Photoresistor Explained

Resistors are often used in our daily lives and work, but I don’t know if you know about "Photoresistor"? This article has collected and sorted out some information, and I hope this article can be of greater reference value for readers.

Main parameters of photoresistor

Text symbol: "RL", "RG" or "R".

Structure-usually composed of photosensitive layer, glass substrate (or tree moisture-proof film) and electrodes.

Characteristics-Photoresistor is a special resistor made of semiconductor photoconductivity effect. It is very sensitive to light, and its resistance value can change with the intensity of external light (brightness and darkness). It is in a high-resistance state when there is no light irradiation; when there is light irradiation, its resistance value decreases rapidly.

Function and application-widely used in various automatic control circuits (such as automatic lighting control circuits, automatic alarm circuits, etc.), household appliances (such as automatic brightness adjustment in TV sets, automatic exposure control of cameras, etc.) and various measurements In the instrument.

The main parameters of photoresistor

1) Bright resistance (kΩ): ​​refers to the resistance value of the photoresistor when it is irradiated by light.

2) Dark resistance (MΩ): refers to the resistance value of the photoresistor when there is no light (dark environment).

3) Maximum operating voltage (V): refers to the highest voltage that the photoresistor can withstand under rated power

4) Bright current: refers to the current that the photoresistor passes when it is irradiated by light under the specified applied voltage.

5) Dark current (mA): refers to the current that the photoresistor passes under the specified applied voltage when there is no light.

6) Time constant (s): refers to the time required for the photoresistor to start from the light jump to 63% of the stable bright current.

7) Resistance temperature coefficient: refers to the relative change of the resistance value of the photoresistor when the ambient temperature changes by 1℃.

8) Sensitivity: refers to the relative change of the resistance value of the photoresistor under light irradiation and no light irradiation.

Photoresistor types

1) Classified by production materials

Polycrystalline and single crystal photoresistors can also be divided into cadmium sulfide (CdS), cadmium selenide (CdSe), lead sulfide (PbS), lead selenide (PbSe), indium antimonide (InSb) photoresistors, etc.

2) Classified by spectral characteristics

Ultraviolet photoresistors: sensitive to ultraviolet light, including cadmium sulfide, cadmium selenide photoresistors, etc., used to detect ultraviolet light.

Infrared photoresistors: mainly lead sulfide, lead telluride, lead selenide. Photoresistors such as indium antimonide are widely used in national defense, scientific research, industrial and agricultural production such as missile guidance, astronomical detection, non-contact measurement, human disease detection, infrared spectroscopy, and infrared communications.

Visible light photoresistors: including selenium, cadmium sulfide, cadmium selenide, cadmium telluride, gallium arsenide, silicon, germanium, zinc sulfide photoresistors, etc. It is mainly used for various photoelectric control systems, such as photoelectric automatic switch portal, automatic on and off of navigation lights, street lights and other lighting systems, automatic water supply and automatic water stop devices, automatic protection devices and "position detectors" on machinery, extremely Thin parts thickness detector, camera automatic exposure device, photoelectric counter, smoke alarm, photoelectric tracking system, etc.

Photoresistor manufacturing materials

The materials used to make photoresistors are mainly metal sulfides, selenides and tellurides and other semiconductors. Usually, coating, spraying, sintering and other methods are used to make a very thin photoresistor body and comb-shaped ohmic electrode on an insulating substrate, and then lead wires are connected and encapsulated in a sealed housing with a transparent mirror to prevent the sensitivity from being affected by moisture.

Brief introduction of photoresistor:

Photoresistor is a kind of resistor made by the photoelectric effect of semiconductor, whose resistance value changes with the intensity of incident light.

Mainly used for light measurement, light control, and photoelectric conversion.

Photoresistors are all made into a thin sheet structure to be able to absorb more light energy. The characteristic of this type of resistor is that the stronger the incident light, the smaller the resistance value, and the weaker the incident light, the greater the resistance value. For example, a photoresistor is used in the sound control lamp as a device to control the light during the day.

If you want to know more about Photoresistor, check this article.

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