The keypad is actually built from two separate ... which are marked SWITCH3 and SWITCH4 on the PC board (5 and 6 on the schematic). Arduino pins 6, 7, 8, and 9 should connect to the four output ...

connect to the column C1-C3 pinouts of the keypad Next is a project example, where the Arduino is instructed to do something based on a correct key (secret number) being entered into the keypad, ...

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 ...