February 2011 Issue

A summary of this month's contents.

Time Delay Photoflash Trigger

A versatile accessory for the keen photographer interested in stop-motion imagery , this project lets you trigger an electronic flash at exactly the right moment in order to capture a dynamic event such as a balloon bursting or a light-bulb shattering.

Triggered by an electret microphone or external trigger (PIR, sensor etc), with switchable time delays from 0-9.99 seconds in 1ms/ 10ms increments. CMOS logic-based circuit. Timing accuracy 1ms or 10ms, output provided include a non-delayed trigger for external shutter release and a delayed triggering for electronic flash.


TempMaster Mk 2 Thermostat

This easy-to-build low cost thermostat can be used to control fridges, freezers, 12V fridges as well as heaters typically used in hatcheries and fish tanks.

Want to convert an old chest-type freezer into an energy-efficient fridge? Or convert a spare ‘standard’ refrigerator into an excellent wine cooler? This updated version of the original Coolmaster (EPE July 2008) is probably the only thermostat you will ever need!


It has expanded capabilities and better energy-saving characteristics. It controls the fridge/ freezer or heater directly via its power cable, so there’s no need to modify internal wiring.  As the new Tempmaster Mk 2 has a relay output it’s possible to control 12V cool / warm boxes as well. 723C – LM335Z based with trimmable temperature control.


Old fridges and freezers can be dangerous. Take care to ensure children do not play with them or accidentally become trapped inside them.


Multi Purpose Car Scrolling Display (Part 3)



The final part showing how to connect this versatile display unit for your car.  It’s set up using some simple command-line routines with the free program downloadable from our Library. Calibration details are provided in a PDF document, downloadable separately.


Teach-In 2011

Our educational series specially written for beginners in electronics continues with the most fundamental active electronic device of them all: the transistor. On-screen simulations are offered using Circuit Wizard software.


Also in this month’s edition:

  • Techno Talk examines some new developments coming over the horizon – will they all see light of day?
  • Max’s Cool Beans Blog – Max opines about the Pico mini projector and wonders whether Windows 7 is worth it.
  • Circuit Surgery outlines the perils of leaving unused gate or op-amp inputs or outputs “floating”.
  • Interface – our occasional series for PC users – offers an optical approach to PC interfacing.
  • Net work – our Internet column has more hints tips and topical views about the latest web developments.


EPE is the No. 1 electronics magazine for hobbyists, students and professionals everywhere. Available on newsstands or downloadable at an irresistible price – subscribe to EPE now!




Source code 0211.zip

PCB files pcb0211.zip


Please Take Note

Time Delay Photoflash Trigger


In December 2011 EPE page 59 we advised that on page 16, Fig 3 of this project unfortunately transistor Q3 is shown the wrong way round. The 'flat' of the transistor's body should be facing the 4k7 resistor, i.e. the collector pin should go to the anode (A) of LED1. The photograph on page 17 is correct.


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