Soil Moisture Sensor

const int redLed=2;
const int greenLed=3;
const int sensorPin=A0;

void setup()
{
  pinMode(redLed,OUTPUT);
  pinMode(greenLed,OUTPUT);
  Serial.begin(9600);//S capital
  digitalWrite(greenLed,LOW);
  digitalWrite(redLed,LOW);
}

void loop()
{
  int value=analogRead(sensorPin);
  Serial.println(value);
  if(value>500){//more value->dry
    digitalWrite(redLed,HIGH);
    digitalWrite(greenLed,LOW);
  }else{
    digitalWrite(greenLed,HIGH);
    digitalWrite(redLed,LOW);
  }
  delay(1000);
}

Ultrasonic Sensor

const int buzzer=2;
const int trigger=3;
const int echo=4;
float duration,distance;

void setup()
{
  pinMode(buzzer,OUTPUT);
  pinMode(trigger,OUTPUT);
  Serial.begin(9600);
  digitalWrite(buzzer,LOW);
}

void loop()
{	
  digitalWrite(trigger,	LOW);
  delay(5);
  digitalWrite(trigger	,HIGH);
  delay(100);
  digitalWrite(trigger,LOW);
  duration=pulseIn(echo,HIGH);//this is in microseconds (use pulseIn)
  distance=(duration/2)*0.034;//this is in cm
  Serial.print("Value : ");
  Serial.println(distance);
  if(distance<70){
    digitalWrite(buzzer,HIGH);
  }else{
    digitalWrite(buzzer,LOW);
  }
  delay(1000);
}

Temperature and Humidity Sensor

#include<DHT.h>
#define DHTPIN 2
#define DHTTYPE DHT11

DHT dht(DHTPIN,DHTTYPE);

void setup()
{
  Serial.begin(9600);
  dht.begin();
}

void loop()
{
  float humidity=dht.readHumidity();
  float temperature=dht.readTemperature();
  Serial.print("Humidity");
  Serial.println(humidity);
  Serial.println("Temperature : ");
  Serial.println(temperature);
  delay(1000);
}

Gas Sensor (OUTPUT not working properly)

const int redLed=2;
const int greenLed=3;
const int buzzer=4;
const int smokeSensor=A5;
void setup()
{
  pinMode(redLed,OUTPUT);
  pinMode(greenLed,OUTPUT);
  pinMode(buzzer,OUTPUT);
  //pinMode(smokeSensor,INPUT);
  Serial.begin(9600);
}

void loop()
{
  int value=analogRead(smokeSensor);
  Serial.print("Smoke : ");
  Serial.println(value);
  if(value>900){
    digitalWrite(redLed,HIGH);
    digitalWrite(greenLed,LOW);
    digitalWrite(buzzer,HIGH);
  }else{
    digitalWrite(redLed,LOW);
    digitalWrite(greenLed,HIGH);
    digitalWrite(buzzer,LOW);
  }
  delay(1000);
}

7 Segment display