Capteur T° et humidité

Le capteur utilisé est un DHT 11 Keyes, soudé sur une carte :

Attention, les connecteurs sont, de gauche à droite broche « S »=Signal, centre = +5v, droite = GND. La broche Signal doit être raccordée à une PIN Digitale d’Arduino, le centre sur la broche 5v, la branche GND sur GND de l’Arduino.

Dans l’exemple ci-dessous, le capteur est relié à la broche Digitale 4 d’une carte UNO. Il est nécessaire de télécharger la libraire ici et de la charger dans l’interface de l’Arduino via la menu Croquis->Importer Bibliothèque et choisir le fichier ZIP.

 /* YourDuino.com Example Software Sketch  
   DHT11 Humidity and Temperature Sensor test  
   Credits: Rob Tillaart  
   http://arduino-direct.com/sunshop/index.php?l=product_detail&p=162  
   terry@yourduino.com */  
 /*-----( Import needed libraries )-----*/  
 #include <dht11.h>  
 /*-----( Declare objects )-----*/  
 dht11 DHT11;  
 /*-----( Declare Constants, Pin Numbers )-----*/  
 #define DHT11PIN 4  
 void setup()  /*----( SETUP: RUNS ONCE )----*/  
 {  
  Serial.begin(9600);  
  Serial.println("DHT11 TEST PROGRAM ");  
  Serial.print("LIBRARY VERSION: ");  
  Serial.println(DHT11LIB_VERSION);  
  Serial.println();  
 }/*--(end setup )---*/  
 void loop()  /*----( LOOP: RUNS CONSTANTLY )----*/  
 {  
  Serial.println("\n");  
  int chk = DHT11.read(DHT11PIN);  
  Serial.print("Read sensor: ");  
  switch (chk)  
  {  
   case 0: Serial.println("OK"); break;  
   case -1: Serial.println("Checksum error"); break;  
   case -2: Serial.println("Time out error"); break;  
   default: Serial.println("Unknown error"); break;  
  }  
  Serial.print("Humidity (%): ");  
  Serial.println((float)DHT11.humidity, 2);  
  Serial.print("Temperature (oC): ");  
  Serial.println((float)DHT11.temperature, 2);  
  Serial.print("Temperature (oF): ");  
  Serial.println(Fahrenheit(DHT11.temperature), 2);  
  Serial.print("Temperature (K): ");  
  Serial.println(Kelvin(DHT11.temperature), 2);  
  Serial.print("Dew Point (oC): ");  
  Serial.println(dewPoint(DHT11.temperature, DHT11.humidity));  
  Serial.print("Dew PointFast (oC): ");  
  Serial.println(dewPointFast(DHT11.temperature, DHT11.humidity));  
  delay(2000);  
 }/* --(end main loop )-- */  
 /*-----( Declare User-written Functions )-----*/  
 //  
 //Celsius to Fahrenheit conversion  
 double Fahrenheit(double celsius)  
 {  
      return 1.8 * celsius + 32;  
 }  
 //Celsius to Kelvin conversion  
 double Kelvin(double celsius)  
 {  
      return celsius + 273.15;  
 }  
 // dewPoint function NOAA  
 // reference: http://wahiduddin.net/calc/density_algorithms.htm   
 double dewPoint(double celsius, double humidity)  
 {  
      double A0= 373.15/(273.15 + celsius);  
      double SUM = -7.90298 * (A0-1);  
      SUM += 5.02808 * log10(A0);  
      SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ;  
      SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ;  
      SUM += log10(1013.246);  
      double VP = pow(10, SUM-3) * humidity;  
      double T = log(VP/0.61078);  // temp var  
      return (241.88 * T) / (17.558-T);  
 }  
 // delta max = 0.6544 wrt dewPoint()  
 // 5x faster than dewPoint()  
 // reference: http://en.wikipedia.org/wiki/Dew_point  
 double dewPointFast(double celsius, double humidity)  
 {  
      double a = 17.271;  
      double b = 237.7;  
      double temp = (a * celsius) / (b + celsius) + log(humidity/100);  
      double Td = (b * temp) / (a - temp);  
      return Td;  
 }  
 /* ( THE END ) */  

Résultat :

http://arduino-info.wikispaces.com/DHT11-Humidity-TempSensor avec l’Internet Shield : http://arduino-info.wikispaces.com/ethernet-temp-humidity

http://playground.arduino.cc/main/DHT11Lib

Autre brochage utilisé pour le DHT11 :

