When faced with having 2 cats with different dietary needs, [Landmanr] had to decide between manually stopping the cat on a diet from eating normal food, or building a dietary robot overlord. [Landmanr] chose the robot route. Using an old cd rom for the opening/closing mechanism, and RFID to distinguish between felines, [Landmanr] no longer has to stand guard while each cat eats. We particularly like the design of the antenna, so that the cat has to stick its head through it to activate the food opening. You don’t see that version in the video, but it is in the instructable.