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Book No. 22235428 (11/03) P425AWIR Family Electrical Manual
The wedge uses an analog signal to communicate
withtheJohnDeereengine.Thissignalhasarangeof
1.1V to 3.7V. This range corresponds to an engine
speed range of 1400 to 2400 RPM.
Figure 2--2 shows the signals between the engine
controller and the WEDGE controller.
Sensors and Transducers
The electronics system contains sensors and trans-
ducersthatareused tocollectdatafrom thecompres-
sor. The temperature is measured by a thermistor.
Thisdeviceexhibitsachangeinresistanceasthetem-
perature changes. The resistance causes an input
voltage change to the WEDGE controller input and is
interpreted as a temperature change.
The electronics system also uses pressure transduc-
erstomeasurecompressorpressurechanges. These
devices have an output signal of .45 VDC to 4.5 VDC,
corresponding to 0 psi and the maximum measured
psi for a particular device. The maximum pressure
transducer ranges are 100 or 225 psi. The 100 and
225 psi devices are gauge pressure devices. These
transducers are provided with 5 VDC excitation to
power the device. These are three wire devices: ex-
citation, signal and ground.
Digital Inputs and Outputs
The WEDGE controller scans digital inputs such as
switch contacts. These are either “ON” (24VDC) or
“OFF” (0 VDC). These digital inputs are connected to
switches within the package such as the key start
switch, air filter switches and IQ filter switches.
The WEDGE controller provides 24 VDC digital
outputstocontrolsolenoids,startcompressorandDC
heaters. These are 24 VDC “ON” and 0 VDC “OFF”.
They are current limited and short circuit protected.
Controller Outputs
The WEDGE controller has four types of outputs: fre-
quency, pulse width modulated, analog and 24VDC
digital (ON/OFF). The analog output is used as the
throttle signal to the engine.
TheWEDGEvariestheanalogsignalfrom1.25to4.25
volts,correspondingto1400to2100RPM. Thissignal
is used with the John Deere engine. The frequency
throttle signal is used with the Cummins engine and
thepulse widthmodulated signalis usedwith the CAT
engine.
Pressure Control
The discharge pressure is controlled by manipulating
theenginespeedandcompressorinletvalveposition.
Theinletvalvepositioniscontrolledpneumaticallyand
the engine speed is determined by the WEDGE con-
troller. The WEDGE measures the pneumatic system
regulation pressure and computes an engine throttle
setting.Thisthrottlesettingissenttotheengineviathe
frequencythrottle,Analog,PWMorJ1939throttle,de-
pending on which technique is used. The engine con-
troller will control engine speed to this throttle setting.
Electronic Engine -- P425 Family of Machines
The P425 Family of machines contains an emissions
certifieddieselengine. In ordertomeetthe emissions
requirements, the engine has an electronic control
system.
The control system handles all monitor, alarm and
controlfunctionsfortheengine. TheWEDGEcontrol-
ler communicates with the engine controller over the
J1939 CAN network.
The WEDGE controller sends throttle settings to the
engineandreceivesdiagnosticandruntimedatafrom
the engine over the J1939 CAN network. An analog
throttle interface is currently used with the engine.
Figure 2--2 shows the connections between the
WEDGE controller and the engine controller.
