Remote measurement and control system based on WSN and GPRS(1)

L0504-Murata muRata common mode inductor 90Ω 150mA

XTL581100-M118-080-1

0 Preface

In recent years, a new type of network called wireless sensor networks has emerged. This infinite sensor network consisting of multiple single nodes with computational processing, wireless communication, sensing or control capabilities is currently the internationally-recognized, multidisciplinary frontier research field with signal acquisition, real-time monitoring, and information. Transmission, collaborative processing, information services and other functions have greatly expanded the network technology and made it possible to monitor various environments and facilities in real time through the network. The sensor network is the core of the Internet of Things. It is mainly used in the information-aware layer of the Internet of Things for tracking, monitoring and decision support to achieve intelligent perception and management.

The embedded system is application-centered, based on computer technology, software and hardware can be tailored, and is suitable for application-specific computer systems with strict requirements on reliability, cost, size, power consumption and other functions. It is usually composed of hardware and software. Among them, the hardware includes embedded microprocessors and peripherals; the software includes embedded operating systems and specific applications. Embedded technology can be widely used to control, monitor or manage other devices.

Measurement and control technology refers to the monitoring and control of a certain characteristic. Remote measurement and control refers to the equipment that the management personnel need to be controlled by the computer network in the remote place to query, configure and modify the remote equipment through the local computer. Remote measurement and control technology can achieve seamless connection between office automation and industrial automation, and has become an emerging research hotspot. With the demand and development of the network, the B/S model has developed rapidly. With this mode, the client can simply perform a remote measurement and control by simply installing a web browser and downloading the program from the web server to the local browser.

The rapid development of computer technology, communication technology and microelectronic technology has made a huge change in the field of measurement and control systems. Networking and informationization have become the development direction of measurement and control systems. The integrated sensor network technology, embedded technology and industrial measurement and control technology, the construction of a Web-based remote measurement and control system can greatly improve the real-time, security and maintainability of the measurement and control products, and is also more conducive to the realization. Centralized monitoring, unified scheduling and optimized management. This paper introduces a Web-based embedded remote measurement and control system based on various technologies, and successfully implements a smart home system.

1 Overall structural design of the remote monitoring system

The basic architecture of the embedded remote measurement and control system based on Web is shown in Figure 1. The remote measurement and control system is mainly composed of an embedded measurement and control unit, a local server and a remote management host.

Figure 1 The basic structure of the remote measurement and control system

The embedded measurement and control unit at the bottom is mainly distributed on each measurement and control node. It consists of central processor, sensor, actuator, network interface, GPS module, GPRS module, etc. It is responsible for collecting the environmental parameters of the site and setting the parameters. For comparison, if the specified range is exceeded, the alarm will be alarmed and the actuators will be operated to obtain the normal parameter range, and the test data will be transmitted to the local server through the customized protocol to reach the remote manager display. The GPS module can clearly locate the faulty device. The GPRS module can be used as a wireless transceiver module to achieve high-quality data transmission in the event of a wired network failure, which provides a very realistic and practical meaning for applying the embedded system to the remote measurement and control system.

Located in the middle as a bridge is a local server, which mainly receives the monitoring parameters uploaded by each measurement and control unit, and saves them to the database, periodically queries and analyzes the status of the measurement and control unit, and if it finds that an error occurs, immediately informs the user of the short message. At the same time, the server also needs to timely feed back the data in the database to the remote manager, so that the user can monitor the situation of each measurement and control device in the first time, and realize the operation of the manager to each measurement and control unit.

The top layer is the remote manager, which can systematically analyze, query and manage each measurement and control unit, receive various information uploaded by the measurement and control server, and issue commands to control and process the underlying unit. The IP address directly controls a specific measurement and control unit and performs unified management on each device. When the wired network fails, wireless connection operations can also be performed via GPRS, allowing the user to control it at any time.

The system collects the parameters of each node through the front-end sensor module and the information receiving module, sends it to the embedded system for processing and storage, and periodically transmits the monitoring information to the measurement and control server, and transmits it to the management machine through the server, thereby realizing the control device for each measurement and control device. control. The remote measurement and control system realizes that small devices are connected to the Internet, and the operation of each device can be monitored in time. For the monitoring system, the network monitoring mode is flexible, the system construction and maintenance cost is relatively low, the amount of data that can be saved is larger, the data storage mode is more, and the system integration is higher. Network-based remote monitoring breaks through time and geographical restrictions. As long as there is a network, users can monitor and monitor on-demand at any time without authorization.

2 Key technology research

2.1 Embedded System Design

The embedded measurement and control unit is equivalent to each node of the sensor network, and is mainly responsible for information collection, and converts other optical signals and chemical signals into electrical signals, and sends them to the microcontroller for processing. The measurement and control device is a system with intelligent detection and control developed by embedded technology. It is based on a central microprocessor with SDRAM, NANDFLASH, network interface RJ-45, 4-wire touch screen interface, serial interface, LCD, USB port, SD card storage interface and A/D and D/A converter. Use UART1 and UART2 to convert TTL levels to RS232 levels via the SP3243ECA chip for GPS and GPRS communications. The hardware block diagram of the system is shown in Figure 2.

Figure 2 Embedded system hardware block diagram

Software systems primarily consider startup programs, various drivers, operating systems, and applications. The open source code of the Linux operating system can cut the kernel and has been running stably and efficiently on various hardware platforms such as Motorola, NEC, and ARM. It has powerful network functions and excellent file system support functions. Therefore, the Linux operating system is selected, and according to the specific application, after being tailored and cross-compiled, an ARM executable file is formed, which is downloaded into the FLASH by means of the serial port and the network port. The application program of the measurement and control unit mainly includes a data acquisition module, a liquid crystal display module, a keyboard control module, a network service module, a communication service module and a control execution module. In order to build a better human-machine interface, the QT/Embedded graphical user interface support system was ported to Linux and the corresponding graphical user interface was developed.