ARC AAA "Candle"

As I mentioned to Darell in another thread, I have poured an in place epoxy lens on an Arc AAA. I have been involved working with LED's of less light output then the Arc, but with wider beams and used for permanent installations. I realized that the Arc is an ideal, self contained, light source for temporary and mobile placements. With a wider beam pattern, it need not be hand held and directed; rather it can be hung or mounted and provide even, area lighting. This portable " Candle "will be very useful and preliminary tests have been very favorable. I like the bonus that the LED, reflector and electronics enjoy even more protection {as a result of} this lens.

I would have pitched this idea directly to Peter but I think he has enough on his plate and needn't be bothered by someone who can't leave well enough alone.

- Don

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by McGizmo:
needn't be bothered by someone who can't leave well enough alone. <HR></BLOCKQUOTE>
Ha. That's about all of us here on the CPF. Peter thrives on us bugging him. Right Peter?

In the picture, you can't even tell that the lens is in place. Looks to be completely clear. Neat how it spreads the beam so evenly. I couldn't imagine making these little lights tougher, but there you did it!

When I need to use a flashlight as a candle, I just stick it in the empty paper tube from a roll of toliet paper, or wedge it someplace where it faces up. Your solutioi is much more elegant.

Don,
what epoxy sets as clear as that - I gotta know !

Did you just "overfill" the head to create a lens. If so, did you alter the epoxy mix for better behaviour ?

Set that in a clear soft plastic tubing, and it would be easy to add/remove too.

lightlover

Dunno what Don (McGizmo) uses yet, but I've had good results with "Castin' Craft" clear casting resin. Available at artsNcrafts shops. Its meant for making those crytalline paperweights with preserved flowers and such - so the transparency is really very good. It comes as 2 parts, the resin itself and the catalyst, which is bought separately and comes as a stinky liquid in a small plastic bottle (versus the resin, which comes in a resealable rectangular tin). Only a few drops of catalyst is required for setting every ounce of resin and the stuff sets in a coupla hours, though you might have to wait longer before it stops being tacky (and trapping your fingerprints forever). If I were doing such a mod, I'd overfill the Arc-head a little, then sand down til flush.

Oh, the resin should retail about US$18 for a 16oz tin and about $5 for a bottle of the catalyst (good for mixing up at least 64oz of the resin).

I started out using a super clear 1:1 epoxy coating called ultraglo and it looks just like this product when it's cured. In browsing their web site, I noticed that they have an industrial epoxy, EX 74 that has improved UV resistance. I got a sample of this from the company and that's what I've been using. Tue Ultra Glo is much more forgiving in terms of trapped air bubbles. When you exhale over the surface of the resin, the co2 causes the bubbles to pop??!?! It is best to use these epoxies in reasonably warm temperatures; the viscosity is thinner and the air bubbles will rise to the surface. I put lenses on some of my tri-cluster lights this winter and the bubbles stayed suspended in the resin like a bug in amber. It would appear that the index of refraction of this epoxy is very close to the epoxy of the LED itself as the LED essentially disappears. I uploaded a sharper picture of the lenswith light reflecting off the surface. The surface is just above flush with the face of the flashlight head. I tested the light tonight and it certainly won't penetrate and light up objects like the standard Arc but it does an incredibly nice job of illuminating a much wider area with sufficient light.

On the subject of epoxy with probably a stupid question for you guys out there:
According to Matt Kessler, formerly of Nichia, the ultimate degradation of a LED is due primarily to the degradation of the epoxy that encapsulates the die. I wonder what epoxy the LED mfg.'s use. I suspect that the LED's longevity will improve dramatically when a material more suited than epoxy is developed. Could the die be placed under a mineral glass dome, filled with an inert gas and then sealed from the back with epoxy?

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by McGizmo:
Could the die be placed under a mineral glass dome, filled with an inert gas and then sealed from the back with epoxy?<HR></BLOCKQUOTE>

But wouldn't that make it as fragile as a normal incandesent bulb?

