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KEYPAD, DISPLAY BOARD,
CONTROL BOARD, REED
SWITCH, DRIVE MOTOR,
AND TACH FEEDBACK
The control board receives commands from
the keypad via the display board. The control
board compares these commands with the
information it receives from the tach
feedback and current sensing reed switch
and sends the appropriate signals to the wire
drive motor. Thus the wire is fed at the
correct speed and at the correct time
dependent upon the commands issued from
the keypad. The display board exhibits the
commands set forth by the keypad as well as
displays the actual arc voltage.
FIGURE E.3 – KEYPAD, DISPLAY BOARD, CONTROL BOARD,
REED SWITCH, DRIVE MOTOR AND TACH FEEDBACK.
GUN TRIGGER
RECEPTACLE
GAS
SOLENOID
AC
AC
DC+
DC-
TACH
DRIVE
MOTOR
REED
SWITCH
42VAC
42VAC
CONTACTOR CONTROL
INPUT CABLE
RECEPTACLE
KEYPAD
CONTROL BOARD
FEEDBACK
DISPLAY
PC BOARD
CURRENT
SENSING
LN-742 & LN-742H
THEORY OF OPERATION
E-4
E-4