Sound Triger

Building your own sound trigger If you would like to build your own piezoelectric sound trigger from scratch, a list of parts and a circuit diagram are given below. The microphone is a piezoelectric buzzer element such as #273-073 available from Radio Shack. (Use the red and black wires only on this part.) The SCR must be sensitive to very small gate currents and must be able to provide up to 400-V isolation.

List of parts Piezoelectric buzzer element NPN general purpose transistor, such as 2N2222 5-kW variable resistor 5-kW resistor 68-kW resistor 400-V sensitive gate SCR 9-V battery and clip