Fullscreen HTML5Med Res (??MB)HTML4

SEPTEMBER 2023 ISSN 1030-2662 09 The VERY BEST DIY Projects! 9 771030 266001 $ 50* NZ $1290 11 INC GST INC GST Stylish Speakers made using IKEA Salad Bowls (page 18) 8- to 40-pin PIC Programming Adaptor (page 64) The most interesting products at Electronex and Australian Manufacturing Week Broadcast Radio the story of 100 years of radio in australia A selection of our best selling soldering irons and accessories at great Jaycar value! 25W Soldering Iron TS1465 $19.95 Build, repair or service with our Soldering Solutions. We stock a GREAT RANGE of gas and electric soldering irons, solder, service aids and workbench essentials. ESD Safe Tweezer Set TH1760 $21.95 Solder Flux NS3070 $21.95 Precision Angled Cutters TH1897 $24.95 1.5 to 3mm Desolder Braid NS3026-NS3028 $6.95EA 0.71mm & 1mm Solder NS3001-NS3096 FROM $3.95 240V Fume Extractor TS1580 $79.95 PCB Holder with LED Magnifier TH1987 $36.95 48W Soldering Station TS1564 $139 160pc Heatshrink Pac k WH5524 $29.95 Shop at Jaycar for soldering essentials: • Battery, gas and electric soldering irons & stations • Wide range of solder • Desoldering braid & tools Explore our great range of soldering gear, in stock on our website, or at over 110 stores or 130 resellers nationwide. • Soldering iron stands, cleaners & PCB holders • Heatshrink tubing • Tools & service aids jaycar.com.au/soldering 1800 022 888 Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. Contents Vol.36, No.09 September 2023 10 Electronex & AMW Report There were some interesting exhibits to see at Electronex and Australian Manufacturing Week (AMW) this year, so here’s a rundown of what we thought were the most fascinating products & services at both events. By Dr David Maddison Trade show report 36 pH Meter Module This module is designed for use as a liquid pH meter to test a swimming pool or the water in a fish tank. It comes with two separate pH probes and can be interfaced by an Arduino or similar microcontroller. By Jim Rowe Using electronic modules 44 100 Years of Broadcast Radio November 23rd 1923 was the date of the first licensed radio broadcast in Australia, by 2SB in Sydney (renamed 2BL). The story of broadcast radio was highly political, commercially competitive and steeped in controversy. By Kevin Poulter Historical feature 18 Salad Bowl Speakers These stylish speakers are surprisingly good performers considering they’re made using salad bowls from IKEA. They are simple to build and can handle 50W RMS per channel. By Phil Prosser Audio project 57 Coffee Grinder Timer Improve your ‘basic’ coffee grinder by adding a custom timer module with programmable presets & an LCD or OLED screen using an Arduino Pro Mini. You don’t need much to build it and it works with other motorised appliances. By Flavio Spedalieri Timer project Page 57 Arduino-based Coffee Grinder Timer Page 64 8– to 40–pin PIC Programming Adaptor Simple Voltage Inverter Doubler Page 90 2 Editorial Viewpoint 5 Mailbag 31 Circuit Notebook Program most newer PIC microcontrollers out-of-circuit with our PIC Programming Adaptor. It works using a PICkit or SNAP programmer and suits 8- to 40-pin micros. You can even use an external adaptors to program SMD chips in SOIC, SSOP or TSSOP packages. By Nicholas Vinen Microcontroller project 42 Online Shop 48 Subscriptions 80 30V 2A Bench Supply, Mk2 – Pt1 73 Serviceman’s Log We’ve updated our 30V 2A Bench Supply to use a more standard and available transformer as the one we used last time cannot be purchased anymore. Otherwise, it’s still a useful and reliable Bench Supply. By John Clarke Power supply project 94 Vintage Radio 99 Ask Silicon Chip 64 PIC Programming Adaptor 90 Voltage Inverter / Doubler Used in our new Bench Supply, this project can produce nearly twice its DC input voltage, or a negative voltage similar in magnitude to the input. It’s a simple design and can operate from 9-15V DC. By John Clarke Power supply project 1. ‘Huygens Beam’ BFO metal detector 2. MPPT Solar Charger update 3. Audio level meter AWA 500M superhet by Ian Batty 103 Market Centre 104 Advertising Index 104 Notes & Errata SILICON SILIC CHIP www.siliconchip.com.au Publisher/Editor Nicholas Vinen Technical Editor John Clarke – B.E.(Elec.) Technical Staff Jim Rowe – B.A., B.Sc. Bao Smith – B.Sc. Tim Blythman – B.E., B.Sc. 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): $65 12 issues (1 year): $120 24 issues (2 years): $230 Online subscription (Worldwide) 6 issues (6 months): $50 12 issues (1 year): $95 24 issues (2 years): $185 For overseas rates, see our website or email silicon<at>siliconchip.com.au Recommended & maximum price only. Editorial office: Unit 1 (up ramp), 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 194, Matraville, NSW 2036. Phone: (02) 9939 3295. ISSN: 1030-2662 Printing and Distribution: 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Editorial Viewpoint Five-year update It has been a little over five years since I took over as Publisher of Silicon Chip magazine from Leo Simpson in July 2018. What a tumultuous five years it has been! I don’t think I have to explain the impact that COVID-19 had on us. We were lucky; the magazine publication side of the business can be operated mostly off-site. For various reasons, I had already set up pretty much everything needed to do that by 2019. So we were able to cope pretty well, although there were still significant impacts on the business. Component shortages – now mostly (but not entirely) resolved – were certainly a challenge, as were paper shortages, the huge cost increases (some of which I wrote about last month) and more. Luckily we were able to see some of that coming and prepare, which allowed us to get through relatively unscathed. More importantly, I think, is how the magazine itself has fared over the last five years. At the outset, I wanted there to be continuity; a more-or-less seamless transition. I would say we achieved that. There have been a few minor changes to the format, but I hope Silicon Chip today is the same magazine that readers already liked. I have tried to keep a similar balance of feature articles, projects and columns, as I think it worked well. I am proud of many of the major articles we’ve published over the last five years. There are too many to list here, but some that stand out are: • Duraid Madina’s DAB+/FM/AM Radio (January-March 2019) • Ian Batty’s series on Videotape Recording (March-June 2021) and Transistors (March-May 2022) • Tim Blythman’s USB Cable Tester (November & December 2021) and Advanced Test Tweezers (February & March 2023) • Phil Prosser’s Hummingbird Amplifier (December 2021), Capacitor Discharge Welder (March & April 2022) and Active Speakers (November 2022 to February 2023) • Dr David Maddison’s series on IC Fabrication (June-August 2022), Display Technologies (September & October 2022) and Computer Memory (January & February 2023) • Geoff Graham’s VGA PicoMite (July 2022) and GPS Analog Clock Driver (September & November 2022) Inevitably, when younger people take over, there will be some changes. I won’t always make the same decisions that Leo did as I have different interests, grew up in a different time (with the rapid development of home computers) and so on. One of the biggest challenges I face is trying to keep everybody happy. For example, many people really like historical articles like the Vintage Radio column and others we publish, like the videotape series mentioned above. I also know that many younger people aren’t very interested in such things. So there has to be a balance of more futuristic articles along with the historical ones. Similarly, while so many project contributions these days are digital designs involving microcontrollers and similar, many people (me included) still like analog designs. Again, a balance is needed. For example, this month, we have two primarily digital designs, the Coffee Grinder Timer and PIC Programming Adaptor, some DIY loudspeakers and an updated Bench Supply design. Hopefully, everyone can find something they like with those articles. I find them all interesting; perhaps I am just easy to please! Feel free to write in with suggestions on how to make the magazine appeal to everyone. by Nicholas Vinen The cover price will be changing to $12.50 from the October 2023 issue and the price of subscriptions will be increasing on the 1st of November this year, see below: New Prices Print (AU) Combined (AU) Print (NZ) Combined (NZ) Online 6 months $70 $80 $82.50 $92.50 $52.50 12 months $127.50 $147.50 $150 $170 $100 24 months $240 $275 $285 $320 $190 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”. Plug-in hybrid cars are the best option After reading Dr David Maddison’s enlightening article about charging electric vehicles (July 2023; siliconchip.au/ Article/15857), I concluded that a fully electric car is not for me. Not now, and not in Australia anyway. The electric cars currently on the market are too expensive and mostly not what I need. Why would I buy a new car that costs almost twice as much as a similar fuel-­powered car, particularly when the cost difference would pay for fuel for many years? I need a car that can reliably take me from point A to point B, not leaving me stranded or waiting hours for a turn at a remote charging station. I really want a car that can run on electric power for at least 30-40km (for daily chores, shopping, going to movies, work commuting etc) and that can continue to run on fuel power when necessary. This car would run on electric power almost all the time and could recharge its own battery from fuel in an emergency. But mostly, I envisage it being charged at home using free solar energy. Importantly, it would not leave me stranded, even if I must travel over 2000km. Looking at what is available on the local market, as far as I can see, only one car meets these basic requirements. And it is not cheap either. Apart from the initial solar installation outlay and with judicious use, such a car would be almost free to run. Even home units could also use a similar scheme by installing solar systems. Richard Allende, via email. Comment: you may need a large solar system to charge a car (depending on how much driving you do), but the basic principle seems sound. Many plug-in hybrids on the market would do what you want; eight were listed in the panel on page 25 of the July 2023 issue. Consider the 2023 Toyota Prius Prime, which starts at $32,350 at the time of writing (although it is a fairly small vehicle). This was just one of many designs that Jamieson/Jim Rowe made for RTV&H, then later for Electronics Australia and now Silicon Chip. It was characteristic of his work – straightforward, clear and skilfully designed. His articles over the years have been a study in lucid, accurate technical writing. He has always performed thorough research and has the rare ability to communicate his concepts clearly. I just read his article in the July Issue of Silicon Chip (“Electronics Magazines in Australia”; siliconchip.au/Article/15862) and found the background to all those years in the technical magazine trade absolutely fascinating. He has a singular talent for writing and teaching and has been an enduring and powerful advocate for electronics and electrical engineering in Australia. He must have fostered thousands of young talents and given them at least the option of a career in the difficult, fascinating subject of electronics. He will leave a great legacy when he finally hangs up his scope probes. John Macleod, Gymea Bay, NSW. Young girl builds old computer game I just wanted to share my excitement since my daughter just finished building the Arcade Mini Pong board I bought from your online shop. I can’t wait to finish the small countertop cabinet that will house it. I’m so glad to have given my daughter the opportunity to build this, and I’m very proud of what she’s accomplished! James VanDever, Hawthorne, CA, USA. Silicon Chip magazine giveaway I have bound volumes of Silicon Chip from 2004 to 2015 inclusive. I am moving to another address soon and would More praise for Jim Rowe I strongly endorse Paul Howson’s letter in the May 2023 issue titled “Praise for Jamieson Rowe”. Way back, I built a design of his printed in Radio, Television & Hobbies, September 1962. It was a “Distortion, Noise and Millivoltmeter”, an all-valve design (of course it was; this was 1962). It had a nuvistor as the notch filter amplifier and was a gem of a design. For a very reasonable outlay, I had a practical high-­ performance instrument that approached the performance of fully professional products from AWA that I could never have afforded. siliconchip.com.au Australia's electronics magazine The finished Arcade Mini Pong PCB. September 2023  5 like to send the volumes where they can be enjoyed at the new owner’s expense. If anyone is interested, please email silicon<at>siliconchip.com.au and they will pass the message on to me. David Voight, Kirwans Bridge, Vic. Editor’s note: we have a similar offer from another reader in Ryde, NSW, who has a complete collection from the beginning until 2020. Memories of ZC1 Mk2 transceiver Dr Holden’s articles on servicing and replacing vibrators (June-August 2023; siliconchip.au/Series/400) have been very interesting. Of even more interest to me was the photo of the old ZC1. My word! That brought back memories! A much-modified ZC1 Mk2 was my first amateur radio transceiver when I got my ham radio license in Fiji in 1962. My callsign then was VR2 EN. A few years later, as I was studying in the famous RNZAF electrical and wireless school in Christchurch, NZ, each student was required to have a personal project. It was marked along with their coursework. My project was to totally strip and re-wire my old ZC1, replacing the rubber-­ insulated wire with PVC-insulated wire. I also incorporated the then well-known ham mods: a mains power supply, increased modulation percentage and power output. I added a meter for tuning. The 6V6s were replaced with metal 6L6s. As my rig for 80m and 40m, it served me well for several years in NZ and later in PNG, where it was used to test HF aerials. I painted it blue. Its unique “bomb-proof” design made it very rugged! Dave Brewster, Lake Cathie, NSW. Dr Hugo Holden comments: The ZC1 was an icon in NZ, and many engineers cut their teeth on them, using the radio as a platform for education, training and all manner of other projects. I may write an article on the ZC1 at some point, as it would be a way to help preserve their history. Oak vibrators stood the test of time I read with interest the vibrator articles by Dr Holden and can identify with what he says about the self-­liquefying sponge rubber vibration isolators that cause them to fail. As just one example, my own ZC1 came with several US-made vibrators that had precisely the same problem as his. I was asked to refurbish an original broadcast radio for The Australianmade Oak V5105 vibrator. a pre-war Ford V8. It came with a box containing several non-synchronous vibrators, which I presumed would be inoperable and in need of repair, as Dr Holden describes. That was the case for all but one of them. Among the faulty US, British and Japanese units, there was an Australian-­ made Oak V5105 shown in the photo below. It had a circlip holding the base to the housing, allowing easy repair without destroying or butchering anything. The rubber isolators were in perfect condition after at least 60 years, the contacts were still clean, and the unit was in good operating condition. It isn’t easy to give credit to you Aussies (especially after the Bairstow LBW last week), but in this case, it would seem churlish not to! John Reid, Tauranga, NZ. Dr Hugo Holden comments: The Oak vibrators were better-­ made than most, and that spring clip was a real asset. I have an odd story associated with them. Back in the 1960s in NZ, my father had a dilemma. Some line-powered 45 RPM record players could have worked when powered from a car’s 12V battery with a stepped-up AC supply, but the quirk was that they were designed to run from a 50Hz AC supply because they had a synchronous AC motor that set their speed. How to get a 50Hz supply from a car? Most radio vibrators ran at around 100 to 120Hz. My father contacted Oak, and they built him a custom batch of special 50Hz units. They did it by increasing the mass on the oscillating armature reed to lower its resonant frequency. They looked like the other Oak units but were painted bright red. I have not seen them for many decades, but my brother in New Zealand might still have one. Pumped hydro storage is not impractical I know I shouldn’t enter the nuclear power debate, but the letters by Dick Smith and Kelvin Jones in the July issue of Silicon Chip demand a response. Dick Smith makes much of the problems building 50 dams and notes that dams are unpopular. Big dams are certainly unpopular, but pumped storage doesn’t need big dams. It needs big generators and pumps, but the dams don’t need to store enough energy to supply power for several years, and small dams that hold only enough energy for a few days can be useful. He also doesn’t mention that nuclear power stations provoke an even bigger NIMBY (not in my backyard) response than dams. Kelvin Jones has analysed the issues thoroughly and has made appropriately scathing remarks about the intrusion of “politics” into the debate. Here in Tasmania, “Marinus” is a very controversial word. The problems converting to renewable energy are real, but they are difficulties, not show-stoppers. Difficulties have solutions, and for renewable energy, most solutions are known. Although nuclear power might be suitable in some countries, it has missed its window of opportunity for Australia. Keith Anderson, Kingston, Tas. GPS-disciplined oscillator works very well Having an interest in such oscillators, I built the GPSDO project featured in the May 2023 issue (siliconchip.au/ Article/15781). I used a NEO-7M GPS module. 6 Silicon Chip Australia's electronics magazine siliconchip.com.au I measured the oscillator frequency over five eight-hour periods using your High-Resolution Frequency Counter (December 2012 & January 2013; siliconchip.au/Series/21) in conjunction with a 1pps external timebase derived from a Trimble Resolution-T GPS receiver. The frequency error did not exceed 0.001Hz (1 part in 110). The counter took 1000s (about 17 minutes) to complete a measurement; that means that short-term frequency variations could have been averaged out. In such a case, it is difficult to say if any error is due to the timebase or the oscillator. Nevertheless, this is impressive performance! The article mentions that some BS250 Mosfets have their source and drain pinouts transposed – I found this to be the case for those made by Diodes, Inc (purchased from element14). I have included the photo shown above of the counter measurement display. Trevor Woods, Auckland, NZ. Comment: we note that the part codes of those Mosfets sold by element14 (Cat 3405170) are listed as BS250P, which might explain the different pinout compared to the plain BS250; the pinout situation with those parts is certainly messy. Still, it’s easy enough to reverse them on the PCB if required. Pumped hydro, battery safety and repairability After reading your Editorial Viewpoint in the June issue, I am reluctant to send comments to you. A thousand emails per day is ridiculous; I don’t want to add to them, but I also want to comment on various subjects. Pumped hydro energy storage has been talked about for a while, but there seems to be a misunderstanding as to the area of land required for such dams. In the late 1970s, a pumped hydro system was built just to the west of Brisbane. It consists of an upper dam, Splityard Creek Dam, and a lower dam, the Wivenhoe Dam, with a power station in between. The Splityard Creek Dam has a total capacity of 28,700ML and a surface area of 105ha (1.05km2) and is solely used for energy storage. The Wivenhoe Dam is primarily a water storage and flood mitigation dam, and of course, contains Silicon Chip kcaBBack Issues $10.00 + post January 1995 to October 2021 $11.50 + post November 2021 onwards All back issues after February 2015 are in stock, while most from January 1995 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 without a computer 8 Silicon Chip far more water than that needed for energy storage. It covers 202.5km2. The associated Wivenhoe power station has an installed capacity of 500MW using a hydraulic head of 76m and can operate at 500MW for 10 hours. This already well-used pumped hydro system provides real figures for land use and energy storage. If, for example, Queensland requires 10GW of pumped hydro with a hold-up time of 10 hours, upper dams would require 2100ha of land and lower dams would require somewhat more. Australia’s total land area (from Wikipedia) is 7,692,024km2, so the proportion of Australia’s land required for the dams would be about 0.00055%. If the other states were to implement the same pumped hydro capability, the total area required would be around 0.0039%. That isn’t an unacceptable land area to use. When designing a PCB, the correct technique is distributing capacitors over the PCB near the ICs. The same technique applies to power distribution. Small scattered pump hydro systems are far superior to a few huge pumped hydro systems for various reasons, except perhaps cost. Next, I must mention a critical thing to consider when replacing Li-ion cells in a battery. This applies to some laptop batteries, which use 18650-size cells and, almost certainly, scooter batteries. Manufacturers have access to a type of Li-ion with a safe terminal voltage of 4.3V that is not available over the counter (to my knowledge). This particular Li-ion cell stores more energy than the Li-ion cells with a fully-charged voltage of 4.2V and, of course, would be more desirable for that reason. If the 4.3V Li-ion cells are replaced with 4.2V Li-ion cells, there is potential for a fire. The charging circuit has been designed to charge to 4.3V and will push 4.2V cells past their safe limit. This may be the reason for some of the recent scooter fires. The problems I have been having with my van have reminded me of a curse upon almost every modern product. Electronics and micro-computers have made it possible to design products that are impossible to service and, when a fault occurs, are impossible to repair, at least at a reasonable cost. This applies to almost every type of product. For products that cost less than say $100, it is an annoyance, but the replacement cost is probably less than the repair cost. However, for expensive products, throw-away certainly is not desirable. It would be preferable to repair them, but where are the manuals and circuits, where are the spare parts; and where are the people with the expertise to repair them? It is getting to the stage where it is not desirable to buy anything new and, sadly, from countries that once were known for making high-quality goods. Their lowering of standards makes it better to buy low-quality goods because throwing them away doesn’t hurt as much. George Ramsay, Holland Park, Qld. Comment: please feel free to email us any comments you might have. Most of those thousand emails are obviously rubbish and are immediately deleted. Regarding your final point about the lack of repairability in modern appliances and devices, that is why the ‘Right to Repair’ movement is so important. We think it’s inevitable that consumer-protecting legislation will eventually be passed to reign in the eWaste problem that Australia's electronics magazine siliconchip.com.au consumer-­ unfriendly, unrepairable products cause. It’s already happening in the EU; see siliconchip.au/link/abp9 Electricity spot prices are not the whole story The interesting article on the Australian Grid in the August 2023 issue (siliconchip.au/Article/15900) quotes the different electricity prices according to the fuel type. The numbers are similar to figures published in many other places; they are all misleading. If I ran a restaurant and I purchased my carrots from two different sources, one sold old and damaged carrots and the other sold nice new carrots, it would be misleading to publish a list of carrot prices and not mention the different costs to the kitchen of dealing with the carrots from the two different sources. Electricity is sold to the consumer with the shop model; that is, all transactions are initiated and transacted solely at the buyer’s discretion; the seller-buyer dynamic is not symmetrical – it is sometimes described as an asymmetric market. Electricity generated from solar energy and sold on the asymmetric market of a national grid is a very different product from electricity generated from coal. The cost metric of dollars per MWh is misleading without a back story in price lists for electricity generated using different fuels. It is a good example of the stark difference between the “truth” and the “whole truth”. The product must be identical for a list of the cost of electricity generated using different fuels to be meaningful. The cost of supplying electricity generated by using solar or wind must include the cost of a storage system of some kind for the cost to have any meaning when listed alongside the cost of supplying electricity generated using coal. Electricity sold into a different market than the shop model of a national grid; these abbreviated costs might be meaningful, but that is not the case with a national grid. These misleading lists are one of the many reasons uninformed opinions are formed by people who want to give advice about technical matters beyond their comprehension. Dr Ken Moxham, Urrbrae, SA. Comment: the article was simply about how the grid worked and did not compare electricity generation methods on a cost basis or any other basis. We published the actual prices currently being paid for electricity by generation type in each state and explained how they are calculated. As stated in the article, the amount paid for wholesale electricity is based on momentary supply and demand. We don’t know the true cost of generating that electricity; an analysis of that would be very complicated and is beyond the scope of that article. Nor do we have the information, knowledge or expertise to calculate it accurately. Perhaps nobody does. It would involve making many assumptions if it were to be projected to any scenario other than the grid’s current state. Solution for dud CR2032 cells I have sorted out the short life and other problems with these ubiquitous parts of life. The answer is to always buy cells stamped “Made in Japan” or “Made in Taiwan” - everything else is rubbish! Since I have made this search a routine, the cells have lasted for years. Keep up the good work. David Humrich, Greenwood, WA. SC siliconchip.com.au Australia's electronics magazine September 2023  9 Dr David Maddison’s report on: Electronex 2023 & Australian Manufacturing Week We saw quite a few interesting exhibits at this year’s Electronex show and thought readers who didn’t get to attend would like to see them. So here is a summary of some of the more fascinating products we saw at the show. O ur article on Electronex in the May 2023 issue (siliconchip. au/Article/15771) was based on what the exhibitors told us would be at the show. Some exhibitors didn’t provide any information in advance, while others were showing off products or services we didn’t cover in that article. This year’s Electronex was held simultaneously at the same location as Australian Manufacturing Week (AMW) at the Melbourne Exhibition Centre, otherwise known as “Jeff’s Shed”. Electronex featured technologies, products and services relevant to the Australian electronics industry. AMW was geared more towards additive manufacturing, CNC machinery, machine tools, plastics technology, raw materials, training, maintenance, machine vision and scanning, welding and heat treatment, among other areas. The combined exhibitions occupied most of Jeff’s Shed. Here are the exhibitors we think our readers will be interested in, in alphabetical order: ADMATEC https://admateceurope.com AMW ADMATEC is a Netherlands-based (Dutch) company that produces high-volume ceramic and metal 3D printing machines – see Fig.1 and the video titled “Animation of the ADMAFLEX 130 process principles” at https://youtu.be/i_ntORKtUTs Altronic Distributors www.altronics.com.au Electronex Readers will be familiar with Altronics via ads in the magazine. Altronics’ stand at Electronex promoted their extensive product range (Fig.2), which you can check via their website or catalog (www.altronics.com.au/catalogue/). For those wondering, their direct competitor, Jaycar, did not exhibit at Electronex, presumably because they market their products primarily to consumers. Fig.1: a range of AMDATEC 3D-printed ceramic parts. 10 Silicon Chip CNS Precision Assembly www.cns.org.au Electronex CNS Precision Assembly is based in Hornsby, NSW. They are equipped for laser engraving and cutting; rework services; purchasing; surface mount board assembly; through-hole and cable assembly; PCB cleaning and conformal coating; and testing and inspection with an environmental chamber, test jig or optical inspection. They are an NDIS-certified employer and offer valued employment for people with various disabilities. element14 https://au.element14.com Electronex Another recent advertiser and component distributor, element14, also had a stand at Electronex. They carry around 950,000 products and components from about 2000 manufacturers. Emona Instruments https://emona.com.au Electronex You will likely also be familiar with Emona Instruments, supplier of many test instruments for hobbyists and professionals, including the popular Rigol brand – see Fig.3. They also have educational and training products, and additive manufacturing equipment, among other items. Among their product line, but not showed off at Electronex, include the Australian-designed Emona TIMS telecommunications training systems, which are exported worldwide. FANUC Oceania Pty Ltd AMW www.fanucoceania.com.au FANUC is a Japanese company that produces a variety of automation products, including robots. It is the largest Fig.2: the Altronic Distributors stand at Electronex. Australia's electronics magazine siliconchip.com.au Fig.3: two of the many Rigol oscilloscopes sold by Emona, with large displays, probing a test board. Fig.4: a FANUC CRX-5iA “collaborative robot”, capable of lifting 5kg with a 994mm reach. Fig.5: a full-scale prototype Black Diamond brand rock climbing helmet produced in a Formlabs 3D Form 3L resin printer. Note the support structure, which will be removed. Fig.6: a Metamako MetaConnect 48 low latency switch for applications such as share trading, produced by GPC Electronics. manufacturer of industrial robots in the world. One product on display was the CRX-5iA “collaborative robot” - see Fig.4. It can lift 5kg and has a nearly 1m reach. See the video titled “FANUC CRX-5iA Demo with Mari Cruz” at: https://youtu.be/8q3OkNQoVQU Faraday Shielding & Design https://faradayshielding.com.au Electronex Faraday Shielding & Design is an Australian company founded in 2002 that specialises in electromagnetic shielding. That includes design and consultancy, supply and installation and testing, including the provision of the extensive magnetic shielding required for MRI machines. Formlabs https://formlabs.com/asia/ AMW Formlabs is based in Massachusetts, USA and offers a range of 3D resin printers. A wide variety of clear and coloured resins are available in cartridge form (similar to an inkjet printer), including for biomedical applications and elastomeric (rubbery) materials. See Fig.5 and the video titled “The Form 3L Ecosystem Workflow” at https://youtu.be/18m4Fbe8IQE Fig.7: electronic enclosures from Hammond Manufacturing. siliconchip.com.au GPC Electronics https://gpcelectronics.com.au Electronex Established in 1985, GPC Electronics is one of Australia’s largest contract electronics manufacturing groups. They began in Sydney and now also have facilities in New Zealand and China. They work in aerospace, defence, medical devices, automotive and transport, communications and industrial – see Fig.6. Hammond Manufacturing www.hammfg.com Electronex Hammond Manufacturing is a Canadian company that makes a variety of enclosures for electronics, including for hobby use – see Fig.7. Some are available at Altronics (www.altronics. com.au/hammond/all/). Hawker Richardson https://hawkerrichardson.com.au Electronex Hawker Richardson is involved in industrial tooling, robotics, electronic production, inspection and industrial X-ray. Among the items they had on display was an X-ray component counter that can X-ray a roll of bulk electronic components, such as reels Figs.8 & 9: the Scienscope X-ray component counter from Hawker Richardson. A close-up is shown at lower right. Australia's electronics magazine September 2023  11 of surface-mount components, to determine the number present; see Figs.8 & 9 and siliconchip.au/link/ablm They also had a manual ‘pick and place’ system on display, the Fritsch LM901, for picking and laying out surface mount electronic components on a PC board – see Fig.10. It is for prototype and low-volume work rather than high-­ volume production. For more information, visit siliconchip. au/link/abln HIKMICRO www.hikmicrotech.com/en/ Fig.10: the Fritsch LM901 manual pick-and-place system from Hawker Richardson. HIKMICRO is a Chinese company that makes a range of thermal and night vision imaging devices. These have various uses in the electronics industry – see Fig.11. IntelliParticle www.intelliparticle.com.au Fig.11: a HIKMICRO infrared camera imaging a block of three fuses. One is hot and therefore likely overloaded. Electronex AMW IntelliParticle makes an electrically conductive paint-on product that can be used to create heating elements. Various formulations are possible, including types that adhere to ceramic surfaces, eg, to make a ceramic cooktop – see Fig.13. Electrical connections can be made to the painted element with adhesive-backed copper tape or other means. The product was invented by a small suburban-based inventor in Sydney working in his garage. For more information, see the video titled “IntelliParticle Heated Metal Plate” at https:// youtu.be/O6EJwt_GdvQ i-Submerge https://i-submerge.com Electronex i-Submerge is an Australian company offering products for monitoring marine environments. They include a micrologger for long-term data collection, scientific camera systems, aerial survey systems, aquaculture systems including underwater monitoring cameras and a series of patented waterproof equipment enclosures (Fig.12), which were on display. Fig.12: i-Submerge underwater equipment enclosures. Fig.13 (above): an IntelliParticle painted heat panel. Meltio https://meltio26.com Meltio is a Spanish company that makes 3D printer machines based on laser metal deposition (LMD), where weld beads are stacked and fused into a laser-generated melt pool. It is much like how a potter creates a vase by stacking a series of long thin lengths of clay on top of each other and merging them – see Fig.14. Apart from depositing wire stock, the deposition head can also lay down metal powder, or both wire and powder simultaneously. Metals that can be deposited include stainless steel, mild steel, carbon steel, titanium, nickel and copper. The deposits are fully dense with excellent microstructure. The general name for the process is Laser Metal Deposition – Wire Powder (LMD-WP). See the video titled “Meltio’s Metal 3D Printing Technology Explained by CTO Brian Matthews” at https://youtu.be/ apA_kgugdR0 Monash Nova Rover www.novarover.space Fig.14 (left): the Meltio LMC process, showing a vase-like object being formed from metal. 12 Silicon Chip AMW AMW Monash Nova Rover is a multi-disciplinary student team from Monash University in Melbourne designing and building rovers suitable for Mars or Lunar exploration. To hone their skills, they participate in the annual University Australia's electronics magazine siliconchip.com.au Rover Challenge (URC) in Utah, USA and the Australian Rover Challenge (ARC) in South Australia. This year’s rover is pink to raise awareness of women in STEM (Science, Technology, Engineering and Mathematics) – see Fig.15. Nitto www.nitto.com Fig.15 (left): the Monash Nova Rover. Fig.16 (below): a range of Nitto PVC-based electrical insulation tape from the 203E series, as typically used in Australia. AMW Nitto is famous for its electrical tapes (see Fig.16) but makes many other products such as adhesive tapes, double-sided tapes, other tapes, membrane materials, gasket materials, fluoropolymer sheets, porous films, medical products and many others. I have seen decades-old Nitto electrical tape that was still good as new, but many modern cheaper tapes lose their adhesion over time. Consider that when using electrical tapes in safety or mission-critical applications. NPA www.npa.com.au Electronex Australian company NPA had a wide variety of cable and wiring accessories, Nylon fasteners and electronic hardware on display at Electronex. Omnia Wheel www.omniawheel.com AMW Omnia Wheel is a trademark of the Australian company Rotacaster Wheel Pty Ltd. They make a range of patented wheels that can work in both a forward direction and in a lateral direction using small rollers at right angles to the forward direction built into the circumference of the wheel. They have uses in applications like robotics, conveyor belts, transfer tables (tables to transfer cartons or other goods from one area or conveyor belt to another; see the series of videos at siliconchip.au/link/ablo), hand trucks and many others – see Figs.17 & 18. Permark www.permark.com.au Figs.17 & 18: an Omnia Wheel transfer table and some Omnia omnidirectional wheels in the cut-out. Electronex Permark performs screen/digital printing and engraving on metals and plastics through to speciality adhesives, membrane keypads and touch screens – see Fig.19. Precision Electronic Technologies https://precisionet.com Electronex Precision Electronic Technologies is an Australian company that provides contract electronic manufacturing solutions and services such as PCB manufacturing, PCB assemblies, cables, wiring harnesses, stencils, plastic and metal enclosures, decals, membranes and turnkey solutions. QualiEco Circuits www.qualiecocircuits.com.au Fig.19: a range of sample membrane keypads from Permark. Electronex QualiEco Circuits is a PCB supplier and contract assembler to hundreds of businesses in Australia and New Zealand. They’ve been involved in the local electronics industry since 2003. They offer PCB manufacturing using a wide range of technologies and methods, component procurement, SMT stencil manufacturing and PCB assembly. Redback Test Services www.redbacktest.com.au Electronex Redback Test Services is an Australian company that offers various electronic test services and products such as test siliconchip.com.au Fig.20: Redback Test Services’ test fixture with an image of a test piece on a monitor. Australia's electronics magazine September 2023  13 probes, test fixtures, test equipment interfacing and production test automation – see Fig.20. Reid Print Technologies https://reidprinttechnologies.com.au Fig.21: wearable and other products from Reid Print Technologies. Reid Print Technologies is an Australian specialist manufacturer of flexible and wearable printed electronics. Products include wearable and stretchable sensors for health monitoring, defence, consumer and industrial applications. Other products include PTC (positive temperature coefficient) heaters, force sense resistors (FSR Sensors), membrane switches, graphic overlays, capacitive sensors, printed UHF antennas, functional and wearable smart printed electronics, proximity sensors, NFC (near field communications) technology, backlighting technologies, touchscreen protectors and waterproof keyboards – see Fig.21. Reid has ISO:9001 and ISO:13485 medical certifications. Rohde & Schwarz (Australia) www.rohde-schwarz.com/au/ Fig.22: the latest Rohde & Schwarz MXO 4 Oscilloscope. Electronex Rohde & Schwarz is a German company established in 1933 and is famous for electronic test, broadcast, cybersecurity, radio monitoring, radio location equipment etc. One of their displays was the R&S MXO 4 series oscilloscope, described as a next-generation device and previously advertised in the magazine. It features the world’s fastest real-time update rate of 4.5 million waveforms per second, a 12-bit ADC (analog-to-digital converter), a sampling rate of 5Gsamples per second, a bandwidth of 200MHz to 1.5GHz and a spectrum acquisition rate of 45k FFT/s (FFT = Fast Fourier Transform) – see Fig.22. Silvertone Electronics https://silvertone.com.au Fig.23: Silvertone’s Signal Hound SM200C is a 100kHz to 20GHz spectrum analyser. Electronex Electronex Silvertone Electronics (https://silvertoneelectronics.com) is an Australian company that specialises in both UAVs and communications. Their equipment includes spectrum analysers, electronic counter-surveillance systems, software-­ defined radio and general test and measurement apparatus – see Fig.23. UAVs were not on display at Electronex, but we looked at one of the Silvertone drones, the Flamingo, in the May 2015 article on the Australian International Airshow (siliconchip.au/ Article/8550). It was designed by Silicon Chip contributor Bob Young, the founder of Silvertone. Sun Industries https://sunindustries.com.au Electronex Sun Industries is an Australian company that does industrial printing, including user interface solutions such as membrane keypads, capacitive switches, backlighting, flexible printed electronics, screen printing, ‘subsurface digital printing’, printing onto and etching of aluminium, lithographic printing and more. They can also use ‘stoving’ to print enamels to metal plates, produce domed urethane badges, do laser etching of serial numbers, production of tooling, graphic design and others. Tektronix www.tek.com/en Fig.24: a Tektronix 4 Series MSO being demonstrated at Electronex. 14 Silicon Chip Electronex Tektronix is a well-known test and measurement equipment manufacturer and now owns the Keithley brand. One of the products on display was the 2 Series MSO, where MSO stands Australia's electronics magazine siliconchip.com.au AMW featured lots of different machinery, such as the metal plate CNC water jet cutter shown in the photo at right. for Mixed Signal Oscilloscope. An MSO can display digital and analog signals at the same time. The 2 Series MSO has a bandwidth of up to 500MHz, can record up to 10M points per trigger, has two or four analog channels and up to 16 digital channels, and has a sample rate of up to 2.5GSa/s. They also had a 4 Series MSO on display – see Fig.24. Traversal Labs https://traversal.io AMW Traversal Labs offers what they call “data engineering solutions”. They turn “operational data into actionable insights”. Areas include machine vision, modelling and visualisation of operations and machine learning to discover useful patterns in operational data, among others – see Fig.25. Vernier Foundation www.vernier.org.au/vernier-foundation/ AMW The Vernier Foundation is the charity arm of the Vernier Society and “has been formed to promote and attract the interest of young people to engineering and assist in their training and education”. The Vernier Society “seeks to inform the wider community about the value of engineering and manufacturing in Australia”. Fig.25: Traversal Labs’ demonstration of “segmentation” to “disambiguate the structure of industrial scenes”, such as identifying pallets, shelves or bulk materials by their geometry. They also show an analysis of “keypoints” of the human body and joint angles to identify problems before harm occurs. siliconchip.com.au More on Electronex & AMW by Tim Blythman Tim also attended Electronex and AMW this year and has the following to add to Dr Maddison’s observations: Boston Micro Fabrication https://bmf3d.com AMW This company showed off tiny and detailed 3D prints and their applications – see Fig.26. One application is the iteration of designs (such as optimising for shape) for a medical microneedle. Such a needle is used to administer medications directly into the skin. The printers used to produce these prototypes have a resolution of 2μm. Once the designs have been finalised, they can be mass-­ produced by traditional methods like injection moulding. Other 3D-printed products on display included a spiral syringe and 3D-printed valves for gene sequencing and lab-ona-chip devices. These resolutions have typically been achieved using TPP (two photon polymerisation), which uses two intersecting beams to accurately polymerise the raw resin. Carbon fibre 3D printing Various Companies AMW Several companies, including Konica Minolta and Markforged, were showing off 3D printers that can incorporate continuous carbon fibre into a print. They claim that such parts Fig.26: very impressive miniature 3D prints from Boston Micro Fabrication. Although not easy to photograph, they also had a microscope set up so that you could actually see the (microscopic!) prototypes in real life. Australia's electronics magazine September 2023  15 Fig.27: Control Devices demonstrated a range of switches, including illuminated, waterproof and specialised types. Fig.28: touch-sensing demonstrations at the Microchip Technology stand. can replace machined aluminium. To demonstrate, they had test prints that visitors were challenged to break! (Nobody succeeded, as far as I know...) Control Devices www.controldevices.com.au Fig.29: LEACH has a factory in Guangdong, China, that can manufacture and test complex PCBs like the ones shown. Electronex We spoke to Monique from Control Devices. They had samples of many of their switches and interface devices on display (see Fig.27). They always have new and interesting switches to show in their ads, and it was good to be able to try them out in real life. Leach PCB Assembly www.leach-pcba.com/en/ Electronex Shenzhen (China) based Leach provides electronic manufacturing services, and they had many large, complex PCB assemblies they previously made on display at the show – see Fig.29. Microchip Technology www.microchip.com Fig.30: Ocean Controls showed off their range of industrial instrumentation products. Electronex Microchip Technology, which makes many of the microcontrollers we use in our projects, was keen to tell us about their low-power touch controllers. These controllers use capacitive touch sensing and can be implemented with little more than a trace on a PCB, thus with no extra cost if a PCB is already required. As well as the microcontroller-integrated peripherals we have explored previously, they also offer standalone touch-sensing chips that communicate over I2C and offer features such as automatic calibration. On display and available to try out were numerous development boards and demonstrations (see Fig.28). One showed a controller consuming single-digit microamps while also detecting touches. Ocean Controls https://oceancontrols.com.au Electronex Ocean Controls had a range of industrial control equipment on display, including a few parts wired together to demonstrate how they can be used – see Fig.30. They told us that they have moved to newer premises in Carrum Downs, Vic. Rolec OKW www.rolec-okw.com.au Fig.31: Germany-based ROLEC OKW has a local presence supplying a wide range of enclosures. 