You need slip rings. You'd have isolated rings that carry the power on one side and spring loaded brushes which contact the rings on the other side, it's pretty simply in theory but construction can be a little complex because the rings have to be isolated. It could be done relativly easily if the main rotation shaft was non conducting, you'd just use brass bushings with wire contact in the inner diameter and form a spring loaded contact for the moving side. Hopefully what I'm describing will make sense, it's very simple. You'll need an absolute bare minimum of two connections, +vcc -vcc you'll need some way to talk to the computer onboard as well which you could do by adding another slip ring, although you'll have noise from the brushes to contend with.