Ultra-low-power Wireless Sensor Nodes Of Gas Monitoring

With the rapid development of Micro-Electro-Mechanical System and modern Internet of things,sensor nodes are becoming more and more compact,low-power,and array-based designs.For most semiconductor gas sensors,its gas-sensing material needs to work at a high temperature,and the conventional heating method is generally constant-voltage heating,so the node needs to consume extra power for providing a high-temperature environment,thereby the semiconductor gas sensor node's power consumption is greater than other sensor nodes.How to effectively reduce the power consumption of the semiconductor gas sensor has become a problem that needs to be solved urgently.Firstly,based on the characteristics of rapid thermal response of the micro hotplate gas sensor,the response of the micro hotplate gas sensor in the second pulse heating mode is studied.The intermittent heating mode is designed to reduce the power consumption of the micro hotplate gas sensor.The sensitivity,repeatability and long-term stability of the gas sensor under intermittent heating mode were verified by experiments.Then,according to the low-power heating mode,two wireless gas sensor nodes are designed,one is a Wi-Fi node,and a lowpower chip which called CC3200 is selected as a core processor.The processor integrates a WiFi wireless chip called CC3100,not only low power consumption but also wireless development easily;the other is NB-IoT node,using ultra-low power(only 1.2?A in LPM3 state)chip called MSP430 F5438 A as the core processor and choose BC95-B5 as Wireless module,and have further reduced power consumption of the node.Based on two different performance processors,the two-node embedded hardware schematic and PCB board-level circuit design are completed.At the same time,the power consumption of the node is further reduced by the software low-power consumption strategy.And to achieve the wireless data acquisition of sensor data,automatic network access and other functions.At the same time,in order to adapt to the ever-changing external environment,a PID temperature control algorithm was designed using DAC and ADC to control the temperature of the micro hotplate gas sensor.In addition,in order to facilitate data collection and analysis,a LabVIEW upper PC platform was developed for Wi-Fi nodes to enable real-time display,analysis,and storage of sensor data.At the same time,a codec plug-in was developed for the NB-IoT node based on the China Internet of Things developer platform,which realized the functions of automatic data upload and warning.Finally,the basic functions of the two nodes are tested.The test results show that both nodes can automatically collect and upload,display,and alarm the sensor signals in a lowpower mode.At the same time,the actual effect of temperature control of the PID algorithm is tested.The results show that the PID temperature control algorithm can achieve accurate temperature control,thus ensuring the stability of the gas sensor in different environments.Finally,the average power consumption of the two nodes is calculated respectively.The power consumption of the wireless gas sensor node designed in combination with the low-power heating mode can be reduced to about 1/40 of the conventional semiconductor gas sensor node.