Car Air Conditioning Control System Development

As the rapid development of the domestic automobile sector, automobile air conditioning attracts more attention from those manufacturers. However, the control of the domestic air conditions in the vehicle is manipulated in the way of operating the mechanical device manually, which is far below the international standards and hence constrains the automobile industry. Triggered by the growth of electronic tech, information system in the vehicle is widely applied in automobile industry and is now forging in the direction of intelligentizing and digitizing. Information system is a kind of control system which collects the various states when the vehicle is running, processes them and displays and stores the results. There are two trends in its development. For one hand, a vivid interface is provided for the drivers who want to obtain the current states of the vehicles timely. For the other, the states stored in the system are the foundations for the analysis of technicians.This paper proposes a new design of air condition control system based on the M68HC08 microcontroller, which is a series of high-performance 8-bit microcontrollers released by Motorola in the 1990s. These microcontrollers have the characteristics of powerful function, rapid speed, small power consumption, low price and high stability. As the IC technology developed, Motorola introduced FLASH and modular design and thus, a new generation of M68HC08 came into being. In the paper, the author concentrates on the chip of MC68HC908GZ16 whose user FLASH is as large as 16KB among its family.By analyzing the needs from users, we conclude that the system has the following main functions: inner and outer temperatures collection through sensors, sending and receiving information such as car speed, engine turning speed and engine water temperature, by using CAN bus, accepting user's key-pressing commands and displaying working parameters of outer devices by I/O module, controlling the air-conditioning by the compressor module, controlling in-out air looping motor, water valve motor and mode motor by motor driving module, controlling the fan motor and its turning scale through corresponding circuit. Further more, there are three different working modes, namely the auto, the manual and the defrosting, for the clients to choose and switch.The system can work normally, after the debugging work is done and the functions required are implemented. Low-costing and easy-making are the characteristics of the system and more further researches can be deepened on it.