Cree XP-L V6 2C led, tested against XM-L2 T6 3C, edit23/7: I repeated the test and measured a dedomed XP-L

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Tom E
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Overall these #'s make sense to me. Even that you are seeing about 7% higher than Match's, it makes more sense to me, considering a 6.5A TN31 de-domed XM-L2 U2 1A seems to be about 1,700 lumens, making Match's #'s look a little low. I thought Match used a U2 1A though. We've been seeing close to 2,000 from domed XM-L2 U2 1A's at above 6A - I just always thought Match's #'s were a bit low, or me and a couple other guys are too high.

In my P60 tests (at 3.5A I believe), I saw the XP-L V6 do about the same as the XM-L2 U2 1A, which I think you would see as well, but the tint is nicer on the XP-L in this head to head.

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Thanks for the comparison test djozz! Great work and very nice equipment!

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Thanks a bunch, Fantastic Work!

I’ll be using mine on 3x noctigons.

I’m a junky, I mod lights so I can sell lights so I can buy more light to mod so I can sell lights to buy more lights to mod.

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Same.  Too bad those quad XP boards were limited production or I'd be trying to talk Richard into carrying them when Carclo optics come out.

The low mode should be lower.

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leaftye wrote:

Same.  Too bad those quad XP boards were limited production or I'd be trying to talk Richard into carrying them when Carclo optics come out.

I got a few of those copper quad boards from member Dsche (with bonus: cool Russian stamps!), I would not be surprised if he still has some, you could try a PM, he seems a very nice guy.

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I think he still has some too.  I ordered a dozen.  They've been sitting in New York for about a week.  I'd like to order more, but it's going to have to wait a little while...I'm sure I'll come to regret waiting.  Too much money spent recently for too many pending projects...

The low mode should be lower.

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Thanks djozz. I have little to add to the conversation right now – all relevant points have been addressed. I just wanted to chime in to reinforce how much your testing is appreciated. I personally use your graphs a lot and often refer people to them. (& Congratulations on your success w/ the integrating sphere.)

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Today I took some time to do some further testing on the XP-L.

I had bought two of the same leds (XP-L V6 2C, from Illumn.com), in one piece of cut reel, so they were right next to each other.  The first one was destroyed in the crash test  of the OP, and today I used the second one to repeat the test in order to find out to what extent the results are reproducable. Of course if the results from the two leds differ much I can not tell what part comes from variations in the method (i.e. it was 5degC warmer today than it was last time) and what part is variation in the led.

I used the exact same equipment, even the same star and led-wires from the first test, I just removed the faulty led and reflowed the other one. I tested the integrating sphere with one of my reference lights to be sure it read within 1% the same as it did last time (it did).

Here's the result, I plotted the results of the second led in the same graph as the first one, for comparison (I left out the XM-L2 3C results from the OP, just the two same spec'ed XP-L leds). I measured up to 8.5A this time to save the led for further use:

The second led measures slightly different from the first one: the voltage reads about 0.05V lower at most currents, with a maximum difference of about 0.1V, the output at most currents matches almost exactly the first led, only above 6A led#2 starts reading a bit lower than led#1. So this is not an efficiency difference (that would affect the entire curve, not just above 6A), but it looks like led#2 shows slightly worse heatsinking than led#1. Perhaps it is the led, perhaps it is the reflow that was not as perfect, I don't know: the difference is not so great that I feel an urge to find out.

What I am happy about is that this integrating sphere system seems to perform consistantly, I am really beginning to trust the thing Smile

 

While I was at it I thought it would be nice to compare this led domed versus dedomed. So after the test, before it was cooled down, I took the copper mount out of the sphere and with the led still hot I dedomed it by lifting the dome off from the side with a scalpel. It wasn't the cleanest dedome I have ever done (usually I do dedomes under a stereo microscope, I had to do with a loupe this time), but the die was clear from silicone afterwards, so the dedome was effective (the led is illuminated from the side to show remaining silicone well):

(stereo pic)

The dedomed led went straight back into the sphere for direct comparison with the domed state. I was very surprised to find this:

(sorry I'm not very good in making chart dimension the same everytime, they differ a bit from the first chart)

So what has happened? The concensus is that dedoming lowers the Vf (that is at least a suspicion) and costs at least 20% output (that is measured by many). This led however dedomes without light loss (that is: nothing under 5A, only slightly above that) and the Vf stays dead-on. Tell me what's going on here?, it looks like the performance is the same, just at very high current the heatsinking seems to have suffered somewhat, but I can explain that if I must by the better heat dissipation properties (surface area) of a dome vs direct air.

