A Versatile, Stand-Alone, In-Field Sensor Node for Implementation in Precision Agriculture

The concept of Precision Agriculture has been conceived several decades ago however, it has never been fully implemented due to several technological constraints, such as the high cost of automated systems. In this paper, a versatile, low-cost and stand-alone sensing node with unique capabilities is presented, suitable for direct soil quality monitoring. The node is equipped with a potentiostat to run electrochemical measurements as well as a circuit for potentiometric measurements, a circuit to accommodate a wide variety of resistance thermometers and a circuit to detect impedance at 1 kHz. All analog circuits feature accuracies of less than 5% with linearity of more than R2 = 0.999. The system is battery-powered and can recharge through a solar panel or a power supply. Bluetooth, WiFi and LoRa communication technologies are supported making the system IoT compatible whilst maintaining a low cost. The designed instrumentation is versatile enough so that it can accommodate other sensors operating under the same principles with different sensitivities, as well as commercial sensors communicating through SPI and I2C protocols. All the modifications to the system can be done through software during sensor calibration.