# XML T6 vs. U2



## CountryBoy19

Anybody doing any mods with the newer U2 bin?

I am in the process of planning and acquiring parts for a 2D XML build and saw the U2 bin with higher output and more efficiency than the T6 bin. Just wondering if anybody can shed some light on the real difference.

I saw that the U2 has a max current of 3.5A and the T6 is only 3A. The driver I planned on using is a 3A driver. Is it worth it to go with the U2 and find a different driver? Is there a good 3.5A driver out there?


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## CKOD

Where did you see that the U2 had a max current of 3.5A? Obviously both can be driven past 3A with correct cooling, just wondering if you saw it specified as having a max rated current of 3.5A in a cree document somewhere. 

I have some XM-Ls, some MCPCBs and a luxmeter on hand and I'll be able to say what the U2 could do vs the T6 later on today.


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## CountryBoy19

CKOD said:


> Where did you see that the U2 had a max current of 3.5A? Obviously both can be driven past 3A with correct cooling, just wondering if you saw it specified as having a max rated current of 3.5A in a cree document somewhere.
> 
> I have some XM-Ls, some MCPCBs and a luxmeter on hand and I'll be able to say what the U2 could do vs the T6 later on today.


Ok, I'll come clean, it wasn't actually in a Cree document, it was in the specs on DX for their XML U2 star. http://www.dealextreme.com/p/xml-u2-1c-320lm-7000k-led-white-light-emitter-with-20mm-base-3-7v-57009

However, they list all T6 working currents accurately at 3000mA, so I guess I made an assumption that the U2 had a higher rated working current. Is that not true? Can the U2 just be driven a bit harder because it is a bit more efficient? I plan to make a fantastic heat sink, would I be ok over-driving the U2 to 3500mA? Or should I just stick with the 3000mA and play it safe?

A couple examples of T6's with 3000 mA listed current at DX
http://www.dealextreme.com/p/xmlawt-1000-lumen-led-emitter-white-light-bulb-3-0-3-5v-51989
http://www.dealextreme.com/p/xml-t60-1000lm-6300k-led-white-light-emitter-3-35v-3000ma-58355

I'm a newb when it comes to modding. Previously I've just stuck with commercial lights but it's time that I take the next steps. It's just all so overwhelming trying to figure out what the best options are.


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## srfreddy

There isn't really any point for you to be driving it that hard. You might get a few more lumens, but the majority result is heat.


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## CKOD

Fun times, reflowed a U2 2S bin onto my MCPCB epoxied to my heatsink, attached a Ahorton aspheric lens, and got 29000 CP (lux @ 1 m) peak beam intensity vs the 23500 CP peak beam intensity the T6 was getting. A 23% increase in lux output is much more then expected, even though I was doing my best to keep the testing identical. Same lense/mcpcb/heatsink/lux meter/both measured at 5m distance, and I was getting the peak beam intensity from the same area of the projected die image. (Around the bond wires) I'll re-flow the T6 back on when I get a chance, maybe cutter didnt have the central heat pad fully soldered or something like that. (They put the T6 down originally, not me) 

I was using a LX1330B light meter. the person on amazon was trying to sell it as an Extech instrument, but there is no Extech branding on it, or no listing of a light meter on Extech's website. I dont know how this meter compares to others, but regardless of that, the comparsion between the 2 LEDs should be valid.

Now for the real trick, do you trust DX enough to actually be shipping U2 LEDs? I may be a bit cynical, but I wouldnt.

EDIT: redid the T6 lux measurement, got 24750 CP for the T6, making 29000CP for the U2 only a 17% increase. The T6 is a 1A tint bin, vs a 2S tint bin, making the U2~5700k and the T6 ~6500K in color temp, which probably explains the difference between 14% theoretical vs 17% empirical. (Sensitivity of the lux meter more meant for incan/warm whites vs cool white) 

So yes, they are brighter, is it noticable by eye? Maybe maybe not, depends on the on the light it goes into. Would it hurt anything getting the brighter bin if it was in a tint you like? Probably not, I wouldnt pay more then 14% extra for the theoretical 14% extra performance.


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## yazovyet

http://www.cree.com/products/pdf/XLampXM_B&L.pdf
page 2 seems to indicate the u2 is a little more luminous. (found through the colour bin info on cutter's page)

cutter.com.au seems to be selling them but last i checked their shipping was at a rather high cost. 

so i guess using a u2 would give you around 7% (up to 14% in theory) more light than a t6. xxx7000k colour temp seems like it would be a bit odd looking but i ma not really familliar with that sort of stuff.xxx ignore that last bit, apparently it is the 1c colour bin so that would be fairly normal i guess


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## CountryBoy19

CKOD said:


> Now for the real trick, do you trust DX enough to actually be shipping U2 LEDs? I may be a bit cynical, but I wouldnt.


 Well, I'm not sure, but for $1 price difference I'd be willing to take my chances. I think either way I'll just stick with the 3A driver and be worry-free.

Is an AL sink enough for the T6 or U2 driven at 3A? Or should I go with copper? I have plenty of AL around, I would have to buy copper (and it is pretty pricey, and this is a budget build). I can make the sink itself pretty large, and have a pretty good contact with outside surfaces of the light.


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## mintec

I can clearly see the u2 have a brighter hotspot than t6 driven @ 2.8amp.


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## bigchelis

Reputable source purchased the U2 bin and the tints are purpleish, maybe they will offer them with 6500K tint eventually


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## Changchung

Good thread, I just wondering the same about the XM-L U2 but I want to drive it with 2.8 or 3 max, I think that is not necesary use 3.5amp. I saw in DX as well, I buy a neutral XM-L from a seller who had the U2, check this ebay Item #: 390309091539


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## mfj197

CKOD said:


> Fun times, reflowed a U2 2S bin onto my MCPCB epoxied to my heatsink, attached a Ahorton aspheric lens, and got 29000 CP (lux @ 1 m) peak beam intensity vs the 23500 CP peak beam intensity the T6 was getting. A 23% increase in lux output is much more then expected, even though I was doing my best to keep the testing identical. Same lense/mcpcb/heatsink/lux meter/both measured at 5m distance, and I was getting the peak beam intensity from the same area of the projected die image. (Around the bond wires) I'll re-flow the T6 back on when I get a chance, maybe cutter didnt have the central heat pad fully soldered or something like that. (They put the T6 down originally, not me)


 
Where did you get your U2 from, CKOD? Was it Cutter?

Edit: Forgot to say, good test and thanks for the info! Useful information.


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## CKOD

mfj197 said:


> Where did you get your U2 from, CKOD? Was it Cutter?
> 
> Edit: Forgot to say, good test and thanks for the info! Useful information.


 Yep, from cutter, Its for a project and I'm being picky about the color bins, and no one else really sells them by the color bin. I'm not trying to get one from DX/KD, and have it end up being a 0S tint, T5 flux that they were selling as a U2 etc... No reason to believe they *are* doing that, but they aren't a distributor, and its on a site selling a bunch of cheap crap stuff, and its a metric that I dont have the tools and equipment to check the quality. I dont have an integrating sphere, or anything to measure the color spectrum, so I'm at the mercy of the vendor. Caveat emptor.


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## hellokitty[hk]

I contacted LedDNA's ebay account regarding the tint of their U2's.


> Hi
> 
> Thank you for your Email.
> The tint of XML is 1c.
> 
> Best Regards,
> Billy
> 
> - led-dna


I also asked via the email listed in the contact page on their website several weeks ago, no response.


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## ergotelis

if you look for similar thread you will see that i posted that it is about 1c, pure white, no greenish/yellowish/blueish tint.excellent white.


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## gillestugan

I have bought both the t6 and the u2 from LED-dna. Have no light meter but cant tell any difference by my own eye at 1,5A. Same tint. I suspect them to be the same bin.


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## hellokitty[hk]

It's unlikely you'll see a difference anyway.


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## SkOrPn

Great thread peeps, thanks for the information.

I have a question though. I would like to know how to calculate possible lumen level given the specs of the driver being used, the led type and batteries types? I see that CREE says the minimum lumen on the XML U2 is 300 lm @ 700 ma, however I "think" the driver I am using is going to provide 600 ma, using only 2x AA Sanyo Pros at 2500 mAh. Not knowing the exact mathematical formula all I can do is guesstimate lol. Will this combo provide at least 200 lumen intensity? That's all I am hoping for minimum really. 

I have a old flashlight with a 20mm CREE XRE and the driver has passed away (very dim light with fresh batts). I replaced it with a dealextreme sku# 25505 (have not yet modded it into the light, but will this week). This driver simply says it is a CREE regulated circuit board, with not much else in the way of information. I also replaced the XRE with a XML, supposedly U2 bin. I might mod in a different reflector later on depending on the performance as-is, however I will not proceed down that route until I know what this driver and LED combo does by itself.

Can someone point me to calculator or link with information so I can learn how to calculate theoretical lumen please? Thank you.

The SkOrPn


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## hellokitty[hk]

For a small step like that you can just look at it as linear so it would be ~250.
You can look at the datasheet.


