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This is a simple project for a weather station.

Initially it reads temperature, pressure and humidity. Next step is to measure wind direction and after that wind speed.

The base of the project is a Raspberry PI A+ which was chosen by its small consumption, since the idea was that the weather station being powered by solar power.

The OS is raspbian distro, with some off the shelve python libraries.

Main program was written in Python.

Weather station uploads all data to www.wunderground.com every 2 minutes.

Step 1: Hardware Description

For the completion of the project we will need the following :

Raspberry Pi A+ (It is possible to use any model)

Temp/Pressure sensor Bosch BMP180

Temp/Humidity sensor HTU21D

Wireless adapter

SD card

10W Solar panel

7.2 Ah 12V battery

Generic 12V solar controler/charger

5V regulator 7805

Bits and bogs needed

Step 2: Setting Up the Basics

I will not waste time explaining how to install raspbian on a Rpi. I assume that whoever wants to build this project is profficient enough in these matters.

Anyways the link for the distributions is http://www.raspberrypi.org/downloads/

Since i own a few Rpi's , i already have na SD image ready to roll with wireless conectivity, so it was just a question of rewriting it to a new card.

If you do not have such a "backup" it is probably better for you to use a B+ or other model with ethernet, and setup everything using one of many tutorials available.

A good tutorial for setting up Rpi is http://www.raspberrypi.org/help/quick-start-guide/

A good one for wireless is http://www.raspberrypi.org/documentation/configuration/wireless/

If everything went alright you should have now a Rpi with wireless internet access.

You still need to have your Rpi ready to use I2C protocol.

A good one is https://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/configuring-i2c

Step 3: Setting Up Other Software

After you set up your Rpi, there are a few pieces of software needed for us to be able to read the used sensors.

I did all using Rpi "Headless" and using command line

I used Adafruit library for the BMP180, just follow the link to install it

https://learn.adafruit.com/using-the-bmp085-with-raspberry-pi/using-the-adafruit-bmp085-python-library

We also need Pigpio library for Reading the humidity sensor. You can download from

http://abyz.co.uk/rpi/pigpio/download.html and follow installation instructions

After that you have to make sure that whenever you reboot the Rpi, Pigpio is also loaded. I did this by adding the following line to /etc/rc.local

sudo pigpiod

In my case this is enough but this depends on where you have installed pigpio. If you run into problems, just put the whole path for the file and you should be ok.

The presented tutorials are pretty straightforward but if you need any help i'm here :D

Step 4: Setting Up the Sensors

I got both sensors from Ebay, since it's easier (and cheaper) to get ready made small boards with the sensors already soldered that to do them by yourself. If you search Ebay for BMP180 and HTU21D you will find them for sure.

These are I2C sensors which are very easy to communicate with. The I2C protocol allows you to connect several sensors in paralell and communicate with each of them because each has a unique address.

I got both soldered together with some skill , matching all signals as seen on the pictures.

The sensors will need +3.3V, GND, SDA and SCL signals from the Rpi.

You can use any wiring you like, but a 4 wire cable (telephony) is probably a nice idea.

Step 5: Main Program

Main program is temp-monitor.py

You should have python installed , if not, just follow http://raspberry.io/wiki/how-to-get-python-on-your-raspberrypi/

The first part of the program shows the libraries needed.

import Adafruit_BMP.BMP085 as BMP085
import smbus
import os
import sys
import getopt
import sqlite3
import math
import pigpio
import time

Following the program we have 2 functions that will read humidity. Read_temperature is a function that will read the temperature of the HUT21D for compensation when calculating the relative humidity. It is necessary for the following function read_humidity.

There is a few calculations inside these functions, but this is all according to the sensors datasheet. Not importante stuff, but you cam always check them if you like

BMP180 http://www.vssec.vic.edu.au/media/41229/BMP180-datasheet.pdf

HTU21D http://www.meas-spec.com/downloads/HTU21D.pdf

The cmd variable is responsible for sending the data to www.wundergroud.com using curl. This website provides some really nice stats and graphs. You need to register (it's free) an account to upload the data.

After that you will have an ID and a password which you sould change in the cmd variable as shown

cmd = "curl "+"'http://weatherstation.wunderground.com/weatherstation/updateweatherstation.php?ID=&PASSWORD=&dateutc=now&tempf="+str((temp*1.8)+32)+"&humidity="+str(round(humidity,2))+"&baromin="+str((pressure/100)*0.0295299)+"&action=updateraw"+"'"

You then have to change again /etc/rc.local and insert a line for the program to start when the Rpi is rebooted :

sudo python /usr/lib/cgi-bin/temp-monitor.py &

The & symbol is important because it will put your program into memory and releasing the command line to be used.

