# Flat Top LEDs



## jeff1500 (Dec 27, 2001)

Has anyone ever sanded the top off an led and polished the flat surface?

What does it do to the beam pattern? Does it make it into more of an area light instead of a spot light? How hard would it be to polish it back to clear after sanding?

I saw such a white led in a reading light at the mall.


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## L.E.D. (Dec 27, 2001)

I have done this befoe, to a 2100 mcd red LED before. I did it for better focusing capability in the 2AA mag light. Here's what I did:

1) I used a large file to take off most of the plastic from the top until the plastic was maybe .3 milimeters from the "guts" of the LED.

2) I got a very smooth stainless steel slab, got pliers, and used almost all of my body weight (150 lbs) to grind the LED top into the steel.

3) I was quite content with the way it worked with the focusing lens on the 2AA mag light. Puts out an almost perfect circle of light when focused to optimum.


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## L.E.D. (Dec 27, 2001)

Oh yeah, while grinding the LED into the steel, I rotated it to make sure it didn't just make a bunch of lines over the top.


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## The_LED_Museum (Dec 27, 2001)

LEDcorp does something similar to this to the LED used in the Turtlelite. Sino Union and one other Korean outfit also tried this, and eventually got Nichia to make 180° LEDs for them so they no longer had to be hand-ground.

For other colors like red or orange, you'll probably still need to make them yourself.


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## snake (Dec 27, 2001)

Hello Coldlight,
Many thanks for your info!
after I start to convert my 2AA mag with LED by drilling a 5mm hole to the original 3mm hole on the reflector, I have wonder to flatten the LED top and make the reflector works better.
lets try it tonight.
bye


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## L.E.D. (Dec 27, 2001)

Ledcorp's bulbs from nichia are, of course, much more high quality than my "home ground" LED's because they have some sort of milling machine to make a round dome over the top, not just a flat top. Flat top still works good though. You notice on the Dorcy Cool Blue (plastic version) the LED has radial geometric figures on the top, probably to disperse the light even backwards! Hey, how did Ledcorp get those milled Luxeon Star bulbs for the LCpro3 though....???


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## JollyRoger (Dec 27, 2001)

Huh? Milled luxeon star bulbs? If you're talking about their pro series bulbs that use the luxeon star, they are simply luxeon emitters (the luxeon star w/o the optics and removed from the aluminum plate they come on) sitting in a custom-machined pr-base type housing...with a resistor inside.


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## L.E.D. (Dec 27, 2001)

Really? so the Luxeon Star with Optics is using a flat LED?


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## The_LED_Museum (Dec 27, 2001)

Yup. If you take the lens off the LS/O LED, you'll find the same LED you see in LEDCorp's bulb.


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## jeff1500 (Dec 28, 2001)

I wonder if tooth paste would make a good led polishing compound. I've used it to polish out scratches on watch crystals.


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## L.E.D. (Dec 28, 2001)

Yes, it is, actually! I did use toothpaste on my LED also! the reason toothpaste works so good is because it contains "diatomaceous earth". these are dead diatoms which have left behind their shell-like bodies.


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## jeff1500 (Dec 28, 2001)

Here's the Dorcy led:
http://az123.com/LED/dorcolblu/

It still has a dome top, but the dome is machined much closer to the light source. Looks like this makes the beam smaller and more concentrated.


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## jeff1500 (Dec 28, 2001)

http://gbalight.freewebsites.com/progress.html

Here's some comparison photos for flat top and dome top. They're about 1/3 of the way down the page.


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## jeff1500 (Dec 30, 2001)

Flat Top Results

I have a 10 mm, red 5000 mcd led from Radio Shack. It gives just enough light to barely see with at night. It's mounted in a PR base.

I wrapped it with electrical tape to hold it firm, then ground it flat and rubbed it against a metal plate with tooth paste for a couple of minutes. The ground surface isn't crystal clear, but you can see through it.

Sure enough, the beam went from a bull's eye ring pattern to evenly dispersed wide angle. When held about 10 inches from the wall I got a smooth red circle about 12 inches in diameter. Any further from the wall and it's just evenly dispersed light.

Then I put it in a couple of different flashlights. In a 2AA it made a beam that projected about 10 feet in roughly the same pattern as a regular incandescent bulb. Other larger reflectors weren't as good but it did make a beam.

All by itself it fills a volume about 2 ft x 2 ft x 2 ft with no rings or hot spots.

Maybe I can get something for my Dremel tool to polish it all the way to clear.


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## KenBar (Dec 30, 2001)

Jeff15, If you want to get real picky, stop by an auto parts house and get a small squeze bottle of Meguiar's Mirror Glaze #17 Clear plastic cleaner and follow up with #10 clear plastic polish. It will make a mirror finish. Normally it is used for motorcycle winshields. I use it with a Q tip to polish my Arc, watch crystal, etc. It makes them totally new. It never seemed to fail that a new watch would get a scratch right down the middle. It will take those totally out...and put a fine shine on a led after a rough sand job.


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## snake (Dec 30, 2001)

Hello everyone,
I wonder again, if we just use the LED (no casing at all, no plastic, no pin, only the LED ) as some other chip resistor, then we didn't need to file, to sand & to polish.. but we need to make pin for it, but may be we can stuff 2 or more LED into the reflector of the 2AA mag...
any idea ?


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## jeff1500 (Dec 31, 2001)

Motorcycle windshield scratch remover is a good idea, and yes, if you file them down, they take up less room, especially the larger 10 mm variety.


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