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Cousin of OSW (Open Sim Wheel)

Discussion in 'DIY Motion Simulator Projects' started by Gadget999, Sep 23, 2017.

  1. The_Raging_Peacock

    The_Raging_Peacock New Member

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    My Motion Simulator:
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    Took a screenshot of my wheelconfig. I do use lut gen for deadzone correction... It rotates well ibt is powered on but when i plug in arduino it gets harder to turn. Thanks for the ideas guys :) I think going DD will be one of last options because there is a lot to change

    Attached Files:

  2. elnino

    elnino Member

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    Perhaps give a 12v power supply a go? You might find that it gives a good tradeoff between constant force and FFB effects.
  3. elnino

    elnino Member

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    So, after a closer look at the datasheet I can see the problem.

    The 74HC244D requires a 'high' input signal of about 3.5v when running at 5v. It's hard to tell exactly but look at the table below. So using the STM32 @ 3.3v signalling puts it 'out of spec' or at least close to the margin for 5v Vcc and is probably what was causing your problems. Longer and/or thinner gauge wires will make it worse again, as will having slightly higher than 5v going to them.

    In theory, running the IBT_2 modules at 3v will resolve this problem when paired with the STM32.
    2018-11-14_13h07_09.png
  4. Gadget999

    Gadget999 Active Member

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    Guys - i use the RFR A~I-wave wheelcheck software and a Arduino Leonardo on my wheel

    lots of people use the MMOS software

    I have not been able to get this software to work with my wheel, does it work with the leonardo ?
  5. Alexey

    Alexey Well-Known Member

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    MMos FFB only works with the STM32F4 board.
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    Last edited: Nov 22, 2018
  6. Gadget999

    Gadget999 Active Member

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    are there any other advantages to the STM32F4 board - i have one knocking about somewhere - is it worth the effort to upgrade ?
  7. elnino

    elnino Member

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    Apparently not but the Leonardo version is a few revisions older than the MMOs one - It is not obvious what changes were made but also remember even MMOs firmware is several years old and has ceased development AFAIK.

    The STM board needs a very specific chip - What you have laying around might not work but the boards are only about $10.

    The STMF407 chip is a beast compared to the leonardo and beats it by leaps and bounds. It's actually massive overkill for this purpose.
  8. Gadget999

    Gadget999 Active Member

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    i got the stm discovery board out this evening, I was unable to program it last time because the usb cable was broken !

    i have it programmed now

    is there a stm compatible version of software later than the mmo ?
  9. elnino

    elnino Member

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  10. Gadget999

    Gadget999 Active Member

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    the STM discovery board has 2 x usb connections - do both of them need to be powered for the wheel to work ?
  11. Alexey

    Alexey Well-Known Member

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    Yes both need to be connected to the PC. I havent actually read into the documentation to see if you can bypass one of the connectors as one is used for data/power and the other is used for power only.
    I've used both usbs as I am lazy.
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  12. Daguru

    Daguru Rally drivers do it in the mud

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    I used both to program the board but only one to use the wheel after that.
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  13. Gadget999

    Gadget999 Active Member

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    i have programmed the board and it goes green in the mmos program
    i have set the options in setup with 360 pulses per rev

    it is detected when i load up LFS
    however i do not seem to have wheel motion when i connect the encoder
    the encoder is connected to 5v and gnd and to PA0 and PA1 (this encoder has no index)

    do I need pullup resistors to get a signal ?

    am i doing something wrong ?
  14. danove_b

    danove_b Member

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    I'm pretty sure you need pullup's. Just measure with a voltmeter on the PAx lines and slowly turn the wheel. If it's constant zero you need pullups. If it's changing between 0 and 3.3 Volts there's no need for it.
  15. Frederiksen

    Frederiksen New Member

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    It took me forever to read through this thread but I'm glad I did. I am interested in making my own wheel and am debating between a direct drive or belt drive. Gadget999 told me on another thread that a wiper motor would not work for this purpose as it is a worm drive but I read on these threads that people have modified them to make them work in this application. Does anyone know of the modification necessary?

    If I were to take the direct drive path could I use a treadmill motor? The one that I have found for a good price is 90v 2.25hp 4800rpm and 18 amps. Would that work if I ran it off 12v?
  16. Gadget999

    Gadget999 Active Member

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    2.25 hp seems pretty powerful

    18 amp at 90v = 1600 watts

    18 amps at 12v is around 400 watts

    I say give it a go, if you need more power run it at 24v

    Does the motor have much stepping or cogging as you turn it by hand ?
  17. Frederiksen

    Frederiksen New Member

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    I don't know about the stepping or cogging as I haven't seen and don't own the motor yet. I am able to get the motor for $30 USD. Is that a good deal? Also how would I power the motor?
  18. Alexey

    Alexey Well-Known Member

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    Unfortunately it does not work that way.

    18 amps @ 90v = a theoretical winding resistance of 5 ohms (theoretical as I cannot physically test myself, therefore R = V/I)
    So if we run the motor at 12V the expected power of the motor would drop to: I = V/R = 2.4 amps. W = AxV = 28.8 watts.

    Suddenly doesn't sound so good.

    Now, thats not the end of the story. This is because when we use a motor for a FFB wheel the motor is perpetually in "stall mode"
    I'ts not uncommon for a motor to use double the amount of current during stall. But that only brings up the power of the motor to ~60 odd Watts.
    Still not great.

    A DC motor will not always draw the same amount of current with different voltages applied, the current drawn by the motor is affected primarilly by the winding resistance and then will be affected by the rpm.
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  19. Frederiksen

    Frederiksen New Member

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    Ah, so what I understand from what you're saying is it would be better to have a large amount of amps and a small amount of volts to create the smallest amount of resistance. Is that correct? Also do you know how a wiper motor could be modified to work for this project as a belt drive?
  20. Alexey

    Alexey Well-Known Member

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    No. Resistance is not created. I would strongly suggest watching youtube videos on electronics fundamentals to get a good understanding of resistance/voltage/current.

    The best thing you could do in this situation is to copy someone elses project that has information readily available and has been proven to work.
    If you don't know much about electronics then you should not try to make something that has not been made before.

    The wiper motor idea is a dead end. To modify the motor you would need some sort of custom gearbox sourced which in itself would cost more than a motor that would do what you need it to do in the first place. Motors that are ideal for FFB wheel generally are motors used in scooters, electric bikes etc.

    What you first need to do is figure out how much money you want to spend on this project as this will dictate what it is that you can buy in the first place