Textile weft detector

The textile weft detector circuit introduced in this example adopts photoelectric control mode and can be used as a maintenance replacement circuit for the inlet jet type shuttleless weft detector.
Circuit Operation Principle The textile weft detector circuit consists of a photoelectric signal detection amplifier circuit and an LED drive circuit, as shown in Figure 8-133.

The photoelectric signal detecting and amplifying circuit is composed of infrared phototransistors V1 and V2, resistors R2-R5 and R7-R9, potentiometer RP, capacitor C1, and N1 inside the operational amplifier integrated circuit IC (N1, N2).
The LED driving circuit is composed of an infrared light emitting diode VL, transistors V3, V4, resistors anal-R4, R6, R10-R16, potentiometer RP, capacitor C2-C4 and an operational amplifier N2 inside the IC.
VL and Vl are mounted on the steel box of the textile machine. When the loom weaves, the computer system issues a command, and the loom moves once, and a weft jet is sent along the steel shovel.
When the weaving machine has the weft line, the infrared light emitted by the VL is blocked, so that the potential of the V1 collector rises, Nl and N2 output a high level, and the high level of the Nl output is used as a sampling signal of the computer, and the computer directs the textile machine to continue working. The high level of the N2 output increases the conduction capability of V3 and V4, and the operating current of VL rises to about 40 mA.
When the weaving machine runs without a weft, Vl is illuminated by the infrared light emitted by the VL, so that both N1 and N2 output a low level. The low level of the mountain output is sampled by the computer and a stop command is issued to stop the textile machine and alarm; the low level of the N2 output weakens the conduction capacity of V3 and V4, and the operating current of VL is reduced from 4OmA to 2OmA.
The RP is used to set the reference voltage for the inverting input of N1 and N2.
Component selection
Rl-Rl5 selects 1/4W metal film resistor for use; R16 selects lW metal resistor for use.
The RP uses a small synthetic carbon film potentiometer or a variable resistor.
Cl uses aluminum electrolytic capacitors with a withstand voltage of 25V; C2 uses aluminum electrolytic capacitors with a withstand voltage of 5OV; C3 and C4 use monolithic capacitors or polyester capacitors.
VL selects HG42l-HG423 type silicon infrared light emitting diode.
Vl selects 3DU41-3DU43 type silicon infrared phototransistor; V2 and V3 select S8050 type silicon NPN transistor; V4 selects S8550 type silicon PNP transistor.
lC selects LM393 type integrated operational amplifier.