DHT11 Sensor

Other Hardware Sensors
1

Help! Does anyone have/know a DHT11 code? I tried using the one from ladyada.net. This is the tester code. It looks like this

// Example testing sketch for various DHT humidity/temperature sensors
// Written by ladyada, public domain

#include "DHT.h"

#define DHTPIN 2 // what pin we're connected to

// Uncomment whatever type you're using!
#define DHTTYPE DHT11 // DHT 11
//#define DHTTYPE DHT22 // DHT 22 (AM2302)
//#define DHTTYPE DHT21 // DHT 21 (AM2301)

// Connect pin 1 (on the left) of the sensor to +5V
// Connect pin 2 of the sensor to whatever your DHTPIN is
// Connect pin 4 (on the right) of the sensor to GROUND
// Connect a 10K resistor from pin 2 (data) to pin 1 (power) of the sensor

DHT dht(DHTPIN, DHTTYPE);

void setup() {
Serial.begin(9600);
Serial.println("DHTxx test!");

dht.begin();
}

void loop() {
// Reading temperature or humidity takes about 250 milliseconds!
// Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
float h = dht.readHumidity();
float t = dht.readTemperature();

// check if returns are valid, if they are NaN (not a number) then something went wrong!
if (isnan(t) || isnan(h)) {
Serial.println("Failed to read from DHT");
} else {
Serial.print("Humidity: ");
Serial.print(h);
Serial.print(" %\t");
Serial.print("Temperature: ");
Serial.print(t);
Serial.println(" *C");
}
}

I'm not sure what's wrong. It says that DHT does not name a type. Im not sure what I'm doing wrong. if someone could tell me, or give me a code for the DHT11, I'd really appreciate it.

Thanks! (:

2

Did you download and install the DHT library in the correct place?

Pete

3

I think I did. I have a MacBook Air, but the instructions I usually see online are for PCs. I think I downloaded it to the right spot. I'm able to open the tester code in the menu bar of the Arduino program.

4

what if u type
#include <DHT.h>
instead of
#include "DHT.h" ?

what is the first error message?

5

Thanks. I'm not on my programming computer, but I'll try that once I get on (:
Hopefully it'll work...

6

So, I tried changing the code to <DHT.h> & it didn't change. The error says:

DHTtester.cpp:4:17: error: DHT.h: No such file or directory
DHTtester.pde:-1: error: 'DHT' does not name a type
DHTtester.cpp: In function 'void setup()':
DHTtester.pde:-1: error: 'dht' was not declared in this scope
DHTtester.cpp: In function 'void loop()':
DHTtester.pde:-1: error: 'dht' was not declared in this scope

and in the orange bar it says:

'DHT' does not name a type.

I assumed this code would be legit since it came from ladyada.net

Heeellppp!!!

7

Think you need to read about libraries again (and carefully :wink: - Libraries - Arduino Reference -

If that does not help you may try - Arduino Playground - DHTLib - tested for both DHT11 and DHT22 (with Arduino 0.22)

8

The first link didn't help too much. Thanks though. I really appreciate it (:

9

robtillaart:
Think you need to read about libraries again (and carefully :wink: - http://www.arduino.cc/en/Reference/Libraries -

If that does not help you may try - Arduino Playground - HomePage - tested for both DHT11 and DHT22 (with Arduino 0.22)

Rob thanks for the library :slight_smile:
I've tried it in arduino 1.0 and I just had to change Wprogram.h to Arduino.h in dht.h and it worked.

10

Incidentally the < > syntax is for refering to libraries, the " " syntax for local .h files (but most compilers then check library directories too if not found locally).

11

@E40Racer

I've tried it in arduino 1.0 and I just had to change Wprogram.h to Arduino.h in dht.h and it worked.

Think I need to add a small note in the article / patch the code. Thanks for the tip.

(done)

12

First, I would like to apologize in advance for bringing up a super old thread, but this was frustrating me to no end.

I just dealt with this same problem for the past few hours and finally figured out what the issue was. I was copying and pasting the library files off of a webpage, and then trying to save them from within a sketch, so every time I saved my ".h" and ".cpp" files, I was actually saving them as ".h.ino" and ".cpp.ino" files, which will of course not be recognized during compile. I rectified this by copying the library code into a text document, then "Save As..." and changing the file type to be "All Files" and they saved as the correct file types. Stick those two files into a named folder in your Arduino Library file, and you should be good to go. This took my far too long to figure out; I am somewhat ashamed.

Hope this isn't way too late and it helps somebody! All the best