Class for DHT11, DHT21 and DHT22 (temperature & humidity)

I've updated the article so that the lib will include a reference to the playground.

Rob, I don't see your combination library here: http://arduino.cc/playground/Main/InterfacingWithHardware#envtop

...and there's a confusing mix of stuff there. (Can we just say your's is the best ?? 8) )

Its under Humidity

  • DHT_lib One library that supports both DHT11 and DHT 22 <<<<<<<<<<<<<<<<<< that one

This is the direct URL - http://arduino.cc/playground/Main/DHTLib

Don't know if mine is the best, best is a subjective term at best (oops recursion) and it allways depends on the project context what is the best match.

Ustedes usan la linea de datos conectada directamente a un puerto?. And not use a resistor entre la linea de datos y Vcc.

Ustedes usan la linea de datos conectada directamente a un puerto?. And not use a resistor entre la linea de datos y Vcc. You use the data line connected directly to a port?. And not use a resistor between the Vcc and data line.

No I did not use a resistor between the data line and the Vcc. But in my project the lines were very short. If your lines are longer you could try a 4K7 resistor (similar to I2C).

Regards, Rob Translation by Google translate


No, no hizo uso de una resistencia entre la línea de datos y la Vcc. Pero en mi proyecto de las líneas eran muy cortos. Si las líneas son más largas que podría tratar de una resistencia de 4K7 (similar a I2C).

Saludos, robar Traducción de Google Translate

I'm trying to build a simple sensor upload to Pachube. I've been troubleshooting this for awhile, and it seems that the problem is with the DHT22 readings, not with the push to Pachube. I'm reading the data from the DHT22 correctly:

+++++++++++++++++++++++++++++++++++++++++++++++++ OK, 47.2, 26.0 sync status code => 200 data count=> 4 , 0,654 1,712 2,1 3,1

That's my serial output. The line after the "+"s is the checksum and humidity and temperature read from the DHT22. The two lines below that are link messages regarding my connection to Pachube. The final 5 lines deal with the data being sent to Pachube. The first two pieces (0 and 1) of data are analog reads from a light sensor and a motion sensor connected to analog lines. The two items following that (2,3) are the temperature and humidity reads from the DHT22. I can read the DHT22 in the first portion of my code. I cannot read them in the second portion of my code. Why? I've tried various methods of placing the initial DHT22 data into variables, and printing those variables. Inevitably the serial monitor prints out a "1" when it is trying to send the data feed to Pachube.

Am I wrong? Am I attacking this the wrong way, and instead should be looking at the Pachube end of things?

Circuit:
* Ethernet shield attached to pins 10, 11, 12, 13
*  Sensors:  DHT22 dataline connected to pin 7.  Suggested 4.7k Pull-up used
              Analog Pin 0 is a photocell to detect light levels
              Analog Pin 1 is a motion sensor

* Based on code:
* Created 22 April 2011
* By Jeffrey Sun
* http://code.google.com/p/pachubelibrary/
* and 
* robtillart
* http://arduino.cc/forum/index.php/topic,58531.0.html
* http://arduino.cc/playground/Main/DHTLib

*/
#include 
#include "ERxPachube.h"
#include 
#include 

dht DHT;
#define DHT22_PIN 7
byte mac[] = { 0x90, 0xA2, 0xDA, 0x00, 0x21, 0xE3 };
byte ip[] = { 192, 168, 1, 20   };                  // no DHCP so we set our own IP address

int Temp;
int Humidity;
int OldTemp = Temp;
int OldHumidity = Humidity;

#define PACHUBE_API_KEY             "PACHUBE API KEY" // fill in your API key PACHUBE_API_KEY
#define PACHUBE_FEED_ID             34665 // fill in your feed id

ERxPachubeDataOut dataout(PACHUBE_API_KEY, PACHUBE_FEED_ID);

void PrintDataStream(const ERxPachube& pachube);

void setup() {

    Serial.begin(9600);
    Ethernet.begin(mac, ip);

    dataout.addData(0);
    dataout.addData(1);
    dataout.addData(2);
        dataout.addData(3);
}

