Head Temperature Sensor - Citizen CL-E700 series Technical Manual

Chapter 2 Operating Principles
2-2.
Operation of Control Parts

(3) Head temperature sensor

The head temperature sensor is used to detect the temperature of the "SA Head". This sensor
is a thermistor incorporated in the "SA Head".
Since the resistance of the thermistor changes according to the temperature change, the
voltage at pin 98 (TMPHD) of the CPU (U1A) changes accordingly. The CPU senses the
voltage at pin 98 (TMPHD) to detect the head temperature. According to the temperature of the
"SA Head", the CPU controls the energizing pulse width applied to the thermal elements to
keep the printing density constant.
U1A
CPU
98
TMPHD
AN4
U5
FPGA
nTMPENB
33_N3
N3
nTMPERR
21_K1
K1
Printing operation when the "SA Head" temperature rises:
When the temperature of the "SA Head" rises to 70  C (158  F), printing will stop after printing
the current label. In this case, the LED on the operation panel blinks in red and the LCD
displays "Alarm Head Hot". When the temperature of the "SA Head" falls below 60  C (140  F),
the LED and LCD returns to normal display, and printing automatically resumes.
* If the temperature of the "SA Head" is too low, the LED on the operation panel blinks in red
and the LCD displays "Error Head Cold". In this case, the printer goes off-line.
Abnormally high temperature detection:
To protect the "SA Head" from being damaged, an abnormally high temperature detection
circuit is provided. If the temperature of the "SA Head" exceeds a set temperature limit, the
LED on the operation panel blinks in red and the LCD displays "Error System Fail", and the
printer goes off-line. To recover from the error status, turn OFF the printer once and then turn it
ON.
A reference voltage, i.e., an allowable temperature limit, is applied to pin 2 of the comparator
(U7A), while the sensor output voltage (TMPHD) from the head temperature sensor is applied
CL-E700 series
R54
R55
C91
TEMP ERROR Detection
+3.3V
U7A
TMPHD
3
R32
+
2
-
R33
BA2903SFVM
C49
L: Error
nTMPERR
(L: Disables ribbon motor drive.)
Printing
60  C
Printing
(140  F)
J2
+3.3V
19
HDTHM1
21
HDTHM2
+3.3V
R34
1
[SA Main PCB]
Printing
(Stop)
2-26
Head Temperature
Sensor
Thermistor
[SA Head]
(Stops)
70  C
(158  F)