1

I've been trying to follow this tutorial to wire my Arduino MKR1000 to a DHT11 temperature and humidity sensor, but my output consists of either 0's or 255's for both values. I've tried several different arrangements of wires, but none seem to work. Here's my current setup:

enter image description here

And here's my code:

// Example testing sketch for various DHT humidity/temperature sensors // Written by ladyada, public domain

#include "DHT.h"

#define DHTPIN A0     // what digital pin we're connected to; MAY BE PROBLEM

// Uncomment whatever type you're using!
#define DHTTYPE DHT11
//#define DHTTYPE DHT22
//#define DHTTYPE DHT21

// Connect pin 1 (on the left) of the sensor to +5V
// NOTE: If using a board with 3.3V logic like an Arduino Due connect pin 1
// to 3.3V instead of 5V!
// Connect pin 2 of the sensor to whatever your DHTPIN is
// Connect pin 4 (on the right) of the sensor to GROUND
// Connect a 10K resistor from pin 2 (data) to pin 1 (power) of the sensor

// Initialize DHT sensor.
// Note that older versions of this library took an optional third parameter to
// tweak the timings for faster processors.  This parameter is no longer needed
// as the current DHT reading algorithm adjusts itself to work on faster procs. DHT dht(DHTPIN, DHTTYPE);

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

    dht.begin();
}

void loop() {
    // Wait a few seconds between measurements.
    delay(2000);

    // Reading temperature or humidity takes about 250 milliseconds!
    // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
    float h = dht.readHumidity();
    // Read temperature as Celsius (the default)
    float t = dht.readTemperature();
    // Read temperature as Fahrenheit (isFahrenheit = true)
    float f = dht.readTemperature(true);

    // Check if any reads failed and exit early (to try again).
    if (isnan(h) || isnan(t) || isnan(f)) {
        Serial.println("Failed to read from DHT sensor!");
        return;
    }

    // Compute heat index in Fahrenheit (the default)
    float hif = dht.computeHeatIndex(f, h);
    // Compute heat index in Celsius (isFahreheit = false)
    float hic = dht.computeHeatIndex(t, h, false);

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

And here's the diagram of an Arduino MKR1000:

enter image description here

This is my first time using a micro controller, so any help is much appreciated.

UPDATE: Here's my setup with 2 10k resistors in parallel added: enter image description here

  • 1. Format the code, please. 2.Is your connection to the board reliable? It doesn't look good. – smajli Nov 28 '17 at 20:57
  • Have you just pushed the wires through the holes on the Arduino? This is not a reliable connection. The pins are too narrow (or the holes are too wide) to make a firm contact. Try soldering the connections to the Arduino. – Wirewrap Jan 3 '18 at 17:18
  • @Wirewrap I thought about that, but it works fine using other sensors. – Spencer Goff Jan 8 '18 at 17:09
0

I have the identical sensor so I've got two suggestions for you.

  1. I don't see the 5k ohm pull-up resistor on either of the pictures you've uploaded. You could try adding it first and see if that solves the problem.

enter image description here

  1. 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. Have a look at this answer for a sample sketch: Arduino Uno Sensor DHT11 Failed to read from DHT sensor.

EDIT: Connect the sensor data line to digital pin 3 on your Arduino MKR1000.

// 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);
}
| improve this answer | |
  • 1. Okay, I got a 5k resistor and put it on the lines between pins 1 and 2 on the DHT11. No change. Is that where I should put it? Not really sure how to read the diagram you posted. I'll update the original question with this new arrangement. – Spencer Goff Dec 3 '17 at 17:17
  • 2. I tried that sketch with the library you recommended and got lots of errors. I'll happily post those errors if it looks like my wiring is appropriate. – Spencer Goff Dec 3 '17 at 17:18
  • @Spencer Goff The resistor is in the right place but it is a 10k ohm, not a 5k ohm. Add another one in parallel. The diagram I posted is from the DHT11 data sheet: micropik.com/PDF/dht11.pdf. I'll update my answer with a sketch to test the sensor. The sketch will ONLY work with this library: github.com/adidax/dht11. – VE7JRO Dec 3 '17 at 21:07
  • Okay, thanks for the sketch. I'll try to find a couple of 10 resistors tomorrow then. – Spencer Goff Dec 4 '17 at 1:39
  • I've added two 10k resistors in paralleled (as seen in updated question), but I'm getting output that says "Failed to read from DHT sensor!" – Spencer Goff Dec 4 '17 at 15:51

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.