void loop() {

    Serial.println("+++++++++++++++++++++++++++++++++++++++++++++++++");
    float fSensorData = 15.23;
        int chk = DHT.read22(DHT22_PIN);
        switch (chk)
        {
          case 0:  Serial.print("OK,\t"); break;
          case -1: Serial.print("Checksum error,\t"); break;
          case -2: Serial.print("Time out error,\t"); break;
          default: Serial.print("Unknown error,\t"); break;
          }
        // DISPLAY DATA
        Temp = (DHT.temperature, 1);
        Humidity = (DHT.humidity, 1);
        //Serial.print(Temp);
        //Serial.print(",\t");
        //Serial.println(Humidity);
        Serial.print(DHT.humidity, 1);
        Serial.print(",\t");
        Serial.println(DHT.temperature, 1);
    dataout.updateData(0, analogRead(0));
    dataout.updateData(1, analogRead(1));
    dataout.updateData(2, (DHT.temperature,1));
        dataout.updateData(3, (DHT.humidity,1));
    int status = dataout.updatePachube();

    Serial.print("sync status code  => ");
    Serial.println(status);

    PrintDataStream(dataout);
        OldTemp = Temp;
        OldHumidity = Humidity;
    delay(30000);
}

void PrintDataStream(const ERxPachube& pachube)
{
    unsigned int count = pachube.countDatastreams();
    Serial.print("data count=> ");
    Serial.println(count);

    Serial.println(",");
    for(unsigned int i = 0; i < count; i++)
    {
        Serial.print(pachube.getIdByIndex(i));
        Serial.print(",");
        Serial.print(pachube.getValueByIndex(i));
        Serial.println();
    }
}

Possibly related, maybe not: I'm getting a fair number of checksum errors (Approximately 1 in 10). Is there a way to reduce that number? Any suggestions?

Probably your sample frequency is too high, IIRC the datasheet advices 2000 millis between samples. Can that be the problem?

A quick update: I started playing around a bit more and fixed the problem. It seems that i needed to drop the comma after the sensor request (dht.temperature) instead of (dht.temperature, 1). I'm not sure why that matters. I'm getting serial prints using the previuos codes.

Sorry, missed a comment in between.

I'm pretty sure I'm sampling every thirty seconds. However, I just realized that my code is getting the data several times in each iteration. I'd think that this would simply get the old values, but perhaps not. I've done some code revisions. I also changed the temperature format to the US standard Fahrenheit, to allow my girlfriend to use the system.

Right now the system is working. I'm still getting checksum errors at about half the rate.

Circuit:
* Ethernet shield attached to pins 10, 11, 12, 13
*  Sensors:  DHT22 dataline connected to pin 7.  Suggested 4.7k Pull-up used
              Analog Pin 0 is a photocell to detect light levels
              Analog Pin 1 is a motion sensor

* Based on code:
* Created 22 April 2011
* By Jeffrey Sun
* http://code.google.com/p/pachubelibrary/
* and 
* robtillart
* http://arduino.cc/forum/index.php/topic,58531.0.html
* http://arduino.cc/playground/Main/DHTLib

*/
#include 
#include "ERxPachube.h"
#include 
#include 

dht DHT;
#define DHT22_PIN 7
byte mac[] = { 0x90, 0xA2, 0xDA, 0x00, 0x21, 0xE3 };
byte ip[] = { 192, 168, 1, 20   };                  // no DHCP so we set our own IP address

float TempC = (DHT.temperature, 1);
float Humidity =(DHT.humidity, 1);
float TempF;
float OldTemp = TempF;
float OldHumidity = Humidity;

#define PACHUBE_API_KEY             "Your API Key HERE" // fill in your API key PACHUBE_API_KEY
#define PACHUBE_FEED_ID             34665 // fill in your feed id

ERxPachubeDataOut dataout(PACHUBE_API_KEY, PACHUBE_FEED_ID);

void PrintDataStream(const ERxPachube& pachube);

void setup() {

    Serial.begin(9600);
    Ethernet.begin(mac, ip);

    dataout.addData(0);
    dataout.addData(1);
    dataout.addData(2);
        dataout.addData(3);
}

void loop() {

    Serial.println("+++++++++++++++++++++++++++++++++++++++++++++++++");
    float fSensorData = 15.23;
        int chk = DHT.read22(DHT22_PIN);
        switch (chk)
        {
          case 0:  Serial.print("OK,\t"); TempC = (DHT.temperature); Humidity = (DHT.humidity); break;
          case -1: Serial.print("Checksum error,\t"); break;
          case -2: Serial.print("Time out error,\t"); break;
          default: Serial.print("Unknown error,\t"); break;
          }
        // DISPLAY DATA
        //Temp = (DHT.temperature, 1);
        //Humidity = (DHT.humidity, 1);
        //int(Temp);
        //int(Humidity);
        //Serial.print(Temp);
        //Serial.print(",\t");
        //Serial.println(Humidity);
        TempF = float((TempC * float(1.8))+32);
        //Serial.print(DHT.humidity, 1);
        //Serial.print(",\t");
        //Serial.println(TempC);
        //Serial.println(TempF);
        
