Quin Etnyre walks to the front of a crowded room at Deezmaker 3D Printers and Hackerspace in Pasadena, California. He adjusts his laptop on the workbench, then looks up and addresses the class. “Thanks for coming out on a Saturday,” he says, his voice barely audible over the steady hum of servomotors. The students, 18 middle-aged men and preteen boys, look on as Quin straightens his MIT T-shirt and swipes an index finger across an iPod. The screen behind him flashes “Intro to Arduino Class.”

He explains to the group, which includes a toy maker, an engineer, and a high-school electronics teacher, that he’ll be showing them how to program an Arduino—a $30 microcontroller board that can convert sensory inputs into outputs, making objects interactive.