First, we prepared the following modules:

1. Soil Moisture Sensor. Each flowerpot needs such a soil moisture sensor to collect the humility data. the best advantage of this kind of sensor is, it is really cheap, while the disadvantage is that it may corrode after long-term usage. Of course, you can also use better humidity sensors, such as the capacitive soil moisture sensor, but you may need to pay ten times the price.

2. A small pump plus a driver. A driver is to provide enough current for the pump, my application needs a spray distance of about one meter, so this pump is enough. But if you need to make a system that needs a large spray range, you may need a larger pump, or even a pressurized device to make the projectile even farther, such as the watering system in a tea garden.

Notice： We have updated the pump, you may need some male-to-male jumper wires to connect the pump with the driver board.

3. Servo and Rotating Platform, to take the water pipe to water the target plot. In order to control the spray distance and angle, 2 servo would be necessary.

4. Of course, the controller is a must, I use the Crowduino platform, plus an Expansion Board for easy connection.

5. Water pipes and the power supply are essential too, and, some wires would also be helpful.

OK, all things prepared, then let's get started!

Step by step tutorial:
https://www.elecrow.com/sharepj/arduino-automatic-watering-system-for-plants-sprinkler-147.html