The led was really dedomed well (see pictures above), and I checked the light colour compared to a few other leds: xml2 3C, Nichia 219B, an xml 'cool white' led from the spare leds box (you can find out which is which Smile , the XP-L is on the right side in both pictures):

 

Pictures do not show tint well, but by eye the dedomed XP-L looks like a little under 5000K and more yellow than both the 3C and Nichia. So it definitely looks like the tint shift that you expect from a succesful dedome.

 

I can think of three theories, all quite unlikely:

1) the tint shift to a warmer tint leads to less output but at the same time the luxmeter is more sensitive to the warmer light, and those two effects level out. This is highly unlikely, the wacky wavelength response of this type of luxmeter can not account for a huge 20% measurement error for a mere 1000K tint-shift. And besides, the by many observed output-loss upon dedoming was very probably done by the same type (or the exact same) of luxmeter as is in my integrating sphere.

2) the slightly altered 'beam profile' of the dedomed led as compared to the domed state causes the 20% measurement error. This is not true, shining a focussed aspheric flashlight around in the sphere at all possible angles causes very little variation in the reading, maximum variation is 2%, only projecting the led image straight onto the baffle shows a reading 10% less.

3) this is the conspiracy theory Laughing : the XP-L's that Cree sells at the moment have domes that do not attach well to the die: domed leds behave like dedomed leds in light colour and output. It would explain why I do not find an efficiency for a V6 that is any better than a T6, it would also explain why Old Lumens notices such a warm tint for his XP-L in that HD2010. I failed to check the tints of my XP-L's beforehand, so I do not know about them. How's that for a theory Big Smile

There must be theory 4 that explains it all, like my measuring methods are flawed after all and such. Enlighten me Smile

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One theory: The CREE data sheets are in fact correct and the XP-L V6 is truly brighter than an XM-L2 U2, but they did a crappy job on the dome because of the tight space on the XP footprint? Smile

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so the XP-L is a good de-doming candidate huh? is the throw much improved with de-doming as one might expect from an XP-E2 or XP-G2 de-dome?

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wight
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#3 may be a better candidate than you think. DBCstm has observed that the dome does not appear to attach to the die. According to him there is actually a pocket of gas above the die!

EDIT:
Post #135 in the "Cree XP-L, XM-L performance in an XP size package" thread.

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wight wrote:

#3 may be a better candidate than you think. DBCstm has observed that the dome does not appear to attach to the die. According to him there is actually a pocket of gas above the die!

EDIT:
Post #135 in the "Cree XP-L, XM-L performance in an XP size package" thread.

the question is then: with what led did Cree measure the bin to be V6, and the tint 2C ? Was the led dome well attached at time of measurement?

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Maybe you should dedome the xml2 from the test and try what the light box says….
That would make sure if it is a xpl specific thing…

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Fantastic work again djozz.  Thank you.  That integrated sphere you built is starting to shine on its own.

I wonder if the product development team for the  XP-L was rushed to bring it to market.

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Werner wrote:
Maybe you should dedome the xml2 from the test and try what the light box says….
That would make sure if it is a xpl specific thing…

+1, if you are willing to sacrifice the led and re-run both tests that is…

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musicmagic wrote:
Werner wrote:
Maybe you should dedome the xml2 from the test and try what the light box says.... That would make sure if it is a xpl specific thing...
+1, if you are willing to sacrifice the led and re-run both tests that is...

I'm afraid that is the way to go (I'm a lazy tester by heart, but measuring things always leads to more tests and checks Sad ). Ideally it should be a 2C tint as well, but I reckon this 3C will provide the information just as well.

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Yeah. Should ideally compare 2C vs 2C or CW vs CW or 65CRI vs 65CRI, or top bin vs top bin. Silly

Although the main purpose of the de-dome test would be to compare before and after so its not that important to use as similar as possible emitter.

When that is said. PM me your address if you want me to ship you a XM-L2 U2 2C mounted on 20mm Noctigon.

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djozz wrote:

The dedomed led went straight back into the sphere for direct comparison with the domed state. I was very surprised to find this:

(sorry I'm not very good in making chart dimension the same everytime, they differ a bit from the first chart)

So what has happened? The concensus is that dedoming lowers the Vf (that is at least a suspicion) and costs at least 20% output (that is measured by many). This led however dedomes without light loss (that is: nothing under 5A, only slightly above that) and the Vf stays dead-on. Tell me what's going on here?, it looks like the performance is the same, just at very high current the heatsinking seems to have suffered somewhat, but I can explain that if I must by the better heat dissipation properties (surface area) of a dome vs direct air.

The led was really dedomed well (see pictures above), and I checked the light colour compared to a few other leds: xml2 3C, Nichia 219B, an xml 'cool white' led from the spare leds box (you can find out which is which Smile , the XP-L is on the right side in both pictures):

 

Pictures do not show tint well, but by eye the dedomed XP-L looks like a little under 5000K and more yellow than both the 3C and Nichia. So it definitely looks like the tint shift that you expect from a succesful dedome.

