream Intel CPUs. Depending on the variant, the Pentium 4 contained between 42 million (Willamette) and 169 million (Prescott-2M) transistors, and was manufactured on process nodes ranging from 180nm down to 65nm – see Fig.31. Itanium Itanium was a family of high-end 64-bit processors from Intel using the IA-64 instruction set, completely unrelated to x86-64. It was aimed at enterprise servers and high-performance systems. See Figs.32, 33 & 34. The design originated at HP as a successor to PA-RISC, based on a new paradigm called EPIC (Explicitly Parallel Instruction Computing). Intel joined the project, and the first Itanium was launched in 2001, with the line eventually discontinued in 2020. Itanium’s defining feature was its VLIW-inspired execution model. Instead of relying on complex hardware to discover instruction-level parallelism at runtime, the compiler packed multiple instructions into ‘bundles’, indicating which operations could execute in parallel. In theory, this simplified the processor and allowed many execution units to stay busy. In practice, it proved extremely difficult for compilers to keep such a wide machine fed, and performance often collapsed unless code was tuned for a specific Itanium generation. This inflexibility earned the architecture the unfortunate nickname “Itanic”. Itanium could run x86 applications through hardware and later software emulation layers, but performance was poor. Ultimately, the architecture failed because of its lack of x86 compatibility, inconsistent real-world performance, compiler complexity, high cost, limited software support and (crucially) the emergence of AMD’s x86-­compatible 64-bit Opteron processors. Intel eventually adopted AMD’s AMD64/x86-64 extension, starting with the Pentium 4 “Prescott” in 2004, then fully committed to it with the siliconchip.com.au Fig.32: an Intel Itanium ES processor module viewed from the pin side. Source: https://w.wiki/GZXx (CC BY 3.0) Fig.33: an Intel Itanium 2 CPU module. Source: https://w.wiki/GZXy Fig.34: an Itanium die shot. Source: der8auer (https://der8auer.com) Australia's electronics magazine March 2026  21 Core 2 series (and every mainstream processor since), effectively sealing Itanium’s fate. Other Pentiums The Pentium 4 was succeeded by the Pentium M (“mobile”; 2003-2006) with 77-140 million transistors on a 130nm-90nm process node, and the Pentium D (“desktop”; 2005-2010) with 230-376 million transistors on a 90nm to 65nm process node. The Pentium D was a dual-core design. The Pentium M did not use the NetBurst microarchitecture, it was based on a modified version of the Pentium III’s P6 microarchitecture with optimised power consumption. It formed the basis of the later Core microachitecture. The D was a performance-orientated dual-core model that did use the NetBurst microarchitecture. The D was Intel’s first mainstream dual-core processor. It was not efficient because the cores could only communicate with each other via the motherboard’s relatively slow front-side bus. To add to the confusion, the Pentium Dual-Core (2006-2010) was based on the more efficient Core microarchitecture. It had 376-410 million transistors and was made with a process node of 65nm or 45nm, depending upon the variant. Also, a revision of the Atom design is used as the “E-cores” in Intel’s hybrid architecture in their 12th and 13th generation Core processor, E-cores are used for task where performance isn’t critical, like handling networking, storage and housekeeping. Core Intel Core brand processors were introduced in January 2006. Yonah was the code name for the first generation of Core processors that replaced Atom the NetBurst microarchitecture. It was The Atom line of x86 energy-­ based on an enhanced Pentium M (P6) efficient mobile processors debuted in microarchitecture and was initially 2008, derived from the Pentium M. It 32-bit only. was discontinued in 2016 due to loss The Yonah core was used in the of competitiveness against ARM-based Core Solo and the Core Duo dual-core processors. However, embedded and mobile products, with 151 million industrial versions of Atom processors transistors on a 65nm process. It was are still available, such as the Atom discontinued in 2008. x7000E or Processor N-series. Core 2 Core 2 was released in July 2006 as the successor to Core. Core 2 used a brand new Core microarchitecture and had 64-bit support (x86-64, compatible with AMD64). Core 2 was released as Core 2, Core 2 Solo (2007), Core 2 Duo and Core 2 Quad models depending upon the number of cores. There were also Core 2 Extreme models for enthusiasts, with a higher clock frequency and an unlocked clock multiplier. Fig.36: the modular structure of a Nehalem (1st Gen Core) processor split into “core” and “uncore” sections. Original Source: https://pcper.com/2008/08/ inside-the-nehalem-intels-new-core-i7-microarchitecture/2/ Core i3/i5/i7/i9 – new naming conventions In November 2008, Intel introduced a new microarchitecture for Core series called Nehalem (see Fig.35), later discontinued in 2010. It came with a new naming scheme, with so-called Tiers representing performance levels. i3 was entry level, i5 mid-range and i7 high-end. i9 was added in 2017 as the top tier. Intel also introduced a new term referring to the Generation of a processor, which corresponds to improvements in performance, power efficiency, features supported and microarchitecture – see Table 5 and Fig.37 overleaf. We discuss the various generations of Intel Core processors in the next section. Nehalem processors used a 45nm process node and had 731-2300 million transistors, depending upon the model. These were called 1st Generation Core processors. A “die shrink” improvement to 32nm was made with Australia's electronics magazine siliconchip.com.au Fig.35: a die shot of a typical Nehalem (1st Gen Core) processor showing various functional elements. Source: https://bjorn3d.com/2008/11/intel-core-i7-920nehalem/ 22 Silicon Chip Table 5 – Intel Core processor generations Generation Brand Intro Year Codename Notable features Original Core Core Solo/Duo 2006 Yonah (mobile) First mobile series, one or two cores Core 2 Core 2 Solo/ Duo/Quad/ Extreme 2006 Conroe, Kentsfield, Wolfdale, Yorkfield, Merom, Penryn First 64-bit support and up to four cores. 1st Gen Core i3/i5/i7 2008-2010 Lynnfield, Bloomfield, Clarkdale, Arrandale Nehalem microarchitecture, integrated memory controller. 2nd Gen Core i3/i5/i7 2011 Sandy Bridge Sandy Bridge microarchitecture, new AVX instructions, integrated GPU. 3rd Gen Core i3/i5/i7 2012 Ivy Bridge Ivy Bridge microarchitecture, 22nm process. 4th Gen Core i3/i5/i7 2013 Haswell, Broadwell-Y Haswell microarchitecture, improved power efficiency. 5th Gen Core i3/i5/i7 2014 Broadwell Broadwell microarchitecture, 14nm process. 6th Gen Core i3/i5/i7 2015 Skylake Skylake microarchitecture, support for DDR4 memory. 7th Gen Core i3/i5/i7 2016 Kaby Lake Kaby Lake microarchitecture and first to abandon tick-tock model. Improved performance and efficiency. 8th Gen Core i3/i5/i7 2017 Coffee Lake, Kaby Lake Refresh, Whiskey Lake, Amber Lake, Cannon Lake Various microarchitectures, increased core counts. 9th Gen Core i3/i5/i7/i9 2018 Coffee Lake Refresh Coffee Lake refresh. 10th Gen Core i3/i5/i7/i9 2020 Comet Lake, Ice Lake, Amber Lake Refresh Various microarchitectures. 11th Gen Core i3/i5/i7/i9 2021 (desktop), Rocket Lake (desktop) 2020 (mobile) Tiger Lake (mobile) Introduced PCIe 4.0 support. 12th Gen Core i3/i5/i7/i9 2021 Alder Lake Hybrid architecture (P-cores + E-cores), Intel 7 process, DDR5 & PCIe 5.0 support. First widely adopted hybrid big. LITTLE architecture. Intel 7 node. 13th Gen Core i3/i5/i7/i9 2022 Raptor Lake Raptor Lake microarchitecture (refresh of Alder Lake). Intel 7 node. 14th Gen Core i3/i5/i7/i9 2023 Raptor Lake refresh Last generation to use “Core I” branding. Intel 7 node. Series 1 Core 3/5/7, Core Ultra 5/7/9 2023 (mobile) Meteor Lake New naming scheme and process, launched in 2023 for mobile with NPU (Neural Processing Unit) for AI. First mainstream Intel processor with chipletbased design. Series 2 Core 3/5/7, Core Ultra 5/7/9 2024-2025 Arrow Lake, Lunar Lake Includes Arrow Lake desktop (2024) and mobile HX/H/U series (early 2025). First Intel desktop processor with chipletbased design. Series 3 Core Ultra 300 Early 2026 series (expected) Panther Lake (mobile) Expected to use the 18A process node the Westmere microarchitecture. Features of this series include a modular and scalable design with separate ‘core units’, which were the execution units and L1 and L2 caches, and ‘uncore units’, which were anything siliconchip.com.au else. Uncore included the L3 cache, the integrated memory controller (IMC) and I/O (USB, PCI Express etc) – see Fig.36. The traditional front-side bus was also replaced with the QuickPath Australia's electronics magazine Interconnect (QPI) for faster communication between processors in multisocket systems, as well as with the rest of the system. Hyperthreading was reintroduced, and Turbo Mode allowed automatic March 2026  23 Fig.37: the naming scheme for Intel Core processors. SKU is the “stock-keeping unit” or the specific model number. Source: www.intel.com/content/www/us/en/ support/articles/000032203/processors/intel-core-processors.html Fig.38: Nehalem’s (1st Gen Core) processor design showing modular building block concept. Source: www.techradar.com/news/computing-components/ processors/intel-s-nehalem-is-a-multi-threading-monster-268687 Intel’s tick-tock model overclocking. Other features included a new SSE 4.2 supplemental x86 instruction set. Nehalem’s modular design allowed Intel to scale the same core building blocks across a wide variety of market segments, from dual-core mobile parts to eight-core server Xeons, simply by adding or subtracting tiles on a die. This modular design should not be confused with the later hybrid architecture. In the Nehalem generation (20082010), all mainstream Core i3/i5/i7 processors were monolithic single-die designs; only certain rare high-end desktop and server processors used a multi-chip module that had a CPU die with an optional separate graphics chip. Regardless of whether the final package contained one or two dies, the CPU itself remained a single monolithic die built from individual building blocks (see Fig.38). The general idea of a modular and scalable design, whether implemented on one monolithic die or multiple dies (later called ‘tiles’ internally and ‘chiplets’ in the broader industry), has been used on all Intel Core processors since Nehalem in 2008. True chiplet (multi-die) consumer Core processors only appeared with Meteor Lake (14th Gen, 2023) and became the standard from Arrow Lake/ Lunar Lake (2024-2025) onward. 2010s: 10nm failures, competitors catch up Fig.39: the tick-tock model for all Intel processors of the 2009-2016 era. The even years bring a new process technology, while the odd years bring a new microarchitecture. The 2010s were characterised by Intel’s repeated delays in moving beyond the 14nm node (introduced with Broadwell, 2014), which saw six generations and six years or more of Core on the same basic node with no reduction in feature size. To be fair, it wasn’t the exact same node used year after year; they did make improvements (leading to the famous 14nm++++ process). Intel failed to reach the 10nm mode in a timely manner (targeted for 2016) and suffered from delays, poor process yields and technical flaws that allowed competitors like AMD, Apple Silicon and ARM to take market share, including in the laptop, desktop and server markets. The tick-tock model was finally abandoned (see panel). Intel’s stock price stagnated, and the decade ended with Intel no longer the unquestioned Australia's electronics magazine siliconchip.com.au Tick-tock was a development model introduced by Intel in 2007 and abandoned in 2016. It was a model that alternated in two-year cycles between reducing the process size (the “ticks”) and improving the microarchitecture of the processor (the “tocks”). Both had the objective of performance boosts via lower power consumption, higher component density and reduced costs. Fig.39 shows how the tick-tock model progressed during most of its period of operation. Note the new microarchitecture (tocks) shown in green and the new process size shown in blue (ticks). The tick-tock model was abandoned because it was no longer economically feasible to keep shrinking dies, ie, Moore’s Law ceased to apply around 2016. 24 Silicon Chip performance and technology leader. Some say Intel’s “10nm disaster” was the result of a technology roadmap that was simply too ambitious. Instead of making a modest shrink from 14nm, Intel attempted to jump directly to a very high-density process with multiple cutting-edge features introduced all at once. Among these were self-aligned quadruple patterning (SAQP) for extremely fine metal pitches, contact-­ over-active-gate (COAG), and the use of cobalt for selected interconnect layers. Each of these was challenging on its own; together, they created a process that was extremely difficult to manufacture at acceptable yields. Compounding these difficulties was Intel’s strategic decision to delay the adoption of EUV (extreme ultraviolet) lithography. The company believed that 193nm immersion lithography, extended through increasingly complicated multi-patterning steps, would remain viable. Meanwhile, competitors such as TSMC and Samsung embraced EUV earlier, simplifying several steps in their 7nm processes. This allowed them to avoid much of the patterning complexity Intel was struggling with, and to achieve usable yields sooner. Another problem was that Intel set extremely aggressive density targets for 10nm: roughly a 2.7× improvement over 14nm. To reach those figures, Intel used very dense standard-cell libraries and restrictive design rules, which caused its design teams to struggle with routing, variability, and timing closure. In essence, the manufacturing process and the design methodology were both too constrained and not sufficiently co-optimised, making it difficult to produce chips that could hit Intel’s desired clock speeds. The result was a multiyear delay in the intended 10nm rollout. The first 10nm generation, Cannon Lake, finally surfaced in 2017-18, but in extremely small quantities, and with key features disabled (most notably the integrated GPU) because yields were still poor. Cannon Lake was essentially a symbolic product launch rather than a viable platform. Real, high-volume 10nm products did not appear until the Ice Lake generation in 2019-2020, two to three years later than planned (and arguably four to five years behind the original roadmap trajectory). siliconchip.com.au These setbacks not only disrupted Intel’s product cadence but also contributed to the end of the company’s historical lead in manufacturing technology – an advantage Intel had held for roughly three decades. While Intel’s mass-production of the 10nm node, intended for 2016, was delayed until 2019, competing foundries such as TSMC started shipping 7nm nodes in 2018. Intel’s 7nm node (branded Intel 4) slipped to 2023 with the release of the Meteor Lake processor. TSMC manufactured many of AMD’s processors using its 7nm process, allowing AMD to obtain increased market share and, in many cases, superior multi-core performance. Core processors During the 2010s and subsequently, Core processors evolved through multiple generations, but all share a common lineage. Some things have changed; others have not. We will not discuss each generation of Core processors, as they mainly represented incremental changes, except for the introduction of the hybrid and then tile architectures. Every Intel Core-branded processor from the 1st Generation (Nehalem/ Westmere, 2008-2010) to the current Core Ultra Series 2 (2024-2025) belongs to the same architectural family that began with the 2006 Core microarchitecture. They all have x86-64 instruction compatibility and include integrated memory controllers, PCIe, and (almost always) graphics, making the Core brand the longest continuous mainstream CPU lineage in the industry. Despite 17 years of massive evolution, a 1st-Gen Core i7-920 and a 2025 Core Ultra 9 285K are still members of the same processor family. Every Intel Core-branded processor from 1st Gen (2008) to the present (2025) has the following aspects in common (from 1st Generation to Core Ultra Series 2). ● All are 64-bit x86 processors using the x86-64 instruction set. ● All descend from the 2006 Core microarchitecture. ● All have an integrated memory controller since Nehalem. ● All have an integrated PCIe controller since Nehalem. ● Most have integrated graphics (except F, KF and X suffix parts). ● Most have Turbo Boost. ● From the Core 2, they all support SSE-SSE3. Nehalem and later add SSE4.1, and all 2nd Gen (Sandy Bridge) and newer include SSE4.2, making the Sandy Bridge family (2011) the practical cut-off for Windows 11 compatibility. ● Intel 64, VT-x, AES-NI, TXT technologies are all present from 1st Gen onward (some added mid-generation). ● Core i3/i5/i7/i9 (later Core Ultra 5/7/9) always indicate relative performance tiers within a generation. The following aspects of Core processors have changed significantly: ● Process nodes (from 45nm to 3nm and beyond). ● The move to a multi-chip module design from monolithic. ● Core counts (from 2 to 38+ in 2025). ● The hybrid big.LITTLE design (from 12th Gen onward). ● The branding shifted to “Core Ultra” (2023+). Fig.40: Intel would normally package their flagship i9 CPUs in interesting boxes. For the 9900K, they used a dodecahedron. Source: www. reddit.com/r/pcmasterrace/ comments/1hhug73/ Australia's electronics magazine March 2026  25 ● New instructions (AVX, AVX2, AVX-512, AMX etc) were added over time. ● Recent chips have a dedicated NPU (neural processing unit). Hardware security problems Further Intel problems emerged in the form of major security vulnerabilities discovered in their processors, beginning with Meltdown and Spectre in 2018. These were not isolated issues, but the first widely publicised examples of a new class of hardware-level side-channel attacks exploiting speculative execution; the very optimisation techniques that had driven CPU performance for years. After the initial disclosures, additional vulnerabilities were uncovered throughout 2018-2020. These included several more Spectre variants and more Intel-specific weaknesses such as Foreshadow (also called L1TF, 2018), which compromised Intel’s SGX secure enclaves, and the ZombieLoad, RIDL, and Fallout attacks (2019), collectively known as MDS (Microarchitectural Data Sampling). Later came SwapGS (2019), TSX Asynchronous Abort (TAA, 2019), CacheOut (2020), Snoop-assisted L1D sampling (Snoop MDS, 2019/2020), and others. Each required microcode patches and/or operating system mitigations, in some cases reducing CPU performance significantly. These vulnerabilities highlighted fundamental defects in speculative execution and cache behaviour, and the need for architectural changes rather than simple software fixes. Intel eventually redesigned parts of its cores (starting with Cascade Lake in 2019, and more fully in subsequent generations) to mitigate some of these flaws in hardware. Earlier processors continue to rely on a combination of firmware and operating system patches, many of which come with performance overheads. These didn’t affect only Intel – AMD processors were vulnerable to some issues too, notably Spectre. However, the vulnerabilities affecting AMD chips were generally far less severe and much easier to mitigate, and the episode clearly shifted the competitive advantage toward AMD’s products. This likely reflects AMD’s more conservative architectural approach to speculative execution, which avoided 26 Silicon Chip many of the pitfalls that plagued Intel’s designs. What is an Intel Core Generation? Intel naming conventions and generations can be very confusing (to say the least). Again, to be fair, AMD’s processor naming scheme isn’t much better. The Generation or Series of an Intel processor is a naming convention that primarily applies to their Core range of processors. Other types of Intel processors such as the Xeon, Pentium, Celeron and “Intel Processor” brand also have generations, but the identification with a specific generation is less prominent and not a marketing feature. The Generation of a Core processor refers to the major product family released roughly every 12-18 months, which usually (but not always) involves a new or refined microarchitecture, an updated manufacturing process, higher core counts, new features, or some combination of these improvements. It is indicated by the first number(s) after the brand in the model name (eg, Core i7-13700K = 13th Generation, Core i9-14900K = 14th Generation). Intel stopped using “Gen” with the 14th Gen and started using Series, eg, Core Ultra 7 200V = Series 2 / Lunar Lake generation – see Table 5. In 2023, Intel introduced a new naming scheme for laptops with the Meteor Lake generation, dropping the old i3/i5/i7/i9 branding and replacing it with the Core Ultra name and a new Series-based numbering system (eg, Core Ultra 7 155H). Desktop processors, however, continued to use the traditional 14th Gen style naming for a transitional period. Core Ultra processors also introduced a built-in Neural Processing Unit (NPU) for on-device AI acceleration. The letters at the end of a traditional Intel CPU model name indicate specific features, for example: ● K means the processor is unlocked and suitable for overclocking ● F has no integrated GPU ● S means special edition ● T means power optimised ● H, HK or HX means the processor is a high-performance type ● P means performance-optimised for thin and light laptops ● U means power-efficient ● Y means extremely low power ● G1-G7 means integrated graphics Australia's electronics magazine of different performance capabilities ● E means embedded with various features (UE, HE etc) Significant changes in the Core lineup were the new hybrid core approach in the 12th Generation and beyond, ongoing improvements in energy efficiency and support for newer features, such as the PCIe 5.0 bus and DDR5 memory. 2020s: hybrid technology, foundry ambitions The 2020s to date have been characterised by Intel’s pursuit of hybrid technology (the use of different processor cores in the one package) and their foundry ambitions to become the “TSMC of the West again”, through their Integrated Device Manufacturing (IDM 2.0) strategy. Intel is also fighting to regain manufacturing leadership and relevance in AI, mobile and beyond-PC markets in an era where “Intel Inside” no longer automatically means dominance. Under Gelsinger’s leadership, Intel’s IDM 2.0 strategy was developed in 2021 as a comprehensive strategy to: a. develop more advanced and competitive chips b. expand manufacturing capacity and capability, particularly in the United States c. launch Intel Foundry Services (IFS) to build chips for other companies d. make strategic use of other foundries such as TSMC when necessary e. develop its own internal foundry model to ensure consistent processes throughout its foundries Some of Intel’s new US foundry developments have also been heavily subsidised by US taxpayers, reflecting a political aim to rebuild domestic semiconductor manufacturing. Under the CHIPS and Science Act, Intel has received billions of dollars in grants, tax incentives and low-cost loans to modernise existing fabs and construct new ones in Arizona, Ohio and other locations. Hybrid architecture: E- and P-cores Intel’s hybrid architecture started with the 12th Generation in 2021 and continues today. These chips contain two kinds of cores: high-performance “P-cores” (big cores) optimised for maximum single-thread speed and heavy workloads, and high-efficiency “E-cores” (little cores) optimised for siliconchip.com.au low power consumption and good multi-threaded throughput at much lower clocks and a smaller die area. The use of the two core types allows less intensive background tasks to use the energy-efficient E-cores, while more intensive high-power tasks, such as video editing, 3D games or CAD, can use the faster P-cores. The main advantage of having the two types of cores is improved energy efficiency without a loss of performance, resulting in greatly improved battery life in mobile devices and less stringent cooling requirements for desktop computers. Windows 11 (and modern Linux) and the Intel Thread Director hardware scheduler decides in real time which threads run on P-cores and which run on E-cores. Alder Lake was the first 12th Generation Core, released in 2021 and discontinued in 2025. It used the Gracemont microarchitecture for its E-cores and the Golden Cove microarchitecture for its P-cores, both fabricated on a single monolithic chip, not separate chiplets or tiles – see Fig.41. Alder Lake used a 14nm or 10nm (Intel 7) process node, depending on version, and had up to eight E-cores and eight P-cores per chip. Intel did not release a transistor count for any version of this processor. Following Alder Lake, the design focus moved to chiplets (known as tiles by Intel), which are individual pieces of silicon in one package, designed with efficiency, cost and flexibility in mind. The first chiplet design was Sapphire Rapids, a Xeon processor, released in 2021. Meteor Lake was the first Core processor to use tiles (Core Series 1, 2023). Next month We’ve run out of space this month, but now that we’ve caught up with the present in terms of Intel’s CPU technology, we’ll shift to look at the current and future technologies they are using to remain competitive. That will include tiles, Foveros Direct 3D interconnections, EMIB, PowerVia, RibbonFET, AI acceleration and their work on dedicated GPUs. We’ll also look into their fabrication facilities, other technologies they helped develop (like USB and Thunderbolt) and provide more detail on their CEOs and other notable people SC who worked for Intel. siliconchip.com.au Fig.41: a die shot of an Alder Lake P with six performance cores, eight efficiency cores and 96 execution units (EUs). EUs assist in computation and/or graphics. Source: https://locuza.substack.com/p/die-walkthrough-alder-lake-sp-and Australia's electronics magazine March 2026  27 Solar Panel Protector and Optimiser by Ian Ashford This simple design offers two useful functions for solar installations, whether it be for the home, the shed or even the caravan. It reduces the chance of damage from lightning while also providing an ‘ideal’ blocking diode function so you can still get power from the panels when some Image source: https://unsplash.com/photos/a-group-of-buildings-with-red-roofs-VgF9kogcU1U are shaded. T he first function of this board is to arrest a lightning-induced surge before damage can occur to the downstream electronics. It also provides a blocking diode function for up to three solar panel strings. A blocking diode allows for the maximum power to be extracted from parallel strings when one or more panels are shaded. The board can be built to provide either or both functions; the choice is yours. Lightning surge protection Lightning is destructive and difficult to defend against. We use lightning rods for tall buildings, Earth conductors above high voltage transmission lines and there are even rockets specially developed for launchpad protection, which will launch themselves into storms trailing an Earthed wire. Many of these protection schemes perform as single-shot devices, but are still a small cost to pay for the protection provided. A single bolt of lightning may release between 200MJ and 7GJ of energy. For comparison, 5kW of solar panels on your roof would take around 11 hours to collect just 200MJ and 16 days to collect 7GJ, yet a storm can 28 Silicon Chip deliver this in a single, instantaneous pulse. And it can do it again, and again, and again in a short period. Lightning can cause significant damage to electrical goods, even if they are not directly in the path of the impact. An induced voltage or current wave can travel in a cable to all your most valued goods from a nearby lightning strike. Complex Earthing routes, including conductive items like train tracks and steel framed buildings, all affect the extent and magnitude of any induced pulses. Any conductive material within close proximity to the strike will likely carry significant currents as the charge dissipates. This design offers a solution for induced pulses. Unfortunately, it can’t do much to help if 7GJ lands in your backyard (or worse, on your panels!). Ultimately, whatever protection you put in place, there can always be a bigger event or a direct hit to thwart your efforts. This surge arrestor is a good start, but it isn’t guaranteed to provide protection for all events and for all causes. Australian and international design standards provide guidance for solar installations and the impact of a lightning induced surge. For example, IEC Australia's electronics magazine 61643 parts 31 and 32 contain relevant information. The standards provide guidance for these effects, and define a typical waveform so the design team can then build circuits and simulations to test their designs against. One of these ‘design’ spikes is a waveform that rises from 0V to 90% of the peak within 8µs (microseconds) and then decays to 50% of the peak within 20µs. This is known as an 8/20 waveform. It is very fast and short lived; this latter part is the key for the success of this design. The actual magnitude of the peak depends on many factors, including the proximity of the protection device to the source and obviously the intensity of the lightning bolt. Measurements conducted by people (who may or may not have been flying kites in a storm) indicate that a surge induced into a roof mounted solar array would require the device to curtail a peak current of up to 20,000 amperes. Even in a low-­impedance wire, this will raise a very high voltage. This circuit is designed to provide an alternative path for the surge, instead of via your panels and connected electronics. It is triggered when the surge voltage exceeds a design threshold. siliconchip.com.au Features & Specifications My installation has three sets of solar panels, all operating around 100Voc. From left to right, 3 strings to catch the westerly sunlight, (2.7kW), 2 strings to catch the sunrise, (1.8kW), and a main bank of 9 pairs of panels facing north, (3.5kW). Maximum protection occurs if the threshold is very close to, but just above, the open-circuit voltage of the connected solar panels. For this design, the fault current that can be absorbed is limited to 20kA with an 8/20 profile. The circuit does not activate under normal operating conditions, and will not affect the normal operation of the solar panels and collection system. For numerous reasons, rooftop solar panels are often installed electrically floating, with neither power conductor referenced to Earth. This design maintains that condition at all times, except during a surge event, when one or more conductors could be shorted to Earth as the device activates. A surge can manifest in one of several ways: it can form between the supply cables or on both conductors, raising a voltage spike between both conductors relative to Earth. The surge can be a positive or negative trending spike and would be superimposed onto the normal operating voltages within the circuit. The surge protection in this design is based on varistors. Until triggered, they exhibit properties similar to a back-to-back pair of zener diodes. Current will flow in either direction once the voltage threshold has been reached. Although small, they can conduct many thousands of amps for very short periods. To operate as a surge arrestor, the siliconchip.com.au varistor is placed between the source of the surge and a safe return path, short-circuiting the surge, while avoiding the downstream hardware. In this design, varistors are installed across the string outputs, to address a surge on one or the other supply line, and also between Earth and each of the two conductors, to provide a path for a surge that raises the potential of both conductors relative to Earth. It is likely that multiple varistors will conduct if a surge propagates through the circuit. Varistors, like zener diodes, are available in a range of voltage and wattage ratings. Ideally, the selection of the varistor should be specific to a particular installation to maximise the protection provided. Commercial surge arrestors are designed for a generic installation, allowing solar string voltages up to 1000V. In this case, the varistor would only provide protection against surges of around 1200V, which for most ● PV panel protection for lightning-induced voltage spikes for up to three strings ● Surge peak capacity of 20kA ● Maximum total throughput of 60A (20A per string) ● 120V maximum open-circuit string voltage ● Maximum protection via selectable surge activation level to suit the installation ● Up to three blocking diodes to prevent energy loss into shaded strings ● Additional units can be connected in parallel if required ● Blocking diodes utilise ‘ideal diodes’ to reduce power losses ● Small footprint ● Low cost installations is already causing damage to your inverters and charge controllers. We want to keep the activation just above the maximum, normal voltage of the system. This may be as low as 25V for a nominal 12V panel, as commonly used in caravans and campers. The varistors must be chosen to prevent activation under normal conditions. As a guide, the voltage rating for the varistor should be above the Voc rating of one panel, multiplied by the number of panels in series, plus an additional 10% to allow for extremely cold weather or minor variances within the components. In this design, there is provision for three solar strings to be connected on one circuit board. Each string has its own surge arrestor components. The positive conductors connect to a common rail, so only one varistor is required to provide a path to Earth, allowing for a reduced parts count. How much energy is in an 8/20 surge? The datasheet states that a surge protector which uses V25S115P varistors will clamp the surge at 295V at 100A. For a peak current of 20kA, and with the varistor clamped at 295V, the peak power would be 5.9MW (295V × 20kA). The duration of the wave, making some assumptions for the decay beyond 20µs, would be around 30µs. So the energy from the lightning surge would equate to the average power level, multiplied by the duration: 5.9MW × 30µs ÷ 2 = 88J. This is the equivalent energy of a 5kg weight suspended 1.8m above the ground. The V25S115P is rated for a pulse of 230J, comfortably over the 88J of the 8/20 surge. Not bad for a device that retails for around $2.50 in batches of 10. Australia's electronics magazine March 2026  29 Multiple boards can be used if required by a particular setup. For maximum protection of downstream appliances, the varistor should have the lowest trigger voltage rating available while staying above the applied solar panel string voltage. For our first example, three identical solar strings are to be connected to the surge arrestor. Each string is comprised of two series-connected 440W solar panels with an open-circuit voltage (Voc) of 52.2V. The string Voc is therefore 104.4V (2 × 52.2V). To ensure against a higher than expected Voc due to cold weather and for component variance, make it 114.8V (10% higher). Thus, we need to select a varistor with a DC voltage rating in excess of 115V. The V25S115P is suitable for an 8/20 22kA peak surge waveform. The datasheet states that the device will commence conducting between 162V (minimum) and 198V (maximum), which is above the calculated value. In our second example, two low-voltage panels are to be connected to the surge arrestor, one per string. Each panel has a Voc of 22V. Allowing an extra 10%, requires a minimum varistor DC voltage rating of 24.2V. In this case, no low-voltage 20kA devices were available for selection. For example, the V20H20P is suitable for an 8/20 5kA peak surge waveform. This device will commence conducting between 30V (minimum) and 36V (maximum). The lower commencement of conduction will offer better protection for voltage-sensitive appliances, even with a lower energy surge capacity. Ultimately, the decision on which varistor to select is something that will need to be addressed for each installation. The PCB has extra holes to cover several different varistor footprints, to account for the different design selections. Datasheets and searchable datasets for these and other varistors are available from major suppliers, including Mouser (https://au.mouser.com/c/circuit-protection/varistors/?mounting%20 style=Through%20Hole&instock=y). Due to cost constraints or other reasons, this is not always the way. Without blocking diodes, the output voltages of the two strings would both be dragged down by the lower illuminated string, resulting in less power being collected. Some of the energy harvested by the illuminated string would also be conducted into the less illuminated string. The only time this system could work optimally is around midday, when the sun is overhead and the strings are equally illuminated. Placing a blocking diode in each string will improve the situation, preventing any losses into the less illuminated panel. For those who enjoy taking a caravan off grid, charging the battery should be easy using the panel on the van roof and an additional plug-in panel, which is shifted around during the day to catch those fleeting rays. Unfortunately, the additional panel rarely doubles the solar collection since the default wiring in most caravans has any additional panel wired in parallel, and they share a single charge controller. Power from the higher voltage panel is wasted, flowing into the other panel instead of charging the batteries. With a blocking diode inserted after each panel, the maximum energy available is sent to the battery, eliminating any waste. To prevent losses, the blocking diodes in this design are provided using ‘ideal diodes’. A standard diode would dissipate around 10W when conducting 10A. The ideal diodes have a voltage drop of around 0.1V and therefore only dissipate around 1W for the same function. For the 200W panel used on a caravan, that saving represents an appreciable portion of the energy