DIY LEDs - The write-up

[Neogenocide]

I would tend to think they would be a little weak as their specs have them list a .24 watts compared to the Cree's that tend to be the favorite in this thread.


Scott


Edit: Zur and I posted at the same time.

 

[mdisalvo55]

Hello Everybody,

Quite the thread you have all contributed to here...I am new to the LED world, but very intrigued. I don't know a ton about them, but am the type to learn by doing, so I went ahead and purchased the "premium" 6 led kit from RapidLED.com to try my hand out. I was hoping somebody could help me with a few questions I have.

First, I went with the 60 degree lenses...am I correct in thinking 60 degree lenses will have a narrower beam than the 80's meaning more light penetrates deeper into the water? I am only going to be using them on a Biocube 14 so I don't think it will make much difference but I wanted to know more on this...

Second, I will need to extend the wires from the Driver to the LED's a few feet, is this okay? I thought I remembered reading something about not extending wires with LED's...

Third, I am planning on mounting these around a pendant I am currently using with a 70 watt halide in it. I was planning on simply attaching them straight to the pendant allowing it to absorb the heat (it's doing a pretty good job with the halide).

So, do I have my head on my shoulders here or should I have done more planning?

 

[der_wille_zur_macht]

First, I went with the 60 degree lenses...am I correct in thinking 60 degree lenses will have a narrower beam than the 80's meaning more light penetrates deeper into the water?

Yes. Think of it this way: LED count and drive current determine overall intensity (literally, how much light is emitted). Optics allow you to choose where that intensity goes. Narrower optics mean more intensity over a smaller area. Generally, you want optics when you need to control spread of the light - i.e. if you have a very deep tank, or you are mounting the LEDs well above the water surface. On a smaller tank, if you're mounting the LEDs close to the surface of the water, you probably don't need/want optics.

Second, I will need to extend the wires from the Driver to the LED's a few feet, is this okay? I thought I remembered reading something about not extending wires with LED's...

That shouldn't be a problem. Shorter is probably better, but "a few feet" is well within the range of what people have successfully done before.

Third, I am planning on mounting these around a pendant I am currently using with a 70 watt halide in it. I was planning on simply attaching them straight to the pendant allowing it to absorb the heat (it's doing a pretty good job with the halide).

We'd need to know more about the pendant - material, thickness, overall dimensions, finish (if any), etc. In terms of light output, an equivalent amount of LEDs will put out less heat than an equivalent MH rig, but in the case of the LEDs, it's far more important to get that heat away from the emitter.

 

[mdisalvo55]

Thanks for your help, I'll post some pics a bit later on. It's actually this pendant. I retrofitted the halide into it. Looks like its brushed nickel. So you would suggest not even using the lenses because it's so shallow?

http://www.lowes.com/pd_269908-2121-269908_4294925666+6_4294937087?productId=1240043&pl=1&currentURL=/pl_$50%2Bor%2Bless_4294925666%206_4294937087_

 

[der_wille_zur_macht]

My take would be to put a shallow "real" heatsink in there, with a small fan. Or even just some heavy aluminum bar stock.

Optics - well, you have them, so you can try with and without. It'll depend on how high up you have that pendant. If it's down 6" off the water I would probably not use them. If it's 12 - 18" up, I would definitely use them. If it's 24" up, I'd send back the 60's and get 40's. And so on.

 

[widmer]

Hey guys, does anyone have experience with:

The Carclo XR-E Tight Lens which has an 8.4 degree FWHM beam:
http://ledsupply.com/10199.php

or the Cree Spot Lens 8 degree illumination pattern beam:
http://ledsupply.com/247-10-lens.php

I just returned my 6 degree L2 lenses because they are absolute trash if you really are looking for a nice clean 6 degree beam, but I can't decide which of the above to get as replacements. I'm looking for a clean beam without garbage spill/artifacts/rings etc...

 

[der_wille_zur_macht]

widmer, you might want to ask at candlepowerforums.com - I don't think anyone here is using optics that tight (yet). Meanwhile, it's right smack in the range that the flashlight hobbyists are using all the time.

 

[TheFishMan65]

Maybe this will help

Maybe this will help

Widmer you and der_wille_zur_macht were discussing this in the "underwater LED setup help" thread (http://www.reefcentral.com/forums/showthread.php?t=1774231&highlight=degree), I think.

Anyway the angle needs to be doubled (I think) because you get the spread in all directions (left, right, back and forward). One of you mentiond the trig would give a of 8 inches, but the other measured it at 13 (close to double and I got 7.5 with my calculations). Here are some number I calculated if it helps.

