THIS IS A MAINS-POWERED DEVICE AND THE CIRCUITRY IS LIVE (240V AC) WHILE EVER POWER IS CONNECTED, EVEN IF THERE IS NO OUTPUT VOLTAGE. DO NOT ATTEMPT TO BUILD THIS PROJECT IF YOU ARE NOT ENTIRELY FAMILIAR WITH MAINS WIRING PRACTICES AND CONSTRUCTION TECHNIQUES.

Initially, this project was designed to turn a swimming pool filter pump on and off at appropriate times. Sure, you can buy a pretty cheap mechanical or electronic timer to do that but with an old 486 lying idle and the possibility – no, make that probability – of controlling a lot more than a pool pump, I thought, why not?

As it turned out, the hardware to do the job is relatively simple and cheap – there are only about twenty components required to give a pretty nifty circuit. The software, though, is a little more complicated – but as I have already done that part for you, all you need to do is build the control box, dust off that old computer, fire it up and load the software.

It uses the parallel (printer) port of just about any PC from, say, 386 vintage onwards. It operates under good, old fashioned DOS (remember that?) – in fact, I wouldn’t recommend it being run under Windoze.

Features Low cost, easy to build Fuse and surge protection Full optical isolation System enable function Efficient relay switching Precision timing Control up to four events Save and open timer settings