The image above shows the internal mechanism of the device. A servo motors has two ice cream sticks attached to it. On the far end of the sticks is a drinking straw. This straw acts as a candy reservoir. We put candies inside the straw, and as the straw moves to position shown, the candies fall down the hole and slide outside. The straw will only move to this position when the plant is watered. The straw has a piece of paper attached to it. This paper has three expressions. A beaming smile, a normal smile and a sad face. If the moisture level is normal, we see the normal smile. If the moisture level goes below a certain point, the straw moves and we see the sad face. If the user gives waters the soil, the straw moves again and we see the beaming smile from the cutout. The straw stays in this position just long enough for a couple of candies to fall out and then changes it position. 

The Circuit Board