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controlling servomotors — Parallax Forums

controlling servomotors

ArchiverArchiver Posts: 46,084
edited 2000-07-12 02:38 in General Discussion
I have built a robotic hand with 8 degrees of freedom , driven by
servomotors. Would I be able to use a basic stamp2 to control the 8
motors to achieve 'simultaneous ' movemment of the finger joints ,
i.e., 'near simultaneous' , ( < 20 / 8 milliseconds , to update all 8
position commands ? ) ? I wish to use a PC as a user interface ,
to enable the user to select from various motion sequences .

Would you recommend using a driver board , as i dont have time to
design my own ? I am aware of two such boards , the Parallax mini
SSCII , and the Milford Instruments 'serial servo driver board' ,
(http://www.milinst.demon.co.uk/ssc_bord.htm) Using a PC as user
interface , would either/both of these boards be suitable for the
task? What are the main advantages of using stampII rather than stampI
in this application ?

I would be most grateful for any design advice ,
Many thanks ,
Michael Hilton

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2000-07-11 16:57
    I have used the SSCII and would definitely recommend it. You can update all
    8 servo's consecutively achieving virtually simultaneous motion. The mini
    SSC is from Scott Edwards Electronics. Go here to get more info on it
    http://www.seetron.com/ssc.htm.

    Mike.

    Original Message
    From: michael [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=03_Ly1DmM6AfqQi8iaekYuEX8Ip26rO5NFMVv_mBQkDxSWErEtl5HVQolX9ktw04AEVNjsKjJaqnklU5EgxpIg]mjh@c...[/url
    Sent: Tuesday, July 11, 2000 7:03 AM
    To: basicstamps@egroups.com
    Subject: [noparse][[/noparse]basicstamps] controlling servomotors


    I have built a robotic hand with 8 degrees of freedom , driven by
    servomotors. Would I be able to use a basic stamp2 to control the 8
    motors to achieve 'simultaneous ' movemment of the finger joints ,
    i.e., 'near simultaneous' , ( < 20 / 8 milliseconds , to update all 8
    position commands ? ) ? I wish to use a PC as a user interface ,
    to enable the user to select from various motion sequences .

    Would you recommend using a driver board , as i dont have time to
    design my own ? I am aware of two such boards , the Parallax mini
    SSCII , and the Milford Instruments 'serial servo driver board' ,
    (http://www.milinst.demon.co.uk/ssc_bord.htm) Using a PC as user
    interface , would either/both of these boards be suitable for the
    task? What are the main advantages of using stampII rather than stampI
    in this application ?

    I would be most grateful for any design advice ,
    Many thanks ,
    Michael Hilton
  • ArchiverArchiver Posts: 46,084
    edited 2000-07-11 18:06
    i have one milford intrements board and i used it for my gcse project
    (automatc doors) using two servo motors i maneged to make them both move
    at the same time. if you want to use a pc to move them then there is a
    dick that you can buy (sold by the same people) that will record the
    movments so you can play them back at a later date

    michael wrote:

    > I have built a robotic hand with 8 degrees of freedom , driven by
    > servomotors. Would I be able to use a basic stamp2 to control the 8
    > motors to achieve 'simultaneous ' movemment of the finger joints ,
    > i.e., 'near simultaneous' , ( < 20 / 8 milliseconds , to update all 8
    > position commands ? ) ? I wish to use a PC as a user interface ,
    > to enable the user to select from various motion sequences .
    >
    > Would you recommend using a driver board , as i dont have time to
    > design my own ? I am aware of two such boards , the Parallax mini
    > SSCII , and the Milford Instruments 'serial servo driver board' ,
    > (http://www.milinst.demon.co.uk/ssc_bord.htm) Using a PC as user
    > interface , would either/both of these boards be suitable for the
    > task? What are the main advantages of using stampII rather than stampI
    > in this application ?
    >
    > I would be most grateful for any design advice ,
    > Many thanks ,
    > Michael Hilton
  • ArchiverArchiver Posts: 46,084
    edited 2000-07-11 20:19
    Hi Michael,

    One thing you might consider is the PAK-VIII -- this chip allows you to
    generate 8 channels of pulse output. You control the "on" time, the "off"
    time and optionally, a count of pulses.

    While you could interface the device to a PC, it uses our PAK protocol,
    which is very easy to work with from a Stamp or most other microcontrollers.
    RC servos usually require an "on" pulse of 1500uS to stay centered and then
    some length of time before you have to pulse it again. The PAK-VIII can
    easily handle this.

    You can read more at http://www.al-williams.com/awce/pak8.htm

    Regards,

    Al Williams
    AWC
    * Floating point math for the Stamp, PIC, SX, or any microcontroller:
    http://www.al-williams.com/awce/pak1.htm


    >
    Original Message
    > From: michael [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=TcPY9qm14K2gkBLIcAysTIb2dgCh4O3N684WyqHzv5sARGPE2q6Fn1jWl4jj67Byi131ATpTG5lxy1xTFZ1ZtQ]mjh@c...[/url
    > Sent: Tuesday, July 11, 2000 9:03 AM
    > To: basicstamps@egroups.com
    > Subject: [noparse][[/noparse]basicstamps] controlling servomotors
    >
    >
    > I have built a robotic hand with 8 degrees of freedom , driven by
    > servomotors. Would I be able to use a basic stamp2 to control the 8
    > motors to achieve 'simultaneous ' movemment of the finger joints ,
    > i.e., 'near simultaneous' , ( < 20 / 8 milliseconds , to update all 8
    > position commands ? ) ? I wish to use a PC as a user interface ,
    > to enable the user to select from various motion sequences .
    >
    > Would you recommend using a driver board , as i dont have time to
    > design my own ? I am aware of two such boards , the Parallax mini
    > SSCII , and the Milford Instruments 'serial servo driver board' ,
    > (http://www.milinst.demon.co.uk/ssc_bord.htm) Using a PC as user
    > interface , would either/both of these boards be suitable for the
    > task? What are the main advantages of using stampII rather than stampI
    > in this application ?
    >
    > I would be most grateful for any design advice ,
    > Many thanks ,
    > Michael Hilton
    >
    >
    >
    >
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2000-07-12 02:38
    I don't know what your budget is, but a company called Kuper
    controls makes an excellent software/hardware card system for driving RC
    servos. It can simultaneously drive up to 30 servos with high (~11 bit)
    resolution positioning. The software has all kinds of sophisticated
    graphing and editing functions, the best I've seen for this kind of
    application. It's about $2k...

    Duncan
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