November 2025

Capacitor Discharger

This project offers a safe and easy way to discharge capacitors both large and small, including those  used to store rectified mains voltages (up to 400V DC peak). It uses a power MOSFET to control a bleeder resistor and is an ideal solution for constructors who work on switched-mode power supplies, vintage radios or any other equipment that has high potentials lurking inside. An easy to build design.

Announcing the start of a brand new series! Our famous Teach-In tutorials have a long heritage in educating and enthusing hobbyists, and our latest series Teach-In 2026 by Mike Tooley explores the world of radio and wireless technologies.

Teach-In 2026 will trace the origins of wireless communications and explore the fundamental principles of radio frequency circuits and modern-day technologies including software-defined radio, Wi-Fi, Bluetooth and more besides.  Readers will be able to build a series of ‘hands-on’ radio modules utilising low-cost parts and stripboard.

This month a modern-day ‘crystal set’ using a radio receiver chip is described. Don’t miss Teach-In 2026 and a fascinating exploration of the world of radio!

5MHz 40A Current Probe

Traditionally current can be measured by using a low value shunt resistor in conjunction with an oscilloscope, but what if the current being measured runs to several amps, or the circuit is not compatible with the use of a grounded ‘scope probe? That’s where our 5 MHz 40 Amp Current probe comes in. It’s a low cost alternative to commercial ones that can cost hundreds of pounds or more.

Combining a current sensor and instrumentation amplifier,  it offers a fully isolated solution with a scale of 0.1V/ A (so ±40A translates to ±4V). BNC probe output and simple terminals connecting to a SOIC sensor chip. Self-contained Li-Ion power. A compact and useful addition to any workbench.

Weird & Wonderful Arduino Projects
Part 11, connecting the console’s 7-segment displays

Max returns to the topic of developing a retro-style games console, exploring more digital design aspects while grappling with the mysteries of seven-segment displays.

3D Printer Filament Drying Chamber (Part 2)

This fan-assisted dryer will help to get consistent results when using a 3D printer. It’s specially designed to keep 3D printer filaments warm, driving out and repelling moisture, prior to being processed. Your 3D printer can then draw ‘print-ready’ conditioned filament straight out of the box. Part 2 this month illustrates all the practical constructional details.

Techno Talk

^ What has this photo got to do with the price of onions? You may well ask. This month Max walks us around the very latest in ‘audio-visual perception’ devices that will appear in robotics, medical imaging and much more besides in the future. The Eyesynth NIIRA comes in for special praise.

Circuit Surgery

Our in-house ‘surgeon’ Ian Bell continues his in-depth tutorial about techniques to measure the frequency response of a circuit using a PC sound card.

Net Work

This month Net Work re-visits the UK’s SMR nuclear power program and bags some money-saving bargains on Temu.

Nikola Tesla (1856-1943)
Part 2

A truly fascinating and illustrated account of one of the world’s greatest inventors and pioneers of electrical applications, Part 2 details more of Tesla’s creations that harnessed the power of electricity. In 1922 he also predicted a future of warfare conducted by drones.

Audio Out

Our analog audio expert delves into the histories and topologies of the guitar Fuzz Box, trying patiently to explain why guitarists hold many long-established but unfounded prejudices against utilising ‘proper’ audio design. The intricacies of fuzz box circuit design at component level are laid bare.

Next month

Battery-powered Model Train; Digital Capacitance meter; Advanced Variable Speed Drive.