NodeMcu DHT11 Tester

/* NodeMCU Pin assigment 

  GPIO Pin  I/O Index Number

  GPIO0  3   GPIO1  10 GPIO2  4    GPIO3  9     GPIO4  2   GPIO5   1   GPIO6  N/A  GPIO7  N/A

  GPIO8  N/A GPIO9  11 GPIO10  12  GPIO11   N/A GPIO12  6  GPIO13  7   GPIO14   5  GPIO15   8   GPIO16   0 */

  D0 : 3      D1 : 10    D2: 4  D3:9   D4 : 2  D5:1  

  D9 : 11     D10: 12

// Example testing sketch for various DHT humidity/temperature sensors

// Written by ladyada, public domain

#include "DHT.h"

#define DHTPIN 2     // what digital pin we're connected to D4

// Uncomment whatever type you're using!

#define DHTTYPE DHT11   // DHT 11

//#define DHTTYPE DHT22   // DHT 22  (AM2302), AM2321

//#define DHTTYPE DHT21   // DHT 21 (AM2301)

// 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");

}

Using a DHTxx Sensor

by lady ada

To test the sketch, we'll use an Arduino. You can use any micrcontroller that can do microsecond timing, but since its a little tricky to code it up, we suggest verifying the wiring and sensor work with an Arduino to start.

Begin by downloading the DHT library from our github repository. To download, click the DOWNLOADS button in the top right corner. Rename the uncompressed folder DHT and make sure that it contains the dht.cpp file and others. Then drag the DHT folder into the arduinosketchfolder/libraries/ folder. You may have to create that libraries sub-folder if it doesnt exist. Restart the IDE.

IMPORTANT: As of version 1.3.0 of the DHT library you will also need to install the Adafruit_Sensor library, which is available from the Arduino library manager:

Now load up the Examples->DHT->DHTtester sketch

If you're using a DHT11 sensor, comment out the line that sets the type:

 Download file

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//#define DHTTYPE DHT22   // DHT 22  (AM2302)

and uncomment the line that says:

 Download file

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#define DHTTYPE DHT11   // DHT 11

This will make the data appear correctly for the correct sensor. Upload the sketch!

You should see the temperature and humidity. You can see changes by breathing onto the sensor (like you would to fog up a window) which should increase the humidity.

Downloads

by lady ada

• Arduino library and example code for DHT sensors
• Adafruit_Sensor library (required by the DHT library above)
• DHT11 datasheet (in chinese, so see the DHT22 datasheet too!)
• DHT22 datasheet