Arduino Keypad Password Lock System with Servo, LCD & Indicator Alerts

This project implements a fully functional electronic door lock system controlled by a 4×4 matrix keypad and an Arduino UNO. The user enters a 4-digit password displayed as asterisks on a 16×2 I2C LCD screen. On pressing #, the system compares the input against the stored password. A correct match rotates a servo motor to 0° (unlock position), lights a green LED, and holds for 3 seconds before re-locking. A wrong password triggers a red LED and 4 buzzer beeps as an alert. The * key resets the input at any time.

Key Features: I2C LCD display · 4×4 matrix keypad · Servo-based lock mechanism · Red/Green LED status indicators · Buzzer alert on wrong password · Startup hardware self-test · Serial monitor debug output

What makes this project unique is the triple-layer feedback system:

An I2C LCD provides real-time status updates.

A Dual-LED array gives instant visual confirmation.

A High-pitch Piezo buzzer alerts the surroundings to unauthorized access attempts.

The mechanical heart is a Servo-driven Rack and Pinion mechanism, housed in a custom 3D-printed enclosure I designed in Solid Edge. It’s not just a lock; it’s a scalable, programmable security solution that proves how we can use DIY electronics to solve real-world safety challenges.”

Circuit Diagram Prompt

A detailed electronics circuit schematic diagram on a white background. Shows an Arduino UNO microcontroller at the center connected to: a 4×4 matrix keypad on the left with 8 wires going to digital pins D2 through D9; a 16×2 I2C LCD display connected via SDA and SCL to analog pins A4 and A5; an SG90 servo motor connected to PWM pin D10; a passive buzzer connected through a 100-ohm resistor to pin D11; a red LED with a 220-ohm resistor connected to pin D12; a green LED with a 220-ohm resistor connected to pin D13. All components share a common ground rail. Clean labelled wire traces, component values annotated, engineering schematic style, black ink on white background.