Questions about LED lenses
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Old 03-03-2014, 02:19 AM   #1
DarkCobra
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Questions about LED lenses


I've been shopping around for some lenses to fit some "bead" type LEDs on stars. The vast majority seem to be of this style:



It's got a cutout on the bottom for the bead LED itself, that's good. But the diameter is slightly larger than the star, and there's no cutout for the wires or solder joints that attach to the star. Which means this won't mount flush and proper, it'll be riding on the solder joints.

Are you expected to Dremel away part of this to accommodate your connections? Or apply big globs of silicone and hope for the best? I have some high temp silicone sold for attaching lenses, but it's so low viscosity it might just flow out of any gap where the parts aren't in direct contact. What am I missing here?

Also, is there any difference in beam uniformity between the "smooth" lens shown above and a "bumpy" lens like this?



Or anything else I should be looking for in a decent quality optic?
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Old 03-03-2014, 04:59 AM   #2
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I don't think the optics (lenses) I have used had that shape. Those just fit over the LED "bead", and were easy to attach with a tiny dab of silicone. It looks like the ones you show here are intended for stars with the wires directly opposite each other, so the cutouts fit over the soldered connections. As far as I have seen there is no standardization for the optics.
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Old 03-03-2014, 05:26 PM   #3
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Hmm, don't think I've come across a star with that configuration yet. Odd.
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Old 03-03-2014, 09:09 PM   #4
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Quote:
Originally Posted by DarkCobra View Post
Hmm, don't think I've come across a star with that configuration yet. Odd.
The plastic part just looks to fit the "wings" on a naked LED "egg".........
But that being said.. most are " opposite" you just need to rotate your vision..


Looks to be for surface mounted.. like this:



side notched style:


3rd style (backside) w/ standoffs..


There is a picture of how this one is mounted..

I commend you for going down that road..
One thing to keep in mind is that they are designed w/ a particular focal length. Gobbing silicon and "pushing" the lens plane forward could change you collection efficiency.. W/ the type you have, mounting the black part as close to the heat sink plane as possible will keep the lens within the design parameters.. Since it appears to be surface mounted "somehow" i.e glue.. there is probably a bit of wiggle room but notching seems best..
Oh and the 3rd style is more accommodative to the type of wiring "we" usually do..
http://ledil.fi/sites/default/files/.../Article_1.pdf


Last edited by jeffkrol; 03-04-2014 at 12:46 AM.. Reason: more styles
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Old 03-04-2014, 02:34 AM   #5
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Thanks, [Jeffkrol]!

I went ahead and pulled the trigger on an order of style #3 from LedFedy. May still have to do a little Dremel modification, but if so, the separate side "skirt" looks like it will make it easier. I'll need plenty of space between lens and star to accommodate my wiring, as I'll have four independent channels and my intended cross-section is this:



Showing:

(1) 2" x 1/2" x 1/8" Aluminum Channel
(2) 1-1/4" x 1/16" Aluminum Flat
(4) 1/4" x 1/16" Aluminum Angle
(1) 2" x 1/16" Acrylic
(2) LED stars
(2) LED lenses

Aluminum/acrylic are off-the-shelf sizes, so all I have to do is cut to length. The angles will be glued to the flats with JB Weld, which has at least some thermal merit over regular epoxy. Then that assembly will be screwed to the channel with thermal grease at the interface, and removable should I need full unfettered access to maintain LEDs. I'm trying for fully passive cooling, and a small scale test looks promising; but if needed I can attach some heatsinks/fans in the inside of the channel.

Inside there will be clusters of four LEDs. One channel of 3W Cree XT-E 4500K's driven by a Meanwell LDD-700H. Three more channels of cheap 1W LEDs (460-470nm, 500-505nm, and 660nm) will be driven by LDD-300Hs. Some simulations on BuildMyLed say I can emulate just about any color balance I desire with this setup, including 5700K sunlight, or the DD Giesemann Midday/Aquaflora combo; with CRI up to 97 possible. LEDs will probably be attached with some silicone thermal glue I just discovered. All electronics short of the LEDs will be off-board, and connected to the fixture via RJ45 jacks and cable. There is some voltage/power loss due to 24-26AWG wire resistance but estimated at less than 1W, which I consider acceptable. Top it all off with a 48V 3A power supply, and a custom MCU/RF board.

Wish me luck! Now after all this frantic planning I gotta wait around a few weeks for orders from overseas. That may be the hardest part, LOL.
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Old 03-04-2014, 03:26 AM   #6
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Quote:
Wish me luck! Now after all this frantic planning I gotta wait around a few weeks for orders from overseas. That may be the hardest part, LOL.
good luck.. shipping is faster now that Chinese New Year is over........
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Old 03-04-2014, 04:09 AM   #7
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Quote:
Originally Posted by jeffkrol View Post
good luck.. shipping is faster now that Chinese New Year is over........
No doubt, I've learned to avoid that, especially after trying to import bettas during that holiday!
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