Jacobsen Eclipse 322, Repair Manual

Page: 137 / 336

ELECTRICAL
4222983 Second Edition 4-63
4
Steering Circuit—Theory of Operation
Power Circuit
Unswitched 48V power is available from stud 3 through
150A fuse (F8) and 0.02 ohm resistor (R6) to key switch
terminal A and liquid crystal display (LCD) terminal
J11-8.
When the key switch is turned to the run position, 48 volts
is provided from key switch terminal B to liquid crystal
display (LCD) ignition terminal J11-5, powering up the
LCD.
With the LCD powered up, a ground is provided from the
LCD switched power contactor output terminal J11-10 to
the power distribution unit (PDU) terminal J1-4. With a
ground provided to J1-4, the 12 and 48 volt switched
power contactors are energized.
With the PDU 12 volt switched power contactor
energized, 12 volts is provided through 0.02 ohm resistor
(R12) to the main control unit (MCU) 12 volt power input
terminal J2-8. PDU terminal J1-5 also provides 12 volts
to splice E and then from splice E, 12 volts is provided to
MCU 12 volt power input terminal J2-6. With the PDU 48
volt switched power contactor energized, 48 volts is
provided to circuit breaker (F4) and MCU 48 volt power
input terminal J2-7, powering up the MCU.
The LCD converts the 48 volts supplied to LCD terminal
J11-8 to 12 volts. The 12 volts is used as the source
voltage for the control panel switches and seat switch.
LCD +12V power supply terminal J11-6 provides 12 volts
to splice G. Splice G provides 12 volts to seat switch
terminal J41-1.
Forty-eight volts is also provided from 12A circuit breaker
(F4) and J104-F to splice C. Splice C provides 48 volts to
the steering wheel input device 48V input terminal J56-8.
Forty-eight volts is provided to 0.08 ohm resistor (R1)
and PDU terminal J1-2 to splice B. Splice B provides 48
volts to steering control unit 48V input terminal J65-1,
powering up the steering control unit (SCU). Splice B
also provides 48 volts to right steering proximity switch
48V input terminal J105-B and to left steering proximity
switch 48V input terminal J57-B.
30A circuit breaker (F6) provides 48 volts to steering
contactor (K7), energizing the contactor. With the
contactor energized, J104-A provides 48 volts to SCU
terminal J53-B+, powering up the SCU. With the steering
control unit (SCU) powered up, the SCU 5V supply
terminal J65-3 provides 5 volts to steering unit 5V power
input terminal J56-1 and to steering motor 5V power
input terminal J55-1.
Steering Circuit
The operator must be on the seat before the main control
unit (MCU) allows the steering control unit (SCU) to
operate the steering motor when the steering wheel is
turned. With the operator on the seat, voltage is provided
from seat switch terminal J41-2 to MCU seat switch input
terminal J4-10, activating the input.
The steering wheel input device steering sensor 1A
terminal J56-2 connects to SCU steering sensor input 1A
terminal J65-10. The steering wheel input device steering
sensor 1B terminal J56-3 connects to SCU steering
sensor input 1B terminal J65-11. As the steering wheel is
turned, a pulsing signal is provided to the SCU between
steering sensor 1 terminals A and B.
The steering wheel input device steering sensor 2A
terminal J56-5 connects to SCU steering sensor input 2A
terminal J65-17. The steering wheel input device steering
sensor 2B terminal J56-6 connects to SCU steering
sensor input 2B terminal J65-20. As the steering wheel is
turned, a pulsing signal is provided to the SCU between
steering sensor 2 terminals A and B.
With the SCU receiving a pulsing signal from steering
wheel input device sensors 1 and 2, the SCU will turn the
steering motor to a relative position in relationship to the
steering wheel.
When the steering wheel is turned, steering wheel input
device steering sensor 1 provides a signal before
steering wheel input device sensor 2. When the steering
wheel is turned in the opposite direction, steering wheel
input device steering sensor 2 provides a signal before
steering wheel input device sensor 1. The SCU uses this
pattern to determine the direction the steering wheel is
turned.
Tactile-feedback is provided to the steering wheel by
energizing the steering brake coil. With the brake coil
energized, a magnetic field is created. The magnetic field
applies torque to the steering wheel rotor.
To energize the steering brake coil, the SCU steering
brake output terminal J65-2 provides a pulsing ground to
steering unit steering brake coil terminal J56-7. The SCU
controls the amount of tactile-feedback applied to the
steering wheel by varying the pulse width of the ground
provided to the steering brake coil.
The right and left proximity switches are normally closed
switches. The switches provide a signal to the SCU right
and left proximity switch inputs until the steering fork
reaches the magnetic trip zone of either the right or left
proximity switch. The right steering proximity switch
output terminal J105-C provides a signal to SCU
proximity switch input terminal J65-13. The left steering
proximity switch output terminal J57-C provides a signal
to SCU proximity switch input terminal J65-19.