Design And Application Of Wireless Temperature Transmitter Based On ZigBee Technology

In recent years, wireless networking has become one of the rapidly developing hotspots in the industrial control field. It is also the new growth points of the future industrial automation products. The costs of wireless networks, in the configuration, installation, modification and expansion, is lower than wired one. Because of the technical, the wireless signal will produce dispersion, multipath delay, interference, attenuation and other issues in the transmission process. But these problems may be overcome or reduced by using appropriate mechanism in wireless communication protocols. Therefore, once the core of the problems in wireless transmission, such as transmission of certainty, interoperability, network security, has been solved, wireless communication technology will achieve universal in the field of industrial control applications.The current wireless network technology applications, in the field of industrial control, focus on short-range wireless networks and wireless local area network. Automation industrial manufacturers concerned more about the short-range wireless network, which is suitable for field device layer in wireless networks. Currently, the mainstream technology is 802.15.4/ZigBee. ZigBee has high reliability in data transmission, high real-time performance, low power consumption, flexible networking, etc. Compared with the new terms of the Wireless HART protocol, ZigBee, as a mature one, has more support in the industry and is easier to be implemented.In the thesis, the 4-20mA temperature transmitter of SAIC is available for study. Through the researching in power, network, protocol and other aspects of ZigBee technology, the wireless temperature transmitter and the wireless communication interface card has been developed. The monitoring and diagnosis to the temperature transmitter through the ZigBee wireless network, by SUPMAX800 control system, has been achieved.In the process of the study which is based on the wireless temperature transmitter’s features and technical specifications, a few key problems and technical difficulties has been solved. In the aspect of the power management, the high-energy lithium battery has been used, the circuit of voltage detection has been designed, including the automatic detection and alarm by the 1-wire bus. In the aspect of the application layer encapsulation, the parameters of the instrument has been mapped to the register of the MODBUS protocol, which is compatible to SAIC’s interface product of the MODBUS protocol. It is convenient to access the wireless transmitter through the DCS system and the monitor interface. In the aspect of the circuit design, the ultra low power chip, MSP430 produced by TI, has been selected as the core CPU, the ultra low power chip, AD7794, has been selected to accomplish the data collection from the temperture sensor. In the aspect of the design of wireless communiction protocol, the use of IP-LINK module of Helicomm implements the ZigBee circuit and the protocol stack. The issues of establishing and maintaining ZigBee network nodes and network equipment has been studied. Several prototypes have been developed, and the ZigBee wireless network has been formed through the SUPMAX800 system.