Make Your Own Arduino RFID Door Lock

Published by Device Plus Editorial Team at January 12, 2022

What is RFID?

“RFID stands for Radio-Frequency IDentification. […] The RFID device serves the same purpose as a bar code or a magnetic strip on the back of a credit card or ATM card; it provides a unique identifier for that object. And, just as a bar code or magnetic strip must be scanned to get the information, the RFID device must be scanned to retrieve the identifying information.” – ©Technovelgy – where science meets fiction.

RFID is used in this project to read data from the RFID tags and send the information to the non-volatile memory of the MCU. The ID read from the tags is compared with the stored information, and if it matches, then the door unlocks/opens.

Hardware

Arduino Nano
RFID RC522
Piezo Buzzer
2x LED
2x 330 Resistor
Keypad 4×4
Adapter I2C for LCD
LCD16X2BL

>Software

Arduino IDE
SketchUp
Github

Wiring the LCD to the Arduino

The LCD has 16 pins which is too much for an Arduino Nano, that’s why it’s important to have an I2C adapter. This allows running the display from only 2 signal pins on the Arduino. It is helpful because of the small number of pins that will have to be controlled from the MCU.

Figure 1: LCD pins

The LCDs have a parallel interface, meaning that the MCU has to manipulate several interface pins at the same time to control the display. The table below gives a description for each of the pins:

Figure 2: Pin specification

First, we will make the connections between LCD and I2C. To do that, we need an I2C LCD display adapter (LCD1602). The adapter converts the 16 x 2 character LCD display into a serial I2C LCD that can be controlled via Arduino by just 2 wires.

Figure 3: Connections between Arduino and LCD

Next, we’ll add library “<LiquidCrystal_I2C.h>” in Arduino IDE. The library allows us to connect the LCD to the Arduino. The built-in LiquidCrystal_I2C library makes it easy to display characters on the LCD.

You can download the LiquidCrystal_I2C.h here.

Installing your new library

Please follow the steps below to install a new library into your Arduino IDE.

1) First, download the files from Github. (I’ll be downloading Keypad library.)

arduino rfid door lock

2) Zip (.zip) each folder.

arduino rfid door lock

3) Copy the .zip files to your Arduino folder.

arduino rfid door lock

4) Open Arduino and add Keypad.zip: : Sketch menu > Include Library > Add .ZIP Library.

arduino rfid door lock

5) Add keypad library: Sketch menu > Include Library > Keypad.

arduino rfid door lock

Codes to test LCD:

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 16, 2); // Set the LCD address to 0x27 for a 16 chars and 2 line display
void setup() {
  lcd.begin();// initialize the LCD
  lcd.backlight();// Turn on the blacklight and print a message.
  lcd.backlight();
  lcd.print("Hello, world!");
}
void loop() {
}

#include <Wire.h>

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2); // Set the LCD address to 0x27 for a 16 chars and 2 line display

void setup() {

lcd.begin();// initialize the LCD

lcd.backlight();// Turn on the blacklight and print a message.

lcd.backlight();

lcd.print("Hello, world!");

}

void loop() {

}

Figure 4: LCD connected to Arduino Nano

Connecting the Keypad

Now, on to the keypad! We will connect the keypad in order to display the numbers on the LCD that we input from the keypad.

Keypad.h is a library which allows the Arduino to read a matrix type keypad.

I used a 4×4 keypad in this tutorial.

The table shows the connection between the Arduino board and the keypad. The keypad pins are connected to Arduino’s digital output pins. Pin D6 was used for the buzzer because it was a PWM pin.

Keypad pin	Arduino pin
1	D2
2	D3
3	D4
4	D5
5	A0
6	D7
7	D8

Figure 5: Connection between Arduino, LCD, and Keypad

Figure 6: LCD and Keypad connected to Arduino

Wiring the RFID

Next, we will add the RFID. In this case, the RFID board uses a SPI communication protocol, where the Arduino will be acting as a master and the RFID reader as a slave. The card reader and the tags are designed to communicate using a frequency equal to 13.56MHz.

