How to Use a Soil Moisture Sensor

Operation

The Soil Moisture Sensor measures soil moisture grace to the changes in electrical conductivity of the earth ( soil resistance increases with drought ).

The electrical resistance is measured between the two electrodes of the sensor.

A comparator activates a digital output when a adjutable threshold is exceeded.

Code

At the time we start writing the code, we define 3 variables :

int sensorPin = A0;

- The first one defines the analog pin of the Arduino

int sensorValue;

- The second defines the analog value of the sensor read by the Arduino

int limit = 300;

• The third defines a limit ( in this case if the sensorValue is larger than the limit, then a LED will light up )
• ----------------------------------------------------------------------------------------------------------------

void setup() {
Serial.begin(9600);
pinMode(13, OUTPUT);
}

After, we initialize the serial monitor by indicating the number of baud ( here 9600 ) and also the thirteenth pin of the Arduino ( LED pin ) by indicating a current output.

-----------------------------------------------------------------------------------------------------------------

void loop() {  
sensorValue = analogRead(sensorPin);

We define the sensorValue as being the value read by the Arduino.

Serial.println("Analog Value : ");
Serial.println(sensorValue);

We display the sensorValue on the serial monitor.

if (sensorValue<limit) {
digitalWrite(13, HIGH); 
}
else {
digitalWrite(13, LOW);
 }
delay(1000); 
}

This part of code allows to light up a LED if the sensorValue is smaller than the limit. Otherwise, the LED stays off.

Results

Connections

• Arduino --> Comparator

3V --> VCC

GND --> GND

A0 --> A0

• Comparator --> Sensor

+ --> +

- --> -

• Arduino --> LED

D13 --> +

GND --> -

Connect a resistance between + and - of the LED.

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MisterBotBreak – Tipeee