A Photo Eye is one of the most fundamental field devices within a manufacturing environment. Such sensors typically send an ON or OFF signal back to an input of a PLC and are used in various applications in manufacturing automation. Such applications include the presence of product, the presence of a safety feature, a system level and more.
This is a companion discussion topic for the original entry at https://www.solisplc.com/tutorials/photo-eye-photoelectric-sensor-wiring