16 Silicon Chip Electronex The Rolec OKW stand had an array of unusual and interesting enclosures, including parts that could be used for making smart watches, pendants and medical devices – see Fig.31. SC Australia's electronics magazine siliconchip.com.au Tilting head to 900 Digital Readout Speed Display 2 Speed Gearbox Digital Depth Display YOUR TURNING SOLUTION 3MT Spindle Work Light Dovetail Vertical Z-Axis Geared Headstock D1-4 Camlock Spindle TU-3008G-20M OPTI-TURN LATHE & MILL DRILL COMBINATION 3MT Tailstock Induction Hardened 3MT Tailstock Sawrf Drip Tray PACKAGE DEAL K149 5,170 inc GST $ SAVE $264 OFF RRP PACKAGE DEAL TU-3008G - Opti-Turn Bench Lathe This new TU-3008G model geared head lathe of very modern design has many convenient facilities ideal for the enthusiastic model engineer for small component manufacturer. A very rigid 180mm cast iron bed width, induction hardened and ground slideways gives a high level of precision turning. The lathe capacity is 700mm between the centres and 300mm swing over the bed and with a generous 38mm spindle bore allowing larger stock to be placed through the headstock. The workhorse that drives this lathe has an upgraded powerful 2hp (1.5kW) motor providing smooth running. Other very useful features included are cross and longitudinal power feeds that's not normally found of small conventional lathes, quick lock tailstock and both metric and imperial thread cutting, ranging from 8-56 tpi or 0.2-3.5mm pitch. Also included are a 4-way indexing tool post with 16mm tool shank capacity, fine adjustment on the tailstock for taper turning and the rear splash guard. A 160mm 3-jaw chuck with reverse jaws is also supplied. ORDER CODE: L691 TU-3008G - Opti-Turn Bench Lathe PACKAGE CONTENTS L691 + M647 ORDER CODE: M647 The BF-20AV mill head attachment has more throat & height capacity than the the BF-16AV and allows for larger work to be machined, it also is specifically designed to suit the TU-2506V & TU-3008G Optimum bench lathes; converting them into a universal combination lathe/ mill when mounted together. In addition this compact setup has the advantage of that it requires less valuable floor space then the two separate conventional machines. SYDNEY BRISBANE MELBOURNE (03) 9212 4422 (08) 9373 9999 1/2 Windsor Rd, Northmead 625 Boundary Rd, Coopers Plains 4 Abbotts Rd, Dandenong 11 Valentine St, Kewdale (02) 9890 9111 (07) 3715 2200 PERTH Specifications & prices are subject to change without notification. Established 1930 06_SC_270723 For full specifications visit www.machineryhouse.com.au/k149 These speakers are retro, stylish and surprisingly good performers. They’re also pretty easy to make and don’t cost the Earth. My wife liked them so much that she actually wanted me to put them in the living room! By Phil Prosser H ere is our take on the IKEA salad bowl speaker concept that has been spreading around the internet, which we think came out really well. This article describes a fully functioning pair of desktop/bookshelf speakers and gives some suggestions for tweaking the design to suit your needs. What initially attracted us to this idea was the mix of an old-school spherical speaker with extreme ease of construction. While the initial motive for building these was style and looks, it quickly became apparent that these little cuties had more to offer than that. Those who make speakers will be quick to comment that a sphere should be highly resonant; however, our tests show this is not the case. The fact that the driver forms a significant portion of the surface area of the sphere results in the Q of the internal resonance being relatively low. As a result, our measurements don’t show resonant peaks in the response. Another benefit of a spherical speaker is that it has no edges. Or is it all one edge? Either way, concerns like edge diffraction and baffle effect are avoided. The fact that these speakers are spherical makes them extremely rigid. Edge diffraction is the effect of sound waves propagating from the driver across a speaker’s front panel, then hitting the edge, which forms a discontinuity from propagation in ‘half space’ to ‘free space’. This change 18 Silicon Chip causes diffraction at the speaker edges, affecting the frequency response and off-axis behaviour. There are many ways a spherical speaker can be mounted. Without creating a solution to this, they will tend to roll around! We have come up with a couple of options, including feet for the desk version and “rocket” floor stands, both shown in the photos. The desktop version uses three small doorknobs as feet. The loudspeaker driver used is the SB Acoustics SB12PFCR25-4-COAX, a bass/mid driver with a coaxial tweeter (mounted in the centre). This allows us to achieve really good performance from about 70Hz upwards. These work brilliantly as desktop speakers and would also match well with any of our subwoofers crossed over at 80-100Hz. If you’re interested in matching these speakers with a subwoofer, check out my Tapped Horn Sub design (September 2021 issue; siliconchip. au/Article/15028), which is inexpensive and easy to build. You could also consider the very high-performance Active Subwoofer (January & February 2023; siliconchip.au/Series/390). We chose this specific SB Acoustics driver because it incorporates the tweeter, and neatly addresses the challenge of finding somewhere to mount the tweeter. The only other solution we could think of was to mount the tweeter externally, which we did with the floor-standing version, but it was a real hassle. We have added a port to our enclosure. This allows us to extend the lower frequency response to about 70Hz, with some useful output below that. That is a good result for such a small speaker and is reasonable in its intended applications of desktop usage or placement in a small room. Don’t try to run a dance party using these speakers, though. There is a bit of a hump in the frequency response in the 100-200Hz region. This is a result of the port and helps fill out the bottom end, given the roll-off below 80Hz. The black line in Fig.2 shows the low-­ frequency response you will achieve Features & specifications – – – – – – – – – Compact full-range loudspeakers with a unique appearance Simple construction Spherical enclosure minimises diffraction Coaxial tweeter for good off-axis response Can be desk or floor mounted (the latter with a simple stand) Frequency response: 70Hz to 20kHz (±3dB typical) Power handling: 50W RMS per channel Impedance: nominally 4Ω Relatively low total cost Australia's electronics magazine siliconchip.com.au Fig.1: the modelled response of these Speakers with a 90mm port (green curve) or tuned for 58Hz with a 160mm port (orange curve). The longer port gives more output below 70Hz, but trades that off against reduced output between about 70Hz and 200Hz. if you simply omit the port. If you use these on a desk backed up to a wall, omit the port. We used a 25mm port from Wagner Electronics, cut to 90mm in length. This tunes the system to resonance at 74Hz. In practice, the vent ends close to the driver magnet, so its effective length is over 90mm. This tuning gains us a couple of decibels of extra bass in the roll-off region. In an ideal world, this port would be 160mm long, tuning the enclosure to 58Hz, but there is not enough room in the enclosure for that - see Fig.1. Cost While these speakers are designed to be relatively inexpensive, we are using high-quality drivers from SB Acoustics that cost around $90 each. We also can’t avoid some relatively expensive air-cored inductors in the crossover, meaning the total cost to build these speakers will be about $350. Still, it’s hard to buy a decent pair of speakers for less than that. You might be able to build a pair for around $300 or perhaps a bit less if you take some shortcuts, eg, if you come up with alternative feet and wind your own air-cored inductors. Crossover The crossover we’re using is based on that recommended by SB Acoustics with some minor modifications. This is a third-order electrical crossover at 2.2kHz. Third-order is a higher order than we would generally want to use. Still, given that the tweeter siliconchip.com.au resonance is at 1300Hz, it’s necessary for the crossover to occur at a sensible frequency. Our measured frequency response of the driver in the spherical enclosure (Fig.2) is very close to that SB Acoustics provides. The only notable difference is that our tweeter was 1-2dB less sensitive than theirs. Fig.2 is a raw measurement of the driver with no processing at all. We are looking for spikes and dips that, if present, will colour the sound. Happily, the response is actually very smooth. We will discuss that chasm at 12kHz or so later; the short answer is that it disappears off-axis. Those wobbles in response at the bottom end are due to floor and room interactions. We were about to start a fresh crossover design when we noticed that SB Acoustics published a recommended crossover circuit. When a manufacturer publishes a reference design, it is usually a great starting point. We duly tested it. Given the tweeter’s small diameter, a third-order design was appropriate. It is important to drive as little energy at 1.2kHz into that tweeter as possible. The woofer also has a third-order crossover, which makes sense from a symmetry perspective. This driver is well-behaved, as shown in Fig.2. So, if not for the tiny tweeter, a second-­ order crossover may have been better. The resulting system response is shown in Fig.3. This is very flat through the main audio range, up to 10-15kHz. The dip between 10kHz and 20kHz can be seen to move as you Australia's electronics magazine You could repurpose a couple of coat racks as speaker stands since the Speakers are small and light, or build similar stands from MDF or other timber. We used a driver without a coaxial tweeter and mounted the tweeter under the enclosure, but it doesn’t look great and is fiddly to assemble. We therefore recommend you stick with the coaxial drivers. September 2023  19 20dB 10dB 0dB -10dB -20dB -30dB 50Hz 100Hz 200Hz 500Hz 1kHz 2kHz 5kHz 10kHz 20kHz Fig.2: the measured frequency response of the SB Acoustic SB12PFCR25-4 driver without any processing or smoothing. The woofer response is in black, while the tweeter is in red. The dip above 10kHz is discussed in the text. 20dB 10dB 0dB -10dB -20dB -30dB 50Hz 100Hz 200Hz 500Hz 1kHz 2kHz 5kHz 10kHz 20kHz Fig.3: the overall Speaker frequency response with 1/6th octave smoothing, with on-axis response in black and 15° off-axis in red. This is very good for such a simple design. The dip at about 12kHz is a consequence of the tweeter location. As the crossover is optimised for a 15° off-axis response, that dip has disappeared in the red curve. move off-axis. This is likely a consequence of the coaxial tweeter and varying path lengths from the exit of the coaxial tweeter to the woofer voice coil former. It is important to note that there is no sign of the crossover at 2.2kHz in the frequency response plot. In short, this crossover works very well with the driver. The following hypothesis hasn’t been proven, but the wavelength of 12kHz is about 27mm, and destructive interference will occur for a path difference of 10-15mm. Given the location of the tweeter cone relative to the coil edge, the dip makes sense. It also explains why the dip changes in frequency and disappears as you move off-axis. This ripple in response is at a frequency near the limit of what most people can hear, so it is not a big deal. Our frequency response plot was made 1.2m above the floor at a distance of 30cm, the same distance at which the manufacturer’s response plots were made. When used on a desk, as we expect these will be, there is no sign of that dip. It’s only apparent when the driver is measured in free space. There are all sorts of other artefacts in the plots, which, in our test location, resulted from our monitor, keyboard and probably even coffee cup! These peaks and dips move all over the place as you move around the Speaker. Running the risk of being told to clear our desk, Fig.4 shows several measurements of the Speaker in different locations. Subjective evaluation 20dB Fig.4: the frequency response of a Salad Bowl Speaker with 1/6th octave smoothing and reflex port installed at various locations. The black curve is about 15° off-axis, red is straight on, blue is elevated about 400mm and again about 15° off-axis, and purple is on the other side of the desk at a similarly elevated location. The low-frequency ripple from the room is very evident. These speakers sound pretty darn good using the standard crossover. We did make two minor changes, though. Firstly, we reduced the tweeter attenuation resistor to boost treble by 1dB. Also, the OEM design used a 0.4mH series inductor for the woofer. We had a bunch of 250µH units available, and calculations showed it would make a negligible difference, so we went with that. Given how well these measured, we shelved any idea of redesigning the crossover. Why break something that works? The final crossover is shown in Fig.5. The change from 2.2W to 1.5W for the tweeter series resistor will increase the tweeter output by about 1dB and slightly improves damping. Given the Australia's electronics magazine siliconchip.com.au 10dB 0dB -10dB -20dB -30dB 50Hz 20 100Hz 200Hz Silicon Chip 500Hz 1kHz 2kHz 5kHz 10kHz 20kHz Fig.5: the crossover circuit provides a third-order high-pass filter (HPF) for the tweeter and a third-order low-pass filter (LPF) for the woofer, crossing over at about 2.2kHz. There is no phase inversion. We have made the resistor 1.5W as that provided better balance in our speakers than the suggested 2.2W. Still, if your tweeters are less or more sensitive than ours, you may wish to tweak its value. frequencies involved, it is not likely that the reduced sensitivity is a consequence of the spherical enclosure; it could be that our samples are slightly less efficient than average (or the ones they tested were above average in efficiency). When building yours, consider experimenting with values of, say, 1W, 1.5W and 2.2W to see which results in the most natural sound in your application. Practical considerations The mounting location for the crossover was a bit of a head-scratcher. Usually, we would make a PCB and screw it to the enclosure. That is not an option here as, being spherical, there are no flat surfaces to use. There is also precious little room to play with. So we made a PCB with rounded edges that you can glue into the speaker base. It just fits through the driver hole, and we have placed the 1.5mH inductor so that you can snug this up against the port and glue them together – see Photo 1. We used neutral-­cure silicone sealant to glue the crossover PCB to the enclosure, as it will stick to just about anything, and once it sets, it is very resilient. Building the speakers The sole ‘tricky’ part of building these speakers is cutting the bottom off one bowl to accommodate the driver. If you have a router or can borrow one, it will be much easier than you might think. We reckon it would be possible to use a tenon saw and do this by hand if you clamp the bowl well, as the bowl wall is only 8mm thick. siliconchip.com.au When we cut off the bottom of the bowl to accommodate the speaker driver, we need sufficient material left to screw into. To achieve this, we took an MDF off-cut and cut it into two 120mm circles using a jigsaw. We then used an 80-grit sanding disc in a drill to get them to be rough fits to the bowls – see Photo 2. The fit does not need to be perfect; we will glue it in with acrylic filler. Use an N95 mask and work outside (if possible) when cutting and sanding MDF. Having a vacuum cleaner pick up the sawdust as you make it is also a good idea. MDF dust is a health hazard. Once you have roughed the wood so it fits with a gap under, say, 5mm, apply acrylic filler liberally around the sloped section and squeeze it into the bottom of the bowl, as shown in Photo 3. It is a good idea to drill a hole in the middle of the MDF to allow air out as you stick it in. Leave it for a week to really set. Photo 1: you can see how the port, driver and crossover fit into the spherical enclosure that was made by gluing two salad bowls together. You can also just see the MDF reinforcement ring behind the circular driver cutout. Photo 2: we roughly cut two 120mm MDF discs from off-cuts (left), then used an 80-grit sanding disc in a cordless drill chuck to shape it to fit in the bottom of the bowl (right). Routing We used our circle jig (described on page 61 of the January 2023 issue) and a router to expand the flat portion of the bowl base to an outer diameter of 122mm, matching the diameter of the SB12PFCR25-4-COAX driver. We placed the bowl top-down on the workbench and drilled a hole in the middle of the base to centre the router. Make this route in two or three cuts, and do not cut too deep. Briefly, the circle jig is a length of aluminium bar with holes drilled in it to allow it to be bolted to the router. There are other holes drilled in it at various distances from the router. Australia's electronics magazine Photo 3: the reinforcement disc is glued into the bottom of the bowl using acrylic gap filler. Before doing this, ensure it is a close fit, leaving gaps less than 5mm wide all around. September 2023  21 After loosely screwing one of these into a centre hole drilled in the bowl, the router will rotate about that point and make a perfect circle. We are pretty sure that a steady hand, some clamps and a tenon saw would do the job, and might actually be easier and make less mess. You need to cut 10mm off the Wagner 25mm port to make it 90mm long; otherwise, it will interfere with the speaker magnet later. We made the hole tight enough that we had to push the port in forcefully. If your hole is too big, glue the port in using some acrylic filler. Cutting the speaker hole Speaker connectors The driver fits into a 102mm hole in the base, visible in Photo 4. Mark this with a compass and cut it with either a handsaw or jigsaw. The hole is fairly small, so only a little elbow grease would be expended doing this by hand. Check that your driver fits, and if necessary, fettle (a fancy word for bodge) the cutout so that the terminals do not interfere with the hole. We used very simple combo banana/ binding posts. The speakers’ power handling does not warrant anything massive, but we think these are better than the cheap spring-loaded terminals. The location of the connectors is largely a matter of convenience; ours are shown in Photo 5. These need an 8mm hole, although we prefer to start smaller and use a file to get a good fit with the chamfered keying on the threaded section. That stops them from coming loose and spinning. Our experience building the prototype showed that it is possible to solder to these terminals once they are in the assembled Speaker, but it is fiddly. We recommend you pre-install the input wiring to these terminals. Solder 300mm lengths of black and red wire to each pair and add 6mm diameter heatshrink tubing over the solder joints. You can trim the wires to length once you have attached them to the crossover. Fitting the port If we were using these on a desk, pushed back against a wall, we would omit the port. The boost in low frequencies using the Speaker in a corner will be sufficient, and you will be better off without the port. If you’ve already added the port, you could put a sock in it for such use cases. If you will use the speakers in more ‘free space’ and without a subwoofer, include the port, as the low-frequency output will benefit from it. If adding a port, drill the hole now. We used a 32mm hole saw and filed the hole to the required 33mm. We centred the hole 50mm below the centreline of the bowl see (Photo 5). This results in the port pointing upwards inside the Speaker. Photo 4: the result of cutting a 102mm diameter hole in both the base of the bowl (already routed to have a larger flat area) and the MDF reinforcement disc, leaving just a ring. 22 Silicon Chip and were easy to fit. They are not individually that expensive, but there are six, so it does add up. You might come up with your own solution. The feet are visible in Photos 5 & 6. They fit through 4mm holes drilled as shown in Fig.6. Whatever feet you choose, make sure you place them so the Speaker is stable; their placement must consider the centre of gravity being pulled forward by the weight of the driver magnet. The Bunnings knobs come with long bolts that you can cut and then file the ends smooth to ensure they thread onto the knobs without sticking. You can use a metal file to do that. Gluing the pieces together As mentioned earlier, they need feet for desktop use. We used brass knobs because we thought they looked nice Sticking the two salad bowls together is as simple as it sounds. We used 120 grit sandpaper to take the gloss off the rim of the bowls and around the inside of the bowls. This ensures there is a good surface for the glue to adhere to. We then mixed five-minute epoxy (Araldite), a teaspoon full or less per bowl. Use a piece of thin wire, 1mm in diameter or so, to apply a small bead around the top rim of the base bowl. Our tips are: ● Do not use too much glue, or it will ooze out around the joint. ● Get everything ready before you start applying the glue. It will set in less than five minutes, so you don’t have time to muck around. ● Be ready to clean up spills; have cloths and isopropyl alcohol/white spirits ready. Photo 5: the flat part of the base opposite the driver cutout provides a place to mount the two binding posts, while the port is offset so it fires downwards and clears the internal crossover assembly. Photo 6: the finished speakers look classy, if a bit unusual. Fans of post-modern art could paint them white and add red wiggly radial lines around the drivers to make them look like eyeballs! Adding feet Australia's electronics magazine siliconchip.com.au ● Know how you want to align the bowls. Ours were so random that we kind of gave up, but you might be more discerning than us. Once you have a thin bead on the bottom bowl, gently place the top bowl over it. Very gently wriggle it to ensure both sides are wet, and check that everything is aligned. Set it aside for a while. Once the main joint is set, mix another batch of glue and, using an icy pole stick or similar, run a bead of glue around the joint inside the glued bowls to ensure the final result is airtight. With the roughened surface, the epoxy bond will be extremely strong. Assembling the crossover The crossover PCB with chamfered corners is coded 01109231 and measures 98 × 104mm – see Fig.7. We etched the PCBs shown in the photos ourselves as the design is simple. PCBs for sale will be the usual green commercial products, but otherwise identical to these. Our photographs show yellow polypropylene 15μF capacitors, which are overkill; we simply used them as they were on hand. We have specified 15μF 100V bipolar electrolytic capacitors as they will work perfectly well and are what we would buy if building another pair of speakers. We have left room for a 400μH inductor to be used in place of the recommended 250μH inductor. All testing was done with 250μH, but you can experiment; we don’t expect much difference in performance over the range of 250μH to 400μH. If you want to experiment, run wires from the drivers out through the port to the crossover. Get the crossover as you want before gluing it into the Speaker. Assembly is straightforward. Fit the screw terminals first; still, you might want to simply solder flying leads and save on this cost. If you choose to do this, solder 300mm flying leads to the bass and tweeter connectors and label them so you know what goes where. The input wires should already be soldered to the input connectors. Next, mount the resistor. This does not need to be proud of the PCB, as if this is getting hot, your tweeter will be in serious trouble. So it’s OK to push it down flat before soldering and trimming the leads. siliconchip.com.au DIAGRAMS ARE SHOWN AT 61.5% SCALE Fig.6: these views of an assembled Speaker should give you a good idea of the relative locations of the driver, feet, port, crossover and terminals. You could vary some of these slightly but we feel our design is pretty close to optimal. Australia's electronics magazine September 2023  23 Install the capacitors next, none of which are polarised. Put a dab of neutral-­ cure silicone sealant under each to stop them from vibrating. Finally, solder the inductors in place. Note that these are all at right angles to the others to ensure the magnetic fields don’t interact. Make sure you stick to this arrangement. Again, glue each in place with a solid dab of neutral-cure silicone. With all the components mounted, check your soldering and that everything is in the right place before moving on. Let the silicone cure before moving on to final assembly. Final speaker assembly The prototype crossover was simple enough that we made the PCB ourselves. We recommend using electrolytic crossover capacitors instead of the two large 15μF polypropylene capacitors shown here. Before you glue everything in place, let’s check that everything works, as it is diffcult to remove the crossover afterwards. Do the following on the bench. Strip a short length of all the flying leads and connect the leads from the input connector to the input terminals. Next, connect the bass driver and tweeter to their respective inputs on the crossover but connect only the ground wires at the driver end at this stage. We want to just touch the positive wire for the test. You can tell which is which as the bass driver connections have heavy-duty tinsel going into the spider on the driver while the tweeter connections run to thin wires going to the rear of the magnet assembly. Apply a signal to the inputs and touch the positive bass wire to the terminal on the driver. You should only hear the lower-frequency parts of the test signal. It won’t have any real bass with the driver on the bench. If you hear treble instead, or nothing, check your connections. Next, touch the tweeter positive wire to the terminal on the speakers. You should hear ‘hissy’ treble. It will not be loud. If there is nothing or all you hear is muted sound, check your wiring and component values. Assuming that it all checks out, test-fit the crossover into the enclosure. Photo 7 provides a pretty good view of how to install it. You need to align the thin axis with the hole and put the 1.5mH inductor in first, as we need this at the back to make room. We also need the weight at the back to improve the balance of the Speaker. Once you are sure you know how Australia's electronics magazine siliconchip.com.au Fig.7: the crossover PCB is straightforward to assemble. While we’re showing the capacitors as axial polyester types, axial crossover bipolar electrolytic capacitors are considerably cheaper, especially for the 15μF cap, and will work fine. Ensure the inductors are mounted as shown so their magnetic fields won’t interact (much). 24 Silicon Chip Parts List – Salad Bowl Speakers Pair of desktop speakers 2 SB Acoustics 120mm coaxial speakers [Wagner SB12PFCR25-4-COAX] 2 25mm diameter, 100mm-long PortBASS reflex ports [Wagner PORT1X4L] 4 IKEA salad bowls [BLANDA MATT 20cm bamboo serving bowl, 002.143.41] 2 16mm MDF sheets or off-cuts, at least 120×120mm each 2 red captive head binding posts for speaker terminals [Altronics P9252] 2 black captive head binding posts for speaker terminals [Altronics P9254] 6 doorknobs for feet [Bunnings Prestige 15mm Brass Ball Knob, 4021268] 3 2m lengths of heavy-duty hookup wire (white/blue, black and red) [Altronics W2270, W2272 & W2274, Jaycar WH3050, WH3052 & WH3040] 1 100mm length of 6mm diameter heatshrink tubing 8 6G × 20mm countersunk head wood screws (ideally black) 2 400 × 150mm (approximately) pieces of 50mm-thick acrylic wadding or similar 1 small tube of 5-minute epoxy [eg, Araldite] 1 310ml tube of White SikaSeal Acrylic 100 Gap Filler [Bunnings 1670226] 2 crossover boards (see below) Crossover board – parts to build one board 1 single-sided PCB coded 01109231, 98 × 104mm 2 250μH air-cored crossover inductors (L1, L3) [Wagner AC20-25] 1 1.5mH air-cored crossover inductor (L2) [Wagner AC201-5] 2 15μF 100V non-polarised electrolytic crossover capacitors [Wagner 15RY100, Jaycar RY6910] 1 5.6μF 100V metallised polypropylene crossover capacitor [Wagner PMT5.6, Jaycar RY6955] 3 dual mini terminal blocks, 5.08mm pitch (optional; CON1-CON3) 1 1.5W 5W 5% resistor (can be varied to adjust treble balance; see text) you will get things in and out and that there is room (fettle the hole if necessary), we are set to finalise the wiring. Trim the input and output wires so that, with the driver in front of the enclosure, you have sufficient length for the crossover to be glued in place. Solder the connections for the bass, tweeter and input. It is important to put some 6mm heatshrink on the speaker terminals when you connect the wires. These terminals are close to the crossover, and we do not want them shorting to it. Now put solid dabs of neutral-cure silicone sealant on the underside of the PCB at each of the rounded corners. Then install the board, with some tissues/rags handy to clean your fingers. Carefully insert the crossover into the Speaker enclosure. As you will have found, it is a little like a puzzle, but it does go in and sits alongside the port. Make sure there is silicone still under the PCB, and where you inevitably rub some onto the enclosure, clean up immediately. siliconchip.com.au We used a long screwdriver to add some extra silicone between the enclosure wall and the top of each corner of the PCB to ensure it won’t move later. Leave it to cure; don’t be tempted to rush this, as silicone has no strength until it cures. We used a small piece of leftover acrylic wadding as damping for the Speaker, as shown in Photo 8. Anything like open-cell foam, acrylic wadding or the contents of a disused cushion would do. Lightly stuff the enclosure and ensure the port is not completely blocked. Now where did that cushion go? Finally, install the driver. We mounted the driver with the terminals horizontal. This ensures that the terminals cannot rub against the crossover components. Ensure each driver has the same rotation so the screws line up. They will look silly if the screws are all over the place. We drilled a 1.5mm pilot hole for each screw and used 6GA wood screws. Do these ‘gently hand Australia's electronics magazine Photo 8: the Speaker just before we finally attached the driver, with acoustic wadding loosely stuffed inside. tight’. These simply need to secure the driver well enough to achieve an air seal. Testing and setup Now for the fun! You will note that the acoustic output is night and day between the driver on the bench and in the enclosure. We were surprised at the bass output these little speakers deliver. Start gently and play some program material, verifying that there is output Photo 7: this close-up shows how the crossover board is orientated so the closest inductor just misses the port tube. September 2023  25 Refrain from facing the speakers straight at your listening position, though this is less of a concern on a desk. The crossover is optimal for a slightly offset listening position. Observations The Salad Bowl Speaker (not shown at actual size). from the tweeters and bass drivers. If there is anything odd, now is the time to check. Once everything is good, you are set to find where to put them! Often you have little discretion in the placement of a speaker. Try to find a spot with free space around and behind the Speakers. We found that when placed right up against a wall/desk junction, there was a reinforcement of bass, with a pronounced peak in the bass region. As mentioned earlier, blocking the port(s) should reduce that. Our most ardent critic at home loves the style. We think it is interesting, both visually and in terms of a speaker free from diffraction, and we see this in the plots. The coaxial driver really met our expectations, with a consistent sound experience at a wide range of angles. The low end surprised us. It is not a disco speaker but does a fine job for moderate listening. As the measurements suggest, the sound is clean and free from annoying characteristics. We could hear the elevated bass when we used the Speaker in a corner, so we would use no port in such a location. While we have rated them at 50W, you should show some discretion if playing deep bass through them. These are intended for small rooms, on computer desks and similar. While the impedance is nominally 4W, they present a fairly benign load with a higher-than-rated impedance over most of the audio range. Any modern amplifier will happily drive them. Our inexpensive, compact Hummingbird amplifier module is ideal (December 2021 issue; siliconchip.au/ Article/15126). These speakers provide useful output from 70Hz to 20kHz and some output below 70Hz. Over the majority of this frequency range, they are quite SC flat, operating within ±3dB. Dual-Channel Breadboard Power Supply Our Dual-Channel Breadboard PSU features two independent channels each delivering 0-14V <at> 0-1A. It runs from 7-15V DC or USB 5V DC, and plugs straight into the power rails of a breadboard, making it ideal for prototyping. Photo shows both the Breadboard PSU and optional Display Adaptor (with 20x4 LCD) assembled. Both articles in the December 2022 issue – siliconchip.au/Series/401 SC6571 ($40 + post): Breadboard PSU Complete Kit SC6572 ($50 + post): Breadboard PSU Display Adaptor Kit 26 Silicon Chip Australia's electronics magazine siliconchip.com.au GOOD Build It Yourself Electronics Centres® Gadget Buys SAVE $30 349 $ K 8600 Sale prices end September 30th. The worlds best selling 3D printer! ZR6302G Dual 4K <at> 60Hz HDMI outputs. 149 $ Pi HAT and camera friendly. Over 1 million sold worldwide. On-board BLE, AC Wi-Fi & wired ethernet 4GB on board memory Pi friendly GPIO connections Welcome to the ROCK! The new Pi alternative. Creality® Ender 3 3D Printer The ROCK 4C+ offers a reliable and high spec alternative to Raspberry Pi. With all the same GPIO connections, form factor and compatability with Pi 4 accessories such as HATs, cameras and cases. You can get started quickly with a range of operating system choices including Android, Debian and Ubuntu linux. The Ender 3 is a compact 3D printer offering excellent print quality with a build volume of 22Wx22Dx25Hcm and is compatible with ABS, PLA and TPU filaments. Supplied mostly assembled and can be up and running within an hour. Covert 1080p CCTV Recorder 1080p video or 20MP still shot. Great for monitoring in remote locations, temporary CCTV monitoring etc. Runs off batteries, so its quick & easy to set up anywhere you need to keep an eye on things. Weatherproof case with LCD screen. Requires 8xAA batteries & DA0329 32GB SD card $12.50. S 9446D NEW! 99 $ S 9843B NEW! Now with 15W charging! 49 .95 $ D 0512 NEW! 68.95 $ Charge any device, anywhere. This high capacity 20,000mAh battery bank has charging cables in-built for USB C, Micro USB and Apple Lightning equipped devices. It even includes the recharging cable! Build wireless charging into your desk D 2322A* Great for the workbench! An ultra-slim desk mount 15W wireless fast charger. Needs 60mmØ hole. Includes power adaptor & USB cable. SAVE $70 129 $ With internal battery - use it anywhere! S 9017A SAVE $20 NEW! 59 $ 129 $ Pan & Tilt Wi-Fi Cloud Camera Battery Powered Wi-Fi Cloud Camera Makes a great baby or pet monitor, this 1080p HD camera tracks movement. 2-way audio with mic and speaker. Requires 5V 1A USB power supply. No cabling required! Charge it up for up to 6 months motion activated surveillance - anywhere you need it. Suits sheltered outdoor installation. 1080p HD. 65W Portable Laptop Battery Bank D 0520 Surprisingly compact battery bank with USB power delivery over 65W for large laptops! Features 2 PD Outputs and 2 QC3.0 outputs for simulataneous charging. Total capacity 20,000mAh. SAVE $60 229 $ S 8864 14” Go-Anywhere Portable Digital TV Perfect for the car or caravan! Powered off internal rechargeable battery, your vehicle battery or mains plugpack. Also fitted with USB connection for recording TV. Order online at altronics.com.au | Sale pricing ends September 30th. Power up & SAVE. 4 x USB Charging USB C Charging Hurry limited stocks at this huge discount! Reading Light 80W Mains Inverter Dual LED Torch SAVE $70 M 8070A SAVE $400 799 $ 199 SAVE $20 SL4581B $ 49 $ 5 YEAR WARRANTY! Mains power from your cup holder. SCOOP BUY! 150Ah Lithium Batteries 240V power in the palm of your hand! This power inverter simply plugs into a cigarette lighter 12V socket & provides 240V power! 150W rated (450W surge). Need longer run time from your remote power system? Upgrade with more capacity from this premium 150Ah LiFePO4 battery, with commercial grade cells & high discharge rating. 12.8V output. M8/F12 terminals. DC Power Distribution Posts M 8197 This air travel friendly portable power generator is fitted with 6Ah battery bank, 80W 240V mains inverter, 18W power delivery USB C charger & QC3.0 USB charger. Offers you cable free power for both AC and DC appliances! Recharge by USB or included power adaptor. Power your camping fridge without risk of draining your battery! High current DC power distribution posts with reinforced nylon base (bolt head is encapsulated). 48V DC max. SAVE $30 SAVE 15% Model Wattage RRP NOW P 2172 Single M8 Red $10.95 $9 $9 $10 $10 $9 $9 $11 $11 P 2173 Single M8 Red $10.95 P 2175 Dual M8 Red $12.95 P 2176 Dual M8 Black $12.95 P 2182 Single M10 Red $10.95 P 2183 Single M10 Black $10.95 P 2177 Dual M10 Red $14.95 P 2179 Dual M10 Black $14.95 21 $ 7.5A W 2412 Red W 2413 Black .50 24 10A W 2416 Red W 2417 Black 29.50 15A W 2420 Red W 2421 Black $ $ 199 $ SAVE $40 Going bush this spring? Have power wherever you go on your next 4WD/ camping adventure. Includes 130W panel, solar regulator, battery connection cables and canvas carry case. 3 stage solar charger. Adjustable stand for best sun placement. Easily connects to the battery pack on right for a complete remote power solution. 664x631x75mm (folded). MPPT Lithium Ready Solar Regulator SAVE $54 185 $ Handyman Hookup Cable N 2026A 40A 19 $ .95 3.7V 2600mAh. S 4732A Unprotected cell (for With Tags use with charging circuits). 5.2A discharge current. 18.6Ø x 65mmL. S 4736A Flat Top 17 $ .95 $ Q 0596 350A* The Ultimate Battery Fuel Gauge. Accurately measures battery voltage, current, power, real capacity and remaining run time of your connected battery (suits any chemistry, 8-120V). Includes shunt with 2m cable. 1% accuracy. Cut out dimensions: 53.5 x 37.5mm. *350A shunt pictured. SAVE 33% 10/m $ Utilises MPPT circuitry to extract up to 20% additional charge from your solar panels compared with traditional regulators. Suits 12 or 24V lead acid, gel battery & lithium chemistry batteries. Red and black hook up cable in 30m lengths. Ideal for auto/marine use. Tinned conductors. 18650 Lithium Batteries For Projects. Includes canvas carry case. N 1130F 130W Remote Power Folding Solar Panel YOU SAVE 22% 129 75 $ Q 0594 50A W 4200 Red W 4202 Black SAVE $40 Quality 4 Gauge Power Cable 119 $ Ideal for high current DC power distributiuon in cars, campers and caravan power systems. 146A <at> 300VDC rated. N 2024A 20A Type C USB Lithium Charging Module Provides 1A charging current from a 5V DC USB C input. SAVE 17% 19 $ Z 6339 5 $ .95 Z 6388A DC-DC Boost Module Allows a 3-34V DC input to be boosted up between 4-35VDC. 2A rated. Input & output voltage display. Your one-stop electronics shop since 1976. | Order online at altronics.com.au Test & Measure. All-Weather True RMS Multimeter Do-It-All Multimeter Handy Auto Ranging DMM A rugged do-it-all meter is perfect for a serious electronics enthusiast, electrical tradesperson or service tech. Striking reverse backlit 9999 count display with non contact AC detection and plenty more features too. Simplicity & functionality in one compact test device. 10A DC current. 1Hz-30MHz counter. Includes test leads & temp probe. Great for students! Q 1133A Top of the range - great features and price! Ideal for marine/mining techs. • True RMS • 40MHz freq. counter with bar graph • Max/min recording • Capacitance to 40mF. • Temp with thermocouple. Q 1068A SAVE $10 Q 1088 NEW MODEL! 49 SAVE $50 109 $ 119 $ $ Water & dust proof! SAVE 15% 27.50 $ Q 1278B Q 3001A Sheath Piercing SAVE 29% 12 SAVE 28% 10 $ $ Q 3000A Spike Measure temps instantly! Handy Car Voltage Probes Folding waterproof spike temperature probe with bottle opener. -50°C to 300°C. Includes battery. A handy tool for troubleshooting wiring faults in vehicles and wiring looms. 6-24VDC range. Standard probe or sheath piercing versions. Tests for both integrity & cable run length! SAVE $20 79 $ Q 2022A ‘Roadies’ Cable Tester BARGAIN! Q 3004 Tests 13 types of leads for continuity. A real time saver! Tests: 3.5mm jack, 6.35mm jack, 3/5/7/8 pin DIN, RCA, 3/5 pin XLR, 4P Speakon, Powercon, banana plugs, RJ45 and USB. Requires 9V battery. SAVE 17% 10 33 $ $ 12V Car Alternator Tester Provides quick and easy way to test alternator/charging system function in 12V vehicles. X 6015 Diagnose car faults via Bluetooth Connects your car via Bluetooth to your phone to provide a wealth of diagnostic info. Works with a number of OBDII compatible apps. SAVE $50 145 $ Network & Coaxial Cable Verifier Tests both cable length and integrity in both RJ45 UTP data and BNC coaxial cabling. It’s wiremap system detects short circuits, split pairs and cable lengths up to 350m. Powered by USB rechargeable internal battery. SAVE $54 Low Current Lab Power Supplies 499 $ 20A Benchtop Power Supply M 8213 A compact 1-30V DC power supply with 3 programmable preset outputs. Fixed 5A aux output also available from front panel. High efficiency design with low noise and ripple for reliable use in electronic servicing. 200 x 90 x 215mm 145 $ Great for servicing, repair and design of electronics. Low noise switchmode design. Fine & coarse voltage and current controls. 3A or 5A max models. Size: 85Wx160Hx205Dmm. SAVE $130 M 8305 5A SAVE $40 M 8303 3A SAVE $44 119 $145 $ Q 1344 13.8V 20A Bench Power Supply A fixed voltage output power supply designed for powering automotive, marine and comms equipment. Low noise and ripple design (<100mV) offers excellent efficiency and performance. M 8254 Order online at altronics.com.au | Sale pricing ends September 30th. Top deals in AV. Do you need an easy way to connect your HDMI sources to a second TV in the house? Computer / Phone Computer TV / Monitor TV / Monitor It’s hard to believe, but these cable adapters have an in-built wireless HDMI sender capable of sending 1080p signals over distances up to 50m. Previously these sorts of senders would cost up to $600! Available in two types, standard HDMI or USB type C for sending your laptop, tablet or phone screen to your TV. Excellent latency performance also makes it perfect for sending your game console signal to a second room or your PC to your couch. All you need is USB power at each end - typically found on the back your TV, or via a USB wall charger. A 3607 HDMI ONLY... A 3608 USB C A 3607 shown transmitting HDMI AV source to a TV in another room. 169 $ USB Charger HDMI Equipped AV Source To Television HDMI Port To AV Source HDMI Output Redback® 30W 2-Way Wall Speakers Offers the flexibility of 8 ohm or 100V line use for commercial installations. Ideal for entertaining areas at home or boutiques, cafes, pubs & clubs in professional installations. Aluminium grill & bracket for rust free outdoor installation (sheltered installation only). 30W RMS. SAVE $150 C 0946 149 $ Add on a Bluetooth 2x25W amplifier for just $50 more! Normally $159 (A1116). Computer To Television USB Port TV / Monitor Wireless Transmission up to 50m. SAVE $40 A 2696A 349 $ Internet radio, digital radio & audio streaming in one. Wi-Fi Internet Radio System with DAB+, FM & Bluetooth. A stylish, easy to use receiver with access to over 26,000 global internet stations, plus DAB+ digital radio, FM frequencies and bluetooth streaming from your devices. Digital S/PDIF and analogue RCA outputs. A 3091 Ideal for multi-source 4K AV systems SAVE $19 55 $ L 2047 SAVE 19% 16 $ Handy problem solver! 