David Carratu
Paul Gelhaus

Geoff the Magician

Our robot Geoff the Magician performs a disappearing ball magic trick. You place the metal ball in front of the robot and Geoff will make the ball disappear with its magic cup. Geoff lowers its arm, spins the cup for five seconds, and raises it, and the ball magically disappears. Then Geoff lowers its arm again, spins the cup for five seconds, and makes the ball reappear.

The secret to our trick is that there is a magnet on the inside of the cup that is able to lift up the metal ball and conceal it in the cup that it raises, giving the appearance that it made the ball disappear. To make the ball reappear Geoff lowers its arm quickly and then raises it back up quickly, jerking the cup. This jerk disconnects the ball from the magnet. Therefore, when Geoff lifts the arm back up again the ball is left behind. It “reappears” in the same spot that it “disappeared from”. This gives the illusion that the ball magically reappears.

We first started by attaching the magnet to the top of the cup at just the right height so that it would not be seen by an audience, but it would still be able to have enough attractive force to lift up the ball. We poked a rod through the bottom of the cup, attached a gear to the rod and then taped the magnet to this gear. After testing out the magnets ability to pick up the ball and adjusting its height several times we attached the rod to the medium motor which spins the rod and the cup creating a more magical effect. Then we created an arm that attaches to a large motor that moves the cup up and down in a perfect vertical motion. Next, we were faced with the task of attaching this arm onto a rotating base since we wanted the arm to be able to swing in a horizontal motion. We spent time designing and building and redesigning and rebuilding a structurally strong base that could withstand the torque the arm put on it. We then mounted this whole base on another large motor so it could swing to the left and to the right.

We used LabVIEW to program the code for Geoff’s magic trick. We implemented a linear sequence that uses motor commands, sound, and wait for’s to move from one task the of the trick to the next. The biggest difficulty with programming was creating a code that lifted up the cup slowly enough so that the ball remained connected to the magnet (since we used a weak refrigerator magnet) and then creating a jerk at the end that looked like a natural motion of putting down the cup, but also was strong enough to disconnect the ball from the magnet. We had to play around a lot with the timing and powers of the motors.