The answer to your question can be affected by a lot of things:
- Which of the many different possible bridge tipping mechanisms are you using?
- Is it controlled by a Spike, or a speed controller? If the latter, Victor or Jaguar?
- Are you using the IterativeRobot template, or a Command-based one?
- Do you want it to respond to user input? If so, should it be button-controlled or joystick controlled? Do you want a button to toggle it?
- Are there any limit switches involved?
I don't want to give you bad advice, so a little more clarity would be helpful.