This is an important step because it helps us to read data from the card and it will decide if the ID corresponds to the information stored in the EEPROM. If it matches, it will give us access and display “Unlocked”. Otherwise, the LCD will display “Blocked”.

Figure 7: Connection between Arduino, LCD, and RFID

Figure 8: Arduino, LCD, and RFID

Adding a buzzer & LEDs

Next step is to add a buzzer and 2 LEDs to simulate a controlled access system. Please review the wire diagram below (Figure 9). The buzzer is set so that it buzzes whenever we gain access (unlocked). The red LED is always on when it is locked, but the green LED will come on when it is unlocked.

In order to protect the modules, I decided to 3D print the housing box/case. If you don’t have a 3D printer, you can just use a plastic case that allows you to fit all of the components inside. This is very helpful because the modules will be placed inside and the only parts outside of the box will be the LEDs, keypad, and LCD.

Figure 9: Wire diagram showing connection between Nano, LCD, Keypad, RFID, and buzzer

Building The Housing Case/Box

For this project, I wanted to create a custom case to house all of the components neatly and keep them free of damage.

I have designed a box using SketchUp, which has a user-friendly interface with simple buttons like Eraser, Lines, and Tape Measure Tool.

The dimensions of the box is 120x125x37 mm.

arduino rfid door lock

If you’re not familiar with Sketchup, I recommend you go through some SketchUp tutorials here.

Figure 10: Housing case (top view)

Figure 11: Housing case (bottom view)

When I designed the box, I took these dimensions into consideration:

Top view:
- 2 openings for the LEDs (5.2 mm)
- 1 opening for LCD (42.2×7.3 mm)
- 1 opening for cable (16×10.5 mm)

Bottom view:
- 1 opening for keypad (27×10 mm)

After I measured the dimensions of the components, I designed a box that’s rather compact. Feel free to change the design to your preference.

Figure 12: Complete housing case with modules placed inside

Code diagram

arduino rfid door lock

Full Code

#include <SPI.h>
#include <MFRC522.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Keypad.h>
#include <EEPROM.h>

int relPin;
int state=0;
byte  COD[10];
byte  AUX[10];
int k=0;
String accessCode="*123456#";
String codpairing="*654321#";
//NFC
#define RST_PIN 9
#define SS_PIN 10
MFRC522 mfrc522(SS_PIN, RST_PIN);  // Create MFRC522 instance
#define NEW_UID {0xDE, 0xAD, 0xBE, 0xEF}
MFRC522::MIFARE_Key key;

//LCD
LiquidCrystal_I2C  lcd(0x27,16,2);

//KEYPAD
const byte numRows= 4;  //number of rows on the keypad
const byte numCols= 4;  //number of columns on the keypad

char keymap[numRows][numCols]=
{
{'1', '2', '3', 'A'},
{'4', '5', '6', 'B'},
{'7', '8', '9', 'C'},
{'*', '0', '#', 'D'}
};

//Code that shows the the keypad connections to the arduino terminals
byte rowPins[numRows] = {2,3,4,5};    //Rows 0 to 3
byte colPins[numCols] = {A0,7,8,9};   //Columns 0 to 3

//initializes an instance of the Keypad class
Keypad myKeypad= Keypad(makeKeymap(keymap), rowPins, colPins, numRows, numCols);

void setup() {
  pinMode(A0,OUTPUT);
  digitalWrite(A0,HIGH);
  pinMode(A3,OUTPUT);
  digitalWrite(A3,HIGH);
  pinMode(A1,OUTPUT);
  digitalWrite(A1,HIGH);
  pinMode(A2,OUTPUT);
  digitalWrite(A2,LOW);
  //NFC
  Serial.begin(9600);  // Initialize serial communications with the PC
  while (!Serial);     // Do nothing if no serial port is opened
  SPI.begin();         // Init SPI bus
  mfrc522.PCD_Init();  // Init MFRC522 card