Don, I think that's the approach that Lumileds is taking with their Luxeon stars - which are apparently filled with some sort of clear gel and only a thin outer layer of epoxy encapsulating it all. This is one of their selling points for the Luxeons ie. it doesn't yellow as much with age, appearing to give a longer usable lifespan.

BTW - that epoxy you're using looks like what I use, but different brand perhaps. I deep potted a 10-LED versalux in this stuff and you're right - the LED's own bodies and lenses disappear! You can actually clearly see the die without distortion.

yclo - mineral glass is really quite tough. If I'm not mistaken, its what they use for scratchproof glass on expensive watches, like those by Rado.

Mineral glass is very hard and scratch proof, but it is not as impact resistant as say Lexan.

Not sure though, we'll have to wait for the experts to chip in on this one.

YC

Hotfoot, I'm not up to speed on the Lumiled line but it's obvious that they have taken things to the next level; witness all the discussion about LS here at CPF. I'm starting to understand some of this and what I read about Nichia's new offerings makes more sense. In reference to what we've been talking about here, I've taken an excerpt from Nichia:
"Nichia developed two new packages to house the larger area InGaN chip. The NSCx180F is an entirely inorganic package; no organic plastics or organic resins are used. As a result, the package is resistant to the increased heat generated by larger area chips and is ideal for housing UV-emission InGaN LED chips. Lifetime is estimated at 100,000 hours. "

If UV degrades an epoxy LED then is a UV LED composed of epoxy an oxymoron or am I just a moron? I think I now understand a UV LED that a friend sent me last year that was a small metal housing with possibly a piece of glass over the die??

- Don

Mineral Glass ain't that hot.

If you have a plastic lense, you can buff or replace it.

Sapphire is the best for watch crystals, but expensive.

Mineral glass is easier to scratch... And more to replace.

Phil "Sapphire only" Alexander

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by PhilAlex:


Sapphire is the best for watch crystals, but expensive.

<HR></BLOCKQUOTE>

Phil, I couldn't agree more on saphire for a lens on a flashlight. I bought a 30 mm saphire watch crystal a few years back for $15. It's for the titanium dive light I still haven't started to make. Might be overkill for discreet LED's unless they're mega units like the LS or the new Nichia. I mentioned mineral glass because that's what most watch crystals are made of. I had a beautiful Omega Seamaster watch that had a saphire crystal that was violet when viewed at an acute angle. Neatest piece of glass I ever saw. Watch got stolen when our house was broken into and the insurance money couldn't replace an item that was no longer in production. I liked the watch so much that I only wore it on special ocassions. Probably a leson there somewhere...

- Don

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by McGizmo:
It's for the titanium dive light I still haven't started to make.<HR></BLOCKQUOTE>

Oh man. *Here's* the stuff I like to hear! Well, right up to the "still haven't started" part.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by darell:
"still haven't started"

<HR></BLOCKQUOTE>

Darell,

How can I make the light when you haven't given me the dimensions for the nano-fusion power cell?

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by McGizmo:
[QBthat had a saphire crystal that was violet when viewed at an acute angle. [/QB]<HR></BLOCKQUOTE>

Do you think the violet is from the sapphire or the anti-glare coating on it?

YC

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by yclo:
Do you think the violet is from the sapphire or the anti-glare coating on it?

YC<HR></BLOCKQUOTE>
I don't know. I don't recall reading about any antiglare coating in the owners manual but that may have been the case. I always assumed it was the saphire crystal itself. If it was an anti-reflective coating, I wonder why Omega didn't or hasn't used it on other watches. It was very stunning and quite unique. I have a hunch you may be right. It was similar in color to what you see on some of the mini-van windshields.

I reckon for that titanium dive light that you still haven't started to make, you should take the sapphire crystal to an optometrist and have them put a anti-reflective coating on it. That will allow more light to pass through, and make the soon-to-be-dive-light brigher.

YC