Homebrew PCBs

> of uv either. UV leds have come a long way in the past couple years. Also,
the
> MCD rating is pretty much useless on most ebay leds. My experience has
that
> they exaggerate the rating...
>  When possible ask for and get the manufacturers datasheet.


Dunno about UV, but the mcd (milli-candela) number even when not exaggerated
is a bit of a lie.  A 'candle' rating is how much light a candle (wax,
flames and all that) puts out in your direction (lumens is total light).

So two LEDs may have the same chip (same power), but the one with the
smaller view angle (more focussed) will have a higher mcd as it appears to
be brighter.  Check the view angle on high mcd LEDs!  It's like measuring
sunlight intensity by using a magnifying glass.

Candle power is also based on how your eye perceives it, so unless you've
had the lens removed (cataracts etc) it's a bit useless for UV.  Can't see
it = 0 candle power.  Same for infra-red.

Tony