4×4 Matrix Keypad Module – 16 Keys | How it’s Works

Hello friends! Welcome back to ElectroDuino. This blog is base on What is 4×4 Matrix Keypad Module | How it’s Works. Here we will discuss the Introduction to 4×4 Matrix Keypad Module,  pin diagram, Working Principle, Features, and applications.

Introduction

Most of the time we are used key, button, or switch to get input value in our projects. When we interface one key, button, or switch to the microcontroller then it needs one GPIO pin. But when we want to interface many keys like 9, 12 or 16, etc., then it needs many GPIO pins of a microcontroller and we will lose many GPIO pins.

Don’t worry! The 4×4 matrix keypad is a device that can solve this problem. The 4×4 matrix keypad is an input device, it usually used to provide input value in a project. It has 16 keys in total, which means it can provide 16 input values. The most interesting thing is it used only 8 GPIO pins of a microcontroller.

4×4 Keypad Module Pin Diagram

 
4x4 Keypad module Pin Diagram
4×4 Keypad module Pin Diagram
Pin NumberPin NameDescription
1R1Taken out from 1st  ROW
2R2Taken out from 2nd  ROW
3R3Taken out from 3rd  ROW
4R4Taken out from 4th  ROW
5C1Taken out from 1st  COLUMN
6C2Taken out from 2nd COLUMN
7C3Taken out from 3rd  COLUMN
8C4Taken out from 4th  COLUMN

4×4 Matrix Keypad Module Hardware Overview

These Keypad modules are made of thin, flexible membrane material. The 4 x4 keypad module consists of 16 keys, these Keys are organized in a matrix of rows and columns. All these switches are connected to each other with a conductive trace. Normally there is no connection between rows and columns. When we will press a key, then a row and a column make contact.

 
4x4 keypad Module Internal Circuit
4×4 keypad Module Internal Circuit

How the 4×4 Matrix Keypad Module Works

To detecting a pressed key, the microcontroller grounds all rows by providing 0 to the output pins, and then it reads the columns. If the data read from columns is = 1111, it means no key has been pressed.

 
4x4 Keypad Module Circuit Works
4×4 Keypad Module Circuit Works

When we will Pressing a button shorts one of the row lines to one of the column lines, allowing current to flow between them. For example, when key ‘Button 1’ is pressed, column 1 and row 1 are shorted.

4x4 Keypad module circuit pressing swich1
4×4 Keypad module circuit pressing swich1

R1 R2 R3 R4 = 0 0 0 0

C1 C2 C3 C4 = 0 1 1 1

If the first column bit value is a zero, this means that the “Button1” key was pressed. For example, if C1 C2 C3 C4 = 0111, this means that a key in the C1 column has been pressed.

how 4x4 Keypad module detects key
how 4×4 Keypad module detects key

This process is continuing for all row & columns

How a microcontroller can read these lines for a button-pressed state

  1. The microcontroller sets all the column and row lines to input.
  2. Then, the microcontroller sets row LOW.
  3. After that, it checks the column lines one at a time.
  4. If the column connection stays HIGH, the button on the row has not been pressed.
  5. If it goes LOW, the microcontroller knows which row was set to LOW, and which column was detected LOW when checked.
  6. Finally, it knows which button was pressed that corresponds to the detected row & column.

Specifications

ParameterValue
Product type4 X 4 keypad module
Maximum Voltage rating24V DC
Maximum Current rating30 mA
Operating temp range32 to 122 °F (0 to 50 °C)
Numbers of Pin8
Keypad Dimensions6.9 cm X 7.9 cm
Cable dimensions2.0 cm X 8.8 cm
Design Ultra-thin

Application

  • Data entry for microcontroller
  • Menu or data selection
  • Password lock

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