Epson Stylus Pro 7400 Service Manual page 155

EPSON Stylus Pro 7400/7800/9400/9800
P EDGE (Paper Width Detection) Sensor
This sensor, mounted at the left-bottom side of the carriage unit, detects paper
edges by moving the carriage.
It detects four points of paper edges, namely, left and right points on the front edge
and a front point on the left and right edges of the paper. Each position is
calculated from the difference in reflection value between the platen and the paper.
A reflective type photosensor is used. Each paper edge position (presence or
absence of paper) is determined by an A/D converted value of the output from the
photosensor.
During printing, the sensor monitors the left and right edges of the paper to detect
a skew.
Detecting distance up to the paper surface:
=3mm to 10mm (Sensor Peak: 7 mm)
It must be ensured that the reflection value of the least
C H E C K
reflective paper is greater than the reflection value of the
P O I N T
platen.
The paper must be free from floating at the detection point.
If external light, such as sunlight, can enter the sensor due to
the construction, mis-detection must be prevented by LED ON/
OFF control. (Same as with Stylus Pro 7000)
In this printer, the P EDGE Sensor works also to detect the
paper front edge. (Same as the Stylus Pro 7600/9600)
NOTE: It is possible to turn this sensor OFF by
The following pages show paper size detection sequence (left and right edges and front
edge).
Operating Principles
1.4.2 Panel Display (p.39).
Print Mechanism Components
Left edge Right edge
Scanning to the HP side
Scanning to the opposite
from the opposite side
side from the HP side
Figure 2-5. Carriage Unit Paper Width Detection Sensor
Revision B
Carriage
HP Side
P_EDGE sensor
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