Big names on YouTube like LockPickingLawyer show us that a skilled individual can pick just about any lock that accepts a key. As it turns out, combination padlocks are also very easy to decode and it is even possible to automate that process so that a robot can do the job. Doing so only requires a few affordable parts and a simple algorithm. Mew463 explains how a Master Lock-cracking robot works and how to build your own.

This cracking process works thanks to the mechanics of combination padlocks. While the combination lock on something like a bank vault is very sophisticated, these padlocks have limited space for their mechanisms. They also tend to be cheap. For those reasons, one can feel the mechanisms engaging when stress is on the shackle.

To find the first number, you just pull on the shackle and turn the dial. It will catch just before the correct number. The third number is more complicated, but it is possible to infer by following the proper steps. The second number isn’t identifiable with tricks, but it is easy to try all of the possibilities once you know the other two numbers.This robot follows those steps for you, opening typical combination padlocks in under a minute. The 3D-printed frame holds both a stepper motor and servo motor. The stepper motor rotates the dial and has a magnetic encoder to give precise feedback on the dial position. The servo motor pulls up on the shackle and has an added analog line for feedback. An Arduino Nano board controls the two motors according to the algorithm. A user can navigate a menu and start the cracking process with a rotary encoder knob. The menu appears on an OLED screen, which also shows the lock’s combination after cracking.