– 45 –
2. Reset Circuit
● 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 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 diagrams.
● When the power is turned on, the voltages of the DC 12V line and DC 5V lines are increased. When the
voltage of DC 12V lines reaches about 7V, ZD511 is turned ON, the potential of Q511’s base rises and Q511
is turned ON. Since Q511’s collector is set to “LO” at this time, Q512 is turned OFF and the reset input of
the micro computer is set to “Lo”. The DC 5V line voltage has already become 5V at this time and the micro
computer starts operation.
● When the power is turned OFF, the voltage of the DC 12V line decreases. When it becomes about 7V, ZD511
is turned OFF, then Q511 is turned OFF, Q512 is turned ON the reset input of the micro computer is set to
“Hi’ and the micro computer is set to the reset mode.
POWER ON
12V
7V
5V
DC12V Line
DC5V Line
Base
POWER OFF
5V
Micro computer
Pin 26
12V
5V
0V
0V
Q511
C512
26
Micro computer
(AX-3U)
RES
Q512
R511
R514
ZD511
R513
R515
R512
+
C511
0285E (08/10/14KH2) 47-71 24/11/05, 10:17 AM50
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