available for collection. This part of the circuit is similar to our Ideal Diode circuits published in the December 2023 (siliconchip.au/ Article/16043) and September 2024 issue (siliconchip.au/Article/16580). This version can be simpler because it’s used in a very specific configuration. The design includes a small heatsink for each Mosfet to allow for measuring of the short-circuit current rating of the attached array, a measurement that is required to be performed before completing the commissioning of a solar installation. Australia's electronics magazine siliconchip.com.au Blocking diodes The second part of the design is thankfully less energetic and much simpler. When two or more solar panels or strings are operated in parallel, even if electrically identical, they will have minor differences in performance. All other things being otherwise equal, the hotter panel will have a marginally lower peak operating voltage than the cooler panel and will produce a little less power. For minor differences, the parallel strings will both provide power at an average voltage and deliver only slightly below the peak power levels expected. If one panel is heavily shaded, though, the output from the shaded string is well below the other. The higher voltage string will push current into the other string, wasting power that could have been delivered to your appliances. If three or more strings are connected together, the shaded string could be damaged by the current from the unshaded strings, fusing internal conductors or even the cables and conductors between the panels. Installation guidelines were recently amended by regulators and now all new installations, where more than two strings are connected, must be fitted with a blocking diode to prevent this reverse current. This was not mandated as a correction for existing installations. A blocking diode will also allow the less productive string to be excluded should its output fall too low. A high-quality maximum power point tracker (MPPT) will still perform faultlessly with the diodes in circuit, and will continue to find the maximum power point whether it be from one string in full sun or with two strings operating at the lower, shaded panel voltage. The blocking diodes will ensure that power always goes to your appliances and never flows from one string into another, avoiding losses. For some households, a north-facing rooftop is not readily available, and the panels may be split into two halves. One string will be on an east-facing roof, the other west-facing. These installations should really be using two solar charge controllers, one to handle each orientation, to ensure that the maximum power is collected throughout the day. Selecting the varistors 30 Silicon Chip The surge protection devices must be installed in a suitable enclosure to prevent inadvertent contact. Choose a location electrically close to the panels, to allow for some additional protection to the downsteam devices due to any additional cable length and resistance offered by any conductors or isolation devices further along the circuit. During the test, the two outputs, labelled Common Positive and Common Negative on this design, may be shorted together, resulting in 0V between the two. Current will continue to flow through the Mosfet, but its driver chip will be unpowered, providing no gate voltage to the Mosfet. Under these unique conditions, the Mosfet’s dissipation will be similar to that of a silicon diode, typically in the order of 1W per amp of current. To prevent damage to the Mosfet, this test should be undertaken only for short durations, monitoring the temperature of the Mosfet. The preferred solution is to measure the short-circuit current by shorting the inputs to the PCB instead, excluding the Mosfets from the short-circuit path. Circuit details The circuit is shown in Fig.1; it contains three nearly identical circuits, duplicated to provide the surge arrest function and blocking diode function for three strings. The circuit can be built for one, two or three strings by omitting the appropriate parts. siliconchip.com.au If surge protection is not required, omit the varistors. If blocking diodes are not required, the Mosfets and associated parts can be omitted and wire links added, shorting the source and drain at each Mosfet location. Two varistors are installed per solar panel string, plus one additional varistor from the common positive rail to Earth. All varistors are identical and should be selected to provide maximum protection to your solar array, as per the accompanying panel. The ideal diodes are based on the ZXGD3111 chip, an active ORing Mosfet controller with a 200V upper limit. This controller requires diodes in the negative leg, rather than the more traditional positive supply conductor. The controller will switch on the Mosfet once the voltage measured between the source and drain connections exceeds the internal threshold of around 3mV. A simple linear power supply based on transistor Q4 and zener diode D1 provides approximately 18V to each of the ideal diode drivers. For string voltages less than 20V, all components associated with the voltage regulator can be Australia's electronics magazine omitted, with power for the driver chip being provided directly from the common positive rail by shorting the emitter and collector pads for Q4. In this case, retain the three bypass capacitors close to the driver chips. For intermediate voltages, in the range of 20V to 60V, one of the 47kW resistors should be replaced with a short length of wire to ensure sufficient current flow to the zener diode and to maintain regulation for the base current flowing into Q4. The Mosfets are N-channel types, which outperform P-channel units in the magnitude of the internal resistance, current capacity and most importantly their cost. When selecting a Mosfet, choose a component that will ensure that the Vds and current rating comfortably exceeds the maximum Voc and Isc of the attached strings and choose a component with an RDSon of less than 10mW. This requirement is easily achieved at lower voltages and lower current levels. At the time of writing, the NTP011N15MC costs a little over $3 a piece. It has a 150V drain-to-source breakdown rating and can conduct March 2026  31 73A. In this design, it is safe to utilise these for a solar array up to 120V and 20A. PCB design The circuit board configuration is shown in Fig.2. Termination points are provided for the solar panel strings on the left-hand side of the board. For each string, the positive and negative terminals straddle a low-impedance Earth conductor, providing a very short path for any surge currents. All terminals to the board are rated well in excess of the 200V upper limit for the ideal diode driver chip, and can handle a continuous current of 80A. During a surge, it can be expected that all conductive surfaces on the left Fig.1: the circuit consists of three virtually identical blocks, with the power supply components (Q4, ZD1 etc) and VAR1 shared between them. Each block has one varistor between the inputs, one from the negative input to Earth and one from the shared positive output to Earth. The ICs make the Mosfets act like almost ideal diodes. 32 Silicon Chip Australia's electronics magazine hand side of the board, including the Earth connection, will be operating at their upper design limits and may even show signs of charring around component legs where the copper conductor areas are smallest. Absorbing or redirecting 20kA is not an easy task. Assembly The device is built on a double-sided PCB coded 17112251 that measures 74.5 × 150mm. A mix of throughhole and SMD parts are all mounted on the top side. All of the SMDs are large enough to be installed by a competent constructor using a decent soldering iron if a hot air rework station is not available. Construction is simple. Start by inspecting the board for any obvious defects; there are only a few finer tracks and these should be an easy task to confirm that they have continuity. Pay particular attention to the supply tracks that start from the bottom of the board, running up the middle, to the controller for Q1. Start by installing the controller chips first; with seven leads, they are difficult to get in the wrong orientation. Then fit the parts associated with the 18V supply along the base of the board, followed by the capacitors beside the driver chips. Clean up any solder bridges and retouch any connections that may be incomplete or lack fusion. Then press the terminals onto the board. They are a firm fit and should not fall out after installation. Turn over the board or solder from the top if you have room. Solder all four legs, ensuring a good conductive path for each. The Mosfets are next; each tab is tied to the drain. No isolation washer was used on the prototype boards as the heatsinks are well spaced and pose no greater touch risk than the adjacent lugged terminals. In each case, secure the heatsink to the Mosfet using a 3mm washers, nut and bolt. Press the heatsink onto the board, aligning the Mosfet leads. After seating the heatsink, solder the support legs to the board and then solder the Mosfet leads. If the blocking diode function is not required, don’t fit the Mosfets but remember to solder a shorting wire between the drain and source at each Mosfet location. Carefully unpack the varistors and place them on the board, as low as they siliconchip.com.au Fig.2: when assembling the PCB, fit the SMDs first and take care with the orientation of IC1-IC3 and ZD1. The ICs should have a dot, divot or beveled edge indicating the pin 1 side and they must be orientated as shown here. ZD1’s cathode stripe goes towards the regulator. Attach the Mosfets to the heatsinks before soldering the pins. will go without cracking any of their rigid coating. Solder the legs from the underside, trimming the excess away. Set-up and testing There are no adjustments to be made to the board. After completing the construction, check for any shorts or dry joints, rectifying as required. Testing is a two-step process. Step one is to confirm operation of the power supply. Connect a DC supply to the output terminals, paying attention to the polarity. Raise the voltage from zero to approximately 30V; the 18V rail will begin to rise, then should be fixed around 18V as the connected supply continues to rise. Do not proceed past 20V if the rail is not performing as expected. The 18V rail can be measured on pin 3 of Q4, with ground being the negative output terminal. siliconchip.com.au Carefully confirm that the 18V rail is present on the top side of the bypass capacitors for IC1-IC3. If all is correct, disconnect the testing power supply and continue with installation. The board needs to be housed in a conductive metal enclosure that is well Earthed. Drill and/or punch the enclosure panels to allow for cable glands and/or MC4 style connectors. Drill a neat hole and remove any paint adjacent ready for bolting an Earth cable to the external face of the enclosure. Use star washers to ensure the bolt has a good electrical connection to the box, as shown in Fig.3. Use a similar connection internally for the PCB’s Earth connection and don’t forget to Earth the door if it is hinged. Fig.3: how to attach an Earthing bolt to the interior of the enclosure. Star washers should be used to ensure a good electrical connection. Australia's electronics magazine March 2026  33 Parts List – Solar Panel Protector (per board) 1 double-sided PCB coded 17112251, 74.5 × 150mm 5-9 4mm screw terminals (CON1-CON9) [Amphenol AMT0440008TH0000G] 5-9 M4 × 6mm panhead machine screws (for CON1-CON9) 3-7 varistors, type depending on PV array details (VAR1-VAR7) (see panel; V25S115P used in the prototype) 1-3 ZXGD3111N7TC N+1 ORing Controller ICs, SOIC-7 (IC1-IC3) 1-3 NTP011N15MC 150V 74A N-channel Mosfets, TO-220 (Q1-Q3) 1-3 PCB-mounting TO-220 heatsinks [Wakefield-Vette 657-10ABPE] 1 PZTA42 300V 500mA NPN transistor, SOT-223 (Q4) 1 SMAZ18-13-F 18V 1W or CMZ5931B 18V 1.5W zener diode, DO-214AC (ZD1) 4 4.7μF 50V X7R M3216/1206 SMD MLCC capacitors 2 47kW ±5% ¼W M3216/1206 SMD resistors 1-3 M3 × 10mm panhead machine screws 1-3 M3 hex nuts 8 M3 × 6mm panhead machine screws 4 12mm-long M3-tapped Nylon spacers * wiring is not included in the parts list Why no fuses? Would a fuse on the supply cables prevent damage downstream? In this application, any fuses must be able to interrupt the surge from arcing over and therefore need an interrupt rating of at least 20kA. If not adequately rated, the fuse will continue to conduct after the wire has evaporated, performing more like a 0W fluorescent tube than a protection device. For a typical solar panel, the short circuit current would be around 9A, so a 10A-rated fuse should be sufficient. During a lightning induced surge, the current will rise rapidly toward the peak at 20kA. Intuition and basic maths tells us that 20kA is much, much bigger than 10A and hence the fuse will blow. Right? Unfortunately fuses don’t operate instantaneously, they take a finite time to melt, even at 20kA. A typical 10A fuse with a rated interrupt value of 20kA will take approximately 50µs to break at 20kA, too long to be of any benefit when controlling an 8/20 surge. For the protection of electronics, very fast acting devices are required; fuses just aren’t fast enough. Another photo showing the internals of the Solar Panel Protector. If you were to use a fuse, it would need a 20kA rating, like this SPF001 1000V DC fuse by Littlefuse. 34 Silicon Chip Australia's electronics magazine If directly terminating cables to the PCB, measure twice and cut once, allowing a little extra length for bends and for any minor mistakes when crimping the lug to the cable. It is better to be looking at the cable rather than looking for it. If using MC4 panel sockets/plugs, use connecting cable of similar cross sectional area; multi-strand, if possible, to allow for tighter bends. Ensure all connecting cables are rated for the currents and voltages being applied. The current rating is specifically important because the solar panels will be delivering their rated current for many hours at a time, often on hot days. Ensure all cables are correctly run and secured using the correct torque for each terminal (1.1Nm/10lbf. in). Connections must be made by an appropriately skilled person for low-voltage applications and, where mandated due to higher voltages, you must use a qualified electrician. If in doubt, have an electrician skilled in solar installations perform the work. Connections to the solar array should only be undertaken with the panels isolated. Do not work on live cables. Once all terminals are connected, visually check for the correct polarity if using colour-coded cable. Close the cabinet and re-energise. If your charge controller is showing an input, assuming it is sunny, then all is going well. If not, double-check the polarity of any connections and rectify as required. The voltage drop across each ‘diode’ is difficult to measure. The best way to do this, is to measure the voltage from the common negative output back to the individual negative inputs, and be very careful around the supply cables. In normal operation, this should be around 10mV for each amp of current flowing. If all is OK, that’s it. Close the lid. Good practice dictates that the Earth conductor should be run with the output conductors in the same conduit and be terminated to the frame of the inverter or Earthed charge controller. Ensure that the downstream Earth connection is well grounded and securely attached. For isolated applications, like a caravan being used off grid, there will be no Earth connection tied to the soil outside. Connect the Earth terminal to the frame of the inverter or charge SC controller. siliconchip.com.au BIG TECH altronics.com.au BUYS! NEW! X 7063A 299 $ With outdoor sensors! Loads of new products. Great deals on DC power, tools and more! X 0217 NEW! LIVE & LOCAL WEATHER. 29.95 $ Wireless Weather Monitoring Station. X 6100 White X 6101 Black SAVE $20 129 $ Cool Air, Anywhere! Our new fully updated weather station displays your local weather data - great for boaties & gardeners. 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Sale Ends March 31st 2025 Shop in-store at one of our 11 locations around Australia: WA » PERTH » JOONDALUP » CANNINGTON » MIDLAND » MYAREE » BALCATTA VIC » SPRINGVALE » AIRPORT WEST QLD » VIRGINIA NSW » AUBURN SA » PROSPECT Or find a local reseller at: altronics.com.au/storelocations/dealers/ Shop online 24/7 <at> altronics.com.au B 0003 © 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. 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. Converting a mousetrap into a third hand for soldering SMDs Small SMDs can be difficult to manipulate, especially when using old and shaky hands like mine. Sticky tweezers and solder flux don’t help either. This low-tech project can help. There are many other variations, but for a very cheap, versatile and semi-precision component pinning device, this one’s pretty good. Once lightly pinned to a PCB, an SMD can be moved slightly (~5mm), or the underlying PCB moved, and/or the SMD rotated to the correct alignment for that all-important first pin soldering. A pair of wooden mousetraps (one for a spare mouse!) will cost around $5-6 or so from a hardware outlet. Disassemble one down to the basic spring element as shown and replace the square-bent wire with the long straight trigger wire as the internal retaining shaft for the spring. Don’t bother trying to straighten the square-bent wire for the long pinning arm; the sharp bends strain harden the metal and it will fracture very easily, even if pre-heated. Visit your local hobby shop and obtain a ‘push-rod’, a tempered straight wire rod used in the fuselage of model aircraft. They are usually 400mm or more long, and ideally 1.6-1.8mm in diameter. A push-rod of this diameter has the correct stiffness siliconchip.com.au needed in this application as the long pinning wire. Cut down the timber baseplate of the mousetrap and prepare to mount it on a scrap piece of chipboard approximately 250 × 250 × 20mm, either with glue or using four countersunk screws; I used the latter. Chipboard is preferred to a polished surface as the texture provides good grip on a bench. The end of the push-rod needs to be more or less centred on the board, around 100mm from the internal spring shaft. Allow another 20mm for the L-shaped bend to the pinning point. Use needle-nosed pliers to bend a fine loop in one end of the trimmed push-rod, insert it over the spring retaining shaft and, when positioned, crimp the loop down firmly. When remounted, use the other spare U-shaped pin and locate it close to the other side of the loop, ie, with one pin on each side of the loop. Pre-drilling two locating holes with a 1.5mm drill bit helps. All three shaft pins can now be seated firmly down onto the timberwork surface to create as much stability as possible. Excess metal from the pins protruding through the timber backing can be trimmed off flush with the timber surface. The other end of the trimmed push- Australia's electronics magazine rod, the pinning point, needs to be sharpened on a grinding wheel. This is best achieved before bending it into the final L shape. The desired outline is much like a miniature version of a new pencil – long and tapered to a point, with a tiny flat on the end to avoid impaling or otherwise damaging a fragile component. Make the job a lot easier by using the attached mousetrap base as a temporary handle to rotate the push-rod shaft while sharpening. In the lateral view of the pinning push-rod shaft, you will notice a slight bend just past the point of application of the spring. This raises the end portion of the shaft parallel to the surface of the baseplate, but more importantly, activates the spring permanently at the same time. The constant spring pressure helps to stabilise the rod in contact with an SMD on a PCB. The pinning pressure of the spring on a component is light and harmless but quite positive. While nothing fiddly is easy, practice makes perfect (almost). I would recommend an afternoon’s practice soldering old SMDs using the third hand. It gave me the confidence to use SMD technology. Colin O’Donnell, Adelaide, SA. ($75) March 2026  39 By Andrew Levido Power Electronics Part 5: power factor correction & EMI filtering In last month’s article, we mentioned the importance of power factor for an efficient electrical grid. This time, we will look at some active techniques that can help in this regard. We will also cover EMI filtering, which is related in the sense that it is also concerned with the mitigation of unwanted current harmonics. E lectromagnetic interference (EMI) is a general term for any disturbance caused by an electromagnetic field that negatively impacts the performance of electrical or electronic equipment. EMI can be radiated through space or conducted from one device to another through signal or power cables. While you can (and should) take steps to make sure your designs are not susceptible to EMI produced by other devices, your main focus should be on making sure your designs are not producing unacceptable levels of EMI that could affect other equipment. EMI standards such as EN55032 require radiated emissions in the 30MHz to 1GHz range to be below certain field strength thresholds when tested with a standard antenna at a distance of 10m. Mitigating radiated EMI requires close attention to shielding of enclosures, grounding, minimising conductor loop areas, optimising PCB layout, the use of ground planes and controlling the slew rate of signals. Conducted EMI We will focus on conducted EMI, specifically signals that are conducted back into the power source by switching converters. The standards are generally concerned with frequencies in the 150kHz to 30MHz range, and require the level of signals within to fall below specified thresholds over different parts of the band, typically measured using a spectrum analyser. To give you an idea of what is required, conducted EMI for a Class A device must be below 79dBµV from 150kHz to 500kHz and below 73dBµV from 500kHz to 30MHz when measured with a ‘quasi-peak’ detector. The dBµV units describe the amplitude of the conducted emissions with respect to a 1µV reference. 79dBµV is therefore about 9mV RMS and 73dBµV is about 4.5mV RMS. Requirements for Class B devices are considerably lower. EMI is usually managed by the addition of filters on the lines. The switching frequency of many modern converters is higher than 150kHz, so the converter’s input filter plays a critical role in meeting conducted EMI specifications. Fig.1 shows a standard buck converter with a simple capacitive input filter Cf and with source impedance Zs. Our task is to analyse this filter and ensure that the voltage amplitude of the switching-frequency ripple (and its harmonics) is below the required threshold. So far in this series, we have used average value analysis to understand the converter’s periodic steady-state (PSS) operation and complex frequency analysis to determine the converter’s dynamic performance. Neither of these will help us now, so we will revert to good old AC time-domain analysis. This is a technique which, as its name suggests, ignores the DC component of the signal and focuses on the AC component. For example, the PSS model shows us that the input current (ix) of the converter in Fig.1 has a rectangular shape with a duty cycle D and an amplitude of Il as shown in the upper chart there. If we remove the DC component of the input current, we get the alternative picture shown in the lower chart. I have shown the current here with a duty cycle of 0.5, which gives the highest AC RMS current. If the duty cycle moves away from 0.5 in either direction, the RMS current decreases, Fig.1: the AC time-domain analysis equivalent circuit of this buck converter replaces everything to the right of the input filter capacitor with an AC current source. 40 Silicon Chip Australia's electronics magazine siliconchip.com.au reaching zero at the extremes when D = 0 or D = 1. This is a common approximation because we usually want to design EMI filters for the worst-case situation. It is also easiest to calculate the harmonics of the AC waveform if it is a true square wave. The lower circuit in Fig.1 shows the AC analysis model of the buck converter. Everything to the right of the input filter capacitor is replaced with an AC current source ix(ac), and the DC voltage source is eliminated altogether. In this case, the current source will be a variable duty cycle rectangular wave with a peak-to-peak amplitude of Il. We will use this model to design a suitable input filter in a moment. First, we should think about how we are going to measure the conducted EMI in this circuit. The voltage that our spectrum analyser would see, vs(ac), is obviously highly dependent on the source impedance, Zs. We can assume this is quite low at DC, but who knows what it will look like over the 150kHz to 30MHz band of interest. Fig.2: to measure conducted EMI consistently, we need to use a line impedance stabilisation network (LISN) like this. The component values are provided in the relevant EMI standard. The LISN To make meaningful and repeatable EMI measurements, we have to specify a standard source impedance at the frequency of interest. For this reason we use a line impedance stabilisation network (LISN) when making conducted EMI measurements. LISNs are used with both DC and AC sources. Fig.2 shows the AC model connected to a voltage source with impedance Zs via a LISN inside the dotted box. I have reinstated the source voltage to indicate that the converter is powered through the LISN, which has a low impedance at DC or mains frequency but presents a load of 50W to the converter input at the frequencies of interest. The LISN’s inductor and capacitor values are chosen so that Cs is effectively a short circuit and Llisn is effectively open-circuit at the measurement frequencies. The impedance at the converter’s input is therefore the 50W input impedance of the spectrum analyser. Clisn blocks any DC or mains-­ frequency AC from reaching the analyser, since the converter has to be powered up to make the measurements. The LISN’s component values are specified in the relevant EMI standard, but typical values might be Cs = 1µF, siliconchip.com.au Fig.3: we have to be concerned with both differential-mode and common-mode EMI currents – each of which poses unique filtering challenges. Llisn = 50µH and Clisn = 100nF. Most LISNs use air-cored inductors to keep stray capacitances low, and there may be a resistor in series with Cs to damp resonances (more on this below). There will probably also be a highvalue resistor (≥1kW) between the measurement terminal and common so that the measurement terminal does not float when no spectrum analyser is connected. Commercial LISNs may also include additional filter stage(s) on the source side to limit the influence that EMI entering from the source has on the measurement. The LISN network shown in Fig.2 is repeated on the positive and negative lines in a DC LISN, and on each phase and the Neutral conductor of an AC LISN so that common-mode and differential-mode measurements can be made. Australia's electronics magazine Common mode versus differential mode So far we have been analysing converters and their input filters using a huge assumption: we have assumed that all current flowing into one input terminal flows out of the other one as per the upper diagram in Fig.3. This has been a reasonable thing to do for everything we have done so far, but it does not stand up when we are looking at higher frequencies. The lower diagram represents an alternative high-frequency current path where there is some parasitic capacitance to Earth, for example between the drain tab of a TO-220 Mosfet and an Earthed heatsink. This current enters via the positive input terminal but returns to the source via Earth – there is no corresponding current coming out of the negative input terminal. March 2026  41 Fig.4: an LC differential-mode filter like this one may require damping to eliminate oscillations caused by gain peaking at the LC resonant frequency. This is just one possible alternative path for current to flow; there will be many in a real converter, including some related to the negative terminal. In reality, both types of current flow will be happening at the same time, so the currents labelled i1 and i2 will be the sum of the two. The current that flows into one terminal and out the other is termed the differential-mode current (idm), and the current that only flows into one terminal is the common-­ mode current, icm. The differential-mode current includes the normal operating current of the converter, including all of its harmonics, while the common-mode current is related to leakage paths. Mathematically, idm is defined to be ½(i1 – i2) and icm is i1 + i2. Note that both i1 and i2 flow into the converter in this model. These definitions give a clue to the names; differential-mode current is related to the difference in currents flowing into the converter, while common-mode currents are related to the total current flowing into both terminals. It is perhaps more intuitive to look at these equations from the other direction – in terms of the currents into the positive terminal and that coming out of the negative one, ie, i1 and -i2, respectively. In this case, i1 = idm + ½icm and -i2 = idm – ½icm. In other words, differential-­ mode current flows into one terminal and out the other, while common-­ mode current flows equally into both terminals and out somewhere else. Differential-mode input filter EMI standards put limits on both differential-mode and common-mode interference, so both have to be filtered. These two filtering problems are different in nature and have different challenges and solutions. We’ll start with the differential-mode filter. To do this, we will go back to the AC analysis model we created in Fig.1. The input filter was a simple capacitor, 42 Silicon Chip and we saw that its effectiveness was dependent on the source impedance. For EMI measurements, we can use a LISN to standardise the source impedance, but for everyday operation, we are stuck with an unknown impedance. We can reduce this dependence by employing an LC filter like that shown in the AC equivalent circuit of Fig.4. I have drawn this filter as it appears in the converter, with its input on the right and its output on the left. You might be wondering why, if this is the case, the inductor is on the output side of the filter and not on the input side, as is usual for LC filters. This is a current-sourced filter, so the source has a much higher impedance than the load (Zs). In a typical voltage-sourced filter, the source has a lower impedance than the load. In both cases, the filter works most effectively if the inductor is on the low-impedance side, since its impedance increases with frequency. The graphs to the right of the schematic show the current transfer function of the filter (ratio of output current is to input current ix), which looks like that of any typical LC low-pass filter. The cutoff frequency is 1 ÷ (2π√Lf Cf), and the roll-off is -40dB per decade. To the right of that is the filter’s impedance characteristic. At frequencies well below fc, the impedance is dominated by the inductance; at frequencies above fc, it is dominated by the capacitance. With ideal components, as we approach the cutoff frequency, the magnitude of the transfer function and impedance are theoretically infinite. With real components, there will always be some degree of natural damping, but LC filters often exhibit significant peaking at the resonant frequency, as shown dotted in the diagrams. LC filters tend to oscillate because of this peaking, especially if excited by a harmonic-rich square wave. This Australia's electronics magazine problem is compounded in power electronics because switching converters often have a negative input resistance. This negative resistance provides ‘negative damping’ and increases the likelihood of oscillation. To understand how a switching converter can exhibit negative input resistance, consider a DC-DC converter with a fixed output voltage and load. Under these circumstances, some amount of power is being delivered to the load and consequently drawn from the input source. If the input voltage were to rise a little bit, the control loop would adjust the duty cycle to keep the output voltage constant. The output power remains constant, so therefore does the input power, causing the input current to drop slightly. Ohm’s Law dictates that the input resistance is the change in voltage (positive in our example) divided by the change in current (negative), so the incremental input resistance must be negative. Damping For these reasons, it is quite common to require some form of damping on the input LC filter of a switching converter. Fig.5 shows one common way to do this. The damping capacitor Cd is larger than the filter capacitor, so it appears close to a short circuit at the undamped filter’s resonant frequency. This puts Rd effectively in parallel with Cf, providing the necessary damping. This series resistor/ capacitor combination is often referred to as a ‘snubber’. Selecting the damping resistor value is an optimisation problem. If it is too small, the damping capacitor appears in parallel with Cf, shifting the cutoff frequency but not contributing much damping. If it is too large, it also does not provide much damping. The optimum resistor value depends on the ratio of Cd to Cf, which is usually denoted by the Greek letter xi (ξ). siliconchip.com.au Their derivation is a bit complicated, but you can use the expressions to the right of Fig.5 to calculate the optimum value of the damping resistor and the resulting maximum impedance of the filter. The latter is important because we need to keep it low to reduce the impact of the converter’s negative input impedance. A realistic example It is probably easier to follow if we work through a simple example. Let’s assume we have a 60W buck converter with a 12V input and 6V/10A output operating at a frequency of 500kHz. The worst-case duty cycle is 0.5, so the AC input current will be a square wave with a peak-to-peak amplitude of 10A. Let us suppose that we want to design an input filter that reduces this current ripple by a factor of 100, to no more than 100mA peak-to-peak. We first have to work out the cutoff frequency of an undamped LC filter that will give us the required attenuation. We do this by initially assuming that most of the energy in the square wave occurs at the fundamental frequency. We know a square wave only has odd harmonics, and that their amplitude is given by In(pk-pk) = 2I(pk-pk) ÷ nπ, where n is the harmonic number. The peak-to-peak amplitude of the fundamental component of current will therefore be 6.37A. Just as a check, the next harmonic (the third) would have an amplitude 1/3 of that, or 2.12A, and each subsequent harmonic will have a proportionally lower amplitude. The desired attenuation factor of 100 means we require the peak-topeak amplitude of the fundamental component of the filter’s output to be 63.7mA or lower. We will use a lower value, say 25mA, to account for the fact that we have only considered the fundamental component. We can now calculate the required cut-off frequency to achieve this level of attenuation from the relationship is ÷ ix = fc2 ÷ fsw2. Rearranging and substituting in the switching frequency and currents gives us a filter cut-off frequency of 31.3kHz. We can use this to choose the filter components using the equation fc = 1 ÷ 2π√Lf Cf. However, we can’t just chose any values for L and C, because we also want to make sure that the filter’s impedance Zf = √Lf ÷ Cf is significantly siliconchip.com.au smaller in magnitude that the converter’s (negative) input impedance to minimise the probability of unwanted behaviour. The converter’s input impedance is easily calculated by Ohm’s law to be -2.4W (-12V ÷ 5A). If we therefore choose Zf to be 0.2W and use both equations, we end up with a value for Lf of 1.01µH and for Cf of 25.4µF. We can safely round these to 1µH and 25µF, respectively. Just out of interest, I simulated the circuit with these values and without any damping. I used a simple square wave current source (no negative impedance) and set the source impedance to zero, as per Fig.6(a). The result is shown in Fig.6(b). The switching frequency is certainly attenuated significantly (you can’t really see it), but the filter oscillates with a peak-to-peak amplitude of 12A at the resonant frequency. Clearly, we do need to add the damping capacitor and resistor. Given the filter capacitance Cf is 25µF, would be convenient to set ξ to 4, making Cd a nice round 100µF. The formulae in Fig.5 give us an optimum value for Rd of 0.14W and a maximum filter impedance of 0.17W. This is not a huge amount of damping resistance, so it is possible that some or all of it can come from the damping capacitor’s ESR if you were to use an electrolytic here – for once, the ESR of a capacitor comes in handy! I simulated the damped filter, with the results as shown in Fig.7. Note the difference in scales between the damped and undamped responses. You can see that the switching frequency ripple has been reduced to about 50mA peak-to-peak, inline with our design criteria, but there is some Fig.5: the addition of a damping resistor and capacitor, as shown here, is often necessary to minimise the oscillation in an LC filter. The optimum values can be determined from the equations on the right. Fig.6: the simulation circuit (left) to check the oscillation of an LC filter. Without damping (Cd and Rd omitted), the filter oscillates at its resonant frequency and with an amplitude of 12A peak-to-peak (below). Australia's electronics magazine March 2026  43 residual ripple (200mA peak-to-peak) at the filter’s resonant frequency. Fortunately, this is well below the bottom end of the EMI frequency range, so it might be something we could live with. Common-mode input filters A differential mode filter like this will have no effect on common-mode signals because there is a low impedance path for common-mode signals through it via the ‘ground’ line. A common-­mode filter therefore has to be effective on both conductors. This is often achieved