| Rapid economic development and further improvement of living standards, increasing demands of automotive safety and comfort, which promote the development of China automobile industry rapidly. With the development of modern automobile, the level of electronics application has increased year by year. The research and development of foreign automotive electronics started in the 60's, after 70's, the development of integrated circuits and the widespread application of microprocessors had made fast development of automotive electronics products. Nowadays, the application level of automotive electronics has become a significant measure of automotive modernization. The use of electronic technology has become an important point in the competition. So car and electronics become more and more interdependently.At present, foreign automotive electronics productions can be broadly divided into following kinds: Automobile engine electronic control, safety self-diagnosis, information display, comfortable and entertainment products, components, multiplex bus, environmentally products and electric vehicles. The research and development of China's automotive electronics product began in 1981, developed slowly in the last two decades. The products were, electronic fuel injection systems, engine control system, automatic transmission, automotive electronic instruments, anti-theft alarm, recorders and so on. However, in general, a number of high-tech products still remain at the level of the laboratory prototype, commercialization ones are some of conventional and small electronic products. But most of them aren't uniform standards or high-tech. The development of the automotive industry promoted new automotive electronics of China. Experts believe that China is the largest potential automotive market in the world. With the development of semiconductor technology, more and more transistors, IC, memory, microcontroller, will be widely used in the automotive electronic equipments. At present, China's automobile industry is developing towards high-performance, comfort, safety, energy saving, pollution prevention. Which indicates that e-technology products in automotive is approaching the climax.Because of the development of the automotive industry, appear more competitive. Providing comfortable and humane care products became the goal of an increasing number of automotive manufacturers. A seat with heating function is such a product, which makes people feel warmer in cold winter. Seat heating device has been developed for more than three decades, the research of relevant technologies and the necessary equipment has been gradually maturing. A complete manufacturing process and technical standards for security have long been formed. While in China as a new concept it just began to be received attention and began to be applied, the research of its system is far from enough. Seat heating system means the electric heating devices in seat, and the electric heating device is provided with adjustable temperature function. Its self-governed circuit design and protective devices will not affect other functions. The seats can make the drivers warm and comfortable in winter. This technology has been applied in the market and had a good market prospects.In this paper, design a PIC12C508A-based seat heating system, it can automatically stabilize the temperature at the desired temperature. The drivers can set the heating temperature with switch, the control signals were sent to the PIC microcontroller, and according to the input it will output differently, in this way to set up the different heating temperature. In addition, in the system a NTC sensor was applied. According to the different seat heating temperature resistance of NTC sensor changes, so that its partial voltage changes correspondingly, compare this voltage to the one that PIC output by a voltage comparator. If the temperature has reached the settings value, the comparator output low voltage, the system stopped heating, so that the temperature automatically stabilize function is achieved.The system was made up with two key components: hardware design and software design. In Hardware aspect, the design principles are system stability, reliability, speed, accuracy and power consumption. In accordance with the requirements of the performance of the system choose appropriate microcontroller, furthermore design the specific analog circuits of the various parts. In view of the functional requirements of the system, PIC12C508A was applied as the core chip in hardware design. It can be capable of the performance requirements of the system. In accordance with the requirements of temperature, a NTC (negative temperature coefficient) sensor was used. This is analog circuit and source of control information in the system, it provides the temperature signal. In temperature range NTC sensor is non-linear, so it must be optimized, thereby enhancing the system temperature measurement accuracy. The system also includes other hardware circuit, pressure circuit, comparison circuits, protection circuits, etc. In this paper, the various parts of the circuit have been made a specific analysis and design respectively.In computer control systems, software and hardware are equally important. In order to facilitate debugging, modification, addition and deletion, modular design is used in the system software preparation. That is, the entire control software formed with independent modules which were connected with software interface. The main work of system software program is initialization. And then wait for the control signal, if the signal is an effective control signal then read the setting temperature and generate a corresponding control output to achieve the purpose of heating seat. This paper analyzes the general requirements for software design and system software needs analysis. Based on the analysis, the program was achieved ultimately. Also the role of each module was explained in detail. Temperature control plays an important role in industrial production and every aspect of our daily life. This paper completed a PIC microcontroller-based seat heating system, which including system design, microprocessor control system, hardware design, software programming, debugging and simulation. |
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