Direction detector for bar coding plate - has photodiodes with output pulses processed without differentiation to avoid ambiguity from noise

摘要

The direction detector detects the pulses produced from photodiodes as an illuminated bar coding plate passes by and computes the direction of motion. Two samples are taken: the firt (A) is passed to a first trigger (7) and the second (B) to third and fourth triggers (9, 10). The outputs of the triggers are processed by logic circuitry to give difference signals and are used to provide a signal for the counter (15) that tells it in which direction to count. The advantage of this detection circuit lies in determining direction of motion without differentiating the output pulses and the circuit is consequently less sensitive to noise. It may also be produced as a MOS IC.