10
3.2.6 Paper near end sensor circuit
This circuit detects paper near end of receipt and journal individually.
The sensor is consist of a LED and a photo transistor.
It attached under the bottom base. There are two windows in order to sense the roll paper,
The light from LED reflect at the paper and be returned to the photo transistor.
Thus sensor output level become “H”(about 4V)
If paper roll slip out from holder, the light from LED cannot reflect, so the photo transistor
cannot receive the return light. Thus sensor output level become “L”(about 0.3V)
There is transistor on the CPU board in order to amplify the inputted signal.
So the inputted signal is not stable, that Q7,Q8 amplify the signal to “0V” or “5V”.
If paper roll slip out from holder, JNEND or RNEND will become to 5V.
When paper roll is on the holder, JNEND or RNEND is “0V”.
R72,R73 limit the current to supply to LED.
2
3
1
Q7
DTC114EUA
2
3
1
Q8
DTC114EUA
R74
4.7K
R75
4.7K
R72
330
R73
330
1
2
3
4
5
6
7
8
J15
B8B-PH-K-S
A
K
C
E
A
K
C
E
C61
0.1u
C62
1000p
C63
1000p
+5V
+5v
+5v
PAPER NEAR END DETECT CIRCUIT
RNE
JNE