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The shell game is a contest in which a person hides a small object (usually a pea) underneath one of three cups and then rapidly shuffles them about on a flat surface. The spectators must pay close attention during the shuffling process in order to try and guess the final location of the hidden object. It is typically a sleight-of-hand swindling game. The shell game dates back to ancient Greece and was originally called “thimble-rig” because it was played using sewing thimbles.


In this project, your challenge is to design and build a robot that can play the shell game with you. The robot will act as the spectator, and you will hide a magnet under one of three cups. The three cups will be lined up in a row with a few inches between each cup. The robot will use a Vernier Magnetic Field Sensor to determine the location of the hidden magnet—the highest sensor reading will correspond to the location of the hidden magnet. The robot should evaluate each cup, make its determination, and give some type of feedback to the operator to let them know which cup it has chosen.

Sensors and Equipment

This experiment features the following sensors and equipment. Additional equipment may be required.

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This experiment is #13 of Vernier Engineering Projects with LEGO® MINDSTORMS® Education EV3. The experiment in the book includes student instructions as well as instructor information for set up, helpful hints, and sample graphs and data.

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