LED question for the gurus

[sutton6989]

so i converted/retrofitted 2 120w tiotronic led lights with new more powerful leds and heatsink. Im still using the original drivers that came with the units and while i was cleaning the units the other day i realized that they are driven at 540ma.... now my leds are rated for 700ma.. is it worth it for me to grab new drivers that run 700ma? as they sit im getting around 150-200 on the sand bed but im shooting for 250-300.. will the 700ma drivers help a ton or am i not doing something right?

thanks everyone

 

[cymaster007]

Yes- get a stronger driver and you should be able to get more light from the LED's just be sure to measure it and dont over drive the LED's or they will burn out quickly. You will need to ensure good heat dissipation for the LED's-

 

[Dave A]

A couple things to keep in mind.
While your LEDs are rated for 700 MA, that is a maximum and, like anything else, they won't last as long if run at their maximum. Would you drive around in 2nd gear all the time with your engine running at the redline?
There is a point of diminishing returns. An LED run at it's maximum does not put out much more light than it would if run around 80%.

If you really want a little more light you could use a 700mA driver but you'd be wise to dim it below 100%. Another option would be using a 600mA driver if you are not set up for dimming. As you can see, that isn't a big improvement over the drivers you have now. I doubt the return on investment would be worth it.

 

[sutton6989]

So to increase par I'd need to add more leds..

 

[Dave A]

More LEDs is the obvious answer. OTOH, I find that PAR is often a useless measurement. More light is only better if you have the right spectrum, I'd rather have a modest quantity of the right wavelengths than tons of useless spectrum. For instance, if your RBs are 455nm, changing to 445, even at a slight loss of PAR, would be an improvement. Likewise, if you have any green LEDs, swap them for something that supports photosynthesis. In cases like this you may lose PAR but gain useable light.
More LEDs will work too.

 

[sutton6989]

OK I have a mix of 10k leds,RB,blue and 4 red.

 

[Dave A]

I'd be inclined to lose the 10000K right off the bat.
LEDs should never be purchased based on color temperature alone, it tells you very little about spectrum. Unfortunately, there is nothing to tell about the spectrum available from any LED above 6500K. I can assure you that there's a narrow spike of RB that is almost half the output of the emitter, it'll peak around 450nm and drop off to almost nothing within a few nm on each side of the peak. There will also be a much wider peak that will come up rapidly from around 500nm, probably peak close to 540nm and taper down to nothing around 600nm this "hump" will be about half as tall as the narrow 450nm spike. Here's the problem, 450nm is RB, you have seperate RB diodes, get your RB from those, it's much more efficient that way, 500nm is Turquoise and that "hump will take you from there, through green and yellow and into yellow/orange. There are only a few Pigments that can make use of this light. A PAR meter will be very sensitive to light in this range but it is simply not very useful for photosynthesis.
I'd suggest replacing these with a neutral white, around 4000K, probably with a few more RB if you want to keep the color temperature of the tank where it is now. A neutral white will not put out as much RB, but it will emit the same spectrum from 500nm to 600nm and even extend it towards the red end of the spectrum. You have reds now, but I suspect they are narrow peaks at 660nm, neutral whites will fill in the gap between 600nm and 650nm (orange and orange-red) which will make several photosynthetic pigments happy and provide a more "natural" looking light for you. I don't know the total number of LEDs you have, but replacing your VCW (very cold whites) with a mix of 75-80% NW and 20-25% RB should leave your overall color temp and PAR readings the same but improve the coloring of your corals and increase PUR a little.

I have no idea which RB you are using. RB is light in the ~435-465nm part of the visible spectrum. LEDs in the bottom half of this range are what you want for photosynthetic corals, the upper half of the range is used by terrestrial plants and algae, but doesn't do much for corals. This area is a catch-22 for a PAR meter, especially the toy ones used by hobbyists (Apogee, etc), because they lose sensitivity at wavelengths below 500nm. I've seen evidence that they pick up only 50% of the light at 450nm and as little as 20% at 420nm. This is unfortunate because 405nm to 450nm is the most important light for the critters in your tank. Some people, who are more hung up on PAR numbers than I am, have taken to measuring their violets, RBs and blues seperately and applying correction factors before adding them to the numbers from their white lights. I have not heard much about the accuracy of these inexpensive PAR meters when used for red and deep red LEDs but we're generally not using enough of them for it to be a big difference. Most fixtures use 50-75% RB, fixtures with cool whites are usually at the low end of the range (because CW is predominantly RB) while fixtures with neutral or warm whites use more.

Blue is anything between roughly 460nm and 490nm. This, and cyan (490-515nm), are the gap between the RB "spike" and the green/yellow "hump" in a white LEDs output. This light is important to a number of photosynthetic pigments. I have no idea which blues you are using but a peak around 475-480nm is common. Keep in mind that this is still in the area where an inexpensive PAR meter will be less that 100% accurate, a correction factor of 20% is a good guess. I like to see blue and/or cyan make up 5-10% of the fixture but when calculating a blue to white ratio, I include these witrh the RBs.

