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Servo calibration problem

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  • Servo calibration problem

    Our servos respond, but are not behaving as we expect.
    We have several HiTechnic 180 degree servos running from a Modern Robotics Core servo controller. We wrote a short test program where a button sends the servo to position zero, and another button sends it to position 1.

    We expected that this would swing the Servo through an arc from 0 (the start position) to 180 degrees. The servo moves back and forth, but only through about 150 degrees, rather than 180. We tried an intermediate value of 0.5, expecting that the servo would stop at 90 degrees from start. Instead, it moves less than that, perhaps around 70 degrees or so.

    It is behaving as though the servo does not understand what one degree is supposed to be. Is there a step we are missing?

  • #2
    The Modern Robotics Core Servo Controller's default settings are for a different range of command pulses than the HiTechnic servos. They will not command the servos the full 180 degrees unless you enable extended range with the Core Device Discovery tool.


    • #3
      Wow, that is critical information. Thanks so much, we spent an entire meeting on this.
      Do you know if there is there a document somewhere that we should have read? We went through the FTC Components list, and the pitsco page on their servos, and these supported our theory that 1.0 "should" give us 180 degrees.

      Of course, anytime a theory incorporates the word "should". it is not a theory...


      • #4
        Not that I know of. It was noticed last year by teams using both legacy and core servo controllers (the HiTechnic/legacy servo controllers came pre-configured for HiTechnic servos).