Overview of photoelectric switches


The photoelectric switch is a member of the sensor fami […]

The photoelectric switch is a member of the sensor family. It converts the change in the intensity of light between the transmitting end and the receiving end into a change in current to achieve detection purposes. Since the output circuit and input circuit of the photoelectric switch are electrically isolated (ie, electrical insulation), it can be used in many occasions.
A new generation of photoelectric switch devices manufactured by using integrated circuit technology and SMT surface mounting technology has intelligent functions such as delay, widening, external synchronization, anti-interference, high reliability, stable working area and self-diagnosis. This novel photoelectric switch is an active photoelectric detection system electronic switch that uses pulse modulation. The cold light source used in it includes infrared light, red light, green light and blue light, etc., which can be non-contact and rapid without damage And control the state and action of various solid, liquid, transparent, black, soft, smoke and other substances. The contact type travel switch has the disadvantages of low response speed, poor accuracy, easy damage to the detected object and short life in contact detection, while the transistor proximity switch has a short operating distance and cannot directly detect non-metal materials. However, the new photoelectric switches overcome their above-mentioned shortcomings, and are small in size, multi-functional, long-life, high-precision, fast response, long detection distance, and strong resistance to optical, electrical, and magnetic interference.

This new type of photoelectric switch has been used for level detection, level control, product counting, width discrimination, speed detection, fixed-length cutting, hole recognition, signal delay, automatic door sensing, color mark detection, punching and Shearing machine and safety protection and many other fields. In addition, the concealment of infrared rays can also be used as an anti-theft warning in banks, warehouses, shops, offices and other occasions when needed.

The step-down overhaul method can be used when repairing the switching power supply. The method is: connect the power plug of the display to an AC voltage regulator, and then adjust the output voltage of the voltage regulator to about 100V, then power on for maintenance, and gradually increase the power supply voltage for maintenance.
Failure example 1: The fuse is burned out when the machine is turned on, and the output voltage is zero. This situation is generally caused by the breakdown of the switch tube and the short circuit between the emitter and the collector. At this time, the switch tube can be removed first, and the resistance of its emitter and collector to ground can be measured. If it is zero or very small, just replace it. But also check whether there are any problems with other components before booting.
Fault example 2: The grating appears "S"-shaped distortion. This kind of problem should focus on checking the filter circuit and the voltage stabilizing circuit. Generally, it is because a diode is open, and the full-wave rectification becomes half-wave rectification. This may also be caused by the reduction in the capacity of the filter capacitor.
Fault example 3: AC 220V rectifier filter circuit has a short-circuit fault, and the fuse is burned when the machine is turned on. First check whether the rectifier diode is short-circuited and the filter capacitor is leaking seriously. You can also unplug the degaussing coil to check whether the degaussing thermistor has a short-circuit fault, and replace it if necessary.
Failure example 4: No grating, no display, power indicator is off, but the insurance is not burned. At this time, check whether the AC mutual inductance transformer is open, whether the current-limiting resistance of the rectifier circuit is open (burned), or whether the rectifier diode is open.
Fault example 5: No grating, no display, and abnormal noises in the machine. If a "squeak" sound is made, it indicates that the oscillation frequency is low, and the components related to the oscillation should be checked. If a "click" sound is made, it indicates that the power supply overcurrent protection should be checked.