Strange observation with 5W

[shiftd]

I was just running my 5W from a BB750. After a few minutes runtime, i turned off the light and looking over the lux. Well, it seemed that the phospor layer of the lux was removed and stand in the middle of the dome. There was like a paper submerged inside a liquid. a few minutes later, after the light had cooled down, the phospor layer came down and get back to the die of the lux, though not as perfect as before. And the beam produced is not as nice anymore. Sure, it is still white, but with optics, 2 of the square die got bluish white while the other 2 got a nice white. The center hotspot is still nicely white (hey, it is U3U anyway).
So, does anyone ever notice this strange phenomenon, or is this just the sign that my lux will die prematurely? /ubbthreads/images/graemlins/frown.gif

 

[Burnt_Retinas]

Spooky, your LED is alive!

I can't imagine this is normal. The LED and phosphor are in a gell. For it to rise with heat one would expect there are 2 different materials each side of the phosphor with different thermal exapansion coefficients. Perhaps you have some air trapped under the phosphor that is expanding and causing the phosphor to rise then lower again upon cooling? In any case, it's seems a suss LED given the colour has changed between power-ups.

Chris

 

[shiftd]

I dunno Burnt. I cannot observe any air trapped inside the dome. It is simply that the phospor layer got removed from the die during the thermal expansion and it got back to the die again during the cooling process, but the re-layering is not perfect, leaving some of the die with more and some with less phospor layer. That is why the beam is strange.

 

[hotbeam]

Sounds like a dodgy 5watter shiftd /ubbthreads/images/graemlins/frown.gif /ubbthreads/images/graemlins/icon8.gif

 

[paulr]

Sounds like it overheated. Those things need a lot of heat sinking.

 

[shiftd]

ahh, yea Paulr.
I think i give it adequate heatsinking, but that just does not seem enough.
oh well, there goes my U3U. /ubbthreads/images/graemlins/frown.gif

 

[MR Bulk]

shiftd,

You should send this one to Craig Johnson. With the LED's phosphor moving around like that and changing colors and beam shape and stuff, it certainly belongs in the -- LED Museum!

 

[shiftd]

Great idea, Mr B. But i just can not part with my precious /ubbthreads/images/graemlins/frown.gif