If you want to add a keypad to your Arduino project, the options are pretty limited. There’s that red and blue 4×4 membrane we’ve all seen in password-protected door lock projects ...

[Travis] and [Fabienne] went a different route, and are emulating the keypad using an Arduino and a set of transistors. They started by reverse engineering the keypad matrix using a continuity tester.

So you finally decided to hop on the Arduino bandwagon and start making electronic projects as a fun hobby. As a beginner ...