March 2020 Issue

A summary of this month's contents.

Diode Curve Plotter

This remarkable piece of test equipment has a touchscreen colour LCD and is both practical and educational. Based on an Arduino Mega with a custom shield, it tests Zener diodes, LEDs, Transient Voltage Suppressors (TVSs), regular and Schottky diodes and more.


It graphically plots diode properties and displays current, voltage, power and impedance at any point in the characteristic curve. Tests up to 100V/ 30mA from a 12V or 5V USB supply.


Audio DSP (Part 3)


In the final part  we test the DSP Crossover modules, then finally connect them together and power up the unit for the first time, going through all the graphics menu options as well.



After testing and installation into the housing, you can set it up before hooking it up between your pre-amp and power amplifier(s), so that it can get to work processing the sound.


Steam Train Whistle/ Diesel Horn Sound Generator

Re-live the exciting days of steam-train travel with this audio effects unit. Use it in a model railway layout, as a doorbell or just as a standalone sound effect. It creates a steam whistle using white noise or generates a diesel horn effect. It can even simulate the Doppler Effect or change of pitch as if a train was passing by.


It has multiple trigger options and can be customised in a number of ways to suit personal preferences.  Direct speaker driver – approx 1W into 8 ohms. Requires 5V d.c @ 300mA. Uses two PIC 12F617 microcontrollers with source codes downloadable from our website.


A little SMD soldering experience will be helpful.

Also consider our Super Digital Sound Effects Module (August and September 2019 issues) which uses .wav files on a microSD card instead.


Using Cheap Asian Modules (Part 22)

Seeed/ Grove-designed galvanic skin response sensor

An insight into a ready built module that measures changes in the resistance of human skin, which in turn can indicate changes in mood, apprehension or other characteristics.


It can also be hooked to a micro or digital multimeter. Our feature shows how to get the best out of a typical unit and how to hook one to a Micromite for further experimentation or maybe to hook to an Arduino serial plotter.

Also in this issue:


  • The Fox Report – how the woeful lack of proper instructions makes for unhappy and frustrated customers
  • Techno Talk – how new trends in batteries for traction could impact us in the future
  • Net Work – How Two-factor authentication (2FA) can help combat misuse; avoiding bogus money-laundering crime
  • PIC n’ MIX - a design update for the Audio Spectrum Analyser. This series will also investigate the 3D-printing of a suitable enclosure. Many more exciting topics are in the pipeline, so stay tuned in to PIC n’ MIX for more news!
  • Circuit Surgery – in-depth exploration of circuitry surrounding strain gauges
  • Audio Out – the PE Mini-monitor crossover  for Wavecor drivers (Part 2)
  • Make It with Micromite (Part 14) – Using Bluetooth to make a wireless link that sets your Micromite free
  • Visual Programming with XOD – Introducing XOD, the free visual programming tool for Arduino, allowing systems to be developed quickly and as easily as drag and drop.
  • Max’s Cool Beans – Max debounces switches and lights up LEDs this month
  • Electronic Building Blocks – an extraordinary alarm that plays your pre-recorded speech samples or sounds, all built with cheap-as-chips parts bought online.


Next month


Flip-dot Display; Ultra Low distortion Preamplifier with Tone controls; iCEstick VGA Terminal; Visual programming with XOD; Contents may be subject to change.


There’s more in PE than ever before! PE is packed with practical electronics projects and theory for the hobbyist. You can order a printed copy of PE for delivery to your door (worldwide), or try the PDF Version (needs Adobe Reader for Windows), or the Pocketmags for your mobile device. Subscribe now!




Source code file * updated 7/3/2020 *

(Diode Plotter; GSR; XODball; DSP; Str guage; Steam Whistle; LED effects)


PCB artwork


As from July 2013 issue PCB artwork is available free to subscribers only.


Non-subscribers may purchase artwork files for a nominal sum. Please contact our Orders Dept for information or to place an order.


EPE Printed Circuit Boards


We can supply ready-made printed circuit boards (8-digit order codes) to the original design specification via mail order or from our Online Shop.

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