Research on community temperature and humidity remote monitoring system based on ARM9 and 3G network

As people's living standards improve, their requirements for living environment are getting higher and higher. What people are particularly concerned about in the home environment are the pollution of harmful gases, temperature and humidity control, etc. Research results show that the most suitable healthy temperature for the human body is 18-24℃, and the healthy humidity is 45%-65%RH. In this environment, the human body feels most comfortable. Most traditional environmental monitoring systems use manual collection or wired monitoring methods. Manual data collection consumes a lot of manpower and material resources, and cannot collect environmental monitoring data in real time, and sometimes brings errors to data collection. Although wired monitoring has many advantages, due to the wide distribution of monitoring points, some monitoring points are remote and dangerous, which brings great difficulties to the implementation of wired monitoring. At the same time, wired monitoring requires a large number of telephone lines for data transmission, which increases huge costs. With the widespread popularization of third-generation mobile communications in my country, remote environmental monitoring systems based on 3G networks and embedded systems have achieved rapid development. The data collected by the monitoring points are transmitted to the monitoring center through the third-generation mobile communications, and remote real-time online monitoring is implemented, and the collected data are summarized, analyzed and processed.

1 System Structure

The remote monitoring system is shown in Figure 1. The system is mainly composed of a remote monitoring terminal, a data transmission system, and a monitoring center. The remote monitoring system processes, encodes, and packages the information collected by the sensor and sends it to the mobile network through a 3G module. The data transmission system consists of a mobile network and an Internet network, and sends the information collected and sent by the remote monitoring system to the monitoring center. The monitoring center analyzes, processes, displays, and stores the received information in a database for query and statistics.

2 Hardware Design

2.1 Remote Monitoring Terminal

The remote monitoring terminal is mainly composed of a data acquisition module, a data processing module, and a wireless transmission module. The hardware structure of the system is shown in Figure 2.

The data acquisition module uses the SHT75 temperature and humidity sensor produced by Sensirion. SHT75 belongs to the pin-type package series in the Sensirion temperature and humidity sensor family. The sensor integrates the sensing element and signal processing circuit on a micro-circuit board and outputs a fully calibrated digital signal. The sensor uses patented CMOSens(R) technology to ensure that the product has extremely high reliability and excellent long-term stability. The sensor includes a capacitive polymer humidity sensing element and a temperature measuring element made of energy gap material. On the same chip, it is seamlessly connected with a 14-bit A/D converter and a serial interface circuit. It has the advantages of excellent quality, rapid response, strong anti-interference ability, and high cost performance.

The data processing module takes into account that the system needs to work continuously for a long time and needs to have strong data processing capabilities and interfaces that support network functions, so the low-power, low-cost, and interface-rich ARM9 processor S3C2410 is selected. Its CPU core uses ARM's 16/32-bit ARM920T RISC processor. The functions integrated in the S3C2410 processor mainly include: 1.8 V core power supply, 3.3 V memory power supply, 3.3 V external I/O power supply; external memory controller; LCD controller provides 1 channel LCD-specific DMA; 8-channel 10-bit ADC interface, with a maximum conversion rate of 500KSPS (Kilo Sample Per Second); 117-bit general I/O ports and 24 channels of external interrupt sources; support for NAND Flash boot loading; advanced architecture with MMU supports WinCE, EPOC32, and Linux.

The wireless transmission module uses CM8350PCDMA20001X EV-DO 3G DTU produced by Xiamen Caimao Company. This DTU has an embedded industrial-grade communication module, standard industrial specification design, supports TCP/UDP/HTTP protocols, and the data interface is the RS232 standard interface, realizing the transparent data transmission function.

2.2 Monitoring Center

The monitoring center is a PC that uses a proxy or has a fixed public IP address. It is the data receiving and displaying end, runs the data receiving and displaying software, and sends control information to the collection end.

3 Software Design

According to the "remote monitoring terminal" and "monitoring center" system, the system software is also divided into two parts: the remote monitoring terminal embedded Linux operating system software and the monitoring center software. The remote monitoring terminal embedded Linux operating system software mainly completes the processing, encoding and packaging of sensor collected information, and connects the system to the mobile network through 3G DTU, and sends the packaged information to the monitoring center through the network. The monitoring center software is programmed in Visual C++6.0, which is an integrated development tool for local C/C++ developed by Microsoft. The monitoring center software mainly receives the data sent by each remote monitoring terminal, displays the calculated temperature and humidity in real time, alarms when there is a temperature and humidity signal that exceeds the set range, and stores the temperature and humidity information received each time in the database for query use. The software design flow chart is shown in Figure 3. [page]

4 Experimental Results

The monitoring center display interface is shown in Figure 4. Set the port number and click Connect to make the system wait for the remote monitoring terminal to connect. If the monitoring terminal requests a connection, the request will be received and the data will be stored in the database. Click the list to select the monitoring unit to be displayed, and set the alarm value through the upper and lower limits of temperature and humidity. When it is lower than the lower limit or higher than the upper limit, the system will automatically alarm. The historical query interface is shown in Figure 5. Select the time and unit to be displayed, click OK to display the query results in the list box, and click Return to return to the monitoring interface.

5 Conclusion

With the improvement of living standards, people pay more and more attention to the safety and comfort of home environment. This system can realize the real-time display and storage of temperature and humidity over a long distance, alarm for exceeding the standard, and provide historical record query function. The paper introduces the principle and process of the overall design in detail from several aspects such as component selection, circuit design, and program design. This design comprehensively utilizes ARM9, sensors, 3G network, data transmission and other technologies, and systematically introduces the composition and design methods of software and hardware.