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Practical Electronics Volume 54. No. 5 May 2025 ISSN 2632 573X Contents Projects and Circuits The Skill Tester 9000, part one by Phil Prosser 8 This old-school dexterity tester has added lights, timers, countdowns, sounds, noises and competition between players! Plus, it has plenty of construction fun, and you can modify it to your heart’s content DIY USB-C Serial Adaptor by Tim Blythman While USB-serial adaptors with Type-C sockets are available, many do not adhere to the USB-C standard and may also have Windows driver problems. Our design, presented here, has no such drawbacks and is relatively simple and compact. 30 Three DC Supply Input Protectors by John Clarke 46 These three simple, inexpensive circuits protect equipment from damage due to an incorrectly connected or malfunctioning power supply. They protect against a higher than expected voltage or a reverse polarity supply. Series, Features and Columns Techno Talk by Max The Magnificent I chat with several companies about their latest and greatest technological offerings. 3 A short history of Sinclair’s handheld calculators by Chris Morris 4 In the 1970s, UK company Sinclair Scientific were leaders in calculator innovation. Circuit Surgery by Ian Bell Topics in digital signal processing – high-pass, band-pass and band-stop filters. 18 Raspberry Pi 5 review by Tim Blythman The Raspberry Pi 5 has been available for a little while now. We look at its advantages compared to the venerable Pi 4B and some other competing SBCs. 25 Max’s Cool Beans by Max The Magnificent 36 Weird & Wonderful Arduino Projects, part 5: creating & optimising display algorithms. Adding Solar Charging to a Renault Kangoo EV by Roderick Boswell 54 Roof-mounted solar panels and an onboard charging system can provide around 10,000 miles of free driving per year if the weather is good. Precision Electronics, part five by Andrew Levido 60 Besides unwanted currents and fixed voltages, there is another type of unwanted signal that can cause all sorts of problems that we refer to as noise. So, how can we quantify its effects on our circuits and reduce the resulting errors? Audio Out by Jake Rothman 66 An audio amplifier circuit that can switch between Class-A and Class-(A)B modes. The Fox Report by Barry Fox The little-known portal shutdown problem increasingly affecting Internet radios. 69 The History of Electronics, part five by Dr David Maddison 70 We wouldn’t have computers, smartphones or AI without the work of thousands of people who created the foundations of modern electronics. This fifth article in the series covers inventions by companies and organisations up to 1962. Regulars and Services Made in Australia & the UK. Written in Britain, Australia, the USA and Ireland. Read everywhere. © Silicon Chip Publications Pty Ltd 2025 Copyright in all drawings, photographs, articles, technical designs, software and intellectual property published in Practical Electronics is fully protected, and reproduction or imitation in whole or in part are expressly forbidden. The June 2025 issue of Practical Electronics will be published on Thursday, 1st of May 2025 (see p80). Practical Electronics | May | 2025 Editorial Ferrite beads are not inductors Reader services – Editorial and Advertising Departments Subscribe to Practical Electronics and save money Practical Electronics PCB Service PCBs for Practical Electronics projects Classified ads and Advertiser index Next month! – highlights of our next issue of Practical Electronics 2 2 59 76 79 80 Renewals paid by PayPal, Visa and Mastercard are now handled via our website: www.electronpublishing.com 1