Executive Summary
This project aimed to develop a wireless sensor node for detecting soil moisture in agricultural settings. A network of these sensors would be used to detect the spatial variation of moisture over large land areas, allowing for more efficient water usage and measurement automation. The current method for determining soil moisture is an expensive, labor-intensive process of weighing and drying wet soil samples. This project serves as a prototype for the IoT Center for Precision Agriculture (IoT4Ag), an NSF Engineering Research Center focusing on developing IoT technologies for precision agriculture and addressing societal scale challenges of food, energy, and water security.
Our project consists of two major components: the sensor node and the base station. The sensor node is based on a capacitor whose value will change depending upon the permittivity of the soil, causing a detectable shift in the resonant frequency of an LC tank. The capacitor’s geometry is traced into a printed circuit board’s copper layer. The base station used to query this sensor is a USRP B200mini software defined radio (SDR). GNURadio and Matlab were used to implement the signal processing tools needed for analyzing received signals and transmitting the interrogating signal.
Within the 902-928MHz frequency band allocated for Industrial, Scientific, and Medical applications (ISM), we were able to observe a 10 MHz frequency shift in soil samples ranging from 0% to 40% volumetric water content.
Overview and Motivation of Project
The world population is projected to grow to 10 billion people by 2050. Feeding these people presents an ongoing strain on the agricultural industry that will consume lots of land, water, and energy. Agriculture currently accounts for 70% of global water usage, and it is estimated that by the year 2050, approximately 57% of the population will live in areas that suffer from water scarcity at least one month each year. [1] Partnering with Iot4Ag, we are developing a cheap, passive sensor node to measure moisture in soil which will provide feedback about the quality of irrigation in agriculture. Our project will act as an incremental prototype, serving as a proof of concept for the finalized version which will be both passive and biodegradable in order to ensure negative environmental impacts are minimized.
This sensor aims to clearly define the parameters of passively probing soil metrics and will serve as a stepping stone for a future, biodegradable sensor system developed by the Center able to be deployed on a broad spatial scale to measure multiple soil parameters. Being passive and small, the system will be both inexpensive and easy to deploy on a wide scale without need for maintenance, giving farmers a precise network of sensors to optimize allocation of resources and improve yield.
Built With
- gnuradio
- python
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