# Why CREE LED's? What's so great about them?



## Mxx

Why CREE LED's? What's so great about them? I'm dangerously on the verge of becoming overly obsessed with lighting now, nevertheless I'm still wondering why everyone here seems so enamored by CREE LED's? 

I was under the impression that CREE's offered very well balanced full-spectrum lighting, but now that I've checked their date sheets, the don't look so different than generic LED's. I realize they are much brighter than other LED's but they then require a great deal of work to solder and set-up, they run so hot they require heat sinks and fans are recommended as well for them to not burn out and lose intensity. In most tank hoods it seems there is easily more than enough room to run enough low intensity LED's to achieve the same amount of lighting as a few CREE's.

I've discussed this matter in part previously, but there are cheap waterproof strips of LED's available on Ebay. I haven't checked the intensities versus the price, but if generic LED's are a fifth the strength of CREE LEDs at a twentieth of the price then the generic ones still seem like a better deal. And a 5 metre roll spool at 60 LED's/metre should go a long ways towards providing the amount of light desired. 

I'm going to suggest that for our tanks to look the most natural to our own eyes and to achieve the best colour rendition, (which is my personal goal), then a spectrum of light intensity as close as possible to natural sunlight would be best. Check out the graphs below, which are natural sunlight, CREE LED's and generic cool white and warm white LED's. 

The CREE's graph showns three lines, the blue being their cool white, the green being their neutral white, and the red being their warm whites. The cool and neutral CREE's genrally have similar spikes in blue as the cool white LED's. The neutral white and warm white do have a good deal of light intensity in the red part of the spectrum useful to plants. But they all have a major drop in the green/aqua part of the spectrum whic will reduce the accuracy of their colour rendition and which might not make some of our fish show to best effect. 
































Generally, the quality of the light produced by the CREE's doesn't seem all that different than the generic cool white and warm white LED's produce though, but perhaps marginally better for plants with their warm and neutral LED's than what generic LED's provide due to a fair spike in their red. I'm not sure that marginal difference is worthwhile though. The generic ones seem easier to adjust to correct lighting spread as well. 

For my next big tank perhaps generic neutral LED's supplemented by few small red, green, and aqua, and maybe even violet LED's would be even better for colour rendition and plants than CREE's, as well as being much cheaper and easier? Or is there something else about CREE's which I've missed which supposedly makes them unmatchable?


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## DarkCobra

What you're getting with Crees is efficiency, quality control, and long-term reliability.

Cheaper LEDs often lose significant intensity in just a year or two, especially the smaller ones that are intended to be decorative rather than a serious lighting source. Check out the luminous intensity vs. time graphs for a few T1-3/4 LEDs and compare it against the Crees.

In the long run, after you factor in the replacement time/cost and electrical usage, the Crees usually win.


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## redfishsc

I could not have said it better myself, DarkCobra. +1,000

That being said, the Rebel and new Rebel ES from Luxeon is VERY good also. The Rebel ES is nearly as efficient as an XPG and probably has better color rendering. 

Also, Bridgelux makes very nice LEDs in some WHOPPING sizes. They aren't as efficient as Cree but are probably just as long lived. I have two of their cool white 402 (7-9 watts) and they are VERY nice LEDs. And for the price they are a bit cheaper (lumen for the dollar) than Cree, and a good bit cheaper than Luxeon Rebels


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## Mxx

DarkCobra said:


> What you're getting with Crees is efficiency, quality control, and long-term reliability.
> 
> Cheaper LEDs often lose significant intensity in just a year or two, especially the smaller ones that are intended to be decorative rather than a serious lighting source. Check out the luminous intensity vs. time graphs for a few s and compare it against the Crees.
> 
> In the long run, after you factor in the replacement time/cost and electrical usage, the Crees usually win.


Thanks for the response. My search for luminous intensity vs. time as suggested hadn't revealed much thus far though. For the benefit of all of us, could you perhaps tell us how their half-lives compare, to save the rest of us the difficult search for that? Or how their efficiencies roughly compare, in case you do happen to know this off the top of your head?


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## DarkCobra

Mxx said:


> Thanks for the response. My search for luminous intensity vs. time as suggested hadn't revealed much thus far though. For the benefit of all of us, could you perhaps tell us how their half-lives compare, to save the rest of us the difficult search for that? Or how their efficiencies roughly compare, in case you do happen to know this off the top of your head?


Sure. Sorry I didn't go into more detail in my original post, I had a dinner date to prepare for. 

