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Thread: White LED lumen testing

  1. #91
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    Default Re: White LED lumen testing

    Quote Originally Posted by 3rd_shift
    One more thing.
    Be very careful with the domeless one.
    It's kinda fragile.
    I just killed another one trying to take it's dome off.
    I ended up successfully removing and testing a working one from a maglite mod I did last month.
    Unpack it carefully in case the gel stuck to the plastic baggie it is in.
    Thanks for the warning. I'll try not to kill it before I have a chance to test it.

  2. #92
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    Default Re: White LED lumen testing

    Quote Originally Posted by Doug S
    If you are not making any special provision to heatsink the cathode lead, a very interesting comparision would be a comparison with and without the cathode lead heat sinked to a few square inches of copper.
    I ran a few tests of both the old and new Jeleds with and without a heat sink. The heat sink consisted of a ~0.75" square of copper soldered on the cathode lead as close as possible to the epoxy body. Here is the relative output for the older Jeleds (red is without heat sink, blue is with heat sink):



    Here is the same thing for the newer Jeleds (again red is without heat sink, blue is with heat sink):



    Based on my tests of these a few days ago they already do substantially better at higher currents than the older Jeleds. There is some improvement with a heat sink but not as much as the older style.

    Here is the percentage improvement versus current for both LEDs (older Jeled is in blue, newer one in red):



    My tests are telling me that the way the LED is made is probably way more important than any external heatsinking. The newer Jeled probably uses a larger die with more contact area with the cathode "cup". It may even be attached with more thermally conductive material. The heat sink still helps, but only to the tune of about 10% at 80 mA.
    Last edited by jtr1962; 01-16-2007 at 03:07 AM.

  3. #93
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    Default Re: White LED lumen testing

    Quote Originally Posted by jtr1962
    I ran a few tests of both the old and new Jeleds with and without a heat sink. The heat sink consisted of a ~0.75" square of copper soldered on the cathode lead as close as possible to the epoxy body.

    My tests are telling me that the way the LED is made is probably way more important than any external heatsinking. The newer Jeled probably uses a larger die with more contact area with the cathode "cup". It may even be attached with more thermally conductive material. The heat sink still helps, but only to the tune of about 10% at 80 mA.
    Thanks for doing this. The differences are in line with what I had expected. I agree with your general analysis. Heatsinking becomes a consideration for those who are inclined to drive the piss out of 5mm leds. While 10% may not be much, it is better than a poke in the eye. 10% is about the span of one cree flux bin and folks have been known to pay a premium for a single bin step. With the 5mm leds, sometimes it is possible to get that 10% for free with a little attention to the thermal paths. BTW, back in the dark ages before Nichia introduced white LEDs, it was not uncommon for LED datasheets to specify a thermal resistance from the junction to a point 3mm down the cathode lead. I remember that for some of the Hewlett Packard products this value was given as 220 C/W. The practice of providing this thermal resistance seems to be uncommon with the current 5mm white products.

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    Default Re: White LED lumen testing

    The older Jeled 50k leds were in drawer for a long time, got humidity from the air. Just wondering if their re-measured brightness were the same as in your original tests or were affected somehow?

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    Default Re: White LED lumen testing

    Quote Originally Posted by Pinter
    The older Jeled 50k leds were in drawer for a long time, got humidity from the air. Just wondering if their re-measured brightness were the same as in your original tests or were affected somehow?
    Actually they were still in the antistatic bag they came in which in turn was in the shipping envelope and then in a small box with my other white LEDs. It wouldn't matter if they had lost brightness anyway since my heat sink tests were solely to measure relative increases in brightness of the same LED by adding a heat sink.

    I don't think humidity would affect the LED all that much anyhow since the epoxy case is designed to protect against that. I have a BestHongKong UWLC white LED sitting in my tester all the time it's not in use. It's therefore exposed to the ambient humidity all the time. It measured around 14 lux at one meter when new. It still does whenever I check it. It's over 18 months old.

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    Default Re: White LED lumen testing

    My apologies for the delay, I finally mailed the leds to you today.
    The icy weather here has been a nightmare all week long.
    Enjoy.

  7. #97
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    Default Re: White LED lumen testing

    Quote Originally Posted by Doug S
    Thanks for doing this. The differences are in line with what I had expected. I agree with your general analysis. Heatsinking becomes a consideration for those who are inclined to drive the piss out of 5mm leds. While 10% may not be much, it is better than a poke in the eye. 10% is about the span of one cree flux bin and folks have been known to pay a premium for a single bin step. With the 5mm leds, sometimes it is possible to get that 10% for free with a little attention to the thermal paths. BTW, back in the dark ages before Nichia introduced white LEDs, it was not uncommon for LED datasheets to specify a thermal resistance from the junction to a point 3mm down the cathode lead. I remember that for some of the Hewlett Packard products this value was given as 220 C/W. The practice of providing this thermal resistance seems to be uncommon with the current 5mm white products.

    I specifically asked Nichia this about a year ago, on their various leaded parts, and they replied with 200-300 C/W, depending on the part.

    It would be interesting to remove the thermal resistance from the base of the package to the cup (grind away the clear epoxy). I know I see considerable differences between these two points when I heatsink the lead. About a month ago, I wound up on a website somewhere, where they had not necked down the lead to the normal size, but brought it out full width- can't recall who it was though. It was also a very high current part for a 5mm LED...

