Manitowoc MLC150-1, Service Maintenance Manual

Page: 68 / 206

ELECTRICAL SYSTEM MLC150-1 SERVICE/MAINTENANCE MANUAL
3-14
Published 03-21-2021, Control # 264-01
Relays
A controller digital output drives the relay coil. The coil
energizes, creating a magnetic field that closes the relay
contacts. Relays use a small control signal to control the flow
of a large current.
Hand Throttle
A controller provides an 8.5 VDC supply to a potentiometer
that is connected to the hand throttle. Power is applied
across the potentiometer windings to ground. Moving the
hand throttle moves a wiper across the potentiometer
windings. The voltage provided at the wiper when referenced
to ground is proportional to the hand throttle position and is
sent to a controller analog input.
Foot Throttle
A controller provides a digital output to a potentiometer that
is connected to the foot throttle. Power is applied across the
potentiometer windings to ground. Moving the foot throttle
moves a wiper across the potentiometer windings. The
voltage provided at the wiper when referenced to ground is
proportional to the foot throttle position and is sent to a
controller analog input.
Travel and Free-Fall Brake Pedals
A controller digital output provides power to a potentiometer
that is connected to the pedal. Power is applied across the
potentiometer windings to ground. Moving the pedal moves
a wiper across the potentiometer windings. The voltage
provided at the wiper when referenced to ground is
proportional to the pedal position and is sent to a controller
analog input.
Pump Displacement Controls
Pump flow is both directional and variable, determined by
position and stroke of a proportional solenoid valve. A
controller sends two pulse-width modulated (PWM) output
signals to two coils that actuate the solenoid valve in
opposite directions. As a PWM duty cycle increases at one
coil, more fluid is ported to the swashplate servo pistons
through the solenoid valve, increasing the swashplate angle
in the direction commanded. As the swashplate angle
increases, so does the piston stroke within the pump,
increasing the pump output volume.
RCL Beacon
A controller provides a digital output to each indicator in the
RCL beacon (red, amber, and green).
Wind Speed Indicators
A controller digital output provides power to the wind speed
sensor. The sensor outputs an analog signal that is
proportional to the wind speed. A controller analog input
reads this output voltage, and controller software determines
the wind speed based upon the signal level.
Proximity Sensors
Proximity sensors sense metal objects by generating
magnetic fields. When no metal object is close to the sensor,
the solid state switch within the sensor is open and there is
no output signal. When a metal object is close to the sensor,
the switch within the sensor closes and outputs a signal that
is 1.8 VDC
less than the sensor supply voltage.
A yellow LED on the sensor displays the switch state.
Control Module Test Voltages
Pump and Motor Voltages and Currents
Table 3-3 shows the voltages and currents of the pumps,
hoists, and travel motor.
Table 3-3. Pump and Motor Voltages and Currents
Pumps
1.6 or 8.8 VDC nominal
200 to 600 mA
1, 2
Hoist Motors
4.5 to 10 VDC
180 mA to 450 mA
1, 2
Travel Motors
0 or 24 VDC nominal
0 or 600 mA nominal
1
Note 1 : Resistance increases as the temperature rises
on the pump or motor solenoid coil, resulting in
decreased current values when measured with a meter.
The listing in the table is the current range for a 21°C
(68.9°F) coil.
Note 2 : The node regulates displacement of the pump or
motor with a PWM output. The values represent the
beginning and end of the control range.
REFERENCE
ONLY