UPDATE

For the curious minds, temp-monitor-online.py is the current program i'm using, with readings for temperature, pressure, humidity, dew point, wind speed and direction and uv and insolation.

Step 6: Building Up the Solar Panel

So if you have all sorted out and working well it's time to put your weather station outside.

I chose to feed my Rpi using a solar powered system, using 3 3,5W modules bought on Ebay.

The modules output 6V, so 3 modules in series will give us 18V, which is the standard for a 12V solar system.

You can arrange them as i did and you will end up with a pretty nice small panel capable of running the system.

Probably you are thinking that 10W and a 7,2Ah battery is a bit much for the Rpi, but since i am in Ireland, i am expecting to run a few days without sun, so...

Step 7: The Solar Shield

I have made the solar shield from discardable plastic plates and 2 cm pieces of plastic tube. I will not go much into this since there are many ways to do this. The important thing is that the sensors are protected from wind and direct sunlight.

If you would like more details i can update with more information.

Step 8: Everything Connected

With everything in place it's time to connect things.

If you have a solar charger with a load output, it's a good idea to use it, since usually there is a way to turn it on/off. Since we are using a 12V battery, we will need a 7805 regulator to reduce to 5V for the Rpi. If you look to the 7805 with the markings facing to you, the left pin is the input(connect it to 12V) , the middle one is GND, and the right one is the output (5V).

You can connect your 5V to the usual Rpi connector or directly to its header, in this case, pin 2 or 4.

The solar charger has connections for the battery and for the solar panel. Make sure that you connect always the battery in the first place.

It's time to connect the I2C, which are pins 3 and 5 (SDA and SCL) and pins 1 and 9 (+3.3V and GND)

Power up the Rpi, check that everything is running well and close your box :D

Step 9: Final Thoughts

This is my first tutorial so please excuse me for anything that you do not like.

I appreciate comments and improvements.

This is a basic setup and will be improved with a few more sensors

I leave you with the link of my weather station

http://www.wunderground.com/personal-weather-station/dashboard?ID=IWICKLOW13

Enjoy

Step 10: Project Update 1 - Wind Direction

It's been a while since the creation of this instructable and things got some improvement.

The weather station runs and uploads now both wind speed and direction. I will now show you how the wind direction is working. It is also reading and uploading UV índex.

There are a few projects around that use a setup of reed swicthes to get the wind heading. I always thought that it does a pretty simple solution, but nowadays with digital compasses it seems more appropriate to use one of these small devices. Also, since my objective was to run all sensors on I2C bus, i was sure that i could find one that would fit in this type of bus. So i did.

I am using a HMC5883L, which is a 3 axis digital compass, using I2C bus. You can find ready soldered modules on ebay as cheap as 1 euro. Just search and you'll find them for sure.

One piece of advice with this sensor. I believe that this kind of sensors are quite sensitive, since i managed to kill one. After a few days of getting wrong indications from it, i got a new one and all sorted out. Just be careful , don't drop it too many often.

The other importante part that i used is called a slip ring. What is a slip ring? It's a small device that allows you to have a rotating axis and connections at the same time. There are several parameters that define such device. One is the number of ways(or wires) and other is the rated current accepted through the wires. Since we are only Reading sensor, and in this case I2c, we will need 4 wires and the current is as low as you can get.

I got a 6 wire , low current which happened to have the axis diameter the same as the inner measure of some plastic tubing that i used to build the vane.

The various pictures show how i managed to build the thing. It's not pretty but it dows the job.

SOFTWARE

It's a pretty simple thing to read from the HCM. I took a few looks on the datasheet, made some research in the web, and i got to these code lines to put it working :

def write_byte(address,adr, value):
bus.write_byte_data(address, adr, value)

- Procedure to write data in a specific address of the I2C bus.

def median(lst):
lst = sorted(lst)
if len(lst) < 1:
return None
if len(lst) %2 == 1:
return lst[((len(lst)+1)/2)-1]
else:
return float(sum(lst[(len(lst)/2)-1:(len(lst)/2)+1]))/2.0

- This is a procedure for getting the average number of a list of readings. It will be needed

write_byte(0x1E,0, 0b01110000) # Set to 8 samples @ 15Hz
write_byte(0x1E,1, 0b00100000) # 1.3 gain LSb / Gauss 1090 (default)
write_byte(0x1E,2, 0b00000000) # Continuous sampling
scale = 0.92
x_offset = 45
y_offset = -82

- Needed declarations for the sensor. The first 3 lines set up sample readings and gain. The fouth sets the scaling. The 2 last ones are values to tune up the sensor Reading. They may vary from sensor to sensor, but most of the times they do not affect much the Reading.

