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MD22 on SSC32 issues — Parallax Forums

MD22 on SSC32 issues

BurkBurk Posts: 17
edited 2010-02-10 01:09 in Robotics
Hi all!

Has anyone succesfully used a MD22 motor driver with a SSC32 controller? I seem to be having some strange issues, when i write a value <1500 to any of the channels both motors start running in reverse and with a value >1500 both motors just stop, =1500 sometimes stops the motor(s) sometimes not. The only way 1 motor will do what it is supposed to do is to write a 0 to one of the channels then the other channel will work as it is supposed to.
I've tried several RC-Servo modes, non-turning, tried several logic power sources etc.etc. no luck so far.

Any help would be appriciated.

Comments

  • FranklinFranklin Posts: 4,747
    edited 2010-02-01 20:28
    How do you have things connected and what code are you using?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    - Stephen
  • BurkBurk Posts: 17
    edited 2010-02-01 23:02
    Connections are pretty straight forward:
    www.robot-electronics.co.uk/htm/md22tech.htm

    Motor 1 on the 2 'Motor 1' pins
    Motor 2 on the 2 'Motor 2' pins
    SDA and SCL go to 2 pulse pins of the SSC32, grounds to their resp. ground, the motor side gets its power from a 6V battery and the logic from a USB port, i can (and had to to test) easily change that to 2 other sources; the regulated 5V from the SSC32 or a separate 5V power supply.

    The code is very simple, the SSC32 runs as default as can be so i just send commands like:
    #2 P1500<cr>
    or
    #2 P1200<cr>
    or
    #3 P1900<cr>

    using channels 2 and 3 for the MD22. Tried some others channels already but giving exactly the same results.
  • FranklinFranklin Posts: 4,747
    edited 2010-02-02 03:11
    And your switch settings are...?

    Also, have you tried running this directly from the stamp?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    - Stephen
  • BurkBurk Posts: 17
    edited 2010-02-02 14:16
    Like i wrote i tried several modes, so the dips were for example on,off,on,off or on,on,off,off.
    Stamp? I have the SSC32 connected to a netbook.



    Would it be possible for someone to test this setup (MD22 + SSC32)? You guys at Parallax for example? I believe you have the possibility to test stuff fairly easy. It would or could tackle where my problem lies, although MD22s don't leave the factory without passing a test it could be possible this one passed the test because it actually does some stuff as it should but not all of what it should do.
    Just trying to figure out if the MD22 could be faulty or not.

    Post Edited (Burk) : 2/2/2010 10:22:34 PM GMT
  • FranklinFranklin Posts: 4,747
    edited 2010-02-03 23:06
    I would find someone in your area with an rc transmitter/receiver and have them test it. Or you could send the whole thing to me and I would be glad to test it for you.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    - Stephen
  • BurkBurk Posts: 17
    edited 2010-02-03 23:49
    Ordering those parts new might be cheaper than sending it to you [noparse]:)[/noparse]

    I'm gonna check with Antratek (Netherlands) where i ordered them to see if they can and want to do a test-run with the same parts, if not... i'll be back...
  • FranklinFranklin Posts: 4,747
    edited 2010-02-04 06:03
    Check you local hobby clubs to see if someone with an rc car or plane can help you. You might find a new hobby and have something else to spend money on [noparse];)[/noparse]

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    - Stephen
  • BurkBurk Posts: 17
    edited 2010-02-05 00:19
    A long time ago in a... errr... i played with RC stuff, was all analog back then but fun too [noparse]:)[/noparse]

    I'm getting a replacement from Antratek, although they doubt the MD22 could be partially faulty, but i hope it is and not the combination of the two components causing the trouble...
  • BurkBurk Posts: 17
    edited 2010-02-09 20:22
    Well, and this one acts the same.

    Ok, just in short, in any servo-mode without turning each channel operates like driving a tank with 2 handles for example or is this where i'm going wrong?. Both with a range of 1000-2000 and 1500 center.
  • ZootZoot Posts: 2,227
    edited 2010-02-09 20:31
    Something isn't quite right here.

    Post your code. Your pseudo-code snippets do not accurately show whether or not you are actually sending the values you think you are.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    When the going gets weird, the weird turn pro. -- HST

    1uffakind.com/robots/povBitMapBuilder.php
    1uffakind.com/robots/resistorLadder.php
  • BurkBurk Posts: 17
    edited 2010-02-09 21:41
    I can verify my code is working correctly by checking my command log and i can verify it by sending the same commands to a servo. Works fine on a servo, depending on the mode of the MD22 it does or doesn't do things. In none of the RC-modes it acts like i expect it to, sort of like a servo or the tank-handle example i mentioned.

    I made a little test-program apart from my robot-program to do some testing, servo's are on channel 0,1 and the MD22 on channel 2 and 3.

    2mgrpyh.jpg

    e6qd77.jpg

    The actual commands are from the # till the last digit and a <CR> is included of course.

    And this works too for the servo, the MD22 reacts only on positions <1500, >1500 just stops the motor(s).

    fddc3k.jpg

    Post Edited (Burk) : 2/9/2010 10:26:54 PM GMT
  • ZootZoot Posts: 2,227
    edited 2010-02-09 23:07
    There is only DIP switch setting for regular R/C (servo pulse control):

    RC Servo On Off On Off


    So use that setting. With one motor full forward (2000us) and one full backward (1000us) your platform should spin. With both at 2000us, you should go full forward. Both at 1500us should stop both motors.

    Make sure everything has a common ground and no ground loops. Remember that logic ground and motor ground are already connected by a track on the MD22. I use the MD22 all the time w/o problems.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    When the going gets weird, the weird turn pro. -- HST

    1uffakind.com/robots/povBitMapBuilder.php
    1uffakind.com/robots/resistorLadder.php
  • ZootZoot Posts: 2,227
    edited 2010-02-09 23:09
    Oh, and remember, in R/C mode the MD22 has a built-in "dead zone" where the motors are stopped -- 7us above and below dead center (i.e. from 1493-1507us pulse width the motors will be stopped).

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    When the going gets weird, the weird turn pro. -- HST

    1uffakind.com/robots/povBitMapBuilder.php
    1uffakind.com/robots/resistorLadder.php
  • BurkBurk Posts: 17
    edited 2010-02-09 23:31
    Well like you wrote and as i expected it to work, 2000 to both channels should make it go forward, 1000 to both backwards and 1500 stop but this doesn't happen. I'm starting to think it's the combination of the SSC32 and the MD22 that may cause the trouble.
  • ZootZoot Posts: 2,227
    edited 2010-02-09 23:39
    With correctly common grounds and no ground loops, it should work fine.

    But I agree with Franklin -- do you have a micro or an R/C transmitter/receiver so you can test just the MD22 servo in / motor out setup and at least lock down exactly where your problem is?

    You might also try your motors at half speed -- 1750 and 1250.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    When the going gets weird, the weird turn pro. -- HST

    1uffakind.com/robots/povBitMapBuilder.php
    1uffakind.com/robots/resistorLadder.php
  • BurkBurk Posts: 17
    edited 2010-02-10 01:09
    No i don't have an RC-receiver, not sure about RC-clubs or anything alike where i could try which would only tell me if an MD22 would work on a RC-receiver. I know the SSC32 is fine, got 2 servo's running on it as they should for months. This is the 2nd MD22 i'm trying, i doubt i get 2 faulty ones which react exactly the same.

    Thanks for the help so far, not sure what i'll try next...
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