Epson GT-1200, Руководство по обслуживанию

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ADF Operating Principles
Rev. A
2-15
2.1.2.6 Sensor Circuits
The timing sensor and the paper eject/reverse sensor are reflex type
sensors, and each of them has an LED and photo-transistor built in it.
Each sensor emits infrared light from the LED toward the mirror attached
across from the sensor and detects paper empty condition when it
receives the infrared light reflected on the mirror.
The cathode of the LED is connected to the collector of Q3. Current output
to the photo diode is controlled at the terminal AN0 of the CPU.
Photoelectric current from the photo transistor is converted into voltage via
the resistor in the input circuit of the sensor, and is input to the
comparator, where the voltage level is compared with the reference
voltage (2V).
If the input voltage is higher than the reference voltage, it means the
paper empty condition, and the compactor outputs a Low signal to the
CPU. Since sensors are generally produced with uneven sensitivities, the
CPU adjusts the input voltage from the sensor to the specified level. When
the ADF is turned on under the paper empty condition, the input voltage
(analog data) from the sensor is input to the CPU as a digital data. The
CPU then manipulates the data to make the proper level of output voltage
(analog data). After this process, the current flows to the LED changes
and the input voltage from the sensor is adjusted to the proper level as the
result.
10
12
+5V
TIMS DA
CN1
+5V
TP13
-
+
IC12
CPU
ANO0
INTP0
ANI1
C49
1000uF
GND
R73
100
R17
100
IC5
Q13
67
+5V
TP11
R25
10K
-
+
+5V
R46
22K
R77
15K
AGND
R58
200K
IC6
72
57
AGND
C38
0.1uF
AGND
R18
10K
R67
3K
11 TIMS
CN1
Figure 2-47.
Timing Sensor Circuit / Reverse Sensor Circuit Block Diagrams