The Fraen 30-degree beamwidth collimators arrived today. These work
with the Luxeon LEDs.

The illumination they provide is totally free of mottling and
patterning, but brightness of "the spot" does vary from the center
outwards. The "spot" at 7" working distance is somewhat larger than
my field of view of a bit more than 2" dia so the brightness variation
within the field of view is probably acceptable.

I then got sidetracked, wondering how these might work as a
head-mounted worklight as opposed to available head lights intended
for camping, hikeing, caving, cycling, etc. I'm thinking worklight
as in working on things within arm's reach. Under hoods, under sinks,
working on machinery and computers, I'll skip deilvering babies in the
field.

They work OK, better than the LED head lights I've tried and vastly
better than incandescant bulb head lights or a 2AA mini Maglight.
The light from these sources is not as bright, not white, and it's
full of mottling and patterning artifacts that confuse the issue.

Then came the surprise. I tried a BAL (bareass Luxeon) smack up
against a lens I got at Ax Man surplus for 35 cents. The lens is .910
dia (real close to the OD of the Luxeon Star), focal length of about
1.8 inches by very crude quick-a-minnit measure. It weighs 4 grams.

I think that combo might make one hell of a worklight. When pointed
at the wall, it makes a large "spot" that looks like a white disc cut
out of paper. More interestingly, when directed at a workbench from
a distance of about 20 inches (forehead height while seated in front
of the bench), it evenly illuminates at least as large an area as I
would be likely to be working in and most of the region I could reach.
It isn't as bright as the spot from other head lights, but it's bright
enough to read the finest print on an AA cell, see the threads on a
4-40 screw -- and find the damned screw if I drop it and it rolls away
from a brighter but smaller spot.

Photo at www.goldengate.net/~dforeman/worklite

The photo was taken from somewhat further than arm's reach of the
bench. You can see my arm holding the light above the bench. That
height is a bit above where my forehead would be if I were seated and
working at that bench.

A shorter focal-length lens would work better for an array of lights
for use on a microscope -- but it's real hard to beat Ax Man's price
of 35 cents per lens and with 4 or more lights I'm quite sure that
full brightness would be ample to uncomfortable at the short (6 to 7")
light-to-subject distance for microscope use.

The 1-watt Luxeon Stars are down to $6.50 ea in onesies now.

(Snip progress report)

Excellent! Thanks, Don.
Are you driving these guys with some kind of current-regulated supply?

Do you envison a switchmode driver in your rechargable light or
are you going to stay with a series resistor?

--Winston

On Fri, 03 Dec 2004 00:36:36 -0600, Don Foreman
wrote:

The Fraen 30-degree beamwidth collimators arrived today. These work
with the Luxeon LEDs.

The illumination they provide is totally free of mottling and
patterning, but brightness of "the spot" does vary from the center
outwards. The "spot" at 7" working distance is somewhat larger than
my field of view of a bit more than 2" dia so the brightness variation
within the field of view is probably acceptable.

I then got sidetracked, wondering how these might work as a
head-mounted worklight as opposed to available head lights intended
for camping, hikeing, caving, cycling, etc. I'm thinking worklight
as in working on things within arm's reach. Under hoods, under sinks,
working on machinery and computers, I'll skip deilvering babies in the
field.

They work OK, better than the LED head lights I've tried and vastly
better than incandescant bulb head lights or a 2AA mini Maglight.
The light from these sources is not as bright, not white, and it's
full of mottling and patterning artifacts that confuse the issue.

Then came the surprise. I tried a BAL (bareass Luxeon) smack up
against a lens I got at Ax Man surplus for 35 cents. The lens is .910
dia (real close to the OD of the Luxeon Star), focal length of about
1.8 inches by very crude quick-a-minnit measure. It weighs 4 grams.

