Research on the design of a small-scale farmland rainfall runoff sampler

This article designs a small-scale farmland rainfall runoff sampler for collecting rainwater during runoff events and performing chemical analysis. The system automatically collects up to 24 samples simultaneously using an STM32 microcontroller as its control unit. The controller adjusts the PWM signal to manage a DC motor's rotation and on/off state, and it accurately positions the sampling bottles via guide slots and position sensors. When the sampling bottle is positioned, the collection end sends a signal to start the peristaltic pump, which delivers water to the receiving end. And The flow rate is measured by a turbine flowmeter equipped with a pulse recorder. After calibration, the error of each 500 ml sample can be controlled within ±2 %, demonstrating relatively high accuracy and making the sampler suitable for actual sampling requirements. Its simple structure also enhances the durability of equipment in complex outdoor environments. Implementing unmanned rainwater collection can save manpower and material costs while avoiding the danger and uncertainty of manual sampling in rainy weather. The cap of the sampling bottle is designed with anti-volatility features to prevent the volatilization of chemicals such as pesticides and fertilizers in the rainwater, which is beneficial for improving the accuracy of soil and water monitoring.