Star Micronics LC-8521, Technical Manual

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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.
Fig. 2-10 Printer head temperature detector circuit
Control Method
Error stop (thermistor open) – –
Normal print ~120 ~100
Unidirectional print 120~130 100~130
Print stop Over 130 Over130
(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.
Fig. 2-11 Home position detector circuit
Output (V) Decision
5 in home position (with shield plate)
0 not in home position (without shield plate)
Temperature
Bit-lmage
°
C
Temperature
text
°
C
Print
+5V +5V
CPU
P90/AND
V
REF
Thermistor
R2
R1
FB11
+5V
R2
R1
C1
R3
+5V
Detecting
signal