A light dependent resistor or LDR, composed of a disk of semiconductor material with two electrodes on its surface. In its function, the LDR is a type of resistor whose value is affected by light.

In an environment of dark or under dim light, the disc material contain free electrons in a relatively very small amount. There are few free electrons to flow of electric charge. This means that, the material is a poor conductor for electrical current. In other words, the value of very high resistance materials.

In an environment with enough light, more electrons can escape from the atoms of this semiconductor material. There are more free electrons that can drain the electric charge. Under these circumstances, the material is of a good conductor. Low electrical resistance material. The more bright light on the material, the more electrons are available, and the lower the electrical resistance of this material.

Below is a symbol of LDR

symbol of LDR
  • LDR is a type of resistor whose value is affected by light
  • In the dark, the LDR resistance is very high
  • In the light of circumstances, the LDR resistance is very low


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