5FF
2-3-3
(2) Operating principle of reflective photosensors PPSENS1, PPSENS2, PPSENS3 and PESENS
Off
On
Off
On
LED
CN6-12
CN6-10
CN6-11
Phototransistor
5 V DC
5 V DC
5 V DC5 V DC
Q9
C
E3
2
11221
2
33
62
1
2
1
2
1
2
1
2
1
2
1
812
9
14
IC6.1
R69
R28
R89R90
IC7.4
R12
CPU
IC8
B2
1
R15
R78
PPSENS3
SGND
SGND
C25R71 R88
SGND
SGND
YA
+
–
Figure 2-3-3 Reflective photosensor (PPSENS3) circuit
The following is the operating principle of paper path sensor 3 (PPSENS3). Paper path sensors 1 and 2 (PPSENS1,
PPSENS2) and the paper empty sensor (PESENS) operate in the same manner.
A pulsating signal from pin 33 of the CPU IC8 turns Q9 on and off, causing the LED on the sensor PCB to flash. When the
flashing LED light reflects on the paper, the phototransistor turns on and off. The on/off signal is then inverted by IC7.4 and
the paper presence signal (pulse) is input at pin 62 of the CPU IC8.
If there is no paper, the phototransistor remains off and 5 V DC is input at pin 62 of the CPU IC8.
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