Pin	Name	Description
1	VDD	Power supply 3 – 5.5 V DC
2	DATA	Serial data output
3	NC	Not connected
4	GND	Ground

Le capteur se connecte sur l’Arduino selon :

DHT11	Arduino
Pin 1	Vcc
Pin 2	Analog(x)
Pin 4	Gnd

Pour son utilisation : http://www.hobbyist.co.nz/?q=documentations/wiring-up-dht11-temp-humidity-sensor-to-your-arduino

1°) Téléchargez la librairie ici (https://app.box.com/s/7sngfwjxmchpk1fcurzg) Fichiers à dézipper dans le répertoire Librairies\DHT

2°) Exemple de code :

 #include <dht.h>  
 #define dht_dpin A0 //no ; here. Set equal to channel sensor is on  
 dht DHT;  
 void setup(){  
  Serial.begin(9600);  
  delay(300);//Let system settle  
  Serial.println("Humidity and temperature\n\n");  
  delay(700);//Wait rest of 1000ms recommended delay before  
  //accessing sensor  
 }//end "setup()"  
 void loop(){  
  //This is the "heart" of the program.  
  DHT.read11(dht_dpin);  
   Serial.print("Current humidity = ");  
   Serial.print(DHT.humidity);  
   Serial.print("% ");  
   Serial.print("temperature = ");  
   Serial.print(DHT.temperature);   
   Serial.println("C ");  
  delay(800);//Don't try to access too frequently... in theory  
  //should be once per two seconds, fastest,  
  //but seems to work after 0.8 second.  
 }// end loop()  

Un autre exemple sans librairie :

 int tempPin=A0;  
 float readTemp(int pin)  
 {  
  float bv=analogRead(pin);  
  float mv=bv*5/1024.0;  
  float temperatureC = (mv - 0.5) * 100 ;  
  return temperatureC;  
 }  
 float readAvgTemp(int pin, int waitDelay, int count)  
 {  
   int k=0;  
   float sum=0.0;  
   for(k=0;k<count;k++)  
   {  
     sum=sum + readTemp(pin);  
     delay(waitDelay);  
   }  
   float avg=sum/(float)count;  
   return avg;  
 }  
 void setup()  
 {  
   Serial.begin(9600);  
 }  
 void loop()  
 {  
  Serial.print("Temperature : ");  
  Serial.println(readAvgTemp(tempPin, 1, 100));  
  delay(100);  
 }  

Un autre exemple :

 #define DHT11_PIN 0   // ADC0  
 byte read_dht11_dat()  
 {  
  byte i = 0;  
  byte result=0;  
  for(i=0; i< 8; i++)  
  {  
   while(!(PINC & _BV(DHT11_PIN))); // wait for 50us  
   delayMicroseconds(30);  
   if(PINC & _BV(DHT11_PIN))   
    result |=(1<<(7-i));  
   while((PINC & _BV(DHT11_PIN))); // wait '1' finish  
   }  
   return result;  
 }  
 void setup()  
 {  
  DDRC |= _BV(DHT11_PIN);  
  PORTC |= _BV(DHT11_PIN);  
  Serial.begin(9600);  
  Serial.println("Ready");  
 }  
 void loop()  
 {  
  byte dht11_dat[5];  
  byte dht11_in;  
  byte i;// start condition  
       // 1. pull-down i/o pin from 18ms  
  PORTC &= ~_BV(DHT11_PIN);  
  delay(18);  
  PORTC |= _BV(DHT11_PIN);  
  delayMicroseconds(40);  
  DDRC &= ~_BV(DHT11_PIN);  
  delayMicroseconds(40);  
  dht11_in = PINC & _BV(DHT11_PIN);  
  if(dht11_in)  
  {  
   Serial.println("dht11 start condition 1 not met");  
   return;  
  }  
  delayMicroseconds(80);  
  dht11_in = PINC & _BV(DHT11_PIN);  
  if(!dht11_in)  
  {  
   Serial.println("dht11 start condition 2 not met");  
   return;  
  }  
  delayMicroseconds(80);// now ready for data reception  
  for (i=0; i<5; i++)  
   dht11_dat[i] = read_dht11_dat();  
  DDRC |= _BV(DHT11_PIN);  
  PORTC |= _BV(DHT11_PIN);  
  byte dht11_check_sum = dht11_dat[0]+dht11_dat[1]+dht11_dat[2]+dht11_dat[3];// check check_sum  
  if(dht11_dat[4]!= dht11_check_sum)  
  {  
   Serial.println("DHT11 checksum error");  
  }  
  Serial.print("Current humdity = ");  
  Serial.print(dht11_dat[0], DEC);  
  Serial.print(".");  
  Serial.print(dht11_dat[1], DEC);  
  Serial.print("% ");  
  Serial.print("temperature = ");  
  Serial.print(dht11_dat[2], DEC);  
  Serial.print(".");  
  Serial.print(dht11_dat[3], DEC);  
  Serial.println("C ");  
  delay(2000);  
 }  

