TOTW 12-3-08 DIY LED Hood for Reef Tank

[CharlotteSteve]

Finally after a few months of research and a LOT of questions I have finally reached the point in this project to begin buying material. I figured I wouldn't post until the boring part was over. Some background first. I am 21 and a mechanical engineer student at UNC Charlotte. I started in salt water 5 years ago. I have two 37g tanks piggybacked, one DT and a HUGE refuge (pics later). First off I have battled and argued for years about the best light for a reef tank. My conclusion PC's and VHO's are decent for softies but the bulbs are too much $$, Halide is beautiful/powerful, but too much heat and the bulbs/energy usage is too much $$. So after a bit of research I discovered the solaris...and then I discovered it's price!!!! Seeing that I'm a sucker for new technology and would really enjoy not buying another bulb for a couple of years, I couldn't stop thinking about this system.

So I propose a dumbed down version of the solaris. After long googling and talking to some Elect Engr at my work, I discovered how feesible this could be. First off I had to decide what kind and how many LEDs I would need. Solaris used Phillips and from what the EE's say they're the best, so Phillips it is. The Luxeon K2 (Cool White) was the best candidate: 100 lm, 750mA, 3.6Vf a peice. For a test run I liked 12 LEDs per side, 2 sides(only trying one at a time). The star emitter is necessary to mount the PCB connection of the LED to soldering pads and also transfers heat from the back of the bulb to the heat sink, therefore prolonging the life of the bulb (We'll get to thermal couples later). Also purchased some thermal grease and small wire 22ga. Next I found a 12.5"x7.25" heat sink on Ebay which I plan to cut in half length ways. The university has a machine shop to do the cutting/milling/tapping.

This should start me off. Next I plan to buy a variable voltage power supply with constant current (no more than an amp). This will act as my temporary driver until I zero in on the exact design. 12 LEDs at 3.6v is a max 50v power supply. I also plan to research ways to cover the bulb side of the system from salt creep. The heat sink will stick out the top of the hood. Will post more pics and cad models later...if I can figure out how, kinda new

[Lucid]

Sweet! I was wondering how long someone knowledgeable about electronics would make a DIY LED system. I have seen/read a lot of mod sites like for computers and am VERY interested in stuff just like this. I hope you are going to post some detailed instructions after you do this right?

Btw, welcome to the site! A nice one I have found it to be so far.

[CharlotteSteve]

Over the last few days I have been ordering the parts. As for the power supply, I wanted to get a variable one for now in case I want to adjust the LED config. Once I get my desing down I will buy a constant voltage driver, which are cheaper. So here's the list of items I've purchased and where I got them

Store Item # Description Qty
Digi-Key - BER268-ND LED star board - 12
Electronix Express - 270024BK 24ga Hookup Wire (Black) - 1 (25ft)
Electronix Express - 270024RD 24ga Hookup Wire (Red) - 1 (25 ft)
Electronix Express - 01PSM6003L1 RSR Variable DC Power Sup - 1
Electronix Express - 05als5 RSR Test Leads - 2
Electronix Express - 01TM902C RSR thermometer - 1
Ebay (greatpcstuf)- 18G New USA thermal grease - 1 (18g)
Ebay (potatopolice)-Aluminum Heat Sink (7.25x12.5) - 1
Future Electronics - LXK2-1-PW12-S00 Luxeon K@ Emitter - 12

All thats needed is mounting hardware and a shield design to block salt creep. Instructions will follow...still trying to load pictures

[charlie]

Mind if I tag along just for grins, this sounds interesting.

[Samper]

tagging along as well.

[sober_pollock]

tagging along

[cyberwollf]

I am a recently graduated Electrical Engineer. I looked into this a while back but couldnt find a great price on the LEDs. What kinda of numbers have you found?

[Poseidon]

Tag for me too!

[CharlotteSteve]

cyberwolf-Luxeon K2's their rated at 750mA but with the heatsink I can probably get an amp out of them without hurting the led. with shipping at electronix express I think they were about 7-8$ a peice. Think of the flip side - to replace 3 CFL I would spend 150$+

Update - I have received everything that I need for the build except the heat sink. Hit or miss with eBay and shipping i guess. This is actually a good thing because it will give me time to work out the heat transfer rates to optimize the smallest amount of heat sink while still protecting the LED's. I have also whipped up an enclosure for the led's. It's a basic wood hood with a plexi-glass cover for salt protection and a wood top for mounting the heat sink. I'll put some pictures up soon I promise. We also fired up one of the LED's to see what kind of light it put out...WOW!!! at only 350mA it was atleast 2x brighter than the LED replacements for MagLights!!! Build should come along quickly now if that heat sink would arrive. Also I am considering using thermal glue instead of grease. The grease allows for easy removal but lacks in heat transfer. Any opinions on the subject?

[CharlotteSteve]

Some pics of the tank that the LED will be going over.

[charlie]

How big is that tank and what are the inhabitants?

