Project tutorial

DIY Plant Moisture Sensor © CC BY-NC-SA

This project will calculate the water content of soil around a plant by measuring the dielectric constant.

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Components and supplies

 Arduino UNO
×1
 Resistor 221 ohm
×3
 Resistor 10k ohm
×1
 RGB Diffused Common Anode
×1
 Nuts and Bolts
×2
×1
 Male/Male Jumper Wires
×8

Apps and online services

 Arduino IDE

DIY Plant Moisture Sensor

See this project on my website!

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.

You will need to gather these things in order to build this project:

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Step 1: 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.
• Keep tightening the nut until you are unable to pull out the jumper cable

Step 2: 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.

Copy and paste this code into the Arduino IDE:

``````int moistPin = 0;
int moistVal = 0;
int tooDry = 150; //set low parameter for plant
int tooWet = 400; //set high parameter for plant
void setup()
{
Serial.begin(9600);
}
void loop()
{
Serial.println(moistVal);
int percent = 2.718282 * 2.718282 * (.008985 * moistVal + 0.207762); //calculate percent for probes about 1 - 1.5 inches apart
Serial.print(percent);
Serial.println("% Moisture ");
if (moistVal <= tooDry) {
digitalWrite(4, HIGH); //Red LED
digitalWrite(3, LOW);
digitalWrite(2, LOW);
}
else if (moistVal >= tooWet) {
digitalWrite(4, LOW);
digitalWrite(3, HIGH); //Blue LED
digitalWrite(2, LOW);
}
else {
digitalWrite(4, LOW);
digitalWrite(3, LOW);
digitalWrite(2, HIGH); //Green LED
}
delay(250);
}
``````

Step 4: 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)

Further Notes:

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. Mine is not going outside though, and will be fine without a container.

Code

Code snippet #1Plain text
```int moistPin = 0;
int moistVal = 0;
int tooDry = 150; //set low parameter for plant
int tooWet = 400; //set high parameter for plant
void setup()
{
Serial.begin(9600);
}
void loop()
{
Serial.println(moistVal);
int percent = 2.718282 * 2.718282 * (.008985 * moistVal + 0.207762); //calculate percent for probes about 1 - 1.5 inches apart
Serial.print(percent);
Serial.println("% Moisture ");
if (moistVal <= tooDry) {
digitalWrite(4, HIGH); //Red LED
digitalWrite(3, LOW);
digitalWrite(2, LOW);
}
else if (moistVal >= tooWet) {
digitalWrite(4, LOW);
digitalWrite(3, HIGH); //Blue LED
digitalWrite(2, LOW);
}
else {
digitalWrite(4, LOW);
digitalWrite(3, LOW);
digitalWrite(2, HIGH); //Green LED
}
delay(250);
}
```

Schematics

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Published on

November 13, 2018

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