introduction
Monitoring technology plays an important role in the security of political, industrial, and cultural facilities. The monitoring system is an important part of the security system. It has now reached the stage of network digital monitoring. GPRS wireless monitoring system adopts GPRS network as the carrier, realizes wireless connection with Internet through dialing, and sends and collects video data in real time.
1. Basic structural design ideas
General packet radio service technology (G enera lPacket Radio Service) is a mobile data service available to GSM mobile phone users. It provides medium-speed data transfer by using unused TDMA channels in the GSM network. GPRS fire monitoring system The monitoring system is a temperature and smoke detector installed in the monitoring environment, and is controlled by a single-chip microcomputer, connected in series and parallel through RS232 bus transmission, collected by different sensors, sent to the single-chip microcomputer through the transmission line, and passed the microprocessor After the processing, it is sent to the administrator's PC or the mobile phone carried by the administrator through the GPRS module as needed, and connected to the administrator downstairs. When a fire occurs, the installed temperature and smoke detectors will sound an alarm, sound the fire alarm, and the display will flash. At the same time, the single-chip microcomputer can send a text message to the mobile phone of the relevant personnel to inform the relevant personnel that a fire has occurred. At the same time, the SCM compares and analyzes the data with the original data, and starts the on-site execution system alarm system control function.
Second, the overall structure of the system
The system is divided into four parts: temperature and humidity sensor and smoke detection module sensor, management and monitoring, wireless network transmission and control center.
Temperature and humidity sensor and smoke detection module Sensor module: The smoke detection module is realized by a pair of infrared emitting and receiving diodes, and the infrared light emitting diodes work in a pulse state. When no smoke enters the optical detection room, the infrared light is absorbed by the optical labyrinth, and the receiving diode cannot receive the light. When a fire occurs, smoke particles enter the optical detection room to scatter the infrared light, the receiving diode receives the scattered light, generates a pulse current signal, and outputs it after amplification. The pulse signal controls the opening and closing of the infrared emitting diode. The temperature and humidity sensor chip measures the temperature and humidity parameters at the monitoring site. The sensor includes a humidity sensitive element and a temperature sensitive element, which respectively generate signals of relative humidity and temperature, and after amplification, they are sent to 14-bit A / D for analog-to-digital conversion, after calibration and error correction, and through a two-wire string The line interface sends the data to the microcontroller.
The wireless network transmission includes GPRS module, GPRS intranet and Internet public network and corresponding network equipment. The control center consists of a central monitoring server, a web server and a video database server.
The monitoring site consists of embedded video terminal, GPRS module interface and sensor group. The sensor group collects the image information of the monitoring site and sends the data to the monitoring center through GPRS DTU wireless data transmission.
There are two options for the connection between GPRS and the monitoring center: GPRS intranet connection; GPRS + Internet connection.
3. Key technologies
The hardware design of the system: the microprocessor and the communication module realize the network connection, and because GPRS technology is a packet-based transmission technology, the data must be encapsulated by TCP / IP technology before transmission. This task is performed by TCP / IP The protocol processing chip is completed, and the sending and receiving of short messages are mainly done through AT commands.
GPRS has two application methods in this embedded system. One is to use GPRS module to send and receive SMS messages, and the other is to use GPRS module to realize wireless Internet access of microprocessor.
After the data collection unit is started, the physical information of the monitoring area is collected through the connected peripherals, and the received data is analyzed and processed. After receiving the data transmission instruction of the main device control unit, the analyzed data is sent Specific device data transmission stream to the PXA270 microprocessing control unit.
The structure of the PXA270 microprocessor development platform is shown in Figure 1.
Figure 1 PXA270 microprocessor development platform
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