Coal mine gas temperature and concentration wireless monitoring system design (1)

O introduction

Coal as an important source of energy in industrial production, and many other aspects play an important role in relation to the national economy.

Coal mining safety issues have always been of great importance. If a security issue, not only causing enormous economic losses, but also a direct threat to the safety of the coal workers. In recent years, China's coal mining safety problem situation is not optimistic, around the mine tragedy occurred from time to time, particularly in small mines more serious security risk. Therefore, to take measures of modern security monitoring is a must.

With the advancement of science and technology, coal mining in the pace of modernization of the Security Monitor is constantly moving forward.

Coal mine safety monitoring of parameters, including gas concentration is a very important parameter, if the concentration is too large, easily lead to an explosion hazard, Tad, the same temperature is also a very important parameter.

Many systems use wired transfer, but the existence of the wiring is difficult, expensive shortcomings.

Based on the above, this article has designed a kind coal mine methane concentration, temperature and wireless monitoring system.

1. system composition and working principle

The entire system is the main PC, PC, slave, communication using the wireless communication method, the system diagram as shown in Figure 1.

The entire system including 240 slave, a PC and a PC.

This system uses wireless communication method, the host computer from synchronization signals, slave turn up in their respective time slot-machine send data that is sent every 15 minutes. Gas sensor will gas concentration into electrical signal, the output voltage amplitude and proportional to the concentration, temperature sensor with digital temperature sensors. Lower computer chip and wireless transceiver modules for site monitoring and data collection to be packaged, and through wireless transceiver module data to the host computer. PC or microcontroller and wireless transceiver modules, the main role is in charge of the whole system of the synchronization and receive lower computer data sent to and the forwarding to the PC.

This system uses TI MSP430F135 SCM production company, it has the following characteristics: low power consumption, operating current is µA; fast, fastest instruction cycle reaches 125 ns, peripheral parts, have A/D converter, comparators, two 16-bit timer, 6 8-bit parallel port, etc.

Wireless communication with CHIPCON company CCl000 wireless transceiver chip, it works in the 300 MHz to 1 000 MHz wide ISM band, usually applied to low-power wireless communications. Temperature sensor using a DALLAS company DSl8820. Gas sensor using our own production of MJC4/3.0L.

2 data collection

DSl8820 single bus communication mode, and single-chip connection only needs to add a 5.1 k Ω or pull-up resistor, selection of an external power supply and peripheral circuit is simple and straightforward.

Temperature measuring range is a 55 ° c to + 125 ° c. The conversion result is 9-12, when the result is 12-bit, minimum resolution can reach O.062 5 ℃. In this system, in the initialization phase will be the conversion result is set to 9-bit, the appropriate resolution O.5 ℃, and complete a conversion need only much less than ms 93.75 12-bit conversion of 750 ms. As in the data frame with a byte that temperature, so you want to make a right, the result is an integer.

Each time the data is sent before the 10th temperature data collection, and then averaged to ensure that data is more reliable and accurate.

MJC4/3.0L-type catalytic sensor according to the principle of catalytic combustion effect from detection and compensation components in pairs of two arm bridge, the case of flammable gas detection components resistance when going to bridge the output voltage changes, voltage variable with the gas concentration increased in direct proportion to the increase in the compensation components up to temperature and humidity compensation function.

It has the following characteristics: bridge output voltage linear, response speed, symbol of stable, capable of H2S poisoning. Is widely used in industrial field of natural gas, liquefied gas, coal gas, flammable gases tropane etc and petrol, alcohol, ketones, benzene and other organic solvent vapor concentration detection.

In this system MJC4/3.OL followed by amplifying circuit, gas concentration is a change in the amount of the corresponding output voltage that followed changes in practice, staff want to get more accurate peak, so the system uses the peak detection circuit, as shown in Figure 2.

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