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thumbwheel potmeter for left-right usage

Discussion in 'Electronic Design' started by Joerg, Dec 28, 2006.

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  1. Joerg

    Joerg Guest

    Hello Folks,

    Been through the usual channels like Digikey. Is there a thumb wheel
    potmeter that has coarse and strong enough "teeth" so an idler wheel (or
    second pot of same type) can be mounted next to it so the wheels mesh?

    Reason is a project coming up where a device needs to be controllable by
    right- and left-handed folks. Kind of like a remote. The potmeter wheels
    coming out the sides of the remote need to go in the same direction for
    both. IOW "forward" for "more".

    The Panasonic EVLHFA seems to go in the right direction but no specs on
    the teeth and the data sheets hardly ever say much about that.
    Definitely not about the material strength for geared usage.
    http://www.panasonic.com/industrial/components/pdf/aok0000ce3.pdf
     
  2. Maybe Alps
    http://potentiometers.com/alps_position.cfm
    and fit your own wheel

    Pity about the 1200MOQ


    martin
     
  3. Brian

    Brian Guest

    Mounting one on the opposite side will make it rotate in the other
    direction.
     
  4. Joerg

    Joerg Guest

    That's exactly what we want. Assume one of them is just a dummy
    potmeter. Then when one sticks out the left side and the other to the
    right the turning direction of the active potmeter when you move the
    thumb forward will become the same.
     
  5. Jamie

    Jamie Guest

    We use mini flat gears for things like that. With gears, you won't
    have any problems with slippage and position falling out of place.
     
  6. Joerg

    Joerg Guest

    If it's not confidential, where do you get flat gears that fit onto
    potmeter shafts?
     
  7. Jamie

    Jamie Guest

    we buy gears were ever we can find them..
    here's a place you can look at gears.

    http://www.sdp-si.com/eStore/CoverPg/Gears.htm
     
  8. Joerg

    Joerg Guest

  9. Brian

    Brian Guest

    I wasn't very clear on that. I meant that if you mount on on the left
    side on the top of the pcb and one on the right side on the bottom of
    the PB, they will both adjust in a forward/backward motion the same.
     
  10. Chris Jones

    Chris Jones Guest

    Does it really need to be a mechanical potentiometer? If you happen to
    already have a microcontroller in this thing, and if you were to put in two
    quadrature encoders (e.g. the cheap ones used in the scroll wheel of a
    mouse, which seem to be mechanical switches even in my optical mouse, so no
    LED power drain), then you could make the value which is being adjusted
    respond to rotation of either encoder in some very easy software. You
    could even use the result to control a "digital potentiometer" if that is
    what you need.

    Chris
     
  11. Guest

    With a largeish single wheel, consider shifting or pivoting the
    mechanism so it
    only protrudes from one side at a time. A DPDT switch that responds to
    the
    pivot or shift motion can change the potentiometer connections (or use
    a simple
    microswitch and some analog-switch elements, or even software).

    Meshing of gears seems so easy, but keeping axles parallel requires
    some complex
    molding or machining.
     
  12. Joerg

    Joerg Guest

    Yes. But I want to mount them on the same side and have the teeth mesh.
    The wheel of the left pot would then come out on the left side of the
    enclosure, the pot on the right would come out the other. You could then
    even hook up both pots in parallel with the polarities reversed, for
    more wiper reliability through redundance.
     
  13. Joerg

    Joerg Guest

    Well, it's all in good old analog right now. Probably will be an ASIC
    some day since uC with next to nothing in power consumption are a bit
    too expensive. But the whole encoder enchilada would have to be as cheap
    as two pots.

    Right now it's up/down keys plus digital potmeter but the client prefers
    a "real" potmeter with tactile and optical feedback which I can
    understand. I was very happy when I saw that the new laptop I ordered
    will arrive with a real potmeter for the volume. Back to the roots. Nice!
     
  14. Joerg

    Joerg Guest

    I've talked about such a scheme with the client but this means lots of
    mechanics. Mechanical parts and switches have a tendency to increase DOA
    rates and field failures.

    We do have access to a good rapid prototyping shop so we can test out
    what would work. The thumb wheels of potmeters you can buy often have
    teeth that are too small to do this reliably. We can tolerate quite some
    slack so coarse teeth plus loose tolerances would work. Pretty much like
    it is done in the "Fischer Technik" experimenters kits for youngsters
    (don't know if those ever made it to the US market). With these you can
    assemble all kinds of complicated gearboxes and they take a heck of
    abuse. Have to, because it's for pre-school kids AFAIR.
     
  15. me

    me Guest

    Been through the usual channels like Digikey. Is there a thumb
    How about a central pot with a gear on it and geared wheels on either side?
    So turning either one turns the pot and the other wheel...
     
  16. Joerg

    Joerg Guest

    That would make the pot turn opposite ways.
     
  17. me

    me Guest

    no, make one gear smaller and have a second gear on it. I'll leave the
    ratios to you.

    Another option is the dreaded dial cord...
     
  18. jasen

    jasen Guest

    Use an open trimpot and put a shaft through the middle. puta a control knob
    each end of the shaft. if that's not right I don't understand your
    description of the problem.
     
  19. jasen

    jasen Guest

    Do that and turning the left wheel forwards will turn the right one
    backward. (IE both will turn counter-clockwise).

    Your second paragraph basically asks for a solid axle with knobs each end.

    Bye.
    Jasen
     
  20. jasen

    jasen Guest

    What does "forwards" mean in your original question?


    Bye.
    Jasen
     
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