Code that runs on an Arduino Uno to monitor moisture levels in an under-the-sink compost bin and alert users via LED lights and a message on an LCD screen whether the compost is too dry/too wet/just right.

ezcompost.ino

#include <LiquidCrystal.h>
#include <Servo.h>

int ledR = 4; // RED pin of LED to PWM pin 4
int ledG = 5;
int ledB = 6;
int moistPin = A0;
int moisture = 85;
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);
Servo myservo;
int pos = 0;
float temp;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(ledR, OUTPUT);
  pinMode(ledG, OUTPUT);
  pinMode(ledB, OUTPUT);
  lcd.begin(16, 2);
}

void loop() {
  // get temperature reading
  
  // display temperature reading on LCD
  lcd.setCursor(0,0);
  lcd.print("T: 25C");
  
  // get moisture reading
  // moisture = digitalRead(moistPin);
  // moisture = map(moisture, 730, 880, 0, 100);
  
  // humidity monitoring
  if (moisture < 80) { // LED turns red
    digitalWrite(ledR, HIGH);
    digitalWrite(ledG, LOW);
    digitalWrite(ledB, LOW);
    lcd.setCursor(7,0);
    lcd.print("Too dry. ");
    lcd.setCursor(0,1);
    lcd.print("Add some fruits!");
    delay(100);
  } else if (moisture >= 80 and moisture <= 90) { // LED turns green
    digitalWrite(ledR, LOW);
    digitalWrite(ledG, HIGH);
    digitalWrite(ledB, LOW);
    lcd.setCursor(7,0);
    lcd.print("Moisture ");
    lcd.setCursor(0,1);
    lcd.print("levels on point.");
    delay(100);
  } else if (moisture > 90) { // LED turns blue
    digitalWrite(ledR, LOW);
    digitalWrite(ledG, LOW);
    digitalWrite(ledB, HIGH);
    lcd.setCursor(7,0);
    lcd.print("Too wet. ");
    lcd.setCursor(0,1);
    lcd.print("Add sawdust plz.");
    delay(100);
  } else {
    // do nothing
  }

//  // temperature control
//  if () { // too hot
//    // switch heat source off
//  } else if () { // too cold
//    // switch heat source on
//  } else () { // temp. in acceptable range
//    // do nothing
//  }

//  // spin mixing rod at regular intervals
//  for (pos=0; pos < 180; pos += 1) {
//    myservo.write(pos);
//    delay(15);
//  }
//
//  for (pos = 180; pos >= 1; pose -=1) {
//    myservo.write(pos);
//    delay(15);
//  }
}