DHT11 and Atmega 8MHz

[Thibthib02]

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.

[Magiske]

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)

[Thibthib02]

The sleeping time is 30 seconds.

[sharath krishna]

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

[Thibthib02]

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

[hek]

This DHT library claim to handle 8Mhz:
https://github.com/Seeed-Studio/Grove_Temperature_And_Humidity_Sensor/tree/master/Humidity_Temperature_Sensor

[A Former User]

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.

[Totche]

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('%');
  }

[Andreas Maurer]

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:

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.

Andreas

[Thibthib02]

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

[Magiske]

@Andreas-Maurer Nice looking board!!