Degree..... 6 ft ...... 5 ft ...... 4 ft ...... 3 ft ...... 2 ft ..... 1 ft
.. 6 ... 7.56750 ... 6.30625 ... 5.04500 ... 3.78375 ... 2.52250 .. 1.26125
.. 8 .. 10.11894 ... 8.43245 ... 6.74596 ... 5.05947 ... 3.37298 .. 1.68649
. 40 .. 60.41517 .. 50.34598 .. 40.27678 .. 30.20759 .. 20.13839 . 10.06920
. 60 . 124.70766 . 103.92305 .. 83.13844 .. 62.35383 .. 41.56922 . 20.78461
. 80 . 408.33229 . 340.27691 . 272.22153 . 204.16615 . 136.11076 . 68.05538
Well if I retyped the number right that is my findings. Does anyone know a better way to do a table?
I also wonder if we can mount them on the ceiling (I was thinking of doing it to). With 8 degree lens even at 6 feet you get a calculated of ten inches to one side. So I think we are already starting with a 20 inches spread.

Now I could be wrong. Someone said 13 inch spread with 6 degree at 6 feet. Which is close to my calculation (15). The problem is I haven't seen any 6 degree optics for sale - and one person was miss remembering 6, but admitted they used 8. Don't remember if it was one of you or some one else (lots of LED threads).

Disclaimer: Lenses are definitely not my specialty

 

[ReefMan1111]

do you have to dim the led lights?

 

[widmer]

Widmer you and der_wille_zur_macht were discussing this in the "underwater LED setup help" thread (http://www.reefcentral.com/forums/showthread.php?t=1774231&highlight=degree), I think.

Anyway the angle needs to be doubled (I think) because you get the spread in all directions (left, right, back and forward). One of you mentiond the trig would give a of 8 inches, but the other measured it at 13 (close to double and I got 7.5 with my calculations). Here are some number I calculated if it helps.

Degree..... 6 ft ...... 5 ft ...... 4 ft ...... 3 ft ...... 2 ft ..... 1 ft
.. 6 ... 7.56750 ... 6.30625 ... 5.04500 ... 3.78375 ... 2.52250 .. 1.26125
.. 8 .. 10.11894 ... 8.43245 ... 6.74596 ... 5.05947 ... 3.37298 .. 1.68649
. 40 .. 60.41517 .. 50.34598 .. 40.27678 .. 30.20759 .. 20.13839 . 10.06920
. 60 . 124.70766 . 103.92305 .. 83.13844 .. 62.35383 .. 41.56922 . 20.78461
. 80 . 408.33229 . 340.27691 . 272.22153 . 204.16615 . 136.11076 . 68.05538
Well if I retyped the number right that is my findings. Does anyone know a better way to do a table?
I also wonder if we can mount them on the ceiling (I was thinking of doing it to). With 8 degree lens even at 6 feet you get a calculated of ten inches to one side. So I think we are already starting with a 20 inches spread.

Now I could be wrong. Someone said 13 inch spread with 6 degree at 6 feet. Which is close to my calculation (15). The problem is I haven't seen any 6 degree optics for sale - and one person was miss remembering 6, but admitted they used 8. Don't remember if it was one of you or some one else (lots of LED threads).

Disclaimer: Lenses are definitely not my specialty

Hi there-

I was working with the 6 degree lenses, but officially dropped them in the mail and returned them yesterday. The thing that's important to understand, which I didn't initially catch onto, is that the 6 degrees is actually the FWHM value. This means that it's not simply that the cone of light will be 6 degrees from edge to edge, but it will in fact be considerably wider. See http://en.wikipedia.org/wiki/Fwhm for more info.

Anyways, I was working with http://ledsupply.com/optx.php lenses, but if you go back a couple pages, you can read about how I found them to be absolute trash.

 

[widmer]

widmer, you might want to ask at candlepowerforums.com - I don't think anyone here is using optics that tight (yet). Meanwhile, it's right smack in the range that the flashlight hobbyists are using all the time.

Thanks I just created a post there. We will see what becomes of it

 

[der_wille_zur_macht]

do you have to dim the led lights?

You don't have to, but you can. Were you wondering about a certain situation?

 

[der_wille_zur_macht]

Widmer you and der_wille_zur_macht were discussing this in the "underwater LED setup help" thread (http://www.reefcentral.com/forums/showthread.php?t=1774231&highlight=degree), I think.

Someone needs to sit down and do some calcs on fixtures that are already up and running, to find out what coverages and overlaps are typically being used. Then, we can extrapolate up from there for fixtures mounted higher.

Anecdotally, I would expect that if you measured the distance from an LED to some magic point in the tank (the middle? the bottom?) in a typical build, you'd find that the FWHM "circle of coverage" was around 20 - 40". Consider the table you posted - most people with "typical" LED mounting heights (say, 8 - 10" above a tank 18 - 24" deep) are using 60's, 80's, or no optics. That puts them right in that range.

If we try to extrapolate that up to pick an optic for use at 6' (mounted in the ceiling), the 8's are probably OK, or maybe even TOO narrow.

