Read Sharp AR-651 (serv.man10) Service Manual online
AR-651/810 SCANNING SECTION 6 - 11
6. 6. Automatic Original Size Detection Circuit
This circuit detects the size of original (standard sizes only) using the reflection type photosensors ar-
ranged on the base frame of the scanner unit.
6. 6. 1. Principle of original size detection
The reflection type photosensors are placed on the base frame of the scanner unit as shown in the Fig. 6.6-
1. Each sensor consists of an infrared light emitting diode (LED) on the light emitting side, and a phototransistor
on the light receiving side.
When there is an original on the original glass, light beams from the LEDs are reflected by the original and
led to the phototransistors. This means that the size of the original is detected by checking which
phototransistors are turned on or are not.
6. 6. 2. Process of original size detection
(1) When the copier is in the original size detection mode, the carriage-1 is set at its home position.
(2) When the RADF is opened, the sensors receive the light reflected from the original and if one of the
matrix conditions shown in (4) for original sizes is satisfied, the size of the original is instantly de-
tected.
(3) The output signal from each sensor is input to the CPU on the scanner control PC board to determine
the size of the original.
Fig. 6.6-2 Original size detection circuit
V
DD
P81
33
30
29
28
GND
PWA-SLG
P80
P96
P95
APS-4
APS-3
APS-2
APS-5
Reflection type
photosensor
[LT Series]
[A4 Series]
V
DD
P81
33
32
30
29
28
GND
PWA-SLG
P80
P96
P95
P94
APS-4
APS-3
APS-2
APS-1
APS-5
Reflection type
photosensor
Fig. 6.6-1
Original
Original glass
[A4 Series]
APS-2
APS-3
APS-4
APS-1
APS-5
[LT Series]
Original glass
Original
APS-4
APS-5
APS-3
APS-2
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