3D-MC: Advanced valve settings

Advanced valve settings in 3D-MC

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3D-MC: Advanced valve settings

To access the Advanced Valve Settings, go to Control > Blade calibration > Valve offsets...

In the Valve Offsets screen, tap on the yellow bar at the top of the screen.

Proportional current settings

The Proportional Current valve has several different settings available. Below are the min/max range for each setting:

  • Drive: Sink/Source
  • Max: 0.00 A - 4.80 A
  • Hysteresis: 1.5% - 12.0%
  • Dither: 0 - 31
  • Dither freq: 0.0 Hz - 12.5 Hz


Drive refers to the method the valve solenoids are actuated. Source valve solenoids work when connected to current. Valve solenoids in a sink circuit work when a connection to ground is made. Most valves will work using source, although many motor grader valves use sink.


The max setting sets the maximum current used by the valve. A proportional current valve corrects for temperature by regulating current. This means that as temperature changes, the performance of the valve offsets will not change. By setting the max current consistent with the type of valve and available voltage, you can ensure that the valve offset calibration uses the full range of movement on the solenoid spool.

Changing max current after setting valve offsets will change the valve's performance dramatically. A max current set higher will result in slower performance of valve offsets. Likewise, a max current set lower will result in more rapid performance of valve offsets.

Topcon recommends the max current to be used with each system in the system installation manual.


Current hysteresis is used to maintain a given current level in the valve coil. The available machine voltage is switched at a rate that will maintain that level. The rate that the voltage is switched is determined by the hysteresis band. This band is a percentage of current above and below the chosen current setpoint.

Voltage is turned on until current reaches the upper end of the hysteresis band. Voltage is then turned off until current reaches the lower hysteresis band. The typical switching frequency will be between 200 Hz and 2000 Hz.


Dither is a technique used to make proportional current valve respond quickly and repeatedly. When a coil is energized, there is a continuous low frequency pulse given to overcome the static friction (that is, stiction) of the spool against the valve body. The dither setting in 3D-MC controls the amplitude of the pulse given to the valve. If the amplitude is too high, the hydraulic system will react to the pulsed signal, and the operator will feel the disturbance. If the setting is too low, control will be difficult since the spool will be less likely to make smaller corrections.  

Dither frequency

In addition to the dither amplitude, the dither frequency, or the speed of the pulse, may be adjusted. Some proportional valves respond to faster or slower frequencies than Topcon supplied valves. If the frequency is too low, pulsing may be felt. 

The default value of 45 Hz will work with any Topcon valve.

Some systems will have additional settings under the More button.

Deadband: This controls the range of the on-grade indication LEDs on the Topcon display. The default value of 3 mm indicates that the elevation may move within 3 mm to either side of on-grade before the lights indicate a correction. This setting DOES NOT control the hydraulic deadband.

SmartLink: This links the elevation sensor to the slope sensor. As the elevation of the blade changes, the signal sent to the slope sensor increases, allowing for a smoother elevation and slope correction. SmartLink values range between 0 and 10. As the value is increased, the greater the coupling between the elevation and slope.

Blade Time Constant: Also known as BTC, blade time constant determines the speed at which the system realizes a change in slope at the slope sensor. A small BTC value makes the system more sensitive to slope changes. Accuracy is increased, but corrections can become quick and choppy. A larger BTC reduces the system's sensitivity to slope changes and can provide a smoother correction. Valves should range between 20 and 60, with the default value being 50. The BTC value is stored in the slope sensor and will need to be reset if the sensor is changed.

Mainfall Cut-Out: This shuts off automatic control when quick, jerky movements, caused by rough terrain or sudden starts and stops, are detected by the mainfall sensor. This will reduce gouging while grading, but only in 2D mode. Mainfall cut-out values range between 0 and 10. As the number is increased, sensitivity is decreased, so a value of 1 is the most sensitive while a value of 10 is least sensitive. Setting the value to 0 disables the feature.

Reset EE: This button resets the control box to its factory defaults. This should only be used when reinstalling the system to a completely different machine. The EEPROM memory is non-volatile memory that keeps track of all machine settings. Loading a new version of code will not affect EEPROM memory.