October 2020

High-Power 45V/8A Variable Linear Bench Supply (Part 1)

This adjustable bench PSU delivers all the power you’ll need for developing or testing projects – the linear supply can deliver up to 8 amps (@16-45V continuous) or up to 50V at lower currents.  The variable voltage, variable current project has low ripple and noise and has a digital display. Inside it uses a 500VA toroidal transformer and is fan cooled. A digital temperature display and thermal shutdown are included. Its largely through-hole PCB construction is described in Part 2 next month.

Precision ‘Audio’ Signal Amplifier

This piece of test gear contains a precision amplifier that can boost a signal to a higher amplitude for times when signals could do with a ‘kick’ – perhaps when a signal generator itself provides insufficient amplitude. In fact it can operate outside of the ordinary audio spectrum, working down as low as 6Hz or all the way up to 230kHz or even higher, at up to 10.6V r.m.s.  The Precision ‘Audio’ Signal Amplifier has two switched gain settings or 0dB or + 20dB.  It uses a surface-mounted ADA4625 precision JFET op amp and a small number of discrete components.

Arduino-based Digital Audio Millivoltmeter

This digital audio millivolt/voltmeter will be useful for setting up and calibrating audio systems, taking performance measurements, faultfinding audio equipment and more. It has balanced and unbalanced inputs with the ability to measure from below -85dBV (56µV r.m.s.)  to above +35dBV (60V r.m.s.)! The test gear is based on an Arduino Nano and LTC2400 24-bit ADC. Other features a backlit LCD readout, automatic ranging and it can upload data to a PC.

 Surface mount components are used throughout. Good soldering skills are needed to complete this project successfully.

Practically Speaking

Mike Hibbett introduces us to the K40 laser cutter and engraver, warns of many perils and pitfalls and offers many essential safety precautions, and hardware / software hints and tips. If you’re looking to get into laser cutting or engraving, be sure to read Mike’s valuable insight into a very popular choice amongst hobbyists.

Pedal Power Station (Part 1)

This project generates real electrical power from scrap or salvaged parts, adapting a universal or stepper motor for use as a generator. And did we mention, it uses an old exercise bicycle? The prototype generates 12V and drives 90 Watts of LED lighting.

Also in this issue

• Techno Talk – advanced research into extending smartphone battery life
• Net Work – more ransomware trends, and swarms of CubeSat nanosatellites
• Circuit Surgery – Ian Bell delves deeply into the area of rail-to-rail and single-supply op amps
• Make It With Micromite (Part 21) – Exploring a GPS module with UART communication
• Max’s Cool Beans – Max adds some realistic multicolour LED fade in/out effects to the giant-size LED 12×12 array
• Audio Out – a low-noise germanium transistor power supply

Next month

The Christmas Tree that grows! Five-way LCD Panel Meter and USB display;  High-Power 45V/8A Variable Linear Bench Supply (Part 2); Pedal Power Station (Part 2). Contents may be subject to change.