Tuesday, September 16, 2014
Overheat Detector Alarm Switch
Circuit diagram:
Overheat Detector Alarm/Switch Circuit Diagram
When the measured temperature exceeds the user-defined level, the comparator pulls its output High to approx. 2.2 V causing transistor T1 to be forward biased instantly. T2 is also switched on, supplying the oscillator circuit around IC3 with sufficient voltage to start working. The 555 set up in astable mode directly drives active piezoelectric buzzer Bz1 to raise a loud alert. Components R7, R8 and C4 determine the on/off rhythm of the sounder. A transistor based relay driver may be driven off the emitter of T1 (TP1). Similarly, replacing the piezo sounder with a suitable relay allows switching of high-power flashers, sirens or horns working on the AC mains supply.
Author: T. K. Hareendran - Copyright: Elektor Electronics 2007
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment