mds82
Enlightened
I definately want to see how this stacks up to the XT-E. I'm planning on making a Huge purchase in the next 1-2 months and would love to see the differences
New 2nd Generation Cree XP-G2 LED!
- Thread starter jasonck08
- Start date
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Warning dumb question
Looking at Cutter's Cree slide are the XP-G2 R3s running hotter using 350mA at 85c than the equivalent XP-G R5s using 350mA at 25c? If the XP-G2's higher temperature at 350mA of 85c is really true then would this mean that the XP-G2 maximum forward current would be a lot less than 1500mA maybe about 1000mA?
Looking at Cutter's Cree slide are the XP-G2 R3s running hotter using 350mA at 85c than the equivalent XP-G R5s using 350mA at 25c? If the XP-G2's higher temperature at 350mA of 85c is really true then would this mean that the XP-G2 maximum forward current would be a lot less than 1500mA maybe about 1000mA?
Check post 7, it lists them both the sameWarning dumb question
Looking at Cutter's Cree slide are the XP-G2 R3s running hotter using 350mA at 85c than the equivalent XP-G R5s using 350mA at 25c? If the XP-G2's higher temperature at 350mA of 85c is really true then would this mean that the XP-G2 maximum forward current would be a lot less than 1500mA maybe about 1000mA?
http://www.candlepowerforums.com/vb/showthread.php?340892-New-2nd-Generation-Cree-XP-G2-LED!&p=3980633&viewfull=1#post3980633
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AnAppleSnail
Flashlight Enthusiast
Short answer: No they aren't, and no it isn't.
Cree has changed their standard test die temperature from 25C to 85C. Their stated reason was to better match real-world conditions. This change has nothing to do with how the LED performs (Any more than changing your ruler alters how strong a beam is). The cutter chart says "Comparing these different LEDs at different temperatures and then extrapolating based on temperature/performance changes, they are pretty well equal. The forward current rating is probably not changed, although details of the performance curve might (Certainly with respect to output, and therefore probably with respect to temperature vs. energy), though I can't say by how much.
It is interesting to note that this "XP-G2 R3 flux bin" LED would be binned to the R5 flux bin if tested at the 25C temperature. Cree is putting a harsher standard on their LEDs for the reasons I cited above. Presumably downgrading paper performance to better-match real-world conditions will give their sales followups better ammunition.
ShineOnYouCrazyDiamond
Flashlight Enthusiast
85*C is just the direction Cree has gone with re-binning their LEDs.
Historically if you looked at Crees binning you would see measurements at 25*C, basically room temperature, a temperature that only exists at the emitter right before it's been on for the briefest moment. Once the emitter temperature increases, relative output deminishes. If you look at the Cree PDF you will see that a relative output of 100% at 25*C can drop to 85-90% as temperatures rise to 85*C.
The re-binning, although confusing, is actually more accurate because you get a truer idea of how much light the LED will produce while being power on. There is no need to de-rate the output of a light by a factor of .8 to .9 to take into consideration heat losses among others.
It does however create confusion when comparing new/old Cree leds and also comparing with other brands which rate their lumens at 25*C.
Historically if you looked at Crees binning you would see measurements at 25*C, basically room temperature, a temperature that only exists at the emitter right before it's been on for the briefest moment. Once the emitter temperature increases, relative output deminishes. If you look at the Cree PDF you will see that a relative output of 100% at 25*C can drop to 85-90% as temperatures rise to 85*C.
The re-binning, although confusing, is actually more accurate because you get a truer idea of how much light the LED will produce while being power on. There is no need to de-rate the output of a light by a factor of .8 to .9 to take into consideration heat losses among others.
It does however create confusion when comparing new/old Cree leds and also comparing with other brands which rate their lumens at 25*C.
Thanks AnAppleSnail and ShineOnYouCrazyDiamond for the explanations.
Now this statement at http://flashlightwiki.com/Cree#XB-D
"This LED is binned at an operating temperature of 85° C instead of 25°, so in order to directly compare its output to other LED's that are typically binned at 25 degrees, the numbers in the table below have been increased by 14% (see XB-D output for the 85° numbers)."
also makes more sense. :candle:
Now this statement at http://flashlightwiki.com/Cree#XB-D
"This LED is binned at an operating temperature of 85° C instead of 25°, so in order to directly compare its output to other LED's that are typically binned at 25 degrees, the numbers in the table below have been increased by 14% (see XB-D output for the 85° numbers)."
also makes more sense. :candle:
But if this a 3mm^2 die, then it will throw better than the xm-l.
But if it was a 3mm^2 die, shouldn't the maximum drive current be roughly 2 amps?
AnAppleSnail
Flashlight Enthusiast
You're oversimplifying both of these statements, but it really only matters on the first. Throw is based on a few things. A simplification of throw is [Surface Brightness] x [Amount of surface focused by optic or reflector]. Most LEDs have primary optics built in. The XP-G2 has a rather different primary optic, which affects the amount of surface which will be focused in the reflector or optic. Lenses will benefit, while TIR and reflectors will suffer, in short. I predict it to throw a bit better in aspherics than the XM-L, and a bit worse in compact reflectors. Big lenses or reflectors will minimize those differences, and leave the 14% brightness boost.
