Paper mill automatic paper cutter circuit

It is a printing paper cutter protection circuit composed of photosensitive transistors , which can prevent manual paper feeding from accidentally stepping on the paper cutting switch and causing work-related accidents. This circuit can control
the paper cutter to automatically stop when feeding paper manually .     The relay has a set of normally open contacts K connected in series to the power supply circuit of the paper cutter's knife operation control coil. Only when the normally open contacts K are closed , the paper cutter will cut the paper.     The K relay coil is connected in series to the collector circuit of VT2, and is controlled by the state of VT2. VT2 is controlled by VT1, VT1 is controlled by the VT3 phototransistor, and VT3 is controlled by light. A light bulb is installed on one side of the paper cutter and shines on the other side. lrf3 is installed on the other side to receive the light from the bulb. .   Working principle: VT1 and VT2 can form an emitter-level coupled bistable trigger. When workers put paper by hand, their hands will block the light from the bulb , causing the VT3 phototransistor to have a high resistance value, which will turn on Vn and cut off VT2. The relay KA coil will be de-energized and its normally open contact will be released. Point KA1 is reset and disconnected, so that the current path of the paper cutter's knife operation control coil is cut off, thereby preventing accidents when the paper cutter worker puts his hand down to cut paper.