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Intelligent meter reading system based on GPRS and arm

1 introduction

at present, many countries have widely used remote automatic meter reading system to establish cobalt industry company this cooperation is based on Yinxi technology's strong preference for new energy vehicle industry to replace the traditional manual meter reading. With the rapid development of computer technology, integrated circuit and communication technology, meter reading system has taken a solid step towards intellectualization. Now GSM network has covered most areas of our country, and GPRS is a mobile packet data service based on GSM mobile communication system. GPRS network function can be used to transmit the electricity meter data of power system. This paper takes the arm processor platform and Huawei gtm900-b wireless communication module as the core. Using wireless data transmission, the collected data can be transmitted to the monitoring server through the Internet. This method has the characteristics of fast transmission, large transmission volume, unlimited distance and so on. It is very suitable for power system with many collection points, wide range and long distance. It not only discards the shortcomings of manual meter reading, which is time-consuming and laborious, but also is more conducive to the statistics of power consumption during peak hours. The intelligent meter reading system based on GPRS and arm includes three main components: data acquisition system, GPRS based communication transmission network and arm based terminal processing system

2 GPRS system

since the development of wireless data transmission monitoring system, the communication technology used has gone through four stages: radio transmission, cluster communication, SMS short message and GPRS. The technical comparison is shown in Table 1. Table 1 four stages of wireless data transmission GPRS (General Packet Radio Service) is the abbreviation of general packet radio service. In the original GSM network based on circuit switching (CSD), two new network nodes are introduced: GPRS service support node (SGSN) and joint point (GGSN). When building GPRS system on the basis of GSM system, we only need to upgrade the software. Such a GPRS system can be regarded as a service expansion of the original GSM circuit switching system to meet the needs of users to access the Internet or other packet data networks using mobile terminals. Technical advantages of GPRS network:

(1) high resource utilization. GPRS introduces the transmission mode of packet radio, and users only occupy resources during sending and receiving data, which means that multiple users can efficiently share the same wireless channel

(2) high transmission efficiency. GPRS can provide up to 115kb/s transmission rate

(3) short access time. The access time of packet switching is shortened to less than 1s, which can provide fast and instant links

(4) support IP protocol and X.25 protocol. GPRS supports the most widely used IP protocol and X.25 protocol on the Internet

3 GPRS Remote Wireless Meter Reading design

the hardware design of the remote meter reading module, including the overall hardware design and the design and implementation of each unit module. The system logic block diagram is shown in Figure 1. According to the function, the hardware module involves CPU, data acquisition, power management, storage, RS485 interface and other modules. Firstly, the data acquisition is completed by the electric energy acquisition chip, and then transmitted to the arm by RS485. After processing, it is transmitted to the GPRS data transmission module through RS232, and then to the control center through GPRS network

Figure 1 system logic block diagram

3.1 system hardware circuit

in hardware, it is mainly the hardware implementation of data acquisition terminal, including GPRS data transmission module and processor, wireless transmission function design, acquisition circuit, serial port circuit interface expansion, power module design, etc. the hardware circuit is shown in Figure 2

Figure 2 system hardware circuit diagram

3.1.1 data acquisition module

smart meter uses electric energy measurement chip ade7757. After the signals output by the voltage sensor and current sensor are input into the two ADC circuits in the ade7757 chip, the voltage and current are multiplied by the built-in multiplier of the ade7757 to obtain the active power to realize the lightweight power of the car. The solution of the ade7757 converting the active power to frequency output through the digital frequency converter is not much

ade7758 has three kinds of registers inside, which are measurement value register, control register and status register. The length of the voltage and current register is 24 bits and the energy register is 16 bits, but there is no separate power memory inside, so the power cannot be obtained through the parameters of voltage, current and so on. Power is the energy value in unit time. Once the energy value in quantitative time is known, the power can be obtained. The method of calculating power can adopt linecyc (line cycle energy accumulation mode). The apparent, active and reactive energy registers store the energy value E in each cycle T, which is refreshed once in each cycle T, resulting in p=e/t. The results of arm processing are sent to gtm900-b module through RS485 interface, and then gtm900-b transmits the data to the PC monitoring end of the corresponding IP address through tcp/ip protocol

