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Gårdsby weather station


Gårdsby weather station is located 10 km northeast of Växjö, south Sweden.

Station height: 204m AMSL. Weathervane /anemometer: ca 9m above ground.

Weathervane /anemometer position (N 56°57'30.93" E 14°54'15.2").
Rain /temp /humidity sensors are in middle of the lawn, height 1.8m (N 56°57'30.12" E 14°54'16.0").

Location of weather station on map


Weather Station: Oregon WMR928nx (manual), delivered by Safecast.
It has 3 outdoor sensors, wind, temp/humidity and rain, which transmit their readings to the WMR928 central console.

Air pressure (and indoor temp/humidity) came from an indoor sensor.

Pressure is compensated to sea level both in wfrog software and WMR928 display.

Rain Gauge is modified with a small funnel to be more correct, adding some 25% to the rain capture area. Rain is not measured in winter (about dec-feb),.see notice on weather page.

Wind speed is probably underestimated from east and south because of forest some 50-100 meters away.

The outdoor mounts are shown below.

Vindmätare på TV-masten
Wind sensor

In winter, it sometimes can be tough for wind measurement with temperatures around 0C can cause the wind speed sensor to get first wet and then freeze, – or icing can reduce sensitivity in very cold weather (see image above at-15C). It is very seldom though.

Temp- och fuktmätare ute. Regnmätare.
Outdoor temp, humidity, rain sensors

Vintermössa på regnmätare.
But in winter, rain gauge is at rest (in its cap), from about 1 december - 1 april.

Weather data processing and web page:
The WMR928 console is connected via a serial port to a Raspberry Pi running Raspbian (Debian Wheezy) and wfrog software.

The serial communication is handled by an RS232-USB adapter (based on chip pl2303).

Wfrog handles the reception of weather data from central unit, logging and web page generation, except that the html page template is modified to include more information.

The web page is generated about 12 times/hour (5 min) and sent to a web server.
The web browser is automatically updating the page view every 2 minutes.

Right: The neat Raspberry Pi computer

Raspberry Pi

Webcam picture
The weather page includes a webcam picture that is updated every 2 minutes to the web server when it is not dark. Only a current webcam picture is shown.

Web camera is a Logitech standard QuickCam E3500 webcam, connected to a NetGear router (Linux). Earlier used a Creative IM Pro webcam, but a webcam facing outdoor seem to wear out in a year or two. Nice thing is that Linux recognizes these webcams directly.

Pictures are taken with the mjpg_streamer software on the router (see forum page 8).

The camera is mounted indoor behind a windows glass, so rain will dim the picture.

Right: Webcam stray light shield

Other data on weather page

The forecast is a widget from vackertvader.se.

Moon and sun data are approximate. The Moon phase is javascript (from John Horton Conway and others) with adapted graphics from Wikipedia (in Swedish).

There is also a disclaimer on the page.


Previous weather computer (NSLU2)
Earlier I used a "slug computer" NSLU2 running Debian Linux. After two years logging, it got more and more difficulties with the csv log (text) file, more than 10 Mbyte (NSLU2 RAM is 32 Mbyte).
Some modifications were neccessary on the NSLU2 to use a serial port: I  have added a serial port to the NSLU2 to communicate with WMR928NX (see pictures). There were fewer serial communications errors when feeding the serial card (SparkFun) with 5 volts Vcc from the slug instead of 3.3 volts. However, it did not work reliably enough, so I changed to an RS232-USB adapter (based on chip pl2303) which 1) was immediately recognized by Debian, 2) is perfectly stable.

Also the slug will not auto power on after power interruption, unless modified.

Thanks Fredrik Nilsson for helping me soldering the tiny NSLU2 connections.

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