ABSTRACT
Photoelectric Sensors. These transducers are among the most widely used sensors in industry [9]. They are used to detect the presence, absence and/or character of objects through the interruption or completion of a light beam. These solid-state devices are very reliable, with no moving parts or mechanical contacts. The photoelectric device that is most commonly recognized by most people is the original "electric eye. " This type of unit has a separate transmitter and receiver and permits relatively long sensing distances. Other types of systems house the transmitter, receiver and power supply in a single package as small as 3 in. long and 3/4 in. in diameter and depend on a reflector to return to the emitted light beam back to the receiver. Also, fiber-optic photoelectric sensors may be used for the detection of parts as small as 0.040 in. In addition, most modem photoelectric sensors utilize an infrared light emitting diode (which reduces the problem of ambient light interference) that is pulsed on and off rapidly. The pulse modulation provides a high peak output from the LED without a damaging heat buildup.
