>Hi to all engineers,
>
>I am testing Luxeon K2 1500 ma 3,6 v led no matter what I do
>it gets real hot 50 degree C in 30 minutes this is what I do.
>
>1. I use constant current module 700ma 3,6 v " I am giving half power"
>2. 1,5 x 1,5 x 1/4 thickness piece of aluminum
>3. I used white compound grease in between heat sink.
>
>when I talked to future electronics engineers one guy said it is not
>suppose to get that hot then other said the heat sink should be 3 times
>bigger then today some one else said what I use is very bad heat sink.
>My question is does any one used K2 leds and know how to dissipate
>heat? I want to use 3 of them in 3-4 inch round aluminum heat sink.
>The thickness can be higher if I needed. any info will appreciate.

Work out what temperature you want to run at. Let's say  15 deg rise above ambient = 40 deg at 25
ambient. 
Work out the wattage - input power is 3.6x1.5 = 5.4w 
Not sure what the efficiency is but assume, say 5w of heat to get rid of
You need a heatsink thermal resistance of 3 deg.C/watt for 15 deg rise at 5W (15 deg /5w=3) - take a
look at heatsinks of this sort of rating in a catalogue to get an idea of the sort of size/surface
area needed. It will be somewhat more than a 1.5x1.5 inch square. 
3 of them on a 3-4" sink is going to need either some very long fins on the back or a fan.


An example can be seen in the Lamina catalogue
http://www.laminaceramics.com/docs/AccessoriesDatasheet.pdf
Page 4 - The Atlas devices are similarly rated to the K2

I

>
>thanks
>
>Andre
>
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