This circuit is a lamp that turns on automatically when darkness falls and turns off when the sun rises. In fact, you can apply this circuit for any type of automatic night light. This circuit can be used to control lights or other electric high power with hundreds of watts
The circuit used an LDR to detect light. When the light is the resistance of LDR is low. So the voltage drop across R2 POT will be high. This keeps the transistor Q1 ON. The collector of Q1 (BC107) is coupled to the base of Q2 (SL100). So Q2 will turn off and so do over. The lamp will remain off.
When night falls, the resistance of LDR increases to cause the voltage across R2 POT fall below 0.6 V. This causes the transistor Q1 OFF turs that in turn activates the relay Q2.The and the bulb will light
* POT R2 can be used to adjust the sensitivity of the circuit.
* You can use bulb of any wattage ,provided that relay should have the sufficient rating.
* The circuit can be powered from a regulated 9V DC power supply.
* Click Here! to get the power supply circuit for this project.
* The relay K1 can be a 9V SPDT relay.
