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From: email@example.com (Bob Wilson)
Subject: Re: luxeon star leds
Date: Tue, 26 Nov 2002 03:52:08 -0000
Organization: Your Organization
X-Newsreader: WinVN 0.99.9 (Released Version) (x86 32bit)
References: <3DDD9A57.58900EFB@RobertsResearchInc.com> <firstname.lastname@example.org> <3DDDB646.96D0D9D2@RobertsResearchInc.com> <3DDE7264.CD48F4F8@RobertsResearchInc.com> <email@example.com> <3DDEB081.884EC92A@RobertsResearchInc.com> <3DE03D65.932BF9BF@RobertsResearchInc.com> <3DE22707.ACD571CE@RobertsResearchInc.com>
In article <3DE22707.ACD571CE@RobertsResearchInc.com>,
>Bob Wilson wrote:
>> In article <3DE03D65.932BF9BF@RobertsResearchInc.com>,
>> Vic@RobertsResearchInc.com says...
>> >Watson 'Atto Parsec' Name wrote:
>> >> I don't buy this convection from the top because I'm using the Luxeon
>> >> Star/O which has the whole top of the LED covered by the lens
>> >You are certainly entitled to your opinion, but don't you
>> >think that the lens assembly will have convective losses
>> >when it gets hot? The lens assembly will, of course, get hot
>> >under steady state conditions if the metal base is not
>> >conected to a heat sink. Considering that the lens assembly,
>> >including its cylindrical holder, has a much greater surface
>> >area than the top of the "bare" Luxeon Star, the "convective
>> >effect" should be more pronounced for a Luxeon with the lens
>> >assembly than for one without.
>> Sounds like you haven't used them, but are only trying to theorize. In
>> last company I worked for, we designed a "wall wash" luminaire (used for
>> illuminating the sides of buildings). It has 60 Luxeon LEDs mounted to a
>> cast heatsink, and sealed with a glass plate above the LEDs. Initially we
>> used the versions with integrated secondary optics (the barrel lenses
>> referred to). Later, we removed the secondary optics and used various
>> mirrors and filters to get the dispersion we needed. There was no
>> significant difference in thermal performance with barreks on or off. The
>> heatsink does all the work. If one is relying on convection cooling
>> the LED, then the design is faulty.
>I am pleased to see that you have had successful results
>with these LEDs.
>Please see my comments on your first note. I agree that they
>should be mounted on a heatsink for normal operation, but
>the question we were discussing in this thread concerned
>some measurements made by another poster on a Luxeon that
>was NOT mounted on a heatsink.
>I am quite familiar with the Luxeon. I have two different
>versions of the Luxeon Star sitting here right next to me as
>I type this note. One has integrated optics and the other
>does not. I picked them up (along with additional Luxeon
>LEDs that were passed on to one of my clients) at Light Fair
>in Las Vegas in 2001.
Well, the company I worked for had its prototype 60-Luxeon-Luminaires at
Light Fair 2002. It was one of the star attractions of the show. Some people
refused to believe it used LEDs! Others kept staring into the diffuser to
see what was generating the light (and going damn near blind in the
process). We even had several of them "doing the wave" with chaning colours.
But the trick wasn't simply using LEDs to produce lots of light. Any idiot
could do that! The trick was to get the right beam shape and distribution
suitabel for "wall washing". In that regard, the secondary optics
(barrel and lens) were useless.
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