On Wed, Mar 19, 2008 at 9:22 PM, Xiaofan Chen wrote: > On 3/19/08, David VanHorn wrote: > > Just for laughs, you could increase the LED current when you detect > > "white" and decrease it when you detect "black". > > Actually this works as kind of hysteresis. I believe similar methods > are used in photoelectric proximity switches. That is exactly the point. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist