DIY LEDs - The write-up

[kentrob11]

OK so I am trying to get an idea of what the best LED layout would be for a 30" x 8" heatsink. I'm putting this over my oceanic 58 (36 x 18 topdown dimension) using 48 LEDS. Here's a pic of what I figured I'd do. The yellow squares are cool whites and the blue dots are royal blues. The grid is to scale, 1" per square...thoughts?

 

[der_wille_zur_macht]

Looks like it'll be "weak" in the corners.

Do you have an overflow box? I'd consider moving LEDs away from that part of the tank to fill in the corners if you want light there, since it'll be wasted near the overflow.

 

[kentrob11]

Heh...Well, there is virtually no overflow on the inside of my tank. I did a custom overflow after ripping out the stock overflow box so basically I've got a full tank to work with. See pics below...

So if you had to do it, how would you lay this 48 led configuration out? This is a little tougher than I thought without going 1:1 blue to white!

 

[der_wille_zur_macht]

Instead of doing 8-10-8 for the three rows of CW, I would do 9-8-9. Similarly, instead of 4-5-4-5-4 for RB, I would do 5-4-4-4-5.

That's a pretty wicked overflow box. Have you run it yet?

 

[widmer]

I have the exact same oceanic in my basement...great relative dimensions.

FYI thats a really slick overflow box...

 

[der_wille_zur_macht]

It IS a nice tank size. Definitely my favorite "small" tank. I had one horded away in my basement too, till I recently gave it to another reefer who's got some really cool plans for it.

 

[kentrob11]

Thanks guys...The overflow works really well combined with a sump I built to go with it...Basically 4 1/2" standpipes with gate valves mounted at sump level to fine tune. I didn't want the tank to be off the wall much and yet didn't want a bulky overflow in the tank. Here's the sump end:

Anyway...back to the thread topic

I decided to just put an extra driver on and go with more led's for coverage...How's this?

 

[widmer]

Very clean setup. Hopefully you've got a safety overflow drain line in case something clogs one of your drains which is gated in the sump, so that the pump doesn't overfill the tank. More LEDs for smoother coverage is probably great IMO, as long as it's in your budget. It could be even cooler if you wanted to split the heat sink in half the long way, and then do half more toward the front and half more toward the back of the tank, having them both angled in for better coverage, because it is an 18" wide tank...Maybe not totally necessary to do though I'm not sure.


der_wille: So my power supply is the only missing link in my plans at this point, and I'd like to build my fixture this weekend, up to the point where I will simply plug it in. Question: In the meantime, can I just connect up one of my dimmable buckpucks to a 12v wall wart, and use that to test each LED because even tho it's 12v, electricity flow is current-limited by the buckpuck?

 

[kentrob11]

Each one of the standpipes is slightly higher than the one before it and only two of them are gate valve adjusted. The redundancy is definitely there and two of them could handle the 500gph that is going through them easily. Less flow through each pipe = less noise...I think that would have been a good idea as far as the tilted heat sink goes but I already ordered it so I'm kinda stuck with an 8.5 x 30 now I think 53 LEDs should be good for coverage with this setup. I'm thinking 60 degree optics on the whites with maybe 80 on the blues? Not really sure there...

BTW, are the Cree XP-E Q5's sold on the black stars on Deal Extreme the same as the ones sold on rapidled.com? Will the same optics used on Q4's fit on the Q5's?

 

[widmer]

der_wille: So my power supply is the only missing link in my plans at this point, and I'd like to build my fixture this weekend, up to the point where I will simply plug it in. Question: In the meantime, can I just connect up one of my dimmable buckpucks to a 12v wall wart, and use that to test each LED because even tho it's 12v, electricity flow is current-limited by the buckpuck?

The good news: I had an extra $4.50 XRE laying around so I just tried it... Actually I used an 18v 300mA wall wart hooked into the buck puck and it didn't fry so hooray.

The bad news: I couldn't tell before because the LED was barely lit, but when pushing 300 mA through it just now, I've found that the 6 degree optics from LEDSupply are VERY disappointing. Sure, the light is brightest in a circle which is cast at 6 degrees, but there is also an enormous amount of light spill in a surrounding area of something I would guess is closer to 20 degrees. So now I'm between playing with the idea of mounting them on risers to focus the light, or returning them to LEDSupply to get my money back and go a different direction...

 

[jma1978]

The bad news: I couldn't tell before because the LED was barely lit, but when pushing 300 mA through it just now, I've found that the 6 degree optics from LEDSupply are VERY disappointing. Sure, the light is brightest in a circle which is cast at 6 degrees, but there is also an enormous amount of light spill in a surrounding area of something I would guess is closer to 20 degrees. So now I'm between playing with the idea of mounting them on risers to focus the light, or returning them to LEDSupply to get my money back and go a different direction...

The light spread you are describing seems to be the spread that is on the data sheet, and therefore should not have disappointed you. They will cast a beam 30 degrees wide, but 50% of the light is within the first 6 degrees.

 

[widmer]

The light spread you are describing seems to be the spread that is on the data sheet, and therefore should not have disappointed you. They will cast a beam 30 degrees wide, but 50% of the light is within the first 6 degrees.

This does not jive with what wikipedia tells me. Full Width at half maximum (FWHM) seems to be the industry standard for describing these optics, and as the name states, this is the range of spread at which the edge decreases to half of the maximum intensity observed (normally half as strong as the dead center), not the same as 50% of the light. Also, nowhere in the data sheet does it say they will cast a beam 30 degrees wide, where did you get this figure?

If you see a FWHM divergence chart such as the one found on wikipedia at:
http://en.wikipedia.org/wiki/Fwhm

Or this one (unable to link wikipedias .png file)

It would appear that something in the very high nineties% of the light would fall within twice of this value, or 12 degrees in the case of the 6 FWHM optic, and there should be no light falling outside of three times this value, or 18 degrees in the case of the 6 FWHM optic.

However, I wish I had a picture, because it seems to leave an asymmetrical, dirty and very wide beam as well as a really disappointing right of light around the edge of the artifacts as well. Also, the rate at which the intensity decreases once it is beyond the FWHM value absolutely does not resemble a standard FWHM curve. I only hope that LEDSupply will allow me to exchange these things.

 

[jma1978]

This does not jive with what wikipedia tells me. Full Width at half maximum (FWHM) seems to be the industry standard for describing these optics, and as the name states, this is the range of spread at which the edge decreases to half of the maximum intensity observed (normally half as strong as the dead center), not the same as 50% of the light. Also, nowhere in the data sheet does it say they will cast a beam 30 degrees wide, where did you get this figure?

If you see a FWHM divergence chart such as the one found on wikipedia at:
http://en.wikipedia.org/wiki/Fwhm

Or this one (unable to link wikipedias .png file)

It would appear that something in the very high nineties% of the light would fall within twice of this value, or 12 degrees in the case of the 6 FWHM optic, and there should be no light falling outside of three times this value, or 18 degrees in the case of the 6 FWHM optic.

However, I wish I had a picture, because it seems to leave an asymmetrical, dirty and very wide beam as well as a really disappointing right of light around the edge of the artifacts as well. Also, the rate at which the intensity decreases once it is beyond the FWHM value absolutely does not resemble a standard FWHM curve. I only hope that LEDSupply will allow me to exchange these things.

I stand corrected, maybe it's not 50% of the light, but if you look at the curve in the figure you posted, it sure seems like there is quite a bit of area under the curve and outside of the FWHM zone. Been a while since I did that kind of math, so I'm not interested in figuring out exactly...
Maybe you did not buy the same lens I looked at, but here is the link: http://ledsupply.com/docs/L2-Optics-Luxeon.pdf
The spot lens in there goes out to 30 degrees. Is this the right lens?

 

[widmer]

Those are 5 degree lenses for Luxeon, I bought 6 degree lenses for Cree XREs I'm using. Actually, I'm not sure if anyone on this forum is using Luxeons. Anyways, here is my spec sheet:

http://www.dialight.com/Assets/Brochures_And_Catalogs/Illumination/MDEXLUMADBCREE.pdf

Also, pertaining to the datasheet you're referring to for the Luxeon 5 degree lens- the only chart that they have provided which attempts to explain divergence for this lens is terribly non-userfriendly in that the x-axis isn't even labeled. But if we were to assume that it were in degrees, then we would somehow find that the 5 degree optic casts a beam which ends up being 60 degrees in diameter rather than 30. This doesn't make sense either...

