Handclap Switch
Approx construction cost US$37
This circuit has been designed to give you an easy life. No need to bend down to turn on awkwardly positioned switches, just clap your hands and the controlled appliance will be turned on for you.
The sound made by a handclap is picked up by an electret microphone, amplified by an op.amp, half-wave rectified and then cleaned up by a Schmitt trigger. There is then a switched choice of either using the Timer circuit, which turns on a relay for a predetermined time set by a potentiometer, or using the Latching circuit, which turns on the relay until another handclap is received to turn it off.
More details on this construction project can be found in the November 2000 issue of EPE Online, the world's first web-delivered electronics and computing hobbyist magazine.
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