12-6) Temp Sensing Circuit - Samsung RB215B Series Service Manual

OPERATION PRINCIPLES BY PARTS OF CIRCUIT

DOOR OPEN/CLOSE

ITEM

CLOSE

F

OPEN

CLOSE

R

OPEN

1) If F-Door is opened,the contact point of the door switch (4-1)becomes closed.Then,the power of

the PCB line flows to the door switch through R404 and 0V is applied to the MICOM

terminal.And, when the door is closed,the contact point of the door switch (4-1)becomes

open.Then,the power of the PCB line supplies 5V to MICOM via R404 and R401,which

recognize the door as closed,turn on the fan at the extra load terminal and control the Room

Lamp Relay (K73)turning off the lamp.

2) If R-Door is opened,the contact point of the door switch (2-1)becomes closed.Then,the power of

the PCB line flows to the door switch through R403 and 0V is applied to the MICOM

terminal.And, when the door is closed,the contact point of the door switch (2-1)becomes

open.Then,the power of the PCB line supplies 5V to MICOM via R403 and R402,which

recognize the door as closed,turn on the fan at the extra load terminal and control the Room

Lamp Relay (K75)turning off the lamp.

1) Sensor uses a thermistor which has a temp coefficient of negative resistance and controls

resistance.When the heat goes up,the resistance gets down and vice versa.R301~R305and

C301~C303 are parts for noise prevention but they are not related to temp sensing

characteristics.

2) If Vf is the incoming voltage to MICOM in case of F-Sensor,Vf equals (Rth *Vcc)/((R312 +Rth).

Where Rth is resistance of THERMISTOR corresponding to Temp.Please refer to the Appendix

Temp-to-Sensor Resistance/Voltage conversion table(Temp-to-MICOM Terminal Voltage

included)on A/S. (89page)

DOOR S/W CONTACT POINT

OPEN

CLOSE

OPEN

CLOSE

49

MICOM

MICOM INPUT

PIN NO

"HIGH"

# 42

"LOW"

"HIGH"

# 43

"LOW"