burn-in data from UX1L after 24 hours ...

wquiles

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I am building a Direct Drive LE for an Aleph, using an UX1L 3W LED and using a single LiIon rechargeable cell. In order to know if I need to put a small resistor in series or not, I decided to do a full 24-hr burn in of the LED at 1000mA.

From the many LED's that I have tested, I decided to use LED # 3-14 (see full table here) , which had a fairly high vf during my initial testing at 3.90 @ 750mA.

Since my setup now has a massive fan cooled CPU heatsink designed to run CPE's in the 60-80 watt range, it does not even get warm with a punny 3W or 5W LED on it :D

Here is the basic setup:
IMG_6549.JPG


IMG_6550.JPG



here is the fan on the bottom of my light box cooling the copper heat sink:
IMG_6556.JPG



I need a fan on top of the DB since it is running too hot:
IMG_6551.JPG


IMG_6552.JPG



Here is the initial vf and LBU (intensity) for LED 3-14:
IMG_6553.JPG


IMG_6555.JPG



Here is how the LED looks like while being tested, with the port open for the "warm" air to exit. When I want to take an LBU reading, I of course plug the hole ;)
IMG_6557.JPG


IMG_6558.JPG



So here are the results:
- Time Zero:
vf = 4.09V
LBU = 425

- 9 hours and 46 minutes:
vf = 3.78V
LBU = 440

- 23 hours and 18 minutes:
vf = 3.75V
LBU = 443

- 26 hours and 19 minutes:
vf = 3.74V
LBU = 445

I took a contact-less temperature probe (the ones with the red laser) and measured 86F on the surface of the copper HS - room temp was about 79-80F. The highest reading I was able to take trying to aim the laser at the LED while it was still running was 92F.

Interesting data, isn't? :naughty:

Now that the LED should be "stable", I will test it with the actual LiIon cell and decide if I need a small resistor at all ;)

Will
 
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evan9162

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a 5% increase in brightness and a 9% decrease in power usage - not bad for simply burning it in, eh?
 

wquiles

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Yes, not a bad tradeoff. You just need a way to do it safely. Of course, my way is a serious overkill, but it works ;)

In fact, I am burning these mainly based on "your" prior feedback and recommendations as I have read here in the forums :bow:

Will
 

revolvergeek

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Very interesting. I had observed that a couple of my LUXIII lights seemed to have gotten a little brighter with use, and it is nice to have a more formal observation of this.
 

wquiles

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Cool - thanks ;)

In this review that I posted for Leef, he did a runtime plot of that LED actually mounted in a DD light. Note on the log plot (our eyes see logaritmically) how reasonably flat the output is :D

Will
 

wasBlinded

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The burn-in will go faster if you let the LED heat up. There is no need to aggressively heat sink it like wquiles did, though you certainly want to keep the LED temperature within published operating parameters to be safe.
 
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