# Spectral Analysis for LEDs for use over planted aquaria; Graphs here!



## redfishsc (Aug 29, 2010)

And let me say my favorite graph was the last one (warm white, cool white, royal blue), and it's the one I will probably use on my 11g rimless build coming up soon.


----------



## plantbrain (Dec 15, 2003)

These look pretty good as far as growing plants, colors for our eyes?
Have to try them and see.
Looks promising though.


----------



## redfishsc (Aug 29, 2010)

plantbrain said:


> These look pretty good as far as growing plants, colors for our eyes?
> Have to try them and see.
> Looks promising though.


Thanks, and I'm so glad you were the first person to respond here. You must have a Google auto-search set up here .

As for our eyes, I prefer the higher K temp look. Right now I'm using a reef-recycled 1:1 cool white/royal blue over my 11g rimless and even at equal power to both colors, it's not too bad. Too blue, but not terrible. 

I prefer to dim the blues down to about 24% of the whites, but I suspect running them all at equal currents in a 1:1:1 (cool white, warm white, royal blue) will look very, very nice. We'll find out in a couple months when I change my LED setup.


----------



## BlueJack (Apr 15, 2011)

Great post!!


----------



## shortsboy (Feb 6, 2011)

Absolutely wonderful! Thanks for putting in the time and effort both to run the tests and to graph it out so cleanly.

Not being an engineer, I'm still a bit lost on the y-axis of the graph; is that radiant flux? Can the y-axes be superimposed, or are they relative units? If they're a function of distance, at what distance were they measured?

Thanks again, and can't wait to see how your led setup looks once you get around to it. I'm also a blue-y kind of guy for lighting, so this is very useful stuff.


----------



## audioaficionado (Apr 19, 2011)

I didn't see it among your photo bucket shots, but I'm trying to imagine the combination of CREE WW & CW LEDs. Great job getting this done and posted in a very useful format that we can get a good idea what the PAR curves are.


----------



## redfishsc (Aug 29, 2010)

shortsboy said:


> Not being an engineer, I'm still a bit lost on the y-axis of the graph; is that radiant flux? Can the y-axes be superimposed, or are they relative units? If they're a function of distance, at what distance were they measured?



The y-axis is some unit of intensity. I will email my friend and double check, but I believe he said that it's basically a unit of intensity that the spectrometer uses but is otherwise an arbitrary unit. 

I'll email him and see what he says. A PAR reading would be nicer though. We were not able to get PAR data due to time constraints (that would have taken a long time with all these LEDs).




audioaficionado said:


> I didn't see it among your photo bucket shots, but I'm trying to imagine the combination of CREE WW & CW LEDs. Great job getting this done and posted in a very useful format that we can get a good idea what the PAR curves are.



My mistake. The NW/WW combo was mislabled. I never did a WW/NW combo because they are so similar. 

I fixed it in the post above. Here is the correct image.


----------



## audioaficionado (Apr 19, 2011)

Thanx. Now I see why you might want to add some RB LEDs to bring up the blue peak a bit more. I'm really liking the straight CREE XM-L CWs more now.


----------



## redfishsc (Aug 29, 2010)

I haven't tried them over a tank yet, but you oughta see them at 3 amps. Actually, you ought NOT see them at 3 amps. It's ludicrous. Really ludicrous.


----------



## plantbrain (Dec 15, 2003)

redfishsc said:


> The y-axis is some unit of intensity. I will email my friend and double check, but I believe he said that it's basically a unit of intensity that the spectrometer uses but is otherwise an arbitrary unit.
> 
> I'll email him and see what he says. A PAR reading would be nicer though. We were not able to get PAR data due to time constraints (that would have taken a long time with all these LEDs).
> 
> ...


A PAR meter is a quick easy thing and someone will get it some time at some point, that I am less worried about.

It can depend on the lens, the spread, driver and area etc more so than say T5 lights.........

You can predict the PAR somewhat based on the graph, but not that much really. You need the lens type, area, distance and pattern of lamps, this can vary all over the place.


----------



## Hoppy (Dec 24, 2005)

plantbrain said:


> A PAR meter is a quick easy thing and someone will get it some time at some point, that I am less worried about.
> 
> It can depend on the lens, the spread, driver and area etc more so than say T5 lights.........
> 
> You can predict the PAR somewhat based on the graph, but not that much really. You need the lens type, area, distance and pattern of lamps, this can vary all over the place.


Tom, I don't believe anyone can predict the PAR at all based on those graphs. There is no absolute value assigned to the vertical axis, and, without that, the graphs are just more illustrations of what the manufacturers provide in their specs for each LED. I would infinitely rather see PAR numbers at various distances, both from the LED on center, and at distances from the center, and at 3 different LED currents. With those numbers it is easy to predict the PAR for any current, any number and spacing of the LEDs.

Unfortunately it also requires a set of those numbers for each optic that would be used, a 60 degree and a 40 degree at minimum. I'm really looking forward to seeing that type of data.


----------



## redfishsc (Aug 29, 2010)

plantbrain said:


> You can predict the PAR somewhat based on the graph, but not that much really. You need the lens type, area, distance and pattern of lamps, this can vary all over the place.



Good points. I shall update the original post to include some of this, but I'll recap it here also. 


Distance from the LED to the radiometer sensor was *12" in all of these cases*; the sensor was not moved and the LEDs all used the exact same mounting bracket to hold them steady. I build 3 small wooden holders to hold them steady on their temporary heatsinks (1/2" thick, 1" square acrylic/Corian bricks with doublesided FastCap SpeedTape). 



No secondary optics were used in any of the graphs listed above. Only 1 graph that has not yet been posted used optics, and it is a comparison of "with/without" optics on a Rebel 3-up. I am awaiting further data for this one. 


Cree XPG and XPE LEDs, Bridgelux LEDs, and Rebel LEDs: Primary optic angle 120 degrees. 

Cree XRE- 90 degrees. 

Satistronics 3w, 10w, and 20w emitters: 140 degrees.


----------



## redfishsc (Aug 29, 2010)

Hoppy said:


> I would infinitely rather see PAR numbers at various distances, both from the LED on center, and at distances from the center, and at 3 different LED currents. With those numbers it is easy to predict the PAR for any current, any number and spacing of the LEDs.
> 
> Unfortunately it also requires a set of those numbers for each optic that would be used, a 60 degree and a 40 degree at minimum. I'm really looking forward to seeing that type of data.


We did plan on doing that but were limited for time. Meanwhile, Joe has received some INCREDIBLY good news that he is now going to work for SeCore in Curacao. So he'll be flying off here in the next couple of weeks and we won't be doing any PAR data together. 

There are other PAR meters around here though, just none that are as nice as the LiCore. They are all Apogee Quantums which is plenty sufficient for us, we don't need the decimal points that the LiCore can give. If I can get my hands on a cheap benchtop power supply that can hold these LEDs at a rock-steady current, I can probably get PAR data for some of the more common LED types. 

No promises though. I wish I could promise :icon_conf


----------



## redfishsc (Aug 29, 2010)

Tom, which graph looks more compelling to you, in regards to spectral output. I know this varies from plant to plant, so assume a "general mixed tank" sort of situation.


----------



## plantbrain (Dec 15, 2003)

Hoppy said:


> Tom, I don't believe anyone can predict the PAR at all based on those graphs. There is no absolute value assigned to the vertical axis, and, without that, the graphs are just more illustrations of what the manufacturers provide in their specs for each LED. I would infinitely rather see PAR numbers at various distances, both from the LED on center, and at distances from the center, and at 3 different LED currents. With those numbers it is easy to predict the PAR for any current, any number and spacing of the LEDs.
> 
> Unfortunately it also requires a set of those numbers for each optic that would be used, a 60 degree and a 40 degree at minimum. I'm really looking forward to seeing that type of data.


Hence all the other variables that mattered added after that was stated


----------



## plantbrain (Dec 15, 2003)

redfishsc said:


> Tom, which graph looks more compelling to you, in regards to spectral output. I know this varies from plant to plant, so assume a "general mixed tank" sort of situation.


