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Potentiometers

Discussion in 'Motor actuators and drivers' started by Andrea 1968, Sep 20, 2015.

  1. Andrea 1968

    Andrea 1968 Member

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    hi, I wanted to point this link, I got them, I tried are great.
    http://www.ebay.it/itm/261797870478?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT
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  2. Ads Master

    Ads Master

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  3. speedy

    speedy Well-Known Member

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    I see they are 5k Ohm and the stander pot resistors that most controllers commonly use is 10k Ohm ...
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  4. Andrea 1968

    Andrea 1968 Member

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    I am not an expert on electronics but I think it's just a difference of current consumption .
    I = V / R
    I = 5/5000 = 1 mA
    I = 5/10000 = 0.5 mA
    the difference and small !!
  5. speedy

    speedy Well-Known Member

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    Hi @Andrea 1968 ...
    FYI, the choice of the 10K Ohm has nothing to do with the current consumption.
    It is a standard value made many years ago for many appliances as far as my readings based on the best linearity ,best output signal sensitivity plus many many different factors.
    you can read more on this FAQ link about Fundamentals of Motion Control .
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    Last edited: Sep 22, 2015
  6. Alexey

    Alexey Well-Known Member

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    As long as it is a quality pot, there shouldn't be a problem with a 5K pot. Most issues arise in potentiometer selection where low input impedance is present. The Arduino ADC has a very high input impedance so current draw isn't an issue and the regulated supply isn't going to be affected by a 5k pot so there isn't an issue there either. Linearity differences between a 10K pot and a 5K pot would only depend on quality control from the manufacturer. Sensitivity would only be effected by the amount of turns in the pot and the resolution of the ADC in the micro controller.
    In terms of feedback in motion control you are looking at voltage change and so in a high frequency environment issues would arise if you were to use pots with values over 100K as they start to get really noisy and that noise on the DC signal can get picked up by the ADC.

    A 10K pot is commonly used in micro controller/logic based systems just because it is a common and easily obtained value.

    Most issues with potentiometer selection comes down to sine wave (or any type of frequency source) applications as they change the filter response in the system overall. Issues also arise if your sensing output requires a given amount of current. The value will also depend on your circuit were other values of resistors are used in series/parallel and would change voltage/current values within the circuit.
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  7. Andrea 1968

    Andrea 1968 Member

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    good explanation, as soon as possible and we will try those 10k'll check if there are differences.
  8. pedrono2

    pedrono2 New Member

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    Hello,
    please What are the best.?
    the lower the value the better.? Not so burdened Arduino processor
    thanks
  9. SixCyl

    SixCyl Member

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    The best result that can be obtained is with better quality potentiometer as possible and not a question of value only.
    Try to write a small code on an arduino board with serial interface and connect a pot in analog pin of your choice and play with it ! If you look at your value in realtime she fluctuate anymore with cheapest potentiometer ! has the quality of the potentiometer depends the quality and the linearity along the range of signal ...
    There are some solution for reduce noise on sensor reading but it's not the subject now. Maybe on another post ?
  10. SixCyl

    SixCyl Member

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    But the really things important are the quality before all on the position sensors !
    Better signal = less parasitic fluctation on the seat.
  11. TFOU57

    TFOU57 Member

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    @Alexey, Thank you for your explanations
    For my part I have Arduino Due ADC with 3.3V and I already have 360 potentiometers with 340 ° race but 20Kohm
    What do you think of these 20Kohm potentiometers with 3.3V?
    Do you think I would gain an important (%?) With potentiometers for 10Kohm Feedback?
    From what I understood from your explanation is that the noise on the DC signal picked up by the ADC affects so depending on the intensity in the covered pot.
    I saw that you can put a non-polarized capacitor between the negative terminal and the cursor.
    The value that I sometimes observed is 100nF.
    How determined?
    By a formula based on the loss of response time arising from the smoothing of the signal?

