Password retrieval system

I needed a reliable, low-cost access control solution for my home lab, so I built an Arduino-powered keypad lock that talks to a Windows app. When you enter the 4-digit code, the system instantly lights a green LED or red LED to show success or failure—and sends the same status back to the PC over a serial link.Designing both the firmware and the C# interface taught me how to handle real-time input, clean up serial data, and give users clear visual feedback. I also added logging so every attempt is recorded on the PC.Now, this modular setup can be adapted to any door, cabinet, or gadget that needs simple PIN protection—no expensive controllers required. Just plug in the Arduino, pick your COM port, compile the app, and secure your space in minutes.