Can I repair continuous rotation servos that no longer "center"?

For my classses, I have a box full of continuous rotation servos that need to be re-centered, but the internal "screw" is worn. If the case is opened, I can adjust the resistance with the flathead end of the supplied screwdriver (or needle-nose pliers), and get the motor close enough to being centered. For this, the motor is attached to the Basic Stamp outside its black plastic housing. I have done this once; it seemed to work

Is this process essentially mechanical, or will I tamper with electrical circuits I don't understand. Otherwise, the only thing I can do is what, throw out the 20 or so motors?

Any thoughts?


  • first, welcome to the forum, second, the answer is yes, if you can mechanically adjust the resistance/potentiometer you are good to go.


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  • iseriesiseries Posts: 408
    edited 2019-03-14 - 19:02:44
    So the servo is at rest with a PWM of 1500ms and 2000ms it rotates forward and 1000ms it rotates backwards.

    The internal electronics use the adjustable resistor to find that center frequency. Turning that screw with the applied frequency should work just fine.


    Also the center frequency has a dead zone of about 40ms so you may need to try 1520 and 1480 just to see how close to center you might be.
  • ercoerco Posts: 19,556
    It's purely mechanical adjustment of the nulling pot to stop the servo at 1500 ms. They can drift slightly over time for a variety of reasons, temperature, mechanical shock, etc. Instead of readjusting the servo, you can fix it in software, where you can specify a custom center value for each servo, for instance 1460 ms or 1530, whatever works for that servo.
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

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