Two clever students at MIT have built this impressive brute force safe cracker. Their target: a document safe with a S&G 8400 lock. The 8400 is a group 1 manipulation proof lock. Group 1 locks will resist manipulation by an expert for at least 20 hours. These guys used a stepper motor to move the dial and built a custom controller for it. The dial has butterfly knob in the center which must be rotated before and after each combination. That job is handled by a hobby servo. The torque required to open the safe is higher than the stepper motor, so when the optical encoder detects that the motor has stalled you know you’ve found the combination.
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