with the use of coupled inductors, as shown in Fig.8. These are also often called common-mode inductors or common-­mode chokes. The windings are arranged such that the flux produced by differential-mode current cancels out, as shown at the left of the figure, while that due to common-­mode currents adds up. With perfect coupling, the differential-mode current, which includes the relatively high operating current, does not produce any flux in the core. No flux means no differential-mode inductance and no flux density, so the core can be much smaller than it would otherwise have to be. With perfect coupling, common-­ mode inductors present an inductance to common-mode signals but appear ‘invisible’ to differential-mode signals. Because the windings on these inductors are often at high voltages with respect to each other, they tend to be wound on opposite sides of a toroidal core, which means there will be some leakage inductance, so in reality there will be some meaningful level of differential-mode inductance, although lower than the common-­ mode inductance. You can see the common-mode inductor with the blue core in Fig.14 towards the top of the picture. The two windings and the spacing between them are clearly visible. Although it only produces a small amount of flux, the differential-­mode current still flows through the windings, so they must be dimensioned appropriately. Common-mode chokes are not restricted to two windings; three-winding common-mode chokes are used to build filters for three-phase systems, for example. When we designed the differential-­ mode filter above, we started with a clear model of the source current ix and worked from there. The source of the common-mode currents is leakage through circuit parasitics, so developing such a model is not really feasible. The ‘right’ way to start the design is to build the circuit without a filter and measure the raw common-mode noise across the spectrum of interest. We could then use the limits in the appropriate EMI standard to determine the required filter characteristic and proceed from there. Most of the time, this is not practical, and there are some practical limitations on the design of mains common-­mode filters that mean that many decisions are made for you. You can usually therefore do a good enough job by selecting ‘reasonable’ component values and validating through testing. Fig.9 shows a typical example of a single-stage common-mode filter designed for mains use, with the supply on the left and the converter (the source of the common-mode noise current) on the right. The common-mode inductance of L and the two Cy capacitors forms the common-mode filter. The leakage inductance of L and the capacitor labelled Cx2 form a differential-­mode filter. Capacitor Cx1 (not always present) provides some filtering of noise coming into the converter and reduces the input source impedance at higher frequencies. The resistor is there to discharge the capacitors when the mains is removed so the mains plug does not pose a shock hazard. Class-X & Class-Y capacitors Fig.7: adding the damping components reduced the ripple to 100mA peak-topeak. The 500kHz switching ripple is attenuated to approximately half of that. Fig.8: a common-mode inductor has two windings arranged so that the fluxes produced by differential-mode currents cancel and those due to common-mode currents add. 44 Silicon Chip Australia's electronics magazine It is no accident that I have labelled the capacitors X and Y. It is mandatory to use safety-certified “Class X” capacitors across the mains and “Class Y” capacitors from Active (or Line) to Earth. Apart from having appropriate voltage ratings, these capacitors are designed to fail safely. Class Y capacitors have the most stringent requirements; they are required to fail open-circuit so that the mains is never shorted to the device enclosure, endangering the user. Class X capacitors, on the other hand, are often designed to fail short-­ circuit. You can use an appropriately rated Class Y capacitor across the mains, but you should never ever use a Class X capacitor between Active/Live (or Neutral) and Earth. Safety-rated capacitors come in various sub-classes that denote the peak siliconchip.com.au voltage they can tolerate. Lower subclass numbers mean higher voltage capability. For our 230V mains voltage in Australia, you should use the X2 and Y2 subclasses as a minimum. The higher-rated X1 and Y1 subclasses are also OK, but not strictly necessary. Never use lower-subclass components or ones without the proper certification. You can easily recognise safety-rated capacitors because their cases are usually smothered in logos from certification bodies. The Class Y capacitors in a common-­ mode filter provide a leakage path from Active to Earth, so their maximum value is dictated by the acceptable leakage current at mains frequency. Industrial products can usually have a leakage current of no more than 0.5mA (at 250V AC), limiting Cy to a maximum value of about 6nF. This is why you will often see 2.2nF or 4.7nF ceramic Class Y caps in these filters. Class X capacitors can be larger; 220nF, 470nF or even 1µF values are not unusual. Much larger than this, and you run into problems discharging them fast enough. You can decrease the value of the discharge resistor only so far before its power dissipation becomes a problem. The higher Class X capacitance means that these filters can provide appreciable differential-mode filtering, even though the differential mode inductance is lower. Typical filters use common-mode inductors in the 0.33mH to 10mH range. If more attenuation is required, it is common to add a second or even third stage in series, rather than using larger inductors. Power factor correction (PFC) EMI filtering is concerned with high-frequency harmonics, but you will recall from the last article that with a sinusoidal voltage source, only the fundamental component of the source current contributes usable power (real power), designated ‹p›, with units of watts. The higher harmonic components of current do however contribute to the RMS value of current and therefore to the ‘apparent power’, S, defined as the product of RMS voltage and RMS current and having units of volt-­amperes (VA). The ratio of real power to apparent power, ‹p› ÷ S, is the definition of power factor. For unity power factor, the current must not only have a purely sinusoidal siliconchip.com.au Fig.9: a typical common-mode filter includes safety-rated Y-Class capacitors from Active to Earth and X-Class between Active and Neutral. It is really important to use the correct parts in these critical locations. Fig.10: a power factor correction circuit ‘spreads out’ the spiky current waveform produced when the capacitor charges at the peak of the mains. shape; it also has to be in phase with the voltage. For example, an inductive load such as a motor will not have unity power factor even though the current is sinusoidal, because of the phase shift between voltage and current. In this case, correcting the power factor can be as simple as adding a capacitor of appropriate value across the load to bring the phase shift between voltage and current back to zero. This is known as passive power factor correction. Things are not this simple with AC-DC converters, as we saw last time. The most common arrangement of a full bridge followed by a capacitive filter results in a current waveform with narrow spikes near the voltage peaks, corresponding to the period in which the capacitor is charged. This is illustrated in Fig.10. Active power factor correction aims to spread these peaks and make the overall source current waveform more sinusoidal in shape. Pushing current into the filter capacitor while the input voltage (shown dotted in red) is lower than the DC voltage implies that the PFC circuit must be capable of producing an output voltage higher than its input. The obvious candidate is a boost converter. Australia's electronics magazine Fig.11 shows the typical circuit of an active power factor corrector. A boost converter is interposed between the rectified mains input and the load (often another DC-DC converter). The boost converter is driven by a current-­ mode modulator, as shown in the diagram at the bottom of Fig.11. Crucially, its input reference current is forced into a ‘rectified sine’ shape. Thus, the boost converter produces a steady DC voltage across C1, but draws a roughly rectified-sinewave-shaped current through L1, and thus a nearsinewave-shaped current from the source. The current-mode modulator monitors the inductor current and controls the Mosfet’s on-time to make the current track the reference current, which is the output of the error amplifier/ compensator multiplied by the rectified sine signal. This latter is derived from the mains so that the input current is in phase with the voltage, resulting in a very good power factor. The load voltage must be higher than the peak of the mains, so it is normally set to about 400V. This allows for a wide range of AC input voltages – say, from 90V AC to 280V AC. You don’t have to use a boost converter, although this is by far the most popular topology due to its simplicity. March 2026  45 Fig.11: the PFC converter uses a current-mode boost converter to generate the output voltage. The reference current is modulated to shape the inductor current into a ‘rectified sinewave’ shape so the input current is sinusoidal. Fig.12: there are several alternative PFC topologies like these, but they all work on the same basic principle as that shown in Fig.11. You obviously can’t use a buck converter because it does not work when its input voltage is lower than its output, a state that will occur near every zero-crossing. PFC variants There are of course many variations on this theme, several of which I have shown in Fig.12. On the left is the interleaved power factor correction circuit. You can see that this is really two parallel boost converters, which are normally driven 180° out of phase with each other, feeding a common filter capacitor. This has the advantage of higher output power and effectively doubles the switching frequency as seen at the input, simplifying the input filtering. The next variant is described a “bridgeless” PFC converter, but this is 46 Silicon Chip a bit of a misnomer since the upper two diodes plus Mosfets and their body diodes clearly form a bridge rectifier. The functions of the rectifier and boost converter are integrated, providing better efficiency since several diode drops are eliminated. It can also be thought of as two boost converters in parallel, although this time each one is operating on alternate half-cycles. In theory, you can get away with a single inductor in one leg, but at the cost of increased common-­ mode EMI. An even more efficient variant is the so-called “totem-pole” architecture. Here, one Mosfet acts as a synchronous rectifier each half-cycle while the other is switching. This is more efficient than the bridgeless PFC because a Mosfet can have a much lower voltage drop than a diode. Australia's electronics magazine An even more efficient version uses four Mosfets, eliminating diodes altogether. There is a penalty to pay in terms of complexity with totem-pole PFC converters because they require a high-side driver. A practical PFC converter It is a bit beyond the scope of this article to run through the complete design of a PFC converter, but we can do the next best thing and take a look at a real example from an evaluation board; in this case, an EVL-4986-350W from ST Microelectronics (Fig.14). This is a 350W boost-converter type PFC based on the L4986 IC, a very typical example of the type of chip that is readily available these days. The circuit, redrawn from the EVL4986-350W data brief, is reproduced in Fig.13. siliconchip.com.au Fig.13: this circuit of the EVL4986-350W PFC evaluation board redrawn from its data brief. See the text for a full description. The mains input on the left is fused by F1 and protected by metal-oxide varistor (MOV) RV1. It is then fed through a common-mode filter consisting of two X2 capacitors and common-­ mode choke L3. This filter is missing its Class Y capacitors because this circuit has no mains Earth connection. There will be some common-mode rejection due to the voltage divider formed common-mode impedance of L3 and the common-mode load impedance (50W during EMI measurement). Diodes D8 and D9 connect the AC input to the HV pin on the controller. This pin is capable of withstanding up to 800V AC and serves several purposes. Firstly, it is involved in the startup of the controller. If a voltage exceeding about 29V is sensed on this pin, the capacitors on the Vcc pin are charged from it via an internal current limiter until it reaches a voltage sufficient for the control chip to start. Once the PFC converter is up and running, the Vcc pin is supplied by the auxiliary winding on the boost inductor L1, via a 100W series resistor, 100nF AC-coupling capacitor and diode D7. Zener diode D6 limits the Vcc voltage to a maximum of about 18V. The HV pin is also used to sense the AC voltage for the undervoltage/ brownout protection circuit and to provide the modulation required to shape the input current. The HV pin can also detect when the mains is removed and switch in a current sink to discharge the X-capacitors, obviating the need for a discharge resistor and its associated power dissipation. That’s a lot of functions for one pin! The AC input is rectified by a 15A 600V bridge rectifier (D3) mounted on one of the two heatsinks. The rectifier is followed by a differential-mode siliconchip.com.au filter comprising L2 and a 1μF capacitor, which reduces the fundamental of the 65kHz switching noise at the input by a factor of around eight and the higher harmonics by a proportionally greater factor. The boost converter consists of the inductor L1, Mosfet Q1 and diode D1, with one 470nF and two 100μF capacitors forming its output filter. Diode D2 precharges these capacitors when the mains is first applied so that the boost converter can start up much faster than it would if it had to charge them from zero. The 1W cold resistance of the NTC thermistor limits the capacitor inrush current, but as current flows through it in operation, the resistance drops by a couple of orders of magnitude and it can be more-or-less ignored. The Mosfet current is sensed across the three parallel 0.22W shunt resistors below L2. The resulting (negative) shunt voltage is fed via a 51W resistor to the controller IC, where it is compared to the current reference to determine the Mosfet switch-off instant. If the CS pin voltage falls below -0.49V, an internal overcurrent comparator overrides the modulator, limiting the peak current to about 6.7A. The Mosfet gate is driven via 3.9W and 6.8W resistors, plus diode D4. This network allows for separate control of the Mosfet’s switch-on and switch-off times. Q1’s gate is charged (to switch it on) via just the 6.8W resistor but is discharged via both resistors in parallel, compensating for the Fig.14: the PFC evaluation board described in the text. The input connector is hidden behind the large boost inductor, and the output connector is at the front right. Australia's electronics magazine 47 Type II compensator, which has two poles and one zero. For more details, see the second article in this series, published in the December 2025 issue (siliconchip.au/Article/19370). The compensator poles and zeroes are positioned to provide dominant-pole compensation to the overall open-loop gain. The red line in Fig.15 shows the frequency response of the PFC’s Fig.15: the compensator for the PFC modulator and output filter. This converter is similar to that for a has a single pole at fco, determined conventional DC-DC converter. The by the converter’s output capaccrossover frequency must be lower than itance and its load resistance, 100Hz or the control loop will try to and a zero formed by the output eliminate the modulation we need to capacitance and its ESR. The outshape the input current. put capacitance is 200µF and the fact that the STF36N60M6 has a much minimum load resistance is 457W slower inherent switch-off time (50ns) (400V2 ÷ 350W), so the pole occurs at than its switch-on time (15ns). about 1.74Hz. Output voltage feedback is proWe don’t need to worry about the vided to the FB pin on the controller frequency of the zero formed by the IC (U1) by the divider formed by the output capacitance and its ESR for reathree 2.2MW resistors, together with sons that will become apparent soon. the series/parallel combination of four The cyan/blue line shows the different-­ value resistors to ground desired open-loop gain required for (16kW, 100kW, 30kW & 360kW). stability, rolling off at a steady -20dB This feedback voltage is internally per decade from the origin (effectively compared to a 2.5V reference to cre- DC), then taking a turn down to -40dB ate the error signal. Like the current per decade at frequency fp. sense input, an independent comparIn a normal converter, we would ator shuts the boost converter off if the position this pole to cancel the filfeedback voltage exceeds the reference ter’s ESR zero to maximise the bandby more than about 7%. width of the control loop. However, If the voltage at the feedback pin for PFC converters, we have to limit falls below about 0.5V, the controller the loop bandwidth so the crossover enters ‘external burst mode’, in which frequency (the frequency where loop switching is inhibited. This prevents gain falls to 0dB) is below twice the the output voltage from rising uncon- mains frequency. trollably in the case that the voltage We have to do this so the control sense resistors become open-circuit loop does not respond to the 100Hz and also allows an external control- ripple on the output and try to counler to switch the converter off via Q4. teract the very modulation we are relyThis feature might be used to reduce ing on to shape the current. power when a following converter was The compensator’s second pole (the disabled or had a very light load. Dis- first is at the origin) is therefore typiabling and enabling the PFC in this cally placed at some frequency, fp, that way is fast because the control chip forces the crossover frequency to be does not go through the whole start-up Fig.16; the upper procedure each time. trace shows the PFC The voltage feedback divider douconverter’s input current bles as an input for the controller’s at near full load. The power-good comparator. If the voltage current is similar in at the PGIN terminal exceeds 2.375V, shape to the input the open collector ‘power good’ (PG) voltage shown below. pin is asserted low. The measured power Compensation less than 100Hz. The filter zero caused by the output capacitance and its ESR is therefore more-or-less irrelevant since the control loop is not effective at this frequency. The evaluation board’s compensator has its zero set by the 62kW resistor and 1.5µF capacitor near to 1.71Hz – pretty much bang on the output capacitance/ load resistance pole. The upper pole is set to 17.1Hz by the 62kW resistor and 150nF capacitor, well below the 100Hz ripple frequency. I have not mentioned transistor Q3 and its associated base drive components yet. The controller chip has a threshold detector on the COMP pin that shuts down the PFC converter if the voltage is below about 0.5V. This can be used to stop and start the converter, but unlike Burst Mode control, the converter goes through a full softstart cycle when enabled. Testing I tested the PFC evaluation board on my bench with a 500W load. The current and voltage waveforms are shown in Fig.16. The current (green trace) is certainly close to a sinusoid, but has some visible vestiges of switching ripple. Its shape tracks the input voltage (yellow trace) almost exactly, including its slightly flat top caused by all those non-PFC converters on my line. The RMS current and voltage measurements on the right must each be scaled by a factor of 10 for 243V and 1.33A respectively, giving an apparent power of 323W. The average DC voltage and current in the load measured 396.7V and 0.785A, respectively, for a real power of 311.4W. The resulting power factor is 0.96, which is about as good as we could expect. We have now covered DC-DC converters and AC-DC converters in a fair bit of depth. Next time, we will dive into the interesting world of DC-AC SC converters. factor was 0.96. The internal error amplifier’s compensation is set by the network hanging off its pin 8. This forms a classic 48 Silicon Chip Australia's electronics magazine siliconchip.com.au By Tim Blythman Decoder Base Station Using DCC Remote Controller DCC Booster So far in this series we have produced a DCC Decoder, Base Station and a Remote Controller unit for the Base Station. The logical progression is a DCC Booster to supply more current and power the track in independent sections. We can also use it as an Automatic Reverse Loop Controller and Image source: https://unsplash.com/photos/a-model-train-on-a-track-with-a-bridge-in-the-background-ADYqbbcjsyk even a Simple Base Station. DCC Booster and Reverse Loop Controller A DCC Booster allows the expansion of a DCC system by providing an extra driver supplying more current than can be delivered by a single Base Station. It should have current sensing to allow it to isolate faults such as short circuits on the track. Another handy thing to have in a DCC system is a reverse loop controller. Certain track arrangements can be prone to short circuits due to the train bridging the circuits of the two tracks. If your track has a so-called balloon loop or three-way Y junction, it will probably benefit from a reverse loop controller. In October 2012, we published the Reverse Loop Controller For DCC Model Railways (see siliconchip.au/ Features & Specifications 🛤 Compact unit fits in a UB5 Jiffy Box 🛤 Simple LED indications 🛤 Optional detailed OLED display 🛤 DCC Booster mode 🛤 Reverse Loop Controller mode 🛤 Simple Base Station mode 🛤 Trip current adjustable in 100mA steps up to 9.9A 🛤 Track voltage: standard range of 8-22V 🛤 Track current: up to 10A (5A with DC jack input) siliconchip.com.au Article/494). That design used a relay to switch the polarity of an existing DCC track signal. By adding polarity control to our DCC Booster, we can combine these functions into a single unit that can provide the automatic polarity switching and offer extra current drive for the track. Thus, the DCC Booster also becomes the Reverse Loop Controller. We have chosen to implement these features with a microcontroller, which makes it possible to generate a DCC signal. Rather than adding a complex user interface, this unit can simply be connected to a DCC Remote Controller to provide the packets that are to be sent to the track. So this unit can also be used as a Simple Base Station. While it has multiple functions, we will refer to the subject of this article as the Booster, or the Simple Base Station when it is working in base station mode. The earlier project in this series will continue to be known as the Base Station. The completed unit you see in the photos can operate standalone, but the bare board is well-suited to being installed under a control panel or similar. All modes can be configured to power on automatically, so there is no need for such boards to be accessible once they are set up. We envisage these units might be used in a layout with multiple Boosters and/or Reverse Loop Controllers. We’ll focus on building the complete 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 & Reverse Loop Controller (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. Australia's electronics magazine March 2026  49 Fig.1: this circuit has much in common with the Base Station and serves much the same purpose, since it can also behave as a Simple Base Station. The CON1 DCC input allows it to receive and repeat DCC signals. standalone unit in an enclosure and allow experienced readers the freedom to utilise the bare board as they see fit. Circuit details The Booster circuit (Fig.1) has much in common with the DCC Base Station. IC1 is the PIC16F18146 microcontroller that controls the circuit. Although it can work with a 5V supply, we have chosen to use 3.3V to maintain compatibility with the Remote Controller, which needs a 3.3V supply. IC1 receives 3.3V power at its pins 1 and 20, with these and pins 4, 18 and 19 also connecting to ICSP (in-circuit serial programming) header CON6. IC1’s supply is bypassed by a 100nF capacitor, while a 10kW resistor pulls pin 4 (MCLR) up to allow normal operation unless overridden by a programmer. Like the Base Station, the main DCC 50 Silicon Chip output is driven by a pair of BTN8962 half-bridge drivers, IC2 & IC3, which are controlled from pins 6, 7 & 8 of IC1 via 1kW series resistors. The resistors are provided to limit the current flowing into the microcontroller if there is a serious fault. The DCCOUTEN line is pulled low by a 100kW resistor to shut down both drivers until driven by the micro. The DCC output is available at screw terminals CON2 and also drives bi-­ colour LED1 via its 2.2kW series resistor. The 100nF capacitors provide local bypassing for IC2 and IC3. The IS pins of the drivers source current in proportion to the driver output current, so the IS currents are combined by dual diode D1 and passed through a 1kW resistor to convert the current to a voltage. This voltage is then smoothed by the 10kW resistor and 100nF capacitor. It goes to pin 15 of IC1 (ANC1) to allow Australia's electronics magazine it to be sensed. Pin 15 is both an ADC (analog-to-digital converter) input and an input to a comparator internal to IC1. The ADC is used to measure this current and also the supply voltage noted earlier. We’ll get to the comparator feature shortly. The incoming DCC signal comes in at CON1 and connects to pins 3 and 5 on IC1 via 100nF capacitors and 10kW series resistors. The resistors limit the current that can flow into the microcontroller, while the capacitors allow the incoming DCC to ‘float’ at a different reference voltage. They AC-couple the signal, with DC biasing by the protection diodes internal to the micro. I/O pins 2, 9 and 10 are connected to tactile switches S1-S3 and are supplied with internal pullup currents by IC1. The switches connect to ground, so they pull those pins low when the buttons are pressed. Status indicator siliconchip.com.au LED2 is driven by IC1’s pin 11 digital output via its series resistor. Pins 14 and 16 of IC1 connect to MOD1, an I2C OLED module, while pins 12 and 13 connect to CON5, an RJ45 socket intended to connect to a Remote Controller. These two pins also have 2.2kW pullup resistors to the 3.3V rail. Pins 12, 13, 14 and 16 go to four jumper headers on JP1, with the other pins on JP1 connected to ground. There are a few different firmware modes, but the main distinction is that the OLED module and RJ45 socket cannot be used at the same time as JP1, since the pins would conflict. Basically, JP1 provides some configuration options in the absence of the OLED screen. Power supply The incoming power supply circuitry is much the same as the DCC Base Station too, with DC jack CON4 in parallel with screw terminals CON3. The power comes through fuse F1 to the nominal 15V rail bypassed by a 1000μF capacitor. Like the Base Station, the 15V rail can actually be between 8V and 22V. Diode D2 is connected in reverse across the supply rails to blow the fuse in the event of reverse polarity being applied. A 10kW:1kW divider with a 1μF capacitor across the lower leg is used to reduce the supply voltage to a level that can be measured by a 3.3V microcontroller at its ANA2 analog input (pin 17). So far, this is all practically identical to the Base Station. LED3 is connected across the 15V rail with a series resistor for power indication. A simple linear regulator and its 100μF capacitor provide the 3.3V rail for the microcontroller and associated circuitry, since this unit We recommend starting construction with the two driver ICs, IC2 and IC3. Note the fuse located on the rear of the PCB for easy access in case it blows. does not require as much current on the logic-level rail. If you are using this unit as a Booster or Reverse Controller, your power supply voltage should be similar to that of your Base Station and able to provide enough current for your purposes. You might use a 5-10A supply for a Booster. Above 5A, use the CON3 screw terminals, since CON4 can’t safely handle more than 5A. A Reverse Loop Controller might not need as much current, since it could be just powering a section of track big enough to handle a single train. It might be reasonable to piggyback it off the supply that is powering the Base Station in this case, but you would need to take care with the current limits. There’s no harm in picking a bigger supply, since the current limit can be set lower. The Booster draws around 25mA on its 3.3V rail when the OLED is operating. With a 12V supply, you should be able to add one or two Remote Controllers to a Simple Base Station before the dissipation is more than the 500mW that REG1’s TO-92 case can handle. Internal logic Newer microcontrollers like the PIC16F18146 have a vast array of peripherals; in fact, there are probably more peripherals available than pins to route them to! The internal CLC (configurable logic cell) unit allows pins and other peripherals to be connected via logic elements. We used the CLC in the Digital Boost Regulator from December 2022 (siliconchip.au/ Article/15588). Once configured, the CLC operates completely independently of the processor. Fig.2 shows the equivalent logic that is implemented in the CLC in this project. We have included the comparator, which is a separate peripheral to the CLC. We use three of the four available CLC instances for this project. The upper circuit with the comparator is used in all modes and at all times. Note that the black labels refer to the lines marked in Fig.1. The blue labels are signals internal to the microcontroller; in effect, they do not require an external pin, and are controlled by software or other peripherals. For example, the latch can be set or cleared (with the SET SIGNAL or RESET SIGNAL) to manually switch on or off the DCCOUTEN line and thus the DCC drivers. The comparator output is one of 40 internal signals that can be routed to the CLC input array. It’s even possible to use CLC outputs as inputs to other instances to create more complex logic. Fig.2: the black labels refer to signals in Fig.1, while the blue signals are internal to the microcontroller. This shows the PCB fitted with all parts except the OLED module. The LEDs and tactile switches should be installed with the front panel in place so they can be accurately aligned. siliconchip.com.au Australia's electronics magazine March 2026  51 The DCC Booster/Reverse Loop Controller fits in a compact Jiffy box or can be used as a bare board if needed on a large layout (with the front panel affixed to a hole in your layout’s control panel to integrate it). Adding a Remote Controller unit allows it to operate as a Simple Base Station. Note that the photo shown above is not at actual size. Table 1 – modes and construction options Mode Parts to be omitted Notes Booster with no display OLED and header, RJ45 socket, S3 Reverse Loop Controller with no display OLED and header, RJ45 socket, S3 Leave off the OLED, RJ45 socket and S3 if you are only planning to use the modes without a display. Booster with display RJ45 socket, JP1 Reverse Loop Controller with display RJ45 socket, JP1 Simple Base Station with display CON1 (DCC in), JP1 To allow the option of using any of the modes with a display, all parts should be fitted except JP1. At least one DCC Remote Controller is needed to use the Simple Base Station mode. Depending on how you want to use this project, you can assemble the board without some of the parts, as indicated here. Table 2 – jumper settings for modes without an OLED screen JP1a (REV) JP1b (+1) JP1c (+2) JP1d (+4) Notes OFF Booster mode operating; LED2 will flash once at startup ON Reverse Loop Controller mode operating; LED2 will flash twice at startup OFF OFF OFF Current limit is 1A ON OFF OFF Current limit is 2A OFF ON OFF Current limit is 3A ON ON OFF Current limit is 4A OFF OFF ON Current limit is 5A ON OFF ON Current limit is 6A OFF ON ON Current limit is 8A ON ON ON Current limit is 10A Without the OLED, JP1a sets the mode while the others define the current limit. 52 Silicon Chip Australia's electronics magazine For clarity, the representations in Fig.2 are simplified versions of the logic. For example, the DAC voltage is actually applied to the non-inverting input of the comparator, and the comparator is configured with an inverted output to achieve the behaviour shown in the diagram. The multiplexer is implemented with an AND-OR gate arrangement. The DAC on this chip has an 8-bit resolution and is configured to use a 2.048V reference, so the DAC OUTPUT can be set in 8mV steps (2048mV ÷ 256). The voltage at DCCOUTI changes in proportion to the current supplied by the driver ICs, with 8mV corresponding to steps of around 80mA. The arrangement shown in Fig.2 means that when the current exceeds the set point, the comparator output goes high, the latch is reset and the drivers are disabled much more quickly than if the checks were done in software. The software can read the state of the DCCOUTEN line to report the fact that a trip has occurred. The second circuit is used to swap the polarity of the DCC signal when the reverse loop controller is active. If POLARITY is low, DCCINA controls DCCOUTA and DCCINB controls DCCOUTB. If POLARITY is high, the two multiplexers swap these, effectively flipping the DCC signal polarity (relative to the input). We have briefly touched on the need for this in previous DCC articles, but now we have the opportunity to examine a concrete example. The top of Fig.3 shows a so-called balloon loop. The train would typically enter on the left and pass around the loop clockwise before exiting at left, but it could travel in the opposite direction. The problem is that the wheels that travel on the outside of the loop (contacting DCCOUTA) come in contact with DCCINA when entering and DCCINB when exiting. This may only be brief, but it is typical that all wheels along one side of a locomotive are joined together to improve current collection from the track. The triangle junction below also shows this problem. So the Booster must detect the conflict and toggle the polarity when the wheels bridge rails that are of opposing polarities. In practice, if it detects an overcurrent condition (such as might be caused by a short circuit), it toggles the polarity; if the fault persists, siliconchip.com.au the power trips off momentarily. If flipping the polarity clears the fault, all is well. The multiplexer circuit is also used to feed the DCC signal from CON1 to CON2 when the circuit is operating in booster mode. In this case, the polarity is fixed at ‘0’ so that DCCINA drives DCCOUTA and DCCINB drives DCCOUTB. Firmware There are five distinct operating modes that the Booster firmware can run in. When it starts up, the mode is fixed until the next time the processor is reset or restarts. Table 1 lists the five modes and the parts that can be omitted during construction if you intend to use only that mode. You can refer to the parts list for other options. There is no reason that all parts cannot be fitted, but remember that any jumper shunts that are installed will conflict with the respective pins on the OLED display and RJ45 socket. Since there are Booster and Reverser modes that can use the display, the most flexible option is to fit the OLED module and leave off the header for JP1. Each mode is fixed at startup, so the firmware is effectively broken down into five different subprograms. Some of them share functions; for example, the two reverse loop controller modes share a common routine that checks whether the comparator has been triggered and decides whether to flip the polarity or shut the power off for the trip period. In the modes with no display, JP1 is used for setting the mode and trip current. We’ll get into more details about how the modes work once the unit is assembled. Note that pushbutton S3 need not be fitted in the modes that do not have a display, since it is used to escape from these modes. The first header on JP1 (JP1a) is used to set whether the booster or reverse loop controller mode is run; having the jumper on selects reverse loop controller mode. After this, the three remaining jumpers allow eight combinations and thus eight trip-current settings. We have programmed them for 1, 2, 3, 4, 5, 6, 8 and 10 amps. Table 2 summarises these selections. Holding S1 or S2 during startup will change the EEPROM setting that determines whether the DCC output is started automatically when power is applied. During operation, S1 and S2 siliconchip.com.au will switch the output on or off, and LED2 will reflect this state. During startup without the OLED module, LED2 also lights, flashing once for Booster mode and twice for Reverse Loop Controller mode. Display Since the jumper shunts are not available if a display is fitted, S3 is used to access different menus that can be used to alter the settings. The normal display screen shows the mode, supply voltage and DCC output (CON2) current. There is also a description of the state that can indicate, amongst other things, if an over-current trip has occurred. We will look at these screens later once construction is complete. Unless you are building several Boosters or Reverse Loop Controllers that will be hidden from sight, such as being distributed around a large layout, we recommend that you build the version with the display. The display means that more information is available for troubleshooting, and the settings allow the mode to be easily changed if you do want to try them out. If you are using the Booster as a Simple Base Station, you must have the display fitted. To accompany a Simple Base Station, you will also need to build at least one of the DCC Remote Controllers, since these will provide the DCC packets that are sent to the track. If no packets are received on the RJ45 socket, idle packets will be sent out to ensure there is always valid data on the track. Construction We’ll cover assembly of the main PCB listing the