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Luxeon star LEDs - heat dissipation?

Discussion in 'LEDs and Optoelectronics' started by npomeroy, Dec 27, 2012.

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  1. npomeroy

    npomeroy

    19
    0
    Dec 9, 2012
    I've acquired some luxeon LEDs - they are tiny - on a 3 x 4mm PCB...
    http://www.luxeonstar.com/Luxeon-Rebel-LEDs-s/1.htm
    ... and run on 700 mA. The tiny board has 2 solder pads and another for a heat dissipation.
    Has anyone used these? I have no idea how hot they would get if run continuously, anthough I intend to run them flashing at about 0.5 - 1 Hz as a model helicopter tail beacon. I can make the "on" flash as short as I like in which case the heat output is minimised, but I'd like to have a rule of thumb starting point. In the absence of advice to the contrary I'll stick the heat pad to a copper strip about 3 x 25mm with heat resistant epoxy (JB wWeld).

    Nelson
     
  2. donkey

    donkey

    1,293
    56
    Feb 26, 2011
    heat resistant epoxy is NOT a good idea.
    you need something that CARRIES the heat through to the heatsinks where it can be dissapated.
    as for using them I would assume it depends on your intentions, have you factored in the need for a regulator to be used?
    also it depends on the aount of current used. the listing says try not to go over 700ma unless precautions are used... I assume they could tell you more but it could quite possibly melt your heli. the cheapest driver I fond is 8.1g and depending on the heli you have that could be a considerable weight.
    I have the luck of being able to talk to some friends for all things rcrelated as they own a shop. But I would advise that you look into your heli and check to see if A) it has the room for any extras and B) it can handle extra weight and C) trying not to make it go off centre too much.
    and just a quick look at the warm white says something along the lines of maximum junction temperature 150 degrees celcius... thats not unlikely... but it could go higher
     
  3. npomeroy

    npomeroy

    19
    0
    Dec 9, 2012
    Hi Donkey
    This is a 1.1m long > 3 kg So don't worry about the weight and balance! I have the BuckPuck CD driver that supplies 700 mA off a 12V input. I was going to switch the output via FETs to flash respective LEDs.
    What I am curious about is how much actual heat they will produce and whether I need bulk heatsinks at, say, 5% duty cycle. Here is the datasheet
    http://www.luxeonstar.com/v/vspfiles/downloadables/DS68.pdf
    Another way I could think of this is what % of the wattage is heat vs light? I have a "feel" for what 1W is like on a small component.
     
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