Posted on Apr 20, 2012

The circuit uses two gates of a 7400 IC cross-connected to form an astable multivibrator driven by the 1-pulse per second output of the digital clock IC. The hee-haw circuit has a low frequency astable modulator added to make a self-contained European-type siren. Tone and rate can be varied as desired by changing capacitor values.

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

If the tone is too harsh, a simple R-C filter will remove the harmonic content— the multivibrator output is almost a square wave. With the resistor values shown, no startup problems occur; but if the 2.2 k or 2.7 k resistors are changed too much, latch-up can be a problem.

Leave Comment

characters left:

New Circuits



Popular Circuits

Infra Red Switch remote control
70Mhz Rf Power Amplifier Circuit
Two sirens sound with ic 555
Automatic blind hooked up to existing projector screen using Arduino
bcd diagram
temp control fan hardware
new laser warning sticker
12V Low Cost Car Battery Charger Circuit PCB
Magnetic core memory reborn
MT8885 Integrated DTMF Transceiver With Power-Down And Adaptive Micro Interface
LM3915 audio power level meter circuit design electronic project
Domestic And Industrial
555 Pocket digital frequency meter schematic