外文翻译原文-基于Web服务器的AVR处理器的空气温度和相对湿度的远程监控系统的设计与开发.pdf

Abstract In this paper improved design of previously developed system for temperature and relative humidity measurement and data acquisition is described. Hardware of the system is extended with Arduino Uno and Ethernet Shield boards. SHT11 sensor is used for obtaining information about air temperature and relative humidity. Storing the results is on the micro SD card in CSV file. Main software improvement is adding of embedded Web server which enables immediate access to sensor readings through Internet. The designed system is tested under different conditions and in all tests the system worked stable and accurately. Keywords data acquisition, microcontroller, relative humidity, temperature, sensors, web-server. I. INTRODUCTION The weather or climate plays an important role in human life. The thermal comfort of human being is known to be influenced mostly by air temperature, humidity, radiation, activity level, air flow and clothing thermal resistance 1. Indoor air quality is a concern for energy and environmental researchers as well as consumers. Humans spend up to 90 percent of time indoors in winter, so it is very useful to know that things like carpeting and furniture can improve quality of indoor environment. Recently many homeowners have added vapor barriers, insulation, weather stripping and caulk to their homes to effectively retain desired air temperature and reduce outdoor air infiltration 2. Indoor temperature conditions and moisture were measured and analyzed for more than 40 homes in different climate regions of the United States 3. Monitoring of environmental parameters is very important in various applications and industrial processes. Researchers all over the world are trying to monitor the environmental parameters of temperature, humidity and pollutant gases more precisely in real time. For example, in 4 systems for monitoring temperature, humidity, and airflow in data centers are presented. Various design and application of data loggers for similar purposes can be found in literature 5-12. This work was financially supported by European Commission in the framework of the FP7 project SENSEIVER, grant number 289481. In 13 authors described impact of relative humidity and temperature on books stored in library. They presented the wireless system which can remotely measure and control relative humidity and temperature of library in real time. In greenhouses, maintaining a higher internal as compared with external temperature can produce better growing conditions. A computer-based system which provides control, coordination and visualization of humidity and temperature in a greenhouse was presented in 14. In 15 the results of experiments in exposure chamber to determine the effects of different ambient air temperature and relatively humidity on the performances of passive diffusive samplers for measuring nitrogen dioxide (NO2) in the outdoor environment are presented. Monitoring and control of temperature and relative humidity is also very important for storing and transportation of medicinal products 16. Based on applications of described systems it is obviously that development of reliable relative humidity and temperature measurement system with data acquisition is very important and has wide range of application in industrial and nonindustrial applications. Various temperature and relative humidity data loggers are available on the market with main characteristics: small dimensions and power consumption, wide measurement ranges, adjustable sampling time between readings, the ability to hold readings and display maximum and minimum readings, storing results on removable disks, Windows software (optional), etc. From the beginning monitoring systems have request for remote access to measured values. In last decade, the most common way of remote access became microcontroller which runs a embedded web server and user has access to sensor readings through Internet. More can be found in 17-24. Some solutions as 25 are commercial products with a much higher price than system proposed in this paper. Main aim of this work is embedding a PC based web server into the microcontroller with temperature and relative humidity measurement in low-cost but reliable system. System presents redesign of system reported earlier 26. All good features of previously developed system are implemented with optimization regarding dimensions and power consumption. Design and Development of Air Temperature and Relative Humidity Monitoring System With AVR Processor Based Web Server Mitar Simi NORTH Point Ltd, Member of the NORTH Group Trg Cara Jovana Nenada 15/8, 24000 Subotica Republic of Serbia mitarsimic 038 2014 International Conference and Exposition on Electrical and Power Engineering (EPE 2014), 16-18 October, Iasi, Romania 978-1-4799-5849-8/14/$31.00 2014 IEEE II. EMBEDDED WEB SERVER At the beginning, general web servers were developed for general-purpose computers. They typically require a fast processor, huge amount of memory and other resources. Microcontroller based control systems also have a request for remote access to the device from a web browser but limitations of available resources in that kind of systems, brought to the development of special type of web server, called an Embedded Web Server 27. An embedded web server is a microcontroller that contains an Internet software suite as well as application code for monitoring and controlling systems. Embedded web servers are integral part of an embedded network and paves way for faster time to market products 27. Figure 1. shows typical embedded web server architecture 27. Figure 1. Embedded Web Server Architecture III. DEVICE STRUCTURE Proposed structure of device for measurement and data acquisition of temperature and relative humidity with built-in web server is presented in Figure 2. System