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Making yellow from bi-color (red/green) LEDs

Discussion in 'Electronic Design' started by Joel Kolstad, Feb 15, 2007.

  1. Joel Kolstad

    Joel Kolstad Guest

    Just curious... if you're trying to use a bi-color (red/green) LED to make
    yellow, how well does it work using an LED with a clear "lens" along with a
    (clear) light-pipe (mounted above the PCB, going through the case)? I've used
    diffused LEDs in the past to do this with no problem, but I'm thinking that
    with a clear lens there won't be enough mixing of the red and green and the
    user will just perceive the two distinct colors rather than yellow as
    intended. Thoughts?

    Given a choice of packages (e.g., 1210 vs. 0605), presumably I'd want the
    smallest one available so that the red and green LED chips are as close
    together as possible, right?

    Thanks,
    ---Joel
     
  2. As long as the viewer does not have a clear image of the two
    die in the LED, the light will appear to be a single color.
    The only problem with not diffused sources like this is
    that the apparent hue may vary a bit with viewing angle.
     

  3. Just wait till they decide to build cheaper traffic lights by using a
    single light housing, with bi-color LEDs to get Red, Green and Yellow.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  4. Joel Kolstad

    Joel Kolstad Guest

    Thanks John; I'm ordering a few to play with and see how it does. In an 0605
    package I suspect that unless you're within inches of the LED you wouldn't be
    able to discern the colors individually. (Harkening back to the time as a kid
    you put your face up to the glass and realize that there are actually three
    different colors there, all arranged in nice little triads...)

    ---Joel
     
  5. Terry Given

    Terry Given Guest

    its called pixel convergence ;)

    followed by image convergence (when there are more than one pixel).

    Cheers
    Terry
     
  6. mkaras

    mkaras Guest

    On Feb 14, 5:07 pm, "Michael A. Terrell"

    ....snip...
    I recall reading someplace that the multi-position lights are
    necessary because of both color blind people and high sunlight
    conditions where even people with normal vision cannot distinguish the
    light color due to the ambient brightness.

    - mkaras
     

  7. That won't stop some greedy politician from trying to have them
    installed, so he can pocket the difference.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  8. Rich Grise

    Rich Grise Guest

    I was absolutely astonished when I did this the first time - I could
    resolve the individual dots, but I still saw the overall picture in
    my peripheral vision, as if it were superimposed over the little dots.

    Kinda boggled my mind, but when you're 8 or 10, that's not hard. ;-)

    Cheers!
    Rich
     
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