The drive current is broadly increased with increasing die size, but also affected by construction and material robustness. You do get more water through a fatter pipe, but you can also build a pipe to take more pressure.
bshanahan14rulz
Flashlight Enthusiast
imsabbel, I think they've used ceramic boards for their LED manufacturing since the XR series, if not earlier. It might just be a different color "solder mask" used to differentiate G1 from G2.
I do remember seeing the die mounted directly on top of a large SiC diode back in the XR days, wonder if they still do that but on a thinner scale, or if they have switched to moving the esd out of the package or off to the side of the die.
I don't think it's a larger die, but then again, they have changed dice size before and not told anybody...
I do remember seeing the die mounted directly on top of a large SiC diode back in the XR days, wonder if they still do that but on a thinner scale, or if they have switched to moving the esd out of the package or off to the side of the die.
I don't think it's a larger die, but then again, they have changed dice size before and not told anybody...
easilyled
Flashaholic
XREs also had narrower viewing angles and had special reflectors designed for them (by McGizmo and other manufacturers)
These reflectors were relatively narrower and deeper than the equivalent reflectors for other emitters with wider viewing angles around at the time like the SSC-P4.
So there is no reason why a change in reflector design cannot be optimised for the XPG-G2 either.
So there seems to be some conflicting info here and I don't have the time to do the proper analysis but let's just say I was expecting the release of this LED but the pictures supplied in Cutter's email don't look like what I expected. Here is a picture of the DA1400.
Note that this die is the same size as the EZ1400 which is in the regular XP-G. Since this die is also the one that is the embodiment of the "SC³ technology" it stands to reason it is the die used in the XP-G2. The pictures in Cutter's email however show a die with top bond wires and a flat substrate. If the XP-G2 in fact turns out to have this flat substrate instead of the faceted DA chip then I will be a happy man as I am no fan of the DA chips as their optical characteristics stink for our applications. The DA chip should have much better thermal characteristics than the EZ based XP-G so the fact that the comparison chart shows equivalent performance in that area it would make one believe that either the data provided is incomplete/wrong or the XP-G2 is indeed the more traditional flat substrate.
Note that this die is the same size as the EZ1400 which is in the regular XP-G. Since this die is also the one that is the embodiment of the "SC³ technology" it stands to reason it is the die used in the XP-G2. The pictures in Cutter's email however show a die with top bond wires and a flat substrate. If the XP-G2 in fact turns out to have this flat substrate instead of the faceted DA chip then I will be a happy man as I am no fan of the DA chips as their optical characteristics stink for our applications. The DA chip should have much better thermal characteristics than the EZ based XP-G so the fact that the comparison chart shows equivalent performance in that area it would make one believe that either the data provided is incomplete/wrong or the XP-G2 is indeed the more traditional flat substrate.
jasonck08
Flashlight Enthusiast
I'm sorry but I think both of you guys are still incorrect, that a wider viewing angle means better throw.
The XR-E EZ1000 out throws the XP-E for example. Both LED's use the same exact sized die 0.98^2. The difference? The viewing angle. The XR-E has a 90 degree viewing angle and XP-E has a 115 degree viewing angle.
Think about it logically. How difficult would it be to focus an LED with a 180 degree viewing angle? Quite difficult. Much easier to focus a narrow viewing angle to a tight beam than a wide viewing angle to a tight beam.
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I don't think it does. It's just that XR-E lights tend to have deeper reflectors.
The old Luxeon I side emitter had something like 180 degree emission and gave crazy throw in a shallow reflector with very little side spill.
ergotelis
Enlightened
I Think i was managing about 42,000 lux with a xp-e R2 and a mag reflector@1,05amp with the classic 3x7135 setup. The Tiablo A10 with an xr-e, used to have a higher diameter and deeper reflector to catch about the same numbers of lux. Xp-E definitely throws, it is all about the reflector. And xr-e throws, but needs a different design reflector.
Anyway, ordered 10 of them from cutter couldn't resist! Then i will see how does it performs, hope i won't be disappointed! I hope it can catch the same throw as a classic xp-g , at the same diameter reflectors!
Anyway, ordered 10 of them from cutter couldn't resist! Then i will see how does it performs, hope i won't be disappointed! I hope it can catch the same throw as a classic xp-g , at the same diameter reflectors!
fyrstormer
Banned
The throw can't be worse than stuffing an XM-L into the same light. At least the smaller emitter die (relative to the XM-L) means more of the light is emitted at the reflector's focal point.
fyrstormer
Banned
On a reflector light, the hotspot part of the beam is made of light emitted from the center of the die and reflected by the reflector. The flood part of the beam is made of light that emanates directly out the front of the light without reflecting off anything. The transition between the hotspot and the flood is made of light emitted from the edges of the die and reflected by the reflector, but not focused properly because wasn't emitted near the reflector's focal point.
So, the more light that hits the reflector, the brighter the hotspot and transition areas will be. That translates to better throw. Sorry, you're wrong.
Colonel Sanders
Flashlight Enthusiast
:thinking:
