White LED Color Fade?

franken2

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my seldom used brinkmanns are still bluish-white. i hope the 1500-6000 hr half life figure isn't true. if it is, i'm glad i have lots of led lights around!
 

RonM

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I've got two Brinkmans and both have a tint of the purple/blue. Not enough to be a problem though.
 

Slick

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I have a few of the Brinkman "Longlife" 2AA LED lights. They've become somewhat of my favorite "around the house" flashlights and I keep one handy in just about every room.

The other day I used one of my Brinkman's (that seldom gets used) and noticed that the LED color was a Blueish-purple. My most often used Brinkman's LED is more of a yellowish tint and less bright. I was thinking that the batteries were weak, so I tested them by switching them between the 2 flashlights.

What surprised me was that there was NO change.. Even with the fresher batteries, the more often used light was still the same dimmer yellowish color.
frown.gif


So now I'm wondering if it's normal for these LED lights to lose their color and intensity after a period of use? I have two of these lights that I used pretty heavily and both of them have faded like this. Is this just someting I should expect to happen with all of my LED lights over time? Will the Luxeons fade too?

I might add that all of my seldom used Brinkman's are still the same blueish-purple hue that they were when new, so I know that it's not just a problem with one particular light.
 

Roy

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Just a little off the subject..try some WriteRight on your Brinkmann's...really smooths out the pattern. I also noticed that with the WriteRight the little blobs of yellow in the center of the beam have disappeared and the overall color seems bluer. Some of the rings are gone also!
 

LED-FX

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LED worlds best kept secret, lumen depreciation of white LEDs,they get dimmer over time.

Phosphors age and uv from blue led die yellows epoxy encapsulant.

Read estimates varying between 1500 and 6000 hours half life, point at which lamp brightness is half that of new.

At mo` treat lamp life with a pinch of salt

Adam
 

Slick

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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by LED-FX:
LED worlds best kept secret, lumen depreciation of white LEDs,they get dimmer over time.

Phosphors age and uv from blue led die yellows epoxy encapsulant.

Read estimates varying between 1500 and 6000 hours half life, point at which lamp brightness is half that of new.

At mo` treat lamp life with a pinch of salt

Adam
<HR></BLOCKQUOTE>

That's kind of a bummer.. I guess there's always some "catch" to everything that seems like THE answer.

The really bad part is that these lights have "color shifted" in less than 20 hours use each.

I did a search on "writewrite" (here on CPF only), and could only find enough info to think that this is a "transparency film" that would be best for light diffusion?

Anyway, I doubt there's anything that can be done about the color shift. I'm just disappointed that it seems to have occurred so fast.
 

Wits' End

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Well let's hope that Brinkmann got a bad batch with a bad phosphor coating. My family has had some of our LED lights (not Brinkmann) for a couple years, I'd guess at minimum 120 hours on them (10 min a day for 2 years). I haven't noticed any light problem except when the batteries need to be changed. Only a few times for battery changes BTW
smile.gif
 

LED-FX

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Think I should clarify my previous post a bit.

Phosphor degradation *appears* to be one mechanism in the light droop of white LEDs, bearing in mind that phosphors are used in fluorescent lamps and TV screens as well, with a much longer life span than 6000 Hours.

Nichia`s main business is in fact phosphor production....

The other factor is `yellowing` of the plastic used to form the led case, think of plastics that yellow over time in the sun.It is the very close proximity of the plastic to the blue LED die that means UV energy desity could be fairly high accelerating the `yellowing`.

Development of more stable plastics should alleviate this problem.

Interestingly Luxeon Star has the phosphor held in a gel beside the die, this could be part of the answer.

Part of the difficulty in estimating life span is, it quite literally takes time, several thousand hours to find out what actually happens.LEDs being semiconductor devices have no real parts to fail, no filament to degrade etc.Hence the 100,000 life often quoted.

As someone looking to market LED products commercially think it is better to be realistic and honest about LEDs shortcomings as well as there advantages.

There is an awful lot of hype about, which could backfire and leave users with a bad impression of LEDs in general.

For a more detailed look at some of the issues have a look at:
http://www.lrc.rpi.edu/library/NN_ies1.pdf

From the Lighting Research Center
http://www.lrc.rpi.edu

Theres a lot of useful info there, not all of it requires a degree in physics to understand :)

Adam
 

L.E.D.

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keep in mind that the brinkmanns DO overdrive the LED's, look on brock's page for the current measurements.
 

signals

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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Slick:
I did a search on "writewrite" (here on CPF only), and could only find enough info to think that this is a "transparency film" that would be best for light diffusion?<HR></BLOCKQUOTE>

WriteRIGHT is a clear plastic film that is marketed as a screen protector for PDAs. Here's a review:

Writeright review at TheLIGHTSite

The stuff is expensive, and for protecting a PDA, I've found a piece of transparency film works just as well, but as a beam diffuser it works pretty good...

-Kevin
 
D

**DONOTDELETE**

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This is all pretty interesting stuff. Just tonight I gave my friend an Arc LE. I compared it to mine (I've had for half a year) and his blew mine out of the water. I knew there was a difference in LED intensity but this really annoyed me. Mine was so inferior to the other. Is this because of this white LED degredation? I thought my Arc LE was bright but gee- this new one is blinding!
 

Slick

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I suppose this color and light output degradation appears to be one of the (somewhat normal?) shortcomings of white LED's, particularly one's that are overdriven.

What really made me stand up and notice this was the fact that I bought two identical Brinkman "Long-Life" lights at the same time. I compared them when new and they seemed identical then. Then after the one being used more than the other, there was such a noticable difference..

Now I'm wondering how much difference in degradation there would be between a white and say a cyan? I'd have to believe that DOT or some other Highway commision performed some serious testing on this prior to using them in traffic signals. In my area some of the the "walk" signals for "go" are comprised of white LED's.

Anyways, it's good to hear that Lumileds is focusing on preventing this degradation in their products.
 
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