Weather Station
This page describes the weather station equipment that is used to run the Taringa weather station and to provide data to Wunderground.
Technology
The sensors used in this weather station are 1-Wire sensors from Maxim. The temperature probes are DS18B20 one-wire thermometers. The humdity sensor is built from a DS2438 and a Honeywell HIH-3602-C.1-wire.org have a document that shows how to build the sensor. Maxim’s application note can no longer be found.
The 1-Wire interface to the computer is a home-made USB interface using the DS2490 bridge IC. This interface has had problems operating through a USB hub, so is now directly connected to the PC. The USB port provides the +5V supply for the 1-Wire and is quite convenient. Commercial interfaces like the AAG DS9490R are available, but I designed my own based on the datasheet for the DS2490 because I could get small circuit boards made for me.
Implementation
The outdoor temperature and humidity sensor is a combination of the DS2438/HIH-3602 on a PCB wired in parallel to the DS18B20. Two-part epoxy has been used to mount the components into an aluminium tube with a waterproof connector (IP68 rating) on the base.
The temperature and humidity sensor is mounted inside an RM Young Model 41003 Multi-Plate Radiation Shield. Ideally the sensor would screw into the shield, but the aluminium tube fits nicely.
Operating Software
The weather station originally used software that I wrote myself (in VB6) that logged into an Access database and supplied Wunderground. Unfortunately the latest 1-wire drivers from Maxim no longer support the COM interface needed by VB6. My options were to find something off the shelf, or to re-write thing in VB.net. I found some great software from Karl Uppiano called WxService. This software is written in Java (the native language of one-wire) and provides a Web Service to communicate with the weather sensors. The service also provides updates to Wunderground and the APRS weather service. My Wunderground station is IQUEENSL46 and my APRS station is VK4TDI-10. I don’t have any wind or rainfall instruments (yet) so this data is missing when I post things up.
Karl has been very obliging with his software and has provided support for the 18B20 high resolution temperature sensors, and support for multiple sensors at my request. I am now able to monitor the water temperature of my swimming pool, but am still working on a web interface for that. In the meantime temperature data is being logged into CSV files.
