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Servos shaking — Parallax Forums

Servos shaking

OualidOualid Posts: 12
edited 2005-12-14 07:25 in BASIC Stamp
Hi!

I am using Parallax Servo Controller (PSC) USB to control 6 servos (Futaba S3001).
Sometimes the servos start to shake.

Is it possible that the controller doesn't send "clean" signals to the servos?

The servos are connected to a separate power supply (5v).

Comments

  • Philip GamblinPhilip Gamblin Posts: 202
    edited 2005-12-11 22:21
    Servos need to have their signals "refreshed "every 20 ms. or so . Does your code do that?
  • OualidOualid Posts: 12
    edited 2005-12-11 22:38
    Parallax Servo Controller (PSC) USB is programmed to controll the servos.
    What I do is to send commands via RS232 that tell the controller which servo will be moved.
  • cyberbiotacyberbiota Posts: 79
    edited 2005-12-11 23:07
    Oualid-

    Are the ground lines of the servos, Stamp and PSC all connected?

    peter

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    Peter C. Charles

    Director, Research and Technology
    CyberBiota, Incorporated
    Peter.charles@cyberbiota.com
    http://www.cyberbiota.com
  • John R.John R. Posts: 1,376
    edited 2005-12-12 00:34
    I have not used the PSC, or done a servo with a stamp (yet). My observations are based on past use in R/C:

    While 5V may work, my experience in R/C suggests this is a little on the low side. Forces tended to be higher (mostly ground based high speed cars and boats), so my opinion here may be incorrectly biased.

    More significantly, it was not unusual to have a slight "shake" depending on exactly where the servo was "pointed" at. Move the control stick a hair one way or the other, and the shake was gone. By hair, I mean just that, a hair.

    As a suggestion, try chaning the position by a few units and see what happens.

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    John R.

    8 + 8 = 10
  • OualidOualid Posts: 12
    edited 2005-12-12 07:22
    The processor used on the PSCusb requires 5 VDC which is supplied by the USB port. Servos
    require far more power than the USB port can supply.
    Therefore I use a separate power supply 5V for the servos.

    The following document shows how to connect the power supply:

    www.parallax.com/dl/docs/prod/motors/PSCusbManBv3_3.pdf

    Maybe the servos need more power, 6V.
  • GearHeadGearHead Posts: 23
    edited 2005-12-12 08:04
    From the PSC docs,

    The processor used on the PSC requires a supply 5 VDC. Use a separate power supply for
    your servos. In general, servos require 4-7.5 VDC. Be sure that the servo power source can
    supply ample current at the proper voltage and will not damage the servos.

    In my experience, make sure your power supply can provide at least an 1 amp when driving multiple servos.

    JJ
  • OualidOualid Posts: 12
    edited 2005-12-12 08:25
    OK, I will check the current.

    Post Edited (Oualid) : 12/12/2005 8:47:35 AM GMT
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-12-12 15:08
    Hello,

    ·· What firmware revision does your PSC have?· There is example code in the documentation to determine this.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • OualidOualid Posts: 12
    edited 2005-12-13 13:51
    The version of the firmware is 1.4
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-12-14 06:22
    Well, that's up to date...Could be power supply related...

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • OualidOualid Posts: 12
    edited 2005-12-14 07:25
    This is right! I changed the power supply that can deliver 5V, 2A and the servos don't shake anymore.

    Thanks for the help everyone!
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