    dataout.updateData(0, analogRead(0));
    dataout.updateData(1, analogRead(1));
    //dataout.updateData(2, (DHT.temperature,1));
        //dataout.updateData(3, (DHT.humidity,1));
        dataout.updateData(2, TempF);
        dataout.updateData(3, Humidity);
    int status = dataout.updatePachube();

    Serial.print("sync status code  => ");
    Serial.println(status);

    PrintDataStream(dataout);
        OldTemp = TempF;
        OldHumidity = Humidity;
    delay(30000);
}

void PrintDataStream(const ERxPachube& pachube)
{
    unsigned int count = pachube.countDatastreams();
    Serial.print("data count=> ");
    Serial.println(count);

    Serial.println(",");
    for(unsigned int i = 0; i < count; i++)
    {
        Serial.print(pachube.getIdByIndex(i));
        Serial.print(",");
        Serial.print(pachube.getValueByIndex(i));
        Serial.println();
    }
}

The statement "float TempC = (DHT.temperature, 1); " makes little sense, You copied it from : Serial.println(DHT.temperature, 1); where it means print the float DHT.temperature with one decimal You cannot copy that into an assigment,

Here a patched (& stripped) version of your code, not tried as I don't have the pachube lib and sensor nearby to rebuild your sketch. Let me know how it works...

#include 
#include "ERxPachube.h"
#include 
#include 

dht DHT;
#define DHT22_PIN 7
byte mac[] = { 
  0x90, 0xA2, 0xDA, 0x00, 0x21, 0xE3 };
byte ip[] = { 
  192, 168, 1, 20   };                  // no DHCP so we set our own IP address

float TempC = 0;
float Humidity = 0;
float TempF = 0;
float OldTemp = 0;
float OldHumidity = 0;

#define PACHUBE_API_KEY             "Your API Key HERE" // fill in your API key PACHUBE_API_KEY
#define PACHUBE_FEED_ID             34665 // fill in your feed id

ERxPachubeDataOut dataout(PACHUBE_API_KEY, PACHUBE_FEED_ID);

void PrintDataStream(const ERxPachube& pachube);

void setup() 
{
  Serial.begin(9600);
  Ethernet.begin(mac, ip);

  dataout.addData(0);
  dataout.addData(1);
  dataout.addData(2);
  dataout.addData(3);
}

void loop() {

  Serial.println("+++++++++++++++++++++++++++++++++++++++++++++++++");
  float fSensorData = 15.23;
  int chk = DHT.read22(DHT22_PIN);
  switch (chk)
  {
  case 0:  
    Serial.print("OK,\t"); 
    TempC = DHT.temperature; 
    Humidity = DHT.humidity; 
    break;
  case -1: 
    Serial.print("Checksum error,\t"); 
    break;
  case -2: 
    Serial.print("Time out error,\t"); 
    break;
  default: 
    Serial.print("Unknown error,\t"); 
    break;
  }
  
  TempF = float((TempC * float(1.8))+32);

  dataout.updateData(0, analogRead(0));
  dataout.updateData(1, analogRead(1));
  dataout.updateData(2, TempF);
  dataout.updateData(3, Humidity);
  
  int status = dataout.updatePachube();

  Serial.print("sync status code  => ");
  Serial.println(status);

  PrintDataStream(dataout);
  OldTemp = TempF;
  OldHumidity = Humidity;
  delay(30000);
}

void PrintDataStream(const ERxPachube& pachube)
{
  unsigned int count = pachube.countDatastreams();
  Serial.print("data count=> ");
  Serial.println(count);

  Serial.println(",");
  for(unsigned int i = 0; i < count; i++)
  {
    Serial.print(pachube.getIdByIndex(i));
    Serial.print(",");
    Serial.print(pachube.getValueByIndex(i));
    Serial.println();
  }
}

robtillaart, Thank you very much! I'm in the process of trying to reduce the number of erroneous readings with the DHT22 sensor. It seems that a 1 in 10 error rate is something to actually shoot for. Some of my test runs are scoring an error rate of closer to 4 in 10 or higher.

