Soil Humidity Sensors Are Working

The soil humidity sensors are really just two nails placed a certain distance apart in the soil. The Arduino senses an analog value based on the voltage drop from one nail to the other. Low resistance means more humidity in the soil, and thus a smaller voltage drop. Mr. Holt had a good idea to coat the tops of the nails, where the wires are soldered, so that they would both be protected and easily seen by anyone gardening. The readings from the soil have been amazingly consistent with our expectations of the soil dryness.