PicDude wrote: > > You could do Doppler microwave underneath the car.... > > Curious -- is this how an optical mouse works? Neil: Optical mice sense motion optically; an LED shines almost parallel (so as to cast the longest possible shadows) onto the surface the mouse is on, a small (on the order of 1K pixels) CMOS image sensor looks at the illuminated surface, and a wee little signal processor compares the image it sees now with the image it saw a moment ago to decide in which direction the mouse is moving. -Andrew === Andrew Warren - fastfwd@ix.netcom.com -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist