Research On Infrared Breath Alcohol Detecting System And Its Development Based On Embedded Linux

With the rapid development of social economic, the retain number of private automobile and the number of motor drivers increase year by year. The road safety situation becomes more and more serious, and the road traffic accidents are remaining at a high level. Among all the possible causes, driving under the influence of alcohol is trend to be more and more predominant. We have lately heard the"6.30"in Nanjing, the"8.04"in Hangzhou and the"8.06"in Shanghai, which are really serious traffic accidents because of drunk driving. Therefore, a stable and accurate alcohol detecting system is eagerly desired. The infrared breath alcohol detecting system designed in this paper can be used to analysis the alcohol concentration of exhalation from the deep lung, which is the Breath Alcohol Concentration (BrAC). At the mean time, this system can depict the alcohol concentration curve in real-time, which supports a sound assurance in controlling drunk driving.Firstly, after analysis and comparison of several infrared gas concentration measurements, the non-dispersive infrared (NDIR) absorbing method is chosen to implement the measurement of BrAC of a person. In the view of other energy absorbing materials besides alcohol possibly existing in the breath of a person after drinking, differential absorption technology is used in the design of the light path. By comparison between the objective signal and the reference signal, the infrared source instability and photoelectric devices zero drift is eliminated and the accurate concentration is got. The hardware is designed under these principles, including light source driving circuit, signal conditioning circuit, A/D conversion circuit and the microprocessor control circuit.Secondly, transplant Embedded Linux into the ARM development platform, introduce the transplantation and the development process of Embedded Graphic User Interface (GUI) Qt/Embedded, and implement the driver code of Frame Buffer and the touch-screen. The GUI of the alcohol detecting system is developed based on Qt/Embedded, which realizes the gathering, process and real-time display of the alcohol concentration.Lastly, the indication error and repetitiveness of the system is analyzed by experiments. A test platform is set up to estimate the performance of the system according to Chinese Standard. Experiments show that the system reaches the set goal, has high precision and good environment adaptability.