  for (byte i = 0; i < 6; i++) {
    key.keyByte[i] = 0xFF;
  }
  lcd.begin();
  lcd.backlight();
  lcd.setCursor(0,0);
  lcd.clear();
  lcd.print( "BLOCKED" );
}

void  readNFC(){  // This function will read the code stored on
  for (byte i =0; i<(mfrc522.uid.size); i++) {  // the  UID
    COD[i]=mfrc522.uid.uidByte[i];
  }
  Serial.print("COD");
  Serial.print(COD[0]);
  Serial.print(COD[1]);
  Serial.print(COD[2]);
  Serial.print(COD[3]);
}

void pairNFC(){
  Serial.println("COD in pair");
  Serial.print(COD[0]);
  Serial.print(COD[1]);
  Serial.print(COD[2]);
  Serial.print(COD[3]);
  long  r=0;
  int c=0;
  for(int i=1;i<=EEPROM.read(0);i++){        //The UID cannot be stored on
  switch(i%4){                               // one variable, it was needed to be
    case 1 :{AUX[0]=EEPROM.read(i); break;}  // split
    case 2 :{AUX[1]=EEPROM.read(i); break;}
    case 3 :{AUX[2]=EEPROM.read(i); break;}
    case 0 :{AUX[3]=EEPROM.read(i); break;}
  }
  if((i)%4==0)
    {Serial.println(r);
      if( AUX[0]==COD[0] && AUX[1]==COD[1] && AUX[2]==COD[2] && AUX[3]==COD[3] ){  //Verify if the code is in EEPROM
        lcd.clear();
        lcd.setCursor(0,0);
        lcd.print("CODE ALREADY IN");
        lcd.setCursor(0,1);
        lcd.print("SYSTEM");
        delay(2000);
        c=1;
        break;}
    }
  }

  if(c==0){int aux2=EEPROM.read(0);
    Serial.println("CODE PAIRED");
    Serial.print(COD[0]);
    Serial.print(COD[1]);
    Serial.print(COD[2]);
    Serial.print(COD[3]);

    EEPROM.write(aux2+1,COD[0]);  //Writing code in EEPROM
    EEPROM.write(aux2+2,COD[1]);
    EEPROM.write(aux2+3,COD[2]);
    EEPROM.write(aux2+4,COD[3]);

    aux2=aux2+4; // Position for a new code
    Serial.println("aux2");
    Serial.println(aux2);
    EEPROM.write(0,0);
    EEPROM.write(0,aux2);    
    lcd.clear();
    lcd.setCursor(0,0);
    lcd.print("CODE PAIRED");
    delay(2000);
  }
}

boolean validationNFC(){
  boolean c=false;
  for(int i=1;i<=EEPROM.read(0);i++){   //Read the EEPROM
    switch(i%4){
      case 1 :{AUX[0]=EEPROM.read(i); break;}
      case 2 :{AUX[1]=EEPROM.read(i); break;}
      case 3 :{AUX[2]=EEPROM.read(i); break;}
      case 0 :{AUX[3]=EEPROM.read(i); break;}
    }
    if((i)%4==0)
    {
      if( AUX[0]==COD[0] && AUX[1]==COD[1] && AUX[2]==COD[2] && AUX[3]==COD[3])
        c=true;  //Verify if the code is in EEPROM and make flag=true;
    }
  }
  return c;
}

int compareCODE(String a)  //We type a code on keypad and this will be compared
{  //with the accessCode;
  if(a.equals(accessCode))
  return 1;
  else if(a.equals(codpairing)) return 2;
  else return 0;
}

