|Technical data for weather station|
|Wind speed sensor||Two halfs of an ordinary can mounted as shown on
The rotation is sensed by two photointerruptors mounted inside the box at the top.
The wind speed is calculated as the number of revolutions per unit of time.
|Wind direction sensor||A weather vane where the position is sensed by three
mounted inside the box at the top.
|Temperature sensor||A Dallas Semiconductor DS1820.
This chip measures the temperature in steps of 1/2 degree Celsius.
The readings are transferred as a digital signals to the electronics.
|Rain sensor||Collected water fills a "spoon" which tilts
The number of tilts is counted.
Added June 1999.
|Cable to indoor unit||An 8-lead cable, about 15 meter long.|
|Electronics||Based on a Microchip 16F84 microcontroller.
Measurements are stored in a Microchip 24LC65 8Kx8erial EEPROM.
Each reading occupies 4 byte.
I store one reading every 15 minutes.
Thus there is room for 3 weeks of measurements.
|PC program||A simple Windows program that
- receives the data
- decodes the format
- calculates correct measurement times
- stores the data in Microsoft Excel format.
|Project schedule||Start August 1998.
Finished February 1999.
Added rain sensor June 1999, and changed wind sensor to use magnetically
trigged reed contacts instead of optical detection. Found that sunlight sometimes
entered the wind direction sensor and corrected this. Earlier wind direction data
collected during direct sunlight may be invalid.
Redesigned the wind speed sensor during spring 2000. The new version revolves
slightly faster and has been calibrated, although I have not yet updated the
presentation to show real wind speed and the documentation.
Redesigned wind direction sensor during spring 2000 (finished June 25).
I had trouble with sunlight entering the box on top, but this is now better.
I have also changed the software for direction sensing. The previous algorithm
chose every 15 minutes the direction sensed during the 4 second period with
fastest speed. The new algorithm counts which direction is most frequent
during each 15 minute period.
Redesigned wind speed sensor spring 2002.
The new version uses ball bearings and runs more silently than the old one.
Redesigned data handling spring 2002.
- The data is collected by a Microchip controller continuously.
- Every two hours when my main PC is on, data is transferred to my PC
by a Delphi program and sent on the Internet as UDP packets to a Linux server.
- On the Linux server a small C program assembles the data and delivers it
to a PHP program.
- The PHP program stores the data in a MYSQL database.
- When you view the collected data, you use a JAVA applet and HTML
code generated by a PHP program that assembles data from the MYSQL database.
weather data Old weather data
Pictures New wind sensor
ZIP file wit all source code
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Last modified 27-oct-2002