Today we used Arduino to test the moisture level of soil.
We also used the relay circuit to turn on and off the LED with a certain frequency.
Then we used the relay circuit to build a time controller of an extension cord, which we took off a certain part of the wrap from and then cut one of the wires, and added relay two bridge two ends. We then tested with a 220v red+blue light bulb. It worked out well.
Here’s the code: