BME280 long term relability.

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BME280 long term relability.

Post by AndyGadget »

As mentioned elsewhere, I'm using BME280 pressure/temperature/humidity sensors in three different places.
The first is in a heating oil tank measuring device. This was initially going to be only for sending oil level, but at the time I thought I'd include the BME280, because I could :D . I redesigned the housing and it is at the front of the house on top of the oil tank, well isolated from any direct contact with rainfall or splash, and oil fumes.
The other two are controlled by the same ESP32 in my greenhouse in the back garden, one inside and one outside. Again, both with no chance of direct water splash.

Both these units are in deep sleep most of the time, only waking once every 30 minutes and 15 minutes respectively to take readings and transmit the data to ThingSpeak. This takes toughly 10 seconds. There will be no significant heating effects from the ESP32 over this period.

Temperature and pressure reading from the 3 BME280 are fine. I can go out with a portable lash-up to verify and the values always agree.
The problem comes with the humidity reading. Readings appeared sensible for three or four months in use but after that the humidity readings drifted higher and higher until two of the BME280 now report a continuous 100% humidity and the third only drops slightly to 95% or so on dry sunny days.

I have seen similar reports on the internet of the same thing happening, and I did try using gently heat from a heat gun for 5 minutes on two of the devices which brought the readings down on one of them for a week or so, but then it drifted up again.

I was hoping to add a pair of DHT22 to the greenhouse unit to measure just the internal and external humidity, and leave the BME280s in placer for temperature and pressure. This is what led me to pick up the DHT22 / AM2302 device again. (I'll update that thread later - Stuff to do now.)
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