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Question Increase Pot range ??

Discussion in 'Electronic and hardware generally' started by jasod943, Dec 1, 2021.

  1. jasod943

    jasod943 New Member

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    Hi everybody ,

    I get some trouble with my Potentiometer fcp22e .

    the maximal and minimal is too short , ineed to increase the motor or potentiometer range
    here is a picture of my problem :
    [​IMG]
    [​IMG]

    How can i solve this please ?
    in smc3 code or simtools ??

    thanks by advance for the help ;)
    jasod943, Dec 1, 2021
    #1
  2. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    noorbeast, Dec 1, 2021
    #2
  3. Zed

    Zed VR Simming w/Reverb Gold Contributor

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    It looks like your issue is not enough change in resistance over that small angle which can effectively decrease resolution.

    Some gear the potentiometer to get more change in resistance for a certain amount of arm movement but you want to watch out for backlash.

    If you decrease your arm length, your motor will have to rotate further to get the same amount of movement in the sim which will also increase the amount of resistance change you see. It will also give your motors more mechanical advantage for more force on the rig while making gear backlash less noticeable.

    You can also switch to a higher resistance pot that will give you more ohms per degree.

    Just my own opinion but especially in situations where you are stuck with sensing a small angle of rotation, I’d switch to a Hall sensor that is specifically designed to show full range over a small angle. They tend to be less noisy than pots and being able to get them configured for small angular rotations is a bonus. A lot of circuits excite the potentiometer to get a voltage off the wiper proportional to position and most Hall sensors output a similar voltage. I used Halls on my sim and the Pololu 12V12 controllers. The Hall sensors I used were a drop-in replacement for pots.
    Zed, Dec 1, 2021
    #3
  4. jasod943

    jasod943 New Member

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    hello noorbeast , i've already set the max limit in smc3utils but doesn't effect the range
    [​IMG]

    is it possible to divide the potentiometer value by 2 in smc code ?
    or any other idea ?

    maybe the problem is the potentiometer ?
    fcp22e
    jasod943, Dec 1, 2021
    #4
  5. jasod943

    jasod943 New Member

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    hello zed ,

    maybe i can try to switch to a hall sensor and see what happen .
    do you know a good hall sensor reference ?
    jasod943, Dec 1, 2021
    #5
  6. Gadget999

    Gadget999 Well-Known Member

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    If i rember correctly you can use a extra pot to adjust the smc3 sensitivity

    You may also be able to put a resistor across the output to create a voltage divider

    It is best to chamge the pots for 180 degree pots that are hall effect as zed suggested
    Gadget999, Dec 2, 2021
    #6
  7. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    Your Max limit is set to zero.

    Clip Input is very low.

    Clip Input Used to create a band at either limit of the target range beyond which any values sent to the SMC3 are clipped. In addition to this clipping, if the motor feedback does move beyond this range (typically through inertia), the SMC3 will attempt to brake the motors hard by driving them in reverse until they are back out of this limit zone. The value can be anything from 0-255 (however can’t be less than the current limit setting). Reverse braking is applied in the band between the Clip Input and the Max Limit settings. Reverse braking can be disabled - refer to PWMrev.

    Max Limits Used to create a band at either limit of the feedback range beyond which if the motors move (typically through inertia) the SMC3 will automatically shutdown the drivers and keep them disabled until reset. This is essentially a safety mechanism if something goes wrong. The value can be between 0-255 (however can’t be greater than the current clip setting).
    noorbeast, Dec 2, 2021
    #7
  8. jasod943

    jasod943 New Member

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    yeah noorbeast it was for tests but whatever if i add clip and max limit it doesn't change the range .
    i'm gonna testing with hall sensor but the Pot come from china so i need to wait :(
    jasod943, Dec 2, 2021
    #8
  9. Zed

    Zed VR Simming w/Reverb Gold Contributor

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    Apologies. i thought you were trying to get full pot travel over the limited range and was answering that which is totally not what you were asking.

    If you’re getting the full swing on voltage over just those 20 degrees or so and want it to instead be over that longer range, I’d listen to Noorbeast.
    Zed, Dec 2, 2021
    #9