An Intelligent Climate Collector Based on CAN-BUS

Transcription

1 Vol. (AITS 0), pp.- An Intelligent Climate Collector Based on CAN-BUS Yujia Zhu, Dong Sun, Shuangquan Li * Automation School, Harbin University of Science and Technology lshq@hrbust.edu.cn Abstract. This article has developed a new intelligent climatic collecting device based on the CAN-BUS, the device not only can achieve the meteorological elements of signal collection, processing, storage and other functions, but also can with other CAN nodes and the upper machine make up the CAN-BUS remote controlled system. The device adapting to the modern meteorological equipment to the general trend of the development of networked and intelligent. Keywords: CAN bus; meteorology element; software; collector Introduction Accurate and reliable meteorological observation data is very important to improve the accuracy of forecast. Modern meteorological service puts forward higher requirements on comprehensive meteorological observation, existing automatic meteorological station, there are serious shortage in observation ability, the technology is relatively backward, functional and specifications are not unified, this situation led to the emergence of a variety of type. In order to further improve the stability of the meteorological observation and automation level, satisfy the needs of the climate collect for the basic meteorological data, we should consider it comprehensively observation acquisition system stride forwards advanced intelligent instrument,intelligent climate collector includes acquisition, ope ration,storage of meteorological elements signal, and through a variety of communica tion methods to realize the information interaction between other climate collector an d upper computer. General structure Intelligent climate collector is based on CAN-BUS intelligent instrument, it realized the temperature, humidity, air pressure, wind direction, wind speed, rainfall and other meteorological elements in collection, processing, storage and transmission. The entire collector mainly consists of three parts, including CPU minimum system, sensor interface and CAN communication interface, its overall structure is shown in figure. ISSN: - ASTL Copyright 0 SESC

2 Vol. (AITS 0) PT00 Humidity S Counter FLASH Wind Speed ainfall Atmospheric pressure Interface AD9 Watch Dog S SPI CH AT90 CAN AM CAN BUS Fig.. Climate collector structure diagram Hardware circuit design. Analog signal acquisition circuit The output form of temperature and humidity signal in the Climate collector are voltage signal, in order to meet accuracy requirements for collecting data, it will require a higher precision AD sampling circuit. So, in the design, we use AD9 chip, it produced by AD company, the device has a high precision measurement applications characteristics of low power, low noise, complete simulation front. The device put inside a low noise, with three 6 bit A/D conversion channel of difference analog input. It also integration on-chip low noise instrumentation amplifier, So small signal can be directly inputted, the gain can be set to ~. Platinum thermistor sensor adopts four wire connection methods, AD collects the difference input voltage, microcontroller can obtain the corresponding collecting temperature through interpolation calculation. While the humidity type of visala HMP temperature sensor output is 0 ~ v, the corresponding humidity for 0 ~ 00%, so the acquired voltage without direct calculation can be obtained corresponding humidity data.. The communication interface circuit of intelligent sensor Nowadays, the collection of meteorological elements mostly adopts the intelligent sensor, this kind of sensor support command interactive data transmission, the communication way adopts the commonly used S and S protocol. This requires a climate collector should have corresponding communication interface, that is S and S interface. Climate collector requires two lines of S Copyright 0 SESC

3 TS X D TXD 6 A U0 MAX D CAN_TXD CAN_XD B V S_ U TXD MAX00 JP X D SHDN S C A N H C A N L 6 CH_INT CH_CSC C 0 p 0 p C K 0 C TXD TS X D Y.M C p C p U9 INT# SCS TXD TS X D CTS I X X 0 CH TS CTS X D HLF# TXD SCK SDO SDI JP TS TXD X D CH_SCK CH_SDI CH_SDO V Advanced Science and Technology Letters Vol. (AITS 0) communication interface, in this design using the AT90CAN integrated roads UAT controller as the control module of the S serial communication The controller integrated roads UAT controller is used as the S communication, while climate collector also need roads S interface, so, in the design, we use CH dual serial port chip to extend the roads S interface. Intelligent sensor interface circuit is shown in Figure. Fig.. Intelligent sensor interface circuit. CAN-BUS interface circuit The CAN transceiver module adopts PCAC0 transceiver chip. The CAC0 connection microcontroller integrated CAN protocol controller and the CAN-BUS physical bus, the chip is mainly used for the demand higher occasion on the transmission speed, the highest transmission speed up to Mbaud, the device provides bus different send ability and CAN protocol controller different receives ability, these fully compatible ISO9 international standards. Fig.. CAN interface circuit Algorithm realization. Quality control of samples values On the quality control of sampling value, sampling value rationality examination, Verifying each samples values within the normal sensor measurement range. When 6 Copyright 0 SESC

4 Vol. (AITS 0) inspection delete sampling inspection which exceeds the set range, and do not use in the further calculation of relevant parameters. Sampling value time consistency detection, verifying the increment between drawing near sampling, checking the unreal jump. After each time sampling, comparing current sampling value with previous samples values, if the variation is greater than the set value, the current sampling value is marked as problematic, not used to compute the value, but it is still used for time consistency check next time.. The platinum resistance temperature interpolation For the resistance of platinum resistance and temperature characteristic has its standard indexing table, but we can't be the whole indexing table store in MCU, it's a waste of micro controller internal resources, at the same time, it also increased the burden of software programs. Considering the above factors, in the software design, we chose to use per temperature of for step interpolation algorithm, so it not only ensure the precision of temperature acquisition calculation, but also reduced the burden of software calculation.. Wind speed and direction acquisition algorithm Wind direction, wind speed using the moving method. it was allowed which use the following arithmetic algorithm or index algorithm one to calculating. The parameters of calculating values as shown in table. Average Average interval (Second) Table. Average calculation parameters Sampling rate (SPS) Sliding step (Second) Calculate he sample of arithmetic Calculate the sample numbr of arithmetic seconds 0. 0.s minutes 60 s 60 minutes 0 s 0 0 minutes 600 minutes 600 The arithmetic value algorithm, with the following general formula, application of different N value, in seconds, minute, minutes, minutes and 0 minutes, wind arithmetic value is calculated respectively. Calculation formula as shown in (). n Y ( ) / n y N n n N n N Y ( y y ) / N Y n n n N n () Copyright 0 SESC

5 Vol. (AITS 0) Index of value algorithm, seconds, minute, minutes and 0 minutes wind direction, wind speed value is calculated by the following index formula. Calculation formula as shown in (). Y Ky ( Y ) Y n n n n () Conclusion This article fully discusses the design of the climate collector,it based on CAN BUS, it includes detailed hardware circuit and software flow chart and data processing algorithms. In this paper design,the collector of climate has high flexibility, strong adaptability, easy to realize network management etc, it after extensive and long-term field experiment, meeting the complex requirements of modern climate monitoring, it has very high practical value and popularization value. eferences. Fang, Y., Jian, S.: Intelligent instrument technology and its application. Chemical industry press, 00: ~. Li, X., Zhang, Q., Ye, J.: Some theory problems of climatology research. Journal of Beijing university: natural science edition, 999, () : 0 ~06. Song, H.: The characteristics of CAN-BUS and development trend. Science and wealth, 00: ~ 0. Su, S.: The current status and development of intelligent instruments and data acquisition system. Journal of Yuncheng University, 00, () : ~ 9. Xiang, K.: esearch and application of CAN-BUS in the intelligent instrument system Master thesis of Guizhou University, 00: ~ 6 Copyright 0 SESC