Monitoring station for Underground Cold Storage (Final setup - extra credit blog 5)

Intro

There is a saying here that translates into something like "better is an enemy of the good" - so, as time is running out, I am finishing with implementing changes and improvements and starting final test.

As previous test results showed some difficult to explain data, I had to modify my sensor boards by adding additional sensors. Then I have bought some silica gel humidity absorber with usage marker, built absorbers, installed everything (again) into enclosures and pun them on test. Fortunately, weather forecasts are forecasting several days of rain so maybe I will get some meaningful measurements.

Sensor update

As it seems that temperature and humidity are not only factors worth considering in this project, I have decided to add some additional sensors.

Having some doubts about precision of installed AM2302 modules, I have added BME280 I had in my possession at first. Unfortunately, I cannot check it's originality - original chips have Bosch logo and clones are said to not have it, but it is so small I cannot recognize it using magnifying glass I have - maybe simple microscope would be needed.

As I have decided to limit a scope of my experiment somehow - it was ever-expanding to this date, I also decided to use ESP32-devkit module I had. Fortunately, it measured at 5mA of current consumption during sleep (unlike my NodeMCU board I have mentioned in the "sensors" part of my blog) so I have decided to use it, despite its peak consumption of 500mA.

Schematics of this sensor board is as below:

In the next step I decided to add BME280 modules to the existing two boards - but considering their recent significant price jump I have selected something cheaper - combined module of BMP280 and AHT20, resulting in final ESP8266 board schematics like this:

One side note - there are forum posts at the Internet that those modules from time to time ship with non-working BMP280 chip. I had such a situation, on one of two modules I bought BMP280 chip returned chip_id of 0x0 instead of correct value (AHT20 was working). Fortunately, seller promptly sent replacement board when notified about this problem.

Silica gel

To reduce the influence of humidity already present in the enclosure to the test results, I have bought some humidity absorbing silica gel. I have decided to use version that is changing color when used-up.

But what use will be of color-changing silica gel when it will be put in a opaque package? So, improvised transparent package was made:

Then absorbers for all three enclosures were created (with about the same amount of the gel - which puts our test enclosure in disadvantage by the way, because of it's bigger volume).

then enclosures were prepared

And put to the test (on the balcony, protected from direct rain and sunlight shining into the sensors - AM2302 datasheet states that direct sunlight can affect measurement results).

Now let's hope that rainy weather persists until enough data will be gathered...