What are Light Sensors, Light Sensors working, Light Sensors uses, Light Sensors applications, ldr, photodiode, Light Sensors
Hello friends, I hope you all are doing great. In today’s tutorial, we will have a look at What are Light Sensors and how to use them. Light sensors are such components that sense the surrounding light and transform it into the current. Such sensors are normally used in different applications such as switching circuits and for security purpose. When they used in different security circuits these sensors detect the variation in the light then they send the signal to the alarm. There are numerous types of light detectors components but there operating principle is similar. The most commonly used types of light sensors are a light-emitting diode, photodiodes, infrared radiation (IR) detectors, etc. In today's post, we will have a look at working, features, circuits, application and some other related terms so let's get started with what are light sensors.

What are Light Sensors

  • Such sensors that transform the light or infrared radiation into the electrical current are known as the light sensors.
  • These sensors are also named as the photoelectrical detector, due to the conversion of the photons of the into the electrical energy.
  • There are 2 main categories of the photosensors first one is that generates the electrical current when light collides with them are known as the photovoltaic sensors.
  •  The second one is that varies its electrical parameters like resistance are defined as the photoconductors.
  • Such photo sensors that produce a voltage directly proportional to the amount of the light collided with them are known as photocells.
  • There are such photosensors used in different circuitries to regulate the value of the current are known as photo junction modules. Such modules are used in different security circuits and electronic projects.
    What are Light Sensors

Photoconductive Cell

  • This light detector module does not transform light into the electric current but the variation in its physical parameters occurs.
  • The photoresistor is the example of these sensors when the light collided with this sensor varies the value of the resistance is also varied not light converted it to the current.
  • Using this photosensor the value of the current is controlled in different circuits and engineering project, the normally used photoconductor is the light-dependent resistor (LDR).
Now we discuss it with detailed.

Light Dependent Resistance

  • Light-dependent resistors are also known as the photoresistors, these light sensors are used in the different engineering projects to control the light strength for different components.
  • It is constructed from the Cds (cadmium) this substance is very sensitive to light and according to the intensity of the light, it varies the value resistance.
  • The working principle of the LDR is based on the photoconductivity, according to this the by an increase of the light the value of the conductive behaviour of materials increases.
  • Light-dependent resistors modules are also called dependent device as its resistance varies according to light in the shadowy resistance is higher while in light resistance is less.
  • In such region where light is not present LDR's resistance is known as dark resistance its value is up to the 1012 ohm.
    What are Light Sensors, Light Sensors working, Light Sensors uses, Light Sensors applications, ldr, photodiode, Light Sensors

What is the Light Dependent Resistor Cell

  • The normally used type of the LDR cell is OPR12 it is manufactured by the cadmium sulphide. This sensor operates for such radiation that has six hundred nanometers wavelength of radiations.
  • This sensor has large value of the resistance in shadow almost ten megaohms but in case of the light, its value is almost a hundred ohms.
  • This cell is less expensive it mostly used in such devices that used at night in streets for illumination. In different cameras and photographic devices, it also used.
  • If we connect this senor with the normal resistance and provide voltage to it than the circuit formed by this arrangments has benefits, that for different wavelengths of the light it produces different voltages. This circuit arrangement is shown in a given figure.
  • The voltage drops across the series resistance R2 can find the voltage divider rule.
    What are Light Sensors, Light Sensors working, Light Sensors uses, Light Sensors applications, ldr, photodiode, Light Sensors


  • The structure of the photodiode is alike to the normal diode, the only difference is that it has a coating of such material that absorbs the light.
  • This coating absorbed mostly such lights that have less frequency than larger frequency.
  • Light-emitting diodes are also recognized as the photo-diode because it can easily send and received light.
  • When the light collides with the surface of the photodiode, hole and electrons pair are created in the module.
  • Due to the formation of the hole and electrons current starts to flow in the diode.
  • These pairs are created when the light collided with the diode has energy almost 1.1 electron volts.
  • When the light energy collides the atoms than the electrons of the atom after gaining this energy left the atom and holes-electrons pairs are created.
  • The charge on the electrons is negative and holes behave like positive charges.
  • Due to the depletion regions, electrons and hole can not move from one part to other of the diode so electrons move towards the positive terminal of the diode and hole to the negative terminal.
    What are Light Sensors, Light Sensors working, Light Sensors uses, Light Sensors applications, ldr, photodiode, Light Sensors

Applications of Light sensors

  • These are the main applications of the light sensors that are described with the detailed.
Brightness Control
  • In our mobile phone and laptops, we increasing and decreasing the resolution of the screen light is varied by light sensors.
  • Ambient sensors are mostly used in electronic devices like mobiles, laptops and computers.
  • These sensors are also used in different street light for the automatic control of light.
Security System
  • In different security circuits, light sensors are used. In shipping, these sensors provide protection for the different products that are moving from one place to another.
  • Light sensors are installed in the cabin where the products are saved when someone tries to open the door light sensor sense slight and sends a signal to the alarm connected with it.
  • The light of the sun plying the significant rule in agriculture for the production of the different crops.
  • Different food seed requires a different quantity of light, so it is important to know which part of the land is under the sunlight.
  •  These sensors are used for the sprinkling of water when the sunlight is not available because most of the water will be converted into the moisture.


It is the detailed article on the light sensors if you have any question ask in comments. Thanks for reading. Take care until the next tutorial.