The Arduino Now Pumps Water!

It was really just a matter of changing a few lines of code and then attaching the relay wires to the breadboard to get the pump working via the Arduino. Although I really didn't have any doubts that it would work, it was nice to see it in action.

What I have now is a small working model of how the automated irrigation system is going to work. Here is the basic setup:

1. On the far left is the Arduino connected to a small white solder-less breadboard. Two white wires connect to the two nails acting as the humidity sensor (input).
2. Two more two white wires connect to the relay (output) that is a small black box between the breadboard and the small pot where the nails are inserted.
3. The relay is connected to the water pump with two more white wires (22 gage).
4. The nails are inserted into the soil and the resistivity of the soil between the nails changes based on the humidity level of the soil.
5. The Arduino reads the resistance as an input that is scaled from 0 to 1024 (theoretically anyway). 0 means maximum resistance, or no electrical flow, and 1024 means no resistance.
6. The Arduino checks this value to see if it is below a threshold, and then sends a LOW signal to the relay. The relay switches (via an electromagnet) and opens up the electrical flow to the pump completing the circuit (its pretty cool, you can hear the "click" of the electromagnet moving in the housing).
7. The pump turns on, the soil gets wet and the Arduino sees the change in the resistivity between the nails, so it then turns off the pump.

I see this being a great lab exercise for students to test out with some nails and a little pump and small container of soil. It really covers the basic control flow of any robotic system - input, decision, output.

There are some modifications that will need to be made, but I will talk about those next time. I will also post the code and schematic as soon as I can.