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Thread: Creating backlight for Projector LCD

  1. #1
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    Creating backlight for Projector LCD

    I have a 8.4" projector LCD which I'm planning to add a backlight to for my carPC.

    I'm in the planning stages for the backlight still. I cant decide if I should go CCFL or LED route...

    Im leaning torwards LED's right now. I found a source for 8000 mcd 3mm white LED's 3.3v .. very bright. I'm thinking 2 rows of 5 LED's on the top and bottom would put out more than enough. I will also have a dimmer for night viewing. Maybe one row of 5 if I can get the light to disperse right. Which brings up my other problem.

    These LED's put out a narrow band like a flashlight. I can sand down the tops flat to help a little. But Im going to need some sort of diffusing board to even the lighting, like they use in laptops. I'm thinking "maybe" a 1/4 sheet of plexi with a white backing would work, then light it up from the sides. Or maybe junking an old laptop, but I dont have any sources for them around here and I dont want to pay $20 shipping for an entire broken laptop on Ebay.

    Now with a laptop, I could also salvage the CCFL tubes + Inverter. I think this could be an easier option. Everything I need is in any old 486 beast of a laptop. But they have less lifespan, less light, and take more power than LED's. And sometimes you get that annoying hum from the inverter that sounds like a fly in your brain ... hate that.


    Anyone have any thoughts/ideas/suggestions?

  2. #2
    Raw Wave Rob Withey's Avatar
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    Re: Creating backlight for Projector LCD

    Originally posted by e_fractal
    I have a 8.4' projector LCD which I'm planning to add a backlight to for my carPC.

    Anyone have any thoughts/ideas/suggestions?
    8.4'...! Dude, that is huge. You got a truck?


    Rob
    Old Systems retired due to new car
    New system at design/prototype stage on BeagleBoard.

  3. #3
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    8.4"

  4. #4
    I'm sorry, and you are....? frodobaggins's Avatar
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    for your diffuser

    go to lowes, home depot

    look in the section for hanging/drop ceilings

    there will be some clear but bubbled or grooved plastic tiles, 'bout 1/16" to 3/32" thick. it's perfect
    [H]4 Life
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  5. #5
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    I used 4 6000 mcd blue leds to backlight a
    ( 2"x4" aprox )character lcd-
    it aint that bright
    thats 8000 mcd over a 15 degree aperture
    lotsa diffusing
    IMHO ccfl is the way to go

  6. #6
    FLAC Skraggy_uk's Avatar
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    Re: Re: Creating backlight for Projector LCD

    Originally posted by Rob Withey
    8.4'...! Dude, that is huge. You got a truck?


    Rob
    Nah not really. I'm mid widening the centre console of my old Saab 900 to get a 10.4" TFT in there.

    So the passenger loses a couple of inches of leg room ( width, not depth). No biggy, I want 10.4" with touch.
    4x4 in a turbo stylee.

  7. #7
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    I have been through this - use ccfl. The LEDS are not as bright as you think once you diffuse. You need a lot and the picture is still very spotty, since its too hard to get good diffusion in the space you are working in.

  8. #8
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    Quote Originally Posted by nxt125
    I have been through this - use ccfl. The LEDS are not as bright as you think once you diffuse. You need a lot and the picture is still very spotty, since its too hard to get good diffusion in the space you are working in.

    Thanks guys. Helpfull as always. I found a good deal on a laptop on Ebay. Cost me $25 total, its a working system without baterry or power supply and no hard drive. So lots of spare parts for other projects, and the small form factor cdrom is a bonus too

    I'm not sure if the CCFL in it will be bright enough, but I found a source for 8" tubes with inverters cheap. I may add a little extra. For testing, I put a 100w lamp in a cardboard box and cut a whole to set the screen on. Then used white paper to even the light. Looks very nice in the dark, can't wait to make this thing glow. I'll post pictures when its installed in the projects forum.

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