Design Of Capsule-sized Wireless Low-power Micro Gas Detection System

With the development of gas sensor technology,electronic nose gas detection systems equipped with sensor arrays are widely used in the field of biomedicine.Among them,the low power consumption,miniaturization and wireless of gas detection systems are important research directions.This paper designs a capsule-sized wireless low-power micro gas detection system for low-power and miniaturized applications of gas detection systems.First of all,the hardware part of the wireless low-power micro gas detection system is designed and implemented.The hardware circuit includes a sensor array,a temperature control circuit,a collection circuit,a main control chip,and a wireless module.Among them,the gas sensor array uses a micro gas sensor array chip that integrates 4 micro hot plates;miniaturized and low power STM32F103T8U6 is used as the main control chip to achieve sensor temperature control and gas data collection;aiming at the problem of weak load capacity of the main control chip,DAC7512 is used to provide heating voltage for the gas sensor array;PW0316 Bluetooth module is used to realize wireless transmission of signals.The final realization of the capsule-sized miniature gas detection system has a diameter of about 10 mm and a length of about 26.8 mm,which meets the design requirements of miniature gas-sensitive electronic capsules.Then,in terms of hardware drivers,a set of programs is adopted to adapt to the two working modes of low-power detection and fast high-precision detection,which realizes the automatic collection and upload of gas information.In terms of host computer software,a dedicated APP is developed based on the Android operating system to display and automatically save gas data;the web server is developed based on Tencent Cloud,which can upload data to the server for storage in real time through the mobile terminal,which is convenient for users to view in the background.Secondly,according to the low-power application requirements of micro gas-sensitive electronic capsules,based on the characteristics of the micro-heat plate gas sensor,a pulse voltage heating method with a heating pulse width far greater than the thermal response time of the micro-hot plate gas sensor is used to make the gas sensor work in a heating-sleep alternate mode.The effects of the heating voltage pulse period and duty cycle on the gas detection performance of the gas sensor are analyzed through experiments,and the best cycle and duty cycle are obtained.Experimental results show that the use of pulse voltage heating can reduce the power consumption of the gas sensor by an order of magnitude and still achieve good gas detection performance.Finally,the performance test of the designed micro gas detection system was carried out.The results show that when the hardware driver of the gas-sensitive electronic capsule adopts a low-power consumption strategy and the micro-hot plate gas sensor uses a low-power operation mode of pulse voltage heating,the average power consumption of the gas-sensitive electronic capsule is as low as 7.269 m W,which is 9.7% of the power consumption required by the conventional constant pressure heating mode.Using 4 SR927 SW silver oxide button batteries,the maximum working time of the system can reach 45 h.Experiments show that the system can accurately collect and transmit gas information and achieve the design goal,which can meet the application needs of biomedical gas detection fields such as bionic olfaction,smart wearable gas detection,and ingestible gastrointestinal gas detection.