Front Cover Open Detection Mechanism; Rear Cover Detector Mechanism - Epson TM-U675 Service Manual

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Front cover open detection mechanism

The front cover open detector is located at the right side of the printer mechanism, and detects
opening and closing of the front cover. This detector consists of an LED and phototransistor. A
screening part, located on the rear of the cover, interrupts light rays when the cover is closed.
When the cover is opened, the light rays reach the phototransistor, resulting in a change in its
output level. This change in output level is used as a detection signal to determine when the
front cover is open.

Rear cover detector mechanism

The rear cover detector is located in the back, right side of the printer mechanism. It detects
whether the rear cover is open or closed. This detector is comprised of an LED and
phototransistor. When the cover is closed, the light interrupter on the back of the cover
interrupts the optical axis. When the cover is open, the optical axis is opened, which changes the
output level of the phototransistor. The detector takes this output level as the detection signal
for the rear cover open detector.
Appendix D-14 Product Overview
Printer side
+5V
GND
Front cover light interrupter unit
Figure D-21
Printer side
Rear cover light interrupter unit
Figure D-22
When light is emitted
High
When light is
interrupted
Low
GND
Signal level at point A
+5V
When light is emitted
High
When light is
interrupted
GND
Signal level at point A
GND
Low
Rev.D