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.
To allow him to send the launch command from a smartphone, he installed the WebIOPi framework on the Pi. A custom web page hosted on the Pi contains a nice, big, orange
LAUNCH button; pressing it runs a Python script which, in turn, controls the GPIO. A portable router provided the wifi hotspot necessary to view the web page on the phone.
Lewis also talks about his fantastic project in this Adafruit Show and Tell (starting at 7m55s), and shows how the system can be tested without actually launching anything—important if, like Lewis, you are working indoors.
We know that every day, Raspberry Pis lie idle when they could be launching rockets, and this makes us feel sad. Read the article Lewis wrote for Make: including links to his code and the parts that he used, and try it for yourself!