Has anyone had any success reducing the error rate with this sensor? I've placed the filter capacitor across the power and ground pins, but that didn't seem to have much of an effect.

More of an update: I added in batch of code that records how often the system is getting Checksum errors. I then left the system running while I went to sleep. Lo and Behold, the error rate is consistently 45%, and I'm frequently getting abberant readings of ~55f (~12c). The room is clearly not that cold.

I know you're not supposed to check the sensor more often than every 2 seconds. I rewrote robtillaart's code a little bit (Which is like having a 4th grader trying to follow Da Vinci, his code is much more succinct):

#include 
#include "ERxPachube.h"
#include 
#include 

dht DHT;
#define DHT22_PIN 7
byte mac[] = { 
  0x90, 0xA2, 0xDA, 0x00, 0x21, 0xE3 };
byte ip[] = { 
  192, 168, 1, 20   };                  // no DHCP so we set our own IP address

float TempC = 0;
float Humidity = 0;
float TempF = 0;
float OldTemp = 0;
float OldHumidity = 0;
float error = 0;
float run = 0;
float errorPerc = 0;

#define PACHUBE_API_KEY             "Your API Here" // fill in your API key PACHUBE_API_KEY
#define PACHUBE_FEED_ID             34665 // fill in your feed id

ERxPachubeDataOut dataout(PACHUBE_API_KEY, PACHUBE_FEED_ID);

void PrintDataStream(const ERxPachube& pachube);

void setup() 
{
  Serial.begin(9600);
  Ethernet.begin(mac, ip);

  dataout.addData(0);
  dataout.addData(1);
  dataout.addData(2);
  dataout.addData(3);
}

void loop() {

  Serial.println("+++++++++++++++++++++++++++++++++++++++++++++++++");
  float fSensorData = 15.23;
  int chk = DHT.read22(DHT22_PIN);
  delay(10000);
  switch (chk)
  {
  case 0:  
    Serial.print("OK,\t"); 
    TempC = DHT.temperature; 
    //Humidity = DHT.humidity; 
    break;
  case -1: 
    Serial.print("Checksum error,\t");
    error = error +1; 
    break;
  case -2: 
    Serial.print("Time out error,\t"); 
    break;
  default: 
    Serial.print("Unknown error,\t"); 
    break;
  }
  
  TempF = float((TempC * float(1.8))+32);
  if (TempF > 150)
  {
    TempF = OldTemp;
  }
  delay(20000);
  int chk2 = DHT.read22(DHT22_PIN);
  delay(10000);
  switch (chk2)
  {
  case 0:  
    Serial.print("OK,\t"); 
    //TempC = DHT.temperature; 
    Humidity = DHT.humidity; 
    break;
  case -1: 
    Serial.print("Checksum error,\t");
    error = error + 1; 
    break;
  case -2: 
    Serial.print("Time out error,\t"); 
    break;
  default: 
    Serial.print("Unknown error,\t"); 
    break;
  }
  if (Humidity > 101)
  {
    Humidity = OldHumidity;
  }
  

  dataout.updateData(0, analogRead(0));
  dataout.updateData(1, analogRead(1));
  dataout.updateData(2, TempF);
  dataout.updateData(3, Humidity);
  
  int status = dataout.updatePachube();

  Serial.print("sync status code  => ");
  Serial.println(status);

  PrintDataStream(dataout);
  if (TempF < 150)
  {
    OldTemp = TempF;
  }
  if (Humidity < 101)
  {
    OldHumidity = Humidity;
  }
  
  run = run+2;
  errorPerc = error / run;
  Serial.print(errorPerc);
  Serial.println("% errors");
  delay(20000);
}

void PrintDataStream(const ERxPachube& pachube)
{
  unsigned int count = pachube.countDatastreams();
  Serial.print("data count=> ");
  Serial.println(count);

  Serial.println(",");
  for(unsigned int i = 0; i < count; i++)
  {
    Serial.print(pachube.getIdByIndex(i));
    Serial.print(",");
    Serial.print(pachube.getValueByIndex(i));
    Serial.println();
  }
}

I'm trying to send information my environmental conditions to Pachube every minute. That's the goal. I'm wondering about the requests to the sensor. The int chk = DHT.read22(DHT22_PIN); and subsequent "case" check, is that a request from the sensor? When I'm asking the sensor for the current humidity and temperature, are those two different requests? Should I space these out as much as possible? (This is what I did in the code above). Or does the int chk = DHT.read22(DHT22_PIN); request call all the sensor information, and load it into the Arduino memory, waiting for the DHT.temperature and DHT.humidity calls?

