Making a screen from tri-colour LED lights

Discussion in 'The Projects Forum' started by nabaza, Oct 4, 2010.

  1. nabaza

    Thread Starter New Member

    Oct 4, 2010
    Hi, team! I'm new on these forums and I've joined because I have a fairly specific question (I've searched old threads, had no luck). I'm interested in finding out more about using tri-colour LEDs to create a screen on which I would be able to show anything live or recorded from a computer. I've seen these screens before at music festivals and other large-scale events, which makes me think that the technology mighn't be too difficult provided I can afford the materials.

    My problem, however, is that I don't know what this kind of screen is called, the name of the connection the LED lights have to have to each other, with the computer or even the kind of program I would have to use (perhaps something like Pure Data?) and as such, I am having difficulty Boolean searching and giving this a shot.

    I believe that to connect the LEDs to the computer, I am able to use the following (though not in conjunction): serial, parallel, usb, firewire, telephone line, PS2, HDMI, DVI. What do you think?

    I'd really appreciate it if someone who knew the names of these things could let me know so I could start trying to do some research. If you think you have any other information which could be useful, I'd be very grateful for that too! It's absolutely imperative that I do this, so if you think that to understand what I need to have to do, I should try a smaller scale project of X - like just linking a few together, I'll do it. You guys know best! There's a time restriction that's pushing all of this: I need to try and have it done in four to five months.

    Just as a quick note, in case this alters someone's advice, my end goal is to attach several thousand LED lights to a bodysuit, thereby transforming it into a kind of screen. I appreciate that this will be a markedly difficult task. Again, I apologise for my ignorance, I ask this question with great sincerity and a thirst for understanding and any help would be much appreciated.
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
    First of all to create good color you're going to need wavelength specific LEDs, red isn't a standard, nor is green etc. nor do they match in brightness but there are some out there that come close to making white light when they're all running.
  3. tom66

    Senior Member

    May 9, 2009
    I'm afraid to sound defeatist, but it is going to cost you much more than you think.

    Say you want a 320x240 display. That's about the lowest resolutions most graphics cards will go down to. You'll need 76,800 pixels, and 3 LEDs per pixel. If you have three colours and choose discrete LEDs (about 20¢ each) the display will cost you nearly $46,080... which is not pocket change. RGB LEDs would probably cost more.

    Of course if you only wanted a very low resolution like 40x30 pixels you'd only need $720 worth of LEDs.
  4. retched

    AAC Fanatic!

    Dec 5, 2009
    Agreed. In this type of application, you are going to be far better off with the savings resulting from MASS PRODUCED panels.

    You can buy the panels in "chunks" and then daisy chain them together to make whatever size you want.

    LED MATRIX DISPLAYS is what you should be searching.

    The first result is:
  5. DickCappels


    Aug 21, 2008
    To answer your question, HDMI and DVI are video standards that include digital data formats, and you can find graphics cards that output video in these formats.

    If you buy 210,000 LEDs, you can probably get a pretty good price on them, but as mentioned, it takes careful shopping to get the right hue for red, green, and blue. Just Google "ntsc primaries" without the quotes for North American or "pal primaries" without the quotes for Europe. Or just pick one as they are pretty similar to each another.

    Once you know the color coordinates, you will have to decide on how much variation you can stand and find a supplier who can select the color you need within the desired tolerance (LED makers call this "binning"). A metric that is useful in describing color difference is "delta e*", which is a Googleable term.

    Other issues to deal with are driving all those subpixels and powering and cooling the display.

    It would be a daunting project, but with the potential of being highly satisfying. And even if not completed, you would learn a whole lot.
  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
  7. Audioguru

    New Member

    Dec 20, 2007
    Besides having thousands or millions of LEDs, each one needs a driver circuit.
  8. tom66

    Senior Member

    May 9, 2009
    Quite true. If you do it the simplest way (similar to TTL logic) you could get away with one transistor per LED (so 3 transistors per pixel.) And you might also need a capacitor to store a charge on the gate to make the pixel persist.

    Then again, charlieplexing 230,400 LEDs would be fun. You'd *only* need a mere 480 wires. But a single failure of an LED could destroy the screen entirely.
  9. marshallf3

    Well-Known Member

    Jul 26, 2010
    Forget the LEDs and use some old laptop screens?
  10. Wendy


    Mar 24, 2008
    The component you originally asked for is a RGB LED (red green blue). They come as common cathode and common anode, and has been mentioned, are quite expensive.