Teenage electronics enthusiast Lewis Callaway thought that an ad in which actors launch rockets from their iPhones was really cool, but he couldn’t find out how it was done, so he decided to start from scratch himself, using (of course) a Raspberry Pi. Model rockets are launched by passing an electric current through an igniter, a device that includes a thin piece of wire in contact with the rocket’s propellant; the current causes the wire to heat up, igniting the propellant. Lewis used a relay board and jumper leads to complete the circuit between a 9V battery and the model rocket’s igniter, and connected power and signal wires between the relay board and his Raspberry Pi’s GPIO pins so he could flip the switch on the 9V circuit with a signal from the GPIO

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Smartphone rocket launcher