 

I can think of three theories, all quite unlikely:

1) the tint shift to a warmer tint leads to less output but at the same time the luxmeter is more sensitive to the warmer light, and those two effects level out. This is highly unlikely, the wacky wavelength response of this type of luxmeter can not account for a huge 20% measurement error for a mere 1000K tint-shift. And besides, the by many observed output-loss upon dedoming was very probably done by the same type (or the exact same) of luxmeter as is in my integrating sphere.

2) the slightly altered 'beam profile' of the dedomed led as compared to the domed state causes the 20% measurement error. This is not true, shining a focussed aspheric flashlight around in the sphere at all possible angles causes very little variation in the reading, maximum variation is 2%, only projecting the led image straight onto the baffle shows a reading 10% less.

3) this is the conspiracy theory Laughing : the XP-L's that Cree sells at the moment have domes that do not attach well to the die: domed leds behave like dedomed leds in light colour and output. It would explain why I do not find an efficiency for a V6 that is any better than a T6, it would also explain why Old Lumens notices such a warm tint for his XP-L in that HD2010. I failed to check the tints of my XP-L's beforehand, so I do not know about them. How's that for a theory Big Smile

There must be theory 4 that explains it all, like my measuring methods are flawed after all and such. Enlighten me Smile

I've got the same results with xp-g2 few months ago(http://budgetlightforum.com/node/25840 post #19)):output and Vf remains the same.

Many reported that dedoming increases Vf,but this isn't true,there is no reason for that.Then I broke one gold wire and measured Vf again,and it was higher,so if you experience higher Vf-lower current after dedoming,you probably damage one of gold wires(or wire-die connection).

My theory why output remains more or less unchanged would be that more blue is converted to green,and green gives much more lm/W,so efficacy drop after dedoming isn't big as it should be. Just check out luxeon lime leds,they have over 200lm/W (2mm^2 die,85C),this is higher than cool whites.

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led4power wrote:

I've got the same results with xp-g2 few months ago(http://budgetlightforum.com/node/25840 post #19)):output and Vf remains the same.

Many reported that dedoming increases Vf,but this isn't true,there is no reason for that.Then I broke one gold wire and measured Vf again,and it was higher,so if you experience higher Vf-lower current after dedoming,you probably damage one of gold wires(or wire-die connection).

My theory why output remains more or less unchanged would be that more blue is converted to green,and green gives much more lm/W,so efficacy drop after dedoming isn't big as it should be. Just check out luxeon lime leds,they have over 200lm/W (2mm^2 die,85C),this is higher than cool whites.

That is an effect that I would not expect to be so high, but perhaps it simply is that high and then it could be a cause of the output not dropping (it is dropping but the drop is just not measured in lux because green counts more than blue, in simple words Smile ). it would also mean that dedoming a cool white led might not cause a lumendrop, but dedoming a more neutral led will cause a lumen drop because in that case you convert more light towards the red area, out of the region of highest 'eye-sensitivity'.

I have the impression that my luxmeter is overly sensitive to blue because the blue XP-E2 that I tested, and also the blue die of the XM-L colour give unexpected high readings. If this is true, it would make your explanation less likely.

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how do so many people produce clean results, while I always struggle to do it right and there's always flaws in the materials and methods that make the results ambiguous Sad    ......

Ok, I ran the dome/dedome test with the XM-L2 T6 3C I still had from the test of the OP. First thing that was not perfect was that the die had a slightly darker spot somewhere. It was not much, and I went ahead with the led:

I did a fresh voltage/output test up to 8A, and with the led still hot I went for the dedome. And apparently the led had cooled down just a bit too much, a bit of the phosfor had come off, say 3%:

Here's the dome with the bit of phosfor:

And the die at 0.5mA, if you look well you can still see the dark spot as well:

Yeah, more variables than I need: does this extra blue add to the lumen-count or will it reduce it? I have the impression that my luxmeter favors blue a bit too much, but perhaps still not as much as green. The 'blue' region of the die occupies about 3% of the die, does that matter much for the test at all? I don't know, so I just went on to the second run testing, and will just dump the results on the net for you to decide what it all means Sad :

At least the dark spot on the die did not get any larger in the course of these tests (I checked afterwards).

So... if you ignore the phosfor damage as a factor involved in the readings, dedoming gave about 10% lumen loss, and has no voltage effects (you see only one voltage curve because the two curve are completely on top of each other).

I think I may carefully assume, perhaps (*sigh*), that 3% phosfor damage could not have counted for 10% light loss on its own, so dedoming a 3C does lead to lumen-loss. The XP-L was a 2C which is cooler, and in the reasoning started by led4power in the above 2 posts, dedoming that tint could cause less lumen loss, because more light converts to the area of maxumum eye-sensitivity by the dedome.

