LoRa低功耗农业传感终端的设计与研发

Design and Implementation of Low-Power LoRa Terminal for Agriculture Environmental Monitoring

针对精细农业生产环境监测场景多、供电难等问题,研发一款锂电池供电低功耗数据采集终端,可集成各类RS485传感器。选用集成主控MCU和LoRa射频的物联网芯片XC30,使用磁保持继电器按需为传感器供电,优化二级降压稳压电路,以此来进行有效的硬件设计。在软件方面,应用LoRa下行消息加载传感器指令,实现通用终端的485传感器的动态接入功能;优化LoRa无线参数:扩频因子SF和发送功率TP;设置终端工作时序流程:休眠、预热、发送和接收四个阶段;分别测量计算传感器、主控和射频在各阶段的功耗,综合计算出终端理论工作时长。在丘陵果园非视距场景下进行实验,终端的丢包率低于5%,信号强度RSSI均值大于-100 dBm,持续工作时长约100 d,可满足农业生产数据采集的需求。

Aimed at meeting the needs of various scenarios and getting rid of the difficulties in power supply which is necessary for sensors in precision agriculture, a low-power environmental monitoring terminal supplied by Li-ion was proposed, which can be integrated with different kinds of RS485 sensor. On the hardware side, a few design was used to reduce energy consumption, such as: using the IoT chipset XC30 which combing the MCU and LoRa RF,controlling sensor power supply by latching relay on demand, keeping voltage stable using two-step buck converter. On the software side, any RS485 sensor can join up the general terminal by sending downlink message delivering the 485 command to terminal. Lora wireless parameters: SF and TP was optimized to enlarge battery endurance. A proper work sequence, including four stages: sleeping, warming-up, sending and receiving was defined. As the power consumption of Sensors, MCU and RF Wireless was calculated individually in this four stages, the total work hours of a terminal can be counted up. In a low-hill orchard, under non line-of-sight environment, packet loss rate less than 5%,average RSSI upper than-100 dBm, the terminal kept working about 100 d, which can meet the needs of environment monitoring in agriculture.