BS2, PSC and Continuous Rotation Server

BrianJAXBrianJAX Posts: 2
edited 2004-10-28 - 16:16:40 in Robotics
Hello out there.· Does anyone know of a series of command strings that can instruct a Parallax continous rotation servo to do one full 360 rotation and then stop?· I'm able to get the servo to rotate clockwise and counter-clockwise, but not able to stop it with the PSC.· Any ideas are welcomed!


  • Jon WilliamsJon Williams Posts: 6,491
    edited 2004-09-28 - 20:30:23
    Regardless of the controller (even if you do it directly from the BS2), to make a CR servo rotate a single revolution will require 1) careful timing between turn and stop commands or, 2) external sensing of the servo's position.

    Note that when using a CR servo with the PSC, the "position" information is no longer relative to position, but rather rotational speed.

    Jon Williams
    Applications Engineer, Parallax
    Dallas Office
  • BrianJAXBrianJAX Posts: 2
    edited 2004-09-29 - 03:20:41
    Cool!· Thanks for the info.· I'm not too worried about sensing whether a complete rotation was made or not, but rather stopping the servo.· This application requires random starts/stops·.· What is the command for the PSC to halt a servo?· It works great once on, but I can't get it to halt...
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2004-09-29 - 05:33:57
    I haven't used the PSC yet -- but with a CR servo sending the centering position (1.5 ms pulse to servo) should stop the rotation if the servo is calibrated properly (newer Parallax CR servos [noparse][[/noparse]made by Futaba] have an adjustment screw so you can align the stop point with a centering pulse).

    Jon Williams
    Applications Engineer, Parallax
    Dallas Office
  • Josiah WoodJosiah Wood Posts: 16
    edited 2004-09-29 - 06:23:24
    You need to send a position of 750 or 2EEh, which is halfway between 250 and 1250, which is the range of the PSC. Remember that you may need to calibrate the servo to a zero position. If you want to make sure that they are set to position (or velocity, rather) 0 before calibrating, I believe hitting the reset button on the PSC will set all positions back to 0.

  • WNedWNed Posts: 157
    edited 2004-09-30 - 00:19:55
    ·· Hey,
    ·· The attached code and explanation will help you find the "stop" position of your CR servo
    without doing any adjustments. It will also help you find·settings for·various speeds.
    ·· Have Fun,
    ·· Ned

    "They may have computers, and other weapons of mass destruction." - Janet Reno
  • squiresquire Posts: 5
    edited 2004-10-21 - 18:42:39
    My Parallax PSC does not have a "reset" button. Did I get a bad one?
    It has an "off" switch that cuts power to all servos.
    This does not center servos but does stop continuous rotation servos.
    Basically, no pulses, no servo motor rotation.
    No power, no servo motor rotation.
  • allanlane5allanlane5 Posts: 3,815
    edited 2004-10-21 - 18:59:21

    You can hold a continuous rotation servo in position by sending it a pulse that says "Go to the center position". For Futaba servos, this is 1500 uSec, or a PULSOUT value of 750 on a BS2, repeated every 20 to 50 mSec.

    If the value is above 750, the servo runs continuously in one direction. Below 750, continuously in the other direction. At 750, it should hold position (IF, that is, the servo resistor is calibrated to the center position).
  • edited 2004-10-25 - 18:34:17
    Mine has a reset button, it is a small blue button to the right of the power switch.· I have put an arrow pointing to it, in the attached image.

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-10-25 - 23:57:28

    ·· I don't know about anyone else, but on my screen your text is black on black...I had to highlight it to read your post.· Just a friendly notice, I have seen this happen once before on the Parallax Forums when someone used a "theme".

    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:··
    Personal Page:···
    Designs Page:···
  • edited 2004-10-28 - 16:16:40
    Thanks Chris, wow, you are right, that's really bizzare.· Can't figure out how to edit it back either.· I just changed my Profile "Style" back to "Parallax"...

    Here's what the post said:

    Mine (my·Parallax servo controller)·has a reset button, it is a small blue button to the right of the power switch.· I have put an arrow pointing to it, in the attached image.

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