The design completes a two-line mine gas alarm system which uses the single chip computer AT89C51 as the core. The system collects the density of gas at fixed time, and transmits it to the computer on the ground through the chip MT8888. As the same time, the system displays the density by the LED displayer under the mine. When the density of the gas exceeds the alarm figure, the system will give alarm. Besides, I place 4keys in the system to change the alarm figure and the fixed time.
Firstly the system transimits the 18-voltage power supply into 5-voltage and 3-voltage power source. The 3-voltage power source is the supply of the gas sensitive element the black and white. And the 5-voltage is the power sources of the other electronic devices. The black and white thansimts the density of the gas into the voltage signal and passes it to the amplifier LM358. The analogue signal is then passed to the V/F transformer LM331, which translate voltage signal into frequency signal. AT89C51 passes the digital signal to the MT8888 chip, which transmits the signal to the up-ground computer through the DTMF signal. Besides, the AT89C51 changes the frequency signal into density signal of 0~4 fen, which is convenient to the miners. When the density of the gas exceeds the alarm figure, the system will shine and raise warning sound. There are 4 keys to change alarm figure and the fixed time which are stored in the x5043.
The soft part of the design includes the main programme and the blocks such as the density, collect, the frequency export, the LED display and the keys search.
Keywords:Two lines system Coal mine gas The frequency converts with the electric voltage Keyboard manifestation