Why can't lenses be cooler...

 

[der_wille_zur_macht]

I decided to just put an extra driver on and go with more led's for coverage...How's this?

That looks fine but it's going to be a pretty high amount of light in your tank. Might want to plan for dimming and/or some other way to mitigate that if it's too much.

BTW, are the Cree XP-E Q5's sold on the black stars on Deal Extreme the same as the ones sold on rapidled.com? Will the same optics used on Q4's fit on the Q5's?

Yeah, from bin to bin the physical specs don't change, so no worries there.

The good news: I had an extra $4.50 XRE laying around so I just tried it... Actually I used an 18v 300mA wall wart hooked into the buck puck and it didn't fry so hooray.

With a buckpuck, any PS with a voltage higher than the output voltage, and enough current capacity, will work fine. Current capacity is hard to figure, since as the voltage difference increases, the waveform the PS sees will get more drastic. But hey if it worked, that's great.

The bad news: I couldn't tell before because the LED was barely lit, but when pushing 300 mA through it just now, I've found that the 6 degree optics from LEDSupply are VERY disappointing. Sure, the light is brightest in a circle which is cast at 6 degrees, but there is also an enormous amount of light spill in a surrounding area of something I would guess is closer to 20 degrees. So now I'm between playing with the idea of mounting them on risers to focus the light, or returning them to LEDSupply to get my money back and go a different direction...

I've definitely seen plenty of variation in the optics I've tried, though this sounds a bit more pronounced. Maybe order just one or two of some other optic to try? Perhaps those other 6 degree optics from ledsupply?

 

[kentrob11]

OK...So I decided to quit making this so complicated for myself and just got in on the group buy for the following:

(24) XR-E Q5 Cool whites
(24) XR-E Royal Blues
(24) 80 degree optics
(24) 60 degree optics
(4) Meanwell eln 60-48p dimmable drivers

So now it looks like I am on the board for just about everything accept the black acrylic for the fixture. I've already got a 3" icecap temp controlled fan to use on it. Can I run 2 of those fans off a single temp controller?

I decided that I would rather dim the lights to acclimate than raise them since I'd like to make the mount for the fixture and not have to touch it. Ho do you dim the lights with that driver? Is there a knob on the side of it?

 

[widmer]

I've definitely seen plenty of variation in the optics I've tried, though this sounds a bit more pronounced. Maybe order just one or two of some other optic to try? Perhaps those other 6 degree optics from ledsupply?

Could you link? For the Crees I have only seen the 8 degree (made by Cree as well) and the 8.4 degree (made by Carlco).

Actually I had picked up some of the ripple medium Carlco (16 FWHM) lenses for another project and did a side-by-side comparison last night between those and these 6 degree lenses. ALL I can say is LOL @ how much cleaner the beam that the carlco produces is cast. As far as I can tell, the carlco beam was pretty much uniform throughout with ZERO artifacts and ugly spillage. What's funnier, is the beam from the carlco 16 FWHM is really not that much wider than this 6 degree lens...

I'm going to call LEDSupply today with hopes of trading these things in, wish me luck (if they're even open on the weekends...)

 

[stugray]

"(4) Meanwell eln 60-48p dimmable drivers"
....

"Ho do you dim the lights with that driver? Is there a knob on the side of it? "

Actually you chose the driver that is the hardest to dim.

You will need a PWM ( Pulse Width Modulation ) circuit to dim that driver.

This can be done with a Microcontroller like the Arduino and you would be able to dim each driver separately.

If you got the Meanwell eln 60-48D dimmable drivers, then you could have done it with an Apex reef controller or a knob.

Stu

 

[kentrob11]

OK well it's not too late to change...I'll go ahead and switch to the D instead of the P. So does the "P" driver have a knob on the driver or is that something I need to put together separately? I have a Reefkeeper lite...I dunno if that helps...

 

[kentrob11]

OK..I went ahead and changed my order to 24 XP-G cool whites and 24 XR-E Royal Blues. I also changed the drivers to the D models...