The Study And Design Of The Control System Of Porphyrin Sensor Based On The Embedded System

Volatile Organic Compounds (VOCs) are kind of important environmental organic pollutants such as aldehyde, esters and organic acids. VOCs are mainly originated from industrial production, food handling and motor vehicle exhaust, which can produce toxicity easily through the respiratory tract, digestive tract and skin. Long-term exposure to VOCs is highly likely to be teratogenic, mutagenic and carcinogenic to humans. At present, routine VOCs detective methods are gas chromatography (GC) and related sensitive detector. However, the high expense and complex procedure and long testing period and only off-line detection limit their applications. Porphyrins are kind of compound whose outer ring is with a subsistent homologues and derivatives collectively. Some porphyrins and their derivatives are characterized by their strong absorption ability and have obvious change in color when mixed with the volatile organic gases which properties make them ideal for use in sensor. Porphyrins can be made into highly specific sensors , which can detect multiple objective volatile organic gases simultaneously when constructed to be an array and has a high-potential prospect.Nowadays , sensors are widely applied in many industrial production and scientific experiments and play an important role in information technology. Sensors and instrumentation have become important components in scientific experiments in biomedical engineering. If the porphyrin sensor can be developed to be tiny,portable and easy operated sensor system,it will conquer the defects of the current detective devices and have prosperous application prospect.Embedded systems are kind of products with the combination of the advanced computer technology, semiconductor technology and electronic technology, which are used in various portable and intelligent control fields. A porphyrin sensor system is designed based on embedded system. The study mainly involves the following aspects:①Light: In order to avoid the influence of the light outset the system, the system is made into shield room in which the inner light is designed. Some general I/O ports of microprocessor are configured as the switch of light. The light need be opened before the reaction between the gas and porphyrin sensor so as to observe the color changes during the reaction and the image collection.②Micro-pump: Owing to the tiny of the system and the narrow of the airway, the gas flow is easy to block when going through the path. A pump is designed to drive the gas flow. Pulse-width modulation is adopted to control the pump accurately which is always digital form during the whole procedure. Keeping the signal in digital way can minimize the noise.③Image collection and processing: To achieve the color change of the porphyrin sensor, a high resolution (1.3M pixels) CMOS image sensor is employed. The concentration can be achieved by comparision the color change during the reaction with the well established standard color library.④Wireless communicaton and data transmission: GPRS is utilized to realize the remote control and wireless data transmission. Utilizing GPRS,embedded microprocessor can send all important information real-timely to remote terminal wirelessly.⑤Human-machine interface: The system utilizes the touch screen as the human-machine interface, with which the functions mentioned above can be performed when the corresponding menu items are clicked.A novel portable system realizing the functions discussed above is developed in the proposed study. Based on the characteristics of the porphyrins and their derivatives and the feature of the embedded systems, we developed a portable porphyrin sensor system, which utilizes the embedded microprocessor to control CMOS image sensor to capture the change of the image of the porphyrin sensor array. Then the image is processed and effective information is analyzed to work out the concentrate of the gas. The imformation can be transmitted to remote terminal wirelessly by GPRS so as to detect the target components of the gas effectively and fast with the isolation to human.