as an interesting aside, led's operate as photodiodes as well, if you reverse bias them the current that flows is proportional to the light falling on it if i rember rightly from a dim and distant lecture. Trouble is it's so small you would probaly not save any parts by using this effect. Regards Alex Rice -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu