Build a Smart 4-Digit PIN Lock System with Arduino & 4x4 Keypad

Every part needed, pre-tested for compatibility, with an AI build companion trained on this exact project. Shipped from Bengaluru in 3-5 days.

Imagine securing your school locker, hostel cupboard, or even a personal drawer with a custom passcode you set yourself—no keys, no combination dials to forget. This kit lets you assemble a 4x4 membrane keypad that accepts a 4-digit PIN, drives a relay lock, and responds with LEDs and a buzzer. Enter the right code, the green LED glows and the relay clicks open. A wrong entry sounds the alarm, and multiple failed tries trigger a temporary lockout, just like a real access control system. Whether you're prepping for a CBSE computer science practical, a B.Tech mini project, or a Smart India Hackathon prototype, you'll have a fully documented, field-ready security module in a single afternoon.

What You'll Build

A standalone access control unit centered on the Arduino Uno R3. You will wire the 4x4 keypad to digital pins, connect the relay module to simulate a door lock or electric strike, and position red and green LEDs for status indication. The active buzzer delivers audible feedback—short beep on key press, continuous alarm on invalid PIN. The final code includes debounce handling, password verification, and a lockout state machine that blocks further input after three consecutive wrong attempts for a configurable cooldown period.

What You'll Learn

• Interfacing a 4x4 matrix keypad to read button presses using row-column scanning
• Coding password authentication and lockout algorithms in Arduino C++
• Wiring a 5V relay module to control higher-voltage external devices safely
• Integrating LEDs and a buzzer for real-time security feedback and alarm logic

Kit Contents

Why Buy This Kit Instead of Sourcing Parts Separately

Who This Kit Is For

Tailored for CBSE Class 11-12 students building working models for computer science or physics practicals, and first-year B.Tech ECE/EEE students who need a reliable mini project. It also fits ATL Tinkering Lab kits and Smart India Hackathon prototypes requiring physical access control. If you’ve already tinkered with an Arduino starter kit and want a structured introduction to embedded security, this project bridges the gap between blinking LEDs and a real-world application.

Built and Backed by Compoden

Every Compoden kit ships with an AI build companion trained on this exact project — accessible via a QR code on the box, with WhatsApp and email backup. We've spent 10 years building projects for makers, schools, and institutions across India. If a part fails because of a manufacturing defect, replace it free within 7 days.