OTP Based Door Lock System

Project Title: OTP Based Door Lock System

Project Overview

The OTP Based Door Lock System is a smart security solution designed to enhance door access control using One-Time Password (OTP) authentication. This system allows authorized users to unlock a door by entering a dynamically generated OTP received via SMS on their registered mobile number. By combining embedded systems and communication technology, this project significantly improves safety compared to traditional lock-and-key systems.

The system is ideal for homes, offices, laboratories, and restricted areas where secure and controlled access is required.

Objective of the Project

• To design a secure electronic door locking system

• To eliminate risks associated with physical keys

• To implement OTP-based authentication for enhanced security

• To demonstrate real-time integration of microcontroller, GSM, keypad, and motor control

Working Principle

1. When access is requested, the system generates a random OTP.

2. The OTP is sent to the authorized user via SMS using a GSM module.

3. The user enters the received OTP using a keypad.

4. The microcontroller verifies the entered OTP.

5. If the OTP is correct, the door unlocks using a DC motor / solenoid lock.

6. If the OTP is incorrect, access is denied and the door remains locked.

7. The OTP is valid for a short time only, improving security.

Main Components Used

• Microcontroller (Arduino / NodeMCU)

• GSM Module (SIM800 / SIM900)

• 4×4 Matrix Keypad

• LCD Display (16×2)

• Relay Module

• DC Motor / Solenoid Door Lock

• Power Supply Unit

• Connecting Wires and PCB

Block Diagram Explanation

• Keypad → Used to enter OTP

• GSM Module → Sends OTP via SMS

• Microcontroller → Generates and verifies OTP

• LCD Display → Shows system status (Enter OTP, Access Granted/Denied)

• Relay + Motor → Controls door locking mechanism

Features of the System

• 🔐 OTP-based secure access

• 📩 SMS authentication

• ⏳ Time-limited OTP

• 🔄 Automatic door locking after access

• 🖥️ LCD status display

• 🚫 Prevents unauthorized access

• 🔋 Low power consumption

• 🧠 Intelligent and reliable system

Applications

• Smart Home Security

• Office & Corporate Access Control

• Bank Locker Security

• Laboratory Safety Systems

• Hostel & Dormitory Rooms

• Restricted Industrial Zones

Advantages

• Higher security than traditional locks

• No physical key required

• Easy to use and cost-effective

• Can be expanded with IoT or biometric systems

• Reduces chances of theft or unauthorized entry

Limitations

• Depends on GSM network availability

• SMS delay may occur in rare cases

• Requires continuous power supply

Future Enhancements

• Mobile app-based OTP generation

• Face recognition or fingerprint integration

• Cloud-based logging system

• IoT dashboard for monitoring

• Camera-based access verification

Conclusion

The OTP Based Door Lock System is a reliable and modern security solution that effectively demonstrates how embedded systems and communication technology can be used to create smart access control systems. This project provides strong protection against unauthorized entry and is suitable for real-world security applications. It is an excellent project for engineering students, IoT enthusiasts, and security system developers.