The photoelectric switch is generally composed of three parts: transmitter, receiver and detection circuit. The transmitter aims at the target and emits a beam of light. The emitted light beam is usually composed of semiconductor light sources, light emitting diodes (LED), laser diodes and infrared light emitting diodes. Continuously emit the beam or change the pulse width.

　　The receiver is composed of photodiodes, phototransistors and phototubes. In front of the receiver, optical components such as lens and aperture are installed. Behind is the detection circuit, which can filter out the effective signal and apply the signal. There are also emitting boards and optical fibers in the structural elements of the photoelectric switch.

At the same time, photoelectric switches have been used in liquid level detection, liquid level control, product counting, width recognition, speed detection, fixed-length cutting, hole recognition, signal delay, automatic door sensing, color mark detection, punching machine, safety protection and many other fields . Moreover, the use of infrared concealment can also be used as an anti-theft warning in banks, warehouses, shops, offices and other occasions where it is needed.

　　The commonly used infrared photoelectric switch is based on the reflection principle of the object to the near-infrared beam. The synchronization circuit senses the intensity of the reflected light and detects the presence or absence of an object to realize its function. The photoelectric sensor first emits an infrared beam to reach or pass through an object or reflect the infrared beam on a specular surface. The photoelectric sensor receives the reflected light beam and judges the existence of the object based on the intensity of the light beam. Infrared photoelectric switches mainly use several types such as retro-reflective photoelectric switches, diffuse reflection type, slit type, through-beam type, and optical fiber type. Including automatic selection of photoelectric switches.

　　Different photoelectric switches are used in different occasions. For example, optical fiber type photoelectric switches are often used in electromagnetic vibrating feeders, and diffuse reflection type photoelectric switches are often used in the supply of packaging film for intermittent packaging machines. Slot-type photoelectric switches are often used in continuous high-speed packaging machines.