parts that we have fitted Fig.3: this balloon loop is one example of a track layout that means a reverse controller is needed. The three-way triangle junction is another common example; note how a train taking the curve on the left requires a different relative polarity to a train taking the curve on the right. Australia's electronics magazine March 2026  53 Figs.4 & 5: the PCB for this project has a mix of SMD and through-hole parts on both sides, so pay attention and watch the orientations of the polarised parts. to our prototype, which is everything in the Parts List, so skip fitting any parts that you’ve determined you don’t need. The main PCB, coded 09111248 and measuring 45 × 79mm, will have SMD parts fitted to the back, then the front, followed by most of the throughhole components. Figs.4 & 5 are the overlay diagrams for the PCBs that you can use as a guide during assembly. The LEDs and switches depend on the front panel for alignment, so temporarily attach the panel and use it to align these parts when you are fitting them. A header is used for the OLED module to provide extra height, and so that it can be detached if needed. For the SMD parts, we suggest having the standard SMD gear on hand, including flux paste, a fume extractor, a magnifier, solder wicking braid and some tweezers. Start by fitting IC2 and IC3, the driver ICs. You may need to turn up your iron or apply extra heat from a hot air tool, since they sit on large copper areas on the PCB. Add flux to the pads and rest one of the driver ICs in place. Tack one of the smaller leads and adjust it to get the position right. Then solder the large tab in place, keeping the iron on the part until the solder flows freely along the width of the tab. Give the solder a moment to harden, then solder the remaining smaller pins. Fit the other driver IC after that. Follow with IC1, the microcontroller, being sure to align the pin 1 marking with that on the PCB. Tack one lead, align the part and then solder the remaining leads. Solder the BAT54C diode next to IC1 using the same technique. Four of the 100nF capacitors are on this side, along with the only 1μF part. Solder these next. Ten of the resistors are also on this side of the PCB. They will be printed with codes that correspond to their values (eg, 1kW = 102 or 1001). Flip the PCB over and solder the other two 100nF capacitors and carefully work through the remaining six resistors. Next, mount the fuse holder to the back of the PCB. This location allows it to be easily accessed without having to fully disassemble the unit. It helps to fit the fuse while soldering, since this will align the pins and ensure that the tabs are correctly orientated, too. Next, solder the through-hole parts except the OLED and its headers, the LEDs and the tactile switches. We’ll fit these later while aligning them to the enclosure and front panel. Work upwards in order of height. Fit D2 with its cathode stripe orientated as shown, then solder it and trim its leads flush with the PCB. If you need to fit JP1 or the CON6 ICSP header, do so next. Follow with any of CON1, CON2, CON3 and CON4 that you need, ensuring the terminal block entries face the outside of the board. Also solder in the two electrolytic capacitors and REG1, being careful to observe their polarities. Be sure to bend the leads of the 1000μF part correctly; the longer lead is positive. Then, snap the RJ45 socket (CON5) into place and carefully solder its leads. At this stage, the PCB is complete enough to allow IC1 to be programmed Our prototype has all components fitted, but you should refer to Table 1 and the parts list to check which are able to be left off. 54 Silicon Chip Australia's electronics magazine siliconchip.com.au if required. Microcontrollers bought from our Online Shop, including in kits, come pre-programmed. If you need to program it, power can be supplied from CON3, CON4 (eg, 12V at the DC jack) or 3.3V from the programmer via the ICSP header. If you are only using the modes that do not require the display, you are probably not too concerned about using the panel PCB and you will probably have specific ideas about fitting the Booster as part of an existing panel; perhaps running flying leads to the LEDs and switches. Remember that you do not need to install S3 if a display is not fitted. LEDs through their holes in the panel and solder them in place. We found that 17mm tactile switches (which are about the longest that are easily available) only just clear the panel if mounted flat. We were able to get some extra height by raising them slightly off the PCB before soldering. Our kits include 18mm switches so that should not be necessary. Take off the panel and attach the socket header to the OLED module’s pins and place that onto the PCB. Refit the panel, secure it and use it to align the OLED module before soldering its pins too. Hardware Fig.6 shows the cutting and drilling needed to fit the assembly into a UB5 Jiffy box, while Fig.7 is a 3D render of the case, so you can check that you are working on the correct faces of the box. The round hole for the DC jack can be made with a drill. We prefer to drill a small pilot hole with a twist drill and then enlarge that with a step drill. The vertical cuts can be made using a fine saw. Use a sharp blade to score the horizontal lines, and then the tab can be carefully snapped off using wide-nosed pliers. Take care with the slots for CON1 and CON2 since they are only separated by a thin tab of plastic, which can be easily snapped off accidentally. If you are mounting the unit in a case with a display, we suggest fitting the tapped spacers to position the panel PCB and align the LEDs and tactile switches. The relatively long 16mm tapped spacers are only needed to achieve clearance for the RJ45 socket. Fit the spacers on the top side of the PCB, secured from behind with machine screws. Thread the switches and LEDs into their holes and then attach the panel PCB with the remaining machine screws. Watch the polarity of LED2 and LED3, but note that the polarity of LED1 does not matter due to the alternating DCC signal. Now you can accurately position the Cutting and drilling The slots for CON1 and CON2 will align with the internal bosses for PCB mounting (which are not used in this project). So it might take some extra effort to snap the plastic, since it will be thicker in these locations. Finally, fit the PCB and panel assembly into the case and secure it with the screws that are supplied with the case. Operation with no display The initial setting of the Booster and Reverse Loop Controller is to operate in the mode that does not require a display. Since the jumper shunts are only checked when the micro starts up, which will typically be when power is applied, it’s a good idea to power off the Booster, change the jumpers and then reapply power. Booster mode (with the REV jumper left off) will cause LED2 to flash once. When the REV jumper is fitted, LED2 will flash twice at startup and the Reverse Loop Controller is started. You can also set whether the CON2 DCC output is enabled at power-on by holding in S1 (on) or S2 (off) during startup. S1 and S2 are used to switch the DCC output on or off during normal operation. You’ll need a valid DCC signal of some sort applied to CON1. Otherwise, LED2 will flash at 1Hz. If this is flashing with a low duty cycle or is Fig.6: to create a standalone device, you can cut a UB5 Jiffy box as shown here and use our 09111249 PCB as a front panel. Fig.7: you can check the locations of your cuts against this diagram. If you are building this project as a Simple Base Station, you can omit CON1 and the corresponding panel cutout. siliconchip.com.au Australia's electronics magazine March 2026  55 Screen 1: the screens are simple and provide a handy amount of information, including supply voltage and DCC track current. Screen 2: the trip current can be set in steps of 100mA. The figure at upper right is the raw DAC setting calculated by the microcontroller. Screen 3: the current measuring offset that is applied by the BTN8962 driver ICs can be manually adjusted on this page. Screen 4: the offset can also be automatically determined on this screen. Note that this will require track power to be shut off. Screen 5: if the AUTOPOWER setting is enabled, the DCC track output drivers will be active as soon as power is applied. Screen 6: the main operating mode can be set here. NO OLED refers to the first two modes listed in Table 1. Screen 7: since the mode is only checked at startup, this page can be used to reset and restart the microcontroller after a mode change. Screen 8: in Booster mode, the word BOOST is shown and ERROR might be displayed if a valid DCC signal is not detected. Screen 9: the Reverse Loop Controller mode shows REV as the mode, as well as a symbol to indicate whether the polarity has been flipped. fully off, the DCC output at CON2 is off. Flashing with a high duty cycle or being fully lit means that the DCC output is enabled. LED1 is powered directly from the DCC signal, so should be lit up both red and green (appearing yellow) if the DCC output is on. If only one colour is showing on LED1, then there may be a wiring fault or a problem with the DCC signal. If LED2 is lit and LED1 is off and flickering on briefly, there is probably a short circuit caused by the trip limit being exceeded. With everything operating normally, both LED1 and LED2 should be either solidly on or solidly off. The current-measuring offset parameter can be automatically calibrated. To do this, short the lower left pad of S3 to ground or press S3 if it is fitted. The DCC output will shut off and LED2 will flicker for two seconds, after which the calibration runs. If all is well, LED2 will light up for a second and switch off. Otherwise, no changes are made. The offset can vary with supply voltage, so it’s a good idea to use your normal operating supply while performing this calibration. These indications are quite terse; the messages shown on the OLED are more helpful, so let’s have a look at those modes next. Most of the settings shown on the OLED screen are also used in the modes that do not use the OLED, so it is possible to temporarily fit an OLED for setup purposes and then remove it later. followed by an offset value, which should be around 4A, but could be anywhere between 1A and 9A. If there is a problem, try again and check your construction in case there are any problems. This can also be manually configured using a similar process to the Base Station from Part 2 of this series. Use Screen 2 to set the TRIP limit to 9A and Screen 3 to set the OFFSET to 0A. Cycle back to Screen 1 and press S1 to switch on the DCC output. Note the displayed current and change the Screen 3 OFFSET to that value. If you return to Screen 1, the displayed current should now be zero. Use S2 to switch off the DCC output and reset the TRIP limit to a suitable value, such as 5A or lower if the controller is being powered from the DC jack. If the OFFSET is not between 1A and 9A, there may be a construction problem. Screen 5 allows you to set the DCC output to switch on automatically at startup. The settings on Screens 3, 4 and 5 are also used in headless mode, so temporarily fitting an OLED module is a way of setting up the Booster with confidence. Let’s have a look at the individual modes. 56 Silicon Chip Display modes Before attempting to use the modes that use the OLED display, make sure that no shunts are fitted to JP1. Don’t connect anything to CON2 (DCC OUT) yet. To enable the display, power on the Booster while holding down S3. LED2 will flash until S3 is released. The unit should then start in the Simple Base Station mode with the display active. Once you have activated the display, you should see something like Screen 1, which is the main operating screen for the Simple Base Station. Screens 2-7 are the various settings that can be accessed by pressing S3 (SEL). Press S3 to get to Screen 6 and select a different mode (BASE STN, BOOSTER or REVERSER). Then press S3 to get to Screen 7 and press S1 to restart the micro. This will ensure that the new mode is properly configured and will be loaded at startup. If you need to go back to one of the ‘headless’ modes, choose NO OLED on Screen 6 and then perform a reset on Screen 7. Remember to detach the OLED after that, so it doesn’t affect the jumpers. Settings Configure the current measuring offset parameter on Screen 4 by pressing S3. The display will show OK, SET Australia's electronics magazine Simple Base station mode You will need a DCC Remote Controller connected to use the Booster to provide DCC track data. Screen 1 should show an asterisk (*) at upper siliconchip.com.au right when packets are received, and the Remote Controller should be allocated a host index, as if it were connected to a Pico-2-based DCC Base Station. Switch on the DCC output with S1 and switch it off with S2 from the main screen. LED2 will indicate what the last action was. The text on the screen will show ON or OFF, or TRIP if the current limit has been reached. You should now be able to control your DCC locomotives through the DCC Remote Controller interface. The commands to control track power (on the DCC Remote Controller) should also work. Booster With the OLED fitted and enabled, you will also have access to the Screen 2-7 menu items, as well as the Booster features seen in Screen 8. Screen 8 is very similar to Screen 1. You might also see the ERROR message, which means that the Booster has not detected a valid DCC signal at the CON1 DCC input connector. In this case, the DCC output shuts off, since it would otherwise continue to supply power to the track with no control signals. If you are operating without a display, LED2 will flicker on or off briefly once per second to indicate that the DCC signal has been lost. Of course, LED1 will not be lit either. Reverse Loop Controller Reverse Loop Controller mode operates in much the same fashion as Booster mode (see Screen 9). Here, the symbol on the right shows whether the polarity is normal or reversed. Silicon Chip kcaBBack Issues $10.00 + post $11.50 + post $12.50 + post $13.00 + post $14.00 + post January 1997 to October 2021 November 2021 to September 2023 October 2023 to September 2024 October 2024 onwards September 2025 onwards All back issues after February 2015 are in stock, while most from January 1997 to December 2014 are available. For a full list of all available issues, visit: siliconchip.com. au/Shop/2 PDF versions are available for all issues at siliconchip.com.au/Shop/12 We also sell photocopies of individual articles for those who don’t have a computer In operation, you will see LED2 flicker off very quickly when the polarity is swapped. If the OLED is not in use, the indications on the LEDs will be identical to that noted in the previous section. Considerations The Booster and Reverse Loop Controller modes both work by reading and then recreating the incoming signal using the driver ICs. This can be contrasted with the earlier Reverse Loop Controller for DCC Model Railways, which fed through signal through directly but used a relay to flip its polarity when required. There is an approximately 3μs delay in the signal propagating through the BTN8962 driver ICs. The logic in the PIC microcontroller also adds a small delay, but this is of the order of tens of nanoseconds; negligible compared to the drivers. This means that using a DCC track signal to drive the input of the Booster or Reverse Loop Controller will result in a noticeable amount of signal skew between two adjacent track sections, enough to cause a potential short circuit due to one driver pulling the track section high while another has already started pulling the other low, or vice versa. One way to avoid this is to use the logic-level signals from the Pico-2based Base Station instead of the track signals, before they are delayed by passing through the driver ICs on that board. That way, the track signals coming from the Base Station and Booster/Reverse Loop Controller will have more-or-less synchronous edges. Fig.8 shows where you can tap off the logic level signals from the Base Station to connect to the CON1 DCC signals on the Booster (the blue and green wires). Note that these are the points that connect to pin 2 (IN) of the IC2 & IC3 driver ICs. Thus, any skew caused by the driver ICs should be the same. We found that using the logic-level signals worked better when the circuit grounds are connected; this may not Fig.8: we recommend tapping the logic level DCC signals from the points on the Base Station shown here if you are building this project as a Booster or Reverse Loop Controller, since it will better synchronise the DCC signals that are sent to the track. siliconchip.com.au Australia's electronics magazine March 2026  57 Silicon Chip Binders REAL VALUE AT $21.50* PLUS P&P Are your copies of Silicon Chip getting damaged or dog-eared just lying around in a cupboard or on a shelf? Can you quickly find a particular issue that you need to refer to? Keep your copies safe, secure and always available with these handy binders These binders will protect your copies of S ilicon C hip . They feature heavy-board covers, hold 12 issues & will look great on your bookshelf. H 80mm internal width H Silicon Chip logo printed in goldcoloured lettering on spine & cover Silicon Chip Publications PO Box 194 Matraville NSW 2036 Order online from www. siliconchip.com.au/Shop/4 or call (02) 9939 3295 and quote your credit card number. *see website for delivery prices. 58 Silicon Chip Parts List – DCC Booster 1 double-sided green PCB coded 09111248 measuring 45 × 79mm 1 black panel PCB coded 09111249 measuring 83 × 53 × 0.8mm 1 UB5 Jiffy box 3 M3 × 16mm tapped spacers 6 M3 × 5-6mm blackened machine screws 2 2-way 5mm/5.08mm pluggable screw terminal blocks (CON1, CON2) [Altronics P2592 + P2512, Jaycar HM3102 + HM3122, or Dinkle 2EHDRC-02P + 2ESDV-02P] 1 2-way 5mm/5.08mm screw terminal (CON3; optional in place of CON4) 1 PCB-mounting DC barrel jack (CON4) 1 RJ45 PCB-mount through-hole socket (CON5; optional•) 1 5-way 0.1in (2.54mm) pitch header strip (CON6; optional, for ICSP) 2 M205 fuse clips (F1) 1 M205 fuse to suit PSU; maximum of 5A if CON4 is used, 10A if CON3 is used (F1) 1 2×4-way 0.1in (2.54mm) pin header (JP1; optional•) 4 0.1in (2.54mm) jumper shunts (JP1; optional•) 1 0.91in (23mm) I2C OLED module (MOD1; optional•) 1 4-way 0.1in (2.54mm) socket header strip (optional•, to suit MOD1) 3 through-hole tactile switches with stems 18mm above PCB (S1-S3) (shorter stems can be used if you do not wish to fit the unit inside an enclosure) 1 power supply unit (PSU) to suit Semiconductors 1 PIC16F18146-I/SO microcontroller programmed with 0911124D.HEX (IC1) [Silicon Chip SC7580] 2 BTN8962TA half-bridge drivers, TO-263-7 (IC2, IC3) 1 LP2950ACZ-3.3 3.3V LDO linear regulator, TO-92 (REG1) 1 BAT54C dual common-cathode SMD schottky diode, SOT-23 (D1) 1 1N5404 or 1N5408 3A silicon axial diode, DO-27 (D2) 1 3mm bicolour red/green LED (LED1) 1 3mm green LED (LED2) 1 3mm red LED (LED3) Capacitors (M3216/1206 X7R 50V unless specified) 1 1000μF 25V radial electrolytic 1 100μF 16V radial electrolytic 1 1μF 6 100nF Resistors (M3216/1206, ⅛W ±1%) 1 100kW 6 10kW 3 2.2kW 6 1kW • optional parts depending on intended use; see Table 1 automatically be the case if the Base Station and Booster are powered from separate power supplies. We’ve included an extra GND pad on the Booster for this purpose. You could use the unused CON3 or CON4 GND pad on Base Station to make this connection and use a gauge of wire that is suitable for your track current. Summary The DCC Booster/Reverse Loop Controller provides the drivers and some logic to implement a DCC Simple Base Australia's electronics magazine Station, Booster or Reverse Loop Controller in a compact UB5 case. It has a fast-acting digitally adjustable current limit that makes use of the newer features in modern 8-bit PICs. It can accept a DCC signal at logic levels, so it could be used as a component of a larger DCC system based on commercial hardware, or even a custom base station generating DCC signals. The interface for the Remote Controller provides another means for DCC signals to be provided in the form SC of serial data. siliconchip.com.au Subscribe to FEBRUARY 2026 ISSN 1030-2662 02 9 771030 266001 $14 00* NZ $14 90 INC GST INC GST Internet Radio io a Raspberry Pi-based music and audio stream player T he h i s to r y of intel from the 1101 SRAM chip Australia’s top electronics magazine and beyond DCC Remote Controller run multiple trains through one 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. DCC Base Station, with up to five Remote Controllers 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 Mains Hum Notch Filter; February 2026 Mains Power LED Indicator; Feb 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 Using Electronic Modules with Tim Blythman Self-powered Wireless Switches These so-called ‘self-powered switches’ do not need a separate power source. You might have heard these referred to as kinetic switches, and seen them in wireless doorbells and remote-controlled light switches. We’ll investigate how they work and ways to interface with them. T hese are RF transmitters that do not need a battery or other power source. The accompanying receivers do require power, but as they are used to control the likes of mains-powered lights and appliances, power is readily available. They use a form of energy harvesting to send a brief transmission. The examples we tested use some interesting strategies to make best use of the limited amount of energy available. All devices mentioned in this article use the 433MHz LIPD (low interference potential device) band, which is actually closer to 434MHz than 433MHz. In the April and June 2025 issues, we presented a series of project articles for building a 433MHz Transmitter and Receiver pair (siliconchip. au/Series/439). The series includes an explanation of the LIPD band, its uses and its limitations. The power limits mean that its range is typically quite short, but useful within a typical household. In this article, we’ll look at a bare module, as well as a complete unit that has a matching receiver. We’ll investigate the energy harvesting circuitry and its operation, since we expect readers will be interested in that. We’ll also delve into the RF transmission protocol and how to receive signals from some of these devices, including sending and receiving compatible signals using our Transmitter and Receiver paired with Arduino code running on a Pico microcontroller module. The DFRobot TEL0146 Photos 1 & 2: The TEL0146 is a compact unit that incorporates an energy harvesting device and RF transmitter. It doesn’t need a battery. The rear of the TEL0146 shows the fixed coil, E-shaped core and moving pole pieces. The return spring for the lever is towards the bottom. 60 Silicon Chip We’ll start with this module since it is a bare unit with visible workings. Shown in Photos 1 & 2, it is just under 5cm long. There is a plastic frame that holds a black PCB and an assortment of other parts, like springs and coils. These modules are available from Mouser and DigiKey for around $16, excluding shipping. Information on the module is available from DFRobot at siliconchip.au/ link/ac84 Pressing and releasing the white lever triggers the transmission, and an onboard LED flashes briefly. The Australia's electronics magazine action is quite firm and has a satisfying click. Interestingly, the transmission occurs on the upstroke, as the lever is released. The lever travel is about 3mm at its outer end. The page noted above mentions that the lever should not be pressed more than three times per second, and that at least one of the configuration DIP switches must be selected. Fig.1 is the circuit diagram for the electronics on the module. It is based around U1, a Cmostek CMT2156B, which is an OOK (on-off keying) RF transmitter IC with integrated energy harvesting. Unlike our Transmitter module, this chip also includes circuitry to modulate the output RF energy and apply encoding. In 2021, Cmostek was bought by HopeRF. Apart from the addition of the extra voltage regulator circuitry at upper left, the circuit design closely matches an application note circuit in the CMT2156B data sheet. The regulator allows the module to be powered by a low-voltage power source like a battery. We applied 5V to the DC INPUT connections and found that this activated the transmitter in much the same fashion as the lever. So this module can be used as a conventional RF transmitter, too. Pins P2N and P2P of U1 connect to the coil, which is mounted behind the PCB. The data sheet appears to show a magnet moving near the coil, hinting that the energy harvesting is based on electromagnetic induction. The snappy action of the lever is siliconchip.com.au Fig.1: the CMT2156B includes internal rectifier and regulator circuitry to harvest energy from the coil connected to pins 10 & 11. When triggered, it sends out an RF signal, encoding the value set by DIP switch SW1. reminiscent of some piezo devices, but it is a simple mechanical spring here. The data sheet for the CMT2156B shows that the V5N and V5P pins have an absolute maximum rating of 6.5V. Based on E = ½CV2, the two 47μF capacitors can store around 2mJ each. The chip contains dedicated AC-DC and DC buck (step-down) circuitry using external inductor L1 to produce a regulated 2.4V at the Vout pin, and this is used to provide power for RF transmissions. This allows the IC to operate longer, as the higher voltage generated from the coil isn’t wasted; effectively, the initial current drawn from the reservoir cap is reduced until it partially discharges. The remainder of the circuit is for selecting and generating the appropriate RF codes. The chip supports so-called 527, 1527, 2262 and 2240 data encodings; it also has an internal EEPROM that can be programmed. The DFRobot page indicates that the 1527 encoding is used by the TEL0146. It also mentions that 600μJ of energy is generated, which sounds reasonable given that the 6.5V rating above is an absolute maximum. The 1527 encoding includes 20 identity bits, giving just over one million unique transmitter IDs, and four data bits, which correspond to the four DIP switch inputs on the TEL0146 Switch Module. There is no checksum for error detection. siliconchip.com.au E1 is a pair of unoccupied solder pads on the PCB. Bridging them causes the device to transmit on both strokes of the switch (press & release). It’s unclear whether there’s any benefit to that configuration, but as that is not the default, we doubt it. Zener diode D1 appears to be the part that clamps the generated voltage to a safe level. Note the interesting connection of crystal Y1, between pin 9 of U1 and GND, rather than between two pins as is commonly seen (Pierce oscillators). We suspect the crystal is being used in parallel resonance mode. and effectively has a two-way bistable action. Coil voltage We were curious what kind of voltages were present around the coil and other parts of the circuit. Scope 1 shows the voltage across the coil during a lever actuation. As the coil is connected to the P2P and P2N terminals of U1 on the PCB, the voltages may be different (and probably higher!) under open-circuit conditions. As expected, there are two spikes of opposite polarity, and the voltages appear to be clamped near to the Coil and mechanism Fig.2 shows the arrangement of the coil and mechanism. The fixed coil is in the centre of an E-shaped core with many turns of fine enamelled wire. The moving part has two pole pieces separated by a magnet. The magnet causes the pole pieces to be attracted to the core, so moving it requires some force. When the lever moves as shown by the arrows, the magnetic field in the core reverses, inducing a current in the coil. In the TEL0146 module, a spring is fitted. This returns the pole pieces to their original positions when the force is removed. Otherwise, the magnet causes one or the other of the pole pieces to remain stuck to the centre of the core. Later, we’ll look at another device that lacks the spring Australia's electronics magazine Fig.2: a moving magnet induces a current in the windings of the coil. The TEL0146 unit includes the spring shown here, and the mechanism returns to the lower position after each actuation. The rocker switch mechanism is bistable and is held in place by the magnets after operation. March 2026  61 Scope 1 (left): the voltage across the coil in a TEL0146 module. It appears there are internal clamps in the CMT2156B chip that keep the voltages within its 6.5V limits (or D1 clamps the voltage; possibly both). Scope 2 (right): the red trace shows the voltage on C1 and the blue trace on C5 (from Fig.1). The green trace is the RSSI signal from a nearby Receiver and shows when the chip is actively transmitting. By waiting for the upstroke, the chip harvests energy from both the down and up actions of the mechanism. 6.5V limits noted earlier. The timing of the pulses depends on the time between the lever being pushed and then released. Scope 2 shows the voltages on the two 47μF capacitors relative to circuit ground. The voltage on C1 (red) rises first, followed by the voltage on C5 (blue). The green trace is the RSSI (received signal strength indicator) voltage from a nearby 433MHz Receiver, from our project series noted earlier; this trace’s height roughly corresponds to the average RF energy received. We can see that the CMT2156B only starts transmitting when the second coil pulse arrives, and the RF is sent in packets. The small dips in the green trace correspond to the changes in the slope of the capacitor voltages. About three packets were sent in this case. Based on our calculations, the circuit draws around 5mA during transmission. The voltage levels out at about 1.8V, after which the resistors slowly bleed off the remaining charge over the course of seconds. The data sheet mentions that the minimum operating voltage of the CMT2156B is 1.8V, so presumably the chip shuts down when it detects this low voltage and stops drawing current. Other devices We also found a complete wireless switch system that appears to be based on the same principle. It includes a large rocker-style switch and a 230V wireless receiver module. The two units are paired, and when the rocker is actuated, the output of the receiver module toggles on or off. As a set, the switch and module worked quite well before we disassembled them. Photo 3 shows the transmitter and receiver set, while Photos 4-6 show how the switch unit comes apart. The main rocker simply pulls off. It is held only by small clips that also Photo 3: This wireless kinetic rocker switch works similarly to the TEL0146 but includes a simple enclosure and mains relay unit. The enclosure (left) measures 8.6 × 8.6cm, while the relay unit (right) measures 4.8 × 5cm Source: www.ebay.com.au/ itm/405115817334 62 Silicon Chip Australia's electronics magazine allow it to pivot on its axis. There is an enclosed transmitter unit that clips onto the rear plate. There are also versions that incorporate two switch paddles, and the backplate clearly has room to carry two transmitters. The transmitters have two arms. Their internals are a little different from the other module, but they appear to use a similar coil and magnet arrangement. Our investigations also revealed that they use the same 1527 protocol as the TEL0146 modules. The set (switch mechanism, relay and tape) cost $20 from eBay, including delivery. That particular item is now out of stock, but other items that appear identical can be found with a search for “kinetic switch”. That search brings up some other items that appear to work in a similar fashion, but we have not tested them. There also appear to be different sets available with dual and triple switch mechanisms and multiple relays. These devices are not supplied with a circuit diagram, although there is a small instruction booklet including details of how to pair other transmitters to the relay. Operation We thought that the TEL0146 modules took a substantial amount of force to actuate, while the rocker switches were easier to toggle. To quantify this, we placed the switches onto a digital siliconchip.com.au Photos 4-6: The front rocker of the switch pulls off to reveal a smaller module attached to the back plate. This module is self-contained and could be incorporated into a 3D-printed enclosure if you didn’t like the appearance of the original. The smaller module contains a similar coil- and magnetbased energy harvesting circuit and RF transmitter. scale and noted how much extra force had to be applied to actuate them. The TEL0146 modules took around 900gf (grams of force) to actuate, while the rocker switches required about 240gf. Given that the TEL0146 modules have a return spring, it makes sense that their operating force is much higher. As a comparison, miniature tactile switches, like those we use in many projects, have an operating force around 100gf. We tried the transmitters over different distances and found that they did not seem to have the same range as other battery-powered transmitters, although they were still capable of working from a few rooms away. Transmission protocol Scopes 3-5 show the RSSI (red) and data (green) traces from a 433MHz Receiver while receiving signals from various transmitters. Scope 3 shows a transmission from a TEL0146 module, Fig.3: the timing of the 1527 encoding is based around a fixed timer period, with the sync pulse being one period of RF on followed by 31 periods with it off. The longer on-period of the ‘1’ bit could also be viewed as the RF being on at the half-way point (after the rising edge) of each bit. siliconchip.com.au while Scope 4 shows a transmission from the rocker-style switch. Although it uses a different encoding, we also recorded a waveform from the transmitter in a Jaycar MS6148 Remote Controlled Mains Outlet, shown in Scope 5. The Jaycar Mini Projects series (siliconchip.au/ Series/417) includes a few projects that interface with this system, including the Arduino Clap Light and the RF Remote Receiver. With the knowledge that the TEL0146 uses the 1527 encoding (seen in Fig.3), we found a couple of Arduino libraries that claimed to be able to receive and decode that protocol. However, it did not report any codes when the module was triggered. Comparing Scope 5 with Scope 3 and Scope 4 gave us a clue. It turns out that this version of the protocol is sent at a much faster rate than other protocols we had seen previously. Importantly, the self-powered modules were clocking their data faster than the libraries were expecting. By tweaking some of the library timing parameters, we were able to see results that corresponded with codes that we found by manually decoding the scope grabs. This was unexpected, but not surprising, given the strict power requirements. Clearly, a faster transmission means less energy is needed! With this in mind, we noted some other aspects of the design that are Scope 3: this waveform is from a TEL0146 module; the green trace is the signal from a 433MHz Receiver, while the red trace is its RSSI signal. The third packet is truncated, probably because the capacitors discharged before it was finished. Australia's electronics magazine March 2026  63 Scope 4: the output of the rocker switch module shows a much faster transmission. Six packets have been transmitted, but the first has not been received correctly, possibly due to the Receiver AGC not settling in time. The last packet has also been truncated due to the harvested power running out. useful in a low-power situation. For example, the 1527 encoding has quite a large gap after its synchronisation pulse (compared to the sync pulse itself). This reduces the duty cycle of the RF transmitter and thus the average power requirement. The receivers work by comparing the instantaneous RF energy to the average, so a 50% average duty cycle provides the best contrast between the RF on (100%) and RF off (0%) states. The codes we saw favoured ‘0’ bits over ‘1’ bits, reducing the average to around 35% duty cycle. For example, the narrow peaks in Scope 3 correspond to ‘0’ bits, which outnumber the wider ‘1’ bits. Unfortunately, the libraries we tested were not able to detect these signals consistently, so we set about creating an Arduino sketch that could receive the codes from these devices. We also wrote a sketch to transmit the same codes to further validate the receiver. Fig.4 shows the wiring diagram for a Pico connected to a Receiver and a Transmitter, respectively. Arduino code Scope 5: a single packet from a typical battery-powered transmitter. This type of unit will keep transmitting as long as the button is held down. It uses a slower data rate than the other units, which have to make the best of a limited amount of energy. Fig.4: how we wired up Raspberry Pi Pico boards to our 433MHz Receiver (top) and Transmitter (bottom) to interface with the modules in this article. The pins used (GP2/GP3 here) can be changed in the software. 