As I'm sure you've noticed, a quantitative comparison is complicated by the fact that many manufacturers of small LEDs don't bother to publish luminous intensity vs. time, or efficiency, at all.

At one time I was seriously looking into something similar to your idea. And after much searching, I did eventually manage to find T1-3/4 LEDs, as well as some 1/4W LEDs, with full data from several manufacturers. It was so disappointing I abandoned the idea and deleted the relevant notes/datasheets.

For the life of me, I can't remember where I found them, and I can't say I'm willing to go through the entire search again.  However, I can offer you a study from the US Department of Energy:

http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/lifetime_white_leds_aug16_r1.pdf

Check out the graph on the first page, and compare the lumen maintenance for high power LEDs vs. 5mm LEDs. It is representative of what I found myself.

I have bought several products incorporating these small LEDs, like screw-in light replacements and nightlights. All had become so dim within a year or so as to be unusable. I suspect that it's also common practice to overdrive LEDs in cheap products in order to be competitively bright, which further degrades the LEDs. 10,000 hour life or whatever can be claimed as long as it still produces any light at all after that time, if the manufacturer so chooses.

As for efficiency, that's somewhat easier, because you can derive it yourself.

As an example, I'm picking the first result from a Mouser search, which is a new Kingbright product, the WP7113VW1C.

It's a 120mw white LED in T1-3/4 package, with 9,100mcd and 20° beam angle. Converting that to lumens using the following calculator:

http://led.linear1.org/lumen.wiz

We find that it produces approximately 0.869 lumens. On that calculator it also says that a 100W incandescent produces about 1,700 lumens.

So let's say we put together 100W of those LEDs to compare:

(100/0.120)*0.869=724 lumens

These LEDs are only 42% as efficient as an incandescent! Try it yourself with some other small LEDs if you want. Some are better and some worse, but none of them are very good.

Crees and other high power LEDs on the other hand are generally around fluorescent efficiency.

Even for Cree, it's not easy to manufacture consistently high quality LEDs. You may have noticed they sell the same part with different "bin" numbers, which have different lumens and efficiency for the same power. Those are all manufactured identically, but some come out better than others.

Some don't meet even their lowest bin. They don't sell these to the public. They don't waste them by throwing them in the trash. Guess where they go.


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## redfishsc

DarkCobra said:


> We find that it produces approximately 0.869 lumens. On that calculator it also says that a 100W incandescent produces about 1,700 lumens.
> 
> So let's say we put together 100W of those LEDs to compare:
> 
> (100/0.120)*0.869=724 lumens
> 
> These LEDs are only 42% as efficient as an incandescent! Try it yourself with some other small LEDs if you want. Some are better and some worse, but none of them are very good.
> 
> Crees and other high power LEDs on the other hand are generally around fluorescent efficiency.



An incandescent bulb hitting 170 lumens per watt? Even plasma discharge bulbs have difficulty hitting that. I highly suspect something's corrupted with the data on this.

According to this page on Wiki (which obviously isn't the authority since even it's LED data is about 4 years out dated) an incandescent only hits about 35 lumens/watt, which would be about 350 lumens. 

Unless I'm missing something in all this....



http://en.wikipedia.org/wiki/Luminous_efficacy


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## Hoppy

redfishsc said:


> An incandescent bulb hitting 170 lumens per watt? Even plasma discharge bulbs have difficulty hitting that. I highly suspect something's corrupted with the data on this.
> 
> According to this page on Wiki (which obviously isn't the authority since even it's LED data is about 4 years out dated) an incandescent only hits about 35 lumens/watt, which would be about 350 lumens.
> 
> Unless I'm missing something in all this....
> 
> 
> 
> http://en.wikipedia.org/wiki/Luminous_efficacy


1700 divided by 100 equals 17, not 170. What you were missing was a decimal point :biggrin:


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## sanoshin

Also, I noticed in their data sheets when I was looking for my bulbs, that the cheaper end models have a spectrum range of ~6500K, but they say it can range from like 3000-8000k. The more expensive models of cree will say the range is 6000k-7000k, really targeting the specifics.


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## redfishsc

Hoppy said:


> 1700 divided by 100 equals 17, not 170. What you were missing was a decimal point :biggrin:


And that, my friend, is why I'm a theology grad student and not a mathematics or engineering student.


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## mrk442

The reason cheapy leds drop of so fast and change color is primarily due to overheating those epoxy bulbs do zero for thermal transfer which is partly why the high power leds are so much more efficent. Run a cree led at 20ma and its brighter then the cheapies due to efficency. Little leds are great for toys and accents and will last well enough if you run them at 5ma but the intensity is so low your wasting your time trying to light anything bigger then maybe a litter..

