Setting Motor Range

Most ESCs have a dead zone at the bottom of their range. This page outlines how to test the size of the range and then set the spin-when-armed and min throttle values appropriately.

Although not required, advanced users may wish to take the next step by measuring and adjusting the motor thrust curve.

Note

Please complete the ESC calibration before setting the motor range

Measuring the deadzone

  • Remove the propellers from the vehicle

  • Connect the LiPo battery

  • Connect the flight controller to the Mission Planner using a USB cable or telemetry

  • Open the Mission Planner’s Initial Setup >> Optional Hardware >> Motor Test page

    ../_images/MissionPlanner_MotorTest.png
  • Increase the “Throttle %” field and push each of the “Test motor” buttons to determine what percentage is required for each of the motors to spin. If all ESCs are from the same manufacturer they will likely all have similar dead zones, but having one or two different by 1% ~ 2% is common. Pick the highest percentage of all the motors - we will use this below.

Setting Spin-Armed and Min Throttle

By default, when the vehicle is armed but not flying, the motors will spin at a slightly slower than normal speed. This speed can be configured using MOT_SPIN_ARMED or MOT_SPIN_ARM paramter (depending upon the version). Once the vehicle is flying, we want to ensure that we never output a value that causes the motors to stop spinning, this lower limit can be configured with the THR_MIN or MOT_SPIN_MIN parameter (depending upon the version).

If using Copter-3.3 (or earlier):

  • set the MOT_SPIN_ARMED parameter to (the percentage discovered above + 2%) * 10. I.e. if you found the deadzone of the ESCs was 7%, set MOT_SPIN_ARMED to 90 (i.e. (7 + 2) * 10).
  • set the THR_MIN parameter to at least 30 higher than MOT_SPIN_ARMED. I.e. if MOT_SPIN_ARMED was 90, set THR_MIN to 120.

If using Copter-3.4 (or higher):

Note

Setting THR_MIN or MOT_SPIN_MIN even higher than recommended above is fine especially because we want to account for voltage drop of the battery but setting it too high reduces the lower range of the motors which reduces control which could be important especially on powerful copters with a low hover throttle.

Note

Copter 3.4 (and higher) also includes the MOT_SPIN_MAX parameter to account for the very top of the ESC/motor range which generally produces no additional thrust. By default this value is 0.95 (i.e. top 5% of the range produces no additional thrust).