1) LED
void setup() {
  pinMode(13, OUTPUT);
}

void loop() {
  digitalWrite(13, HIGH);  
  delay(1000);  
  digitalWrite(13, LOW);  
  delay(1000); 
}

2) 3 LED

void setup() {
  pinMode(13, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(11, OUTPUT);
}

void loop() {
  digitalWrite(13, HIGH);  
  delay(1000); 
  digitalWrite(13, LOW);  
  delay(1000);  
  digitalWrite(12, HIGH);  
  delay(1000);  
  digitalWrite(12, LOW);  
  delay(1000);  
  digitalWrite(11, HIGH);
  delay(1000); 
  digitalWrite(11, LOW);  
  delay(1000);  
}

3)PUSH BUTTON

void setup(){
  pinMode(10, INPUT_PULLUP);
  pinMode(12,OUTPUT);  
}

void loop(){
  if (digitalRead(10)==0)
    digitalWrite(12,HIGH);
  else
    digitalWrite(12,LOW);
}

4) potentiometer

int ledPin=9; 
int potPin=A0; 
int potValue=0; 
int ledBrightness=0; 

void setup() {
  pinMode(ledPin, OUTPUT);
  pinMode(potPin, INPUT); 
}

void loop() {
  potValue=analogRead(potPin); 
  ledBrightness=map(poyValue,0,1023,0,255);
  analogWrite(ledPin, ledBrightness); 
  delay(10); 
}


5) Buzzer

#define buzzer 8
void setup() {
  pinMode(buzzer, OUTPUT);
}

void loop() {
  tone(buzzer, 1000,500);
  delay(1000);
  noTone(buzzer);
  delay(1000);
}


6)DHT 11 SENSOR

#include "DHT.h"
#define DHTPIN 2 
#define DHTTYPE DHT11 
DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  Serial.println(F("DHTxx test!"));
  dht.begin();
}

void loop() {
  delay(2000);
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  float f = dht.readTemperature(true);

  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println(F("Failed to read from DHT sensor!"));
    return;
  }

  float hif = dht.computeHeatIndex(f, h);
  float hic = dht.computeHeatIndex(t, h, false);

  Serial.print(F("Humidity: "));
  Serial.print(h);
  Serial.print(F("%  Temperature: "));
  Serial.print(t);
  Serial.print(F("°C "));
  Serial.print(f);
  Serial.print(F("°F  Heat index: "));
  Serial.print(hic);
  Serial.print(F("°C "));
  Serial.print(hif);
  Serial.println(F("°F"));
}


7) DHT 11 NODEMCU

#include "DHT.h"
#define DHTPIN D2  
#define DHTTYPE DHT11  
DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  Serial.println(F("DHTxx test!"));
  dht.begin();
}

void loop() {
  delay(2000);
  float h = dht.readHumidity();
  float t = dht.readTemperature();
  float f = dht.readTemperature(true);

  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println(F("Failed to read from DHT sensor!"));
    return;
  }

  float hif = dht.computeHeatIndex(f, h);
  float hic = dht.computeHeatIndex(t, h, false);

  Serial.print(F("Humidity: "));
  Serial.print(h);
  Serial.print(F("%  Temperature: "));
  Serial.print(t);
  Serial.print(F("°C "));
  Serial.print(f);
  Serial.print(F("°F  Heat index: "));
  Serial.print(hic);
  Serial.print(F("°C "));
  Serial.print(hif);
  Serial.println(F("°F"));
}

8) 1 LED using Node MCU


void setup(){
  pinMode(D2, OUTPUT);
 
}

void loop() {
  digitalWrite(D2, HIGH);
  delay(1000);
  digitalWrite(D2, LOW);
  delay(1000);
  
}


9) 2 LED USING NODE MCU


void setup(){
  pinMode(D2, OUTPUT);
  pinMode(D7, OUTPUT);
}

void loop() {
  digitalWrite(D2, HIGH);
  delay(1000);
  digitalWrite(D2, LOW);
  delay(1000);
  digitalWrite(D7, HIGH);
  delay(1000);
  digitalWrite(D7, LOW);
  delay(1000);

}



10) LM35 SENSOR

#define sensorPin A0
void setup() {
  Serial.begin(9600);
}

void loop() {
  int reading = analogRead(sensorPin);
  float voltage = reading * (5.0 / 1024.0);
  float temperatureC = voltage * 100;
  Serial.print("Temperature: ");
  Serial.print(temperatureC);
  Serial.print("\xC2\xB0"); 
  Serial.print("C  |  ");
  float temperatureF = (temperatureC * 9.0 / 5.0) + 32.0;
  Serial.print(temperatureF);
  Serial.print("\xC2\xB0");
  Serial.println("F");
  delay(1000);
}