| Wireless Sensor Network (short as WSN) is a bran-new technology using for data collection and management, it integrate four important technology as sensor, embeded calculation, network and wireless communication. It could cooperate real-time monitoring, apperceive and gather data in different kinds of environment or from different monitor object, and then manage the data, transmitted to the place which need it. The development of the wireless sensor is not only the development of thchology but also the demand of application. As a new area, WSN has very broad application prospects, and brings heighly regard of academe and industry. In recent years, WSN has a great development in the area of intelligent household. WSN could be used in different area, such as construction status monitor, space search, maintenance of complex machine, management and monitoring of traffic system, data gathering of public project.Here we focus on the application of WSN used in water meter, and design a long-distance transmission water meter based on WSN.Energy consume water meter will use much energy when collection data. The main proper of the design is to solve the problem. The former energy consume water system is very complex, and has some hidden trouble. It impacts both the economic benefit of the department which provides the energy consume water meter, and the social visualize. The design of the data collection system will solve the problem effectively, and show it's advantage in every respect.Ⅰ.Hardware DesignWe focus on the design of the water meter node here. Water meter node is composed by some units as follow: center processor unit, sensor unit (water meter basic board), frequency emission unit and power supply unit. The design adopts the ultra-low power MSP430F149 chip from TI company as the center processor unit; CC2420 chip which meets the standard of IEEE802.15.4 as frequency emission unit, the chip include many extra function, it is the first high-integration industry transceiver chip meets the ZigBee technology; we choose the intelligent long-distance water meter form Ningbo water meter factory. Center processor unit is Single Chip Micyoco and is the smallest system, it control the entire system. Sensor unit (water meter basic board) achieve the measure function mainly—to measure the value of water flux, and then send out the metric value by inner circuit. Frequency emission unit is used to receive and transmit wireless signal. Power supply unit is to supply power to all of the units.Dividing the hardware design into five parts—data collection part, valve part, anti-disassembly part, voltage check part, frequency emission part. The water meter fetch out 14 lines, we connect them direct or indirect to the Single Chip. The Single Chip gets the water flux value and all kinds of states from water meter by controlling the lines, and controls the switch of the valve. The frequency emission part adopts official classical circuit and special PCB antenna.PCB of the hardware has already been accomplished, and approved that the all parts of circuits could operate normally by experiment.Ⅱ.Software DesignBecause of the particularity of the sensor network, it has big difference between sensor network and traditional operation system in the demand of operation system. Here we adopt TinyOS as the imbedded operation system of sensor node, TinyOS is designed by California University which meets the characteristic and requirement of modern wireless sensor, it realized the function of data collection, communication between nodes, basic board control, found and maintain of routing.TinyOS is written by C language and assembly language at the beginning. But later the designer found that C language is not effective and expediently. It can not sustain the exploitation of apply and operate system which face to sensor network. So they improve the C language, bring forward nesC language which sustains module program, band together subassembly,module design and execute model based on event driven.ⅰBasic Hardware Control PartThere are three programs in the basic hardware control part. Frequency receiving program,data collection program and basic board control program. Frequency receiving program is focus on the programming of frequency transceiver chip CC2420. By writing the data into the register of chip CC2420 to control it. Data collection program is serial communication program between single chips. We visit the single chip of the water meter base on the protocol provide by the water meter factory, by the manner, we get the water flux value form the inner of the water meter. Basic board control program mainly indicate valve control program,voltage detect program,warming program and so on.ⅱRouting PartThe detection and maintain of routing is a core technology of WSN, which is responded by network layer. The mainly task is set up route between sensor node and sink node, transfer data reliably. The mainly characteristic of WSN is limitation of resource, so the most important principle of route protocol is saving energy, prolong the subsistence period of the network system. Route protocol is the soul of WSN, we study all kinds of the WSN protocol in existence, then designed a water meter system as the route protocol.After a lot of investigation and research, careful planning and repeated practice seriously, designed a long distance meter reading system based WSN. The wireless meter reading system adopts an advanced wireless transciver modules and reliable transmission protocol, reading data rapidly, accurate, easy-to-use, low cost and is suitable for urban estate construction, it has broad market prospects.Wireless meter reading system is a kind of wireless network and is closely related to the practical application environment, develop products suitable for the actual situation, it is the key whether the system can be widely used in the market and survive a long time. With the WSN technology gradually mature and the development of computer communication network, the wireless meter-reading system will be more mature and practical. |
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