Epson U675 - TM Color Dot-matrix Printer, Service Manual

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Appendix D-12 Product Overview Rev.D
Confidential
Roll paper near end detector mechanism
The roll paper near end detector mechanism is made up of the N.E. detector lever and a
microswitch. It is attached to the right side of the paper feed unit, and it detects the amount of
roll paper remaining.
The tip of the N.E. detector lever is pushed against the edge of the roll paper by a spring built
into the microswitch. Therefore, the N.E. detector lever touches the edge of the roll paper when
there is a substantial amount of roll paper remaining, which keeps the microswitch turned ON,
as shown in the following illustration. The tip of the N.E. detector lever moves in the direction
of the arrow as the amount of roll paper remaining becomes lower than the prescribed amount.
The tip of the N.E. detector, thus, moves toward the core of the roll paper center thereby turning
OFF the microswitch to generate a detection signal.
Figure D-17
Validation detector mechanism
The validation detector mechanism is located near the bottom of the paper insertion position to
detect the presence of a validation sheet.
The validation detector mechanism includes an LED and a phototransistor. Reflected light is
used to detect the presence of paper. Inserting validation paper causes the LED light to reflect,
which changes the output level of the phototransistor.
This detector mechanism detects the change in output level and outputs a detection signal for
the presence of the validation paper.
Figure D-18
Unit case
Roll paper
Micro switch
N.E. detector lever
Roll paper axis center
Roll paper axis center
GND
High
+5V
GND
Low
When light is
interrupted
When light is emitted
Printer side
Validation paper
Signal level at point A