Shop OBEX P1 Docs P2 Docs Learn Events
Servo Speed — Parallax Forums

Servo Speed

Dan TaylorDan Taylor Posts: 207
edited 2008-05-21 19:10 in Robotics
Hey,
· Is the fastest the right wheel can go on the boe-Bot 850 and the fastest the left wheel can go 650?

Could you do like 950 with out wrecking it...

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Dan Taylor

Comments

  • ZootZoot Posts: 2,227
    edited 2008-05-20 21:34
    Since the mechanical "stops" have been removed, and the pot wiper disconnected, no you will probably not damage anything. Standard servos (even if modified for cont. rotation) have a standard pulsewidth of 1.0ms-2.0ms. So sending 500-1000 in 2us increments won't hurt.

    According to the legendary Mike Green, however, for many continuous rotation servos, including the ones sold by Parallax, sending widths greater than 1700 and less 1300 doesn't get you going any "faster". In other words, while you shouldn't hurt anything, the actual effective "range" of your pulses is supposedly limited to ~1300-1700us range.

    That said, the best way to find out -- experiment! If you get your servos moving much faster at 2000us than you did at 1700us then you've more range to play with.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    When the going gets weird, the weird turn pro. -- HST

    1uffakind.com/robots/povBitMapBuilder.php
    1uffakind.com/robots/resistorLadder.php
  • Dan TaylorDan Taylor Posts: 207
    edited 2008-05-20 23:38
    Ok, Thanks for the info... But mine unfortunatly do not go any faster if I do 800 or 2600.· shakehead.gif

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Dan Taylor
  • ZootZoot Posts: 2,227
    edited 2008-05-20 23:45
    Yeah... well, Mike Green always knows what he's talking about smile.gif

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    When the going gets weird, the weird turn pro. -- HST

    1uffakind.com/robots/povBitMapBuilder.php
    1uffakind.com/robots/resistorLadder.php
  • Mike GreenMike Green Posts: 23,101
    edited 2008-05-21 00:02
    Did I actually "say" that?· Just goes to show you·what you can·get with an uncritical reading of my
    comments.· I have a few servos, all from Parallax at one time or another, scarcely a fair sampling of what's out there marketed as continuous motion servos.· I don't think I got much faster movement with control pulses shorter than 1300us or longer than 1700us.· I suspect most of the control is within that range and the speed sort of plateaus outside that.· Your mileage may vary.
    ·
  • Dan TaylorDan Taylor Posts: 207
    edited 2008-05-21 19:00
    Do you know what are the ones the can go faster than 850?· smilewinkgrin.gif

    P.S. Thanks for posting!

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Dan Taylor
  • ZootZoot Posts: 2,227
    edited 2008-05-21 19:10
    Well, continuous rotation servos are essentially "hacked" from regular servos. If you want a "faster" continous rotation servo, then you could look at:

    a) larger wheels -- faster platform speed, less power, but could be quick and simple

    b) getting a little more voltage to the servos (say 6-7 volts rather than 5)

    c) getting the fastest regular servos you can, then hacking them to be continous rotation (regular servos have specs for time/rotation angle, i.e., if the servo spec says it will turn 60 degrees in .2 seconds at 6 volts, that's obviously slower than a servo that turn 60 degrees in .16 seconds at 6 volts).

    d) at certain point, if speed/power is the issue, you may want to think about small DC motors rather than servos (but then you will have the added complexity of driving the motors -- servos have their "drivers" already built in).

    Others with much more experience in using the myriad servos out there will (hopefully) have more to say on this.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    When the going gets weird, the weird turn pro. -- HST

    1uffakind.com/robots/povBitMapBuilder.php
    1uffakind.com/robots/resistorLadder.php
Sign In or Register to comment.