3″ long 8-pin cable terminates in standard 2.54mm (0.1″) female header.
These membrane keypads work well for adding key input for a project.
The construction makes them durable and weatherproof.
The keypad terminates in an 8-pin cable which has 4 row and 4 column pins.
The row pins are on the left as you are looking at the front of the keypad and they have a dark strip near the connector to help identify them.
The connector is a standard 2.54mm (0.1″) pitch 1×8 female header.
The matrix is resistive which means that when no button is pushed, none of the pins are electrically connected. When a button is pressed, the corresponding Row and Col pins have a resistance of approximately 60-90 ohms between them.
This membrane keypad with an adhesive back has a 4×4 matrix of letters and numbers including 0-9 and A-D along with the ‘*’ and ‘#’ symbols for good measure.
The membrane is a thin but rugged plastic with adhesive on the back. The protective liner can be left in place to keep the keypad mobile or it can be removed and the keypad permanently mounted if desired.
The MCU monitors for key presses by setting a row or column as an output and setting the pins LOW one at a time. It then looks for a LOW logic level on one of the pins on the opposite axis. It does this in a continual scanning process.