LEDs

Discussion in 'Electronics' started by imadoofus, Jan 3, 2009.

  1. imadoofus

    imadoofus Hardcore MB Enthusiast

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    Is it the case that some LEDs emit noticeable heat?

    I have an application for which I need six LEDs (probably 3mm, maybe 4) mounted 20mm apart in an aluminium panel, and faced with clear acrylic (8mm x 130mm), such that the LEDs will touch the acrylic. I am hoping (yet to be tested) that this will give the acrylic a soft(ish) glow, sufficient for my purposes, but obviously, I don't want the LEDs to generate too much heat for the acrylic to withstand.

    Assuming the more powerful the LED, the hotter it gets, what would a suitable compromise be?

    I know it's a very non-specific question requiring a definite answer, but one of you lot is bound to know.

    Green LED, BTW.

    TIA

    PJ
     
  2. Ade B

    Ade B Hardcore MB Enthusiast

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    We have done a couple of led lightbox installations in clubs and have found that the leds themselves emit very little heat, certainly not enough to melt acrylic.

    If you have the leds touching the acrylic you'll get brightspots, best thing is to get as much of a gap as reasonable (up to a limit) and make a reflective surround for the leds (a white box works well).

    Anyway, what are you building? Fibre glass, leds?

    [​IMG]


    Ade
     
  3. OP
    OP
    imadoofus

    imadoofus Hardcore MB Enthusiast

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    I have a bank of six switches in a dashboard, and I want them to be at least partially lit at night, and the markings to be visible too, so if the markings were on a piece of acrylic, with LEDs behind I hope that'll get the result I want.

    In cross section, it'll look like this:

    O|I
    I|
    III

    And front on, it'll look like this

    IIIIIIIIIII
    ||||||
    IIIIIIIIIII

    Where O is an LED, | is acrylic and I is aluminium.

    So the LEDs will be hidden when viewing from the front, but will hopefully provide enough light to the acrylic to illuminate the markings, and provide a soft glow to the switches themselves.
     
  4. Ade B

    Ade B Hardcore MB Enthusiast

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    If I'm reading your drawing properly it should be fine as it looks like you are blanking off the light source - you might get alternating bright and dark patches depending on the spacing and intensity of the leds. A bit of trial and error will sort out optimum set up.

    You building a kit car then? ;)


    Ade
     
  5. OP
    OP
    imadoofus

    imadoofus Hardcore MB Enthusiast

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    Excellent, thanks! I am happy to play trial and error, I just don;t want to use LEDs that are too bright, and damage the acrylic.

    Nope. Upgrading my Midget.
     
  6. mattc

    mattc Hardcore MB Enthusiast

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    Your midget pops off to the Big Brother house for a few days and you decide it needs upgrading :rolleyes: :D
     
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