Eric Betts created a computer combination lock.
The lock uses the Teensy, rotary encoder, circular led bar graph, and the encoder library. You twist the knob to the correct position as indicated by the LEDs, push down on the knob to set that value, and on the 3rd value the sequence will be checked against the first 3 bytes of EEPROM. If the combination is correct, “Secret Word” is sent as keyboard input.
The code for the project is available on GitHub.