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Calibrating 360 Degree Servos For :MOVE mini

This is a guide for calibrating 360 degree servos for use with :MOVE mini for the BBC microbit. To make the task a little easier we created a couple of custom blocks for the Microsoft MakeCode editor.


The :MOVE mini uses 360 degree servos to drive the wheels. Unlike a 180 degree servo, these do not have a position feedback. To let us drive the :MOVE mini accurately we need to use some knowledge of how fast it moves, and then let it move for a certain amount of time.

Before getting started, there is a guide for adding these blocks to the MakeCode Editor, which you can find here.


Calibrating 360 Degree Servos For :MOVE mini:

To calibrate the servos for angle and distance first you need to write a little bit of code to determine how far the :MOVE mini moves (distance and angles) in a certain time.

Button A turns for 1 second. Measure the angle that the :MOVE mini turns through and then put that into the calibrate turn speed block in an on startup bracket.

Similarly, button B drives forward for 1 second. Measure how far it travels and put that into the calibrate distance block.

These values will all be slightly different for each :MOVE mini due to manufacturing tolerances in the components.

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4 thoughts on “Calibrating 360 Degree Servos For :MOVE mini”

  • I wonder is there a way to include a programmatic trim feature as a calibration function between the left and right servos on a buggy?

    The challenge we have is that it seems to be super difficult to ensure that the left and right servos are going to turn at exactly the same speed and it's a huge ordeal to change the mechanical trim once the device has been assembled (unless you changed the design of the bottom plate) and it's also the range is very very small.

    What we'd love is a way to say that if a signal is being sent to each motor that we could add a value (say +2 or -2) to one side to make them turn at the same speed?

    • Hi Eamonn, The mechanical trim should only ever need to be done once, once done the servos will continue to respond correctly to the signals that they receive. Building in a calibration system would likely be prohibitively expensive for this type of buggy but would certainly be something to explore in a different model.

  • Kevin Fleming April 8, 2018 at 2:04 pm

    I would like to second the request for a programatic trim feature. I don't see that this would be a lot of work to add to your existing custom block set. There is really no point in calibrating turns if the buggy does not move in a straight line in the first place. None of the buggies that I have built do this without adjusting the relative rotational speed of the servos.

  • I agree, programatic trim please otherwise dismantling to screw trim is awkward. However a great item, LED lights a bonus and another bonus is batteries attached so when slotted out of buggy the microbit does not have dangling batteries.

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