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Practical Electronics Volume 54. No. 7 July 2025 ISSN 2632 573X Contents Projects and Circuits Compact OLED Clock/Timer by Tim Blythman 14 This handy, portable, rechargeable device combines a clock, timer and stopwatch and can display different time zones. It has an internal crystal and incorporates a WiFi time source, so it is always accurate, even if a leap second occurs. 180-230V DC Motor Speed Controller, part one by John Clarke 34 High-voltage DC motors are commonly used in lathes, treadmills, industrial conveyor belts and similar equipment. This Speed Controller can control such a motor over a wide range of speeds, from very slow to maximum, maintaining a constant speed. Repurposing the Mains Power-up Sequencer by John Clarke 52 Generators and inverters are not always powerful enough to run more than one highcurrent appliance at a time. The Mains Power-Up Sequencer from the February & March issues can be programmed to do that automatically. Intelligent Dual Hybrid Power Supply, part two by Phil Prosser 64 Our new Dual Hybrid Supply uses switchmode and linear regulators, so it has very quiet outputs. They can be used independently or together in series or parallel, all controlled through a single easy-to-use digital interface. Series, Features and Columns The Fox Report by Barry Fox Robotic mowers are a labour saver, but they take some effort to set up properly. 4 Circuit Surgery by Ian Bell 6 Topics in digital signal processing – Implementing DSP on a microcontroller, part two. Techno Talk by Max The Magnificent 24 HITL used to stand for hardware-in-the-loop. Now, HITL also stands for human-in-theloop, where human judgement is added to automated systems. Max’s Cool Beans by Max The Magnificent Weird & Wonderful Arduino Projects, part 7: predictably random. 26 Precision Electronics, part seven by Andrew Levido 44 Last month, we covered the various sources of analog-to-digital and digital-to-analog conversion errors. This month, we will focus on analog-to-digital converters (ADCs) and, as usual, we’ll include a practical example. Audio Out by Jake Rothman 57 Pretty much all linear amplifier circuit designs these days use the standard long-tailed pair (LTP) at their input. There’s another way to do it, though, using a complementary cascode. That method has some advantages, so I decided to give it a try. Regulars and Services Made in Australia & the UK. Written in Britain, Australia, the USA and Ireland. Editorial ChatGPT can analyse circuit diagrams Reader services – Editorial and Advertising Departments Subscribe to Practical Electronics and save money Practical Electronics Back Issue DOWNLOADS – 2024 now available! Teach-in Bundle – what a bargain! 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 3 33 51 76 79 80 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 August 2025 issue of Practical Electronics will be published on Thursday, 3rd of July 2025 (see p80). Practical Electronics | July | 2025 Renewals paid by PayPal, Visa and Mastercard are now handled via our website: www.electronpublishing.com 1