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Thread: Extremaly durable RED LEDs

  1. #1

    Default Extremaly durable RED LEDs

    Hello!

    I'm making a design of LED obstruction lamp and I need very durable <font color="red"> RED </font> LEDs with high luminous output. LEDs should be able to work in military condition: -55C to 55C. [img]/ubbthreads/images/graemlins/help.gif[/img]

    Luxeon LEDs look good but they operate only from -40C. May be someone know if there are military (industrial) version of Luxeon <font color="red"> RED </font> LEDs or similar LEDs from other manufacturer and where to get them?

    Thanks for help!! [img]/ubbthreads/images/graemlins/smile.gif[/img]

  2. #2
    Flashaholic*
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    Default Re: Extremaly durable RED LEDs

    I don't think that the Luxeon Red LEDs can take only -40C. Someone here (evan I think) has cooled it with a high power peltier and brought the temperatures really low. Plus Red LEDs hate heat, 55 degrees may be a problem ,but -55 sure isn't. It'll get brighter as it gets colder, @ 55C, I think the output will drop significantly.

    Hope I've been of help. [img]/ubbthreads/images/graemlins/smile.gif[/img]

  3. #3

    Default Re: Extremaly durable RED LEDs

    OK [img]/ubbthreads/images/graemlins/thumbsup.gif[/img], I will try to test some Luxeons.

    But I wonder about if they realy are able to operate at -55C since Lumileds writes in data sheets (Thermal Design Using Luxeon Power Light Sources):

    <font color="blue"> operating temperature: -40C to 75C </font>

    It is possible that Luxeon is able to operate at lower temperatures of ambient but it probably may result in lower life time and lower reliability od light fixture. (But may be not? [img]/ubbthreads/images/graemlins/thinking.gif[/img])

    LED obstruction lamp, which I desig, should go trough test during it is cooled to -55C for 24 hours in a thermal chamber with input power off and after that period shall be turn on for 1 hour.

    I think that Luxeons may not pass this test... [img]/ubbthreads/images/graemlins/jpshakehead.gif[/img] May they?

  4. #4
    Flashaholic* Xrunner's Avatar
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    Default Re: Extremaly durable RED LEDs

    I'm not a Luxeon expert, but I would say that they would stand a very good chance of passing the test. A post a while back comes to mind (about testing Luxeons at low temperatures), I'll see if I can find it.

    -Mike

  5. #5
    Flashaholic* Xrunner's Avatar
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    Default Re: Extremaly durable RED LEDs

    Found it, here is the post I was thinking of. It's an interesting read, and the last post brings up an interesting point about things becoming brittle at very low temperatures.

    -Mike

  6. #6
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    Default Re: Extremaly durable RED LEDs

    Most manufacturers have little motivation to test things outside of the normal 'comercial', 'industrial', 'automotive', or 'extended' ranges. (most of those are synonyms, anyway) There is so little volume outside of that set of ranges that there is little incentive to qualify *all* of their product there. I bet you would get a useful response if you wrote them and told them of your need.

    Like Xrunner, I don't think you're going to see any problem with low temp operation--I've dunked the things in LN2 and they've survived. -55C ain't nothin' compared to that. He (Mike is usually a he, right?) is also right in that the high end is what's going to get you. You're going to need a very good heatsink to keep the junction cool enough at a 55C. But, check the thermal datasheet and crunch the math to see if it looks like it'll be a problem for you.

    Oh, if it makes you feel better, just keep them running in the -55C environment and the LED will probably be in the -40C or &gt; range. [img]/ubbthreads/images/graemlins/smile.gif[/img]

  7. #7

    Default Re: Extremaly durable RED LEDs

    That all sounds nice. Thanks for all posts. I will tray to ask Lumileds about reliability of Luxeons in low temperatures.

    Iíve found also interesting manufacturer from Switzerland. They produce pretty well diodes but they are poorly know company and I donít know if their diodes are so good as Lumileds LEDs. Somebody hear sth about ACOL diodes or try these diodes?



    How do you think is it better to use 36 Luxeon with a complicated power dissipation or to use 180 ACOL diodes with very good thermal management ???

  8. #8
    Flashaholic*
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    Default Re: Extremaly durable RED LEDs

    [ QUOTE ]
    How do you think is it better to use 36 Luxeon with a complicated power dissipation or to use 180 ACOL diodes with very good thermal management ???

    [/ QUOTE ]

    Heat has to go somewhere at +55 C with either solution...

    Adam

  9. #9
    *Retired* NewBie's Avatar
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    Default Re: Extremaly durable RED LEDs

    These are somewhat bright, http://www.mouser.com/index.cfm?hand..._pcodeid=59902

    Only about 1938 lumens, but the light output goes up by about 1.6 at -40C.

    At least it is as bright as 44 Red LumiLED Luxeons, in one device. Thermal resistance is 0.75 C/W max, which is much better than a luxeon at 13-15 C/W, which will keep the die cooler, which will help at the high end of the temperature range, and keep the die cooler at the low end of the temperature range, cooler die = more light output...

    Also, you can under power it, and get much higher efficiencies.

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