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Cousin of OSW (Open Sim Wheel)

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

  1. danove_b

    danove_b Active Member

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    To Benu:

    Correct. I misunderstand you thinking you meaning the feeding voltage not the nominal voltage of the motor.

    To Alexey:
    Of course voltage affect the torque, but again, the torque is proportional to the current, and if I can get the desired current with the lower voltage I see no use for more.... Theoretically if i feed my motor with 36 VDC at stall and had the required supply I should get 241 A and 21,6 Nm... maybe for 1 second...
  2. Alexey

    Alexey Well-Known Member

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    My Motion Simulator:
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    Yes if you only want to use a portion of the available torque then yes by all means lower the voltage. My response was in regards to Benu asking if the running the motor at lower voltage will still get maximum current, which it will not.
  3. danove_b

    danove_b Active Member

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    That's depending of what you define the maximum current as of course...
    In my case as an example:

    The motor is according to the little information that's available can theoretically handle a (average) power loss at about
    220 w if you reverse calculate. (1000 w with a efficiency at 0.78) . So i have set my maximum current by looking at the
    average power loss during a 1 hour race, which ended up with about 85 A. Little bit track depended, but that seems to be a
    good average. To generate that 85 A in current, I only need little more that 11 volts, but the motor is built for 36 Volts.
    And that's because the motor is always in a "stall" mode and doesn't generate any back EMF.

    I made a short video, but I realize that is hard to show what it really feels like. I had my first online race
    last night with the wheel, that didn't went as i expected, but at least I had the least tire wear of all the ones who
    finished the race. I think I can thank the wheel for most of that...

    https://photos.app.goo.gl/m7028CJqpLnvQLTJ3
    • Like Like x 1
  4. Gadget999

    Gadget999 Well-Known Member

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    My Motion Simulator:
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    Good effort - using RF2 ?

    what type of steering wheel do you use ?
  5. danove_b

    danove_b Active Member

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    Yep, RF2 is the one and only now. Once you started with RF2, you cannot go back.
    The wheel is taken from my old Logitech MOMO Red. From the beginning I had
    a pro micro inside and wired connection, but in this movie I have upgraded it with a wireless solution. (Wemos Mini D1 and vJoy)
    • Like Like x 2
  6. ste94

    ste94 New Member

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    Awesome project, i've been following it for some time and i think i'll use the information to build my wheel when i'll be done with pedals/shifters/rig.
    To summarize danove's project, you use a MY1020, 3 BTS7960 in parallel to handle higher Ampere ratings, 2 PSU in parallel to provide more current and used a Pro Micro, correct?. Will it be better if i used a MY1020 48V 1000W and an Arduino Uno or Leonardo?
    Lastly, if you're pleased with the results i think a detailed guide will help a lot of people, since a 7Nm direct drive at less than 200€ will be great, since there isn't a single "wheel only" solution in that price range.
    Thanks again for your work guys!
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  7. danove_b

    danove_b Active Member

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    Was hoping that someone could confirm the function of the BLDC outputs on STM32 with MMos firmware, so we could use a brushless motor like this for example:

    https://www.aliexpress.com/item/12V...04a237c&transAbTest=ae803_5&priceBeautifyAB=0


    The MY1020 actually doesn't fit that well for the mission, although I'm happy with it. If you gonna take out that amount of torque with the MY1020 maybe you should consider a 60 VDC motor and and feed it with 24VDC. It would be the same amount of heat in the motor, but there will be less current to handle with the h-bridge and cables.


    Also a different motor with bigger diameter should be preferable. (Give you more torque with the same amount of magnetic field)
    When I first started to think about a DIY wheel, I was looking to get a second hand hoover-board. It has BLDC motors with a big diameter and must
    deliver a lot of torque. But i didn't see how to fit a encoder to it... And also the BLDC driver thing....

    Skewed rotor or magnets is also preferable (like the BLDC motor i linked to above) to minimize the "cogging", but again, this isn't really a problem for me...

    Buy a leonardo (or the STF32 for the MMOs). All the current already wroten guides will work.
    I bought the pro micro because it has the same chip as the Leonardo, but i didn't realize that
    one of the needed output pin was missing, so I ended up writing my own software that only works with Rfactor2.

    Still consider buying this when they release it. If you already have pedals your satisfied with, the wheel isn't that far from the price range you mentioned.
  8. Benu

    Benu Member

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    Thanks @danove_b and @Alexey for the explanations. It seems to me, that you do not share the same opinion on this. Please correct me if I am wrong.

    I assumed that using the nominal voltage would give best performance as all the components are optimised for that. Using lower voltage should then lead to a performance loss in a specific area. Maybe this area is not relevant as in a DD-Wheel the motor is not used as intended by the manufacturer (spinning at some rpm -vs- stall).

    I still can't wrap my head around it. Doesn't the IBT-2 "translate" the PWM signal from the Arduino into pulses of input voltage to the motor? Even in stall mode these pulses still have maximum input voltage. Having an input voltage lesser than the nominal voltage would reduce performance of the motor. Doesn't higher voltage in this case correspond to better responsiveness of the wheel?
    • Agree Agree x 1
  9. Alexey

    Alexey Well-Known Member

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    Danove and myself have the same view, I am assuming there is a translation error in what we are trying to convey to each other. You are correct in what you have stated. What I was originally posting about was a statement that sounded like in a very basic description was that voltage would not affect the current draw, which is false.

