Soil moisture-sensing by hacking a solar light
Sarah Al-Mutlaq 
Introduction
In this tutorial, we are going to take a simple solar powered pathway light from a department store and rewire it to be a soil moisture sensor. The finished design will turn on an LED when the soil dries up.
For this tutorial, I purchased a $2 solar pathway light from McGuckins Hardware, but most any standard solar pathway light should do the trick. As far as the circuitry goes, most path lights use a very specialized chip, for which a datasheet can be difficult to find. The chip in my path light was an XY8018 which was set up with an inductor, the solar panel, an LED and a Nickel-Cadmium rechargeable battery. It seems others have had the same issue identifying the IC. While it's always wise to know what you're working with, this project is easy to accomplish without that information.
Materials Used:
Tools Used:
- Wire
- Soldering Iron
- Solder
- Hot glue gun
Other Materials You Could Use:
- Galvanized nails
- Steel rods
- Copper tape
- Gypsum plaster