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Large LED display?

Discussion in 'Misc Electronics' started by [email protected], Oct 6, 2006.

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  1. Guest

    Hi all,

    Has anybody here ever tried to create a large display
    using just LEDs, like a 640x480 display for eventual
    use with a computer after control logic is added?

    I know, skeptics will say that's too much soldering
    to do, and then control logic wouldn't be compatible
    with any existing video circuitry, but then again
    individual LEDs nearly last forever and if multicolor LEDs
    are used it could be pretty pleasant to look at.

    The key would be finding a cheap source of LEDs,
    since even a 640x480 display needs 307,200 of them
    and most people these including myself prefer
    at least 800x600 for 480,000 total.

  2. Boris Mohar

    Boris Mohar Guest
  3. Forget that! Look at this site:
    It is hugh displays using a single line of led's on a spinning arm. Makes
    full color video..
  4. The largest one I ever played with was a 640*200 CGA compatible display. Its
    dimensions were roughly 4x1.4m and it was build up with 16x16 5mm LED tiles.
    It was placed in the Congresgebouw at The Hague at the time. The LEDs were
    bi-color types, red and green, but only red was ever used. Some simple calcs
    learn that it contained 133120 LEDs. The thing was also pretty noisy as it
    required a lot of cooling fans. These days you'd look for 3mm tricolor LEDs
    in tiles of 32x32. So it can be done but I will not go for it (unless
    someone's gonna pay me)

    petrus bitbyter
  5. Here's a couple of LED array systems that are build for such purposes.
    I worked on developing testing, binning, and color balance systems for
    production runs of these: led array 01.jpg led array 02.jpg led zoom 01.jpg

    These use three separate supplies for red, green, and blue, include
    current DACs and support for PWM for intensity built into them. They
    burn some power, so I included the backsides in the first picture so
    you can see the method used as part of the heat sinking for them.

  6. Those are neat. But I think a better approach would be to have a fixed
    strip of LEDs and scan the image using a rotating mirror and optics to
    make a projection system. The size of spinning arm displays is limited
    by the arm length and swing radius. And you don't have to figure out how
    to upload image data to a spinning arm.
  7. Tam/WB2TT

    Tam/WB2TT Guest

  8. Impmon

    Impmon Guest

    LED adds up. Each single color LED is about 20mA. Toss in 138,240
    LEDs for a smaller display, tri color element taking probably over
    60mA and that easy gets over 8 amps top.

    LED are great for outdoor display and other major area like sports
    stadium. But defiantly not for in home use.
  9. John B

    John B Guest

    Have a look here:

    and click on "Chain Reaction". There's some of my work buried inside it.
  10. Tam/WB2TT

    Tam/WB2TT Guest

    How do you get that, 138000 x .06 = 8280 amps.
  11. skenn_ie

    skenn_ie Guest

    You need it if you compete with the sun...even on a small scale !
  12. Rich Grise

    Rich Grise Guest

    Map your pixels to polar coordinates and just spin the arm in a circle,
    like half of an airplane propellor.

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