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Forum Index : Windmills : Concept for two wire anemometer
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| KiwiJohn Guru  Joined: 01/12/2005 Location: New ZealandPosts: 691 |
The easiest way to get an anemometer nowadays is probably to pay a call to your favourite electronics shop and by one. But for those who like to actually make stuff an anemometer can be quite a challenge, especially if you want to include speed and direction, want to avoid slip rings and you dont want half a dozen wires. So here is my concept for a wind speed and direction sensor using only two wires and no inscrutable electronics. 
The direction vane and the speed cups are mounted on a common axis. An arm on the shaft of the speed cups carries two coils connected together, coil 'b' has a voltage induced in it every time it whirls by magnet 'N' which is attached to the direction vane, it also passes magnet 'S' which is in a fixed position. So for every rotation of the speed cups there will be two pulses, one positive and one negative. For example we will say the positive pulses result from passing the fixed magnet and obviously the number of pulses per second gives us the wind speed. The negative pulses will be at some time depending upon the position of the direction vane, so the position of this pulse in relation to the first gives us the direction of the wind. Coil 'b' is connected to coil 'a' which is magnetically coupled to fixed postion coil 'c'. A PC sound card would probably make an easy project of processing these pulses to give both speed and direction. Well, there it is, my idea though I have never made one! 
(I am not really sure about the polarity of the magnets, maybe one should be turned up the other way!) |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5116 |
I think they must make good coffee in New Zealand, you keep coming up with these new idea's  Or is it the clean air down there?
After drinking my own cup of coffee and reading your description, yes it would work and its a clever design. The rotating head in VCR's use a similar method to get AC signals from the video heads across a rotating gap, you could even possibly use one from a dead VCR to experiment with. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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