Though, we have to consider other things - the shape of the cone for an LED mounted 18" above a coral with 80 degree optics is going to be pretty fat. This means that as you move the coral higher or lower in the tank, there will be a large variation in light intensity. On the contrary, if you mounted the LED at 6' high and used an 8 degree optic, the cone would be skinny - this means that intensity would be very consistent from the top of the tank to the bottom, so the two situations are not totally equivalent. Light from the "high" fixture with tight optics would also be much more laminar, so shading would be much more severe. If someone is going to go this route, it might be prudent to spread the LED panels out farther apart than the length/width of the tank and angle some of them, to get some light at a steeper angle, to prevent shading from killing off lower branches on coral colonies.

 

[widmer]

der_wille:

From my experience with the six degree FWHM optics, I can guarantee that the spread of light is certainly too wide still if the goal is to limit your spill of light projected outside the edges of the aquarium, unless you are working with a tank which is at least 18 inches front to back (which I guess most people are). Still, I would guess that the best FWHM value is closer to 2 or 3 degrees believe it or not. Remember, FWHM does not describe the diameter of the spot which is cast. It in fact only describes a fraction of the diameter.

As far as spreading out the panels is concerned, this has been exactly my thinking as well, and I am in the process of constructing a fixture from two thin (1.25") heatsink strips with one at the front and one at the back, angled inward. But even if they sit at the perimeter of the aquarium, at the height of 6 feet, the light is still coming in at such a slight incident angle that it will still be virtually laminar. Consider the hypotenuse of a triangle which is 72 inches long and only 12 or so inches wide. However, this is not such a bad thing, considering that the more perpendicular the angle is at the interface of air:water, the less refraction that will occur which spills light back out into the room, and thus the greater efficiency of the light entering the tank. And I am actually predicting that once it is up, there should be some pretty cool shadow effect occurring under overhangs, in caves etc.

So I have (temporarily) abandoned my dream of mounting the fixture directly on the ceiling of the room. The light spill is simply too great with the optics which are made for the Cree LEDs at this time. I just want to get this thing put together ASAP after talking about it for several months, and it should be completely built by the weekend or Monday at the latest.

And finally, what I believe is the biggest thing the LED industry needs right now as it pertains to all of the aquarists and potentially other groups as well [IF YOU ARE AN LED COMPANY PROSPECTING YOU SHOULD PAY ATTENTION HERE] are optics which can be adjusted to focus the light to any spread desirable. This is actually a very simple thing to do; all it would take is a convex lens and a simple holding apparatus from which the user can fine-tune the distance that the lens is held from the LED emitter (think, the way a flashlight works). I'm sure I will eventually be doing some sort of retro version of this, but maybe not until the summer.

 

[TheFishMan65]

Another thought on light spread

Another thought on light spread

Light is measured on optical density, which is logarithmic. An OD 1.0 is ten times less light. The FWHM is the 50% point. This is an OD of about .3. If I remember right the eye is right on the edge of being able to detect a 50% change in light. So if you are worried about alga growth on the glass we maybe OK (they may not get enough light). If on the other hand we are worried about what our eyes see in terms of overspill then we maybe in more trouble. I can't seem to find a reference now, but I will look some more.

 

[mm95z71]

Potentiometer

Potentiometer

Does abyone knoiw if you can run more than one buckpuck off of one potentiometer? Was thinking of running all blues on one and all whites on one. Keep me from having 6 knobs to control my array. Thanks.

 

[kcress]

widmer; You should try some different optics. I've used some that were cheap and put a small artifact-free circle on the wall six feet away. Infact I was working on a commercial luminaire and the spots were way too small for me to work with.

I believe you just got crappy optics there. I remember I got mine from Digikey.

 

[der_wille_zur_macht]

Does abyone knoiw if you can run more than one buckpuck off of one potentiometer? Was thinking of running all blues on one and all whites on one. Keep me from having 6 knobs to control my array. Thanks.

The REF pin on a buckpuck can supply 20mA at 5v. Each buckpuck's CTRL pin takes ~5mA at 0-5v DC. Based on those specs, you could run 4 buckpucks on one pot, using one buckpuck's REF pin to power the pot.

Or, you could use an external power supply (i.e. a 5v wall wart) and ground it to the LED- pin as shown in the datasheet. Then you could run as many buckpucks as you wanted from a single pot.

 

[TheFishMan65]

I just checked and Digikey has a 6 degree lens by Ledil, $2.10, but unclear if you need a holder. If you check out the data sheet it shows a 3 degree lens in the same family. If 100% is center light, then at +/- 5 degrees we are down to 25% and almost 0 at +/- 10 degrees. Of course Digikey does not carry the 3 degree. We might be talking ceiling here!

6 degree lens: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=711-1047-ND

I should add these are for Cree XR-E

 

[der_wille_zur_macht]

One of the LED vendors might be able to get stuff at a better rate than digikey, or might already have it - I'd check ETG at least, they seem likely to have hidden treasures like this.