I connected the DH11 :

1-GND to GND

2- vcc to 5v

3- Data to pin 4.

LED

1-(+ve) to pin 2

2-(-ve ) to resistance

Push button

1- to resistance

2- to GND

• the Arduino code

#include "DHT.h"

#define DHTPIN 4

#define DHTTYPE DHT11

DHT dht(DHTPIN, DHTTYPE);

int LED = 2;

int state =1;

void setup() {

Serial.begin(9600);

Serial.println(F("DHTxx test!"));

dht.begin();

pinMode (LED, OUTPUT);

}

void loop() {

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"));

if(Serial.available())

{

char x = Serial.read ();

if ( x == 'a'){

if (state ==0) {

state = 1;

digitalWrite (LED, HIGH);

}

else if (state == 1) {

state == 0;

digitalWrite (LED, LOW);

}

}

}

}