Recovery System
67
Service Manual – SC1500
• The
Solid State Relay
(
K1
) controls the
voltage to the
Vacuum Motor
. Note that
the
Solid State Relay
has an LED that
lights when the
Relay
is on.
• The
Flyback Diode (D2)
reduces the high-
voltage spike through the Solid State
Relay that can occur when the Vacuum
Motor is switched off. The inductive
nature of the motor can cause a large,
reverse polarity voltage spike across
the solid state relay. The flyback diode
permits this energy to be dissipated
through the motor windings without
the large voltage buildup at the relay.
The flyback diode uses a bridge
rectifier simply for its power handing
capabilities.
on page 106 for more information on the squeegee components and
operation.
Circuit Descriptions
Vacuum Motor Off
S1
2
1
Bat -
Pin 6
J3-6
24v
Bat -
J3-12
Bat +
Bat -
Brake -
2
1
1-
2+
CB3
4-
3+
1
2
M4
D2
M
+
~
~
-
BRN/VIO
BLU/ORN
WHT
GRA/BLK
BRN
RED/WHT
SPST Key
Switch
Vacuum
Contactor
Vacuum
Motor
Fly-back
Diode
Solid State
Relay (K1)
A1
Control Board
E1
Curtis 1210
Speed
Controller
Motion Input 24v
Circuit Breaker, 20 Amp
When the
Vacuum Motor
is off:
• The
Brake -
switch on
Pin 6
in the
E1 Curtis Speed Controller
is open and is not sending the drive signal to
the
Motion Input
line on pin
J3-6
on the
A1 Control Board
• The
Vacuum Contactor
switch on pin
J3-12
is open, the
Solid State Relay (K1)
is de-energized and open, and
the
M4 Vacuum Motor
is off.
Solid State
Relay (K1)
Fly-back
Diode (D2)
