Hardware Design Of Transmission Visibility Measurement Based On WSN

The measuring elements of the transportation meteorology consist of wind direction, wind velocity, precipitation, pressure, temperature, humidity, visibility, and so on. The visibility has the most important impact on traffic safety, traffic accidents caused by the poor visibility on the highways is becoming serious nowadays. The intelligent transportation systems usually transmit the meteorological informations such as visibility to highway management control centers through the optical networks, so that the real-time control to the vehicles can be undertaken. And the highway management control centers make the decision that whether it is necessary to shut down the highway to reduce the accident rate according to the weather informations.If the cable networks is used, it needs very long cables and high cost of cable laying, which is easily destroyed by thunder and humanbeings.As the development of the integration of the telecommunication techniques, controlling techniques and monitoring techniques, the wireless communications and the unattended solutions are used more and more in many fields. The Wireless Sensor Network (WSN) transmits the detected datas from the wireless coveraged area to the data aggregation nodes or the host computers in wireless ways. This artical first elaborates the theory of the measuring of the atmospheric visibility, and then proposes a new transmission type method of measuring the visibility based on the wireless sensor networks. This system uses the chip CC2430 as the core of control, data process and communication. It consists of the measuring nodes and the wireless communications, including transmitting module, receiving module and signal processing module. In the measuring node, the photoelectric sensor 2CR1133 is used to detect the optical signal which reflects the visibility status. Meanwhile, the communication is carried out by the wireless sensor networks to transmit the communication and control signals between the host node and the receiving node. So the real-time monitoring of the visibility of the highways is realized. Temperature detection module is added to realize the temperature compensation to reduce the measuring errors because the laser semiconductor and photoelectric detector have futures of temperature affected obviously by the temperature.The innovation of this artical is that it first combines the transmission type measurement principle and the wireless sensor network technology. The transmission type measurement principle realizes the full monitoring of the changes of the highway visibility. The wireless communication solution reduces the cost of the whole system, while ensures the reliability of the communication system. The system reserves some microprocessor I/O interfaces to meet the further extensions of fonctions, which makes the system more flexible and more adaptable.