How to Build a Simple Photoresistor Circuit

Now we will build a very simple photoresistor circuit to make a photoresistor do what it does: make the circuit work when there is light and stop working when there is darkness. For this circuit, we connect a photoresistor to an LED. When the photoresistor is exposed to light, the LED is on and stays lit. When the photoresistor is exposed to darkness, the LED turns off and does not light. This project demonstrates the function of a photoresistor.

Parts

9-Volt Battery
Photoresistor
A LED

This is the schematic of the circuit to be built:

This is a more real life like representation of the circuit.

Photoresistor with Light

This is the photoresistor circuit when the photoresistor is exposed to light. When exposed to light, the photoresistor has very little resistance, so current can flow through the circuit. The LED receives current and lights up; it stays lit as long as the photoresistor is exposed to light.

Photoresistor in Darkness

Now put a thick cloth or pen lid or any object that doesn't absorb light over the photoresistor.

Or, if you can, just turn off the room lights if it can lead to total darkness:

This is the photoresistor circuit when the photoresistor is exposed to darkness. When exposed to darkness, the photoresistor has very high resistance, so current cannot flow through the circuit. The LED receives no current and, thus, does not light up. The LED stays off as long as the photoresistor is exposed to darkness.

Related Resources

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