DHT22 readings not smooth

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Zodiac69
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Joined: 13 Jun 2016, 17:20

DHT22 readings not smooth

#1 Post by Zodiac69 » 13 Jun 2016, 17:40

Hi all

I am new to ESPEasy.
I have connected a DHT22 to GPIO5 and i have linked it to Domoticz.
All look fine except that the readings look a bit "choppy", i expected a much smoother graph that this, readings are updated every 30sec.

Anyone that can shed some light on this?
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dduley
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Joined: 06 Feb 2016, 17:56

Re: DHT22 readings not smooth

#2 Post by dduley » 13 Jun 2016, 21:40

Hi

How are you powering your dht11? The sensor really wants 5 volts. I had one doing something similar and I was trying to run it on 3.3volts.
Running the sensor on 5 volts won't affect your Esp because the output of the sensor is open drain (thus the required pull up resistor). Just make sure the pull up resistor pulls up to 3.3v and the sensor power is 5v.

Regards

Dave

pbertra
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Joined: 30 May 2016, 12:19

Re: DHT22 readings not smooth

#3 Post by pbertra » 13 Jun 2016, 21:42

Same thing for me... It's in the tolerances for the DHT22:
Accuracy humidity +-2%RH(Max +-5%RH); temperature +-0.2Celsius
Resolution or sensitivity humidity 0.1%RH; temperature 0.1Celsius
Repeatability humidity +-1%RH; temperature +-0.2Celsius

If you take the same measure several times, it could vary from 0.2°c and % humidity. The resolution also makes it so that if you are right between two steps (+-19.55°c), you could read 19.5 or 19.6...

You can still smooth the measure in software with node-red for example if you use it.

pbertra
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Joined: 30 May 2016, 12:19

Re: DHT22 readings not smooth

#4 Post by pbertra » 13 Jun 2016, 21:45

dduley wrote:Hi

How are you powering your dht11? The sensor really wants 5 volts. I had one doing something similar and I was trying to run it on 3.3volts.
Running the sensor on 5 volts won't affect your Esp because the output of the sensor is open drain (thus the required pull up resistor). Just make sure the pull up resistor pulls up to 3.3v and the sensor power is 5v.
I run it on 3.3V without problem... But if you go below this then you don't get any reading. Measurement are acurate or are not provided.

fluppie
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Posts: 81
Joined: 09 Oct 2015, 13:23

Re: DHT22 readings not smooth

#5 Post by fluppie » 02 Aug 2016, 12:36

I have something weird. With the ESP8266 my DHT22 Humidity readings are 15-20% off...
See: http://www.emoncms.org/Edegem/dht22comp

Any idea why the open energy monitor ones give another result? They're using the same DHT library...

harry56
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Joined: 26 May 2017, 06:41

Re: DHT22 readings not smooth

#6 Post by harry56 » 26 May 2017, 09:06

I am sure you will be able to find help to your problems on here.


คาสิโนออนไลน์
Last edited by harry56 on 27 Mar 2018, 15:47, edited 1 time in total.

vojtishek
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Joined: 12 Jan 2017, 08:00

Re: DHT22 readings not smooth

#7 Post by vojtishek » 26 May 2017, 11:31

I have the same output, in detail choppy +- 0.1 C°. Probably as mentioned related to sensor accuracy.
My friend recommended me to try "HTU21D Temperature and Humidity Sensor" should be more accurate so will see.

I have two identical dht22 sensors, difference between temperature 0.5 but humidity 8.

nightshark
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Joined: 29 Apr 2016, 06:54

Re: DHT22 readings not smooth

#8 Post by nightshark » 27 May 2017, 18:50

I had to give up on them. Try the BME280. It works really well.

vojtishek
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Joined: 12 Jan 2017, 08:00

Re: DHT22 readings not smooth

#9 Post by vojtishek » 27 May 2017, 20:38

Ah, ok didn't know about this one, Im gonna try it out

Shardan
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Joined: 03 Sep 2016, 23:27
Location: Bielefeld / Germany

Re: DHT22 readings not smooth

#10 Post by Shardan » 27 May 2017, 20:51

It's another name for the SI7021.
Far more precise then the DHT22 series sensors.
I've tested some, running nicely.

If you want a really precise sensor you'll have to pay a lot more money.
For that i'd take the Sensirion SHT11 or SHT15.
Swiss made precision sensor, keep your wallet ready :)
There are cheaper versions on AliExpress, but i doubt if they are as precise as the genuine ones.
Regards
Shardan

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