Access control management system based on RFID and Web services

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, it is no longer limited to simple management of door locks or keys, but a new modern security management system that integrates automatic identification technology and modern management technology, and has become an extremely important part of the security system. It is widely used in intelligent buildings, offices, hotels and other places. At present, the main control methods of access control systems include: fingerprint recognition, face recognition, iris recognition and radio frequency cards. The first three methods are all biometric technologies, which use the characteristics of certain parts of the human body as identification carriers and means. Their uniqueness and non-replicability determine that they are the safest identity verification methods, but they are expensive and difficult to popularize. When it comes to personal privacy, it is only suitable for high-end and absolutely confidential places.

RF card is a product that combines wireless radio frequency technology and smart card technology. It has the characteristics of simple use and convenient maintenance.

In order to improve the modern management and remote monitoring capabilities of the access control system, an access control system based on Web technology is introduced. The system uses wireless radio frequency technology. When a non-contact IC card appears within the radio frequency range of the reader/writer, it reads the card and transmits the information to the server through serial communication for related data processing, and builds a management platform based on C/S mode. , the administrator can query and control the access controller through the Web page, thereby effectively realizing real-time monitoring of information anywhere on the Internet.

1 System architecture

The system uses non-contact IC cards and uses radio frequency identification technology RFID (Radio Frequency Identification Technology) to detect the IC card. When the IC card is close to the reader/writer, the reader/writer can accurately identify it and send its serial number to the main controller. and PC, connect to the background database through the application to obtain the user information corresponding to the card number.

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, access will be prohibited and the cardholder will be informed to leave.

The system consists of five parts: electronic tags, readers and writers, serial communication, servers and user terminals. As shown in Figure 1. The reader/writer is the core of the system. It communicates with the IC card (electronic tag) through radio frequency signals to complete the work of reading the card, storing and sending data. It can work independently or networked. In this article, RS232 serial port communication is used to connect to the server. .

The C/S structure is adopted between the server and the client. The connection between the application software and the database SQLSERVER2000 is realized through the ADO object, and the two are interconnected through the LAN. With permission granted by the system administrator, users can query, count, and print all relevant records of the management system.

2 Hardware design

2.1 Overall hardware design

The RF reader is the core of the system, consisting of a main control circuit, a RF read-write circuit, an antenna coupling circuit, an antenna and other circuits. It is responsible for the processing of RF signals and data transmission, and completes the task of reading the IC card serial number. as shown in picture 2.

The electronic tag, that is, the radio frequency card, consists of an IC card and an induction antenna, and is packaged in a standard PVC card. The chip and its antenna do not have any exposed parts. The card does not require power. When it is close to the reader within a certain range, the data is read and written through the transmission of the antenna. This article uses Philips' Mifare1 card, which is based on the ISO14443TYPEA international standard. Each card has a globally unique serial number and has an anti-collision function.

The function of the antenna is to generate magnetic flux, provide power for the card, and transmit information between the reader and the card. The effective electromagnetic field range of the antenna is the effective working area of the system.

The reading and writing chip selects the special chip MFR500 produced by Philips for reading and writing Mifare1 cards, and the working frequency is 13.56MHz.

The main controller is composed of AT89S52 microcontroller and its peripheral circuits. It is responsible for controlling the read-write module, serial communication with the PC, and control operations of external devices. Among them, the operation of the read-write module by the microcontroller is to realize the operation of the Mifare1 card by controlling the MFRC500.

It is a bridge for data transmission between microcontroller and IC card.

2.2 RF circuit design

The core of the radio frequency circuit is the read-write chip MFRC500, which is the bridge for data transmission between the microcontroller and the IC card.

