Need guidance/advice on LED build

[reickler]

Hello,

I'm new here (at least as a registered user), so go easy on me...

I'm looking to upgrade the lighting in my tank and thought I'd take the DIY route. I've read a good deal of info on the subject and really liked the results some of you have achieved. While I'm fairly certain I've made a selection and I can "do it [my]self", I don't wanna try without first bouncing a few ideas off the community and getting confirmation that I'm taking the right approach.

So to try and preemptively answer a few questions about the tank; I've got a 75 gallon "uniquarium" with mostly LPS and soft corals, though I do have a birds nest and a clam right at the top of the tank just inches below the lights. It's got 2 white 54 watt T5 and 2 blue 54 watt T5 (48") bulbs in there now...and now the questions:

LED's:

1) From what I've been reading, it sounds like the rule of thumb for determining the number of LED's to use is "( L x W ) / 16". So for a 48" x 18" (21" deep) tank like mine, that'd be 54 LED's. Since my tank has the plumbing in the back, do I subtract that space from this calculation, as it seems it would mean the difference of 14 LED's and 2 drivers (or about $100)?

2) I've been reading that Cree is the "standard" in DIY, but that Bridgelux is an acceptable alternative. For roughly the same price, I can get either 48 Cree OR 72 of the Bridgelux. Putting aside the cost for a minute, I've got a hood on the tank with about 7" of clearance. With a heatsink and fan, I'm guessing that'd put the lights about 4" off the water. With the lights so close to the tank, would it make sense to use more of the lower output lights, closer together as opposed to less of the higher-output lights spaced further apart?

3) Seems most example lighting rigs I've seen are suspended from the ceiling over an open-top tank. I've got a lexan lid on the tank (under the hood). I'm guessing there's no "UV protectant" or whatever would block light rays from going through (aside from maybe some salt). Is that something I need to worry about/consider when choosing the lighting? Will the LED's penetrate it OKAY?

Drivers:

1) For the drivers, it seems a lot of people are using the Meanwell ELN-60-48P (I plan to eventually use Arduino to dim them). What's the reason for this model being so popular? From what I've gathered, the number of LED's you can run per driver is determined by dividing the forward voltage (3.7 in the case of the Cree) into the wattage of the driver. In the case of the ELN-60-48P, that's 48w / 3.7v = 12 LED's. I see that there's an LPF-90D-48 model that supports pulse width modulation that's 90W. Would that give me twice the number of LED's ( 90w / 3.7v = 24 LED's)? The price of 2 of the 48 watt ones far exceeds the price of a single 90 watt.

2) Regarding the Meanwell drivers, I've read that they have a 10% lower limit or something like that. Am I to understand that to mean it can only be dimmer to ~10%? If so, how would you turn it off completely?


Heat sink:

1) What is the consensus on multiple small vs. single large heat sink? Would it be better to have say 1, 24" heat sink or 2, 12"? Would the added surface area/open space between two smaller ones provide any benefit or is one larger hunk of metal better from a heat dispersion perspective? Along those same lines, I found some old PC heat sinks on Ebay. Would say, one heat sink per LED, spaced out and connected to an aluminum frame (if you can picture that) work out okay?

2) Screw or glue? Seems like a lot of people "glue" down the LED's. Seems kinda permanent to me. What would be the downside to thermal greasing/screwing them down so they can be replaced/moved later if need be vs using the thermal adhesive?

3) Black or silver? I see on the various sites that sell LED's for tanks, that they usually have either black or silver heat sinks for sale. Does the reflectiveness on the silver do anything for the lighting/cooling? Does the black retain more heat? Enough where it matters?


Vendors:

1) If I go with Cree, I might purchase from rapidled. I've read good things about them, and they seem reasonably priced. Is this a good option for Cree lighting in the US?

2) Aquastyle Online - This is probably where I'd get the Brigelux, though they'd charge like $80 for shipping! Is there somewhere better for Bridgelux?

Thanks in advance for all of your assistance!

