4×4 Matrix Membrane Keypad (16-Key Membrane Switch Keypad)

The 4×4 Matrix Membrane Keypad is a low-cost human-machine interface device that provides 16 programmable keys using only 8 microcontroller I/O pins. Internally, the keys are connected in a matrix arrangement of four rows and four columns, allowing efficient key detection through row-column scanning. The keypad features a flexible polyester membrane construction with a self-adhesive backing for easy mounting on project enclosures and control panels. It is commonly used in password entry systems, access control units, calculators, industrial control panels, and embedded electronics projects.