安徽工程大学机电学院毕业设计（论文）
附录B 外文文献及翻译
外文文献：
Temperature Monitoring System Based on AT89C51 Microcontroller
Abstract
To the problems of online real-time temperature inspecting of the electric cable interface, this paper designs an inspecting and alarming system based on AT89C51 microcontroller. The hardware circuit of this system is composed of collector, host control machine and PC. Through the key courses of collection, storage, conversion and transmission, the temperature data of electric cable interface is sent to real-time show and alarm, achieves inspecting and alarming for the interface of electric cable and avoids the happenings of fire effectively. 1、Introduction
In the actual process of power transmission, at the point of every 100 meters or so in the long- distance electric cable line equips an electric cable interface. Cable fires caused by both the internal and the exterior breakdown easily happening in numerous electric cable interface approximately account for more than 50% in the total numbers of electric cable accidents. In fact, the electric cable interface breakdown’s development is an evolutionary process. To avoid occurrences of the electric hazards effectively, a method of monitoring the real-time temperature of electric cable interface, aiming for understanding the working condition of each interface accurately and comprehensively and determining the service plan, may ensure safety of the power transmission.
This temperature inspecting and alarming system to the cable connector takes a monitoring plan at the core of which is AT89C51 microcontroller. Three major part composing the whole system are respectively: gathering and transformation of temperature parameter, data transmission of temperature, and data’s central demonstration and processing. 2. system design
This system is composed of superior PC machine, the host control machine and the temperature collector. Structurally, the whole system can be divided into three layers: one of user’s monitoring of superior machine constituted by the microcomputer system, one controlling level of master control machine composed of AT89C51 and one measuring level at the collector. Superior PC exchanges data with the host control machine through GPRS. The system is a kind of principal and subordinate structure made up of one PC and several collectors, through the RS-485 communication network, they can transmit data of long distance.
In this system, superior PC machine regularly sends out to the host control machine the commands of reading the temperature data. After receiving these orders, the host machine will send back the preceding data read from collectors and saved in SRAM. After finishing the transmission, the host control machine also sent out orders of reading the temperature to each collector. Once the collector receiving them, the data saved in the collector SRAM will be send back to the host control machine that will receive and renew original data at the relevant position. During this correspondence gap collectors constantly read the newest temperature
25
田丰：基于单片机的温度控制器的设计
value to prepare for the real-time reading command of the host machine. All orders and transmission of the data have formulated the strict communication protocols, and adopted the different check-up ways, greatly enhanced reliability in the process of transmission. 2.1 Temperature collector
The collector consists of mainly six parts including the microcontroller AT89C51, select electric circuit of the temperature measurement port, the communication circuit, registering and booking circuit of the DS18B20 sensor, electric circuit of the memory and the temperature sensor
Through select electric circuit of the temperature measurement port ,the microcontroller may control the temperature sensor DS18B20 gathering the temperature. The temperature data being saved first in the exterior memory SRAM will be sent back to the host control machine when requested at any moment.
The temperature sensor uses digital DS18B20 temperature collector. DS18B20 may provide temperature value of 9 to 12 rank number and has a warning function of users’ programmable bound of temperature without non-volatility. The information can be send in or out from DS18B20 through the single bus connection, therefore only connecting a line can meet the need. The power source in the course of writing and reading and completion of the temperature change can be provided by the data line itself without need of outer power supply. Because each DS18B20 has the only series number, many DS18B20 may exist on the single bus. In the course of design, each electric cable parallel several dozens temperature sampling point, constituting a working form of serial line. For the temperature signal sent out by this microcontroller is the digital signal, it simplifies A/D transformation, and improves efficiency and the precision of the measurement.
The temperature measurement port select electric circuit uses idirectional analog switch CMOS component CD4051 as the multi-channel gathering cut switch. The CD4051 has 8 groups in total one of which is responsible for controlling one single bus while 3-8 decoder coordinated by microcontroller’s address line is responsible to select channels of the CD4051. In the design, each collector use 2 pieces of CD4051 that can control 16 groups of single bus. In addition, each collector has the channel extended socket, may expand the channel to 64 groups, meeting the actual needs fully.
The DS18B20 registration port electric circuit completes registration and book of new temperature sensors. Before turning on system and working, Each DS18B20 must be registered or booked first make the microcontroller record its 64 bit series code, in order to be recognized when measuring temperature. Therefore, a registration book port that first is turned on by the DS 18B20teperature sensor is designed in each collector to meet to the microcontroller. Establishing a logical address through the keyboard, the microcontroller can read out its serial codes, then store them in relevant unit of SRAM in preparation for its use when the sensor is read or wrote.
Meanwhile in the collector a piece of 32K non-volatility SRAM DCM0256 is also expanded as the data storage used for storing up 64 bit serial codes of DS18B20 and gathering multi-spot temperature figures. This memory is characterized with a quick access speed, not losing its data in a case of power failure, realizing actual requirements of the system.
The communication module is a key for the system to realize the long-distance transmission and correspondence among many machines. Because the required distance of
26
安徽工程大学机电学院毕业设计（论文）
data transmission of cable connectors’ temperature measurement is commonly more than several kilometers, the communication module usually uses the RS-485 communication interface having an ability of suppressing disturbance after making use of the balanced transmission and the difference receive. In addition that the receiver has the Authorized licensed use limited to: Huaiyin Institute of Technology. Downloaded on April 15,2010 at 06:40:58 UTC from IEEE Xplore. Restrictions apply. high sensitivity, it can examine voltage of 200MV-Minimum, therefore the transmission signal can obtain the restoration outside several kilometers.
2.2 Host control machine
The Figure 3 is a structure diagram of the host control machine mainly including the communication circuit, electric circuit of the memory and the display circuit.
The primary mission of the host control machine is to read and save temperature data of the collectors, then send them to the superior computer, in convenience of analysis, demonstration and users’ inquiry. Therefore, the host control machine actually is a processor with function of memory and correspondence. Because the host control machine can exchange data both with collectors and with superior computer, the communication selecting circuit can be used to change work of serial in microcontroller of the host control machine.
The data transmission between the host control machine and collectors selects the RS-485 communication method. A host control machine can connect at most 256 collectors, therefore, the application of the RS-485 bus is able to realize a distributional system constituted by many linking collectors. Host control machine corresponds with the superior PC machine by means of GPRS (general grouping wireless service). Transmitting the data at a high speed and online at all time, the GPRS correspondence , a high-technology system integrating technology of modern wireless communication and the signal gathering as well as the computer network , is inexpensive, highly effective and applied in widespread fields. What’s more, it can provide for users highly effective, economical, safe and real-time monitoring methods .When IP data packet based on GPRS communications network is transmitting the data, host control machine through RS-485 bus connects to GPRS Modem that’s also corresponding with GSM base. But being different from circuit exchange or the data call, the GPRS data groups are transmitted to the SGSN node from the base, not connected in the speech network, SGSN and gateway support node GGSN through mobile service switching center M SC to carry on the correspondence. Between GGSN and between superior PC machine, Internet can directly be used to complete transmission. 2.3 Management system of superior machine
This system's management software is developed and completed in the VB language under the environment of Windows XP. Because of its rich graphical interface, a good integration rate of controlling parts, short-period of the development cycle and high efficiency, the VB language is quite suitable for this system software's development. Function
In the course of data transmission, the use of the technology of asynchronous serial communication, coordinated with the hardware, can realize transmission of control command as well as of the data between superior PC machine and the host control machine. System's online monitor function may dispose configuration off-line, and has the good man-machine contact surface. In the online observation system the map of cable tunnel condition and temperature measurement distribution is designed to directly demonstrate each collector's
27
田丰：基于单片机的温度控制器的设计
position and the current temperature value, under the normal condition, the color of connector is green. When the temperature of one collector surpasses the setting value, the color will turn red, it will turn yellow when its temperature figure is close to the setting value, which can be referred to a warning on exceeding temperature. From this, the graph dynamic description for the electric cable movement's actual scene can be provided.
The online observation system may also demonstrate or print the temperature data with a form.
From the concrete temperature figures of all cable connectors, the surface temperature and the three-phase temperature value of each cable connector at the corresponding time can be checked out only by means of inputting the date and the time. Besides, the temperature value and temperature trend of each cable connector can be observed clearly though its temperature curve,Because the diagram of curves may respectively use the year line, the month line, the date line and time line to draw out curves of any connector, this chart not only may monitor the real-time temperature of connectors, but may also analyze joint's temperature trend. This effect is very good.
The online observation system may carry on the real-time monitor to system's running status, including operational aspect of each collector and network and so on. In the case of exception, it can discover and take the measure promptly to carry on the maintenance or the repair. Moreover, monitor parameter may be revised momentarily online, like upper limit setting value of temperature, the cycle of tour examination and so on. According to the temperature change of the electric cable’s working condition, the system not may only set up automatically demonstration of cable connectors’ warning temperature and warning temperature’s change gradient, but may also the automatically track ambient temperature. With the help of service platform, administrators are also provided more functions such as monitoring online system's running status, alerting the breakdown, picture-switching, printing forms, analyzing historical data, storing data and online revising parameter 3.concluding remarks
The innovation of this paper are mainly indicated as follows.This system take the computer and the microcontroller serial communication theories as a foundation, using formidable data-handling capacity of the microcomputer, the technology of the serial communication and the GPRS communication, the data-gathering and data-monitoring function of the microcontroller, designing the bus system of bearing low temperature and the anti-strong electric field, and suitable to apply in the long-distance monitor to the surface and the ambient temperature of cable connector . Through a series of the real-time monitor to the electric cable connectors, analysis of the characteristics of overheating fault in the cable ,analysis and forecast of its ambient temperature , it may prevent effectively fires resulted from the overheating fault and environment due to decrease of the power connector’s insulation. The design of hardware has taken both the traditional AT89C51 microcontroller, the RS-458 bus, and the current popular GPRS data transmission module, to complete system's temperature examination and the temperature data transmission together cheaply and reliably. Moreover, the use of VB in the design of correspondence procedure between superior PC machine and host control machine as well as of the online observation system to cable connector’s temperature, creates friendly man-machine contact surface and makes operation easy. Countless tests and experiments were carried on in the course of the design.
28
安徽工程大学机电学院毕业设计（论文）
The results have revealed that this system is more reasonable, the technology is quite advanced, the transmitting and processing of the correspondence data are accurate. It has gained high praise of the user because it can promptly provide the position of the fault and the overhaul instructions, and can effectively avoid the occurrence of serious accidents which generally has achieved the expectancy. This system can be applied in enterprises such as electric power, metallurgy, coal mine and harbor, to realizing online monitoring to power connectors’ temperature. Moreover, only being transformed slightly, it may substitute those systems used to monitor and control the temperature in the grain storage, the archive office, the library, the large vegetables awning
29