"Hee-Haw" Electronic Siren


Posted on Sep 7, 2012

The oscillator based on IC2 is responsible for producing the sound. Its output is connected to the base of TRl,


Click here to download the full size of the above Circuit.

which amplifies it to drive the speaker. Resistor R4 is included in the circuit to limit the current through TRl to a safe and reasonable level. The oscillation frequency of IC2 is partially dependent on the values of R3 and C2. Another factor that governs the frequency of oscillation is the magnitude of voltage fed to pin 5 of IC2. If a voltage of varying magnitude is fed to pin 5, the internal circuitry of the IC is forced to reset at a different rate, which changes the frequency. IC1 is also connected as an oscillator,but it runs much slower than IC2: around 1 Hz. Each time the IC triggers, the voltage at pin 3 goes high. As pin 3 is connected to pin 5 of IC2, this forces IC2 to change its note. That produces the "hee-haw" sound of the siren.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Low-voltage-indicator
motion detector sensor circuit
probl
Crystal audio oscillator circuit
vhfuhf tv modulator
Spring Reverb
Basic circuit diagram connection ISO120 121 signals and power supply
2 -Y- connection automatic three-speed motor acceleration control circuit



Top