# Technical evaluation - Cree XR-E Q4 bin



## evan9162 (Aug 17, 2007)

Technical evaluation - Cree XR-E Q4 bin

The Cree XR-E has been out in the market for almost a year now. It was a bit of a revolution when it came out, even at the 70-ish lm/W level (which is considered "low" these days), it was far above and beyond any offering prior in terms of efficiency; and easily became the brightest single-junction LED and essentially single handedly doubled LED efficiency.

I figured I'd produce a report just as I've done with the 100 lumen rebel and improved K2 (yet unreleased). While I may not be presenting new or amazing information, it'd still be nice to have this all in one place in the LED forum.

The partcular XR-E I'm testing is a Q4 bin, which is supposed to produce 100-107 lumens at 350mA. It's not the absolute brightest XR-E available (the Q5 bin gets that honor), but seems to be easily widely available, and I didn't particularly feel like going out of my way or spending tons of extra for the Q5 bin. Perhaps in the not to distant future, I'll obtain one and present test data on it as well.


Just in case you haven't been around here for the last year, here is what a Cree XR-E looks like:







This is a 4 bond wire version of the XR-E. The P4 I've tested prior only had 3 bond wires. The extra bond wire should help reduce the Vf at higher currents. While extra bond wires do help, there's only so much that packaging can do for the Vf of a device. Ultimately, the dominant factor in the Vf is the LED chip its self, and there is still variation among individual samples. So having extra bond wires still doesn't ensure a low Vf.

The optical system of the XR-E is interesting - there's a thick silver ring, with the optical dome (made of glass). The LED chip sits quite deep down relative to the glass dome, indicating that the beam pattern will be relatively narrow and forward projecting, compared to other power LEDs that we've become accustom to that have nice, wide, lambertian distributions. This could pose a problem for certian reflector configurations.

Here's the backside of the XR-E:






The XR-E is intended to be reflow soldered to a PCB. Because of this, there are power contacts on the bottom of the package, connected to the power contacts on top. This can present a problem if you want to directly mount the XR-E to bare metal for a heatsink, as the heat sink could short the power pads together. The top and bottom contacts are connected with vias in the corners of the package substrate. There are quite a few solutions that are possible to address the shorting issue: clipping the corners of the package, grinding down the bottom contacts, using a thin insulating layer of thermal epoxy, or raising the central portion of the heat sink to isolate the power contacts. I chose to use my dremel and a sanding disk to sand down the contacts in the corners where the vias are present. To me, this is the least destructive solution that allows the simplest mounting, as I can use as thin of a layer of thermal compound/epoxy as possible, and not worry if part of the package makes physical contact with the heat sink.

The central pad is the thermal pad, indended for heat transfer from the package to the heat sink. The thermal pad is fully isolated!!! YAY!! When using multiple XR-E's in various electrical configurations, there is no need to electrically isolate the thermal pads on XR-Es, simplifying mouting and usage.


Here's the XR-E amongst similar power LEDs: the updated K2, and Rebel-100:







The XR-E is about the same size as the K2 (and original Luxeon, Luxeon III, and Luxeon V). The Rebel is substantially smaller (and much more difficult to deal with).


The beam profile of the XR-E is substantially different than other power LEDs. It is significantly more narrow and forward projecting than other power LEDs, and projects much less out the sides. 

Here is the XR-E's beam profile, compared to the Rebel-100:






The relative intensity is a good way to compare different beam profiles, but it doesn't tell the whole story. Another way is to compare the absolute beam intensity at a given current, for two different LEDs with the same brightness. This will show which part of the beam each LED delivers its lumens to, and allows you to estimate how a given optical system will behave with the given beam distribution.

Here's the beam profile for the rebel and XR-E, at 310mA. This is the actual beam brightess in lux, not scaled relative to 0 degrees, like in the previous graph:






In the central 35 degrees, the XR-E delivers more lumens, while in the part of the beam outside 35 degrees, the rebel delivers more lumens. Thus, the rebel could create a brighter focused beam with a reflector, but the XR-E would produce a brighter beam with optics (such as an aspherical lens). The lack of side-emitted light makes the XR-E less than ideal for reflectors. An especially deep reflector would be needed to be optimal with the XR-E.

