I don't think it'll be a problem. You can run a Star pretty close to
1 watt without more heatsink if it's surrounded with free air. My
3-watt "night burner" lantern just uses a 2" square of .090 aluminum
for a heatsink. It gets warm, but not hot. Using the heatsink
calculations from National's Regulator Applications Handbook (adapted
to use in MathCAD) I figure 3 watts on a 2" square sink would run at
about 130F with 68F ambient. This one doesn't run that warm,
probably because some of that 3 watts is emitted as light. One rule
of thumb is that 1 watt of radiant flux is about 43 lumens, though
that would depend on spectral distribution. (Light Measurement
Handbook by Alex Ryer) The Lux running at 1 watt nominally
produces 25 lumens which would be about .58 watts emitted as light
leaving only .42 watts to dissipate locally as heat.

On Thu, 25 Nov 2004 01:56:04 -0800, Winston
wrote:

Don Foreman wrote:
After nearly finishing a microscope ringlight using 10 "regular" white
LED's last winter -- and then getting sidetracked -- I've decided to
ditch that design. I'd even made the little plastic spheres that
would aim the little "projectors" with lenses.

I'm ditching it because 1-watt Luxeons have come down in price to the
point where 4 of those with Fraen 30-degree beamwidth collimators are
under $50. I ordered parts today.

(Snip)

How are you going to get rid of the ~4 W thermally?

--Winston