The Development Of Microcontroller-baslid Suspension-weighing Lysimeter For Potted Plants

Crop water requirement is the most important part of agricultural water. The waterrequirement patterns of crops are of important significance to studying hydraulic cycles,irrigation decision making and implementation, intensive water resources management.Crop water requirement mainly includes plants transpiration and soil surface evaporation andplants body water. In order to study the water requirement and consumption patterns of thepotted plants, a weighing lysimeter was developed based on microcontroller technology,sensor technology, communications technology, Keil software and Visual Studio2008software programming technology and database technology, and the combination ofintegration, test, optimize between slave microcontroller and host computer. The main contentand conclusions of the paper are as follows.(1) The overall structure was designed based on the technology needs and use conditionsof the lysimeter. The weighing capacity of100kg was determined and weighing sensor waschose based on the calculation of weighing capacity and measuring precision.(2) The controller, data collection, display, real-time clock and storage, communicationand power modules were separately designed and the printed circuit boards (PCBs) weremanufactured as well. STC89C52microcontroller was adopted as the controller of thelysimeter. The amplifying and filtering circuits was designed using INA129and OP07CP. TheA/D converting circuit was designed based on TLC2543. LCD12864was used to designdisplay circuit. The real time clock and storage circuits were designed integrating AT24C256and PCF8563respectively, and the power circuit was designed based on ICL7662andLM2575and REF5050.(3) The software of slave microcontroller of lysimeter includes four modules,initialization, data collection, data displaying, real-time clock, data storage and serialcommunication, were developed with C language. The software of the host computer wasdeveloped in the runtime environment of Microsoft Visual Studio2008and written in C#,realizing the communication with slave microcontroller and the display and storage oftransmitted data.(4) With its accessories such as stands and connecting pieces ready, the lysimeter wasfully developed. The test of hardware and software joint debugging and the application experiment of the whole system were made. Performance tests showed that without humansupervision, the slave microcontroller was able to automatically collect, display, store andcommunicate data through serial interface to the host computer and then the host computerdisplayed, analyzed and stored the transmitted data. The lysimeter was characterized by highstability and repeatability and its absolute and maximum relative error were150g and0.75%,respectively, and the ET of potted plants obtained with the instrument were proved wellmatched with their actual ET of potted plants with time. Therefore, it could meet with therequirements of convenience, high accuracy and real time in ET measurement.