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3. Fan Motor Drive Circuit
Microcomputer
No. of
45
rotation output
No. of
68
rotation detect
The waveform of
voltage at the
point
At T2
At T1
The waveform of
voltage at the
point
T1
The waveform of
voltage at the
point
T2
The 610Hz PWM pulse shown in Fig. 3-2 from the microcomputer
pin 45 is output to point
instruction number of rotations.
This pulse changes to analog voltage by R751 and C751 and it is
applied to the fan motor as instruction voltage number of rotations.
The relationship between the voltage of point
rotations becomes as shown in Fig. -3. (The gap may arise
depending on the condition of unit.)
The feedback pulse of number of rotation is outputted from the
fan motor and input to micro computer pin 68 . The frequency of
this pulse is 12/60 of the number of rotations. (Ex: 1000min
12/60=200Hz) The microcomputer observes this frequency and to
make it as the instruction number of rotation all the time, adjusts
the output pulse width of pin 45 .
If the feedback pulse becomes lower than 100min
lock or failure of a fan motor, the fan output stops temporary as
the fan lock is faulty. The pulse will output again after 10 seconds.
If the abnormal in fan lock is detected twice in 10 minutes, the unit
is completely stopped and change to the fault mode which the
timer lamp blinks 10 times.
5V
A
L751
Q751
R752
0V
C631
C
0V
T1
T1 = Low No. of rotation
T2
T2 = High No. of rotation
. The width of this pulse changes with
and number of
3
35V line
5V line
B
R751
C751
0V
R631
Fig. 3-1
Fig. 3-2
(about 1200)
-1
-1
min
caused by
-1
54
CN10
6
0V
4
3
2
1
)
(
2
0
1
3
Voltage of point
⃝
(V)
B
Fig. 3-3
M
Fan Motor
4
5
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