– 59 –
9. Reset Circuit
●
Reset circuit performs initial setting of the microcomputer program when power is turned on.
●
Microcomputer resets program with reset voltage set to Lo, to enable operation at Hi level.
●
Fig. 9-1 shows the reset circuit, and Fig. 9-2 shows waveform at each point when power is turned on/
off.
●
After power is turned on, 12V line and 5V line voltages rise: When 12V line voltage reaches 7.2V (Zener
voltage of ZD201), ZD201 turns ON and Q208 and Q209 turn on, and reset voltage becomes Hi. Reset
voltage is not set to Hi until VDD of microcomputer rises to 5V, enabling operation, due to ZD201.
●
After power turns off, when 12V line voltage drops, ZD201 also turns OFF. However, Q208 is left ON since
reset voltage is fed back by R294, until 12V line drops to about 7.6V. This prevents chattering of reset
voltage due to voltage change in 12V line.
12V line
12V line
5V line
5V line
Fig. 9-2
Reset voltage
Reset voltage
12
6
0
V
oltage when power is turned ON
12
6
0
V
oltage when power is turned ON
Time
Time
Fig. 9-1
Содержание RAM-18QH5E
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Страница 10: ... 9 RAM 18QH5E MODEL RAM 18QH5E ...
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Страница 12: ... 11 AC 220V 240V ONLY L N INDOOR 1 C1 D1 C2 D2 INDOOR 2 RAM 18QH5E ...
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Страница 25: ... 27 heating ff BASIC MODE MODEL RAM 18QH5E ...
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Страница 71: ... 77 Lighting mode self diagnosis lamp 2 RAM 18QH5E ...
Страница 72: ... 78 TROUBLESHOOTING OF THE SYSTEM POWER MODULE ...
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Страница 75: ... 81 ELECTRIC EXPANSION VALVE PIPE THERMISTOR POSITION CHARTS MODEL RAM 18QH5E ...
Страница 78: ...HITACHI PM NO 0276E Printed in Malaysia RAM 18QH5E ...