UnCursing the Darkness. - test-drb@ccmp.vtda.org

26 Dec 2001

On Dec 26, 21:39, John Allain wrote:

...
  I recently bought 2 each of all the white LED's
that Jameco
 sells.  While *white*s are OT, they are nonetheless impressive.
 The light density, efficiency, color, and longevity they have is
 pretty amazing, to me anyway.   Jameco rated them at 4 foot
 candles at 20ma, which seemed a little 'opto'mistic.
 I tried them out, and they reach near peak light at more like
 180ma, getting just noticeaby warm.  At 250ma they are
 'uncomfortably' warm, hence question:
   Did they really mean 20ma?  at that proportion they're
   putting out <10% peak, but 180ma is WAY above spec,
   Jameco's spec anyway.  So I guess Jameco's wrong?
   Could I be loosing lifespan at this current?  Maybe the
   not-too-warm test is good enough? 
I had a look in my Farnell catalogue.  Most of the white LEDs they stock
are rated between 400 and 5600 mcd (millicandelas) at between 20mA.  20mA
seems to be a standard current to quote the light output at, for most LEDs,
not just white.  However, Farnell also give lots of other data, including
the maximum rated forward current, and the highest for any of the white
LEDs is 30mA (made by Infineon and Multicomp).

I don't think you should let them get warm :-)

-- 
Pete						Peter Turnbull
						Network Manager
						University of York