Copier paper tail detection circuit composed of photoresistor sensor

Shown is a copier paper tail detection circuit composed of a photoresistor sensor. This circuit is mainly
composed of voltage comparison integrated circuit TA75339P, photoresistor transducer RG and other devices, and is widely used in copiers.
    In the figure, ICl (TA75339P) is a voltage comparator. Its ① pin is the reference voltage terminal. This voltage is
obtained from the input +5 V voltage after code and voltage division. ② Pin is the comparison voltage terminal. The ② pin is the comparison voltage terminal. The pin voltage is obtained by dividing the voltage by R2, RP and photoresistor RG.
    When the copier is turned on, the lamp L lights up, the photoresistor is exposed to light, and the resistance value decreases, ICI. The @ pin inputs a low level, and
the ③ pin outputs a high level to the control circuit, and the copier enters the special printing state.
    When the copier receives the instruction and starts printing, and the paper passes through, the paper blocks the light of the lamp, and the photoresistor value resistor The value increases
, and when the tail of a piece of paper passes through the lamp L, the light can illuminate the photoresistor , causing its resistance value to change, so that the ICl@
pin outputs different voltage signals to the control circuit, and the control circuit After detecting the paper feeding situation, the corresponding control instructions are issued.