Citizen CL-S400DT - Head Temperature Sensor

Chapter 2 Operating Principles
2-2. Operation of Control Parts
2-19 CL-S400DT
(3) Head temperature sensor
The head temperature sensor is used to detect the temperature of the “SA2 Head”. This
sensor consists of two thermistors incorporated in the “SA2 Head”. The resistance of the
thermistor varies with the change in temperature. Using 2 thermistors, a change in printing
quality due to temperature is minimized and also an abnormal temperature rise is detected.
The thermistor output (HDTMP0) is input to pin 7 (HDTMP) of CPU (U1A). The CPU can
monitor the temperature of “SA2 Head” by detecting this voltage at pin 7. Based on the
detected temperature, the CPU controls the width of printing pulse that is used to heat the
thermal elements, to keep the printing density constant.
Printing operation when the “SA2 Head” temperature rises:
When the temperature of the “SA2 Head” rises to 70
°C (158°F), printing will stop after printing
the current label. In this case, the POWER LED blinks in red and the LCD displays "Alarm
Head Hot". When the temperature of the “SA2 Head” falls below 60
°C (140°F), the POWER
LED stops blinking, and printing automatically resumes.
Abnormally high temperature detection:
The CPU monitors the thermistor output (HDTMP1) for detecting an abnormally high
temperature. If the temperature of the “SA2 Head” exceeds 100
°C (212°F), the voltage at pin 6
(nTEMP_ERROR) changes from “High” to “Low” and the FPGA output a signal to turn OFF the
power to the “SA2 Head” and “Unit, Motor”.
In this case, the POWER LED blinks in red and the LCD displays "Alarm System Fail".
Turn OFF the printer once and then turn it ON to recover from the error status.
60°C
(140
°F)
70°C
(158
°F)
Printing
(Stop)
Printing
Printing
(Stops)
J4
+3.3V
4
U1A
CPU
ANI2
7
+3.3V
R66
R67
U17B
5
6
7
HDTMP
R65
R68
U26
U25
U27
ADCH
PAH9
45
R149
U11
FPGA
B2-27
C6
U13B
5
6
7
nTEMP_ERROR
C11
R54
+3.3V
R52
+3.3V
R51
B2-28
nTEMP_ENABELE
BA2903
HD/THM1
HD/THM2
C38
C74
C73
2
2
1
1
4
4
4
2
HDTMP1
HDTMP0
HDTMP1
5
SA2 Head
[SA Main PCB]
Thermistors