Application of GPRS technology in remote monitoring system of tailings pond

0 Introduction
The ore mined from metal or non-metal mines, after the valuable concentrate is selected by the concentrator, produces sand-like "waste residue", which is called tailings. Tailings ponds are an important link in the safe production of metal and non-metal mines, and are also one of the major sources of danger in this field. As a man-made debris flow hazard source with high potential energy, once an accident occurs, it will cause huge losses to the safety of life and property of the people downstream, cause serious pollution to the local environment, and also have a serious negative impact on the local economic development and social stability. The safety monitoring of tailings ponds is of great significance for strengthening the safety supervision of tailings ponds, grasping the safety status of tailings ponds, and reducing the occurrence of accidents in tailings ponds. At present, the main technical parameters for the safe operation of tailings ponds in China, such as dam deformation displacement, reservoir water level, and immersion line burial depth, are all measured manually on site using traditional instruments on a regular basis. The workload of safety monitoring is large, and it is affected by many factors such as weather, labor, and on-site conditions. There are certain system errors and manual errors. At the same time, manual monitoring also has shortcomings such as being unable to monitor the various technical parameters of the tailings pond in a timely manner and difficulty in timely grasping the various safety technical indicators of the tailings pond, all of which will affect the safe production and safety management level of the tailings pond.

1 Overall block diagram
of the system 1.1 Parameters monitored by the system
The system can monitor the infiltration line, the internal deformation of the dam, the water level, and the rainfall.
1.2 System block diagram
In the mine control center, one GSM modem, one monitoring host, and one management host are configured. The management host is installed with information management software and data analysis software, and the monitoring host is installed with data acquisition software. The front-end acquisition equipment communicates with the monitoring host through the public network, uploads all sensor data to the monitoring host, and the management host analyzes and manages all data, as shown in Figure 1.

This design system uses MCS-51 single-chip microcomputer to collect signals from sensors such as temperature, displacement, and water level, and after analog-to-digital conversion, transmit the information to the GPRS mobile communication base station. It realizes the interconnection between the GPRS wireless network and the Internet through a mobile gateway. The GPRS mobile network transmits data or information to the Internet through the gateway, and then the Internet, based on the IP protocol, transmits the data packet directly to the monitoring host of the mine control center with the specified IP through routing. After receiving the information, the network server displays it in time and stores the data in the specified database file. [page]

2 Implementation of system communication
2.1 Main components for establishing system communication
(1) MCS-51 series microcontrollers are powerful and have large memory.
(2) GPRS module. The system uses the GPRS module LT8030 developed by Lishida Information Technology Co., Ltd., which uses a standard RS 232 interface. Users can use the corresponding AT commands to control the module through the UART port of the microcontroller or other CPU to easily enter the GPRS network.
(3) Server. To establish a SOCKET connection, a public IP address must be available. Therefore, it is necessary to ensure that the computer in the mine control center is connected to the Internet and obtains a public IP address. Before the microcontroller controls the GPRS module, the server needs to run the SOCKET port listening program and set it to the listening state. The port number must also be set, such as port: 1024.
2.2 Main implementation process of system communication
(1) Initialize the GPRS wireless module through AT commands, attach it to the GPSR network, obtain the GPRS terminal IP address dynamically assigned by the network operator, and establish a connection with the destination terminal.
(2) Through serial port 0, the MAX232 standard serial port is extended to connect with the external controller (such as the data acquisition terminal). The external controller is connected to the standard serial port. According to the agreed protocol, the controller of this design can be easily used for communication.
(3) P1.2 and P1.3 are reused, that is, serial port 1 is connected to TXD0 and RXD0 of the GPRS module respectively, and the initialization of MC35 and the control of the GPRS module's data transmission and reception are completed through software setting. The receiving server of the mine control center supports two access methods: one is to directly access the Internet through an asymmetric digital subscriber line (Asymmetrieal Digital Sub setiber Line, ADSL)/local area network (LAN)/public switched telephone network (Public Switched Telephone Network, PSTN)/ISDN (Integrated services digital network). At this time, the dynamic IP address or fixed IP address of the receiving server is sent. If the receiving server is in a local area network, the second access method can be used, that is, to access the Internet through a proxy server that supports SOCKET. At this time, the public network IP address of the proxy server will be sent.