Exemple de Sketch stockant les valeurs dans une chaîne :

 //**** Put temperature in a String   
 #include <dht11.h>  
 //-- Define var  
 dht11 DHT11;  
 #define DHT11PIN 4  
 int chk;  
 float nFloat;  
 String sMessage;   
 char buffer[3]; //--Nombre total de chiffre y compris la virgule   
 //-- Setup  
 void setup()    
 {  
  Serial.begin(9600);  
  Serial.println("DHT11 TEST PROGRAM ");  
  Serial.print("LIBRARY VERSION: ");  
  Serial.println(DHT11LIB_VERSION);  
  Serial.println();  
 }  
 //--Sketch  
 void loop()    
 { chk = DHT11.read(DHT11PIN);  
  Serial.print("Read sensor: ");  
  switch (chk)  
  {case 0:   
     nFloat=(float)DHT11.temperature;  
     sMessage=dtostrf(nFloat,2,0,buffer);  
     nFloat=(float)DHT11.humidity;  
     sMessage=sMessage+"c"+dtostrf(nFloat,3,0,buffer)+"%";   
     Serial.println(sMessage);       
     break;  
   case -1: Serial.println("Checksum error"); break;  
   case -2: Serial.println("Time out error"); break;  
   default: Serial.println("Unknown error"); break;  
  }  
  delay(1000);  
 }  

Exemple de sketch affichant l’heure, la date, la température et l’humidité :

 ////////////////////////////////////////  
 // Print Time and Date from DS1307 I2C  
 // And Temp with DHT 11  
 ///////////////////////////////////////  
 #include "Wire.h"  
 #include <dht11.h>  
 //-- Define var  
 dht11 DHT11;  
 #define DHT11PIN 4  
 #define DS1307_ADDRESS 0x68  
 String sMessage;   
 int chk;  
 float nFloat;  
 char buffer[3];  
 //-- Setup  
 void setup(){  
  Wire.begin();  
  Serial.begin(9600);  
 }  
 //-- Sketch  
 void loop(){  
  sMessage="";  
  printDate();  
  printTemp();  
  Serial.println(sMessage);  
  delay(1000);  
 }  
 //-- Function  
 byte bcdToDec(byte val) {  
 // Convert binary coded decimal to normal decimal numbers  
  return ( (val/16*10) + (val%16) );  
 }  
 String sNb(int nNb)  
 {if (nNb<10)  
   return "O"+String(nNb);  
  else  
   return String(nNb);   
 }  
 void printDate(){  
  Wire.beginTransmission(DS1307_ADDRESS);  
  byte zero = 0x00;  
  Wire.write(zero);  
  Wire.endTransmission();  
  Wire.requestFrom(DS1307_ADDRESS, 7);  
  int second = bcdToDec(Wire.read());  
  int minute = bcdToDec(Wire.read());  
  int hour = bcdToDec(Wire.read() & 0b111111); //24 hour time  
  int weekDay = bcdToDec(Wire.read()); //0-6 -> sunday - Saturday  
  int monthDay = bcdToDec(Wire.read());  
  int month = bcdToDec(Wire.read());  
  int year = bcdToDec(Wire.read());  
  String sSec, sMin, sHour, sDay, sMonth, sYear;  
  //print the date  
  sMessage=sNb(monthDay)+"/"+sNb(month)+"/"+sNb(year)+" "+sNb(hour)+":"+sNb(minute)+":"+sNb(second);  
 }  
 void printTemp(){  
  chk = DHT11.read(DHT11PIN);  
  switch (chk)  
  {case 0:   
     nFloat=(float)DHT11.temperature;  
     sMessage=sMessage+" "+dtostrf(nFloat,2,0,buffer);  
     nFloat=(float)DHT11.humidity;  
     sMessage=sMessage+"c"+dtostrf(nFloat,3,0,buffer)+"%";       
     break;  
   case -1: Serial.println("Checksum error"); break;  
   case -2: Serial.println("Time out error"); break;  
   default: Serial.println("Unknown error"); break;  
  }  
 }