How Does The Membrane Keypad Work Arduino?

how does the membrane keypad work arduino

Introduction: How Does The Membrane Keypad Work Arduino?

Membrane keypads are widely used in various electronic projects and devices due to their compact size, versatility, and ease of use. When combined with an Arduino microcontroller, membrane keypads provide a convenient input interface for controlling and interacting with electronic systems. In this article, we will explore how a membrane keypad works with Arduino, from the basic principles to the practical implementation, allowing you to incorporate this input device into your Arduino projects.

Understanding Membrane Keypads:

A membrane keypad is a type of input device that consists of three main layers: a top graphic overlay, a middle spacer layer, and a bottom circuit layer. The top graphic overlay features printed symbols and icons, while the bottom circuit layer contains conductive traces arranged in a matrix pattern. When a button on the keypad is pressed, it makes contact with the corresponding conductive trace on the bottom layer, completing a circuit and registering the input.

Connecting a Membrane Keypad to Arduino:

To interface a membrane keypad with an Arduino, we need to establish a connection between the keypad and the Arduino’s digital input/output (I/O) pins. The number of pins required depends on the size of the keypad, with larger keypads requiring more pins for row and column scanning.

Here’s a step-by-step guide to connecting a membrane keypad to Arduino:

Step 1: Identify the Pinout: Examine the membrane keypad and identify the pinout configuration. Typically, the keypad will have rows and columns labeled with numbers or letters.

Step 2: Connect Rows to Arduino: Connect the rows of the keypad to Arduino’s digital output pins. Each row pin should be connected to a separate digital output pin on the Arduino. Use jumper wires or a breadboard to make the connections.

Step 3: Connect Columns to Arduino: Connect the columns of the keypad to Arduino’s digital input pins. Each column pin should be connected to a separate digital input pin on the Arduino. Again, use jumper wires or a breadboard for the connections.

Step 4: Enable Internal Pull-Up Resistors: To ensure reliable input readings, enable the internal pull-up resistors on the Arduino’s digital input pins connected to the keypad’s columns. This can be done using the pinMode() function in the Arduino code. Alternatively, external pull-up resistors can be used.

Step 5: Upload the Sketch: Write the Arduino code to read input from the membrane keypad and upload it to the Arduino board. The code will implement a scanning technique to detect button presses and take appropriate actions based on the detected inputs.

Scanning Technique for Membrane Keypads:

To read input from a membrane keypad, a scanning technique known as matrix scanning or row-column scanning is commonly employed. The process involves sequentially activating each row while checking the status of each column to detect button presses.

Here’s an overview of the scanning technique:

  1. Set all row pins as output and all column pins as input.
  2. Begin the scanning loop:
    • Set the current row pin to HIGH and all other row pins to LOW.
    • Check the status of each column pin.
    • If a column pin reads LOW, it indicates that a button in the current row and column combination is pressed.
    • Register the button press and perform the desired action.
  3. Repeat the scanning loop for each row.

Implementing the Scanning Technique in Arduino Code:

To read input from a membrane keypad using Arduino, you need to implement the scanning technique in your Arduino code. Here’s a simplified example code to get you started:

cppCopy code// Define the number of rows and columns in the keypad
const int ROWS = 4;
const int COLS = 4;

// Define the keypad matrix
char keys[ROWS][COLS] = {
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}

// Define the row and column pins
int rowPins[ROWS] = {9, 8, 7, 6};
int colPins[COLS] = {5, 4, 3, 2};

void setup() {
  // Set the row pins as OUTPUT and the column pins as INPUT
  for (int i = 0; i < ROWS; i++) {
    pinMode(rowPins[i], OUTPUT);
  for (int j = 0; j < COLS; j++) {
    pinMode(colPins[j], INPUT_PULLUP);

void loop() {
  // Scan the keypad
  for (int i = 0; i < ROWS; i++) {
    // Activate the current row
    digitalWrite(rowPins[i], HIGH);
    // Check the status of each column
    for (int j = 0; j < COLS; j++) {
      if (digitalRead(colPins[j]) == LOW) {
        // Button in the current row and column is pressed
        // Do something with the detected input
        char key = keys[i][j];
        delay(200); // Add a small delay to debounce the button
    // Deactivate the current row
    digitalWrite(rowPins[i], LOW);

In the above code, the keypad matrix and pin configurations are defined, and the setup() function sets the pins as input or output. The loop() the function performs the scanning process, detecting button presses and performing actions based on the detected inputs. The detected input is printed to the serial monitor, but you can customize the code to suit your specific project requirements.


How Does The Membrane Keypad Work Arduino? Membrane keypads provide a convenient and reliable input interface for Arduino projects. By understanding the basic principles of membrane keypad operation and implementing the appropriate scanning technique, you can easily incorporate a membrane keypad into your Arduino projects. With this knowledge, you can design interactive systems, control devices, and create user-friendly interfaces with ease. So go ahead, experiment with membrane keypads, and unlock the full potential of your Arduino projects.