Program tips > How to Centre Servos without losing your trim settings

by Mike Shellim

This article describes the MPX way of re-centring your servos. It is more effective than 'sub-trim' used on other sets, because you don't lose your trim settings.

Calibration Mode

The key is the Evo's 'calibration' mode. In Calibration mode the Tx ignores the current stick and trim positions, and sends a 'calibration' signal to the servo. This calibration signal is made up of the standard neutral signal (1.5 mS pulse) plus an adjustable offset. Before your first flight, you adjust these offsets so all your control surfaces are perfectly centred.

Calibration mode is entered by pressing the key in the Servo/Calibrate menu.

Step 1 - choose calibration reference positions for your control surfaces

First decide on an easily verifyable centre position for your servo. For example, your aileron servo centres will be calibrated so the ailerons are flush with the wing root. A rudder servo centre will be calibrated so the rudder points straight down the fuselage.

Step 2 - calibrate the servos

For each servo:

  1. Go to the Servo Calibrate screen.
  2. Select the middle point P3
  3. Press the digi-adjuster
  4. Press button to enter 'calibrate' mode.

    The servo - and vertical bar - will now jump to the centre, i.e. the servo will see the calibration signal.
  5. Adjust the digi-adjuster to re-align your control surface with your chosen reference position.
  6. Press the button again to release. This exits calibration mode, and trim and mixer settings are restored.

Subsequently, if you suspect that your servo has drifted or that you have bent a linkage, simply enter Calibrate mode and readjust the centre offset value until your control surfaces are correctly aligned.

The beauty of this system is that any trims you had previously will automatically be restored when you exit the calibration screen.

Comparison with SubTrim

Most Far Eastern sets provide a 'Sub-Trim' menu. However, Sub-Trim does not cancel trim and mixing, so it's impossible for the user to distinguish between trim offsets applied by the user, and inaccuracies (mechanical or electrical) in the R/C command chain. The Evo way is SO MUCH BETTER !!

Note

Calibration only affects the centre point of the curve (P3). If calibration changes the centre point by a large amount, you may wish to alter the other points as well to maintain the same response.