[Solved] DHT-11 Temperature Value Includes Letters and Doesn't Change

Other Hardware Sensors
1

I'm using the DHT-11 Temperature and Humidity Sensor to make a re-mix of the Arduino Starter Kit Project 03: The Love-O-Meter on pages 43-51 in the Arduino Starter Kit Projects Book. The code for the original project is available on the Arduino IDE in File>Examples>Arduino

In the project, the sensor used is a TMP36 temperature sensor. The schematic can be found on page 44 of the Arduino Starter Kit Projects book. The only variations I made on it was to connect the Data pin of the DHT-11 to digital pin 6 instead of analog input pin 0 (A0).

I learned how to use the DHT-11 on Arduino and DHT11 Temperature Measurement: 3 Steps (with Pictures) on Instructables. Here is my code:

#include <DHT.h>

#define DHTPIN 2
#define DHTTYPE DHT11

DHT dht(DHTPIN, DHTTYPE);

const float baselineTemp = 25.00;

void setup() {
  // open a serial connection to display values
  Serial.begin(9600);

  dht.begin();
  
  // set the LED pins as outputs
  // the for() loop saves some extra coding
  for (int pinNumber = 2; pinNumber < 5; pinNumber++) {
    pinMode(pinNumber, OUTPUT);
    digitalWrite(pinNumber, LOW);
  }
}

void loop() {
  // read the value on AnalogIn pin 0 and store it in a variable
  float temperature = dht.readTemperature();

  Serial.println('It is ');
  Serial.print(temperature);
  Serial.print(' degrees Celsius');

  // if the current temperature is lower than the baseline turn off all LEDs
  if (temperature < baselineTemp + 2) {
    digitalWrite(2, LOW);
    digitalWrite(3, LOW);
    digitalWrite(4, LOW);
  } // if the temperature rises 2-4 degrees, turn an LED on
  else if (temperature >= baselineTemp + 2 && temperature < baselineTemp + 4) {
    digitalWrite(2, HIGH);
    digitalWrite(3, LOW);
    digitalWrite(4, LOW);
  } // if the temperature rises 4-6 degrees, turn a second LED on
  else if (temperature >= baselineTemp + 4 && temperature < baselineTemp + 6) {
    digitalWrite(2, HIGH);
    digitalWrite(3, HIGH);
    digitalWrite(4, LOW);
  } // if the temperature rises more than 6 degrees, turn all LEDs on
  else if (temperature >= baselineTemp + 6) {
    digitalWrite(2, HIGH);
    digitalWrite(3, HIGH);
    digitalWrite(4, HIGH);
  }
  delay(1);
}

When I opened the serial monitor, it displayed

nan3006729472

over and over again.

I don't know what this means, but I had hoped it would display

It is [temperature] degrees Celsius

I think that the letters in the printed value may have affected the section of code where temperature is compared with baseLineTemp.

The other significant problem is that the LEDs don't light up. When I press the temperature sensor, I had hoped they would light up in proportion to my body heat, but they never even light up at all.

Here are some things that I think might be the matter:

--My code is not configured correctly

--My sensor is not exact enough to measure the difference in body temperature

--I am not connecting the sensor correctly

--My sensor is faulty

I have checked, and I do not think that these things need fixing:

--Power connection is not good

--My Arduino Board is faulty

2

"nan" means not a number.

The only variations I made on it was to connect the Data pin of the DHT-11 to digital pin 6 instead of analog input pin 0 (A0).

But your program tells the DHT library to use pin 2 for DHT communications, then it initializes pin 2 as OUTPUT and writes a LOW.

That is probably not a good idea.

--I am not connecting the sensor correctly

It could not be less clear what you have done. Do not expect us to look up wiring diagrams in books, etc. then try to guess what you have done. Post a wiring diagram, derived from the actual wiring.

3

Thank you for the answer. I'll try it out.

I'm sorry I didn't post a wiring diagram. I'll make sure to have one in my future posts.