using a UV LED as a detector

Why don't you just use a proper sensor? They can be had for around $20:

I experimented a bit with LEDs as detectors, and found that, generally, only wavelengths shorter than they emit are detected. You might have to use a blue LED to detect long wave UV. The problems you might have include low detection efficiency, and packaging material that absorbs UV.

Check out:

and

Forrest Mims is the guru on the subject.

Al

.... and, sadly, another $33 shipping to --------+ | | | ..................................................|....................... . never trust a man who, when left alone ...... V . . in a room with a tea cosy ...... Marlow, England . . doesn't try it on (Billy Connolly) .....................................

However, John holds out some hope that a blue/UV LED will detect at shorter wavelengths. I guess I'll pick up a variety of LEDs and do a bit of playing - see what I come up with.

As I said, it's only a hobby project. If nothing comes of it at least I'll have learned something and had fun in the process

Pete

I think this short wave blue (428 nm) would be an interesting candidate:

WOW!

The EDN article is an eye opener. I knew that LEDs could be used as detectors, but had no idea that they were so selective. That opens the door to all sorts of cheap amateur colorimetry experiments.

Thanks, Al.

Tom

I ran across some related links, and discovered that Digikey sells a a couple small GaN UV detectors.