High-Output Pulsed-Tone/Light-Activated Alarm Circuit


Posted on May 15, 2012

This circuit can produce up to 1 W of audio power to drive a speaker or horn. When the CDS cell is struck by light, its resistance decreases thus activating NOR gate (a) thereby causing (a) and (b) to produce a low-frequency (10-Hz) square wave. This pulses the 1-kHz oscillator (c) and (d), causing it to generate a pulsed 1-kHz tone at a 10-Hz rate.


High-Output Pulsed-Tone/Light-Activated Alarm Circuit
Click here to download the full size of the above Circuit.

Ql and Q2 amplify this signal. Q2 (2N3055) drives the speaker.




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