Room Temperature Thermistor Circuit; Heat Exchanger Thermistor Circuit; Humidity Sensor Circuit - Hitachi RAF-25NH4 Service Manual

3. Room Temperature Thermistor Circuit

A room temperature thermistor circuit is shown in Fig. 3-1.
According to room temperature, the voltage of point
5V
Room Temperature
Thermistor
R305
R301
A
Fig. 3-1

4. Heat Exchanger Thermistor Circuit

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
5V
Heat exchanger
thermistor
R306
A R302
0V

5. Humidity Sensor Circuit

5V
1
2
3
Humidity sensor
0V
2.5
2.0
1.5
1.0
20
Humidity ( )
Fig. 5-2
Micro computer
Room
62
temperature input
C302
Micro computer
Heat exchanger
61
input
C303
0V
Fig. 4-1
R308
＋
C301
C305
−
0V 0V
Fig. 5-1
40
60 80
％
becomes as it is shown in Fig.3-2.
becomes as it is shown in Fig. 4-2.
5
4
3
2
1
0
Micro 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.
172
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
(℃)
40
30
℃