Master FC-28 Soil Moisture Sensor with Arduino in 5 Minutes

				
					
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

const int soilPin = A0;          // FC-28 AO pin connected to A0
const int dryThreshold = 30;     // Alert when moisture < 30% (Note: 0% = driest)
const int airValue = 1023;       // RAW value in dry air (0% moisture)
const int waterValue = 200;      // RAW value when fully submerged (100% moisture, needs calibration)

void setup() {
  Serial.begin(9600);
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println("OLED initialization failed!");
    while (1);
  }
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
}

void loop() {
  int sensorValue = analogRead(soilPin);
  // Map RAW value inversely to percentage (1023→0%, 200→100%)
  int moisturePercent = map(sensorValue, airValue, waterValue, 0, 100);
  moisturePercent = constrain(moisturePercent, 0, 100); // Limit to 0~100 range

  // Display on OLED
  display.clearDisplay();
  display.setCursor(0, 0);
  display.print("Soil Moisture:");
  display.setCursor(0, 20);
  display.print("Raw: ");
  display.print(sensorValue);
  display.setCursor(0, 40);
  display.print("Percent: ");
  display.print(moisturePercent);
  display.print("%");

  // Low moisture alert (lower % = drier)
  if (moisturePercent < dryThreshold) {
    display.setCursor(0, 55);
    display.print("!! NEED WATER !!");
  }
  display.display();

  // Serial output (optional)
  Serial.print("Raw: ");
  Serial.print(sensorValue);
  Serial.print(" | Percent: ");
  Serial.print(moisturePercent);
  Serial.println("%");

  delay(1000);
}