WWZMDiB 3.3V Capacitive Soil Moisture Sensor v1.2 For Arduino Raspberry Pi DIY Automatic Watering Capacitive sensing principle is used to detect soil moisture to avoid corrosion problems. Supports 3.3V wide voltage working environment. Micro PCs such as Raspberry Pi need an external ADC (analog signal to digital signal) conversion module to work. With an external screen and a motherboard, you can talk to your plants!