20 Gallon Long LED Build

[Zack]

Sometime this Summer I plan to move my existing livestock into a 20 gallon long. With that, I'm going to need a new light and I've decided to go with the 24 LED DIY kit from rapid led. Has anyone on here done a 20 long build? If not, I'm sure some of you more experienced people can help me. Here's what I'm looking for.

1) I would like it to look 20k. I am going dimmable but I've read a couple of different reefers online who said that no matter how much they dim, it never looks right going 1-1 Blue to white. On another site I've read that a 3:2 ratio of Blues to Whites works well so for now my starting number is: 14 Royal Blue to 10 Whites (either Cool White or Natural White). I could be wrong and maybe 1:1 is the way to go so feel free to jump in here.

2) I honestly have no idea where to start on the heat sink size. I've read several different build threads and they seem to be all over the place and most are either not done or the user just stopped posting. This is a standard 20 long and the dimensions are 30 1/4 x 12 1/2 x 12 3/4. I mostly want to focus on LPS and softies.

Here's what I'm thinking of right now for my layout.

WBWBWBWB
BBWBBWBB
BWBWBWBW

Maybe this layout might seem weird, but I've never worked with LED's so if anyone could help me out that would be awesome!

[rrasco]

I went 2:1 with royal blue to neutral white. Then, I substituted four of the neutral whites for some two cool white and two warm white. I also subbed two royal blues for two pinks. This was for 36 LED units, I was building 3 for my 210. I've stalled now as I had to get a replacement tank, so I have no in-use experience with this system yet, so I can't speak for it's effectiveness, but I can answer most of the theoretical questions you can throw at me. :shades:

These pictures are varying intensities, but the blue and white were running at the same current. When I run them on the tank, the whites will have a higher current than the blues.

147741477514776

[Zack]

Awesome! Ok so for the heat sink, what size would you recommend for a 20 gallon long? Also, for my potential layout, do you see any problems with coloration? I want the entire tank to have a uniform color and that for me is giving me the biggest headache. I was thinking of even just going for something like:

BBBBBBB
WWWWW
BBBBBBB

Or something like that, but then again I have no idea what result that would give me. Also, just curious, what are the pink LED's for? Is it to bring out certain colors in your coral?

[rrasco]

I wouldn't do it like that, you would probably end up with one solid line of blue, white, blue. I would do something like:

BBWBBWBB
WBBWWBBW
BBWBBWBB

It can be tricky to get a symmetrical layout. I added the pinks (and the WW and CW) to add as many possible spectrums of light as I could. LEDs have a much more narrow light spectrum, meaning they are not full-spectrum like T5 or MH so you have to add more colors to get a wider spectrum. I tried to add as many as I could of each, even if it was just two per unit, because I'd rather the spectrum be there at a low intensity than not there at all.

I don't recall the 20L dims right off hand so I'm not sure about the heatsink, but I would recommend trying to get as much coverage as you can by spacing the LEDs out instead of relying on optics for the spread. My units are roughtly 20x18 which was for a 72x24 tank. I originally bought 8x16 heatsinks but saw a 210 with the same type of layout and each unit was spotlighting bad. That's when I opted to use c channel and went with a larger unit.

You also want to make sure you match the LEDs to what your driver is. My drivers run strings of 6 LEDs each, so putting 8 white and 16 blue would be difficult for me. I have 36 LED units so I just run 6 drivers per unit and am able to keep the strings matching my drivers.

This is the layout I went with.

14777

[Zack]

Wow, I actually didn't even consider the driver to LED aspect of it however the Drivers in the kits say that they can run 8-14 LEDs so I should be right on that lin. The dimensions are 30 1/4 x 12 1/2 x 12 3/4 so I'll look into a heatsink with some good dimensions. Have you made a case for your LED unit? And are you running any cooling fans?

[rrasco]

I'm going to trim the sides with black acrylic and put a splash guard of clear acrylic on the bottom. I am leaving the top open to cool. These things don't get that hot at all, I've had one running for a good 30-40 minutes and it wasn't even warm. The LED stars got warm when I tested them off the channel, but with the channel, no heat at all. I don't want to close the top of my units in fear of trapping any heat, but I may end one later depending on if the light reflects up or it's necessary for some other reason. The heatsinks people are using for DIY LEDs are extremely overkill IMO. I have three 8x16 I'm not sure what I am doing with yet. Not planning any fans.

These are the units I am building. I will only be using two of them for my 105 which is 48x24 though.

14778

[Zack]

Wow those look sick. Just curious, how did you mount your LED's to the heatsink? I see some people using thermal adhesive and some using thermal pads. Also, what is the point of drilling and tapping a heatsink? Is it to run the wires through the back?

[rrasco]

I drilled and tapped my c channel, which is my heat sink. When you can replace an LED by unscrewing it and putting another one on, it is easier IMO. I used thermal grease instead of thermal adhesive, which is the way to go without drill and tap. I didn't run my wires through the back, I just used a thin c channel and wrapped them behind it and used the channel as a wire raceway.

1478414785

[Zack]

Oh ok, so the drilled/ tapping is to make the LED system easier to perform maintenance on? Also how do you screw the LED into the heatsink? Do you have to drill the actual LED frame itself? I might have to go check out your setup sometime this summer before I start my build. Just curious, in your opinion, are the multiple small heatsinks with open space between them the way to go over one solid heatsink? It seems like it would allow for much better heat dissipation.

[bfoleyiii]

Heat sink size will vary depending on if you want to go active or passive cooling. I have two 20x7 heatsinks running about 38 LEDs on each, at about 80% power they don't need cooling fans. You need to decide if you are using optics or not, and how high the fixture will be above the tank. I ran a 2 blue to 1 white mix, and with the dimmable drivers you can go from extreamly blue to a very crisp white, to an almost yellow if you want. If I was doing it over I would try to mix some of the UV in to get some of the other colors to pop better.

I used the little sticky thermal pads to attach mine and they are doing fine for thermal transfer. I didnt have a drill press so I wasnt interested in trying to drill and tap with my hand held. Running the wires on the back side of the heat sink is really only cosmetic and since mine sits inside my canopy I didnt bother.

[Zack]

Can I see some pics of your setup? And how do you make sure the thermal pads don't come un-stuck? Are they just that sticky? I may just drill/tap them. I emailed rapidled and I'm going to see what they have to say and post that here.

[bfoleyiii]

There are a few pictures here: http://www.maast.org/showthread.php?69294-Couple-of-pics-for-my-DYI-LED-build.