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[on:]

Hi there all...i am into a project wich read temperature,i have used the LM35 before but beacause of acuracy,and limited lenght of the cable,errors and such ....i decided to do it with the DHT22/RHT03.Reading the temperature with the <DHT22.h> library works great.The code i use is:

Code:

#include <DHT22.h>
// Only used for sprintf
#include <stdio.h>

// Data wire is plugged into port 7 on the Arduino
// Connect a 4.7K resistor between VCC and the data pin (strong pullup)
#define DHT22_PIN 7

// Setup a DHT22 instance
DHT22 myDHT22(DHT22_PIN);

void setup(void)
{
  // start serial port
  Serial.begin(9600);
}

void loop(void)
{
  DHT22_ERROR_t errorCode;
  
  // The sensor can only be read from every 1-2s, and requires a minimum
  // 2s warm-up after power-on.
  delay(2000);
  
  errorCode = myDHT22.readData();
  switch(errorCode)
  {
    case DHT_ERROR_NONE:
      Serial.print(myDHT22.getTemperatureC());
      Serial.print(" Celsius      ");
      Serial.print( myDHT22.getHumidity());
      Serial.println("% Humidity");
      // Alternately, with integer formatting which is clumsier but more compact to store and
 // can be compared reliably for equality:
 //  
      char buf[128];

  }
}

my intencion is to keep it most simple as posible.can anyone help me with the code to add another sensor,so i can read 2 DHT22?
i realy apreciate it,thank you all of you.
                                                                                                                          Juycce

[Reply #1 on:]

this way?

Code:

#include <DHT22.h>
// Only used for sprintf
#include <stdio.h>

// Data wire is plugged into port 7 on the Arduino
// Connect a 4.7K resistor between VCC and the data pin (strong pullup)
#define DHT22_PIN 7
#define DHT222_PIN 8 /// <<<<<<<<<<<<<<<<<<<

// Setup a DHT22 instance
DHT22 myDHT22(DHT22_PIN);
DHT22 myDHT222(DHT222_PIN);

void setup(void)
{
  // start serial port
  Serial.begin(9600);
}

void loop(void)
{
  DHT22_ERROR_t errorCode;
 
  // The sensor can only be read from every 1-2s, and requires a minimum
  // 2s warm-up after power-on.
  delay(2000);
 
  errorCode = myDHT22.readData();
  if (errorCode == DHT_ERROR_NONE)
  {
      doPrintTH(myDHT22.getTemperatureC(), myDHT22.getHumidity())
  }

  errorCode = myDHT222.readData();
  if (errorCode == DHT_ERROR_NONE)
  {
      doPrintTH(myDHT222.getTemperatureC(), myDHT222.getHumidity())
  }
}

void doPrintTH(float t, float h)
{
  Serial.print(t,2);
  Serial.print(" Celsius      ");
  Serial.print(h,1 );
  Serial.println("% Humidity");
}

[Reply #2 on:]

:D:D thank you so much  robtillaart ...it works,I realy apreciate it.

[Reply #3 on:]

note you can specify the number of decimals for floats with the second number e.g. Serial.print(t,2);

[Reply #4 on:]

Furthermore is you want to add more, you might consider using an array of DHT22's instead of single objects.

[Reply #5 on:]

could u please explain me what are (t,2) and (h,1 ) do....I mean i know the 't' is temperatue and 'h' is humidity but what about the numbers 2 and 1 ? what are they doing

Code:

void doPrintTH(float t, float h)
{
  Serial.print(t,2);
  Serial.print(" Celsius      ");
  Serial.print(h,1 );
  Serial.println("% Humidity");
}

thankyou

[Reply #6 on:]

as explained 2 posts before, for printing a floating point this number indicates the number of decimals.

print(PI, 1) => 3.1
print(PI, 2) => 3.14
print(PI, 7) => 3.1415927
etc