    Texte original :
    @Alexey, merci de vos explications
    Pour ma part j’ai des Arduino Due avec un ADC en 3,3V et j’ai déjà des potentiomètres 360° avec une course de 340° mais en 20Kohm
    Que pensez vous des ces potentiomètres 20Kohm sous 3.3V?
    Pensez-vous que j’aurais un gain important ( % ? ) avec des potentiometers de Feedback de 10Kohm?
    D’après ce que j’ai compris de vos explications, c’est que le bruit sur le signal DC ramassé par l'ADC influe donc en fonction de l’intensité parcourue dans le potentiomètre.
    J’ai vu que l’on peut mettre un condensateur non polarisé entre la borne moins et le curseur.
    La valeur que j’observe parfois est de 100nF.
    Comment la déterminer ?
    Par une formule en fonction de la perte de temps de réponse découlant du lissage du signal ?
  12. speedy

    speedy Well-Known Member

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    @TFOU57 ...
    Can you search in Google for three or four questions at the same time ?
    Why ?
    What language ?
    Elaborate more ?

    Thanks
  13. TFOU57

    TFOU57 Member

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    @speedy, Sorry, i'm French and I translated by Google Translate.
    If several questions at once bothers you, I will separate my questions

    Is the use of a feedback potentiometer 20Kohms increases the signal noise ?
    (I already have 20kohms potentiometers on 340 ° and my ADC Arduino Due is 3.3V)

    Texte original :
    @speedy, Désolé, je suis Français et j’ai traduit par Google Translate.
    Si plusieurs questions à la fois vous gêne, je vais vous séparer mes questions

    Est-ce que l’usage d’un potentiomètre Feedback de 20Kohms augmente des bruits du signal ?
    (J’ai déjà des potentiomètres 20kohms sur 340° et mon ADC de l’Arduino Due est 3.3V)
    Last edited: Oct 31, 2015
  14. Cvetan Cvetanov

    Cvetan Cvetanov Member Gold Contributor

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    I think just 3.3v is low than 5v and noise is the same but in your signal is proportional increased with 1,5 times. Pot is just for dividing voltage.
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  15. bruce stephen

    bruce stephen Hammer doesnt fix it, must be electrical

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    How the potentiometer is mounted on the rig and the amount of force it takes to turn the potentiometer can also affect performance. I started with very inexpensive carbon film pots. They worked ok with with a little noise pollution to start but wore out quickly. This resulted in oscillation because of the worn pot. So then I switched to cheap wire wounds these worked ok but were harder to turn. The difference resulted in a flex of the mounting bracket which again introduced oscillation. So I finally bit the bullet and ordered non contact potentiometers, also known as magnapots. The best investment, they are about 15.00 dollars each as compared to the others I only paid a couple dollars each for . I have almost completely eliminated oscillation while being able to turn up the power. I use the 8858-6127V1A360L.5FS from Www.mouser.com.

    What I'm getting at is SPEND THE MONEY ON GOOD POTENTIOMETERS you don't have to invest a million dollars but stay away from the cheap stuff.
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  16. Alexey

    Alexey Well-Known Member

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    Anyone got any links to hall sensor pots/magnepots on ebay? All I seen to get is throttle position sensors on the search returns. I've found them on element 14 website but they are priced at $30. So if i can get them slightly cheaper on ebay that would be great but if not.... Element14 it is.
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  17. bruce stephen

    bruce stephen Hammer doesnt fix it, must be electrical

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  18. Stealthelius

    Stealthelius Member

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    Ciao @Andrea 1968. Io ho preso i potenziometri che hai linkato sul primo posto e vanno benone. Puoi dimenticare anche il glifo oscillante :thumbs
  19. josemanuelrm26

    josemanuelrm26 my 2dof

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    hola mount 100k potentiometers in error and did not work well simulator. Now with 10k it works fine but the mechanical are cheap. the better the hal. do not?
  20. bruce stephen

    bruce stephen Hammer doesnt fix it, must be electrical

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    yes hall is better.
  21. Nick Moxley

    Nick Moxley Well-Known Member

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    Hall effect's are 100X more durable as well. I had a Pot lock up back when i first started and sure as shi* its still alive to this day, and to think back. I had a BIG a** pair of pliers on that sucker to get it turning again but once the flex coupler's were installed it was smooth sailing from there on out. $ for $ Hall effects are 1000% worth the investment.
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