One must wonder how the beam profile and total output would change if the thick silver ring were absent, and a shorter silicone dome were in the place of the ring/glass dome combination. The output could be significantly higher if the side emitted light were permitted to escape directly. This might be one reason why the Seoul P4 was hitting near 100 lumens last year when the XR-E was at around 80ish, when they both used the same blue die underneath. Granted, there are phosphor differences between the two, but I have a feeling the optics of the packages also have an effect on that.


Here's the raw performance data for this Q4 XR-E. 


```
Current (mA)	0.1	30	130	310	670	980	1260	1570	1930
------------------------------------------------------------------------------------
Vf		2.53	2.82	3.15	3.37	3.62	3.75	3.86	3.96	4.06
Watts				0.41	1.04	2.43	3.68	4.86	6.22	7.84
Lumens				42	94	178	234	278	312	341
Lumens/W			103	90	73	64	57	50	44
```



The extra bond wire in the Q4 XR-E's construction should help lower the Vf. This isn't a guarantee, since the Vf is mostly dependent on the individual LED die. Let's see how the Vf of this particular XR-E stacks up:








This particular XR-E actually has a rather high Vf. This will hurt it in the efficiency department. This doesn't mean that all XR-Es will have such a high Vf, but this particular one does. Even though it is the 4 bond wire version, it still has a higher Vf across all current levels than even my 3 bond wire P4 XR-E. So, when it comes to Vf, your milage may (and will) vary.


Here is how the Q4 stacks up to other power LEDs with overall brightness:






The Q4 XR-E (100-107 lumens at 350mA) performs almost identically to the Rebel-100 (100-120 lumens at 350mA). In fact, it starts to peform a bit better than the Rebel at very high current levels. The better packaging of the XR-E allows for a better thermal path, and makes heat sinking much easier. The Q5 XR-E should perform even better.


Here's efficiency/efficacy:






The high Vf of this XR-E hurts it efficiency wise. With a lower Vf, the XR-E will be much more efficient. The efficiency of this XR-E could be about 10% higher if it had the same Vf of the P4 XR-E.


Finally, the infamous "droopyness" graph - an indication of how efficiency scales with drive current:






The Q4 XR-E scales about the same as all other current power LEDs. 


So the Q4 XR-E has about the same performance specs as the Rebel-100, and performs pretty much identically as well. Ultimately the choice as to which one to use depends on a lot of factors. As far as ease of use and mouting, the XR-E wins hands down - it's much easier to deal with than the rebel, even with the bottom electrical contacts - it's also much easier to get good thermal transfer to the heat sink with the XR-E as well. The only gotcha would be with the beam profile, which is much different than other power LEDs that have a more lambertian beam distribution. This could affect performance with certian optical configurations.

So which one to use? Don't ask me!  I'm still up in the air - with power LEDs coming in different packages, with different levels of performance, and varied aspects of beam profiles, electrical configurations, etc, there are more choices now than ever in the power LED market, but it's less and less clear what the best "go-to" power LED is for general applications. 

Given that, the Q4 XR-E is a great performer, and should definitely be seriously considered for any application.


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## Bullzeyebill (Aug 17, 2007)

evan9162 , thanks for the nice thorough eval. I bookmarked it. Neat you are doing this. Sort of what Newbie was doing and important stuff that can help us make decisions for different applications. 

Have you looked at recent Seoul P4's developpment to see if their has been some improvement in heat management. Many modders jumped on the Seoul P4 bandwagon and are running them at 1+ amps. I do like the Seoul P4's low vf (H).

