In this DIY guide I will show you how to make your own security check system based on Arduino! This project started out as a Bachelor's thesis by me - John Vasilakis (supervised by Grigoris Tziallas) - Electronic Engineering Department of Stereas Elladas University. We are supporting the open hardware - software community so this project will be marked as an open-source. Before share/copy/change anything of below guide, make sure to read and agree with the ​CC BY-NC-SA licence agreement! We used the RFID technology to read scanned card and the RS485 electrical data bus protocol for communication. In this project I decided to make my own PCB that is based on Arduino UNO microcontroller - Atmega328p. We can have up to 254 slave-check point stations and one master station in the RS485 data bus. The master station is communicating with one computer in security room via serial USB port. We will describe the communication protocol in the following steps! https://www.ardumotive.com/arduino-security-check-system-en.html