A very simple and useful circuit of a emergency lamp. The circuit is using 12 volt battery. The circuit will turn on 1 watt LED when there is no light on the surface of the LDR. This is a versatile circuit and can be used for many purposes. You can use it in your room if you are facing power failure problems.
You can setup up this circuit near your room lamp so when the LDR surface detect no light it will turns on the 1 watt LED. This circuit is so small can be easily fitted in a small box.