| Electronic White Board is a hi-tech product assembling advanced electronic and software technology. Aid by a computer and a projector, it can help realize the office paperless with the employment of wireless location technology and electromagnetic induction principle. Electronic White Board is developed from ordinary white board. It is a short time for it to achieve such a dramatic development.Since first developed in Canada in 1991, it has been accepted generally. It is the Electronic White Board that will bring the information reform in education sector. It's popular with the users because of its merits of being pollutionless, interactive and multi-media. The problem of capturing and saving the characters and figures was solved when it come out. It can save handwriting on board in the computer, helping the students attending class and the staff at meeting out of making notes. That's why it is widely used in European countries and the U.S.Now, there are the scanning Electronic White Board, the touching Electronic White Board, the Electronic White Board based on wireless location and laser Electronic White Board and so on in America and Europe. The scanning Electronic White Board can capture handwriting on board by a figure sensor (such as CCD). Because there is time delay between scanning and writing, it can not track user's handwriting in real time, also, the White Board is big, expensive, it restricts the board's application and popularization. The touching electronic board tracks the user's writing by the pressure the pen posed on the board. Compared with the scanning White Board, it can track the handwriting in real time with poorer precision. The laser Electronic White Board not only can track handwriting, but also has better precision, whereas the system is expensive, besides it is big and cumbersome. The Electronic White Board based on wireless location solves the problems above primely. It can track handwriting in real time and has good precision. It is also small, portable and cheap. Presently, the scanning Electronic White Board and the touching Electronic White Board have been developed inland. It is the DM-4601 of DM Co. Jilin University that fills the blank on the Electronic White Board based on wireless location.The DM-4605 Mini Electronic White Board is another new Electronic White Board based on wireless location after DM-4601. It has the merits of high precision, being portable, pollutionless, interactive and networked. Different from the big White Board, it is designed for personal use. It can also be matched up with big ones to realize the interactive operation and answering questions online in real time through the internet.The DM-4605 Mini Electronic White Board in mainly comprised of four parts: a signal pen, a signal receiver, personal computer and a smooth writing board. The signal pen sends ultrasonic and infrared signal periodically. In location, timing begins when the signal receiver receives the infrared signal which is the time base of the system until two ways of ultrasonic signal are both received by the sensor. Then, the delay time will be confirmed as the delay time of the system. The information of the location will be transmitted to the personal computer. Meanwhile, the location of the signal pen will be ascertained through TOA algorithm, consequently location is achieved.The contents of this dissertation are summed up as follow. In chapter one, the background and significance of the developing of Electronic White Board has been explained. There is a comparison of kinds of White Boards. The function, main parts and the working principle of the White Board have been introduced briefly.In chapter two, the design theory of the circuit is the main focus. Some methods of wireless location and the location algorithm of DM-4605 Electronic White Board have been introduced. What is noise and how to control it is another main point. Sensors have been classified and their features have been introduced, as well as their application in the Electronic White Board.In chapter three, the structure and design of the two main parts of Mini Electronic White Board (signal pen and signal receiver) have been introduced. In chapter four, the working principle of signal pen has been introduced in detail. Based on the former work, the optimization of the hardware circuit and software of the signal pen has been described.In chapter five, the working principle and the improvement of hardware circuit of signal receiver have been analyzed in detail. There are optimization in ultrasonic signal receiver, infrared signal receiver and single-chip outside circuit. At last, the design of the software of the signal receiver has been discussed. In chapter six, the results of test and comparison with other products of the same kind of the Mini Electronic White Board after optimization have been summarized. In chapter seven, the conclusion of the dissertation has been summarized. The contribution and deficiency of the system have been discussed. The main contribution of this paper is listed as follow.1. The sorts of the Electronic White Board and their working principle are summed up. The predominance and significance of the Mini Electronic White Board is introduced.2. The characteristic of the ultrasonic sensor is introduced. Appropriate circuit is chosen to match with it to improve the signal noise ratio (SNR).3. Employed new infrared receiving model, the anti-jamming ability of the system is raised dramatically.4. The size of the circuit board in signal pen and signal receiver is reduced, the signal receiver from to 20mm×115mm from 54mm×145mm, while the signal pen from 20mm×50mm to 9mm×41mm.5. The un-working power consumption is reduced by 96%.There are several problems that needed to be solved on the Mini Electronic White Board based on wireless location.1. Designing a new signal pen to substitute the mouse completely with the right and left click function.2. How to strengthen the system's interference killing feature at the strong noise condition.3. Finding a better algorithm to acquire time delay more efficiently and realize the hardware easier. |
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