2012年12月05日
Multi-gas Detection System
A gas sensor array collected gas information core unit to AT89C51 and ADC0809 data acquisition and data processing, and display the results to the LED display, identify and detect a variety of gases.
The gas sensor is a gas species can be converted into an electrical signal with the information about the concentration apparatus. Based on the intensity of these electrical signals can be obtained with the test gas present in the environment related to information, which can detect, monitor, alarm. Intelligent gas sensors and pattern recognition systems constitute odor identification instrument has a wide range of application areas, such as the food industry, chemical industry, environmental monitoring, medical diagnostics, safety checks, more and more attention.
Traditional gas detection mostly single gas detection and measurement of a gas to a measuring instrument . An instrument can be performed a variety of gas detection and identification of the development trend of the gas detector, the alcohol sensor methane sensor, CO sensor, etc. This design uses a variety of gas sensors to form a sensor array, the gas through the sensor array can specific component is detected, and is converted into an electrical signal, and then using ADC0809 converts the analog signal of the sensor output as a digital signal , using AT89C51 for data processing and calculations, and the gas type and concentration information via LED display, and on the realization of Qualitative identification and detection of a variety of gases.
1. hardware circuit designThe design of hardware circuit of data acquisition, data conversion, data processing, result display and alarm components involved in chip AD0809 analog-to-digital conversion chip, AT89C51 microcontroller , SUN7474 frequency generator and some gas sensor, drive circuit, reset circuit and LED display modules.
1.1 The gas sensor arrayThe gas sensor array is a key component of the electronic olfactory system unit, the equivalent of the primary olfactory neurons, has a broad spectrum of response characteristics, the cross-sensitivity of different odor / gas gas components of different sensitivity .
The gas sensor is composed of a core of gas sensor array devices. The gas sensor is a specific component in the gas is detected and converted into an electric signal device. Typically, the gas sensor array can be used to separate gas sensor combination, and using the integrated production process, small size, low power consumption, easy to focus on the collection and processing of the signal. Single gas sensors and pass sensitive array have a qualitative difference in the characteristics of a single gas sensor odor / gas response available strength in addition to the response of each sensor, gas sensor array is formed in the multidimensional space of all sensors response pattern, in the case of certain environmental conditions, the response pattern on the array and its excitation is one to one, which is the system of a wide range of odors and gases identification key.
The design requirements to achieve qualitative and quantitative analysis of alcohol, methane, carbon monoxide gas, the first and most important task is to select the appropriate sensor, can be achieved through the performance, price comparison, select MQ-alcohol gas 303A alcohol sensor for methane gas, is used in the semiconductor gas sensor of the MQ-4 , V-40 CO sensor for carbon monoxide gas, the choice is, composed of the sensor array by the three sensors.
The design gas information collected by the gas sensor array, and the collected information into electrical signals, and then sent ADC0809 analog to digital conversion.
1.2 Data acquisition and data processing systemPretreatment, by their respective signal amplifying circuit of the signal provided by the output electrical signal of the gas sensor array, it is converted to a DC signal changes within the range of O ~ 5V, sent to A / D conversion circuit is converted into a digital signal, its data acquisition and processing.
In order to facilitate connection of the 89C51 microcontroller, the system selects the the ADC0809 chip analog-to-digital conversion of the information collected gas. Its resolution of 8 bits, do not have to zero and full scale adjustment, and has a high impedance chopper stabilized comparator, 8-channel multiplexer switch provides direct access to one of the eight single-ended analog signal. The use of single-chip write to start the A / D converter, the conversion to complete before the 89C51 issued by the ADC0809 to the interrupt request signal, the CPU responds to the interrupt request. Through the read operation of the decoder, the conversion result is read and sent to the corresponding memory area to be measured. Re-select to be measured, and again to start the A / D converter interrupt return. ADC0809 89C51 microcontroller connection line, as shown in picture 2.
