July 2025

The Fox Report

Barry Fox earns his stripes this month by trying out a supermarket robotic lawnmower – and is left unimpressed with the effort needed to install and operate it successfully.

Circuit Surgery

Ian Bell continues his highly insightful exploration of the principles of implementing digital signal processing (DSP) on a microcontroller.

Compact OLED Clock/ Timer

This highly accurate standalone timer provides a multitude of timing functions and means there’s no need to tie up your smartphone to monitor time periods. Using a crystal-clear OLED display, this project has a countdown timer, stopwatch and alarm and uses a Wi-Fi time source to uphold accuracy. Menu driven, the timer uses a PIC micro, the circuit utilises a Raspberry Pi Pico W, and is powered by a Li-Ion battery.

Some samples of the OLED menus are below (not actual size):

Techno Talk

Max marvels about the prospect of Humans In The Loop (HITL) – where human judgment is added to automated systems.

Max’s Cool Beans – weird and wonderful Arduino Projects (Part 7)

More on using shift registers, XOR feedback and switch debouncing techniques.

180-230V DC Motor Speed Controller

High-voltage DC motors will be found in consumer-grade treadmills, machine shop lathes, conveyors and similar equipment. This sophisticated project for advanced constructors utilises back-EMF sensing to provide constant speed under load and a wide range of rotational speeds from ‘inching’ to full speed. It has safe start-up and automatic over-current. Rated 1-10A (¼HP – 2.5HP)

Mains voltage is present throughout and this project is suitable only for skilled constructors experienced in mains interwiring and control

Precision Electronics
Part 7: Analog-to-Digital Conversion

This month’s feature examines the field of Analog-to-Digital Conversion (ADCs) and includes some practical examples.

Repurposing the Mains Power-Up Sequencer

This adaptation suggested by a reader uses updated software to enable the project to sequence the output to several loads, such as fridges or freezers, over time. This can prevent generators or inverters that power them from becoming overloaded. Three software versions are offered for maximum versatility.

Mains voltage is present throughout and this project is suitable only for skilled constructors experienced in mains interwiring and control

Audio Out

This month’s column for audiophiles presents a very thoroughly sorted, scratch-built design for a sophisticated complementary cascode amplifier using discrete semiconductors.

Intelligent Dual Hybrid Power Supply (Part 2)

This advanced Dual Hybrid PSU has very ‘quiet’ outputs given its use of switchmode regulators to provide good efficiency and high power output in a small form factor. The outputs can be used in series or parallel, all controlled through a single easy-to-use interface. This month’s article describes assembly and calibrating the supply.

Next month

8-Channel ‘Learning’ IR Remote; Dual Rail Load Protector;  Flexidice; Micromite Explore-40. Contents may be subject to last minute change.