Need to be quiet? A small switch on the side shuts off the vibrations. The 4×4 keypad really allowed [Turi] to cram in a bunch of features using both short and long press to do different things.

They started by reverse engineering the keypad matrix using a continuity tester. Once they worked out the column and row layout they connected each to an NPN transistor. The Arduino sketch ...

This proposed Arduino-based automatic bell device is an electronic system that rings bells at predefined times without manual ...