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Making continuous rotation servo stop! — Parallax Forums

Making continuous rotation servo stop!

ArchiverArchiver Posts: 46,084
edited 2003-11-12 04:27 in General Discussion
Hey guys,
I bought a continous rotation servo. I read the manual which said i
should use a 9 volt battery, which i did. I have a Board of
Education rev. B BS2, so i plugged the servo into pin 14 of the
servo slot (not sure if thats the name of it). I put in the code
that came with the servo. I thought the servo would stop at a
specific point with different duration values, but instead it
rotates in one direction for one range of values and in the other
direction for another range of values and i can't make it stop. Is
there a way that i can make it stop at a specific point.
I appreciate if anyone can help. Thank you!

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2003-11-10 04:23
    > I thought the servo would stop at a
    > specific point with different duration values

    That's the way a normal servo would work, but he _continuous rotation_ servo
    you purchased is modified so that instead of the pulses controlling the
    position, they control the motor's speed. If you want to move the servo arm
    to a specific position, you should use a standard servo; continuous-rotation
    servos are mainly for use as drive wheels.

    --
    Greg Courville
    www.gee-enginuity.com
    "Make it idiot-proof and somebody'll make a better idiot"
  • ArchiverArchiver Posts: 46,084
    edited 2003-11-10 13:49
    I understand that i made the mistake in buying the continuous
    rotation, but is there any way that i can make this one stop at a
    specific position. Because the standard servo, i think only has 180
    degress of rotation, I need one that goes 360 and also stops. I
    bought this because i thought that it would have both the stopping
    ability and that 360 movement. If anyone knows any code to make
    this stop at the 12, 3, 6, 9 o'clock positions, will be greatly
    appreciated. Thank you!
  • ArchiverArchiver Posts: 46,084
    edited 2003-11-10 17:48
    At 01:49 PM 11/10/03 +0000, ll_deep_soul_ll wrote:
    >I understand that i made the mistake in buying the continuous
    >rotation, but is there any way that i can make this one stop at a
    >specific position. Because the standard servo, i think only has 180
    >degress of rotation, I need one that goes 360 and also stops. I
    >bought this because i thought that it would have both the stopping
    >ability and that 360 movement. If anyone knows any code to make
    >this stop at the 12, 3, 6, 9 o'clock positions, will be greatly
    >appreciated. Thank you!

    With 360 degrees as the criteria, and no linkage involved in the solution,
    your best bet may be to look at a winch servo used on R/C model sailboats.
    The downside to that solution may be that they travel 3 or 3.5 x 360 at
    their maximum travel. I don't know if you can stop them at specific locations.

    I don't believe you can due much with the servos you have, since they have had
    the feedback unit removed or disabled to provide the continuous rotation.

    Bruce Bates
  • ArchiverArchiver Posts: 46,084
    edited 2003-11-11 12:54
    The continuous mod replaces(with fixed resistors) or fixes the feedback pot in
    one position,
    thus it will only stop at the one spot where the feedback pulse width matches
    the input's.
    To do what you want would require a 360 degree pot(don't know if they make them)
    or a
    multiturn pot(which would still have a 5,10, or 25 turn limit).
    > I understand that i made the mistake in buying the continuous
    > rotation, but is there any way that i can make this one stop at a
    > specific position. Because the standard servo, i think only has 180
    > degress of rotation, I need one that goes 360 and also stops. I
    > bought this because i thought that it would have both the stopping
    > ability and that 360 movement. If anyone knows any code to make this
    > stop at the 12, 3, 6, 9 o'clock positions, will be greatly
    > appreciated. Thank you!
  • ArchiverArchiver Posts: 46,084
    edited 2003-11-12 00:25
    --- ll_deep_soul_ll <ll_deep_soul_ll@y...> wrote:
    > I understand that i made the mistake in buying the
    > continuous
    > rotation, but is there any way that i can make this
    > one stop at a
    > specific position. Because the standard servo, i
    > think only has 180
    > degress of rotation, I need one that goes 360 and
    > also stops. I
    > bought this because i thought that it would have
    > both the stopping
    > ability and that 360 movement. If anyone knows any
    > code to make
    > this stop at the 12, 3, 6, 9 o'clock positions, will
    > be greatly
    > appreciated. Thank you!

    There's no mistake...You can stop a continuous
    rotation servo...All you have to do if find that value
    of pulses that's right in between directions. I have
    done this before. One value makes it go in one
    direction, and one the other, but as you move slowly
    from one value toward the other, the servo runs
    slower, then stops, then slowly gains speed in the
    other direction.



