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Continuous rotation servos: What's the modification? — Parallax Forums

Continuous rotation servos: What's the modification?

RaymanRayman Posts: 14,641
edited 2010-06-08 00:37 in Accessories
Just looked at a couple hacks and it's not really clear what's going on...

One site suggests that it's the pot that mechanically stops the servo from doing a 180.
(I find it hard to believe, but he shows several pictures on how to·modify the pot·it)

Another says it's an extrusion on a gear that does it...·
(This one looks more believeable).

Anybody know how to turn a Parallax "standard servo" into a "continuous rotation" servo?


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My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm

My Prop Products:· http://www.rayslogic.com/Propeller/Products/Products.htm

Comments

  • GranzGranz Posts: 179
    edited 2010-05-19 02:40
    Not sure about Parallax's standard servo specifically, but to modify a standard servo, check out:
    www.kronosrobotics.com/an116/GAN116.shtml

    Basically, you are taking the pot (which acts like two varying resisters to tell the control system where the motor is pointing) and either center it and remove it from the motor shaft so that it is more like two fixed resistors, or you replace the pot with two fixed resistors. This will tell the control system that the motor is centered. Next you remove the extrusion on the shaft so that when the control tells the (currently centered - so it thinks) motor to turn so that the shaft is pointing a bit to the clockwise, it will turn (of course the pot never changes to reflect the new position, so the control keeps trying to move the shaft a bit to the clockwise. This results in the motor continuously moving, trying to change the resistance of the pot. The extrusion on the shaft is to prevent continuous rotation, which you do not want on a standard servo.

    Art
  • RaymanRayman Posts: 14,641
    edited 2010-05-19 14:14
    Just took the "standard" servo all the way apart and now see that both the gears and the pot prevent full rotation...
    I'd like to open up a "continuous" servo to see what they did with the pot, but I don't want to destroy my BoeBot yet...

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    My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm

    My Prop Products:· http://www.rayslogic.com/Propeller/Products/Products.htm
  • Jessica UelmenJessica Uelmen Posts: 490
    edited 2010-05-19 16:13
    Hello!

    This post is being moved from the Propeller Chip forum to the Sensors forum, as it is not specifically Propeller related.

    Thank you!

    -- Jessica

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    Jessica Uelmen
    Education Department
    Parallax Inc.

    Post Edited (Jessica Uelmen (Parallax)) : 5/19/2010 4:22:01 PM GMT
  • lardomlardom Posts: 1,659
    edited 2010-06-08 00:37
    I might be a little late for this post but I 'dremeled' the notch off and I replaced the pot with two equally matched resistors.·The wiper on the pot·would drift over time. I don't remember the resistance but I·used a meter to find·the best matching pair.

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