Hitachi RAK-18QXB, Service Manual

Page: 54 / 92

Approx.
420 s.
5V
[Typical communication waveform]
Approx. 400 ms.
Enlarged reception waveform
Fig. 5-2
An infrared signal from the remote control unit is converted to an electrical signal by the remote
control light-receiving unit (IC821) and is received by the microcomputer. Data is transmitted as
digital data 0 and 1 by changing the interval of the basic pulses at about 420 s.
Remote control reception input
(pin
of microcomputer)
Beep (reception tone)
INPUT
+
GND
66
s7HENTHEBUZZERSOUNDSANAPPROX
K(ZSQUARESIGNALISOUTPUTFROM
BUZZEROUTPUTPINOFTHEMICRO
computer. After the amplitude of this
signal has been set to 12Vp-p by a
transistor
ITISAPPLIEDTOTHEBUZZE r.
4HEPIEZOELECTRICELEMENTINTHEBUZZER
OSCILLATESTOGENERATETHEBUZZERgSSOUND
R640
C632
The indoor fan motor and drive circuit are connected to the primary power supply. They therefore have voltage to ground.
Guard against electric shocks.
7HILETHEPRODUCTISENERGIZEDDONOTUNDERA
ny circumstances detach or reattach a connector. Any such practice would
cause a high voltage to r UNRESULTINGINTHEINDOOR fan motor and board circuit being destroyed. (Check the discharge of
the C003 before detaching or reattaching the connectors.)
Caution
Caution
5
Vcc1(5V)
R822
R823
IC821
C822 C823
VDD
66
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