Light - Dependent Resistor

Nowadays, Everyone has smartphone.

When we operate the smartphone, we see it have some brightness level.

We adjust the brightness according to our requirement.

But when we do auto-brightness mode.

Its brightness level varies according to the amount of light falling on its screen.

When we go to dark place brightness gets increase and in the lighted place, its brightness gets decrease.

Brightness is controlled according to the amount of light falling on this device.

It happens because of the light-dependent resistor is connected with the circuit inside the mobile.

In the next section, we will explain the structure and working of the light-dependent resistor.

Let's explain the structure and working of the light-dependent resistor.

Light-Dependent resistors (LDR), are light-sensitive devices.

Most often used to indicate the presence or absence of light, or to measure the light intensity.

A light-dependent resistor is also known as a photoresistor.

And it is a type of resistor whose resistance varies depending on the amount of light falling on its surface.

An LDR is made of a high resistance semiconductor.

And the representation of the light-dependent resistor as shown above.

Let's see the structure of the light-dependent resistor.

The structure of a light-dependent resistor consists of a light-sensitive material

Which is deposited on an insulating substrate such as ceramic.

The material is deposited in zigzag pattern in order to obtain the desired resistance and power rating.

But this zigzag area separates the metal deposited areas into two regions.

Materials normally used are cadmium sulphide, cadmium selenide, indium antimonide and cadmium sulphonide.

In the next section, we will discuss the working of the light-dependent resistor.

Let's discuss the working of the light-dependent resistor.

This resistor works on the principle of photo conductivity.

When the light falls on its surface, then the material of conductivity reduces

And also the electrons in the valence band of the device are excited to the conduction band.

These photons in the incident light must have energy greater than the band gap of the semiconductor material.

And this makes the electrons to jump from the valence band to conduction.

These devices depend on the light when light falls on the LDR then the resistance changes.

When an LDR is kept in the dark place, its resistance increases

And when kept in the light place its resistance will decrease.

We have discussed the structure and working of the light-dependent resistor in detail.

Revision

Light-Dependent resistors (LDR), are light-sensitive devices.

Most often used to indicate the presence or absence of light, or to measure the light intensity.

The End