Just in general, they are better than I expected, less high peaks and skewed spectral radiation.

Or put another way, as far as plants, a good graph if you are "a plant".

The energy(as watts) to PAR to growth rates seems pretty good based on the output. So we ought to get pretty good color, pretty good growth from these.

I'd likely use a mix of bulb type, and then mix and match to suit the user's preferences, aesthetics. Since these aesthetics vary person to person, hard to say. It's personal. I think over time, folks will have a general preference, but till things settle down more with the LED light, that's not going to happen anytime soon. Maybe 1-2 years or so for commercial marketed units at a fair widely available etc.


----------



## Steve001 (Feb 26, 2011)

If this isn't sticky it should be.


----------



## leprechaun (Apr 29, 2011)

Hoppy said:


> Tom, I don't believe anyone can predict the PAR at all based on those graphs. There is no absolute value assigned to the vertical axis, and, without that, the graphs are just more illustrations of what the manufacturers provide in their specs for each LED. I would infinitely rather see PAR numbers at various distances, both from the LED on center, and at distances from the center, and at 3 different LED currents. With those numbers it is easy to predict the PAR for any current, any number and spacing of the LEDs.


The vertical axis is dependent on several things, such as the detector, grating, and A/D converter settings. Although it could be considered an arbitrary measurement, it gives a certain amount of information with respect to intensity as a function of wavelength.

I am actually quite familiar with the S2000, although I don't recall Ocean Optics being the manufacturer. This spectrometer used a PDA detector and had a choice of several different gratings depending on the desired application. If one assumes the integration time is adjusted appropriately, we have quite a bit of noise in these measurements. Some of these spectrographs have noise approaching 10% of the maximum intensity value, which is a little concerning. An interesting bit of experimental design info would involve how the light was collimated from the LED module into the spectrometer. This is a fiber-optic input (600um if I recall correctly) and would need to be lined up perfectly (machined fixture perfectly) if an external collimator was not used. Normalizing this data would make it a bit more useful, as it would become instrument-independent.

Different currents/distances and PAR measurements would yield some interesting results, however this assumes the LED performs in a linear manner, which many LEDs do not.


----------



## redfishsc (Aug 29, 2010)

leprechaun said:


> Some of these spectrographs have noise approaching 10% of the maximum intensity value, which is a little concerning.


The 10-reading was ambient sunlight from the windows and it was very much indirect--- and resulted in a nominal value of 10 all across the board (no spikes). All artificial lights were turned off. The 10 was consistent across the board, which we verified about 30 times (glancing at it in between LEDs) and never once saw a spike. 

The 10 ambient noise is quite consistent in every graph. How is this concerning? I admit a 0 would be perfect but I don't see how it would be necessary since it was consistent across the board. 



> An interesting bit of experimental design info would involve how the light was collimated from the LED module into the spectrometer. This is a fiber-optic input (600um if I recall correctly) and would need to be lined up perfectly (machined fixture perfectly) if an external collimator was not used. Normalizing this data would make it a bit more useful, as it would become instrument-independent.


Once my finals are over for the semester in a few weeks I can upload a pic of the wooden jig I built to hold these steady. While I can't claim any sort of extreme accuracy, the wooden jigs held the LED's quite tight in their arrangement. 

The wooden jig was placed under the probe to fit on all 4 sides along a marker-line that was drawn, so there would have been no more than 1/8" difference in the placement of the LEDs from one test to the next. At a 12" distance I see no reason to suspect this would corrupt the data enough to worry about, for our purposes. 



> Different currents/distances and PAR measurements would yield some interesting results, however this assumes the LED performs in a linear manner, which many LEDs do not.


Agreed. They definitely drop in efficiency as current increases above their "sweet spot", which seems to be around 350mA for most of the 3-w types. 

But taking a couple reference points would help make it predictable enough, I suspect. I did a spectral graph of the XML at 3 different currents and was glad to see how consistent the spectral output stayed.


