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hooking up a potentiometer — Parallax Forums

hooking up a potentiometer

ArchiverArchiver Posts: 46,084
edited 2000-04-03 20:33 in General Discussion
In a Basic Stamp breadboard project I'm building one of the parts used is a
manual potentiometer. This part has three pins in a "triangle"
configuration and I'm confused as to how to wire it up. Are potentiometers
the same as resistors in that the connected direction is irrelevant or do
each of the pins have a specific connection requirement like an IC?

Thanks,
/* Andrew */
Software Engineer
BSQUARE Corporation
email: andrewt@b...
phone: 425-519-6103
homepage: http://www.halcyon.com/ast

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2000-04-03 18:58
    In every case I've ever seen, the two ends will be across the entire
    resistance. A 10K pot, for example, should read 10K between those two pins.
    The middle pin will be the wiper and will change as the knob changes. The
    difference between the ends will be the amount of resistance. For example,
    say you twist the knob to 25% of full scale. The R between the center and
    one pin will be 25% FS and the other pin will read 75% of full scale. So how
    you wire it can influence what "up" and "down" looks like. Usually you want
    clockwise motion to be "up" but that doesn't always mean more resistance. To
    turn up volume, you might decrease resistance.

    You often see one side shorted to the wiper. That's ok because it just
    shorts out the part you aren't using. This makes the 3 terminal poteniometer
    into a 2 terminal device that has varying resistance.

    Hook and ohmmeter up to your pot and you'll quickly see what I'm saying.

    On the subject, some pots are linear (sort of). That means that 25% turn of
    the knob should get you about 25% of the R and 75% should get you 75%.
    Others are "audio taper". That's because your ears are not linear. If you
    made a linear volume control you'd find most of the useful volume bunched up
    at one end. An audio taper pot has a log response that more closely matches
    a normal ear's response.

    Not sure if that pegged your question or not.

    Regards,

    Al Williams
    AWC
    * Stamp project of the month: http://www.al-williams.com/awce

    BSquare... the Windows CE guys, right?


    >
    Original Message
    > From: Andrew Tucker [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=rh3xa9_Syw5i1dOXZBkPjM9eRLuzcubJaeBNvl8wZr7Sh7kgbyumQVJIUXEUKl2Ibz2dcZsVmHOH6E-xPPE]AndrewT@b...[/url
    > Sent: Monday, April 03, 2000 12:43 PM
    > To: 'basicstamps@egroups.com'
    > Subject: [noparse][[/noparse]basicstamps] hooking up a potentiometer
    >
    >
    >
    > In a Basic Stamp breadboard project I'm building one of the parts
    > used is a
    > manual potentiometer. This part has three pins in a "triangle"
    > configuration and I'm confused as to how to wire it up. Are
    > potentiometers
    > the same as resistors in that the connected direction is irrelevant or do
    > each of the pins have a specific connection requirement like an IC?
    >
    > Thanks,
    >
    >
    > /* Andrew */
    > Software Engineer
    > BSQUARE Corporation
    > email: andrewt@b...
    > phone: 425-519-6103
    > homepage: http://www.halcyon.com/ast
    >
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2000-04-03 19:00
    Andrew:

    The 2 outside pins are the ends of the actual resistor, the middle pin will
    be what is called a wiper. depending on which way you connect the 2 outside
    pins, will determine in which direction the resistance either increases or
    decreases at the middle or wiper pin.

    Hope this helps, let me know if you need any further info. I could draw a
    simple schematic and send it to you.

    Randy A.
    cnc002@a...
  • ArchiverArchiver Posts: 46,084
    edited 2000-04-03 19:17
    At 10:43 AM 4/3/00 -0700, Andrew Tucker promulgated:
    >
    >In a Basic Stamp breadboard project I'm building one of the parts used is a
    >manual potentiometer. This part has three pins in a "triangle"
    >configuration and I'm confused as to how to wire it up.

    Where did the part come from - manufacturer and part number ?

    Are potentiometers
    >the same as resistors in that the connected direction is irrelevant or do
    >each of the pins have a specific connection requirement like an IC?
    >
    >Thanks,
    >
    >
    >/* Andrew */
    >Software Engineer
    >BSQUARE Corporation
    >email: andrewt@b...
    >phone: 425-519-6103
    >homepage: http://www.halcyon.com/ast
    >
    >
    >
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2000-04-03 20:33
    This really confused me for a while too. Think of it as two resistors. The
    center pin common for both. You have a 10k limit. When one resistor goes up,
    the other goes down. Get it?
    -William


    Original Message
    From: Andrew Tucker <AndrewT@b...>
    To: <basicstamps@egroups.com>
    Sent: Monday, April 03, 2000 1:43 PM
    Subject: [noparse][[/noparse]basicstamps] hooking up a potentiometer


    >
    > In a Basic Stamp breadboard project I'm building one of the parts used is
    a
    > manual potentiometer. This part has three pins in a "triangle"
    > configuration and I'm confused as to how to wire it up. Are
    potentiometers
    > the same as resistors in that the connected direction is irrelevant or do
    > each of the pins have a specific connection requirement like an IC?
    >
    > Thanks,
    >
    >
    > /* Andrew */
    > Software Engineer
    > BSQUARE Corporation
    > email: andrewt@b...
    > phone: 425-519-6103
    > homepage: http://www.halcyon.com/ast
    >
    >
    >
    >
    >
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