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How do I stop PSC from sending pulses? — Parallax Forums

How do I stop PSC from sending pulses?

squiresquire Posts: 5
edited 2004-10-29 14:09 in General Discussion
Servos are not well balanced. Motor servos are very hard to stop.
Is there a !SC command to tell the Parallax Servo Controller
to stop sending pulses on a specific channel?
Stop on all channels?

I want to stop, use the Devantech SRF08 scanning left and right,
then steer in a new direction. I need a dead stop.
Trying for the 1.5ms pulse, even inputting position,
is not good enough.

Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2004-10-20 21:59
    You may be sending the wrong values. If you're using CR servos then sending a centering pulse will stop them.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas Office
  • squiresquire Posts: 5
    edited 2004-10-21 17:57
    I am using Futaba RC servos.
    In experimenting, I try to keep 6VDC into the PSC terminals.
    I am driving 11 servos and the voltage varies.
    I find that the width of the centering pulse to stop the servo does
    depend on applied voltage. Surprising, yet true.

    OK, What is the command to reset or turn off the PSC?
    I really need to stop the pulses.
  • John BJohn B Posts: 82
    edited 2004-10-22 15:36
    Hi there,
    ·· First, we'll cover the basics.· The range in pulses for a servo is 250 to 1250 with the center being 750.· If you send a command for 750 ($02EE) and the servo still moves, there are only three reasons (that I know of) that would cause the servo to continue moving.
    1)· The servo has not been properly calibrated to center.
    2)· The servo is malfunctioning.
    3)· The servo is overvoltaged.· Most hobby servos will tolerate 7.2 V without odd behavior.· You may have a servo that must run on 4.8V· (5V should be OK).

    · Have yout tried a diffferent servo, or running that one on 5V?

    John B.
  • John BJohn B Posts: 82
    edited 2004-10-22 15:39
    Hi again,
    · I should have mentioned that we are working on a version (1.4) that will allow you to stop sending pulses to a particular servo, but at the rate things are going around here, it won't be released until December.· The new version will offer a few other nifty commands as well, but I'd rather not go into detail at this time.

    John B.
  • squiresquire Posts: 5
    edited 2004-10-25 06:13
    The rate things are going with my robot, December will be just in time.
    The ridiculusly small number of bytes for variables in the BS2 on the BOE makes
    it very diffciult to calibrate the SRF08 beam pattern.

    By the way, in an attempt to reduce peak current, I put a PAUSE 2 between
    each SEROUT to the PSC. I was hoping this would distribute the pulses.
    It did not seem to help? Does the PSC do its own spreading out of when the
    pulses are sent?
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2004-10-25 15:31
    You could use a BS2pe and take advantage of the Scratchpad RAM and I2C commands when dealing with your SRF-08.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas Office
  • John BJohn B Posts: 82
    edited 2004-10-25 15:34
    Hi Squire,

    ·· The PSC sends pulses to each servo every 20mSec continuously.· Due to your request, and the request of a few others.· I have bumped up the new firmware for the PSC by a couple of weeks.· I think the next rev will really help people with trickier implementations.



    John B.
  • Jonny555Jonny555 Posts: 46
    edited 2004-10-29 01:11
    Would we send in the PSC in order to get an updated firmware?
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-10-29 14:09
    Jonny555,

    · I've had to send mine in before for firmware updates, so, yes, you would.



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    Chris Savage

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

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    Designs Page:··· http://www.lightlink.com/dream/designs
    ·
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