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. Diversity of 10 is better than
diversity of 4, but I think 4 will be enough diversity to avoid bad
shadows and specular reflections, and I expect that the illumination
level will be much brighter with four 1-watt Luxeons than with 10
"regular" white LED's. That expectation is based on a couple of
experiments with Luxeons I have at hand to play with.

I couldn't resist ordering another 3 watt "burn the night" Luxeon
emitter. They make seriously neat flashlights using very cheap
reflectors found at Harbor Freight and Home Depot. Eat yer hawrt
out, Maglight 3D.

It's "shop season" again in Minnesota...

It's "shop season" again in Minnesota...

Don't you feel sorry for those folks in California, or wherever, that have
to work outside all year?

Karl

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

"Winston" wrote in message
...

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

I doubt all of the 4W goes into heat.

In article , jtaylor says...


"Winston" wrote in message
...

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

I doubt all of the 4W goes into heat.

It does eventually! g

Jim


--
==================================================
please reply to:
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==================================================

In article , Don Foreman says...

...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. Diversity of 10 is better than
diversity of 4, but I think 4 will be enough diversity to avoid bad
shadows and specular reflections, and I expect that the illumination
level will be much brighter with four 1-watt Luxeons than with 10
"regular" white LED's. That expectation is based on a couple of
experiments with Luxeons I have at hand to play with.

Even the fiberoptic ring lights will give specular reflections
now and again. Get it just right (wrong) and it's really
pretty painful when looking at things like a large polished
wafer. You've got me thinking - I wonder if I could fit (and
heatsink) ten of them in a ring, about 2.5 inch dia?

Thanks for the ideas - Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

Don Foreman wrote:

snip


It's "shop season" again in Minnesota...

Nah, white stuff is not forecasted until tonight, still have ALL DAY for
outside projects! (From one who is having turkey at 7:00PM and will be
running around on ladders cleaning gutters until then!)

Not quite, if you use the Fraen collimators. 2.5" dia is 7.8"
circumference, the collimators are each about 1" dia.

TerraLUX has reflectors that are .75" dia, used in their minimag
retrofits with Luxeon sideshooters. If you could buy just the
reflectors from them, you could get 10 of those in a 2.5" dia ring if
you use Luxeon emitters (rather than Stars) epoxied directly to the
ring. You wouldn't need their electronics.

Nothing saying you must run them at full power. I think 3 or 4 watts
will be puh-lenty of light, regardless of how many Luxeons are used
for diversity.

On 25 Nov 2004 07:27:05 -0800, jim rozen
wrote:

In article , Don Foreman says...


Even the fiberoptic ring lights will give specular reflections
now and again. Get it just right (wrong) and it's really
pretty painful when looking at things like a large polished
wafer. You've got me thinking - I wonder if I could fit (and
heatsink) ten of them in a ring, about 2.5 inch dia?

Thanks for the ideas - Jim

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. Diversity of 10 is better than
diversity of 4, but I think 4 will be enough diversity to avoid bad
shadows and specular reflections, and I expect that the illumination
level will be much brighter with four 1-watt Luxeons than with 10
"regular" white LED's. That expectation is based on a couple of
experiments with Luxeons I have at hand to play with.

I couldn't resist ordering another 3 watt "burn the night" Luxeon
emitter. They make seriously neat flashlights using very cheap
reflectors found at Harbor Freight and Home Depot. Eat yer hawrt
out, Maglight 3D.

It's "shop season" again in Minnesota...




Yeah, it's snow and slush season here in Red Sox country too Don.

We had our first ****e weather last weekend and young son (17) managed
to find some "black ice" at nite while driving on a gradual curved
street in the next town, slid to the curb and stood his recently aquired
Honda Civic on its head on the sidewalk.

He kicked the door open and got out without a scratch on him, thank G-d.
While he was standing there calling the cops on his cell phone a Ford
with five young girls in it encountered the same slippery spot and slid
a similar path, smashing into his upside down car, then bouncing off it
to hit a parked car across the street.

None of the girls got hurt either. I guess not one of the guardian
angels who were looking after those teen agers were taking a coffee
break then, but every once in a while one of them has to go to the
bathroom or something and we have another sad funeral to attend in town.

I feel quite bad for the kid, he worked for a year to earn most of the
money to buy that 85 Honda, and he'd spent a lot of spare time "pimping
it up" which is what the young bucks around here call what we used to
call "customizing" when we did similar stuff to our '49 Fords. The event
made the front page of the town paper too, he's got his 15 minutes of
fame now.

Documented at the bottom end of the web page I've been keeping to chart
his progress:

http://home.comcast.net/%7Ejwisnia18/ben/index.htm

Happy and safe holidays, guys,

Jeff


--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"

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

Don Foreman wrote:
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.


I see here on the Star data sheet (DS23.pdf) that at peak power,
the device converts power at a rate of 1.19 W. That's 3.4 V times
0.35 A. Think of it as a (admittedly nonlinear) 9.7 ohm resistor.

From other sources, I recall these LEDs are about 3% efficient.
Only about 0.036 W of that 1.19 W gets emitted as light.
So you get to design a heatsink to keep die temperature below 60 C
for *each* LED while losing 1.14 W of heat per LED.

Things get squirrley quick when you have two or more thermal power
sources connected in parallel like this. My little brain boggles
at trying to SWAG a heatsink for 6 or 10 devices!

Some empirical experiments are in order, methinks.

