Can we talk about LUMILEDS emitter testing?

[yaesumofo]

I Received a rack of LUMILEDS stars today. I tested them by checking them with a meter with a diode checker. I noticed that one was much brighter than the others(they all glow a bit when tested). I suspect that the 1 out of 6 will be a real winner. We will see.
What do you guys do to examine and test your LED's for your personal stash? How do you decide which ones will be the best?
Yaesumofo

 

[IlluminatingBikr]

Okay, I gotta know.... How many LEDs come in a "rack"? /ubbthreads/images/graemlins/eek.gif Did you get to pick a bin or anything?

 

[yaesumofo]

They come 8 to a rack. I got 6 All the same bin (TV0J).
1 looks brighter than the others.
Yaesumofo

 

[Doug S]

I have found that brightness at very low currents doesn't correlate very well with brightness at design current.

 

[MR Bulk]

I would put a glob of good thermal paste (NON-epoxy, of course) on a good-sized aluminum block and test your Luxeons at actual current/voltage to be used, to determine which ones will Really be best in your intended application.

For example when making LGIs I used to test mine at near an amp (800mA) and 4.5V; as Doug says they will give false readings if tested too differently from your final intended drive levels.

 

[idleprocess]

LS low-current behavior is erratic at best from what I've heard and read.

The luminousity binning is also a wide swath.

 

[IsaacHayes]

I have powered my 5W green at low levels by unscrewing the tailcap adding resistance. It's fun to watch the current flow through the die. It looks like waves splashing on a peice of plastic. It tends to shoot across the die at different spots and costantly move. Kind of like a tiny neon red-orange gas bulb that flickers.

Anyone else notice this?

 

[evan9162]

I got 48 stars, bin Q2J, on 3 racks of 16, all the same bin, with sequential serial numbers for the racks.

The most consistent thing was Vf - about 90% within 0.05V of 3.33V.

Next was brightness. A couple really stand out, but they were pretty consistent.

Worst was color. I got a couple that were definitely 1 or lower, most 2, a handful that would qualify as 3, and a couple outliers that were 4s or 5s!

 

[3rd_shift]

L5's do that at low levels?
Cool!
I'll watch for that whenever I get any L5's. /ubbthreads/images/graemlins/wink.gif

#2Thanks for your findings evan9162. /ubbthreads/images/graemlins/thumbsup.gif
Now we know some more of the truth about the luxeon lottery. /ubbthreads/images/graemlins/tongue.gif

 

[shiftd]

L5? who talks about L5?

 

[IsaacHayes]

I assume he means Lux V.