Infrared light controlled broken wire detector circuit

It is used for wire breakage detection during wire winding in the textile industry.
    It uses the electrical signal generated by shaking in the photoelectric probe during the wire forming process, and is completed after amplification. The infrared light-emitting
diode VL is the transmitter head, and the phototransistor VTi is the receiver head. When the wire sways in the middle, a weak
positive pulse signal is generated at point A. This signal is amplified by the direct coupling amplifier composed of transistors VTz and VT3, and then coupled
to the switching circuit composed of VT4 through capacitor C4. When the winding is normal, the yarn will continue to rock back and forth. VT4 keeps turning on and off.
When VT4 is turned off, the power supply charges the capacitor G through resistors R9 and Rio; when VT4 is turned on, G is discharged through resistors Rio and VT4.
If the time constant of the wind and G of the charging circuit is 4 to 5 times the turn-on and turn-off cycle time of VT4, the voltage at point C cannot
rise to the point where VTs and VT6 in the output circuit are turned on, and the relay KA is in release state. When a broken wire occurs during winding
, VR will no longer conduct, and the voltage at point C will gradually increase until VTs and VT6 conduct, KA will be electrically closed, and the
KA contact will be used to control the winding motor to automatically stop running. and send an alarm signal.