Photoelectric control power saving circuit

When cutting paper in a printing factory, very thick paper is often put into the paper cutter by hand. If the paper cutting switch is mistakenly stepped on with your foot, the cutter will automatically
cut the paper, which can easily cause work injuries. Using photoelectric control to stop the paper cutter during operation can avoid accidents, as shown in the figure.
    Its working principle is: the emitter coupling bistable trigger circuit is composed of VT1 and VI'2 . When the paper cutter puts the paper by hand (a light bulb
is installed and shines on the other side, and a receiving photosensitive transistor is installed on the other side) ), the hand just blocks the light from the bulb, causing the phototransistor to increase
its resistance, so VT1 turns on. VT2 is cut off and the relay is released. Because the normally open contact of the relay is connected to the coil circuit of the paper cutter's cutting operation,
at this time, even if the paper cutter's cutting switch is accidentally stepped on, the cutting will not be carried out, thereby avoiding the occurrence of accidents. .