64 Silicon Chip Australia's electronics magazine The two sketches are named RF_ RX_EV1527 and RF_TX_EV1527 for reception and transmission, respectively. They include simple header files with some useful functions and variables. The pins used are set by #defines, so can easily be changed. These examples use the Pico Ticker library, so they should work with any RP2xxx board. The RF_RX_EV1527 sketch looks for a sync low period of at least 700μs (adjustable), so it will sometimes confuse noise with a valid signal. It will record and report (to the serial port or serial monitor) the timer period (which is 1/31 of the sync low pulse period), since the timer period is also needed for the transmitter sketch. You can look for consecutive matching packets to filter out noise, since the transmitters should send multiple packets each time they are activated. Checking the timer period can also help to filter out invalid packets. The TEL0146 module resulted in a timer period of 82μs, while the rocker switch has a timer period of around 27μs. As you can see from the scope grabs, the rocker switch sends out about five packets, compared to three for the module. The sketch simply reports the timer siliconchip.com.au period and a 24-bit result. These 24 bits consist of the 20-bit identity value and four bits that could be changed by toggling the DIP switches on the TEL0146 module. The rocker switch does not have DIP switches, but it appears that there are four sets of jumper pads that can be set using 0W resistors. The RF_TX_EV1527 sketch requires the RF_TX_TIMER_PERIOD to be set. We were able to trigger the relay of the rocker switch to activate by copying the code and timer period from the output of the RF_RX_EV1527 sketch. We could also get the RF_RX_ EV1527 sketch to produce the same code and, as expected, the scope grabs of the module and RF_TX_EV1527 sketch match quite well. In our research, we found some reports that devices like the rocker switch emitted different codes depending on whether they were being switched ‘up’ or ‘down’. This seems reasonable, since the IC would see different pulse polarities from the coil depending on which way the mechanism was moving. But we did not find that to be the case, with our unit reporting the same code every time it was toggled. The toggle action makes sense if the relay was paired with multiple transmitters, which appears to be possible. Summary These are interesting devices, and it is handy that they work without batteries. The TEL0146 is just a bare module and takes an unexpected amount of force to operate. It could be useful if incorporated into a suitable enclosure, possibly including an ergonomic lever mechanism that reduces the amount of force needed for its operation. The rocker switch unit is complete and works well, and if you need a simple switch for a mains appliance or light, as it comes with a matching wireless relay unit. The switch is unobtrusive and needs much less force to operate. Subjectively, we also found that we were able to receive its transmissions more reliably, since it usually sent more code cycles per press. Both units appear to produce only a single code each, and we were able to interface to the RF signals for both transmitter types, so it will be straightforward to create custom projects using either. Our demo software can be downloaded from siliconchip.au/ SC Shop/6/3316 siliconchip.com.au Silicon Chip PDFs on USB The USB also comes with its own case ¯ 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). THE FIRST SIX BLOCKS COST $100 OR PAY $650 FOR ALL SEVEN (+ POST) NOVEMBER 1987 – DECEMBER 1994 JANUARY 2005 – DECEMBER 2009 JANUARY 1995 – DECEMBER 1999 JANUARY 2010 – DECEMBER 2014 JANUARY 2000 – DECEMBER 2004 JANUARY 2015 – DECEMBER 2019 OUR NEWEST BLOCK COSTS $150 → JANUARY 2020 – DECEMBER 2024 WWW.SILICONCHIP.COM.AU/SHOP/DIGITAL_PDFS Australia's electronics magazine March 2026  65 Feature by Julian Edgar Tips & Tricks for wiring new homes If you are building a house, or might do so one day, we have some helpful ideas that will help you get the most out of it. If you think of these things after it has been constructed, it’s usually too late! I am about 80% through building our new home. As an owner-builder, there’s been a lot to learn – and a few surprises along the way. One of the surprises is the amount of wiring. Not just mains wiring, but data cabling, for security cameras, HDMI cables, speaker cables... so many wires! So, if you’re building – or thinking of building – a new home, you need to know what wiring aspects to keep in mind. We’ll start with mains wiring. Mains wiring First, note that in Australia, you will need an accredited electrician to do the wiring. Of course, you can discuss your requirements or plans with them first. In more free countries like New Zealand, you can do some of the work yourself. If you do, it’s a good idea to get an electrician to check over your work and to provide advice. In many respects, mains wiring has changed little over a long time – but the way we use mains power has changed. One example is power points. Once, power points tended to be used for just high current devices – floor heaters, vacuum cleaners, the kitchen kettle and the like. Sure, there were lower-current uses like radios, TVs and hifi systems, but there wasn’t the plethora of low current plugpack-powered devices and USB chargers that now exist. So the number of power points fitted to old homes – perhaps a couple per main room – is now quite inadequate. 66 Silicon Chip In our new home, we have 63 double power points, and through contact with other owner-builders, I’ve found this is often regarded as a low number! Power points located outside are often overlooked – we have ten, including one for the legally required (NSW) rainwater tank pump, and another for a pool pump. Each bedroom typically has four – one on each side of the bed (for a light, clock or phone charger), another easily accessible (for a standing lamp or vacuum cleaner) and one inside each built-in wardrobe (for plugpack-­ powered low-voltage LED lights). One bedroom, where the double bed can be orientated in two different ways, has four bedside power points, so there will be one on each side of the bed irrespective of the two different bed orientations. Sourcing parts If your electrician is happy for you to source the mains cable and parts, do so! There are several Australian suppliers selling cable, power points, lights, switches and so on at excellent prices – often half the retail price. This isn’t for no-name brands, but for quality brands like Clipsal. You can save many thousands of dollars by taking this approach – but ensure you work closely with the electrician so that he or she gets exactly the parts they want. Australia's electronics magazine My home office has eight power points, with six located behind the L-shaped desk. It is cheaper to mount two double power points side-by-side than to use a quad (four-outlet) power point. Quad power points are expensive, and their mounting plates/boxes are also expensive. Of course, you can use power distribution boards rather than multiple power points positioned next to each other – the choice usually depends on whether they will be hidden or able to be seen, and on the total power draw of the devices (limited to a total of 10A or 2300W per outlet). Other power points installed include eight spaced apart in the loft. This large area may be used for all sorts of purposes in the future, possibly including a model train layout; many power points will make any use easy. There’s also a high-mounted power point for the wall-hung TV and high-mounted 15A power points in the bathrooms for infrared heaters. Remotely switched power points Importantly, there are also multiple power points that are switched on and off by normal wall switches. For example, wall switches are used to control two power points located inside the kitchen pantry. These each have plugpacks to power local low voltage LED lighting – one for a lighting strip under the wall-mounted siliconchip.com.au If the electrician is happy for you to source the parts that he or she will use, do so, as you’ll save plenty. Here I am picking up conduit for the underground supply cable. The ute’s tray is also full of cable, power points, switches and many other electrical parts. Seven outside floodlights will be controlled from this six-way switch. Cable is cheap, and when the house is still being built, easy to run. kitchen cupboards, and another that illuminates display shelves in high glass-fronted kitchen cupboards. Another remotely switched power point in the kitchen is for a booster fan for the range hood. Another two remote switched power points are located in the loft, allowing wall switches in the lounge to turn the sound system amplifiers on and off. Wall plate switches for remotely switched power points should include a pilot light to show the remote device is powered. The exception is where it is obvious that the remote power point is on; for example, it controls lighting. Neon pilot lights are available that slot straight into normal wall plates; for example, replacing one of the switches on a two-gang plate. On the advice of our electrician, the kitchen fridge is on a separate circuit. There are two reasons for this: 1. He suggested that the most common Earth leakage problem is caused by the fridge, and so isolating the problem is easy if that’s all that is on that circuit. 2. When people go away on holiday, they often switch off everything but the fridge – this is easily achieved if the fridge is on a separate breaker. Another two power feeds that are on separate circuits are for the pool water pump and the waste treatment system (the modern name for what was once a septic tank). The reason for running these on separate circuits is that, by fitting appropriate controllers at the siliconchip.com.au switchboard, it will be easy to operate these on excess solar power or offpeak tariffs. EV charging A major cable that we installed was for an outside charging point for an electric vehicle (EV). Single-phase AC chargers for EVs are typically rated at up to 7kW (about 30A at 230V). This high current requires its own circuit and, depending on the length of cable required, may need cable with quite a large cross-section of copper. The calculator at siliconchip.au/link/ ac69 is a useful tool to double-­check the cable being used by the electrician. In our case, because of the length, he used 10mm2 cable. Mains cable usually comprises Active, Neutral and Earth wires in a flat white cable. This is called TPS (thermoplastic-­sheathed) cable. A shut-off switch is needed at the EV charger – killing two birds with one stone, he used a 32A three-pin weatherproof external power outlet that has an inbuilt switch. The charger plugs into this power outlet. Many EVs now also have V2L (vehicle to load) functionality, where the car can act as a mains source. I own an MG4 EV that can provide up to 3kW – expect EVs in the future to be able to deliver more. So, rather than firing up a generator when we have a (not infrequent) blackout, another cable was laid to the EV charging point to allow the house to be powered by the EV. To protect anyone working on the external mains power lines when this occurs, the connection with mains must be broken by a switch – ie, the house is switched to back-up power The electrician will ask for your desired location and spacing of the various wall switches and fittings, so work this out ahead of time. From left to right, these mounting plates are for a light switch, isolation switch for a remote-controlled ceiling fan, space for the fan remote and the room temperature sensor mounting plate. Australia's electronics magazine March 2026  67 Where to locate the electronics Early in our house planning, I was thinking of making my home office the electronic ‘centre of things’. I envisaged a wall-mounted cabinet with terminations for Cat 6 cabling, cabling from the outside shed (for the security cameras) and speaker cabling for a whole-of-house audio system. Then I realised the cabinet would need to be huge because it would also contain the audio amplifiers, the digital video recorder (DVR) for the security system, the network switch/router and so on. So instead, I nominated some shelves in the loft space for all these functions. In a house without a loft, or where you want ground level access, you could use the equivalent of a linen cupboard. When designing a house, incorporating such an extra space is straightforward. Deciding on the location for the information centre is very important because it determines the route of many of the cable runs – especially the Cat 6 cables. If you choose to remote mount audio amplifier(s), it will also determine the location of speaker cables, line level (RCA) signal cables and possibly HDMI cables. and in doing so, disconnected from the mains. Note that this is not V2H (vehicle to house), where the EV’s battery seamlessly becomes part of the house system, charging and discharging in a two-way process. Unfortunately, because of power company regulations and the lack of suitable cars in Australia, V2H is still on the horizon. Heavy loads and dimmers Another pair of cables that surprised me because of their size were those for the stove and cooktop. Our electrician used 6mm2 for the cooktop and 4mm2 for the oven – this took into account any size or type for these two appliances, now or in the future. Another mains power aspect to keep in mind is lighting dimmers. The benefit of dimmers is that the current consumption falls proportionally as you dim the lights, so you can have plenty of lighting brightness available when required, but typically use little power at normal brightness levels. Modern smart dimmers have memory and slow-dimming functions, and the dimmer knob can be used as a normal on/off switch just by pressing it. These dimmers can also be easily wired to operate in two, three and even four way switching circuits, giving a lot of versatility in how you control lights. Nearly every internal light in our new house is operated by a dimmer, and the hallway lighting is controlled by three-way switching – one switch at each end and one in the middle. If using dimmers, ensure that you select LED lights that are dimmable. Some aren’t. The switchboard Consider where you want the switchboard to be located. It doesn’t need to be in the meter box; a location nearer to the area of maximum current draw (eg, the kitchen) will reduce the required lengths of expensive heavyduty cable. Standard 1.5mm2 cabling – typically for lighting – and 2.5mm2 for power points are both quite cheap because they are used in vast quantities. Thicker TPS cable is disproportionately much more expensive – it’s cheaper to make the main power feed, that doesn’t use TPS cable, longer. I chose to mount the switchboard centrally in the house loft. The advantages include proximity to the hot water system, kitchen & laundry, and plenty of space to mount the switchboard and later expansions (solar diversion relays etc). The disadvantage is that access to the switchboard is via dropdown loft steps. Modern smart lighting dimmers are energy efficient, remember their last setting and can be programmed for maximum and minimum light output. They are also easy to wire for two, three or even four way switching. 68 Silicon Chip Australia's electronics magazine Run any cables that might be needed in the future while the house is being built. This outside box contains a power feed for an air conditioner, should one be needed. When considering mains wiring, don’t forget outside lighting. Two-way switching of lighting in an outside shed is useful (you can operate the shed lights from both the house and shed), and house-mounted floodlights can provide excellent yard illumination, especially in dark rural areas. Many people also use decorative lighting along the side of driveways. Finally, on mains wiring, it costs little to run extra cables at the time the house is being built – regular thickness TPS cable is cheap, and access for the electrician through a half-built house is quick and easy. Therefore, if you can foresee any potential future requirement for power in a location, get the electrician to run that cable at construction time. For example, we do not plan on having air-conditioning since our energy modelling suggests we shouldn’t need it. But what if that modelling is wrong? In case it is, 15A cables have been run to each end of the house, terminating in outside weatherproof boxes. If air conditioners do need to be later installed, accessing power will take only moments, with isolation switches replacing the blank front faces of the boxes. Audio-visual cabling Cabling for audio-visual purposes can be bigger than Ben Hur – but let’s start with speaker wiring. While the current fashion is for Bluetooth speakers (eg, the rear speakers in a home theatre system), I much prefer hard wiring. If it’s done when the house is being built, it is quick, simple and easy – and of course, you can do it yourself. siliconchip.com.au Note that depending on the type of home theatre system you are running, you may need to wire in a lot of speakers! Speaker cable can be expensive, but there is a solution. If instead of speaker cable you select low-voltage garden lighting cable, you’ll find a 100m roll costs about $200 – and that’s for cable with a 3.4mm2 cross-section! This is about the equivalent of AWG 12, but it is much cheaper than similar-size cable sold as speaker wire. This cable is sufficiently thick for any length of speaker runs in a normal house – for short runs, you can of course use thinner cable. It will work just as well as speaker cable. Audio guru Douglas Self agrees that the type of cable used for speakers doesn’t really matter. In his book “The Design of Active Crossovers” (Elsevier, 2011), he writes, “The main factors in speaker cable selection are therefore series resistance and inductance. If these parameters are less than 100mW for the roundtrip resistance and less than 3μH for the total inductance, any effects will be imperceptible.” So speaker cable doesn't need to be anything special, as long as its resistance is low enough. You will need to decide how to terminate each end of the speaker cables. Normally, termination at the speaker end is via a wall plate with binding posts or jacks. However, this adds considerable expense and requires further cables to connect the wall plates to the speakers. An alternative is to use a brushed plate. With this approach, the cable simply passes through the wall plate brushes to the speaker or amplifier. When cabling for speakers, don’t forget any outside areas like a patio or deck. Depending on where the various amplifiers and signal sources are, you may also need to use HDMI and/or RCA (line level) connections between them. For example, in my house, the subwoofer amplifier is remote-mounted in the loft and is connected via long line level cables to the sub-out connection of the home theatre amplifier (near the TV) and a short line level cable to a Bluetooth audio input. It connects to both sources via a custom mixing cable, as described in an article from March 2025 (siliconchip.au/ Article/17787). siliconchip.com.au Low-voltage garden lighting cable is one of the cheapest ways of getting heavy-duty cable suitable for long runs. It’s usually much cheaper than similar size speaker cable. Cable for a speaker in an outside deck area. I chose not to use a wall plate with sockets but to simply feed the cable through a sealed hole in the wall cladding to the speaker. We didn’t have a home theatre system in our previous house. Because I was a little uncertain how all the cabling would play out, we set up the entire system in the unfinished house so that all cable runs could be checked before plasterboard closed off access. RJ45 plugs to Cat 6 cable and finding it very difficult (especially with thicker 23AWG cable), I decided to buy pre-terminated cables. Because these cables are available in a wide variety, it was easy to select cables of the right length. Wall plates are also available with female/female Cat 6 connectors, so running the Cat 6 cabling is as easy as just plugging the cables into the back of the wall plates. Cat 6 cabling Cat 6 is the most universal cable you can run in your house. It can be used to network computers, printers, security cameras, security systems, games consoles, smart TVs and VoIP phones. It can even network one switch to another switch and connect a wireless access point to the network. Additionally, it can be used as low-voltage power cabling, eg, for operating remote relays or intercoms, or for sensing environmental factors like temperature or wind speed or for powering a wireless internet dongle. Via adaptors, HDMI and USB signals can be sent down long runs of Cat 6. In short, think of Cat 6 cabling as the communications backbone of the house. In our house, I have run Cat 6 cabling from the information centre in the loft to: • my home office • my wife’s work desk • the two main bedrooms • the kitchen • the TV in the lounge • the shed • each external security camera location After fiddling with fitting my own Australia's electronics magazine Security cameras Security camera systems are available in three types: wireless (no cabling), analog (using coaxial cable for the signal and a pair of wires for power) and digital IP cameras (using Cat 6 cabling and POE [power over Ethernet]). In our house, built on a five-­hectare rural block, we use wireless for long-distance monitoring, and IP cameras for the house and shed. A major advantage of IP cameras in our application is that the shed is connected to the house via Cat 6 cable, and by Optic-fibre based cables can be used for long HDMI runs. For example, these can be used to connect a security camera digital video recorder (DVR) to the main TV, allowing review of footage on a large monitor. March 2026  69 using a network switch in the shed, multiple security camera feeds can be fed via this single cable to the DVR in the house. Depending on the location of the DVR, you may need to use a long HDMI cable to connect it to a viewing monitor. Many people use their main TV as the security monitor (it’s likely to be the largest display in the house), so either the DVR needs to be located near the TV (and thus all the camera cables also need to come to this spot), or a long HDMI cable needs to connect the DVR to the TV. We chose the latter approach. Conventional HDMI cables are limited to about 15m. However, longer active fibre-optic HDMI cables are available in lengths up to 30m. Note that these must be connected the right way around; they have a transmitter (labelled ‘source’) and receiver (labelled ‘display’) built into the respective plugs – something I initially didn’t realise! Fibre-optic HDMI cables are also subject to less RF interference than conventional HDMI cables (and produce less interference) but they have a downside. Should the electronics in the transmitter and receiver (integrated into the plugs) fail, they will be difficult to replace. A more reliable alternative is to use RG-6 coaxial cable with SDI (Serial Digital Interface) converters at each end. However, there is a further subtlety with a remote-mounted DVR. To operate the DVR (eg, to play back security footage) requires a mouse connection to the DVR, and that mouse needs to be operable from where you can see the TV. Conventional USB cables are limited to about 5m (for a longer cable you need an amplified ‘repeater’ cable), but a Bluetooth mouse will usually work over the required distance. Selecting a Bluetooth one-handed finger trackball mouse means you don’t have to rest the mouse on a surface when using it, and the mouse can easily be stored near the TV when not being used. Other stuff If you are building a house – or having one built for you – don’t forget you can do whatever idiosyncratic things you want with the non-mains wiring. For example, in our solar passive house, I want to be able to display and log temperatures throughout the house, including temperatures in every room, in the concrete slab (that stores heat and can act as a heatsink) and near the ceiling in two rooms with raked ceilings. This sensing is achieved using thermistors, including some buried in plastic tubes inside the concrete when the slab was poured. Signals are fed to two Picolog 1012 analog loggers with data displayed on a touchscreen PC located in the hall, with an HDMI-fed repeater screen in my office. Several hundred metres of cables are used. Home automation I decided against using full home automation because its advantages (automatic control of door locks, light dimming, air conditioners, opening and closing of vents etc) seemed to me to be outweighed by its complexity and the likely life of such specific hardware. A finger trackball mouse is a convenient way of operating a remote security camera DVR when the main TV is being used as the monitor. It overcomes the need for a long, active USB cable. Of course, you might decide otherwise, in which case you’d definitely want to run as much of the wiring as possible during construction of the home. Many home automation devices will work over Cat 6, so make use of that where possible. Conclusion The wiring decisions that you make have the potential to greatly alter the liveability, energy efficiency and cost of a new home. Think through the different systems very carefully, as it is easy and cheap to install wiring when the house is being built, but expensive and difficult to do so afterwards. Where possible, test the wiring as it is being installed. If it can be done, temporarily set up whole systems (eg, security cameras) to ensure you’ve not forgotten any required cables. Finally, by working closely with an electrician for the mains wiring, and doing the other cabling yourself, it’s also possiSC ble to save a lot of money. What about wireless? A brush plate on an internal brick feature wall. Brush plates allow cables to pass straight through, so pre-terminated cables (eg, HDMI) can be easily used. 70 Silicon Chip Australia's electronics magazine A good rule of thumb to use is: when connecting to a portable device, use wireless. When connecting to a device that stays in one location, use Cat 6. Cables are more reliable and have higher bandwidths than wireless. They are also far less subject to interference. For example, we have experienced WiFi dropouts near the kitchen when a microwave is running! siliconchip.com.au Internet Radio Part 2: by Phil Prosser This new Internet Radio, introduced last month, is very capable; it runs your choice of media player on Linux with a large touchscreen. It’s built using pre-assembled modules and 3D-printed pieces, so once the parts are ready, you can put it together in an afternoon. T he first article last month described our goals, its resulting capabilities, the 3D-printed case construction and how the modules connect together. If you’ve decided to build it, by now you should have the case pieces ready and the modules in hand. You should also have the operating system installed on the Raspberry Pi. That means we’re ready to put it all together! Mechanical and electrical assembly First, check the fit of the Raspberry Pi into the case. If any dags need to be cleaned up from the slots for the Pi, do this now. The Raspberry Pi installs by inserting the corner next to the USB-C connector and then rolling the Pi in, so the corner at the far end from the USB faces up to its matching slot. After that, jiggle the front slot in. It is somewhat tight, but it fits – refer to Photo 4. Leave the Pi loose until the HDMI and USB-C connectors are in, to make it easier to jiggle those into place. We have included screw holes on the fourth standoff for the Pi. If yours is loose, you can use a Jiffy box screw to hold it still, but we did not need to add this screw. Next, install the DC-to-DC converter using 9mm Jiffy box screws and flat washers to the screw holes printed under the handle. Mount it with the wires facing the rear of the case – see Photo 5. Wiring 1. Solder 150mm extensions to the power input pigtails using red and black light-duty hookup wire. We want sufficient length in these to allow easy assembly. Use 10mm lengths of 3mm heatshrink tubing to cover where the wires are joined. 2. Run the USB cable under the Pi Photo 4 (left): when installing the Raspberry Pi, start with the back corner and roll it into the slot. In this picture, the Raspberry Pi is half installed. Photo 5 (below): the power supply (highlighted in yellow) screws into holes printed into the top of the case, underneath the handle attachment location. siliconchip.com.au Australia's electronics magazine March 2026  71 Photos 6 & 7: the input wires & switch connection on the amp module; the middle input pin (ground) is not connected. The two black wires go to a switch that allows us to select between Bluetooth and the Raspberry Pi input. Connect the amplifier’s audio input ground pin directly to the power supply V− output. to keep things neat and plug it into the power connector. This is a snug fit but it goes in. 3. Prepare to install the amplifier. There are two sets of wires that need to be soldered to the amplifier board, for the input selector and audio input: 4. Solder 300mm lengths of red and black light duty hookup wire to the audio input connector “IN” left and right pins; these are the outside ones (Photo 6). 5. Connect a 300mm length of green light-duty wire to the power V− pin. This means that the middle “GND” pin on the input connector is not used, and the green ground pin goes to the amplifier module V− connection – see Photo 7. Put a 30mm length of 5mm heatshrink tubing over these, snug up against the PCB to keep them tidy. 6. Now terminate these three wires to a 3.5mm stereo jack plug (see Photo 8 & Fig.7). We also need to include a 400mm length of light-duty green wire, which will extend from this plug through to the power supply ground point on the rear panel. 7. Put a piece of 5mm heatshrink over the wires, making sure that the green wire goes to the outermost connection, and also that nothing shorts. Be sure to put the backshell on the wires before you solder it all together. Use a pair of pliers to gently crimp the strain relief over the heatshrink, securing the wires, then screw the backshell on. 8. We now need to connect to the “SW” connection on the amplifier PCB. This connection switches between the Bluetooth module and the “IN” connector. Use two 250mm lengths of light-duty hookup wire; these can be any colours as they only 72 Silicon Chip go to a switch. Solder these to the two “SW” pins and then put a 15mm length of 3mm heatshrink over these at the PCB to keep things tidy. 9. Use a zip tie to secure these wire bundles to the rear mounting hole of the amplifier board. This will stop the wires from bending and causing shorts and breaks at the solder connections. 10. Solder these two wires to an SPDT toggle switch and insulate with heatshrink. Make sure you insulate the connections at the switch using 3mm heatshrink. The final arrangement is shown in Photo 10. Photo 8: the wiring to the 3.5mm plug that goes into the Raspberry Pi. This includes an extra ground wire soldered to the ground tab that runs to the power input connector. Keep this tight, and it will still fit in the backshell. 11. Use light-duty hookup wire for the power and speaker connections, all 340mm long. We used red and green for the speaker connections. You only need to connect to the V+ input on the power input as the ground goes via the 3.5mm jack. These wires are connected via pluggable two-way headers. If you don’t have the right crimping tool, simply use sharp pliers to secure the wire in the crimp, then add a small amount of solder. Make sure you get the power connection correct; the positive is closest to the corner of the amplifier board (as shown in Photo 9). Photo 9: the power wiring for the amplifier. Photo 10: the amplifier module, wired up and ready to install in the case. Fig.7: the wiring for the 3.5mm jack plug. Note the two ground wires of different lengths; in practice, it’s easier to solder one to the top and one to the bottom. Make sure it will still fit in the shell despite the extra wire. Australia's electronics magazine siliconchip.com.au 12. The speaker connectors terminate at the speaker terminals; use 30mm of heatshrink over these as it assists with strain relief and keeps things tidy. Now install the amplifier PCB in the case. It is held in by its volume control shaft bush and two ridges printed into the inside of the case to keep it aligned properly. Make sure the board is aligned with the ridges and tighten the pot nut well. We have also printed an indent in the case to accommodate the locating lug on the volume control, so everything should sit neatly. Next, plug the 3.5mm jack into the Raspberry Pi audio output connector. Mount the input switch to the case, making sure to put a shakeproof washer on the outside. Tighten this well. Plug in the power connection and the speaker connectors, making sure not to mix these up. We labelled our cables so it is less likely we will make a mistake. Use a 100mm zip tie to secure the input wiring to the DC-DC converter. We will come back to the flying leads for the power and ground connection when we wire up the rear panel. Photo 11: the LCD screen has an onboard on/off switch that needs to be left on. Mounting the handle We used four 16mm-long M4 machine screws, washers and nuts to do this. Use shakeproof washers to ensure these bolts remain tight with movement and vibration. After that, you can install the LCD screen. We built two Internet Radios to check the design & instructions and found that the LCD alignment between the top and bottom was asymmetrical on one of our units, while it was perfectly centred on the other. This really affects the mounting hole locations. We worked around this, but on visiting Altronics the next day, we checked a few other samples and found that they were all well centred. The staff offered to swap the crooked unit, but we had a fix, and it seemed wasteful to scrap an otherwise perfectly functional unit. If you experience this crookedness, we drilled new 2mm holes in the back of the front panel and used them to attach the screen with 6mm-long self-tappers. Now check that the screen’s “On/ Off” switch is set to on, as shown in Photo 11. Present the LCD to the internal front panel; the connectors face the wide section. Install self-tapping Jiffy box screws in the three holes you can siliconchip.com.au Photo 12: the connections for HDMI and USB to the LCD screen; this is tight, but it does fit. The USB socket is for power and touch sensing. Photo 13: the Raspberry Pi in the case and plugged in. The cable at the bottom supplies power to the LCD screen; it pokes out of the USB hole in the rear of the case a bit. Australia's electronics magazine March 2026  73 Photo 14: the wiring from the power input to the switch and bypass capacitor. We use the leads of the capacitor as connection points for the amplifier and Raspberry Pi power converter wiring. Photo 15: the finished rear panel wiring. The top four new connections are both for the speakers. access. The Raspberry Pi obstructs one, although you may be able to get a screw in if you take the Raspberry Pi out. Three is enough, though. The next bit is one of those jobs where having three hands and needle-­ nosed pliers for fingers would be really helpful. Go steady, as it does all fit. First install the 90° HDMI connector to the HDMI input on the LCD screen. We then used the provided short HDMI to HDMI cable and connected it to the Raspberry Pi’s micro HDMI connector via a right-angled HDMI adaptor and a micro HDMI to HDMI adaptor. You may find alternative parts and approaches, but this fitted well for us. Again, everything is very snug, so gentle persuasion is the order of the day. Now install the micro Type-B USB to Type-A USB cable, which is in the LCD box. This goes from the “TOUCH” connector on the LCD to a USB Type-A port on the Pi. Secure this to the HDMI cable with a couple of cable ties. Photos 12 & 13 show where things go on the LCD and Raspberry Pi. Now turn your attention to the Radio’s rear panel and mount the barrel power input connector and power switch. Photo 14 shows how this should look. The middle pin of the power jack is normally positive; this comes out in the middle of the socket. However, do check that your power supply’s centre pin is positive first. Start by installing the 2.1mm barrel connector and a SPDT switch in the rear panel, then add the supply bypass capacitor. This needs to be rated at 35V (or more) and at least 1000μF. We used a 2200μF, 50V capacitor. We have printed a holder on the rear panel that suits an 18mm diameter capacitor. Insert the capacitor in the holder and bend the leads as shown to connect to the power input connector. The negative pin of the capacitor goes to the barrel connector on the socket. This is at the top in Photo 14. The positive pin of the capacitor goes to the switch; this might need to be extended with a short length of wire. You should not need to glue the capacitor as, with the snug fit of the holder and the leads being bent and soldered to the barrel connector, the capacitor will be secure. Next, solder a 75mm length of red light-duty hookup wire to the outer terminal of the switch; this goes to the positive pin of the barrel connector. Insulate these joints with two 15mm lengths of 3mm diameter heatshrink tubing. Make sure that you leave 5-10mm of the capacitor leads free, as these form your positive and negative power supply connections. At this point, you should have two positive and two ground wires waiting to be connected, one pair from the DC-DC converter and the second from the amplifier power connections. Solder the power wires from the DC-DC converter and amplifier to their respective connections on the capacitor. Now connect the amplifier output wires. These are 340mm long in red and green, with pluggable headers for the amplifier end. Solder these to the speaker terminals and insulate with 15mm of heatshrink tubing. Refer to Photo 15 for how this should look. At this time, you can plug in the 74 Silicon Chip Australia's electronics magazine amplifier output wires and zip-tie them together. The final looming should protect the solder junctions from being flexed and make things quite tidy. Now install the speaker terminals. We have printed holes to accommodate combined screw terminal/banana sockets. Mount these and connect to the wires coming from the amplifier board. We have included printed feet in the case design, but it’s ideal to stick four rubber feet to the bottom of the case. At this point, all the internal wiring should be finished, with a few zip ties added to keep everything neat and tidy, like in Photo 16. Clip the rear panel on. This will require you to fit the LCD USB cable through the hole in the rear panel. It should all go together very neatly; the inbuilt clips hold the rear panel in place. There are four screw holes into which you can insert 9mm Jiffy box screws to hold it together. You should be able to power up the central unit and get to the Raspberry Pi desktop. Optional speakers We used fairly low-cost Altronics C0635 100mm drivers. We tried cheaper ones, but preferred these. Because the boxes are built to the size available, we have made them sealed, which tends to roll the bass response off early, avoiding nasty peaks that can occur with poorly designed bass reflex alignments. We then use the equaliser in VLC media player to correct this early rolloff, which works surprisingly well. siliconchip.com.au The underlying hint here is that unless you really do some homework, spending too much on the drivers is probably a poor investment. Building the speakers is straightforward. Use four 9mm 4GA Jiffy box screws and 3mm washers to attach the drivers to the case. We have included pilot holes in the 3D print, so you should have an easy time locating the screws and drivers. Install the speaker connectors in the holes in the rear panel and solder light-duty hookup wire to the speaker terminals – see Photo 17. Get some fibre fill; sheep’s wool or anything that is likely to absorb energy from resonances, and stuff the speaker loosely full. In our case, it was about a 150mm square piece of fibre wadding that we found in the sewing cupboard. Pretty much anything like that will do. Now secure the rear of the case with four more 9mm Jiffy box screws. We have printed feet on the unit, but if you’ve stuck rubber feet on the main unit, it’s best to do the same on the matching speakers. Note that if you want to bolt the speakers to the central unit boombox style, you should do this using M4 machine screws prior to installing the Raspberry Pi (or temporarily take it out to attach the speakers). At this point, you should be able to wire the speakers to the terminals on the main unit and power the system up. Getting it up and running We can now connect everything together and set it to work. Power the system up and open VLC Media Player. We went to the main menu, right-clicked on VLC and added it to the taskbar. Out of the box, the Pi drives the 7-inch LCD screen well, but if this is to be a dedicated media player, you probably want a simplified display and much larger fonts and buttons. Setting up the display to use large icons and text is not hard. 1. Click the Raspberry icon and scroll down to Preferences. 