Automatic Street Light

The objective here is to build a light that switched on by itself when the surroundings gets dark and back off when its bright. That is at night the light becomes light at night and switches off at day time.This can be used for powering outdoor lights if you often forget to turn it off regularly or want the light to be lit when you arrive so you can have a good walk from your vehicle to main door, this can even be installed on streetlights.You can even have a switch beyond this to switch it completely off when needed.

The gadget provides you a lot of savings as it can cut your power bill by a considerable amount as it would turn the light off even if you didn’t do so.
In standby this circuit consume less power that an LED on your power supply board would.

This fit for ready outdoor installation like Automatic Street Light or Outdoor Light, but if you need to place the light inside, you can do so by keeping the LDR to open or just make the whole circuit in a whether proof container and place the bulb inside. Just make sure no water reaches the circuit.

Automatic Street Light

For details about the voltage of operation check description.


C1,C2 0.1uf ,400V
Switch AC switch that fits to your power supply
Bulb Ordinary Bulb that fits to your power supply


This circuits work on a simple logic i.e. when there is light the LDR conducts and the GATE of the TRIAC is kept with a potential, this make the potential at MT2 terminal to fall down, in absence of light the GATE terminal is at zero as the LDR does not conduct this makes the potential at MT2 to rise up, thus the bulb lights.

You can operate this circuit safely at 220V AC , when the AC supply is change remember to check the power rating of bulb.

Operating this circuit above 240V AC is not Recommended.