This is a project of an automatic night lamp using a triac. The circuit is simple and low cost and can be used to automatically switch on any 60 to 100 watt AC lamp or bulb after the sunset. As you see in the schematic that the circuit is not using any transformer and it is
directly connected with the AC mains supply through a capacitor power supply.
The circuit is divided in two parts, first is a capacitor power supply and second part is an automatic night lamp circuit. The power supply circuit is using a 330nF capacitor, which drops the mains voltage, which is rectified by the four 1N4007 diodes and filtered by a 330uF capacitor. The 6.2V zener diode steps down this voltage to operate the second part of the circuit.
The second part of the project is a dark sensor circuit. The circuit is using an LDR as a dark sensor, when the circuit will be in dark then resistance of the LDR increases due to which the transistor will conduct and turn on the BT136 triac. When the triac will turn on the AC current start passing through it and the bulb will become activated.
Note: Many points of this circuit 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.