3 System hardware design
The system hardware circuit diagram is shown in Figure 2.

(1) The AT89C52 microcontroller is a low-voltage, high-performance CMOS 8-bit microcontroller. It contains 8 KB of repeatedly erasable read-only program memory (EPROM) and 128 B of random access data memory (RAM). The device is produced using the high-density, non-volatile storage technology of Atmel Corporation of the United States, and is compatible with the standard MCS-51 instruction system. It has a built-in general-purpose 8-bit central processor and FLASH storage unit. The AT89C52 with a built-in powerful microcomputer provides a cost-effective solution. This design uses a 11.059 2 MHz crystal oscillator, which is set by a timer to be consistent with the communication frequency (9 600 Hz) of the GPRS module.
(2) Data acquisition of the ADC0809 analog-to-digital conversion chip. The ADC0809 has an output latch inside, which can be directly connected to the AT89C52 microcontroller. The chip select signal of the ADC0809 converter is controlled by the right P2.7 line select, and its channel addresses INO~IN7 are 7FF8H~7FFFH respectively. When the microcontroller generates a write signal, an NOR gate generates the start signal START and address latch signal ALE (high level valid) of the converter, and latches the channel addresses A, B, and C sent by the address bus. The analog quantity is sent to the A/D converter through the selected channel, and the bit-by-bit conversion begins at the falling edge of START. When the conversion is completed, the conversion end signal EOC becomes a high level, and after passing through the inverter, an interrupt request can be sent to the CPU. When the microcontroller generates a read signal, an NOR gate generates an OE output enable signal (high level valid), and the A/D conversion result is read into the microcontroller.
(3) GPRS module. The design uses the LT8030 GPRS IP Modem. The LT8030 is based on the SIEMENS MC35 GPRS module and has a complete TCP/IP protocol embedded, providing users with a simpler network interface. The GPRS technology used by the LT8030 has seamless coverage, is always online, and is charged by traffic. [page]

LT8030 contains two main parts: IP part and GPRS module. There is a serial connection between them (Serial 2). The user host computer and LT8030 are also connected by serial port (Serial 1). These two serial port connections can be configured and operated independently. LT8030 has a complete TCP/IP protocol family embedded, including TCP, UDP, FTP, PPP, TELNET, HTTP, Web Server, SMTP, POP3, etc. The embedded TCP/IP enables LT8030 to access the Internet.
LT8030 has two transmission modes that can be switched by software. When LT8030 is in different transmission modes, the flow of data is also different. When the user uses the AT instruction set, LT8030 automatically enters the transparent transmission mode, the user application can directly access the GPRS module, and the user data directly enters the GPRS module through Serial 2; when the user uses the AT+i instruction set, LT8030 automatically enters the non-transparent transmission mode. After the user data enters LT8030 from Serial 1, it is packaged into TCP/IP packets by the IP part, and then sent to the GPRS module through Serial 2. GPRS then packages it into GPRS data packets and transmits it to the GPRS wireless data gateway. At the remote terminal, the user data is collected and processed by the data acquisition device and sent to LT8030 (through the AT+i command interface).
LT8030 first packages the data into TCP/IP data packets, then converts them into GPRS data packets, and transmits them to the wireless data exchange center (MDEC) through a wireless link. MDEC strips the GPRS data packets and transmits the TCP/IP data packets to the Internet through the gateway. The center receives the TCP/IP data packets through the Socket socket and restores it to the original data. When the data is from the center to the terminal, the situation is the same.
(4) Connection of LT8030: The microcontroller is connected to the GPRS module through the level conversion circuit MAX232. MAX232 is used for level conversion between the serial communication interface and the RS 232 communication interface.

4 Design of software
4.1 Software implementation process
The software design of the front-end machine of this system adopts C51 programming, the server monitoring software adopts C language programming, and the database adopts Microsoft Access database. The software implementation first initializes the entire hardware system, then collects data and displays the data in the digital tube. Finally, through AT commands, a connection is established to realize data transmission.
4.2 Introduction to related GPRS AT commands
(1) Basic settings

(2) SOCKET settings
The following is an example of establishing a TCP communication.

5 Conclusion
The realization of the remote monitoring system of the tailings pond based on GPRS is to convert the data into voltage (0~5 V) through the sensor and transmit it to ADC0809 for sampling and quantization, and convert it into binary data. At the same time, the data is stored in the single-chip microcomputer and transmitted to the GPRS module through the single-chip microcomputer communication serial port. The single-chip microcomputer initializes the GPRS wireless module through the AT command, attaches it to the GPRS network, obtains the IP address dynamically assigned to the GPRS terminal by the network operator, and establishes a connection with the destination terminal or server to realize wireless data communication. The system provides an accurate, real-time, low-cost, and all-weather monitoring method for emergency command of tailings dam breach.