For an interesting challenge and also to find out combinations for rotary locks, reddit user "gurtdotcom" created a fascinating Arduino-based device that holds a combination lock, rotates the dial and after a ... process of elimination can tell you what the combination is via an LCD. The device uses a stepper motor mounted over the lock to rotate the dial, and a solenoid to test if the combination has been successful. The following video shows the final moment of success:
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