July 2019

10A Universal Motor Speed Controller

This highly-effective full-wave power controller offers smooth, full-range speed control of universal (brush-type) motors rated up to 10 Amps/ 2.2kW. The PIC microcontroller design includes advanced features like soft-start and current feedback to ensure full power delivery even at low speeds. It’s cheaper and less complex than some previous designs and is sure to become the ‘go-to’ project for universal mains motor control. Free microcontroller source code available from our web site, see link (top right).

Intended for 220-250V a.c. mains only. Not suitable for 110V a.c. supplies nor induction or synchronous motors, nor should fan-cooled universal motors (eg power drills) be used for extended periods at low speeds otherwise they may overheat.

For induction motor control, see our 1.5kW Induction Motor Controller in the January & February 2019 issues.

WARNING MAINS VOLTAGE

High Voltages  are present throughout. This design is suitable for skilled and experienced constructors only.

Recurring Event Reminder

A simple and easy to build gadget that gives both a blinking LED and optional ‘chirping’ audio reminder to perform a routine task, such as feeding the pet or taking medicines.

Time intervals of every 6, 8, 12 or 24 hours can be set, or it can go off every week or every fortnight.  Compact design, 3V coin cell powered. PIC micro powered with free microcontroller source code available from our web site, see link (top right).

Temperature Switch Mk2

More than a decade has passed since we published the first “Temperature Switch” in the August 2008 issue, and this update uses a microcontroller to power a relay on or off, operating in heating up or cooling down mode. The Temperature Switch is a dedicated 12-15V d.c.  module with a thermistor sensor and has a miniature 30V 5A relay on board, which can be used to drive a solid state switch or slave relay for higher loads. Its operational range is -10°C to +125°C and variable hysteresis allows you to select the difference in on-off switching points. The module function is set up using a multimeter.

Discrete design, straightforward to build. PIC micro powered with free microcontroller source code available from our web site, see link (top right).

Build the superb PE Theremin!

In this month’s Audio Out our Theremin designer Jake Rothman outlines the construction of the pitch control circuit board, with specific recommendations for choosing the best components. The circuit board CAD files are downloadable from our web site, see link (top right).

Using Cheap Asian Modules (18)

This month we explore two more low-cost RF/ UHF modules – a digital counter module based around an ATMega48PA MCU, and a low-noise wideband amplifier.

MIDI Ultimate Synthesiser (Part 6)

In this, the final article, our attention turns to the fabrication of the Ultimate Synthesiser’s wooden cabinet ready for the finished p.c.b. to be installed in its new home.

This month we also present a downloadable package for constructors, featuring larger-scale circuit schematics that are easier to read, the MIDI Ultimate block diagram, a blank patch sheet, MIDI code and full parts list with sourcing suggestions. Click the Zip file link, top right.

Teach-In 2019
Powering Electronics (Part 8)

Our tutorial series on power supply design theory concludes this month with an investigation into batteries – comparing different types and characteristics and how to get the best out of them. An index covering the entire series is also included.

Also in this issue:

• The Fox Report, by Barry Fox: Britain’s B&W audio meets the Audition range of mesh-technology wireless loudspeakers.
• PIC n’ MIX – In Part 3 our PIC expert Mike Hibbett continues his exploration of the tiny PIC 10F202 micro, explaining circuit design techniques.
• Techno Talk – Mark Nelson highlights problems in the USA where land lines are being forcibly replaced by fibre; Russia is accused of spoofing GPS data.
• Net Work – whole-home mesh wi-fi, Powerline pitfalls and the Google Nest Hub.
• Make It with Micromite – Electronic Dice
• Electronic Building Blocks – some cheap and cheerful security gadgets
• Circuit Surgery – Ian Bell starts a new series on understanding bipolar transistors.
• Max’s Cool Beans – Max the Magnificent grapples with the dynamic range of his Awesome Audio-Reactive Artifact breakout board, see

Next month

Arduino Brainwave Monitor; Super Digital Sound Effects Monitor; IR remote control for computers; Watchdog Alarm; PE Theremin (Part 3).