Seoul P4 initial Evaluation- Production LEDs

[NewBie]

Currently, on the production Seoul P4 parts that I've got, they are binning by Kelvin temperature, and this one is 6500K. This is more like the old LumiLEDs method that they used with the LXHL-BW01 parts when they had the blop/glob phosphor. LumiLEDs went to great efforts in the early days to sell everyone on this technique in their techical presentations and training seminars. Thank goodness common sense won out, and they went to the color binning method based on the eye response to color that they use now. Under the old system, they take the Planckian BBL radiator line, and draw lines perpendicular to it, and create a binning structure from that. One of the big drawbacks of this system is that within one bin, you could get anything from an X1 to a X0, to a WA bin, which takes you from green to cool white to pinkis/purplish white, if anyone remembers the old days. So, under the old LumiLEDs system, this would fall in Bin Code 4, if anyone is interested.

Example:

Unfortuneately, that chart there doesn't have the tints on it, so use this as a reference:

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[Draper Knives]

Very interesting...Thanks for your research!!! Do you happen to have comparison pics of the base of LUX III and the Seoul P4 LED?

Have you tried using a dryer fabric softener sheet for static...:thinking:


Mike

 

[IsaacHayes]

Newbie, whats with that milky gel on top of the die? It seems too as though the extra phosphor below/on the edge of the die is what causes the yellow hallo. But the XRE is sprayed all over too, but I'm guessing that either the same thing is happening, but blocked by the ring on the cree, or that there is less light shining out the side of the die to excite this phosphor, where the P4 does and shines that out.

If the "yellow edge" wasn't there, and just the center hotspot from the led, is the color even? Like would it be all blue/white, or does it go from yellow, white, to nasty blue like the older SSC zleds?

Also, can you confirm the slug size on the P4? Is it larger than the luxeons?

 

[NewBie]

Here is a side profile of the Seoul P4 beam, with the McGizmo HD45 reflector which has a bumpy reflector surface:

 

[3rd_shift]

Excellent photos Newbie! :twothumbs: :bow:

It looks like a fairly inexpensive led to produce.
It just doesn't look like a lot of effort was put into durability and consistency.

I just justed off an older SX1L binned Luxeon3 and it seems to be of a good build quality with only relatively low performance, and an all around, even, nonfat milk greenish white tint.

It looks like SSC has a little ways to go imho.

A lot of light is good if it looks good.
If it looks like a white sheet of paper from inside the pet's litter box, then I'll pass for now.

 

[NewBie]

Okay, did a quick Vf run, since folks were asking me about Vf on the Seoul P4:

One thing I noticed, is the overall tint on these changes a lot with current, but how much is for later testing. For now, above 1 Amp, whatever phosphor mix they are using really starts shifting hard, up at 2 Amps, it gets a pretty scary shade of blue (much like the overdriven 5mm do- a.k.a. angry blue). Comming back down, I noticed the tint shifts considerably over the current range as you move it around, but I'll need to some calibrated measurements to get more specific. Extremely low and very agressive thermal resistance solutions may help this issue, I'll have to look into that further.

 

[Draper Knives]

 

[NewBie]

Hey, that looks great right about now, time for a break!

 

[chimo]

Hey, that looks great right about now, time for a break!

Hawaiian pizza is my favourite. However, crock pot chicken stew will have to do tonight - time for supper.

 

[hotbeam]

Interesting read Jar.

I use a drop of water or saliva to remove the dust from the dome.... and then promptly cover up the LEDs so nothing else sticks on it. Here is a photo of the dome after 5-6 months of it in an uncovered environment. Under macro, it doesn't look that good. But that is after 5-6 months. If you cover it up soon after it is in your flashlight, you won't have these issues.

As far as the lens is concerned, a silicon lens allows for much better heat dissipation than epoxy. I suspect that is one reason why it was used.

As suggested, the orange peel McGizmo reflector will definately come in handy. I won't be happy with the visible bond wire.

Oh, at 2A, everything else would look pretty 'angry' Their rated maximum is half of that!

I look forward to getting my reels of U's so I can check it out also. Although I will concede to you Jar right now, my equipment range is nowhere near the capabilities of your lab.

 

[NewBie]

Interesting read Jar.

I use a drop of water or saliva to remove the dust from the dome.... and then promptly cover up the LEDs so nothing else sticks on it. Here is a photo of the dome after 5-6 months of it in an uncovered environment. Under macro, it doesn't look that good. But that is after 5-6 months. If you cover it up soon after it is in your flashlight, you won't have these issues.

As far as the lens is concerned, a silicon lens allows for much better heat dissipation than epoxy. I suspect that is one reason why it was used.

As suggested, the orange peel McGizmo reflector will definately come in handy. I won't be happy with the visible bond wire.

Oh, at 2A, everything else would look pretty 'angry' Their rated maximum is half of that!

I look forward to getting my reels of U's so I can check it out also. Although I will concede to you Jar right now, my equipment range is nowhere near the capabilities of your lab.

I take it that is the older glop LED in that photo?


