Practical
Electronics
Volume 54. No. 12
December 2025
ISSN 2632 573X
Contents
Projects and Circuits
Variable Speed Drive for Induction Motors, part one by Andrew Levido
16
Induction motors are robust and inexpensive so they are used widely, but you can’t
control their speed easily. You need to synthesise three high-voltage, variablefrequency, variable-amplitude sinewaves. This elegant design does just that.
Digital Capacitance Meter by Stephen Denholm
53
This straightforward piece of test equipment measures capacitor values over a
wide range, from about 10pF to 10,000μF (10mF). It’s easy to assemble with all
through-hole parts, fits into a UB1 Jiffy box, and also won’t break the bank.
Battery-Powered Model Railway by Les Kerr
66
If you let model railway tracks oxidise, power won’t get to the trains, causing all
sorts of problems. By making the train battery powered, it no longer needs to draw
power from the tracks, making it much more reliable!
Series, Features and Columns
Teach-In 12.2: the World of Wireless by Mike Tooley
4
This month, we start by examining a simple radio frequency (RF) circuit before
moving on to explore the principal components on which it is based. Our practical
project features an improved portable medium-wave AM receiver.
Audio Out by Jake Rothman
30
I introduced my new germanium-transistor-based Transmanium fuzz box last month,
presenting the circuit and PCB. To use a fuzz box, you need it in a sturdy box with
accessible controls and sockets, so let’s finish putting it all together and start using it!
Techno Talk by Max The Magnificent
36
Global Navigation Satellite Systems (GNSS) like GPS are really handy, but how do you
nagivate if you’re underground (or underwater) and can’t pick up satellite signals?
Max’s Cool Beans by Max The Magnificent
38
Weird & Wonderful Arduino Projects: building a ‘retro’ gaming console. This part, #12,
concentrates on combining and driving the 7-segment displays we’ve already introduced so they can show the scores for our upcoming games console.
The Fox Report by Barry Fox
45
When shopping online, you have to consider how you will be receiving the goods
Circuit Surgery by Ian Bell
46
Measuring the frequency response of a circuit using a PC sound card, part three.
This month we’re looking at op amps circuits in general, with the goal of using them
in signal-conditioning systems for making frequency response measurements.
Net Work by Alan Winstanley
60
This month’s column brings updates on the SpaceX Starship program, welcome
news for Windows 10 users, some puzzlement over smart battery chargers and the
end of an era for one of the most popular names in electronics book publishing.
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 December 2025 issue of Practical Electronics will be
published on Friday, 5th of December, 2025 (see p80).
Practical Electronics | December | 2025
Editorial
The lost art of backward compatibility
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