8K DisplayPort Switch Boost your TV signal! Switch between two PC sources to DisplayPort monitors. Supports 4K <at> 120Hz or 8K <at> 30Hz. Simple to install in-line booster for added gain to your existing antenna. Great for fixing choppy reception issues. USB powered. Build It Yourself Electronics Centres® Sale Ends September 30th 2023 Find a local reseller at: altronics.com.au/storelocations/dealers/ SAVE $36 NEW! 119 $ 149 $ A 1117 A 3082 Add Bluetooth® to your favourite speakers! 4 Way HDMI Switcher With RS232 Control Why buy new bluetooth speakers when you can add this module to existing speakers? 2 x 10W RMS output. A commercial quality 4K 60Hz HDMI switcher with audio extraction for connection connection to stereo analog audio systems. RS-232 remote controllable. Mail Orders: mailorder<at>altronics.com.au Victoria Western Australia » Springvale: 891 Princes Hwy » Airport West: 5 Dromana Ave 03 9549 2188 03 9549 2121 » Auburn: 15 Short St 02 8748 5388 » Perth: 174 Roe St » Joondalup: 2/182 Winton Rd » Balcatta: 7/58 Erindale Rd » Cannington: 5/1326 Albany Hwy » Midland: 1/212 Gt Eastern Hwy » Myaree: 5A/116 N Lake Rd 08 9428 2188 08 9428 2166 08 9428 2167 08 9428 2168 08 9428 2169 08 9428 2170 New South Wales Queensland » Virginia: 1870 Sandgate Rd 07 3441 2810 » Prospect: 316 Main Nth Rd 08 8164 3466 South Australia © Altronics 2023. E&OE. Prices stated herein are only valid until date shown or until stocks run out. Prices include GST and exclude freight and insurance. See latest catalogue for freight rates. *All smartphone devices pictured in this catalogue are for illustration purposes only. Not included with product. B 0009 Please Note: Resellers have to pay the cost of freight & insurance. Therefore the range of stocked products & prices charged by individual resellers may vary from our catalogue. CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions will be paid for at standard rates. All submissions should include full name, address & phone number. ‘Huygens Beam’ beat frequency oscillator (BFO) metal detector In the March 2023 issue of Silicon Chip magazine, I introduced a regenerative BFO metal detector, which greatly boosted the range of a typical BFO detector (siliconchip.au/ Article/15706). This design joins two such detectors, introducing an innovation to stabilise operation, which is highly desirable in a metal detector. This circuit’s ease of set-up, stability, discrimination and sensitivity make it a metal detector to rival many published designs. On the surface, there is no real connection between the two detector circuits. However, it takes advantage of an effect that Christiaan Huygens first observed in 1665. Huygens hung two pendulum clocks on a beam, which after ~30 minutes, mysteriously began to tick in sympathy with each other. Here, a similar principle is used to cause the two BFO detectors to oscillate in sympathy with each other at about 160kHz. The ‘beam’ is the circuit’s positive rail in this case. The 270W resistor that limits the supply current to the circuit is critical to its siliconchip.com.au success. This causes the oscillators to pull on each other, achieving extraordinary stability. The disadvantage is that one can load this circuit only lightly. For this reason, a wire is attached to an AM radio aerial. The two circuits individually work as described in the Regenerative BFO description (March 2023 issue). Coils L1 & L2 need not overlap for the circuit to function. However, they must overlap about 40mm at the centre for discrimination to work. Due chiefly to varying component tolerances, one of the oscillators will run faster than the other. This faster oscillator requires VC1 for rough tuning to equalise the frequencies. A frequency counter may not be necessary, as LED1 extinguishes when the perfect frequency is found. Variable resistor VR1 is then used for fine-tuning. VC1 could be a preset capacitor, but you would need to figure out the approximate value to use first, or experiment with a few in the range of 0-270pF. Australia's electronics magazine The circuit may have other uses. For instance, if IC1a or IC2a pin 1 is attached to a fine metal grid, the circuit will perform as a stable Theremin. In this case, L1 and L2 may be replaced with small wire-wound inductors of roughly the same value. The circuit might even be stable enough to place the grid under a doormat, and it would then signal someone’s arrival via the radio loudspeaker or LED1. After the circuit has settled down for about a minute, the frequencies will usually stabilise. LED1 can be used instead of the radio for detection, but viewing fluctuations in light level is not very practical. No ballast resistor is required for LED1 due to the 270W resistor already limiting the circuit’s overall operating current. Note that the model of the hex inverter ICs could be critical to the operation of this circuit. In this case, I used the popular Texas Instruments CD40106BE. Happy hunting! Thomas O. Scarborough, Cape Town, South Africa. ($100) September 2023  31 Updated MPPT Solar Charger John Clarke’s last solar charger project, the February & March 2016 “Solar MPPT Charger & Lighting Controller” (siliconchip.au/Series/296), is quite refined, but it bugged me that it lacked a display. I realise that simple LED indicators are cost-effective and are all you really need, but I wished it could show more about the state of the charger, the solar panel and the battery. As the PIC16F88 that John Clarke used is getting close to being obsolete, I decided to create a version using an “Enhanced Mid-Range” PIC. 32 Silicon Chip I discovered that the PIC16F1847 (or -1827) is pin-compatible with the PIC16F88 but I would have to rewrite the software to suit this new chip. I ported the assembly language source code from the PIC16F88 to the PIC16F1847 but I had to go back to the older MPLAB IDE v8.92. This charger has handled a 12V 12Ah SLA battery and a few 3W LED lights with an 80W 12V solar panel for a couple of years without any problems. Four screens can be shown on the LCD: charge mode, solar panel state, Australia's electronics magazine battery state and load state. It can also display the temperature, relevant voltages, currents, power and PWM state. Since I needed to add an LCD screen to the design, I decided to design a new PCB. The circuit is similar to the 2016 design but with some tweaks and the added display, via header CON1. I initially intended to make a 10A/12V charger, but 10A seemed a waste as my evening load (LED lights) was rarely above 10W, and the solar panel rarely put more than 3A into the battery. By recalibrating it for 5A, I could use smaller 0.1W 3W current sensor resistors and 5A M205 fuses. If siliconchip.com.au designing the PCB again, I would go for mini blade fuses as used in most cars nowadays. For Sleep mode, Mosfet Q1 disables the LCD and turns off the battery voltage monitor divider via a Mosfet-based opto-coupler. This is necessary as bipolar transistor based opto-couplers introduced too much error due to their collector-emitter voltage drop. For simplicity, I used an LM335Z three-terminal temperature sensor (TS1) to measure the battery temperature and provide charge voltage compensation. The hardware would work with a 10kW NTC thermistor, although siliconchip.com.au the software would need changes to handle the non-linear characteristic of a thermistor. I used an MCP1702-5002E high-­ accuracy (0.4%) 5V regulator instead of a 78L05 regulator (typically only 5% accurate). That makes voltage measurements by the microcontroller much more accurate as it uses the 5V rail as a reference. The MCP1702 has a maximum input voltage of 14.5V compared to 35V for the 78L05 but consider that the 330W resistor in series with an input drops a few volts. I also added one LED in series with it, mainly as a power indicator, but Australia's electronics magazine 15V zener diode ZD2 ensures that its rating is not exceeded. I also changed Mosfet Q5 to the more commonly available IRF4905 type compared to what John used in his design. Pushbutton switch S1 is used to adjust the display. Short presses scroll through the menu while medium-­ length presses toggle the load on or off at any time. A long press reboots the unit. S1 enables equalisation charging if pressed during boot-up, which is indicated on the screen. Absorption charging is enabled once per day but is currently limited ...continued on page 35 September 2023  33 Audio Level Meter When using, maintaining and commissioning audio systems, I have always found it a bit difficult to measure system levels using a regular level meter. The levels to be measured can often be anywhere between -60dB to +30dB, depending on whether you’re dealing with (respectively) mic or line levels. The difficulty is borne of the majority of audio level meters, that use a linear (voltage) calibrated scale which at, say, just -20dB down, is reading only 10% of full scale. It is hard to get an accurate reading without constantly adjusting the scale setting. This circuit uses a logarithmic detector, and the re-scaled analog meter provides two scales at the flick of a switch. The scales read either -60dB to 0dB (nominally mic levels) or -30dB to +30dB (nominally line levels). This could have been done with a single scale, but that would result in a wide dynamic range being shown in a limited space. 34 Silicon Chip The unit I built has three inputs: XLR balanced, TRS balanced and TS unbalanced, all effectively connected in parallel. There is also a Hi-Z/Lo-Z switch to determine the input impedance of the balanced inputs. It is around around 6.2kW (unbalanced)/12.4kW (balanced) in the high position or around 600W in the low position. The AD8307 logarithmic detector IC is typically used in RF systems, as it will operate up to 500MHz. It will, however, work down to very low frequencies (20Hz or so), providing appropriate components are used. The circuit necessarily includes protection against picking up stray RF signals. The signal is fed from one of the three inputs at upper left to the first stage, a balanced input amp built around op amps IC1b & IC1a. The signals are AC-coupled and biased to half the Vcc supply, allowing it to work from a single 9V battery. The 100pF capacitors on both input legs provide a degree of RF immunity. Dual op amp Australia's electronics magazine IC1 is a rail-to-rail type due to the relatively low supply voltage. S3 switches VR1 and its 100W series resistor between the op amp inputs. This provides 30dB of signal attenuation for range switching. The output of the audio stage is then fed to the input of the AD8307 log amp, which is arranged as per the Analog Devices application note but with the capacitors values scaled up from picofarads to microfarads. The 50W input (RF) terminating resistors have also been completely removed. 1kW potentiometer VR2, in series with the AD8037 input, provides adjustment so it can work in the best input level window. I checked this by connecting a 0dBV signal at the audio input and adjusting VR2 while monitoring the DC output level of the AD8037 to the point where it began to compress. The output of the AD8307 is then fed to a threshold-adjustable DC amplifier (IC3b). The threshold is adjusted to just siliconchip.com.au A bit about decibels The term “decibel” (dB) derives from two sources. The “Bel” was initially developed by AT&T for measuring absolute and relative audio levels over long-line telecommunications systems and was named in honour of Alexander Graham Bell. It is simply a logarithmic ratio of two power values. If we double the power (eg, the power output of an amplifier), the log ratio would be close to 0.3. Accounting for the ISO prefix “deci” (one-tenth) by multiplying by ten, this becomes the familiar +3dB. A reference power level is often required, which was related to the nominal 600W impedance of an open-wire line back in the day. The 600W figure still (unfortunately) persists, and power levels in audio systems are sometimes specified in dBm or, more commonly, dBu. dBm is derived from the level of a signal that will provide 1mW into a 600W load, so 0dBm = 0.775V (RMS). dBu uses that same voltage reference but can be applied to any impedance level. The difference between dBV (where 0dBV = 1V RMS) and dBu is 20 × log(1.0 ÷ 0.775), thus 0dBV = +2.21dBu. You can convert the ratio of two voltages to a figure in decibels using the formula 20 × log (V1 ÷ V2), as we just did. This works because, if you double the voltage into a given load, you will get four times the power. move the output meter with an input level of -60dBV, ie, the lowest end of the meter scale. That output is then fed to a simple follower amp with a network ahead of it so that the meter will read either average or peak power, depending on S4; a very helpful tool in a ‘live’ environment. Potentiometer VR4 provides fullscale calibration by adjusting the output of a signal generator up from the -60dBV that was used above to 0dBV, then adjusting VR4 for full-scale deflection. Its value might need to change if you don’t use a 100μA FSD meter as I did. The dBV/dBu switch, S5, simply increases the meter reading by 2dB when switched to dBu (on). That is the difference between the two ‘standards’. I prefer to use dBV; dBu is related to a much older (dBm) standard when everything was referenced to (now non-existent) 600W long-line (telecom) impedances. I used a large, older-style analog meter for the best visibility. A digital meter could be used with some modifications, but the analog meter seems to provide an inherently better ‘feel’ for reading audio levels. I made a custom meter scale by carefully disassembling and removing the actual meter scale, flipping it over to the blank side and sticking down a label I printed. The AD8307 can be bought as a discrete component or as part of a small PCB assembly. Be careful ordering through the grey market; I have received several deliveries that weren’t even the correct component! Graham Bowman, Duncraig, WA. ($100) Continued: Updated MPPT Solar Charger to 30 minutes; when bulk charging, it goes directly to float charging if it reaches the endpoint voltage in under one minute. When there is no power from the solar panel or little power for 30 minutes, it goes into dusk mode. The screen then shows a timer, the battery temperature and the battery voltage. The load is generally off until dusk, when it automatically turns on (if the battery voltage is above 12.5V) to enable night garden lights, for up to four hours and 15 minutes (the default is three hours, but that can be changed by modifying the code). When the timer expires or the battery drops below 12.5V, it turns off the load and goes into sleep mode, disabling the LCD and everything else it can. In the sleep state, when sufficient siliconchip.com.au power is detected from the panels, it reboots to exit the sleep state and go back to normal charging. When it reboots, it switches the load on if the battery is above 12.5V, although the code could be changed to keep the load off after a reboot. The LCD backlight is connected across the load terminals, so it is on when the load is on (generally at night) and off the rest of the time to save power. The circuit draws about 20mA from the battery during operation with the LCD backlight on (not including any load current). It’s under 7mA with the load and thus LCD backlight off, and less than 0.1mA in the sleep state. Australia's electronics magazine In the sleep state, the chip wakes up periodically to see if any significant voltage is coming from the solar panel. If not, it goes back to sleep to save power. The software can be downloaded from: siliconchip.com. au/Shop/6/246 Phil Nicolson, Mentone, Vic. ($100) September 2023  35 Using Electronic Modules with Jim Rowe Analog Liquid pH Meter This module is designed to form the basis of a liquid pH meter, for testing the acidity or alkalinity of things like the water in fish tanks or swimming pools, or the liquid in a vat when you’re making beer or wine. It comes complete with two pH sensor probes, and can be easily hooked up to an Arduino or other microcontroller to form a pH meter. T he ‘pH’ of a liquid indicates how strong of an acid or alkali it is; or perhaps it’s midway between the two and thus ‘neutral’, like distilled water. In my school days (long ago!), we used strips of ‘Litmus paper’ to test this – the paper changed colour when it was dipped into a liquid, with the colour providing a guide to whether the liquid was an acid or an alkali. Nowadays, though, this kind of testing is done using a more precise device called a pH Meter. The concept of ‘pH’ was first proposed in 1909 by Soren Sorenson, a Danish chemist working at the Carlsberg Laboratory. It is generally regarded as indicating the inverse concentration of hydrogen (H+) ions in an aqueous liquid, or the ratio between H+ ions and OH− (hydroxide) ions in the liquid. As shown in Fig.1, the pH scale runs from 0 to 14, with 0 representing an extremely strong acid, like battery acid, and 14 representing an extremely strong alkali (or base), like liquid drain cleaner. In the middle of the scale (pH = 7) is the neutral point. The first electronic method for measuring pH was developed in 1934 by Arnold Beckman, a professor at the California Institute of Technology, to help local citrus growers test the pH of lemons they were picking. He formed a company to manufacture and market pH meters, and since then, pH meters have been used in a wide range of industries. They include testing water quality, swimming pool maintenance and wine or beer brewing. They are also widely used in healthcare and food processing. The pH probe The key component of a pH meter is the pH probe. This contains two electrodes, designed so that when they are both in contact with the liquid to be tested, a small voltage difference is developed between them. The polarity and amplitude of this voltage difference is proportional to the pH of the liquid. Originally, pH meters used two separate electrode probes: a hydrogen ion sensing probe and a reference probe. But nowadays, most pH meters use what is called a ‘combination’ probe, which includes both electrodes in a single probe body, shown in Fig.2. The main H+ sensing electrode is Fig.1: the table on the left shows the pH scale from zero to 14 with hydrogen and hydroxide concentrations (pH values normally lie in this range). The right-hand table shows example liquids with their typical pH values. 36 Silicon Chip Australia's electronics magazine siliconchip.com.au inside a small central glass tube which usually ends in a small spherical bulb of very thin, porous glass. This sensing electrode is generally made of silver, with a very thin silver wire used to make the electrical connection to it. The interior of this H+ sensing electrode tube is filled with a solution of silver chloride (AgCl), its electrolyte. The reference electrode is similar in construction, but housed in the outer part of the probe body and surrounded by a different electrolyte; usually, a solution of potassium chloride (KCl). This area of the probe ends in a porous ‘reference junction’ around the central glass tube, just above the glass sphere housing the main H+ sensing electrode. As a result, when the bottom of the probe is submerged in a liquid, a voltage difference is generated between the two electrodes. The small hole shown in Fig.2 near the top of the inner glass tube is provided because some of these probes are designed to allow the H+ electrolyte solution to be ‘topped up’ from time to time, if it has seeped away through the porous sensing membrane at the bottom. Many pH probes do not offer this feature, though. The electrical output of an ‘ideal’ probe is shown in Fig.3, which plots the voltage difference between the H+ electrode and the reference electrode for liquids with a pH varying from 0 to 14. The voltage rises from 0mV at pH = 7 to over +400mV for pH = 0 (red line), while it falls to beyond -400mV for pH = 14 (blue line). Both the red (acid region) and the blue (alkali region) lines have a slope of -59.16mV per pH unit, assuming the liquid being tested is at 25°C. So an ideal composite pH probe has a linear output voltage swing of from +414.12mV to -414.12mV for the pH range of 0-14, swinging positive for acids and negative for bases from 0mV at the pH = 7 neutral point. The output from a pH probe has a very high source impedance, typically between 10MW and 100MW. So it needs to be connected to a very high impedance load to avoid attenuation. (analog-to-digital converter) inside a microcontroller unit (MCU) like an Arduino. The module shown in the photos is a low-cost unit we obtained from an AliExpress vendor in China, “Mi Yu Koung”. It comes complete with two pH sensor probes (one ‘refillable’ and the other not), each with a 1m-long cable fitted with a BNC plug. They also came with a small container of electrolyte for topping up the refillable probe, four 10mm-long M3 screws and four matching nuts, for mounting the module. There was also a mounting nut and spring washer for the module’s BNC socket, providing the alternative option of mounting it behind a panel. This module ‘kit’ cost us $11.52 plus $9.75 for shipping, for a total of $21.27. We found an identical kit is available from an eBay supplier called Garmenthouse No.1, for just under $20 with free delivery. We found that another module called the DFRobot Gravity pH Meter V2.0 is available in Australia, from suppliers such as Core Electronics and element14. This one comes with only one pH probe, for about $82.00 plus $10 for express delivery. Module circuit details Returning to the module shown in the pictures, it is on a 42×32mm PCB with the input BNC socket protruding from one end, and a 6-pin SIL output header at the other. The full circuit is Fig.2: an example of a combination probe, which has both electrodes in a single probe body. The main electrode is located inside a very thin, porous glass membrane. Fig.3: the electrical output of an ‘ideal’ probe should be a linear change in voltage relative to pH as shown in this graph. The sensor module The job of the pH meter module is essentially to amplify this low output voltage swing from the probe, boosting it to a level where it can be measured accurately by the ADC siliconchip.com.au Australia's electronics magazine September 2023  37 Fig.4: the circuit diagram for a cheap pH module which was purchased from AliExpress. The top half of the circuitry involves processing the signal from the pH probe, while the lower half provides an analog signal indicating the module’s temperature. shown in Fig.4, but don’t be fooled by its apparent complexity. The only section involved in processing the signal from the pH probe connected to CON1 (the BNC socket) is the top half, involving shunt regulator VREF1, op amps IC1a and IC1b and, to a lesser extent, IC2a. The lower half of the circuit, involving IC2b, TH1, IC3a and IC3b, is purely to provide an analog signal indicating the temperature of the module, via pin 6 (TO) of CON2. That could be useful as a way to adjust for the temperature’s effect on the pH readings, although the module’s temperature won’t necessarily be the same as the temperature of the liquid being tested. The pH+ electrode signal from the probe via CON1 goes directly to input pin 3 of op amp IC1a. IC1 is a TLC4502, a dual self-calibrating precision CMOS op amp with an input bias current of only 1pA (0.001nA). It therefore provides very little loading to the signal from the pH+ electrode. Since IC1a has negative feedback applied via the 20kW and 10kW resistive divider, it amplifies the pH+ signal by three times, sending the amplified signal to pin 4 (PO) of output connector CON2. The purpose of the circuitry at upper left, involving VREF1 and IC1b, is 38 Silicon Chip to generate a ‘bias offset’ voltage to the pH− reference electrode of the probe. Since the output voltage from the probe can swing either positive or negative with respect to zero, that could be a problem for IC1a since its output can only swing between +5V and ground (0V). By feeding a bias voltage to the probe’s P− reference electrode, the These two buffer solutions were purchased from an Australian supplier and came in 125mL containers. Most buffer solutions will have tolerance of ±0.01pH, which explains the labelling of 7.01 for a 7pH buffer. Australia's electronics magazine pH=7 ‘zero’ voltage of the P+ electrode is shifted upwards so that the output voltage of IC1a at pH=7 moves up to +2.5V, allowing it to swing up or down without problems. This also means the ADC monitoring the output signal doesn’t need to be able to deal with negative voltages. Trimpot VR1 and the 5.1kW resistor reduce the 2.5V output of VREF1 to around 0.83V, which when amplified by three times by IC1a, gives the correct 2.5V offset. The offset voltage is buffered by voltage follower IC1b before being fed to the pH− probe connection of CON1. If the pH=7 output of the probe is exactly zero (as with an ideal probe), and the gain of IC1a is exactly three times, the bias voltage applied to pin 5 of IC1b would need to be exactly 2.5V ÷ 3 = 833mV. However, with a real probe and real resistors that differ from their nominal values, that might vary. VR1 allows the bias voltage to be adjusted until the output of IC1a is close to +2.5V when pH = 7. The circuitry at centre right in Fig.4, around VR2, IC2a and LED1 detects when the output voltage from IC1a rises above a certain threshold. IC2a is connected as a simple comparator, comparing the output of IC1a siliconchip.com.au Fig.5: a plot of the nominal output voltage over the full pH range for the module, taken at pin 4 of CON2 (PO). with a reference voltage set by trimpot VR2. So when the output voltage of IC1a rises just above that level, the output of the comparator will drop to near-zero and LED1 will light. The voltage level at pin 5 (DO) of CON2 will also drop to near zero, allowing the situation to be detected by the MCU if required. At the same time, LED2 simply acts as a power-on indicator. Fig.5 is a plot of the nominal output voltage of the module at CON2 pin 4 (PO) for the full pH range from pH=0 to pH=14. It should provide an output voltage of 2.50V for a pH of 7.0, rising to 3.74236V for a pH of 0 and falling to 1.25464V for a pH of 14. DFRobot Meter differences Before moving on, I should mention that the DFRobot Gravity pH Meter V2.0 module mentioned earlier only provides an amplified analog version of the pH probe’s output, with no added ‘frills’. It also allows the pH− output of the probe to be connected directly to ground. This is done by using a DC-DC converter to provide the main op amp with a -5V supply as well as the +5V supply. It is also provided with a mini polarised 3-pin output connector (instead of the 6-pin SIL header), siliconchip.com.au plus an output cable with a matching 3-pin plug. In addition, it comes with four small containers of pH standard buffer solution, two with pH = 7.0 and two with pH = 4.0. Connecting to an MCU Since the module has an analog voltage output within the 0-5V range and is designed to operate from a DC supply voltage of 5V, it is quite easy to connect it to an MCU such as an Arduino Uno or Nano. You just need to connect its + and - power pins to the +5V and GND pins on the MCU board, and its PO output pin to one of the MCU’s analog input pins, such as A0, as shown in Fig.6. Fig.6 also shows the Arduino connected to a 16×2 character alphanumeric LCD with an I2C serial interface, so it can display the pH reading. More about this shortly. Now we just need firmware to sense the module’s output voltage and convert it into the equivalent pH value. After a bit of internet searching, I found the website www.circuitdigest.com that has an article by Debasis Parida describing a pH Meter using the module we are focusing on here, together with an Arduino Uno and a 16×2 LCD display. Australia's electronics magazine A close-up of the tip of the probe that came with the pH meter module. You should just be able to see the two electrodes, The main electrode is a very thin winding wire in the centre. September 2023  39 Fig.6: a wiring diagram showing how to connect the pH meter module to an Arduino Uno or similar. We have also incorporated a 16x2 LCD module with I2C serial interface so that it can display the pH reading. He also provided an Arduino sketch, although there were a few drawbacks: he had a parallel interfaced LCD, rather than one with an I2C serial interface, and his code for converting the module’s analog voltage readings into equivalent pH values was a bit convoluted and difficult to follow. So I decided to write a sketch of my own. It is named “Arduino_pH_ meter_sketch.ino” and is available to download from the Silicon Chip website. When you upload the sketch to the Arduino and it begins running, it gives you this opening display: Silicon Chip Liquid pH Meter After pausing for two seconds, it starts measuring the output voltage from the pH amplifier module, converts it into the equivalent pH value and then displays both the pH value and the amplifier module’s output voltage, like this: pH = 7.0 Vaverage = 2.50V It continues doing this every two seconds. If you’re wondering why the second line displays “Vaverage”, that is because the sketch calculates the average of 10 measurements to compensate for minor fluctuations in probe output. The sketch also sends the pH value and the average module output voltage back to your PC or laptop via the Arduino’s serial port if you have it connected. So if you start up the Arduino IDE’s Serial Monitor, you’ll see the 40 Silicon Chip same information appearing every two seconds. Once you have the pH module and probe connected to an Arduino as in Fig.6 and have uploaded the sketch to the Arduino and seen that it works, there is still one further step before your pH Meter is ‘ready to go’. This the important step of calibration. Probe and module calibration This step is particularly important because every pH probe is slightly different in terms of its pH to voltage conversion characteristic. Before you can start using the probe seriously, you have to test its response with liquids at a minimum of two known pH levels. This calibration needs to be done not only before you start using the pH Meter, but every time you change probes or clean/refurbish your probe. Calibration is a two-step operation. First, you place the probe into a ‘neutral’ liquid like distilled water, with a known pH of 7.0. Then you can adjust trimpot VR1 on the module (the one nearer CON1, the BNC input connector) until the LCD readout gets as close as possible to show pH = 7.0 and Vaverage = 2.50V. The second calibration step is to place the probe into a different liquid, with a known pH that is well away from 7.0; say, 4.0 or 10.0. This will allow you to work out the effective slope of the probe’s transfer characteristic. If you get a pH reading that differs significantly from the correct figure, you can make a change in the Meter’s sketch to correct for this error. Australia's electronics magazine And while you can use distilled water for the pH 7.0 reference buffer, it is not so easy to find another liquid with a known pH of 4.0 or 10.0. You really need to get a reference solution from a reputable supplier. While you can find many suppliers of reference buffer solutions on the internet, many are overseas and can only supply them in large containers that cost a lot to ship. Luckily, I found a local Australian supplier offering two 125mL bottles, one of pH7 buffer and the other of pH4 buffer, for the modest cost of $15.50 plus $8.95 for shipping. This supplier is My Slice of Life Pty Ltd, located at Shop 2, 159 Vincent Road, Wangaratta Victoria 3677. Phone: (03) 5798 3489 Web: https://mysliceoflife.com.au I ordered one of these packs of buffer solution, and they can be seen in the photo. When they arrived, I was therefore able to have a go at calibrating the pH module and one of its probes. Running into difficulties Unfortunately, I soon struck a puzzling problem: when the hardware was hooked up as in Fig.6 and either of the probes connected to CON1 of the module with its tip end submerged in the pH = 7 buffer solution, no adjustment of trimpot VR1 would allow the pH value to be displayed at anywhere even close to 7.0. The maximum pH displayed remained no higher than 2.60, with Vaverage no lower than 3.28V – much higher than the correct figure of 2.50V. At first, I suspected that trimpot siliconchip.com.au VR1 was faulty, but when I replaced it, there was no change. Then I wondered if there might be a dry joint on the module’s PCB, in the vicinity of IC1. But resoldering any joints that looked dubious still didn’t cure the problem. So it wasn’t possible to calibrate the pH module with either of the two probes supplied with it. I suspected that either the probes themselves had ‘dried out’, or that IC1a has been damaged due to static charge on one of the probe cables. One further thing I should mention: I could not find any way to gain access to the ‘refill’ opening near the top of the refillable probe. The cover ring seemed to be stuck in position, so there was no way to top up its inner electrolyte. In the hope of providing some answers to these problems, we ordered another module and an accompanying non-refillable probe. When these arrived we tried seeing if the new module and/or the new probe would give more sensible results. Cutting a long story short, the replacement module and probe didn’t perform any better than the first ones. With the probe in a pH = 7.0 solution, trimpot VR1 still would not allow the value of Vaverage to be taken below 2.93V, giving a pH reading of 4.58. Way off! I tried various things to see if I could track down the cause of this problem, including re-checking my sketch to see if I had made any programming errors, measuring the actual gain of op amp IC1a (it turned out to be 2.997 – very close to 3.0) and trying to run the module from 3.3V instead of 5V. But none of these provided any clues as to the real cause of the problem. Then I decided to see if I could make trimpot VR1 able to bring the Vaverage level down to 2.50V when the probe was in a pH = 7 buffer solution. After a bit of experimenting, I found this could be done by connecting a 5.6kW resistor in parallel with the 5.1kW resistor connecting pin 5 of IC1b to ground, bringing its effective value down to 2.67kW. This allowed the module and probe to give correct readings of pH = 7 when the probe was in either distilled water or the pH7.00 buffer solution. Astute readers may have spotted the design flaw in the circuit earlier – the reference attenuator, including siliconchip.com.au trimpt VR1, does not have enough range to reduce the 2.5V reference to the 833mV needed for calibration. By shunting the 5.1kW resistor, we are fixing that flaw and providing enough range for correct calibration. Why it was designed this way is a mystery. However, when I tried swapping the probe over to the pH4.00 buffer solution, there was still a problem: the module was now giving a pH reading of around 5.14, rather than the correct 4.00. So I had to change the value of the variable “Senslope” in my Arduino sketch, from the ‘ideal probe’ figure of 0.05916 volts per pH unit to 0.0234. So finally, after fiddling with both the hardware and software, I was able to get the probe and module combination calibrated – at least, at the two pH levels of 7.0 and 4.0. Mind you, there was still no real explanation as to why these hardware and software changes were necessary. Nor was there any way to be sure that the output characteristic of the module was still linear, so the twopoint calibration would ensure correct pH measurements at levels well away from pH = 4.0 or pH = 7.0. After further testing and analysis, I determined that the high impedance of the probe and the module’s input circuitry means they pick up a fair bit of noise and 50Hz hum, causing the readings to vary up and down. This means that the module needs to be housed in an Earthed metal case, to provide shielding. That would at least give you a chance of being able to calibrate them out-of-the-box. Summarising I can’t give these particular modules and their probes a glowing report, given that I wasn’t able to achieve calibration using the normal procedure, and it’s unclear whether the readings could be relied upon over the full pH range! The circuit design may seem to make sense at a theoretical level, and the probes and modules seem to be made correctly. The problem is that they don’t provide sufficient instructions on how to assemble the device to avoid RF and mains hum pick-up from interfering with the results. We think the DFRobot Gravity pH Meter V2.0 is more likely to work without modification, given its higher price and availability from more repSC utable sources. The AliExpress module also includes two separate pH probes (one ‘refillable’ and the other not), a small bottle of electrolyte and some mounting hardware. Australia's electronics magazine September 2023  41 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. 09/23 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 24LC32A-I/SN ATmega328P Digital FX Unit (Apr21) Si473x FM/AM/SW Digital Radio (Jul21), 110dB RF Attenuator (Jul22) Basic RF Signal Generator (Jun23) ATmega328P-AUR RGB Stackable LED Christmas Star (Nov20) ATtiny85V-10PU Shirt Pocket Audio Oscillator (Sep20) PIC10F202-E/OT Ultrabrite LED Driver (with free TC6502P095VCT IC, Sep19) PIC10LF322-I/OT Range Extender IR-to-UHF (Jan22) PIC12F1572-I/SN LED Christmas Ornaments (Nov20; versions), Nano TV Pong (Aug21) PIC12F617-I/P Model Railway Level Crossing (two required – $15/pair) (Jul21) Range Extender UHF-to-IR (Jan22), Active Mains Soft Starter (Feb23) Model Railway Uncoupler (Jul23) PIC12F617-I/SN Model Railway Carriage Lights (Nov21) PIC12F675-I/P Train Chuff Sound Generator (Oct22) PIC16F1455-I/P Digital Lighting Controller Slave (Dec20), Auto Train Controller (Oct22) GPS Disciplined Oscillator (May23) PIC16LF1455-I/P New GPS-Synchronised Analog Clock (Sep22) PIC16F1459-I/P Cooling Fan Controller (Feb22), Remote Mains Switch Receiver (Jul22) PIC16F1459-I/SO Multimeter Calibrator (Jul22), Buck/Boost Charger Adaptor (Oct22) PIC16F15214-I/SN Tiny LED Icicle (Nov22), Digital Volume Control Pot (SMD; Mar23) Silicon Chirp Cricket (Apr23) PIC16F15214-I/P Digital Volume Control Pot (through-hole; Mar23) PIC16F1705-I/P Flexible Digital Lighting Controller (Oct20) Digital Lighting Controller Translator (Dec21) PIC16F18146-I/SO Digital Boost Regulator (Dec22) PIC16LF15323-I/SL Remote Mains Switch Transmitter (Jul22) W27C020 Noughts & Crosses Computer (Jan23) ATSAML10E16A-AUT PIC16F18877-I/P PIC16F18877-I/PT High-Current Battery Balancer (Mar21) USB Cable Tester (Nov21) 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) PIC32MM0256GPM028-I/SS Super Digital Sound Effects (Aug18) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sep19) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) RCL Box (Jun20), Digital Lighting Controller Micromite Master (Nov20) 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) $20 MICROS ATmega644PA-AU AM-FM DDS Signal Generator (May22) dsPIC33FJ64MC802-E/SP dsPIC33FJ128GP306-I/PT PIC32MX470F512H-I/PT PIC32MX470F512H-120/PT PIC32MX470F512L-120/PT 1.5kW Induction Motor Speed Controller (Aug13) CLASSiC DAC (Feb13) Stereo Echo/Reverb (Feb 14), Digital Effects Unit (Oct14) Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) Micromite Explore 100 (Sep16) $25 MICROS $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 PIC PROGRAMMING ADAPTOR KIT (CAT SC6774) (SEP 23) CALIBRATED MEASUREMENT MICROPHONE (AUG 23) Includes all parts, except the optional USB supply (see page 71, Sept23) $55.00 SMD version kit: includes the PCB and all onboard components except the XLR socket. You also need one ECM set (see below) (Cat SC6755) $22.50 Through-hole version kit: includes the PCB and all onboard components except the XLR socket. You also need one ECM set (see below) (Cat SC6756) $25.00 Calibrated ECM set: includes the mic capsule and compensation components; see pages 71 & 73, August 2023 issue, for the ECM options (Cat SC6760-5) $12.50 ARDUINO ESR METER (AUG 23) DYNAMIC RFID/NFC TAG (JUL 23) RECIPROCAL FREQUENCY COUNTER KIT (CAT SC6633) (JUL 23) BASIC RF SIGNAL GENERATOR (JUN 23) - 20x4 blue backlit LCD with I2C interface (Cat SC4203) - red & black PCB-mount banana sockets (two sets are needed; Cat SC4983) - two 1nF ±1% capacitors (Cat SC4273) Smaller (purple PCB) kit: includes PCB, tag IC and passive parts (Cat SC6747) Larger (black PCB) kit: includes PCB, tag IC and passive parts (Cat SC6748) GPS DISCIPLINED OSCILLATOR (MAY 23) - CH340G-based USB/serial module with panel-mount USB ext. (Cat SC6736) - NEO-7M GPS module with SMA connector (Cat SC6737) - GPS antenna with 3m cable and SMA connector (Cat SC6738) - DD4012SA 12V to 7.5V buck-converter module (Cat SC6339) SONGBIRD KIT (CAT SC6633) (MAY 23) DUAL RF AMPLIFIER KIT (CAT SC6592) (MAY 23) SILICON CHIRP CRICKET (CAT SC6620) (APR 23) Includes all parts required, except the base/stand (see page 86, May 2023) Includes the PCB and all onboard parts (see page 34, May 2023) Complete kit: includes all parts required, except the coin cell & ICSP header TEST BENCH SWISS ARMY KNIFE (APR 23) WIDEBAND FUEL MIXTURE DISPLAY (CAT SC6721) (APR 23) DIGITAL VOLUME CONTROL POTENTIOMETER (MAR 23) Short-form kit: includes PCB, all onboard SMDs, boost module, SIP reed relay & UB1 lid. Does not include ESP32 module, case, 10A relay or connectors (Cat SC6589) $50.00 - ESP32 DevKitC module with WiFi and Bluetooth (Cat SC4447) $10.00 - 3mm black laser-cut UB1 Jiffy box lid (Cat SC6337) $10.00 Short-form kit: includes the PCB and all onboard parts. Does not include the case, O2 sensor, wiring, connectors etc (see page 47, April 2023) $120.00 SMD version kit: includes all relevant parts except the $15.00 universal remote control and activity LED (Cat SC6623) $6.00/set Through-hole version kit: includes all relevant parts (with SMD PGA2311) $2.50 except the universal remote control and activity LED (Cat SC6624) $5.00 $7.50 Includes all parts, except the case, TCXO and AA cells (see page 57, July 2023) $60.00 Kit: includes everything but the case, battery and optional pot (Cat SC6656) - 0.96in SSD1306-based yellow/blue OLED (Cat SC6421) siliconchip.com.au/Shop/ $100.00 $10.00 $15.00 $20.00 $10.00 $5.00 $30.00 $25.00 $25.00 ACTIVE MAINS SOFT STARTER (FEB 23) Q METER SHORT-FORM KIT (CAT SC6585) (JAN 23) RASPBERRY PI PICO W BACKPACK (JAN 23) $60.00 $70.00 Hard-to-get parts: includes the PCB, transformer, relay, thermistor, programmed micro and all other semiconductors (Cat SC6575; see page 41, Feb23) $100.00 Includes the PCB, all required onboard parts (excluding optional debug interface) and the front panel. Just add a signal source, case, power supply and wiring $100.00 Complete kit: includes all parts in the parts list, except the DS3231 real-time clock IC (Cat SC6625; see page 56, January 2023) - DS3231 real-time clock SOIC-16 IC (Cat SC5103) - DS3231MZ real-time clock SOIC-8 IC (Cat SC5779) DUAL-CHANNEL BREADBOARD PSU $85.00 $7.50 $10.00 (DEC 22) Power Supply kit: complete kit with a choice of red + green, yellow + cyan or orange + white knob colours (Cat SC6571; see page 38, December 2022) Display Adaptor kit: complete kit (Cat SC6572; see page 45, December 2022) NEW GPS(/WIFI)-SYNCHRONISED ANALOG CLOCK $40.00 $50.00 (SEP & NOV 22) GPS-version kit: includes everything in the parts list with the VK2828 GPS module (Cat SC6472; see September 2022 p63) $55.00 WiFi-version kit: includes everything in the parts list with the D1 Mini module instead (Cat SC6472; D1 Mini is supplied not programmed, see November 2022 p76) $55.00 *Prices valid for month of magazine issue only. All prices in Australian dollars and include GST where applicable. # Overseas? Place an order on our website for a quote. PRINTED CIRCUIT BOARDS & CASE PIECES PRINTED CIRCUIT BOARD TO SUIT PROJECT SHIRT POCKET AUDIO OSCILLATOR ↳ 8-PIN ATtiny PROGRAMMING ADAPTOR D1 MINI LCD WIFI BACKPACK FLEXIBLE DIGITAL LIGHTING CONTROLLER SLAVE ↳ FRONT PANEL (BLACK) LED XMAS ORNAMENTS 30 LED STACKABLE STAR ↳ RGB VERSION (BLACK) DIGITAL LIGHTING MICROMITE MASTER ↳ CP2102 ADAPTOR BATTERY VINTAGE RADIO POWER SUPPLY DUAL BATTERY LIFESAVER DIGITAL LIGHTING CONTROLLER LED SLAVE BK1198 AM/FM/SW RADIO MINIHEART HEARTBEAT SIMULATOR I’M BUSY GO AWAY (DOOR WARNING) BATTERY MULTI LOGGER ELECTRONIC WIND CHIMES ARDUINO 0-14V POWER SUPPLY SHIELD HIGH-CURRENT BATTERY BALANCER (4-LAYERS) MINI ISOLATED SERIAL LINK REFINED FULL-WAVE MOTOR SPEED CONTROLLER DIGITAL FX UNIT PCB (POTENTIOMETER-BASED) ↳ SWITCH-BASED ARDUINO MIDI SHIELD ↳ 8X8 TACTILE PUSHBUTTON SWITCH MATRIX HYBRID LAB POWER SUPPLY CONTROL PCB ↳ REGULATOR PCB VARIAC MAINS VOLTAGE REGULATION ADVANCED GPS COMPUTER PIC PROGRAMMING HELPER 8-PIN PCB ↳ 8/14/20-PIN PCB ARCADE MINI PONG Si473x FM/AM/SW DIGITAL RADIO 20A DC MOTOR SPEED CONTROLLER MODEL RAILWAY LEVEL CROSSING COLOUR MAXIMITE 2 GEN2 (4 LAYERS) BATTERY MANAGER SWITCH MODULE ↳ I/O EXPANDER NANO TV PONG LINEAR MIDI KEYBOARD (8 KEYS) + 2 JOINERS ↳ JOINER ONLY (1pc) TOUCHSCREEN DIGITAL PREAMP ↳ RIBBON CABLE / IR ADAPTOR 2-/3-WAY ACTIVE CROSSOVER TELE-COM INTERCOM SMD TEST TWEEZERS (3 PCB SET) USB CABLE TESTER MAIN PCB ↳ FRONT PANEL (GREEN) MODEL RAILWAY CARRIAGE LIGHTS HUMMINGBIRD AMPLIFIER DIGITAL LIGHTING CONTROLLER TRANSLATOR SMD TRAINER 8-LED METRONOME 10-LED METRONOME REMOTE CONTROL RANGE EXTENDER UHF-TO-IR ↳ IR-TO-UHF 6-CHANNEL LOUDSPEAKER PROTECTOR ↳ 4-CHANNEL FAN CONTROLLER & LOUDSPEAKER PROTECTOR SOLID STATE TESLA COIL (SET OF 2 PCBs) REMOTE GATE CONTROLLER DUAL HYBRID POWER SUPPLY SET (2 REGULATORS) ↳ REGULATOR ↳ FRONT PANEL ↳ CPU ↳ LCD ADAPTOR ↳ ACRYLIC LCD BEZEL RASPBERRY PI PICO BACKPACK AMPLIFIER CLIPPING DETECTOR CAPACITOR DISCHARGE WELDER POWER SUPPLY ↳ CONTROL PCB ↳ ENERGY STORAGE MODULE (ESM) PCB DATE SEP20 SEP20 OCT20 OCT20 OCT20 NOV20 NOV20 NOV20 NOV20 NOV20 DEC20 DEC20 DEC20 JAN21 JAN21 JAN21 FEB21 FEB21 FEB21 MAR21 MAR21 APR21 APR21 APR21 APR21 APR21 MAY21 MAY21 MAY21 JUN21 JUN21 JUN21 JUN21 JUL21 JUL21 JUL21 AUG21 AUG21 AUG21 AUG21 AUG21 AUG21 SEP21 SEP21 OCT21 OCT21 OCT21 NOV21 NOV21 NOV21 DEC21 DEC21 DEC21 JAN22 JAN22 JAN22 JAN22 JAN22 