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From: Victor Roberts
Organization: Roberts Research & Consulting, Inc.
X-Mailer: Mozilla 4.78 [en] (Win98; U)
Subject: Re: luxeon star leds
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>
Date: Mon, 25 Nov 2002 13:33:48 GMT
NNTP-Posting-Date: Mon, 25 Nov 2002 05:33:48 PST
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 assembly.
> >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 the
> 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 being
> 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 around
> 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.
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