January 2016

This month’s highlights

Isolating High-Voltage Oscilloscope probe

This low-cost project is designed to allow you to use your oscilloscope to observe and measure a.c. mains and other high voltage waveforms with confidence.

It has high-voltage opto-isolation built in (>10 GΩ 500V) so your scope can take safe mains measurements involving connections to live or neutral. Three attenuation factors are available (10:1 100:1 and 500:1). Input resistance 2.0M || ~10pF.

 Surface mount design needs good soldering skills

High-energy Multi-Spark CDI (Part 2)

This capacitor discharge ignition system provides very high energy multi-spark discharge each time the spark plug is fired. It generates a shorter-duration ‘hotter’ spark than traditional ignition and is usable up to 1,000 sparks per second.

In this follow up article we give the assembly details for six different versions to suit your car’s trigger source. Not recommended on 6-cylinder or V8 engines without attending to the HT lead separation (see article).

  • Reluctor pickup
  • Points triggering
  • Hall Effect or Luminition
  • Engine management triggering
  • Crane optical pickup
  • Piranha optical pickup

Transformer winding and installation techniques are also described.

This circuit produces an output of up to 300V DC and can deliver a severe or even fatal electric shock. High voltage design suitable for experienced constructors. Using this project may affect a vehicle’s insurance policy.

The Currawong Valve Amplifier (Part 3)

The final article describes the Currawong Valve (vacuum tube) amplifier’s IR remote volume control, also details of the essential acrylic safety cover and the final setting up routines.


High Voltages  are present throughout.  Never operate the unit unless the lid is in place. This design is suitable for skilled and experienced constructors only.

Also in this month’s issue:


Mike O’Keeffe, our PIC microcontroller expert, offers a mini home-grown Christmas tree, with PIC-powered LEDs adding some seasonal cheer.

Max’s Cool Beans

Max progresses with his Cunning Chronograph LED Clock and muses about its coding and practicalities.

  • Circuit Surgery – Our in-house surgeon Ian Bell offers a very comprehensive walk-through of the applications of Darlington transistors and an in-depth analysis of the issues surrounding their use
  • Techno Talk ponders the potential for Internet-aware cars being subjected to hacking or terrorist attack
  • Practically Speaking – Robert Penfold’s workshop series explains how best to handle static-sensitive components to avoid damaging them
  • Audio Out – Jake Rothman  our audio enthusiast outlines a variety of audio filters with practical examples included.
  • Electronic Building Blocks – Julian Edgar adapts a budget-price opto module to provide a snap-action switch
  • Net Work – EPE’s Alan Winstanley looks at a £20 Android HDMI dongle that converts a TV or monitor into a useful Android-powered computer, and explains how to get rid of the “Get Windows 10” popup.

Next month

6-digit Retro Nixie Clock (Part 1); CGA-to-VGA Video Converter; Car Engine Spark Energy Meter.

January 2016 files for download - 0116.zip

  • HV probe
  • Multi spark CDI panel a/w
  • PIC n MIX Xmas Tree
  • Audio Out PCB

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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