So nothing can be ruled out for certain, jay!

Maybe.

Or not.

 

(Not going to try this again, can I now just go back modding some flashlights, please? Wink )

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Thank you very much djozz. I know it’s frustrating when things do not go as planned.

Thank you also for furnishing us with your raw data despite the possible problems and your frustration. At a glance your assumption looks safe to me.

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This is still very useful info. Only downside I see is not using a XM-L2 U2 1A, the only XM-L2 I dedome, and seems to be the most common dedomed. I've seen de-domed 3C's and they turn a pretty strong yellow - I got a bunch laying aroung here: 3 from a someone else's modded Shocker that I had to re-mod, and one that de-domed itself in one of my lights. The roughly 10% measured drop is interesting, but suspect a U2 1A would lose a little more. I've measured close to 20% from what I recall between domed and de-domed Shockers for example, at what should have been equal everything else.

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Tom E wrote:

This is still very useful info. Only downside I see is not using a XM-L2 U2 1A, the only XM-L2 I dedome, and seems to be the most common dedomed. I’ve seen de-domed 3C’s and they turn a pretty strong yellow – I got a bunch laying aroung here: 3 from a someone else’s modded Shocker that I had to re-mod, and one that de-domed itself in one of my lights. The roughly 10% measured drop is interesting, but suspect a U2 1A would lose a little more. I’ve measured close to 20% from what I recall between domed and de-domed Shockers for example, at what should have been equal everything else.

How are you dedoming your emitters?

Slewflash 

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Gas - of course! "A Perfect Dedome?" (http://budgetlightforum.com/node/20156) Smile. The cut/heat method works of course, it's just more prone to error for me. I could view vinh's video a 100 times and I'm still unsure exactly how's it's done, or how to be sure to get consistent results. The gas method is very consistent. Dale is bringing up some good pts about possibly less tint shift using the cut/heat method, some may say less output loss as well. Since we lack accurate data on this, it's a tough call but hopeful sign, just don't have data or a technical explanation/theory on why.

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Tom E wrote:

Gas – of course! “A Perfect Dedome?“ (http://budgetlightforum.com/node/20156)

If djozz still reports a 10% lumen loss on a XML2 1A, it would make me question if the heat method yields a lower lumen loss than petrol. But we’ll see… Of course to do scientific method he’d have to use both heat and petrol to de-dome the led and measure the lumen loss on both. Unless someone else has already done the objective testing though.

Slewflash 

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I even managed a hot de-dome on a Luminus SST-50. Color is still very good, appears to my eye to have gone more white from a bit blue/white, and the beam profile has a tighter hot spot. Still not a true thrower but it’s doing quite well now (except for the mass amounts of heat it’s making at 5.6A)

That one was interesting. The die is covered with a shiny seal even under the dome. That part is still there as is the dome window frame. Might need to pry that frame off now and see if tightens up the beam a bit more…

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DBCstm wrote:
I even managed a hot de-dome on a Luminus SST-50. Color is still very good, appears to my eye to have gone more white from a bit blue/white, and the beam profile has a tighter hot spot. Still not a true thrower but it’s doing quite well now (except for the mass amounts of heat it’s making at 5.6A)

That one was interesting. The die is covered with a shiny seal even under the dome. That part is still there as is the dome window frame. Might need to pry that frame off now and see if tightens up the beam a bit more…

If SST50s are anything like SST90s you can just stick a knife in between the corner of the metal frame and the dome and pry the dome out cold. It’ll come out extremely clean.

Slewflash 

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and that slew of bond wires was a bit frightening! lol
I de-domed it with the light in Turbo mode, didn’t see it release like I do the XM-L2’s it just popped out.
Is the frame glued or taped down around the die itself? Wonder if it’ll pop off? But this one is in the big TK61 and I can’t get the head off that light, so I have to work down in the hole as it were.

I know I know, this was an experiment…

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Thanks djozz.  More great info.

Does the texture of the 2 dedomed emitters appear different in real life?  It almost looks like the xml emitter appears more "flaky", but it's too hard to tell in the pictures.  Here's a mouse over (xpl mouse out).

There appears to be a difference in the number of 'dots" between the 2 emitters.  The dots are also clearer on the xpl.  It almost appears that there is some type of coating on the xpl.

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When I have collected enough motivation to go on with this, and I have bought two cool white (2C or 1A) XM-L2 leds, I could go for a petrol/hot dedome comparison. For the moment I want to do some mods again.

The texture of the XP-L die and the XM-L2 die/phosfor looks the same to me (yellow fine grainy stuff), just the 3C die has a thicker layer.

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