Sandraw is a unique machine that never fails to delight audiences whenever we present it.  It is a microprocessor controlled machine that draws pre-programmed images by use of a magnet that pulls a ball bearing through a thin layer of sand.  It was inspired by Bruce Shapiro, the originator of the concept, and you can view his machines at http://www.taomc.com/.  The magnet that pulls the bearing is attached to a rubber belt that is mounted to a piece of extruded aluminum.  At one end of the belt is a pulley, and at the other end, is a stepper motor controlled by a Propeller microprocessor https://www.parallax.com/.  Originally, long time member Paul Atkinson programmed the original Basic Stamp microprocessor, but it was later replaced by the more powerful Propeller microprocessor which was programmed by another long time member Gray Mack.