Mechanism is a simple geared motor connected to a balance beam. The ball serves as a switch to connect two electrical contacts that will provide voltage to turn the motor in one direction or the other. The electrical contacts were initially pieces of aluminum can, then I used 4 stainless steel rulers which conducted better as I had to sand a non-conductive coating off the aluminum strips. I used two adjustable power supplies. For just allowing the ball to roll back and forth, a single supply would be sufficient and also both switches could run the motor in the same direction. It is slightly more efficient to have the motor run in two directions based on which switch is turned on by the ball.
For future work, I need to build a servo driver which I believe will execute fast enough to make the mechanism actually balance the ball. As it stands now, the geared motor responds too slowly to allow the beam to react quickly enough to actually balance the ball. Also, the motor sometimes has to complete a cycle in the opposite direction of the desired beam movement - a servo would always turn in the correct direction and respond more quickly.