Weather Underground PWS IGAUTENG72




How it started

The whole idea of monitoring the weather started in 2008. As a school project, my son made a simple project to determine the height at which clouds will form. The initial project used two thermometers (one dry bulb, one wet bulb). With the thermometer readings, he was able to determine the humidity and dewpoint. With these values, together with some estimates for mean air pressure, he could calculate the height of the clouds using look-up tables.

CJ's 1st System

The method he used, was the basic method used in aviation.

Converting to electronics

Having some knowledge of microprocessors, I soon started to design a simple electronic version that could replace the look-up tables. It started off with inexpensive LM35 temperature sensors and a Microchip PIC 12F675. Data was captured with a PC and a simple Visual Basic program.

After the first winter, it soon became clear that the LM35 temperature sensors did not accurately capture negative temperatures, and the circuit was modified to make use of Dallas DS18B20 digital temperature sensors. This made the system much more accurate, without the need for any calibrations.

Complete home-build Unit

Electronic Unit


Wet and Dry thermometer

Data logging

Data logging soon followed, and history up to a year was available. This software was upgraded on a regular basis, and eventually included a Visual Basic web server, and a USB weather camera. This system was in use up to 16 December 2011. 

Visual Basic software


As the old system made use of a wet thermometer, it required some maintenance in keeping the bottle filled with water. When the water evaporated, this had a major effect on the readings. When I then spotted the Origon WMR88 weather station at a very reasonable prise, I was reluctant to retire my old system. But with so much features and more sensors, this money was well spend. All sensors are wireless, making installation a pleasure.


Wind speed and direction sensor


Rain Meter


Outdoor temperature and humidity sensor


Oregon WMR-88 Base Station


Virtual Weather Station 14.01 Base Edition software


Foscam FI8904W Outdoor IP Camera