[Enrico] tackled this problem using 6 Ni-MH batteries and an LM2956 simple ... by an Arduino pin via an NPN transistor. He also incorporated a potentiometer to adjust the servo calibration ...

oomlout has posted some interesting plans for a simple robot. It’s based around an Arduino and is a platform similar to the Parallax Boe-Bot. The Arduino sends PWM signals to continuos rotation ...

and is controlled using the included Arduino’s Servo Library. The code is simple too and I’ll try to explain it after this video where I made a short presentation of the project in action.