I think that combo might make one hell of a worklight. When pointed
at the wall, it makes a large "spot" that looks like a white disc cut
out of paper. More interestingly, when directed at a workbench from
a distance of about 20 inches (forehead height while seated in front
of the bench), it evenly illuminates at least as large an area as I
would be likely to be working in and most of the region I could reach.
It isn't as bright as the spot from other head lights, but it's bright
enough to read the finest print on an AA cell, see the threads on a
4-40 screw -- and find the damned screw if I drop it and it rolls away
from a brighter but smaller spot.

Photo at www.goldengate.net/~dforeman/worklite

The photo was taken from somewhat further than arm's reach of the
bench. You can see my arm holding the light above the bench. That
height is a bit above where my forehead would be if I were seated and
working at that bench.

A shorter focal-length lens would work better for an array of lights
for use on a microscope -- but it's real hard to beat Ax Man's price
of 35 cents per lens and with 4 or more lights I'm quite sure that
full brightness would be ample to uncomfortable at the short (6 to 7")
light-to-subject distance for microscope use.

The 1-watt Luxeon Stars are down to $6.50 ea in onesies now.



So Don, how does someone north of seattle get one of those lenses from
the Ax Man? Does he do mail order?
Thanks,
Eric

On Fri, 03 Dec 2004 00:56:40 -0800, Winston
wrote:

(Snip progress report)

Excellent! Thanks, Don.
Are you driving these guys with some kind of current-regulated supply?

Just a resistor so far. I'll probably use LM317's as current
regulators for the microscope lights because it's easy, simple,
cheap, and neither size nor power efficiency is important there.

Do you envison a switchmode driver in your rechargable light or
are you going to stay with a series resistor?

I designed a little SEPIC regulator and had a few printed wiring
boards made, piggybacked on another project. They're about 1"
dia, fit nicely behind a Luxeon Star. SEPIC is good if 3 or 4 cells
are used because it can operate with supply voltage either higher or
lower than load voltage. For 2-cell operation (boost only) I can
omit a few parts and it then degenerates to the Zetex appnote circuit.

Ian Sterling's approach of using a micro is the way to "do it right".
That should provide much better regulation than the so-called "LED
driver" chips do and it offers other features like different
brightness levels, etc.

On Fri, 03 Dec 2004 14:24:52 -0800, Eric R Snow
wrote:
So Don, how does someone north of seattle get one of those lenses from
the Ax Man? Does he do mail order?

I doubt it. You never know what he'll have on hand any given day. I
bought 10 lenses today. I think he now has about 5 left in that
store but he may have a barrel full of 'em at other stores or at the
warehouse.

If you just want one, send me your addy by email and I'll pick one up
for you next time I'm in the neighborhood. I get over there at least
once a week. It's next to the beer store.....

"Don Foreman" wrote in message
...
On Fri, 03 Dec 2004 14:24:52 -0800, Eric R Snow
wrote:
So Don, how does someone north of seattle get one of those lenses from
the Ax Man? Does he do mail order?

I doubt it. You never know what he'll have on hand any given day. I
bought 10 lenses today. I think he now has about 5 left in that
store but he may have a barrel full of 'em at other stores or at the
warehouse.

If you just want one, send me your addy by email and I'll pick one up
for you next time I'm in the neighborhood. I get over there at least
once a week. It's next to the beer store.....

I swung by the AxeMan near my house in St. Paul on Saturday and couldn't
find anything like this lens.

grumbleI was dropping off a large box of electronics parts (mostly
connectors including a lot of stainless steel hardware with gold-plated
connectors) from a few lines of cameras we've discontinued at work and they
wouldn't even look at them; "*we* don't take anything for free". Everything
was in plastic inventory bags, no less than quantity 5 or 10 on almost
everything. I gave the whole box to a couple of guys who looked like they
are EE students at the U of MN. /grumble

Pete

The Fridley store still has a few -- or did on Saturday anyway.

On Mon, 6 Dec 2004 13:08:54 -0600, "Pete Bergstrom"
wrote:


I swung by the AxeMan near my house in St. Paul on Saturday and couldn't
find anything like this lens.