4×3 12-Key Matrix Keypad

Description

4×3 12-Key Matrix Keypad

This input device has 12 buttons arranged in 4 rows and 3 columns. When a key is pressed, it connects a row to a column so the controller can identify the key. It is suitable for projects that need several input options, such as security systems, access-control systems, and automation projects.

Detailed Specifications

• Configuration: 4 rows x 3 columns
• Number of keys: 12
• Operating voltage: 5V DC
• Contact type: Membrane
• Dimensions: 70mm x 77mm
• Interface: 7 pins (4 rows, 3 columns)
• Service life: Up to 1 million presses per key

Operation

The keypad scans its rows and columns to detect pressed keys. Pressing a key connects a row to a column, enabling the microcontroller to identify it. The scanning process is generally managed by a library in development environments such as Arduino.

Applications

• Security systems: Entering codes for access control.
• Automation: User interfaces for machines or home-automation systems.
• Electronics prototyping: Development projects that require user input.

How to Use It with an Arduino Uno

You will need:

• 1 x 4×3 12-key matrix keypad
• 1 x Arduino Uno
• Connecting wires
• Breadboard

Wiring instructions:

1. Connect the keypad: Connect its 7 pins to Arduino digital pins (for example, pins 2 through 8).
2. Use the Keypad library:
   • Install the Keypad library in the Arduino IDE.
   • Use the code below to read keypad input.

Arduino Uno code example:

#include <Keypad.h>


const byte ROWS = 4; // quatre lignes
const byte COLS = 3; // trois colonnes
char keys[ROWS][COLS] = {
  {'1','2','3'},
  {'4','5','6'},
  {'7','8','9'},
  {'*','0','#'}
};


byte rowPins[ROWS] = {9, 8, 7, 6}; // Connecté aux pins des lignes du clavier
byte colPins[COLS] = {5, 4, 3}; // Connecté aux pins des colonnes du clavier


Keypad clavier = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);


void setup() {
  Serial.begin(9600);
}


void loop() {
  char key = clavier.getKey();
  if (key) {
    Serial.println(key);
  }
}

Code Explanation

1. Keypad library: The code includes the Keypad library to handle the matrix keypad. Install this library in the Arduino IDE before using it.
2. Row and column declarations: ROWS and COLS define the number of rows and columns. The keys array assigns a character to each key.
3. Row and column pins: The rowPins and colPins arrays specify the Arduino pins connected to the keypad rows and columns.
4. Keypad initialization: The Keypad object is created using the key map (makeKeymap), row and column pins, and keypad dimensions.
5. Serial communication setup: setup() initializes serial communication at 9600 baud to display pressed keys in the Serial Monitor.
6. Reading keys: In the main loop(), getKey() reads a pressed key. If a key is pressed (if (key)), its character is displayed using Serial.println(key).

Pinout

• L1 – L4: Connected to Arduino digital pins (for example, 9 through 6) for the rows.
• C1 – C3: Connected to Arduino digital pins (for example, 5 through 3) for the columns.