Led build help. Calling all led experts.

[Mhayes462]

I am building a led fixture for my 58g reef. It is 36"x18dx21h. I have a coralife 36" pc fixture that I have gutted to fit my heatsink and make a nice enclosed fixture. It will sit directly on top of the glass top and will be about 1.5" off the water. I will have 56 LEDs total and they will be mounted on 5 pieces of 35" c channel. 11 on each piece of channel about 3" apart. Would I need optics on these? Any other advice would be greatly appreciated.

Mike Hayes

 

[PSU4ME]

Hmmm, you will need fans and I'll let an expert chime in on the c channel, not sure how it will handle the heat. Being 1.5 inches off the water might cause some spotlighting..... Adding optics certainly will.

 

[Mhayes462]

I am putting two 80mm fans on top of the heatsinks. I already have the 3" holes cut in the fixture. Plus, there are the 4 1.5" fans. I know on the biocubes, they don't use optics with it being so close to the water.


Mike Hayes

 

[PSU4ME]

My JBJ 28 didn't have optics so you may be ok.... Although the JBJ had cheap LEDs so who knows!! Nice DIY

 

[carlfike]

The c channel will be fine as long as its cooled properly. You could go no optics or maybe 80 degree. I'd raise it up a bit though. Like 3-4" off the water. What kind of drivers are you using. I'd Def recommend a dimmer option. Led light is different than mh or t5. Coral needs to adjust to it slowly. If you just blast away full power things are gonna get pissy.

 

[Mhayes462]

I am using 3 Meanwell dimmable drivers with pots to dim them. 2 80mm intake fans and 4 1.5" exhaust fans.


Mike Hayes

 

[carlfike]

You'll be fine.

 

[BigAl07]

I'd get rid of the glass tops ASAP! They trap heat, inhibit water to air gas exchange, and as you can see in the picture get water droplets on them which GREATLY decrease any useable light getting into the tank where you NEED it. All those tiny droplets are redirecting your light in every direction except down. It takes very little "distortion" on the glass surface to really sabotage your hard work. Glass tops are great for certain tanks but IMHO they are a pretty big No-No in reefing where light is so important. For the record I'm speaking from first hand experience not just re-typing what I've read online.

I think your idea is a GREAT one! That's probably the best use of that light fixture possible. I ran one for a while back when I first started out and it ended up as a Fuge Light which was a good use but yours is a LOT better. I like the nice clean design you're working with for sure.

What type and color of LED are you running and how many of each one? IMHO the brand of LED makes all the difference in the world both in quality of light and longevity of their useful life.

 

[Mhayes462]

I am using Bridgelux LEDs. I'm using 28 royal blue, 8 10000k, 6 6500k, 6 cool blue, 3 red, 3 uv, and 2 cyan


Mike Hayes

 

[StirCrayzy]

Update?

 

[lilj104]

I am using 3 Meanwell dimmable drivers with pots to dim them. 2 80mm intake fans and 4 1.5" exhaust fans.


Mike Hayes

your good,

 

[Mhayes462]

No updates. I wish there were. I have everything built and ready to mount the LEDs. I just haven't figured out the layout to start doing it. I started this to go over a new 58g reef that I was upgrading to from a 29g Biocube. I ran into some big problems with both and that's why this has been on hold. Now everything is transferred and doing exceptional in the 58. So no it's time to get started again. Any suggestions on a layout?


Mike Hayes

 

[Mhayes462]

Finally got around to making some progress. Done the layout and then drilled and tapped each one.

Then I got all the LEDs mounted with 4-40 screws and plastic washers.

Anyone see any problems with the layout or the spacing?


Mike Hayes

 

[PIMPALA]

Nope. Looks good.

But you won't know about optics or spread until you actually get it on the tank. And he's right about the glass tops.


Also, don't waste your time with intake fans. Use intake holes, and exhaust fans. Intake fans are a complete waste of time, energy, electricity, and they create noise you don't need. You're better off turning all of those fans to exhaust fans and making holes that can flow the same as the fans for intake.

 

[Mhayes462]

You would suggest NOT blowing air directly down onto the heatsink? The tank is currently running with no tops on it and I'm not gonna put them back on, so no worries there.


Mike Hayes

 

[reefer gladness]

Kinda hard to see which colors are which but the spacing looks pretty good. I have the exact same size tank but went with a different mix of LED's.

Couple suggestions. If you can get the heatsink about 6 inches above the water 80 degree optics really help with the penetration to the sandbed and effectively allows you to run them at a lower intensity and generate less heat. At least with the royal blues since you have a good number of them. I'd leave optics off the colors you have just a few of so they spread better.

If you have a temp probe place it on the heatsink about midway between the fans and see how hot those C-channels are getting. That will give you an idea how effective they are as heatsinks. Some Arctic Alumina or thermal grease between the LED's and heatsink will help transfer heat better too if you didn't do that already.

My heatsink is running about 15 degrees above room temp for comparison. That's with 8 of the 5-watt XML's running at 40% and 36 of the 3-watts (RB and UV) running at 60%. That's making 200 PAR at the sandbed with 80 degree optics with LED's mounted 6 inches above the waterline.

Nice looking build!

 

[PIMPALA]

You would suggest NOT blowing air directly down onto the heatsink? The tank is currently running with no tops on it and I'm not gonna put them back on, so no worries there.


Mike Hayes

Correct.

You want air moving across the heatsink as quickly as possible. And the way to accomplish this, is with the most fans possible sucking the hot air OFF of the heat sink. You don't blow air ON for maximum efficiency. Hot air rises. Why try to force the hot air that's created by the fixture, back on to itself?


... If you have a sealed box with a fan on both sides that both are rated at 350CFM, and they are set up in a "push pull" configuration. Guess how much air is moved? That's right. 350cfm.

Now... Same box, but you remove the "push" fan. Still leaving a hole on one side, and a 350cfm fan on the other. Now how much air is moving? Right again. 350cfm.

Now cut another pair of holes, and move the fans to the same side, and two holes on the other side. BOOM. Now your box moves 700cfm of air.


For some reason, no one ever seems to understand this, and I see a "push-pull" type of fan setup on a regular basis. Even after I explain it in detail, people still can't wrap their noodle around it for some reason.

 

[Mhayes462]

Thanks for the input. I used the good silver thermal paste on the LEDs. Makes sense about the fans. Good input on catching that before I have it all back together. I'm not really wanting to shoot for a lot of PAR at the bottom. I like to keep LPS on the bottom that need lower light.


Mike Hayes

 

[PIMPALA]

Also, you would be MUCH better off putting some kind of washer, or spacer between each channel. when you flatten them up against each other like that, you are losing quite a bit of surface area for cooling. the more flat surface you have with air moving over it, the better. any type of air gap there would be sufficient, even if its just 1/8"

 

[BigAl07]

Mike that looks good. Very nice work.

I don't use INTAKE fans at all unless I have a very specific (and unavoidable) need (pulling air from a very specific area). Use exhaust fans and give them plenty of openings to pull the cooled air in.