(Happy Thanksgiving)

--Winston

On Thu, 25 Nov 2004 14:32:13 -0800, Winston
wrote

From other sources, I recall these LEDs are about 3% efficient.
Only about 0.036 W of that 1.19 W gets emitted as light.
So you get to design a heatsink to keep die temperature below 60 C
for *each* LED while losing 1.14 W of heat per LED.

Yup, I blew it on the watt/lumen ratio. I checked the book again.
Your 3% figure is probably more in the ballpark for photopic vision.

Things get squirrley quick when you have two or more thermal power
sources connected in parallel like this. My little brain boggles
at trying to SWAG a heatsink for 6 or 10 devices!

Some empirical experiments are in order, methinks.

Definitely! At my bench, a horizontally-oriented 1-watt star with
no other heatsink stabilizes at 40.6 deg C above ambient when
running 350 mA with Vf of 3.08 volts. The Vf sounds low but is
consistent with bin QX0HW, which this part is. That Vf bin (H) runs
from 3.03 to 3.27 volts. Temp was measured with type T
thermocouples (one for ambient, one on the Star) and an Omega model
HH23 temperature meter.

Specified thermal resistance junction-to-board is 17 degC/watt, so
junction is running about 58 degC above ambient. Tjmax is 120C so
we could operate in ambients of up to 62C or ~144F. If the star
is open to free circulation of ambient air and ambient is at or below
27C (about 80F) then we have 36C of margin -- with no additional
heatsink at all.

Other parts with higher Vf at rated current will have slightly higher
Pd.

On Thu, 25 Nov 2004 13:05:14 -0500, Jeff Wisnia
wrote:

(snip)

Bummer! But no one hurt, lessons learned, not all bad.

Don Foreman wrote:
(Snip interesting yet geeky stuff.)

Definitely! At my bench, a horizontally-oriented 1-watt star with
no other heatsink stabilizes at 40.6 deg C above ambient when
running 350 mA with Vf of 3.08 volts. The Vf sounds low but is
consistent with bin QX0HW, which this part is. That Vf bin (H) runs
from 3.03 to 3.27 volts. Temp was measured with type T
thermocouples (one for ambient, one on the Star) and an Omega model
HH23 temperature meter.

Specified thermal resistance junction-to-board is 17 degC/watt, so
junction is running about 58 degC above ambient. Tjmax is 120C so
we could operate in ambients of up to 62C or ~144F. If the star
is open to free circulation of ambient air and ambient is at or below
27C (about 80F) then we have 36C of margin -- with no additional
heatsink at all.

Other parts with higher Vf at rated current will have slightly higher
Pd.

I hope that you let us know when your product is on the shelf.

I want one.

--Winston

On Fri, 26 Nov 2004 00:57:12 -0800, Winston
vaguely proposed a theory
.......and in reply I say!:

remove ns from my header address to reply via email

I think you feel as lost as I do..

I hope that you let us know when your product is on the shelf.

I want one.

--Winston

Product? Who said anything about product? I try not to make more
than one or two of anything. I'll report on how it works (or
doesn't), though.

On Fri, 26 Nov 2004 00:57:12 -0800, Winston
wrote:


I hope that you let us know when your product is on the shelf.

I want one.

--Winston

Old Nick wrote:
On Fri, 26 Nov 2004 00:57:12 -0800, Winston
vaguely proposed a theory
......and in reply I say!:

remove ns from my header address to reply via email

I think you feel as lost as I do..


I hope that you let us know when your product is on the shelf.

I want one.

--Winston

Well, yeah, probably.


--Winston

Don Foreman wrote:
Product? Who said anything about product? I try not to make more
than one or two of anything. I'll report on how it works (or
doesn't), though.

On Fri, 26 Nov 2004 00:57:12 -0800, Winston
wrote:


I hope that you let us know when your product is on the shelf.

I want one.

--Winston

That's a good compromise.

--Winston

jtaylor wrote:

I doubt all of the 4W goes into heat.

To all practical purposes, it does. Even the most efficient light
sources are struggling to get up to 10%. The rest is heat.

Ted

In article , Ted Edwards says...

jtaylor wrote:

I doubt all of the 4W goes into heat.

To all practical purposes, it does. Even the most efficient light
sources are struggling to get up to 10%. The rest is heat.

And even that ten percent goes into heat, eventually.

By the end of the day, all those photons has smacked into
somthing and warmed it up.

Jim


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On 26 Nov 2004 15:26:09 -0800, jim rozen
wrote:

In article , Ted Edwards says...

jtaylor wrote:

I doubt all of the 4W goes into heat.

To all practical purposes, it does. Even the most efficient light
sources are struggling to get up to 10%. The rest is heat.

And even that ten percent goes into heat, eventually.

By the end of the day, all those photons has smacked into
somthing and warmed it up.

Jim
Speaking of photons, does all matter emit photons until it's
completely still and cold? E G lets say you heat up some hydrogen
molecules and spit them out a gun into the vacuum of space. Will they
retain all their heat, or at least some level of heat, as long as they
don't collide with something else? Or do atoms keep emitting longer
and longer wave lengths until they reach some level, microwave or
something, where that last photon removed the last bit of energy and
the atom is now at absolute zero.
ERS

jim rozen wrote:

And even that ten percent goes into heat, eventually.

Yeah but the photons that leave the immediate area aren't part of the
heat sinking problem in the fixture.