A photocell is a device that uses a photovoltaic or photovoltaic effect or photoconductivity to create a current or voltage when exposed to light or other electromagnetic radiation. Basically, a photocell is a type of resistor that can change the value of its resistance depending on the light intensity.


It is a resistor that changes the resistance according to the amount of light events. The photocell affects the photoconductivity of the semiconductor. The energy of the photons entering the semiconductor releases the flow of electrons, which reduces the resistance.

It’s easy to get a variety of sizes and specifications. Each photocell will perform differently than other modules, even if they are from the same family. In fact, the changes can be large, large, etc. They are used in light meters, burglar alarms, etc., also called photocell or electric eye.

Definition of Photocell

The photocell is a device that converts light energy into electrical energy, which is called a photocell. It converts light into electrical energy or electrical signals by generating voltage or uses light to regulate current as in a photovoltaic cell.

A photocell is a type of sensor that can be used to detect light. The main features of solar cells include the fact that they are very small, low power, economical, and very easy to use.

Working of Photocell

The principle of operation of a photocell may depend on electrical resistance and the effect of the photoelectric. It can be used to convert light energy into electrical energy. The electrons of the photon participate in the direction of the collector.

Here, the collector terminal is a positive terminal with reference to the emitter terminal. Therefore, the current will flow in the circuit. If the radiation intensity increases, the photovoltaic current will increase.

Phototransistors are two-device devices, including an emitter and a collector, while the base is a sensor (base). The ammeter is connected to the lead negative (-ve) terminal, and the collector terminal is connected to the positive (+ ve) battery terminal. The radiation frequency will exceed the emitter’s material’s threshold frequency, and then the photons will be emitted.

The working process of a photocell is equivalent to the principle of direct reflection photocell. The only difference is that the beam of the light source is focused at a certain distance. Reflection occurs when the subject is in the spotlight. The recipient responds and locates the object.

Photocell Uses or Applications

Photocell has thousands of applications, especially as switches and sensors. They are used instead of photocells and variable resistors.
Automatic lighting is used to activate photocells when it gets dark, and turning street lights on and off depends largely on the day, whether it is day or night.

They are used as a running timer to calculate the runner’s speed. It is used to count vehicles on the roads. It is used in robotics wherever they instruct the robot to hide from sight in the dark. Otherwise, they follow the beacon or line. They are used in lux meters to determine the intensity of light.

They are used in exposure meters to use a camera to determine the exact exposure time for a good image. It is used to reproduce sound in cinematography. They are used to regulate the temperature of the oven. It is being used to turn street lighting on and off automatically.

Photovoltaic cells are also used to generate electricity from sunlight during space travel. The photocell can be used instead of variable resistance and photocell. Some applications include display meters and light control relays.

Types of Photocells

1:  Photovoltaic Cells

2:  Photo emissive cell

3:  Charge-Coupled Devices Cell

4: Photoresistor Cell

5: Photoconductive cell

1: Photovoltaic Cell

A photovoltaic cell makes from the semiconductor. Photovoltaic cells convert sunlight into electricity using a photoelectric effect. The incident light strikes the cells and creates mobile charged particles in the semiconductor, detaching from the device’s structure to generate an electric current.

The main function of a photocell is to convert electricity from solar energy into energy. Useful current is generated when the photons expose the electrons on the cell to a high-energy state. The photons strike the electrons in the cell itself in a state of high energy, which produces a useful current.

The two semiconductor layers in a solar cell generate an electron current. Materials such as silicone are suitable for making these semiconductor layers, and each has its own advantages and disadvantages for different applications.

In addition to semiconductor materials, solar cells consist of two metal grids or electrical connections. One is located above the semiconductor material, and the other is located below it. The high grid or contact semiconductor collects electrons and transfers them to external loads. The rear contact layer is connected to complete the electrical circuit.

Most solar cells are made of silicon crystalline. Monocrystalline cells are the most efficient, but cheap polystyrene cells are also popular. Even cheap amorphous silicon cells are available widely used in small consumer products but rarely used in electrical systems.

2:  Photo emissive cell

The device detects or measures luminous energy by measuring the net emission of electrons from the photocathode’s surface, called a photoemissive cell—incidentally, the removal of solid (less than most liquid) electrons by electromagnetic radiation. Photomation is also called the external photoelectric effect.

The scientific community uses charge-coupled device cells (CDC) as a highly reliable and accurate photosensors. Charges produced by light-sensitive sensors are used to analyze various things, from galaxies to individual molecules.

Photoemissive Cell, also known as Photo Photo. These cells are known as electric eyes, which cause the door to open automatically when a person blocks the light. These cells can be used in the same way as photoconductive cells to control the system and the system.

3:  Charge-Coupled Devices Cell

Charge-Coupled Devices Cell (CCD) is a highly sensitive photon detector. The photons of light entering an area defined by one pixel will be converted into one or more electrons. The number of electrons accumulated will be directly proportional to the intensity of the scene in each pixel.

When the Charge-Coupled Devices Cell becomes inactive, the number of electrons in each pixel is measured, and the scene can be restored.

A charge-coupled device cell is an integrated circuit consisting of a pair of pairs of capacitors. Under the external circuit’s control, each capacitor can transmit its electrical charge to the adjacent capacitor. One of the main technologies used in digital imaging is the CCD sensor.

It uses the electrical charge amount to represent the same value, such as the pattern of light intensity at disc times. The function of memory is to place these charges in a row of cells simultaneously, also from time to time. Thus, a CCD is a discrete-time device, i.e., a patterned or constant signal at proportional times.

4:  Photoresistor Cell

Photoresistors, also called LDRs (light-dependent resistors). A Photoresistors or LDRs is an adjustable light resistor. As the light intensity of the event increases, so does the resistance of the photoreceptor. It can be used in photosensitive detector circuits as well as in light and dark active switching circuits.

A Photoresistor or light-dependent resistor consists of a photoconductor material. When light hits this material, it absorbs radiation, and the electrons move from the semiconductor balance zone to the transmission zone. The more electrons in the resistor’s transmission band, the lower the resistance of the resistor.

The resistance of the Photoresistors decreases with increasing light intensity. In other words, it represents photoconductivity. It is used in photosensitive detector circuits and light and dark activated switching circuits that act as resistant semiconductors.

In the dark, the photoresistor can have a resistance of several megaohms (MΩ), and in light, the photoresistor can have a resistance of only a few hundred ohms.

5:  Photoconductive cell

The photoconductive cell is a light-sensitive resistor whose resistance to light decreases with increasing light intensity. These devices consist of a thin monocrystalline line or polycrystalline line film of complex semiconductor materials.

Lightly hitting the surface of a material can provide enough energy to force the electrons inside the substance to separate from its atoms. Thus, free electrons and holes charge carriers are produced inside the material, and therefore its resistance is reduced. This is known as the photoconductivity effect.

The photocell uses photoconductivity to increase the light, reduce the electrical resistance, and allow more electric current to flow.

An electrical component whose electrical conductivity depends on the amount of light incident on it. Therefore, the voltage applied to the cell will vary depending on the light intensity.

A device that uses semiconductor substances such as cadmium sulfide or germanium is known as photodiodes and is sensitive enough to be used to measure the brightness of variable stars. The most commercially available photoconductive elements are made of cadmium sulfide (CDS), which are used to illuminate the spectrum’s visible region.

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