Bill


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## evan9162 (Aug 17, 2007)

Bullzeyebill said:


> Have you looked at recent Seoul P4's developpment to see if their has been some improvement in heat management. Many modders jumped on the Seoul P4 bandwagon and are running them at 1+ amps. I do like the Seoul P4's low vf (H).
> 
> Bill



Vf bin doesn't really tell you very well what the Vf of the device will actually be. Seoul's H Vf bin (3.00-3.25V) is about the same as lumiled's H Vf bin (3.03-3.27V). That's a huge range. Emitters with a Vf of 3.25V at 350mA aren't particularly low, but still considered in the "H" bin. In fact, the Seoul P4 that I have was binned in the H Vf range, but it's on the top end of that bin. So while it appears to have a "good" Vf based on the bin, it is, in fact, only average. 

Interestingly, Cree doesn't even bin Vf at all. So you don't even know what range they will be in.

The "new" V-bin Seoul P4 has an output range of 118-154 lumens, again a huge range. Without parts in a higher bin, we must expect that the parts will tend to cluster at the low end of the bin range.

Given the ratio of performance between the XR-E and Seoul P4, I'd expect the new Seoul to be performing in the low 120s initially. The P4's beam profile is much more like Luxeons and other nicely lambertian distributions, but there's still that pesky positively-connected heat sink slug to worry about.


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## Kiessling (Aug 17, 2007)

Thanx for doing this !


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## luxlunatic (Aug 17, 2007)

Great info and write-up, thanks!


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## mahoney (Aug 17, 2007)

Thanks for all your work on this.

FWIW, I just got a few Q5 Crees., It's a tiny sample size, and I use a crude testing method, but compared to the 8 or so P4s I've had, the Vf for the Q5s seems higher. Direct drive from a 3 volt battery pack, the P4s would pass 50 to 80 ma, the Q5s were all between 33 and 37 ma


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## VidPro (Aug 18, 2007)

wow Evan, you are are a meticulous writer/illustrator in the post, i understood almost all of that . oh my what is happening to me oo:


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## RoGeR (Aug 18, 2007)

Thanks for the test!

Will you test the Cree Q5 bin too?


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## evan9162 (Aug 18, 2007)

When I get around to obtaining one. I only really got this Q4 because I needed thermal epoxy, and the sandwich shoppe happened to have Q4 Crees in stock. 

Right now, I have a parts drawer with over 60 various power LEDs, mostly luxeons. I really should stop collecting LEDs and start using them.


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## greenLED (Aug 18, 2007)

Man, evan, I find myself bookmarking your threads more and more often. Great job! :twothumbs


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## skalomax (Aug 18, 2007)

I thought the Seoul P4 was the King of LEDs.

Guess not oo:


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## 1 what (Aug 18, 2007)

Loved the write-up and photos. Thanks.
One question:  how obvious is the connection between the top and bottom electrical contacts? 
I'm just about to receive some Q5's and want to direct mount to a heatsink. Is it obvious how much of the corners to remove ? do you need to remove all 4 corners or just 2 of them ? Do you have a photo of a "doctored" Q4 ?
Thanks again.


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## evan9162 (Aug 18, 2007)

My photo above is of a "fixed" XR-E. I've removed the minimum amount of the bottom contacts that need to be removed in order to ensure that the bottom contacts are isolated.

There is one electrical via in each corner. On the bottom side, you must grind down the copper over each of the vias until you reach the ceramic substrate. Then you will have removed the electrical contact between the top and bottom power pads.

After you've ground things down, check that the bottom pads are isolated. Use a DMM in either continuity check, or resistance measurement mode. Place one contact on the bottom power pad, and another on the corresponding top power pad. If there is continuity, or your meter reads around 0 ohms, then you must grind down a bit more material. You only need to remove material on each of the corners the bottom of the package, since those are where the electrical vias are. I would leave the top contacts alone, since that's what you'll be soldering to, and they are small enough already.

[edit]

Here are close-ups of the 4 ground away areas of the bottom power pads, showing the vias underneath (starting at the top left corner from the original image, going clockwise):


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## 45/70 (Aug 18, 2007)

evan9162 said:


> Vf bin doesn't really tell you very well what the Vf of the device will actually be. Seoul's H Vf bin (3.00-3.25V) is about the same as lumiled's H Vf bin (3.03-3.27V). That's a huge range. Emitters with a Vf of 3.25V at 350mA aren't particularly low, but still considered in the "H" bin. In fact, the Seoul P4 that I have was binned in the H Vf range, but it's on the top end of that bin. So while it appears to have a "good" Vf based on the bin, it is, in fact, only average.