consists of three boards: Control board, Arduino Uno and Arduino Ethernet Shield board, and measuring device - sensor SHT11. The hardware of control board has been built around a microcontroller (AVR ATmega128 28) that interfaces with user via a display and a keyboard. The microcontroller is used with a supply voltage of 5 V and an external quartz crystal of 16 MHz. Other parts of control board are micro SD card, real time clock DS1307 29 and LCD. Alphanumeric LCD is used for displaying results and configuration on the field. Real time clock DS1307 with backup battery is used to provide time measuring. Time and date values are used for presentation on display and for additional information for every result in report on micro SD card. These values are also sent to web page with results of measurement. Keyboard with two navigation and two confirmation keys is connected to the control board to ensure easy manipulation through menu system for configuration and measurements. Menu system is based on finite state machine and it can be accessed by external keyboard with two navigation keys (Up and Down) and two confirmation keys (OK and Esc). Device also has an ON/OFF key for turning on and turning off device (toggle operation). ATmega128 Arduino Uno Board Ethernet Internet LCDRTC SHT11 Keyboard uSD Arduino Ethernet Shield Board Control Board Figure 2. Block scheme of the system Sensor device SHT11 30 is attached directly to the microcontroller ATmega128. SHT11 is a Sensirions family of surface mountable temperature and relative humidity sensors. The sensors integrate sensor elements plus signal processing and provide a digital output. No additional calibration is needed. Relative humidity is measured by capacitive sensor element while band-gap sensor is used for temperature measurement. The SHT11 has operating range of temperature between -40 and +123.8 C and range for relative humidity between 0 and 100 %RH. Measured values of relative humidity and temperature are stored on 2 GB micro SD card. FAT16 file system is used to allow manipulation of file with results on PC and off-line processing. The main advantage for using a micro SD card as data storage system is the ease of transferring data directly to other electronic devices which support the FAT format as a file system. Device also has three LEDs for signalization of regular (green LED) and critical conditions (two red LEDs for low and high alarm). A prototype hardware outcome of Control board with attached SHT11 sensor is shown in Figure 3. Figure 3. A prototype hardware outcome of Control board with connected SHT11 sensor Arduino Uno is a microcontroller board based on the ATmega328. It has 14 digital input/output pins, 6 analog inputs, a USB connection, a power jack, a 16 MHz ceramic resonator and a reset button 31. The Arduino Ethernet Shield allows an Arduino board to connect to the internet. It is based on the Wiznet W5100 Ethernet chip. The Wiznet W5100 provides a network (IP) stack capable of both TCP and UDP. It supports up to four simultaneous socket connections 32. 039 The Arduino Uno (a) and Ethernet Shield (b) boards are presented in Figure 4. (a) (b) Figure 4. (a) Arduino Uno board (b) Arduino Ethernet Shield board PC browser view of the SENSEIVER 33 data logger web page is shown in Figure 5. Date, time, relative humidity and temperature are presented. Default value for refresh time is 5 seconds. It is planned that in next revision of the system refresh time of web page can be adjustable regardless sampling time of measurements. Figure 5. Browser view of the SENSEIVER data logger web page A prototype hardware outcome of complete system is shown in Figure 6. Figure 6. Hardware outcome of device for temperature and relative humidity monitoring with embedded web server System is also successfully tested with access via mobile phone as shown in Figure 7. Figure 7. Testing of the system with mobile phone Mobile phone browser view of the SENSEIVER data logger web page is shown in Figure 8. Figure 8. Mobile phone browser view of the SENSEIVER data logger web page System described in this paper also can be used as standalone device without connection with embedded web server. In both cases, device can be used in two modes for data collecting: continuous and manual. In continuous mode, the device collects data from sensor automatically with defined sampling time and stores it on micro SD card. In manual mode, the user has an option to manually choose the moment of recording the results. More details about implemented options can be found in 26, where results of comparison with commercial temperature and relative humidity data logger are presented. As reliability test of redesigned system, during more than 7 hours indoor temperature and relative humidity were monitored. Sampling time was set to 2 seconds so more than 8600 samples were stored. Size of generated report is 319 kB. Offline processing of generated report can be easily performed and curves of temperature and relative humidity changes are presented in Figure 9. 0100020003000400050006000700080009000 24 26 28 30 32 34 36 38 40 Sample Temperature C Relative Humidity %RH Figure 9. Curves of indoor temperature and relative humidity changes during more than 7 hours 040 IV. CONCLUSION The main task in this study was to provide remote access to the sensor readings as upgrade of the previously developed monitoring system. Remote access was accomplished with web server embedded in AVR microcontroller placed on additional board which is connected with serial interface to previously developed system. Obtained system is low-cost but it has most of the features available at commercial devices. The future plans of this work are to improve the functionalities of measuring and data acquisition system with adding new hardware and software features. 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