RFID access control system

Access control system, also known as entrance and exit control system, is a system that manages and controls the entrances and exits of important areas or passages. With the development of society, a new modern security management system that integrates automatic recognition technology and modern management technology has become an extremely important part of security prevention systems and is widely used in intelligent buildings, offices, hotels, and other occasions. At present, the control methods of access control systems mainly include fingerprint recognition, facial recognition, iris recognition, and radio frequency cards. The first three methods all belong to biometric technology, which uses the characteristics of a certain part of the human body as the identification carrier and means. Its uniqueness and non replicability determine that it is the safest identity verification method, but it is expensive, difficult to popularize, and involves personal privacy. It is only suitable for high-end and absolutely confidential places.

In order to improve the modern management and remote monitoring capabilities of access control systems, a web-based access control system is introduced. The system adopts radio frequency technology. When a non-contact IC card appears within the RF range of the reader writer, the card is read and the information is transmitted to the server through serial communication for relevant data processing, and a management platform based on C/S mode is constructed. The administrator can query and control the access controller through the Web page, thus effectively implementing real-time monitoring of information from any location on the Internet.

System Architecture

The system adopts a non-contact IC card and uses RFID (Radio Frequency Identification) technology to detect the IC card. When the IC card is close to the reader, the reader can accurately recognize it and send its serial number to the main controller and PC. The user information corresponding to the card number is obtained by connecting to the backend database through the application program. If the card has been registered, it will be verified and the controller will be notified to open the door, and the card number and opening time will be recorded. Otherwise, passage will be prohibited and the cardholder will be informed to leave.

hardware design

The RF reader is the core of the system, consisting of a main control circuit, RF reader/writer circuit, antenna coupling circuit, and antenna circuit. It is responsible for processing RF signals and transmitting data, and completing the task of reading IC card serial numbers.

RF circuit design

The core of the RF circuit is the read-write chip MFRC500, which serves as a bridge for data transmission between the microcontroller and IC card.

Antenna Circuit Design

In order to obtain stable and reliable RF signals, the performance of the antenna is crucial, as it directly affects the operating range and sensitivity of the reader/writer. The performance of an antenna is related to its quality factor Q, which is influenced by factors such as the geometry, size, and number of turns of the antenna.

software design

The system software consists of two parts: the lower computer and the upper computer management system. The lower computer is based on AT89S52 microcontroller, which realizes the reading of the reader/writer, control of access control, and serial communication. The programming language used is C, and the compiler is KeilC51. The upper computer management software runs on the server and uses Visual C++6.0 and SQLSever2000 for system management and database development, including three parts: serial communication, monitoring management, and information publishing. The monitoring and management software is used to implement tasks such as user registration, record query, and deletion, while information dissemination is used by administrators to view access control log records through web pages.

Lower computer software design

The software runs on the microcontroller and completes the reading of card numbers, control of door locks and accessory circuits, and serial communication. The software core is to achieve communication between MFRC500 and Mifare1 card, and the communication needs to follow the ISO14443TYPEA standard transmission protocol. The card reading process must strictly follow a fixed sequence, namely resetting, responding, anti-collision, card selection, authentication, card reading and writing.