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LAN_403

lhl_henrylui

Fri Apr 17 2009, 02:18PM

Registered Member #1498 Joined: Thu May 22 2008, 07:08AM
Location: Hong Kong
Posts: 72

Hey,what's the price of the LED?
I saw 100W LED in China,its price was few hundred yuan

tesla500

Sat Apr 18 2009, 05:38AM

Registered Member #347 Joined: Sat Mar 25 2006, 08:26AM
Location: Vancouver, Canada
Posts: 106

aonomus wrote ...

The slashdotting was probably mitigated since most of /. uses Firefox, and those without IE7 wouldn't load the images (thus saving alot of bandwidth).

Actually, the images do load, they're just far off to the right. Stupid MS Frontpage...

David

aonomus

Sat Apr 18 2009, 11:19AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

They didn't render in my browser at all sadly....

I think the next thing we'll see is TDU burnt into wood somehow :D

Dalus

Sat Apr 18 2009, 11:40AM

Registered Member #639 Joined: Wed Apr 11 2007, 09:09PM
Location: The Netherlands, Herkenbosch
Posts: 512

He'll make a CNC LED plotter for that aonomus

Would actually work quite well when the LED is focused and moves slowly.

Tesladownunder

Sun Apr 19 2009, 06:21AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Up to 100,000 hits and now on over 70 forums, blogs etc. About a dozen cycling forums and interest from scuba divers as well.

Interestingly Firefox accounts for about 69% of my last 4000 hits in terms of browsers. Guess that is the Slash dot crowd. The page should work fine now now that the offending table from eBay was removed. (Tell me if it still has problems).

These are now available on eBay for US$118 (mine was over twice this but heck, that was 2 weeks ago).

I have now arranged a 3 amp constant current supply using an LM350 regulator. I made a simple mistake and nearly overheated the LED. I tap the 3 SLA batteries at 12V to supply the fan but completely forgot about that when I ran it at 3 amps from the supply so no fan. I happened to touch one of the scorching hot heatsink bolts then realised. Probably lost 10,000 hours of lifetime then. Only 90,000 to go.

Running at 100 W results in temperatures with the standard fan of over 55C. I now plan to run the fan on 24V instead of 12 with a separate regulator all cooled by the same fan that cools the LED. The main supply regulator and fan regulator will lose perhaps 15W as it they are series regulators for simplicity. And I need an over temp cutout too.
Then once I have made a mains supply I will work on audio modulation. But that's another story....

Mattski

Mon Apr 20 2009, 09:48PM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

Looks like someone on ebay is selling a lens especially for this particular LED: here.

Tesladownunder

Tue Apr 21 2009, 01:31AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Thanks for that. I picked one up and will see how it goes.

klugesmith

Wed Aug 12 2009, 01:05AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Steve McConner wrote ...

I wonder if there's some law of optics that limits how fine you can focus it, given that the light is relatively diffuse and coming from a large area, compared to something like a 100W short arc lamp.

Yes -- with geometric optics the theoretical maximum image brightness is equal to the source brightness, give or take a factor of pi. Here's a good reference:

[edit] First qualification: the referenced formulas give image illuminance (e.g. lumens/m^2) in terms of directional source luminance (cd/m^2 or lumens/steradian/m^2). So for an emitter with lambertian* beam pattern, such as a fluorescent tube or LED die without optics, the power density at focused image can't exceed the power density leaving the source. No magnifying glass in sunlight can make a spot more intense than same size spot on the solar surface (reduced by atmospheric attenuation).

We can do much better if the source is collimated. For an extreme example, a broad laser beam can be focused to a spot of much higher power density. Need to look up the datasheet beam width of the 100 watt LED array.

*lambertian: brightness falls off as cos(theta), just like the projected area of the source. Thus "viewing angle" as defined in LED datasheets is 120 degrees.

Proud Mary

Wed Aug 12 2009, 06:06AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Klugesmith wrote ...

Yes -- with geometric optics the theoretical maximum image brightness is roughly equal to the source brightness,
give or take a factor of pi. Here's a good reference:

I wonder if there hasn't been some misunderstanding here. I understood Steve to ask "how fine you could focus it" and not about source brightness.

The answer, gentlemen, is that the wavelength of light is the principal (but not only) determinant in the absolute minimum possible diameter of a focal point, known as an Airy Disc. . The shorter the wavelength, the finer the possible focus, and vice versa.

In the case of a laser beam, Steve, even where it is focused by a notional 'perfect lens' it can still only image a frequency-dependent Airy Disc at its point of focus.

There must be thousands of papers about Airy Discs on the web, so I'll leave you to them and Google if you want to get stuck into the theory of Airy Discs and optical resolution.

Steve Conner

Wed Aug 12 2009, 09:38AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

No, the question I intended was the one that Klugesmith answered, thanks.

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