[CharlotteSteve]

Charlie - Sorry the pictures are misleading, I mess with my tank every day so it is continuously changing, as i'm sure you know. I have two 37g tanks staggered, mostly refugium, DSB, RO/DI, water movement and hang-on skimmer for filtration. Current livestock is:
2X Green Chromis
Pajama Cardinal
O. Clownfish
Coral Beauty
4 stripe damsel
purple psuedochromis
skunk shrimp
emerald crab
red sea star (I heard these are impossible to keep in a small tank but I've had mine for 8 months)
Elegant Coral
Devils hand coral
leather coral
hammerhead coral (favorite)
various richordia/mushrooms
very bright yellow leather
chile coral
green star polyp
glove/clove polyp

In the refugium:
Russells's Lionfish (I'm pretty sure it's not a volitan, not dark enough)
blue leg hermit
cabbage coral
various polyps/shrooms

Mostly softies...maybe if this project goes well and there is a lot of light I will go to hard corals, but for now I am designing around a soft coral/marine plant tank. The current light config is 3x 65w CFL per tank.

[Lucid]

Also I am considering using thermal glue instead of grease. The grease allows for easy removal but lacks in heat transfer. Any opinions on the subject?

Hey I used thermal adhesive on my northbridge heatsink. After it fell off, I used Arctic Silver to glue it on. Works very well and my heat buildup seems the same or less than before. It's definitely permanent.

[CharlotteSteve]

Thanks Lucid. I will def. use thermal glue for the permanent attachment. I have heard of artic silver before, as far as I can tell the thermal properties of the glues are linerally proportional to the $$. Artic Silver sits somewhere in the middle.

At any rate here are pics I took last night to give you an overview of the system.

[CharlotteSteve]

Whats the hold up? Well waiting on a heatsink that I ordered two weeks ago!!!!! So to solve it I am going to ACE hardware and getting a 3/8" thick peice o aluminium and hopefully I can get the junction temperature low enough with just a plate. The only risk with using a smaller heatsink is that you have to watch it very closely for the first two hours and monitor the j temp. the easiest way to make sure the screw holes are in the correct place for mounting is to plot a tempelate out at 1:1 scale and trace it. When this is done I will include pics of the wood hood and the aluminum plate design. Hopefully once I get the LED's soldered and ready to go I will include pictures of the final product!!!!

[Poseidon]

Sounds good to me! I was going to suggest an Al block/plate from a local supplier.

[BengBear]

Do you need any lens over the LED to focus the light into the tank?

[CharlotteSteve]

Per the photometric the LED should be focused well enough for this application. There is a piece of plexi-glass between the LEDs and the tank but it is for salt protection. Back to the specs, 0 deg. is perpendicular to the surface of the LED, or looking directly into the light. At +/- 90 deg. 4% Light Intensity. At +/- 80 deg. 20% L.I. At +/- 60 deg. 50% L.I. At +/- 40 deg. 75% intensity. At +/- 20 deg. 94% L.I. At +/- 0 deg. 100% L.I. With the location of the lights anything under 60 deg. will have direct projection on the water, while anything above 60 will reflect off the fixture and hopefully some of it will help illuminate the tank.

Update - The structural component is finished. Just took the heat sink to the grinder for some last minute polishing and will be putting the LED's on to the sink over the vacation. I am fairly confident that I will be purchasing a 40v 700mA (30w) constant current driver for the final install. The range on the specs reads: min=2.79Vf, typ=3.42Vf, max=4.23Vf. I will still use the variable voltage to "dial in" the LEDs, just to confirm my math. Will post more come dec.

[BengBear]

I read about Aquaillumination and they uses P4 Leds with some lenses.

Would it be better to have lenses to bring the other 'stray light' into the tank?

Do You think the P4 leds without len would do better or at the least equal the K2 by Luxeon?

[CharlotteSteve]

There is no doubt that with a lens more of the light will be directed towards the tank. The debate is whether there is enough light wasted to offset the cost of lenses. The nice thing about LEDs that you don't find with other forms of light is that they're basically focused without any reflectors. The way i see it, when the light hits the water it's going to go in all directions, so as long as i am close enough to the water the light should react similar to a focused light.

I looked at CREE before purchasing the K2's. The first problem with the P4 is that it requires a PCB. Which isn't a problem if someone has access to PCB's, I didn't. So I focused my search on surface mounted LED's. The CREE X-lamp is a comparable LED. Really it came down to the fact that Phillips had so much testing and information on their lamps and i found a decent deal on them. If I could find a star board for the Phillips Rebels, I would have purchased those at over twice the light intensity!

Finished the final touches on the wooden portion of the hood. I also have wired the LED's and mounted them. Did some temp testing: Way cooler than I first thought, no problems here. The only thing I am second guessing is my choice to run the LEDs in parallel. In series I would have a even current distribution, therefore all the lights will be at the same intensity where as in parallel the voltage drop is unique to the LED and therefore controlling the intensity. I will include pics of the tank with 12 LEDs above it. Also i have aquired a light meter from my work, so I will also include readings of before/after. Just for ****s/giggles we tested it at the office and found 1400 foot candles at 12" (if I remember correctly) so that is encouraging.