I'm struggling to get the DHT11 sensor to work on Arduino. My code compiles without any problems but in the serial monitor the output I keep on getting is " Read sensor: Time out error"
I've tried multiple libraries, from Adafruit etc but still none of them worked. I also set the serial monitor to the same speed (115200) but it didn’t fix the problem.
I'm using:
Mega2560
DHT11 Temp+Hum sensor
Windows10 x64
Arduino 1.6.9
Library DHT11.h v0.4.1 source: Arduino Playground - DHT11Lib
Wiring : Blue = GND Yellow = 2 Red = 5V (Also see the picture)
My code:
#include <dht11.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;
}
#include <dht11.h>
dht11 DHT11;
#define DHT11PIN 2
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 chk = DHT11.read(DHT11PIN);
Serial.print("Read sensor: ");
switch (chk)
{
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
//
Serial Monitor Output:
Temperature (°C): 0.00
Temperature (°F): 32.00
Temperature (°K): 273.15
Dew Point (°C): nan
Dew PointFast (°C): nan
DHT11 TEST PROGRAM
LIBRARY VERSION: 0.4.1
I will be kindly thankful If you have at least an idea of what could be wrong,
Natalie.
