DHT22 stuck on 99.9% Humidity

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sheppy
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DHT22 stuck on 99.9% Humidity

#1 Post by sheppy » 20 Aug 2018, 03:04

I've a SOnOff 4Ch with a DHT22 wired to GPIO1 for detecting moisture from a Shower. I'm using mega-20180114 and I think the humidity sticks at 99.9% once it gets that high, whilst the temperature keeps updating. After 38 minutes I rebooted it and the Humidity started moving again.
Is this a known bug?
I would try a later version but thought I'd ask first as its a lot of work to uninstall this one for a reflash

whatsupskip
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Re: DHT22 stuck on 99.9% Humidity

#2 Post by whatsupskip » 03 Sep 2018, 07:22

If the sensor really is at 99.9% humidity then that could be causing problems in itself. 99.9% implies it is actually wet and that could mean short circuits or abnormal mode that is only cleared by a reboot.

I haven't used a DHT22 on such old firmware, but I would first look at preventing the sensor getting that damp.

sheppy
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Re: DHT22 stuck on 99.9% Humidity

#3 Post by sheppy » 03 Sep 2018, 07:43

It’s mounted above a shower, so it will get a lot of humidity :) I want it to operate a 2 speed ventilation fan. It doesn’t go directly to 99.9% though. Is there any known version of firmware that has a bug fix that could effect this? Updating is a lot of work with this location so I don’t want to update unless I know which version to install. Sadly OTA updates don’t work on this module or any of my other SOnOff’s

whatsupskip
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Re: DHT22 stuck on 99.9% Humidity

#4 Post by whatsupskip » 03 Sep 2018, 07:58

I am not aware of any bug fix for that. The DHT22 is a very basic (cheap) sensor, so that is why I suspect the problem is with the sensor.

If you can't easily relocate the sensor, an alternative might be to create a rule to reboot the device if the humidity is too high. That might not be an option of the ESP device is doing many other things.

sheppy
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Re: DHT22 stuck on 99.9% Humidity

#5 Post by sheppy » 03 Sep 2018, 08:06

I’ll experiment with a reboot, I don’t need any real accuracy with this sensor as long as whatever it says is repeatable. As the humidity lasts after the shower has ended I can safely reboot once the light has been turned out

whatsupskip
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Re: DHT22 stuck on 99.9% Humidity

#6 Post by whatsupskip » 03 Sep 2018, 08:12

I have a humidity sensor in the shower room. It is not located above the shower, it is actually close to the door. It is quite obvious when the humidity is too high in the room, except for the time when my wife placed a wet towel right next to the sensor.

sheppy
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Re: DHT22 stuck on 99.9% Humidity

#7 Post by sheppy » 03 Sep 2018, 08:23

That makes sense, it was a particularly insensitive old vent axia sensor mounted nearby that led me to move the replacement sensor nearer.

tykenicol
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Re: DHT22 stuck on 99.9% Humidity

#8 Post by tykenicol » 19 Mar 2019, 09:42

Dht22 get stuck on 99.99% because it get dirty. Was it in mentholated spirits.

sheppy
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Re: DHT22 stuck on 99.9% Humidity

#9 Post by sheppy » 19 Mar 2019, 09:45

It was a brand new sensor, I switched to Tasmota and it’s been working fine for 6 months :D

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