Automatic Night Light Circuit

The working of this circuit is very simple, during the day time the resistance of the LDR is high, and it block signals to go to the base of the BC547 transistor. When it is night, the resistance of the LDR rapidly decreases and it cause control signal to flow through the base of the transistor.

Then output energizes the coil of the 5V SPDT Relay, which makes the external circuit, connected across the COM & NC terminal of the relay.