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My 2-3DOF Scale build Basics - get up and running?

Discussion in 'DIY Motion Simulator Projects' started by John458, Feb 9, 2016.

  1. John458

    John458 Member Gold Contributor

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    Hi @RufusDufus @noorbeast @Pit and all the other awesome people out there.

    I have finally created a feedback pot system that attaches to my worm gear motor, however I think its flawed in some way.

    I set the feedback pot to 0 on the SMC3 config tool so the feedback line is in line with the blue target recv line. (turn the power on and nothing moves which is great)

    Then I use the tool to test for motion and getting some mixed results, but eventually the feedback and blue line separate (see pic)
    SMC screen 1bc.png
    which leads me to believe there is some slipping going on with the connection. at the moment I have a m4 hex head bolt tapped into the end of my motor shaft. then i 3d printed a connecting shaft with a hex shape on one end and a round one on the other end for the pot shaft. Once its attached i then have a screw that goes through the round end and should pin the pot shaft to the connecting shaft.
    pot feedback.jpeg
    Can anyone recommend a better way to do this?

    Cheers and thanks for your help.
  2. Pit

    Pit - - - - - - - - - - - - - - - - Staff Member Moderator Gold Contributor

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    Check PWMmax which is very low, increase the power and look at the green line. Does it change anything?
  3. John458

    John458 Member Gold Contributor

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    Hi @Pit

    Ill give it a go with higher PWMmax, although I have pulled it apart for some closer inspection then ill definitely try that :)

    Cheers mate
  4. John458

    John458 Member Gold Contributor

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    Hi @noorbeast , @SixDegreesOfFlight quick question about power if I may;)

    I have made the move to sabertooth 2x32's as the moto's are just to unreliable .. and I am running 4 of these worm gear motors from motion dynamics

    https://www.motiondynamics.com.au/worm-drive-motor-12v-24v-200w-180-rpm-20nm-torque.html

    they have a load of 16amps by the looks of it and I been driving them with previously with 12v 30A versions of these

    https://www.ebay.com.au/itm/AC100-2...3d:m:m8c0L98zBn1oYWsDPJQgzwQ&var=621700958168

    which has been fine with the monster motos as you can power each moto/motor individually, however the sabertooth only has one power input. I was thinking of running them in parallel but everything ive been told and read is saying thats a bad idea...however not sure.

    any suggestions i could look at? there are 12v 50A power supplies available..

    any help is much appreciated
  5. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    I am not sure I understand how you plan to hook these up and a sketch may help.

    I am presuming you have two Sabertooths, each to handle two motors, and will wire each like this:

    [​IMG]

    With respect to PSUs for future proofing I would cover what the Sabertooth is capable of, not what motors you happen to use with it right now. One Sabertooth offers a continuous current of 32A. Current peaks up to 64A for a few seconds will be handled without problems. The hard current limit is above approximately 70 amps which protects the Sabertooth from a shorted motor.
  6. John458

    John458 Member Gold Contributor

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    Hi @noorbeast,

    thanks for your prompt reply.. I have attached a sketch of the previous and new setup.. the main limitation of the sabertooth for me now is only 1 power input for the saber vs the motos setup which I could attached a power supply per moto.. new-setup.jpg
  7. John458

    John458 Member Gold Contributor

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    Hi @noorbeast

    I completed a sketch of past and current systems and have found a powersupply for a reasonable cost of a 12v 50A... do you think this will be enough long term for pushing both motors?

    I have seen modded server supplies, but im a bit limited on skills in that department and with this many amps... better to be safe than fried :)

    Cheers
  8. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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  9. John458

    John458 Member Gold Contributor

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    Thanks @noorbeast .. ill check it out, I want to avoid using batteries as much as I can, but might have to...

    Cheers :)
  10. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    You should be able to get away without batteries with the 2x32s, as per that link.
  11. John458

    John458 Member Gold Contributor

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    Hi @SilentChill Quick question :)

    in regards to this thread...https://www.xsimulator.net/community/threads/sabertooth-2x32-battery-in-parallel.10564/

    just wondering what each LED PSU you are using is rated at?

    I have 12v 30amp supplies and need to wire them up parallel as well, however I found the same concerns on the web that @gigi did with everyone saying that the voltage has to match exactly or otherwise current can go from one supply to the other in an unbalanced fashion causing boom :)

    im running 4 of these motors

    https://www.motiondynamics.com.au/worm-drive-motor-12v-24v-200w-180-rpm-20nm-torque.html
  12. John458

    John458 Member Gold Contributor

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    Hi @noorbeast

    Just looking for some help on voltage clamp resistors. As mentioned I have gone the sabertooth 2x32 route , ordered my new power supplies (wasn't comfortable paralleling the supplies ) now just trying to figure out the regenerative resistor config.

    Been learning some basic electronic equations (back to ohms law and such) and spoke to dimension engineering about the most suitable resistor.

    There response is as follows ( i am using a 50amp 12v supply and running the motors above.)

    so 12v/8Amps = Result 1.5 Ohms dissipates 96 Watts at 8 Amps

    or Alternative 2 Ohms dissipates 72 Watts at 6 Amp

    "You'll need to use 8A because it's the max the power outputs can handle.
    The ohms are too low on that resistor. Here's the calculation you want: https://www.dimensionengineering.co...or?batteryvoltage=12&current=8&calc=Calculate
    Here is a list of possible: https://www.digikey.com/products/en...35&quantity=0&ColumnSort=0&page=1&pageSize=25
    You can always parallel them to get the resistance and wattage you need.

    and

    "When calculating, for amps you need to use your motor current draw (actual draw under load- not what the motor is rated at) or 8A- whichever is lower.
    So, you always use 8A unless your motor is drawing something less. This is because the power outputs on the 2x32 cannot sink more than 8A."

    So i think that a 1.5 Ohms resistor at 96 Watts should do the trick, to protect the power supplies.

    however because they said "always use 8 amps unless the draw is less" I'm not quite sure this is still correct because the motor will be moving back and forth a lot and drawing all sorts of current levels to make it move.

    Would the 1.5 Ohms resistor at 96 Watt be suitable?

    Many thanks :)
  13. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    That is what the Dimension Engineering calculator indicates.
  14. John458

    John458 Member Gold Contributor

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    Hi @RufusDufus and @noorbeast

    I am making some good progress on the build and have just received my new power supplies and resistors for the voltage clamps.

    So moving to the sabertooth instead of the motos has been really easy in terms of setup and wiring so happy about that and I have followed this awesome thread to the letter

    https://www.xsimulator.net/communit...ket-serial-pid-motor-driver-w-softstart.9277/

    the issue I am having now is very strange, did not encounter this with the motos, just curious if you may be able to help or point me in a fault finding direction.

    1. I have my feedback pots (vishay) connected to the shaft of my motor and they seem to work great. I know this because when I launch the SMC Utils it finds both motors and when i manually turn the shaft with my hand the green feedback line moves away from the blue line and vice versa the other way. So i have manually turned the shaft until the green feedback line meets the blue line so everything should be centered.

    With the sabaertooths I have used the describe software to set the baud rate and set the dip switches as shown. Pots are connected to A0 and A1 and 5v and GND

    I then read from Six degrees of Flight that with the softstart SMC version he powers up the sabertooth first and then the arduino, beacuse it caused trouble for him...so i did that.

    So here goes ...

    1. Open SMC Utils to get Both feedback pots on motor 1 and two moved to match the center blue line by hand - so fully centered..close SMC Utlis
    2. I then power the sabertooth Open and Open SMCUtlis and select motor 1 and select square(or motion) on the outmode monitor function... then slowly move the PWMax up till the motor starts moving..
    3. This works the motor starts moving back and forth as expected but the green feedback line is dead straight (it doesn;t move at all. just the blue line going up and down through the green line( see video)
    4. so then i go to monitor manual mode (still on motor 1) and click the middle minus button on the right to get it back to center to stop moving. (this doesnt mean the physical feedback pot is back to its center thou)
    5. Ok then i switch to motor 2 and and the feedback line has moved below the blue line So strange as this was centered just before).. and this motor wasn't moving at all. I have only been moving motor 1
    6. So seems like there is some confusion with the pots?
    7. then when I apply power to the second motor anyway... both motors move...strange..



    Hope fully the video helps and look forward to any help.

    Cheers

    John
  15. noorbeast

    noorbeast VR - The Next Generation Staff Member Moderator

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    Just letting you know the video is not working.
  16. John458

    John458 Member Gold Contributor

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    @noorbeast

    opps I checked and it had defaulted to private... should work now... thanks for the heads up
  17. John458

    John458 Member Gold Contributor

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  18. John458

    John458 Member Gold Contributor

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    Well found the problem, one slightly loose wire with the pot connection system.. and then the motor connectors to the saber need to be mirrors of each other not opposites, so right to left motor connectors on the saber 2x32 . Motor 1 (BLACK RED) motor 2 (RED BLACK)..things seem to be working now...just got to finish the back motor mounts and then back to testing with Simtools. See pic below for current power and electrics..(taken before I changed the motor connections) also missing the emergency shut off button and pot noise suppressors.

    SMC Saber setup electrics and power.JPG
  19. John458

    John458 Member Gold Contributor

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    Hi @noorbeast and @Pit

    Hope all is well, just putting the sim back together after a backend rebuild and one of the motors is turning one way faster than the other when running say a square test with SMCUtils, so the feedback pot line gradually gets out of alignment with center.

    Troubleshooting thus far.

    I swapped to my second sabertooth and power supply for my other two motors and same problem.

    I had a chat to motion dynamics and they said I could try and retime the motor, something to do with aligning the brushes and magnets.

    I had already ordered a new motor from them as I thought I had damaged this one. The new motor does the same thing.

    It is being driven with a Sabertooth 2 x 32 and the motor one is moving correctly.

    IM still learning about electronics so my trouble shooting skills are a bit limited but I have my multi meter and im not afraid to use it.. just not sure how :)

    here is a video of whats happening.



    is it the alignment of the motors? seems strange both the old and new motor are doing the same thing.

    Any help would be much appreciated

    Cheers :)

    Attached Files:

  20. bixler13

    bixler13 New Member

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    @John458 Which voltage clamp resistors did you end up going with? Do you have a link? I am trying to find similar ones you are using. Thanks!