Exactly right on the use of the internal battery resistance to limit
the current. A local inventer in Bend had us build a bunch of LED light
units for him. They go in skate board lights! The units had two coin
batteres and three LEDs, as I recall. These were white LEDs and I think
they would run for a couple of hours and then the batteries had to be
replaced.

We were way too expensive for him, so he is having the units mfg.
elsewhere.

I wonder what the UV LEDs are being used for and how did the poster
know if they worked or not?

Paul,
Jodeco, Inc.
Redmond, OR