Electronic Brick - Moisture Sensor
The moisture sensor bricks detect the conductivity in soil due to the presence of moisture. The 4 pins are GROUND, Vcc (5VDC), ANALOG and DIGITAL. The onboard switch allow the sensor to be used in one of the ANALOG or DIGITAL modes. In ANALOG mode the SIGNAL can be read from an Arduino analog input. in DIGITAL mode the potentiometer adjusts the set point. If the moisture level exceeds the set point the SIGNAL level goes HIGH.