Quote:
Originally Posted by OceanicCorals-Eugene-
At 50C the LEDs will surely work close to there rated 50,000hrs life time. But the decrease in intensity will be larger over the course of the bulbs overall life.
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actualy a temp of 50 degrees is well with in the specs that the LEDs are rated at so they should do better than the rated hours and less intensity drop that the spec since the specs are at 80 degrees.
I will agree that there is the ability to create a heat sink that could keep temps down to 40 degrees but it would be in a controled enviorment.
the problem I have with Passive cooling is that there is so much requirement for "space" around the fixture so the heat has some place to disapate to. so you would have restrictions ie. no use in a closed canopy, must be so far away from surfaces to ensure good air movement around it. must be used under a specific ambiant temp, and possibly must be used in low humidity unless some other means of suplementry air flow is provided.
Just like the spot bulbs that are being sold now, if the air access to them is restricted in any way they burn out as they found when people were using them in closed fixtures.
the problem with high humidity is it can actualy form an insulation barrier around the heat sink preventing cooler air from getting in contact to adsorb the heat efficently.
so many factors involved, and you guys are making me have to remember all my coursing in theromal dynamics which hurts my head
lets just agree while it would be nice to have a pasive system, a active system of some sort that will not condense moisture in the air will be the best answer, but I will add a few things and give away a couple things that I am building into my system as I am going opposite of Ron as I am starting with the controler, but I have the time to do it that ways.
you don't need much air flow, and if done right you will never hear the fans. by using the fans you can get away with larger spacing of the fins on the heat sink and also use shorter fins, reducing the hight and weight of the fixture. now I will be playing around to insure that even with out the fans I stay under 75 degrees in an operating enviorment, and I will be incorperating a shut down feature into the micro controler which will shut off every second LED to reduce the amount of heat going into the sink and enable it to cool its self off. if the heat still goes up it will shut off all lighting. I am aiming to have the fist stage kick in at 45 degrees and the second at 50. I am also toying with the idea of fan redundency so therte is another set of fans on the heat sink that only come on if the system hits a specific temp. now the temps I have listed are just off the top of my head, maybe the secondary fans will come on at 45 and everything else will be bassed off that, still have to play and figure out what I think will work the best.
Steve