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Adding instrumentation to a garden windmill

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  • Adding instrumentation to a garden windmill

    I would like to get some wind data, seems the weather people
    don't report the wind speeds much any more, and my
    location is much different from the local weather office.

    Instead of buying one of those cup like wind speed
    meters, and a tail like direction indicator, I was wondering
    about adding a speed meter and direction device to
    one of those garden type 6' tall windmills. I think
    it could look nice and provide some data at the same time.

    I realize that the blade type they have are not linear,
    but could a calibration chart be programmed into the display ?

    Was thinking about mounting this on the roof of the shop.

    tnx
    Doug

  • #2
    Adapting the windmill can be done - the electronics being no different from the cup anemometer. One problem to overcome is getting the wind speed signal past the vertical pivot. Slip rings are the usual method, but are complicated, and unless robustly made and well sheltered, can be fussy.

    The effort spent building slip rings is equal to or greater than building the cup anemometer from scratch.

    In either case, the electronics can be as simple as a reed switch or Hall sensor tripped by a magnet on the rotor. The pulses are counted at the other end of the wire, and the number of pulses in a given time period is converted to wind speed with a chart.

    Another method uses a DC motor as a generator, turned directly by the rotor. The motor also provides the mounting and bearings. Output from the "generator" is fed to a DC meter and the voltage displayed is converted by a chart to wind speed, or if an analog meter is used, the meter dial can be drawn with wind speed numbers.
    Either electronic output can be processed by electronic or computer circuitry to calculate and display wind speed. Once it is in a computer, things like peak, average, etc. can be recorded and graphed.

    Once it is in a computer, things like peak, average, etc. can be recorded and graphed.

    How about a purely mechanical solution? Modify the garden windmill so that the rotor directly, or through gears, turns a crank positioned directly above the pivot point. The pivot is made hollow and a rope, cable or rod, with a suitable swivel, connected to the crank drops down to ground level where it pulls the lever on a mechanical counter. Count for a minute, then look up the conversion from a chart.

    Calibrate by clamping to your pickup bed or car and driving up and down the road on a calm day, recording count/speed for specific time intervals.
    Last edited by Weston Bye; 06-02-2008, 01:36 PM.
    Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
    ~Practitioner of the Electromechanical Arts~

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    • #3
      Originally posted by Wes1
      In either case, the electronics can be as simple as a reed switch or Hall sensor tripped by a magnet on the rotor. The pulses are counted at the other end of the wire, and the number of pulses in a given time period is converted to wind speed with a chart.

      Idea: Why not rig up a bicycle speedometer to read revolutions of the wheel? I just bought a bike speedo for $10 at Target to use in another application and it will accept wheels down to a few inches in dia.

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      • #4
        If you need only relative wind speed you could try a variation on Evan's audiolumitron and aim a photo cell at such a windmilll and see what kind of sounds the light from it creates. I would think that changing wheel speed and light angle and time of day would produce patterns that would be recognizable and yet always different every hour, every day.

        http://bbs.homeshopmachinist.net/arc...p/t-28711.html

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