Description Of Main Circuit Operation - Hitachi RAD-25NH7 Service Manual

DESCRIPTION OF MAIN CIRCUIT OPERATION

MODEL RAD-18NH7, RAD-25NH7, RAD-35NH7, RAD-50NH7
1. Reset Circuit
Light receiving
Voltage supply to
pin 2 of IC521
Voltage at pin
of microcomputer
The reset circuit initializes the microcomputer program when power is ON or OFF.
G
Low voltage at pin
G
When power "ON" 5V voltage rises and reaches 4.4V, pin 1 of IC521 is set to "Hi". At this time the
G
microcomputer starts operation.
When power "OFF" voltage drops and reaches 4.2V, pin 1 of IC521 is set to "Low". This will RESET the
G
microcomputer.
5V
R419
unit
C405
0V
0V
Voltage
5.0V
Reset release at 4.4V
voltage
5.0V
7
resets the microcomputer and Hi activates the microcomputer.
7
R611
C611
0V
Fig. 1-1
Fig. 1-2
– 55 –
Wireless input
13
Microcomputer
Reset enter at 4.2V