Hitachi RAD-18NH7 - Description of Main Circuit Operation

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● The reset circuit initializes the microcomputer program when power is ON or OFF.
● Low voltage at pin 7 resets the microcomputer and Hi activates the microcomputer.
● When power “ON” 5V voltage rises and reaches 4.4V, pin 1 of IC521 is set to “Hi”. At this time the
microcomputer starts operation.
● When power “OFF” voltage drops and reaches 4.2V, pin 1 of IC521 is set to “Low”. This will RESET the
microcomputer.
DESCRIPTION OF MAIN CIRCUIT OPERATION
MODEL RAD-18NH7, RAD-25NH7, RAD-35NH7, RAD-50NH7
1. Reset Circuit
Fig. 1-1
Fig. 1-2
Voltage
5.0V
Reset enter at 4.2V
Reset release at 4.4V
voltage
5.0V
Voltage at pin
7
of microcomputer
Voltage supply to
pin
2
of IC521
0V
C405
R419
0V
0V
Light receiving
unit
Microcomputer
Wireless input
C611
R611
5V
13