Does anyone else have a similar error rate? That's what I'm really trying to drive down.

int chk = DHT.read22(DHT22_PIN);

The read22() call tries to read data from the sensor and fills the variables DHT.temperature and DHT.humidity. The return value tells if something went wrong during that "exercise". Some people work with the "good weather" scenario and leave out all the checks, that's a design choice.

When I'm asking the sensor for the current humidity and temperature, are those two different requests?

NO, if you do a read22() both temperature and humidity are read. They can be obtained by reading the members DHT.temperature and DHT.humidity

Or does the int chk = DHT.read22(DHT22_PIN); request call all the sensor information, and load it into the Arduino memory, waiting for the DHT.temperature and DHT.humidity calls?

Yes, if you dive into the code of the library (don't be afraid ;) , you see that temp and humidity are both filled in the read22() call.

MY errorrate with this sensor was definitely lower, no figures at hand.

I've posted on the retailer's website. I'll let you folks know what develops. Thanks again!

[quote author=Terry King link=topic=58531.msg425671#msg425671 date=1303415383]

Here's my first pass: http://arduino-info.wikispaces.com/TemperatureHumidity PLEASE critique / comment!!

[/quote]

Hi Terry, i´m new with Arduino and my first project is building a temperature-regulator. just i see your project and take parts from your code, but i can not see negative values on my display. have you got an idea, which part i must change? Sorry, i´m newbie and my english is not the best, but i hope, you or everyone can help...

thank you

olli

/*
Basierend auf einen Artikel auf dieser Seite:
http://arduino-info.wikispaces.com/PROJECT-Temp-Humidity-Display

den aktuellen Stand findest Du hier:
http://alturl.com/rpods
*/

/*-----( Import needed libraries )-----*/
#include 
#include 
#include 
/*-----( Declare objects )-----*/
LiquidCrystal lcd(8, 9, 4, 5, 6, 7); //##### DFRobot LCD Keypadshield V1.0
 // legt die pins auf dem shield fest

/* begin des tastatur-bereichs */
int lcd_key = 0; // legt nutzung der tasten fest und dann die tasten selber
int adc_key_in = 0;
#define btnRIGHT 0
#define btnUP 1
#define btnDOWN 2
#define btnLEFT 3
#define btnSELECT 4
#define btnNONE 5
/* ab hier: einlesen der werte der tasten (wiederstands gebilde mit
unterschiedlichen spannungswerten zu jeder taste...*/

int read_LCD_buttons()
 {
 adc_key_in = analogRead(0); // read the value from the sensor 
 // my buttons when read are centered at these valies: 0, 144, 329, 504, 741
 // we add approx 50 to those values and check to see if we are close
 if (adc_key_in > 1000) return btnNONE; // We make this the 1st option for speed reasons
since it will be the most likely result
 if (adc_key_in < 50) return btnRIGHT; 
 if (adc_key_in < 195) return btnUP; 
 if (adc_key_in < 380) return btnDOWN; 
 if (adc_key_in < 555) return btnLEFT; 
 if (adc_key_in < 790) return btnSELECT; 
 return btnNONE; // when all others fail, return this...
 }
/* das wars mit dem tastatur-bereich */

dht11 DHT11;
/*-----( Declare Constants, Pin Numbers )-----*/
#define DHT11PIN 2

float alarmwert (20);

void setup() /*----( SETUP: RUNS ONCE )----*/
{
 Serial.begin(9600); 
 lcd.begin(16,2); //##### Display Size for DFRobot LCD Keypadshield V1.0
 lcd.home ();
 lcd.println ("Olliduino "); //##### schreibe willkommensnachricht und springe eine zeile weiter
 lcd.setCursor (0,1);
 lcd.print ("2011 by olli "); //##### schreibe willkommensnachricht
 lcd.home ();
 delay(3000);
 lcd.clear ();

}/*--(end setup )---*/
  

void loop() /*----( LOOP: RUNS CONSTANTLY )----*/
{

 // digitalWrite(13, HIGH);


 int chk = DHT11.read(DHT11PIN);

