LED's and Heat

Discussion in 'General Electronics Chat' started by LED Man, Jun 17, 2010.

  1. LED Man

    Thread Starter Active Member

    Jan 15, 2008
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    Hey guys,

    I'm having an argument...err.... discussion about LED's and whether or not they are notorious for producing heat.

    Who is right? Any resources would be great, thanks.
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. Markd77

    Senior Member

    Sep 7, 2009
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    Typically they have about 10% efficiency which means that 90% of the power into them is given off as heat. This is better than a lot of other types of lighting, however LEDs can't tolerate high temperatures like flourescent or incandesant bulbs, so there is more than one side to the story.

    http://en.wikipedia.org/wiki/Lighting_efficiency#Lighting_efficiency
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    The high power units need heat sinks. Figure 3.6V Vf at 700mw works out to 2.5W, the 1.4A units are double that.

    In LEDs running at 20ma it is negligable, but there.
     
  5. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    U know LED's can burn ur figures
     
    Last edited: Jun 21, 2010
  6. retched

    AAC Fanatic!

    Dec 5, 2009
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    AND they can burn you fingers too! ;)
     
  7. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Sheeeeesh....
    I need to get some sleep....
    I am having too many typo's
     
  8. cjdelphi

    New Member

    Mar 26, 2009
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    most 5mm LED's can't generate enough heat unless you put too much voltage through them even some of the cheaper IR led's these days you can run them at up to 100ma and i've touched it and got stung (but no burn)....

    however, the more expensive LED's, Cree Q5,R2,R3,R4 they all take up to 1000ma and without good heatsinking, YES they can and WILL burn your fingers reaching 150c at core junction temperature hence the reason for decent heat sinking.

    Maximum junction temperature: 150°C
    Maximum drive current: up to 1 A
    Low thermal resistance: as low as 9°C/W

    http://www.cree.com/products/pdf/XLampXP-E.pdf

    (also, check out the Cree MCE, SSC P7, 3amp LED's, plus the new XPG, R5 leds)
     
  9. Audioguru

    New Member

    Dec 20, 2007
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    The datasheet for every LED spec's its max allowed current which makes it hot.
    LEDs are powered with current, not voltage.

    I made a night-light with 36 Luxion SuperFlux LEDs that have a max current of 70mA but I used "only" 53mA. Boy oh boy oh boy did they get hot even when they were not at their max current and I housed them in a case full of holes.
     
  10. retched

    AAC Fanatic!

    Dec 5, 2009
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    Thats a bright night light! Juh-eez!

    36 Luxion SFs for a night light... I use two 1300 mcd kingbright white 5mm LEDs @ 20ma and that was fine for not bumping into things around the house.

    I would like to see a photo of that beast.
     
  11. Audioguru

    New Member

    Dec 20, 2007
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    At night it lights up my entire neighbourhood.
    I housed it in the case for a compact cassette tape (the one on tne right side):
     
  12. cjdelphi

    New Member

    Mar 26, 2009
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    Audioguru, that's about the same amount of light you get from an SSC P7 or an MCE, it's not all that bright these days, the SST-90 (with lens) anyway if you want to see a real BEAST in action check out the youtube video below.

    http://www.youtube.com/watch?v=VHEXz0g2iB4

    [​IMG]
     
  13. Audioguru

    New Member

    Dec 20, 2007
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    Why do you talk in letters and numbers that don't mean anything to me?
     
  14. cjdelphi

    New Member

    Mar 26, 2009
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    I dunno, you did you mentioned you wired up luxon emitters to light up the back yard so i figured you knew something about flashlights guess i was wrong, but i did post a youtube video link....
     
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