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What are Proximity Switches?

Proximity switches open or close an electrical circuit when they make contact with or come within a certain distance of an object. They are most commonly used in manufacturing equipment, robotics, and security systems. There are four basic types: infrared, acoustic, capacitive, and inductive. Infrared proximity switches work by sending out beams of invisible infrared light. A photodetector on the switch detects any reflections of this light, which allow the device to determine whether there is an object nearby. As a switch with just a light source and photodiode is susceptible to false readings due to background light, more complex models modulate the transmitted light at a specific frequency and have receivers which only respond to that frequency. Even more complex sensors are able to use the light reflected from an object to compute its distance from the sensor.