Universal optical/magnetic encoder disc

Parametric encoder disc for mounting on a round shaft. Original design is for an 4WD RC car and mounded on the drive shaft. By default it fits the Exceed Magnet RC truck drive shaft.

Updated to be used with either optical sensor or magnetic/hall effect sensor. Added a 2nd scad file setup for magnets mounted for radial sensing. The default design and stl file is for the Exceed Magnet drive shaft using 4mm x 2.75mm magnets.