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THEORY OF OPERATION
4-5. Detectors
(1)
Print head temperature detectors
The A/D converter in the CPU detects the print head temperature at power on and before each line begins to print.
Control Method (by Text printing)
Print
Normal print
Unidirectional print
Print Stop
(2)
Home Position Detector
A photo-interrupter is used in the home detector on the printer.
ON/OFF signals are generated according to the position of the carriage. (Shield plate mounted at the base of the
carriage.) The printing position is determined by these signals.
V
REF
AN1
CPU
Fig. 2-8 Printer head temperature detector circuit
(LC-4511)
~ 130
130 ~ 135
Over 135
Detecting
signal
+5V
Fig. 2-9 Carriage home position detector circuit
Output (V)
5
in home position (with shield plate)
0
not in home position (without shield plate)
+5V
+5V
Thermistor
L1
L2
R1
R2
°
Temperature
C
+5V
R2
R1
C1
R3
Decision
– 28 –
±
°
(
8
C)
(LC-4521)
~ 120
120 ~ 130
Over 130
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