LED conversation

Capt_Cully

Active member
I was talking with my brother in front of my tank yesterday, giving him the rundown. Flipped open the hood to reveal my new LEDs. A little background on him. He has a PhD in physics, specifically for his work with conductive polymers. He is heavily involved in the design and application of flexible display screens being tested and utilized by our military. He is also a professor of electrical engineering at Arizona State. He was just on CNN discussing it a couple of months ago. NO I WASN'T ADOPTED!

His mentor and eventual business partner at Cavendish Labratories in Caimbridge England recently won the Nobel Prize in Physics for his work with.....LEDs.

Anyway, as it pertains to our hobby, I was showing him how the lighting ends up having a blotchy appearance on the sand bed. My tank has an area where it is bare bottom. This allows the light to shine down onto the stands floor. There you can really appreciate just how blotchy the lighting is.

He was explaining, for scientists, this is a major problem they are working on. THe light source itself is pinpoint and difuses extremely poorly. Many cars headlights are now converting to LEDs. In Asia many cities are converting street lighting to LEDs. Part of the benefit is that they are dirt cheap (tell that to reef lighting manufacturers) and pump out an incredible amount of light for their energy consumption. Trying to get that light to diffuse evenly to the point that they can be utilized in a household setting is what they are working toward.

So what's my point? I believe it was Nate (der_willie) that forwarded his theory about the differences in comparable PAR readings from T5s, MHs, and LEDs. Why are corals requiring so much acclimation despite similar PAR? Like he said, it's much more pinpoint and less diffuse. Does it cause a localized irritation stressing the entire colony? Perhaps. Are PAR meters incapable of measuring the light, at a distance, over smaller surface area, making them less reliable with less diffuse lighting coverages? Sure makes you think.
 
Couldn't say. He was way over my head with the specifics. The grasp on what he was discussing is what I stated above. I can certainly pick his brain when he rolls back through before heading out to Az. Are you referring to a general answer like lumens? Or PAR? I'm fairly certain, in his line of work, PAR isn't a concern. I may be wrong as I'm sure it has applications beyond reef keeping. Botany for example? Dunno.
 
Ha, can't blame a guy for tryin'. They sold that business to DuPont a couple of years ago. He's an employee of AZ State now.
 
It's hard to answer a question like "how to measure light" without getting into real exact specifics, i.e. are you measuring the energy of the light? Or the "brightness" perceived by humans? Or the energy available for photosynthesis? And so on.

I'm no biologist (but I did stay at a Holiday Inn last night) but I don't think the "issue" we have with corals sometimes not acclimating well to LEDs has as much to do with improper measurement as it might have to do with the way a coral gets illuminated and/or uses the light that hits it.

We can solve some of the visual impact of the blotchyness with different arrangements of LED spacing and optics, for sure. But I'm not totally sure that (visual) issue is related to the way corals react, though it may well be.

What would be really awesome would be to get right into the development/manufacturing process with an LED manufacturer so we could work with them on choosing semiconductors and phosphors to get a spectrum that more closely mimicked typical reef lighting - then we'd be able to eliminate the weird specta you get with LEDs as part of the "problem."

I'm pretty well convinced that in 4 or 5 years LEDs will be so insanely powerful and so incredibly dirt cheap that our current issues implementing them on reef tanks will seem totally trivial, since you'll be able to just toss more and better chips on an array vs. the struggles we have now trying to balance performance with cost. By that point even us DIY'ers probably won't even be playing with individual LEDs any more, it'll all probably be plug-n-play modules that you can control with software to get whatever spectra/intensity/distribution you want.
 
I've looked at LED's, specifically making a diy fixture. I've looked at Cree LED's, non Cree LED's, pot controlled and PWM controlled.

There's just not enough consensus yet on how many, what coverage, which colour spectrum etc. Every manufacturer makes claims about their lighting doing X,Y and Z, charge a small fortune for their fixture and yet in 6 months want you to drop another chunk of change on the "new improved" design.

I'll wait until we have some sort of baseline about which corals like which colour spectrum, how many we need for good coverage without burning our livestock or dimming them down to 20%. When I look at MH and T5 lighting there are a lot of general rules of thumb that let's me make an informed choice, when I look at LED's I'm not seeing it .... yet.

In time I do think LED's will become much more widely accepted but it's going to take time and people willing to experiment before we get there.
 
To be fair I think we're very close to a "rule of thumb" point with LEDs right now, though there are clearly still some corals that just don't like some LED rigs - but that's very much true of MH and T5 as well. I've put corals that were doing great under one MH lamp in a tank with another brand of lamp and watched them fade or bleach even though relative intensities were very similar.

LEDs are changing really, really fast and probably always will change fast, which is the real thing that makes them different from MH or T5. And it's a double edged sword, because while the new LEDs are technically better according to most criteria, the differences aren't always obvious or easy to apply when designing a reef lighting fixture. Think of it this way: If there were two or three dozen totally new T5 lamps coming out every 6 or 8 months, and the manufacturers described and sold them using terms that were not common in the hobby, there would be lotsa confusion about T5, and it would be difficult to know which lamps to pick.
 
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