August 2018

This month’s highlights

Universal Temperature Alarm

This compact and handy alarm can monitor the operating temperature in a variety of applications and is ideal for eg tropical aquaria, home brewing, fridge freezer, domestic hot water systems and more. Based on the classic LM335Z temperature sensor, it acts as an over- or under-alarm and monitors a temperature range -33°C to +125°C.  On-board piezo disc alarm sounder. A straightforward double-sided PCB with discrete components make this project easy to build. 9V-12V power supply required. Full details of an aquarium temperature probe are included.

Touchscreen Appliance Energy Meter (Part 2)


Since Part One was published last month, a minor change to the circuitry has been made. We added a 100nF capacitor between the earth (ground) terminal on CON8 and the VREF (pin 10) of IC2. We now only supply the RevI PCB (see this issue, page 21) which uses an ACS718 (SOIC-16, IC4) and one extra 1nF 0805 SMD capacitor. This is needed as the previous ACS712 current sensor, shown on the original circuit diagram last month, had insufficient reinforced voltage rating for double-insulated use. Consequently, also please note a slightly amended circuit schematic which is downloadable below.

Energy Meter Circuit Diagram Revision   (PDF)

The Silicon Chip USB Serial Port Driver for legacy PC systems can be downloaded  here

This sophisticated appliance meter incorporates a 2.8” touch screen to display energy usage data, running costs, graphical displays and data logging. In Part Two this month we cover the process of building the PCBs and assembling the whole unit, as well as describing some of the interesting features of the meter’s software.

‘Banggood’ DSO138 LCD ‘scope kit

We’ve looked at some very cheap electronics modules from China recently, but the one reviewed here brings you a real, working, digital sampling oscilloscope in a kit for just £24! It’s from Chinese vendor Banggood and we describe what’s involved in assembling and using this value for money kit.

Power supply for battery-operated valve (vacuum tube) radios

Batteries for vintage radios can be hard to get and expensive, so this mains power supply design could be the ideal solution for vintage radio enthusiasts.  Offers 90V and 135V and A & C rails as well.

Using Cheap Asian Electronics Modules (Part 8)

This month’s peek at cheap and cheerful Far Eastern modules looks at two battery controllers, one suited for Li-Ion cells and another designed for Lithium-Ion Polymer cells.


Our PIC expert Mike O’Keefe returns from a break and straight away delves into Microchip’s latest offering, the PICkit 4. Mike takes one apart and explains what advancements the PIC enthusiast can hope to see.

Audio Out – Analogue Synthesis (Part 1)

Analogue lives! Our in-house analogue audio expert delves deep (and we mean deep!) into the world of analogue synthesisers.

This month we offer you a fascinating and well-illustrated introduction to generating audio signals, including the latest version of the classic Dubreq Gen X-1 Stylophone!  If you love synthesisers or want to delve into the circuitry behind them, don’t miss this mammoth series in Audio Out, starting this month.

 CORRECTION – Please Take Note – a revised Fig 5 of Part 1, with correct TL431 pinouts is shown below.

Also in this issue:

  • Circuit Surgery offers a full primer on the theory of summing differentiator circuits
  • Lucy’s Lab – our brand new column for makers and hobbyists offers some great hints and tips for soldering components together
  • Techno Talk  relates the latest news of electronics aids for automotive applications
  • Electronics Building Blocks – ideas for a low cost key-fob controlled remote control
  • Net Work – the Internet column – more on the GDPR, Eudora lives again, Pinterest.

Next month

Touchscreen Energy Meter for Appliances (Part 3); Dead-easy Superhet IF Alignment using Direct Digital Synthesis; 3-Way Fully Adjustable Stereo Active Crossover for Loudspeakers; Ultra-Low-Voltage MINI LED Flasher; Low-cost Electronic Modules (Part 9) – Using an AD9850 based circuit.

August 2018 files for download -

  • Appliance Meter case artwork and firmware

Printed Circuit Boards

We supply PCBs for all our projects going back to 2013.

New PE service – Programmed PICs

Buy programmed PICs for most of our projects.

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