Pressure example BMP085

[Heinz]

The forecast of my weatherstation is always "stable". The wrong factor could be an explanation for that. I changed the sketch some minutes ago, now I am curious if the forcast algorithm works as expected.

[sundberg84]

@Heinz Yesterday we had a thunder forecast... but the sensor reported cloudy so i will also try this :)
Thank you! I will try and report back - well done!

[Heinz]

Well, after the changes the forecast obviously works well. I will try to submit the changed code the next days.

[epierre]

For all the v2 library is out, although the v1 is the one commonly provided today
https://learn.adafruit.com/bmp085/using-the-bmp085-api-v2

The BMP085 has been discontinued by BOSCH and replaced with the BMP180 which is smaller and less expensive but is identical in terms of wiring and software!

to have a correct pressure you need to correct this:

 float pressure_raw = bmp.readPressure();
+  float pressure = pressure_raw/pow((1.0 - ( myAltitude/44330.0 )), 5.255);

now I have values that I can validate with other barometers. You just need to know your altitude from sea level.

[Heinz]

The library used in the pressure example of the mysensors project already supports this:

	float pressure = bmp.readSealevelPressure(ALTITUDE) / 100.0;

Btw I fixed some issues in the sample see also
https://github.com/mysensors/Arduino/tree/master/libraries/MySensors/examples/PressureSensor

[Andreas Maurer]

Hi all,

the forcast is working as expected for a while now. It follows the pressure values from the device.

First diagram shows pressure and forcast. Looks like the calculation is ok.
But the weather doesnt know anything about the forecast :) 100% Humidity because it rains Dogs and Cats :)

This is no question. Just a little reminder about crystalballs :)

Andreas

[Heinz]

Mine is also working well...here is my FHEM screentshot of today. Right now it is clearing up again after a short thunder storm...

I also added a weather situation indicator which works like a common barometer: it shows sunny when the pressure is above 1013hPa and rainy if the pressure is below this world wide average.

The field "Vorhersage" shows the forecast "sunny" as the pressure raised last last hours significantly.

[5546dug]

@Heinz
I too am having reading issues with the new 180 pressure sensor.

a couple of questions,
Is altitude stated in meters I think?

The code revisions;
Are they to added to sketch in place of the existing parts, while the algorithm is to be totally replaced with the revised code you have supplied?

Thanks

[Heinz]

@5546dug
Yes, the altitude is in meters.
A complete sketch containing the changes and some bug fixes is part of the mysensors library 1.5. So you don't have to merge the code from above, simply download it from github.

[5546dug]

@Heinz thanks I am still on 1.4.1 and will look it up

[5546dug]

@Heinz
Well once again I am stumped, I can't find this library I need, do I need to upgrade my system to 1.5 to find this file., or am I just not seeing what I need to see?:blush:

[korttoma]

@5546dug -> https://github.com/mysensors

[Heinz]

You don't need to upgrade to 1.5, you can simply download the sketch from here
https://github.com/mysensors/Arduino/tree/development/libraries/MySensors/examples/PressureSensor