A single-channel photoelectric switch cannot directly determine the direction of motor rotation, as it can only detect the presence or absence of an obstruction—a single state change. Detecting direction relies on acquiring two pulse signals with a phase difference.
In applications requiring detection of motor rotation direction, speed, and relative position, photoelectric or magnetic encoders are generally chosen. This is a standard, professional, and straightforward solution.
However, in situations where only the direction needs to be determined and high precision for position information is not required, using an encoder may unnecessarily increase product costs. An alternative is to use a single-channel photoelectric switch with a custom code wheel featuring asymmetric patterns (e.g., alternating wide and narrow slots). By analyzing the duty cycle or the duration of high/low levels of a single pulse via a microcontroller, the direction can be inferred. However, this method offers lower accuracy and reliability and is more susceptible to speed variations.
Now, to introduce a dual-output photoelectric switch: the Kodenshi SITAB74 assembly consists of an infrared emitting diode paired with two NPN silicon phototransistors, all housed in a black thermoplastic case. The detectors are triggered whenever an opaque object passes through the slot between the emitter and detectors. Its dual-channel design enables simultaneous detection of both the speed and direction of the interrupter's movement.
For detailed product specifications, please refer to the attached document.