[Images and videos missing, will update later]

Dial Holder/ Homing Switch Version 1

Originally designed to fit a nema 17 stepper motor shaft. The holes around the dial adapter are for M3 screws to tighten around the dial and the inner black ring was printed from flexible TPU for both protection and grip.

A key difference between V1 and v2 is the DIY homing switch. A brass wire was inlayed at the tip of the pointing notch. When the dial spun it would make contact between two prongs to signify a known zero point. You can see the physical representation of this in the photos below. While it was very nice on the eyes and relatively accurate, over time it became less precise.

Dial Holder Version 2

A larger nema 23 motor shaft and slots for bolt inserts served to upgrade this adapter to become more durable.

Homing Switch Version 2

A separate part is attached to the safe dial so that the motor adapter can be removed without interfering with the zero position calibration. The optical switch replaces the contact switch for perfect precision and accuracy.

Homing Switch and dialing in action


According to original instructions the safe has a three number combination and 100 possibilities for each number: 100 * 100 * 100 = 1,000,000 potential combinations

Upon further reading the last number of the combination cannot be set between 0 and 20 or 80 and 100: 100 * 100 * 60 = 600,000 potential combinations

The last detail that really brought this project to life was that when a correct combination is entered. The dial will stop, after rotating about 30 degrees clockwise. In addition to that, each number can be off by one and the dial will still stop: 50 * 50 * 30 = 75,000 potential combinations

Control Unit

The control unit was originally designed with the Esp8266 but later upgraded to the Esp32 because of watchdog timing issues.

Before each attempt the dial zeros, attempts the combination, then rotates twice to the right. If the optical switch trips twice then the combination is incorrect, otherwise the dial must have stopped on a potential correct combination. The Esp32 then uploads the attempted combination to a server for future investigation.

An adapter board was made to easily swap between MCUs when new versions of the software were developed.


Unfortunately, the safe was never opened. After several thousand combinations the plastic slot for the motor would wear out allowing the shaft to freely spin without dial movement. Also without any torque control there was a risk of stripping the safe's internal mechanical components by over-driving the dial. I shelved this project after moving out of state.