Epson Stylus Pro 7400, Service Manual

Page: 155 / 428

EPSON Stylus Pro 7400/7800/9400/9800 Revision B
Operating Principles Print Mechanism Components 155
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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)
NOTE: It is possible to turn this sensor OFF by 1.4.2 Panel Display (p.39) .
The following pages show paper size detection sequence (left and right edges and front
edge).
Figure 2-5. Carriage Unit Paper Width Detection Sensor
C H E C K
P O I N T
„
It must be ensured that the reflection value of the least
reflective paper is greater than the reflection value of the
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)
Left edge
Carriage
HP Side
P_EDGE sensor
Right edge
Scanning to the opposite
side from the HP side
Scanning to the HP side
from the opposite side