Using optical elements to change the light beam in the middle of the medium; Reflect an object with a light beam; So that the light beam can return immediately after a long distance. The photoelectric switch consists of a transmitter, a receiver and a detection circuit. The transmitter aims at the target to emit light beams, which generally come from light emitting diodes (LEDs) and laser diodes. Continuously emit light beams or change the pulse width. The radiation intensity of the pulse modulated beam is selected many times in transmission, and it will not be indirectly directed at the target. The receiver consists of a photodiode or a phototransistor. In front of the receiver, optical elements such as lens and aperture are installed. Behind it is a detection circuit, which can filter out effective signals and apply them. Optocoupler is an electrical-optical-electrical conversion device that transmits electrical signals through light. It consists of a light source and a light receiver. The light source and the light receiver are assembled in the same closed housing and separated from each other by a transparent insulator. The pin of the light source is the input end and the pin of the light receiver is the output end. The common light source is light emitting diode, and the light receiver is photosensitive diode, phototransistor and so on. There are many types of photoelectric couplers, including photodiode type, phototransistor type, photoresistor type, photo-controlled thyristor type, photoelectric Darlington type, integrated circuit type and so on. Working principle: An electrical signal is applied to the input end of the photoelectric coupler to make the light source emit light, and the intensity of the light depends on the excitation current. After this light irradiates the encapsulated photoreceptor, it generates photocurrent due to photoelectric effect, which is led out from the output end of the photoreceptor, thus realizing the conversion of electricity, light and electricity.
After the modulation pulse generated by the oscillation circuit passes through the reflection circuit, the light pulse is emitted by the light emitting tube GL. When the measured object enters the action range of the optical receiver, the reflected light pulse enters the phototransistor DU. Photoelectric lighting is fast, easy to optimize, and can be automatically selected and recorded. The optical pulse is demodulated into an electrical pulse signal in the receiving circuit, amplified by an amplifier, gated and shaped synchronously, then the interference is eliminated by digital integration or RC integration, and finally the driver is triggered to output the photoelectric switch control signal with delay (or without delay). Generally, photoelectric switches have good return error characteristics, so even if the detected object shakes in a small range, it will not affect the output state of the driver, thus keeping it in a stable working area. At the same time, the self-diagnosis system can also display the light receiving state and stable working area, so as to monitor the working situation of photoelectric switch at any time.