Anyone remotely aware of wind generation systems and such knows how greatly all this equipment is overpriced. Commercially available anemometers cost way too much. So here is how to build one for under $30. List of parts needed:
Tachogenerator (or tacogenerator)
Flexible epoxy resin.
Baby toy or Christmas tree ball
The following is how to make a hemispherical cup anemometer.
Step 1: Find Hemispherical Cups
Find hemispherical cups for the apparatus. Ideas: hollow plastic Christmas tree balls, baby rattle balls, ladles, hardshell plastic balls, round plastic bottles, old style hard shell beer cans, deodorants with hemispherical caps etc.
The idea is to use something sturdy but lightweight. In my case I used a baby rattle. It was way cheaper and had three rattle balls on a string with yellow, red and green balls, which I cut in half to use as the hemispherical cups.
Make 3 identical size aluminum pipes (less then ¼ of an inch in diameter from hardware store). Also, find screws that will fit inside the aluminum tube.
Use flexible epoxy resin to make a rotor. I used a piece of plywood and drew a circle and three beams from the center at a 120 degrees each. Molded the resin into a pyramid like rotor and placed it in the center of the circle. Connected tree aluminum tubes to the semi-pyramid shaped rotor. My tachogenerator had a connector thingy that was detachable from its axis, so, I put that in the center of the rotor as well and let the rotor harden.
Drill wholes in the hemispherical cups close to the “equator”. Connect the hemispherical cups to aluminum tubes using screws. Also, use some the epoxy in between the screw and the cup order to make the cups stick to the pipe stay in their place without rotating.
Step 2: Buid & Test It Out
When the entire contraption hardens, connect it to a tachogenerator and test for electrical current being generated when the cups rotate. Oh, yes, you should find a tachogenerator. These may be found on ebay or the internet for under $30
Using a pvc pipe and some hot silicone glue put the anemometer together. Use aluminum tape give your piece of weather measurement equipment an aesthetically appealing look.
Put the anemometer way up there and run the wires to your voltage meter.
Figure out what its measuring: We need to use the tacogenerator because of its rpm/voltage ratio. In Russia, the cheapest of all tachogenerators is the "TGP-3 (also used inside our world-famous ICBM missiles), which has a rpm to voltage ratio of 1000 to 4. The voltage meter gave me a reading, which I translated into meters per second using the following mathematical formula: Wind Speed Pi*Diameter_in_meters*(Voltage*RPM_Ratio/60seconds)
The diameter of the hemispherical rotor with cup, in my case was 10.5 centimeters = 0.105 meters. Here is the formula to figure out wind speed in Miles per Hour:
Wind_Speed_mph = Pi*Diameter_of_rotor_in_miles*(Voltage*RPM_Ratio*60minues)
The tricky part would be to figure out the diameter of the 4 inch rotor in miles (6.31313131 × 10-5 ,thank you google) however, if you're reading about this project, I have no doubt you will be able to figure out this one...
Calibrating – drive while holding your anemometer outside and log data. Wear a seat belt...
Logging the data: You may find various “smart” voltage meters out there that are able to do this for you. However, I would recommend a computer-connected voltage meter like the one I have from LabJack that will do the logging for you. My perl script for this one is at http://www.pashanoid.ru/code/veter.txt
Best Regards, and Happy Wind Logging!