Marine wind sensor

Discussion in 'The Projects Forum' started by jamh, Jul 4, 2013.

  1. jamh

    Thread Starter New Member

    Jul 4, 2013
    3
    0
    Hello everyone,

    I know there are things out there to do what I want to do, but at prohibitive prices and not quite the same way that I want to do it.

    I was thinking to build a wireless top-of-the-mast wind sensor with no moveable parts. The key to it would be this little guy:

    http://shop.moderndevice.com/products/wind-sensor

    What it needs to detect is the speed and direction of the wind. To do the direction, 4 of them N/S/W/E? Or perhaps just 2 would do? Most of the time you're either almost with the wind or almost against it.

    For power, a small solar panel. For wireless, something. Initially I thought the new Electric Imp, but they stupidly send the data all the way to their servers. On a sailboat in the middle of the ocean, a bit overkill :)

    So what do you guys think? Doable? Under $200?
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,151
    3,058
    I think it's doable under $200. Could you live with a windvane movement to provide direction information, and to orient the sensor properly? It's a moving part but I think it would simplify things.

    Resisting harsh conditions and maintaining reliability is going to be a major challenge. I wouldn't want to be reliant on this device for any life-critical functions until it had proven itself.
     
  3. jamh

    Thread Starter New Member

    Jul 4, 2013
    3
    0
    Compromise already?

    The problem with wind vanes is that they need maintenance. They get knocked off by strong winds, or a combination of sun and wind. Having no moveable parts is important.
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,151
    3,058
    I think direction will be tough to determine with just this device, even if you have several. It's not - by itself - terribly sensitive to direction, just speed. If you have to arrange wind tunnels for multiple sensors, it becomes a pain.

    And even 2 of them would draw ~50mA which makes the solar panel a problem too, size-wise. If you only need it to run on sunny days it will be fine, but if you need to get through nights and cloudy days, you'll need a decent battery.
     
  5. #12

    Expert

    Nov 30, 2010
    16,338
    6,824
    Google: thermistor wind direction
    Maybe this?
     
  6. cork_ie

    Member

    Oct 8, 2011
    348
    58
    The device you intend to use is not a particularly new concept - it is basically the same as the mass airflow meters used in most modern motor vehicles.

    Sorry to dismiss your idea but the sea is wet and salty and this will not work well, if at all and is likely to be unreliable.

    You can use two Hall sensors - one for wind speed and the other for direction.

    Wind speed is easy enough - you just need to generate the correct number of pulses per Knot. You will have the added bonus that the wind speed anenometer can be used to act as a micro generator so you won't need a solar panel.
    I would go with wind cups from an existing anenometer - they are readily available as a spare part from most marine instrument manufacturers and are cheap enough.

    For wind direction you could adapt this guys idea using an A1202 sensor chip.http://simhq.com/forum/ubbthreads.php/topics/3225807/all/DIY_hall_sensor.html

    Again you will get a suitable wind vane off the shelf or you can make one with some .5mm stainless steel sheet. Balance is very important for any kind of accurate results as sailing boats rarely sail dead upright.

    The electronics cost peanuts, your biggest problem is making up the masthead unit. You will need very high quality stainless steel bearings for accuracy and long life.
     
    Last edited: Jul 4, 2013
  7. jamh

    Thread Starter New Member

    Jul 4, 2013
    3
    0
    I was thinking about the draw for multiple units.

    Yes Hall effect, etc. you are right of course. But I am stubborn. At least for discussion purposes. The reason the anemometer draws so much current is for sensitivity. Perhaps this is not needed when you're measuring 30 knot winds? And where is the difficulty in collecting data from multiple sensors? It's not like you need to sample oozes of data. 10 measurement per second from each of the 4 might suffice.

    As for making it weatherproof, I wasn't sure what to expose to the wind. Just a small PVC tube going to the heated element? How does it not get wet? Can everything be encased in something except the element? What about heat dissipation?
     
  8. cork_ie

    Member

    Oct 8, 2011
    348
    58
    A cup driven pulse generator will be more sensitive than any other type of wind speed sensor, that is why they are still universally used in weather stations, boats etc.Typical stall speed is 1-2 Knots. You will find that the sensitivity is directly related to the quality of your bearings.

    Hot wire will only be accurate to +/- 10% and will deteriorate due to oxidation from the day it goes in service.

    I've spent a lifetime doing cars and boats and have seen all kinds of efforts to make solid state Masthead Units, due to the hassle of having to replace the cups and windvanes every couple of years.Every single one of them proved to be unreliable and short lived.

    I remember when the MHU's used very very expensive wire wound pots for wind direction and reed switches for wind speed which rarely lasted more than a season. Thank God for electronics which has made everything more reliable. Raymarine now offer a self powered wireless MHU as an option.
     
Loading...