White LED lumen testing

Pinter said:

Interestingly, at 5mm leds heat exits not only through the leads; if you hold the "dome" with your fingers, the Vf will start decreasing slowly. Within 10-20 seconds I saw -0,02 V change in Vf, while the current went up by 0,2mA (simple resistored setup from NiMH batteries).

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With 250C/W through the leads, it's not surpising that a considerable percentage of the heat is being dissipated through the epoxy encapsulent. This will not hold true for power LEDs - heat dissipation through the dome/lens of a power LED will be negligable - the dome does not prodivide an appreciable thermal path.

FYI - when you held the dome, you were actually causing the LED to heat up, reducing the amount of heat dissipated by the epoxy. The Vf of LEDs drop when they heat up.

I finally got around to testing the two Cree XR-E emitters 3rd_shift sent me. The purpose of this test was to determine the difference between an emitter with and without the dome. The unmodified Cree XR-E bin P2 emitter tested as follows:



Output was 70.67 lumens at 350 mA. This is right in the middle of the P2 bin (67.2 to 73.9 lumens). The same bin emitter with the dome removed only had an output of 54.35 lumens at 350 mA. The beam angle was wider as well (122° versus 83.3° for the unmodified emitter). The relative intensity versus angle for the two emitters is shown below (domeless emitter in magenta):



Apparently the silicon encapsulant combined with the dome helps to extract a considerable amount of light from the die. The output of the domeless emitter is 24% less than the stock emitter.

Seoul Semiconductor W42180 bin U (tested February 2007)

I purchased a U bin Seoul Semiconductor emitter from milkyspit recently. The results of the test are shown below:



I believe the results speak for themselves. The efficiency at 350 mA is a very impressive 82.1 lm/W and the output is 96 lumens. This is a new record for power LEDs and also matches my best results for single die 5mm LEDs. Beam angle is close to 130° which means these have a light distribution similar to a Luxeon emitter. Since the emitter is rated for 1000 mA I felt comfortable going to 1500 mA, at which point output more or less leveled off. The output scales with current almost identically to the Cree XR-E bin P4 which I tested in December but this is no surprise since both emitters use the same die. Note that the U bin has a range of 91 to 118.5 lumens so these are at the low end (which I expected). I anticipate that the Cree XR-E Q3 bins will offer similar results. Shown below is a chart of Vf, power, and lumens at various currents.

Great job Jtr!!!!

Erasmus said:

Great job Jtr!!!!

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+1! :bow:

This is terrific data. Speaking very selfishly, this will help me a great deal in my builds to get good estimates of the outputs of various configurations... but beyond that, you've done and continue to do a great service to the entire community. Hat's off to you, JTR! (but there's no hat's off icon, well, here ya go...)

:thumbsup: :naughty:

+2 Great data! Thanks for continuing to do these! :goodjob:

Paul

+3 :bow: very very valuable information

:twothumbs :bow:

Awesome job!
:bow:

Nice, very nice...

I did a chart of efficiency versus time of manufacture for the LEDs I've tested:



While it's difficult to draw many conclusions, three things are apparent. One, the trend is towards increasing efficiencies. Two, the spread between best and worst LEDs is increasing. The worst are no better than similar ones of five years ago while the best are perhaps 4 times better. Three, the majority of the LEDs made today fall in the 60 to 70 lm/W area.

Lots of good data!

By the way, I think the new THC3 LEDs might be single-die rather than 4-die.

If you look at the die, you'll probably only see two bond wires. I'm not sure if this means this is single-die, but I would expect four bond wires for a 4-die.

Toshi

TMorita said:

Lots of good data!

By the way, I think the new THC3 LEDs might be single-die rather than 4-die.

If you look at the die, you'll probably only see two bond wires. I'm not sure if this means this is single-die, but I would expect four bond wires for a 4-die.

Toshi

Click to expand...

+1... although the Quickar 5m100ma performance is virtually identical and that one DOES have four bond wires... go figure...
:thinking:

jtr1962 said:

Seoul Semiconductor W42180 bin U (tested February 2007)

I purchased a U bin Seoul Semiconductor emitter from milkyspit recently. The results of the test are shown below:

Click to expand...

It is interesting comparing the differences between the three of them.

Do you happen to know the tint bins of each one?

How were these mounted in each case, and what were they heatsinked with for the testing?

Were these all bare LEDs mounted on the channel aluminum, or were any of them on MCPCB or other mounting methods?

Which meter model do you use for your testing?


Thank you *very* much for taking the time to do the testing and putting the results here on cpf for everyone!


.

NewBie said:

It is interesting comparing the differences between the three of them.

Do you happen to know the tint bins of each one?

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The P4 Cree is tint WH, the P2 is tint WC. I don't know about the SSC. It looks similar in tint to the Cree WC so maybe it's XO.

NewBie said:

How were these mounted in each case, and what were they heatsinked with for the testing?

Were these all bare LEDs mounted on the channel aluminum, or were any of them on MCPCB or other mounting methods?

Which meter model do you use for your testing?

Thank you *very* much for taking the time to do the testing and putting the results here on cpf for everyone!

Click to expand...

To answer your questions in order:

1) Here's my power LED testing apparatus:



I soldered the LED to be tested directed to the PCB, making sure it sat on the piece of copper bar shown covered in thermal grease. I didn't bother cooling the heatsink with a fan, although it did get a little warm when I cranked the current up to 1.5 amps.

When I test stars I can screw them directly to the aluminum channel.

2) My light meter is a CEM model DT-1300.

3) You're quite welcome-I'm glad the results are useful and the work is appreciated.

I thought you might be interested in this, a spectral scan of a Seoul P4 USXOI bin and a CREE P3 WC bin. I originally did it for another thread, but thought you might find it useful:




There will be an un-marked up one which I'll put in my Seoul thread.

I noticed the Seoul has a slightly deeper blue, significantly less "cyan-green", and a bit less red. It does have more of a peak in yellow. The blue human eye has a hard time telling the differences at the 460-470nm wavelength range anyhow.

Both parts had 700mA passing thru them in this view here.

I don't think the LVEHK 140ks were rated at 80ma.

Here's a link to the specs:

http://cgi.ebay.com/100p-10mm-SUPER...hZ002QQcategoryZ66952QQtcZphotoQQcmdZViewItem

The DC forward current is 20ma.

Toshi