Samsung SR-S25NTA Service Manual page 27

8-4. DOOR S/W sensing circuit
Voltage MICOM
On DOOR CLOSE 5V (HIGH)
F-room
On DOOR OPEN] OV(LOW)
On DOOR CLOSE 0V (LOW)
SV(HIGH)
DOOR OPEN/CLOSE of R-room sensing is performed by connecting of CN31 to GROUND, supplying
Vcc (DC SV) to through resistance R403 (4.7 KQ) and supplying "Low" (OV) /"High"(5V) to MICOM by
DOOR OPEN/CLOSE of R-room.
If there is any problem in DOOR SM, Fan in the relevant room will not work and alarm function will
operate. So, DOOR S/W should be checked if there is any problem on A/S.
For FAN in the relevant room will stop on DOOR OPEN, if there is any problem in the contactpoint of
S/W, MICOM will judge that DOOR is opened and stop FAN operation, although DOOR is closed.
8-5. Temperature sensing circuit
F-SENSOR MICOM Terminal Voltage
F-EVA SENSOR PIN #58 (F-SENSOR)
Vitaage in
PIN #57 (R-EVA-SENSOR) ~ MCOM
R-SENSOR me
PIN #56 (R-SENSOR) — | ™emalls
clainged
R-EVA SENSOR
;
PIN #59 (F-EVA-SENSOR) _ | acercling to
bia _|temerature.
SENSOR PIN #60 (AMBIENT-SENSOR)
SENSOR works on the basis of the characteristics of THERMISTOR with temperature coeffice nt of
negative resistance that resistance value decrease when temperature is High and resistance realue
increase when temperature is low.
R306 ~ R310 and C302 ~ C306 are parts to prevent NOISE.
They have no relation with temperature sensing.
In case of F-SENSOR, when the voltage inputted to MICOM is considered to be Vf, Vf is (Rthx Vcc)
/(R303 + Rth). In this equation, Rth is the resistance value of THERMISTOR corresponding ti
temperature. See the conversion table of the resistance and voltage of sensor according to the
temperature in the Reference No. 8 of this manual. Use the table on A/S because MICOM Terninal
voltage is also described in the table.