Photoelectric Sensors

Photoelectric sensors, also known as photoelectric switches, photoelectric proximity switches, are sensors used to detect the movement and position of objects without contact. Photoelectric sensors are mainly used in automatic production lines, transportation, paper cutting machines and other fields. The photoelectric sensor consists of three parts: transmitter, receiver and detection circuit. The emitter emits an infrared light source through a light-emitting diode or laser diode. The receiver transmits the changes in the received infrared light source to the detection circuit in the form of an electrical signal. The detection circuit filters out the valid signal and outputs the control signal to the control device.

According to the structure, photoelectric sensors can be divided into the amplifier separate type, the amplifier built-in type and the power supply built-in type. The amplifier separate type photoelectric sensor without built-in amplifier, has the advantages of small size and high applicability. The amplifier built-in type photoelectric sensor has built-in amplifier, which has the advantages of strong anti-interference ability and can detect high-speed moving objects. The power supply built-in type photoelectric sensor has built-in amplifier and power supply device, which has strong anti-interference ability and can be directly used in strong current control circuit.

According to the detection method, photoelectric sensors can be divided into the diffuse-reflection type, the retro-reflection type, the through-beam type (or thru-beam type) and the slot type. The diffuse-reflection type photoelectric sensors integrate a transmitter and receiver, and the light emitted by the emitter enters the receiver after being reflected by the object. The retro-reflection type photoelectric sensors integrate a transmitter and a receiver, and the light emitted by the transmitter is reflected by the the reflector and enters the receiver. The transmitter and receiver of the thru-beam type photoelectric sensor are placed on either side of the detected object, and when the detected object blocks the light, a switching signal is generated. The slot type photoelectric sensor is a U-shaped structure, and its transmitter and receiver are located on either side of the U-shaped slot, and when the detected object blocks the light, a switching signal is generated.

According to the output form, photoelectric sensors can be divided into NPN type (two-wire), NPN type (three-wire), NPN type (four-wire), PNP type (two-wire), PNP type (three-wire), PNP type (four-wire), AC type (two-wire) and AC type (five-wire).

According to the output state, photoelectric sensors can be divided into normally open (NO) and normally closed (NC).

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