Re: UPDATE LED Life Test at 2 Months

From: Warren (hiview_at_bresnan.net)
Date: 07/07/04 

Date: 7 Jul 2004 07:22:33 -0700

Kevin McMurtrie <mcmurtri@dslextreme.com> wrote in message news:<mcmurtri-9B28DE.23370306072004@corp-radius.supernews.com>...
> In article <10ejul0jvd4ok4c@corp.supernews.com>,
> "Watson A.Name - \"Watt Sun, the Dark Remover\""
> <NOSPAM@dslextreme.com> wrote:
>
    My 2 cents worth>> Have had a "Hong Kong" white LED on for 70
days. Runs off of 2 pen cells (3.12 volts when fresh) no series
resistor and draws 26.4 mils. After 70 days battery voltage down to
2.628 volts. Drawing 7.92 mils. LED is dimmer with this current draw.
Going to let it go util led won't light. Gave a quick check with fresh
batterys and led still very bright. Warren

  
> > I I've had the 4 LEDs operating at 25 mA for all of May and June, and
> > the first few days of July. This is about 1500 hours so far. The LEDs
> > are two Nichia NSPW500BS white LEDs, and two white LEDs from Hong Kong
> > that I got off Ebay. All four are in series so there is no doubt that
> > they are all running at exactly the same current.
> >
> > The two Nichias are going strong, with no noticeable signs of dimming.
> > The two Hong Kong LEDs, sad to say, are so dim that they wouldn't make
> > good panel lights, so can't even consider them suitable for
> > illumination. They're really quite dim.
> >
> > Of the hundred Hong Kong LEDs I bought, all I've used have had this
> > dimming problem after a few hundredds of hours, so I decided to put the
> > four on a PS to control the conditions and verify that I'm not imagining
> > things. I think one problem might be that the Hong Kong LEDs use an
> > organic phosphor that degrades faster than Nichia's, and might
> > contaminate the LED chip. But I'm not an expert on this at all, so I'm
> > open to any other ideas.
> >
> > I posted an update of the progress of the dimming at the beginning of
> > last month, and now this one shows that the hong kong LEDs are so dim
> > that it's probably not worth continuing the test. I may solder two more
> > unused hong kong LEDs into the circuit, and start the test again, just
> > for the halibut.
> >
>
> I've had problems with several white LEDs from Fry's Electronics failing
> too. They dimmed after a few months of use then they started blinking.
> It sucks because some are inside a night hiking flashlight to keep it
> glowing while switched off. It's hand crafted inside a tough acrylic
> tube like a ship in a bottle. The LEDs can't be removed. I didn't
> think I'd need to make LEDs replacable.
>
> I'm going back to green LEDs for the next flashlight.

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