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Led question

R

RHRRC

Jan 1, 1970
0
The white 'phosphored' leds are maturing products and, from the major
manufacturers at least, now have decently predictable lifespans.

Fairly new to the market are the 5mm (T13/4) coloured (Red,Yellow etc)
'phosphored' leds and I am wondering if the teething problems of the
white leds will be repeated for these coloured devices or whether
lessons have been learnt.

Most white development is (and was) toward upward of 1W devices in the
manufacturers various proprietry packages but I wonder if there still
are pdegradation roblems with 5mm 'phosphored' led packages and/or
whether these new 'coloured' phosphors themselves have know
degradation characteristics.

The phophored yellows in particular appear to have superior efficacies
to the normal PN junction devices.
 
A

Adam Aglionby

Jan 1, 1970
0
The white 'phosphored' leds are maturing products and, from the major
manufacturers at least, now have decently predictable lifespans.

Fairly new to the market are the 5mm (T13/4) coloured (Red,Yellow etc)
'phosphored' leds and I am wondering if the teething problems of the
white leds will be repeated for these coloured devices or whether
lessons have been learnt.

Most white development is (and was) toward upward of 1W devices in the
manufacturers various proprietry packages but I wonder if there still
are pdegradation roblems with 5mm 'phosphored' led packages and/or
whether these new 'coloured'  phosphors themselves have know
degradation characteristics.

The phophored yellows in particular appear to have superior efficacies
to the normal PN junction devices.

Early , couple of years back, pink phosphor LEDs, think was organic
phosphors, had lifetimes in hours, after 24 they would have faded to a
rather pretty pastel blue.

Having had some, er, problems with `warm` white LEDs would think that
there is more than one phosphor mix that works, and probably only one
that lasts... Remember the Taiwanese electrolytic capacitor disaster.

Nichia`s orginal business is phosphors and would expect them to be one
of the better performers, depends on client expectations and budget

Adam
 
J

JohnR66

Jan 1, 1970
0
RHRRC said:
The white 'phosphored' leds are maturing products and, from the major
manufacturers at least, now have decently predictable lifespans.

Fairly new to the market are the 5mm (T13/4) coloured (Red,Yellow etc)
'phosphored' leds and I am wondering if the teething problems of the
white leds will be repeated for these coloured devices or whether
lessons have been learnt.

Most white development is (and was) toward upward of 1W devices in the
manufacturers various proprietry packages but I wonder if there still
are pdegradation roblems with 5mm 'phosphored' led packages and/or
whether these new 'coloured' phosphors themselves have know
degradation characteristics.

The phophored yellows in particular appear to have superior efficacies
to the normal PN junction devices.

There's good information over on candlepowerforums.com about LED lifespan.
The 5mm white LED diven at max current (20ma typ) are only going to last a
few thousand hours before the light degrades to 50%.
If I were going to design a device using these LEDs and desired good run
time, I'd use more LEDs and drive them in the 10-15ma range or consider a
power LED. OTOH, if I was going to use them in a flashlight where the usage
is very limited, I'd over drive them a bit because a life span of 500 hours
is good enough.

Drive current and keeping them cool seem to be the ingredients to longer
life.
John
 
A

Adam Aglionby

Jan 1, 1970
0
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Are they still problematic?  If using white LEDs, should onme stick with the
non-"warm-white"?

It is a bit like early whites where the difference between a Far
Eastern `commodity` LED and top line Nichia/Toyoda/Cree was like day
and night, now best of the Far Eastern whites are pretty comparable to
a big brand part.

Warm White is still very much a question of life testing before buying
or deploying quantity, and be aware of the miserably lower efficiency
of them, even from big names.

Adam
 
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