Is the Luxeon Lottery Rigged?

[zapper]

Anybody else notice no one has received any xWAx or xWOx BIN Luxeons unless they were P or S BIN? Looks like it is rigged and most of us get just the dregs! I guess that's why you can buy them for $6.40. The bad ones you can either sell off for next to nothing or throw away and the good ones for at least twice the price to make up the difference!

 

[gadget_lover]

It must be rigged somehow.... I just put a tv1j (star) LuxIII on a pair of AA lithiums and only read 143ma. Puzzled, it should have been close to 300ma, as the lithiums provide 3.4 vollts when fresh and in series. I put it on a bench supply and found that it did not pull the requisite 350ma till it reached 3.61 volts. That's clearly a Vf in the K bin, not J.

I'm not placing blame anywhere, but if they don't get the Vf right, how close to the LUMEN output are they? Especially knowing that almost no-one can (afford to) check the lumens to confirm their claims. A more paranoid and cynical person might notice that they could probably inflate their claims with impunity.

BTW, Zapper, I've had some TWAK Lux III before. I can't confirm that they lived up to their spec, but that's what it said on wrapper. /ubbthreads/images/graemlins/smile.gif

Daniel

 

[rdshores]

At what temp did you make your measurements?

 

[NewBie]

[ QUOTE ]
gadget_lover said:
It must be rigged somehow.... I just put a tv1j (star) LuxIII on a pair of AA lithiums and only read 143ma. Puzzled, it should have been close to 300ma, as the lithiums provide 3.4 vollts when fresh and in series. I put it on a bench supply and found that it did not pull the requisite 350ma till it reached 3.61 volts. That's clearly a Vf in the K bin, not J.

I'm not placing blame anywhere, but if they don't get the Vf right, how close to the LUMEN output are they? Especially knowing that almost no-one can (afford to) check the lumens to confirm their claims. A more paranoid and cynical person might notice that they could probably inflate their claims with impunity.

BTW, Zapper, I've had some TWAK Lux III before. I can't confirm that they lived up to their spec, but that's what it said on wrapper. /ubbthreads/images/graemlins/smile.gif

Daniel

[/ QUOTE ]

J bin 3.27V 3.51V
K bin 3.51V 3.75V

Also note that you must keep the junction temperature at 25 degrees C while doing the measurement for current. And we are not talking about the slug temperature. So, if you are using the star like you said, it has about a 20 C/W rating, and you are putting in about 1W, so you'll need to hold the star at 5 degrees C. Either that, or pull out the test equipment, and get an instantaneous measurement when you first apply the power.

Bins:
http://www.lumileds.com/pdfs/protected/AB21.PDF

 

[Doug S]

[ QUOTE ]
gadget_lover said:
It must be rigged somehow.... I just put a tv1j (star) LuxIII on a pair of AA lithiums and only read 143ma. Puzzled, it should have been close to 300ma, as the lithiums provide 3.4 vollts when fresh and in series. I put it on a bench supply and found that it did not pull the requisite 350ma till it reached 3.61 volts. That's clearly a Vf in the K bin, not J.

I'm not placing blame anywhere, but if they don't get the Vf right, how close to the LUMEN output are they? Especially knowing that almost no-one can (afford to) check the lumens to confirm their claims. A more paranoid and cynical person might notice that they could probably inflate their claims with impunity.

Daniel

[/ QUOTE ]

I put it on a bench supply and found that it did not pull the requisite 350ma till it reached 3.61 volts. That's clearly a Vf in the K bin, not J.

Not clear to me at all. Your measurements are more consistant with an "L" bin Lux III. Remember that the Lux III binning is done at 700mA. Using your 350mA measurement of 3.61V and adjusting upwards using the datasheet value of 0.8 ohm for the incremental resistance would yield a value of 3.89V. Assuming that you took your measurement fairly quickly, this would need to be adjusted upwards by about .04V to 3.93V to match datasheet binning conditions [to account for emitter heating. Datasheet Vf tempco is -2mV/C though I believe the actual is a bit higher]. This places it squarely in the "L" Vf bin.

Now, let me feed your paranoia [you may need to adjust you meds /ubbthreads/images/graemlins/wink.gif ] Per the Luxeon document that describes their optical testing, AB08, the flux measurement is to +/-10%. This means that *theoretically* you could have an "S" bin that is 22% higher in flux than a "T" bin and still have full compliance with their measurement specification.
BTW, the tolerance on the binning Vf measurement is +/-0.06V so it is clear that your "J" bin was mis-binned.

 

[gadget_lover]

Thanks Doug. I'd forgotten that Lux III Vf was measured at 700ma. Your math is impeccable.

Yes, I started at room temperature (74f) and read the value within 1 second of hooking it up. I let it cool for 10 minutes before trying a second time.

Dang. I was going to try a direct drive in a small light for an in-law. This clearly won't do.

Thanks for the feedback/info.

Daniel