AT89C51 chip microprocessors.
The 89C51 microcontroller compatible with the 80C51 ATMEL, PHILIPS and SST produced low-power, high-performance 8-bit microcontroller with more hardware resources than 8031, in particular the increase in its internal flash memory Flash ROM can be electrically rewritten brought a lot of convenience to the microcontroller development and application, and the chip price is very cheap. 89C51 In this system, the collected data is processed, its concentration is calculated by the mathematical model of the concentration of various gases, from the digital display of the respective gas type and concentration value, an alarm when the concentration exceeded.
The system also uses a divider SUN7474 divider divide 2 n one-pulse signal, for example, 32768HZ the pulse signal into 1HZ second signal. Is usually T flip-flop, each to a pulse trigger state changes after treatment after n T flip-flop can be one of the n-th power of 2 crossover signal. For the ADC0809 89C51 pick 12MHZ crystal, and output to the divider after ALE end 2MHZ, divider divide clock work .
1.3 Shows the circuitIn this design, the LED display is a display method using the dynamic display. LED dynamic display basic approach is that the public end of the the timeshare rotation digital tube strobe, making the digital pipe turns conduction, the appropriate LED strobe glyph code is displayed in the display field. In this way not only can increase the effective rate of digital tube light hair , and the field of digital tube line is used in parallel, which greatly simplifies the hardware line. The design of treatment results using four LED display , first gas category, after three shows gas concentration. Bitwise rotation lit each LED 1ms keep a lit again within 10 ~ 20ms, repeated more than. So take advantage of the human visual stay like four LEDs are lit simultaneously.
In sum available, based on data acquisition, data processing, and the results of the single-chip multi-gas detection system circuit shown in picture 3.
The design consists of data acquisition, data conversion, data processing, display and alarm several modules.
This article describes the hardware and software design of electronic olfactory system of multi-gas analysis. Used in the design of multi-sensor sensor array, for a variety of different gases, information collection, information conversion and data processing, and finally displays the gas type and concentration of information, and provide a viable solution for the detection of a variety of gases .
Article source from: 3cbuzz.blogspot.com
The gas sensor is a gas species can be converted into an electrical signal with the information about the concentration apparatus. Based on the intensity of these electrical signals can be obtained with the test gas present in the environment related to information, which can detect, monitor, alarm. Intelligent gas sensors and pattern recognition systems constitute odor identification instrument has a wide range of application areas, such as the food industry, chemical industry, environmental monitoring, medical diagnostics, safety checks, more and more attention.
Traditional gas detection mostly single gas detection and measurement of a gas to a measuring instrument . An instrument can be performed a variety of gas detection and identification of the development trend of the gas detector, the alcohol sensor methane sensor, CO sensor, etc. This design uses a variety of gas sensors to form a sensor array, the gas through the sensor array can specific component is detected, and is converted into an electrical signal, and then using ADC0809 converts the analog signal of the sensor output as a digital signal , using AT89C51 for data processing and calculations, and the gas type and concentration information via LED display, and on the realization of Qualitative identification and detection of a variety of gases.
1. hardware circuit designThe design of hardware circuit of data acquisition, data conversion, data processing, result display and alarm components involved in chip AD0809 analog-to-digital conversion chip, AT89C51 microcontroller , SUN7474 frequency generator and some gas sensor, drive circuit, reset circuit and LED display modules.
1.1 The gas sensor arrayThe gas sensor array is a key component of the electronic olfactory system unit, the equivalent of the primary olfactory neurons, has a broad spectrum of response characteristics, the cross-sensitivity of different odor / gas gas components of different sensitivity .