JAN22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 MAR22 MAR22 MAR22 MAR22 MAR22 PCB CODE 01110201 01110202 24106121 16110202 16110203 16111191-9 16109201 16109202 16110201 16110204 11111201 11111202 16110205 CSE200902A 01109201 16112201 11106201 23011201 18106201 14102211 24102211 10102211 01102211 01102212 23101211 23101212 18104211 18104212 10103211 05102211 24106211 24106212 08105211 CSE210301C 11006211 09108211 07108211 11104211 11104212 08105212 23101213 23101214 01103191 01103192 01109211 12110121 04106211/2 04108211 04108212 09109211 01111211 16110206 29106211 23111211 23111212 15109211 15109212 01101221 01101222 01102221 26112211/2 11009121 SC6204 18107211 18107212 01106193 01106196 SC6309 07101221 01112211 29103221 29103222 29103223 Price $2.50 $1.50 $5.00 $20.00 $20.00 $3.00 $12.50 $12.50 $5.00 $2.50 $7.50 $2.50 $5.00 $10.00 $5.00 $2.50 $5.00 $10.00 $5.00 $12.50 $2.50 $7.50 $7.50 $7.50 $5.00 $10.00 $10.00 $7.50 $7.50 $7.50 $5.00 $7.50 $35.00 $7.50 $7.50 $5.00 $15.00 $5.00 $2.50 $2.50 $5.00 $1.00 $12.50 $2.50 $15.00 $30.00 $10.00 $7.50 $5.00 $2.50 $5.00 $5.00 $5.00 $5.00 $7.50 $2.50 $2.50 $7.50 $5.00 $5.00 $7.50 $20.00 $25.00 $7.50 $2.50 $5.00 $2.50 $5.00 $5.00 $2.50 $5.00 $5.00 $5.00 For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT 500W AMPLIFIER MODEL RAILWAY SEMAPHORE CONTROL PCB ↳ SIGNAL FLAG (RED) AM-FM DDS SIGNAL GENERATOR SLOT MACHINE HIGH-POWER BUCK-BOOST LED DRIVER ARDUINO PROGRAMMABLE LOAD SPECTRAL SOUND MIDI SYNTHESISER REV. UNIVERSAL BATTERY CHARGE CONTROLLER VGA PICOMITE SECURE REMOTE MAINS SWITCH RECEIVER ↳ TRANSMITTER (1.0MM THICKNESS) MULTIMETER CALIBRATOR 110dB RF ATTENUATOR WIDE-RANGE OHMMETER WiFi PROGRAMMABLE DC LOAD MAIN PCB ↳ DAUGHTER BOARD ↳ CONTROL BOARD MINI LED DRIVER NEW GPS-SYNCHRONISED ANALOG CLOCK BUCK/BOOST CHARGER ADAPTOR AUTO TRAIN CONTROLLER ↳ TRAIN CHUFF SOUND GENERATOR PIC16F18xxx BREAKOUT BOARD (DIP-VERSION) ↳ SOIC-VERSION AVR64DD32 BREAKOUT BOARD LC METER MK3 ↳ ADAPTOR BOARD DC TRANSIENT SUPPLY FILTER TINY LED ICICLE (WHITE) DUAL-CHANNEL BREADBOARD PSU ↳ DISPLAY BOARD DIGITAL BOOST REGULATOR ACTIVE MONITOR SPEAKERS POWER SUPPLY PICO W BACKPACK Q METER MAIN PCB ↳ FRONT PANEL (BLACK) NOUGHTS & CROSSES COMPUTER GAME BOARD ↳ COMPUTE BOARD ACTIVE MAINS SOFT STARTER ADVANCED SMD TEST TWEEZERS SET DIGITAL VOLUME CONTROL POT (SMD VERSION) ↳ THROUGH-HOLE VERSION MODEL RAILWAY TURNTABLE CONTROL PCB ↳ CONTACT PCB (GOLD-PLATED) WIDEBAND FUEL MIXTURE DISPLAY (BLUE) TEST BENCH SWISS ARMY KNIFE (BLUE) SILICON CHIRP CRICKET GPS DISCIPLINED OSCILLATOR SONGBIRD (RED, GREEN, PURPLE or YELLOW) DUAL RF AMPLIFIER (GREEN or BLUE) LOUDSPEAKER TESTING JIG BASIC RF SIGNAL GENERATOR (AD9834) ↳ FRONT PANEL V6295 VIBRATOR REPLACEMENT PCB SET DYNAMIC RFID / NFC TAG (SMALL, PURPLE) ↳ NFC TAG (LARGE, BLACK) RECIPROCAL FREQUENCY COUNTER MAIN PCB ↳ FRONT PANEL (BLACK) PI PICO-BASED THERMAL CAMERA MODEL RAILWAY UNCOUPLER MOSFET VIBRATOR REPLACEMENT CALIBRATED MEASUREMENT MICROPHONE (SMD) ↳ THROUGH-HOLE VERSION ARDUINO ESR METER (STANDALONE VERSION) ↳ COMBINED VERSION WITH LC METER WATERING SYSTEM CONTROLLER DATE APR22 APR22 APR22 MAY22 MAY22 JUN22 JUN22 JUN22 JUN22 JUL22 JUL22 JUL22 JUL22 JUL22 AUG22 SEP22 SEP22 SEP22 SEP22 SEP22 OCT22 OCT22 OCT22 OCT22 OCT22 OCT22 NOV22 NOV22 NOV22 NOV22 DEC22 DEC22 DEC22 DEC22 JAN23 JAN23 JAN23 JAN23 JAN23 FEB23 FEB23 MAR23 MAR23 MAR23 MAR23 APR23 APR23 APR23 MAY23 MAY23 MAY23 JUN23 JUN23 JUN23 JUN23 JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 AUG23 AUG23 AUG23 AUG23 AUG23 PCB CODE 01107021 09103221 09103222 CSE211002 08105221 16103221 04105221 01106221 04107192 07107221 10109211 10109212 04107221 CSE211003 04109221 04108221 04108222 18104212 16106221 19109221 14108221 09109221 09109222 24110222 24110225 24110223 CSE220503C CSE200603 08108221 16111192 04112221 04112222 24110224 01112221 07101221 CSE220701 CSE220704 08111221 08111222 10110221 04106221/2 01101231 01101232 09103231 09103232 05104231 04110221 08101231 04103231 08103231 CSE220602A 04106231 CSE221001 CSE220902B 18105231/2 06101231 06101232 CSE230101C CSE230102 04105231 09105231 18106231 01108231 01108232 04106181 04106182 15110231 Price $25.00 $2.50 $2.50 $7.50 $5.00 $5.00 $5.00 $7.50 $7.50 $5.00 $7.50 $2.50 $5.00 $5.00 $7.50 $7.50 $5.00 $10.00 $2.50 $5.00 $5.00 $2.50 $2.50 $2.50 $2.50 $2.50 $7.50 $2.50 $5.00 $2.50 $5.00 $5.00 $5.00 $10.00 $5.00 $5.00 $5.00 $12.50 $12.50 $10.00 $10.00 $2.50 $5.00 $5.00 $10.00 $10.00 $10.00 $5.00 $5.00 $4.00 $2.50 $12.50 $5.00 $5.00 $5.00 $1.50 $4.00 $5.00 $5.00 $5.00 $2.50 $2.50 $2.50 $2.50 $5.00 $7.50 $12.50 SALAD BOWL SPEAKER CROSSOVER PIC PROGRAMMING ADAPTOR REVISED 30V 2A BENCH SUPPLY MAIN PCB ↳ FRONT PANEL CONTROL PCB ↳ VOLTAGE INVERTER / DOUBLER SEP23 SEP23 SEP23 OCT22 SEP23 01109231 24105231 04105223 04105222 04107222 $10.00 $5.00 $10.00 $2.50 $2.50 NEW PCBs We also sell the Silicon Chip PDFs on USB, RTV&H USB, Vintage Radio USB and more at siliconchip.com.au/Shop/3 Image source: https://unsplash.com/photos/i2BcaGXomv0 Broadcasting in Australia 100 years of Broadcast Radio The story of early broadcast radio was very political, highly commercially competitive and steeped in controversy – both at the time and many years later. By Kevin Poulter A ustralians watched as major countries started radio broadcasting in 1919, including the Netherlands, Canada and the UK, then the USA in 1920. But we were not idle, with many amateur experimenters and large companies like AWA running test broadcasts and developing circuits. Many well-known international scientists and Australians developed the components and techniques to prove that radio was a viable news and entertainment medium. They also had to counter critics, who thought radio would be politicised, or would negatively influence family life. Marconi Italian inventor Guglielmo Marconi is acknowledged as one of the foremost driving forces for developing news and entertainment radio. Reminiscing in November 1931, he said: The seed for wireless was the discovery made by Michael Faraday, that it was not necessary for two electrical circuits to be in actual physical contact for electric energy to pass across a small space between them. This great discovery was followed by the masterly electromagnetic theory of [James] Clerk Maxwell, published in 1865, in which he clearly visualised the existence of electric waves in space. Scottish physicist Maxwell’s theory suggested that electromagnetic waves could be generated in a laboratory. Such wave generation was first 44 Silicon Chip demonstrated by German physicist Heinrich Hertz in 1887. In 1895, Marconi began research utilising electric waves for telegraphy across considerable distances. He successfully transmitted and received intelligible telegraphic signals over about 1¾ miles (2.8km). A microphone was essential Scottish-born Dr Alexander Graham Bell demonstrated the first practical form of the telephone in 1876. It was later modified for commercial use, employing a bar magnet, a speech coil at one end, and an iron diaphragm. For the carbon microphone, which was invented two years later, we are indebted to Professor David Edward Hughes (UK), Thomas A. Edison (USA) and Rev. Henry Hunnings (UK). The trio’s discoveries in this field were all made public in the same year, 1878. Fessenden’s Experiments Professor Reginald A. Fessenden (Canada/USA) made the first attempt to transmit speech through space by electric waves in 1900, communicating over a distance of one mile (1.6km). As is well known today, the speech waveform was superimposed on a high-frequency carrier wave, which must be unbroken, not intermittent. Still in the spark transmitter era, Fessenden endeavoured to make the wave trains of the sparks overlap to Australia's electronics magazine achieve continuous transmission by increasing the number to 10,000 per second. Spark-based radio transmitters had the advantage of simplicity, which was significant when most electronic components were costly as they had to be custom-made. However, sparks are broadband radiators, so such transmitters could not readily share the available spectrum. Hence, the technology was short-lived. Communicating across the Atlantic Ocean In 1906, Fessenden engaged a high-frequency alternator, which gave him a useful carrier wave of 20,000 cycles per second (20kHz). This enabled him to transmit speech from Brant Rock, Massachusetts to Jamaica, New York (USA) the following year, a distance of 300km (~190 miles). In the meantime, in December 1901, Marconi transmitted and received telegraphic signals across the Atlantic Ocean, from Poldhu in Cornwall to St John’s, Newfoundland, a distance of 3400km (~2100 miles). This showed that long-distance transmissions were possible, because the electrical waves would follow the Earth’s curvature around the globe. At the end of 1915, the American Telephone and Telegraph Co (AT&T), working in conjunction with the Western Electric Co, transmitted speech from the US naval station at Arlington, siliconchip.com.au Guglielmo Marconi with his wireless equipment on board his yacht “Electra”. At the time, he believed he had received radio signals broadcast from Mars. Virginia to the Eiffel Tower Station, Paris, a distance of 6200km (~3800 miles). Over 300 valves were used in the oscillator and modulator circuits! 1920: a memorable year The year 1920 is memorable for several important wireless telephone transmissions that had both news and entertainment value and thus had the same character that broadcasting has today. Australia’s world-renowned opera singer Dame Nellie Melba gave her first broadcast recital on the 15th of June 1920, from Marconi’s New Street Works factory in Chelmsford, UK. She was shown around the factory, including the roof area, where the imposing transmission tower was visible. On seeing the height, she said, “Young man, if you think I am going to climb up there, you are sadly mistaken!” Such was the lack of knowledge of how radio worked. On the 30th of May 1924, Marconi spoke from Poldhu to Sydney, thus conveying intelligible speech by wireless from England to Australia for the first time. That was a distance of 17400km (~10800 miles). The first broadcast demo The first radio demonstration “broadcast” in Australia is normally credited to Ernest Thomas Fisk of Amalgamated Wireless (Australia) Ltd (AWA) on the 19th of August 1919. siliconchip.com.au However, many others were making experimental transmissions around that time. Fisk arranged for the national anthem to be broadcast from one building to another at the end of a lecture he gave on the new medium to the Royal Society of New South Wales. Government permission After two further years of exhaustive experiment and demonstration, in 1920, AWA and several other commercial interests approached the federal government for permission to establish systematic broadcasting as a public service. A conference was called by the Postmaster-­G eneral’s Department (PMG, part of which became Telstra), which was held in Melbourne in May 1923. It was this occasion that saw the genesis of commercial radio in Australia. Internationally-famous Australian opera singer Dame Nellie Melba sang over the airwaves at the Marconi building in 1920. that the station licensees should make their own subscription charges. The most controversial feature of the sealed sets was that only one of two stations could be received. The stations pushed the federal government for this feature, thinking it was a brilliant idea – forcing listeners to listen to only their station. The public thought it was a dreadful idea, Sealed receiver sets The conference unanimously decided on a scheme that became known as the “Sealed Set Scheme”. This meant A 1923 sealed set made by AWA, restored by Robert McGregor. The public was not happy with the single-station reception of such sets. Australia's electronics magazine 45 Confusion over the date of the first commercial broadcast In researching the dates in this article, I came across some incorrect dates that were published several times. For example, The Sun newspaper (Sydney, NSW), published on Tuesday, 9th of November 1948, stated that 2FC began broadcasting on the 5th of December 1923. However, that was the official opening ceremony for the station, not the first day of broadcasting. Another example is from the editorial “HIGH STANDARDS OF AUSTRALIAN RADIO”, published in The Sun (Sydney, NSW) on Wednesday 1st of July 1953, on page 3: “The first commercial broadcast went on the air in Sydney in 1923”. That is not correct if you consider that it wasn’t until 1924 that the first ads appeared on the radio in Sydney (which I consider necessary for them to be ‘commercial’). The dates given in this article are clear enough in the newspapers published at the time and are supported by the findings of several of my peers. and let the government know in no uncertain terms. The four stations that supplied services under this scheme were: • 2SB Sydney, owned by Broadcasters Sydney, Limited, subsequently renamed to 2BL. • 2FC Sydney, owned by Farmer & Company. • 3AR Melbourne, owned by Associated Radio Company. • 6WF Perth, owned by Westralian Farmers, Limited (now known as Wesfarmers). Under the “Sealed Set Scheme”, the listener in Sydney had to decide which of the two stations they desired to listen to, then pay the company controlling that station a fee of either £10/(for 2SB) or £63/- (for 2FC). However, between the 1st of October 1923, and the 30th of June 1924, only 1400 listeners were licensed under these new regulations. The first Australian broadcast The first officially-licensed broadcast station to go to air was 2SB Sydney (soon renamed 2BL), at 8pm on the 23rd of November 1923. The station was established by a small company, “Broadcasters (Sydney) Limited”. Note that this was not a ‘commercial broadcast’ as there were no ads on the station in those early days. Before this event, Australia’s leading amateur, Charles MacLurcan, received a licence for his 2CM station in Sydney in 1921. However, it was primarily an experimental station, so most By 1924, thousands of Australians were making wireless receivers, producing programs, magazines & selling radios. The horn speaker petals are made of thin timber. – including the media at the time – credit 2SB as the first fully established station, with corporate backing, well-published, regular programs and receivers available at a range of radio stores. Early broadcasts came increasingly under the jurisdiction of the PMG, which was one of the reasons that MacLurcan left the broadcast band and transmitted on short wave. Commercial radio broadcasting, with paid advertising, commenced in 1924. During the evening of the 23rd of November 1923, people across Sydney gathered eagerly in their homes around pieces of wondrous new technology to hear the first radio broadcast in Australia. At precisely 8pm, they tuned in to hear the St Andrews Choir with soloists Misses Deering & Druitt and Messrs Saunders, Pick & Thorp. The ensemble performed “Le cygne” (The Swan) from Camille Saint-Saens’ Carnaval des animaux (The Carnival of the Animals). The advent of the ‘wireless’ and the first radio broadcast was a keenly anticipated event. The radio station’s call sign was 2SB, for Broadcasters (Sydney) Ltd. The company staff breathed a sigh of relief at the success of their radio broadcast, particularly as they had beaten their rival station, Farmer and Co (2FC), who did not achieve transmission for another two weeks (starting on the 5th of December 1923). Soon after their initial broadcast, 2SB changed their call sign to 2BL. 2FC went on to become Radio National. More about the stations The pioneer broadcasting station of Australia was 2BL (Sydney). This station, with its aerial system, was located on the “Daily Guardian” building in Phillip Street, Sydney. The station was designed by radio experts and was very successful in transmitting over long distances, no doubt enabled by the lack of electrical interference at that time. Farmer’s station Renee Kelly performed on stage in the UK and the USA, then Australia. She broadcast on 3LO on Christmas night in 1925. 46 Silicon Chip Australia's electronics magazine Station 2FC (Sydney) was next in the field, and it was claimed to be one of the most up-to-date stations in the world. It was constructed by Amalgamated Wireless (Australasia) Ltd (AWA) for Farmer and Co Ltd. The aerial system was a cage type, siliconchip.com.au suspended between two lattice steel towers, each 200 feet (61m) high and about 600 feet (183m) apart. The transmitting apparatus was described as most modern, and the station had no trouble working over long distances. Landlines connected the studios with theatres etc. Music and speech from these places and the studios were sent to the Northbridge station by landline for transmission. Westralian Farmers The next big station was that of Westralian Farmers Ltd, Perth. This station was supplied by AWA – it was manufactured in Sydney and transported to Perth. The aerial system was on top of the West Australian Farmers building, Murray Street, Perth. The masts were 180 feet (55m) above the pavement and 270 feet (82m) apart. The studios were located in the same building and were very large, to accommodate bands, choirs etc. As with the other studios, this one was designed with a view to making it absolutely soundproof. The Premier of Western Australia (Philip Collier) officially opened station 6WF on the 4th of June 1924. Melbourne station Melbourne’s broadcasting station was located at Braybrook, about six miles (~10km) from the city’s centre. It was built by AWA for the Australian Broadcasting Company (ABCo). The station was on a four-acre (16,000m2) area of flat land. Two lattice steel masts supported the aerial system, each 200 feet (61m) high and 575 feet (175m) apart. The operating house and quarters for the staff were situated directly beneath the aerial. The transmitting set was of the latest type, and the station was considered one of the best in the southern hemisphere. The station studios were located on the roof of the Melbourne Herald newspaper office, the music and speech being conveyed to the transmitting station by a landline. The following year, 2KY Sydney, 2UW Sydney, 2MK Bathurst, 3UZ Melbourne and 4GR Toowoomba were licensed. During the next year (1926), three more licences were issued: one to 2GB Sydney, one to 3DB Melbourne and the other to 5KA Adelaide. The sealed system was an outstanding failure. It was replaced in 1924 siliconchip.com.au Left: a GECoPHONE BC2050 five-valve receiver from 1924/5. Right: a GECoPHONE BC2001 (1922-24) two-valve receiver (HF and detector). It was an Australian sealed set. The radio is sitting on a matching BC2580 (1923-24) low-frequency amplifier. From Evan Murfett’s collection. with an ‘open’ system. The new system comprised two groups of stations: Class A and Class B. Class A stations received revenue from licence fees paid by listeners and from limited advertising, while all revenue for Class B stations came from advertising. In 1929, the federal government acquired all Class A stations, which were then operated by the PMG with programming supplied by the ABC. The number of listeners’ licences in the country had grown from 1400 at the end of 1924 to 329,600 by October 1930. In 1937, there were 21 national stations on the air, and 80 commercial stations were operating, while the number of listeners’ licences had risen to 940,068. This grew to 101 commercial broadcasting stations and, by the end of 1948, the number of listening licences was approximately 1.8 million. There should have been more licences, but some people could not afford a radio licence. Knowing there were radio inspectors who could knock on their door at any time to look for unlicensed radios, some residents hid their radio, or removed the valves between uses so they could say it was not working. Radio went on to become a massive industry, with millions of radios in Australian homes and vehicles. SC References ● Let’s look at radio: a review of commercial broadcasting in Australia, by the Australian Federation of Commercial Broadcasting Stations, circa 1950 (https:// catalogue.nla.gov.au/Record/1661052) ● Listener In magazine, 10th of January 1925 ● Listener In magazine, 17th of January 1925 ● The Sydney Evening News Wireless Handbook, 1924 (https://catalogue.nla. gov.au/Record/1715208) ● The Dawn of Australia’s Radio Broadcasting, an Electronics Australia publication by Philip Geeves, 1993 ● The Magic Spark, 50 years of Radio in Australia, by R. R. Walker, 1973 ● Various issues of Wireless Weekly magazine ● HRSA Members: Ron Langhans, Bruce Carty (https://austamradiohistory.com), Richard Begbie and Robert McGregor. Australia's electronics magazine September 2023  47 We have the perfect gift for father’s day! Australia’s top electronics magazine Don’t fret about what gift to give your Dad for Father’s Day when you can give him a subscription to Silicon Chip, one of the best DIY electronics magazines in the world. It’s also the perfect time to lock in a subscription before prices go up in November. If you have an active subscription you receive 10% OFF orders from our Online Shop (siliconchip.com.au/Shop/)* Published in Silicon Chip Rest of World New Zealand Australia * does not include the cost of postage Length Print Combined Online 6 months $65 $75 $50 1 year $120 $140 $95 2 years $230 $265 $185 6 months $80 $90 1 year $145 $165 2 years $275 $310 6 months $100 $110 1 year $195 $215 2 years $380 $415 All prices are in Australian dollars (AUD). Combined subscriptions include both the printed magazine and online access. Prices are valid for month of issue. Try our Online Subscription – now with PDF downloads! High-Altitude Aerial Platforms; August 2023 Watering System Controller; August 2023 Electric Vehicle Charging; July 2023 Dynamic NFC Tag; July 2023 An online issue is perfect for those (and their partners!) who don’t want too much clutter around the house and is the same price worldwide. To start your subscription go to siliconchip.com.au/Shop/Subscribe 21 DIGITAL CONTROL PANEL Great Gifts for Dad ON SALE 23.08.2023 - 03.09.2023 1500+ OF DAD'S FAVOURITE GAMES CONNECTS TO YOUR TV OR MONITOR NOW FROM 179 $ SAVE $120 NOW 199 $ SAVE $50 BARGAIN BUNDLE Retro Arcade Game Console 1.28" TOUCHSCREEN SAVE $29.95 Features phone push notifications, heart rate & blood pressure monitor and more. Smart Band QC3112 RRP $19.95 Smart Watch QC3110 RRP $59.95 HALF PRICE WIDE 170° ANGLE LENS In-Car Handsfree Kit 1080p HD DVR Dash Camera FM transmitter. Make calls or stream music from a Smartphone. Dual USB ports. 2.9A shared. AR3140 Automatic recording on impact with G-sensor function. Records to microSD (sold separately). QV3872 Boom Box with Bluetooth®, Cassette and Radio SPECIAL OFFER 4995 $ XC0366 NOW FROM 5995 $ . SAVE<at>$100 Wireless Weather Stations Measures and records temperature, humidity, wind speed, XC0434 wind chill etc. Includes moon phase display, calendar & more. Range of compact, monochrome, and colour display models available. XC0366-XC0440 1 hour click & collect available Scan code to find your local store 2.5" LCD . . SAVE 40% Smart Watches NOW 3995 $ 95 QC3112 95 NOW 14 $ QC3110 49 Great compact fridges with enough space to keep dad's food and drinks cold for day trips and light-packed weekenders. Standard GH1623 NOW $179 Optional Battery Powered* GH2068 NOW $229 * Battery sold separately SEE MORE OFFERS ON THE BACK PAGE All in one gaming console with over 1,500 solo and multi-player games. Includes a 32GB microSD card to add your own games. Ages 15+. GT4286 BUY BOTH FOR ONLY $ 12V 15L Portable Fridge/Freezers NOW HURRY, LIMITED STOCK GO RETRO CRANK UP THE TUNES SAVE $30 Just like an old style ghetto blaster but with modern features. AM/FM/SW radio Cassette, USB & SD card playback & recording Stream music from your Bluetooth® enabled device CS2443 Enjoy free delivery on online orders over $99* at jaycar.com.au *Conditions apply - see website for full T&Cs. For Car Loving Dads 12,000MAH POWERBANK WIRELESS QI CHARGER 110° VIEWING ANGLE 2 X USB PORTS 4.1A SHARED 66 37 MB 5" LCD TORCH & SOS BEACON NOW FROM 199 $ SAVE<at>$100 WATERPROOF UP TO 1000A 199 $ WILL START ALMOST ANYTHING! 12V Compact Jump Starter, Powerbank & Wireless QI Chargers SAVE $80 NOW 79 95 . EA SAVE<at>$20 19 95 89 SAVE 15% Automatic recording on impact. Wide 140° angle lens. Records to microSD card (sold separately). 12/24VDC. QV3848. 16GB microSD card XC5015 $12.95 ONLY 149 $ $ SAVE<at>$40 GREAT VALUE 12VDC High Performance Air Compressor Compact and lightweight with easy-to-use controls. Quickly inflate tyres or power air tools with 160L/min airflow and 150psi output. MC7204 *Please note password 123456 is needed for B/T connection. NOW 69 $ 80 PCE . GPS 1080p Dash Camera with GPS & Wi-Fi Easy to install and use. 2.4GHz digital signal for crystal clear picture. 12-24VDC operation, also suitable for trucks. QM3842 Designed for charging and maintaining the battery in your car, caravan, boat etc. Suit LiFePO4 and Lead Acid batteries. 6/12VDC 4A 8 Stage MB3906 NOW $89 SAVE $30 (Shown) 12/24VDC 7.5A 10 Stage MB3908 NOW $119 SAVE $40 Accurately identify car problems. View vehicle speed, RPM, fuel consumption, fuel pressure etc. With 2.4" LCD PP2147 NOW $79.95 SAVE $10 With Bluetooth® PP2145 NOW $79.95 SAVE $20 $ SAVE $40 Bluetooth® Intelligent Multi-Stage Battery Chargers ODB-II Engine Code Readers NOW INFRARED FOR NIGHT VISION NOW FROM PP2147 $ 2.7" LCD 149 Wireless Reversing Camera Kit Features high-powered jump starter, powerbank and torch. 850A Able to jump start a 3.0L diesel or 5.0L petrol motor. MB3764 NOW $199 SAVE $70 1000A Able to jump start a 5.0L diesel or 7.0L petrol motor. MB3766 NOW $249 SAVE $100 NOW $ NOW 95 REFLECTS CORRECTLY ONTO WINDSCREEN NOW 99 $ . SAVE $20 Automotive Crimp Tool with Connectors SAVE $40 Head Up Display Speedometer with GPS & OBD-II Data Keep your eyes on the road and read important driving info, such as speed, reflected off the windscreen. OBD-II or GPS operation. LA9036 Cut and strip wire and crimp connectors. TH1848 STAY SAFE ON THE ROAD Personal Breathalyser Mouthpieces and 1 x AA battery supplied. QM7320 Note: Readings are for reference only. We hold no responsibility for the use of these devices. Gifts for Dad's Car NOW FROM 19 $ $ . NOW 1995 $ . EA SAVE<at>30% NOW 1995 $ . SAVE 20% SAVE 20% BUILT-IN VOLTMETER . SAVE 25% HS9039 Universal Phone Holder Suction cup & air vent mount models available. HS9039-HS9048 12V RGB LED Light Strips for Car Interior Add colour and lighting effects to your car interior. SL3948 NOW 2795 95 12V 6" Oscillating Fans Suction mount GH1399 NOW $19.95 SAVE $5 Clamp mount GH1400 NOW $24.95 SAVE $8 Dual Car Cigarette Lighter Adaptor with 3 x USB Ports GH1400 Expand your 12V socket and add USB A & C charging to your vehicle. PP2119 The perfect gift idea, guaranteed! Gift cards can be purchased in increments of $20 to $500* *Conditions apply - see page 3 for full T&Cs. For Dad's Outdoor Adventures WIRELESS QI CHARGER ULTRA BRIGHT 1W LED LIGHT 12V OUTPUTS MI5308 ZM9049 NOW FROM NOW FROM 29 $ 44 95 $ SAVE<at>$10 95 449 SAVE $50 150W to 1500W Modified Sine Wave Inverters High efficiency, small footprint solar panel kits with leads and clips. 5W ZM9049 NOW $29.95 SAVE $5 10W ZM9051 NOW $49.95 SAVE $10 20W ZM9052 NOW $59.95 SAVE $10 NOW FROM 49 $ 44 95 95 WEATHERPROOF LED TORCH BUY 2 FOR 298 $ . SAVE $15 SAVE $100 WIRELESS QI CHARGING 550 Lumen Rechargeable Head Torch Powerbanks with Wireless QI & Solar Recharging 10,000mAh MB3828 NOW $49.95 SAVE $10 20,000mAh MB3830 NOW $89.95 SAVE $10 Adjustable light beam and head strap. High, low & flashing modes. ST3299 NOW 249 $ 500W PURE SINE WAVE INVERTER FOR ALL YOUR CAMPSITE POWER NEEDS Advanced, compact, feature rich and lightweight. Keep your 12V, USB and mains powered devices running when you don’t have access to mains power. MB3774 SAVE $10 . 4 USB PORTS 300Wh Portable Power Station Get 230VAC (mains) from 12/24VDC (i.e. batteries). Ideal for powering small to medium appliances such as laptops and phone chargers. 150W up to 1500W models available. MI5300-MI5310 NOW NOW $ SAVE<at>$50 12V Compact Solar Panels with Clips $ MI5302 REMOVABLE FLEXIBLE ANTENNA IP67 WEATHERPROOF M B 3 82 8 4K SAVE $30 4K Outdoor Trail Camera NOW 99 $ 200W Inverter with 4 USB Outlets Monitor local wildlife or use as an outdoor security camera. Motion detection and time lapse recording. QC8051 32GB microSD Card XC5016 $19.95 12PK AA Batteries SB2333 $8.95 SAVE $20 Powers 230VAC equipment like shavers, battery chargers and small laptops from your car's 12V battery. 2 X USB ports (5VDC, 2.1A). Modified sine wave. MI5131 5W Handheld UHF Radio 80 channels. Up to 20km range. Feature packed with VOX hands-free function, CTCSS and more. Rechargeable batteries and charging cradle included. DC1068 RRP $199EA WATER RESISTANT HOUSING Gifts for the Outdoor Dad BUILT-IN WHISTLE NOW 4995 WEATHERPROOF $ . NOW 14 95 $ . SAVE $5 Multi-function Survival Knife Fire starter, belt cutter, window breaker. TH1960 Age restriction laws apply in some Australian states. SAVE $20 NOW 24 $ 95 HEATS UP IN MINUTES . SAVE $10 Mosquito Zapper with LED Lantern Multiple light modes. Rechargeable. YS5544 NOW 24 95 $ . 12V Kettle SAVE $10 Features a water level window, auto-shut off and a boil dry protector. GH1386 12V Portable Stove Cook and warm up food whilst on the road or at the campsite. 3L capacity. YS2811 TERMS & CONDITIONS: Prices valid from 23/08/23 to 3/09/23. Stock may be limited on sale items. No rain checks. Savings on Original RRP (ORRP). For full gift card T&Cs see www.jaycar.com.au/giftcards. Page 1: BUNDLE: Buy 1 x QC3110 & 1 x QC3112 for $49.95. Page 3: MULTIBUYS: 2 x DC1068 for $298. Page 6: MULTIBUYS: 2 x GT4106 for $29. Page 8: MULTIBUYS: 2 x AA2165 for $29. 2 x ST3522 for $40. 2 x MB3810 for $49. 10% OFF BRASS MONKEY ACCESSORIES with purchase of a full priced Brass Monkey fridge/freezer. Excludes Lithium Batteries. Discount on accessories applies at time of purchase. All items must be purchased in the same transaction. SUPPLY CHAIN DISRUPTION. We apologise for factors out of our control which may result in some items not being available on the advertised on-sale date of the catalogue. + For details and terms on payment options see www.jaycar.com.au/paymentmethod. DIY Networking & Security ELIMINATE WI-FI DEAD SPOTS NOW FROM 499 $ PLUGS STRAIGHT INTO A POWER POINT YN8374 64 ALL IN ONE, EASY TO INSTALL Dual Band Wi-Fi Range Extenders Features two-way audio, built-in infrared LEDs for night vision up to 12m, and Thermal Detect Technology. Records to NVR or cloud. Expandable to 8 cameras. with 2 Battery Cameras QV5520 NOW $499 SAVE $100 with 4 Battery Cameras QV5522 NOW $849 SAVE $150 Boost your network's coverage to hardto-reach areas and provide, wall-to-wall Wi-Fi connectivity. 1200Mbps, 1800Mbps and high power models available. YN8372-YN8376 Includes: Network Video Recorder, power cable, mouse & HDMI cables. 24 2 Way Powerboard with 4 USB Ports Connect mains equipment and charge multiple USB devices from a single outlet. MS4104 27 95 Extend the connectivity of your devices with these slimline hubs. 4 Port XC4979 7 Port XC4957 44 YN839 5 . Bullet Camera QC3864 NOW $99 SAVE $40 PTZ Camera QC3859 NOW $109 SAVE $40 PTZ Camera w/ Solar Panel QC3908 NOW $229 SAVE $70 10/100/1000Mbps Ethernet Switches Provide additional ports to an internet router, firewall, or a standalone network. Supports ultra-fast gigabit speeds. 5 Port YN8395 ONLY$44.95 8 Port YN8397 ONLY $69.95 NOW 95 SAVE $5 QC3908 FOR STANDBY, EMERGENCY & BACK-UP POWER APPLICATIONS FROM 3995 $ EA . Regulated output voltage. Suitable for thousands of different applications. 7 output plugs. 5V to 12V. 1.5A to 3A. MP3480-MP3486 44 $ PAN TILT ZOOM Weatherproof Outdoor IP Cameras Slimline Mains Power Adaptors . USB 3.0 Hubs 95 SAVE<at>$70 95 . FROM $ 99 $ ONLY $ FROM 26 $ . SAVE $10 REPLACE YOUR LOST OR BROKEN POWER SUPPLIES 79 49 XC 95 6995 NOW FROM Wireless 2K 8 Channel NVR Kit SAVE<at>$30 $ NOW FROM $ Bullet Camera QC3906 NOW $69.95 SAVE $10 Pan Tilt Camera QC3900 NOW $89.95 SAVE $10 95 ONLY Wireless security cameras ideal for the home and office. All models feature easy setup, 2-way audio, motion detection, infrared night vision, and more. Records to microSD card (sold separately). Indoor & Outdoor options available. Indoor IP Cameras NOW FROM $ 1TB HDD 2 YEAR WARRANTY REMOTE VIEWING VIA SMARTPHONE ON ALL MODELS QC3900 SAVE<at>$150 1080p Smart Wi-Fi IP Cameras PERFECT FOR APPLE® MACBOOK® AND ULTRABOOKS® 12V Alarm & NBN Backup Batteries Avoid being left unsecure or without internet and comms in case of power outage. 7.2Ah SB2486 ONLY $39.95 9.0Ah SB2487 ONLY $46.95 FROM 179 $ SMART POWER BACK-UP Uninterruptible Power Supplies Keep your surveillance system, PC and other devices running longer during a power failure. 650VA/390W Up to 25min backup time MP5205 ONLY $179 1500VA/900W Up to 94min backup time MP5207 ONLY $379 USB 3.0 Ethernet Converter Connect an Ethernet cable to an existing USB port. YN8418 Tech Gifts for Dad FOLDS DOWN FOR EASY STORAGE MB3671 NOW FROM 2495 $ SAVE<at>$10 2995 $ MB3673 15W Wireless Qi Chargers Pad MB3671 NOW $24.95 SAVE $8 Stand MB3673 NOW $29.95 SAVE $10 NOW SAVE $20 Folding Bluetooth® Headphones with FM Radio Great sound with built-in mic. AA2128 ALARM CLOCK & WIRELESS CHARGER NOW 3495 $ SAVE $30 LED Clock with Light & 10W Wireless Qi Charger Features twin alarm, USB A port and more. AR1940 Smartphone not included. NOW 3995 $ SAVE $10 DAD CAN TAKE HIS BEATS ANYWHERE 8.5W RMS Mini Bluetooth® Boom Box Built-in FM radio. AUX, USB or SD card playback. Rechargeable. CS2469 DAD CAN WATCH TV WITHOUT WAKING THE FAMILY For Dad's Home Entertainment 299 GREAT VALUE NOW 12V HD Off-Grid Android Smart TVs SAVE $30 2.4GHz Wireless Rechargeable Stereo Headphones Hours of listening, plus charging dock. Direct digital TOSLINK connection. AA2036 XC5242 Suitable for caravans and other places where mains power might not be available. Includes Bluetooth® remote. 24" GH5190 ONLY $299 32" GH5192 ONLY $349 GH5192 3 X HDMI, 2 X USB, AV & ETHERNET INPUTS NOW FROM 119 $ NOW FROM 5995 $ . SAVE<at>$30 DAD CAN LISTEN TO NEWS FROM AROUND THE WORLD SAVE $30 World Band Radios Waterproof 360° Speakers with Bluetooth® Great True Wireless Stereo (TWS) sound. Perfect around the house or outdoors. 8.6W RMS Surround Sound XC5240 NOW $59.95 SAVE $20 15W RMS 2-in-1 XC5242 NOW $99 SAVE $30 Listen to the latest news and music from around the world. Uses Phase Lock Loop (PLL) for stable reception. Compact with SSB AR1780 NOW $119 SAVE $30 Large with clock & alarm AR1748 NOW $169 SAVE $30 VARIABLE RGB COLOUR & EFFECTS NOW $ $ . NOW SAVE $20 5m Flexible Multi-Coloured Waterproof LED Strip Lights 4K Android Media Player 12VDC. Adhesive backing. Remote control and power adaptor included. SL3942 RGB LED LIGHT NOW 40W RMS 12" Rechargeable PA/Party Speaker . SAVE $15 AR1780 SAVE $20 5995 95 AR1748 279 4K 49 $ FROM $ 139 $ 12V OR MAINS POWERED. PERFECT FOR ENTERTAINMENT AT HOME & ON-THE-GO Browse the web, run Android games and apps, or watch your favourite media. Wi-Fi or ethernet input. XC6012 Play music through Bluetooth®, USB, microSD card or AUX. Built-in amplifier and FM radio. Remote control EXTENDABLE TROLLEY and wireless microphone HANDLE & WHEELS included. CS2497 NOW 7995 4K $ . SAVE $10 NOW 24 95 $ SAVE 15% HDMI to VGA + Stereo Audio Converter Convert a HDMI source (e.g. Blu-ray player) to a VGA display. AC1724 NOW 7995 $ . PROTECT & POWER YOUR VALUABLE EQUIPMENT . 2 Way HDMI Splitter NOW 4995 $ Split a single HDMI input to multiple devices. AC1710 . SAVE $10 SAVE $20 Composite AV to HDMI Converter Enable old devices such as DVRs, or VHS players to playback video & audio on HDMI equipped displays. AC1722 10-Way Surge Protected Powerboard With EMI/RFI filters including data and antenna protection, 2 x USB power. MS4033 Retro Gifts for Dad DAD CAN REVISIT HIS CD OR TAPE COLLECTION 2.8" COLOUR DISPLAY NOW 14 $ 95 . SAVE 20% AM/FM Pocket Radio Requires 2 x AAA batteries (sold separately). AR1458 NOW 24 $ 95 . SAVE 15% GAMES Retro Style Handheld Console Available in black or red. Ages 15+. GT4280 NOW 4995 $ 256 . NOW 4995 $ . SAVE $20 Portable CD Player Includes earphones, AUX out and anti-skip. GE4085 SAVE $30 Shoebox Cassette Player & Recorder Play and digitise cassettes to a USB. Built-in speaker and microphone. GE4106 Big Boys Toys 40CM LONG 34CM LONG TILT ADJUSTABLE VIA REMOTE CONTROL LED UNDERGLOW LIGHT 1080P CAMERA RC RANGE UP TO 80M LINE OF SIGHT RETURN HOME FUNCTION LARGE ALL TERRAIN TYRES ONE KEY TAKE OFF & LANDING ONLY 99 $ UP TO 38 KM/H NOW 149 95 $ RC FPV Drone with 1080p Camera Quality vehicle with metal wheels, rear differential, drive shaft and axles, and fully independent suspension. 2.4GHz long-range remote control included. Ages 12+. GT4257 Smartphone not included. DON'T FORGET THE BATTERIES 40 ¢* NOW 79 $ 95 2" LCD 49 95 SAVE $10 Super fast. Features auto self-righting in case of capsizing, and remote controlled LED lights for extra effects. GT4268 99 SAVE<at>$30 4K UHD Wi-Fi Action Camera 2 Pack Laser Tag Battle Guns . $ 170° WIDE ANGLE LENS . GREAT VALUE NOW 6995 $ NOW FROM SAVE $30 ONLY 29CM LONG RC High Speed Racing Boat AA, AAA, AAAA, C, D & 9V. Various pack sizes available. *AA or AAA price when purchased as a 100 bulk pack SB2323 or SB2325 EA . Built-in microphone and speaker. Includes waterproof case, Li-ion battery, and camera mounts. QC8071 64GB microSD card XC5017 $29.95 Single shot, laser, machine gun & plasma gun effects. Full colour lighting, sound effects & vibrations. Available in mixed yellow/red and blue/green. Ages 8+. GT4079 JUST ADD YOUR OWN CLOCK FACE PERFECT FOR DADS LEARNING ELECTRONICS & PROGRAMMING NOW 14 SAVE $10 Easy to fly. Built to last with its shock absorbent nose. Rechargeable. Includes spare blades & USB charging cable. Ages 14+. GT4105 General Purpose Alkaline Batteries FROM BATTLE DAD $ . RC Plane with LEDs RACE THROUGH THE WATER 2WD RC High Speed Buggy Watch a live video feed from the high-definition camera onboard. Headless & altitude hold modes & more. Includes USB charging cable. Ages 14+. GT4118 MAKE OR REPAIR YOUR OWN CLOCK 95 SAVE $30 GREAT VALUE $ NOW 49 $ QP2308 QP2302 NOW 2995 95 $ . PERFECT FOR BEACHCOMBING DADS . SAVE 25% SAVE $10 Metal Detectors Keyes Max Development Board Quartz Clock Movement Accurate quartz crystal movement. Supplied with three sets of hands. Requires 1 x AA battery (sold separately). XC0100 Learn to code Arduino® without using breadboard circuits. Features a powerful board, essential components, and comprehensive manual. XC4417 Ideal for beachcombing, prospecting and more. Adjustable sensitivity. Beginner with auto tune QP2302 NOW $99 SAVE $20 Pro with waterproof coil QP2308 NOW $169 SAVE $30 Gadgets for Dad NOW 19 $ 95 . NOW 1995 $ SAVE $5 SAVE $5 8 colours available. 75mm long. Ages 3+. GT4259 95 . SAVE $5 BUY 2 FOR 29 $ SAVE 25% TRICK DAD . RC Car in a Can NOW 19 $ Portable Table Tennis Set Includes a retractable net, two paddles and two ping pong balls. GH1162 Fart Machine with Sounds and Remote Control Remote control, 7 farts. 4 x AA batteries required (sold separately). GH1088 Mini Boomerang Spinner Drone Boomerang, frisbee & spinner in one! Ages 14+. GT4106 RRP $19.95EA For Dad's Workbench EASY TO USE AUTORANGING METER NOW 4995 $ ULTRA FAST PRINTING SPEED UP TO 120MM/S . SAVE $10 PCB Holder with 95 LED Magnifier NOW 24 $ . SAVE $12 Ideal aid for soldering work, model making etc. 2x magnification. TH1987 RELIABLE & EASY TO USE. PERFECT FOR HOBBYISTS & BEGINNERS FILAMENT AUTO-FEED Autoranging Digital Multimeter 1 YEAR WARRANTY Measures voltage, resistance, capacitance, temperature and more. CATIII 600V 10A. 4000 count display. QM1323 ONLY 399 $ DAD'S COMPANION FOR URGENT SOLDERING NEEDS COLOUR LCD SCREEN GREAT VALUE NOW 59 $ 95 SAVE $30 HANDY CARRY CASE INCLUDED Pro Gas Soldering Tool Kit Sturdy, portable, self-igniting soldering iron tool kit with 3 tips. 1300°C adjustable flame for low end brazing. TS1113 NOW 39 $ HEATED PRINT BED Creality Ender-3 V2 Neo Filament 3D Printer Ideal for printing highly durable large models up to 220Hx220Wx250Lmm. TL4752 NOW $ . $ 95 . . SAVE $10 SAVE $5 SAVE $10 2000W Adjustable Temperature Heat Gun Heavy Duty Wire Stripper, Cutter & Crimper Gas Blow Torch Adjustable flame. Temp range up to 1300°C. Piezo ignition with safety lock. TS1660 Butane Gas NA1020 $7.95 Powerful heat gun with 2 heat settings. Four nozzle attachments included. Mains powered. TH1609 NOW 3995 39 95 Strip all types of cable from 10-24 AWG (0.13-6.0mm). 204mm long. TH1827 2.4" LCD NOW 119 $ 5995 $ . SAVE $15 SAVE $30 0.01G RESOLUTION NOW SAVE $40 1000A True RMS AC/DC Clamp Meter 200g Mini Bench Scale Extremely accurate. Weighs in grams, carats, and pennyweight. QM7259 NOW 129 $ Inspection Camera Excellent for inspecting or locating objects in tight spaces. 1m long gooseneck. QC8710 Non-contact voltage testing. CAT III, 6000 count. QM1634 Tools for Dad COMFORTABLE GRIP ONLY 24 $ 95 . 127mm Precision Angled Side Cutter Easily cut leads, ideal for fine PCB work. Carbon steel. TH1897 NOW 24 $ 95 . SAVE $12 240 Lumen Rechargeable Worklight Includes magnet and hang hook. 3 light level settings. ST3494 NOW 24 $ $ . SAVE $10 Smartphone Repair Kit NOW 2995 95 . 27 PCS All the necessary tools needed to fix dad's Smartphone. TD2118 SAVE $5 Screwdriver Set Dad can repair his electronic gadgets and devices. Made from S2 steel. TD2134 48 PCS Score 30% Off these Brass Monkey Fridges Keep your food and drinks cold or frozen on the trip. Superb energy efficiency. Powerful compressor and electronic control module. 12/24V or 240V via adaptor. NOW FROM 36 299 $ NOW 279 $ REMOVABLE DIVIDER 106 SAVE $120 589 $ SAVE $260 SEPARATE LIDS WITH DUAL HINGES SAVE<at>$170 NOW WHEELS & HANDLE INTERNAL LED LIGHT STURDY METAL CASE GH1640 36L, 50L & 60L Convertible Dual Zone Fridge/Freezers 25L Fridge/Freezer with Metal Case 1995 $ Compact Multiband Radios Battery sold separately 2995 Lithium Fridge Batteries 5.2Ah - 15.6Ah. GH2049-GH2084 PERFECT FOR HOBBYISTS $ SAVE<at>$20 FROM 109 $ NOW FROM AR1736 FITS OPTIONAL LITHIUM BATTERY Large size, low profile design with separate fridge and freezer zones. Perfect for long adventures or big families. GH2080 Ultra-versatile with removable divider that lets you run as a fridge and freezer or fridge or freezer. 36L Holds 52 Cans GH1640 NOW $299 SAVE $150 50L Holds 76 Cans GH1642 NOW $349 SAVE $150 60L Holds 98 Cans GH1644 NOW $379 SAVE $170 Compact and fits easily in the boot with enough space for day trips and light-packed weekenders. GH2006 NOW FROM 75L Dual Zone Fridge & Freezer SAVE<at>$30 DAD CAN LISTEN TO THE FOOTY AR1721 Compact AM/FM/SW radios. Features a 3.5mm headphone jack for private listening. Pocket Sized AR1736 NOW $19.95 SAVE $15 Rechargeable with MP3 Player AR1721 NOW $29.95 SAVE $20 10 16 TS Soldering Stations Great for those starting out in electronics. Mains powered. 