String takeCode(char x)  //Will display on the LCD the code typed
{ char vec[10];
  vec[0]=x;
  lcd.setCursor(0,0);
  lcd.clear();
  lcd.print('X');
  for(int i=1;i<8;i++)
    {vec[i]=myKeypad.waitForKey();  //Waits for 8 keys to be pressed and after that  
     lcd.print('X');}  //is taking the decision
  vec[8]=NULL;
  String str(vec);
  return str;
}

void loop() {
   
  switch(state){
  case 0: {
    mfrc522.PCD_Init();
    if ( mfrc522.PICC_IsNewCardPresent() && mfrc522.PICC_ReadCardSerial() ){

      readNFC();  //It will read the card and it will search for UID in its
      if(validationNFC())  //memory
        { state=1;
          lcd.clear();
          lcd.setCursor(0,0);
          lcd.print( "VALID NFC CODE" );  //The door will be opened
          delay(1000);
          return;
        }
      else{
        lcd.clear();
        lcd.setCursor(0,0);
        lcd.print( "INVALID NFC CODE" ) //If the code was wrongblocked
        delay(1000);
        lcd.setCursor(0,0);
        lcd.clear();
        lcd.print( "BLOCKED" );
        return;
        }
    }

    char c=myKeypad.getKey();
    if(c != NO_KEY){

      String codcurent=takeCode(c);
      int A=compareCODE(codcurent);
      if(A==0){  //A is a variable that stores the current code
        lcd.clear();
        lcd.print("INVALID CODE");
        delay(2000);
        lcd.setCursor(0,0);
        lcd.clear();
        lcd.print("BLOCKED");
        return;
      }
      if(A==1){
        lcd.setCursor(0,0);
        lcd.clear();
        lcd.print( "VALID CODE " );
        delay(2000);
        state = 1;
        Return;
      }
      if(A==2); {
        state=2;
        lcd.clear();
        lcd.setCursor(0,0);
        lcd.print( " Pairing..." );
        delay(2000);
        return;}
    }
    break;
  }

  case 1:{
    lcd.clear();
    lcd.setCursor(0,0);
    lcd.print( "UNLOCKED" );
    digitalWrite(A3,LOW);
    digitalWrite(A1,LOW);  //The red LED will be off
    digitalWrite(A2,HIGH);  //The green LED will be on
    tone(6,3000,5010);  //The buzzer will make a sound
    delay(5000);  //After 5 seconds the system will be blocked
    digitalWrite(A3,HIGH);
    digitalWrite(A1,HIGH);
    digitalWrite(A2,LOW);
    state=0;
    lcd.setCursor(0,0);
    lcd.clear();
    lcd.print( "BLOCKED" );
    return;
  }

  case 2:{
    mfrc522.PCD_Init();
    if (  mfrc522.PICC_IsNewCardPresent() && mfrc522.PICC_ReadCardSerial() ){
      readNFC();
      pairNFC();
      state=0;
      delay(2000);
      lcd.clear();
      lcd.setCursor(0,0);
      lcd.print( "BLOCKED" ); }

    break;
  }
  }
}

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#include <SPI.h>

#include <MFRC522.h>

#include <Wire.h>

#include <LiquidCrystal_I2C.h>

#include <Keypad.h>

#include <EEPROM.h>

int relPin;

int state=0;

byte COD[10];

byte AUX[10];

int k=0;

String accessCode="*123456#";

String codpairing="*654321#";

//NFC

#define RST_PIN 9

#define SS_PIN 10

MFRC522 mfrc522(SS_PIN, RST_PIN); // Create MFRC522 instance

#define NEW_UID {0xDE, 0xAD, 0xBE, 0xEF}

MFRC522::MIFARE_Key key;

//LCD

LiquidCrystal_I2C lcd(0x27,16,2);

//KEYPAD

const byte numRows= 4; //number of rows on the keypad

const byte numCols= 4; //number of columns on the keypad

char keymap[numRows][numCols]=

{

{'1', '2', '3', 'A'},

{'4', '5', '6', 'B'},

{'7', '8', '9', 'C'},

{'*', '0', '#', 'D'}

};