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## SkOrPn

Thanks for the reply kitty. Ok, so what does it mean that 700ma is 100%? Does this mean what it is designed for and everything above this needs either active or passive cooling?

EDIT, after reading the datasheet again, I am going to guess its about 225-250 lumen or abouts at 600ma. I will check my math later but I think this will work for what I want.

Thanks hellokitty


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## awenta

Any reason you must have an XM-L for such a low current? Maybe an XM-L2 if your stuck on XM-Ls


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## DellSuperman

SkOrPn said:


> Thanks for the reply kitty. Ok, so what does it mean that 700ma is 100%? Does this mean what it is designed for and everything above this needs either active or passive cooling?
> 
> EDIT, after reading the datasheet again, I am going to guess its about 225-250 lumen or abouts at 600ma. I will check my math later but I think this will work for what I want.
> 
> Thanks hellokitty



Driving it at 700ma is at 100%.
Anything higher is overdriving & you definitely need cooling measures because a T6 at 2000ma or higher is gonna generate alot of heat. 

Sent from my HTC One X using Tapatalk 2


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## SkOrPn

awenta said:


> Any reason you must have an XM-L for such a low current? Maybe an XM-L2 if your stuck on XM-Ls


Yes, I was specifically looking for a LED that would provide as much efficiency as possible and I was not aware of the XML2 until after I purchased the XML U2, lol. If I find a good deal on the XML2 I will go that route.


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## Justin Case

By 100%, are you referring to the relative luminous flux? The XM-L lumens rating is given as the output at 700mA drive current. For a T6 flux bin, the rating is 280 lumens when driven at 700mA. To calculate lumens output at other drive currents, you refer to the graph of relative luminous flux vs. forward current. As you can see from that graph, at 700mA, the relative luminous flux by definition is 100%, which means that to calculate the output at 700mA, you multiply 280 lumens by 100% to get ... 280 lumens.

Driving an XM-L at greater than 700mA is NOT overdriving the LED. The datasheet spec clearly states that the max forward current rating is 3000mA. What percentages greater than 100% mean is that for forward currents greater than 700mA, the output is greater than 280 luimens, which should not be any surprise.

So, for example, if you drove an XM-L T6 at the max of 3000mA, the relative luminous flux is about 325%. Thus, the calculated output at that drive current is 280 * 3.25 = 910 lumens.

At the other end, if you drove the XM-L at say 600 mA, the relative luminous flux looks like it is halfway between 75% and 100%, or about 87.5%. So the calculated output is 280 * 0.875 = 245 lumens.


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## ledmax

i direct drive a xml t6 on a 26650, its insain bright and draw 3.4 [email protected] and [email protected], used for 2month and led is still ok after 22 charg, its close to 1000lm fully charg


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## dxcom

CKOD said:


> Fun times, reflowed a U2 2S bin onto my MCPCB epoxied to my heatsink, attached a Ahorton aspheric lens, and got 29000 CP (lux @ 1 m) peak beam intensity vs the 23500 CP peak beam intensity the T6 was getting. A 23% increase in lux output is much more then expected, even though I was doing my best to keep the testing identical. Same lense/mcpcb/heatsink/lux meter/both measured at 5m distance, and I was getting the peak beam intensity from the same area of the projected die image. (Around the bond wires) I'll re-flow the T6 back on when I get a chance, maybe cutter didnt have the central heat pad fully soldered or something like that. (They put the T6 down originally, not me)
> 
> I was using a LX1330B light meter. the person on amazon was trying to sell it as an Extech instrument, but there is no Extech branding on it, or no listing of a light meter on Extech's website. I dont know how this meter compares to others, but regardless of that, the comparsion between the 2 LEDs should be valid.
> 
> Now for the real trick, do you trust DX enough to actually be shipping U2 LEDs? I may be a bit cynical, but I wouldnt.
> 
> EDIT: redid the T6 lux measurement, got 24750 CP for the T6, making 29000CP for the U2 only a 17% increase. The T6 is a 1A tint bin, vs a 2S tint bin, making the U2~5700k and the T6 ~6500K in color temp, which probably explains the difference between 14% theoretical vs 17% empirical. (Sensitivity of the lux meter more meant for incan/warm whites vs cool white)
> 
> So yes, they are brighter, is it noticable by eye? Maybe maybe not, depends on the on the light it goes into. Would it hurt anything getting the brighter bin if it was in a tint you like? Probably not, I wouldnt pay more then 14% extra for the theoretical 14% extra performance.



Hey CKOD,

Yes, we are actually shipping XM-L2s! Only a few lights feature this LED at the moment but we are planning to add a lot more. Will have a listing in MarketPlace soon.

~joseph DX


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