Samsung RS20NCSW - Refrigerator Door Switch Detection Circuit; Refrigerator Temperature Sensor Circuit

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10-4. Door S/W detection circuit
10-5. Temperature detection circuit
Reset circuit is that initializes many internal parts of the MICOM and makes the all programs to act in the initial
state in case that power is impressed to MICOM by instantaneous interruption or power input. Reset terminal
voltage becomes to scores of us “ LOW” compared to the MICOM Vcc((DC 5V) voltage on power
impression, and keeps “ HIGH” (Vcc voltage) on the normal action.
CN30℃ is connected to GND and ② is supplied Vcc(DC 5V) by passing through Resistance R401
(10℃), and it detects F room door open/close by impressing to MICOM “ HIGH(5V)/LOW” . CN30 ℃ is
connected to GND and ① is supplied Vcc(DC 5V) by passing through resistance R403(10℃), and it
detects R room door open/close by impressing to MICOM “ HIGH(5V)/LOW” If there are some faults in
door S/W at this time, the corresponding fan is not act or alarm occurs. Check the door S/W whether it has
an abnormality. If the door is opened, the internal corresponding fan stops. This is occurred because
MICOM stops the fan deciding door open although door is closed when being S/W contact point
abnormality.
Terminal Door state MICOM input
F room
CLOSE
OPEN
0V (LOW)
5V (HIGH)
R room
CLOSE
OPEN
0V (LOW)
5V (HIGH)
MICOM terminal Voltage
PIN #56 (F-SENSOR)
PIN #57 (F-DEF-SENSOR)
PIN #58 (R-SENSOR)
PIN #59 (ATMOSPHERE SENSOR)
Outdoor
temperature
MICOM terminal
voltage is
changed by the
temperature.
Sensor makes use of the character that resistance value becomes smaller when temperature is high, and bigger
temperature is low by use of thermistor having a indeterminate resistance temperature coefficient. R302,4,6,8 and
C301,2,3,5 have no concern with temperature detection because they are for noise
protection parts. In case of F-sensor, if the voltage that input to MICOM is supposed to Vf, Vf= (Rth x Vcc)/(R301
+ Rth).At this, Rth is a thermistor resistance value. Refer to attached appendix for MICOM terminal voltage
corresponded to temperature and resistance/voltage conversion table of sensor.