Site-Specific Water and Nutrient Application by Wireless Valve Controller Network

Abstract

Variations in plant water and nutrient demand and environmental regulations to protect water quality provide significant justification for development of site-specific irrigation/fertigation systems. But to be accepted by growers, a system must be easy to install and operate. We have developed wireless valve controllers that self-assemble into a mesh network. Mesh networking means that controllers pass messages to extend the effective communication range without using high power radios. We are currently designing a system using low-power wireless modules designed specifically for sensor networks. Solar energy is collected with a miniature panel to operate each controller node without yearly battery replacement. In lab testing, nodes properly responded to commands to open or close a latching valve. Transmission range using 900 MHz radios with dipole antennas varied from 32 m to 217 m depending on obstructions and antenna height above ground. Node current consumption during idle periods was about 180 µA. Current consumption during radio transmission and receiving was about 15 mA. The solar panel produced 52 to 81 mA-h in full sun and 6 to 10 mA-h in shade. Soil moisture, pressure, temperature, and other environmental sensors will be used for feedback control and detection of problems. Such a network of intelligent valve controllers will allow growers in orchards, vineyards, nurseries, greenhouses, and landscapes to develop management practices that improve water and fertilizer use efficiency.