Hitachi RAS-18SX8 Manuel De Maintenance page 135
7. Indoor/outdoor communication circuits
Indoor microcomputer (IC601)
Indoor/outdoor communication
chopper output (30kHz)
Indoor transmission output
Indoor reception input
< Typical communication waveform >
< Enlarged waveform >
Signal sent by indoor microcomputer
0V
・
Indoor and outdoor communications are conducted by using lines B and C of F cable. Line B of F cable is shared with a
transmission channel that powers the outdoor unit.
・
Data communicated between the indoor and outdoor units are outputted from the microcomputer as serial signals and are
transmitted as demodulated by a 30 kHz carrier wave. (Both the indoor and outdoor microcomputers directly output a signal
demodulated at 30 kHz.)
Check
If a cable poorly inserted in the indoor terminal board or some other failure overheats the terminal board and the
temperature fuse of the terminal board blows out, the power to the indoor communication circuit will be shut down to stop
the communications function. (In that case, the failure will be displayed by the timer lamp blinking 3 times.)
Check
If communication fails between the indoor and outdoor units for some reason, the product will give a self-diagnosis
display either by "the timer lamp blinking 3 times" or "the timer lamp blinking 12 times" depending on the cause.
Downloaded from
www.Manualslib.com
Power supply
Power relay
12Ｖ
Terminal board
temperature fuse
Ｔ301
Indoor transmission circuit
Ｑ331
88
Ｒ331
Ｒ332
52
a
Ｑ332
0Ｖ
51
Indoor unit reception circuit
b
Microcomputer
a
transmission signal
Microcomputer
b
reception signal
c
Signal between F cables B and C
Microcomputer
d
transmission signal
Microcomputer
e
reception signal
a
Signal sent by outdoor microcomputer
0V
30 kHz demodulated waveform
５ ｍs.／DIV
５ ｍs.／DIV
manuals search engine
Indoor unit side
Outdoor unit side
A
A
B
B
c
C
C
Ｒ342
Ｃ341
R804 C804
Fig. 7-1
The unit is receiving a signal that it sent
(it is not used particularly as a signal).
Approx.
Approx.
200 ms.
200 ms.
d
Signal between F cables B and C
30 kHz demodulated waveform
0V
５ ｍs.／DIV
Fig. 7-2
– 168 –
Inverter circuit
12V
C807
Outdoor
microcomputer
0V
L801
e
R803
Outdoor
78
Outdoor
reception
reception
circuit
input
Outdoor
transmission
circuit
d
60
Outdoor
transmission
Q203
output
0V
Signals sent by indoor and outdoor
microcomputers
b
e
c
0V
５ ｍs.／DIV
