SHAFT AS-DRIVE 6T2770 - Caterpillar

Right Joystick Thumbwheel Position Sensor Operation
The pulse width modulated (PWM) signal that is sent to the ECM from the position sensor is calibrated automatically by the ECM every time that the key switch is turned to the ON position. An allowable "zero position" for the thumbwheel is set as a default in the ECM based on where the thumbwheel is expected to be at rest, when there is not pressure of any kind on the thumbwheel. When the left section of the thumbwheel is completely depressed, the ECM will interpret the signal received as a maximum left position command or -100%. When the right section of the thumbwheel is completely depressed, the ECM will interpret the signal received as a maximum right position command or +100%. The ECM will interpret the first 3% of thumbwheel movement in either the left or the right direction as a 0% command. The ECM will interpret 97% of thumbwheel movement in either direction as a 100% command, consequently, the ECM sees a 97% thumbwheel movement in either direction as either a -100% or +100% command. The PWM duty cycle value for these three positions are shown in Table 2.
Table 2
Thumbwheel Position Command    PWM Duty Cycle (%)    
Initial Zero Position     50    
Allowable Zero Range (ZP)     48 to 52    
-100% (Full Left)     33    
+100% Full Right)     67    When the key switch is turned to the ON position, the ECM reads the duty cycle from the sensor. If the duty cycle is within the allowable zero range, then that duty cycle value will become the zero position for the duration of the key switch ON cycle. If the duty cycle is not within the allowable zero position range, then the ECM will assume that the thumbwheel is pressed and will use the last known zero position duty cycle for the current zero position duty cycle value.During machine operation, as the thumbwheel is depressed further in either direction, the duty cycle signal to the ECM will result in an increased current output to the medium pressure solenoids. This will allow the ECM to increase or decrease the hydraulic flow rate to the tool.For all medium pressure functions that use the right hand thumbwheel for operation, when the thumbwheel is pressed on the right hand side, the ECM will output a proportional signal to medium pressure solenoid 2. When the thumbwheel is pressed on the left hand side, the ECM will output a proportional signal to medium pressure solenoid 1.Medium Pressure Enable
Illustration 2 g01152481
Medium pressure switch medium pressure enable selectionWhen the medium pressure switch is in the medium pressure enable position, switch 1 contacts are closed to +battery which will energize the medium pressure enable solenoid. The ECM will receive this input at contact J2-31 (wire L998-OR). The ECM will activate one of the medium pressure solenoids with an output current that is dependent on the right hand thumbwheel position sensor signal that is received at contact J1-50