Low Power Sounder

Low-Power Piezoelectric Alarm Circuit

A simple and efficient sounder circuit utilizing an inductor to amplify the voltage across a piezoelectric audible warning device. The design employs a Colpitts oscillator with an adjustable inductor, specifically tuned to resonate with the sounder's inherent frequency.

By incorporating the sounder within the tuned circuit, the root-mean-square (RMS) voltage across it becomes amplified by the loaded Q-factor of the tuned section. Additionally, the resonant frequency is pulled towards that of the sounder, further enhancing its efficiency.

These combined effects produce a piercing 5 kHz whistle, ideal for applications such as burglar alarms. This circuit achieves this functionality at low power consumption, operating with supply voltages as low as 4 volts and a current draw of only 2.5 milliamps.