Jonathan & Daria's Weather Station, Netley Marsh, Hampshire

Overview

This page describes the technical implementation of our weather station. Current and logged weather data is viewable on the weather station data page.

The weather station started as a requirement to be able the monitor the temperature in Daria's greenhouse, which is about 20m from the house. Commercial wireless weather stations did not really met the requirement, as they were either inflexible from a point of being able to add additional sensors, or expensive for a flexible set up.

After a bit of research, we built a sensor network based on the Dallas Semiconductors one wire system. This allows us to add sensors as we require. The 1 wire network runs on telephone cable, from a computer in the sitting room (with interior temperature and pressure sensors), along the back of the house to a patch box in the garage, and then along the garden to the greenhouse, where there are internal temperature and external soil temperature sensors, as well as heated propagator temperatures in seaon. Rain fall, humidity and temperature sensors have been attached to the north wall of the garage and to a shaded path at the side of house. The cabling runs in a fairly disorganised star topology (diagram [PNG], [SVG]).

The garden is surrounded by trees, so we dispensed with the anemometer, instead obtaining that data from the SotonMet WAP feed.

The USB interface and major sensors were acquired from Audon Electronics. Some additional DS18S20 (temperature-only) sensors were acquired from Quasar Electronics and assembled from these instructions. One transistor sized chip, two wires. So simple.

Images

There are images of our setup in the image gallery. Most of the images on this page link to larger images when clicked.

Hardware and Software

The acquisition and logging system runs on a Epia MiniITX  600Mhz computer, running Ubuntu Linux. The 1-wire network is connected through a DS2490 USB adaptor.

The software, w1retap, is based on the Dallas/Maxim public domain reference implementation, and is responsible for logging the sensor data.

The 1-wire network is polled every 2 minutes for data, which is logged to a postgresql database. A set of Ruby scripts periodically update this site and feeds data to wunderground.com (we're the Netley Marsh station). There is also an GNOME applet.

w1retap currently supports the following sensors:

• TAI8520 (DS1820 / DS18S20) Temperature sensors;
• TAI8540B (DS2438) Humidity Sensor;
• TAI8570 Pressure Sensor;
• TAI8575 Rain Gauge;
• TAI8515 Weather Station (DS2423,DS18S20,DS2450);
• DS2409 Microlan coupler;
• DS2490 (DS9490R) USB adaptor;
• DS2480 (DS9097U-S09) Serial adaptor;
• SHT11 based humidity sensor (details);
• MPX4115A based pressure sensor ('fronted' by DS2438, details);
• MS-TH Humidity sensors (and temperature) based on DS2438 / Honeywell HiH400). This also supports the Hobby Boards Humidity / Temperature sensor;
• The Hobby Boards Pressure sensor.

w1retap logs sensors readings using one or more "plugin" modules, these currently include:

• Sqlite (version 3)
• PostgreSQL
• MySQL
• ODBC

• Text file
• CSV file
• XML file

Downloads

w1retap (GPL)

Read the fine manual

Sensors

The 1-wire sensors (other than the temperature sensor in Daria's greenhouse), are housed in a home made enclosure in a shady and covered passage. The rain guage has been modified (by having a funnel located above its collector) to have a larger collection area (to give 0.0105" of rain per bucket tip, compared to 0.0204" in the original).

Who?

This site is brought to you by Jonathan Hudson (who does the computer bits) and Daria Hudson, who, as well as being much better looking, also does the gardening.