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[milkyspit]

Very useful read, Newbie. Thanks.

Thanks, too, to those who have chimed in... JTR1962, Hotbeam, McGizmo, etc.

Nice job guys. :thumbsup:

 

[wquiles]

Awesome thread - thanks NewBie :rock:

Will

 

[hotbeam]

I take it that is the older glop LED in that photo?

Yes, from the P3 range. One would hope the P4s are equal to or better than that.

 

[NewBie]

I decided to do a set of side profiles in the smooth MagLite D cell reflector.

As you look at the photos at different exposures, you should be able to see the various tints in different areas that are not captured by a single photo. One item to take note of, for example, is in picture 3, you'll notice the cooler white center hotspot on the right hand side at the very end of the paper, then you will see the warm surround, then the very cool white flood area. Also, some of various the ring artifacts can be seen at different exposures more than others. The technique of various exposure levels is called bracketing, and is used to help make up for the short commings of digital cameras.

(keep in mind, when looking at very, very slight tinting, from monitor to monitor, some of the tints will look a bit more greenish, warmish, purplish, bluish, etc, depending on the monitor settings and the quality of the monitor)

 

[SuperTorch]

How large is the hot spot in the Mag, the Luxeons are a tad small and on tightest focus I was hopeing the new stuff, Cree XR-E and the Seoul P4 would have a larger hot spot, maybe 50% larger. Now that its night time and since you were kind to the whitewall hunters can you make a comment for the throw junkies, thanks.

 

[chris_m]

Does anybody know how these compare to a SSC P3 LED in terms of dimensions and beam pattern? Are they a drop in replacement for those? I have some P3 optics (though never had any P3s - bought in mistake when I had SSC P1s which were the highest efficiency power LED before the Cree XR-E), so hoping I can just drop some P4s in.

 

[NewBie]

SuperTorch

I don't really see any difference in the focused hot portion of the hotspot size itself between the Luxeon III and the Seoul P4 in the MagLite reflector.

What I did notice is there is some tinting in the hotspot which changes as you move it in and out of the focus.

With a particular 2D MagLED that I know runs close to 350mA, I find that the Seoul P4 registers the same on my light meter @ 230mA.

 

[NewBie]

Okay, I dug out the manual and figured out how to lock the movie camera exposure setting and color correction settings.

Color tint shift with current adjustment

I specifically noticed during my forward voltage testing of the Seoul P4, that the color shifts dramatically with current levels. Two things can cause this, one being the die color output, and the other is the phosphor (some YAG phosphors will drop as much as 60% lower output as the die heats the phosphor).

An example of what happens to one type of YAG phosphor is shown here, with the red line:
http://ledsmagazine.com/press/14132


It is unknown to me as to what is actually causing this in the Seoul P4 LED.


Anyhow, like I mentioned, I locked the exposure and white balance in the camera for this movie I took to demonstrate the color shift. The current runs from 400mA to 1.1 A in the video.


The movie is located here:
http://www.molalla.net/~leeper/seoulp4t.wmv


I'd estimate the part is moving from a very strong X1 bin (greenish-yellow) to way out beyond the end of the YA bin. At 400mA it is greenish-yellow and at 1100 mA it is blue. Pay attention to the corona color around the hotspot, since the camera is oversaturated in the hotspot and doesn't represent color that well there.


Thoughts-

The P4 LED appears to tint shift a lot more than other LEDs with drive current level changes, and hopefully it is just due to heating effects on the phosphor.


Early thoughts-
I'd consider agressively pursing very good thermal transfer techniques in an attempt to help mitigate the tint shift in the Seoul P4.


My plans for checking this out further-
Getting a thick copper plate and directly soldering the Seoul P4 to it. Then to thermal paste this plate to a large CPU heatsink with a strong fan. Then retest to see if it actually will help or not.


The Seoul P4 has a rather low thermal resistance 6.9 C/W vs. 8 C/W for the CREE XR-E, and they use the same CREE EZ1000 die in them. The LumiLEDs K2 has a 9 C/W. I don't notice tint shifting in the K2 or the XR-E that is anything like what the Seoul P4 is demonstrating. (or even the Luxeon III with a 13 C/W for that matter)

With the Seoul P4's very low thermal resistance being in the same range of other newly introduced LEDs one would figure the shifts should be similar. The shift in the blue wavelength (affects interaction with the phosphor), and also the shift due to YAG phosphor heating, should be less, unless they are using a different phosphor blend than LumiLEDs or CREE is utilizing (which is quite possible).

I hope to explore this further by directly soldering the part down to get rid of the thermal resistance of thermal epoxy and agressively heatsinking the thermal energy out of the Seoul P4 die.


The movie doesn't work for some folks, so I snapped a snapshot from two points in the video:

 

[Nereus]

Okay, did a quick Vf run, since folks were asking me about Vf on the Seoul P4:

What a difference between Vf of Cree and Soeul! I wonder where this comes from since aren't they using the same Cree die? Does Cree give its highest Vf dies to Soeul...?

On the other hand this means that Cree parts should perform better than Soeul when it comes to lm/W.

-N