Design And Realization Of Digital Electronic Compass Based On The Chip Of AVR

Along with the development of sience and technology,the areas of activity of human are expanding, so compass as an important navigation equipment is becoming an indispensable part of transportation device. On the navigation, people main installed gyro compass on ship. Compared with magnetic compass, gyro compass has the advantages of stable point and the efect from enviroment is small, but scince the structure of gyro compass is very complex, it is easy to product faults and maintenance costs is very high. So under normal circumstances, although we installed gyro compass, we also need a magnetic compass, so we also can goon navigation on the help of magnetic compass when the gyro compass is not working. In addition, the magnetic compass can pass the signal of direction of navigation to radar and the system of electronic navigational map, constitute a magnetic navigational system with other navigation equipments. The characters of high accuracy and low cost make magnetoresistive electronic compass to the best choice for auxiliary equipment of gyro compass.On the basic of brief the development direction of magnetic compass and the magnetic measuring principle, this paper introduced the design of a digital electronic compass, its core is AVR single-chip microcomputer,and used magnetic component HMC1022, which is a two-axis magnetoresistive sensor producted by the company of HONEY WELL. In the compass system, according to the character of output signal of sensor, we choose AD7705 as the acquisition module of output data of sensor. AD7705, producted by ADI company,has 16 duble channels differential input. Used the unique function of SET and RESET of magnetoresistive sensor, we effectively eliminate the error caused by common signal such as temperature drift and circuit parameters drift. Through programing AVR single-chip mega64, we realized digital filtering and course angle calculating. This compass does not only display the course angle data on digital, but also has a RS232 serial port, wich can used with other navigation equipmetns, such as radar and electronic navigation map.Developed a digital compass system prototype, and made debugging. As the experiment show, the electronic compass can realize the dynamic measurement, and in the range of 0~360°, the course angle measurement accuracy can up to±1.5°. The designed digital electronic compass has the charater of small size,simple structure,quick start,low power consumption,and so on. In the field of aviation,marine,vehicle navigation,as well as in areas such as handeld devices, it has a wide application prospect.