README

Introduction

Receive La Crosse TX4 weather sensor data with Arduino and send to serial (USB) port. Also calculates the dewpoint from current temperature and relative humidity, and records indoor temperature from a DS1631 digital sensor and barometric pressure from an onboard BMP085 pressure sensor. The Arduino does not output the time of measurements, so a timestamp should be added when the data are logged by a computer. A sample logging script is included.

Pressure is reduced in the plotting script to sea level using the equation given in the BMP085 datasheet:

p0 = p/(1 - altitude/44330)^5.255

My elevation is 139 m.

This project is based on the Weather Station Receiver from the book Practical Arduino by Jon Oxer and Hugh Blemings, and uses some of their original code, which may be found at GitHub. Further help in decoding data packets came from Jean-Paul Roubelat’s page on LaCrosse sensors. BMP085 pressure sensor code is based on code from Interactive Matter (used and relicensed under the GPL with permission).

Dewpoint formula is from :

Lawrence, M., The relationship between relative humidity and the dewpoint temperature in moist air: A simple conversion and applications, Bulletin of the American Meteorological Society, 86, 225–233, doi:10.1175/BAMS-86-2-225, 2005

More information is at http://kjordahl.net/weather.html.

These programs are released under the GPLv3. Please see the file COPYING or http://www.gnu.org/licenses for details.

Kelsey Jordahl kjordahl@alum.mit.edu

Time-stamp: <Sun Feb 19 14:15:26 EST 2012>

CONTENTS

README.org

This information file

README.txt

ASCII version exported from README.org

lacrosse.pde

Arduino code

logserial.py

Simple python script to log from serial port and add timestamp

plotweather.py

python script for plotting and uploading data to website

template_py.html

blank HTML file used as template by plotweather.py

seriallogrotate

shell script to rotate serial log files (run by cron daemon)

logserial.conf

file for /etc/init to start logserial.py automatically (for upstart daemon used by Ubuntu and Debian Linux distributions)

INSTALL

Required hardware for this project is an Arduino-compatible platform with a 434 MHz RF receiver connected to digital pin 8, a 10k themistor on analog pin 1, and a BMP085 pressure sensor connected to analog pins 4 and 5. A compatible 434 MHz temperature sensor (e.g., La Crosse TX4) is also assumed. Please see the references above for details for details on hooking up these components.

The Arduino sketch lacrosse.pde will, when uploaded to the Arduino, send output to the USB serial port of an attached computer. For automatic logging and plotting, use the included files (which have been tested on an Ubuntu 10.10 system). Copy the files logserial.py, and plotweather.py to /usr/local/bin or another directory in your path. The HTML template template_py.html should be kept in a directory that will be updated with the static web page and plot (e.g. /home/user/html/weather). To run the scripts automatically, copy logserial.conf to /etc/init and seriallogrotate to /etc/cron.weekly. To run the plotting script every 15 minutes, you may wish to edit your user crontab file to the following:

1,16,31,46 * * * *  /usr/local/bin/plotweather.py -u

You will probably need to edit the scripts to the desired paths for logging and HTML files on your system.

Changelog

v1.1.1 (19 Feb 2012)

Update logging script

v1.1 (25 Apr 2011)

Swap indoor temperature sensor to DS1631

v1.0.6 (19 Feb 2011)

plotweather.py takes optional arguments; this README file reformatted in Emacs org-mode

v1.0.5 (7 Jan 2011)

Add files and instructions for automatic logging and plotting

v1.0.4 (15 Dec 2010)

change to more robust python script for plotting

v1.0.3 (3 Sep 2010)

improve plotting, including pressure and better autoranging

v1.0 (14 Aug 2010)

Release full version

v0.9.9 (3 Aug 2010)

Added support for BMP085 pressure sensor on board

v0.9.2 (18 April 2010)

Update plotting scripts for daily high & low temperatures (in Fahrenheit).

v0.9.1 (14 March 2010)

Add GMT plotting scripts and HTML template

v0.9 (9 March 2010)

Initial release of Arduino script