Receiver Circuit; Buzzer Circuit - Hitachi RAK-25NH4 Service Manual

2. Receiver Circuit

12V
R201
The light receiver unit receives the infrared signal from the wireless remote control. The receiver amplifies
and shapes the signal and outputs it.

3. Buzzer Circuit

When the buzzer sounds, an approx.
3.9kHz square signal is output from buzzer
output pin of the microcomputer. After
30
the amplitude of this signal has been set
to 12Vp-p by a transistor, it is applied to
the buzzer. The piezoelectric element in
the buzzer oscillates to generate the
buzzer's sound.
R1
V
DD
R2
C1
IR1
V
out
GND
0V
Microcomputer
30
Buzzer output
Fig. 3-1 Buzzer Circuit
R611
0V
Fig. 2-1
R219
Metal diaphragm
Sound wave
Fig. 3-2 Buzzer Operation
– 63 –
13 RECEIVER I/P
Microcomputer
12V
BZ1
BZ
Q722
0V
Pizoelectric element
V
V