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Absolute encoder for anemometer direction indicator?

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hermetic:
 Speedometer cable? Simple and reliable!

John Hill:
BillTodd,  that might have been from one of my ideas!  The problem I found in advancing that principle further was the difficulty of designing thoroughly reliable slip rings. 

Speedo cable? Well not so daft when you consider that some 'professional' systems used solid rod drive to the indicator with Hook's joints etc.  Dynes make pressure tube systems with a pitot head and a rather large container filled with water!

raynerd:
Do you need absolute resolution. I made an anemometer with an arduino but not direction. If you didn't need perfect direction could you not use a series of Hall effect sensors and display the last trigger as the direction. I appreciate this is only an approximate direction but would be good enough for N, NE, E, SE, S, SW, W, NW display with 8 sesnsors. Sorry, probably a silly too simplistic suggestion but thought I'd mention it!
I struggled calibrating mine, have you considered this yet? I ended up with an arbitrary wind speed value which day by day was comparable but struggled to calibrate it with actual wind speed.

John Hill:
Hi, this is for our replica WWII control tower and will feed multiple displays.  I would use a Selsyn transmitter but I do not have one available and besides it would be 70 years old if I did have one.  I am going for the best possible solution bearing in mind that I do not want sliding contacts of any kind up the mast and I want it to be still going after I am nailed in my box.

I am just about at the stage to mount three hall sensors in the direction sensor then the challenge will be software for an Arduino to simulate selsyn signals to drive the indicators I have on hand.  If the old indicators dont work I will use steppers for the direction displays,  I have to use a stepper in the wind speed displays too as I do not have any 300 degree meter movements.

My idea for calibration of wind speed will be to count the pulses from the sensor (it has a disk and photo diode sensor) over a period of time while running another 'professional'  anemometer of the 'distance run' type.  That will give me a somewhat average value for wind speed.

The stainless steel anemometer cups arrived yesterday  so everything is coming together nicely!

BillTodd:

--- Quote ---BillTodd,  that might have been from one of my ideas!  The problem I found in advancing that principle further was the difficulty of designing thoroughly reliable slip rings. 
--- End quote ---

It would not be too difficult to convert the reed switches to LED + opto sensor thus allowing the electronic parts to remain stationary while the light is directed by plastic guides or mirrors.

Or you could make the slip ring from a capacitive (touch) sensor ic

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