Arduino - Door Lock System using Password

In this tutorial, we learn how to make door lock system with password. The tutorial include two main parts:

LCD is optional. It just makes the system a little more convenient.

When the door is unlocked by a correct password, It keeps the door unlocked for 20 seconds, and then automatically lock the door again. The Arduino code supports multiple passwords.

Hardware Required

1×Arduino UNO or Genuino UNO
1×USB 2.0 cable type A/B
1×Keypad 4x4
1×Relay
1×12V Power Adapter
1×Electromagnetic Lock
n×Jumper Wires
1×LCD I2C (optional)
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About Keypad and Electromagnetic Lock and LCD

If you do not know about electromagnetic lock and button (pinout, how it works, how to program ...), learn about them in the following tutorials:

Wiring Diagram

  • Arduino - Door lock system with password using keypad, electromagnetic lock
  • Arduino door lock system wiring diagram

    Image is developed using Fritzing. Click to enlarge image

  • Arduino - Door lock system with password using keypad, electromagnetic lock and LCD
  • Arduino door lock system lcd wiring diagram

    Image is developed using Fritzing. Click to enlarge image

Arduino Code - Door lock system with password using keypad, electromagnetic lock

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-door-lock-system-using-password */ #include <Keypad.h> const int RELAY_PIN = A0; // the Arduino pin, which connects to the IN pin of relay const int ROW_NUM = 4; //four rows const int COLUMN_NUM = 4; //four columns char keys[ROW_NUM][COLUMN_NUM] = { {'1','2','3', 'A'}, {'4','5','6', 'B'}, {'7','8','9', 'C'}, {'*','0','#', 'D'} }; byte pin_rows[ROW_NUM] = {9, 8, 7, 6}; //connect to the row pinouts of the keypad byte pin_column[COLUMN_NUM] = {5, 4, 3, 2}; //connect to the column pinouts of the keypad Keypad keypad = Keypad( makeKeymap(keys), pin_rows, pin_column, ROW_NUM, COLUMN_NUM ); const String password_1 = "1234ABC"; // change your password here const String password_2 = "5642CD"; // change your password here const String password_3 = "4545B"; // change your password here String input_password; void setup(){ Serial.begin(9600); input_password.reserve(32); // maximum input characters is 33, change if needed pinMode(RELAY_PIN, OUTPUT); // initialize pin as an output. digitalWrite(RELAY_PIN, HIGH); // lock the door } void loop(){ char key = keypad.getKey(); if (key){ Serial.println(key); if(key == '*') { input_password = ""; // reset the input password } else if(key == '#') { if(input_password == password_1 || input_password == password_2 || input_password == password_3) { Serial.println("password is correct"); digitalWrite(RELAY_PIN, LOW); // unlock the door for 20 seconds delay(20000); digitalWrite(RELAY_PIN, HIGH); // lock the door } else { Serial.println("password is incorrect, try again"); } input_password = ""; // reset the input password } else { input_password += key; // append new character to input password string } } }

Quick Steps

  • Connect Arduino to PC via USB cable
  • Open Arduino IDE, select the right board and port
  • On Arduino IDE, Go to Tools Manage Libraries
  • Arduino add library
  • Search “keypad”, then find the keypad library by Mark Stanley, Alexander Brevig
  • Click Install button to install keypad library.
  • Arduino keypad library
  • Copy the above code and open with Arduino IDE
  • Click Upload button on Arduino IDE to upload code to Arduino
  • Put the armature plate close to electromagnet.
  • In put a wrong password, and then input a correct password
  • See the attraction between armature plate and electromagnet during 20 seconds.

Arduino Code - Door lock system with password using keypad, electromagnetic lock and LCD

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-door-lock-system-using-password */ #include <Keypad.h> #include <LiquidCrystal_I2C.h> const int RELAY_PIN = A0; // the Arduino pin, which connects to the IN pin of relay const int ROW_NUM = 4; //four rows const int COLUMN_NUM = 4; //four columns char keys[ROW_NUM][COLUMN_NUM] = { {'1','2','3', 'A'}, {'4','5','6', 'B'}, {'7','8','9', 'C'}, {'*','0','#', 'D'} }; byte pin_rows[ROW_NUM] = {9, 8, 7, 6}; //connect to the row pinouts of the keypad byte pin_column[COLUMN_NUM] = {5, 4, 3, 2}; //connect to the column pinouts of the keypad Keypad keypad = Keypad( makeKeymap(keys), pin_rows, pin_column, ROW_NUM, COLUMN_NUM ); LiquidCrystal_I2C lcd(0x27, 16, 2); // I2C address 0x27, 16 column and 2 rows const String password_1 = "1234ABC"; // change your password here const String password_2 = "5642CD"; // change your password here const String password_3 = "4545B"; // change your password here String input_password; void setup(){ Serial.begin(9600); input_password.reserve(32); // maximum input characters is 33, change if needed pinMode(RELAY_PIN, OUTPUT); // initialize pin as an output. digitalWrite(RELAY_PIN, HIGH); // lock the door lcd.init(); // initialize the lcd lcd.backlight(); } void loop(){ char key = keypad.getKey(); if (key){ Serial.println(key); if(key == '*') { input_password = ""; // reset the input password lcd.clear(); } else if(key == '#') { lcd.clear(); if(input_password == password_1 || input_password == password_2 || input_password == password_3) { Serial.println("password is correct"); lcd.setCursor(0, 0); lcd.print("CORRECT!"); lcd.setCursor(0, 1); lcd.print("DOOR UNLOCKED!"); digitalWrite(RELAY_PIN, LOW); // unlock the door for 20 seconds delay(20000); digitalWrite(RELAY_PIN, HIGH); // lock the door } else { Serial.println("password is incorrect, try again"); lcd.setCursor(0, 0); lcd.print("INCORRECT!"); lcd.setCursor(0, 1); lcd.print("ACCESS DENIED!"); } input_password = ""; // reset the input password } else { if(input_password.length() == 0) { lcd.clear(); } input_password += key; // append new character to input password string lcd.setCursor(input_password.length(), 0); // move cursor to new position lcd.print('*'); // print * key as hiden character } } }

Quick Steps

  • On Arduino IDE, Go to Tools Manage Libraries
  • Arduino add library
  • Search “LiquidCrystal I2C”, then find the LiquidCrystal_I2C library by Frank de Brabander
  • Click Install button to install LiquidCrystal_I2C library.
  • Arduino LiquidCrystal I2C library
  • Copy the above code and open with Arduino IDE
  • Click Upload button on Arduino IDE to upload code to Arduino
  • Put the armature plate close to electromagnet.
  • In put a wrong password, and then input a correct password
  • See the attraction between armature plate and electromagnet during 20 seconds.
  • See text on LCD

※ NOTE THAT:

  • In the above codes, To make it simple, we used the delay function. It is better to use millis() instead of delay(). See How to use millis() instead of delay()
    • You can add a piezo buzzer to make the beep sound each time keypad is pressed.
      • In the above codes, the door is locked again after 20 seconds. You can replace it by a door sensor . The door is locked when the door sensor detect the door is closed by user.

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