Design Of Distributed Control System Of Central Air-Conditioning Based On Ethernet

With the rapid development of economic, many high buildings are built. It makes the widespread use of the central air-conditioning. Though central air-conditioning makes people comfortable, it consumes a large amount of resources. The data shows, the energy consumption of the central air-conditioning can be more than half of the energy consumption of the whole building. So, energy-saving of the central air-conditioning is very necessary.Most of central air-conditionings are controlled separately, each controller can only control a single unit of one central air-conditioning. In order to open or close all the units, we need to operate one by one. And we can not know the status of the whole central air-conditioning. That is not conductive to intelligent management system, and also waste a lot of energy and manpower. With the rapid development of the single-chip technology and the improvement of the network environment, it creates the conditions for the design of our central air-conditioning control system.The main task of this paper is to design a central air-conditioning control system with long-distance communication. The system is divided into four parts:the end, hubs, repeaters and control platform. On the one hand, the end can collect the room temperature and the status of the central air-conditioning, and send the data to the control platform through the hubs and repeaters in order to know the overall operational status of the central air-conditioning. On the other hand, control platform can also send commands to the end to change the status and set temperature through repeaters and hubs in order to achieve centralized control of the central air-conditioning. If the set temperature is too low, the central air-conditioning control system we designed can modify the set temperature to prevent unnecessary waste of energy. It can also be time-off to prevent the situation that the central air-conditioning is on for the whole night. It can improve the efficiency of the central air-conditioning and save energy. The end and the hub are connected through RS-485, and it is also between the hub and the repeater. RS-485 can save the cost and reduce the design difficulty. The repeater and the control platform are connected through Ethernet. Ethernet can achieve long-distance communication. This paper briefly introduces the development of the central air-conditioning control system, describes the structure and function of the whole system, introduces the end, hub and repeater, describes the basic structure of the control platform in detail, describes the process of producing the setup with Setup Factory, introduces the process of designing ACCESS database and the method of visiting ACCESS database with ADO objects in Visual Basic, introduces some knowledge of the Ethernet, Ethernet controller ENC28J60 and properties of the Winsock.The system is stable in practical applications, it can meet customer's requirements, but need further study on reliability and the function of the control platform. Finally, the paper summarizes the work and makes the prospect.