 Serial.println("---------------------------"); //der Lesbarkeit erstmal eine Zeile
 switch (chk) // teste, ob ueberhaupt daten fliessen
 {
 case 0: Serial.println("DHT11 ist OK");
 Serial.print ("gelieferter Wert: ");
 Serial.println ((float)DHT11.temperature,1); 
 break;
 case -1: Serial.println("Checksum error"); break;
 case -2: Serial.println("Time out error"); break;
 default: Serial.println("Unknown error"); break;
 }
Serial.print((float)alarmwert, 1);
 Serial.println("C Darunter-Gibt-es-ALARM-Temperatur");
 Serial.print((float)DHT11.temperature,1);
 Serial.println("C IST-Temperatur");
if ( DHT11.temperature < alarmwert ) 
 { 
 digitalWrite(13, HIGH);
 Serial.println("### !!! Alarm erreicht !!! ###"); 
 lcd.setCursor (15,0); //##### schreibe ab zeichen 14 in zeile 1 (zeile 1 ist gleich 0)
 lcd.print("!");
 lcd.setCursor (0,1);
 }
else
 {
 digitalWrite(13, LOW);
 Serial.println("Alarm nicht erreicht, alles OK");
 lcd.setCursor (15,0); //##### schreibe ab zeichen 14 in zeile 1 (zeile 1 ist gleich 0)
 lcd.print("*");
 lcd.setCursor (0,1);
 }


 //lcd.noAutoscroll();
 lcd.setCursor (0,1);
 lcd.print(alarmwert,0);
 lcd.print("Cs ");
 lcd.print((float)DHT11.temperature,1);
 lcd.print("Ci ");
 lcd.print((float)DHT11.humidity,1);
 lcd.print("%");

 digitalWrite(13, LOW);

 delay(1000);




 // jetzt lesen wir noch die tasten ein und machen was draus

 lcd_key = read_LCD_buttons(); // read the buttons
switch (lcd_key) // depending on which button was pushed, we perform an action
 {
 case btnRIGHT:
 {
 lcd.setCursor (0,0);
 lcd.print("> ");
 break;
 }
 case btnLEFT:
 {
 lcd.setCursor (0,0);
 lcd.print("<");
 break;
 }
 case btnUP:
 {
 alarmwert = alarmwert + 1;
 lcd.setCursor (0,0);
 lcd.print("^");
 break;
 }
 case btnDOWN:
 {
 alarmwert = alarmwert - 1;
 lcd.setCursor (0,0);
 lcd.print("v");
 break;
 }
 case btnSELECT:
 {
 lcd.setCursor (0,0);
 lcd.print("*");
 break;
 }
 case btnNONE:
 {
 lcd.setCursor (0,0);
 lcd.print(" ");
 break;
 }
 } 










}
/* --(end main loop )-- */

updated the code to support Arduino 1.0 - as allways comments still welcome

Hi Rob, Thank you so much for writing such an easy to use library! I wanted to ask you a question if I may - I'm using the DHT-11, I tried supplying it with different voltages (3V, 3.3V, 5V - using the Arduino Uno's 3V,5V and the Arduino Fio's 3.3V power supply) and for each voltage there are different readings for the temperature and humidity (a very big difference between 3V and 5V). what is the correct voltage that it should be supplied with? (or is there a way to work around this?) according to the datasheet it can be supplied with 3V - 5.5V.

thanks!

I wanted to ask you a question if I may -

you may,

I tried supplying it with different voltages (3V, 3.3V, 5V - using the Arduino Uno's 3V,5V and the Arduino Fio's 3.3V power supply) and for each voltage there are different readings for the temperature and humidity (a very big difference between 3V and 5V). what is the correct voltage that it should be supplied with?Ac

As you say according to the datasheet, any voltage between 3 and 5.5V should work. I only can confirm that the readings makes good sense at 5Volt.

(or is there a way to work around this?)

External powersupply for the sensor? does also make sense if the sensor is a bit further away, long wires.

If you use 3.5 volt and you take longer delays between the readings, does the accuracy of the reading increase?

I just wanted to say THANK YOU for all of the work! I just received a Freetronics Eleven and the DHT22 sensor. I tried the Library suggested, but just kept getting error during the compile process. And then I found your tutorial!!! Although it took me a bit to figure out how to create the Library from your work, once I did, everything started working. Now I am trying to figure out how to combine the Dew Point and C to F conversion from the DHT11 sketch with the DHT22 sketch so I can have the most information from just the one sketch.

Thanks again,