DIY LEDs - The write-up

[der_wille_zur_macht]

That's not going to provide very even coverage on a tank that large. You're going to need more LEDs, or space the currently-planned 48 LED out farther and use no optics or wide optics on all of them.

What are you hoping to keep in this tank? Your intensity will be on the low side with only 48 LEDs.

 

[ludnix]

The dimensions you listed are for a 120g tank not a 125, those are usually 6ft long.

I'm going to be using 84 leds over my 120g, I don't see you getting enough light evenly spaced enough with only 48.

 

[staggeringwade]

I need to know what the average spacing is that you guys would use on my aquarium so I could get an idea of what else I need to purchase.
I'm in no big hurry to get this project done.
I assume I needed 2 more heat sinks for the 48 leds I have now. That would be 10"x14" of heat sink per 24 leds.
I was also going to slip in another 24 leds when I have more money for a total 72 leds if it is necessary.
I have LPS, SPS, zoas, clams, a couple softies.
I'm currently using 2-250 watt MH-14K and 1 T8 50/50 tube.
If I have read this thread correctly 24 leds= 250 Metal Halide. I understand there are variables and this is a ball park guess.
The light will be mounted 12" above the water. And I intend to try the optics and If it looks awful I will buy 24 more Leds to fill in the middle more.
Thanks,
Wade

 

[staggeringwade]

O.k. I just found Taqpol's LED thread and re-read it.
His spacing is roughly 1 3/4" from side to side and 2" front to back. Which is what I thought the average spacing was with these builds just need confirmation-i was going to space the front to back leds 3" apart.
Taqpol stated that 48 leds over a 48"x24" should be good using the right optics.
I will order another heat sink today so I will have 24 leds per a 10"x14" heat sink.
I just re-read the summary of led builds that thefishman65 complied to get my information from before I placed the order-that is how I chose the optics to use.
I just checked my order and I received 18 each 40 degree optics for the outer perimeters of the light fixture and 30 each 80 degree optics for all other leds. I think I said 60 degree in the last post.
I will leave room in the middle of the fixture to add another set of Leds if the light is inadequate.
Does this sound like a better plan now?
Thanks,
Wade

 

[der_wille_zur_macht]

Don't get wrapped up in spacing. Instead, determine the total LEDs and drive current you need to get the intensity you want, then position as you desire - spaced evenly for even coverage, bunched above live rock islands, etc.

 

[Taqpol]

O.k. I just found Taqpol's LED thread and re-read it.
His spacing is roughly 1 3/4" from side to side and 2" front to back. Which is what I thought the average spacing was with these builds just need confirmation-i was going to space the front to back leds 3" apart.
Taqpol stated that 48 leds over a 48"x24" should be good using the right optics.
I will order another heat sink today so I will have 24 leds per a 10"x14" heat sink.
I just re-read the summary of led builds that thefishman65 complied to get my information from before I placed the order-that is how I chose the optics to use.
I just checked my order and I received 18 each 40 degree optics for the outer perimeters of the light fixture and 30 each 80 degree optics for all other leds. I think I said 60 degree in the last post.
I will leave room in the middle of the fixture to add another set of Leds if the light is inadequate.
Does this sound like a better plan now?
Thanks,
Wade

On my LED fixtures I have 24 LEDs on a 8.4"x10" heatsink.

PAR wise, with 60 degree optics this is easily as strong as a 250W MH, but it has nowhere near the coverage. I believe in my thread I stated 48 LEDs (two fixtures of 24) would provide sufficient coverage of a 120g 48"x24" if they had no optics, but the PAR really suffers in this situation. If I were to light my old 120g for high light SPS I would definitely have use three fixtures of of 24 LEDs, 72 total, with 60 degree optics and some eighties thrown in.

 

[swannking]

I finished one out of the 5 modules with 24 LEDS and have it dimmed by the aquasurf. The input voltage to the aquasurf is 9.5V and the max output from the dimmble signal is 8.6V. So after adjusting the current pot on the MW, I checked the current being drawn from the aquasurf's signaling lead. It was only 2mA. :bounce3: So I should be able to dim 3 MW with each channel.