def get_heading():
x_out = (read_word_2c(0x1E,3) - x_offset) * scale
y_out = (read_word_2c(0x1E,7) - y_offset) * scale
z_out = (read_word_2c(0x1E,5)) * scale
bearing = math.atan2(y_out, x_out)
if (bearing < 0):
bearing += 2 * math.pi
if ((math.degrees(bearing) + 90) < 360 and (math.degrees(bearing)+90) > 90):
heading = math.degrees(bearing)+90
# print round(heading,0)
elif math.degrees(bearing)+90 == 360:
heading = 0
# print round(heading,0)
else:
heading = math.degrees(bearing)-270
# print round(heading,0)
return heading

- This is the main reading procedure. It gives you the heading of the vane in degrees from 0 to 359

So now that we have all declarations and procedures, the only missing past is insert the next code into the main program :

dir = 0
lista = range(500)
print('Reading 500 times wind direction separated by 10mS each for smoothing final reading ...')
for dd in range (0, 500):
lista[dd] = get_heading()
time.sleep(0.01)
direction = median(lista)
print('Done !')
print('Wind dir is ',direction)

I found that doing just one reading would result in huge variations in the direction, so what we are donig here is taking 500 measurements separated by 10mS each, and outputting the average of all values. All print lines can be deleted since they only serve for debugging purposes.

Do not forget to update the upload line to wunderground, now we have more data, so you have to put in windir=direction, in my case.

Cheers, folks!

Step 11: Project Update 2 - New Software

Hi folks

Still waiting for the new slip rings from China, hope i'll get them in a couple of weeks, and then as promissed i will update with the howto of wind direction and wind speed.

I've made some changes on the main program which you can download. The reasons for this are:

  1. If one of the sensors get disconnected accidentally from the I2C bus, the program will crash. So i've made 4 new test functions which will test if the sensors are really connected, and if not, the program assumes the value 0 for the respective sensor. This can be changed at your will.
  2. I'm using a cron job to run the program each 5 minutes instead of being running all the time. This actually makes a lot more sense, since you now don't have a program running 24/24 wasting resources and prone to crash. You can also change the 5 minute to whatever you like.

I find easy to setup cronjobs with the aid of a GUI program called gnome-schedule. If you do not have it installed, just do sudo apt-get install gnome.schedule to do it.

After that you just add a new recurrent cron job, give it some sort of name and setup the run command as sudo python temp-monitor.py. After that you just need to setup your time interval , save the task and reboot .

