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Steve |
For Cooling check out this online calculator:
http://www.novelconceptsinc.com/calc...resistance.cgi Cree has a page regarding thermal management: http://www.cree.com/products/pdf/XLa...Management.pdf And their page about XP-E's: http://www.cree.com/products/pdf/XLampXP-E.pdf Sooooo.... I'm planning on a build with 120 LED's. The Thermal Resistance in the LED's are 9°C/W(XP-E Blue/White) and a good junction to the heatsink is 1°C/W per LED i can calcualte the minimum heatsink resistance needed driving them at 750mA at an ambiant 30°C(my house has AC, should never get that high). Thermal resistance is how much hotter something gets to disapate 1W of heat, so lower is better for a heatsink. Aluminum is about 237 W/m*K at 26 Celcius.(wikipedia) Use the formula for Heat from cree: Tj = Ta + Ptotal (Rth j-sp/ NumLED + Rth sp-h + Rth h-a) P = 120*.750A*3.25V = 292.5W Rth h-a = (145°C - 30°C –9°C/W x 292.5W/120 – 1°C/W x 292.5W/120)/292.5W = 0.31°C/WIn I need a min 0.31°C/W heat sink. Using the calculator on novel i can find the size i need to meet that. I used the slab calculator and the one linked above and came up that a 10"x42" heatsink with 1" fins and .25cms of air flow, asuming .25cms average flow over the entire thing, 1 computer fan is .25, it would probably take 2 to make this consistant. This would have a C/W of : 0.0653926108°C/W, far more than needed. Couple other pages for info on Cooling LED's: http://www.qats.com/cpanel/UploadedP...a_0909_web.pdf http://sound.westhost.com/heatsinks.htm |
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Lampshade you should put together an online calculator for all that. Be a huge hit with the DIY LED crowd. Nicely done!
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No start on a LED build yet... I've been doing a "bit" of research on this so i can justify the nearly $2000 expense. looks good so far, I'll probably start with some suppliment lighting to my MH's and eventually replace them. The tank's a 150gal 6" long, so i was planning on a fixture that size(10x48) and 40° optics, possibly 60°. Should get decent spread, i just want to avoid the zebra color's like i've seen some people have with 40° optics.
As for an online calculator, probably a good idea, haha, maybe i could get vertex or even cree to give me product for advertisements :P. |
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