There are two major types of lottery machine – ‘gravity pick’ and ‘air mix’. A gravity pick machine has a chamber with rotating paddles inside, spinning in opposite directions. Numbered balls are dropped into the chamber and mixed until a sliding door opens, allowing the desired number of balls to pass through, one at a time. Air mix machines, on the other hand, have a fan in the bottom that blows the balls around. A valve to a tube opens, and the balls that are blown into the tube are the winning numbers. The balls are evenly weighted and are usually locked away in vaults when not in use, in order to prevent tampering.
Answered by Rik Sargent