| With the development of national economy and constant improvement of people's life, people's demands on the environment become higher and higher, so the application of central air conditioner grows to be abroad. The central air conditioner system improves people's living condition, but it also uses up a lot of energy sources. Actually, most of central air conditioners are controlled separately, each controller can only monitor and control one air conditioner's status, that not only makes against the intellective management, but also wastes of much energy. A few of controller product manufacturers of central air control conditioner tried to use network to control the whole system concentratively, however, mostly, the technology they applied was behindhand, the communication length was not very long, and the number of terminals they controlled was limited.In recent years, the technology of network has become more mature, its security, and reliability have future improved, so we can apply network technology to the control field gradually. In addition, the single-chip technology also develops rapidly, many single chips have the characteristics of multifunction, high speed, low power, low price, big memory and strong I/O, all that make us be able to design low cost remote control system based on single chips, and then apply it to central air conditioner.The main task of this thesis is to develop a concentrative control system about central air conditioner with long-range communication function, which can communicate with control center via Internet, and then we can monitor and control all terminals' status in one building or several buildings. The concentrative control and management can improve the efficiency of central air conditioner, and reduce energy consummation. The whole system uses multi-level distributed control architecture.In stage which connects to Internet, we develop an Ethernet transmit scheme based on ATmegal28 and Enc28j60. It transplants the Microchip TCP/IP protocol stack into ATmega128 to implement remote real time supervise and control by communicating with remote computer.The system expands RS485 bus for data transmission in building to save the cost and reduce the difficulty to design. The terminals aim to control the room's temperature directly, they transmit status data to its upper layer and receive control command by RS485 interface. We make use of visualized programming tools Visual Basic and its Winsock control to develop network application program for the client in remote computer. The paper summarizes the situation of remote control system about central air conditioner in brief, introduces its architectures and functions, and discusses the choice of the whole system scheme in detail, including transmission bus in building, remote transmission method, remote communication mode. The thesis concretely describes the hardware design method and the soft design ideal of each part. Hardware parts design the circuit based on AVR top grade MEGA series single chip, then expand Ethernet interface and RS485 bus interface to transmit data, with some key-display module and other control modules. The soft sections emphasize the method of embedding the TCP/IP protocol stack into ATmega128, design of RS485 communication program, and some keyboard display program. The thesis offers a majority of circuit diagram and some key source program or flow chart, the reliability and the capability of anti-jamming are also described in simple. The client segment describes how to use ADO object to connect and access ACCESS database at length, it also introduces some important properties of Winsock and its technique, so as to develop network program.The application shows that this system runs stably and accurately. The technology and methods adopted in the system are practical and worthy of using abroad, with the characteristics of low cost, good expansibility. Finally, the subject is briefly summaried, and some remarks on further improvement to the system are also presented. |
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