This is my implementation of a white board string-plotter. The mechanical parts are designed to use inexpensive 28BYJ-48 5V stepper motors (search for them on Amazon - they sell for ~$6, including driver). More details under 'Instructions'. UPDATE: I added links to the sources of some of the software I wrote for this project under 'Instructions'.All parts are modules inside the provided .scad file - the code is not exactly pretty, but should be usable. The pen guide on the carriage in the original design was to short, so I printed an extension (just cylindrical pipes, really) and super-glued them to the existing carriage (they don't have to take any real mechanical load). The guide is sized to hold an 'Expo' brand dry erase marker. There is a small 9g servo on the bottom of the carriage that allows the pen to be retracted, so that the plotter can move without drawing a line. After experimenting with various types of fishing line I settled on using dental floss as string and two pieces of knitting yarn to hold the carriage such that it can easily roatate. For electronics I am using a Teensy 3.0 microcontroller board (ARM-based, but mostly Arduino compatible - a regular Arduino would work just fine, too) and a HC-05 (check Amazon) bluetooth module as a serial pipe (yes, the plotter is wireless). On the software side, I have implemnted two solutions: