I. Introduction Fiber breakage sensors are essential devices for detecting broken fibers in chemical fiber drafting equipment. Traditional fiber breakage sensors mostly employ charge induction, offering high sensitivity but being significantly affected by ambient temperature and humidity, thus impacting their reliability and accuracy. Photoelectric fiber breakage sensors overcome these shortcomings, greatly improving the accuracy and reliability of fiber breakage detection. II. Principle of Photoelectric Fiber Breakage Sensors Photoelectric fiber breakage sensors enable non-contact detection of fiber breakage in textile machinery and can work in conjunction with a fiber cutter to promptly cut broken fibers, preventing them from entangled in machine parts. The photoelectric fiber breakage sensor utilizes the infrared photoelectric principle to detect the fiber's movement. When the fiber is normal, the drafting or winding action of the machine causes slight vibrations in the fiber located in the sensor's U-shaped groove. These vibrations continuously block the emission and reception of infrared light on both sides of the U-shaped groove, generating continuous infrared pulses. When a fiber breaks, these continuous infrared pulses decrease or disappear. The fiber breakage sensor determines whether the fiber has broken by detecting and judging the frequency of these infrared pulses. III. Circuit Equipment and Function Implementation Circuit Composition: Infrared emitting circuit, infrared receiving circuit, amplification circuit, shaping and modulation circuit, demodulation circuit, touch sensing delay circuit, overcurrent protection circuit, and output circuit. 1. Infrared Emitting and Receiving Circuit. To ensure the brightness of the LED remains constant, a constant current source infrared emitting circuit is constructed using LED1, N1, R0, ZD1, and R1. The infrared receiving circuit consists of IC 2B, PH, and R2-R4. The signal is coupled out through C1. When the infrared light energy received by PH remains constant, the output level of pin 7 of IC 2B remains constant, and C1 outputs no coupled signal. When the infrared beam is repeatedly cut by the oscillation of the wire, changing the light energy received by PH, C1 couples out a pulsating signal of the same frequency. 2. The preamplifier and shaping/modulation circuit consists of resistors R5-R9 and IC 2A. R5 and R6 provide the input bias for the static operating point, amplifying the weak spike signal coupled from C1. Its gain depends on the ratio of R8 and R9. The shaping/modulation circuit consists of resistors R11-R13, C3, and IC2D, shaping and modulating the preamplifier spike signal into a constant-amplitude square wave pulse signal. 3. The demodulation circuit consists of D1, resistors R15-R18, C6, and IC 2C, with positive feedback introduced through R18. When the preamplifier signal frequency is below a certain value F1, pin 8 of IC 2C outputs a low level; when the preamplifier signal frequency is above a certain value F2, pin 8 of IC 2C outputs a high level. The critical transition frequency range FW = F2 - F1. An appropriate FW can effectively prevent output oscillation in the critical transition region of the detection signal, ensuring reliable detection. 4. Touch-sensing delay circuit, overcurrent protection circuit, and output circuit: IC 1D, C8, R24, and D4 constitute the touch delay control. When the wire is broken or in the lead-in state, because the pulse signal F is less than F1, the signal input terminal in Figure 4 is at a low level, and the wire probe outputs a signal. When the delay sensing terminal is touched, pin 14 of IC 1D outputs a high level, quickly charging C8 and cutting off the output. The delay time is determined by C8 and R24. Through this touch delay, the lead-in wire extension operation can be performed. The overcurrent protection circuit consists of IC 1C and R27. R27 can limit the peak current and simultaneously feed back the overcurrent signal to pin 10 of IC 1A, causing the output to cut off quickly. D5 acts as a freewheeling current, preventing damage to the circuit when the inductive load is switched on and off. IV. Conclusion After repeated design and testing, the infrared photoelectric wire detector sensor has achieved good technical performance in all aspects. Its low-level output is less than 0.1V, normal power consumption is less than 0.3W, load current can reach 800mA, short-circuit protection current is 1A, wire breakage response time is less than 0.5s, power supply delay time is 4s, and touch delay time is 15s. It can detect wire breakage of different materials.