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Build/Makin a Wind Sensors

Discussion in 'Electronic Basics' started by Kevin, Apr 8, 2004.

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  1. Kevin

    Kevin Guest

    Hi all,

    I'm having some difficulty working out the best approach to creating a
    wind sensor, and hoped someone might be able to point me in the right
    direction.

    I want to use some sort of propeller to detect the wind speed, but I
    haven't been able to find what I should connect it to.

    I've seen some rotary switches in my local electronics shop, but it's
    very hard to rotate. This project involves someone blowing, so the force
    will be very light.

    Can anyone recommend a component that detects rotation that's
    exceptionally easy to move? Alternatively, I can build a switch like
    this myself too, if necessary.

    I'll eventually be creating 6 sensors that will be hooked up to a
    microcontroller to interpret the input.

    thanks,

    - Kevin
    kevin!multiblah!com
     
  2. Tim Auton

    Tim Auton Guest

    An optointerrupter similar to those you get in ball mice adds zero
    friction and only a little inertia. Basically you want a disc with n
    holes that rotates between a light source and a light sensor. Every
    time you detect the light that's 1/n rotations. The ones in mice
    actually have two detectors per axis (though sometimes in a single
    unit) and use quadrature encoding to detect both speed and direction.

    Searching for "optointerrupter" and "quadrature encoding" should find
    you a load of information.


    Tim
     
  3. CFoley1064

    CFoley1064 Guest

    Subject: Re: Build/Makin a Wind Sensors
    If you want to make an anemometer with an optocoupler, you can just use an
    opto-interrupter like the Fairchild H21A2, and make a small slotted disk out of
    cardboard. You will probably want to do some signal conditioning of the output
    to clean up the signal and prevent multiple clocks per transistion. You could
    look at something like this with a 74HC14 to clean up the output (view in fixed
    font or M$ Notepad):

    VCC VCC
    + +
    | |
    .-. .-.
    180| | | |10K
    | | | | 2/6 'HC14
    '-' '-'
    | 1 H21A2 | |\ ___ |\
    '-----. o------|H>O--|___|-o----|H>O----o
    | 3| |/ 22K | |/
    V ~ |/ ---
    - ~ | .01uF ---
    2 | |> |
    .-----' 4| |
    | | ===
    === === GND
    GND GND

    created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

    http://www.fairchildsemi.com/ds/H2/H21A2.pdf

    I believe most anemometers actually use very small magnets on their rotating
    shaft and reed switches to do the job.

    Good luck
    Chris
     
  4. Mikal Hodvik

    Mikal Hodvik Guest

    Kevin,

    It's possible to make a wind sensor without any moving parts, by measuring
    thermal loss due to air movement around a heated transistor or similar
    sensing element. Its generally necessary to use a matched transistor/sensor
    that's *not* in the air flow to null out ambient temperature changes, but
    the circuitry can be remarkably simple. Here's a link to some relevant
    information: http://www.elecdesign.com/Articles/Index.cfm?ArticleID=3990

    Mikal Hodvik
    Decade Engineering
    www.decadenet.com
     
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