PHOTOELECTRIC SWITCH

PURPOSE:To set the detection sensitivity automatically when a set signal is inputted simply by successively increasing the intensity of the light to be projected by the set signal successively from zero and fixing the light intensity when the receiving light exceeds the set threshold value. CONSTITUTION:When a set signal (a) is applied to a control terminal P, a counter 5 is reset, and counts a pulse (b) of an oscillation circuit 6. The output of the counter 5 is converted into an analog voltage (c) by a D/A converter 4, and converted into a pulse (b) and pulse current (d) increasing successively from zero by a waveform synthesis circuit 3. The current (d) is inputted to an flood element 1, and projects the light pulse to be increased successively from zero. This pulse light is received by a light receiving element 7 after transmitting a subject 100 to be detected, inputted to a comparator 9 through an amplifier circuit 8, and inputted to a detection circuit 10 as a constant output (f) when it is more than the threshold value (h). The circuit 10 performs the detection in synchronizm with the output (b) and the detection signal from the output circuit 10 is outputted. It is inputted to a set signal (g) to the counter 5, maintaining the count value.