Re: Do super-red LEDs emit 'pleasing' light?

On 23 Feb 2006 23:54:13 -0800, dagmargoodboat@xxxxxxxxx wrote:


Joerg wrote:
Hello James,

Some of the Chinese eBay-type 5mm white LEDs are very pleasing in
color, but have rapid degradation of output intensity. ...

That would not be good. Why do you think that is? Dirty process?

I understand it's real hard to grow good GaN crystals, and that this
is part of Nichia's advantage. OTOH, Cree sources many of the
clone-makers dice, and Cree is top-notch, so I don't know what the deal
is. Maybe someone's growing them in their bath tub!

Skimping on silicon real estate?

That would be skimping on GaN of course. I don't know what the
physical cause for the rapid aging is, but I've seen several reports.
Watson A. Name posted here in sed, for example, that his eBay wonders'
output faded to nothing remarkably quickly, though I can't find his
posts for anything.... By contrast, the Nichia parts (NSPW500CS, IIRC)
handle severe abuse (e.g. 60mA continuous) with aplomb.

Some white LEDs are blue with a fluorescent material in the package to
convert the blue light into an approximation of white. The
fluorescent material degrades with time.

Regards,
Allan
.

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