Research On 125KHz Access Control Reader

With the ongoing advancement of urbanization, the construction of large residential areas and office space is increasing. People not only want to have a warmer and more comfortable living environment, but also put a higher demand for security and intelligence. Thus, the security of residential and office space has become the focus of their attention.RFID (Radio Frequency Identification, RFID), also known as RFID technology, is a non-contact automatic identification technology.The technology which utilizes the coupling of electromagnetic signals to achieve non-contact transfer of object information, nowadays, is widely used in access control system and achieves good application results. Those access control systems which are currently popular on the market are based on close-coupled inductor design to identify the distance to certain restrictions; however, there exists various defects in them in different degrees, such as a single communication interface, short distance reader, large power consumption and so on. In addition, companies and users have an increasing demand on the cost, power as well as functions of the product with the development of electronics. Therefore, the development and research of electronic access control systems used in family and office space is increasingly being valued by research institutions and enterprises.As semiconductor technology advances, the integration of chips is higher, their function becomes more powerful, the operating speed is faster and faster. Selecting High-performance MCU to replace the existing low-end MCU to develop products has become inevitable. The traditional access control readers mostly employ low-end MCU, and use radio frequency chip to operate on the label, resulting in that a major breakthrough cannot be achieved in the stability of performance.The project is designed to overcome deficiencies of the traditional access control reader in cost and performance, to decode software on the label information with the use of MCU high-speed processing capability, and to develop a low-cost,high-stability access control reader mainly for residential quarters and office space.The main contents of this paper are as follows:(1) Analysis of the current situation and the shortcomings of existing access control readers;(2) Taking EM4001 card as an example to introduce the structure of read-only ID card and the means of communication between the card and the reader;(3) The design of system hardware, including chip selection, functions of the selected chip and reasonable design of chip peripheral circuits. The main contents include:design of minimum system chip circuit design, of power circuit, of the detector circuit, of antenna driver circuit and of keyboard circuit; completion of the printed circuit board (PCB) design;(4) The design of system software, including the software plan of the system, a detailed analysis showing design of software decoder of Manchester coding label information as well as the communication protocol between the host computer, and the flow chart of this design.Finally, the paper summarizes the full text and makes a number of issues which need further study.