Gadget Master

According to one of its creators (on YouTube):

It attempts combinations using what we like to call "intelligent brute force". It takes a lot of factors into account such as the tolerance of the lock (basically you can forget the? odd numbers even exist) and certain impossible combinations, which cuts the possible number of combinations down by a very large number and enables us to solve the lock extremely quickly.

We intentionally designed the system such that it could be very easily modified for other locks or locks that were actually attached something. That said we were also very conscious of the legality of the system. We didn't want to design something that could be interpreted as a machine intended to be used for theft.

Effectively, they say, three main requirements must be satisfied for their system to be able to open a combination lock: the lock's dial must be turnable to the required numbers of the combination (a stepper motor is used for its precision and level of control); a component was needed to pull on the lock latch (they used a pull-in solenoid that is attached to the latch); and feedback was necessary to indicate the latch had opened (they attached a limit to the baseplate just in front of the latch connection to the solenoid).

In terms of writing the circuit. They write:

Our stepper motor required an input voltage of 12V. It was driven by a stepper motor driver which contains input pins for the step number and direction. By wiring these pins to the PIC we were able to specify the number of steps to turn for each combination number and which direction to turn (clockwise or counter-clockwise). The driver contains H-bridges to interface with the motor and translate the PIC's instructions to mechanical motion. The stepper motor driver also has several transistors that close the connection to the 12V source across the motor, which protects the PIC and H-bridge from the high voltage build-up when the motor is turned.

Once the stepping action on the dial is done and the combination is dialled the stepper motor stops turning and the PIC sends a signal to the solenoid asking to pull on the latch. The solenoid is connected to the PIC using a driver we built using a single TIP120 transistor to send a 'pull' signal to the solenoid when actuated by the PIC and a D1-1N4004 diode to prevent voltage spikes from damaging the PIC as the solenoid is turned abruptly on/off during the process.

Of the mechanics of the system, they write:

"In order to solve the combinations of our MasterLocks, we utilized a stepper motor to spin the dial and a "pull" style solenoid to pull on the lock's latch. The challenge for our mechanical design was to mount these components and the lock in such a way that allowed for the lock to be easily inserted and removed, but hold everything securely in place while the combinations were being tried. We also wanted to use only engineering materials and screw fasteners. Finally, the goal of our design was to minimize the amount of material used in the assembly without sacrificing performance."

Finally, as for the software, Python was their language of choice for controlling the PIC-PC and PC-User interaction:

"PIC-PC interaction is possible via the use of a USB cable. Data is sent and received across the USB line from the PC to the PIC and back. The PC sends the PIC every new combination to try on the lock. The PIC controls output to the stepper motor's direction, the stepper motor's number of steps, and the solenoid. It also takes input from the limit switch. The status of the switch is sent via the USB back to the PC every time a combination is tested. The procedure to enter a combination of 3 numbers is sent from the PC's Python code to the PIC (when to go clockwise, counterclockwise, and converting from lock numbers to step numbers)."

"When the lock is finally opened and the limit switch's input is sent as 'high' to the Python Code, it displays a GUI on the PC with the discovered MasterLock combination."

A very impressive, well-documented piece of work

[Via Wired]