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Servo comparison — Parallax Forums

Servo comparison

demodemo Posts: 19
edited 2007-03-29 03:30 in BASIC Stamp
Hi,

I'm working on a project which has several servos which should move 90degrees and back.
I've done it with continuosly rotating servos, and seems like those aren't precise enough for this.

Are standard servos better for this purpose?



Thanks for your help.

Comments

  • allanlane5allanlane5 Posts: 3,815
    edited 2007-03-27 19:25
    Yes, standard servos are MUCH better for this.

    You see, a standard servo has a variable resistor feedback element built into it, as well as comparator electronics. So when you give that servo a "PULSOUT" of a certain width (repeated every 20 mSec to 50 mSec) the servo moves the output shaft (and the feedback element) to a particular position which matches that width.

    And it can do this through 180 degrees.

    Now, when you modify the servo, you disconnect the feedback element and 'stick' it at half-way. When you attach a wheel, now you can control the wheel Forward, Reverse, and Stop. But you lose that precise positioning.

    Thus, for what you are asking, a standard servo would work much better.
  • demodemo Posts: 19
    edited 2007-03-27 19:33
    Thanks for the reply!

    Is there a way to modify continuosly rotating servo to standard? or do I have to buy new ones?
  • Shawn LoweShawn Lowe Posts: 635
    edited 2007-03-27 19:44
    I think you'll have to buy new ones.

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    Shawn Lowe


    My last words shall be - "NOT YET!!!"
  • Sarten-XSarten-X Posts: 32
    edited 2007-03-27 20:37
    Usually, modification means cutting out the physical parts that stop the servo from going all the way around. This is not reversable.
  • allanlane5allanlane5 Posts: 3,815
    edited 2007-03-27 21:02
    Yup, buy new ones. But since they're like $12 each, this shouldn't be too bad. Unless you have a lot of them...

    Parallax may take back your 'modified' servo's, if you haven't broken them.
  • toitoi Posts: 7
    edited 2007-03-29 03:21
    why did the standard servo moves slightly inaccurate to the position desired?is there any error might occur in standard servo?
  • FranklinFranklin Posts: 4,747
    edited 2007-03-29 03:30
    Hobby servos are not designed as precision devices. They were designed to translate a joystick movement into a relative movement at a remote location. Encoders will make them more accurate but you would have to spend a bit of money if you wanted absolute repeatability.

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    - Stephen
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