I have a relative who enjoys gardening, so I decided to try something that would help them keep their plants alive. This project will calculate the water content of soil around a plant by measuring the dielectric constant (the soil's ability to transmit electricity) and will alert you with a red LED when the plant needs more water or a blue one when it has too much.
Step 1: Materials
You will need to gather these things in order to build this project.
• Arduino UNO or equivalent (x1)
• 220Ω resistors (for LED) (x3) - red red brown
• 10kΩ resistor (x1) - brown black orange
• RGB LED (x1) or 3 different colored LEDs
• Long Jumper Cables (x2)
• Jumper Cables (x6)
• Breadboard (x1)
• Steel bolts of any size (x2)
• Steel nuts same diameter as bolts above (x2)
Step 2: Create Sensor Prongs
You will need to repeat this step twice (once for each prong).
- Begin to tighten the nut around the bolt
- Slide the end of the long jumper cable between the nut and the head of the bolt.
- Finish tightening the nut until you are unable to pull out the jumper cable
Step 3: Create the Circuit
Follow the schematic or the breadboard image - whichever one works better for you. The wires labeled "out" are the two prongs you just created.
Step 4: Upload This Code
Pretty self explanatory here. Just upload this code to your Arduino!
Step 5: Place Sensor Prongs
- Insert the prongs you made about 1" to 1.5" apart in soil close to the plant you want to monitor.
- Give the plant a healthy amount of water and open the serial monitor
- It should give you readings around 25 - 30% if you gave it the right amount of water
- If not, try moving the prongs around to get it right (or you just added too much water)
Step 6: Outdoor Protection
If this is going outside you will want to put your circuit inside of a Tupperware or other waterproof container to protect it from the elements. Then drill some holes for the sensor wires to come through and add a battery box to power it (see here for how to do that). Mine is not going outside though, and will be fine without a container.