Recently we had our cellar isolated because of some wet walls and I wanted to check if the humidity of the air will be fine from now on.
I ordered some DHT11 sensors on Amazon and made myself a small test setup with two of these and some Arduino-clones. Sadly the sensors I bought were no good. The measured data consisted more of wildly fluctuating noise than usable values. I’m not sure if this was a problem with my setup, my specific set of sensors or if it is a general issue with these DHT11.
On my quest for better data I bought a bunch of Bosch BME280 Sensors from Watterott and (for good measures) threw in a handful of ESP8266 ESP-01 Wifi-modules as well. The ESP8266 is a funny little WiFi-enabled microcontroller with a growing community and a whole bunch of options regarding the programming and usage.
After a little bit of mass production (I built six of these boards) I implemented a human readable “website” on these things as well as a JSON output for automatic collection of data.
Finally I threw together a Python-Script which collects the data and puts it into a RRD database as well as a small PHP-Site which displays the generated images.