A question I've been meaning to ask, aren't SSC's Vf binned at 350mA, and Luxeon's at 700mA? If so, there is little comparison between an SSC H bin and a Lux H bin. Then again, maybe I'm wrong about that. 

Dave


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## chimo (Aug 18, 2007)

Thanks for posting your data! I know that takes a whole lot of time and effort. :goodjob::thanks:

Paul


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## evan9162 (Aug 18, 2007)

45/70 said:


> A question I've been meaning to ask, aren't SSC's Vf binned at 350mA, and Luxeon's at 700mA? If so, there is little comparison between an SSC H bin and a Lux H bin. Then again, maybe I'm wrong about that.
> 
> Dave




It depends on the model.

regular Luxeons are binned at 350mA.
Luxeon III and V are binned at 700mA.
Luxeon Rebels are (currently) binned at 350mA.
Luxeon K2 Pxx2 parts are binned at 350mA.
Luxeon K2 Pxx4 parts are binned at 1000mA.

Seoul P4 parts are binned at 350mA.
Cree XR-E parts are binned at 350mA.


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## 1 what (Aug 18, 2007)

A big thank you Evan 9162!
Like everything else in life it's so bleeding obvious when you know the answer.
The photos of bottom contact modification were great and I now see that it was obvious in your original photos only I didn't realize what I was looking at.
I've only recently discovered CPF but it impresses me how helpful many people are on this site. Thanks again.


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## 45/70 (Aug 18, 2007)

evan9162 said:


> It depends on the model.


I was thinking only of Lux III applications, as that's what I'm usually replacing. So, in effect a Lux III H bin is actually a considerably lower Vf than a SSC H bin. I've seen this, of course, in the real world. I just wanted to confirm it.

Thanks evan9162. :thumbsup:

Dave


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## Bullzeyebill (Aug 19, 2007)

I think that the vf comparison that evan9162 made is the difference in H of a lumileds luxeon and a Seoul, both being run at 350mA's to led. They are very close, the Seoul ranging somewhat higher. This would pertain to a lux I, lux III, or Seoul P4 run at 350mA's to the led. 

Bill


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## Anglepoise (Aug 19, 2007)

Thanks for taking the time to undertake all these tests. Much appreciated and such important info.


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## 45/70 (Aug 19, 2007)

Bullzeyebill said:


> I think that the vf comparison that evan9162 made is the difference in H of a lumileds luxeon and a Seoul, both being run at 350mA's to led. They are very close, the Seoul ranging somewhat higher. This would pertain to a lux I, lux III, or Seoul P4 run at 350mA's to the led.
> 
> Bill


Hi Bill,

Yes, but not for the Lux III. It is not Vf binned @ 350mA.

Granted I don't have 100 H bin Lux III's and a 100 H bin Seouls to work with, but what I've seen is, @ 700mA, H bin Lux's have a Vf between 3.1 and 3.3 Volts and the H bin Seoul's have a Vf between 3.5 and 3.7 Volts. They may both be "H bins" but, the parameters that determine which bin they are, are not the same. If they binned Seoul's @ 700mA, I'd say the present "H" bins would actually be "J" bins ("K" bin Lux equivalent).

Dave


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## nanotech17 (Aug 20, 2007)

evan,
how do you solder the lead wires on both -ve & +ve pads?
it seems the X-RE emitter pads are PITA to solder on.


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## evan9162 (Aug 20, 2007)

I just use a 30W pencil iron. I tin the pads and wires first, then just apply heat to reflow the solder on both. It's not really too hard. Make sure your iron is well tinned and clean, with a very sharp tip, and that you're using extremely thin solder.


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## uk_caver (Aug 20, 2007)

I found with a small tip, my iron had problems heating up the tinned wire/Cree fast enough once the Cree had been AA-epoxied onto a heatsink. A larger tip seemed to help me.

