YL-69 soil moisture sensor was interfaced to the arduino through a digital a PCB drive. The PCB drive has a digital potentiometer and a LM393 comparator. The LM393 comparator is used to compare the voltages across the sensor probes and the set Vcc voltage.[7] The digipot is used to alter the sensitivity of the sensor when connected in digital mode. The out of the PCB drive has four connections pins as shown in the table below.