A real life example of using the soil moisture sensor would be in the area of smart irrigation systems. Smart irrigation systems are becoming very lucrative because they help in conserving water. Basically, the water outlets that feed irrigation canals are controlled by central microcontroller-based devices. These microcontrollers get soil moisture data from various sampling points spread over the agricultural lands. Depending on the saturation of water in the sampled area of land, the water outlets feeding the corresponding irrigation canals are opened. Thereafter, the water outlets remain open until the soil moisture saturation level reaches an acceptable level. The water outlets are usually opened and closed using solenoid valves controlled via AC powered relay devices. Later in this book, you will learn how to use AC powered devices via relay modules.
Now, to make the irrigation system smart, the microcontroller can check the weather channel forecast by consuming the weather channel's web service over wireless internet methods. If there is a forecast of rain in the next 12 hours, then the water outlets are not opened, thus saving water! Later in this book, you will learn about wireless communications and connecting to the internet. Thus, the microcontroller unit orchestrates the entire activity of the smart irrigation system.
After completing this book, you will be able to use the Arduino platform as a very handy tool to rapidly develop a working prototype of the preceding real-world example of a smart irrigation system.
This chapter showed us how to measure soil moisture. Chapter 8, Day 6 - Using AC Powered Components on using AC powered devices will help you to understand how to use relay devices for controlling AC powered devices; you may then apply that knowledge to control solenoid valves (as shown in the preceding figure). The operation of a solenoid valve is very simple--switching it on will open the valve and release water. While switching it off will close the valve and stop the water supply. From Chapter 9, Day 7 - World of Transmitters, Receivers, and Transceivers onwards, you will learn various wireless control and communication device techniques to use with the Arduino platform and will be able to apply them to build this smart irrigation prototype.