April 2026

Versatile Battery Checker

This sophisticated PIC-micro based battery checker displays on an OLED screen the internal characteristics of almost any type of cell or battery from 1V to 30V, with test currents up to 30 amps. The mono screen is used for configuration, calibration and, of course, displaying test results.

Power Rail Probe

This project could be classed as one of those items of test equipment that you don’t really need, until you do! The handy-sized unit allows for the measurement and evaluation of ripple, switching noise and transients riding on DC supply rails.

The Pico 2 Audio Analyser

This project is a handy little tool based on the Raspberry Pi Pico 2 and not much else! It sports a menu-driven mono OLED display and has oscilloscope and spectrum modes. The project also incorporates a signal generator with selectable frequency and waveforms. It can run in a sweep to plot a frequency response, or perform harmonic analysis to check signal quality.

Teach-In 2026
Part 6: RF testing and measurement

Our tutorial series on all things to do with ‘wireless and radio frequency’ continues with a primer on using test equipment dedicated to RF measurements, including voltage, power and frequency. This month we include details of an RF probe that you can build yourself.

New series: Power Electronics
Part 1: DC-DC Converters

The start of a comprehensive and fascinating series outlining the principles of converting electrical energy from one source into another. The theory behind DC ‘buck’ and ‘boost’ converters are amongst the topics discussed this month.

Max’s Cool Beans
Weird & Wonderful Arduino Projects
Part 16: etching sketches and snake shenanigans!

Work on Max’s Arduino-based retro games console continues – a few tweaks of code are all it takes to produce a simple “Etch A Sketch”. Can it really be that simple? Find out this month!

Circuit Surgery
Part 7: op.amp output impedance and compensations

Continuing the topic and techniques for mitigating the problems of capacitive loads on stability in op amp circuit design.

Techno Talk

Max cites some seriously stunning developments in the area of micro-miniaturised microphone element and sensor manufacturing. (Shown: a nanoscale sensor on a hypodermic needle.)

Audio Out

Our analogue  audio expert lays bare the principles of signal phase inversion and describes the design and application of all-pass filters.

Next month

SSB Shortwave Receiver; Tool Safety Timer; DIY 433MHz Transmitter Module