Soil Moisture Sensor - Complete Guide

1// ================================================================================
2// Read values from a soil moisture sensor and blink LEDs accordingly
3// This code works with resistance-based soil moisture sensors
4// Created on 17 July 2024
5// Created by Lucas Fernando (https://www.youtube.com/@lucasfernandochannel)
6// You are free to use this code the way you want
7// ================================================================================
8
9#define GREEN_LED 2 // Green LED connected to digital pin 2
10#define YELLOW_LED 3 // Yellow LED connected to digital pin 3
11#define RED_LED 4 // Red LED connected to digital pin 4
12#define SENSOR_PIN A5 // Soil moisture sensor connected to analog pin A5
13// Defining soil moisture readings thresholds
14// From 0 to 500 - extremely wet
15// From 501 to 800 - wet
16// From 801 - dry
17#define DRY_THRESHOLD 800
18#define WET_THRESHOLD 500
19
20void setup() {
21  pinMode(GREEN_LED, OUTPUT);
22  pinMode(YELLOW_LED, OUTPUT);
23  pinMode(RED_LED, OUTPUT);
24
25  digitalWrite(GREEN_LED, LOW);
26  digitalWrite(YELLOW_LED, LOW);
27  digitalWrite(RED_LED, LOW);
28
29  Serial.begin(9600);
30}
31
32void loop() {
33  int sensorValue = analogRead(SENSOR_PIN);
34  // Print the sensor reading values
35  Serial.print("Soil moisture sensor value: ");
36  Serial.println(sensorValue);
37
38  if(sensorValue > 0 && sensorValue <= WET_THRESHOLD) {
39    // Extremely wet (green LED)
40    digitalWrite(GREEN_LED, HIGH);
41    digitalWrite(YELLOW_LED, LOW);
42    digitalWrite(RED_LED, LOW);
43  } else if (sensorValue > WET_THRESHOLD && sensorValue <= DRY_THRESHOLD) {
44    // Wet (yellow LED)
45    digitalWrite(GREEN_LED, LOW);
46    digitalWrite(YELLOW_LED, HIGH);
47    digitalWrite(RED_LED, LOW);
48  } else {
49    // Extremely dry (red LED)
50    digitalWrite(GREEN_LED, LOW);
51    digitalWrite(YELLOW_LED, LOW);
52    digitalWrite(RED_LED, HIGH);
53  }
54}

1// =====================================================================================
2// Read values from a soil moisture sensor and turn on or off a water pump accordingly
3// This code works with capacitance-based soil moisture sensors
4// Created on 17 July 2024
5// Created by Lucas Fernando (https://www.youtube.com/@lucasfernandochannel)
6// You are free to use this code the way you want
7//========================================================================================
8
9// Defining soil moisture reading threshold
10// From 0 to 400 - wet soil
11// Above 400 - dry soil
12#define THRESHOLD 400
13#define RELE_PIN 2 //Relè is connected to digital pin 2
14#define SENSOR_PIN A5 //Soil moisture sensor connected to analog pin A5
15
16
17void setup() {
18  pinMode(RELE_PIN, OUTPUT);
19  digitalWrite(RELE_PIN, LOW);
20  Serial.begin(9600);
21}
22
23void loop() {
24  long sensorValue = 0;
25  for (int i = 0; i < 100; i++) {
26    sensorValue += analogRead(SENSOR_PIN);
27  }
28  sensorValue = sensorValue / 100;
29
30  // Print the sensor reading values
31  Serial.print("Soil moisture sensor value: ");
32  Serial.println(sensorValue);
33
34  if (sensorValue > THRESHOLD) {
35    // Turn on the water pump
36    digitalWrite(RELE_PIN, HIGH);
37  } else {
38    // Turn off the water pump
39    digitalWrite(RELE_PIN, LOW);
40  }
41
42  // Wait one second before measure the soil moisture again
43  delay(1000);
44}