Robotics on transpor ...

1. Introduction

This project demonstrates how to design a simple security system using an Arduino, keypad, and servo motor (acting as a lock).

The system unlocks only when the correct password is entered. It’s a good foundation for door locks, safes, and access control systems.

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Component	Quantity	Description
Arduino Uno	1	Main controller board
4×4 Keypad	1	For password input
Servo Motor (SG90)	1	Acts as the door lock
16×2 LCD Display	1	To show status messages
Breadboard and jumper wires	—	For connections
Buzzer (optional)	1	To give alarm or sound feedback

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3. Circuit Connections
🔌 Keypad → Arduino

Keypad Pin	Arduino Pin
R1 → 9
R2 → 8
R3 → 7
R4 → 6
C1 → 5
C2 → 4
C3 → 3
C4 → 2

Component	Arduino Pin	Description
Servo signal	10	Lock control
LCD RS	12	Display control
LCD EN	11	Enable signal
LCD D4–D7	A0–A3	Data pins
Buzzer	13	Optional alert

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#include <Keypad.h>
#include <LiquidCrystal.h>
#include <Servo.h>
// LCD setup
LiquidCrystal lcd(12, 11, A0, A1, A2, A3);
// Servo setup
Servo lockServo;
// Keypad setup
const byte ROWS = 4;
const byte COLS = 4;
char keys[ROWS][COLS] = {
{'1','2','3','A'},
{'4','5','6','B'},
{'7','8','9','C'},
{'*','0','#','D'}
};
byte rowPins[ROWS] = {9, 8, 7, 6};
byte colPins[COLS] = {5, 4, 3, 2};
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);
// Variables
String password = "1234";
String input = "";
void setup() {
lcd.begin(16, 2);
lcd.print("Enter Password:");
lockServo.attach(10);
lockServo.write(0); // locked position
pinMode(13, OUTPUT); // buzzer
}
void loop() {
char key = keypad.getKey();
if (key) {
if (key == '#') {
if (input == password) {
lcd.clear();
lcd.print("Access Granted");
lockServo.write(90); // unlock
digitalWrite(13, LOW);
delay(3000);
lockServo.write(0); // lock again
lcd.clear();
lcd.print("Enter Password:");
} else {
lcd.clear();
lcd.print("Wrong Password!");
digitalWrite(13, HIGH);
delay(2000);
digitalWrite(13, LOW);
lcd.clear();
lcd.print("Enter Password:");
}
input = "";
} else if (key == '*') {
input = "";
lcd.clear();
lcd.print("Enter Password:");
} else {
input += key;
lcd.setCursor(0, 1);
lcd.print("*");
}
}
}

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When the system starts, the LCD shows:
“Enter Password:”
The user enters digits using the keypad.
Each key press is shown as “*” on the LCD for security.
When the user presses ‘#’, Arduino checks the input:
✅ If the password is correct, the servo rotates (door unlocks).
❌ If the password is wrong, the buzzer sounds an alarm.
The door automatically locks again after a few seconds.

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6. Possible Upgrades

Add EEPROM to save password permanently
Use keypad input to change password
Add RFID reader or fingerprint sensor
Connect to Blynk app or Wi-Fi for remote access
Add motion sensor + camera for smart security

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7. Applications
🔒 Smart home door locks
🏫 School lab security systems
🏢 Office access control
🧳 Safe and locker systems

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