05 June 2009

Here's an easy-to-build accessory for the Time Delay Photoflash Trigger described in our February 2009 issue. It triggers the delay unit and your photoflash in response to an object interrupting an invisible beam of infrared (IR) light. Alternatively, it can be used on its own to directly trigger a photoflash.

01 June 2009

Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates.

18 May 2009

If you'd like to be able to use our Digital Audio Millivoltmeter to measure AC voltages up to 140V RMS, this add-on project is the answer. It's a simple switched input divider which lets you add 40dB, 20dB or 0dB of attenuation ahead of the meter at the touch of a knob.

16 May 2009

When it comes to contributed projects or circuits, there are few things more frustrating than finding the circuit has been drawn (apparently) by "a thumbnail dipped in tar" - or near equivalent. Here's an easy way to make them look good!

15 May 2009

If you're looking for a mains "switch" which can be operated from some distance away, this low-cost, simple project could be just what you want. With a UHF remote control and two switched "channels", it needs very little power thanks to the use of latching relays.

12 May 2009

During preparation of the Precision Voltage Reference project elsewhere in this issue, we consulted with Trio Smartcal on the subject of calibration. This article gives a brief overview.

10 May 2009

Have you ever checked the calibration of your digital multimeter? Yeah, we know - you haven't because there is no easy (read cheap) way of doing it. But now you can with this precision DC voltage reference that can be built in a few hours. Without any need for adjustment it will provide you with a 10.000V DC source accurate to within ±3mV, ie, an accuracy of ±0.03%.

08 May 2009

It's taken a while but at last, High Intensity Discharge (HID) lamps are starting to appear in places other than just in car headlights.

06 May 2009

Looking for a digital clock that's always dead accurate? This one derives its time signals from the GPS (Global Positioning Satellite) system, so it never needs setting or adjusting. It features big, bright 58mm-high digits for the hours and minutes, plus smaller digits to indicate the seconds.

04 May 2009

This story is dedicated to those fearless men and women who, every day, brave dark and stormy phone calls from the unknown, un-named, ill-informed, querulous public; to those who, with no regard for their personal safety nor deep intrusions into their mental sanity, face hurt, shame and embarrassment in their quest to answer the challenging questions they are thrown.