[Frank Herrmann] had an interesting idea to turn a geared DC motor into a servo motor assembly ... up to the motion controller upstream. The Arduino source for this can be found on the project ...

To do this in Arduino/C code, a new intermediate position for the servo is specified for each main loop until it reaches the final position. The intermediate value is the sum of 95% of the current ...

If you have an interest in electronics and have been hanging around DIY tech forums for a while now, chances are you already know what an Arduino ... servo motor to twist toward that light source.