4*4 MATRIX KEYPAD

A Matrix keypad is a small compact input device that accepts user input and is processed by the microcontrollers. These keys are arranged as rows and columns.  4*4 matrix keypad is a non-encoded keypad consisting of 16keys in parallel with a built-in pushbutton that is connected to row and column. The keys of each row and column are connected through pins outside, pin Y1-Y4 to control rows, and pin X1-X4 to control columns. When the key has been pressed the row and column make contact with each other, otherwise, there is no communication between them. A microcontroller can scan these lines when a button is pressed. These are mainly used in controls systems, embedded systems, digital circuits, calculators, ATMs, etc.

When any key is pressed down, power is connected to rows, so they are High level. Then all the rows R1-R4 are set as Low and then detect the status of the columns. Any Low indication in the column means there is key pressing and that the key is among the 4 keys of the column. Whereas, If all columns are High, it means no key is pressed down. Afterwards in order to locate the key. As the pressed key column is identified, knowing the line would finalize the testing. Thus, set the rows as Low in turns until any is unveiled accordingly – other rows will still be High. Now the row can be identified. Detect the status of each column in turns. Thus column tested Low is the one intersecting with the line is just the key pressed.

Applications

• Security systems.
• Vending machines.
• Industrial machines.
• Engineering systems.
• Measuring instruments.
• Data entry for Embedded Systems
• Hobby projects.
• Basically any where INPUT device is needed