Got my XT-E drop-in today; first impressions.

I got mine 5-mode today and I'm afraid I must agree with you. I did'nt notice at first but now I see the same bluish hotspot and I have a little yellow center in it.

I had great hopes that the new shape of the die (mountain-like) would get rid of the normal (for wide dies) yellow hotspot with bluish corona but they did it a little too much, I think so it's almost the opposite now.

The 5 mode is with the good old NANJG 47 (-A this time) with the small stars for programming on the back. It has the ATTiny13 (Hurrah) so I will modify with my own program.

The stock setup was:

Low-Medium-High-Strobe-SOS

20-120-360 lumens @ 56-330-1047 mA measured at 3.9V

16-106-360 lumens @ 42-280-1049 mA mesured at 3.6V

so the regulation seems fine (3x7135) but the PWM seems to vary with the voltage [ edited]

At 3.3V I measured 319 lumens on High (out of regulation).

So it seems to be a very efficient LED and it runs cooler than XP-G.

A pity with the mis-coloring.

I also got a "20"mm and a "14"mm star. They both gave 162 lumens at 350 mA so they are truly R5. The CCT was 5980K and they fit in bin 2B.

I wonder if these actually work better in a diffused material ..if the colors will all blend ..Do you have a decent diffuser ?? just curious

Yeah, with a diffusion lense you should get a nice overall tint I would imagine. My only diffused P60 lense is over a 2.5A regulated XM-L 5500k which I took out of my Olight S65 though and I'm not taking it off ;)

It's frustrating in the UK as due to the high humidity and cold nights you often find the inside of well-driven P60 lights fogging up. So when I get a very low humidity day (rare) I take my P60s out and re-assemble them outside. This normally fixes the fogging up issue but means I am stuck with leaving them assembled unless I really want to change out the drop-in or until another low humidity day..

Wow I did not know that Sherwood is a rain forest???

I live in Oxford and never have any problems with my drop-ins fogging up.

Maybe you should try changing them in doors with the central heating on? Laughing

Got mine today also. Exactly the same results with the OP reflector. The beam is a bit throwier than an XPG close to an XPE, but nowhere a replacement for an XRE. The ugly beam pattern can be easily forgotten outside though. It is a bright and throwy drop-in as is.

Not bad... 360 Lumens / 3.77W = 95 Lumens per Watt at nominal Vbatt

Cooler running than the XPG is a big bonus too.

Have you really never had any problems? It's common for me, with my normal assembly being done inside with central heating on.

It only normally happens with drop-ins driven over 2amps when in use outdoors for more than 2-3 minutes continuously. It has also happened with well-driven lights in stock form as well and is very common with bike lights as they have a lot of airflow onto their lense. Another thing to note is that the wider the lense is the greater chance that it will mist up.

Mine is still in the mail on the way here :(

How much will an XP-G R5 do with NANJG 47 @ 1Amp lumenswise?

Luckily, I have one dropin just for the comparo, R5 driven with 1A :)

From the Cree datasheets, at 1 amp the XP-G R5 is 348-370 lumens while the R5 XT-E is 320-340. So the XT-E is acting a little more like an XP-G R4. However the XT-E output is rated at a higher temperature and if the XP-G were rated at the same temperature it would be a little lower too. So apples to apples, you could increase the XT-E output by 15% and get 368-391 lumens at 25 degrees C to compare with the XP-G. Now the XT-E is a bin brighter at 1 amp.

Around 260-300 OTF depending upon conditions and lense/bezel used according to my own measurements. The XT-E should be around 8-10% more efficient in total output.

[/quote]

The stock setup was:

Low-Medium-High-Strobe-SOS

20-120-360 lumens @ 56-330-1047 mA measured at 3.9V

16-106-360 lumens @ 42-280-1049 mA mesured at 3.6V

At 3.3V I measured 319 lumens on High.

So it seems to be a very efficient LED and it runs cooler than XP-G.

[/quote]

So it drops 40 Lumens as the Vin depletes from 3.9-3.3V.

What is causing the drop in output? thermal warming?, lower Vin?... both? I would not expect it to drop that much if it is running cool.

At Vin of 3.3V, you are getting below Vf at 1A for the LED so the current draw is probably down as well. The driver is taking some of the Vin for itself.

You are spot on, brted. The 7135 are out of regulation at Vb = 3.3V and the current drops.

I think I will have to take this dropin to integrating sphere to see, what it gives OTF.

The output for XT-E is given at 85'C. It has to be multiplied with 1.14 before comparing it to XP-G.

So XT-E R5 gives 143x1.14 = 163 lm @350mA at 25'C.

XP-G R5 gives 143 lm @350mA at 25'C.

I use a spreadsheet with formulas derived from Cree data and get:

XP-G XT-E at 1.0A

Led cold: 356 376 lumens

Led varm: 326 346 lumens *)

OTL varm: 261 277 lumens *)

junction temp: 68'C 65'C *)

*) this is for a typical host (L2)

Because these LED's are spec'd based on 85 degrees, would these be perfect for a low driven triple in a small host?

Or a multi emitter headlamp with next to no reflector creating a floody beam and stopping what could be an issue with the colour fringing beam?

I don't think the spec temperature means anything. It is just a setting at which they measure performance. Maybe some people complained that Cree was evaluating their LED's at room temperature when, realistically, the LED is going to get hot very quickly and it would be more realistic to measure the output when the LED is hot. The datasheets allow you to generate numbers at any temperature you want, it's just the default (100%) value is at 25 degrees for the XP-G while for the XT-E it is 100% at 85 degrees.

So runtime should be amazing with this thing, huh?

Exactly equal to any other LED driven at 1 Amp. An XML, XPE, XRE or XPG driven to 1 Amp would have identical run-time**.

**Assuming a linear driver where Vf is irrelevant. A switch-mode driver would vary the run-times a little according to differences in LED Vf.

PPtk

Correct, and XT-E is 114% at Tj=25 degrees.