 

[marinelife]

Has anyone tried this stuff to cover the LEDs:
https://www.reefledlights.com/products-page/leds/led-seal/

 

[kcress]

Has anyone tried this stuff to cover the LEDs:
https://www.reefledlights.com/products-page/leds/led-seal/

I would not do that. It often causes more problems than it prevents. It reduces the all important cooling of the LED's dome. It can make future repairs a disaster. You are supposed to be protecting your fixture/LEDs from direct water contact anyway, and since the fixture is the warmest thing around you should have no condensation issue at all.

 

[laverda]

I would not do that. It often causes more problems than it prevents. It reduces the all important cooling of the LED's dome. It can make future repairs a disaster. You are supposed to be protecting your fixture/LEDs from direct water contact anyway, and since the fixture is the warmest thing around you should have no condensation issue at all.

While I would not coat the LEDS themselves, I am surprised to hear you say that. Since I will have my LEDs close to the tank I plan to coat the connections with something to protect them from corrosion. I think it is foolish not to do so around salt water and eletricity. Even if your LEDs are 6 inches above the water the constant humidity is going to creat problems eventually.

 

[jusmee]

I would not do that. It often causes more problems than it prevents. It reduces the all important cooling of the LED's dome. It can make future repairs a disaster. You are supposed to be protecting your fixture/LEDs from direct water contact anyway, and since the fixture is the warmest thing around you should have no condensation issue at all.

Don't know about this particular stuff, but there's proper electronic lacquer available for coating and protecting electronics in this situation. Future repairs are no problem as you can solder right through the coating. It won't reduce the cooling in any significant way as nearly all of that happens via the LED to circuit board to heatsink path (you don't coat the heatsink). Also, condensation is a problem because most lights get turned off at night, when they cool, moisture can collect.

 

[kcress]

I think it is foolish not to do so around salt water and eletricity. Even if your LEDs are 6 inches above the water the constant humidity is going to creat problems eventually.

No, it is not foolish, it's knowledge from years of designing electronics for industrial control systems, many in hostile environments.

And, NO it will not, "creat problems", eventually.



I will never recommend coatings on DIY LED fixtures. I will certainly recommend splash protection and sane design.

If you don't have direct splashing or bubble spritzes, and sane, intelligent design precludes this, then all you are left with is humidity that can condense out of vapor form onto your circuitry.

How often do you see moisture in your steamy kitchen condensing out on hot dishes or pans? You don't. It can't. It won't.

Electronics mounted out in extreme temperature swings can benefit from conformal coatings. Indoor electronics and any electronics, generally above ambient temperature, do not benefit from conformal coatings - they suffer from them.

 

[koensayr]

mounting LED

mounting LED

I have my LED temporarily running for now. Circuits are still on a breadboard, and the whole thing is sitting on a acrylic cover over the tank. However, I need to raise the light higher up. An adjustable solution would be best. I tried it with my tiny goose-neck lamp and the heat-sink is too heavy for it.

Do you guys have any suggestions for a way to mount the heat-sink higher up? I've attached a picture. Hope that helps. Thanks

 

[HndMafia]

try an adjustable light hanger from someplace like premium aquatics

 

[laverda]

No, it is not foolish, it's knowledge from years of designing electronics for industrial control systems, many in hostile environments.

And, NO it will not, "creat problems", eventually.


I will never recommend coatings on DIY LED fixtures. I will certainly recommend splash protection and sane design.

If you don't have direct splashing or bubble spritzes, and sane, intelligent design precludes this, then all you are left with is humidity that can condense out of vapor form onto your circuitry.

How often do you see moisture in your steamy kitchen condensing out on hot dishes or pans? You don't. It can't. It won't.

Electronics mounted out in extreme temperature swings can benefit from conformal coatings. Indoor electronics and any electronics, generally above ambient temperature, do not benefit from conformal coatings - they suffer from them.

I did not mean to imply your foolish. I am sorry if you got that impression.

However my experience tells me differently. I have had several nano cubes fail due to corrosion of electrical connections in the hood. They are sealed on the bottom side protecting them from direct splashing or bubble spritzes. The also get hot and have condensation inside them. Clearly our LEDs are subjected to tempature extreames, although at higher average tempatures then if it was an eletrical component outside. Having worked in the business I have seen plenty of corroded eletrical connections in assorted light figtures with splash shields.

 

[Frode]

Hello there,

It has been a while since I posted my DIY LED project http://www.reefcentral.com/forums/showpost.php?p=17101317&postcount=3509

Soon I will be upgrading my tank to a 600 L corner tank.

I am planning to only light the center part of this tank. My ATI 6 x 39W T5 Sun Power fixture will fit just perfect.

My plan is to rebuild this T5 fixture. Loosing 2 x T5 and replacing them with my DIY LED bars. As you can see in my former posting, I placed 16 LEDs on a 100 cm (39,4") aluminium cooling bar, approx 6 cm (2,4") spacing between the LED's from center to center. I will have to shorten these bars to 90 cm (35,4") to fit them in the T5 fixture.

And I want add more LEDs (CREE XP-G).

My question: will I get in to trouble when I when put 29 LED's on each 90 cm Bar. Spacing of the LED's will be 3 cm (1,18") center to center. Running them at 700mA ?

 

[kcress]

laverda; No worries mate!

I would submit that a lot of the the corrosion you see is in regard to incandescent or hot fluorescent sockets. In those cases the corrosion looks the same as humidity problems but is actually oxidation from the oxygen in the air reacting with the hot metals.

I can see a LED fixture suffering from humidity issues if the fixture is essentially sealed in with the tank air. This could occur if someone made a very poorly vented fixture. I'd lump this under bad design though and try to fix that rather than... spray it.

 

[swannking]

I can see a LED fixture suffering from humidity issues if the fixture is essentially sealed in with the tank air. This could occur if someone made a very poorly vented fixture. I'd lump this under bad design though and try to fix that rather than... spray it.

With the current DIY design, the underside of the heat sink has no "active" air circulation. I have a splash guard about 1/2" from the LED stars. Most of us use the PC fans on the top of the heat sink to cool it. Can you elaborate on what you meant by "very poorly vented fixture"? Should I drill some holes throught the heatsink to allow PC fans to circulate air to the underside of the heatsink.

 

[kcress]

Hi swannking. We're kind of talking at different angles here. My recent discussion with laverda has been about.. say, building a LED fixture, then surrounding it with a box on top, bottom, and all sides. Then, having the sides sit on the tank. Perhaps having a fan mounted on the side that blows thru everything to vent out the other side. Now the user has the fan run with the lighting. But at night, the lighting and fan are off. This would allow a pretty large increase in the humidity surrounding the fixture because there is no reason for the air to circulate any more.

A better design would have some gap around the the bottom of the sides between the tank and the fixture housing. Perhaps having the exit air hole be on the top surface, instead of the same level on a side, thus allowing stack effects. Or running the fan all the time, perhaps with a very low, "night setting".

swannking; I believe your question is completely different. It is very important however. You may have you seen lots of modern car headlights that have fogged over horribly. Now only half the light exits. This is because the plastic lenses are failing due to UV and oxidation from elevated temperatures, both from running, and being heat concentrators into the fixtures during the day. You don't want this same process happening with the plastic domes on your HB LEDs! Our HB LEDs are actually more susceptible to this plight because they are coated with phosphors that can change over time with elevated temperatures. So yes, you definitely want the air around the little domes to be as cool as possible.

The best scenario is to somehow include this space in any cooling scheme you use. If you have a fan involved then you should definitely have some ducting or other logical air paths included to provide for this. I'd prefer some sort of gap on one end so air can be drawn as a sheet along the whole army of domes, but baring this, yes, you may need to drill the sinks if you have no alternative.

Your actual design is not clear to me. If you have a gap open to the air all around the splash guard that's good, not perfect but good. If you can influence that front-side air to move, it would be much better.

 

[TheFishMan65]

Frode,

I don't think anyone can answer if you will have heat problems. .18 is kind of close, but with good ventialation probably ok. I am also not clear on the specifics of your heat sink.