Soil Moisture Sensor With Arduino

If you happen to have flowers you need to water often in your home, this can be the beginning of a cool adventure. You can use the soil moisture combined with the Arduino board to help you remember to water your plants when needed.

We can add a buzzer and a LED to singal that the flowers need water.

Let’s get started

What you need

Let’s start with a quick explanation of how this sensor works. Basically, the electrodes (the legs) work as an open circuit. Those electrodes help measure the conductivity of the soil when inserted into the soil. These electrodes when inserted into the soil give an analog value depending on the degree of conductivity of the soil.

Now that you know how this sensor works, use the schematic below to connect your parts.

The board between the Arduino and the probe is a controller that helps calibrate the sensing capabilities of the sensor. The connections between the sensor controller and the probe can be done without caring about the polarities of the probe (the probe has no polarity). Make sure you connect the analog output of the sensor to the Arduino. There is also a digital output but we won’t use it here.

And the last part of this: the code.

The code uses basic functions like the analogRead(), delay() and digitalWrite(). You don’t need any additional library to get it working.

Here is how it works:

If the value of sensor’ output is smaller than 950, nothing happens
If the value is bigger than 950 and smaller than 1000 it makes a short beep and flashes the LED few times repetitively at a slow rate
If value is bigger than 1000 it beeps for a second and then flashes the LED repetitively at a fast rate

[code]
void setup() {
Serial.begin(9600);
pinMode(6, OUTPUT);
pinMode(7, OUTPUT);
}
void loop() {
if(analogRead(A0) &amp;gt; 950 &amp;amp;&amp;amp; analogRead(A0) &amp;lt; 1000){
digitalWrite(6, HIGH);
digitalWrite(7, HIGH);
delay(500);
digitalWrite(6, LOW);
digitalWrite(7, LOW);
for(int a = 0; a &amp;lt; 10; a++){
digitalWrite(7, HIGH);
delay(500);
digitalWrite(7, LOW);
delay(500);
 }
}
if(analogRead(A0) &amp;gt;= 1000){
digitalWrite(6, HIGH);
digitalWrite(7, HIGH);
delay(1000);
digitalWrite(6, LOW);
digitalWrite(7, LOW);
for(int a = 0; a &amp;lt; 10; a++){
digitalWrite(7, HIGH);
delay(200);
digitalWrite(7, LOW);
delay(200);
}
}
}
[/code]

As you can see in the video, when the sensor’ electrodes are buried in the pot, the sensor signals that there is a need to water the plants, After watering, it stops beeping. And should start signaling again when the pot is dry again.