Also, I found grinding off the in-place tinning and retinning the copper with my own solder made the process easier. Someone else found that scraping the in-place tinning clean was useful, so maybe it acquires a bit of an oxide coating or suchlike in storage.
I'm sure grinding off is a bit extreme, but with a Dremel to hand, it's as quick and easy as using a knife.


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## nanotech17 (Aug 21, 2007)

Thanks all for sharing info.
Appreciate it.


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## PocketBeam (Aug 21, 2007)

Great job evan. I found this very useful. BTW, since I think our collective knowledge is better by sharing I think this thread ties into this very well and is also very helpful. Hope it is OK to post the link here - https://www.candlepowerforums.com/threads/156772


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## RoGeR (Aug 21, 2007)

evans,

I haven't found the datas of tests of Cree XR-E P4 and SCC P4 LEDs. Can you link them?


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## evan9162 (Aug 21, 2007)

I have not done a formal report for them. I could easily display them in raw form (like the table above)


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## Anglepoise (Aug 21, 2007)

As said above, it helps to have very thin solder.
However the thiner the solder the less flux, and IMHO flux is one of the keys to soldering. A small bottle of non acidic flux will do wonders for ease of soldering.


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## mofiki (Nov 4, 2007)

Great information on the Q4. Just what I've been looking for because I just recieved three Q4 emitters and the MagD heatsink from the Sandwich Shoppe for a build I want to do, (Bike handlebar light). 

I chose to go with three Q4's for the following reasons, (1) I already own a 3021 1000 Buckpuck and Li-Ion 14.8v battery pack from Battery Space and (2) the availability of lenses from Khatod. I ordered three different degrees of field in the tripple lenses because I didn't want three single lenses and reflectors. I got them for free so I'm not out any money too. 

My question is; I really wanted to put four Q4's in there but was concerned about the source voltage of my pack and the drops of each emitter and the drop of the Buckpuck - 1.5 to 2 volts. I measured the voltage of the pack and after burning a halogen bulb for almost two hours it still measured 15.2 volts. On a full charge it measures 16.4 volts. Yes it does have a tendency to blow 20W bulbs every once in a while. I understand the emitters can drop up to 3.7 volts each running at the 1000 mA output of the Buckpuck. If you are up to it can you think about this and give me an answer whether or not I could put 4 emitters in the Mod. Also is the bFlex a better driver to use in this circuit?


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## evan9162 (Nov 4, 2007)

Lots of things to consider with your setup.

To be absolutely sure, it's best to take the worst case scenario and see if things hold up.

First, the 4 XR-Es - 3.7V x 4 = 14.8V
Next, the dropout voltage of the buckpuck = 2V
Finally, you should consider wiring/contact/switch resistance which could introduce additional voltage drops - that could be as much as 0.2-0.3V

So you're looking at nearly 17V needed for your input voltage. 

The 4 XR-Es and 14.8V battey pack is one of those wierd combos where the battery voltage is higher than the load at first, then nearly equal or lower later. In these scenarios, neither buck nor boost drivers are entirely appropriate. A buck/boost driver is made specifically for this scenario - but they are not as widely available.

In this case, you can either just go with 3 XR-Es, which would work with the buckpuck, or get a buck/boost driver which will work both when the battery voltage is higher and lower than the LED Vfs.


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## mofiki (Nov 4, 2007)

Thank you for responding so quickly. Your input really helps. I was hoping to achieve a light that would at least equal the HIDs out there. I will look into the Buck/Boost options and upgrade in the very near future. One more thing, is there any formulas I can use to figure run time with the boost circuit or is it just try it and see. Just thought I'd ask to save me some time.


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## evan9162 (Nov 4, 2007)

You can calculate the power input requirement based on the power output and efficiency of the circuit.

So let's say you're running 4 XR-Es in series at 1A, with a total Vf of 14.8V. The load is then 14.8W (14.8V * 1A). 

Let's also assume your boost converter is 85% efficient. Now, that is just a ballpark guess, and will be different depending on the input voltage, output current, etc. THis is just a back-of-the-enveolpe calculation.

