What it does
It tracks a person's mouth using facial recognition software and then launches gobstoppers into his or her mouth.
How I built it
The mechanical design incorporates a pan/tilt mechanism to aim the launcher. The launcher itself consists of two counter-rotating wheels, a magazine tube, a barrel, and a push rod to activate a shot.
The pan and tilt mechanism operates using one stepper motor per axis. Each stepper motor drives a timing belt which has ends fixed to a cylinder on the underside of each rotating axis. With 2026 total steps per revolution of each machine axis, this provides an accurate means of positioning the launcher. Concerns include over-travel as the pulley system is not a continuous loop. A potential fix is to keep track of absolute machine coordinates and relative machine coordinates, but has not been implemented due to time constraints.
The launcher mechanism went through an iterative design phase. The original goal being to launch Skittles, we pursued two parallel development paths: the first being the launcher currently used, and the second being a system based on a rotating disk attached to a fan motor taken from a microwave.
The second option had many drawbacks, one of them including the issue of shattering Skittles on contact instead of launching them. It also had no way to vary the angular velocity of the disk, which would severely limit tuning and distance compensation. This option was abandoned early on in favor of the counter-rotating wheel mechanism.
The final launcher presented consists of two counter-rotating brushless DC motors. Adhesive foam on the outside of the motors allows the system to grip the candy being fed into it and also takes up some of the variability in the size and shake of the candy. Candy is fed into a vertical magazine tube which deposits a single candy into the chamber. A servo acts as a push rod to manipulate the candy into the wheels while blocking the magazine. When the push rod retracts, another candy drops into the chamber. The wheels accelerate the candy and the candy gets funneled into the barrel. The barrel helps to minimize angular variability in launches. The speed of the motors is variable and allows for close-range launching or distances in excess of 20 feet.
Challenges I ran into
Accomplishments that I'm proud of
The cannon frame, launching mechanism, and, rotation mechanisms were made entirely by hand here.
What I learned
What's next for Skyttle
We are going to launch skittles and try to keep the cannon's aim and power as consistent as possible.