The microcontroller adopts interrupt control mode for the read-write chip, and the interrupt control port INT0 is connected to the IRQ pin of MFRC500. There are 64 registers inside the MFRC500. The microcontroller configures and operates it by writing control commands into the registers. The power-down detection pin RSTPD is connected to the P2.0 pin of the microcontroller, the NCS pin is connected to the P2.7 pin, and NWR and NRD are connected respectively. Connect to the WR and RD pins of the read-write port of the microcontroller. The data ports D0~D7 are connected to the P0 port of the microcontroller. The quartz crystal oscillator generates an operating frequency of 13.56MHz. The low-pass filter composed of L1, L2, C5, and C6 is used to suppress the crystal oscillator circuit at the same time. The higher harmonics produced. The receiving circuit is composed of R1, R2, C3, and C4. It uses the VNID potential generated internally in the MFRC500 as the input potential of the RX pin. In order to reduce interference, the VIND pin is connected to a capacitor C3 to ground, and a branch must be connected between RX and VNID. voltage regulator (R1), it is best to connect a capacitor (C4) in series between the antenna coil and the voltage inverter. For better performance, these components should be placed close to the MFRC500 chip antenna pins RX, TX1, and TX2 when routing the circuit board.

2.3 Antenna circuit design

In order to obtain stable and reliable radio frequency signals, the performance of the antenna is crucial, which directly affects the range and sensitivity of the reader. The performance of the antenna is related to its quality factor Q, which is related to the geometry, size, number of turns and other factors of the antenna.

The system is designed for a close-coupled IC card. The PCB antenna is used for antenna production, that is, the antenna circuit board is made directly on the PCB board. This method has better stability.

When the antenna is connected to the read-write chip, an additional matching circuit is required. As shown in Figure 4. The system made a rough estimate of the antenna and changed the capacitance value of the matching circuit to achieve the best reading and writing distance.

3 Software design

The system software includes two parts: the lower computer and the upper computer management system. Among them, the lower computer uses the AT89S52 microcontroller as the core to realize reading of the reader, access control and serial communication. The programming language used is C language, and the compiler is KeilC51. The host computer management software runs on the server, using Visual C++6.0 and SQLSever2000 for system management and database development, including serial communication, monitoring management and information release. The monitoring and management software is used to implement user registration, record query, deletion and other tasks, and information release is used for administrators to view access control log records through web pages.

3.1 Lower computer software design

The software runs on the microcontroller and completes reading of card numbers, control of door locks and ancillary circuits, and serial communication. The flow chart is shown in Figure 5. The core of the software is to realize the communication between MFRC500 and Mifare1 card. The communication must follow the ISO14443TYPEA standard transmission protocol. The card reading process must be carried out in strict accordance with the fixed sequence, that is, reset response, anti-collision card selection, authentication and reading and writing cards. Since the card is readable, you only need to read the serial number of the card and do not need to write to the corresponding sectors, so the authentication step can be ignored. The main code is as follows:

3.2 PC software design

In the VC++6.0 programming environment, the CSerialPort class is used to implement serial communication, receive the sent IC card serial number, and then access the database through ADO technology to obtain the user information corresponding to the card for verification processing.

The system is based on SQLSERVER2000 for database development. Administrators must enter their account and password to enter the system to prevent non-system administrators from illegally logging into the system. Afterwards, the administrator can complete the registration, query, modification and deletion of card number information, and record the visit information (user and passage time) in the database for data statistics and query. The functional modules of the monitoring and management software are shown in Figure 6.

The information publishing module is implemented based on ASP.net. The implementation process is mainly to read the monitoring and management information table of the SQLServer database through ado.net, create an information publishing website and deploy it to the IIS server. In this way, users can access web pages at any location. View system information and access control records.

4. Program running

Taking the laboratory access control management of the School of Electronic Engineering of Guilin University of Electronic Science and Technology as an example, the software and hardware design of the system was realized. After the administrator enters the account number and password, he enters the main interface of the monitoring and management software as shown in Figure 7.

After testing, the effective working distance of the IC card is 6cm. When the IC card responds, the system automatically displays the card number, card user information and entry time, and automatically Stores them in the background database. Since the Mifare1 card has a globally unique serial number, member information can be bundled with the IC card serial number and stored in the database when members register. In this way, when checking information, you can search accurately by time or directly by name.

  5 Conclusion

The proposed access control management system based on RFID and Web services provides intelligent control and remote management mechanisms for the access of important departments. It uses wireless radio frequency technology RFID to achieve keyless access, which is not easy to lose and can be reused; it uses SQL database and Web services to achieve remote monitoring of access control, which is easy to operate, flexible and safe. It has broad applications in smart homes, office access, logistics and other occasions. Application prospects.