DHT11 and Atmega 8MHz



  • Hello everybody,

    I have trouble with DHT11 on Atmega328 3.3V 8MHz. I use the Humidity sketch and I have a lot of reading error.

    When I try the exemple sketch included in Arduino IDE, everything is ok, no error during 5 hours.

    With the humidity sketch, I have an error every 5 or 7 readings. Maybe an error in the library with timing communication with DHT11??

    Anybody can help me??

    Thank you in advance.



  • How often do you read from the DHT11, might not be an issue. But think you need to wait 1-2 sec pr. poll. (Depending on DHT11/22)



  • The sleeping time is 30 seconds.



  • @Thibthib02 Modify the arduino ide example sketch to work with mysensors and try it .



  • The example sketch is too complicated to modify to work with mysensors. Nobody here use the Humidity sketch with arduino @ 8MHz?


  • Admin



  • Did you try what they suggest here:
    http://forums.adafruit.com/viewtopic.php?f=19&t=46863
    This is for the DHT22, but maybe it relates to the DHT11? They also use a different library I think, but you could integrate that easily, I suppose.



  • I use this one => Adafruit

    #include <DHT.h>
    
    #define HYGRO_PIN 4         // Pin DHT11
    
    DHT dht(HYGRO_PIN, HYGRO_TYPE);
    
    float hygrometrie_mem; 
    float hygro_temp_mem;  
    
    // hygrometrie
    MyMessage msg_hygro(HYGROMETRIE_CHILD, V_HUM);
    
     float hygro_temp = dht.readTemperature();
     float hygrometrie = dht.readHumidity();
     // isnan => Is Not A Number
     if (isnan(hygro_temp) || isnan(hygrometrie))
     {
        Serial.println("Echec lecture du DHT");
     } 
     else if (hygro_temp != hygro_temp_mem) 
     {
       hygro_temp_mem = hygro_temp;
     }
    
      Serial.print("Temperature hygro : ");
      Serial.print(hygro_temp);
      Serial.println('C');
      if (hygrometrie != hygrometrie_mem) 
      {
        hygrometrie_mem = hygrometrie;
        gw.send(msg_hygro.set(hygrometrie, 1));
        Serial.print("Hygrometrie : ");
        Serial.print(hygrometrie);
        Serial.println('%');
      }
    


  • Hi,

    no problem at all. The humidity scetch is running fine with a pure atmega328p-pu and a DHT11.

    I have build it on a breadboard for you to see if it is working:

    IMG_1213.JPG

    As you see, the sensor starts and sends temperature and humidity value:

    sensor started, id 99
    send: 99-99-0-0 s=255,c=0,t=17,pt=0,l=5,st=ok:1.4.1
    send: 99-99-0-0 s=255,c=3,t=6,pt=1,l=1,st=ok:0
    read: 0-0-99 s=255,c=3,t=6,pt=0,l=2:M
    
    send: 99-99-0-0 s=255,c=3,t=11,pt=0,l=8,st=ok:Humidity
    send: 99-99-0-0 s=255,c=3,t=12,pt=0,l=3,st=ok:1.0
    send: 99-99-0-0 s=0,c=0,t=7,pt=0,l=5,st=ok:1.4.1
    read: 99-1-0 s=0,c=0,t=7,pt=0,l=5:1.4.1
    send: 99-99-0-0 s=1,c=0,t=6,pt=0,l=5,st=ok:1.4.1
    read: 99-1-0 s=1,c=0,t=6,pt=0,l=5:1.4.1
    send: 99-99-0-0 s=255,c=3,t=0,pt=1,l=1,st=ok:62
    read: 99-1-0 s=255,c=3,t=0,pt=1,l=1:62
    

    Normally I am using a DHT22 on my selfmade board.
    IMG_1185.JPG

    Andreas



  • Maybe a bad DHT11. I will more investigate tomorrow. Thank you guys.



  • @Andreas-Maurer Nice looking board!!


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