| 摘要 |
PROBLEM TO BE SOLVED: To provide a reflection photoelectric switch whose fail safe is excellent, capable of certainly detecting the failure of a photoelectric switch by one photoelectric switch. SOLUTION: This reflection photoelectric switch is provided with a reference pulse generating circuit 2, a pulse current circuit 3, a light emitting diode(LED) 4 for projection, a photodiode(PD) 5 for light reception, a current/voltage converting circuit 6, a synchronization amplifier circuit 7, a comparator 8, and a DC voltage converting circuit 9, and light is projected from the light emitting diode(LED) 4, and reflected light LR reflected by a detector 10 is received by the photodiode(PD) 5, and is current/voltage converted, and is synchronization amplified to output received light signal VS which is turned into a pulse signal V0 whose duty rate is large. Then, the pulse signal V0 is rectified and filtered to generate a DC voltage Va, and the DC voltage Va is superimposed(added) to the DC power supply voltage VC so that a detected output VD1 which is larger than a DC power supply voltage VC only by the DC voltage Va can be obtained.
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