The 85% efficient means that if it draws 1W, only 0.85W will go to the load. Or, to supply 1W to a load, 1.17W must be drawn from the power supply.

So if we want to deliver 14.8W to a load with an 85% converter, we must draw 17.4W from the power source. 

Lets say we're using a 12V battery. 17.4W / 12V = 1.45A. Then you divide your battery capacity in Ah by 1.45 to get the runtime in hours; or divide the capacity in mAh by 1450.

So if our 12V battery has a 3000mAh capacity, then the runtime will be 3000/1450 = 2.06, or about 2 hours.

Remember, the 85% is only going to be ballpark. Efficiency of a converter depends on a lot of factors - the ratio of input to output voltage, the current being supplied to the load, the current drawn from the power source, etc. So it could still vary considerably from the stated value. In the end, the only way to know for sure is to just test it with your desired setup.


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## mofiki (Nov 4, 2007)

OK. I understand that easily enough. I was just wondering the net for a boost driver and you were right. Trying to get something to work with my battery pack is going to be hard to find, if I could even find something. It's any wonder most of the mods I've seen in the forums are just power driven with resistors in the circuit. I just thought it would be safer to have regulation.

As I was looking at the specs of some of the boost regulators one spec caught me and, call me stupid but, confuses me. Max input current. Is that something the user controls by battery choices or what? 

I just thought about this too. I also have a Li-Ion 7.4volt 4000mAh pack that is only a couple of months old. I think this might be an option but run-times will suck.


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## evan9162 (Nov 4, 2007)

The maximum input current basically limits how much of a voltage boost the converter can supply at a given current level. Since boost converters take a lower input voltage and convert it to a higher output voltage, the current drawn from the batteries will be higher than the current supplied to the load. The larger the voltage differential, the larger the current drawn from the supply. The max input current is a limitation in the circuit that defines how much boost you can get.

For instance, driving 3 XR-Es in series (11.1V) at 1A will require 11.1W. If you use a 6V battery, then your input current will be 2.17A. If your circuit has a max input current of 2A, then it won't be able to supply that power - it will only be able to supply about 10W from a 6V supply.


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## mofiki (Nov 4, 2007)

Thank you. I think I am alot better off now to figure out if I can get a combination that will work. From what I've read maybe this proccess will be easier in the future with the new generation of LEDs, more lumens at less power, hopefully coming out next year.


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## KevinL (Nov 5, 2007)

Evan, thank you for the awesome report and the even more detailed graphs!!

I've read datasheets from SSC that imply 100Lu at 1A, either that or I am reading it wrong: the datasheet is not very clear at all. Your report, which I feel is better presented, shows the SSC P4 is still a solid contender although the Crees have a little bit more light coming out the front. 

The advantage of the P4 is that it is easier to work with, having star mounts and readily available reflectors. 

I like your bit about 'if you haven't been around in the past year' - that about describes me (18 months actually)


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## Lightingguy321 (Nov 6, 2007)

evan9162 said:


> Technical evaluation - Cree XR-E Q4 bin


 
Sorry for the overly long quote, but what is the bin code on those New Luxeon K2s. Basically my question is, are LXHL-PW14-U000 (UYAN) K2s considered the new generation, or are they stuck along with the older ones?


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## evan9162 (Nov 6, 2007)

I really don't see the point in quoting the entire report. It unnecessarily lengthens the thread and doesn't add significance to your question. I would suggest you edit it out.

The "new k2" part number is LXK2-PW14-0160. However, those parts are not available yet.

The best K2s available now are LXK2-PW14-V00.


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## Lightingguy321 (Nov 6, 2007)

The PW160 is slated for release in early 2008 right? So where do the UYAN LXHL-PW14-U000 K2s sit in terms of performance?


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## evan9162 (Nov 6, 2007)

Pretty low compared to the current crop of competitors: the Seoul P4, Cree XR-E, and Rebel-100. 

The U-bin K2 outputs around 100 lumens at 1A. The best LEDs today output that much at 350mA.


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## Burgess (May 14, 2008)

Wow !

Lotsa' great information here.


*Thank you* for your time and effort !

:thumbsup:

_


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