10W with temp. range 100-450˚C TS1610 NOW $29.95 SAVE $15 48W with temp. range 150-450˚C TS1620 NOW $49.95 SAVE $30 A Gift for Dad, A Gift for You BUY 2 FOR 29 $ SAVE OVER $10 Wireless TWS Earbuds Great sound. Built-in microphone. Compatible with all Bluetooth® devices. AA2165 RRP $19.95EA BUY 2 FOR 40 $ SUPER BRIGHT 500 LUMEN BUY 2 FOR 49 $ SAVE SAVE OVER $30 OVER $30 Rechargeable LED Torch 10,000mAh Powerbank Aircraft aluminium. Multiple light modes. ST3522 RRP $36.95EA Charge via USB Type-A or Type-C. Up to 3A combined output. MB3810 RRP $39.95EA WITH QUICK CHARGE™ & POWER DELIVERY SALE ENDS SUNDAY 3.09.2023 Scan QR Code for your nearest store & opening hours 1800 022 888 www.jaycar.com.au Over 100 stores & 130 resellers nationwide HEAD OFFICE Rhodes Corporate Park, Building F, Suite 1.01 1 Homebush Bay Drive, Rhodes NSW 2138 Ph: (02) 8832 3100 ONLINE ORDERS www.jaycar.com.au techstore<at>jaycar.com.au Flavio Spedalieri’s Arduino-based Coffee Grinder Timer Take your coffee grinder (or other motorised appliance) to the next level with a custom timer module, programmable presets and an LCD or OLED screen. G ood coffee grinders are expensive – even basic, manual models operated by a simple switch can cost over $500, and some well over $1000! You’d think that they’d throw in a timer for that much money, but there’s often a premium of several hundred dollars on models with timers. Having a programmable timer in a coffee grinder used for making espresso is a big advantage. Once you’ve determined the correct grind setting and time to make a good coffee, it will produce a consistent amount of grounds so that each cup is consistently good. Too many grounds will choke off the water flow, while too few will make weak coffee. You want minimal variation from cup to cup. It would be ideal to buy a grinder that does an excellent job of making the coffee grounds without spending siliconchip.com.au too much money, then add a timer if it lacks one. That’s what I did, and you can do the same. Why spend so much when you can get a coffee grinder at Kmart for $18? Because it won’t be ideal for making good-quality espresso. It won’t grind finely enough or consistently enough, won’t be adjustable enough, and will take quite a long time to produce enough grounds for one cup. It also won’t last very long. While this project is designed to add a timer to a coffee grinder, it could be used for just about any appliance that runs off the mains and can be switched using a solid-state relay. It could also be used to switch low-voltage AC or adapted to switch low-voltage DC. The circuit is simple, and the parts are inexpensive; with some work, you can upgrade just about any grinder with this programmable timer. In my case, I wanted to add a timer to a used Compak K6 grinder (a well-­ regarded unit) that was generously donated to me by Dean and Rose Kiner of Siboni’s Coffee in Pymble NSW. I had two main jobs to do. One was to design the electronics and create the software for the timer itself. The other was to figure out how to modify the grinder to nicely integrate the electronics. A timer should be easy to use and free from complexities, with a simple menu for making adjustments. I considered using a DIN-style timer; however, they can be difficult to use and require substantial clearance to fit, meaning it would have to be external to the grinder. So I decided to base it on an Arduino module, as I am familiar with that ecosystem. The first part of this article will concentrate on the timer module and its functions. It could be adapted to many other applications or even built as an external module, making it easy to add to use with any suitable appliance. It is incredibly handy for more precise measurement and dosing of the coffee grounds. Note that some timerless grinders have a ‘doser’ mechanism that catches the grounds and apportions them to suit the coffee machine. This has several disadvantages, including stale coffee getting stuck in the doser, especially since you have to keep it close to full for the doses to be accurate. If adding this timer to a grinder with a doser (as I did), it would be necessary to remove the doser and replace it 230V AC Mains Safety The entire timer module can be built, tested, and made functional without touching mains voltages. However, should you wish to interface the module to a solid-­state relay (SSR) for mains switching as described, please follow all the precautions described in this article for safely working with 230V AC mains. That includes using correctly rated parts and wiring, properly insulating all exposed conductors and avoiding touching any part of the circuit when the mains cord is plugged into an outlet. Australia's electronics magazine September 2023  57 Photo 1: the Arduino Pro Mini is basically a shrunk version of the Uno. It’s no longer officially made, but plenty of clones are still available. Photo 3: the three buttons that control the Timer all have integral LEDs. You could use three similar types of buttons if you want. with a chute that dispenses the ground coffee straight into a ‘portafilter’ basket or similar. an I2C serial interface, the addition of a ‘manual grind’ display, a rotary encoder for easier time setting, the reconfiguration (and reduction) of the buttons, adding visual feature through LED fades and flashes, plus an ‘offset mode’ and the ability to display the firmware version and disable the splash screen. I eventually added support for multiple display types, including OLEDs. Timer design I found some code online for a very basic two-preset timer to control an electrical appliance. A 16×2 character backlit LCD with a parallel interface was used as the display, with four control buttons (+/−, P1, P2 & manual) for control. It integrated with the appliance’s multi-switch, which was rewired to activate the timer (effectively giving it five buttons). I loaded this code to understand how the timer would work from an end-user/operator perspective. Still, I knew I would have to redesign the circuit and rewrite the code to suit my needs better. Some improvements I made include the ability to drive the LCD through Arduino software Besides being easy to use with a clear display, I decided the software should have a screen saver mode (where the screen is turned off after five minutes of inactivity) and the visual LED fades. The Arduino platform I ended up using is the Pro Mini board (Photo 1) with the usual ATmega328 microcontroller. One advantage of using the Pro Mini is that I could prototype the system using an Arduino Uno (Photo 2) and then transfer it quickly to the compatible Pro Mini later. I split the software up into nine source code files: 1. the main program 2. button press handling 3. display driving 4. rotary encoder sensing 5. utility functions 6. initialisation 7. LED driving 8. & 9. splash screens for the two OLED display options These files and the compiled HEX file are available for download from siliconchip.com.au/Shop/6/248 Button configuration Photo 2: the prototyping rig used to develop the software, based on a few small modules and jumper wires. 58 Silicon Chip I reduced the button requirement to three; one button to select between the two presets, one to trigger the selected preset and one for manual grinding. The rotary encoder is used to set the Australia's electronics magazine times and has a fourth integrated button to access the menu. Photo 3 shows how I mounted the three buttons, and you can see the rotary encoder above them. However, the code also has the option to have two different trigger buttons, one which triggers preset 1 and one which triggers preset 2. Editor’s note: that is how the grinder at our office works, as it makes it convenient to select between single- and double-shot espresso. Display options As mentioned earlier, the original concept used a 16×2 character LCD. However, I realised that a smaller screen would be needed to fit within a limited space inside the grinder. I therefore modified the software to support a 128×64 pixel OLED display with an SSD1306 controller using the U8G2 Display Library – see Photo 4. After testing several OLED screens, I arrived at the Digole Digital Solutions DS12864OLED-2W white-onblack OLED (Photo 5). As driving it is different from the generic SSD1306 screens, there are two different versions of the firmware to handle both types of 128×64 OLED screen. Table 1 shows the various software versions I have developed that are available to download. The Digole screen (www.digole. com) is a graphic type with a fast update response and only needs a small library to drive it. It does need fonts to be loaded into the four user font addresses. The more common 128×64 graphic OLEDs using an SSD1306 or SH1106 controller can also be used, but they have a slightly slower display response. For these, the I2C communication speed may be improved by adding the function call “u8g2.setBusClock(600000);” in the initialisation code. If using the Newhaven character OLED, the display has a reset pin which can either be driven from the Arduino or connected to an RC circuit to pull it low for about 40ms during power-up. It uses the US2066 chipset; however, the I 2 C Display library is used (www.dcity.org/portfolio/ i2c-display-library/). This requires the following code changes to function correctly. Inside the function I2cChar­ Display::oledBegin(), where the siliconchip.com.au Photo 4: the graphic OLED screen (left) is much more compact than the alphanumeric version (right). Photo 5: the selected OLED screen fits neatly behind the new custom-made front panel, painted black. following two lines are found, change 0x00 on the second line to 0x10: // Set SEG Pins Hardware Configuration sendCommand(0xDA); // Enable SEG Left, Seq SEG pin config sendCommand(0x00); The 16×2 character LCD with I2C interface is the simplest display from the software point of view, but it is much larger than the other options, and isn’t capable of displaying graphics. Circuit details The resulting circuit is shown in Fig.1. The Arduino Pro Mini, OLED/ LCD screen and rotary encoder modules are powered by 5V DC from the switch-mode power supply. The Arduino updates the screen using a two-wire I2C serial bus, via its A4 (SDA) and A5 (SCL) pins. Internal pull-up currents are enabled on digital input pins D5, D7 & D8 to detect when pushbuttons S1-S3 are pressed. The integral LEDs in those buttons are driven by digital outputs D10, D11 & D9. Two of these (D10 & D11) have series current-limiting resistors to set the LED currents to around 9mA, while the third does not because the switch includes a series resistor for its LED. While the resistor integrated into switch S3/LED3 is designed to allow it to operate from 12V, it isn’t too much dimmer when driven from 5V. The LED in the solid-state relay is driven directly from the D12 digital output. It has an integral 1.5kW resistor and supports a control voltage range of 4-32V DC. As it only draws less than 4mA at 5V, the Arduino output can easily drive it. The SSR’s outputs are connected in series with the mains supply to the grinder motor, so it switches the motor on while the D12 output is high. The rotary encoder I used is mounted on a small PCB, which includes three pull-up resistors for the two encoder contacts and the integral switch. Pins 1 & 2 are for ground and the power supply that drives the pull-ups, while the remaining three pins are for the encoder and switch contacts. These go to digital inputs D2-D3 and D4 on the Arduino, respectively. They are debounced and decoded in software. Fig.1: the Timer circuit is straightforward, with the Arduino module controlling all functions and updating the display over a two-wire I2C serial bus. It controls the SSR that switches the grinder motor via a digital output and uses three buttons (with integrated LEDs) and a rotary encoder for user input. siliconchip.com.au Australia's electronics magazine September 2023  59 If you want to use a different rotary encoder than I did, refer to “Encoder Setup” in the main code file to adjust its behaviour. While there are no doubt various SSRs that could be used in this application, I chose a high-quality unit, with much higher voltage and current ratings than necessary, for a long life. My grinder motor is rated at 245W (1.02A) <at> 240V AC. You should check yours against the ratings of your selected SSR; the one I specified should suit most grinders. The operation and functions of the Timer are listed below: #1 Splash Screen As a departure from traditional nomenclature, I adopted a more generic “PRESET 1” and “PRESET 2”. By default, the firmware uses single button control as fewer holes needed to be drilled in the grinder. In this case, pressing the Select button toggles between the two presets. The Run button illumination will Flash once when Preset 1 is selected and twice when Preset 2 is selected. The firmware also supports two buttons, one for Preset 1 and a second for Preset 2. Pressing the associated button will change the preset program accordingly. This second switch can be connected to pin D6 of the Arduino Pro Mini and then to Ground. #4 Program Mode Photo 6: the grinder I started with; it had seen a lot of use. Note the large doser assembly attached to the front and the original, tall hopper on top. If “Display Start” is enabled, the splash screen will be displayed on power-up for four seconds (see above and Screen 1). The displayed message is preconfigured in the initialisation file. If “Display Start” is disabled, it will instead immediately display the default Preset 1 (Idle Mode). The Run button illumination increases from off to bright as it enters idle mode. #2 Idle Mode Pressing the encoder button/knob (Program) enters the program mode for the currently displayed preset. The Run button illumination extinguishes in program mode. The display changes to show “PROG <> PRESET”. Turning the encoder knob will change the preset time. Pressing the encoder button will return to the current preset (Idle Mode) and will save the time if it was changed. The Run button will flash four times on exit. #5 Offset Mode Screen 1: an example of the splash screen displayed on the OLED module. Screen 2: the Firmware Version Display screen on the OLED module. 60 Silicon Chip Following power-up, the timer defaults to Preset 1 with the displayed time loaded from EEPROM. The Run button continuously cycles between dim and bright every three seconds. #3 Switching Preset Program The firmware has two preset times, inspired by commercial timed grinders that usually have ‘single cup’ and ‘double cup’ options. The ‘double cup’ grind is not necessarily twice the time of the ‘single cup’, as single and double espresso filters usually hold 7-10 grams and 16-18 grams of coffee, respectively. That, and the way roasted coffee beans vary, mean the times both need to be adjustable. Australia's electronics magazine Offset mode allows for ‘on-the-fly’ preset time adjustment throughout the day without changing the saved preset time. This lets you experiment with the amount of coffee without changing the stored presets. Rotating the encoder dial/knob in Idle Mode automatically enters Offset Mode. When the displayed time is lower than the preset, the LCD will show “<OFFSET”, and when higher, it shows “OFFSET>”. If you turn the encoder to return to the preset value, the display will return to “PRESET”. While in Offset Mode, pressing the encoder (Program) button will enter Program Mode and clicking again (to exit) will update the stored preset value in EEPROM with the new siliconchip.com.au value. The Run button will flash four times on exit. Note that for the V2.65 firmware (single button configuration), once Offset Mode has been activated, when returning to normal Idle Mode, the Preset button must be pressed twice to change the preset. #6 Grinder Activation Pressing the Run button runs the grinder for the currently selected preset time. The Run button illumination will extinguish when the grinder is operating, during which time a countdown is shown on the screen. When it finishes, the display returns to idle mode and the Run button will re-­ illuminate. #7 Manual Grind/Purge A manual grind/purge button is an important feature of any grinder. Pressing and holding the Manual button causes the grinder to run while the button is held down. The display shows “MANUAL GRIND” during this time while the Run button cycle-flashes. #8 Enable/Disable Splash Screen To enable or disable the splash screen, press and hold the Select button (or P1 if you’re running the dual preset button firmware) for four seconds. The Run button will flash at 1Hz. Release once the display shown above appears. Again, on this screen, hold that button for four seconds to save the change. The Run button will flash four times on saving the change to EEPROM and returning to the Idle screen. The Splash Screen is toggled on or off each time you go through this procedure. #9 Firmware Version Display Press and hold the rotary encoder siliconchip.com.au Table 1 – software versions Name Screen Preset buttons HEX file? 1B_128x64OLED 128×64 graphic OLED (SSD1306) 1 Yes 2B_128x64OLED 128×64 graphic OLED (SSD1306) 2 No 1B_DS12864OLED 128×64 Digole DS12864OLED-2W OLED 1 Yes 1B_NW1602OLED 16×2 character Newhaven NHD-0216AW-IB3 OLED 1 No 1B_1602LCD 16×2 character LCD 1 No 2B_1602LCD 16×2 character LCD 2 No (Program) button until the Run button begins flashing, then release it. The firmware information will be displayed for four seconds before returning to Idle Mode (also see Screen 2). The Run button flashes once on exit. Note that most of the screengrabs shown are for the 16×2 alphanumeric displays. As seen in Screens 1 & 2, the OLED has a more square aspect. In most cases, it shows the same information as the LCD screens, just reformatted to better fit the OLED. Grinder conversion The coffee grinder to which I added this timer was an old Compak K6 that I refurbished and modified at the same time. Photo 6 shows it in its original state. As it was ‘well-loved’, I completely stripped the grinder (Photo 7), cleaned everything and sandblasted the housing (Photo 8). Converting it to be doserless required the removal of the old dosing chamber, re-engineering the outlet port and mounting a spout or cone. A Rancilio Rocky doserless grinder spout (which Dean also provided) was my first choice (see Photo 9). I also considered retrofitting a dose cone from a Mazzer Mini but decided against it as they are expensive (over $250). Also, it would have been too tall, pushing the placement of the portafilter holder much lower than where the display is positioned. You might notice that I reduced the size of the hopper, something that was not required but that I decided to do. I accomplished this by marking, hand-cutting and sanding the hopper. A felt strip on the inside edge of the hopper lid made for a snug fit. One of the main challenges was Australia's electronics magazine Photo 7: the cut-down hopper and the curved front panel with the doser removed. That made attaching the new chute and display challenging. Photo 8: the stripped chassis after sandblasting. Note how I have ground away some of the metal around the opening at the top so the new flatflanged chute can be fitted. September 2023  61 Photo 9: after reshaping the orifice, the chute (designed for a different type of grinder) fits nicely. Photo 10: this handmade timber piece covered up the gap left by removing the doser. modifying the existing casing, which had a curved section where the outlet port is, to mount the spout with its flat mating flange. This required modification to both the case and the original plastic coffee outlet adaptor. If you can modify a grinder that has a flat front face, that will make everything a lot easier! To pay homage to Siboni’s Coffee and one of my favourite blends, “Romeo”, I programmed the “Romeo” graphic to appear on the splash screen, as seen in Photo 5 and Screen 1. With the timer ready, I started cutting and drilling holes in the grinder case for the switches, screen, and mounting point for the portafilter fork. I used the portafilter holder from a Mazzer Mini grinder. Depending on the design of your grinder, its motor might be switched by a manual switch or a relay. In my case, it was a 16A mechanical relay. I simply removed this and connected the SSR in its place. I securely mounted the SSR and switch-mode power supply inside the grinder case and wired up the switchmode supply to the incoming mains (after the power switch). One question was how to fill in the original gap at the top of the grinder, where the doser used to attach, and how to tidy up the front face. For the top of the grinder, I wanted to use a piece of timber as it would add a ‘warm tone’ to the project. I cut three sections of Tasmanian Oak, glued them together, then sanded and contoured the piece (Photo 10). Two Neodymium magnets secure it to the body and allow for its removal if the front needs to be disassembled, eg, to remove the spout for servicing. I gave the timber piece several coats of walnut stain before two coats of Scandinavian Oil and final coats of beeswax. I also needed to produce a new front face to attach the spout, portafilter holder and timer display. I first mocked up the plate for the front face with card (Photo 11), then 3mm ply, and eventually translated it to 1.2mm-thick aluminium (see Photo 12). I hand-cut the aluminium stock (using a nibbling tool) and finished it by hand. I conducted a final fitment test before painting it (Photo 14). I added an indentation above the portafilter holder to position the filter directly under the spout. As a bonus, it can aid in holding the filter in place during grinding (shown in Photo 14). With the grinder housing completed, all holes cut, drilled & tapped, fitment tested and the timber in-fill finished, it was time to sandblast the case and prepare for final painting. I gave the case five coats of black satin paint with a final sandy texture finish, sealed with a clear topcoat. As you will see from Photo 16, I opted to mount all the new controls along the side of the base, as there was plenty of room, except for the rotary encoder, which is mounted above the Photo 12: the metal face plate was made from 1.2mm-thick aluminium and painted to match the body. Photo 13: the OLED screen fits nicely near the base. The new front panel will cover its mounting screws. Aesthetic details Photo 11: I cut and folded this card to figure out how to shape the new metal front panel. 62 Silicon Chip Australia's electronics magazine siliconchip.com.au buttons on the side of the main body. Wiring it up As I had already installed the switch-mode supply and SSR, as mentioned earlier, all that was left was to wire the Arduino and other modules as per the circuit diagram (Fig.1). Given the simplicity, I mostly used point-to-point wiring to connect the components to the Arduino. You can see how it all (just) fits inside the grinder base in Photo 15. If your grinder does not already have a relay to control the motor, you will need to cut one of the wires going to it and connect the two ends across the SSR’s mains terminals. The power supply and SSR both need to be solidly anchored to the case. Use mains-rated wire for the new connections to the switch-mode power supply and fully insulate all new or modified mains connections. Cable tie the Active and Neutral wires to the switch-mode supply together at both ends. Also, cable tie the mains wires to the SSR together if possible. I haven’t gone into great detail about how I modified my grinder because most of the steps will depend heavily on the specifics of your grinder. Still, if you want to see exactly how I did it, you can see all the details on my website at www.nightlase.com. au/?pg=coffee The lead photo and Photo 16 shows the final result with the grinder up SC and running! Photo 14: a bracket and a detent in the front panel hold the portafilter in place during grinding. siliconchip.com.au Parts List – Timer for coffee grinders 1 Arduino Pro Mini (MOD1) [Core Electronics 018-MINI-05] 1 230V AC to 5V DC 1A enclosed switch-mode power supply [Jaycar MP3295] 1 USB/serial adaptor (to program MOD1) 1 Digole DS12864OLED-2W or SSD1306/SH1106-based 128×64 pixel graphic OLED (MOD2) 1 25A 480V AC solid-state relay (SSR) [Kyotto KD40C25AX] 1 chassis-mount momentary pushbutton with integral white LED (S1/LED1) [Core Electronics ADA1479] 1 chassis-mount momentary pushbutton with integral red LED (S2/LED2) [Core Electronics ADA1439] 1 chassis-mount momentary pushbutton with integral green LED and current-limiting resistor (S3/LED3) [Jaycar SP0804] 1 five-pin rotary encoder module with integral pushbutton plus knob (RE1) [www.aliexpress.com/item/32790788377.html] 2 220W ¼W resistors various lengths of mains-rated wiring, heatshrink tubing, cable ties etc various screws, nuts and other mounting hardware Photo 15: this photo inside the grinder base shows the added 5V power supply (upper left), SSR (bottom middle, under Presspahn insulation), buttons and some of the new wiring. Cable ties were used extensively to prevent wires from floating around in case they came loose, and all mains connections were fully insulated. Photo 16: the finished grinder conversion, with the OLED screen, buttons and rotary encoder visible towards the bottom. Compare this to the original (shown in Photo 6) to see the transformation. Australia's electronics magazine September 2023  63 This small, low-cost adaptor lets you program most newer PIC microcontrollers out-ofcircuit. It works in conjunction with a PICkit or SNAP in-circuit programmer and provides five different modes to suit a range of chips from eight to 40 pins. It can even be used with SMD chips in SOIC, SSOP or TSSOP packages. Nicholas Vinen’s PIC Programming Adaptor T his new programming adaptor board is compact, easy to build and suits a large range of PICs released in the last 5-10 years, including many that we use in our projects. As we sell programmed PICs (and other microcontrollers) to build the projects described in our magazine, we have a box full of programming sockets, adaptors and other rigs to suit the many different types of chips. Lately, I realised that most of the time, we were using just a few of those adaptors because we have transitioned to mainly using recent PICs (released in the last 5 years or so). However, we still have to switch between several rigs because recent PICs still use a few different pinouts. For example, many of the latest 8-bit PICs use one configuration, while PIC24s, dsPICs and PIC32s use another. Some larger (eg, 40-pin) 8-bit PICs use further configurations. We previously published a fairly comprehensive PIC & AVR programming adaptor in the May & June 2012 issues (siliconchip.au/Series/24). While we still use that board quite often, it was geared towards the chips that were available back then, and things have changed substantially. Features & Specifications > Adapts an in-circuit programmer like the Microchip PICkit or Snap to a ZIF socket > Can deliver 3.3V or 5V to the target; target power can also come from the programmer (if supported) > Programs DIP chips directly or SMD SOIC/SSOP/TSSOP via low-cost adaptors > PTC protection for the device being programmed (eg, in case it’s inserted in the socket incorrectly) > Supports most newer 8-bit PICs and most 16-bit and 32-bit PICs (including PIC24, dsPIC, PIC32MM and PIC32MX) with 8-40 pins > Tested PICs include 16F15213/4, 16F15323, 16F18146, 16F18857, 16F18877, > > > > 64 16(L)F1455, 16F1459, 16F1709, dsPIC33FJ256GP802, PIC24FJ256GA702, PIC32MX170F256B and PIC32MX270F256B Many more chips are supported than listed above LEDs indicate source power present, target power present, voltage range and programming activity Simple to use with just five switches and silkscreened instructions Includes ‘mouse clicker’ option to automatically trigger programming when the target is powered Silicon Chip Australia's electronics magazine Because it had to support so many different pinouts, it had certain compromises this newer design doesn’t have to deal with. Uses and function You may not need this board if you always design or build boards with in-circuit serial programming (ICSP) headers. However, there are times when it is convenient to program a chip out of circuit; for example, if your board is so compact that there’s no space for an ICSP header, or you want to swap chips out in the field. Or, like in our case, you want to supply someone with a pre-programmed chip. You can build individual programming jigs for each type of chip – which is what we did – but it can be annoying. You end up with many that you must dig through to find the right one each time. With this board, you just flick a few switches and it’s ready to program various chips. Fig.1 shows the five different pin configurations it offers. Each is colourcoded; the labels with that colour in the background indicate the function assigned to that socket pin in that mode. There are two settings for mode A and one for modes B, C and D. The two A modes suit almost all modern 8-bit PICs, which are inserted with the pin 1 end at the bottom of the ZIF socket. These all use the same pins for VDD, GND and MCLR and mostly use the siliconchip.com.au same pins for programming (PGD = data and PGC = clock). The exception is devices with more than eight pins, like the PIC16(L)F1455 and PIC16(L)F1459, which can use the same programming pins as the other devices – shown in red in Fig.1 – but only for low-voltage programming (LVP). Sometimes, low-voltage programming is disabled. In that case, you must use mode A2, via the mauve labelled pins. Also, LVP could be disabled once you program them, so you might need to use the alternative mode for reprogramming. Not all chips support programming on those pins (especially 8-pin devices, which don’t extend that far!), so we can’t always use the alternative pins. Hence we use a dedicated switch to select between the two A modes. A separate four-throw switch selects between the A, B, C and D modes. In B, C and D modes, pin 1 is placed at the top of the ZIF socket. Mode B is for a few of the larger (40pin) 8-bit PICs that use a different pinout than provided in mode A for backwards compatibility with certain older chips like the PIC16F877 (you can use mode B to program those older chips too). One example of a newer chip that needs mode B is the PIC16F18877 that we’ve used in a couple of projects, such as the USB Cable Tester (November & December 2021; siliconchip.au/ Series/374). Somewhat annoyingly, the 28-pin version of that chip, the PIC16F18857, cannot be programmed in mode B because its supply pins are in different locations (again, likely for backwards compatibility). So mode C leaves PGD, PGC and MCLR in the same places as mode B but changes VDD and GND to suit those chips. Finally, mode D suits a very common pinout used by many 28-pin devices, including much of the 16-bit PIC24 range, the 16-bit dsPIC range and the 32-bit PIC32MX range. We’ve opted to use pins 4 and 5 as PGD and PGC, respectively; many of these chips support multiple different (usually three) sets of programming pins, but this pair (#1) is the most consistently supported. The only other slightly unusual thing about mode D is that, in addition to connecting PGD, PGC, MCLR, VDD and GND to various pins, a highvalue, low-ESR capacitor also needs siliconchip.com.au to be connected between pin 32 (pin 20 on the 28-pin chip) and GND. This board connects a 47μF ceramic capacitor through a low-resistance Mosfet to provide that function. One advantage of this circuit compared to the 2012 Programming Adaptor is that because modern PICs mostly use one of just a few pinouts, we only need four modes, making the switching considerably simpler. That means shorter paths between the ICSP socket and the ZIF socket pins and fewer components connected to those pins. As a result, programming is more reliable and programming speeds are higher. The older Adaptor sometimes requires you to reduce the programming speed to “slow” for it to work, but this new Adaptor generally works at “normal” and even “fast” programming speeds. Circuit details The full circuit is shown in Fig.2. It looks complicated but isn’t hard to understand if you break it into chunks. All of the switching for MCLR (which also sometimes carries VPP, the high programming voltage), PGD (data) and PGC (clock) is done by fourpole, four-throw slide switch S1. S1a switches MCLR from the ICSP header (CON1) to the appropriate pin on SK1 for each mode, with mode A at the top and mode D at the bottom. Similarly, S1b switches PGD (data) and S1c switches PGC (clock) to the pins of SK1. Thus, the only components in the path of these programming signals are CON1, SK1, S1 and some short PCB tracks, minimising signal degradation. One exception is that the PGC/PGD signals also pass through switch S2 in mode A, providing the two sub-modes, but the tracks connecting it to SK1 are very short. The fourth pole of S1, S1d, handles all the power pin switching (plus VCAP). It does this by grounding one of the four remaining switch pins. For pins that need VDD applied in this mode, that switch terminal connects to the gate(s) of P-channel Mosfet(s) with a shared gate pull-up resistor. So when that terminal is grounded, the gates are pulled to ground, giving them a negative gate-source voltage and switching them on. In other modes, the resistor pulls up the gate(s), and they switch off, no longer driving those pins. For pins that need GND applied in Australia's electronics magazine a specific mode, the grounded pole is connected to the gate of one of the six inverters within IC1, a 74HC04 hex CMOS inverter (with a pull-up resistor, if one is not already present). The inverter’s output goes high when that pole is selected (pulling its input low), and that high level drives the gate(s) of one or more N-channel Mosfet(s), pulling the appropriate ZIF socket pins to GND. The only variations from this scheme are when multiple modes need to drive the same pin. In this case, diode logic is used to send the right voltages to the Mosfet gates. For example, dual diode D2 is configured so that input pin 9 of IC1d goes low in mode C or D. That causes IC1d’s output pin 8 to go high, switching on Q3, which pulls SK1’s pin 8 low. There are 100nF capacitors throughout the circuit connected between socket power pins via the switching Mosfets. That is, they connect between the source pins of the P-channel (VDD Fig.1: this shows how the five programming pins are mapped from the serial programmer to the ZIF socket in each mode; pin 1 is at bottom right for modes A1 & A2 and upper left for the others. Some pins have the same function in multiple modes, where the background colour is split between two or three modes. The only pins with different roles in different modes are 32, 39 & 40. September 2023  65 Fig.2: routing of the MCLR, PGC and PGD signals from serial programmer header CON1 to ZIF socket SK1 is straightforward, via 4P4T slide switch S1 and DPDT slide switch S2. Connecting GND, VDD and the 47uF capacitor to the appropriate pins of SK1 is a bit more complicated. Switch pole S1d and hex inverter IC1 plus some diode logic control Mosfets Q1-Q11 to apply the correct voltages to the right pins. The VDD indicator circuit is at lower right. switching) and N-channel (GND switching) Mosfet pairs. That is so they do not affect any SK1 pins when those Mosfets are off. Pins 39 & 40 These are the only two pins that need to be switched between programming (PGD/PGC) and power pins. They are only used as power pins in mode D, for the PIC24/dsPIC/ PIC32MX series of chips, where they are the AVDD and AVSS pins. These pins draw almost no current during programming and a maximum of a few milliamps if the chip is running code that uses the ADC peripheral. Mosfets have capacitance when off; the AO3400 and AO3401 Mosfets we’re using to switch power to the 66 Silicon Chip other pins have rated output (drain) capacitances of 75pF (15V/1MHz) and 115pF (115pF/1MHz) respectively. The figures at 0-5V would be even higher and could easily be high enough to interfere with programming. Therefore, we are using much smaller Mosfets to switch power to these pins. Q10 (2N7002K) is an N-channel Mosfet with an output capacitance of 13pF at 25V/1MHz, while Q11 (BSS84) is a P-channel Mosfet with an output capacitance of 10pF under the same conditions. That’s a lot better, but it still could possibly interfere with programming, so 22W isolating resistors have been added to reduce the effect on programming signals at those pins when the Mosfets are off. That value was Australia's electronics magazine chosen to balance minimising the voltage difference between AVDD/AVSS and VDD/VSS while also providing reasonable isolation. Pin 32 (VCAP) The VCAP pin needs to be connected via a capacitor to ground in mode D. That’s achieved simply by permanently connecting a 47μF capacitor to that pin but switching its other end to ground via N-channel Mosfet Q5. This Mosfet is only on in mode D. When off, the Mosfet’s ~100pF output capacitance is in series with the 47μF capacitor, making it effectively a 100pF capacitor. LED5 and its 4.7kW series resistor across the VCAP capacitor are there to discharge it should it become charged siliconchip.com.au Adaptor is switched into mode D and Q9 switches off, the 47μF capacitor rapidly discharges to around 1.8V via LED5 (in around one second). LED5 will briefly light to let you know this is happening. Once it extinguishes, it is safe to insert a chip that’s programmed in mode D. Target power switching The target device (PIC) can be powered from a PICkit plugged into CON1. However, there are many cases where it’s more convenient to supply power externally, and if you’re using a Snap programmer, it can’t deliver power. Therefore, switch S4 applies power to the target device via PTC1, which goes high-resistance if the target draws too much current. That’s only likely if you have the wrong chip in the socket, the wrong mode selected, or the target is orientated incorrectly. In these cases, PTC1 might prevent it from being damaged. PIC16LF, PIC24, dsPIC and PIC32MX devices all need a 3.3V supply, while PIC16F devices can usually run from 3.3V or 5V. Some older chips require 5V for programming, although most modern PICs can be programmed at 3.3V. Therefore, switch S3 can generally be left at its 3.3V setting, although you can supply 5V to the target if you wish. Both the 3.3V and 5V sources come from a Raspberry Pi Pico, MOD1, which would typically be powered from a USB charger or a computer (presumably, the same one doing the programming). LED1 indicates when power is available from the Pico. The Pico also provides the mouse clicker function – more on that later. If you don’t need that function, it’s still a reasonable way to provide power to the board, but you can leave it off and fit USB connector CON2, regulator REG1 and its input and output capacitors. REG1 is a low-dropout regulator providing a 3.3V rail from the USB 5V supply. Programming indication above about 1.8V. That’s because pin 32 is also VDD in modes B and C, so if you have the power on and switch between modes C and D, there will be a brief overlap between the application of VDD to pin 32 and Q5 switching on, so the 47μF capacitor will charge to VDD. siliconchip.com.au This capacitor could hold that VDD voltage for a long time. When a target device is later inserted in SK1 that uses pin 32 as VCAP, that capacitor’s charge would be dumped into that pin, which is only intended to handle up to about 1.8V. To prevent that, as soon as the Australia's electronics magazine LED2 lights when there is an AC waveform at the PGD pin of CON1. This signal is coupled via a 100pF capacitor and biased to 0V with a 1MW resistor to minimise any effect on the actual programming. Whenever PGC goes low, the 100pF capacitor discharges through diode D4. When it goes high, input pin 13 of inverter September 2023  67 VDD is above 5.5V; however, the USB supply should never be high enough to allow that, nor should the VDD output of a PICkit. Also note that if you change the colour of LED3 to anything other than red, yellow or amber, it might not light up for lower VDD voltages (1.82.2V and possibly higher, depending on its colour). Mouser clicker The underside of the PIC Programming Adaptor shown at actual size with and without the Raspberry Pi Pico. These photos are just prototypes, in the final version D1-D5 are BAT54A diodes, while D6 is the sole BAV99 as shown in Fig.2. IC1f goes high, so its output goes low, lighting LED2, which draws around 1-2mA. Because PGD toggles very fast, LED2 should appear to light solid when PGD is toggling, albeit at reduced brightness. You might notice that the prototype was built with LED1 as green and LED2 as blue, while everything else shows it the other way around. That’s because a blue LED typically has a forward voltage of at least 3V, so it seemed to make more sense in hindsight for LED1 to be blue, as it’s powered from 5V, while LED2 could be powered from 3.3V or less. In practice, the blue LED2 on our prototype lights up just fine with VDD at 3.3V, and we don’t intend to program chips at voltages below that. Ultimately, it’s up to you how you arrange the colours. LED3 and LED4 are provided so that you know when power is applied to the target and that it is in the expected voltage range. Dual comparator IC2 provides this function. A ~0.6V reference voltage is developed at pins 3 and 5 of IC2 by half of diode D6, which is forward-biased by a 5.1kW resistor from the VDD rail. 68 Silicon Chip A 22kW/5.6kW/4.7kW divider across the VDD rail applies two fractional voltages to pins 2 and 6 of the same chip. These are roughly 16% and 33% of the VDD voltage. Therefore, the output of comparator IC2a goes low when VDD exceeds 0.6V ÷ 33% = 1.8V, and the output of IC2b goes low when it exceeds 0.6V ÷ 16% = 3.75V. Note that the ~0.6V reference from D6 varies slightly with VDD; hence, the percentages and voltages above are not exact. LED3 comes on with a supply voltage just below 1.8V (dimly, since that’s barely above the LED’s forward voltage), while LED4 comes on a little over 3.8V, which is higher than the 3.6V indicated. Still, in most cases, VDD will either be below 3.6V or above 4.5V. If VDD > 3.8V and output pin 7 of IC2b is low, LED4 is forward-biased and lights with around 6mA ([5V – 2V] ÷ 470W). At the same time, diode D5 is forward-biased and pulls the anode of LED3 low, so LED3 cannot also light. If VDD < 3.8V and LED4 is off, LED3 will light if output pin 1 of IC2a is low. That is the case when VDD is between 1.75V and 3.8V. The 470W resistor limits its current to a few milliamps. Note that LED4 will not extinguish if Australia's electronics magazine The mouse clicker using the Raspberry Pi Pico was previously described in Circuit Notebook (February 2023; siliconchip.au/Article/15668). When connected to the computer, the Pico appears as a mouse and triggers a click whenever its GP1 pin (pin 2) is pulled externally high. This will be the case when VDD is switched on as long as slide switch S5 is in the correct position. You position the mouse cursor over the “Program” button on your software, then, with the programming rig already set up, you put the chip in the ZIF socket and switch target power on. The Pico will click the Program button, and the chip will be programmed. You can then switch the target power off, remove the chip and insert another one, ready for programming. The whole process can take just a few seconds per chip. The Pico will do nothing with S5 off as there is nothing to pull its pin 2 high; an internal pull-down current keeps that pin low. Construction The Programming Adaptor is built on a 65.5 × 66mm PCB coded 24105231. We had ours made with a blue solder mask because we thought it’d look nice, especially as many people would use it as a bare board. There are components on both sides; Figs.3 & 4 show where they are mounted. The top side mostly has the connectors and switches, with almost all the Mosfets on the underside. The Pico mounts on the underside too. We have purposefully avoided putting any components under it, but there are solder joins for SK1, S3 and S4 under it, so it needs to be mounted on headers for spacing. We’ll get to that a bit later. The first parts to fit are the SMDs, as they are pretty flat. Because most of them are on the underside, it’s best to start there. All SMD components on the underside are either 3.2 × 1.6mm (imperial 1206) passives (including siliconchip.com.au the PTC) or three-pin SOT-23 package Mosfets or diodes. Start with the SOT-23 package devices, ensuring you don’t mix up the six or seven types. Their orientations should be evident but watch that you don’t accidentally try to solder them upside-down, with their leads sticking up in the air, ‘dead bug’ style. You don’t need to fit REG1 if you will use the Pico (which we recommend). For parts like Q2, where its central pin is very close to a through-hole pad, avoid getting solder on that nearby pad. If you do, and it goes into the hole, you might have difficulty soldering the ZIF socket later. If you get some in there, clean it up as best you can with flux paste and some solder wick or a solder sucker. For each 3-pin device, tack one lead, check the positioning, then solder the other two. Adding a tiny bit of flux paste on the three pads from a syringe before locating the part will make the solder flow much more easily. Verify that all three solder joints are shiny and have adhered to both the pin and the pad; if they are not shiny, add a touch of flux paste to the joint and touch your iron to it to reflow it. With all the SOT-23 devices in place, move on to the resistors, capacitors and PTC thermistor that mount on the underside, none of which are polarised. The two capacitors right next to REG1 do not need to be fitted if you are not using REG1. The resistors will be printed with codes like 102 or 1001 for 1kW, 1005 We designed this as a compact board so it doesn’t take up much space on your workbench, even with a PICkit or similar hanging off the side. That requires the controls to be closely spaced together, but we find them all to be accessible enough during use. This version of the PCB lacks SMD LED5, which was added later. or 106 for 10MW etc. Use a magnifier to read them, if necessary. The capacitors will not be labelled, so take them out of their packages one lot at a time and solder them in place so you don’t get them mixed up. Now is a good time to clean flux residue off the board; we really like Chemtools’ Kleanium Deflux-It G2 Flux Remover, but you can use some alcohol or acetone instead if that’s all you have on hand. Inspect the solder joints under magnification to verify they’re all good. The only remaining components to fit on the underside are either the Pico or USB socket, depending on which you’re using, but leave them off for now and flip the board over. Solder the two SMD ICs, ensuring their pin 1 indicators (dots, chamfered edges etc) are at upper left, as shown in Fig.3. These are in SOIC packages with relatively widely spaced pins. After tacking one and checking the placement and orientation, you can either solder the remainder individually or apply some flux paste along the edge and drag solder the pins. Then mount Q5 (the only SOT-23 package device on the top side), then the resistors and capacitors, using the same technique as before. None of the passives are polarised. Note that the 47μF capacitor may be the same size as the others or a little larger. Larger pads are provided that suit a range of components from 2.0 × 1.2mm (imperial 0805) up to 3.2 × 2.8mm (imperial 1210). Figs.3 & 4: fit the components on the relatively compact PCB as shown here. We recommend doing it in two stages, with the first stage mostly involving fitting the SMDs, starting on the underside, plus a few of the through-hole parts. Watch the orientations of the ICs and LEDs. siliconchip.com.au Australia's electronics magazine September 2023  69 With all the SMDs in place, clean any flux residue off the top of the board, as you did for the underside, and inspect the solder joints. Next, install the five LEDs. The four 3mm through-hole types are all orientated the same way, with the shorter (cathode) leads and flat lens edges towards the nearest edge of the PCB. We pushed them down flat onto the PCB before soldering the leads to keep them neat, but you could stand them off a little if you want to. The SMD LED, LED5, is soldered similarly to the resistors and capacitors. It should have a small green dot or perhaps a T on the underside indicating the cathode, which faces towards the bottom edge of the board. If you aren’t sure, set a DMM on diode test mode and probe the two ends of the LED. When it lights up, you have the red probe on the anode and black on the cathode. The three remaining components to Step 1: check continuity Mode A1 – CON1 pin 1 to SK1 pin 24 – CON1 pin 4 to SK1 pin 19 – CON1 pin 5 to SK1 pin 18 Mode A2 – CON1 pin 1 to SK1 pin 24 – CON1 pin 4 to SK1 pin 16 – CON1 pin 5 to SK1 pin 15 Mode B – CON1 pin 1 to SK1 pin 1 – CON1 pin 4 to SK1 pin 40 – CON1 pin 5 to