1. introduction
In digital technology, the rapid development of network technology, the access control technology has been developing rapidly.
Access control system already goes beyond the mere doorway and key management, it has gradually developed into a comprehensive access control system. Access control system development in the wake of a single password for keyboard access control system, IC card entrance guard system, contactless IC card entrance guard system, and now the latest biometric access control system. Non-contact IC card entrance guard system because its technology is mature, affordable, easy-to-use, superior performance, has been widely used. A conservatory piano room 14 storey building 300 piano room, has been adopted by the management approach is a student at the piano room Management Center registration reception for the key using the piano room. This management approach there is a lot of drawbacks, such as Student Union secretly with piano room key so you do not register through the the piano room Central Administration uses the piano room without permission, or leave the keys in the returned students cannot guarantee that the piano is no one in the room. But the piano room equipment expensive millions is difficult to determine if there is damage, damage to school property security risk. Therefore to the piano room management creates certain difficulties. In order to reach the piano room scientific and efficient management, this article offers an on-line type of access control system design to whole floor piano room for centralized control and centralized management.2. system structure
This article from the National Natural Science Foundation of China (number: 60472044) and Beijing University of young teachers in natural science research fund (number: QN0518) funding.
System using hierarchical distributed centrally control programmes, will all access control reader to form a distributed network, its composition as shown in Figure 1.
The entire system including the Central Administration Server, floor PC, access control reader three hierarchies.Central Administration Server for the entire access control system of management and control center, at the same time run a piano room management system programs and databases.
The database used to support network communications, database structure, easy for function extension. In order to achieve all the piano room for unified management purposes, the use of the piano room students with student card in the control center through the the piano room management system registration and allocation of the piano room and student personal information into the database. Use to control center through the the piano room management system returned to the room to attendance and queries. Through the management system that can clear the query to each room use, records, etc.Floor PC that access control service, is responsible for access control reader and a bridge between Central Administration Server.
Access control service program for data forwarding function, realization of the RS485 and TCP/IP communication protocol conversion, itself does not directly control access control reader. Up through a local area network with the TCP/IP protocol to communicate with the Central Administration Server, passing the door card reader of the credit card request and the Central Administration of the various control commands to the server. Down by 485 through round homing mode and access control reader interaction information. Records from the access control reader acquisition time of data collection, such as
Figure 1 system chart
Fruit long cannot and Central Administration server address, the time to drop off obsolete card data.
Access control service only with the background data exchange and forward functions, apart from the process is started and stopped, and the user interaction information, design as a Windows system service process is running, without the need for interaction design and user interface, only run the log file.3. access control reader design
System to students of non-contact IC card card as a system user card, contactless IC card is based on the principle of electromagnetic induction, simply place a card in the access control reader induction zone will be able to realize the data exchange, without any contact, use a very convenient, fast, and difficult to damage.
Therefore in the public transport, access control, campus, enterprises and personnel management has a wide range of applications. PHILIPS Mifare card companies are now non-contact IC card mainstream products, their typical model for Mifare S50 1, it has to hold the EEPROM 1K, divided into 16 sectors, each sector has its own separate password, complete security, enable Mifare1 S50 has a smart card. Mifare card is a smart card (smart card), with central microprocessor (MCU) and ASIC, etc. for its security confidentiality, authentication logic, arithmetic operations, such as micro-operation control in an orderly manner [1].1. the principle of work
Non-contact IC card entrance guard reader to radio frequency identification technology as the core, mainly use a Mifare card dedicated read-write processing chip MFRC530.
It is a small, maximum operating distance up to 10 cm of the Mifare card RF base stations with features including modulation, demodulate, produce RF signal, security management and anti-collision system. Internal structure is divided into radio frequency area and interface: RF zone contains the modem and the power supply circuit, connected directly with the antenna. Interface areas and MCU port connected with RF area linked to transmit/receive, 64B data buffer, storage 3 set register initialization file of EEPROM, holds 16 sets of keys for a write-only memory and three authentication and data encryption password mechanism, anti collision handling of anti-collision module and control unit. This is the RF card for wireless communication of core modules, it is read-write Mifare card key interface [2].Access control reader, and Mifare card dedicated card chip connected to the antenna coil MFRC530 constantly to a set of fixed frequency of electromagnetic waves (13.56M), when the non-contact IC card close to the card includes an LC Series resonant circuit, their frequency and the reader of the same frequency.
This-Like in electromagnetic wave excitation, resonant circuit produces resonance, so that the capacitor charge taken as a result of charge. The other end of the capacitor, and a one-way conductive e pump will charge sent within the capacitance to another within the storage capacitor. When the capacitor charging to 2V, this capacitor is used as power for a card for other circuits provide working voltage, the card data launches out or receive access control Reader for data and save the [3]. This system when a card into the RF antenna induction zone, access control reader read non-contact IC card card number and the card number and credit card in time to the floor at the same time, store them in the PC memory FM24C256, and in the LCD monitor displays the service information. No card to enter the access control reader antenna active area, the MCU read real-time clock chip time and displays the current time and date.2. hardware components
Each access control reader is equivalent to an intelligent nodes, it can finish the door status and lock status monitoring, judgment of card types, real-time monitoring of card action, control electromagnetic locks and alarms, set access codes, and a series of operations.
