How Auto ON/OFF sensor light works?

How Auto ON/OFF sensor light works?

In this post, you will learn how a simple auto ON/OFF sensor light works. Nowadays many types of auto ON/OFF sensor lights are available. In this post, we will discuss a simple auto ON/OFF sensor light.


The working of this sensor light is very simple. There is a transformerless power supply, which provides power to the LEDs. An IC of the bridge rectifier is used to convert AC to DC.


A Light Depende Resistor(LDR) is connected between the LEDs and the supply. The resistance of the LDR depends on the light. During the daytime the resistance of the LDR is very low, so current directly flows through the LDR to the ground.


So LEDs are not illuminated. During the night the resistance of the LDR is increasing and becomes very high so the current cannot flow through the LDR, it flows through the LEDs. So LEDs are illuminated.

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