Reanimating a B&G Network Wind Instrument

$_12

In one of my previous projects I built a masthead wind sensor using an Arduino to process the signals and output a NMEA string. Next I wanted to make an instrument on the boat to display the information. I found a cheap non-working B&G Network Wind display on eBay which fit the bill and set about taking it apart. The display is analogue with a motor and hall sensor to move the wind angle arm. I found that the arm was on too tight and was rubbing on the backing, making it hard for the motor to drive it. After fixing this, I also changed the coin cell battery in the unit which was dead flat. Next I investigated how to simulate the inputs!

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Before I bought the unit, I did some research and found that B&G have freely available documents on their website describing the signals that their masthead anemometers generate. The speed input is a simple pulse of varying frequency, and the direction input consists of three analogue inputs that follow an offset sine wave pattern through 360 degrees.

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So to drive these three analogue inputs from an Arduino, I used the analogueWrite function combined with a low pass filter for smoothing. This Low-pass Filter Calculator is a great tool for finding suitable values to experiment with. I ended up with a 2K resistor and 22uF capacitor for each of the three signals. I also ignored the fact that the proper signals peak at 6.3V and just used the 5V peak from the Arduino, which seems to work fine.

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With a bit of testing I was able to plot the speed vs pulse frequency relationship in order to display the apparent speed correctly. Although my current algorithm (code here) is quite rough and needs to be more accurate, I will also rewrite it so it uses proper timer interrupts. Otherwise I have successfully given new life to an old wind display by simulating a masthead sensor, and can now work on merging it with my other projects for a complete DIY wind system! Stay tuned!

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7 Responses to Reanimating a B&G Network Wind Instrument

  1. I have thought it would be interesting to send pulses like this to an inexpensive bicycle computer, to display speed over ground, or wind speed, or depth.

  2. Pingback: DIY Marine Anemometer System | Mechinations

  3. Phil Watkins says:

    Hi
    Did you figure out what the internal battery does. I have that unit and it has suddenly gone dead so wondering of it is just this battery
    Thanks for any advice

    • Tom says:

      It’s hard to say exactly, but I think the battery would just keep the settings in memory when the unit is switched off. I don’t expect it would be critical to the unit working or not.

  4. charl du plessis says:

    how did you take the unit apart? I’m wanting to rewaterproof mine. There are no obvious screws holding the cover to the back that I can see!

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