raspberrypi expansion module

Request new hardware or ideas for the controller

Posts: 33
Joined: Thu Sep 20, 2012 2:34 am
PostPosted: Tue May 28, 2013 3:46 am
Just to follow up to my earlier posts so anyone finding this thread in the future can get the solution if they are having a similar problem. It turns out that it was in fact changes to the atmospheric pressure that caused my offset error. It manifested as the sensor reading either too high or too low over a number of days and usually after a shift in the weather.

What I did to overcome this was to add a Bosch BMP085 barometric pressure sensor to my bus. This allowed me to implement a calibration process where the atmospheric pressure is measured and noted while the sensing tubes are lifted out and exposed to the atmosphere. Then upon each reading of the level sensors, the atmospheric pressure is again measured and compared to the stored calibration value. I convert the BMP085 readings into kPa (the water level sensor uses 1v per kPa). The water level sensor value is then adjusted by 10% of the difference between the current and stored pressure reading.

I believe this works by accounting for the difference in the atmospheric pressure at the time of reading as compared to the atmospheric pressure (in the trapped air) when the tube was submerged. This appears to correct the offset error to within a millimetre or two, which is good enough for my needs. More testing is required to determine if the amount of offset error remains linear or if there is a boundary where this becomes problematic. I expect the summer storm season will provide some good test case large swings in barometric pressure to see if this works over the possible range of conditions.

Dennis

Posts: 11
Joined: Tue May 14, 2013 3:07 pm
PostPosted: Wed Jun 19, 2013 9:35 pm
Are they any updates on this concept yet? I have many plains for my RA that would having a Raspberry pi as a middle man would really help with.
The Idea that I was looking to and landed me here is, setting up a a ping monitor on systems around the house. I would be able to use this info to things like a power failures, then turn my MHs off to save power of the UPS, and email me to fix it.

Posts: 12043
Joined: Fri Mar 18, 2011 6:47 pm
PostPosted: Wed Jun 19, 2013 10:32 pm
I have a PI that has a wifi dongle, so the only thing it needs is power.
I can remote control it with VNC.
I was able to connect the USB-TTL cable to the other USB port and upload codes to RA just fine.
Nobody created any software for PI yet though.
So, you would not be able to use the smart phone apps, for example.
If you can code python, you can create a program to link the serial to the Ethernet/wifi port. Want to try?
You may be able to do Java too, but I'm not sure.
Roberto.

Posts: 11
Joined: Tue May 14, 2013 3:07 pm
PostPosted: Sat Jul 13, 2013 8:19 am
I don't program very well yet but here is something I found that might help.
http://www.buttcrackbrewery.com/2012/11 ... er-part-2/

Posts: 12043
Joined: Fri Mar 18, 2011 6:47 pm
PostPosted: Sat Jul 13, 2013 8:34 am
Cool.
Thanks for contributing.
This would solve the incoming portion of the puzzle.
We still need to push data to the Portal.
If you don't care about the Portal, this solution works fine :)
Roberto.

Posts: 11
Joined: Tue May 14, 2013 3:07 pm
PostPosted: Sun Jul 14, 2013 8:43 am
With the RaspbarryPi running LAMP I was thinking that it would be the host for a private portal.

Posts: 12043
Joined: Fri Mar 18, 2011 6:47 pm
PostPosted: Sun Jul 14, 2013 9:37 am
Yes, it can.
And it would easily communicate with RA too with the zip files the author has provided :)
Want to try?
Roberto.

Posts: 11
Joined: Tue May 14, 2013 3:07 pm
PostPosted: Sun Jul 14, 2013 1:19 pm
I'm all about trying it. I just got to talk the wife into letting me get a Pi. It only took 2 years to get my RA :)

Posts: 11
Joined: Tue May 14, 2013 3:07 pm
PostPosted: Tue Jul 16, 2013 6:10 pm
I will get my Pi Friday!!! I'll be starting to play with it then.

Posts: 12043
Joined: Fri Mar 18, 2011 6:47 pm
PostPosted: Mon Aug 05, 2013 8:33 am
I found this:
http://www.bareefers.org/forum/index.ph ... ler.15583/
Roberto.
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