  8. #98
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    Default Re: White LED lumen testing

    Quote Originally Posted by NewBie
    I specifically asked Nichia this about a year ago, on their various leaded parts, and they replied with 200-300 C/W, depending on the part.

    It would be interesting to remove the thermal resistance from the base of the package to the cup (grind away the clear epoxy). I know I see considerable differences between these two points when I heatsink the lead. About a month ago, I wound up on a website somewhere, where they had not necked down the lead to the normal size, but brought it out full width- can't recall who it was though. It was also a very high current part for a 5mm LED...
    Since the geometry is simple, this is a straight forward calculation. I just grabbed a random 5MM white LED off of the litter on my workbench. Measuring from where the relatively massive die cup structure necks down to the square lead crossection I get 6mm to the point 3mm outside the package. The lead crossection is 0.55mmX0.55mm. Using the 3.8W/cm-K conductivity of high purity copper would give a thermal resistance of 52C/W for this 6mm distance. This shows that the bulk of the thermal resistance from the junction to 3mm outside the package lies in the die attachment. I feel pretty confident that we can generalize that conclusion to the larger power LEDs. The high die attachment thermal resistance of the 5mm products is a function of their small area. As a reality check, lets assume that all of the Cree XR-E 8C/W thermal resistance is at the die interface. Cree uses a 1mmX1mm die. IIRC, the typical 5mm LED uses a 0.2mmX0.2mm die so it has an area of 25th that of the Cree. At best, we would expect the die interface resistance to thus be 25 times higher or 25X8C/W=200 C/W. Add this to the 52C/W for the lead as I calculated above and you have 252 C/W which is pretty near the middle of the range that was given to you by your Nichia contact.
    Last edited by Doug S; 01-19-2007 at 02:58 PM. Reason: typo

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    Default Re: White LED lumen testing

    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).

  10. #100
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    Default Re: White LED lumen testing

    I almost forgot to mention that these are P2 binned Cree XRE's that I sent over.

  11. #101
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    Default Re: White LED lumen testing

    Quote Originally Posted by Pinter
    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).
    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.

  12. #102
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    Default Re: White LED lumen testing

    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.

  13. #103
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    Default Re: White LED lumen testing

    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.


  14. #104
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    Party Re: White LED lumen testing

    Great job Jtr!!!!

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    Default Re: White LED lumen testing

    Quote Originally Posted by Erasmus
    Great job Jtr!!!!
    +1!

    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...)

    --Scott

  16. #106
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    Default Re: White LED lumen testing

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

    Paul

  17. #107
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    Default Re: White LED lumen testing

    +3 very very valuable information

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    Default Re: White LED lumen testing


  19. #109
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    Default Re: White LED lumen testing

    Awesome job!

  20. #110
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    Default Re: White LED lumen testing

    Nice, very nice...

  21. #111
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    Default Re: White LED lumen testing

    I added 2 samples (New LS Diodes THC3 4-die 5mm white, Quickar 5m100w 4-die 5mm white ) sent to me by CPF member milkyspit to the list in the first post and updated the graphs accordingly. You might need to refresh your browser to see the updated graphs. The relevant spreadsheets were added to the .zip file linked to in the first post of this thread.

  22. #112
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    Default Re: White LED lumen testing

    I added 13 samples (SuperbrightLEDs 7,500 mcd superflux white, LVEHK 10,000 mcd 3mm white, SpectrumLEDs 2,000 to 4,000 mcd 4.8mm white , SuperbrightLEDs 18,000 mcd 15° 5mm white, SuperbrightLEDs 18,000 mcd 30° 5mm white, BestHongKong 35,000 mcd 5mm white, LVEHK 55,000 mcd 5mm white, LVEHK 65,000 mcd 8mm white, LVEHK 140,000 mcd 10mm white, BestHongKong 135,000 mcd 10mm white, Nichia NFSW036L, SuperbrightLEDs RL5-W45-360 5mm white, SuperbrightLEDs RL8-W110-3608mm white) sent to me by CPF member TMorita to the list in the first post and updated the graphs accordingly. You might need to refresh your browser to see the updated graphs. The relevant spreadsheets were added to the .zip file linked to in the first post of this thread.

  23. #113
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    Default Re: White LED lumen testing

    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.
    Last edited by jtr1962; 02-17-2007 at 04:28 AM.

  24. #114

    Default Re: White LED lumen testing

    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

  25. #115
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    Default Re: White LED lumen testing

    Quote Originally Posted by TMorita
    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

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

  26. #116
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    Default Re: White LED lumen testing

    Quote Originally Posted by jtr1962
    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:




    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!


    .
    Last edited by NewBie; 02-17-2007 at 05:21 PM.

  27. #117
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    Default Re: White LED lumen testing

    Quote Originally Posted by NewBie
    It is interesting comparing the differences between the three of them.

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

  28. #118
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    Default Re: White LED lumen testing

    Quote Originally Posted by NewBie
    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!
    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.

  29. #119
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    Default Re: White LED lumen testing

    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.
    Last edited by NewBie; 02-17-2007 at 06:08 PM.

  30. #120

    Default Re: White LED lumen testing

    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-...QQcmdZViewItem

    The DC forward current is 20ma.

    Toshi

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