SK1 pin 39 Mode C – CON1 pin 1 to SK1 pin 1 – CON1 pin 4 to SK1 pin 40 – CON1 pin 5 to SK1 pin 39 Mode D – CON1 pin 1 to SK1 pin 1 – CON1 pin 4 to SK1 pin 4 – CON1 pin 5 to SK1 pin 5 Step 2: check voltages Mode A1 / A2 – SK1 pins 21 (red) & 20 (black) Mode B – SK1 pins 11 (red) & 12 (black) – SK1 pins 32 (red) & 31 (black) Mode C – SK1 pins 32 (red) & 8 (black) – SK1 pins 32 (red) & 31 (black) Mode D – SK1 pins 40 (red) & 39 (black) – SK1 pins 13 (red) & 8 (black) – SK1 pins 13 (red) & 31 (black) 70 Silicon Chip solder at this stage are switches S1 and S2 and header CON1. Before soldering the pins, ensure the switches are fully flat on the PCB. As S1 has many fairly small pins, it’s a good idea to dab a little flux paste on each before soldering them to ensure they flow properly. Any bad joints here will cause problems later. S2’s solder lugs go into generously-­ sized slots on the PCB. The solder should flow in and quickly join them to the PCB; if in doubt, add more. We suggest using a right-angle header for CON1, with the pins sticking out over the edge of the PCB, to keep the serial programmer out of the way in use (see our photos). Still, you could use a vertical header if you want to. Testing We now have enough components mounted on the board that we can do most of the testing before fitting the ZIF socket or Pico. You can still fix problems after that, but it will be harder, so let’s test it now. Fit four tapped spacers to the corners of the board using short machine screws so it will sit flat on your desk. We used two male/female jumper wires to connect to pins 2 & 3 of CON1 for applying power to the board from a bench supply. We suggest you do similar. Be careful with the polarity; the middle pin (pin 3) is GND, while pin 2, closer to the top, is VDD. If possible, start at 0V and slowly wind it up while monitoring the current draw. It should not exceed 30mA; if it does, switch it off and check for faults. Once VDD exceeds about 1.8V, you should see LED3 starting to light. It will be pretty dim, though. LED1 will remain off as we are feeding power directly into VDD and not the 5V rail. LEDs 2 & 4 should also stay off at this stage. Wind up the voltage to about 3.8V, and you should find that LED3 switches off and LED4 switches on. Continue increasing VDD to 5.5V, at which point LED4 should be pretty bright and the circuit should be drawing around 20mA. That confirms that IC2 is functioning correctly. If something different happens, check the soldering on IC2 and its surrounding components. Check that IC2 has been installed the right way around and that the surrounding component values and types are Australia's electronics magazine correct. Also check the orientations of the LEDs. Assuming that’s fine, wind the supply back to 3.3V. We are now ready to check all the routings for programming chips in the five different modes. To help you do this, we’ve added ZIF socket pin numbers to the top of the PCB since building the prototype. While you could work out the connections based on Figs.1 & 2, to make things easier, here are all the connections you need to probe. We’ll start with MCLR, PGD and PGC. Set a DMM to continuity test/buzzer mode (or low ohms if your meter doesn’t have such a mode) and then check that all the pin pairs in the Step 1 box are connected in each mode, set using S1 & S2. If any of these lack continuity or have a resistance reading above 1W, that suggests a bad solder joint on CON1, S1 or S2, so check those. They are the only components making those connections. The only other problem could be a faulty PCB, but that’s very unlikely. Still, if you’ve ruled the other parts out, you will have to trace the tracks and check them. Next, we check that GND and VDD are fed to the correct pins in each mode. Set your DMM to measure volts (eg, 20V range or similar) and then probe the pairs of pins in the Step 2 box in each mode. In each case, you should get a steady 3.3V (or whatever the exact voltage you are applying to the circuit is). If any of those are wrong, look for soldering or component placement problems with IC1 and the components like Mosfets, diodes & resistors associated with the problematic pin(s). Finally, measure the capacitance between pins 32 and 31 with it still set to mode D. You should get a reading close to 47uF. If you don’t have a suitable meter, check the voltage between pins 32 and 31. It will likely be around 1.8V, slowly dropping as the capacitor discharges through your meter. If it’s near 0, switch to mode C and back to mode D (LED5 should light briefly), then check again. If you measure more than 2V between pins 32 and 31, something is wrong with the protection circuitry involving LED5, so check its orientation and soldering, and the soldering of its 4.7kW series resistor. Finishing it Remove the spacers from the corners siliconchip.com.au of the board and solder switches S3, S4 and S5 in place, making sure they are pushed all the way down and neatly aligned and vertical (solder one pin, check, then solder the rest). That leaves SK1 and the Pico (or USB socket CON2 if you aren’t using the Pico). If not using the Pico, solder CON2 now, checking that its small pins are correctly aligned with their pads before soldering the four through-hole mounting tabs. Then solder the signal pins, being careful not to bridge them (use flux paste and wick to fix it if you do) as they are very close together. Mounting the Pico is a little tricky since one of its rows of pins is opposite the ZIF socket. The ZIF socket has only about half a millimetre of clearance between its plastic body and the top of the PCB, and we’ve used throughhole headers for simplicity. Luckily, it isn’t all that hard to work with this arrangement. Our solution is as follows, although we’ll mention another possibility later. We started by inserting two low-­ profile 20-pin female headers into the rows of Pico pins on the underside of the board. Then we inserted two 20-pin regular male headers with the short sides into those sockets and placed the Pico on top, with the longer pins going through its pads. The Pico’s USB socket faces away from the main board (see the photos). We then pushed the two sockets fully onto the PCB and made sure they were perpendicular to it before soldering all their pins. After that, we soldered the headers to the pads on top of the Pico. Note that you could solder the headers in the usual manner – with the short pins on the Pico side – but then the headers will not fully insert into the low-profile sockets. A neater option would be to use low-profile headers on the Pico, allowing you to use slightly shorter (eg, 12mm) spacers as feet for the board. The trick now is to use a pair of sharp sidecutters to snip all the header socket solder joints as close to the PCB as possible that will be under the ZIF socket. Don’t cut the whole solder joint off but try to keep each one to a maximum of around 1mm above the top of the board. You can then insert the ZIF socket into its pads (straightening its pins if necessary). It won’t quite push down all the way, but all its pins should go through the PCB and stick out the other siliconchip.com.au Parts List – PIC Programming Adaptor 1 double-sided PCB coded 24105231, 65.5 × 66mm 1 6-pin header, straight or right-angle (recommended), 2.54mm pitch (CON1) 1 Raspberry Pi Pico (MOD1) (optional; alternative power supply parts are listed below) 1 40-pin universal ZIF socket (SK1) 1 4P4T vertical PCB-mount slide switch (S1) [SS-44D02-G10] 1 DPDT sub-miniature vertical solder tag slide switch (S2) [Jaycar SS0852, Altronics S2010] 3 SPDT micro vertical slide switches (S3-S5) [Jaycar SS0834] 4 M3-tapped 15mm hex spacers (can be 12mm if low-profile headers are soldered to Pico) 4 M3 × 6mm panhead machine screws 2 20-pin low-profile female headers, 2.54mm pitch (for MOD1) 2 20-pin headers, 2.54mm pitch (for MOD1; ideally low profile but regular headers will work) Semiconductors 1 74HC04 hex CMOS inverter, SOIC-14 (IC1) 1 LM393 dual single-supply comparator, SOIC-8 (IC2) 5 AO3400 logic-level, low Rds(on) N-channel Mosfets, SOT-23 (Q1-Q5) 4 AO3401 logic-level, low Rds(on) P-channel Mosfets, SOT-23 (Q6-Q9) 1 2N7002K logic-level N-channel Mosfet, SOT-23 (Q10) 1 BSS84 logic-level P-channel Mosfet, SOT-23 (Q11) 4 3mm LEDs with diffused lenses; blue, green, red & yellow (LED1-LED4) 1 SMD high-brightness red LED, M3216/1206/SMA package (LED5) 5 BAT54A dual common-anode schottky diodes, SOT-23 (D1-D5) 1 BAV99 dual series signal diode, SOT-23 (D6) 1 100mA PTC thermistor (PTC1) [eg, 1206L050YR] Capacitors (all SMD X7R ceramic, M1206 or M0805 size unless noted) 1 47μF 6.3V X5R or X7R, M3226/1210, M3216/1206 or M2012/0805 size 7 100nF 1 100pF Resistors (all SMD 1%, M3216/1206 or M2012/0805 size unless noted) 1 10MW 5% 1 1MW 2 100kW 1 22kW 1 5.6kW 6 5.1kW 2 4.7kW 1 1kW 3 470W 2 22W Parts for optional USB power supply 1 SMD micro-USB socket (CON2) 1 MCP1700T-3302E/TT 3.3V low-dropout linear regulator, SOT-23 (REG1) 1 10μF 6.3V X5R or X7R ceramic capacitor, M3216 or M2012 size 1 100nF 50V X7R ceramic capacitor, M3216 or M2012 size Optional SMD adaptor recommendations Narrow SOIC (0.15”), 8-16 pins [AliExpress; siliconchip.au/link/ablr] Wide SOIC (0.3”), 20-28 pins [AliExpress; siliconchip.au/link/abls] MSOP-8 [AliExpress; siliconchip.au/link/ablt] SSOP-28 [AliExpress; siliconchip.au/link/ablu] TSSOP-28 [AliExpress; siliconchip.au/link/ablv] (unsuitable for SSOP, despite what the description says!) side by about 1mm, which is enough to solder them comfortably. You might want to put ~1mm shims under it at both ends so it’s sitting evenly, although we evened it up by eye. Optionally, add a little flux paste onto the ZIF socket pads before soldering all 40 pins. That will ensure the solder flows smoothly and wicks into the through-holes around the pins, giving a solid mechanical and electrical bond. The other option we considered, Australia's electronics magazine which is a bit simpler, was first fitting SK1 pushed all the way down, then soldering headers to the Pico in the usual way. It is then possible to insert those headers into the PCB pads until they touch the underside of the ZIF socket, making sure it is parallel to the main PCB, then solder them from the side. However, that will make the Pico captive. We purposely avoided putting any components under the Pico, so that is not unreasonable, but half the ZIF September 2023  71 The PIC Programming Adaptor can be used with a variety of SMD-to-DIP adaptors, allowing you to program SMD chips. For example, the adaptors shown above plug directly into the 40-pin ZIF socket. The adaptor on the right is actually for an ATmega328; we’ll have more on programming SMD chips in next month’s issue. socket solder joints will be inaccessible. So you’ll want to ensure they are all good before doing that. Only pins 2, 36, 38 & 39 of the Pico need to be soldered. All the GNDs are connected on the board, but one (eg, pin 38) is sufficient. So you could solder just those pins, allowing you to desolder it later if necessary. Finally, reattach the spacers to the corners of the board to act as feet. Final testing You can now plug the board into your computer via a USB cable and check that LED1 lights. Switch on S4, and either LED3 or LED4 should light, depending on the position of S3. Switching S3 should alternate between LED3 on/LED4 off and LED4 on/LED3 off. You can now test program a chip. Switch it off, select the appropriate mode and put the chip in the ZIF socket. Plug your serial programmer into CON1 and ensure S3 is set to the appropriate voltage (3.3V is safe). Set S5 off, then switch on target power with S4. Check that your programming software can connect to, program and verify the chip. If you are using the Pico, switch off the target power and set S5 on to test the mouse clicker. Put your computer’s mouse over something that will let you know if it’s clicked, then switch S4 on. Your computer should act like the mouse was clicked. Using it It’s pretty straightforward, but we have a few hints. Firstly, you might want to stick a rubber foot to the underside of your serial programmer or place PIC Programming Adaptor Kit SC6774 ($55): a complete kit is available which includes the Pi Pico, but does not include the optional USB power supply parts. 72 Silicon Chip something about 12mm thick under it, so it doesn’t try to pull the board over. While you can change the mode with the target power on, doing that with it off is safer. Don’t change the mode with the target power on if there’s a chip in the ZIF socket. In general, it’s best to fully set up the programming rig before inserting a device to program. All the chips we tested can be programmed at 3.3V, so you can generally leave S3 on that setting. That way, you won’t accidentally apply 5V to a chip with a maximum 3.6V rating. Some older chips that are compatible with this board need 5V for programming; if doing that, we suggest changing back to 3.3V immediately afterwards to be safe. If you change to mode D with the power on, ensure LED5 is not illuminated before inserting a device in the ZIF socket. You might notice LED5 glowing very dimly with target powered enabled in mode D; that is normal. If programming several chips using Microchip MPLAB IPE, after you’ve used the Connect button to let the programmer identify the first chip, hover the mouse cursor over the “Program” button, then switch on the target power. It should trigger programming almost immediately. When that finishes, switch off the target power, remove the chip, insert the next one, and switch the target power back on. Repeat as needed. If you have a PICkit, you can let it power the target chips. In that case, you will need to Disconnect/Reconnect each time so that you aren’t pulling a chip out of the ZIF socket while it’s powered. When powering the target from the PICkit, leave S4 off. Programming SMD chips You can also use this Adaptor to program compatible chips with up to 28 pins in packages like SOIC, MSOP, SSOP and TSSOP. To do that, you need Australia's electronics magazine the appropriate SMD-to-DIP adaptor (also known as “test sockets”). They are not overly expensive, but you may need a few different types. Some we recommend are in the parts list; here are more details: 1. A 28-pin TSSOP adaptor will let you program any TSSOP chip we have come across, from 8 pins to 28 pins, although the common pin counts for TSSOP chips are 14, 20, 24 or 28 pins. 2. Similarly, a 28-pin SSOP adaptor will let you program any SSOP chip. While TSSOP and SSOP are very similar, they are not the same width, so you can’t program an SSOP chip in a TSSOP socket and probably can’t do the reverse. 3. Some 8-pin PICs are available in the even smaller MSOP package. For those, you will need an MSOP-­ specific socket. 4. SOIC/SOP chips come with 8 to 28 pins and, unfortunately, in different widths. Most chips below 16 pins are 0.15” (3.8mm) wide, while most chips from 20 to 28 pins are 0.3” (7.6mm) wide. 20-pin chips can come in either width. The sockets in the parts list suit these two widths, but be aware that 0.2” (5.1mm) wide SOIC/SOP chips also exist. Coming up Programming other SMD chips out of circuit, like SOT-23-5/6, TQFP32/44/48/64/100 and others is possible, but it is less commonly required than the DIP and SOIC chips this Adaptor can handle. Still, we need to do it as we sell those chips programmed, and some readers may want to do that as well. We have designed suitable rigs, and they are not easy to find commercially (or at reasonable prices). So we will have an article next month explaining how to program various types of micros (PICs, AVRs and others) in those packages. SC siliconchip.com.au SERVICEMAN’S LOG The Dogs’ Collars Dave Thompson Our resident Serviceman recently replaced some failed GPS modules and dud batteries in numerous dog collars for a local hunter. It turned out to be a pig of a job! A while back, I did some electronics repair work for a local hunter. I’m not big on the hunting ethic, but I understand its appeal, especially if one (or one’s family, friends etc) will consume what gets taken. And there is often a valid reason for hunting (and fishing): clearing stocks, keeping wild herds down to manageable numbers, reducing the impact of pests on arable land and so on. I used to go out with Dad as a lad to help rid farms of rabbits, but that is about the extent of my hunting experience. The roughest it got was if we had to four-wheel-drive into some light bushland. This hunter, however, is one of those guys who gears himself up, takes half a dozen very large dogs and walks 20km into dense New Zealand bush to hunt wild pigs. I must admire his fitness and tenacity, especially as he has to carry anything he catches back out, and those are heavy beasts. His dogs are all fitted with heavy-duty GPS tracking collars because they are easily lost in the bush. He carries a handheld Garmin GPS and tracks his dogs’ positions using it. He can also train them remotely, because some of the collars have a built-in shock-training feature. It’s all very clever stuff, and the collars need to be heavyduty because if these dogs encounter wild pigs, things often siliconchip.com.au get bloody! The collars that arrived had antennas ripped off, teeth marks in the heavy plastic mouldings and some of the rubberised bits torn off too. The GPS module is embedded in a plastic moulding at the end of a hard-rubberised collar. It connects via a shielded wire with a soldered joint inside the main body of the collar, which also holds a battery and the rest of the electronics. While this wire is embedded into the collar material, it is still vulnerable, and several had been ripped out. All the collars I received had stopped being recognised by the handheld unit. New GPS modules are difficult to get for these older collars, but a colleague found some for sale from Russia and ordered them. Gutting the faulty collars In the meantime, I set about disassembling these ones. Each main module is held together with five long screws and one shorter one. The heavy antenna cable, which is usually wrapped into and constrained by a rubberised moulding around the circumference of the collar, is also bolted to the main housing with a larger M3 screw. This doesn’t have to be removed to swap a battery, but as I would have to take the PCBs out, it was much easier to do that without the antenna springing about the bench. Australia's electronics magazine September 2023  73 Tearing most of the collars down was a matter of routine, and usually, the two parts of the main housing separated quite easily once the bead seal around the inside of the case was broken by using a gentle side-to-side rocking motion while pulling the smaller ‘half’ away from the main body. One thing that’s hard to describe is how they smell, not just of dog, but all manner of dried fluids (that I don’t want to think about) trapped in the nooks and crannies of the collar and modules. It’s quite a grubby job! Aside from that, a couple of the collar modules had cases that had been distorted slightly – by pig bites if the teeth marks were anything to go by – enough to make separating them a bit tougher. That could also affect the weatherproofing, so I’d have to consider that when I got to putting them back together. Two small inline plugs must be removed from the main PCB so the two halves can be fully separated. The space inside is tight, and the cables from the battery and the indicator LED PCB that live in the main part of the housing are very short. Some positional juggling is required to pull the plugs from their sockets cleanly. Getting them back on later would be just as much fun! The first thing I did was get all the weatherproofing o-rings and seals out of the housings, very carefully because they’d have to go back in. I then used an old toothbrush to remove the dried whatever-it-is, dust, and dirt from the edges and other obvious places. I didn’t want that all over my workbench or dropping into the work or joints as I soldered them. A bit of a faff Two of the collars were the shocker types. These are easily distinguished by the two metal-tipped probes poking out of the main module into the collar’s neck area. Aside from being able to shock the dog, just wearing these types of collars cannot be that comfortable for the poor pooch running around the countryside! The issue with replacing the GPS module on this type is that those prongs are hard soldered into the PCB inside the module, and I was going to need to flip the board over to access the GPS module’s signal wires underneath. The boards are held down with four small screws, but to get the board off, I’d have to simultaneously heat two large soldered joints (about 3mm across and 30mm apart) on one edge of the board, as well as four PCB-mounted transformer leads on the other side (I assumed this was the step-up transformer for the shocker side of things) or completely desolder all of them to the point that I could lift the board. I knew this would be unlikely to succeed because of the size and number of the joints and their locations. The transformer’s core was physically glued into the case and couldn’t be lifted with the board, so I had no option but to free its leads. What to do... What I used was a combination of both strategies. I desoldered the posts and transformer leads as much as I could, using suckers and solder wick. Then, with the soldering iron heating one large terminal, I very gently lifted the board a fraction of a millimetre using a hard plastic spudger. I found a spot to pry between a tiny bare section of the board and the plastic moulding below. Twisting the spudger would give about 1mm of lift at 74 Silicon Chip full turn, so I could control the amount the board moved. The PCB was very thin, so I had to be very careful not to use too much pepper. I ensured the part of the PCB I could lever on had nothing on it and no tracks near it. After moving the first one a smidgen, I then let everything cool and did the same on the other terminal. Once I had it a millimetre or so up on this side, I had enough room to do the same on the transformer leads. I then repeated this process until I could lift the board clear. It was a real faff to do, but there was no other practical way for me to do it with my limited soldering tools. The trial wasn’t over once I had the PCB flipped. The GPS signal cable feeds through the main module body and is soldered onto the board. This whole area, including the aperture through the module and the adjacent area on the PCB, is covered in a very strong sealant for weatherproofing. It all had to be removed before I could access the cable and the solder joint on the board. I’m not sure what this stuff is, but it is hyper-strong and very adhesive. Since I was replacing the GPS module anyway, I simply cut the cable as close as I could and used my various dental picks and tweezers to pry the goop out. I had to be especially careful on the board because of the adhesion to all the SMDs underneath and the fact that the tracks are very fine; the solder pads are surprisingly easy to peel, as I discovered with the first one I did. It is incredibly finicky work, and I made good use of my headset and illuminated desk magnifiers. Spare parts that come with fixings Once all the goop was off, installing the new GPS module was a simple job. It comes with a short length of collar attached, along with the signal cable, and these new ones differed in that instead of a tough rubberised compound for the collar part, they had braided Nylon; no doubt just as tough, while being more flexible. Australia's electronics magazine siliconchip.com.au To start the reassembly, I first threaded the new collar’s cable through the gap in the main module housing, now cleared of resin, and screwed the Nylon part of it (using holes burned into it) onto the module’s housing with three new small PK-type screws that came with the kit. Even this was difficult, because of the location of the screws and the need to hold three different assemblies in such a way that I could get to the screws and wind them in. By the last collar, I had this process down pat! With the new collar screwed on and not moving about (much), I could then position the new cable, which was about 15mm too long, near the solder pads on the PCB. I cut it to length, stripped it back and soldered it onto the pads I’d cleaned earlier after removing the old bits of cable. All pretty straightforward, just challenging due to the size and position of everything. And as I mentioned earlier, I had an extra repair step because I’d lifted one of the solder pads and a little of the track while trying to take the sealant off the first board I cleaned. I had to now get this under the scope to see what damage I’d done and how I could repair it. The missing pad was the ground to which the shielding foil from the GPS signal cable was to be soldered. Luckily, there was enough copper on the board right next to where it used to be. This rang out as part of the ground plane layer, so I carefully scraped off the lacquer and green mask until I had bright copper. I fluxed and tinned that, creating a new pad, and then soldered the signal wire in as usual. Disaster averted! Replacing the goop Before replacing the PCB into position, I had to put some new goop on it. The new parts came with a large syringe filled with clear replacement sealant, the problem being that once opened, this would go off within a day, even the stuff in the syringe. To mitigate this, I prepped all the boards on all the collars this same way so that I could do all the sealing and then all the reassembly at the same time. The process went well, and I cleaned up what runoff there was on each collar as I reassembled it. Once the sealant had hardened, I tested each one before putting the siliconchip.com.au Items Covered This Month • • • • • Hunter-gatherer serviceman Repairing a Simpson washing machine Putting a TV on ice A mixed bag of coffee machines All good repairs come in threes 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 final covers back on, using a known charged battery to try all of them. I don’t get a good GPS signal in the workshop, so I sat them outside and waited until the GPS signal light turned green to indicate satellites were acquired. At this point, I made a rookie mistake. I’d used one module to test all the collars and then reassembled them back with their own module halves and batteries. I bet you can see where this is going... Before that, though, I had to reinsert all the o-rings and rubber gaskets I had removed earlier. I also had to straighten some of the plastic mating surfaces that had been distorted by pig bites, so they made a better-sealed contact. I used a sharp hobby knife to tidy up those faces that were a little off. This part of the reassembly, putting the two ‘halves’ of the main module back together, is another juggling act. I needed to position the two parts of the module in such a way that I could reattach those two very short inline plugs from the battery holder half of the module to the PCB part on the collar, while keeping the very flexible collar in a position that isn’t fighting against me with gravity. I ended up sitting the bulk of the collar on a stack of boxes on my workbench, to take the weight, and used a strong pair of tweezers to connect each plug to its socket. I needed to take care as the plugs are easily inserted at an angle into the sockets, which would bend one or more pins out of the way. That would be a nightmare to fix. Dropping the ball Once assembled, I returned the collars to the customer, not realising that some had dead batteries from sitting unused without being charged. I just thought they were flat and assumed they’d been working beforehand, as nothing was mentioned about that. I’ll certainly be more thorough next time. The collars also use a weird charging clip that I didn’t have, and I assumed the owner would just charge them up and go. So, of course, back they came; how embarrassing. This time, I was also provided with brand-new batteries to be fitted, a set of charging clips and a nice new handheld unit so I could test them all properly. Something fun to play with! But first, it’s back to the workbench! What I like about these parts is that they come with everything I need to do the job. For example, the battery in each module is held in by a form-fitted and quite heavyduty metal bracket, screwed into the moulding using four tiny PK screws. The new battery came with a new bracket and a tiny bag of screws. I like when manufacturers think things through. Australia's electronics magazine September 2023  75 Getting the battery out was as simple as undoing those screws and tipping everything out. One thing I didn’t think to do was to check the position of the lead on the battery before I removed it. It transpired that the pre-welded lead is offset slightly, and is so short that if the battery is installed rotated toward the bottom, it will be a real pain to connect to the PCB. While forcing the cable to reach the PCB with the battery mounted the wrong way is possible, I wasn’t about to make things harder for myself! I double-checked my positioning theory against the factory-installed batteries and performed the same battery replacement in all the others (including dropping two of the screws I was taking out; thank the servicing Gods that spares were provided). When I was sure everything was good to go, I reassembled them as outlined above. This time, things went a lot smoother. Once charged, all lit up and tested fine in the handheld. Now convinced, that all were ready for the rough and tumble of the hunt, I returned them to their owner, and imagine they are out there, deep in the bush somewhere, doing their jobs. Simpson washing machine repair S. S., of Strathfield, NSW decided to try a repair himself rather than pay for an expensive service call. That was a good decision... I ran the washing with my usual deep rinse cycle for one hour and 17 minutes. I went off and did other chores, but when I checked it a little while later, I noticed that the machine was off with no lights or display. The power point was still on, and the room lights were working, but after switching it off and on a couple of times, there were still no lights or display. I unplugged the Simpson SWT704 machine and plugged in a radio, which worked, so the washing machine had died. I thought it was about eight to 10 years old; I asked my wife when we bought it, but she couldn’t remember exactly. I considered putting in a service call to Simpson, but after Googling “dead Simpson SWT704”, I found that a few others had this problem due to a failed control board. After more reading, I figured that’s probably what had happened to ours. So I decided to give myself a few days before arranging a service call. I undid a few screws at the back and was surprised at how easy it was to remove the top control panel; it just dropped forward. I must give Simpson five stars for this. There was a 2012 date on a sticker, so we were probably right that it was about 10 years old. The control board has mains coming in and a couple of other plugs, with one going to the display board. I took the front panel knob off and removed the control board. The whole board was potted with a rubber gel and designed not to be repaired. I noticed a few spots that were browned, but not greatly. It looked like a low-power switcher with an LNK306 control chip and, surprisingly, no fuse. A few resistance checks didn’t reveal anything. So I looked up the control board and found it available at a few places, some overseas (China) and a few local ones. The local ones were more expensive, but I decided to go with a local supplier as I could get it quicker and, should there be a warranty claim, it would be easier. I settled on Genuine Appliance Spares in Melbourne at a cost of $188, including postage; still cheaper than a service call. It was in stock; I ordered it on a Sunday night, and it arrived on Tuesday. I checked it against the original and it all seemed OK; hats off to Genuine Appliance Spares for super fast service. I compared the new board to the original one and saw that the brown spots could be where it failed. After replacing the control board, I connected it up and left the assembly dropped down while I tested it. I turned it on, and bingo, it beeped and the display was back on. I checked the selector switch and other buttons, and they all worked. I turned it back off and screwed the whole thing back together. I put a small load on and ran a quick cycle, and it was up and running again. I was happy with another successful repair for a reasonable cost. It has now been four months, and it is still going; I hope we get another 10 years out of it. The early days of pay-to-view TV J. B. of NZ worked for a national TV rental company back in the 1960s, a time when servicing was thriving and employees had to deal with a wide range of people... In those days, renting your TV was more usual than buying it. TVs breaking down was common, so the cost of repairs was a major factor driving the rental market. If the family had a poor credit rating, the TV would be fitted with a coin slot mechanism; that was the early form of ‘pay to view’. There was one particular address where the man who Both sides of the replacement control board for the Simpson SWT704 washing machine. 76 Silicon Chip Australia's electronics magazine siliconchip.com.au emptied the slot meters never found any money in the mechanism and the TV was never on or warm when he visited. I happened to be servicing in the area and phoned into the local shop to ask if they had a particular valve in stock. This led the local branch manager to request that I pop around the corner to check the offending address. From the front door, I could hear the TV was on, so I knocked to gain entry. The household was dirty and smelly (I am sure all TV techs know exactly what I mean). I was led into the front room by two scruffy kids about eight years old. I examined the slot mechanism and found it empty, so I asked the children how they got the TV to work. The answer was to get the money from the refrigerator. I said, “Show me how that works”, and they promptly returned with a tray from the freezer that had coin-sized indentations filled with ice. These were the coins to operate the TV! I reported my findings after I finished for the day to avoid having to ‘pull’ the set myself. A tale of three coffee machines The COVID-19 lockdowns had some unexpected effects for D. T., of Sylvania Southgate, NSW… For my wife and me, one was that we missed good coffee – for a while, the cafes were all shut, and when they opened, you couldn’t sit down and/or they gave you coffee in a takeaway cup like you were buying it from a service station. So we decided we needed a home coffee machine and promptly bought a Breville machine at an estate auction. Estate auctions are a real mixed bag – they’re often a third party selling the contents of a deceased estate, so no one knows the history of any of the items. In my experience, many of the items on offer have faults, especially electrical items. Ironically, this works really well for me since I get such a kick out of fixing things, but you wouldn’t want to pay too much money for anything you find there. This machine was no exception; when we got it home and tried to make our first coffee, we found it didn’t work properly – little or no water came out to brew the coffee. Luckily for us, the Breville is pretty popular. With the help of a few YouTube videos, I soon had the covers off and all the good bits exposed. I was pleasantly surprised at how serviceable the Breville machine was. All of the water connections after the pump are made with o-rings and removable/reusable metal push clips that enable disassembly and reassembly without the need for replacement parts. The two valves can be disassembled and cleaned without any special tools, the chassis comes apart without any magic tricks, and when it is open, it can be tested without putting it all back together. The only consumables are the cable ties that secure each pipe connection to the pump inlet. Overall, it is quite a good machine for those of us who like to fix things ourselves. Before too long, I managed to clear a blockage in the valve set, and I was soon making passable cappuccinos at home. Having experienced one of my cappuccinos, my son mentioned that he wouldn’t mind his own coffee machine, so my wife duly bought another machine at auction. This one turned out to be an older model, but very similar in most respects. That one worked pretty much out of the box after a bit of cleaning. However, a couple of problems remained – the grinder didn’t grind very well, and there was no ‘group cup’. Fixing siliconchip.com.au Australia's electronics magazine September 2023  77 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. the grinder requires a new ‘core’. You can get away without a grinder simply by using pre-ground coffee; however, the group cup is the thing that holds the coffee while it’s brewing, so it’s vital. All testing had been done using the group cup from the first machine. They proved elusive when we tried to buy one for the new machine. New ones cost more than the machine had cost us, and used ones were nowhere to be found. After searching for a good while, we gave up, and the second machine was packed up and stashed away. My wife is tenacious; she was straight on to looking for another one. It took a while, but recently, one came up that was shown with the group cup and some other cleaning items. She walked in triumphantly last week with a third Breville coffee machine, almost identical to our original. Unsurprisingly, this machine was also faulty. It powered up OK and made all the noises like the others did, but virtually no water came out when we tried to make a coffee. Having been down that road, I quickly had it apart on the dining room table and first attacked the valve unit. Unfortunately, while the valve unit was a little grimy, there was no distinct blockage, and it was no better after cleaning. The pump was my next target, but it wouldn’t be easy to get out, so I started looking at all the other pipeware to see if I could find a blockage. While I was at it, I drew a schematic for the plumbing, hoping it would help me figure out where the fault could be (see Fig.1). The pump outlet was pretty accessible and seemed like a convenient point to test, so I decided to see if I could test the pump in situ. When you power on the machine, it runs the pump for about a second, presumably to ensure there’s water in the heater unit before it turns on. I pulled the other machine out of storage and fed its pump outlet into a coffee cup. If I powered up the machine four times, I ended up with about half a cup of water. I got virtually no water when I did the same thing with the new machine. So out came the pump. It’s a bit hard to get to, but not impossible. Once out, it can be disassembled without any special tools. It consists of a piston pump with springs and valves, and I was disappointed that I couldn’t find anything wrong with it either. So I installed the pump from the parts machine into the new one and reran my test with the same result – minimal water output. Looking at the schematic, there wasn’t much left to go wrong – a flow meter and filter, the pump solenoid and the drive to the solenoid. Both solenoids measured roughly the same resistance and made similar noises when activated. I could easily pop the top off the flow meter, so I looked inside – it was nice and clean, and the impeller spun freely. So I cut off the cable tie holding the filter pipe to the flow meter and blew into the pipe. I was encouraged to find that Fig.1: a rough ‘schematic’ diagram for the plumbing section of a Breville BS870 coffee machine. 