ACE 3505 Matrix Keyboard 4 x 4 / 16-Key Membrane Switch Keypad

This 4×4 matrix membrane keypad provides an easy interface for embedded systems such as an Arduino. It has 16 buttons, arranged in a telephone-line 3×4 grid + 4 extra keys – A, B, C and D. It’s made of a thin, flexible membrane material with an adhesive backing (just remove the paper) so you can fix it in a surface. The keys are connected into a matrix, so you only need 8 microcontroller pins (4-columns and 4-rows) to scan through the pad.