tattoo machine wiring

Might get burned. But i was wondering if any one had a good wiring diagram for a tattoo machine. Im Working on building my own I have The coils and hard ware and frame. Im doing this just for a learning experience.Posibly might use it to practice on my self. Iv looked all over the web. I got a pretty good idea of the set up. I keep seeiing what looks like a wire conected at the spring screw? Ill figure it out threw trial and error i know. Just wondering if any one was willing to share. Hell i should just go buy one i guess:)) But im real stuck on learning to make and set up one from scratch.

My email is d1g1tal_s0ul:@yahoo.com Thanks