cree vs luxeon

[ledstein]

I am having a hard time agreeing with this information.

a) Designed for 350 vs 700
- Normally, an LED designed for 700ma operation will be more efficient at 350m.
- I may be entirely wrong, and one die may be different than the other technically, but this is not the reason IMHO.

I didnt want to go into details but it seems i should. Also i will stick with white color because i have much more experience with white.
Luxeon K2 TTFC LXK2-PWC4-0200 (ignore the recall problem, just focus on the numbers) is marketed at with 200lm@1A (Min) and 170lm@700mA (Typ). If you dig in the datasheet you also find the flux at 350mA which is 95lm.
Cree X-RE Q5 is marketed with 107lm@350mA (Min).

So i say again, the best led is the one the has the highest flux at the lowest current (if the voltage is the same). Its better because of the heat issue.

Ic) Binning vs Marketing
- While your general concept might have some merit, that binning is a factor in marketing, it is not "just marketing"
- While it is quite difficult to stand around and shine an LED on the wall and exactly tell the bin, I know plenty of people that can easily identify which "similar" LED is brighter, has a nicer beam, and has a more pleasant color "for their eyes".
- I suggest you take the time to build or buy a few flashlights and go for a walk through the woods, or try cooking a steak by the light of an LED flashlight before you decide that color temperature and binning are not useful and significant.

Binning is more about the problems with the way the leds are produced then its with marketing. The same problem have cpus. Ofcourse u need to know the bin of the each led you compare.

d) The web link
- Surely you do not believe the numbers from an on-line retailer as your main source of information about LEDs ?

Actually i take all the numbers with a grain of salt. First because the industry doesnt have (yet) standards for measuring led performance. Second it seems to me that all the big producers try to confuse you with their datasheets. Some give the numbers as typical values, others minium, others maximum.
Third, is no use comparing two leds based on their luminous flux if the current at which was obtained is not the same.

And forth, considering online shops are the most used way to get our hands on leds there must be a degree of trust in what they say. Otherwise where can you buy them from? No official distributor will look at a small customer.

e) Lumens per die
- The "typical" results today from the major producers are all in the range of 100 Lumens per 1 x 1 mm die for similar packages and white color temps.
- After that, it is a matter of binning, packaging, and marketing.
- I will admit that some suppliers are more active in promoting their products on internet forums than others through stealth memberships.

Actually i admit that considering the lack of standards and the fact that buying leds in small qtys is sort of a lottery any brand name will do. Its more a factor of brand awarness then its performance.

 

[Axkiker]

WOW you all sure know way more than I thought anyone could ever know about leds.

My goal here is to find the brightest possible blue led. Reason being is this is for an under water project where water conditions can be murkey. So weak blue leds suck.... As we know blue is a pain when it comes to light output and I just cant double the amount of leds used due to size constraints etc... Im also in the process of experimenting with lenses etc.

so let me answer a few questions others above have asked.

The cree led used was XREBLU-L1-0000-00K01
30.6 min lux at 350 ma. I was very specific as to needing these leds so hopefully its what I got.

The other led which I used was one of the lumi leds which I purchased off ebay. They are the 3W version and who knows what the exact output is because it seems all the fools on ebay lie.

Each of the leds were soldered to a thin flexible pcb in series... I added a couple extra leads so I could run them individually as well as in series.

The pcb was then attached to a piece of .125 thick aluminum which was roughly 3"x3". I added a blob of heat paste on the bottem to promote heat dissipation.

The first test was running them in series at 700ma. From a visual inspection the cree seemed to be brighter. Not by a great deal but still brighter.

I then ran them individually for several minutes to see if either or produced more heat. The cree was running significantly cooler.. Or at least thats what I gathered by feeling the heat sink. I dont have an IR thermometer so I cant give an exact reading.

anyways hope that clears up everything... Or at least makes it as clear as mudd.

 

[ledstein]

That blue cree LED is from the brightest bin.
From Luxeon there is LXK2-PB14-Q00 which can go "up" to 35lm at 1A.
It seems Osram Platinum DRAGON has also 35lm.
Seoul P4 blue has 22lm.

Maybe "silly" question. Why dont you use cyan leds? Luxen K2 Cyan LEDs have up to 100lm@1A.

 

[Axkiker]

That blue cree LED is from the brightest bin.
From Luxeon there is LXK2-PB14-Q00 which can go "up" to 35lm at 1A.
It seems Osram Platinum DRAGON has also 35lm.
Seoul P4 blue has 22lm.

Maybe "silly" question. Why dont you use cyan leds? Luxen K2 Cyan LEDs have up to 100lm@1A.

Yeah thats the reason I was specific to order from that bin. I need the highest output possible.... I figure if its pushing out 30lm at 350 ma I should be somewhere around 50lm at 700ma.... Or somewhere close anyway.

I am pretty new to this whole LED deal...... I havent messed with the cyan leds but am considering ordering a couple just to see what they look like.

The blue is only for astetics so im not sure how close in color cyan is to blue. If its close it would probably work out. Or at least be another option.

 

[Axkiker]

ya know after thinking a little I thought I would ask. How close to blue is cyan.....

anyone out there experiment with both. Im curious how much of a difference there is. From my understanding the cyan is more of a greenish color....

any thoughts.

 

[SemiMan]

Even the ceiling bounce test will not necessarily be accurate, but it will be much better than looking at the LEDs. Cree is a 70 degree emitter, the Luxeon is 120degrees. That is a huge hugh difference in candela when looking right at it.

