LED Design

[giulianom]

Started with an idea for designing the LED lighting for my new 150G Acrylic tank, in my other thread:

http://www.atlantareefclub.org/forums/showpost.php?p=654729&postcount=54">http://www.atlantareefclub.org/forums/showpost.php?p=654729&postcount=54</a>

Moving this to a seperate thread for clarity...


Working with some 7.28" wide x 54" long x 1.3" high heatsinks from HeatsinkUSA, I came up with an idea to embed the LEDs in the fin-side of the heatsink instead of on the opposite flat side. (because that would be easy.. ;) )


So as I like to do, I modeled the el gigante heatsink in SketchUp, and started laying out where the holes would go.


This particular heatsink will have 36 LEDs.

I plan to try and fit 108 LEDs in a second heatsink, a 10" wide one.

Total of 144 LEDs to cover a 1440 square inch area (60" x 24").


In any case, here's the cut-outs shown for the first 6...

I plan to cut them out on a benchtop milling machine with a fly cutter.


[IMG]http://i.imgur.com/5nDty.png>

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[jaustin]

What's the reasoning for putting the LEDs on the fin side? Do you plan on running optics? If you don't run optics the fins may block some of the light.

Do you plan on cooling the fixture with fans, if so, where will you put them?

 

[giulianom]

LEDs on the fin side to make the LED array shallower in depth, mostly.

The heatsink is 1.3" tall, and the inside of the canopy will be less than 12"... I figure I can attach the heatsink itself to the top of the canopy with some bolts and adjust the height from there.


May be running optics.. the tank is 24" deep, and the LED placement would probably be 6-12" above that..


Fans will go on either end of the heatsink, on the sides of the canopy.

I plan to put some 120mm on each end, in a push-pull configuration... there should be some good airflow.

 

[rockdog]

Just a couple of thoughts.

Push pull on fans means CFM X1 both push or both pull is CFM X2.

Heat rises, even in a solid. The heat sink is less efficient mounted upside down. The fins are to allow the heat a place to go up and contact more air.

Just a little food for thought. I love your plans. I'm in the process with a 60X24X24 myself.

Jason

 

[giulianom]

How tall are the LEDs, with optics? An inch?

And yes, push-pull would be fans pulling the air in on one side, pushing it out on the other.

I found some 120mm fans rated 100+ CFM.

 

[guerry]

IMO your making a big mistake there, as stated above your going to loose heat tranfer and your fans should be blowing down on the fins. Your also looking at some pretty wide spacing there I myself am running 48 emitters per 18" x 8.46 heatsink X 3 over my 84" x 24" surface area.

 

[darcurr]

What a unique idea. JAustin is probably right about the fins blocking some light, but you're good to go thermally. I've asked the guys at rapidled a few questions. Shoot them an email and see what they think about the need for optics.

 

[giulianom]

Fans blowing down on the fins, as opposed to along the length?

I'm thinking I may just ditch the original idea, and re-design for fins up, lens down...

 

[giulianom]

In addition to that, if I upped the number of LEDs and decreased the spacing with the fins-down design... Well, I'd have hardly any fins left.

 

[coolsurf]

^ correct.

See my 55 build thread for my LED setup. It may give you an idea or 2.

 

[ichthyoid]

FWIW- heatsinks work because of their increased surface area. You are planning to cut much of that high surface area off (what you are paying for).

I understand the desire to reduce overall height. If you do this, make sure you increase the LED spacing accordingly.

Intriguing concept, but personally, I would look at other alternatives. -JMHO

 

[giulianom]

Increase the spacing?

Put the LEDs farther apart, or closer together?


Perhaps a 2"x2" grid?

 

[coolsurf]

2 x 2 seems to be the average and produces good results. Depending on optics, they will determine how much light gets directed where. I am starting w/o optics and seeing how it works. A deeper tank will more than likely need optics.

 

[giulianom]

I think I will plan for fins up, leds down. Spacing would be 2" circles in a diamond pattern to maximize available space...

Is there such a thing as too many leds?


I figure there will be a mix of royal blue, white, and perhaps red/yellow/green?

 

[coolsurf]

You will not know your par until the lights are on. I would suggest dimmable so you can adjust the lighting accordingly. If too much, just dim it down. Too much light is just as bad as too little IMO.

As for colors, I have been told that a good realistic sunrise/sunset can be done with just blue and whites. Reds do a great job of growing algae but may be beneficial in a sump area. No knowledge on my end of yellows being beneficial and the same with green. Follow your LED spectrum and give the corals what they need. Best rule to follow...once again, IMO.

 

[giulianom]

Ok.. I will probably go with royal blues and whites...

Any ratio thoughts?

1:1 For blue/white?
Or 2:1, or 1:2..

 

[coolsurf]

Depending on what K you want to go with? I'm trying to mimic a Pheonix 14K so I am going 1:1. I can always add or subtract later if needed but the coloration I have seen looks realistic and not overdone with blue.

 

[giulianom]

Probably start with a 1:1, then..

 

[guerry]

Two royal blues to one white is your best bet IMO here's some pic's of my leds

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and for those who want to see par this is my lights 12" below suface of water with divers at 50%

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and this is my tank lit with two to one combo

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[giulianom]

Here's a test layout for 1:1 blue:white LEDs, spaced on 2" diameter circles tangent to each other.

104 LEDs on this heatsink, 7.28" wide x 54" long.


I'll have to model the 10" x 54" heatsink next, see how many I can squeeze onto that one...

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