Dark-activated 230V Lamp

Posted on Oct 15, 2012

This device allows one or more lamps to illuminate at sunset and turn off at dawn. Q1 and Q2 form a trigger device for the SCR, providing short pulses at 100Hz frequency. Pulse duration is set by R2 and C1.

Dark-activated 230V Lamp
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When the light hits R1, the photo resistor assumes a very low resistance value, almost shorting C1 and preventing circuit operation. When R1 is in the dark, its resistance value becomes very high thus enabling circuit operation.

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