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Masuring the atmospheric pressure

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: 

BMP180 board

BMP180 base1

BMP180 base2

BMP180 base3

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: 

  • Connecting the SDA SCL GND and 3V3 pins,
  • Checking with command: "i2cdetect -y 1" if at 0x77 address a new device was found,
  • Downloading from Adafruit libraries for I2C connection and using the BMP180 sensor with command: "git clone https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code.git",
  • Running the file "Adafruit_BMP085_example.py", which can be found in Adafruit-Raspberry-Pi-Python-Code/Adafruit_BMP085 pliku Adafruit_BMP085_example.py directory.

Here are the readings from my sensor:

Temperature: 20.40 C
Pressure: 994.18 hPa
Altitude: 159.83

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: