Capacitive Io T Grain Moisture Detection System Based On ARM

Our homeland is a big country in the production and consumption of grain.Without grain,the country will not be stable,and the people will not be secure.The drying stage is one of the key links before grain storage,the use of large dryers is the preferred drying measure in most areas,but the resistance moisture meter is still widely used to measure the degree of drying.And most of thes moisture meters are tested by rolling,it will cause the loss of grain and is not suitable for continuous real-time detection.Secondly,due to its own mechanical structure,it will also cause the machine to jam and stop,resulting in poor user experience.In order to improve this situation and increase the efficiency of the drying process,a capacitive grain moisture meter with controllable cost,convenient installation and easy maintenance was designed to make the process more accurate and visualized.This grain moisture meter uses STM32F411RCT6 as the main controller.It uses RS-485 hardware circuit and uses Modbus-RTU protocol to interact with Kunlun Tongtai industrial control screen or computer.At the same time,this high-precision temperature control solution uses AD7793 and PT100,with fuzzy Control PID algorithm to accurately control the temperature of the hot air inlet of the dryer.For the measurement of moisture,according to the basic principle that the capacitance value of grain changes due to different moisture content,the moisture value can be obtained indirectly by detecting the capacitance value.For the measurement of the capacitance value,a method similar to the industry standard "555" RC oscillator is used to convert its capacitance into a square wave pulse signal,and the CPLD is used to collect the frequency value of the square wave.For the cloud,the One NET platform was selected,the M5310-A chip was selected for the hardware,and NB-Io T was used for the networking method.Zig Bee is selected for the establishment of the data transmission local area network.The data of each moisture meter is collected on the gateway and then sent to the One NET platform for later data analysis.Users can also send control instructions or parameter information to moisture meter remotely through onenet platform.Secondly,the MCU firmware of the moisture meter can also be upgraded remotely through the One NET platform.The One NET platform also provides one-stop development of mobile apps.Developers can use the components provided by the platform to develop apps that are applicable to both Android and IOS systems without using professional software such as Android Studio.This design finally completed all the hardware and software designs,and went to a drying plant for field installation testing.The test results show that the moisture meter communicates with the industrial control screen normally,the air inlet temperature control is accurate,the Zig Bee network is working properly,and the data can be uploaded through the NB-Io T module,and instructions can be issued remotely through mobile phone.The moisture detection accuracy does not exceed 0.3%,in line with the design requirements,and the overall operation of system is stable.