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Continuous rotation servo question — Parallax Forums

Continuous rotation servo question

Velvet LeopardVelvet Leopard Posts: 47
edited 2004-08-16 14:15 in BASIC Stamp
Hewwo, all.· I have heard somewhere that you can modify a hobby servo to create a "continuous rotation" servo.· Can this be done?· Would this be advisable, or is there a better choice?· If it is possible and a good choice, how would I do this?

Comments

  • jakjrjakjr Posts: 88
    edited 2004-08-11 04:26
    http://www.parallax.com/dl/docs/books/edu/roboticsservomod.pdf (copy/paste into browser)

    See page 27 (33 in adobe).

    I dont really think its worth doing it though, parallax sales continous roatation servos for $13 which is a steal compared to what places like tower-hobbies want.
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2004-08-11 06:37
    Yes, it can be done (it has been done for a long time). You can save yourself trouble by ordering pre-modified servos from use. They even have a "stop" adjustment point for fine-tuning.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas Office
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2004-08-11 07:04
    RESPONSE

    Some people want the pleasure of DIY.
    If so, go to Seattle Robotics Club's site - The Encoder. There you will find articles and discussion about doing this (with photos).

    At times, you may also want a bigger or smaller servo in a 360 degree rotation and knowing how to do it, gives you the option.

    There are also interesting articles there on modifying the inside the servo to add an encoder using a wheel from the inside of a mouse and an IR device. Good luck and use an old servo or be willing to 'waste' one on trials.

    COMMENT about buying from Parallax
    I did not know about the "stop" adjustment point for fine-tuning in Parallax's continuous rotation servos, but it makes sense and is quite useful as you either have to adjust the software (by finding the optimal pulse) for each and every servo -or- adjust the hardware to a standard. The latter choice eliminates a lot of needless tweaking, just set all your servos the same and forget about those added software details.

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    G. Herzog in Taiwan
  • Ken GraceyKen Gracey Posts: 7,386
    edited 2004-08-11 20:03
    The servos sold by Parallax are made by Futaba - they're an S-148 case/electronics with a potentiometer accessible through the back of the servo. There area couple of real benefits to buying pre-modified continuous rotation servos:

    1. The stop tab is properly removed by replacement with a molded part with no stop tab. Sometimes people can't trim the stop tab properly and you'll hear it "click" with each rotation.
    2. You don't need to open the servo to "center" it. Each is set at 1.5 ms and you can fine-tune with a screwdriver through a hole in the case.

    And finally, these are cheap because we buy them in a very big volume. I wish I could tell you how many we buy each year, but I'll let you know they arrive on multiple pallets.

    Sincerely,

    Ken Gracey
    Parallax, Inc.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2004-08-16 14:15
    Add Futaba is considered the best quality!

    I see other appeals for help on the Forum with HiTech and other brands of servos. I have some Great Westerns as they are easily purchased in Taiwan.

    Obviously, they do not all have the same levels of quality control or lead the industry in improvements (Futaba does the leading).

    As time goes by, it seems that there are more brands and greater variation in quality.
    Futaba is going to all digital for very tight control in R/C helicopters, but I am not sure that it is needed for hobby robotics.

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    G. Herzog in Taiwan
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