joseph inegbenebor
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Joined: Mon Oct 06, 2014 8:51 am

pi weather station

Mon Oct 06, 2014 8:54 am

I have been asked to create a weather station for my A-level engineering project. I have decided to make a pi station, but I have no idea on what to do or how to start. I have watched several YouTube videos and looked at various websites like tinker forge and blogs but none of these have relayed important information on what I need to get a fully functional weather station. The aim of my project is to make a weather station that measures temperature, humidity, wind speed and wind direction. I have to complete the project by the 20th of April 2015 in order to get a grade. I would really need your support on carrying out this project. Help of any form will be greatly appreciated especially information on what I will need to make a pi weather station. Thank you.

BMS Doug
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Location: London, UK

Re: pi weather station

Mon Oct 06, 2014 1:13 pm

start with research and definition:
what is a weather station?
what elements do you need to measure?
what do commercially available weather stations consist of?

next compose a list of components for your weather station:
list all the types of sensors desired,
where will the weather station be located
will you use mains or battery power?
how often will the weather station gather its data?
how will you access the weather station data?

now start selecting specific sensors:
how will they communicate with the pi?
how frequently can each be sampled?

Connect each sensor to the pi and gather its data:
add one in isolation and get it working, disconnect and move on.
once all sensors are working individually then try getting them all working together (adding one at a time until all are connected and interfacing correctly).

make a weatherproof enclosure for the pi and attach sensors. Mount in final location.
Doug.
Building Management Systems Engineer.

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aTao
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Location: Howlin Eigg

Re: pi weather station

Mon Oct 06, 2014 1:22 pm

Temperature and humidity, theres a chip for that.
Wind direction, a vane and some rotary encoder, for the most basic, just 8 positions would do (thinking magnet and microswitches here.
Wind speed, now thats not so easy, but with a few straws, plastic cups and some hot glue you can knock up an anemometer.
>)))'><'(((<

Massi
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Location: Italy

Re: pi weather station

Tue Oct 07, 2014 2:36 pm

joseph inegbenebor wrote:I have been asked to create a weather station for my A-level engineering project. I have decided to make a pi station, but I have no idea on what to do or how to start. I have watched several YouTube videos and looked at various websites like tinker forge and blogs but none of these have relayed important information on what I need to get a fully functional weather station. The aim of my project is to make a weather station that measures temperature, humidity, wind speed and wind direction. I have to complete the project by the 20th of April 2015 in order to get a grade. I would really need your support on carrying out this project. Help of any form will be greatly appreciated especially information on what I will need to make a pi weather station. Thank you.
First of all, Doug is (as always) right, you should give it a thought befor starting "doing" things..
This is also a nice part professors love :)

BUT

seen that i've all what you say connected to my pi, i can give you my experience :)

Hardware part:
- Temperature and humidity: take a simple DHT22 sensor. There are also versions with already soldered pullups and capacitors, they are easier to use obviously
- Barometric pressure: BMP180 IIC sensor (this also gives temperature, if you need a double reading..)
- wind speed and wind direction: i bought a TX23 lacrosse sensor. quite easy to connect and use, the fun part is decoding the bitstream sent..
- i also have rain quantity sensor (a pluviometer) which is a simple contact that switches with rain.

The nice part is that you have a lot of different types of sensor:
- bmp180 is iic
- DHT22 is single line (but you can use it also with SPI)
- TX23 is another single line
- pluviometer is just a contact to be managed with interrupts

Now, in my case the PI is in home and sensor are outdoor, so i have not the problem of power, but i have the problem of cable lenght.
You probably will only create something that has to work only one time, so neither this is a problem..

Finally, the software part: what do you expect to do? i read sensors once every 5 minutes and log data. If you only have to show "instant" data, also database part is useless..

Thats all :)
bye

BMS Doug
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Joined: Thu Mar 27, 2014 2:42 pm
Location: London, UK

Re: pi weather station

Tue Oct 07, 2014 3:56 pm

pattagghiu wrote:
First of all, Doug is (as always) right,

I'm not always right, but don't tell anyone my kids I admitted it.
Doug.
Building Management Systems Engineer.

Massi
Posts: 1691
Joined: Fri May 02, 2014 1:52 pm
Location: Italy

Re: pi weather station

Tue Oct 07, 2014 4:00 pm

Ok, you need to link(*) your kids to the pi first, than you'll be always right :)

(*) i think soldering is not going to be a good idea..

sarnold42
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Joined: Wed Jun 19, 2013 2:23 am

Re: pi weather station

Tue Oct 07, 2014 5:37 pm

@pattagghiu: Did you have any specific tips on decoding the data from the Lacrosse? I found some code/discussion on the arduino forum (along with a lot of questions). Don't suppose you have some python code on github or similar? Thanks in advance...

Massi
Posts: 1691
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Location: Italy

Re: pi weather station

Tue Oct 07, 2014 6:49 pm

sarnold42 wrote:@pattagghiu: Did you have any specific tips on decoding the data from the Lacrosse? I found some code/discussion on the arduino forum (along with a lot of questions). Don't suppose you have some python code on github or similar? Thanks in advance...
my bible:
https://www.john.geek.nz/2012/08/la-cro ... -protocol/

i also used start frame to find exact timing of "bits" and then used this timing to find bitstream :)

I can give you my python code with no problem (it's not that nice, but it seems to work), but i'm sure you would have more fun doing it by yourself :) let me know..

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yv1hx
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Re: pi weather station

Wed Oct 08, 2014 5:38 am

@ joseph inegbenebor:

As a long time Weather Station operator and former Head (in Charge) of a small meteorology research unit in my country most know research institute, I cannot resist to offer you my two cents:

* The rain gauge circuit can be solved using a counter with the appropriate debouncing circuit.

* Maybe this device Parallax Altimeter sensor module MS5607 http://www.amsys.info/sheets/amsys.en.ms5607_02ba.pdf can be used as the barometer. (Note: I'm not tried by myself this device)

* As usual, some parts of any design can be challenging, maybe you want to put your RPi in a outdoors box then hook up directly the external sensors (rain gauge, Temp/Hum sensor, Barometer, Wind Vane, anemometer, etc) ? If no, then you should use a already know weather station protocol between your external suite of sensors and your RPi, then you can pick up your favorite Weather Station software (PyWeather , wview, weewx, and possibly other Zillion of choices.. :oops: ) and save some of your brain cells ;) Be aware, this can require some effort programming a micro-controller and possibly dealing with analog signals, unwanted noise and filtering.

Some protocols are released and well documented by the manufacturers for some of his models (Vaisala WXT520, Davis Vantage Pro 2), but others has been reverse engineered by enthusiast's and very clever guys (LaCrosse 23xx series, FineOffset, Radio Shack WX-200, and others than I certainly I don't know).

I hope this can be helpful for you.
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