    =====
    Chris Savage
    Knight Designs
    324 West Main Street
    Montour Falls, NY 14865
    (607) 535-6777

    http://www.knightdesigns.com

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  • ArchiverArchiver Posts: 46,084
    edited 2003-11-12 01:07
    With the parallax continuous rotation servos is there a common value for
    the wheel to move left or right? If not, what is the best way to test
    to find these values?
    Thanks
    Mark

    Original Message
    From: Chris Savage [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=f-k7hUXgGsJrQeb5sDYh87LlDll-pTMNbo0x1b3jX1FcNVRLB05NZ1o6UIgvi5poSS6JlryNricI2PMF7_oq]knight_designs@y...[/url
    Sent: Wednesday, November 12, 2003 8:25 AM
    To: basicstamps@yahoogroups.com
    Subject: Re: [noparse][[/noparse]basicstamps] Re: Making continuous rotation servo stop!

    --- ll_deep_soul_ll <ll_deep_soul_ll@y...> wrote:
    > I understand that i made the mistake in buying the
    > continuous
    > rotation, but is there any way that i can make this
    > one stop at a
    > specific position. Because the standard servo, i
    > think only has 180
    > degress of rotation, I need one that goes 360 and
    > also stops. I
    > bought this because i thought that it would have
    > both the stopping
    > ability and that 360 movement. If anyone knows any
    > code to make
    > this stop at the 12, 3, 6, 9 o'clock positions, will
    > be greatly
    > appreciated. Thank you!

    There's no mistake...You can stop a continuous
    rotation servo...All you have to do if find that value
    of pulses that's right in between directions. I have
    done this before. One value makes it go in one
    direction, and one the other, but as you move slowly
    from one value toward the other, the servo runs
    slower, then stops, then slowly gains speed in the
    other direction.



    =====
    Chris Savage
    Knight Designs
    324 West Main Street
    Montour Falls, NY 14865
    (607) 535-6777

    http://www.knightdesigns.com

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  • ArchiverArchiver Posts: 46,084
    edited 2003-11-12 04:27
    I think the center or "stop" value is usually around 1.5ms, although with
    the hacked servos each one can be slightly different. I suggest that you
    write a program that lets you step through different pulse values while
    displaying the values in the debug terminal, then put a little sticker on
    each servo with its exact center value, so you can remember them easily.

    --
    Greg Courville (KG6SGY)
    www.gee-enginuity.com
    "Make it idiot-proof and somebody'll make a better idiot"



    Original Message
    From: "MARK DEVINE" <mdevine@s...>
    To: <basicstamps@yahoogroups.com>
    Sent: Tuesday, November 11, 2003 5:07 PM
    Subject: RE: [noparse][[/noparse]basicstamps] Re: Making continuous rotation servo stop!


    > With the parallax continuous rotation servos is there a common value for
    > the wheel to move left or right? If not, what is the best way to test
    > to find these values?
    > Thanks
    > Mark
    >
    >
    Original Message
    > From: Chris Savage [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=mT8D3sK0l3btbB8g1AsnL7loz9iqDMXElav96-vCDoRUxJh2JcqyKc7D1TKuAMbOg9BIi4l0sDE3BhL4o1RK_b4XAQ]knight_designs@y...[/url
    > Sent: Wednesday, November 12, 2003 8:25 AM
    > To: basicstamps@yahoogroups.com
    > Subject: Re: [noparse][[/noparse]basicstamps] Re: Making continuous rotation servo stop!
    >
    > --- ll_deep_soul_ll <ll_deep_soul_ll@y...> wrote:
    > > I understand that i made the mistake in buying the
    > > continuous
    > > rotation, but is there any way that i can make this
    > > one stop at a
    > > specific position. Because the standard servo, i
    > > think only has 180
    > > degress of rotation, I need one that goes 360 and
    > > also stops. I
    > > bought this because i thought that it would have
    > > both the stopping
    > > ability and that 360 movement. If anyone knows any
    > > code to make
    > > this stop at the 12, 3, 6, 9 o'clock positions, will
    > > be greatly
    > > appreciated. Thank you!
    >
    > There's no mistake...You can stop a continuous
    > rotation servo...All you have to do if find that value
    > of pulses that's right in between directions. I have
    > done this before. One value makes it go in one
    > direction, and one the other, but as you move slowly
    > from one value toward the other, the servo runs
    > slower, then stops, then slowly gains speed in the
    > other direction.
    >
    >
    >
    > =====
    > Chris Savage
    > Knight Designs
    > 324 West Main Street
    > Montour Falls, NY 14865
    > (607) 535-6777
    >
    > http://www.knightdesigns.com
    >
    > __________________________________
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    >
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    >
    >
    >
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    >
    >
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