I'm working on a school science project that makes a machine to weigh and fill pasta. I can build a scale using a load sensor but now i have to control an arm/ flap that will quickly close when the weight reaches a pre determined weight to stop the flow of dried pasta elbows I'm thinking have the pasta on a decline slide and once the arduino detects the preset weight, the flap quickly closes down. I'll have a button to press to allow it to flow again.
Question is, what kind of parts do i look for to open and close this flap quickly? It's going to weigh half a pound at a time most likely. Has to be fast because if it takes too long then too much time will lapse between the sensing of the right weight and closing of the flap so it will allow extra weight through