2. Select the “Appearance Settings” tab. 3. Go across to Defaults. Click “Defaults” against the line “For Large Screens”. 4. Click OK. If you have another monitor, a micro HDMI cable can plug into the second video port and run through the rectangular cutout in the rear panel. The Raspbian system deals with this pretty much exactly like a Windows or macOS system. We won’t go into detail here, but encourage you to explore some of the extensive documentation online and learn the subtle differences that exist. Setting up media streams This bit is probably as fiddly as it will get. The aim is to create some desktop icons for your favourite radio stations that you can simply double-­ click on to launch VLC Media Player and listen to them. Not every station has an internet stream, but it seems that most do, and worldwide there are thousands. There are websites that list the addresses for radio stations; this one worked well Photo 16: the fully assembled unit, with the wiring zip-tied together. The final product should be pretty tidy. Photo 17: assembly of the speakers involves little more than installing the drivers and some sound-dampening material. siliconchip.com.au March 2026  75 Table 2 – Station name Link 3D Radio http://sounds.threedradio.com:8000/stream ABC National https://mediaserviceslive.akamaized.net/hls/live/2038318/rnnsw/index.m3u8 ABC News http://live-radio01.mediahubaustralia.com/PBW/mp3 Triple J unearthed https://mediaserviceslive.akamaized.net/hls/live/2038305/triplejunearthed/masterhq.m3u8 MMM Adelaide http://legacy.scahw.com.au/5mmm_32 The Bone FM San Francisco https://playerservices.streamtheworld.com/api/livestream-redirect/KSANFM.mp3 Triple R http://realtime.rrr.org.au/p1h for us: https://fmstream.org/index. php?c=AUS This site has a massive list. If you select “Links”, you can copy the web links below. Put the text into a file with the extension “.m3u”. Some example links to internet radio stations are shown in Table 2. Our approach to this Internet Radio is more about making a really simple way for you to get going with the Linux environment, avoiding unnecessary complexity. Once you are happy with what we have set up, we are sure you will seek more complexity and move on from this minimum but sufficient capability. To create some desktop icons, you can: 1. Click on the Raspberry symbol in the top-left corner of the screen. 2. Scroll down to “Accessories”, then choose “Mousepad” from this Screen 5: opening the mousepad program in Raspberry Pi OS. menu (see Screen 5). This will open an editor screen. 3. Type http://sounds.threedradio. com:8000/stream 4. Click “File” in the top menu. 5. Select “Save As”. 6. Double-click on “Desktop” to save this to the desktop. 7. This will open a screen with “Name” at the top. 8. Type “Three D Radio.m3u” (see Screen 6). 9. Click Save in the bottom-right of this window. 10. Close all the windows you have opened. You will now see an icon on the desktop named: “Three D Radio.m3u” (Screen 7). The m3u extension indicates that this is a stream, and VLC should open it. Double-clicking this icon will open VLC Media Player and start streaming the station. You can do exactly the same for any station with an internet stream that you choose. If you only have a few stations you want to play, which is true for most of us, this will be a good way to start. Similarly, if you have a folder with a load of music files, you can use VLC to play them. Setting up VLC Screen 6: using mousepad to save the file “Three D Radio m3u”. 76 Silicon Chip Australia's electronics magazine Why do we recommend VLC for this project? VLC media player is baked into the full Raspbian install, and it ‘just works’. Even in 2001, when we first saw VLC, it was famous for playing anything. Over the intervening years, development has continued, and it remains a very stable player that many people will be at home with. Now let’s apply some equalisation to the speakers. The ones we’ve designed are not hifi, but with the power of the Raspberry Pi and VLC Media Player, we can add equalisation to get the most out of them. Open VLC Media Player, select “Effects and Filters” (Screen 8) and you will find a 10-band equaliser (see Screen 9). siliconchip.com.au We needed to change the sliders on each band, then click Enable a couple of times to update the EQ. If you add a lot of gain to the bass, you will find the system clips, so you will need to reduce the gain on the leftmost slider, “preamp”. We recommend that you fiddle with these until you are happy with the sound from the speakers you have chosen to use. If you are running the Internet Radio from a 24V plugpack, you will have oodles of power that can be used to get some bass boost, but be aware that you will probably run out of physical capacity in the speakers (principally cone excursion) before the amplifier runs out of power. The speakers specified needed some bass boost, with the midrange attenuated and treble boosted, in a typical ‘loudness’ curve (see Screen 9). This counteracts the roll-off these speakers exhibit in such a small box, and the final result sounded way better than we expected. The 7-inch screen we’re using is more than enough to drive VLC, but for anything beyond that, it is not large enough. If you want to use the Internet Radio for anything more than playing music, plug a micro HDMI to HDMI adaptor into the second HDMI port on the Pi. Assemble it with the HDMI socket outside the case; the cable will fit through the hole we have for the USB connectors. You can then plug in a decent external monitor. That will give you plenty of real estate to work with. If you want to use this computer for more than just music, we recommend that you get yourself a Raspberry Pi 5 with 8GB of memory (16GB is available, but there is a big step in cost). The Raspberry Pi 5 does not have a 3.5mm audio socket, so you will need to add an audio output. You can do this by adding an audio DAC Hat, such as the Raspberry Pi DAC+, or you can plug in a USB audio adaptor. To set these up, click the audio icon on the top right of the screen, and select your audio interface. Screen 7: internet radio links on the Pi desktop. Double-clicking these will launch VLC Media Player and open the stream. Screen 8: VLC’s Tools menu lets you open the Effects and Filters dialog. Conclusion Wow, you’ve built a Linux-­powered Internet Radio boombox and computer. We trust that you got this working, and for those with little Linux experience, that it went well. We look forward to hearing how you modify SC and tailor this to your needs. siliconchip.com.au Screen 9: click on the “Equaliser” tab on the left and adjust the EQ until it sounds good with the speakers you have selected. Australia's electronics magazine March 2026  77 Sometimes measuring the temperature is just not enough; you need to see how the temperature changes over time. This simple, compact and inexpensive thermometer provides a low-cost solution. Graphing Thermometer Andrew Woodfield’s O ver the past year or so, I’ve found myself designing an increasing number of circuits with surface-mount devices (SMD). That required a set of tools for building prototype SMD printed circuit boards (PCBs) in my workshop. One of those tools is a hot plate reflow soldering system, made from a 500W electrically heated metal plate measuring about 100 × 200mm. The controller adjusts the heating of the plate so it matches the recommended temperature profile for reflow soldering of SMD components. To design the controller and build the reflow plate system, I needed a way to measure temperatures as high as 300°C. As Lord Kelvin once said: When you can measure what you are speaking about, and express it in numbers, you know something about it. When you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science. This certainly applies to SMD reflow soldering. Without careful and accurate temperature Photo 1: a typical low-cost non-contact infrared temperature measurement ‘gun’. 78 Silicon Chip low-cost measurement directly on the PCB, ideally as close as possible to the solder paste and components, and a method to observe the temperature variations as changes are made to the reflow hot plate hardware and controller software, it is very difficult to understand what is going on. Temperature measurement devices Initially, I purchased an inexpensive infrared (IR) ‘gun’ for these measurements, shown in Photo 1. It displays the average temperature of 3-10cm diameter sections of the hot plate. This is the approximate area that the gun’s sensor measures. The measured area also depended on the distance between the gun and the hot plate. It was challenging to get consistent temperature measurements. The reflow controller I was designing measured the hot plate temperature with a thermocouple mounted inside the hotplate. This temperature was shown on the controller’s LCD screen. Thermocouples are made from two dissimilar metal alloy conductors welded together at one end. The measurement point looks like a tiny metallic ball. This sensor generates a tiny voltage that is proportional to the temperature of that ball. Commonly available low-cost K-type thermocouples can be used to measure temperatures from about -200 to +1370°C. However, results sometimes differed between the infrared gun and the hotplate thermocouple. Which value was correct? Given that they were Australia's electronics magazine measured at slightly different locations, they could both be correct. As the saying goes, “A person with two clocks never knows the right time”. I needed another thermometer, ideally using a small, low-mass temperature sensor to precisely measure the temperature at the desired location. Thermocouples come in many forms. Some are enclosed in a protective cover or are physically large. These can have a significant ‘thermal inertia’, taking some time to report the temperature, so I wanted to avoid using those. Also, I wanted a thermometer that was small enough to be shifted easily around the workbench to measure temperatures at different locations in the reflow equipment. I also recognised that it was essential to graph the measured temperatures during the entire reflow process. These ‘temperature profiles’ (the temperature variation over time) can vary dramatically with each change in configuration, equipment, control software and reflow materials. That made it all the more important to view the overall result for each four to five-minute reflow test run. It is possible to buy a low-cost thermocouple-based thermometer interface for use with a laptop or tablet. However, such arrangements are quite unwieldy in many situations. All the required power cables add to the muddle on my already untidy bench. I tried to find a ready-made graphing thermometer, ideally a compact, portable, battery-powered device. You might think there are many such devices for sale. But surprisingly, at siliconchip.com.au least when I searched, I could not find anything suitable aside from several rather expensive meters from US retailers. This led me to design this simple and very low-cost thermocouple graphing thermometer. Design objectives As I mentioned, I need to measure temperatures up to 300°C. A measurement accuracy of ±10°C is acceptable in this case, provided the results are repeatable. When reading 300°C, that equates to a ±3% error. This appears to be in line with many commercial thermometers. Since there are other applications for this type of thermometer, I felt other ranges would be useful. The Thermometer’s design therefore allows for maximum temperatures on the LCD screen vertical axis ranging from 50°C to 600°C. While some K-type thermocouples can handle temperatures up to 1300°C, the materials used in the least expensive sensors appear only suitable for temperatures up to about 600°C. However, health and safety risks (and my anxiety) substantially increase above 600°C, so that sets the upper limit. Temperature samples taken at rates from once per second to, say, once every 5-10 seconds seemed suitable. Looking at a number of potential LCD screens, and allowing for graph axes and labels, 100 samples plotted along the horizontal axis of each graph appeared to be the practical limit. That gave an equivalent horizontal time axis span of between 100 and 1000 seconds (less than 2 minutes to a little over 15 minutes) per screen. Most reflow profiles run for 3-6 minutes (180 to 360 seconds), so this was well within this measurement range. To allow for other uses, I extended the sampling rate range further. The final range of 1-900 seconds per sample (up to 15 minutes) provides a maximum screen x-axis span of up to 25 hours or just over one day. Hardware considerations The typical approach for temperature measurements is to use a lowcost K-type thermocouple, an Analog Devices (originally Maxim) MAX6675 or MAX31855 8-pin IC as the interface device, and a microcontroller. The display, whether a 7-segment LED display, LCD screen or OLED screen, is also driven by the microcontroller. siliconchip.com.au Parts List – Graphing Thermometer 1 single- or double-sided PCB coded 04102261, 70 × 56mm 1 ATtiny85-20PU 8-pin, 8-bit microcontroller programmed with 0410226A. HEX, DIP-8 (IC1) 1 8-pin DIL IC socket 1 1.7-inch 128×64-pixel LCD screen with 3.3V UC1701X controller (LCD1) [AliExpress 32215047945] 1 0.9-3.3V to 3.3V boost regulator module (REG1) [AliExpress 4000252822321] 3 4-pin PCB-mounting tactile switches (S1-S3) [Altronics S1122, Jaycar SP0603] 1 DPDT slide switch (S4) [Altronics S2010, Jaycar SS0852] 1 AA or AAA cell holder (BAT1) [Altronics S5026/S5054 or Jaycar PH9203/PH9261] 1 AA or AAA cell (BAT1) 1 2-way barrier screw-type terminal block connector (CON1) [RS 144-8151, AliExpress 4000170287617] 1 8-pin header socket and matching header strip (CON2) 1 2-pin header socket and matching header strip (CON3) Capacitors 1 47μF 16V electrolytic 2 100nF 50V ceramic Resistors (all axial ¼W ±5% or better) 3 10kW 2 4.7kW 1 150-1000W (depending on desired backlight brightness; see text) I was keen to minimise the component count, along with the overall size and cost of the device. I wrote some software a few years ago for a soldering iron temperature controller. Originally designed for cheap thermistor-monitored soldering iron handpieces, some builders had encouraged me to try to modify it for the less common thermocouple-based handpieces (see www.zl2pd.com/ SolderingStation.html). It proved possible to do this with the 8-pin ATtiny85 that I’d used for the original controller. I didn’t develop that option any further – I already had the thermistor-type soldering station I’d designed. That software used an unusual analog-­to-digital converter (ADC) feature available on a few members of the ATtiny microcontroller family. This is a two-input balanced ADC interface that also includes an optional integrated 20× gain stage. There is also a 1.1V internal ADC reference available. Those features make these ATtiny microcontrollers suitable for thermocouple sensors. The ATtiny85 was the smallest in this family, coming in an 8-pin package. Would it be possible to connect everything else that would be necessary for a graphing thermometer within that 8-pin package limit? Australia's electronics magazine To answer this question, I turned to the display. I wanted to graph the results on a small graphics-­ capable display. One set of possibilities was the compatible and well-known 128×64 pixel 0.96in (24mm) or 1.3in (33mm) OLED screens. While the text on these is perfectly readable, my eyesight is no longer ‘fighter pilot’ quality. Tests confirmed that the individual graphed pixels were just a bit small. I did not want to be trying to peer at a display located in close proximity to something at 300°C. I value my eyebrows! Another option was one of the larger legacy KS0108B or T6963Ctype 128×64 pixel LCD screens. While low in cost, these demand a cluster of processor pins for data and control. A 1.8in (46mm) colour TFT LCD screen also looked possible, but the software necessary to drive its larger 160×128pixel display looked likely to exceed the limited 8kiB firmware space in the ATtiny85. I found the solution in a low-cost UC1701X-based 128×64 pixel 1.7in (43mm) LCD. It’s large enough to be readable, includes an excellent integrated LED backlight, and is controlled over a simple three-wire SPI serial peripheral interface, along with chip select (CS) and reset inputs. March 2026  79 Fig.1: the Graphing Thermometer is based on ATtiny85 microcontroller IC1. Its eight pins are just sufficient to handle thermocouple sensing, LCD updates and pushbutton sensing. Three pushbuttons would also be required for the Up, Down, and Next user control pushbuttons. When I added all this up, it would require ten I/O pins. The ATtiny85 only has six. However, with a little software and hardware effort, it proved possible to squeeze everything onto that device. The LCD screen also determined the power supply design, as it requires a 3.3V supply. Tests during development showed that this voltage is surprisingly critical. If the LCD supply voltage falls below 2.7V, it starts to misbehave, reversing and inverting text and graphics in quite disconcerting ways. So, in case you are tempted, this is not a design to power from a pair of 1.5V cells. Circuit description Fig.1 shows the circuit of the graphing thermocouple thermometer. You will see there’s very little hardware in this meter! The Microchip (Atmel) ATtiny85 microcontroller handles the measurements, drives the LCD screen and senses button presses. It’s clocked from the ATtiny85’s internal 8MHz RC oscillator divided down to 4MHz to reduce current consumption. A tiny boost regulator module increases the AAA cell’s 1.5V output to a reliable 3.3V supply, as required for the LCD screen. Most of these modules at the time of writing use the very efficient ME2108A switching regulator. However, the prototype’s module used a TPS61201. These operate similarly. These regulators are rated up to 1A, but the current drawn by this meter is a miserly 6mA at 3.3V. The 80% regulator efficiency results in about 15mA being drawn from the 1.5V battery. This gives a reasonable battery life for typical intermittent use. Since omitting the typical MAX6675 thermocouple interface chip results in the need to use one of the balanced analog-to-digital converters in the ATtiny85, two input pins are required on the ATtiny85 for the thermocouple. These are both internally configured as ADC inputs. One of these pins (pin 2) is then tied to ground. This may seem to be a significant waste of I/O resources, but that’s the only option when using the balanced ADC mode. The user pushbuttons connect to a single pin on the ATtiny85 via four resistors. Each pushbutton produces a different DC voltage on pin 1 of the ATtiny85. This voltage is read by the internal 10-bit analog-to-digital converter, allowing the pushbutton status to be determined by the software. Unusually, this pin is also used as an output. It drives the active-low chip select line for the LCD’s UC1701X on-glass controller. The UC1701X controller inside the LCD only sees a voltage that falls below 0.7V as a valid CS low signal. The pushbutton resistors are therefore selected to avoid this voltage range. The prototype Graphing Thermometer (shown at actual size here) was built on a singlesided PCB. The AA or AAA-cell holder on the back props it up at a useful viewing angle for the LCD. I used a 1kW backlight resistor. 80 Silicon Chip Australia's electronics magazine siliconchip.com.au Even if a pushbutton is pressed during a display update, the selection is (briefly) ignored. The resistor values ensure that the LCD only sees the processor’s commands. Once the display is updated, the processor can go back to detecting the pushbutton status. This novel arrangement ensures there is no disturbance to the operation of the display, yet key presses can be detected as needed. The LCD’s SPI connections use the three remaining pins. The LCD’s remaining pin, the reset input, is only toggled when the LCD’s power is applied. It’s not otherwise used. A resistor and capacitor are used to generate this power-on-reset signal. This avoids using another processor pin. The LCD has an integrated LED backlight. A 150-1000W resistor supplies 2-10mA current for this from the 3.3V rail. Higher values provide extended battery life – with a 1kW resistor, the backlight current is just 2mA. Alternatively, the backlight supply resistor may be removed (using reflected light only to see the screen). Another option is to connect an external toggle switch connected in series with it to save power when making use of the longer sampling intervals that are possible, while still being able to use the backlight when required. A 1kW backlight resistor gives a relatively modest light level. If brighter light levels are required, this can be changed, for example, to 560W (moderate brightness) or 150W (high brightness). voltage and calculates the temperature from this. This value is reported on the LCD screen, in the lower lefthand corner, and the value is plotted on the graph. After 100 samples are plotted, the screen is erased and a new plot begins automatically. Accurate thermocouple measurements require cold-junction compensation. This method measures the temperature at the thermocouple meter terminals (the ‘cold junction’) using another thermometer and corrects the thermocouple measurement accordingly. The ATtiny85 has an internal temperature sensor, but I am not using it. Instead, a simple ‘thermocouple offset’ value is entered in the meter, a method suggested by Horowitz and Hall in the reference textbook “The Art of Electronics”. As the authors suggest, it works well when measuring over these temperatures (see below). Construction The graphic thermometer is built on a single-sided 70 × 56mm PCB that’s coded 04102261 (see Fig.2). All the components are mounted on this, including the AAA cell holder. No additional wiring is necessary, which makes for a fast and easy build. Start by soldering the resistors and capacitors. Then, using some of the cut-off leads of those resistors, install the three PCB links located at the top-centre of the board (if you’re using a commercially made board, it might not need links fitted). Next, gently bend the leads of the 47μF capacitor at right angles and then mount it as shown in Fig.2. This polarised component must be mounted so that the shorter negative lead is closest to the edge of the PCB. The three standard tactile 6×6mm pushbuttons can be fitted next. The pushbuttons come in a variety of shaft Cold-junction compensation for thermocouples The meter software is written in Bascom, the Basic-like compiler for the AVR processor family. This allows for relatively quick software development. The compiler generates surprisingly efficient code, and the resulting software occupies about 90% of the available program space. After initialisation and user selection of settings, the device spends most of the time waiting for the current sampling period to expire. During this time, the pushbuttons are checked for a user ‘Next’ command. That will result in the meter exiting the display mode and returning for new user settings and a new graph plot. After each sampling period has passed, the ATtiny’s analog-to-digital converter samples the thermocouple A conductor generates a voltage proportional to the temperature difference across it (Fig.a). This is called the Seebeck effect. We described this in detail on page 51 of the November 2023 issue (siliconchip.au/Article/16013). This tiny voltage cannot be measured directly because it is cancelled out by the voltage generated as a result of the connections required by the measurement circuit. However, by joining two conductors, each made from a different material, the difference between the voltages generated by this pair of conductors can be measured. These wires are welded together at one end to form the ‘thermocouple’ (Fig.b). K-type thermocouples made from Chromel and Alumel are the most common. These produce about 41µV/°C. This value varies slightly due to slight manufacturing and materials differences. They are typically used to measure temperatures from -200°C to +1350°C. However, the thermocouple’s voltage is proportional to the temperature difference between the hot Fig.a: a temperature junction (the measurement point) difference across a conductor and the cold junction (the connecgenerates a small voltage. tions to the measurement circuit). The temperature at the cold junction must therefore also be known to calculate the actual temperature at the hot junction. The best way to do this is to integrate another type of temperature sensor into the measurement chip. However, since an instrument like Fig.b: a thermocouple temp sensor. this is normally used over a relatively narrow range of ambient temperatures (eg, the indoor temperature may normally only vary between 20°C and 30°C), and the required accuracy may not be high, a simpler cold-junction calibration method may be employed. By measuring the thermocouple’s output voltage at a known temperature with another sensor, it is possible to determine the hot junction temperature. If calibrated this way, as long as the ambient temperature doesn’t vary much, the readings will still be reasonably accurate. siliconchip.com.au Australia's electronics magazine Software March 2026  81 Fig.2: the single-sided PCB holds all the parts required for the meter, including its power supply. If a doublesided PCB is used, the wire links are not required. The 2-way socket above S1 provides a solid mounting for the LCD. lengths but, in this case, any length will work just fine. Next, mount the 8-pin DIL socket for the ATtiny85 IC and install the 12-way and 2-way socket strips for the LCD connections. In the prototype, I only installed eight of the 12 pins (LCD pins 5-12), since pins 1-4 are not actually used by the display. The matching pin-strip connectors should then be fitted to the LCD. The pins on the prototype had a conical taper and a flat pin face (see Fig.3). These were soldered with the flat pin face mounted against the LCD. This ensured the longer pin shafts are free to mate with the matching pin-socket strip. Do not plug in the LCD screen yet. This will be done after completing some initial tests. Next, solder the DPDT slide switch and the two-way 7.62mm spacing screw connector for the thermocouple. Don’t connect the thermocouple itself just yet. It tends to get in the way of the remainder of the assembly. The boost regulator module can now be mounted on the PCB. It should be installed close and parallel to the board, to allow the LCD screen to be plugged into place. Mount the AA or AAA cell holder on the solder side of the PCB. If you have a commercially made PCB, you can solder this in place easily from the component side of the PCB, since the pads are almost always throughplated. If you have made the PCB at home, you will need to leave a 3-5mm space between the base of the battery holder and the PCB so you can carefully solder these pads with the tip of your soldering iron. You’ll find that when the thermocouple thermometer is operating, the battery holder gives the user a convenient viewing angle for looking at the LCD screen. Initial testing Do not plug in the ATtiny85 IC or LCD screen yet. Insert a fresh AA or AAA 1.5V cell. Zinc-carbon or alkaline types may both be used. Connect a DC voltmeter between pin 8 (positive meter lead) and pin 4 (negative meter lead) of IC1’s socket. Switch on the power and confirm that the meter reads between 3.0 and 3.3V. Next, making sure no buttons are pressed, check that the voltage on pin 1 of IC1’s socket is also 3.0-3.3V. Press the Up button only, then the Down button only, and finally the Next button only. The voltmeter should read 2.1V, 1.5V and 1.0V (±0.1V) for these tests, respectively. If these are not correct, check that the resistors are fitted in the correct locations, soldered correctly, and that there are no solder bridges. Programming the ATtiny85 Fig.3: the pin-strip connector should ideally be fitted as shown. 82 Silicon Chip You may have purchased a preprogrammed ATtiny85. In this case, you may ignore this section. If not, you will need to program your ATtiny85’s flash program memory with the project’s HEX file, then program the ATtiny85’s fuse settings. These configure some internal ATtiny85 settings. The complete details are shown in Australia's electronics magazine the panel titled “Programming the ATtiny85”. Final assembly Carefully insert the programmed ATtiny85 into its socket, then plug the LCD screen into its sockets. You may wish to add a couple of small self-­adhesive rubber feet to the lower underside edge of the PCB, to avoid scratching your test bench. The battery holder provides the upper edge footing and allows the meter to rest on the bench or table at a useful viewing angle. If you wish, the meter may also be mounted in an enclosure, but this is not essential. Finally, connect your K-type thermocouple to the screw connectors (CON1). Thermocouples are polarised. It must be connected correctly or the meter will not operate properly, so if you get strange measurements, try swapping the leads. Operation After switching on the power, a ‘splash screen’ graphic will briefly appear on the LCD. This is cleared, then a prompt asks the user to select the maximum temperature for the vertical axis graph display. Use the Up and Down keys to change the value (in 50°C steps), or press the Next key to continue with the default value of 300°C. The second and final prompt asks the user to select the required sampling rate. There are various possible values for this period, from 1 to 900 seconds. Use the Up and Down keys to change the period, or press the ‘Next’ key to use the default period of three seconds. 100 temperature measurements are then taken and plotted on each screen. The value of each measurement is also briefly written in the LCD’s siliconchip.com.au Programming the ATtiny85 Unless you purchase a programmed ATtiny85, it is necessary to program your blank ATtiny85 before using it. A programmer like the USBasp (www.fischl. de/usbasp) is required. It can be purchased online from many suppliers often for less than $10. Such programmers are used with a PC or laptop. Suitable software is available for Windows, Linux and macOS online. This description will focus on the Windows platform. You will also need an adaptor to connect the appropriate DIL IC pins to the programmer. My 8-pin adaptor was published in the September 2020 issue (on page 47; siliconchip.au/Article/14563) and the PCB is still available (from siliconchip.au/Shop/8/5642). The drivers for the chosen programmer must be installed prior to using it. The drivers for the USBasp can also be obtained from the link above. Programming software is required to actually program the ATtiny85 from Windows, Linux or macOS. Suitable free software for Windows includes eXtreme Burner (siliconchip.au/link/ab3m), AVRDUDESS (siliconchip.au/link/ab3n) and Khazama (siliconchip.au/link/ac9e). There are a number of websites and YouTube videos describing the setup and use of these programs. Here is a summary of the procedure required to program the ATtiny85 for this project: O Load the USBasp drivers onto the Windows PC O Plug in and complete the installation of the USBasp programmer. If the option is present on the USBasp programmer, and some boards support this feature, select 5V operation rather than 3.3V for programming the ATtiny85. O Download the programming software and install it. Once running, select “ATtiny85” as the target device. O Download the HEX file for this project (siliconchip.au/Shop/6/3578) and select it as the file to be used to program the ATtiny85. Note: Some versions of the Extreme software require the replacement of the chips.xml and fuselayout.xml device files to program the ATtiny85. These two files are found (in a typical Windows install of Extreme) under C:\Program Files\Extreme Programmer AVR\Data. Rename the original file called chips.xml to oldchips.xml and fuselayout. xml to oldfuselayout.xml. Then unzip the new files from the file extremeXML­ update.zip into that directory. Restarting Extreme will allow the programming of this and several other AVR devices. lower left-hand corner. When the graph reaches the right-hand side, the ATtiny85 clears the display, redraws the graph axes, then proceeds to plot another 100 measurements. Holding the Next key down for a second at any time during the graph display will cause the meter to exit the measurement and display process and then prompts the user for new settings again. Calibration Holding the Next key down when the meter is switched on enters a special routine to calibrate the meter with its low cost K-type thermocouple. These thermocouples vary slightly due to materials and manufacturing. This routine allows an offset to be entered to better match the display to the actual temperature, particularly in the 0-200°C range. siliconchip.com.au Connect the thermocouple to the meter and check the current room temperature from another thermometer. Let’s say it reads 18°C. Switch on the meter while holding the Next button down. After the splash screen, it will then report the temperature as seen by the thermocouple, and prompt the user to adjust this to match the correct value. Use the Up and Down keys to do this. Then press the Next key again. The meter will then save the required offset in the ATtiny’s internal EEPROM for future use. With a 10-bit ADC, the temperature resolution is around 4°C. Thus, you may not be able to get the calibration exact; within about ±2°C is good enough. This usually only needs to be done once. From this point onward, the meter will use these settings. They Australia's electronics magazine Screen 1: one of the graphs produced by my Thermometer from my reflow hotplate. The thermocouple was placed on top of a PCB, and the temperature was sampled once every three seconds. The latest measurement is reported in the lower-left corner of the screen. Screen 2: a domestic oven was set to 170°C and the internal temperature was monitored with the thermocouple mounted centrally above a wire tray. The graph shows the oven reaching temperature after about eight minutes, rising and falling slightly as the oven holds that temperature. remain set at these values until you decide to reprogram them. Powering down does not alter them. Final comments I found that this meter met practically all of my requirements. I’ve used it extensively to plot numerous runs of my reflow hot-plate system. I’ve also used it, for example, to check the operation of our oven. A feature I would have liked to include in the design was a method to save the results shown on the LCD screen for long-term documentation. Sadly, there were no free pins available to support that function. Taking a photo of the LCD screen is probably the easiest solution. In the meantime, it’s proving very handy. No doubt, other uses will come to mind now it is in my workshop. I hope you find it equally useful! SC March 2026  83 SERVICEMAN’S LOG Doing the dirty work When a kitchen appliance fails, among the most dreaded must be the dishwasher. When it stops midcycle and refuses to proceed, you can’t troubleshoot without first removing the dirty dishes and bailing out the greasy, soupy water in the sump. It is tedious and unpleasant, to say the least. The second, more physically demanding chore, is to extract the beast from its cavity under the kitchen bench. At some 50kg, our failed dishwasher is no lightweight, and its German designers never thought to equip it with roller wheels (for some reason). Despite putting up stiff resistance, with a combination of tugging while simultaneously rocking it side to side, it gradually emerged, exposing 10 years’ worth of grime and dust. Now at last I could remove the metal side panels and get to the inner workings. This unit had performed faultlessly for 10 years and had always delivered great results. Its sudden and unexpected failure suggested a problem that might be simple or obvious. At least that’s what I hoped. I decided to run a short cycle to better observe its behaviour leading up to the point where it would stop. It began normally. The drain pump cleared the residual water, then it refilled and began the pre-wash cycle. However, after a few minutes, it just stopped with the time remaining indicator showing zero. It had failed to progress to the main wash, which was baffling. The water was getting to where it should be, the circulation motor was running and the water was pumping out during the initial drain. All conditions necessary to proceed seemed to have been satisfied, so why did it stop prematurely? 