78 Silicon Chip Australia's electronics magazine siliconchip.com.au it felt partially blocked, but it was hard to know if that was normal. To confirm, I did the same thing to the filter from the parts machine, and was relieved to find it was much more open. I quickly connected the machine up with the spare filter and made us two coffees to celebrate. After the coffee, it was just a matter of picking up the pieces, of which there were many, and rebuilding the machine. In the process, I returned the original pump to its rightful machine since it was in slightly better condition. Then it was a matter of putting it all back together and making another cup, just to be sure it was still working. I gave it to my son, who is now making his own coffees. Chalk one more up for my wife. Tri-servicing: toaster, TV & soundbar S. M., of Learmonth, Vic went away for a couple of weeks, and when he got back, three different appliances had given up the ghost. Luckily, all turned out to be fixable... My wife and I went on a two-week interstate holiday that we had booked over two and a half years previously, but COVID had intervened. We were deciding what to do about the pets in our absence when a neighbour recommended a house-sitting group that worked very well for them. We were a little apprehensive, especially after having watched Rowan Atkinson in “Man vs Bee” with the grandchildren. Still, we went ahead, and the whole experience was very positive. The dog and cat seemed very happy, seeing the photos sent to us frequently. About a week into the holiday, we had a message from them saying our Smeg retro toaster had stopped working; when switched on, the circuit breaker tripped. They said they had one in their caravan, and it wasn’t a problem. A day or two later, we had another message to say there was a popping noise and the Toshiba 47VL900A TV stopped working. We had owned this for getting on to 10 years without a problem. They said they could cope and use the one in the kitchen area. All else went well from then on, and a good time was had by all. On our return, I pressed into action an old Russell Hobbs toaster that still worked but was somewhat intermittent with the toast level. We decided to replace the TV, as I wasn’t sure when I would get to look at it and had doubts if it was repairable. Sometime later, I got the toaster into the workshop to see what had happened. On first inspection, it looked fine, so I dug deeper. That was not so easy as the outer cover not only had screws but quite a few of those hidden plastic clips that won’t let go without a fight, then more screws, and finally, pressed metal plates that locked into each other with tabs that break off when bent more than twice. Eventually, I reached the elements to reveal the problem. One of the outer elements, mounted on a mica-like substance, had a riveted link that had come off one end and sprung out to touch the case. This link contacted the element wire on the other side to connect to another part of the element. The end that had come off was a little burnt and had obviously not made good contact, causing arcing and eventually burning off part of the rivet. I could see the element was not replaceable as all the connections were spot welded. I eventually decided that the best option was to carefully drill out the rivet (or what was left of it) and use a very small brass bolt to hold it all together. It was very tricky, as the mica-like material was very fragile. After clipping the excess length off the bolt, I reassembled it. It is still going strong after some months without a problem. Even later, I had a quiet afternoon and decided to look at the TV. I laid it out on the bench face-down on a blanket to try to access the power supply. I removed about 25 screws and, to my surprise, it came apart quite easily. I looked over the board, particularly the power supply section, and saw no apparent problems. However, there was a tiny soldered-on fuse that measured open circuit. The surrounding components checked OK. It was somewhat dusty inside, so I gave it a good blowout and removed the odd cobwebs. I decided to replace the fuse and give it a go. To my surprise, it started up fine, and I ran it for some days without a problem. My son’s old TV had just died, so I passed this one to him, and it hasn’t missed a beat since. My only conclusion is that the dust and cobwebs in the very damp conditions caused a short and blew the fuse. After installing the new TV, I was checking some things and noticed that the subwoofer attached to the Yamaha soundbar was dead. It is not immediately obvious when it is working, as the only light is an LED at the rear that comes on when it has a wireless connection. Out to the workshop it came and, upon opening it, it was clear what the problem was. These subwoofers have a side sound vent hole in the case which is very convenient for mice to come in and live. Urine had shorted the board and blown the fuse. I cleaned it all up and replaced the fuse, and it worked again. I put a small car speaker grille over SC the hole to stop the re-occurrence of this fault. Raspberry Pi Pico W BackPack The new Raspberry Pi Pico W provides WiFi functionality, adding to the long list of features. This easy-to-build device includes a 3.5-inch touchscreen LCD and is programmable in BASIC, C or MicroPython, making it a good general-purpose controller. This kit comes with everything needed to build a Pico W BackPack module, including components for the optional microSD card, IR receiver and stereo audio output. $85 + Postage ∎ Complete Kit (SC6625) siliconchip.com.au/Shop/20/6625 The circuit and assembly instructions were published in the January 2023 issue: siliconchip.au/Article/15616 siliconchip.com.au Australia's electronics magazine September 2023  79 Mk2 0-30V 0-2A bench supply Part 1 by John Clarke Every workshop or laboratory needs an adjustable voltage, current-limited DC power source. This revised 0-30V Supply includes adjustable current limiting up to 2A with voltage and current metering, plus load switching. Most of the parts are commonly available; the two harder-to-get parts and the PCB are available from the Silicon Chip website. i f you have a feeling of déjà vu, that’s because it was originally published recently, in the October and November 2022 issues (siliconchip.au/Series/389). That version used an MM2005 transformer that became unavailable shortly after we published those articles. As a result, we had several constructors ask us for an alternative transformer supplier or transformer. The transformer was rather unique and had several voltage taps; we used the 24V tap for the main 30V 2A output but we also used the 30V tap to generate a negative supply rail. That is critical to allow the supply output to be adjusted down to 0V. Unfortunately, no alternative transformer could provide the required voltage taps and power in the available space. We eventually found a different transformer that’s readily available, with the same power ratings as the original. It has a significant larger 80 Silicon Chip iron core, allowing it to run cooler when delivering full power, but that also means it wouldn’t easily fit in the original design. Also, while, the new transformer has a suitable 24V winding, the other taps are not the same and so the original design had to be revamped. The resulting circuit changes are not major. Basically, we add a separate negative supply generator that is described elsewhere in this issue, as it can be used in other applications. It can even be used as a voltage doubler instead of as a voltage inverter. See the article starting on page 90 for details. A new main PCB design was required to allow for these changes and also so we could take a ‘bite’ out of the side to give the larger transformer more room, so it will fit in the same neat instrument case we used before. The mounting hole positions on the PCB and for the two parts that mount against the heatsink are in the same Australia's electronics magazine positions as the original PCB. Therefore, if you want to install this new PCB in an existing enclosure, few changes will be required. That just means new transformer mounting holes will need to be drilled, as the larger transformer has four mounting points against the original’s two. You might wonder why we’re presenting the new version in its entirety rather than just as an update. By the time we’ve published the new circuit diagram, PCB overlays, wiring diagram, parts list and other changes, the required article wouldn’t be much shorter than just describing the whole thing. We decided that doing it this way would be more clear for our readers, especially those who might not have seen the original articles. The features and specifications of the Mk2 version are essentially the same as before. The Mk2 Supply includes metering that shows the voltage and the current being drawn from it. A load switch siliconchip.com.au ▬ ▬ ▬ ▬ ▬ ▬ ▬ ▬ ▬ ▬ ▬ ▬ ▬ Features & Specifications Easy to build using mostly standard components Low noise output Excellent regulation Output voltage: 0-30V Current limit: 0-2A (non-foldback) with indicator Regulation method: linear Load regulation: better than 0.5%, 0-2A Output noise & ripple: <8mV RMS, <50mV peak-to-peak <at> 2A Meters: voltage (100mV resolution), current (10mA resolution) Voltage adjustment: single-turn or multi-turn knob Load disconnect: load switch, load indicator Over-temperature protection: disconnects load when heatsink reaches 60°C Other features: short circuit protection, clean switch on and off is used to connect or isolate the load when required, with an indicator LED to show when the output is on. The current limit can be adjusted from near zero to 2A to protect circuitry from excess current should there be a fault. A current limit indicator LED is also included. Load switching is overridden if the heatsink gets too hot, in which case the output is disconnected. If that happens, the load indicator LED will remain off regardless of the load switch position. Our power supply includes power-­ up and power-down circuitry that ­ protects the load as the Supply is switched on and off. This ensures the voltage from the regulator is fully settled before being applied to the load. Similarly, the load is disconnected quickly at power-off, well before the output drops significantly, preventing unexpected voltages from being applied to your load. Another valuable feature of our power supply is that you can adjust the output right down to 0V. Some very basic supplies will only go down to about 1.2V and there are times when that isn’t low enough. For example, if you are testing a circuit that runs from a single 1.2-1.5V cell and want to see how the circuit behaves when powered from a discharged cell at or below 1V. For the voltage adjustment, you can use a standard 270° potentiometer. However, we recommend getting a multi-turn potentiometer, especially if you want fine adjustment at low voltage settings. More on that later. The Supply is housed in a folded metal enclosure with an aluminium base and ventilated steel top cover. The front panel has the mains power siliconchip.com.au switch, knobs to adjust the output voltage and current limit, the load switch, the two indicator LEDs and the voltage and current meters. There is just the mains power input socket and a heatsink on the rear panel. Performance As this Supply uses linear regulation, it has excellent load regulation, clean current limiting and low output noise and ripple. Load regulation is tested by setting the voltage to a fixed level and changing the load resistance so that the output current rapidly swings between two extremes. With the output set to 16V, it dropped by less than 100mV when the load changed from 0A to 2A at the output terminals. When measured directly on the PCB, the voltage drop was 60% less. So most of the voltage drop is due to the wires from the PCB to the terminals on the front panel. We set the oscilloscope to monitor the AC voltage so that only the sudden changes in voltage are shown. Scope 1 shows what happens with a sudden load change. This revealed that the output momentarily dropped by 58mV when the load jumped from 0A to 2A. Similarly, when the 2A load was released, there was a positive shift of 34mV before recovery. Note the waveform does not show the DC voltage change, just the momentary shift in voltage from 16V. There is no visible change in voltage when the oscilloscope is set to show DC voltage at 2V/div so that the full DC voltage can be seen. That’s because 58mV and 34mV are only 0.4% and 0.2% of the output voltage, respectively. Output noise We measured the output noise and ripple under three different conditions: with the Supply unloaded, at 2A load and with the current limit active just below 2A. All three results showed low levels of noise and ripple. Scope 2 shows the output noise and ripple at 16V with no load for the top waveform, a 2A load for the middle waveform and current limited at 1.92A Scope 1: the Supply’s output voltage only dropped by 58mV with a 2A load step and recovered in about 300ms. Australia's electronics magazine September 2023  81 Everything fits neatly into the fairly compact and attractive instrument case. Transistor Q1 is located behind the large capacitors at left, and is attached to the case opposite the heatsink, with the thermal switch above it. The blue multi-turn voltage adjustment pot is also clearly visible. for the lower blue waveform. There is no discernible difference between the loaded and unloaded waveforms. However, there is a little more ripple for the current-limited waveform as current limiting is taking over from voltage regulation. Operating principles The basic circuit for our power supply (Fig.1) is based on an adjustable three-terminal regulator (REG1) and current boost transistor (Q1). REG1 is an LM317 that, in its standard arrangement, can deliver a voltage ranging from about 1.2V up to 37V at 1.5A. The regulator has internal protection such as current limiting, thermal shutdown and safe operating area (SOA) protection. The output voltage is set using resistors connected between the output and adjust pins (R2; 100W) and between adjust and ground (VR1). The resistor between the adjust and output pins sets the quiescent current of the regulator, which needs to be at least 12mA if it is to maintain regulation when the output is otherwise unloaded. When the adjust terminal is connected to ground, the output voltage equals the reference voltage, which appears between the output and adjust pins. This is between 1.2V and 1.3V, depending on tolerances in the regulator manufacturing. For our circuit, the resistance is set at 100W to provide the 12mA minimum load current for the worst-case specification when the regulator reference is 1.2V. There is a minimal current of typically 50μA flowing out of the adjust terminal, which is small enough that it can usually be ignored. The output voltage calculation then simplifies to the following equation: Vout = Vref × (1 + VR1 ÷ R2). If you need to include the adjust terminal current, that current, multiplied by the VR1 resistance, adds to the output voltage. What the simplified circuit of Fig.1 does not show is that, in the full circuit, the lower end of VR1 is connected to a negative supply that is greater in magnitude than Vref. That way, the output can be adjusted down to 0V. With the reference voltage cancelled out, the output voltage calculation simplifies to Vout = Vref × VR1 ÷ R2. Current boosting Scope 2: output noise and ripple with no load (top), 2A load (middle) and 1.92A current limited (bottom). 82 Silicon Chip Australia's electronics magazine As shown in Fig.1, REG1 is used in conjunction with PNP power transistor Q1. This transistor supplies the bulk of the load current but with the output voltage controlled by REG1. siliconchip.com.au The new inverter module is mounted to the main PCB, and can be seen just in front of the transformer. The wire soldered from the unused transformer tap to the top of the inverter PCB is just for physical support. The input voltage is applied to the base of Q1 and the regulator input via a 33W resistor. As current is drawn from the output, it also flows through the 33W resistor, so the voltage across it rises. When 18mA flow is reached, the voltage between the base and emitter is 0.6V. At this point, transistor Q1 starts to conduct and bypasses extra current around REG1. The result is that the circuit can supply more current than the 1.5A limit of the LM317, while the LM317 remains in control of the output voltage. However, we do lose the over-­ current shutdown feature provided by the LM317, limiting the output to 1.5A. But that’s what we need to get a higher output current. We use extra circuitry to add back current limiting, with the advantage of being able to adjust the limit over the 0-2A range. This boost circuit includes a hidden bonus in that it prevents the regulator from shutting down due to high power dissipation (assuming Q1 has sufficient heatsinking). This way, the circuit can supply the full 2A across the entire voltage range. Without the boost transistor, the regulator would shut down when there is high dissipation, ie, high current at low output voltages. For example, if the regulator output voltage is 12V, the input is 32V and there is a 1A current flow, the regulator (without Q1) will be dissipating 20W ([32V − 12V] × 1A). The specifications for the device package show a 5°C/W temperature rise between the siliconchip.com.au case and junction. Thus, at 20W, the junction temperature will rise 100°C above the case (20W × 5°C/W). For a case temperature of 25°C, the junction will be at 125°C and the device will shut down. So the Supply wouldn’t be able to provide 1A at 12V without shutting down. By adding the boost transistor, REG1 is only handling 18mA and dissipating about 360mW in this case (18mA × [32V − 12V]) and the junction will only be 1.8°C above the case temperature. The dissipation is instead handled by Q1. Its junction temperature will not be anywhere near as high as the regulator, as it has a much lower junction-to-case thermal resistance of 1°C/W. So at 20W, its junction will only be 20°C above the case temperature. Using a large enough heatsink, we can maintain the case temperature at a reasonably low value. We do lose the thermal shutdown feature of the LM317 as a consequence of directing the primary current through Q1. The junction temperature for REG1 will essentially follow the temperature of the heatsink. To solve this, we attach a separate thermal switch to the heatsink to provide an over-temperature shutdown. It opens at 60°C, disconnecting the power supply load and allowing the transistor to cool. We haven’t mentioned the capacitors in Fig.1. The bank of three 4700μF capacitors at the input smooths out the ripple from the pulsating DC derived from rectified AC. This is required to keep the regulator’s input voltage at least 2.5V above the output to maintain voltage regulation. The capacitor between REG1’s ADJ pin and ground reduces ripple and noise at the regulator output, while Fig.1: the basic regulator arrangement is essentially the standard LM317 application from its data sheet but with current booster transistor Q1 added to increase the maximum output current and improve heat dissipation. As REG1 draws more current, the voltage across the 33W resistor at its input rises until Q1’s base-emitter junction becomes forward-biased, and Q1 takes over delivering the load current. Australia's electronics magazine September 2023  83 the capacitor between Vout and GND prevents oscillation and improves transient response. Diode D1 protects REG1 from the capacitor discharging through REG1 if the output is short-­ circuited. Full circuit details The whole circuit is shown in Fig.2 (overleaf). Power for the Supply is derived from the mains via transformer T1. T1’s primary winding is supplied with 230V AC via fuse F1 and power switch S1. The secondary winding of T1 comprises two 12V windings with a 9V tap in each. To obtain 24V AC, the two windings are connected in series, with the 12V end of one connected to the 0V end of the other. That maintains the output phase so the two 12V AC voltages add together. It should be mentioned that the labelling of the winding as 0V one end and 12V on the other end with a 9V tap is entirely arbitrary. It all depends on which end you set as the 0V reference. You could label the ends in the opposite way, with the 12V end being 0V and the 0V end being 12V. The tap would then be at 3V instead of 9V. Using the windings in this reversed way allows us to get a 15V output, by adding the 12V from the other winding to a 3V tap. The resulting 0V, 15V and 24V connections from the transformer then go to the PCB via CON1. The AC voltage between the 0V and 24V taps of T1 is full-wave rectified by bridge rectifier BR1 and filtered using three paralleled 4700μF 50V capacitors to produce a nominal 32V DC. Typically, the DC voltage is higher than this as the mains is usually above 230V AC, and the transformer is not usually heavily loaded. This filtered voltage is applied to the emitter of transistor Q1. The output of the regulator and the collector of Q1 are applied to the load via the normally-open contact of relay RLY1. The relay control circuitry will be described later. Bringing the output to 0V The circuitry around REG1 differs from that shown in Fig.1 in that, instead of connecting to GND, VR1 is connected to the output of op amp IC1a. IC1a produces a negative voltage below ground, to cancel out the reference voltage of REG1. Setting IC1a’s output negative by the same 84 Silicon Chip Parts List – 30V 2A Bench Supply 1 double-sided PCB coded 04107223, 100 × 140mm (main board) 1 double-sided PCB coded 04105222, 56 × 61mm (front panel control board) 1 vented metal instrument case, 160 × 180 × 70mm [Jaycar HB5446] 1 24V 60VA EI-core transformer (T1) [Altronics M2165C] 1 voltage inverter module (see article starting on page 90) 1 current and voltage meter [Core Electronics 018-05-VAM-100V10A-BL] 1 fan type heatsink, 72mm high [Altronics H0522, Jaycar HH8572] 1 SPDT 10A, 24V DC coil relay (RLY1) [Altronics S4162C, Jaycar SY4067] 1 IEC male chassis connector with integral fuse holder [Altronics P8324, Jaycar PP4004] 1 500mA M205 fast-blow fuse (F1) 1 rubber boot for IEC chassis connector [Altronics H1474, Jaycar PM4016] 1 DPST neon illuminated mains-rated switch (S1) [Altronics S3217, Jaycar SK0995] 1 SPDT toggle switch (S2) [Altronics S1310, Jaycar ST0335] 1 normally-closed 60°C thermal cutout (TH1) [Jaycar ST3821] 1 red binding post [Altronics P9252, Jaycar PT0453] 1 black binding post [Altronics P9254, Jaycar PT0454] 1 green binding post [Altronics P9250, Jaycar PT0455] 1 silicone insulating washer for TO-3P package devices 1 silicone insulating washer and bush for TO-220 package devices 1 3-way pluggable terminal socket, 5.08mm spacing (CON1) [Altronics P2573, Jaycar HM3113] 1 3-way screw terminal plug (for CON1) [Altronics P2513, Jaycar HM3123] 1 4-way pluggable terminal socket, 5.08mm spacing (CON2) [Altronics P2574, Jaycar HM3114] 1 4-way screw terminal plug (for CON2) [Altronics P2514, Jaycar HM3124] 2 14-pin IDC boxed headers (CON3, CON4) [Altronics P5014] 2 14-pin IDC line sockets (for CON3 & CON4) [Altronics P5314] 1 3-way screw terminal with 5.08mm spacing (CON5) 2 2-pin vertical polarised headers, 2.54mm spacing (CON6, CON7) [Altronics P5492, Jaycar HM3412] 1 2-pin polarised header plug (for CON7) [Altronics P5472 and 2 x P5470A, Jaycar HM3422] 1 8-pin DIL IC socket (optional; for IC1) 2 5mm LED bezels 2 knobs (one to suit VR1, and another to suit VR3) 10 1mm PC pins (add 13 if using them for all test points) Wire & cable 1 150mm length of 14-way ribbon cable 1 150mm length of brown Active wire stripped from three-core 7.5A mains cable 1 150mm length of blue Neutral wire stripped from three-core 7.5A mains cable 1 150mm length of green/yellow Earth wire stripped from three-core 7.5A mains cable 4 100mm lengths of 7.5A hookup wire (assorted colours) 2 150mm lengths of 7.5A hookup wire (one red, one black) Hardware etc 6 M4 × 10mm panhead machine screws 6 M4 hex nuts 6 M4 star washers 4 6.35mm-long M3-tapped Nylon spacers 8 M3 × 5mm panhead machine screws 2 M3 × 20mm panhead machine screws (for Q1 and REG1) 4 M3 × 15mm panhead machine screws 1 M3 flat steel washer 6 M3 Nylon washers Australia's electronics magazine siliconchip.com.au magnitude as REG1’s reference voltage will allow the output to go to 0V. 6 M3 hex nuts 2 small M3.5-threaded right-angle brackets [Jaycar HP0872, pack of 8] 2 crimp eyelets (Earth connections to chassis) 4 blue female spade crimp connectors (connections to mains on/off switch) 5 150mm cable ties 5 100mm cable ties 1 50mm length of 25mm diameter heatshrink tubing 1 50mm length of 6mm diameter heatshrink tubing 1 50mm length of 3mm diameter heatshrink tubing 1 small tube of thermal paste Semiconductors 1 TL072P dual op amp, DIP-8 (IC1) [Altronics Z2872, Jaycar ZL3072] 1 INA282AIDR or INA282AQDRQ1 shunt monitor, SOIC-8 (IC2) [SC6578] 1 LM317T three-terminal adjustable regulator, TO-220 (REG1) [Altronics Z0545, Jaycar ZV1615] 1 LM336-2.5 voltage reference, TO-92 (REG2) [Altronics Z0557, Jaycar ZV1624] 1 TIP36C PNP 100V 25A power transistor, TO-3P (Q1) [Altronics Z1137, Jaycar ZT2294] 1 2N7000 N-channel Mosfet, TO-92 (Q2) [Altronics Z1555, Jaycar ZT2400] 3 BC547 45V 100mA NPN transistors, TO-92 (Q3-Q5) 1 BC327 45V 500mA PNP transistor, TO-92 (Q6) 2 5mm high-brightness red LEDs (LED1, LED2) 1 33V 1W zener diode (ZD1) [1N4752] 2 12V 1W zener diodes (ZD2, ZD3) [1N4742] 1 GBU806 bridge rectifier (BR1) [Jaycar ZR1362] 5 1N4004 400V 1A diodes (D1, D4, D7, D8, D10) 1 1N5404 400V 3A diode (D2) 3 1N4148 75V 200mA signal diodes (D5, D6, D9) Capacitors 3 4700μF 50V radial electrolytic 1 2200μF 35V radial electrolytic 1 47μF 16V radial electrolytic 1 10μF 50V non-polarised/bipolar radial electrolytic 1 10μF 35V/50V/63V radial electrolytic 2 10μF 16V radial electrolytic 1 1μF 16V radial electrolytic 1 1μF multi-layer ceramic 4 100nF 63V/100V MKT polyester Potentiometers 1 16mm 5kW linear single-gang potentiometer (VR1●) [Altronics R2224, Jaycar RP7508] 1 16mm 10kW linear single-gang potentiometer (VR3) [Altronics R2225, Jaycar RP7510] 2 5kW multi-turn top-adjust trimpots (VR2●, VR4) [Altronics R2380A, Jaycar RT4648] 1 500W multi-turn top-adjust trimpot (VR5) [Altronics R2374A, Jaycar RT4642] 2 10kW multi-turn top-adjust trimpots (VR6, VR7) [Altronics R2382A, Jaycar RT4650] ● alternatively and ideally, replace VR1 with a 2.5kΩ multi-turn pot [Bourns 3590S-2-252L – element14 2519607; Digi-Key 3590S-2-252L-ND; Mouser 652-3590S-2-252L] and delete VR2 Resistors (all 1/2W, 1% unless otherwise stated) 2 100kW 1 33kW 4 10kW 2 4.7kW 2 2.2kW 2 1kW 1 330W 4 100W 1 33W 1 20mW 1W M3216/1206-size SMD resistor [Vishay WSLP1206R0200FEA or similar – element14 1853240; Digi-Key WSLP-.02CT-ND; Mouser 71-WSLP1206R0200FEA; part of SC6578] siliconchip.com.au Australia's electronics magazine Negative supply A negative supply is required to power the negative rail of op amp IC1. This is so that its output can go negative. This supply is derived from a voltage inverter module that converts a positive supply voltage of around +12V to a negative supply of around -8V. The details of the small circuit board that does this conversion are in the article starting on page 90 of this issue. Diode D4 prevents the -8V supply from going more than one diode drop above 0V. That could otherwise occur at power-up. Note that there is no diode D3 in the circuit. D3 was used in the original design, and to maintain similarity with it, we kept the same diode numbers. The -8V supply provides a bias current for REG2, an LM336-2.5V shunt regulator. It produces a regulated negative supply with its positive terminal connected to ground, and its negative terminal connected to the -8V supply via a 2.2kW current biasing resistor. As a result, the voltage at its negative terminal is a stable -2.49V, even with temperature variations, due to diodes D5 and D6 providing temperature compensation. Trimpot VR7 is adjusted until there is very close to -2.49V across REG2. This reference voltage is bypassed with a 10μF capacitor. Trimpot VR6 connects across the -2.49V reference to provide an adjustable negative voltage to offset the reference voltage produced by REG1. This negative reference is obtained from the wiper of VR6, which is adjusted to provide a fixed voltage between -1.2 to -1.3V to counter REG1’s reference voltage between its output and adjust pins. The wiper of VR6 connects to the non-inverting input of IC1a. IC1a acts as a unity-gain buffer, where the output voltage follows the input. IC1a’s output then sinks 12-13mA from REG1 at the lower end of VR1. With VR6 correctly set, REG1’s output is zero when VR1 is fully anti-clockwise. Current monitoring IC2 measures the current drawn by the load. This measurement, in conjunction with op amp IC1b and Mosfet Q2, is used to provide current limiting. IC2 is a current monitor that measures the voltage drop across the 20mW shunt in the GND supply line. The September 2023  85 Fig.2: the complete Supply circuit. Note how many signals are routed to CON3, then via a ribbon cable to CON4 on the front panel control board, and in some cases, back through the cable to another pin on CON3. voltages at either end of the shunt are applied to pins 1 and 8 of IC2, which amplifies the difference by a factor of 50. We selected the shunt so that the pin 5 output of IC2 provides 1V per 1A of output current. There is a 20mV voltage drop across the 20mW shunt at 1A, which, when multiplied by 50, gives 1V. But note that IC2’s output voltage is with respect to the -2.49V reference rather than the 0V rail. 86 Silicon Chip The calibration is linear, so IC2 will deliver 2V above the -2.49V reference for a 2A current flow or proportionally lower values at intermediate currents. For current limiting, we compare the current measured by IC2 with the maximum set current level. The current setting for limiting is provided by a voltage divider across the -2.49V supply. The main adjustment is potentiometer VR3, with VR4 & VR5 setting the maximum and minimum Australia's electronics magazine current range limits. Ignoring VR5 for the moment, VR4 is set so that when VR3 is fully clockwise, the voltage at its wiper will be 2V above the -2.49V reference, corresponding to a 2A current limit. VR5 provides a small voltage offset above the -2.49V reference. It is used to set the minimum setting of VR3 to match the output of IC2 when there is no load current. Typically, IC2’s output will always siliconchip.com.au be above the -2.49V reference due to the small standby current drawn by the reference, IC1, IC2 and the meters. Also, there will be an offset voltage inherent to IC2 even with no current flow. siliconchip.com.au VR5 allows us to dial out this voltage so that the voltage between test point TP10 (at the top of VR5) and TP3 (at the wiper of VR3) ranges between 0V and 2V, matching the 0-2A current limit Australia's electronics magazine range. If the VR5 adjustment is made carefully, that will also allow VR3 to be rotated fully anti-clockwise without entering current limiting when there is no load. September 2023  87 Potentiometer options We have provided the option of using a standard single turn (300° rotation) potentiometer for VR1, which adjusts the Supply output voltage. In this case, it’s a 5kW linear potentiometer connected in parallel with a 5kW trimpot. This is the cheapest option, but not the best. The alternative is to use a 2.5kW multi-turn potentiometer, making it easier to adjust the output voltage, especially for low values. While we are using a potentiometer for the voltage adjustment, it is used as a variable resistance (or rheostat) rather than as a potentiometer. With a potentiometer, the wiper can produce a range of voltages between the voltages applied at the two ends of the potentiometer’s track. The wiper and just one end of the potentiometer are used to produce a variable resistance. The unconnected end of the potentiometer is often connected to the wiper, but this does not alter the resistance-versus-rotation law. When using a standard 300° potentiometer to adjust the voltage over a 0-30V range, a slight adjustment causes the output voltage to change quickly. So, for example, a 0.3V change is made with each 1% (3°) of rotation. So to change the voltage by 1V, just over 3% of rotation (10°) is required. Another problem is that while the physical end stops are 300° apart, the actual resistance element generally only changes over a 270° range, further ‘squashing up’ the adjustment range. Also, we don’t use a 2.5kW single-turn pot since they are difficult to obtain and rather expensive. Instead, we use a 5kW linear pot in parallel with a 5kW resistance to provide an overall 2.5kW range. This means that the plot of resistance vs rotation is not linear, further exacerbating the adjustment sensitivity for low voltage values, as shown in the plot below. The cyan line is for a 2.5kW linear pot, while the red line plots the resistance law for the 5kW pot in parallel with a 5kW resistance. The parallel resistances do not provide a linear change in resistance versus rotation, with the largest difference being near the ends of the pot rotation, making accurate low-­voltage adjustment even more difficult. For the first 10% of rotation, the linear 2.5kW pot changes resistance by 250W, while the 5kW pot and 5kW parallel resistance changes by nearly 500W. At half rotation, the 2.5kW pot measures 1.25kW (half the total resistance value), while the 5kW pot gives 1.67kW (2/3 of the resistance value). At 90% rotation, the 2.5kW pot is at 2.25kW (90% of the total resistance), while the 5kW pot gives 2.37kW (95% of the resistance). This non-linearity causes the adjustment at the low end to be much coarser than in the middle of the range. This plot shows the difference in resistance vs rotation for a regular 2.5kW pot and a 5kW pot shunted with a fixed resistance. They start and end at the same points, but the shunted pot’s resistance law is not linear. If you can get the multi-turn 2.5kW potentiometer to use for the output voltage adjustment, you’ll be able to set the output voltage much more easily and accurately. 88 Silicon Chip Australia's electronics magazine The current limit setting voltage from VR3’s wiper is applied to the inverting input of IC1b via a 1kW resistor. This voltage is compared with the output from IC2, which goes to the pin 5 inverting input of IC1b via a 10kW resistor. When IC2’s output is lower than the setting for VR3, IC1b’s output (pin 7) is pulled low, towards its pin 4 supply (-8V). In this case, current limiting indicator LED1 is reverse-biased, so the gate of Mosfet Q2 is held at its source voltage, with no current flowing through the Mosfet. When the output from IC2 goes above the threshold set by VR3, the output of IC1b begins to go high, lighting LED1 via the 1kW resistor between Q2’s gate and source pins. This also starts to switch on Q2 as its gate voltage rises. The channel of Mosfet Q2 then begins to conduct, pulling the adjust terminal of REG1 down to reduce its output voltage. Note that the adjust terminal is isolated from the voltage setting resistance of VR1 via a 330W resistor. This allows Q2 to drive the adjust terminal without being loaded by the voltage setting resistance. The 100nF capacitor between pin 5 of IC1b and the drain of Q2 acts as a compensation capacitor for the current limiting feedback, preventing it from coming on too rapidly, possibly leading to oscillation. Compensation for the op amp is also provided using a 1μF capacitor between the pin 6 inverting input and the pin 7 output. While this capacitor could be as low as 47pF to prevent oscillation, the 1μF value minimises output ripple voltage when the supply is in current limiting. Load switching As mentioned previously, we use a relay to switch the Supply’s output to the load. This relay (RLY1) allows the circuitry to disconnect the load during power-up, power-down or if the heatsink gets too hot. Disconnecting the load when power is first applied, and when it is switched off, prevents unexpected voltages from being applied to the load. This circuit section comprises diodes D7 and D8, transistors Q3 to Q6 and associated components, plus RLY1. We use the 15V transformer tap to derive a 21V supply. Diode D7 halfwave rectifies the AC, and a 2200μF siliconchip.com.au There isn’t much on the rear panel – just the heatsink and IEC mains power input. Note how the heatsink hangs down below the bottom of the case as it is slightly taller. We get around this by making the case’s feet taller. capacitor filters the resulting voltage to a relatively smooth 21V DC or so. The positive power supply for op amp IC1 is taken from this rail via a 100W resistor. As the negative supply for IC1 is from the -8V rail, ZD1 is included to ensure that the overall supply to IC1 does not exceed 33V. Diode D8 also provides half-wave rectification of the 15V tapping, but this is not filtered so that we have a pulsating voltage. This way, the voltage from diode D8 will immediately cease when power is disconnected, allowing us to quickly detect when the power is switched off. When power is applied, the positive voltage at D8’s cathode switches on transistor Q3 for half of every mains cycle. With our 50Hz mains, the positive excursion is over a 10ms period. Q3 discharges the 1μF capacitor via a 100W resistor each time it is switched on; this capacitor begins to charge via a 100kW resistor from the 21V supply during the negative half of the waveform. This capacitor will stay mostly discharged, provided that Q3 repeatedly discharges it every 10ms. Somewhat similarly, transistor Q4 controls the charge on the 47μF capacitor. When Q4 is off, it allows the 47μF capacitor connected to TP8 to charge via the 100kW and 100W resistors. Q4 remains off, provided that the 1μF capacitor connecting to Q4’s base is discharged. siliconchip.com.au So when there is an output from the transformer, the 47μF capacitor charges up. The base of Q5 needs to be above 13.2V to switch on due to the voltages across diode D9 and zener diode ZD2, the latter being biased via a 2.2kW resistor from the 21V supply. As a result, when power is first applied, there is a five-second delay before the 47μF capacitor charges enough to switch Q5 on. But when the power switch is flicked off, within a few tens of milliseconds, the 1μF capacitor at Q4’s base charges enough to switch it on, discharging the 47μF capacitor and switching Q5 off. When Q5 is on, it pulls current from the base of PNP transistor Q6 via a 4.7kW current-limiting resistor. The current from Q6 flows through the load switch (S2), then through thermal switch TH1 and to the relay coil. So the load is only connected by RLY1 when Q6 is on, S2 is on and thermal switch TH1 is not open. To put it another way, the load is disconnected during power-up, power-­ down, when S2 is off or when the temperature of TH1 is too high. Diode D10 clamps the negative voltage when the relay coil is switched off. By the way, we sneakily reuse the 12V supply from zener diode ZD2 to power IC2, the INA282 shunt monitor. Metering The voltmeter and ammeter connect to the regulated output of the Supply. Australia's electronics magazine The voltmeter measures the voltage before the relay contact. The shunt for current measurements is in the negative supply line; it has a very low resistance, so there is a minimal voltage drop across it. The meter is supplied from the 21V positive rail and uses the MI- terminal as its ground. Next month We have now described what our updated Supply can do and how it works. Next month’s follow-up article will have the assembly details for the two PCBs, chassis assembly instrucSC tions and wiring details. The voltage inverter module is based on a 555 timer IC and a handful of other components. For use in this Supply, it's built with ZD1 = 12V and R1 = 220W 1W. September 2023  89 Simple Voltage Inverter Doubler This simple and low-cost circuit can produce a voltage around twice its DC input, or instead, a negative voltage of similar magnitude to the input. That can be handy in many situations, such as running op amps from a battery or DC supply, driving Mosfet gates, or providing a wider output range for adjustable regulators. by John Clarke I f you are building a project and the power supply voltage is insufficient to drive some components, or you need to derive a negative supply from the positive supply, this little project can be the answer. It is based around a 555 timer, a few diodes, resistors and capacitors on a reasonably compact printed circuit board (PCB). The circuit acts as a voltage inverter or almost doubler, depending on how you build it. It can deliver an output of a few tens of milliamps. A voltage inverter can be very useful for many applications. Suppose you need to use an op amp for processing audio. A negative supply can make the circuit easier to design with fewer parts as the audio signal can be ground-referenced. Without the negative supply, the audio signal would need to be raised to around half the positive supply and coupled with capacitors. In some cases, using a split DC supply can mean insufficient headroom for signal processing, while using the negative supply almost doubles the op amp input and output swings. A voltage doubler can be helpful in 90 Silicon Chip many situations, for example, if you need to bias an N-channel Mosfet gate above the positive supply to use it as a high-side switch, or to power a small 24V DC relay from a 12V DC supply. Note that there are some losses in the circuit. As a result, when used as a ‘doubler’, the actual output will be around 3-3.5V less than double the input voltage. Similarly, when used as an inverter, the resulting negative voltage is a couple of volts less in magnitude than the positive input. Most of the voltage losses are from the 555 IC for both doubling and inversion, as its output does not go entirely to the positive supply when under load. There are also voltage drops across the diodes. But if you are prepared to accept these losses, the circuit can be useful. The output current is up to about 30mA, although more is available with higher input voltages. Performance Figs.1 & 2 are plots of output current and voltage against input voltage. They should allow you to decide whether the circuit suits your application. The current versus Vout graphs Australia's electronics magazine Features & Specifications ▬ Operates from 9-15V DC (Vin) ▬ Produces either a ‘doubled’ or ‘inverted’ DC output ▬ ‘Inverted’ output voltage is about -(Vin − 3V) (see Fig.1) ▬ ‘Doubled’ output voltage is about Vin x 2 − 3.5V (see Fig.2) ▬ Output current up to about 30mA (see Figs.1 & 2) ▬ compact PCB (37 x 42.5mm) ▬ Inexpensive and few parts required (555 timer plus a few diodes, capacitors and resistors) are shown only for 9V, 12V and 15V supply inputs; below 9V, the output is possibly too low to be useful. The input voltages are the voltage applied to the 555 timer, which is not necessarily the same as at the Vin terminal. If you want a voltage doubler or inverter that runs from 1.5-5.5V, see the text under the “Alternatives” heading for ICs that can do that efficiently. We created this circuit because we needed a negative voltage to revise our 30V 2A Bench Power Supply, originally published in the October & November 2022 issues. We’re changing it because the mains transformer it used is now unavailable, and the new transformer does not have a tap for us to derive the -8V supply like the original design. So, we use this circuit as a voltage inverter to deliver the required -8V from the +12V DC rail. The inverter is ideal since we only need about 13mA at between -9V to -8V. That’s within its capabilities. The circuit was designed to be simple and use commonly available parts. Because of its simplicity, it can easily be configured to provide either voltage inversion or doubling. Circuit details Fig.3 shows the circuit for the Voltage Inverter/Doubler, or VI/D for short, with two output options to implement the doubler and inverter functions. Much of the circuitry is common for both versions, including the 555 timer and its associated timing components. The incoming supply comes from the Vin and the GND terminals. From Vin, the supply passes through either diode D3 or resistor R1. D3 is to prevent damage should the incoming supply polarity be reversed. If you siliconchip.com.au are permanently connecting the VI/D to the incoming supply, you could bypass D3 with a wire link so that there is more available output at Vout. When using D3 or the wire link, zener diode ZD1 and R1 are not installed. The 555 timer (IC1) supply cannot exceed 16V. If the upstream supply can be higher than that, or you wish to set Vout to a particular level, then R1 and ZD1 should be installed instead of D3 or a wire link. ZD1 and R1 provide voltage limiting for the VI/D supply. The zener diode limits the voltage, while R1 limits the current through the zener to a safe level. These component values depend on your application; we will provide examples later. Figs.1 & 2: plots of the output current and voltage against the input voltage for the Voltage Inverter (left) and Voltage Doubler (right). Oscillator IC1 is connected to run as an oscillator with a duty cycle close to 50%. Pin 3 provides a square wave output, and the 1nF capacitor, 47kW resistor and 4.7kW resistor at pins 2 and 6 set the frequency and duty cycle. The 1nF capacitor is charged via 4.7kW and 47kW resistors from the positive supply. While it’s charging, output pin 3 of IC1 is high (near the positive supply). When the capacitor voltage reaches 2/3 of the supply voltage (as detected by the pin 6 threshold input), pin 7 (the discharge output) goes low, as does the pin 3 output. With pin 7 low, the capacitor is discharged via the 47kW resistor until its voltage reaches 1/3 of the supply, as detected by the trigger input at pin 2. Now the pin 3 output goes high again, and the pin 7 pin goes high-­ impedance, allowing the capacitor to recharge. The process repeats continuously. As the capacitor is charged via the 47kW and 4.7kW resistors (a total of 51.7kW) and discharged via the 47kW resistor, you can expect the output to be high for a little longer than it is low. However, it is close enough to 50% for this application. The oscillation frequency is 14kHz (1.44 ÷ [{4.7kW + 2 × 47kW} × 1nF]). The waveform can be seen in Scope 1, where the top yellow trace shows the capacitor voltage, and the lower cyan trace shows the 555’s pin 3 output. That was taken with the output (Vout) unloaded. The pin 3 output of IC1 drives the voltage doubler or inverter. Fig.4 siliconchip.com.au Fig.3: the circuit diagram for both the Inverter and Doubler. D3 is an optional component that prevents damage if the supply polarity is reversed, while R1 is only installed when D3 is not present. shows how the inverter section works, while Fig.5 explains the voltage doubler. For simplicity, the voltage drop across the diodes is shown as 0.7V, and the voltage sag at pin 3 of IC1 is ignored. Voltage inverter operation When IC1’s pin 3 is high, C1 charges to 0.7V less than the supply via D1 (left side of Fig.4). When pin 3 goes low, the positive side of C1 goes to 0V and the negative side goes negative. Note that the voltage across C1 does not change between the two halves of the diagram. C1 charges C2 via D2 to a negative voltage similar to the positive input Australia's electronics magazine Scope 1: the IC1 (555) timer waveform at pins 2 & 6 is shown in yellow, while the output (pin 3) is shown in cyan. The frequency is around 13.2kHz. September 2023  91 capacitors C1 and C2 are rated at 35V for voltage doubling. While C1 could be a lower-rated type, using 35V for both avoids confusion. Practicality Both the Voltage Doubler (top) and Inverter (bottom) modules only require a 555 timer IC and a handful of other components to build. voltage minus the 1.4V worth of diode drops; in this case, -7.6V (-1 × [9V – 1.4V]). Voltage doubler operation For the voltage doubler, diode D1 charges capacitor C1 to the supply voltage (minus 0.7V) when IC1’s pin 3 output is low (left side of Fig.5). If this is when power is first switched on, then the initially discharged capacitor C2 will charge about 1.4V below the supply via D1 and D2, shown as current i2. When IC1’s pin 3 goes high (right side of Fig.5), the negative side of C1 is lifted to the supply voltage, so the positive side of the capacitor will be close to twice the supply (9.0V × 2 − 0.7V). Note that the voltage across the capacitor is the same as before (8.3V). Diode D2 is forward-biased, and C1 charges C2, with another 0.7V loss. After a cycle or two, the voltage across C2 will be twice the supply voltage minus the 1.4V drop across D1 and D2. Since IC1 can be powered from up to 15V (the recommended maximum), 92 Silicon Chip As mentioned earlier, IC1’s pin 3 output does not swing fully to the positive supply rail or ground (0V) when under load. There is about a 2V drop at pin 3 when high and under load. The effect is that the output (Vout) does not reach the voltage expected. These losses also mean you will need at least a 9V supply to gain any reasonable voltage at the output. If the circuit doesn’t provide enough voltage for your application, you could use 1N5819 schottky diodes instead of D1, D2 and D3 (if D3 is used). That will give a little more output voltage due to their lower forward voltages. A CMOS equivalent to the 555 timer, such as the 7555 or LMC555, won’t improve the output voltage. While at very low load currents (less than 0.8mA), the outputs will swing reasonably close to the supply rails once there is a load, the voltages will drop substantially. You can simulate the 7555 pin 3 output with an 875W resistor in series when high and a 62.5W series resistor when low. We simulated the inverter in an LTspice file that you can download from the Silicon Chip website. If you want to test the doubler function, you can rearrange C1, C2, D1 and D2. The main problem with the simulation is that the 555 pin 3 output does not reproduce the actual voltage drop for the positive level output under load. Alternatives If you are after a voltage doubler at a higher output current, you may be interested in the Circuit Notebook entry “High-Current Voltage Doubler” by Dayle Edwards (September 2009; siliconchip.au/Article/1564). That circuit provides voltage doubling from an input of 5V, 6V, 9V or 12V with an output current of up to 1.5A. Specialised ICs are also available, although they usually have somewhat limited input voltage ranges. For example, the Intersil ICL7660 (1.5-10V), ICL7660A (1.5-12V) and ICL7662 (4.5-20V) are all capable of operating as voltage doublers or inverters. They are all still available (although the 7662 is only made by AD/Maxim now). For an efficient voltage inverter that can run from 1.5V to 5.5V with a 25mA output current, consider the Analog Devices ADM8828 IC, especially for inverting the voltage from a USB supply. Similarly, the LM2662 is suitable as an inverter or doubler at up to 200mA output and can also operate from 1.5V to 5.5V. Other similar chips are on the market; we can’t list them all here. Diode D3 vs zener diode ZD1 As mentioned earlier, ZD1 and R1 can be installed instead of D3 if the supply voltage could exceed 15V. ZD1 can be selected between 9.1V and 15V, depending on your required output voltage. You will then need to calculate an appropriate value for resistor R1. For example, say you want to use the VI/D as an inverter delivering around Fig.4: the two phases of the Inverter charge pump. Fig.5: the two phases of the Doubler charger pump. Australia's electronics magazine siliconchip.com.au -9V at up to 13mA. Fig.1 shows that the circuit needs to be supplied with 12V to obtain this voltage at the output at the required current. Therefore, you can select a 12V 1W zener diode for ZD1. The value of R1 will then depend on the expected supply voltage. For example, if Vin is 21V, the voltage across R1 will be 21V − 12V or 9V. A 12V 1W zener diode’s maximum current is 83.33mA (1W ÷ 12V). Typically, the zener should be used with at least a 50% power derating to prevent overheating. Also, the minimum current through the zener diode should be about 5mA to maintain voltage regulation. So the zener diode current range of operation should be 5mA to 41.6mA. The value for R1 is Vin minus the zener voltage (12V), then divided by the 50% power derating current of 41.6mA. This gives 216W, so a 220W resistor can be used. Its dissipation will be V2 ÷ R1, ie, 368mW (9V2 ÷ 220W). A 1W resistor is thus ideal; a 1/2W or 0.6W resistor could be used, but it would run hot. We can draw up to about 36.6mA (41.6mA – 5mA) before the zener current drops to 5mA. If we want 13mA at Vout, assuming 75% efficiency for the converter (which is about right), the input current will be 17.3mA (13mA ÷ 75%). That means some 17.7mA remains flowing through ZD1, more than enough to maintain regulation. There is also sufficient current headroom to allow for the current drawn by the oscillator, around 5mA. Construction The circuit is built on a PCB coded 04107222 that measures 37 × 42.5mm. The orientation and positions for D1, D2, C1 and C2 for the inverting version Parts List – Voltage Inverter / Doubler 1 double-sided plated through PCB coded 04107222, 37 × 42.5mm 1 NE555P timer or equivalent, DIP-8 (IC1) 2 1N4004 400V 1A diodes (D1, D2) 1 1N4004 400V 1A diode (D3; optional – see text; not used for Supply) 1 1W zener diode (ZD1; optional – see text; 12V for Bench Supply) 1 100μF 16V radial electrolytic capacitor 1 100nF 100V MKT polyester capacitor 1 1nF 100V MKT polyester capacitor 1 47kW ¼W 1% metal film axial resistor 1 4.7kW ¼W 1% metal film axial resistor 1 1W axial resistor (R1; optional – see text; 220W for Bench Supply) Additional parts 2 100μF 35V radial electrolytic capacitors (C1, C2 – for voltage doubler) 2 100μF 16V radial electrolytic capacitors (C1, C2 – for voltage inverter) are shown on the top of the PCB. For the doubler version, they are on the underside of the PCB instead. These positions are shown in Fig.6. Note that only the inverter is shown with the different options for D3 and ZD1/R1 in Fig.6, but you could also use ZD1/R1 with the doubler. You would just leave off D3 and fit ZD1/ R1 instead. The components are intended to be installed on the top side of the PCB for all versions. The screen printing was placed on the underside for the doubler components to avoid clashing with the inverter markings on the top side. There are four mounting points on the PCB for standoffs. The PCB can also be mounted vertically using stiff tinned wire at the Vin, GND and Vout terminals. An extra pad is provided at the top of the PCB for extra mechanical support if required in such an application. As mentioned, diode D3 is installed for reverse polarity protection if required or replaced with a wire link if not required. Alternatively, if input Fig.6: the PCB overlay for the Inverter or Doubler project. While the Doubler version’s silkscreen is on the underside of the PCB, the components are installed on the top side of the PCB. siliconchip.com.au Australia's electronics magazine supply regulation is needed to obtain a particular output voltage or to limit the supply voltage to IC1, R1 and ZD1 should be installed instead of D3 or the wire link. Begin construction by fitting the axial components for the version you require (resistors and diodes). Ensure the diodes are orientated as shown, with all their cathode stripes towards the top of the PCB. IC1 can be soldered directly to the PCB, ensuring it has the correct orientation. Follow with the smaller MKT capacitors, which are not polarised. The three electrolytic capacitors have space to lie flat onto the PCB, although you could mount them vertically if desired. Pay close attention to their orientations as they are reversed between the inverter and doubler configurations! In all cases, the striped end is negative, which is also the side with the shorter lead. Testing There isn’t much to it; apply a voltage to the input that’s close to what you’re using in the final application and check that the output is higher (for the doubler) or negative (for the inverter) and about the expected magnitude. Apply a load (eg, using a 5W resistor) and check that it doesn’t drop further than expected. If it doesn’t draw any current, draws too much current or the output voltage(s) are wrong, check that all the components are in the correct locations and of the right types as per whichever of Fig.6 matches your use case. Also check that the solder joints have formed properly and that there are no shorts between pads or component leads. SC September 2023  93 Vintage Radio AWA 500M superhet mantel radio By Ian Batty The 500-series mantels were a ‘cheap and cheerful’ budget offering, released in four versions. They are tidy-looking sets that fit just about anywhere. I picked this one up at a Historical Radio Society of Australia (HRSA) auction some years back. A ppearing in 1946, the 500M was a well-tested design using all octalbased valves. It’s a compact set with little wasted space inside its Bakelite cabinet. The 500M is almost a conventional superheterodyne radio (‘superhet’). The difference – which I didn’t appreciate at first – is that it has only one audio stage. In other words, it has only three signal stages (see Fig.1). There are well-performing fourvalvers about, but they use audio reflexing in the intermediate frequency (IF) amplifier stage, giving it a dual role. In that case, there are effectively four signal stages (converter, IF amplification, audio preamplification, and audio output), like a typical domestic superhet. So this one is a bit unusual. 