//Code that shows the the keypad connections to the arduino terminals

byte rowPins[numRows] = {2,3,4,5}; //Rows 0 to 3

byte colPins[numCols] = {A0,7,8,9}; //Columns 0 to 3

//initializes an instance of the Keypad class

Keypad myKeypad= Keypad(makeKeymap(keymap), rowPins, colPins, numRows, numCols);

void setup() {

pinMode(A0,OUTPUT);

digitalWrite(A0,HIGH);

pinMode(A3,OUTPUT);

digitalWrite(A3,HIGH);

pinMode(A1,OUTPUT);

digitalWrite(A1,HIGH);

pinMode(A2,OUTPUT);

digitalWrite(A2,LOW);

//NFC

Serial.begin(9600); // Initialize serial communications with the PC

while (!Serial); // Do nothing if no serial port is opened

SPI.begin(); // Init SPI bus

mfrc522.PCD_Init(); // Init MFRC522 card

for (byte i = 0; i < 6; i++) {

key.keyByte[i] = 0xFF;

}

lcd.begin();

lcd.backlight();

lcd.setCursor(0,0);

lcd.clear();

lcd.print( "BLOCKED" );

}

void readNFC(){ // This function will read the code stored on

for (byte i =0; i<(mfrc522.uid.size); i++) { // the UID

COD[i]=mfrc522.uid.uidByte[i];

}

Serial.print("COD");

Serial.print(COD[0]);

Serial.print(COD[1]);

Serial.print(COD[2]);

Serial.print(COD[3]);

}

void pairNFC(){

Serial.println("COD in pair");

Serial.print(COD[0]);

Serial.print(COD[1]);

Serial.print(COD[2]);

Serial.print(COD[3]);

long r=0;

int c=0;

for(int i=1;i<=EEPROM.read(0);i++){ //The UID cannot be stored on

switch(i%4){ // one variable, it was needed to be

case 1 :{AUX[0]=EEPROM.read(i); break;} // split

case 2 :{AUX[1]=EEPROM.read(i); break;}

case 3 :{AUX[2]=EEPROM.read(i); break;}

case 0 :{AUX[3]=EEPROM.read(i); break;}

}

if((i)%4==0)

{Serial.println(r);

if( AUX[0]==COD[0] && AUX[1]==COD[1] && AUX[2]==COD[2] && AUX[3]==COD[3] ){ //Verify if the code is in EEPROM

lcd.clear();

lcd.setCursor(0,0);

lcd.print("CODE ALREADY IN");

lcd.setCursor(0,1);

lcd.print("SYSTEM");

delay(2000);

c=1;

break;}

}

if(c==0){int aux2=EEPROM.read(0);

Serial.println("CODE PAIRED");

Serial.print(COD[0]);

Serial.print(COD[1]);

Serial.print(COD[2]);

Serial.print(COD[3]);

EEPROM.write(aux2+1,COD[0]); //Writing code in EEPROM

EEPROM.write(aux2+2,COD[1]);

EEPROM.write(aux2+3,COD[2]);

EEPROM.write(aux2+4,COD[3]);

aux2=aux2+4; // Position for a new code

Serial.println("aux2");

Serial.println(aux2);

EEPROM.write(0,0);

EEPROM.write(0,aux2);

lcd.clear();

lcd.setCursor(0,0);

lcd.print("CODE PAIRED");

delay(2000);

}

boolean validationNFC(){

boolean c=false;

for(int i=1;i<=EEPROM.read(0);i++){ //Read the EEPROM

switch(i%4){

case 1 :{AUX[0]=EEPROM.read(i); break;}

case 2 :{AUX[1]=EEPROM.read(i); break;}

case 3 :{AUX[2]=EEPROM.read(i); break;}

case 0 :{AUX[3]=EEPROM.read(i); break;}

}

if((i)%4==0)