It sounds like you have older Luxeon as well.

That said, Cree does have superior blue right now... perhaps 20% better at the top end.

Luxeon if older will be running hotter in all likelihood, it will likely be about 20% hotter from a higher typical forward voltage of the older Luxeons.

Cyan is very green.... think some of the green approaching blueish traffic lights (the green in many is actually Cyan).

That said, bright blues are often at a higher wavelength.

Semiman

 

[ledstein]

I think you should try cyan if your choice for the type of blue is more based on taste. The answer to your question is too subjective.

 

[lyyyghtmaster]

I agree cyan is pretty greenish. IIRC they are nominally 505 nanometers, but ordering cyan Luxeons, I have gotten ones between about 490 and 510nm.

With Lumileds at least, playing the lottery sometimes resulted in blue Luxeons of 480-485nm. This color is visually bright, to me calming and peaceful, and yet reads as blue. It is a light aqua blue with just the faintest hint of green at 350mA. Think ceramic blue C 9-1/4 Christmas lights.

It often takes a fair number of separate purchases spread out over time/LED package types to get the exact color you want, and then if you do get that rare color, you re-order immediately and still aren't assured of getting the same bin with your new order. I've gotten Luxeon blues between about 460 and 485nm.

I don't know if these observations are true of the Cree blues as well. Do they ship a wide range of blues, or are they all right around the typical 465-470nm medium blue <rant>that everyone thinks everyone always wants? :thinking:</rant>

Regarding royal blue, I think the Crees don't go quite as deep as Luxeons. Cree is only binned down to 450nm, while I've gotten Luxeons/Rebels between 440 and 460nm. The deeper versions of this color are starting to get fairly dim, but boy oh boy is that a striking blue! I've had numerous people (not flashaholics) ask me if it's blacklight!

 

[ledstein]

Well there is another important aspect. Lumileds offers also star versions directly unlike cree leds which are made into stars by 3rd praties. On the back of each original star luxeon there is the exact bin including a number thats shows the wavelenght interval.For cyan bin code 1 is 490-495nm and 2 495-500nm.

Luxeon k2 star leds come in packs of 56 and usually all are o the same bin. Its really not hard for a online led shop person to take a look in their stock and see the bin especially for a few leds. Just call them or email and ask in a convincing manner for a 1 or 2 bin. Or u can just ask what bins they have.

 

[deusexaethera]

For what it's worth, I was recently upgrading my father's collection of Mag-Lites to use LEDs, and I experimented with a few different configurations: one was a cheap 3xLED with a cylindrical reflector, the next was a 1W Luxeon LED with built-in regulator, and the last was a 5W Cree Q-something LED with built-in regulator. Obviously the 3xLED setup couldn't compete, but I was surprised to find that the 5W Cree LED wasn't any brighter than the 1W Luxeon was, and the Luxeon produced more yellow light to boot.

Now, preference of light color is a personal thing I guess -- some people like the dazzling effect of blue-white light and others don't -- but the human eye is designed to see using yellow light, while blue light is only useful for establishing color balance. That's probably why I thought the 1W Luxeon was just as bright as the 5W Cree, because the yellow content of the light was probably pretty close to equal.

Given that, the Luxeon is probably the better choice unless you really need snow-white light.

 

[asdalton]

There's no way that a Luxeon emitter will be equal in output to a Q-bin Cree emitter at the same drive current. Not even close. Tint is irrelevant here, because the Cree is greatly superior.

But the stock Mag reflector is a poor choice for the Cree emitter, because the Cree's angle of emitted light is too narrow, and the reflector will catch only a small fraction of the light. You won't get a strong beam with this setup.

 

[Axkiker]

well guys I have been stressing with these blue leds. Constantly trying to figure out which blue was gonna give me the best results.

I picked up a small piece of blue translucent plex the other day and have been messing with that. I have been putting white leds behind it and have been getting great results.

So Im thinking I may be just as well off to use a few extremly bright white leds and use the blue plex to produce the blue lightinsted of blue leds

Even though the blue plex will reduce the light output. I think by switching to a superior white led will compensate. I kinda think it may even give a brighter blue. Maybe not as true of a blue color as a true blue led however that doesnt matter in this application.

anyways ill let you know when I do some testing.

 

[blasterman]

If you use a blue filter in front of a 'super-white' emitter, like a Cree R2, you'll likely get a much brighter blue simply because the bandwidth of the filter is much wider.

In some respects this is an advantage because mixing deep blue with just a bit of red, as per some Rosco gels, produces a more aethestically pleasing color even though the LED is producing a more pure blue. I've been trying to get blue LEDs to match the blue-blue-violet look of blue colored CFLs, and haven't been able to do so for such a reason.

However, filters will eventually have to be replaced.

As per my other posts to you on the topic, I suggest trying the 3-watt blue ProLights from BestHongKong. The are significantly brighter than my blue Lux III's, and they are cheaper.

 

[lyyyghtmaster]

I've been trying to get blue LEDs to match the blue-blue-violet look of blue colored CFLs, and haven't been able to do so for such a reason.

CFLs have a strong peak in the blue/violet wavelength of 435nm. The deepest blue power LEDs I have found (Luxeon/Rebel royal blue wavelength bin 3) bottom out at 440nm and most are not even this deep. The non- royal blue are shallower still. Try getting 3-bin royal blue Rebels, they look pretty violetish. Then mix in some regular blue and a small amount of cyan. That will get you pretty close to a blue CFL.