Sent from my LS670 using Tapatalk


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## Hoppy

mrk442 said:


> The reason cheapy leds drop of so fast and change color is primarily due to overheating those epoxy bulbs do zero for thermal transfer which is partly why the high power leds are so much more efficent. Run a cree led at 20ma and its brighter then the cheapies due to efficency. Little leds are great for toys and accents and will last well enough if you run them at 5ma but the intensity is so low your wasting your time trying to light anything bigger then maybe a litter..
> 
> Sent from my LS670 using Tapatalk


I don't think we are discussing the really cheap LEDs intended to run at 20 mAmps. Instead I think we are discussing the 3 watt and 1 watt LEDs that are on Ebay now. Those appear to have nearly the same specs as the Cree LEDs, but with more variation allowed. They appear to provide about the same light at 350 mAmps, for example, as Crees. Whether they will last 10's of thousands of hours is another story, but who has run the newer Crees that long either? You can save a lot of money with the Ebay ones, but there is more risk of them failing prematurely, in my opinion. I chose to take the risk, because then I could afford the light.


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## redfishsc

^For our purposes on a planted tank, the LEDs from Ebay (such as the Satistronics LEDs) are plenty enough. 

I still prefer Cree, myself, but that's just because of a mild OCD that I have about efficiency lol. 

The LED build I'm working on right now will include stuff from Satistronice, Bridgelux, and Cree


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## DarkCobra

The OP had mentioned using waterproof LED strips, containing a bunch of little 20ma LEDs. I definitely wanted to talk him out of that, at least.

Where is Mxx anyway?


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## Hoppy

DarkCobra said:


> The OP had mentioned using waterproof LED strips, containing a bunch of little 20ma LEDs. I definitely wanted to talk him out of that, at least.


On that we agree 100%.


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## Mxx

I'm here lurking and listening, and I realized I had some actual work which needed attending to unfortunately. 

The LED's I was talking about were actually the 20 ma LED's which come in 5 metre rolls containing 300 diodes. (But not the 5 mm LED's in any case. I'm using 5050's currently on my nano tank and they seem to be working just fine for that, though I wanted to study this matter in much greater detail before I'd consider using them on my planned 250g. 

Each 5050 diode is 1/4 watt, and produces 7 lumen. Thus, they're producing 28 lumen per watt. And at 300 diodes in a 5 metre $60 spool they cost $0.028/lumen. 

The luminous efficacy I'd seen for incandescent bulbs is about 14, or half that. 

So the high-powered LED's such as CREE's are producing up to 143 lumens per watt? Is that what you are achieving in your fixtures? That's quite a substantial difference if so and supposedly would make them worthwhile. Can anyone provide an estimate of what the CREE fixtures are roughly costing per watt by the time they're installed, just so that we can compare fairly?

For my planned 250 gallon, (68x30x30) I'd been thinking that about five 5 metre spools of 5050's would provide 10,500 lumens (with 1500 diodes). I haven't checked at all whether that would actually be the right amount of light to achieve a medium light intensity though as that figure was based just upon a very crude intensity comparison. But if the difference in luminous efficacy is that big then I'll certainly have to rethink it. 

I thought that with the small size of the 5050's, and as you do stick them to some sort of a backing, they would potentially run cool enough to last a good while. I haven't been able to find any information whatsoever on their luminous efficacy over time though. 

At least several people here have volunteered information about the LED's they are using which provides some alternatives to research certainly. So if I was to use CREE's then does that mean that I'd have about 100 diodes to wire and solder?...


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## redfishsc

I don't know for sure that I'm hitting 140 lumens per watt. Actually, I know I'm not if I run them at a full 1,000mA since most of them hit, at best, 100 lumens/watt at full max current.

But still, 100 lumens/watt is pretty dang good. 



Right now, the Cree XPG (139 lumens/watt at the best) runs about $5 each. 

The Cree XML (160 lumens/watt, at best) runs about $7 each, but can be driven to a ridiculously high current and generate upwards of 900 lumens (that is not a typo). That's ONE LED. 


Over 68" long tank that's 30" deep, you will definitely need to use optics (40 or 60 degree). You could use around 50-70 LEDs (spaced evenly) and drive them at around 600-1,000mA. 

In your case, the Cree XPG is going to be the best bet since there aren't many optic choices for the XML. But you can get 40 or 60 degree optics for $1-2 for the XPG. 


