The next caprice of mine in the frenzy of registering everything what is possible was measuring the atmospheric pressure. Initially I planned to use the BMP085 sensors available for USD 11 for 5 pieces including shipment. At the end, however, I figured out that it has been enough of all that soldering. I wanted to be a bit lazy. I bought at Aliexprees a ready connection board with the BMP180 sensor costing USD 4.7 a piece (obviously, including shipment).
The BMP180 uses I2C to communicate with the world. It could easily be a part of 1-wire extension as it also uses the I2C. The board is small enough to fit into every device. At the end I prepared a very easy "base", which fits into 1-module DIN case. It all now hands in my central cabinet with the RPi and all the other devices. Here are some photos:
If anybody wants to ask what the whole pressure measuring is for - I can say - for no good reason. It just costs so little and is so easy to connect that giving it up would be a shame.
At learn.adafruit.com one can find a very detailed article describing all the steps needed to connect the sensor to the RPi. It all boils down to:
Here are the readings from my sensor:
Temperature: 20.40 C
Pressure: 994.18 hPa
It is quite impressing if you remember the device costs some 5 dollars :)
I was analyzing for some time if the measurements made in the cabinet in the basement makes any sense and if the sensor should not be placed outside. I am currently of the opinion, that the place of measurement cannot have a too great impact. The house is not hermetic and the pressure in side and outside must be even. Even if there is a delay in capturing the pressure changes it should not matter too much. What is important for a amateur enthusiast are the changes and the dynamics. The absolute values tell me nothing.
And, as usuall, a simple graph with some data: