Linear Potentiometer with 60-degree Rotation

Discussion in 'General Electronics Chat' started by monster_catfish, Apr 8, 2011.

  1. monster_catfish

    Thread Starter Active Member

    Mar 17, 2011
    110
    107
    For the past few weeks I have scoured the net in search of a linear-taper rotary potentiometer whose full-scale deflection is limited to 60 degrees. Such rotary pots are evidently used in most joystick applications, yet my extensive searches have so far only located linear-taper, single-turn rotary pots designed for 300 to 350 degrees of angular deflection.

    I already have a work-around solution in mind, which entails running the output of a 350-degree rotation linear-taper pot through a non-inverting amplifier with a gain of 5 or 6, so as to produce the full 5-volt swing over the 60-degree limited rotation of my DIY throttle lever, BUT, I would rather not add that extra circuitry if there does in fact exist a 60-degree rotation potentiometer that will give me that 0 to 5 volts output without the need for signal amplification.

    So, I would be very grateful if any of you seasoned circuit-meisters would point me in the right direction to the website of a reliable vendor that stocks linear-taper, 60-degree rotation 100Kohm potentiometers. I wouldn't bother you guys with this question if I had not myself conducted an insanely long search for a rotary pot with the above specs. :(

    Thanks in advance

    Tony
     
  2. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    Just use silver conducting paint to paint over the remaining portion of the circular resistance track which you don't want to have any resistance.
     
  3. monster_catfish

    Thread Starter Active Member

    Mar 17, 2011
    110
    107
    That is truly an innovative idea that I have never encountered, Mr.Chung. I may well wind up trying out this method if I am unable to locate a 60-degree rotation linear-taper pot, though applying that conductive paint does sound like a delicate task that would require some precision work to produce the right results.

    All the same, if there happens to be anyone who can still think of a vendor for the part I really need, I would be grateful to hear of it, though it is good to know that a Plan B alternative exists, if my search is ultimately futile.

    Thanks
     
  4. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,004
    1,525
    With all the game controllers out there why not just get one from a unused game box and pull one of the pots from it? 'Green electronics.' :)
     
  5. kingdano

    Member

    Apr 14, 2010
    377
    19
    why not use mechanical stops?
     
  6. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
    141
    +1

    It's usually straightforward to put a pin in the knob and have it sit in a circumferential slot in the panel. It's easy to lay the slot out with dividers, chain drill it, then file it to shape.
     
  7. monster_catfish

    Thread Starter Active Member

    Mar 17, 2011
    110
    107
    Shortbus I may wind up going the recycling route as you suggest. I have a couple of old joysticks laying around here, which I may wind up "sacrificing" for use in the throttle quadrant I'm cobbling together. Still and all though, I do find it a bit odd that 60-degree linear-taper pots, despite being so common in assembled products, are as scarce as hens teeth when sought off the shelf.

    Should I opt to spare my "donor" joysticks from surgery, the fabrication of rotation-limiting stops described by Kingdano and Someonesdad might just be the fix that would suffice, to limit the deflection of a 350-degree rotary, linear-tapered potentiometer of the sort commonly available.

    Guys I sure do appreciate the alternative fixes described here, but just in case anyone does recall a internet link advertising off-the-shelf linear taper pots with that 60-degree rotation spec that I seek, I'd still default to a new purchase if that option materializes before the construction is complete.

    Regards

    Tony
     
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    I saw the insides of many joysticks over a lot of years. Most had standard 270' POTs that were positioned so that only the bottom 60' or so was used.
     
  9. monster_catfish

    Thread Starter Active Member

    Mar 17, 2011
    110
    107
    Now that is an eye opener, RB. It is beginning to look as though the fabled 60-degree rotation pots are not as common as I once assumed. I might have to stop holding my breath in anticipation of finding one, and just select one of the practical hints provided here.
     
  10. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    Yeah it was pretty common to use partial rotation of the pots and the PCB in the joystick would have an opamp with a couple of trimpots to "trim" (and I assume amplify) the joystick pot voltages.
     
Loading...