Fig. 2.16 Reset (Hpsensor) Circuit; Fig. 2.17 Timing (Pts) Sensor Circuit - Epson MX-80 Technical Manual

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Reset and timing sensor circuits
The reset (HP sensor) circuit is provided to detect the left end home position of the print
head when the power sWitch is turned on or signal INIT is applied to the Printer. The
detection of this position is performed by a photocoupler utilizing photoelectric conver-
sion. Fig. 2.16 shows the reset circuit.
From LED of Timing
Sensor Circuit
r---------------------~
+5V
15 kO R28
4.7 kO
TC 4093
Io----To T1 of 8041
R39
I
C34 0.01 ,...F
Fig. 2.16 Reset (HPSensor) Circuit
The output signal from the phototransistor used as the photocoupler is integrated and
input to the Schmitt circuit which prevents the waveform of the output signal from being
disturbed due to noise or mechanical vibrations.
The timing (PTS) sensor circuit functions to confirm the position of the print head driven
by the carriage stepper motor. Fig. 2.17 shows the timing sensor circuit which is exactly
the same as the reset circuit in the principle of operation.
~----------------------~-----------------------
+5V
To LED of
Reset Circuit
REV. A
R29
15 KO
TC 4093
1 > - - - -
To TO of 8041
I
C33 0,01 ,...F
Fig. 2.17 Timing (PTS) Sensor Circuit
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