Photoelectric counting circuit diagram

As shown in the circuit in the figure, when the phototransistor VT1 receives the infrared light from the infrared light-emitting diode, VT1 is turned on, and the inverting input terminal 6 of the comparator IC2-B is at low level, and pin 7 outputs high level. Add it to the inverting input terminal of comparator IC2-A to make pin 1 output low level, then the luminous tube in the photoelectric coupler 4N35 will light up, the corresponding photosensitive tube will be turned on, the transistor VT2 will also be turned on, and the collector of VT2 will output low level. When an object passes between the infrared light-emitting diode VD1 and the receiving tube VT1, the infrared ray is blocked, VT1 is cut off, pin 1 of IC2-A outputs high level, 4N35 cuts off, VT2 cuts off, and the collector of VT2 outputs high level, so when there is When the object passes through VT1, a counting pulse signal is output on the collector of VT2. The signal is sent to the decimal counter and then to the decoding display circuit to display the corresponding data.