Access control reader hardware parts mainly include the monitoring and control, sound and light alarm circuit, RS485 interface circuit, storage, clock display section, access control, the settings section, watchdog and the reset circuit, RF base station section. Circuit of hardware diagram as shown in Figure 2 [4].
Figure 2 access control Reader systems
Use STMicrolectronics company (STMicroelectronics) company STC89C53RC microcontroller made MCU, i.e. common MCS, it has good temperature characteristics and stability and price/performance ratio.
Built-in Flash memory and 15 k 512 bytes RAM, with three 16-bit counters, and a standard serial communications port, and has a P4, supports ISP program download.Access control, set the circuit using 8-bit into conspiracy out shift register chip 74HC165 with two 4-digit dial switch form the 8-bit set access number unit.
System power after the 74HC165 are parallel data to the serial transfer method sends to the MCU as 485 network address of the machine ID number.RF base station partly by the Philips company MFRC530 chip, MFRC530 is and RF card for wireless communication of core modules.
It according to the register set to send the data in the buffer are sent to the modem, through the TX1, TX2 pin driver's antenna to send to the form of electromagnetic waves, non-contact IC cards using RF field load modulation to respond. Antenna picks up non-contact IC card response signal antenna matching circuit to the RX pin, MFRC530 internal receive buffer on signal detection and demodulation and according to the register set for processing. The processed data is sent to the data bus waiting for MCU reads. MCU and MFRC530 adopts SPI bus ways to communicate, and non-contact IC card data wireless transmission.A card into the induction area credit card is required to record the time card, available external hardware real-time clock chip approach to system provides an accurate and reliable clock, 3V battery guarantee system blackout when normal timekeeping.
This design choice the volume small, the interface is simple, real-time clock chip DALLAS DS1302, is the United States the company launched a low-power serial communication interface chip, using the 3-wire serial and single chip for data communication: SCLK as clock input, SDA as serial data input and output, RST as communication allows signal. Its internal register address 00H ~ 06H corresponding storage of seconds, minutes, hour, day, month, week and year information in the register, a write-protected 07H control registers, 08H control registers for battery charging. Clock data to the format stored in the BCD code 00H ~ 06H these seven registers.System storage section with RAMTRON INTERNATIONAL Corporation produced a ferroelectric memory (FRAM) is a 256kbit FM24C256, fram, memory was logical organization of 32768 8 bytes of storage mode, the address space is 0000 ~ 7FFFH.
The bus frequency up to 1MHz, with 10 million times more read and write times and low power consumption, and the external interface uses the industry standard for IIC bus. Because of the MCU does not have the IIC bus interface, therefore adopts the P2.3 and P2.4 mouth line to simulate the IIC bus, the SDA and SCL FM24C256 as open drain output, it received 10 k Ω with pull-up resistor.Monitoring part real-time monitoring doors, lock status and communicate status and to long exception state make alarm; control section is primarily responsible for the implementation of the various control host computer information, such as the implementation of the lock, execute alarm; LCD display section selection to ST7920 as controller of 1286 LCD with Chinese fonts to display time, date, and various service information, as the human-computer interaction interface.
In order to prevent outside interference, the system selects MAXIM company MAX813L as System Hardware watchdog.3. software design
Access control reader programs include: MFRC530 on Mifare card operation procedure, MCU and MFRC530 communication interrupt handler, 485 communication interrupt handler, read-write clock and LCD display program, access control, program, test the door and lock state programs and memory read and write program.
The main program the flowchart shown in Figure 3.On the operation of the process is a very complex program execution, internal to the MFRC530 a series of registers to be configured, but these operations are very strict on time.
On non-contact IC card of typical operationsBy: Alex card (card type code), anti-collision (card number), the selected card, verify the password, read and write operations, pending and which must be performed by a fixed order. Because access control Reader only need card card number and only perform the search cards, anti-collision, hangs you can meet the requirement, on the card type judgment after the card number through the floor of the PC is sent to the server from the server to determine if the card is legitimate. In the absence of the card into the RF antenna effective range, the LCD displays the current time and date, when the card into the valid range of RF antenna, the card number is displayed on the LCD and display a "Please wait ...", and other service information.
Figure 3 access control Reader main process
4. concluding remarks
This article will RFID theory applied to the access control areas, the use of multi-layer network system structure and proposed a MCU core, combined with the RF base station MFRC530 and microcontroller peripheral circuits of non-contact IC card entrance guard reader hardware and software design.
Door control system has been successfully applied to music school of piano room management system. Practice shows that the system runs stable, the real good.Reference documents:
[1] Wu Yong Shyang. radio frequency identification technology (RFID) research and development prospects [J]. a micro-computer information, 2006, 11-2: 234-236
[2] Philips semiconductors.mifare MF RC530 ISO14443A IC Reader.
Philips Corporation .2002[3], Huang Wei Li is, Mr. Guo. non-contact IC card read-write module MFRC530 works and application [J]. in electronics, 2003, 6-2: 159-162
[4] Sun yingdi, Zhang jingmin, preferable a MF RC500 's mifare1 card reader of the design and implementation [J]. a micro-computer information, 2006, 2-2: 6-9
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