94 Silicon Chip The power supply uses a 6X5GT full-wave rectifier valve. The HT filter includes the electrodynamic speaker’s field coil and two 8μF electrolytic capacitors (C21/C22), forming a pi filter. The mains transformer provides two mains voltage tappings: 200~230V and 230~260V. C18 (100nF) provides RF/IF filtering for the common HT line; there is no decoupled/HT2 supply for the RF/ IF section. The converter uses a 6A8G, the octal pentagrid based on the original 2A7 and its follow-on 6A7. These earlier types were mounted on 7-pin UX bases. The converter has no self-bias, as its cathode returns directly to ground. Bias is supplied via the antenna Australia's electronics magazine circuit’s L3 from the back bias/AGC circuit. The screen grid supply is shared with the IF amplifier via dropper R3 and bypass C11. The antenna circuit uses an IF filter (L1/C1) which, unlike the Astor Mickey I reviewed in the January 2022 issue (siliconchip.au/Article/15179), causes little or no loss of sensitivity. The antenna circuit’s gain is improved at the top end by top-coupling capacitor C2, also known as a ‘gimmick’ capacitor. The antenna coil’s L2 primary ‘steps up’ to the tuned L3 secondary, giving a voltage gain of around three times. As L3 has no adjustable slug, this set’s RF alignment is done by adjusting the LO coil’s tuned winding (L4) to meet siliconchip.com.au siliconchip.com.au Fig.1: the circuit diagram for the AWA 500M. The radio has a standard IF of 455kHz. Interestingly the original service manual has separate listings for the 500M-Z and 500M-Z, with the 500M & 500-M-Z using a 40Hz transformer (T2), while the 500M-Z used a 50Hz transformer with a directly-heated 5Y3GT rectifier valve. L3 at 600kHz – more on that later. The local oscillator uses the ‘Armstrong’ design, with untuned primary L5 feeding back to its L4 tuned secondary. The tuning gang uses identical sections, so padder C8 ensures local oscillator/antenna circuit tracking. Grid resistor R1 returns to the cathode as usual – that just happens to be ground in this set. The converter feeds its IF signal to the slug-tuned first IF transformer primary L6. The transformer comprises L6/L7, with both windings tuned. The secondary, L7, feeds the 6G8G IF amplifier. This duo-diode pentode is commonly used either for IF or first audio stage amplification, with its diodes operating separately as the demodulator and for AGC, or combined (as here) demodulator/AGC. As with the converter, the IF amplifier has no self-bias; it’s biased (via L7) from the back bias/AGC circuit. The IF amp feeds its signal to the second IF transformer primary, L8. Its secondary L9 feeds the demodulator/AGC diodes in the 6G8G. Both transformer windings are slug-tuned. Demodulated audio, and a DC voltage proportional to the incoming signal, are developed across volume control R7. Audio is taken from R7’s wiper and fed via C17 to the output amplifier grid. The DC voltage across R7 is fed, via R4, to the AGC line. This has a standing bias of about -2V, derived from 40W back-bias resistor R6 via R5. This supplies bias to the converter and IF amplifier, which lack individual biasing circuits. The AGC voltage develops across volume control R7 and audio is filtered out by C4. It’s applied to the control grids of the converter and IF amplifier via the R4/R5 divider. This simple circuit has no effective delay, with a measurable AGC voltage for an input signal of only 100μV. The 6V6GT output stage uses cathode bias. Be aware that the near-­ identical 500s used back bias for all its valves. Audio, fed from the volume control, is applied to the control grid via R9. This ‘stopper’ resistor reduces the high-gain 6V6GT’s tendency to oscillate. Its anode feeds the primary of output transformer T1, bypassed by C20. This capacitor suppresses the output transformer’s natural resonance caused by its combined winding inductance and capacitance. Australia's electronics magazine September 2023  95 forms. These initial releases were given the “G” (glass) suffix (6A8G, 6G8G etc). They used a flattened ‘press’ at the bottom of the envelope to seal the lead-in wires, as with the previous 4-to-7-pin UX construction. Fig.2 shows 2V/1.5V pentagrid converter development from the initial 1C6 issue to the final 1A7 that preceded the all-glass 1R5. With the push towards compact equipment, manufacturers simplified the glass envelope and released tubular types. The original metal types had short lead wires between the base pins and the internal elements. The G and original GT types used press construction, so they were quite tall compared to metal equivalents. Also, they did not perform as well The dial markings are painted onto a fancy-looking piece of cloth. Another at higher frequencies due to extra lead separate piece of this cloth is then used as a speaker grille. inductance and capacitance. Notably, the high-performance 6AB7/6AC7 Notice that C20 is connected from guided by their invention of all-metal ‘video pentodes’ were not generally the anode to ground, giving it a stand- valves. These committed pin 1 to released in glass envelopes. ing voltage of some 230V. Should it grounding the metal shell/envelope, The Bantal (‘bantam-octal’) line go short-circuit, it will ground T1’s both for signal shielding and electri- reduced the envelope’s overall height anode connection, possibly burning cal safety in case of internal anode- by lowering the height of the press. out the output transformer. It’s best to shell leakage. Some Bantals used a metal shell to reconnect the capacitor so it’s across This meant that initially, only seven secure the envelope to a disc-shaped the output transformer’s primary. If it pin connections were available, so base; others simply continued with does short out, the only effect will be some valves (twin triodes such as the the Bakelite ‘bucket’. Fig.2 shows one a lack of audio. 6SN7) could not be released in metal of each: a 1A7GT and an equivalent V3’s 315W cathode bias resistor envelopes. 1A7GT(M). is a parallel pair of 630W resistors. While you can use a metal valve to Confusingly, some were initially These are the original fitment but of a replace a glass type, be sure that the set denoted GT/G or G/GT. Many types non-standard value; the nearest E12 manufacturer has not used pin 1 as an were never issued in the intermedi(10%) values are 560W and 680W. HT tie point; the metal valve envelope ate ‘long envelope’ style (the 1A7G The E24 (5%) series does have a 620W will be at (dangerous) HT potential! It example) but went directly from value, so maybe AWA just went off on has happened! the stepped tubular (‘G’) form to the their own with the 630W. Glass-envelope octals were orig- reduced-height GT cylindrical form inally released in the ST (stepped-­ (the 1A7GT). The 6V6GT and 6X5GT G, GT and GT/G valves tubular ‘coke bottle’) form previously in this set both used the reducedRCA’s design of the octal valve was used by the 4-, 5-, 6- and 7-pin UX height construction. Left: the rear of the AWA 500M chassis. Below: the grommet-and-knotted cord fitting on the underside of the chassis is not a very safe arrangement. 96 Silicon Chip Australia's electronics magazine siliconchip.com.au Eventually, ‘GT’ was applied to all tubular-envelope octals, regardless of base construction. Restoration The Bakelite case was in good condition, only needing a polish to restore it. Electrically, it was also in good condition, having been previously restored. All three electrolytic capacitors (HT filters, output cathode bypass) had been replaced, as had the paper types. All low-capacitance mica types were still in place. These are generally more reliable, but are known to suffer leakage over time due either to internal dendritic (‘metal whisker’) growth, or (as mica is hydrophilic) from gradual moisture absorption. A fellow HRSA member once reported a radio with a mysterious ‘crackling’ sound. The fault was traced to intermittent leakage in the mica capacitor bypassing the first audio amplifier’s anode to ground. How good is it? At first, I thought it was pretty poor. But looking at the circuit reminded me that I had not fully appreciated its budget design. Thinking about the Astor Mickey, I’d fallen into the trap of expecting tens of microvolts sensitivity at worst. Adding a first audio stage, with a gain of maybe 50 times, would easily have given the performance I’d had in mind. I went stage-by-stage and measured the signal needed at each grid to get the standard 50mW output. I use two Fig.2: examples of different types of glass-envelope and tubular-envelope valves. The base and envelope both evolved to produce more compact valves. references: my own testing and my preferred servicing manual for this class of radio, Markus and Levy’s Elements of Radio Servicing. If you don’t have a copy, I suggest you get one. The output stage needed around 500mV at its grid to give a 50mW output. I test at 400Hz, as I’ve found some sets that begin cutting off at 1kHz! Going to the IF amp’s grid, I needed 25mV of 400Hz modulated signal for 50mW of output power. The converter grid needed 1.5mV at 600kHz and 1400kHz. For the standard 50mW output, it needed 500μV at 600kHz or 400μV at 1400kHz injected into the antenna. Due to its low gain, the signal-plus-noise-to-noise ratio (S+N:NR) exceeded 20dB in both cases. These figures are consistent with Markus & Levy’s and my own experience. The audio output was about 1.5W at clipping. At 50mW, Total harmonic distortion (THD) was 3%. Audio response from the volume control to the speaker was 170~1500Hz, but from the antenna to the speaker, it was only 190~900Hz. The IF bandwidth at -3dB was ±2.9kHz and ±30kHz at -60dB. AGC action was only moderate, with a 20dB input signal increase giving a 6dB rise in output level. That results from the R4/R5 circuit combining the back bias and AGC voltages. For a The underside of the chassis. Very little was required to polish up the radio, as the electrolytic and papertype capacitors had already been replaced. Note the use of a cord anchor to replace the original and unsafe knotted cord. Australia's electronics magazine September 2023  97 strong signal of 100mV at the input, around -40V is developed across volume pot R7 but only about -11V is conveyed to the AGC line. Also, the ‘undelayed’ AGC cuts in early. At 1400kHz, I needed 400μV at the antenna terminal for 50mW output, but shorting the AGC to ground cut the required input signal level to only 270μV, a sensitivity increase of some 3.5dB. This is moderate sensitivity by any measure, but my 500M is a budget set with three signal stages. You’d expect to use it with a few metres of antenna wire connected. With that, all Melbourne stations rocked in, and I was able to get my distant station, 3WV, at a reasonable volume with just a 2m-long antenna. All in all, it’s a simple mantel set without any pretensions. It’s also a straightforward design that’s easy to work on and fix. Hint on LO testing If a superhet’s local oscillator is not working, the set will do nothing, but many other faults can result in no audio output. So, if the set is not functional, how can you be sure the LO is OK? Some repairers measure the oscillator’s negative grid voltage. I was able to do this with the 500M (as noted on the circuit diagram), but with most sets I’ve tried this on, the LO stops due to the extra loading on the circuit. My preferred method is to use a good set as a monitor, tuned to the top end of the band (this works for any superhet – valve or transistor – on any band). Slowly tune the suspect set from the bottom up towards the top of the band. For the broadcast band, you’d tune the monitor set to the top end at 1600kHz. Assuming an IF of around 450kHz, the suspect set should produce a ‘swoosh’ or ‘birdies’ in the monitor at around 1150kHz on the suspect set’s dial. If the suspect set is a really old one with a 175kHz IF, expect a response from the monitor just above 1400kHz on the suspect set’s dial. As a bonus, you don’t even have to take the suspect set out of its cabinet/ case! Is it worth buying one? If you see a 500M, don’t be put off by its modest performance – it’s a nice-looking set with a compact design that lets it sit anywhere and provide entertainment. Radiolette ‘500’ versions I could not find a model identifier on my set – you may need to pull the chassis and inspect the wiring to discover whether you have the ‘all back bias’ version or its alternative with cathode bias on the output. There are several 500Ms. Kevin Chant’s listing for the 500MY uses back bias for all valves. AGE also released the set as their G64ME. Radiomuseum lists two circuits: 500M and 500M-Z, both identical and applicable to the 500M, 500M-Z and 506. These show cathode bias for the output stage and an alternative power supply using a directly-heated 5Y3GT/G in the 500M-Z. Special handling It’s an easy set to work on but heavier than I expected, probably due to the combination of the electrodynamic speaker and a larger-than-expected power transformer. The VE301 (February 2023 issue; siliconchip.au/Article/15671), had no mains cord security – the active lead had actually broken off and was floating about under the chassis and had to be fixed! My 500M had the commonly-­ used (and unsafe) grommet-­ a ndknotted cord fitting. References & links • Marcus, A. H., & Levy, W. H, “Elements of Radio Servicing”, McGrawHill Book Company, Inc. (1947). • Radiomuseum AWA 500M-Z: siliconchip.au/link/ablq • Kevin Chant’s website, under 500MY: siliconchip.au/link/ablp • Verrall, Bill, “The AWA Radiolette Model 500MY”, Radio Waves, HRSA, Issue 84, April 2003, p8. Bill’s article SC has a parts layout diagram. From the side you can see the 6C8G valve has the label “goat patented” on it. These Goat Shields were very common in the 1940s-50s and went out of use when the straight-sided glass tubular (GT) forms came into use. 98 Silicon Chip Australia's electronics magazine siliconchip.com.au ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Send your email to silicon<at>siliconchip.com.au Watering System Controller query Will you produce a kit for the Watering System Controller from the August 2023 issue (siliconchip.au/ Series/402)? (D. M., Cougal, NSW) ● There is no kit for that project; all the kits we sell are at siliconchip. au/Shop/20 Part of the reason why there is no kit is that there is the option for how many valves you need, so we can’t easily pre-make kits; the SSRs are among the most expensive parts. Also, not many parts are used in this project, so they are not overly difficult to gather. Most of the part sources are given in the parts list. The only non-generic parts are REG1, the SSRs and the Raspberry Pi Pico W. Since Mouser part codes for the SSRs are shown in the parts list, if you’re going to order from them, you could get the LM2574YN and Pico W at the same time. You could also get most of the remaining parts from them (or Jaycar/Altronics). We can supply the PCB: siliconchip. au/Shop/8/6800 Identifying integrated circuits I have a query on the identification of two ICs, from your Reciprocal Frequency Counter and Dynamic RFID Tag kits. The boost regulator is specified as an MCP1661 or MP1542DK for the former. The part supplied has the marking AAAL248UTT. In the latter, the NFC tag chip is specified as ST25DV04K. The part supplied has the marking DV2DERB. Before I solder them onto the PCB, I want to check that they are the correct parts. Can you confirm that I have received the correct ICs for these two projects? Also, with the chip supplied in the Dynamic RFID Tag kit, I cannot locate pin 1. Your diagrams indicate the presence of a dot to mark pin 1, but I can find no evidence of a dot, chamfer or any other way of identifying which pin is pin 1. Can I assume that if the product identification symbols are the right way up, pin 1 is at the bottom left? (J. H., Nathan, Qld) ● MCP1661 marking information is in the data sheet that you can download from Microchip’s website at www.microchip.com/en-us/product/ mcp1661 It says the marking is AAAL, followed by a one-digit year code, a twodigit week code and a three-character traceability code. So if it starts with AAAL, it is the MCP1661. If we supplied an MP1542DK, the data sheet says the marking would be 1542D. ST Micro has the ST25DV marking information at siliconchip.au/ link/abp8 It shows DV2DERB, matching your chip. The ST logo appears to be the pin 1 indicator for this IC – see the adjacent photo. The data sheet also shows a chamfered edge along the pin 1 side. You might be able to see it if you look at the chip end-on. Replacing 4V or 6V vibrators I have been very interested in the (now) two articles by Dr Hugo Holden in the June and July 2023 issues on replacements for electromechanical vibrators (siliconchip.au/Series/400). It has been a subject of interest to HRSA members for many years, given the interest in restoring vibrator-based receivers, which many manufacturers produced during the 1940s, 1950s and beyond. siliconchip.com.au Australia's electronics magazine Vibrator receivers running from the lower voltages of 4V and 6V from lead-acid accumulators were popular in rural households without AC mains or locally generated DC, and when dry cell batteries were very expensive. The accumulator usually sat on the floor below the radio, with the radio connected to the battery via two heavyduty cables with large bulldog clips for attachment to the battery posts. My father had to travel from our dairy farm to our local town every 2-3 weeks to have the battery charged at the “battery shop”. I clearly recall the acrid smell of sulfuric acid in the battery shop, where all the local farm batteries were taken to be charged. There were typically 30-50 batteries being charged at a time. My mum operated the radio, a Tecnico Aristocrat, to listen to the ABC News at noon, “Blue Hills by Gwen Meredith” at 1:00pm, and “When A Girl Marries” at 7:15pm. The radio was operated for around 45 minutes per day, five days per week. Woe betide anyone who forgot to disconnect the battery between the listening sessions! I have recently restored a 4V version of the AWA 433MC receiver. This receiver was sold with the following power supply build options: 1. 4V lead-acid accumulator (vibrator supply). 2. 6V lead-acid accumulator (vibrator supply). 3. Dry cells: 1 × 1.5V “A” battery, 2 × 45V “B” batteries and 1 × 3V dial light battery. Does Dr Holden have plans to provide plug-in vibrator replacements that can operate from 4V DC or 6V DC? The July 2023 article mentions that the Darlington circuit shown in Fig. 7 on page 83 of the July 2023 issue “…operates with a supply voltage as low as 3V”. While it will operate very nicely from a 4V or 6V battery, exactly as sought, the complex metalwork will be pretty expensive to prepare commercially. It is also tricky for the home constructor to replicate with basic tools. September 2023  99 Are there suitable TO-220 Darlingtons available for this application instead of the TO-3 devices? This would allow a PCB to be used in the style of the PCB shown on page 79, using TO-220 devices. (G. D., Bunyip, Vic) ● Dr Holden responds: The bipolar transistor replacement vibrator design, presented in the August 2023 issue (siliconchip.au/Article/15912), is probably the best one for 4V or 6V DC operation because all you need to do is reduce the number of primary windings on its small feedback transformer. That should run down to about 3V, given the low 0.3V base-emitter threshold voltages of the NPN germanium transistors. However, of the replacement vibrators presented in the series, it is mechanically the most complicated and thus, building it requires quite a bit of effort. A possibly simpler solution is the circuit shown on page 86 of the July 2023 issue that uses two IRL540 Mosfets and a 7400 quad NAND gate IC as the oscillator. The Mosfets only require about 3V to switch on, although the logic IC might stop oscillating below about 4V. Still, for most car radios that used 6V vibrators, the supply voltage was generally between 6V and 7V when the battery was charging. The other option worth a try would be the self-oscillating Mosfet version that was presented in the July 2023 issue (siliconchip.au/Article/15871), but using IRL540 logic-level Mosfets or equivalents instead of the IRF540 Mosfets specified. As for the TO-3 Darlington issue you mentioned, there are some flatpack Darlingtons with a TIP prefix that would work in the circuit shown in Fig.7. It is just that I prefer the TO-3 ones myself because of their robust nature; I was trying to build a near-­ indestructible unit for my ZC1 radio. The metalwork for a project is often more than half the battle. Many projects are challenges in mechanical engineering as much as they are electronic engineering, depending on your desired outcome. I see many versions of circuits for this and that, strung together on protoboard, but the result is unreliable. I agree it is harder for the home constructor, but I am one too, and I managed it. Source for UA9639CP for GPSDO Can you please tell me an equivalent replacement chip for the UA9639CP chip? I am gathering the parts required for the GPS-Disciplined Oscillator from the May 2023 issue (siliconchip. au/Article/15781). (V. H., Wodonga, Vic) ● The UA9639CP is not required to build the GPSDO. It is an optional component to allow the GPS module to be mounted some distance from the device itself. Since no matching ‘transmitter’ circuit has been presented, few constructors are likely to use it. If you do need to use it, use the UA9639CP chip specified. It is available from various retailers, including: element14 3118802 Mouser 595-UA9639CP Digi-Key 296-11150-5-ND Multimeter Checker fault due to soldering I have built the Multimeter Calibrator & Checker (July 2022; siliconchip. au/Article/15377), but I can’t get it to work. If I leave the jumper off and hold TEST MANY COMPONENTS ITH OUR ADVANCED TEST T EEZERS The Advanced Test Tweezers have 10 different modes, so you can measure ❎ Resistance: 1Ω to 40MΩ, ±1% ❎ Capacitance: 10pF to 150μF, ±5% ❎ Diode forward voltage: 0-2.4V, ±2% ❎ Combined resistance/ capacitance/diode display ❎ Voltmeter: 0 to ±30V ±2% ❎ Oscilloscope: ranges ±30V at up to 25kSa/s ❎ Serial UART decoder ❎ I/V curve plotter ❎ Logic probe ❎ Audio tone/square wave generator It runs from a single CR2032 coin cell, ~five years of standby life Has an adjustable sleep timeout Adjustable display brightness The display can be rotated for leftand right-handed use Components can be measured in-circuit under some circumstances Complete kit for $45 (SC6631; siliconchip.com.au/Shop/20/6631) The kit includes everything pictured, except the lithium coin cell and optional programming header. See the series of articles in the February & March 2023 issues for more details (siliconchip.com.au/Series/396). 100 Silicon Chip Australia's electronics magazine siliconchip.com.au S1, the 100Hz LED starts flashing once per second. But with the run jumper in place, nothing happens. Could it be that I received an unprogrammed PIC? I have done the obvious and checked the board under a microscope. (R. T., Hove, UK) ● If the LED flashes under some conditions, the PIC has almost certainly been programmed. It sounds like a bad or intermittent connection; pressing S1 might flex the board enough for the connection to come good. We checked the photo you sent; while you said you checked everything thoroughly, it looks like IC1 is off to one side a bit, and those pins (11-20) along the left-hand side of IC1 are critical to the operation of the AC oscillator and reference. We suggest you give the PCB another look-over, concentrating on those pins. Editor’s note: we were subsequently informed that removing and resoldering the PIC fixed it. Troubleshooting Spectral Sound Synth I recently purchased the Spectral Sound MIDI Synthesiser kit (June 2022; siliconchip.au/Article/15338). Having built the kit and plugged all the appropriate leads into it, on powering it up, it just lay there dead as far as I could tell, Is there a test program I could download to give me a sign of musical life from the unit? I’m confident that my assembly techniques are good, and I have downloaded the required software. Can you help? (C. R., London, UK) ● The designer, Jeremy Leach, responds: I’m sorry to hear you’re having some trouble getting it working. Here are my immediate thoughts. Firstly, an error in the article originally published in S ilicon C hip magazine showed diode D2 with the incorrect orientation. Its cathode stripe should be to the right, toward the immediately adjacent resistor, R4 (220W). It won’t work if that diode is facing the other way. That was corrected in the online issue and when it was subsequently republished in PE magazine. The chips will be pre-programmed in the kit. If you program them yourself, the best way is to program from the available HEX file, rather than compile yourself. If you compile the code yourself, you must use the best optimisation level in Microchip MPLAB that is only available with a Pro Licence, because only this optimisation level will allow the code to run quickly enough. The module must have a patch loaded before it will make any sounds. The Windows Patch Editor software will open with a default patch (a simple sinewave). To transfer this patch to the module, you need to: 1. Connect a USB cable between the computer and the module, and turn the module on. The Editor should show a ‘Connected’ symbol at bottom left. 2. Click on the Sync button (that should show as enabled because the connection with the module is detected). 3. On the module itself, you should see the Busy LED flash as the patch data is loaded. Next, send MIDI data to the module. Connect your MIDI device to the module using the 5-pin DIN socket. Your MIDI device should be set to transmit MIDI data on channel 1. Keyboards will have a setting screen where you can change the transmit channel. It’s GPS-Synchronised Analog Clock with long battery life ➡ Convert an ordinary wall clock into a highlyaccurate time keeping device (within seconds). ➡ Nearly eight years of battery life with a pair of C cells! ➡ Automatically adjusts for daylight saving time. ➡ Track time with a VK2828U7G5LF GPS or D1 Mini WiFi module (select one as an option with the kit; D1 Mini requires programming). ➡ Learn how to build it from the article in the September 2022 issue of Silicon Chip (siliconchip. au/Article/15466). Check out the article in the November 2022 issue for how to use the D1 Mini WiFi module with the Driver (siliconchip.au/Article/15550). Complete kit available from $55 + postage (batteries & clock not included) siliconchip.com.au/Shop/20/6472 – Catalog SC6472 siliconchip.com.au Australia's electronics magazine September 2023  101 also a good idea to turn off any unnecessary MIDI transmissions (such as MIDI clock messages). On the module, ensure the potentiometer knob is turned up (best if it’s at maximum); otherwise, you won’t get any sound output. Remember that the module’s output is at line level. It needs to feed into an amplifier of some sort; it is not a headphone output. To save patch data permanently to the module (so it will exist when you power it up again), you need to go to the Module Data tab, create a new PatchSet and download it to the module. See the Help file section as shown below. This takes a while to download into the EEPROM chip on the module. If you’re still stuck, the help file in the Editor has a troubleshooting section. See under the Help Menu at the top of the app (Help → View Help). Editor’s note: we later found out that the correspondent got the Synthesiser working after familiarising himself with the software. Adding balance control to Stereo Preamp I have been looking at trying to add a balance control to my Ultra-Low Noise Stereo Preamplifier (March & April 2019; siliconchip.au/Series/333) as my soon-to-be 60-year-old ears keep insisting the right channel level is slightly higher than the left channel. Testing with an oscillator and VU meter doesn’t indicate a level discrepancy between channels. Around September 2020, I had to replace both pot track wafers with 10kW log track wafers to repair an open-circuit Earth connection on both original 5kW wafers. The donor wafers were from two different pots, and there was about a 20W difference in resistance between them. The motorised pot motor assembly won’t survive another surgery attempt to install exactly matching track wafers. I read the suggestion in Ask Silicon Chip, February 2023, to cut both Earth tracks to the dual pot and install a single linear pot with its wiper to ground to achieve a balance control. I tried a 1kW pot, and it works as a balance control, but it raised the minimum resistance of the volume control pot. That is very noticeable when the balance pot is centred, raising the minimum volume level. What are your thoughts about using 102 Silicon Chip a dual 10kW linear pot (there isn’t a great range of 16mm dual linear pots) wired as variable resistors in place of the unused (4.7kW) R1 and R2? This should alter the signals to IC1b and IC2b in opposite directions, but it will somewhat lower the overall gain of the preamp. Still, the preamp can drive an SC200 amplifier to deafening levels at half volume. (D. C., Rotorua, NZ) ● There are various ways to add in the balance. Your suggestion will work, although the balance between channels will vary depending on volume settings. A better option, we think, is shown at the top of the diagram above. It involves lifting the ends of the two 2.2kW resistors that previously connected to ground from pin 2 of IC1a & IC2a (or cutting the tracks) and connecting the resistors instead to either end of the track on a 1kW linear potentiometer with its wiper wired back to PCB ground. That will vary the relative gains of IC1a and IC2a without affecting anything else. It will give a control range of about ±1.8dB, which should be Australia's electronics magazine plenty. If it’s too sensitive, the four 2.2kW resistors could all be replaced with slightly higher values, eg, 3.3kW or 4.7kW (or use a lower value for the potentiometer, if you can find a suitable pot; shunting it with a 1kW resistor might also help). The small circuit snippet below that shows a simple, passive way to add a balance control to any preamplifier. It will reduce the signal level by about 3dB, but as you say, most preamps have plenty of gain, and that can be compensated for by advancing the volume control. If necessary, its sensitivity can be reduced by using a higher-­ value potentiometer. Instrumentation amplifier IC failure I built the Milliohm Adaptor for DMMs (February 2010; siliconchip. au/Article/19) a year or two ago, and it worked fine when first constructed. I recently went to use it to test a threephase alternator winding but could not get any reading on the DMM. continued on page 104 siliconchip.com.au MARKET CENTRE Advertise your product or services here in Silicon Chip KIT ASSEMBLY & REPAIR FOR SALE 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 Lazer Security KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com LEDs and accessories for the DIY enthusiast LEDs, BRAND NAME AND GENERIC LEDs. Heatsinks, LED drivers, power supplies, LED ribbon, kits, components, hardware – www.ledsales.com.au VISIT THE NEW TRONIXLABS parts clearance store for real savings on new parts at clearance prices, with flat rate express delivery Australia-wide – go to https://tronixlabs.com PCB PRODUCTION PCB MANUFACTURE: single to multilayer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au For Quality That Counts... After 38 Years, I am looking to move and semi-retire. Lazer Security needs a young and dedicated person to evolve and grow. We are currently based in Wolli Creek, NSW and we sell new components, unused (recycled) components and kits with an emphasis on LED lighting. If you are interested in purchasing the business from me, please contact tony<at>phoslighting.net SILICON CHIP ASSORTED BOOKS FOR $5 EACH Electronics and other related subjects – condition varies. Some of the books may have been sold. See photos (recently updated): siliconchip.au/link/abl3 Email for a quote (bulk discount available), state the number directly below the photo when referring to a book: silicon<at>siliconchip.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 or 0431 792 293. WARNING! Silicon Chip magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of Silicon Chip magazine. Devices or circuits described in Silicon Chip may be covered by patents. Silicon Chip disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Silicon Chip also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable. siliconchip.com.au Australia's electronics magazine September 2023  103 Advertising Index Altronics.................................27-30 Dave Thompson........................ 103 DigiKey Electronics....................... 3 Emona Instruments.................. IBC Hare & Forbes............................. 17 Jaycar............................. IFC, 49-56 Keith Rippon Kit Assembly....... 103 Lazer Security........................... 103 LD Electronics........................... 103 LEDsales................................... 103 Microchip Technology......... 7, OBC Mouser Electronics....................... 4 SC Advanced Test Tweezers.... 100 SC Breadboard Power Supply.... 26 SC GPS Analog Clock............... 101 SC Pico W BackPack.................. 79 Silicon Chip Back Issues............. 8 Silicon Chip Shop.................42-43 Silicon Chip Subscriptions........ 48 The Loudspeaker Kit.com.......... 77 Tronixlabs.................................. 103 Wagner Electronics....................... 9 104 Silicon Chip The only thing that had changed since I first built the adaptor and when I found it not working last week was that the 9V battery had gone flat. (M. R., Middle Park, Vic) ● First, measure the voltage across the supply pins on IC3, pins 7 and 4. Probe the IC pins where they go into the package in case the socket or soldering is a problem. If the supply voltage is getting to the chip, but there is no output on pin 6, either the chip is faulty or input signals are not reaching it. If it has power and there is continuity between IC3’s pins 3/2 and the SENSE+/SENSE− terminals, then you will need to replace IC3. Using one charger for multiple batteries Have you ever published a circuit for a battery charger output switcher? I run a smart charger on my batteries in the shed: car, lawnmower, tractor, boat etc. All these batteries need to be maintained by switching the leads from one to the next. A circuit that switches a charger between all these batteries with a programmed timing cycle would make a good project. (Craig, via email) ● We haven’t published a sequencer timer like that. However, if you can accept that each battery is connected to the charger for the same period, you could use a circuit like the Circuit Notebook entry “One-in-five timer” (June 2009; siliconchip.au/ Article/1459). It comprises a 7555 timer and 4017 counter. The output drives a transistor that powers a relay. The relay could be used to switch the charger to the required battery. The transistor and relay circuitry can be duplicated and connected to the subsequent 4017 out- Errata & Sale Date for the Next Issue I have double-checked everything, put a new 9V battery in and rechecked the initial four setup adjustments. Adjusting VR1, VR6, VR2 and VR3 all produced responses as expected. I also rechecked the voltage null detailed in the “final setup” instructions, and the voltage responded as expected; it was easy to set it to zero. However, the final setup test using VR4 and a known 10W resistor was a complete failure. I got no voltage readout and could not obtain any voltage change by varying VR4 across its entire range. I attempted this setup for both a 4-terminal and 2-terminal test with the same result. I have triple-checked all my cables, the Milliohm Adaptor switch settings, DMM settings, the PCB itself for shorts or broken tracks and the orientation of all components on the PCB. Everything is spot on. I also tried three different DMMs with the same results. All parts of the circuit appear to be responding correctly except the output from IC3 (AD623AN). Is it possible the AD623AN has gone faulty? Or can you think of another reason I cannot get an output from the Milliohm Adaptor to my DMMs? put for more than one battery. You can use this circuit for up to 10 batteries. The reset section is set up to go back to the first output after a count of five, but you could change how it is connected to the 4017 to give a different number of steps. The 7555 timer frequency sets the period. Its output would probably need to be divided down by a frequency divider, such as a 4020, to get the desired battery charging period. Increasing mains timer duration I purchased and constructed the ‘Mains Timer for Fans and Lights” from an Altronics kit (K6047). This is a Silicon Chip project, but I don’t know when it was published. I am using it to switch off a water pump after a pre-set time. If I forgot and left the pump running, we could send huge volumes of precious rainwater into the paddock. Can C1 be replaced with a value larger than 330nF to increase the maximum time to more than one hour? I am considering finding a capacitor near 600nF or 700nF to increase the maximum time to around two hours. Thanks for the enjoyable, informative read every month. (D. R., Goughs Bay, Vic) ● You can find out when the design for a kit was published by searching for the kit code here: siliconchip.au/ Articles/ContentsSearch That project is from the August 2012 issue. Yes, you could increase C1 above 330nF to get a delay over one hour as it determines the oscillator frequency. Note that such long delays may not be too accurate; 680nF is a reasonable choice if you’re aiming for around two hours. SC Reciprocal Frequency Counter, July 2023: on the PCB, test point TP3 actually connects to pin 12 of IC1a (same as TP2), not pin 5 of IC2a as shown in the circuit diagram. If you need to monitor the COUNTEN signal, probe the Arduino Nano D3 pin. Wideband Fuel Mixture Display, April-June 2023: some PCBs supplied have diode D2 incorrectly labelled as D5. On those same boards, the 100nF capacitor just below IC3 lacks a proper pad to solder its lead to on the underside. It can be bent over and soldered to the pad for the nearby 100nF SMD capacitor on the underside. Also, in Fig.15 on p75 of the June 2023 issue, the mauve “A/F” wire going to the multimeter should connect to MV+, not MS+ as shown. Next Issue: the October 2023 issue is due on sale in newsagents by Thursday, September 28th. Expect postal delivery of subscription copies in Australia between September 26th and October 13th. Australia's electronics magazine siliconchip.com.au “Rigol Offer Australia’s Best Value Test Instruments” Oscilloscopes NEW 200MHz $649! New Product! Ex GST RIGOL DS-1000E Series RIGOL DS-1000Z/E - FREE OPTIONS RIGOL MSO-5000 Series 450MHz & 100MHz, 2 Ch 41GS/s Real Time Sampling 4USB Device, USB Host & PictBridge 450MHz to 100MHz, 4 Ch; 200MHz, 2CH 41GS/s Real Time Sampling 424Mpts Standard Memory Depth 470MHz to 350MHz, 2 Ch & 4Ch 48GS/s Real Time Sampling 4Up to 200Mpts Memory Depth FROM $ 429 FROM $ ex GST 649 FROM $ ex GST 1,569 ex GST Multimeters Function/Arbitrary Function Generators New Product! RIGOL DG-800 Series RIGOL DG-1000Z Series RIGOL DM-3058E 410MHz to 35MHz 41 & 2 Output Channels 416Bit, 125MS/s, 2M Memory Depth 425MHz, 30MHz & 60MHz 42 Output Channels 4160 In-Built Waveforms 45 1/2 Digit 49 Functions 4USB & RS232 FROM $ 479 FROM $ ex GST Power Supplies 725 ONLY $ ex GST Spectrum Analysers 789 ex GST Real-Time Analysers New Product! RIGOL DP-832 RIGOL DSA Series RIGOL RSA Series 4Triple Output 30V/3A & 5V/3A 4Large 3.5 inch TFT Display 4USB Device, USB Host, LAN & RS232 4500MHz to 7.5GHz 4RBW settable down to 10 Hz 4Optional Tracking Generator 41.5GHz to 6.5GHz 4Modes: Real Time, Swept, VSA & EMI 4Optional Tracking Generator ONLY $ 749 FROM $ ex GST 1,321 FROM $ ex GST 3,210 ex GST Buy on-line at www.emona.com.au/rigol Sydney Tel 02 9519 3933 Fax 02 9550 1378 Melbourne Tel 03 9889 0427 Fax 03 9889 0715 email testinst<at>emona.com.au Brisbane Tel 07 3392 7170 Fax 07 3848 9046 Adelaide Tel 08 8363 5733 Fax 08 83635799 Perth Tel 08 9361 4200 Fax 08 9361 4300 web www.emona.com.au EMONA