42
- FORM NO. 56043071 CMAX
™
28/34ST / I-MAX
™
28/32C, BA 750/850ST, BA 750C
WHEEL DRIVE SYSTEM
RED
FUSE, 150A
F1
1
2
RED
BT1
+
-
BATTERY
24VDC OR 36VDC
BLK
BLK
A1
CONTROL BOARD
RED
GRN
F2
1
2
CIRCUIT BREAKER
5 AMP
S3
SWITCH
SPST KEY
GRN
GRA/BLK
4
13
B-2
B-3
14 B+2
1 B+1
BRN
5
6
7
11
12
FO
R
/RE
V
B-
1
2
9
8
3
10
BLK
RED
F3
1
2
CIRCUIT BREAKER
30 AMP
WHT/YEL
BR
N
YEL
YEL
R1
POT. 5K OHM THROTTLE
A2
1208 SPEED CONTROLLER
M1
M
MOTOR, WHEEL DRIVE
+
-
BRN/BLK
YEL/RED
B-
(T2)
B+
(T1)
B+
B-
P2
(T3)
M1
(T4)
M2
+ WHEN
FORWARD
P1
1
2
1
2
3
4
5
6
OUTPUT
OUTPUT
KEYSWITCH
REVERSE
WIPER
FORWARD
+
-
VIO
BRN/WHT
GRN/YEL
1
3
2
POT. 25K OHM SPEED LIMIT
1
2
2
3
1
RED/BLK
GRA
R2
GENERAL FUNCTIONAL OVERVIEW
See Figures 1 and 3. A 1/2 horsepower permanent magnet (24V or 36V) motor (M1) is used for the wheel drive on all machines. The motor output
is delivered to a single front mounted drive wheel driven by a chain as shown in Figure 3. A Curtis PMC solid state speed controller (A2) regulates
the variable speed and Fwd/Rev wheel drive motor functions. Location of the controller is in the rear handle housing electrical compartment
(accessible by removing the 4 screws securing the large rear electrical panel). The potentiometer R1 mounted in the drive paddle inputs to the
A2 controller the machine operator’s throttle (variable speed) and direction demands. A second pot R2 (knob adjusted) is mounted on the top
surface of the handle housing and controls the machine’s maximum transport and scrub speeds.
Drive Motor System Function
See Figures 1 and 2. With the key switch S3 closed the Brn wire inputs 24V or 36V to the A2 speed controller (terminal #3) to make its internal
control circuits operational (powering it up). The F3 circuit breaker (30 Amp) supplies the positive load circuit voltage input to the B+ controller
terminal (Wht/Yel wire). The black wire from the battery negative standoff supplies the (NEG.) input to the B- controller terminal.
Moving the 5K Ohm R1 pot off its centered balanced neutral setting of approximately 2500 Ohms, activates the operator input to the speed control.
Forward or reverse movement of the drive paddle rotates the pot shaft and the pot’s variable resistance value changes which generates the internal
voltage signals (0-5Volts) needed for the controller’s output operation. These control board voltage input signals are what energizes the Fwd and
Rev directional relays, which then selects the motor polarity and final voltage level outputs at the M1 & M2 terminals.
When the operator turns the R2 speed limit Pot from min. to max. (CW) this causes an input resistance relationship change between the pot high
(+) and wiper terminals (high to low Ohms) thus increasing the maximum wheel motor operating speed range. Turning the knob (CCW) increases
the resistance and the motor speed range is reduced.
FIGURE 1
Electrical Diagram
*For complete description of all callouts see Electrical System
Wiring Diagram
.
revised 11/02