Humidity Sensor Circuit - Hitachi RAF-35NH5 Service Manual

3. Room Temperature Thermistor Circuit
ODEL RAF-25NH5, RAF-35NH5, RAF-50NH5
A room temperature thermistor circuit is shown in Fig. 3-1.
According to room temperature, the voltage of point becomes as it is shown in Fig.3-2.
5V
Room Temperature
Thermistor
R305
R301
A
Fig. 3-1
4. Heat Exchanger Thermistor Circuit
ODEL RAF-25NH5, RAF-35NH5, RAF-50NH5
Heat exchanger temperature is noticed inside the room
(1) Preheating
(2) Low-temperature defrosts at cooling¥dehumidification operation time.
(3) Not working of reversing valve or detection of opening of heat exchange thermistor is controlled.
According to heat exchange temperature, the voltage of point becomes as it is shown in Fig. 4-2.
5V
Heat exchanger
thermistor
R306
R302
A
0V

5. Humidity Sensor Circuit

ODEL RAF-25NH5, RAF-35NH5, RAF-50NH5
5V
1
2
3
Humidity sensor
0V
2.5
2.0
1.5
1.0
20
Humidity ( )
Fig. 5-2
icro computer
Room
62
temperature i n put
C302
icro computer
Heat exchanger
61
input
C303
0V
Fig. 4-1
R308
C301
＋
C305
−
0V 0V
Fig. 5-1
40
60
80
％
5
4
3
2
1
0
icro computer
humidity
60
From the output ( pin) of humidity sensor, the 5V pulse3 of different width
②
is output according to detected humidity. Smooth output pulse is carried out
by C301 and it changes into the characteristic of voltage-humidity as shown
in Fig.5-2. The micro computer detects and controls humidity by reading
this voltage directly.
- 244 -
5
4
3
2
1
0
0 10
Room temperature
Fig. 3-2
0
-10 10
20
Room temperature ( )
Fig. 4-2
20 30 40
(℃)
30 40
℃