Punch in your secret key (or Jenny's number) into this numeric matrix keypad. This keypad has 16 buttons, arranged in a telephone-line 4x4 grid. The keys are connected into a matrix, so you only need 8 microcontroller pins (4-columns and 4-rows) to scan through the pad. Check the tutorials tab for links to an Arduino library and example code.We include some header so you can plug this into a breadboard with ease, some light soldering is required to attach it. Or you can use plain wires if you like. It's basically a sturdier version of our Membrane 3x4 Matrix Keypad. Starting from the left there are four row pins, and then to the right are the four column pins.