Author Topic: Wind vane position measurement  (Read 4785 times)

PhildOwen

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Wind vane position measurement
« on: October 14, 2013, 05:12:08 PM »
Hello,

I'd like to pick your collective brains if I may. I am going to make (not buy) a wind vane to connect up to an Arduino. Any ideas what component(s) I could use to measure its position. I've seen some on the market that use magnetic switches but only report 8 points. I'd like to be able to record the direction to a single degree (if possible).

All suggestions gratefully received.

Thanks

Phil Owen.

Mr Eastwood

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Re: Wind vane position measurement
« Reply #1 on: October 15, 2013, 10:43:51 AM »
I've seen some on the market that use magnetic switches but only report 8 points. I'd like to be able to record the direction to a single degree (if possible).

Perhaps a hall-effect sensor approach might work?
Hey! Frisbee! Far out!

PhildOwen

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Re: Wind vane position measurement
« Reply #2 on: October 15, 2013, 06:44:30 PM »
Thanks for that suggestion. My thinking (please correct me if I'm wrong) is that a hall effect sensor would be useful for a wind speed sensor but I can't think how it would help with a vane. Would if be possible for you to elaborate on how you see the hall effect sensor working for a wind vane?

A component like a continuous pot would be handy as I could relate the voltage drop to position. But as I'm a very new newby to electronics I don't know if there is such a component available.

Thanks for all help offered.

Phil.

SeanB

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Re: Wind vane position measurement
« Reply #3 on: October 16, 2013, 12:29:10 AM »
You can see if you can get a servo pot ( a variable resistor designed to be able to rotate 360 degrees and go through the zero), use an absolute optical encoder ( used in machinery to give the position of a shaft) or use 4 linear hall sensors to detect a magnet on the bottom of a shaft by the varying magnetic fields.

The servo pot works and gives an output voltage almost directly in degrees, but has a limited life and needs to be waterproofed very well.

The absolute encoder is digital and very accurate, but will be expensive, and again needs very good waterproofing.

4 linear hall sensors are simple, cheap and rugged, but need you to do some maths either using a look up table or calculating the sines and cosines on the go to get the position information. With this you will probably find it easiest to build it, and record the values for every degree of rotation then use it to make a look up table for the device.

Mr Eastwood

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Re: Wind vane position measurement
« Reply #4 on: October 16, 2013, 05:48:09 AM »
Would if be possible for you to elaborate on how you see the hall effect sensor working for a wind vane?

Not sure if any of these would work they were just ideas that popped into my head but they would be fun to try.   The first one is using those opto-switches, and by using 11, 10, 01 sequence read by 2 sensors on 2 tracks you could set it to north and calibrate it and then detect the rotation in either direction by the next 2 bit sequence read.  The middle one is a greyscale printed disc and photo-transistor to detect the light level, thus position of rotation on the disc.  The last is the hall-effect idea with a magnet offset on the disc - maybe you could try only 3 hall-effect sensors.

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PhildOwen

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Re: Wind vane position measurement
« Reply #5 on: October 16, 2013, 04:13:42 PM »
Brilliant guys those ideas have given me plenty to chew on. 8)

Many thanks.

Phil.