The gas sensor is composed of a core of gas sensor array devices. The gas sensor is a specific component in the gas is detected and converted into an electric signal device. Typically, the gas sensor array can be used to separate gas sensor combination, and using the integrated production process, small size, low power consumption, easy to focus on the collection and processing of the signal. Single gas sensors and pass sensitive array have a qualitative difference in the characteristics of a single gas sensor odor / gas response available strength in addition to the response of each sensor, gas sensor array is formed in the multidimensional space of all sensors response pattern, in the case of certain environmental conditions, the response pattern on the array and its excitation is one to one, which is the system of a wide range of odors and gases identification key.
The design requirements to achieve qualitative and quantitative analysis of alcohol, methane, carbon monoxide gas, the first and most important task is to select the appropriate sensor, can be achieved through the performance, price comparison, select MQ-alcohol gas 303A alcohol sensor for methane gas, is used in the semiconductor gas sensor of the MQ-4 , V-40 CO sensor for carbon monoxide gas, the choice is, composed of the sensor array by the three sensors.
The design gas information collected by the gas sensor array, and the collected information into electrical signals, and then sent ADC0809 analog to digital conversion.
1.2 Data acquisition and data processing systemPretreatment, by their respective signal amplifying circuit of the signal provided by the output electrical signal of the gas sensor array, it is converted to a DC signal changes within the range of O ~ 5V, sent to A / D conversion circuit is converted into a digital signal, its data acquisition and processing.
In order to facilitate connection of the 89C51 microcontroller, the system selects the the ADC0809 chip analog-to-digital conversion of the information collected gas. Its resolution of 8 bits, do not have to zero and full scale adjustment, and has a high impedance chopper stabilized comparator, 8-channel multiplexer switch provides direct access to one of the eight single-ended analog signal. The use of single-chip write to start the A / D converter, the conversion to complete before the 89C51 issued by the ADC0809 to the interrupt request signal, the CPU responds to the interrupt request. Through the read operation of the decoder, the conversion result is read and sent to the corresponding memory area to be measured. Re-select to be measured, and again to start the A / D converter interrupt return. ADC0809 89C51 microcontroller connection line, as shown in picture 2.
The 89C51 microcontroller compatible with the 80C51 ATMEL, PHILIPS and SST produced low-power, high-performance 8-bit microcontroller with more hardware resources than 8031, in particular the increase in its internal flash memory Flash ROM can be electrically rewritten brought a lot of convenience to the microcontroller development and application, and the chip price is very cheap. 89C51 In this system, the collected data is processed, its concentration is calculated by the mathematical model of the concentration of various gases, from the digital display of the respective gas type and concentration value, an alarm when the concentration exceeded.
The system also uses a divider SUN7474 divider divide 2 n one-pulse signal, for example, 32768HZ the pulse signal into 1HZ second signal. Is usually T flip-flop, each to a pulse trigger state changes after treatment after n T flip-flop can be one of the n-th power of 2 crossover signal. For the ADC0809 89C51 pick 12MHZ crystal, and output to the divider after ALE end 2MHZ, divider divide clock work .
1.3 Shows the circuitIn this design, the LED display is a display method using the dynamic display. LED dynamic display basic approach is that the public end of the the timeshare rotation digital tube strobe, making the digital pipe turns conduction, the appropriate LED strobe glyph code is displayed in the display field. In this way not only can increase the effective rate of digital tube light hair , and the field of digital tube line is used in parallel, which greatly simplifies the hardware line. The design of treatment results using four LED display , first gas category, after three shows gas concentration. Bitwise rotation lit each LED 1ms keep a lit again within 10 ~ 20ms, repeated more than. So take advantage of the human visual stay like four LEDs are lit simultaneously.
In sum available, based on data acquisition, data processing, and the results of the single-chip multi-gas detection system circuit shown in picture 3.
This article describes the hardware and software design of electronic olfactory system of multi-gas analysis. Used in the design of multi-sensor sensor array, for a variety of different gases, information collection, information conversion and data processing, and finally displays the gas type and concentration of information, and provide a viable solution for the detection of a variety of gases .
Article source from: 3cbuzz.blogspot.com
Posted by novaking at 10:05│Comments(0)
