| Coal mine safety is the most important work in coal mining, and coal mine gas safety is the key part of coal mine safety, and it's related directly with coal mine workers about the real-time detection of gas in mines, so detecting the gas concentration and distribution in air more immediatly, more accurately, more conveniently, and more intelligently is the core technology of mine safety field. The highly sensitive, small size, integratable and wireless gas sensing technology is the strong demand of mine safety. Surface Acoustic Wave(Surface Acoustic Wave, SAW) gas sensors have all the above advantages, which is just the need of mine safety research, and this kind of gas sensor are expected to be applied in the mine gas monitoring and intellectual mine construction.In this research, the sound and light alarm system for SAW gas sensor is investigated, and it contain two main parts with lower machine system and upper computer.In the research on lower machine system, the SAW gas sensor detection principle and detection ways were analyzed, and the dual channel delay-line structure was selected to be the target. The center frequency of the SAW sensor in this system is 300 MHZ, and the frequency signal will be mixing, and the difference frequency and the multiple frequency signal will be processed by second-order low-pass filter, and then we will get low frequency difference frequency signal to the warning system. The signal will be amplified and shaped by the amplifier circuit of AD708 and the shaping circuit of LM393 respectively, and they are sent to the master STM32 chip TIM3 CH1 channel for the signal detection. In the signal judgment, the convenient and flexible counting frequency method is used, and the detection period is set as 60 ms. The adopted signal is classified with three kinds of voice alarm, which is realized by the voice chip of AP89042 A corresponding with the concentration of "1%", "5%" and "9.5%" respectively. The light alarm is realized by highlight LED light. Besides, the display port of 4x8 LCD12864 with Chinese characters display available is used as the monitor. Moreover, The SD card with 2G memory and FATFS file system is applied. The record, adjudgement, alarm, display, data storage and communication functions are given.In the research on upper computer, we used the C++ Builder software to design the operation and monitoring system. The communication is realized by RS232 protocol between lower machine system and upper computer, and data package is wraped according to the rule of the check nodes, the alarm and the real data with 4 bytes, and the data is transmitted in 8 bits by the MSComm ActiveX. There are three interfaces, and one is password login interface, which includes logging, password modification and user addition. The second is the calibration interface which complete the sensor calibration; The third is monitoring interface which includes the settings of serial port and acquisition cycle, and also includes data, graph and alarm display.In this research, the sound and light alarm system is investigated systemically. The sensing signal detecting, processing and recording are studied on, and the accurate sensing and real time alarming are realized, and the lower machine system and the upper computer are designed, and the communication between the lower machine and the upper computer is done well, moreover, the alarming operation system in upper computer is constructed. All of the research and fabrication are done according to the standard of coal mine safety, and which can meet the requirement of coal mine safety, and it will be expected to applied in the coal mine gas monitoring, and promote the coal mine safety technology. Of course, this sound and light system is also available for universal related SAW sensing systems. |
PDF Full Text Request