Wind speedometer

Thread Starter


Joined Jun 25, 2007
i can't figure this out
i need to build a slightly advanced wind speedometer so can u please help me on this because i have about 4 weeks to do 4 months of work so please help me i know ill need a windmill or turbine to take the wind itself but from there on im stuck so please help me
Thank You


Joined Jul 22, 2007
Four weeks to read the wind speed... Good luck. Might take that long to calibrate something. Might look for a digital weather station...


Joined Jul 5, 2006
A 3-cup anemometer works well. DIY anemometer builders used to use half of the egg-shaped containers that "LEGGS" nylon panty-hose were sold in. I don't know if they are still on the market.

So you make an impeller with three arms with 1/2 LEGGS cups mounted on their ends, mount the shaft on instrument ball bearings, use a opto-interrupter to detect passage of slots you cut in a disk mounted on the shaft, count the slots with either a PIC microcontroller or a frequency-to-voltage-converter IC, and display the result on a digital display or an analog (d'Arsonval) meter.

The main difficulty comes from the calibration of the rotor. Most people who try to calibrate an anemometer try holding it out the window of a car or mounting it on a short mast projecting above the roof of the car. The problem is that the influence of the air diverted around the car extends MUCH further from the car than most people imagine. This results in significantly higher air velocity past the anemometer than the actual ground speed of the car, which they assume is the air speed past the anemometer. Unfortunately, I can't give you a precise number for how far from the car the anemometer must be for reasonably accuracy, but being forwarned, you can research it. I imagine it is a function of both the car dimensions and the rotor diameter.

One good approach would be to borrow a calibrated anemometer and adjust your device to read the same as the known good unit at several wind speeds. If you do this with the anemometers mounted on a car, you should do a number of runs in both directions on an isolated road to average out any ambient wind speed and should be sure the two units are identically mounted relative to the car body.

Have fun.