LED Intensity

[Aquattro]

A question came up in a different thread, asking why almost everyone runs their LEDs at less than 100%, often much less. Why is that?

Does it not make sense, mathematically, that if I run 4 lights at 50%, I can get the same results with 2 lights at 100% ? Sure, coverage is a different, but lets say 3 lights, higher up but brighter, doesn't that do more than 4 lights at 60%??

So what do you run your LEDs at, and why?

[Nano]

I have my AI Sol, running at about 35% over my cube, I find anything higher is too bright, and ticks off the coral. From what I am seeing online and first hand, LEDs are right up there with MH in terms of brightness, but are not as prone to browning out corals.
I think that if you dont mind minor dark areas, you can definitely run them higher hang them higher and get the same results, also as we know many leds have options on optics that you can choose from, I believe AI has 70 or 90 degree, I cant remember which, but with a wider lens I see no reason that you couldnt run less lights at higher intensity. after all, to me 4 sols on a 4' tank seems like a waste, 2-3 would be more then adequate. provided they are suspended just right. It may limit what you can keep on the sand bed once you get to a certain height, as we know light gets less intense the deeper it has to penetrate, but for me, my softies on the sand bed and sps high, lps low to middle, it seems to be perfect! thats just my opinion though

[Reef Pilot]

When I first installed my Radions, I started them at 30%, and they were still brighter than my old T5's. I then raised it to 40%, but noticed that my corals were shrinking a bit, so I dialed them back to 30%. Since I don't have any SPS (only softies and LPS), I thought I would go even lower and see how they do. I am currently running them at 20%, and corals are doing better than ever now. Seems like my softies just don't like bright light.

I have a 6ft tank, 18" deep, with 3 Radions 8" above the water. I use the natural mode setting, so it gradually ramps up and peaks at mid day, and then down again to dusk. Then a low blue for moonlight thru most (totally off for about 3 hours) of the night.

[justincgdick]

From a mathematical perspective, you will have more uniform par if the lights are higher up, assuming you have lights strong enough. There will be a drastic difference between par at the surface and at the sand bed if the lights are in the rim. If you can raise the light up a few feet the difference in par will be less.

[WindowMaker]

there is also the factor that constantly running an LED at 100% will cut its lifespan almost in half.

[Aquattro]

Originally Posted by WindowMaker

there is also the factor that constantly running an LED at 100% will cut its lifespan almost in half.

That makes sense, but when the industry is stating X number of years worth of life, at what intensity are they rating them?

[troni]

Originally Posted by WindowMaker

there is also the factor that constantly running an LED at 100% will cut its lifespan almost in half.

its lifespan is determined by running at 100%.
what i think you mean running them at a lower percent will increase life.



I'm curious as how long till the spectrum starts to change, if at all.

[Nano]

Originally Posted by troni

I'm curious as how long till the spectrum starts to change, if at all.

I "Heard" once 5% per year at 100% but I am sure that not accurate, and could be more. also depending on the types of features you use (I.E) thunderstorms etc, it could cause varied results IMO.

[StirCrazy]

Originally Posted by troni

I'm curious as how long till the spectrum starts to change, if at all.

the spectrum doesn't change on LED's only there intensity. and at there rated live they are usaly still at 85% of there new intensity. of course different brands/models will have different numbers.

as for the life span, running them at 50% or 100% will make no difference on life span if the junction temp is the same, so in other words if you can keep them below there max junction temp even at 100% the life will be longer. this is why it is very important to think out your cooling (heatsink/fan) setup when building your own LEDs. If you buying them you would assume the company did there home work to be able to allow them to be run at 100% while keeping the junction temp under the max.

Steve

[windcoast reefs]

Originally Posted by troni

its lifespan is determined by running at 100%.
what i think you mean running them at a lower percent will increase life.



I'm curious as how long till the spectrum starts to change, if at all.

As far as ive heard, there isn't any spectrum change. I called up Cree and talked to a tech about it before I built my unit and he said as long as you don't over heat them, the spectrum will stay the same. Basically the shortened down explanation of what he said was that the compound that is used to give an led there specific spectrum is stable as long as it isn't over heated. So if you burn your leds to hot they can have a spectrum change because of the compound breaking down into something else Like the zinc based compound used in blue breaks down into something that makes it kinda purple when it gets really hot.

They aren't really line halides or t5 which actually burn a compound to create the spectrum.

Just what I've heard anyways!