49
OPERATION PRINCIPLES BY PARTS OF CIRCUIT
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. (Next page)
ITEM
F
R
DOOR OPEN/CLOSE
CLOSE
OPEN
CLOSE
OPEN
DOOR S/W CONTACT POINT
OPEN
CLOSE
OPEN
CLOSE
MICOM
PIN NO
# 42
# 43
MICOM INPUT
“HIGH”
“LOW”
“HIGH”
“LOW”
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.
12-6) TEMP SENSING CIRCUIT