3.1.2 power supply module

through simplified system power supply circuit, the design input voltage is 5V DC regulated power supply. In this system, 5V, 3.3V DC regulated power supply is needed to supply power to CPU, SDRAM, flash, LCD, GPRS modules, etc. According to the actual power consumption of the system, choose LDO (low dropout linear regulator) cmlll 3 provide DC regulated power supply for the system, and the system power circuit is shown in Figure 3

Figure 3 power module figure

3.1.3 embedded arm module

this system uses the ARM7TDMI S3C44BOX embedded processor designed by arm company for SamSung company. The processor is a 32-bit RISC structure, with a maximum operating frequency of 66MHz, an external addressing range of 1g, and rich on-chip resources. Two asynchronous serial communication ports are used in the system design. The on-chip real-time clock is used for timing data acquisition, processing and transmission. The on-chip watchdog is provided to prevent the system from crashing and accurate system reset. 2MB norflash and 8 MB nandflash are extended to store system programs and meter reading data, and 16MB SDRAM is used as system memory. Such a configuration fully meets the needs of system hardware and program compilation

3.1.4 GPRS module

Huawei gtm900-b is a two band gsm/gprs wireless module, which supports 900mhz/1800mhz dual band automatic selection. It supports standard at commands and enhanced at command interactive data mode, provides rich voice and data services and other functions, and is an ideal solution for various applications such as high-speed. Therefore, the tensile machine for testing high-molecular polymers has a certain difference from the general tensile testing machine for material tensile properties, data transmission and so on. Gtm900-b adds the at command of data transmission, which is suitable for the occasion of small amount of data transmission. With built-in tcp/ip protocol stack, users can realize data transmission without the support of background computer and PPP protocol

because GPRS module is based on IP protocol, data transmission between server and GPRS module uses IP protocol based packets, which indicates that all data should be based on IP. Examples of at commands for data transmission are as follows:

at%etcpip=[], [], []//initialization commands

at%ipopen=,, [[, [local_port>]]//open a TCP or UDP link command

at%ipsend=//send data commands in single link mode

at%ipdr=[]//data reading commands

3.2 system software design

in the monitoring software design, including the transplantation of embedded operating system and hardware driver.Programming, The establishment of data transmission protocol, the software implementation of data acquisition module, the programming of tcp/ip protocol with socket, and the implementation of server application program of upper computer and client application program of lower computer. The overall idea of terminal software design is to integrate real-time embedded operating system μ C/OS II is transplanted to the MCU of meter reading system, and then the program is written on this operating system. The software adopts modular design, with clear and concise structure, which is convenient for future modification, debugging and expansion. When μ After the successful transplantation of c/os II, you only need to complete the programming of the relevant design, and the real-time and reliability are guaranteed by the real-time embedded operating system

monitoring server is composed of server with fixed IP address, monitoring data software and database. The collected energy meter data will be transmitted to the fixed IP address of the server. The monitoring software processes and stores these data uploaded by the data terminal through the software end. In the monitoring software corresponding to this system, its function can not only store the data transmitted by each GPRS terminal and display the data on the interface, but also add practical functions such as electricity theft warning, electricity meter fault prompt and insufficient electricity charge prompt

Figure 4 terminal software structure diagram

4 conclusion

the power meter reading system has been widely distributed throughout the country, with large scale and wide distribution, which requires a lot of human and material resources. Therefore, how to better achieve fast and accurate meter reading is of great significance. General meter reading methods will have various disadvantages. Wired meter reading is affected by distance and wiring, and will be affected by the on-site environment of meter reading, so the staff can't get the data in time. Now, the GPRS meter reading method proposed in this paper can solve these problems well. After field testing, the accuracy and reliability fully meet the design requirements. Relying on the extensive GPRS network of telecom operators, the meter reading platform is built to realize wireless meter reading, which saves a lot of human and material resources, reduces human intervention and the impact of the on-site environment, and improves the working efficiency and social and economic benefits of the power system on the premise of ensuring smooth data communication

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