{

if( AUX[0]==COD[0] && AUX[1]==COD[1] && AUX[2]==COD[2] && AUX[3]==COD[3])

c=true; //Verify if the code is in EEPROM and make flag=true;

}

return c;

}

int compareCODE(String a) //We type a code on keypad and this will be compared

{ //with the accessCode;

if(a.equals(accessCode))

return 1;

else if(a.equals(codpairing)) return 2;

else return 0;

}

String takeCode(char x) //Will display on the LCD the code typed

{ char vec[10];

vec[0]=x;

lcd.setCursor(0,0);

lcd.clear();

lcd.print('X');

for(int i=1;i<8;i++)

{vec[i]=myKeypad.waitForKey(); //Waits for 8 keys to be pressed and after that

lcd.print('X');} //is taking the decision

vec[8]=NULL;

String str(vec);

return str;

}

void loop() {

switch(state){

case 0: {

mfrc522.PCD_Init();

if ( mfrc522.PICC_IsNewCardPresent() && mfrc522.PICC_ReadCardSerial() ){

readNFC(); //It will read the card and it will search for UID in its

if(validationNFC()) //memory

{ state=1;

lcd.clear();

lcd.setCursor(0,0);

lcd.print( "VALID NFC CODE" ); //The door will be opened

delay(1000);

return;

}

else{

lcd.clear();

lcd.setCursor(0,0);

lcd.print( "INVALID NFC CODE" ) //If the code was wrongblocked

delay(1000);

lcd.setCursor(0,0);

lcd.clear();

lcd.print( "BLOCKED" );

return;

}

char c=myKeypad.getKey();

if(c != NO_KEY){

String codcurent=takeCode(c);

int A=compareCODE(codcurent);

if(A==0){ //A is a variable that stores the current code

lcd.clear();

lcd.print("INVALID CODE");

delay(2000);

lcd.setCursor(0,0);

lcd.clear();

lcd.print("BLOCKED");

return;

}

if(A==1){

lcd.setCursor(0,0);

lcd.clear();

lcd.print( "VALID CODE " );

delay(2000);

state = 1;

Return;

}

if(A==2); {

state=2;

lcd.clear();

lcd.setCursor(0,0);

lcd.print( " Pairing..." );

delay(2000);

return;}

}

break;

}

case 1:{

lcd.clear();

lcd.setCursor(0,0);

lcd.print( "UNLOCKED" );

digitalWrite(A3,LOW);

digitalWrite(A1,LOW); //The red LED will be off

digitalWrite(A2,HIGH); //The green LED will be on

tone(6,3000,5010); //The buzzer will make a sound

delay(5000); //After 5 seconds the system will be blocked

digitalWrite(A3,HIGH);

digitalWrite(A1,HIGH);

digitalWrite(A2,LOW);

state=0;

lcd.setCursor(0,0);

lcd.clear();

lcd.print( "BLOCKED" );

return;

}

case 2:{

mfrc522.PCD_Init();

if ( mfrc522.PICC_IsNewCardPresent() && mfrc522.PICC_ReadCardSerial() ){

readNFC();

pairNFC();

state=0;

delay(2000);

lcd.clear();

lcd.setCursor(0,0);

lcd.print( "BLOCKED" ); }

break;

}

Conclusion

So, we managed to build a low-cost Arduino RFID door lock. It was an interesting project for me because I made it for my personal use. Moreover, building such a device will provide you not only the satisfaction of doing something useful, but also a lot of knowledge and an initiation in the first steps of custom electronics. Dealing with a wide range of boards will be definitely very challenging. The project presents a lot of interesting tasks, such as:

Working with other Arduino libraries
Understanding the use of EEPROM
Working with multiple communications like I2C, SPI

Click here to see Part 2 of this article, where we enable unlocking from a smartphone! Check out our Arduino projects section for other fun and challenging Arduino projects!

Want to learn more about how to make the most of your Arduino projects? Explore some of our in-depth Arduino guides: