Build your own sensors!

This wonderful site has instructions for many kinds of home made sensors.

Check here for all the sensors.

Smokey has constructed multiple sensors using this website as a guide, including a button sensor (conductive fabric and neopreme), a pressure sensor (using velostat and conductive thread), a tilt sensor (conductive fabric, thread, and a ‘bead’ made out of a nut). He has also constructed a linear encoder using 2 limit switches and an encoding pattern cut into cardboard.