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Continuous Servo — Parallax Forums

Continuous Servo

HeshamHesham Posts: 2
edited 2006-05-17 15:16 in Robotics
I am having trouble using the continuous servos with Basic Stamp 2. I really cannot control them to go to the position I want them to go to. First of all they do not center. Whereever they are, they count it as the center. Secondly, I cannot send them to a specific position. They start turning and turning. So, I have no idea what to do with them. Maybe I should have a closed loop control for it. Any suggestions?

Comments

  • A.C. fishingA.C. fishing Posts: 262
    edited 2006-05-14 22:37
    Try
    '{PBASIC 2.5}
    '{STAMP BS2}
    PULSOUT 12, 650
    PULSOUT 13, 850

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    ·
  • HeshamHesham Posts: 2
    edited 2006-05-14 22:46
    I'll try it. I have the commands in a loop. That might be the reason. I used the code that was given in the manual. Thanks for the help.
  • SSteveSSteve Posts: 808
    edited 2006-05-15 00:58
    It sounds like you want standard servos not continuous servos. You can't move a continuous servo to a specific position. You can only make it rotate at different speeds (or stop).

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  • allanlane5allanlane5 Posts: 3,815
    edited 2006-05-15 17:27
    Yup, when a servo is "modified", so it becomes a "continuous rotation" servo, you lose the ability to command it to a certain position. That's what the "modification" does -- remove the hardware connection to the internal variable resistor, that provides the absolute positioning feedback.
  • Ryan ClarkeRyan Clarke Posts: 738
    edited 2006-05-16 15:38
    A.C. fishing said...
    Try
    '{PBASIC 2.5}
    '{STAMP BS2}
    PULSOUT 12, 650
    PULSOUT 13, 850

    You will need to repeat the above, and note that the above will drive the servos to turn, not stop:

    '{PBASIC 2.5}
'{STAMP BS2}

Here:
   PULSOUT 12, 750
   PULSOUT 13, 750
   PAUSE 20
goto Here



    In reality the servos should be centered before doing anything with them:

    '{PBASIC 2.5}
'{STAMP BS2}

Here:
   PULSOUT 12, 750
   PULSOUT 13, 750
   PAUSE 20
goto Here



    at which point you adjust the POT until the servos are stopped.

    Ryan

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    Ryan Clarke
    Parallax Tech Support

    RClarke@Parallax.com
  • AmaRobotDudeAmaRobotDude Posts: 14
    edited 2006-05-17 02:20
    I am just beginning my boe bot and was also wondering about the continuous rotation servos. Does 750 center the servos in the same location?
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-05-17 03:39
    Technically on a continuous rotation servo it doesn't center at all.· It merely stops it (after calibration).· That is what centering is in that context.


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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • AmaRobotDudeAmaRobotDude Posts: 14
    edited 2006-05-17 04:34
    Oh, So its not really centering its just stopping it. I thought maybe if it stopped in the same location that could be used to make a servo go to spacific locations and use the continuous rotation at the same time. Thanks......Didnt mean to hijack the thread...... freaked.gif

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  • Ryan ClarkeRyan Clarke Posts: 738
    edited 2006-05-17 15:16
    You will often hear the term 'centering' even when talking about continuous rotation- the reason for this is the servo 'thinks' that it is centered when it gets the proper pulse signal (750 -> 1.5ms)- Even though the wheel stops (at an arbitrary position) it does so because it thinks that it is already at its center position.

    Ryan

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    Ryan Clarke
    Parallax Tech Support

    RClarke@Parallax.com
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