84 Silicon Chip I hoped that a Google search might help me locate some service information or a schematic, but the corporate world protects its secrets. However, I found an abundance of YouTube videos pointing toward the usual suspects being blockages, pump failures, or a failed heating element. These all checked out OK on our machine. The heating element is part of the main pump unit. Being connected to the control unit by heavy-duty wiring makes it easy to identify for the purpose of checking the resistance. This was as it should be, at around 20W. Having eliminated the prime suspects, the remaining possibilities seemed to be that the control module itself may have failed, or perhaps a malfunctioning sensor could have confused the control module, leading to a shutdown. I removed the control module for close inspection, but it looked pristine with no components damaged or burnt. From past experience, I knew that a sensor that failed to return the expected signal could cause a dishwasher to stop mid-cycle. Years ago, many dishwashers (and washing machines for that matter) had a motor-driven switching mechanism. The motor advanced the mechanism, and a large knob on the front of the dishwasher rotated accordingly to indicate the progress through the program. I had a dishwasher like that; it had both cold and a hot tap connections. The main wash cycle used only hot water. When the hot water solenoid went open-circuit, the motorised switch would be paused, waiting for a signal from the water level sensor. With a failed solenoid, the required water level would not be reached and, in the absence of a signal, the motor would not be powered on. At that point, the program would be abruptly halted. The result was not unlike what I was experiencing with the current unit. Motorised switches have long been replaced with microprocessor electronics, enabling more advanced functions, including the reporting of error codes. Unfortunately, I had no error codes for guidance and no service information that might have given a clue about how many sensors there were or what functions they performed. Australia's electronics magazine siliconchip.com.au I was on the verge of giving up. Judging by the wiring that snaked throughout the machine, most of the sensors appeared to be well buried in the bowels of the device. However, there was one sensor that stood out. Most of the space on one side of the dishwasher is taken up with a large, translucent plastic box containing an intricate labyrinth of water galleries. I’m guessing that its purpose is to store and regulate the inflow of water, and it may also save energy by warming the stored water using heat released during the wash cycle. Mounted in a recess on the plastic box is one very obvious sensor that is easily accessible, shown in the accompanying photo. I decided it was worthy of closer examination as a last resort. It appears to be a flow meter, which lives in the water inlet path. A small, bladed impeller with an embedded magnet rotates with the flow of incoming water. With a torch, I could faintly see it spin inside its translucent housing. Sitting outside in a recess was a reed switch, a glass capsule with metallic contacts that should close each time the impeller magnet passes. I can only speculate about the purpose of this sensor. It is obviously able to inform the controller about the flow rate and volume of water entering. Maybe it’s a safety device. Perhaps a runaway count might signal an overflow of water, prompting a shutdown. Alternatively, if the impeller seized or the reed switch failed to register, the controller might be programmed to halt the process due to failure of the device for safety reasons or because insufficient water had been received. The reed switch was mounted on a small circuit board and was easily removed for testing using a simple magnet and multimeter. The contacts inside the glass envelope would close as they should when the magnet came near. I could not fault it, but decided to reinstall it anyway. I ran the short cycle again. This time, the cycle progressed properly, and the machine ran for the full duration of the main wash but then stopped, showing an E14 error code for the first time. It had failed to perform the final, critical drain. It wasn’t a complete cure, but it was pleasing progress nevertheless. siliconchip.com.au A quick consultation with the internet confirmed that E14 was indeed associated with a flow meter fault or a problem with the water intake. Could it be that the reed switch had aged and become unreliable? I have had some previous experience with reed switch faults. In the 1980s, new telephone exchange equipment was installed that employed reed switches. Error reports showed that some reeds mounted on circuit cards were prone to sticking. To prove the fault, the cards needed to be very gently removed and the suspect reeds checked with a multimeter. Sure enough, certain reeds on the board were sticking with contacts closed. The gentlest tap on the card was enough to cause the contacts to open with an audible click. A quick trip to Jaycar and I obtained a visually identical reed switch for less than the cost of a cup of coffee. I soldered the new one in place of the old one on its circuit board and reinstalled it. I pressed Start. Success! The dishwasher ran perfectly, advancing through every stage, including the final drain. Incredibly, an expensive dishwasher had been brought to its knees by quite possibly the cheapest component in the entire device. Alan Preacher, Briar Hill, Vic. The red arrow points to the recessed sensor located in a plastic housing. This sensor is likely a flow meter. Australia's electronics magazine March 2026  85 Dredge boat radio repair In the distant past, I was married to a Sydney girl, but we lived in Newcastle. One weekend, we were visiting the relos in Sydney when the brother-in-law, an electrician, stated he was on call for the port of Botany Bay for the weekend, and had a call out for the dredge that had twoway radio problems. He said, you know more about electronics than I do; can you come with me? We went to the dock, and a tug was waiting to take us to the dredge. When onboard and taken to the radio room, we found that the radio was relaying all calls received and making an echo on the network. I picked up the mic and asked the harbour master for a radio check. He told me that the problem was still there. I then realised that I had not heard the clunk of the relay switching to transmit mode. We opened the box (about half a meter square) and found the relay. It was plugged into the circuit board. The points were fused together. We managed to separate them with a screwdriver. We found the onboard chippy and got some sandpaper from him to smooth them out. That got it working again, for the time being. We also asked the chippy to tell the electrician, on return from his break, to order a new relay. They fed us dinner and gave us some beer. As my brother-­ in-law was on call, he was not allowed to drink, but I was, so that was my pay for doing the job! We had to wait about two hours for the tug to come back. Mick Toomey, Newcastle, NSW. Breville microwave repair My wife told me that there was something wrong with our microwave, as it sounded different from usual. I could tell from how it sounded that the cooling fan had stopped working. I was hoping that it was just the fan motor, as that would be an easy fix as long as I could find a replacement part. We found this microwave at one of the local tip shops about four years ago. It was in almost-new condition but needed a good clean as it had obviously been stored for an extended period. Until now, it had been very reliable. I took the microwave to my workshop and removed the six screws that hold the cover on. The fan is located in the back right-hand corner. I disconnected the two wires going to it and got out my multimeter to check the resistance of the winding. The winding was open-circuit, so that explained why the fan no longer worked. The next question was whether I could find a replacement fan motor. I started by unscrewing the circuit board on top of the fan housing, then I removed the screw from the back of the microwave that was holding the fan motor housing in place. To remove the fan motor housing from the microwave, I had to first remove the magnetron, as it was stopping the fan motor housing from tilting forward enough to remove it. An eBay search for a fan motor to suit this model of the microwave was not successful, although I did see one or two listings. I changed my search to the part number of the motor, and I found a couple more listings from China, but when I switched from default to Australia only, there were none. I changed my search to worldwide and set the search to price plus postage, lowest first. This showed many listings for this part, and it also showed that this exact fan motor is used in a multitude of different brand microwaves. I was able to purchase a replacement fan motor for $15.27 with free postage, but I would now have to wait for it to arrive from China, which could take up to four weeks. In the meantime, my wife found another microwave at the local tip shop for $10 and it was still in very good condition. It had been tested before she purchased it to make sure that it worked. Amazingly, the new fan motor arrived in just 11 days from China. It was obviously an after-market replacement, as it did not have the part number on the side like the original motor. The next problem was that I was unable to remove the fan from the old motor. However, I was able to change the rotor, with the fan blade attached to it, into the new stator. The two motors were almost exactly identical, enabling me to swap the parts, and the rebuilt motor worked as expected. I reassembled the microwave and tested it by putting a cup of water in it and running it. I could hear that the fan was running, and the microwave sounded the same as it did before the fan failed. Good-sized new microwaves cost around $150-300, so being able to repair this one for less than $20 was well worthwhile. The spare microwave for just $10 was a bonus. The interior of the Breville microwave (left), fan motor (above) and the repaired device (right). 86 Silicon Chip Australia's electronics magazine siliconchip.com.au WARNING: Microwave ovens contain very high voltages that are extremely dangerous. A microwave can retain these high voltages even after it has been turned off and unplugged, and even a dead microwave can kill you, as this high voltage may not dissipate for a long time in some circumstances. So if you are not experienced in repairing microwave ovens, do not remove the cover. Bruce Pierson, Dundathu, Qld. Turntable inverter repair This story has a lesson about buying semiconductors from online vendors. I recently built the turntable inverter from the May 2016 issue (siliconchip.au/Article/9930). Everything went well with the assembly, and I decided to benchtest it before fitting it into its diecast box. This meant that the Mosfets were not yet heatsinked. I connected a 12V car test lamp, drawing approximately 180mA at 12V, across the transformer terminals on the circuit board, with an oscilloscope probe connected as well. I connected a linear power supply set at 14V DC. To my disappointment, the test lamp flickered randomly, and within about 10 seconds, there was a burning smell. I quickly switched it off and found that the IRF9540 Mosfets were stinking hot. Surprisingly, the IRF540 Mosfets were at about room temperature. Troubleshooting was going to be difficult as I had to connect scope probes to the circuit, switch it on, quickly make measurements, then switch off. I tried tracing waveforms using this tedious procedure. It was getting ridiculous, so I removed IC3 from its socket, then bent pins 1 and 7 horizontally so they would be disconnected when I plugged IC3 back in. I was now able to trace all the waveforms up to the inputs of IC3. They were all correct 50Hz sinewaves (I had set the inverter to 50Hz mode). The output pins of IC3 (1 and 7) were putting out square waves, but they were not driving the transistor section, so I desoldered all four Mosfets, bent the pins of IC3 back to their original positions and powered it up again. I could detect sinewaves at the bases of Q5, Q6, Q7 and Q8. I powered it down and performed continuity checks to verify that each component in the circuit was connected correctly. I couldn’t find any faults; all components tested OK and were in the correct places. To make troubleshooting easier, I soldered header sockets siliconchip.com.au Items Covered This Month • A prematurely stopping dishwasher • Dredging up a boat radio • Breville microwave repair • Finding the culprit in a turntable inverter • Following the breadcrumb trail • Repairing a NAD 701 stereo receiver 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 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. in the Mosfet positions so I could easily swap them over. I put in all new Mosfets and powered it up. The same fault appeared; the Mosfets got hot again quickly. I then tried bypassing IC3 by removing it from its socket and using tinned copper wire. I bridged IC3b pins 5 to 7 and IC3a pins 3 to 1. This produced a square wave at the transformer terminals, and the Mosfets ran cool. I suspected that IC3 could be faulty and replaced it with the one spare I had on hand, with no improvement. As the pinout of IC3 is the same as an LM358, I tried that again with no success. I then noticed that the output waveform to the transformer terminals was a half sinewave, but it had oscillations superimposed on it at about 15kHz. If I powered the circuit off and then on again, the circuit would start up without oscillations, and the Mosfets would run cool with a clean sinewave at the transformer terminals. As soon as I put a scope probe on the output or anywhere in the circuit, the oscillations would start and the Mosfets would again overheat. Everything checked out up to IC3, the Mosfets had been replaced and I could find no faults in the driver circuit, so I purchased a couple of LMC6482AIN op amps from Jaycar (to replace IC3) and that was it. The inverter sprang to life, and I could not get it to oscillate anymore. I have purchased lots of components online over the years and had good luck with only one dodgy purchase (previous to this one) in that time. I have noticed that there are a lot of YouTube videos online regarding testing for dud op amps, Mosfets etc. Online bargains could be duds, so you should put the device through its paces and ensure that the test results agree with the device datasheet specifications before installing it. This is time-consuming but can save you a lot of work and time later. Australia's electronics magazine March 2026  87 In spite of all the frustration, I did learn a lot about this circuit, and it was very satisfying to be able to finally nail the culprit. Geoff Coppa, Toormina, NSW. Russell Hobbs toaster repair We have had a Russell Hobbs four-slice toaster for some years. While a little bulky for the benchtop, its saving grace is its capacity to toast all four slices evenly on both sides at the same time. Previous toasters had achieved only various patterns of brown and tan, sometimes black, so when the Russell Hobbs ceased to function, it was a sad day indeed. While one side of the toaster still functioned, the other, much more frequently used side (the one closest to reach!) refused to light up. It had started to work erratically a few days leading up to the final failure. There is a history in the house of repairing white goods and appliances instead of replacing them, so the toaster duly made its way to the workbench. Taking the top cover off, the workbench and the technician was quickly covered in crumbs – quite an amazing amount, really. The internals of the plastic chassis included the toasting chamber with the heater elements and components of the two bread carriages, including springs and bread racks. In front of the chamber, a set of contacts for each of the carriages is connected to the mains supply. These close when the bread carriage lever is depressed. Beside the contacts, a release solenoid, visible at the top of the photo (shown below), holds the carriage down when energised until the desired level of toastiness has been achieved, then releases the carriage. On each side of the chamber, a small circuit board receives mains from the carriage contacts. It has various components, including an DPST relay that energises the carriage solenoid. This board also supplies 12V DC to, and is controlled by, a timing circuit board mounted in the top cover. The timing board has various functions, such as defrost and warming, and energises the relay. At the top centre of this photo, you can see just a bit of the release solenoid, while below it is the 12V DC DPST relay. 88 Silicon Chip Once all the breadcrumbs were cleaned up, the diagnosis of the fault was quick. On the side that wasn’t working, the DPST relay had lost a large portion of its plastic cover due to contact arcing, judging by the look of the relay contacts. As with most appliances these days, they are not made to be repaired, and extracting the circuit board without breaking all the plastic fastening tabs was a mission in itself. Once removed, further examination revealed that the board had got rather hot underneath the bridge rectifier, which was mounted flush on the board. The rectifier failed testing and was replaced but elevated off the board. The electrolytic cap also tested bad and was replaced. All other components tested OK. The DPST relay was not so easy to replace due to its size and pin layout. A replacement was found from one of the major component suppliers, but with a rather eye-watering cost once postage was included. The parts cost less than a new toaster, but not by much! After testing the other circuit board, replacing the bridge rectifier and capacitor, two replacement relays were ordered – might as well replace both. Delivery was prompt, and the new relays were installed. The opportunity to check the mechanical operation of the toaster was also taken, cleaning the carriage contacts, straightening some bent components of the bread carriage, and general de-crumbing. After reassembly and testing, both sides were found to be working correctly. All up, the time to repair the toaster was around two hours. Still, there is the satisfaction of keeping an appliance in service and not going into the hard waste collection. Richard Dilena, Ocean Grove, Vic. NAD 701 stereo receiver repair The ad stated, “NAD 701 parts only untested with the display not working”. For $50, it had to be worth a try. In the worst case, replacement displays are available, and swapping them can’t be that hard. So I bought it, opened up the case and looked at the display PCB. The display is backlit, and one of the incandescent lights had failed. The power to the lamp was 12V DC, so I replaced the 4.7W current-limiting resistor with a 560W value and inserted a high-intensity green LED in place of the incandescents (see the photo opposite). That got the display working. The power amplifier voltages are regulated (along with most supply rails in this amplifier) and they were all within tolerance. I checked out the amplifier by playing a CD, and the amplifier was working with no apparent distortion. I also tested the phono preamp, which was also functional. Next, I tested the tuner. It is built around three ICs and an FM tuner front-end from Mitsui. I could change the AM & FM tuning frequency on the display, but there was no change in the sound. It was like the oscillator was not working. In this receiver, AM and FM are tuned with varactor diodes powered from an LM7000 IC through a Darlington transistor pair amplifier. The LM7000 has an onboard oscillator with an external 7.2MHz crystal followed by a frequency divider of 145 times for AM and 1007 times for FM. There is a second divider programmed from the display output that is fed by the AM or FM voltage-controlled oscillator (VCO). Australia's electronics magazine siliconchip.com.au Shown above is the circuit diagram for the tuner and the replacement I made for the backlight, using a high-intensity green LED and 560W series resistor. Below is the front panel of the NAD 701 stereo receiver and a close-up of the tuner section of the board showing some of the adjustment points. The frequency and phase difference between the two divider outputs is compared and converted to a voltage proportional to the phase and frequency difference. The amplified voltage determines the VCO frequency; as the comparator ramps the voltage up (or down), the AM (or FM) oscillator frequency changes until they match. Test point 1 (TP1) is the voltage applied to the VCO (AM or FM) and it was stuck at 40V. Pin 17 of the IC (charge pump output) was also fixed, so the transistors were likely alright. An oscilloscope on pin 20 of the IC showed no oscillator output. Adjusting the small variable capacitor in the crystal circuitry made no difference, so I replaced the LM7000. Once the decision to remove an IC is made, avoiding siliconchip.com.au damage to the PCB is the highest priority. So I cut every leg of the IC near the chip and desoldered them individually. I then soldered a socket in place and inserted a replacement IC. Adjusting the trimmer capacitor brought the circuit into oscillation. The AM tuner then worked well, but there was no change in the FM behaviour. The supply to the FM frontend module is 12V through an inductor/capacitor RF filter. There was 12V on the supply side of the 2.2μH inductor but not the tuner side. Replacing it brought the FM tuner to life as well. The story could have ended very differently, but in this case, it was $50 well spent. SC Jim Greig, Mount Helen, Vic. Australia's electronics magazine March 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. 03/26 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) PIC12F675-I/SN Tiny LED Xmas Tree (Nov19) 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) 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 DCC BOOSTER / REVERSE LOOP CONTROLLER KIT (SC7579) 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) DCC REMOTE CONTROLLER KIT (SC7552) (FEB 26) MAINS HUM NOTCH FILTER (SC7598) (FEB 26) DCC BASE STATION KIT (SC7539) (JAN 26) (DEC 25) siliconchip.com.au/Shop/ RP2350B DEVELOPMENT BOARD (MAR 26) $45.00 $7.50 (AUG 25) 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) 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) VERSATILE BATTERY CHECKER KIT (SC7465) (MAY 25) RGB LED ‘ANALOG’ CLOCK KIT (SC7416) (MAY 25) USB POWER ADAPTOR COMPLETE KIT (SC7433) (MAY 25) PICO/2/COMPUTER (SC7468) (APR 25) 433MHz TRANSMITTER KIT (SC7430) (APR 25) ROTATING LIGHT FOR MODELS KIT (APR 25) PICO 2 AUDIO ANALYSER SHORT-FORM KIT (SC6772) (MAR 25) Includes all required parts, except for the case and wire/cable (see p63, Feb26) $35.00 Includes everything except for the case and power supply (see p53, Feb26) Includes the mostly-assembled board and all non-optional components except the power supply (see p43, Dec25) EARTH RADIO KIT (SC7582) Includes everything to build the radio itself except the case and battery, plus the plug for the antenna (see p65, Dec25) $80.00 (DEC 25) $55.00 DCC DECODER KIT (SC7524) (DEC 25) RP2350B COMPUTER (NOV 25) Includes everything in the parts list (see p73, Dec25) 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) - 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 PICKIT BASIC POWER BREAKOUT KIT (SC7512) Includes all parts except the jumper wire and glue (see p39, Sep25) $50.00 (SEP 25) $25.00 $90.00 $7.50 $5.00 $10.00 $10.00 $10.00 $20.00 Includes all parts except a CR2032 cell (see p64, Aug25) Includes all non-optional parts except the case, cell & glue (see p39, Aug25) 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) $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 Includes an assembled PCB, separate Raspberry Pi Pico 2 and front/rear panels $120.00 Includes the PCB and all onboard parts (see p75, Apr25) $20.00 Complete kit which includes the PCB and all onboard components (see p60, Apr25): - SMD LEDs (SC7462) $20.00 - Through-hole LEDs (SC7463) $20.00 The Pico Audio Analyser kit from Nov23, but with an unprogrammed Pico 2 *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. $50.00 PRINTED CIRCUIT BOARDS & CASE PIECES PRINTED CIRCUIT BOARD TO SUIT PROJECT PI PICO-BASED THERMAL CAMERA MODEL RAILWAY UNCOUPLER MOSFET VIBRATOR REPLACEMENT ARDUINO ESR METER (STANDALONE VERSION) ↳ COMBINED VERSION WITH LC METER WATERING SYSTEM CONTROLLER CALIBRATED MEASUREMENT MICROPHONE (SMD) ↳ THROUGH-HOLE VERSION SALAD BOWL SPEAKER CROSSOVER PIC PROGRAMMING ADAPTOR REVISED 30V 2A BENCH SUPPLY MAIN PCB ↳ FRONT PANEL CONTROL PCB ↳ VOLTAGE INVERTER / DOUBLER 2M VHF CW/FM TEST GENERATOR TQFP-32 PROGRAMMING ADAPTOR ↳ TQFP-44 ↳ TQFP-48 ↳ TQFP-64 K-TYPE THERMOMETER / THERMOSTAT (SET; RED) MODEM / ROUTER WATCHDOG (BLUE) DISCRETE MICROAMP LED FLASHER MAGNETIC LEVITATION DEMONSTRATION MULTI-CHANNEL VOLUME CONTROL: VOLUME PCB ↳ CONTROL PCB ↳ OLED PCB SECURE REMOTE SWITCH RECEIVER ↳ TRANSMITTER (MODULE VERSION) ↳ TRANSMITTER (DISCRETE VERSION COIN CELL EMULATOR (BLACK) IDEAL BRIDGE RECTIFIER, 28mm SQUARE SPADE ↳ 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 DATE JUL23 JUL23 JUL23 AUG23 AUG23 AUG23 AUG23 AUG23 SEP23 SEP23 SEP23 OCT22 SEP23 OCT23 OCT23 OCT23 OCT23 OCT23 NOV23 NOV23 NOV23 NOV23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 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 PCB CODE 04105231 09105231 18106231 04106181 04106182 15110231 01108231 01108232 01109231 24105231 04105223 04105222 04107222 06107231 24108231 24108232 24108233 24108234 04108231/2 10111231 SC6868 SC6866 01111221 01111222 01111223 10109231 10109232 10109233 18101231 18101241 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 Price $5.00 $2.50 $2.50 $5.00 $7.50 $12.50 $2.50 $2.50 $10.00 $5.00 $10.00 $2.50 $2.50 $5.00 $5.00 $5.00 $5.00 $5.00 $10.00 $2.50 $2.50 $5.00 $5.00 $5.00 $3.00 $5.00 $2.50 $2.50 $5.00 $2.00 $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 For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT COMPACT OLED CLOCK & TIMER USB MIXED-SIGNAL LOGIC ANALYSER (PicoMSA) DISCRETE IDEAL BRIDGE RECTIFIER (TH) ↳ SMD VERSION MICROMITE EXPLORE-40 (BLUE) PICO BACKPACK AUDIO BREAKOUT (with conns.) 8-CHANNEL LEARNING IR REMOTE (BLUE) 3D PRINTER FILAMENT DRYER DUAL-RAIL LOAD PROTECTOR VARIABLE SPEED DRIVE Mk2 (BLACK) FLEXIDICE (RED, PAIR OF PCBs) SURF SOUND SIMULATOR (BLUE) COMPACT HIFI HEADPHONE AMP (BLUE) CAPACITOR DISCHARGER PICO COMPUTER ↳ FRONT PANEL (BLACK) ↳ PWM AUDIO MODULE DIGITAL CAPACITANCE METER 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 DATE SEP24 SEP24 SEP24 SEP24 OCT24 OCT24 OCT24 OCT24 OCT24 NOV24 NOV24 NOV24 DEC24 DEC24 DEC24 DEC24 DEC24 JAN25 JAN25 JAN25 JAN25 JAN25 JAN25 FEB25 FEB25 FEB25 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 PCB CODE Price 19101231 $5.00 04109241 $7.50 18108241 $5.00 18108242 $2.50 07106241 $2.50 07101222 $2.50 15108241 $7.50 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 DCC BOOSTER / REVERSE LOOP CONTROLLER ↳ FRONT PANEL SOLAR PANEL PROTECTOR (WHITE) GRAPHING THERMOMETER MAR26 MAR26 MAR26 MAR26 09111248 09111249 17112251 04102261 NEW PCBs $5.00 $5.00 $7.50 $3.00 We also sell the Silicon Chip PDFs on USB, RTV&H USB, Vintage Radio USB and more at siliconchip.com.au/Shop/3 Vintage Radio RCA Radiola 17 (AR-927) radio from 1927 The Radiola 17 is an interesting seven-valve ACpowered tuned radio frequency (TRF) set from 1927. By Jim Greig T he Radiola 17’s price on release was US$157.50 with valves, equivalent to around US$2900 or $4450 today. A TRF radio comprises one or more tuned RF amplifier stages in series. Each stage includes a bandpass filter tuned to the same frequency, which amplifies the desired signal while attenuating others. After several stages, the selected signal is significantly amplified, while out-of-band signals are progressively filtered out. The earliest such sets had individual tuning capacitors for each stage, making tuning to a station an art. By 1927, the use of a ganged tuning capacitor meant that only a single tuning knob was required. Radios were operated almost exclusively from batteries until around 1925. Early battery sets used directly heated valves, where the filament also served as the cathode. Later designs introduced indirectly heated valves with separate filaments and cathodes, solving several technical problems. One minor problem was uneven voltage distribution, both along the length of the filament in a single valve, and between the filaments of different valves. A more serious problem arose when sets began using mains power: if the filament also acted as the cathode, powering it with AC introduced 92 Silicon Chip significant hum. Various methods were developed to minimise this, including: 1. Using DC for the filament supply. This often meant using a battery in the 1920s, as high-current, low-­ voltage rectifiers were not yet available. 2. Centre-tapped hum-balancing potentiometers. A pot across the filament with its centre tap grounded made the ends of the filament equal and opposite in phase, helping to cancel the hum. 3. Special filament coatings. These may have reduced temperature variation along the filament over the AC cycle. 4. Lower filament voltages. Any AC ripple imposed on the signal would be less than it would be with a higher voltage. 5. Separating the cathode and filament. The filament then acted purely as a heater, with the cathode isolated electrically, eliminating the main source of hum. The first AC-powered set may have been the Rogers Batteryless from Canada. Rogers designed and produced their own AC valves (type 32) with a separate cathode. Powering the radio from AC saved the costs of batteries, making radio accessible to many more people. In 1927, RCA introduced a new tube, the UX-226 (also known as the type 226 Australia's electronics magazine or type 26), a triode that could be used for any stage of a receiver except the detector (unless the designer was willing to accept inferior performance). It had a low-­voltage (1.5V) coated filament that was optimised to produce very little hum when run on AC power. The same year, RCA announced the UY-227. The type 27 had the same shape as the type 26, but its filament was arranged to heat an oxide-plated cathode connected to a fifth pin in the base. Its filament was isolated from the electron path, and the new tube made an excellent detector (or audio amplifier). The RCA 17 was RCA’s first AC-­ powered receiver, and it uses the following valve types: UX226 (first RF), UX226 (second RF), UX226 (third RF), UY227 (detector), UX226 (audio preamp), UX171 (audio output) and UX280 (mains rectifier). Circuit details Much of the following information was derived from the RCA Service Notes and Service Data. The main part of the circuit, shown in Fig.1, is deceptively simple. The first RF stage is untuned, with the antenna connected to the grid through the volume control. Unlike in early battery sets, where the volume was siliconchip.com.au siliconchip.com.au Fig.1: at first glance, the RCA Radiola 17 circuit seems to be little more than seven valves connected in series with coupling transformers, some with tuning. often controlled by varying filament voltage, AC-powered sets required a different method. In this case, the volume control is simple but effective: a potentiometer in series with the antenna provides adjustable attenuation of the incoming RF signal before it reaches the first RF amplifier. The second and third stages are tuned RF triodes. The triode has significant anode-to-grid capacitance, and this, multiplied by the gain (Miller Effect), results in capacitances of tens of picofarads. A triode RF amplifier with high-Q tuned circuits at the grid and anode is especially susceptible to parasitic oscillation. Something must be done to ensure stability. This may be: 1. Neutralisation. Feed back an outof-phase signal from the anode circuit through a carefully selected capacitor to the grid. This was subject to a patent by the Hazeltine Company. 2. Including a resistor, often in the tuned circuits, to reduce the Q. However, Don Sutherland argues it is the phasing of transformers and the layout that have the most effect. In this radio, the coils are all at right-angles to reduce mutual coupling and improve stability. There is also a resistance (800W in the circuit, but my resistors were actually 1kW) added in series with the grids. There is a section in the Service Notes on “Uncontrolled Oscillation”, with a number of possible remedies, including dropping the filament voltage (and therefore gain) of the type 26 valves. The third stage is coupled to the grid-leak detector through a mica capacitor of around 150pF. A gridleak resistor bleeds off any charge that might accumulate on the grid from rectification of the incoming RF signal, preventing charge build-up and allowing the grid to operate at a slightly negative voltage. In a grid leak detector, the grid/ cathode of the tube acts as a rectifier, albeit an inefficient one. While the grid voltage to plate current transfer relationship may not be perfectly linear, non-linearity is not required for detection, unlike in an anode bend detector. The RF is filtered off at the plate, and only the average voltage remains; the audio interstage transformer does this from its limited bandwidth and any residual RF is filtered out by the capacitor in parallel with the transformer Australia's electronics magazine March 2026  93 Fig.2: the power supply circuit is similarly quite simple. The connector strip on the left corresponds to the one on the right in Fig.1. That’s how they are physically connected in the radio. 