Owamanga wrote:

Kidding aside, I have a BSc in Digital Electronics and was wondering
how the LEDs are used as sensors - you seem to imply that a red LED
can detect red light - is this primarily because it has a red filter,
(ie a clear-case red LED can't do this?), and what's so special about
the white LEDs in this respect?

Way back when ('87 I think..) I remember noticing in the lab that
red low-power laser light will generate voltage across a bog-standard
red LED. I always think there ought to be nice applications of
this..given the low price of standard red leds and (now) laser pointers,
you could make a cheap detector panel like you say..

--
Ken Tough