Smart Door Lock Using Keypad and GSM

Abstract: Smart security solutions are emerging as efficient replacements for traditional mechanical locking mechanisms, offering improved protection, dependability, and adaptability. In particular, authentication techniques that combine embedded systems with wireless communication modules provide secure and economical access control alternatives. This study focuses on the design and review of an OTP-enabled smart door lock system that utilizes a 4×4 keypad and a SIM800L GSM module for dynamic verification. The system employs a two-step authentication process—first, a user password is entered, and upon repeated incorrect attempts, a one-time password (OTP) is generated and transmitted to a registered mobile number. The Arduino Uno microcontroller manages the entire operation, while an LCD module displays real-time interaction feedback. This layered approach minimizes the risks associated with fixed passwords, such as brute-force intrusions or credential misuse. Furthermore, the paper analyzes prior security systems, highlights their shortcomings, and demonstrates how GSM-based OTP verification enhances affordability, resilience, and ease of use. Potential future developments include incorporating biometric recognition, IoT-driven cloud access, and smartphone-based control to further optimize system reliability and functionality.