For this project, I used a servo motor to control a Nerf gun. I built it and installed it in my HCI lab room. The idea was to have the gun automatically fire at unsuspecting visitors to the room. I left it armed last night and look forward to the results! Here’s a simulation of what will happen to the first person entering my lab room tomorrow morning:
To arm it, one manually cocks the gun, loads a dart and resets the program by pushing the button on the Arduino board. The program then allows 10 seconds for the door to be open before it arms the system. When the system is armed, the servo activates and shoots the gun as soon as the door is opened.
As you can see, I generously used rubber bands and binder clips in this project. I used them to fasten the servo motor to the Nerf gun. I also used them to harness a telephone cable by wrapping a rubber band around the RJ11 connector, carefully inserting jumpers, and applying additional pressure (to ensure contact) with binder clips. This hacked telephone cable stretched from the gun to the door sensor.
Initially I used external power and a transistor to control the gun, but then realized that the Servo I borrowed from Roboclub can in fact be powered by the Arduino directly. The circuit here is dead simple, so I will not include it.
Arduino Sketch: shooter