On Thu, Nov 20, 2008 at 11:01 PM, Michael Rigby-Jones wrote: > FWIW I have used a red LED as a photodiode before, it did work but > wasn't very sensitive. That is strange. You might use a better photodiode. I would say that a Photodiode should be much more sensitive than a LED as the detector. Xiaofan -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist