Go Down

Topic: DHT11 test program (Read 3 times) previous topic - next topic

estratos

Hi,

I'm currently playing with the DHT11 Humidity&Temperature sensor with the following code:
http://www.nuelectronics.com/download/projects/sensor_pde/dht11.pde
provided by Nuelectronics.

The program seems to run fine excepts for the fact that both the temp and the humidity readings show no decimal values:

Current humdity = 37.0%  temperature = 26.0C

Has anyone experience with these sensors and the above code? It's not very important since the accuracy of the temp sensor is +-2C and the humidity sensor is +-4% but I wanted to be sure of doing things correctly. I've also tried this other code:
http://sheepdogguides.com/arduino/ar3ne1humDHT11.htm

but the program gets stalled somewhere when doing the first reading.

Thanks for your feedback!

Big Oil

I don't see anything at the first link, and there are several programs on the second link.  You can post the code here with #

robtillaart

Quote
The program seems to run fine excepts for the fact that both the temp and the humidity readings show no decimal values: Current humdity = 37.0%  temperature = 26.0C Has anyone experience with these sensors and the above code?

The DHT11 does not provide decimal parts. It outputs zero's. Today I wrote a playground article about a DHT11 class. The "bigger" DHT22 does provide decimals. For the lib and a simple testprogram see - http://arduino.cc/playground/Main/DHT11Lib. If you have remarks please send them to me.

No experience with the code mentioned,

Quote

It's not very important since the accuracy of the temp sensor is +-2C and the humidity sensor is +-4% but I wanted to be sure of doing things correctly. I've also tried this other code: http://sheepdogguides.com/arduino/ar3ne1humDHT11.htm but the program gets stalled somewhere when doing the first reading.

Since you have working code its not important. You should see the humidity and temp rise when you breath to it.
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

estratos

Quote

The DHT11 does not provide decimal parts. It outputs zero's.


OK.

Quote

The "bigger" DHT22 does provide decimals.


Very interesting! Much more accuracy, support for negative temps...Only a drawback IMO if you're powering the sensor from batteries: voltage range is 3.3-6V whilst DHT11's is 3-5.5V. I'll give it a try though when I have the opportunity.

Thanks for your help!

robtillaart

Quote
DHT22 - voltage range is 3.3-6V

That means 3.3 volt is sufficient ...
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

GaryP




Very interesting! Much more accuracy, support for negative temps...


Damn! Are you saying that DHT11 won't show the only temperatures we have in Finland? Summer is coming, and someday soon, within months, we are going to have a chance to drink water OUTSIDE without ice...

Seriously, is that part only for over 0c temperatures?

Cheers,
Kari
The only law for me; Ohms Law: U=R*I       P=U*I
Note to self: "Damn! Why don't you just fix it!!!"

estratos


Seriously, is that part only for over 0c temperatures?


From the DHT11 datasheet:

Quote
Measuring range:
humidity 20-90%RH
temperature 0-50 Celsius


IMO, DHT11 is a sensor for indoor use only in your case.

GaryP

Yep! And that is ok, I have a plave for that.
:)

Cheers,
Kari
The only law for me; Ohms Law: U=R*I       P=U*I
Note to self: "Damn! Why don't you just fix it!!!"

robtillaart

FYI - a new DHT lib is in BETA - it will support both DHT11 and DHT22 - as soon as DHT22 arrive the lib can be tested.
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

Go Up