Which better Temp/Hum sensor to replace DHT22 ?

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tparvais
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Which better Temp/Hum sensor to replace DHT22 ?

#1 Post by tparvais » 27 Apr 2020, 11:15

Hello

I have 2 DHT22 sensor connected to 2 different ESP installed few months ago but not in use yet.

One in Greenhouse
One in a sauna (max 70°)

I re-activated the ESP connected.
Temperature is still working, but humidity are always indicating 0%.

Are they dead ?

Do you know better sensors, more robust for exterior ? (DS18B20 can be ok for temp, for for humidity ?)

Thank you

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Ath
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Re: Which better Temp/Hum sensor to replace DHT22 ?

#2 Post by Ath » 27 Apr 2020, 12:01

I'm getting quite good results from BME-280 (not to be confused with BMP-280), though it may need some temperature calibration by applying a formula to the value (%value%-6), as in my situation (bought cheap clones from Aliexpress) they return a bit too high temperature values. Humidity and barometric pressure seem fine though.
/Ton (PayPal.me)

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grovkillen
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Re: Which better Temp/Hum sensor to replace DHT22 ?

#3 Post by grovkillen » 27 Apr 2020, 20:11

My go to sensor is the BME280. Like always, if you want reliable values, calibrate.
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Re: Which better Temp/Hum sensor to replace DHT22 ?

#4 Post by TD-er » 28 Apr 2020, 11:59

Ath wrote: 27 Apr 2020, 12:01 I'm getting quite good results from BME-280 (not to be confused with BMP-280), though it may need some temperature calibration by applying a formula to the value (%value%-6), as in my situation (bought cheap clones from Aliexpress) they return a bit too high temperature values. Humidity and barometric pressure seem fine though.
The BME280 plugin has a temp offset parameter, which also corrects the humidity.
Those are tightly related, so just offsetting the temp will render the humidity invalid.

Problem with the BME280 is that it is quite small and thus easy to heat up.
Make sure to put the sensor outside the box to get a proper environment reading and then you should not need to apply an offset.
The offset is only useful when it is placed in a small enclosure with something that produces a constant heat, like the ESP does.
And even then the offset is only linear for a small temp range.

tparvais
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Re: Which better Temp/Hum sensor to replace DHT22 ?

#5 Post by tparvais » 28 Apr 2020, 12:02

grovkillen wrote: 27 Apr 2020, 20:11 My go to sensor is the BME280. Like always, if you want reliable values, calibrate.
mmh I wonder if he will survive in a sauna (Temp max 80°)

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Re: Which better Temp/Hum sensor to replace DHT22 ?

#6 Post by TD-er » 28 Apr 2020, 12:05

tparvais wrote: 28 Apr 2020, 12:02
grovkillen wrote: 27 Apr 2020, 20:11 My go to sensor is the BME280. Like always, if you want reliable values, calibrate.
mmh I wonder if he will survive in a sauna (Temp max 80°)
That's quite humid and warm.
I doubt using an I2C sensor is the way to go then, as the max. length of I2C is rather limited, so you need to have the rest of the parts also close to the sensor.

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Re: Which better Temp/Hum sensor to replace DHT22 ?

#7 Post by tparvais » 28 Apr 2020, 12:14

I have ordered sht30 to test ..

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Re: Which better Temp/Hum sensor to replace DHT22 ?

#8 Post by TD-er » 28 Apr 2020, 13:11

Regarding the initial question.
I think these DHT sensors may become somewhat saturated.
I keep thinking I've read somewhere that these sensors could be 'revived' by drying them.
Not sure where I've read it though, nor how to revive them.

Maybe putting them in a bowl of rice or drying in an oven for some time.

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