Arduino Soil Moisture Check

soil_moisture.ino

const int VAL_PROBE = 0; // Analog pin 0
const int MOISTURE_LEVEL = 90; // the value after the LED goes ON
 
void setup() {
  Serial.begin(9600);
}
 
void LedState(int state) {
  digitalWrite(13, state); // connect LED to 13
}
 
void loop() {
  int moisture = analogRead(VAL_PROBE);
  float val = fmap(moisture, 0, 1023, 0.0, 5.0); // use 5V
  int percent = val / 5.0 * 100; // convert to percent
  Serial.println(percent); // print percent

  if(percent < MOISTURE_LEVEL) {
    LedState(HIGH); // if less than 90%, alert us with LED on
  } else {
    LedState(LOW); // else, turn off LED
  }

  delay(1000); // repeat every...
}

float fmap(float x, float in_min, float in_max, float out_min, float out_max) {
  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}