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New build, arduino, motomonster, 2dof

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by substatica, Jan 2, 2015.

  1. substatica

    substatica Member

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    Hey all,

    Phil here, looking to start a new motion platform build and want to make sure I'm understanding the core concepts correctly thus far.

    I think 2dof will suit my purposes, as if I'm not mistaken I can get pitch and roll simultaneously with 2dof, I've attached a crude mock-up of the initial plan showing a combination of motor directions and resulting platform angle, if folks could let me know if this is off in some way that'd be great.

    Are mounting holes the only reason some motors come in left and right versions? For the motors I'm looking at, I don't see any mounting holes so I'll have to make brackets I would think.

    Components

    2x - 12 Volt Gear Motor, 150 RPM, 25/1, 180 W, 30-40 NM
    2x - Linear 10k Pot
    1x - Monster Motor Controller Shield
    1x - Arduino

    As I understand it, not counting additional software the arduino reads the pots for motor position and then sends a PWM signal to the moto shield for each motor, the PWM determines the speed of the rotation and duration of the PWM signal determines the amount of rotation, since the rig should only use a quarter or so of the motor's rotation how does one avoid over torquing and destroying the pots? Also, any leads on an appropriate power supply easily available in Canada, as well as safety features I could build in, that'd be great!

    Glad to have found this community, I was going to go with Linear Actuators until I found these forums and learned most folks go with DC motors.

    2dof.jpg
  2. Ads Master

    Ads Master

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  3. substatica

    substatica Member

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  4. value1

    value1 Nerd Staff Member Moderator SimAxe Beta Tester SimTools Developer Gold Contributor

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    My Motion Simulator:
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    Hi @substatica
    15 A is not enough. You'll need about 30 A per axis. So you better look for two power supply units with 30 A or one with 60 A. A decent PC PSU will do.
    • Agree Agree x 1
  5. substatica

    substatica Member

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    Okay, I've got a bunch of those laying around then.
  6. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
    3DOF, DC motor, JRK
    • Like Like x 1
  7. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    My Motion Simulator:
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    have fun with your project!

    you may find an arduino code fitting motomonster in my signature ;)
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  8. substatica

    substatica Member

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    Thanks! Initially the setup, assuming it turns out safe, will be used as a base for my infant son's bassinet -- this is why I was asking about safety features, I was thinking an accelerometer I can read to kill the power if any undue force is detected. I'm hoping to program some smooth wave, walk, rumble motions. Then when he's a bit older I'll replace the bassinet with a seat and controls and convert it to a simulator of some sort.
  9. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    My Motion Simulator:
    2DOF, DC motor, Arduino
    I had the same concern :)
    Maximum speed is a parameter of the code: low value makes the movment smooth and calm.

    Adding an accelerometer on top of this would be possible, some simple lines code to add...
    • Informative Informative x 1
  10. substatica

    substatica Member

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    One thing I don't have is a lot of metal working tools, a small MIG welder, drill press, grinder, that's about it. It looks like the motors I'm planning on buying need shafts, pivoting arms and linkages, I ordered two of these Heim Joints, does anyone have a go to place online where I could source more of the linkage parts?
  11. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    You will find plenty of sources for heim joints on Ebay.

    The levers and rods are for the most part specific to the design of each sim so make those to suit. Leavers generally have the holes 40 - 60 mm Center to Center, mine are drilled for 40, 50 and 60mm CTC.

    The rods depend on the design. Material wise they do need to be substantial as stuff like threaded rod would flex under the loads. You can use say 30 or 40mm box steel with nuts welded either ends to take threaded rod for the heim joints. My rods are billet aluminum, that is unusual but easy to make. Take solid round bar aluminum drill and tap a hole either end.
  12. substatica

    substatica Member

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    This shaft, cut down to size, should work for the 1/2" motors I referenced above and these couplings should work to attach the pots, no?

    1/2 in. x 3 ft Keyed Shaft
    2x - 1/2 in. Shaft Coupler

    I'll try to give back to the forums with a full parts list, how-to and results when it's all done ;) Thanks for the help!
  13. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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  14. eaorobbie

    eaorobbie Well-Known Member Staff Member SimTools Developer Gold Contributor

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    My Motion Simulator:
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    Sorry but your motor position is in the worst case scenario , your motors will have to work too hard to gain any real fluid or sim comparable motion. specially with 25:1 boxes, it doesn't work. People have tried this and it fails badly , again Sorry.
    • Informative Informative x 1
  15. bsft

    bsft

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    @substatica , I agree with Rob, your kid and your weight are two massive differences.
    If you develop a code that gently rocks the kid, then yes, but DO NOT put a race track through it or even a roller coaster.
    Also, design is bad, after 14 designs, depending on how much overall weigh you plan to put on it, you will have to move the motors to connect a lot higher, like a foot motor mount or shoulder mount at rear.
    You could use 50:1 or higher boxes and use like a taller desk racer mount on the side, but again, platform design needed.
    People have done this sort of design over and over and they eventually had to rebuild and or re-design. Even me.
    I have pictured a foot motor mount, where obviously your feet would sit, so make the motor connections are higher than your toes.
    This keeps the design compact and will perform better.
    2dof.jpg
    • Informative Informative x 1
  16. substatica

    substatica Member

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    So you're both saying I need the arm mounts on the platform to be higher? This build will not be for me, just the kid, I may re-purpose the setup later for a chair. I also asked the motor seller if they could send me 50:1's which they also offer instead of the 25:1's I won the auction for.
  17. SilentChill

    SilentChill Problem Maker

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    My Motion Simulator:
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    I would recommend buying hall effect pots too as they are far superior to the normal pots only slightly more expensive but worth it.
    • Agree Agree x 1
  18. bsft

    bsft

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    @substatica , if its for your child, then yes 25:1 and the current frame design will be fine.
    Its just later if you plan to convert it for yourself, then you may need to look at frame re-design and different gearboxes.
  19. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    My Motion Simulator:
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    It would help greatly if the connection mount is about seat swab height. This is my compact sim and it is now running 60:1 gearboxes, as 25:1 were not up to the task: http://www.xsimulator.net/community/threads/dx-racer-compact-simulator.5866/page-7#post-67552
  20. substatica

    substatica Member

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    I ordered a couple of these to use as pots, initially at least, do you have an example of the type of flexible coupler you're referring to? All I found is hoses with hose clamps when I search for that. Planning on writing my own software, initially at least as it won't need any sim interface, only some pre programmed motions which I can stream or hardcode on the Arduino. I've also got a spare RasPi kicking around I can use to talk to the Arduino.

    I appreciate all the help, if folks are interested I maintain a blog with other projects I've undertaken,

    http://unmaintained.com/
    • Like Like x 1
  21. bsft

    bsft

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    so you are not going to use Simtools then?