Pyroelectric Fire Sensor

This Pyroelecrtic Fire Alarm is one of my popular circuit published in Electronics For You Magazine December 2009 issue.The circuit exploits the direct piezo electric property of an ordinary buzzer element to sense fire. This is an unusual application of the Piezo element. This device is used in buzzer to produce sound and in transducers to generate electric signals.When the piezo crystals in the element are electrically stressed, it generates sound but if it is mechanically stressed, it generates electricity. In the circuit, it is stressed by heat and thus is act as a very good fire sensor.Full circuit in PDF.