    So yes a lower voltage will produce a lower torque, which means a lower current. Also when you hear someone saying that they need to control the current then really what they are saying is that they need to control the voltage. Current draw will always be I = V/R

    Just as a bit of a bonus to you, PWM is effectively controlling the voltage level. If you were to place a volt meter on a pwm signal then you would read the average voltage of that signal, which is what the motor effectively sees. So a lower %PWM corresponds to a lower average voltage = Lower torque/current/speed and the opposite is Higher %PWM = Higher voltage/torque/current/speed.
    • Like Like x 2
  10. Benu

    Benu Member

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    That looks like a decent and reasonably priced motor even considering shipping!

    Couldn't the Arduino be programmed to output wheel forces to feed the controller? Forgetting about the closed loop with the encoder for a moment, as far as I know the PWM signal just tells the brushed DC motor controller how fast to go. There would be no need then for the MMos BLDC output that seemed to be built to control the three phases of a BLDC.

    Found this link http://www.motorbank.kr/goods/goods_view.php?goodsNo=1000008068#zoom-layer to your suggested motor. Contains some more specs. The motor does not look too bad with a rated torque of 3.8 Nm and it is reasonably priced too. They also offer a controller for the motor.

    Or this power steering motor (EPS) from LG Innotek: http://www.lginnotek.co.kr/en/itk_product/motor-for-electric-power-steering/
    The rack version is listed to have 7.5 Nm torque. They list cogging torque as 0.040 Nm. I haven't found a price for that one.

    Or some EPS from Nidec:
    http://www.nidec.com/en-NA/product/motor/category/A010/B020/P0000142/
    with a momentary maximum torque of 3.9 - 5.2 Nm
    http://www.nidec.com/en-NA/product/motor/category/A010/B020/P0000143/
    with a momentary maximum torque of 4.2 - 7.3 Nm
    Haven't found prices for those either.

    Or maybe these bike/trike motors https://www.goldenmotor.com/frame-bldcmotor.htm
    at 4 - 8 Nm or 6.1 - 9.1 Nm
  11. danove_b

    danove_b Active Member

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    The nominal voltage is perfect if you have plans to run the motor at a nominal speed, like 3000 rpm with my MY1020, but here we talking about 0 rpm...
    As an example when you fit this motor on a bike or whatever, it is very important that you have the correct gearing so it reaches it's nominal speed in a not to long time. Otherwise the current will be to high and the motor will fry.

    I could in theory feed my my H-bridges with 36 VDC (The BTS7960 are max 24 VDC though), but since I'm still are limited to about 85 A to not fry the motor, I must limit the PWM to about 33%.
    100% PWM would result in 36 VDC on the motor and should generate a current about 3 x 85 A if i had the supply that could deliver...


    By limit the PWM to 33%, I should have the same max torque as with my current voltage, 12 VDC, but with much lower resolution on the PWM.
    The Leonardo PWM have a resolution of 400 steps at 20 khz frequency (That's what you want, because your ears cannot hear it).
    So I will end up with a resolution of 0,33 * 400 = 132 steps instead of 400.

    If you find a motor that has a nominal speed at about 300 rpm, the nominal voltage should be fine i think...
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  12. Alexey

    Alexey Well-Known Member

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    My Motion Simulator:
    3DOF, DC motor, Arduino
    You can run motors past the nominal current as long as you provide sufficient cooling directly to the motor windings. So drilling holes in the front and rear face plate and adding an enclosed fan over the face plate will keep the motor cool. I ran a 200W motor at 400W by doing this method.

    For this one I have used some tin sheet. I cutout the side walls, soldered tabs along the edges to make the shell and filled in the air gaps with epoxy. Slots were cut out of the body of the motor instead of the face plate because the gearbox was in the way. Always set the fan to pull air through the motor.
    I am currently making a DD FFB wheel and have come up with a far neater solution and will post when things progress.
    IMG_0554_zpsjik3e7tu.jpg
    • Creative Creative x 1
  13. danove_b

    danove_b Active Member

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    You are absolutely right about that. I'm already feeding my 36 VDC motor with 2.4 times the nominal current with 11.1 VDC.
    That's because when you use it in a ffb wheel application, the motor is always in stall mode. The application in that picture shows a motor that is actually rotating (at nominal speed, or close to it) when you feed it with voltage. To increase the nominal current at nominal speed, you must increase the nominal voltage...
  14. Vdub180

    Vdub180 Member

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    Hi ive just started building mine but have some issues the the CWZ6C encoder, Dont seem to be active on the RFR wheel config, ive tested the buttons with the ard and they work but not the encoder, any ideas please.
    rig.jpeg WhatsApp Image 2018-03-31 at 11.54.16.jpeg
    WhatsApp Image 2018-03-31 at 12.10.27.jpeg WhatsApp Image 2018-03-31 at 14.18.16.jpeg
  15. Gadget999

    Gadget999 Well-Known Member

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    My Motion Simulator:
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    You may need a pullup/pulldown resistor
  16. Vdub180

    Vdub180 Member

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    Pull-up pull down what's that then lol is it right I need to add 5v to each signal wire to encoder with 4.7k resistor to get it working like this
    IMG-20180331-WA0028.jpeg
  17. Vdub180

    Vdub180 Member

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    Like this one wired as above

    Attached Files:

  18. Gadget999

    Gadget999 Well-Known Member

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    My Motion Simulator:
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    Yes for pull up use 5v to signal

    For pull down use gnd to signal
  19. Vdub180

    Vdub180 Member

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    What would u do on signal ground or 5v
  20. Gadget999

    Gadget999 Well-Known Member

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    My Motion Simulator:
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    Use 5v if it does not work try gnd instead

    Your encoder will either send 5v or pull to gnd