Thanks for the interest

<p>Any update on the new split rings, the wind speed or the UV sensor? </p>
Not much time to this since a newborn is in the house for the last 9 months :D . I have the new slip ring assembly with the sensor pretty complete but no time to put it out. Hopefully in a few weeks, since the weather is getting a bit better here. I've managed to find a good I2C candidate for the UV sensor in the VEML 6070, and I've found some modules on ebay based on that sensor. Ordered a few and waited for more than a month and they didn't arrived... Tough, have to find a new seller to get it, since this is a proper UV sensor.
<p>Many thanks for this...</p><p>Have a test set up here and it seems to be working fine.</p><p>Mine is updating on the Wunderground site once every 5 minutes.</p><p>Can you point me to the part of the code that sets the timing of this 5 minute interval please.</p><p>Thank you</p><p>Regards</p><p>Phil</p>
<p>I believe the 5m is a limit of the wundergound website itself, since the program is set up to do all readings, send them to wundergound and them wait 60s (the last instruction on the program time.sleep(60). I gave up using that system, and i'm using a cron job on the pi which runs the program each 5 minutes(you can setup whatever time frame you want), and that does the job. The reason for this approach change was because sometimes my pi would &quot;hang&quot; because of some error on the I2C bus, or the program itself would hang. So using the cron job would only run the program as needed instead of keeping the program running 24/24. Seems the logical way to go. About the I2C bus, because pythonsmbus doesn't have any testing function as far as i know, if one of the sensors fails to connect, the program will crash, so i created test functions for each sensor, and that problem is also solved. I'll put here my latest version of the prog later on. Thanks for your interest.</p>
<p>Hi</p><p>Many thanks for the reply, very interesting.</p><p>I'm very very very new to all this and have learned a lot implementing your script on my Pi A+.</p><p>I have the sleep (120) on the end of the script. Having run the test setup overnight, I see that in fact, Wunderground shows data from me every six minutes.</p><p>Great fun and look forward to any updates you may post...</p><p>Thanks for shareing your work, much appreciated by this old guy :)</p><p>Phil</p>
<p>Have you had any issues with water getting on the temperature and humidity sensors in the solar radiation shield? </p>
None whatsoever, and it's been out for more than a year now. You can see some oxidization on the pads but that's it. I though of using silicone to waterproof the boards, but since this is not an issue so far, i didnt't use it.
<p>Hiya,</p><p>I notice on wunderground that you're now reporting Windspeed and direction, do you have an update to this fantastic instructable?</p><p>Thanks!</p>
Hi there. Thanks for the interest.<br>I will post soon the update, there is also a UV sensor now, and as you stated, wind direction and wind speed. This last , was installed yesterday and code was complete this afternoon, now showing pretty good readings. Stay tuned for the next days
<p>Is it a ML8511 UV sensor that you are using?</p>
<p>Its a SI1145 that I'm using.</p>
<p>Any update on your new sensors? :) Love the project.</p>
<p>Nice update on wind direction. I still haven't completed my build, life tends to get in the way of hobbies. Good idea with the digital compass. I just always thought that reed switches were the only real choice. Thanks for the update.</p><p>Any plans on the wind speed update?</p>
<p>As you stated so well, life sometimes gets in the way. I'll try to put that update in the next couple of weeks. Thanks for your interest.</p>
<p>Updated wind direction. Wind speed coming next</p>
<p>I noticed that on your wunderground page you don't currently have wind direction available. Did you have another HMC5883L go bad? Or is it something more serious?</p><p>Any update on wind speed build?</p>
<p>No, the sensor is OK, but the ring sleeve I use was not working properly, so I had to order a new one. Since they come from China very cheap, I ordered 2 more that never arrived... Bad luck though... I've already ordered from another seller and hope to get that working in a few weeks. I'll try to putvthe wind speed soon.</p>
<p>Thanks for this instructable. I've been thinking about building a weather station for quite some time. I'll be using this as my guide to get it built.</p><p>Any plans on showing how to build it up a bit to do wind speed and direction?</p>
Those are the next steps. Wind direction is already implemented, i just need to put it together. Wind speed i am still deciding if i will build the cups from scratch or use a ready made solution. I will update the instructable as soon as any mod is done. Thanks for your interest
<p>Ordered the sensors this evening. I'm not getting a RaspPi model A right now since I have a spare B+ on hand. Once I get things running, I'll change over to an A+ to take advantage of the lower power. I'll also do the solar thing at a later time. What's that box you mounted it all in? </p>
<p>It's a generic garden watertight box. I have a smaller one inside the big box, which contains de Rpi, to keep it from moisture. Just check if the box you use, has some sort of rubber gasket to seal up...</p>
<p>Thought I'd give an update. I decided that I would get the RasPi model A. That came in the mail today. I connected it up and have all the software installed. Just waiting for the sensors to come in so I can solder them and test things out.</p>
<p>That's good news. Keep us informed :D</p>
<p>China parts are trickling in.</p><p>I have a question about your 7805 voltage regulator. Are you connecting the battery directly to the input and the output directly to the RaspPi? Or do you have other components in that part of the build?</p>
<p>I actually have it directly connected, since it is working with a pure DC source. Datsheet for the 7805 shows the use of a 10uF capacitor on the input side and a 100nF on the output side. They are used for decoupling purposes, but i believe that it doesn't make much sense as we are working with batteries. Then again, you can use them. I'ts the most correct way. I'll be throwing some pics of the wind direction sensor aswell as the code for it in a few days.</p>
<p>I agree that it seems that they are not really required. I was just curious how you had it set up. I've made use of 7805 regulators in the past without having any sort of capacitors in the circuit.</p><p>Since you have had this running for a while, how does the battery keep up with the draw of the Pi? Any issues with running out of juice when you have multiple days without good sun exposure?</p>
<p>The system runs without sun for more than 3 days. I had the battery drained once but there were a number of days with bad weather , so this is an issue that i think it has a lot to do with where you are. For exemple, here in Ireland i will expect to have a few problems with this setup so, i will probably install another set of solar cells. In the meantime i'm more interested in the wind speed, i bought a 3 cup module from maplin, so now i need to take a few measurements to get the code showing correct values. Tomorrow i will install another sensor, this time is a SI1145 which will give me UV &iacute;ndex readings. Hopefully i will post more pictures of the setup tomorrow,</p>
<p>Excellent. Look forward to the updates.</p><p>I'm in the U.S. and Maplin doesn't ship to me. But I've seen that anenometer and they have a tipping bucket system as well that looks nice.</p>
Nice! Thanks for the inspiration. I've been thinking about doing something similar for my brother. I will definitely us this as a starting point.

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