Egg plotter

The egg plotter i made for my kids for Easter. they love to paint on eggs but that is quite difficult. it is much easier if there is a picture or text on the egg that they just fill in with colors. The plotter made from parts of an old printer and 2 diskette drives. the pen is loaded with a spring and a potentiometer senses the position of the pen and moves the pen forward or backwards so that the pressure from the pen on the egg is constant. i used an avr 8535 cpu that has a built in a/d converter.