Sadly, I don't see any mention of violet. Violet is light between ~400 and 430nm (this is not UV, which is below 400nm) and there is evidence that this is just as important, or even more important, than RB. Our eyes are not sensitive to this light, it is at the very edge of the visible spectrum, and PAR meters have trouble picking it up at all. As a result, violet LEDs are under utilized in most aquariums. I've seen comments like "they are dim" and "they don't make PAR," but the truth is that they are not dim to photosynthetic organisms, they are only dim to things that are not sensitive to violet light (like human eyes and PAR meters). Chlorophyll A is the predominant pigment in the marine environment, 70-80% of the photosynthetic pigment in your tank is Chlorophyll A. There are several peaks that are absorbed by Chlorophyll A, I don't have my notes handy but IIRC they are around 430nm, 447nm and 660nm, violet, RB and deep red. Violet is important. I would not consider using a fixture that was not, at least, 10% violet. Like the blue LEDs, I include violet with the RBs for calculating my blue:white ratio. Basically, anything under 500nm is blue, anything over 500nm (like your reds) goes with the whites.

Blue:white ratio is the proper way to select the color temperature of your fixture. a 14000K overall look is typical of the old RB:CW 50/50 combo but can also be accomplished with RB:NW 60/40 or with a 70/30 mix of RB and WW. I like the 14000K look but if you are into 20000K you can increase the percentage of RB (and violet and blue) all you like.

All the above will increase the light that can be used for photosynthesis in your tank. It will probably not increase your PAR reading and may even lower it, but it will increase the amount of light that supports photosynthesis. If you just want higher PAR numbers, add some 550nm green LEDs. this will not help your corals since none of them use this wavelength, but a PAR meter is overly sensitive to it by about 10%. In the end, I suspect your best bet it to simply add LEDs, but the above will work if your fixture can't accomodate additional emitters. You can use this info to help choose the best emitters to add.

 

[ReefLEDLights]

Dave A

I think you nailed it.

I've been experimenting with different Bins of Cree XP, XM and XT series of LEDs and there is a significant noticeable difference between bins and how good the corals look. This experience would not translate to the Bridgelux or Luxion ES and their are slight difference in intensity of specific wavelengths.

I posted this graph on a previous post. As far as looks if you excite these pigments and your Royal blue is less than 460nm the lower the better the better the looks. I'm not a fan of neutrals because I feel the right Cree Cool White hits these spectrums in the perfect proportion. For a warmer look I prefer only a couple warms without optics

UV/Violet 410-430nM are great but their efficiency is not close to the Cree XT-E Royal Blue.

Sutton 6989

For Cree 5 Watt LEDS 700-1000mA is the sweet spot. Generally after 60-70% max depending on the led your producing more heat than light and at some curves you actually get less light out of a LED driven at Max, especially if the heatsink is weak. I would keep your current drivers...Excuse the PUN.

Bill

 

[Dave A]

Bill, I can't help but notice that your graph cuts off at below 600nm on the excitation side. I assume that this is due to the use of cool whites with no supplemental emitters. My notes indicate that several pigments have excitation wavelengths above this point, Chlorophyll A at 662nm, Chl C1 at 634nm and Chl C2 at 630nm come to mind. It's hard to tell if your graph includes the 584nm wavelength that is another peak for Chlorophyll C1.
If I were doing a build with cool whites, I would consider it essential to add 630nm and 660nm emitters to fill in the missing spectrum. A build using neutral whites should not require supplementation at 630nm but will still need some "help" at 660nm. I am even inclined to add 660nm emitters when using warm whites, even though the WW should be producing some light in this part of the spectrum. I've seen some reports that there may even be excitation wavelengths above 700nm for some pigments. IR light does not penetrate the water's surface in any great quantity but, considering the quantity of IR light available in nature, shallow water corals are probably exposed to some light above 700nm. Many warm white LEDs emit small quantities of light above 700nm, there's no proof yet whether or not this is beneficial but it can't hurt to replicate nature and it just might be helpful.
I'm not commercially involved with any manufacturer or distributor of LEDs so I am free to try, and use, any brand I want. As far as I'm concerned, every brand has it's pro's and con's and each LED should be judged on it's own merits. Efficiency is great, but spectrum is more important. What good is "more light per watt" if it's not the right wavelength? That said, I really don't care if a RB is more efficient than a violet LED (violet, not UV), the RB can't produce the 410 and 428nm peaks required by Chlorophyll A (the predominant pigment in our tanks), the 418nm used by dinoxanthin, the 425nm used by diadinoxanthin/neo-dinoxanthin or the 430nm used by beta-carotene. I view "inefficiency" as a reason to use more of them rather than less. As far as the XT-E RB goes, I've used them in the past but even the lowest bin is still too high for my taste. Its great if you are lighting a fuge and want to hit the peak of Chlorophyll B, but it won't do much for corals. IIRC, the XP series had better bins than the XT-E, but then you can't be worried about efficiency. As I mentioned above, efficiency is great, but it doesn't matter how efficient it is if the spectrum is wrong. I find a mix of <450 RB and violet hits more of the wavelengths that need to be hit. Again, I have no commercial interest in any LED so I am able to choose a wavelength and then find the emitter that covers it best, rather than just choose from one product line.

I would encourage anyone considering a XT-E RB and cool white build to do the following. Get the spectrograph from the data sheets for the emitters and mark the most important wavelengths. Chlorophyll A is, by far the most common pigment, make marks at 410, 428 and 662nm. Next, mark 448, 584 and 634nm for Chlorophyll C1 and 444 and 630nm for Chlorophyll C2. This probably covers more than 80% of the zooxanthellae found in corals, still like that RB/CW combination?

 

[ReefLEDLights]

Bill, I can't help but notice that your graph cuts off at below 600nm on the excitation side. I assume that this is due to the use of cool whites with no supplemental emitters. My notes indicate that several pigments have excitation wavelengths above this point, Chlorophyll A at 662nm, Chl C1 at 634nm and Chl C2 at 630nm come to mind. It's hard to tell if your graph includes the 584nm wavelength that is another peak for Chlorophyll C1.
If I were doing a build with cool whites, I would consider it essential to add 630nm and 660nm emitters to fill in the missing spectrum. A build using neutral whites should not require supplementation at 630nm but will still need some "help" at 660nm. I am even inclined to add 660nm emitters when using warm whites, even though the WW should be producing some light in this part of the spectrum. I've seen some reports that there may even be excitation wavelengths above 700nm for some pigments. IR light does not penetrate the water's surface in any great quantity but, considering the quantity of IR light available in nature, shallow water corals are probably exposed to some light above 700nm. Many warm white LEDs emit small quantities of light above 700nm, there's no proof yet whether or not this is beneficial but it can't hurt to replicate nature and it just might be helpful.
I'm not commercially involved with any manufacturer or distributor of LEDs so I am free to try, and use, any brand I want. As far as I'm concerned, every brand has it's pro's and con's and each LED should be judged on it's own merits. Efficiency is great, but spectrum is more important. What good is "more light per watt" if it's not the right wavelength? That said, I really don't care if a RB is more efficient than a violet LED (violet, not UV), the RB can't produce the 410 and 428nm peaks required by Chlorophyll A (the predominant pigment in our tanks), the 418nm used by dinoxanthin, the 425nm used by diadinoxanthin/neo-dinoxanthin or the 430nm used by beta-carotene. I view "inefficiency" as a reason to use more of them rather than less. As far as the XT-E RB goes, I've used them in the past but even the lowest bin is still too high for my taste. Its great if you are lighting a fuge and want to hit the peak of Chlorophyll B, but it won't do much for corals. IIRC, the XP series had better bins than the XT-E, but then you can't be worried about efficiency. As I mentioned above, efficiency is great, but it doesn't matter how efficient it is if the spectrum is wrong. I find a mix of <450 RB and violet hits more of the wavelengths that need to be hit. Again, I have no commercial interest in any LED so I am able to choose a wavelength and then find the emitter that covers it best, rather than just choose from one product line.

I would encourage anyone considering a XT-E RB and cool white build to do the following. Get the spectrograph from the data sheets for the emitters and mark the most important wavelengths. Chlorophyll A is, by far the most common pigment, make marks at 410, 428 and 662nm. Next, mark 448, 584 and 634nm for Chlorophyll C1 and 444 and 630nm for Chlorophyll C2. This probably covers more than 80% of the zooxanthellae found in corals, still like that RB/CW combination?

In a perfect world one would be able to find an efficient cost effective 420-430nm LED. Sadly there are none out there. The closest is the Semi P2N-U but in sufficient quantity to have a serious impact on overall looks would add about $50-75 to the average fixture. Instead manufactures add only a couple for marketing or to say they have this spectrum covered. I've found that proper binning of the Cree LEDs will give you better looks than some of the fixtures using a couple Violet LEDs. Its a balancing act when you mix cost, looks and growth. The DIY hobbiest has ultimate flexibility but can easily spend more than necessary chasing a full spectrum.

The above graph was taken from a research article and I think it includes C1. I have a few 630nm and 660nm on my system and honestly can live without them. I'm more of a fan of the ReefSpectrum v Full Spectrum. I've been growing corals for years using only 450-460nm Royal blue with a few various cool white mixed in for looks. Only recently have I added some 410nm to my system. I started out as a DIY Hobbiest and have used my experience to help in the commercial development of a couple fixtures. I've found the corals adapt very well to the 450nm. Here a a few charts from a presentation we've done that support the fact that one can grow coral using only 450nm.

Bill