GUSSET 1138137 - Caterpillar

Outputs
The ECM responds to inputs by sending electrical signals to the outputs. The outputs can create an action or the outputs can provide information to the operator or service technician.PWM Solenoid Outputs
To control the proportional solenoid valves, the ECM will use a pulse width modulated (PWM) signal to energize the solenoids. The ECM will vary the duty cycle of the pwm signal to control the amount of electrical current that is sent to the proportional solenoids. A PWM duty cycle is the percentage of time that the signal is "high" compared to the amount of time that the signal is "low". As the duration of the high signal increases, the percentage of the duty cycle and the amount of electrical current in the circuit will increase.To control a solenoid, the ECM will depend on the input signals involved in the control of the system to apply the correct current. The distance of travel of the solenoid valve plunger is proportional to the electrical current that is sent by the ECM. The position of the valve plunger controls the amount of pilot oil pressure that is applied to the valve spool. As the ECM increases the current to a solenoid, the spool allows more hydraulic oil flow to the hydraulic cylinders. This condition will cause the rate of movement of the implement to increase. As the ECM decreases the current to a solenoid, the pilot oil flow decreases. The spool allows less hydraulic oil flow to the hydraulic cylinders, and the movement of the implement will decrease.Medium pressure solenoidsThe medium pressure port "A" and port "B" solenoids are mounted on the medium pressure valve stack. Refer to the illustrations at the beginning of this section for the location of the solenoids. When the medium pressure function is installed on the machine, the ECM will use a pwm output signal to control the solenoids. The ECM will determine the amount of electrical current that is sent to the solenoids. The determination is based on the pwm input signal that is received from the left joystick thumbwheel position sensor. The electrical current that is applied to the solenoids will range from 205 mA to 700 mA.When the left thumbwheel is moved to the left, the ECM will output between 205 mA and 700 mA (full left position) to the medium pressure port b solenoid.When the left thumbwheel is moved right, the ECM will output between 205 mA and 700 mA (full right position) to the medium pressure port a solenoid.When the left joystick thumbwheel is in the center position, the ECM will send no current signal to either solenoid.For more information the operation of the medium pressure hydraulics system, refer to Systems Operation, "Medium Pressure Hydraulic System".Solenoid (Auxiliary Valve Port A and B Flow Solenoids)
The auxiliary valve port "A" and port "B" flow solenoids are used to control the hydraulic flow from port "A" and port "B" on the MCV valve.The machine ECM will use the PWM input signal from the