Vermilion Sands Weather Station forecast * solar panels * blog

All our weather information is collected by a cheap and cheerful automatic weather station, the Watson W-8681. Despite being cheap, it's now been running continuously for 5 years (May 2010-May-2015).

Hardware

The outside unit, comprising the rain gauge, anemometer, wind direction vane and temperature/humidity sensors, is sited in our back garden. The unit transmits data wirelessly every five minutes to a base station, which in turn is connected via USB cable to a Raspberry Pi (previously an NSLU2 low-power miniature (paperback-sized) computer). The wind sensors are somewhat sheltered by the house, so it under-reads speeds and the direction is not very accurate, while the thermometer tends to over-read by 2 or 3°C when in full sun.

Power

The outside unit takes two AA batteries; good-quality alkalines last at least a year, rechargeables about three months. The base unit takes three AAs, but is normally powered from the USB connection.

Software

A power cut in January 2016 corrupted the NSLU2 flash drive, so we took the opportunity to move the system to a Raspberry Pi. This turned out to be fairly simple, and had the advantage of improving the output and adding extra features.

The NSLU2 (or "Slug") is controlled by a Linux variant called Unslung, running from a USB memory stick. This in turn runs a software suite called pywws, which regularly grabs the data from the base station and generates a series of graphs, tables and reports, which are then uploaded to this web site every hour; all data is backed up every day to our NAS. The whole process is automatic.

Maintenance

Spiders occasionally get in the rain gauge. Their webs stop the tipping mechanism working, so every so often there's a trip up the ladder to clean it out.
The only major problem in the last five years was the wind direction vane seizing up. Fixing this involved removing the unit, popping off the cover, cleaning the rust off with WD40 and re-greasing. Fortunately, others have fixed this problem before me.
In August 2015 the anemometer seized up. Unfortunately, a doomed attempt to remove the cups resulted in breaking the connecting plastic rod. We tried a quick repair by glueing the parts together with a toothpick, and although it did work the cups wouldn't rotate as freely as they should.
Luckily Maplin supply a spare anemometer (part no. N09QR) for the very reasonable price of £2.49. Replacement was easy, and it works fine.