----------



## leprechaun (Apr 29, 2011)

redfishsc said:


> The 10-reading was ambient sunlight from the windows and it was very much indirect--- and resulted in a nominal value of 10 all across the board (no spikes). All artificial lights were turned off. The 10 was consistent across the board, which we verified about 30 times (glancing at it in between LEDs) and never once saw a spike.
> 
> The 10 ambient noise is quite consistent in every graph. How is this concerning? I admit a 0 would be perfect but I don't see how it would be necessary since it was consistent across the board.


I suppose a "dark" measurement taken when LED is off could eliminate the ambient sunlight. If it was consistent, I suppose it doesn't really matter. I guess I'm used to seeing maximum intensity around 68000 counts with approximately 100 counts for background noise, but we're talking about a whole different arrangement. Background noise of 10% would indicate a massive problem in our systems.




> Once my finals are over for the semester in a few weeks I can upload a pic of the wooden jig I built to hold these steady. While I can't claim any sort of extreme accuracy, the wooden jigs held the LED's quite tight in their arrangement.
> 
> The wooden jig was placed under the probe to fit on all 4 sides along a marker-line that was drawn, so there would have been no more than 1/8" difference in the placement of the LEDs from one test to the next. At a 12" distance I see no reason to suspect this would corrupt the data enough to worry about, for our purposes.


I suppose at 12" it wouldn't really make much difference for this application. I guess I'm too picky here also, as slight misalignments (a few um) cause me major problems.


----------



## redfishsc (Aug 29, 2010)

leprechaun said:


> I suppose at 12" it wouldn't really make much difference for this application. I guess I'm too picky here also, as slight misalignments (a few um) cause me major problems.


But I greatly appreciate your criticism. There are always things we can improve on. 

If I could afford one of these, I'd buy it. I'd rather have this than a PAR meter since, if one is clever, you could probably produce some sort of way of getting PAR numbers based on the intensity levels given by the machine. Besides, you can find PAR meters all over the place if you live near a larger city.

Then again, I am just an average hobbyist with very NOT-average interests. Most people would do better with a PAR meter if they can afford it. 

I look forward to the day we can get them more affordably. I've thought about buying the sensor and hooking it up to my multimeter, which should be accurate enough (it measures down to 0.0 millivolts) but I can't justify the expense right now.


----------



## Rockhoe14er (Jan 19, 2011)

great post


----------



## leprechaun (Apr 29, 2011)

redfishsc said:


> But I greatly appreciate your criticism. There are always things we can improve on.
> 
> If I could afford one of these, I'd buy it. I'd rather have this than a PAR meter since, if one is clever, you could probably produce some sort of way of getting PAR numbers based on the intensity levels given by the machine. Besides, you can find PAR meters all over the place if you live near a larger city.
> 
> Then again, I am just an average hobbyist with very NOT-average interests. Most people would do better with a PAR meter if they can afford it.


Actually, if you still have access to the S2000 you could calibrate the unit to ambient sunlight, then use the spectrometer to collect a power measurement of the LED. If you are using a fiber in the arrangement, the type of fiber chosen will impact the results. Fused silica would be my recommendation if taking this route. Collimation of light is not really necessary, as it will not be indicative of the conditions of LED use within a planted tank.

In terms of a PAR meter... I'd love to play with one as well, but I am limited to spectrometers. One bit of info a spectrometer yields that a PAR meter does not is the distribution of the light across the UV/Vis spectrum. This may help match light sources to the specific needs of the chromophores in the plant, but as said before, different species of plant have slightly different wavelength needs.


----------



## leprechaun (Apr 29, 2011)

For those interested (and who haven't already seen it) here is a study of PAR calculations from a MH bulb. Maybe not directly related to this topic, but it has some nice background and gives me a few ideas... although the wife will probably kill me.


----------



## audioaficionado (Apr 19, 2011)

Even ambient sunlight is highly variable as to the time of day and year, atmospheric conditions, latitude, etc.


----------



## 4f1hmi (Apr 22, 2009)

VEry nice information! Thanks for sharing. Your graphs literally cemented my 100% confidence with LED's for our planted tanks. Excellent job!