[pwreef]

L1 = 1 LED per gallon. so you need like 70+ or you will not be able to cover well. look here for most of your questions: http://reefledlights.com/ledmytank/
L2 you need the same amount of either cree or bridgelux unless you get XML. that close to the water you cannot use any optics so your tank is going to look much dimmer than with optics. you also need to be ventilating well.
L3 you dont need any protectant, only from salt spray if you are that low. Light will be reduced by any protectant you put between leds and water.
D1 Always divide volts by volts. so if driver is 36 volts max you can put roughly 36v/3v = 12 leds. Go by what the vendors recommend. inventronics drivers are also a very good choice. they are 1/2 the size of meanwells.
D2 yes, you will need an on/off timer like regular lights

H1. its just more work if you have so many of them. you will have wires all over the place. one or two makes it simple and neat. there is no benefit thermally to have so many. at least not for this application
H2 drilling and tapping a heatsink is a labor intensive and long process. glue is fast. You can always remove later, depends on the glue.
H3. only for looks. leds point down as they are a point source of light.

V1. many other vendors exist. reefledlights also a sponsor here
V2. they charge that much for heatsink packages because these are heavy. u can get just the leds cheaper. do not get 10K leds from this vendor, they make your tank look like crap.

[MosMike]

OK, my recommendations:
L1 - use Cree. They are more efficient and more consistent in color.
L2-L3 - 4" is rather low, I would recommend using "LED seal" to protect the circuits from salt.

D1 - 48V is the "Reefcantral accepted" maximum voltage for DIY builds. With a 90W driver you'll have more parallel string, thus increasing the risk of failure of the LEDs on this driver. And after soldering the stars and fixing them on the heatsink check for short-circuits on the heatsink. with a multimeter.

H2 - glued stars are easy to remove - just twist them with a tweezer.

[reickler]

Awesome. Great answers, guys.

[joelespinoza]

Originally Posted by pwreef

L1 = 1 LED per gallon. so you need like 70+ or you will not be able to cover well. look here for most of your questions: http://reefledlights.com/ledmytank/

Not with decent Cree LEDs. 1 per 15-20 square inches of surface area up to around 22" deep is a common rule of thumb with Crees. I went with more to adjust colors how I like, but 41-42 would have been plenty for my 55 gallon tank.

Originally Posted by pwreef

L2 you need the same amount of either cree or bridgelux unless you get XML.

No, Cree XT-E and XP-G are more efficient than bridgelux, so more light and less heat.

Originally Posted by pwreef

that close to the water you cannot use any optics so your tank is going to look much dimmer than with optics. you also need to be ventilating well.

No, I have 40 degree optics about 6" off the water, you can easily use 60 degree optics from that height

Originally Posted by pwreef

L3 you dont need any protectant, only from salt spray if you are that low. Light will be reduced by any protectant you put between leds and water.

I built a clear box to go over the whole fixture. Personally I think that its worth the small loss in light for the protection.

Here is my fixture, its similar to what you would want, You could do a fixture identical to this, or get individual LEDs and simply drive them harder (1000mA for the crees) or add another row of LEDs. This is for a 48x12 55 gallon:

LEDs:

14 XP-G Neutral White (40 degree optics, 700mA max)

36 XT-E Royal Blue (40 degree optics, 700mA always)

6 3W True Violet (60 degree optics, ~600mA)

6 3W Turquoise (60 degree optics ~600mA)

6 3W Deep Red (60 degree optics~600mA)

I bought 14 "3up" LEDs that contain 1 neutral white and 2 royal blue Cree LEDs on a single star. I am not sure if I would recommend them. You could get a cheaper setup from rapidled and individual LEDs can be driven harder due to better heat dispersion.

Heatsink: 10"x46" from heatsinkusa, because huge heatsinks are cheaper, quieter, and have lower maintaince in the long run. If I was you I would get the same heatsink, or even a 12"x46" one. Passive cooling rocks.

In total this fixture cost me almost exactly $750 for everything, including shipping. It is capable of growing anything photosynthetic and should last 10+ years.

All LEDs on full:


Whites all the way down:


Whites, Reds and turquoise all the way down: