– 36 –
2. Reset Circuit
Model RAS-07CH1, RAS-09CH1
17
Q202
NORMAL
RESET
HI
LO
+
–
RES
R203
D201
ZD202
R210
R211
R208
Q201
R202
C201
R204
C202
R201
R209
ZD201
35V 5V
0V
5V 12V 5V
MICON
POWER ON
35V
24V
5V
DC35V Line
DC5V Line
Q201’S Base
POWER OFF
5V
Q202’S Collector
Fig. 2-1 Reset Circuit
POWER ON
35V
24V
5V
DC35V Line
DC5V Line
Q201’S Base
POWER OFF
5V
Q202’S Collector
Fig. 2-2
● The reset circuit is used to reset the program to its initial settings when the power is turned on or when the power is
recovered after a power failure.
● The micro computer is reset when the reset input is “Hi”, and reset operation is possible when the reset input is “Lo”.
● The waveforms at each point when the power is turned on and off are shown in the Fig. 2-2.
● When the power is turned on, the voltages of the DC 35V line and DC 5V line are increased. When the voltage of DC
35V line reaches about 24V, ZD201 is turned ON, the potential of Q201’s base rises and Q201 is turned ON. At this time
the collector of Q201 is set to “LO” and cause Q202 to conduct. The collector of Q202 is set to “HI” and the reset input
of the micro computer is set to “HI” also. The DC 5V voltage has already become 5V at this time and the micro computer
starts operate.
● When the power is turned OFF, the voltage of the DC 35V line decreases. When it drops about 24V, ZD201 is turned
OFF, and this will turn Q201 and Q202 OFF rapidly. The reset input of the micro computer is set to “LO” and the micro
computer is set to reset mode.
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