1、 PDF外文：http:/ 毕业设计外文资料翻译 外文出处： 2007 Second IEEE Conference on Industrial Electronics and Applications 学 院： 信息工程 系： 电子信息工程 专 业： 电子信息工程
2、 班 级： 学 号： &nbs
3、p; 学生姓名： 外文原文： A Design of the Temperature Test System Based on Grouping DS18B20 LI Ping ZHOU Yucai Xiangjun ZENG YANG Ting-fang Changsh
4、a University of Science and Technology, Changsha 410077, Hunan, P. R. China. E-Mail: Abstract- All the DS18B20 sensors, used for the multipoint test temperature, are connected with MCU on one of IO bus, and temperature data are collected by turns. If the system has a large amount of se
5、nsors, the time of MCU used in processing the temperature data is obviously prolonged, so the cycle of alternate test gets longer. In this paper, a new method that DS18B20 are rationally grouped is presented, and some measures are taken in software； as a result, the speed of alternate test advances
6、distinctly. Key words- DS18B20 Group ,temperature test, time spent on the alternate test. I. INTRODUCTION As the simple structure, convenient installment, low loss and wide range of temperature test, DS18B20 temperature test sensors are applied to the fields which need the multipoint temperatu
7、re test, such as the chemical industry, the grain, the environment supervision and so on. Because of the adoption of one bus in the DS18B20 multipoint temperature test system, all DS18B20 are hung on one bus, and then the temperature conversion value of each test point is read by turns. As the conve
8、rsion value must be read after reading-pin state for 8 times, and position and store data must be moved, so time spend much in reading one point of the data system by every time. If the temperature test system is large-scaled, the system loss caused by it is rather much, and then the alternate test
9、speed of the system decreases obviously, which influences the efficiency of the multipoint temperature test system seriously. In this paper, DS18B20 are hung on some I/O buses by grouping DS18B20 evenly, and the conversion temperature data is obtained by reading the state of DS18B20, then the system
10、 loss decreases and the alternate test speed increases obviously, which wont influence the precision and the reliability of the conversion. A set of multipoint temperature test of artificial environment laboratory is achieved in this paper, which increases the test efficiency of the former system. &
11、nbsp; . CHARACTERISTICS OF DS18B20 DS18B20 is the single bus digital temperature sensor from American Dallas Company. DS18B20 is consisted of the 64 figures ROM engraved by laser, the temperature sensitivity component, non-volatile temperature alarms trigger (Device TH and TL).DS18B20 c
12、ommunicates with the microprocessor by the single bus port and the test range of DS18B20 is from -55 centigrade to +125 centigrade, and the incremental value is 0.5 centigrade. The temperature can be changed into figures within 720ms and each DS18B20 has the sole 64 figures serial number. The specif
13、ic content is revealed as Fig 1: There are two 8 figures storages (No.0 and No.1) for storing temperature value in DS18B20. No.0 storage stores complement of the temperature value, and No.1 stores symbols of the temperature value. The user can define non-volatile temperature alarms sets and distingu
14、ish the alarms search order and seek the component temperature alarms state outside the scheduled limit. There are two alternative ways of power supply: Signal bus high-level borrow power is adopted, or the +5v power supply externally is adopted directly. Fig 1 DS18B20 64bit ROM . APPLI
15、CATION THE GROUPING TEST METHOD This paper illustrates the grouping method with the interface of DS18B20 and 89C52. Assuming the amount of the buses on P1 port is 4 and the temperature test system needs 100 DS18B20 sensors, which can be distributed equally to the 4 I/O lines. If the num
16、ber of sensors cannot be divided by the number of buses even, the number disparity of sensors on buses is no more than one, which can be handled while reading numbers. The power is supplied externally. Owning to the synchronistic conversion in each DS18B20, the intense current is needed, and the sig
17、nal bus cannot be used for the power supply, otherwise the system cannot work in order. The schematic circuit is shown as Fig 2 (the DS18B20 signal buses of the same group are hung on some buses of P1 port). When read and write the DS18B20, the strict schedule must be kept. First a reversion pulse i
18、s sent to all DS18B20. After the reversion, Skip ROM order is sent to each circuit simultaneously from the I/O port, and the conversion order is sent, then all sensors begin transform. After the conversion, Match Rom order is sent to each circuit simultaneously, and 64 bits serial number is sent. DS
19、18B20 is selected for each group, and Scratch Pad data is read. Finally the data is transformed. The data of serial-read is transformed into the actual temperature value. One alternate test is finished after the DS18B20 temperature data is read completely by the cyclical reading for 25 times. The whole flow chart is shown as Fig 3.