----------



## redfishsc (Aug 29, 2010)

leprechaun said:


> Actually, if you still have access to the S2000 you could calibrate the unit to ambient sunlight, then use the spectrometer to collect a power measurement of the LED. If you are using a fiber in the arrangement, the type of fiber chosen will impact the results. Fused silica would be my recommendation if taking this route. Collimation of light is not really necessary, as it will not be indicative of the conditions of LED use within a planted tank.
> 
> In terms of a PAR meter... I'd love to play with one as well, but I am limited to spectrometers. One bit of info a spectrometer yields that a PAR meter does not is the distribution of the light across the UV/Vis spectrum. This may help match light sources to the specific needs of the chromophores in the plant, but as said before, different species of plant have slightly different wavelength needs.


I don't have access to it, at least not easily. My friend Joe has taken a job with SeCor and will be leaving soon and he's the only access to a spectrometer I have. 

PAR meter is a different story, lots of those around. I just need a good benchtop power supply to keep the numbers dead constant from one LED to the next.


----------



## redfishsc (Aug 29, 2010)

4f1hmi said:


> VEry nice information! Thanks for sharing. Your graphs literally cemented my 100% confidence with LED's for our planted tanks. Excellent job!


Thank you, and glad I could be of help. 

LEDs make good reading lamps too , the neutral whites are very soft on the eyes. Warm whites are too orange for my eyes.


----------



## vee (May 13, 2011)

Excellent post! Thank you.


----------



## redfishsc (Aug 29, 2010)

Let me officially say that I love the following combo for beautiful good looks. 

1 warm white, 1 cool white, 1 neutral white, 1 royal blue. 


I've used this for 4-5 months now and it is extremely colorful. 

Here is a fairly low quality pic. It reminds me a LOT of the colors we can get from T5's. But, with the awesome shimmer. 











I will be converting this tank to a reef soon, though. I'll just add a few more blues and use a cheap DealExtreme driver.


----------



## plantbrain (Dec 15, 2003)

redfishsc said:


> Thanks, and I'm so glad you were the first person to respond here. You must have a Google auto-search set up here .
> 
> As for our eyes, I prefer the higher K temp look. Right now I'm using a reef-recycled 1:1 cool white/royal blue over my 11g rimless and even at equal power to both colors, it's not too bad. Too blue, but not terrible.
> 
> I prefer to dim the blues down to about 24% of the whites, but I suspect running them all at equal currents in a 1:1:1 (cool white, warm white, royal blue) will look very, very nice. We'll find out in a couple months when I change my LED setup.


No, I just look and am interested in LED's and the various drivers and types. I also dim the blues.....the bridge lux are surprisingly good.

I'll be redoing the various tanks I have with different arrays, 6000K Cree's and the 8000K mostly, maybe some 10K with the 6000's.


----------



## WingoAgency (Jan 10, 2006)

I personally like a tank with Cree CW and Neutral White plus some 12,000K BridgeLux combo.

Additional colors are a splash of red and green.

I will add blue only if the tank is for cichlid


----------



## redfishsc (Aug 29, 2010)

plantbrain said:


> No, I just look and am interested in LED's and the various drivers and types. I also dim the blues.....the bridge lux are surprisingly good.
> 
> I'll be redoing the various tanks I have with different arrays, 6000K Cree's and the 8000K mostly, maybe some 10K with the 6000's.



Yeah I would probably dim the blues a touch (maybe 30% lower) if I could with that 11g tank, but they are all on the same driver so I just live with it since it looks great anyhow. 


If you are using 10K combined with anything, I recommend you try warm whites (3,000K). A warm white LED is much more "amber" than it is "ugly yellow" to the eye...... at least the Cree, Rebel, and Bridgelux are. 

A 10K LED and 6000K LED are going to be remarkably similar in blue output, but the red/yellow/amber portion will be quite low, which means the tank will have an overall anemic look, if my predictions are right. 


A 10K and warm white combo I imagine would look much more pleasing and be just as photosynthetically useful.


----------



## redfishsc (Aug 29, 2010)

Anyone else have any particular LED combos they've used based on this spectral study?


----------

