Control, Logic And Procedure Boards - Lincoln Electric NA-5N Service Manual

E-4
CONTACTOR CLOSURE (#2 AND #4)
ARC VOLTS (SET & ACTUAL)
REMOTE VOLTAGE CONTROL (A, B, C)
WORK SENSING (#21)
INPUT
POWER
CIRCUIT
SWITCH
BREAKER
#31
CONTROL
1 1 5
CABLE
V A C
RECEPTACLE
#32
1
0
V
A
C
VOLT
METER
BOARD
DIGITAL
METER
CONTROL, LOGIC AND
PROCEDURE BOARDS
The logic board interprets and processes the signals it
receives from the various PC boards, switches and con-
trols. The logic board also houses a DC power supply
(+5 -10) which is derived from the 22VAC received from
the T2 transformer. This DC voltage is also used on the
procedure board.
Upon receiving voltage reference level commands from
the procedure and voltage boards, or the user-operated
switches, the logic board sends the appropriate com-
mand signals to the control and power boards to drive
the wire feed motor to the proper speed and direction.
When the "start" signal is received by the logic board the
power source contact relay (3CR) is energized along
with the travel relay (2CR) and the flux relay (1CR). The
"inch down" and "stop" switches signal the logic board
which then directs the control and power boards to apply
the appropriate armature and field voltages to the wire
drive motor. The "inch up" switch, which is connected
directly to the control board, dictates that the wire drive
motor reverse direction, backing the electrode wire away
from the work piece. When the welding current closes
the reed switch the logic board directs the procedure
NOTE: Unshaded areas of block logic diagrams are the subject of discussion.
THEORY OF OPERATION
FIGURE E.4 Control Logic and Procedure Boards
115VAC
ODE SENSING (#67)
R
T
C
TACH
E
L
E
MOTOR
A
V
R V
F
O
M O
I L
A L
T
T T E
A
U A
L
G
R G
D
E
E E
P
O F2
R1(2 OHMS)
W
E
R
F1
B
O
FIELD DIRECTION
A
R
D
T1 T2
115VAC
36VAC (18+18VAC)
22VAC
WIRE FEED SPEED (SET & ACTUAL)
SPEED
METER
BOARD
DIGITAL
METER
1/2 AMP
F501
VOLTAGE
BOARD
TRAVEL
RECEPTACLE
D
C
S
A 3
U
R
CR
A
C
P
N
P D
V
O
L
2
S
L
Y H
CR
T
U
INCH A
START STOP
T
DOWN G
V
SWITCH D
SWITCH SWITCH E
O O
1
W
L
CR
N
T
A
G
E
DC SUPPLY VOLTAGE
LOGIC
STRIKE/WELD PROCEDURE
ENABLE
BOARD
SIGNAL F
E
E
D
MOTOR ARMATURE E
WELD
G
N
CURRENT
A
A
REED SWITCH
T
B
E
L
E
S
I
G S
N I
A G
SET SPEED
L N
S A
L
10VDC REFERENCEVOLTAGE
DC VOLTAGE
CONTROL
BOARD
INCH
UP
SWITCH
board to proceed from the "strike" settings to the optional
start board if used, or to the welding wire speed and arc
voltage parameters.
The control board receives information from the logic
board, the procedure board and the tach feedback cir-
cuit. The control board then applies the appropriate gate
signal to the SCR power supply on the power board.
This variable and regulated DC voltage is applied to the
motor armature thus controlling the speed of the wire
feed motor. The preset and actual wire feed speed infor-
mation is sent to the speed meter board where it is
processed and displayed on the digital meter.
The procedure board incorporates the many options
available with the NA-5. The "strike" and "weld" controls
are part of the procedure board and are not optional.
The wire feed speed and arc voltage settings for the vari-
ous modes are "programmed" through the procedure
board and are then sent to the logic, voltage and control
boards at the appropriate times during the welding cycle.
The burnback time is also coupled through the procedure
board. This control determines the length of time of
burnback delay after the stop circuit is energized.
Depending on the connections on the logic board, it may
also determine the length of time the wire feed motor
reverses after the stop button is pressed.
NA-5
TACH FEEDBACK (MOTOR RPM)
SET VOLTAGE
FLUX
RECEPTACLE
OPTIONAL
P VOLTS SPEED
START
START
TIMER
BOARD
R
STRIKE
O
B
OPTIONAL
CRATER
C
CRATER
O
TIMER
BOARD
E
A
D
R
OPTIONAL
WELD
U
TIMER
D
R WELD
E BURNBACK
VOLTS SPEED
TIMER
TACH FEEDBACK (MOTOR RPM)
E-4