Working with DHT sensor example and get this error

Projects Programming
1

I have an uno running a DHT11 was going to try it out so I loaded the Library from IDE manager and compiled but got an error on the Library so I went to the auto select type compiler ran it and got this error but don't see anything wrong..

expected primary-expression before '.' token.

help I have written c code before and have several successful Arduino IDE compiled programs but I can't figure this one out????

void loop()
{
Serial.println("\n");
int doit = DHT.read(DHTPIN);----- error is highlighted here

Serial.print("Read sensor: ");

switch (doit)
{
case DHTLIB_OK:
Serial.println("OK");
break;
case DHTLIB_ERROR_CHECKSUM:
Serial.println("Checksum error");
break;
case DHTLIB_ERROR_TIMEOUT:
Serial.println("Time out error");
break;
default:
Serial.println("Unknown error");
break;
}

2

So, what is DHT? The compiler is telling you it doesn't recognize DHT as a valid primary expression.

http://snippets-r-us.com would be happy to help you with your snippets.

3

DHT11 is a temp humidity sensor and there are several instances of Library codes for it but it seems that I have tangled the situation I used the later code and had to remove DHT11 from the primary expression but DHT turns read but doesn't pass the compiler check. Thinking I have put too much variability into the term DHT?

4

Thinking I have put too much variability into the term DHT?

I'm thinking you spun a roulette wheel to come up with the order of words in that sentence. No more hints.

POST ALL OF YOUR CODE!

5

Sorry, Paul, about the gramer I'm not an English major by any means!
I pulled up the DHT Tester code and put it together and it worked fine. So there has to be something in the Adafruit library that I'm not doing right in the front of the code to define that variable so I'll work with the library code and see if I can get that to work with a few more definitions in the right places.

tenphumid.ino (2.73 KB)

6

You have not created an instance of the DHT class. You can't call members of the class without an instance.

Are there examples that came with the library?

You only need to attach code when it exceeds 9500 characters. Yours is half of that.

#include <DHT.h>






// 
//   FILE:  dht11_test1.pde
// PURPOSE: DHT11 library test sketch for Arduino
//

//Celsius to Fahrenheit conversion
double Fahrenheit(double celsius)
{
  return 1.8 * celsius + 32;
}

// fast integer version with rounding
//int Celcius2Fahrenheit(int celcius)
//{
//  return (celsius * 18 + 5)/10 + 32;
//}


//Celsius to Kelvin conversion
double Kelvin(double celsius)
{
  return celsius + 273.15;
}

// dewPoint function NOAA
// reference (1) : http://wahiduddin.net/calc/density_algorithms.htm
// reference (2) : http://www.colorado.edu/geography/weather_station/Geog_site/about.htm
//
double dewPoint(double celsius, double humidity)
{
  // (1) Saturation Vapor Pressure = ESGG(T)
  double RATIO = 373.15 / (273.15 + celsius);
  double RHS = -7.90298 * (RATIO - 1);
  RHS += 5.02808 * log10(RATIO);
  RHS += -1.3816e-7 * (pow(10, (11.344 * (1 - 1/RATIO ))) - 1) ;
  RHS += 8.1328e-3 * (pow(10, (-3.49149 * (RATIO - 1))) - 1) ;
  RHS += log10(1013.246);

        // factor -3 is to adjust units - Vapor Pressure SVP * humidity
  double VP = pow(10, RHS - 3) * humidity;

        // (2) DEWPOINT = F(Vapor Pressure)
  double T = log(VP/0.61078);   // temp var
  return (241.88 * T) / (17.558 - T);
}

// delta max = 0.6544 wrt dewPoint()
// 6.9 x 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*0.01);
  double Td = (b * temp) / (a - temp);
  return Td;
}




#define DHTPIN 5

void setup()
{
  Serial.begin(115200);
  Serial.println("DHT11 TEST PROGRAM ");
//  Serial.print("LIBRARY VERSION: ");
//  Serial.println(DHT11LIB_VERSION);
  Serial.println();
}

void loop()
{
  Serial.println("\n");

  
  int doit = DHT.read(DHTPIN);

  Serial.print("Read sensor: ");
  
  switch (doit)
  {
    case DHTLIB_OK: 
    Serial.println("OK"); 
    break;
    case DHTLIB_ERROR_CHECKSUM: 
    Serial.println("Checksum error"); 
    break;
    case DHTLIB_ERROR_TIMEOUT: 
    Serial.println("Time out error"); 
    break;
    default: 
    Serial.println("Unknown error"); 
    break;
  }

  Serial.print("Humidity (%): ");
  Serial.println((float)DHT11.humidity, 2);

  Serial.print("Temperature (°C): ");
  Serial.println((float)DHT11.temperature, 2);

  Serial.print("Temperature (°F): ");
  Serial.println(Fahrenheit(DHT11.temperature), 2);

  Serial.print("Temperature (°K): ");
  Serial.println(Kelvin(DHT11.temperature), 2);

  Serial.print("Dew Point (°C): ");
  Serial.println(dewPoint(DHT11.temperature, DHT11.humidity));

  Serial.print("Dew PointFast (°C): ");
  Serial.println(dewPointFast(DHT11.temperature, DHT11.humidity));

  delay(2000);
}
//
// END OF FILE
//