Here is a project of a simple automatic night lamp circuit or dark activated 230V lamp circuit, which will automatically activate an AC lamp / bulb when sun set or if the circuit will receive no light. The circuit is very easy to build using no more than five components.
The LDR is working as a light/dark sensor and SCR is working as a switch. When light falls on the LDR its resistance will decrease and the SCR will remain in the off condition but when the LDR will receive no light its resistance increases which will switch on the SCR and 230V AC voltage will start passing through the SCR which will power on the 230V lamp. The sensitivity of the circuit can be adjusted with 4.7M variable resistor.
Note:Many of its points are at AC mains voltage. It could give you lethal shock if you are not careful. If you don't know much about working with AC line voltages do not attempt to construct this circuit.