Electronic-siren


Posted on May 3, 2012

The wailing sound of a siren is generated by a VFO consisting of Q1 and Q2. Capacitor C2 provides the feedback for the oscillator. The frequency of the oscillator is varied by the voltage applied to the base of Q1 through R3. When switch S1 is closed, capacitor Cl charges, thus increasing the oscillator frequency. When S1 is released, capacitor {;1 discharges, and the oscillator frequency decreases.


Electronic-siren
Click here to download the full size of the above Circuit.

Capacitor C3limits the maximum oscillator frequency. The average battery current drain is about 15 mA.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Audio Analogue Level Meter
Mains variable Delay circuit
current controlled oscillator
Isolated Full-duplex Rs232 Interface
Making a Remote Controlled Car using Sun SPOT
CD4013 circuit
TDA1602A Application Circuit



Top