Arduino Uno Sensor DHT11 Failed to read from DHT sensor

Question

I get this error every time. I used the DHT tester file from this library. Which gives me an error.

And then I realized that in my code Arduino recognizes only the readTemperature function, not readHumidity, but it doesn't give any compile error. Also, when I read the sensor, this is the output:

Humidity Sensor Test
Temp: 0C, Humidity: 0%
Temp: 0C, Humidity: 0%
Temp: 0C, Humidity: 0%

My code is here:

//DHT11 Sensor:
#include "DHT.h"
#define DHTPIN 5 // which digital pin we're connected to
#define DHTTYPE DHT11

DHT dht(DHTPIN, DHTTYPE);

//I2C LCD:
#include <Wire.h> // Comes with Arduino IDE
#include <LiquidCrystal_I2C.h>

// Set the LCD I2C address
LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE); 

void setup() {
  Serial.begin(9600);
  delay(300);
  lcd.begin(16,2);
  Serial.println("Humidity Sensor Test");
  dht.begin();
  delay(300);
}

void loop() {
  // Reading temperature or humidity takes about 250 milliseconds!
  // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
  int h = dht.readHumidity();
  int t = dht.readTemperature();

  // set the cursor to (0,0):
  lcd.setCursor(0, 0);
  // print from 0 to 9:

  lcd.print("Temp: ");
  lcd.print(t);
  lcd.print("C");

  // set the cursor to (16,1):
  lcd.setCursor(0,1);
  lcd.print("Humidity: ");
  lcd.print(h);
  lcd.print("%");

  Serial.print("Temp: ");
  Serial.print(t);
  Serial.print("C, Humidity: ");
  Serial.print(h);
  Serial.println("%");
  delay(2500);
}

Also I have the 10k resistor between data and Vcc pins. Data is connected to digital pin 5. Has anyone had this problem before?

Please, post the actual sketch your are using. This one doesn't compile and your lcd declaration is wrong. — user31481
– user31481, Commented Oct 18, 2017 at 19:21

VE7JRO · Accepted Answer · 2017-09-18 18:56:01Z

There are several versions of the DHT11 library for Arduino out there. This is the one that worked for me: https://github.com/adidax/dht11. Here is a simple sketch to test the sensor with the output going to the serial monitor.

// 5k ohm pull up resistor is used on the data line.
// Sensor operates at 5VDC.
// Data line connects to Arduino Uno pin 3.

#include <dht11.h>
dht11 DHT11;
#define DHT11PIN 3

// Sensor calibration. Start with 0 for each.
const int HumidityCorrection = -10;          // -10 worked with my sensor.
const int CelsiusTemperatureCorrection = 2;  // 2 worked with my sensor.

const float FahrenheitTemperatureCorrection = CelsiusTemperatureCorrection * 1.8;

// Update the serial display every 60 seconds.
const float UpdateSerialDisplay = 60000;

// Celsius to Fahrenheit conversion.
double Fahrenheit(double celsius){
  return 1.8 * celsius + 32;
}

void setup(){
  Serial.begin(9600);
  // Minimum wait for good data recommended is 1 second.
  delay(2000);
  Serial.println("DHT11 TEST PROGRAM ");
  Serial.print("LIBRARY VERSION: ");
  Serial.println(DHT11LIB_VERSION);
}

void loop(){
  Serial.println("");
  int chk = DHT11.read(DHT11PIN);
  switch(chk){
    case DHTLIB_OK: 
      //Serial.println("OK"); 
      break;
    case DHTLIB_ERROR_CHECKSUM: 
      Serial.println("Read sensor: Checksum error"); 
      break;
    case DHTLIB_ERROR_TIMEOUT: 
      Serial.println("Read sensor: Time out error"); 
      break;
    default: 
      Serial.println("Read sensor: Unknown error"); 
      break;
  }

  Serial.print("Humidity: ");
  Serial.print("\t");
  Serial.print(DHT11.humidity + HumidityCorrection);
  Serial.println(" %");

  Serial.print("Temperature: ");
  Serial.print("\t");
  Serial.print(DHT11.temperature + CelsiusTemperatureCorrection);
  Serial.println(" C");

  Serial.print("Temperature: ");
  Serial.print("\t");
  Serial.print(round(Fahrenheit(DHT11.temperature) + FahrenheitTemperatureCorrection));
  Serial.println(" F");

  delay(UpdateSerialDisplay);
}

Once you get this working you can add the LCD code to it. Here is a link to the DHT 11 Humidity & Temperature Sensor manual / data sheet: http://www.micropik.com/PDF/dht11.pdf

Stack Exchange Network

Arduino Uno Sensor DHT11 Failed to read from DHT sensor

1 Answer 1

Hot Network Questions

Arduino Uno Sensor DHT11 Failed to read from DHT sensor

1 Answer 1

Related

Hot Network Questions