Good paper on the issues involved in using linear accelerometers as tilt sensors. Having your feet / legs / wheels on the ground at the time rather helps. http://www.freescale.com/files/sensors/doc/app_note/AN3461.pdf Russell McMahon -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist