Samsung RS257BABB Service Guide - Page 39

Door S/W Sensing Circuit, 5 Temperature Sensing Circuit

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Circuit Descriptions 10-4) Door S/W Sensing Circuit Terminal Operation Volt(state) DOOR CLOSE 0V (LOW) Freezer DOOR OPEN 5V (HIGH) DOOR CLOSE 0V (LOW) Ref. DOOR OPEN 5V (HIGH) 1) The terminals, ② and ⑥ of the connector (CN30) are grounded, and DC5V (Vcc) is supplied to the terminals, ⑤ and ⑥ through the resistors, R404 and R403 for the freezer and the refrigerator door, respectively. 2) The micro-processor senses the door's open and close based on engaged voltages, "Low(0V)" and "High(5V)," respectively. Note) The door switch always should be checked when the evaporator fan is not running while the door is closed. 10-5) Temperature Sensing Circuit # of terminal in MICOM PIN #49 (F-SENSOR) PIN #50 (F-DEF-SENSOR) PIN #52 (R-SENSOR) PIN #53 (R-DEF-SENSOR) Remark Micom terminal voltage may change according to temp. 1) A thermistor with a negative temperature coefficient (NTC) is used for a temperature sensor. 2) Resistors, R 301 � R304 and capacitors, C 301 � C 305 are used for a noise protection purpose. 3) For the F-sensor, the input voltage into the micro processor (MICOM), VF is calculated by (Rth x Vcc)/(R301+ Rth), where Rth is a corresponding resistance to the thermistor's output (See Ref. 6 in Appendix). 4) The F-Def sensor is connected with a bimetal and a temperature sensor is in parallel. In a normal operation of the system, the bimetal is on and 0V is input into the micro-processor. During a defrost cycle, the bimetal will be off from 54℉, and a divided voltage with R304 enter to the micro-processor to keep sensing the set temperature. 39

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39
Circuit Descriptions
10-4) Door S/W Sensing Circuit
10-5) Temperature Sensing Circuit
1) The terminals,
②
and
⑥
of the connector (CN30) are grounded, and DC5V (Vcc) is supplied to the terminals,
⑤
and
⑥
through the resistors, R404 and R403 for the freezer and the refrigerator door, respectively.
2) The micro-processor senses the door’s open and close based on engaged voltages, “Low(0V)” and “High(5V),”
respectively.
Note) The door switch always should be checked when the evaporator fan is not running while the door is closed.
Terminal
Operation
Volt(state)
Freezer
DOOR CLOSE
DOOR OPEN
0V (LOW)
5V (HIGH)
Ref.
DOOR CLOSE
DOOR OPEN
0V (LOW)
5V (HIGH)
# of t
erminal in MICOM
Remark
PIN #49 (F-SENSOR)
PIN #50 (F-DEF-SENSOR)
PIN #52 (R-SENSOR)
PIN #53 (R-DEF-SENSOR)
Micom
terminal
voltage may
change
according to
temp.
1)
A thermistor with a negative temperature coefficient (NTC) is used for a temperature sensor.
2)
Resistors, R 301
�
R304 and capacitors, C 301
�
C 305 are used for a noise protection purpose.
3)
For the F-sensor, the input voltage into the micro processor (MICOM), VF is calculated by (Rth x Vcc)/(R301+ Rth),
where Rth is a corresponding resistance to the thermistor’s output (See Ref. 6 in Appendix).
4) The F-Def sensor is connected with a bimetal and a temperature sensor is in parallel. In a normal operation of the
system, the bimetal is on and 0V is input into the micro-processor. During a defrost cycle, the bimetal will be off from
54
℉
, and a divided voltage with R304 enter to the micro-processor to keep sensing the set temperature.