Capstone Homemade Moisture Sensors! | Anjelica Harlow + Albert Lui

We are very proud of the fact that instead of buying every sensor we needed for our project, we worked together and made our very own moisture sensor! Granted it wasn't the most difficult thing to build, we still think we can be proud of hand making a sensor from scratch!

To do this we followed a tutorial we found on Instructables here.

I found two nails laying around the house and brought them to class. Next, we would need some kind of wire to attach to these nails. We went down to the shop and asked Taylor for some wire. He cut off a length of thick black cable and then striped it to reveal a few multi-colored cables inside. He lent us a fancy wire stripper that grabs hold of the cable sleeve with one clamp while striping it with the other - an insanely awesome tool. 

We went back to our classroom and proceeded to strip the multi-colored cables to reveal a bunch of skinny copper wires. Angelica took 3 of these wires and braided them together to give them some thickness (she's an expert at braiding hair and was able to do this with extreme speed and consistency). By doing this twice, we had our 2 copper wires! 

The next step was the cover the bare wire up with something so it didn't end up touching other components and messing things up. We were actually able to pull the original multi-colored cable sleeves back up onto our braided wires. We added some electrical tape for safe measure.

Finally, we wrapped these below the heads of the nails and added some gorilla tape to hold them in place to complete our moisture sensors.

Close-up showing the braided wires.

Where the moisture sensors are located within the planter box.

The code was extremely simple to get moisture readings. I guess it works by detecting how much electricity is going into the analog pin that the moisture sensor is plugged into on the Arduino board. If there's more moisture (water conducts electricity), the electricity will flow better from one nail to the other. If we touched the two nails together, the reading would spike into the thousands. We checked the readings by doing an analog read on the pin and using Serial.println to see the values in the Serial Monitor.

One problem we would run into in the future is the rusting of the nails. I should have used galvanized nails like the tutorial suggested.