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Tutorial DIY load cell brake pedal (short tuto)

Discussion in 'DIY peripherals' started by RacingMat, Nov 26, 2014.

  1. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    Take an unused bathroom scale @10€ or buy load-cells at eBay
    20130608213747-RacingMat-Load-cell-pese-personne-2-.JPG

    you got this piece :
    20130608213833-RacingMat-Load-cell-pese-personne.JPG

    You need 2 load-cells to make a wheatstone bridge :
    20130627205348-RacingMat-montage-ampli-op-5.jpg

    Check the 3 wires to find the wire in the "middle"
    20130613214516-RacingMat-jauge-contrainte-pese-personne-7-.JPG 20130613214431-RacingMat-jauge-contrainte-pese-personne-4-.JPG
    check the 3 combination, you should obtain 2 equal measures and one twice bigger
    2000 ohm blue - white
    1000 ohm red - blue
    1000 ohm red - white

    hence wire the red (middle) to the Amplificator
    blue Loadcell 1 with white Loadcell2

    You can make a small board or use a protoboard
    20130703111143-RacingMat-PCB-loadcell-adjustable-gain.GIF

    20130720182509-RacingMat-platine-load-cell-2-.JPG

    you need
    - operationnal ampli (INA122PA ou INA125) to amplify the signal 6€
    - condensator to filter 100 nF
    - resistor to adjust the gain 1,0 kΩ cermet 25 tours

    20130720182449-RacingMat-platine-load-cell-1-.JPG
    based on the design of Andrew on www.hux.net

    or you can buy a dedicated board
    - derekspearedesigns
    Freestanding Load Cell Amplifier with Variable Gain LCA1C à 26$
    - another board 28$ chez Elane.net

    it works!



    more information in french here
    http://www.racingfr.com/forum/index.php?showtopic=46056
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    Last edited: Oct 13, 2015
  2. Pit

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

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  3. mazak515

    mazak515 Active Member

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    bon voilà j'ai des pb de freins sur certains jeux, je réfléchis depuis un bon moment a un système avec un capteur de préssion
    pour le moment j'ai rajouté un gros amortisseur de modelisme 1/5, il est aussi long que le truc rouge de la pedale du g25,
    ça procure une bonne sensation, mais pas un rendu réel ! vu que je fait du modelisme j'ai essayé plusieurs truc, huiles ressorts etc j'arrive vraiment a un rendu assez réél, mais electroniquement c'est pas ça !
    j'ai donc quelques questions ... avec ma voiture la vraie lol !
    quand je freine il y a un mou, puis ça durcis ... puis si tu continus tu finis dans le volant !
    bref l'idée c'est de coupler un potar et un load cell, deja est ce que ce serai possible, pour un le potar reproduire la course de la pédale jusqu'au point dur repris par un loadcell
    alors ?
    right now I have bp brakes on some games, I think for a long time has a system with a sensor préssion
    this time I added a big damper modelisme 1/5, it is as long as the red tip of the pedal g25,
    it gives a good feeling, but not one made real! since I made the modelisme I tried several things, oil springs etc. I really can has made quite real, but that's not it electronically!
    so I have some issues with my car ... lol true!
    I brake when there is a soft and hardened it ... then you end if you continued in the steering wheel!
    in short, the idea is to couple a knob and a load cell, already is what it will be possible for the knob replicate the travel of the pedal until you feel taken over by a loadcell
    then?
  4. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    no need to do that in my opinion...
    I made this sketch in the french post:

    you just have to use 2 different springs at different location and a hard sleeve.

    first spring:
    - between pedal and basement
    - not connected to load-cell
    - only here to find the pedal under your foot
    - like in your car: first you "feel" the pedal and the first centimer you press but no pressure is applied on brake
    - rather weak spring

    second spring:
    - this spring is between pedal and load-cell
    - the pressure is converted into braking
    - rather strong spring
    - in your car, your foot can still go down and braking is effective

    hard sleeve:
    - between pedal and load-cell
    - the total pressure (less the first weak spring) is full applied to the load-cell
    - no pedal travel is possible
    - pressure = braking at no move
    20130930113650-RacingMat-spring-load-cell-brake-pedal.png
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  5. WowaDriver

    WowaDriver Waldemar Jost

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    Hi Racingmat,

    will it work also fine with only one load cell? I will buy the leo bodnar
    USB controller board, but his LC amplifier are only fixed ones and the DSD
    ones are to expensive. So i'm searching for an DIY alternative!

    My Plan is to use only one 150kg load cell for the brake pedal, like the HE Ultimate/Pro ones...
    So my questions is if your circuit works fine for my sultan too?

    Best regards

    Waldemar Jost
  6. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    @WowaDriver : what are the specs of your load cell?
    like this one?
    3133_0_Web.jpg
    if so it will fit. You can see 4 wires because it is in fact 2 load cell in wheatstone bridge ;)
    It only requires to output 0-5V range (for 0 to 150 kg range)
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  7. WowaDriver

    WowaDriver Waldemar Jost

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    Thanks Racingmat for your reply. Yes it would be a load cell like the one you post with the normal structure of 4 wires... And i thought the output range is between 0-5V!
    Thanks a lot, so i have to experiment with it! Thanks again!

    Didn't remember that there are to DMS on the stick :D
    Last edited: Jul 24, 2015
  8. WowaDriver

    WowaDriver Waldemar Jost

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    @RacingMat Here is the link to the loadcell i want to use... There stand Rated Output 2 mv/V do you mean this with our statement about 0-5V output range? Or do you mean the
    Recommended Excitation? Than this AMP wouldn't works with this load cell i think? or i'm wrong?

    http://www.mavin.cn/productsmore.aspx?CateID=168&ProductsCateID=168&ProductsID=259

    If it wouldn't work fine with these loadcell, do you can change the parts for this load cell? The curcuit must be the same i think, have only to change the chip and pot i think or?
    Last edited: Jul 25, 2015
  9. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    Attached Files:

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  10. WowaDriver

    WowaDriver Waldemar Jost

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    Just tested out right now! It works! But i have a little
    sough at the beginning... is that normal?
  11. RacingMat

    RacingMat Well-Known Member Gold Contributor

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  12. WowaDriver

    WowaDriver Waldemar Jost

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    @RacingMat no not a humming sound... what i mean is, when you go to the joystick settings (in my case the bonder USB board) than you will see the scale for the load cell. If the variable gain is completely of, so i mean the pot is full turn in one direction (left) to be off, the scale is still at one position. But if i adjust the variable gain with the pot, the scale work faster right, but at the beginning it doesn't be still on one position. If i can say it extremely: It jumps left right on one point.
  13. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    "sough" translation was bad :-/

    what amplifier are you using?
  14. WowaDriver

    WowaDriver Waldemar Jost

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  15. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    You should check your soldering carefully... Maybe?

    Or check your Gain pot linearity: if pot is broken, it could behave like you describe
  16. WowaDriver

    WowaDriver Waldemar Jost

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    Hmm i think the pots can't be broken... They are new ones and i tested it out with two different pots... with the one the effect was much bigger than with the other one... The soldering have to be correct... i mean it is a very simple soldering, but will check it too. When i've got news i will to inform you! May it is a prob with the load cell itself... was just an cheap alternative from amazon to test your circuit ... will test it in 4 weeks with my load cells from mavin...
  17. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    please post some pictures :)
  18. WowaDriver

    WowaDriver Waldemar Jost

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    @RacingMat Yes sure no problem. But please don't laugh... it is only a ten minutes prototype to test :D ...

    I tested out also a normal pot too... It didn't have the precision of the blue one, but it works too
    IMG_1394.jpg IMG_1395.jpg
  19. fzxj520

    fzxj520 Member

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    Will this one be OK?
    TB2avA4dFXXXXcPXXXXXXXXXXXX_!!1026430339.jpg_430x430q90.jpg QQ图片20150910213513.png
  20. RacingMat

    RacingMat Well-Known Member Gold Contributor

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