As a side note, you should also consider using Bridgelux LEDs. They are MUCH bigger than Cree. Not as efficient--- keep that in mind. 


But you can get a Bridgelux 402 (7-9 watts) for $7 at Newark or Digikey, along with the Ledil 32.5 degree reflector (actually it's a 65 degree reflector since Ledil measures a half angle for whatever reason). 

The cool white Bridgelux 402 is lovely, and bright, and still hits around 80-100lm/watt.


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## DarkCobra

Mxx said:


> For my next big tank perhaps generic neutral LED's supplemented by few small red, green, and aqua, and maybe even violet LED's would be even better for colour rendition and plants than CREE's, as well as being much cheaper and easier?


I ran across this patent abstract earlier today, which might be of interest:

_"A system to allow a fluorescent lamp to be dimmed or otherwise improve color performance of the lamp while maintaining a constant spectral distribution. In one embodiment, the lamp will dim in light output and not shift in color temperature. An LED array is positioned under a fluorescent lamp such that its light injects back into the lamp that part of the color spectrum that diminishes as a fluorescent lamp dims. The LED array is positioned centrally along the underside of the lamp. The light from the LED is never directly visible but shines through the lamp; the lamp acting as a diffuser. The brightness level of the LEDs can be determined as a preset level relative to a predetermined dim setting or can be regulated through an electronic monitoring sensor. The monitoring could evaluate the shift in color spectrum and or intensity and render the appropriate injection of light spectrum to maintain a constant unwavering color temperature."_

A standard fluorescent provides the bulk of the light, and a relatively small wattage of LEDs allows tuning the color? That's awesome.

I am officially adding this idea to my DIY list. Don't know when I'll get around to it though, my list is getting out of hand.


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## Mxx

Thanks, redfishsc, that's certainly very helpful. 

I'm now seeing CREE's listed at between 92 up to 132 lumens per watt, which is impressive. And I guess around $250-$350 for 50-70 CREES isn't bad, especially taking into consideration their efficiency. 

Are the CREE XPG 3 watts or 5 watts though? If they're 3 watts, then 50 of them would be 150 watts of lighting running at 139 lumens/watt then that's 20,850 lumen. And at a price of approximately 1.2 cents per lumen, or 83 lumen per dollar, which is less than half of what the SMD 5050's are. 

Is that too much lighting to achieve medium lighting levels?? I have no idea!... If the tank is 30 deep, then from top surface to substrate is likely about 26" at most. The tank's footprint would be about 11.33 square feet, (with 3D background and in tank bio sump behind background). So that would be about 1840 lumen/sf at the surface. I'd be planning to have a carpeted foreground so I'd still need a decent light intensity at substrate level. Say that I had 44 CREE's or another similar LED placed every 6 inches. That would equal 4 LEDs per square foot. At that spacing would that still require optics for widening their throw? I suppose however that wider angle beams would light the crevices of the tank and underneath the plants better, as well as light up the iridescence of the fish more effectively if the lighting isn't all beamed just straight down?

Nevertheless, can we figure out an easier lighting solution for the average hobbyist who is a little less technically adept and DIY inclined? Are there any good high efficiency LEDs that are available in LED strips/LED tape, so that one could just coil the LED strip back and forth in the hood instead of having to deal with endless soldering? 

(For disclosure, I need to answer this myself as I'm an architect, and am planning to soon use a significant amount of LED tape for predominantly indirect lighting placed within coves/reveals/etc for my own house renovation. I do see that some available LED strips project their light to the side, which would make them easier to coil around corners as well. As such, the less bright LEDs which are placed closely together in strips might very well be more appropriate as they'd provide more uniform of lighting, but I'd nevertheless want something that was of high-efficiency and which wouldn't lose intensity quickly, if possible.


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## shawnhu

Mxx,

I just learned that the 3W represents max capacity energy consuption. For example, the CREE XP-G Neutral Whites will run 3Watts per HR at 1500mA, giving off roughly 500 lumens. At 350mA, the same CREE LEDs will be giving off 122 lumens at around 1W.

Hope this helps.


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## Mxx

shawnhu said:


> Mxx,
> 
> I just learned that the 3W represents max capacity energy consuption. For example, the CREE XP-G Neutral Whites will run 3Watts per HR at 1500mA, giving off roughly 500 lumens. At 350mA, the same CREE LEDs will be giving off 122 lumens at around 1W.
> 
> Hope this helps.