94 Silicon Chip Australia's electronics magazine output. If no audio interstage transformer is used, the RF can be removed by a capacitor in combination with the valve’s anode resistor and its plate resistance. The rectified signal is fed via an audio transformer to the first AF stage. Its output is transformer-coupled to the output stage, which has a 1:1 transformer to the speaker. AF transformers were used in early radio for coupling as the valves had little gain, and the (typically) 1:3 voltage ratio offered by a transformer was basically free (sometimes capacitive coupling was used too). The amplification factor of the type 26 is around eight times; the two audio transformers add another nine times, or as much as an additional 26 valve. Today, the amplification factor of a 12AX7 (for example) is around 100 times, and the losses from RC-coupling a 12AX7 are easily covered. The transformers are just two windings with no interleaving and minimal iron, resulting in high leakage inductance and limited bandwidth, limiting this radio’s audio frequency range. The expected loudspeaker response at the time was also limited, so this was not a concern. Audio transformer properties Audio interstage transformers in vintage radios are special parts; they cannot be analysed with the usual equations for a transformer because no power is transferred. The grid of the following stage (operating in Class-A) draws no significant current. The analysis that applies to them is that of a damped, coupled resonant circuit. The damping is provided by the anode resistance of the valve driving the transformer. The resonant frequency is defined mainly by the self-capacitance of the secondary winding, with contributions from the primary. The mutual inductance (and therefore leakage inductance) is very important in the balance of factors that result in a flat frequency response. When the manufacturer gets the balance of factors just right, the transformer behaves as an astonishingly effective bandpass filter in the audio spectrum, with a flat response. They should always be preserved where possible. Their band-pass response typically extends from as low as 100Hz, up to around 7-10kHz. They provide improved dynamic siliconchip.com.au range compared to anode resistor loads as they hold the anode voltage closer to the B+ voltage. They can provide passive voltage amplification up to around three times, or at high as five times; the higher the gain, the more difficult it is to attain a flat response. A block of five wax/paper capacitors is included to bypass the type 226 filaments (both sides) to the chassis, bypass the 135V line to the chassis, and bypass the ‘ground’ to the 135V and -9V rails. There are some unexpected connections in both this and the main filter block in the power supply. I expect the engineers were minimising the component count and making the best use of the space available. The three RF and first audio stage valves (type 26) have a grid bias of -9V. While it is easy today to generate any DC voltage, in 1927, ingenuity was required to keep the design simple. Cost and the availability of skilled repair people required that these early mass market sets were straightforward. Power Supply The AC is rectified with the UX280 valve, new for 1927. It was followed by a choke input filter, with the inductors in the 0V path, probably to minimise flash-over to the frame and electrolysis of the wires. A resistive divider and wax paper filter capacitors provide the four supply voltages and the ‘cathode bypass’ for the output. The connections to the series dropping resistors in the power supply were arranged so that the chassis is at -9V with respect to the filaments of the type 26 valves. Their grids connect to the chassis through transformer primary windings and the volume control to provide the required -9V grid bias. The detector has zero bias, and the output valve is self-biased with a 1690W cathode-bias resistor from the tap on the balancing pot across the UX171 filaments to the -9V rail. The power supply, shown in Fig.2, generates DC voltages of -9V, 45V, 135V and around 170V for the output stage, as well as 1.5V AC, 2.5V AC and 5V AC for the filaments. These DC voltages are measured from the ‘ground’ tap on the resistor chain, not the chassis, which is at -9V. Restoration At around 17kg, the radio is heavy. It was in good condition when I received it, with no major rust visible, and the cabinet had no major damage. The circuitry is in two parts: a power supply, with the radio linked to it via a multicore cable and secured with metal screws through the cabinet. I was able to remove these sections easily, separating them by undoing the screws connecting the cable to a tag strip on the radio. I have worked on many transistor and valve radios, but this was the dirtiest job so far. 100 years of dust and fine dirt on the surface with wax and pitch to be encountered later. I first checked the mains transformer. If it was damaged, I felt it would be best to preserve the radio as-is. I replaced the mains cabling with a three-core cotton-covered cable, with a small fuse added in the Active line, and the Earth connected to the chassis. I applied 50V AC from a variac to the mains input and left it for several hours. The 220V/240V switch was set to 240. I measured 62V a side for the HT, 1-2V for the filaments and the transformer The original waxed-paper capacitors were all packed into a small metal box. Not surprisingly, 100 years later, they have become leaky. did not heat up. It was left to run for a while on 120V AC, then 240V AC. I estimated the HT current requirement as being 15mA for the output valve and 5mA for the others, giving 40mA in total. To emulate this, I connected an 18kW across the HT windings. With 230V AC at the input, the outputs were 586V AC across the whole HT winding (~293-0-293V AC centre-tapped), 1.49V AC, 2.21V AC, and 5.05V AC, and the transformer stayed cool. So, the mains transformer was functional, and the restoration could continue. The two chokes (reactors) were next. One measured around 11H, the other 0.6W, a likely short circuit as the insulation on the wires to it was crumbling. They were encapsulated in pitch. Two removal procedures are suggested: warming with a heat gun, or dissolving with paint thinners. I used paint thinner; the heat gun approach would probably have been less messy. With both inductors out, The rear of the Radiola 17 with the back taken off. The power supply circuitry is contained in the enclosure on the far left of the interior and its circuit is shown in Fig.2 opposite. siliconchip.com.au Australia's electronics magazine March 2026  95 Table 1: replacement resistors Original resistance Nominal New resistor voltage 410W 135V 390W 5W 3750W 45V 3.9kW 5W 2140W 45V 2.2kW 5W 205W -9V 200W 5W 1690W 30V 3.3kW 1W || 3.3kW 1W they looked alright, so I checked them with a bridge. The second one measured 18H; my simple RLC transistor checker gives up at 15H, so it read as a resistor. The wires were in poor condition and heavily oxidised. I cut them near the choke and cleaned them with many passes over the ends with folded emery paper. I then applied flux paste and soldered new wiring to both, then insulated the joints with heatshrink tubing. More of the original wiring was in poor condition, so I replaced it with segments from a length of HRSA seven-­ conductor battery cable. The cabling was laced to keep it tidy and preserve some of the original appearance. All filter capacitors showed significant leakage, so I replaced them. They are housed in a large metal case and held in with extra wax. It’s a beautiful design that filters six different voltages within a limited space. Unfortunately, heating the wax did not release them, so I had to cut a few out so the remainder could be extracted. I replaced them with multiple 1μF 200V Mylar capacitors. As there is plenty of room, I doubled the value of each capacitor to provide additional filtering. The multi-tap wire-wound resistor The volume control had degraded over time and needed a delicate repair. showed signs of overheating; most segments were open, and the rest intermittent. Ideally, new wire would be wound on the ceramic former and tapped, but I am not that skilled. Using the voltages and other data from the service notes, I calculated the power for each segment. Assuming the original values would be accurate to within 10% at best, I selected a combination of standard resistors, as shown in Table 1. The remaining working segments on the original resistor were permanently broken and new resistors placed under the tags and connected to them. If a future owner wishes to restore the original resistor, it is still there. Seized tuning capacitor The tuning capacitor would not move. I oiled the shaft near the tuning wheel and left it for days. Eventually, it could be moved slightly, but it was still very stiff. The tuning wheel is made of pot metal (a brittle zincbased alloy), which was cracking, so I had to treat it carefully. The only way to free the movement was to remove the wheel. This required knocking out the pin on the shaft and, given the state of the wheel, it may have disintegrated. I took measurements and photos so a new wheel could be created if needed. Once the pin was out, the tuning wheel slid off, and the shaft rotated easily. The pot metal had expanded and was binding to the screw locating the shaft. I filed the binding end to allow the shaft to move sideways, to centre the variable plates within the fixed portion. The wheel had to be stabilised, or it would break in future. A local company suggested using epoxy glue, so I purchased some E-143 metal epoxy from Technicqll in Poland. I washed the wheel to remove grease and oil, then forced the glue into the cracks, small sections at a time. I blocked the shaft and tension screw holes with Blu-Tack so I wouldn’t accidentally get glue in them. Once the wheel was repaired, I refitted it with thin stainless washers added to ease its movement where the shaft was binding. I connected the dial wire to the tuning shaft, stretched it over the grooves in the wheel and tightened it with the screw and clamp. The radio had resistor/capacitor coupling added between the first audio valve and the output type 171, suggesting the coupling transformer was broken. Resistance checks showed the primary was open circuit. The transformers are located in a metal shell clipped to the chassis, so I unsoldered the wires from both transformers and unclipped the transformer case. It was filled with wax – better than pitch, I suppose; I used a heat gun to melt it. Both transformers are roughly made, with no clamping of the laminations; they are ‘glued’ together with wax. A suitable transformer (very small, with a 3:1 turns ratio) was donated by an HRSA collector. I connected the wires from the failed The tuning capacitor wheel had seized. Care was required in dismantling and fixing it as it was made of pot metal that had become brittle. The series wirewound resistors (encased in black, at top) were bad so I bypassed them with a string of modern resistors. 96 Silicon Chip Australia's electronics magazine siliconchip.com.au transformer to it and refitted both in the case. Ideally, they would be installed at right-angles to each other, but the new unit was slightly larger, so I had to make them parallel. The antenna volume control was another casualty of time; the resistive element was corroded in places, and the resistance wire had broken. Advice from another HRSA member was to bridge the broken sections by finding the ends, gently scraping off the insulation with fine emery paper and twisting them together. The resistive wire does not solder, so the twisted section was covered in conductive silver paint. There will be tiny (1-2 wire) sections of the control that are missing, but for its use as a volume control, it will not matter. This repair worked perfectly. The grid stopper resistors are wire wound and tested alright. The grid leak resistor is supposed to be 4MW but measured as 3MW. I replaced it with a 3.9MW ½W resistor hidden under the original red 4MW resistor. The bypass capacitors are held in metal cases clipped to the chassis. I tagged and desoldered the connecting wires, then removed the assembly. I then heated the cases and removed the capacitors. The cases were washed with vegetable oil (to dissolve the wax) and detergent, glued together and the capacitors replaced with 1μF and 2.2μF 250V polyester types. I emission tested the valves and replaced any that failed. With everything tested, I figured the radio should work. The output transformer is a 1:1 type and the recommended anode load for the UX171 (type 71) is 4.8kW at 180V. For initial testing, I used a 5kW to 3.5W transformer and 4W speaker. Fig.3: the frequency response of the set, either injecting a signal directly into the detector output transformer (cyan) or directly to the antenna (red). Expectations were lower in those days! Having attached the multi-core cable from the power supply to the radio, I powered it slowly through a variac with the UX280 out of circuit. All valve heaters were operational. Plugging in the rectifier gave the voltages shown in Table 2. All were a bit high, so I needed to swap in a ‘worse’ type 80. For further testing, I employed the HRSA mini transmitter and a 1m wire antenna. The signal was tuned in easily, and the volume control had to be wound down to minimise distortion. With no signal, there was some 100Hz buzz from the medium-fidelity test speaker. Examining the output with an oscilloscope, there are noise spikes of around 1V peak-to-peak at 100Hz. Tracing back through the circuit, they were present on the detector anode but not on the grid. The +45V rail (and other voltages) had some ripple, but no noise. I suspect it is coupling between the two audio transformers causing the problem. 50Hz hum was also visible, the minimum residual after adjusting the three filament potentiometers. I tested the receiver audio bandwidth but there is no specification for this in the original documents. Removing the type 27 detector, I connected a signal generator to the detector audio coupling transformer through 10kW to simulate the anode resistance. Audio bandwidth is often specified between -3dB points on the amplifier response curve, but today’s amplifiers have broad flat responses, and I feel applying -3dB to this radio is not fair. -10dB, or half the perceived loudness, would be easily detectable but not prevent the signal from being heard. Here, the -10dB bandwidth is around 4507500Hz (see the cyan curve in Fig.3). The frequency response from the antenna to the output is a similar shape, with a more useful -10dB bandwidth of 200-4500Hz (the red curve in The transformer between the audio preamp and audio output stages had gone open-circuit. Table 2: voltages on initial power-up The tuning capacitor wheel after filling the cracks with glue. siliconchip.com.au Australia's electronics magazine Rail Reading Raw HT 175V 135V 151.3V 45V 52.8V 9V 9.1V UX171 filament (5V) 5.1V UX226 filament (1.5V) 1.5V UY227 filament (2.5V) 2.2V Bias on UX171 filament (-30V) -26.8V March 2026  97 A better look at the chassis of the Radiola 17. Fig.3). The RF bandwidth of the TRF is generally much wider than a superheterodyne set, but in this set, it tapers off from about 1kHz. A possible cause is that there are no trimmer capacitors on the tuning gang, and it is quite likely the three sections are not aligned, leading to unpredictable bandwidth of the tuned signal. The lack of trimmer capacitors made factory alignment critical and limited user retuning. The audio from a music CD played over the mini transmitter was quite intelligible on the bench test speaker and not (to my tin ears) greatly distorted. Cabinet restoration The timber cabinet for this radio is in very good condition for its age. There are scratches and a probable burn mark on the top, but the other surfaces are reasonably clear. It is missing the hood over the dial light, a common problem with these radios. I considered refinishing the cabinet, but it is 100 years old and you can’t expect it to be in mint condition. So I simply cleaned the timber and rubbed it down many times inside and out with a mixture of 50/50 white spirits and linseed oil. The appearance remains consistent with its age. Over time, the brass escutcheons have oxidised and discoloured. I washed them but didn’t polish them, so that they and the cabinet look right with each other. RCA Speaker Model 100A The RCA 100A speaker was sold with this radio, and this one was bought at an HRSA auction. The case is made of pot metal and it is breaking up in parts; small sections have flaked off. I will clean it up and repaint it in the future. The speaker is a high-impedance device, as were the horn speakers and headphones of the time. When connected to a (late model) radio through ◀ Fig.4: the unusual construction of the RCA Model 100A loudspeaker. 98 Silicon Chip Australia's electronics magazine a step-up transformer, it works with no grating or scratching noises. It is a moving armature design (sometimes called ‘balanced armature’). Fig.4, from the RCA Model 100A Service Notes, shows the mechanism. Not shown is the armature sitting close to the pole pieces of a horseshoe magnet. Changes in the magnetism of the armature from the coils will cause it to move to one or other pole piece at one end and move the drive pin at the other. The motor is small, at 40 × 25 × 40mm, and sits within the magnet. There is a low-pass π filter between the input and the drive coils; possibly the speaker mechanism rattles if driven with high-frequency signals, so they are filtered out. At the low-­ frequency end, the cone is very stiff, which would limit the low-­frequency response. I checked the speaker frequency response with the PC-based AUDio MEasurement System (AUDMES). The RCA 100A loudspeaker is housed in this early Art déco style pot metal and fabric case. siliconchip.com.au Table 3: model 100A speaker Frequency Input impedance 100Hz 4.36kW 525Hz 11.82kW 2730Hz 2.0kW 4700Hz 8.7kW A good-quality line transformer was connected between the PC to the speaker for impedance matching and to increase the drive voltage. The -10dB response is around 200-3500Hz – see Fig.5. The speaker resistance is reflected back to the output valve, so I thought it would be interesting to see how close it was to the desired 4.8kW load specified for the type 71 valve. I estimated the speaker resistance by connecting it to a signal generator through a variable resistance. When the voltage across the speaker equalled the drop across the resistor, the resistances would be equal, and the variable resistor could be measured. With the π filter and the speaker coils, a complex impedance was likely. I took measurements from 100Hz to 8kHz and recorded the highs and lows in Table 3. The input impedance drops below the desired 4.8kW over the range of 2-3kHz, but generally it is well above it. Listening to a CD received from the mini transmitter via the radio and RCA speaker, it is not HiFi, but the music was clear. I expect at the time it was released, people would have been very impressed. Fig.5: the frequency response of the RCA Model 100A loudspeaker. Screen 1: the repaired radio set picked up some mains hum and buzz. Partly this could be due to its unshielded TRF construction, but my replacement audio coupling transformer having to be reoriented might have also negatively impacted its EMI rejection. References • Deeth Williams Wall: siliconchip. au/link/ac7v • RCA Victor Service Notes: 1923 to 1928 • RCA Service Data: 1923-1932 Vol. A • RCA Loudspeaker Model 100A Service Notes, June 1927 • Don Sutherland NZVRS Bulletin, Vol 5 Number 2, August 1984 • RCA Radiola 17, Eric L. Santanen, Bucknell University • https://sourceforge.net/projects/ SC audmes/ siliconchip.com.au A close-up of the loudspeaker moving armature motor. Australia's electronics magazine March 2026  99 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 Synchronising two RGB LED Stars The RGB LED Star in the December 2025 issue was impressive, especially the programming (siliconchip.au/ Article/19372). It exceeded my expectations frankly, and they were not low. I bought a second kit and have two out the front of my flat, which look really good. They start off with similar displays, but after a few hours, timing differences make them produce very different displays in the sequence. How would you make two stars (or more) display identically? I have no knowledge of WS2812 programming or protocols, and saw two ways of possibly achieving this. One way was to have a ‘master’ Star driving second (and possibly subsequent) units. The master would have the PIC fitted, but the slave units would not. Instead, pin 11 on all the stars would be connected together, effectively all in parallel. Alternatively, could the final 6.8kW loading resistor be omitted from all but the last Star, and they be daisy-chained from LED80 pin 2 to pin 4 of LED1 on the next (and subsequent) Stars, effectively putting them in series? What is the limit to how many LEDs may be driven by the PIC? There surely is one? Is the number of LEDs defined/ controlled within the software? Or might there be a third way involving the retention of all the PICs and syncing them some other way? Any help you could give would be appreciated, as next year I would like to expand this display. Seeing a large group of these performing identically could look fantastic. (B. C., Gympie, Qld) ● You’re right; even a tiny timing difference will cascade and result in them producing different patterns after a while because the pseudo-random number generators will not remain synchronised. You can’t daisy-chain them without modifying the software because of the way the serial data works. Essentially, 100 Silicon Chip each LED ‘knows’ its position in the chain, so any beyond #80 will ignore the data. You could make the software duplicate the 80 LEDs of data before sending the reset pulse, and then it would work with daisy-chaining, although that would slow down the update rate since twice as much data needs to be sent each time. Connecting them in parallel should work, as long as the grounds are joined (otherwise, keep the power supplies separate). It’d be best to power them up simultaneously. You could synchronise the PICs, but it’d require changes to the code. You could do it using serial data on a single pin. At the end of each cycle, unit #1 would send its RNG seed and the number of ticks that have elapsed to unit #2 over that serial connection. Unit #2 would wait to get the seed before updating the LEDs using the same tick count. That way, they should remain synchronised. We think it’d be easier to simply fit one PIC and have it drive both sets of LEDs. We don’t know how many strings one PIC could drive in parallel, but it would surely handle at least a few. GPS Speedometer questions I have questions related to the “Miniaturised GPS Speedometer” item in Circuit Notebook, November 2025 (siliconchip.au/Article/19229). 1. In that small confinement of the Australia's electronics magazine 47mm diameter pipe, where is the GPS module located? 2. How is the GPS module exposed to the GPS satellites, which is essential for the speed measurements? (S. Bera, Kolkata, India) ● The designer, Glenn Percy, responds: Since the “case” for the project is plastic pipe, I have noticed no problems with GPS reception. The module I used is a V.KEL model, but most of them with inbuilt antennas seem to be a similar size. The GPS module sits at the rear so that the antenna faces upwards. There’s not a lot of space there, so being confined, it tends to stay that way (see the photo below). You could use some fastening like double-sided tape or a tie wrap, perhaps, if worried about it moving. Implementing filters with Digital Preamp I am thinking of building Phil Prosser’s Digital Preamp (October to December 2025; siliconchip.au/Series/449) to use it as a preamp/three-way crossover and follow the recommendations from the Linkwitz articles in Wireless World and Speaker Builder from the 1970s, as well as Douglas Self’s book on active filters. The ability to do some truly amazing things with shelving filters and equalisation is, for me, a standout. I’ve been looking at Analog Device’s SigmaStudio with a view to using it with your preamp. The documentation siliconchip.com.au is terrible, and even a simple configuration gets into interesting territory. Even getting the darned thing takes a bit of not so interesting navigation around the Analog Devices website. They don’t even explain well how to interface it with the chip. Working out how to implement Linkwitz-Riley 24dB filters took a while. Figuring out how to do transitional LR/Bessel/Thomson filters may be just as interesting. Do you have any advice on how to do this? By the way, Douglas Self advises that the NE5532 and NE5534 are on the way to obsolescence in favour of devices with lower distortion. (K. J., Cleveland, Qld) ● Phil Prosser responds: The code already has the calculations for shelving filter coefficients in it. All that is needed is to add the filter type and user interface to set frequencies and shelf offsets. In the scheme of things, that isn’t too hard. There are some really useful and simple documents that assist with calculating the IIR coefficients. Douglas Self has written a lot of really great material. His general audio texts are the best I have read. His great strength is a relentless analysis of things he gets into, but this also leads some of his stuff to get quite obsessive. At times, he sets aside ‘what is good’ and the question of ‘does it make a difference’ for a pursuit of a goal such as the lowest distortion. On the surface, a laudable goal, but in the real world, what is the difference between 0.001% and 0.0001% distortion? Although it would take a supreme effort to get an NE5532 to generate that much distortion. Given a choice of course, you would choose 0.0001%, but it is important to keep in mind this is borderline philosophical. There are sometimes consequences too. Then you connect a loudspeaker, which renders the above meaningless by three or four orders of magnitude. Where to get DSP board for Digital Preamp I note on page 32 of the October 2025 issue, in the article on the Digital Preamplifier (siliconchip.au/Series/449), the enclosed box headed “Soldering the LFCSP-88 ADAU1467 chip” mentions ordering a carrier board with the chip already mounted. siliconchip.com.au Ethernet-based Watering System Controller wanted A question about the Watering System Controller project by Geoff Graham from August 2023 (siliconchip.au/Article/15899): could this be made to work in a nonWiFi environment using an Ethernet connection? There are various ways suggested online for adding Ethernet to a Raspberry Pi Pico. I was wondering what Geoff Graham thought about the practicality of doing this. I guess there could be problems with electrical isolation from the rest of the LAN in case of thunderstorms, lightning etc. (P. H., Warwick, Qld) ● Geoff Graham responds: an Ethernet connection for the Watering System Controller is not possible due to several factors, the main one being that the software environment (WebMite/MMBasic) does not support Ethernet; only WiFi. Other difficulties are that running an Ethernet cable to the controller would be difficult for most installations, and most home systems have WiFi, so the audience for an Ethernet-only solution would be small. I’m guessing that your installation point for the Watering System Controller would be a long way from your main network (hence your asking about Ethernet cabling). You could still run the cable, but terminate it with a WiFi/Ethernet bridge that can communicate with the Controller design as published. I can’t find the carrier board in your Online Shop. Are there still plans to sell the carrier board? Thanks for a wonderful magazine. (G. M., Blue Mountain Heights, Qld) ● The ADAU1467 carrier board is a commercial product that’s available from AliExpress: www.aliexpress. com/item/1005001448154711.html Increasing DCC Power Shield current A couple of years ago, I built the Arduino DCC Power Shield from your January 2020 issue (siliconchip. au/Article/12220). I’m using the DCC booster with the optical connection as a standalone unit; the Arduino supervisor sketch provides current/DCC signal lost trip protection. It works perfectly, but I would like to reprogram the default trip limit of 120 to a higher setting and I would like to know what this value equates to in terms of real current level seen by the booster. I calculated the 120 trip limit to be equal to 0.5865V at the Arduino analog sense pin, A0. I read the BTN8962TA datasheet, and it is not clear or easy to calculate the current out of the output sense voltage of the H-bridge. There is an extra 20kW resistor on the power shield board that is not shown in the datasheet. Do you know mV/A value at the sense pin or a way to calculate that value for the Arduino shield? (D. G., Sherbrooke, Quebec, Canada) ● The provided value worked well with our prototype, but unfortunately, the BTN8962’s sense current output Australia's electronics magazine can vary over a wide range, so we’ve had to perform some tests. There is a variable offset (ie, a nonzero sense current when the load current is zero and the drivers are on) and the ratio of the currents can also vary. Also, it appears that the offset varies with supply voltage. The 20kW resistor and 100nF capacitor simply filter the signal; it is only the 1kW resistor that is critical to the current/voltage conversion. The offset current of 50-440μA mentioned in the BTN8962 datasheet maps to 50-440mV across the 1kW resistor. There are two devices (sourcing current via the diodes), so this is doubled. In other words, a zero load current could create a voltage from 0.10V to 0.88V (ADC reading of 20 to 180). All the BTN8962s we’ve tested were between 0.40V and 0.55V (about 80-112 on the ADC). The range of ratios means that a 10A change in load current will result in a change of 0.72V to 1.28V in the output (meaning a 1A load step increases the output by 7-12 ADC steps). A value of 10 ADC steps per amp seems common here. The easy way to check the offset is to measure the ISENSE ADC value when the output is on but there is no load. That is your base level. You can add something like “Serial.println(p); to loop() after p=analogRead(ISENSEPIN);” in the Supervisor sketch to allow this to be monitored. For every 1A you want at the output, add 10 ADC steps to your baseline reading. You could also apply a known load (eg, a power resistor) and see what the difference in the reading is. March 2026  101 Since you have it working with the value of 120, you could also try increasing this by 10 steps to get an extra amp of trip current. For example, if it is tripping at 2A and you want it to trip at 4A, increase the value to 140. You could also use some load resistors of known values to verify that it is behaving as expected. Why are Majestic speakers two-way? I built your two-way Majestic speakers (April 2014 issue; siliconchip.au/ Article/7897) in 2015. Now I plan to convert it to become three-way by adding separately additional midrange box speakers above the existing speaker boxes. I want to use an active crossover because I heard the sound from it much better than conventional RC crossover. What is the power distribution between the three speakers? I plan to use a 10W small amplifier for its woofer (3W is already loud), 5W for the midrange and 5W for the tweeter. Each of the amplifiers has volume control. What do you reckon? (J. N., St Albans, Vic) ● The designer, Allan Linton-Smith, responds: well done for you to build up a Majestic pair of speakers to enjoy the excellent response! I’m not sure why you would want to re-engineer them to a three-way design – is there something wrong with their sound quality? The two-way design we settled on took a lot of engineering effort to get the crossover balance correct between the woofer and tweeter, even with high-end B&K microphones plus Agilent and Audio Precision instruments. The result is a system that is economical, has great sound quality and uses a cost-effective (and low phase shift) crossover, in a nice-looking cabinet at a fraction of the price of similar high-end speakers. Importantly, the drivers were selected so that a third was not needed, allowing a passive crossover to be used, with a low phase shift and natural crossover effect to keep the sound clean. Power distribution is needed for a three-way system because each and every driver has a different sensitivity, and they can vary a lot. You might like to check out my article on a “High Performance Dipole Speaker” in the November 2017 issue (siliconchip.au/Article/10865), which is a three-way setup with an electronic 102 Silicon Chip crossover. It needs 30dB more to feed the woofer than goes to the tweeter. Sure, this is a different setup, but you are going to need something better than a 3W bass amplifier to get a smooth response. Your 3W amplifier may also be a problem because it will probably clip at its full power output and the sound will be distorted (and sound louder), so I recommend that you experiment with a better-quality, more powerful amplifier. Why drive a high-quality speaker with a tiny amplifier? Would you run a Ferrari with a lawnmower engine? Once you get clipping, square waves will be going into the drivers and can be very damaging; especially to tweeters, but to a lesser extent also to midrange drivers and woofers. I have had tweeters go open-circuit with only a few hundred milliwatts of poor quality sound input! You mentioned active crossovers; generally, they are very good, but need careful management so as not to push too much low frequency-sound into a tweeter, which will most likely destroy it. Without a frequency response measurement system, you will find that you may never be happy with the sound from a three-way setup even if you fiddle around with the crossover control for hours. So you will need to test your setup with an audio frequency generator and adjust things from there. Cheap solar charger is badly designed I built a few of the solar controllers (“Battery charger regulator”) from Circuit Notebook, January 2004 (siliconchip.au/Article/3334). These worked well on my boat until the salt air caused some corrosion and one of them failed. I am trying to fix it now. In the meantime, I bought a very cheap ($16) solar controller through Amazon. There was probably a fault in the unit delivered – it did not stop charging after reaching the set voltage limit (14.2V) and went on until I had to shut it off at 16V! I contacted the vendor, “Atcdlmu”, and they said the unit must be faulty and quickly sent me a replacement controller, but it exhibited the same behaviour! They suggested that testing the unit with a constant voltage power supply Australia's electronics magazine might not work and suggested a constant current power supply (which I have), but I doubt that information is correct. I have a 100W solar panel at home, so I hooked that up, but it made no difference; it still keeps charging after the cutoff is reached, and I had to shut it down at 16V. There is a saying, “pay peanuts – get monkeys”, which seems to be the case here. Do you think the vendor’s comments regarding constant current vs constant voltage may be correct? (J. K., Freshwater, NSW) ● The fact that you used it with a solar panel and it didn’t shut off shows that the unit is definitely faulty. We suspect that all these units have a design fault. The voltage shut-off should occur regardless of whether it is a constant-voltage or constant-­current supply. We have a similar charger from Jaycar, and it works as expected, shutting off charge at the 14.2V limit. AI answer on crossovers is wrong I submitted the following question to the AI in a web browser: “If you have an 8 ohm woofer and a 4 ohm tweeter, both rated for a sensitivity of 89dB (2.83V at 1m), does this mean that neither should be attenuated to blend with a flat response?” I got this response: No, the drivers will not have the same output level in a typical amplifier setup and the tweeter will likely need attenuation. The sensitivity rating of 89dB at 2.83V is measured at a constant voltage, which results in different power levels due to the different impedances. Here is a breakdown of the power delivered: • 8 ohm woofer: At 2.83V, the power is 1W. • 4 ohm tweeter: At the same 2.83V, the power is 2W. Since the 4 ohm tweeter receives twice the power (+3dB) for the same input voltage, it will be approximately 3dB louder than the 8 ohm woofer at the specified sensitivity rating. In practice, tweeters often have higher inherent sensitivity than woofers, and most crossover designs incorporate a resistor network (L-pad) to attenuate the tweeter and achieve a balanced frequency response. 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 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 September 2025 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 PICKit Basic Power Breakout Board 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. 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 March 2026  103 Therefore, you will likely need to attenuate the tweeter to blend properly with the woofer and achieve a flat response. This adjustment is usually handled within the design of the speaker’s passive crossover network. I believe this response is incorrect since it assumes that both drivers have the same efficiency. I think the AI is correct that the 4W tweeter will pass twice the current and hence twice the power, but this does not in itself mean that the tweeter will produce 3dB more sound. This would only be true if both had the same efficiency. The fact that both are rated to produce the identical sound pressure level of 89dB established during actual tests must show that the tweeter is half as efficient as the woofer. In my opinion, the AI is ignoring this information and assuming that if the tweeter draws twice the power, then it must produce twice the sound pressure level. (P. T., Casula, NSW) ● Your question states that, fed with Advertising Index Altronics.................................35-38 Blackmagic Design....................... 5 Dave Thompson........................ 103 DigiKey Electronics..................OBC Emona Instruments.................. IBC Hare & Forbes............................ 6-7 Jaycar............................. IFC, 12-15 Keith Rippon Kit Assembly....... 103 Lazer Security........................... 103 LD Electronics........................... 103 LEDsales................................... 103 Microchip Technology.................. 9 Mouser Electronics....................... 3 PCBWay....................................... 11 PMD Way................................... 103 SC PICKit Breakout Board........ 103 Silicon Chip Back Issues........... 57 Silicon Chip Binders.................. 58 Silicon Chip PDFs on USB......... 65 Silicon Chip Subscriptions........ 59 Silicon Chip Shop.................90-91 The Loudspeaker Kit.com............ 8 Wagner Electronics..................... 10 104 Silicon Chip the same voltage, both drivers will produce the same sound level. But since you stated one has an 8W impedance and one has a 4W impedance, at a fixed voltage level, the 4W speaker is running at 2W and the 8W speaker is running at 1W. That means the 4W speaker is 3dB less efficient than the 8W speaker. However, because their sensitivity rating is being given relative to a voltage, if you connected them in parallel and drove them from a voltage source, they would give roughly the same sound output level. The lower efficiency of the 4W driver is cancelled out by the fact that it will draw more power when driven with the same voltage as the 8W driver. Still, this is an odd way to specify efficiency; it’s more commonly specified as a decibel level at a specific power level (typically 1W). You might be surprised to find that if you test this in the real world, the speaker output levels may not be well-matched if connected in parallel. Whether the tweeter will need attenuation depends on the actual measured on-baffle responses and the crossover. Toroidal core spec for electric fence I’m going to build the “New High Power Electric Fence” project from the April 1999 issue (siliconchip. au/Article/4577). I’m having trouble understanding which E30 ferrite cores I should use. I found several sizes available, for example: NEE30/15/14, NEE30/15/11, NEE30/15/7 and NEE30/11/11. The numbers between the slashes indicate the width and thickness of the core. These measurements substantially alter the Ae and Le parameters of these cores. The article doesn’t include the Jaycar store code, so I don’t know which one to use. Can you help me by providing this information? (N. B. E., Sao Paulo, Brazil) ● The 30/15/14 cores you mentioned are suitable. Jaycar doesn’t sell this size of core, so there wasn’t a catalog code to provide. HV supply wanted for testing capacitors Are you going to design a high-­ voltage power supply, say 50-300V DC at up to 3mA? I want to charge capacitors to test them. (R. M., Melville, WA) ● The Insulation Tester circuit (May 1996; siliconchip.au/Article/5007) has a high-voltage generator that could be easily modified to provide a 50-300V DC supply. By removing (shorting out) one of the 4.7MW resistors in the feedback divider, you can get output voltages of 500V, 300V, 250V, 125V or 50V (switch positions 1 to 5) at the cathode of diode D3. Everything after diode D3, including the lower half of the circuit, is not required. Alternatively, use the circuit we designed specifically for testing capacitors, the Electrolytic Reformer & Tester from August & September 2010 (siliconchip.au/Series/10). The circuit board and programmed PIC microcontroller are still available. Substituting tantalum for aluminium caps I am currently building the Audio Signal Injector & Tracer from June 2015 (siliconchip.au/Article/8603) and am having difficulty finding electrolytic capacitors short enough to fit in the case. Is it feasible to use tantalum capacitors instead (100μF 16V and 1μF 16V)? (J. A., Townsville, Qld) ● Yes, you can use tantalum caps instead of aluminium electrolytics for SC the Signal Injector and Tracer. Errata and on-sale date for the next issue Ultrasonic Cleaner part 2, October 2020: in the winding instructions in Fig.9, the reference to pin 19 should say pin 8 instead. Scale Speed Checker for model railway, January 2026: the 120Ω resistors should be in series with pin 2 of the connectors for the IR sensors (and the photodiodes), not pin 1 (the collectors). Also, the IR LED anodes and cathodes should be swapped. Next Issue: the April 2026 issue is due on sale in newsagents by Monday, March 30th. Expect postal delivery of subscription copies in Australia between March 27th and April 13th. 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