So if you run an XPG at a quarter of the mA and a third of the watts then it will give off a quarter of the lumens so you'd need four times as many to achieve the same intensity of light? That does seem to make sense in any case and seems of roughly linear equivalence. But I'm unsure of how that would supposedly guide my planning or what would be achieved by running them at lower intensity?

I'm appreciating what I'm learning from this discussion in any case, and am finding it helpful to do a critical comparison in regards to these LED's now, especially now that we're really getting into the details of it. It was unexpected for this discussion to evolve into a discussion about intensity and efficiency versus cost and half-life, as opposed to being more about the quality of the light.


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## Hoppy

Look at the charts in the pdf that Cree provides giving the characteristics of their LEDs. You should notice that the light output is not directly proportional to the current or the operating power of their LEDs. From what I have seen, Cree rates their LED's lumen output at 350 mAmps, not at maximum power. As the current goes up, so does the lumen output, but not proportionally - the efficiency drops off a bit with higher current. And, it appears that the improved versions of Cree LEDs, with a single emitter, all produce about the same lumens at 350 mAmps, but the improved ones can be driven at much higher current.


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## Mxx

Hoppy said:


> Look at the charts in the pdf that Cree provides giving the characteristics of their LEDs. You should notice that the light output is not directly proportional to the current or the operating power of their LEDs. From what I have seen, Cree rates their LED's lumen output at 350 mAmps, not at maximum power. As the current goes up, so does the lumen output, but not proportionally - the efficiency drops off a bit with higher current. And, it appears that the improved versions of Cree LEDs, with a single emitter, all produce about the same lumens at 350 mAmps, but the improved ones can be driven at much higher current.


Thanks, would you like to give us the benefit of your experience and advise us what you might recommend in terms of mAmps? Is it simply finding a personal balance between initial costs versus energy efficiency, or are there other factors which come into play there as well?


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## Hoppy

Designing an LED light involves many variables, all of which have to be tweaked to get whatever you are looking for. I think first you need to figure out what effect each variable has, so you know how to decide what value you want it to have. Then you need to decide what light, with what qualities you want, and where in the tank. Then, add in the LED driver(s) which also has multiple variables, so you can match the driver to the circuit you want so you can meet the light qualities you want. While doing that you need to be thinking about how important it is to you to be able to adjust the drive current to the LEDs, or program it, or adjust it relative to the other LEDs in the circuit. By now, you will probably just be confused, so you will be willing to decide on some easy to decide variables, and work with that. At this stage of the game I don't think it can be done easily, with predictably results. I picked my way to reach the results I wanted, as discussed in this thread http://www.plantedtank.net/forums/diy/123797-diy-led-light-45-gallon-tank.html Others would pick a different way to get the result they want. There are many roads to follow to reach the objective you have.


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## shawnhu

Mxx, I would think that most would tend to stay under the 700mA rating for the XP-G's. That's the most efficient, and without investing too much into heatsinks, can keep the life of these bulbs to it's intended 50,000 hour usage. Anything higher in mA for these XPG's and you will require better heatsinks(which are expensive) and potentially shorten the life of the LEDs.

Hope the more experienced chimes soon to give their take on mA and the XPG's.


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## audioaficionado

Cree XL Cyan Led on 20mm Star.

Perhaps this might fill in that cyan notch in the CREE white LEDs.


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## Mxx

audioaficionado said:


> Cree XL Cyan Led on 20mm Star.
> 
> Perhaps this might fill in that cyan notch in the CREE white LEDs.


Ah, so they do make a Cyan, I wasn't aware of that. The problem then however would be to try to get that cyan light distributed evenly around the tank instead of having just one distracting spot of cyan light. And I haven't seen any LED optic lenses that can provide a 180 degree spread, not to mention a uniform spread. Depending upon what your hood looks like, you could aim one or more of these upwards onto say a white reflector which would diffuse it in all directions. Another option would be to tack low power LEDs such as these cyan LED strips I found on Ebay to the sides of your channels and see how they work and how long they last. [Ebay Link Removed]
I was particularly concerned about trying to get some light in the cyan and green range into a tank as for my next tank I'm planning to do a large tank with turquoise discus, and a lack of light in the turquoise range I presume might therefore not display the fish to quite their best appearance. I don't have any cyan light on my current tank, and my cardinal tetras do nevertheless look decent, but I still wonder if they might have a better glow to them under more even a spectrum of light.


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## evilc66

Those cyan Crees have long been discontinued, and Cutter's stock is the last of them. If you want cyan LEDs that are of similar high quality, go with Luxeon Rebels.


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