Weather Station Hardware > What Weather Station Should I Buy?

Open source anemometer with replaceable bearing

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LR:
Hello everyone, apologies if I'm asking in the wrong section, I'm new to this forum and the weather station field in general.
I'm currently looking for an anemometer that is easy to setup in order to export the data online and and that has replaceable bearing for my thesis work. The idea is that I need the data coming from the anemometer and of a vibration sensor that I'm going to mount on the anemometer itself.
After looking for a while online I found the Davis DW-6410 anemometer that has some guides to plug it into an arduino (https://www.wxforum.net/index.php?topic=31867.0) but I was wondering if there was something more plug and play for a raspberry pi.
The other reason I'd like something easier to install is that I'll probably not be the one that will physically manage it thanks to remote working and COVID restrictions.
One last thing I was wondering is if it's possible to infer the angular velocity of the anemometer from the the data readings of the wind speed.

johnd:
There are all sorts of anemometers available but the Davis 6410 is probably the best-known and most cost-effective option with an easily-replaceable bearing on the speed sensor. There are certainly anemometers, including eg ultrasonic types with say an RS232 or SDI-12 interface, but they're usually a different order of price .

I'm not sure you're going to find anything that's any simpler to interface to a microcontroller like an Arduino than a 6410. At some point in the interface you're going to have to count pulses from the speed sensor and also, if you want direction too, measure the resistance on the direction sensor via an A/D converter. You could use some intermediate MC device to converted the anemometer readings into say I2C or SPI format but really that's just going to replicate the same process that you'd need to run on the Arduino anyway. I'd guess that there are already libraries available to interface a 6410 to an Arduino (though the 'library' must be fairly simple, ie just a timer-driven pulse counter and an A/D read).

Re angular velocity, but which I presume you mean rpm effectively? The 6410 speed calibration is 0.444Hz = 1mph or, put another way, 1 complete cups rotation in 2.25secs = 1 mph.

LR:
Thanks for the answer johnd.

So if I understand this correcly, I can calculate the rpm using the equations you gave me from the wind speed?
Do you know if it's possible to do what I'm trying to do with the arduino with something like this (https://www.davisinstruments.com/transmitters-and-sensors/#block1)?
Or maybe this https://www.scaledinstruments.com/shop/ocean-controls/ocean-controls-ktl-250-12v-anemometer-modbus-interface-with-lcd/?
I'm willing to spend more if it means not having to deal with arduino firmware and skipping directly to sending raw data to a raspberry. Would it still be possible to calculate the rpm from the data these two transmitters send?

johnd:

--- Quote from: LR on May 14, 2021, 05:08:53 AM ---So if I understand this correcly, I can calculate the rpm using the equations you gave me from the wind speed?
--- End quote ---

Yes, exactly as I said. The cups are designed to give a linear response with wind speed and so you just count the revolutions. If you want high accuracy on speed then there is a secondary correction you can apply, but that's a different topic.


--- Quote ---Do you know if it's possible to do what I'm trying to do with the arduino with something like this (https://www.davisinstruments.com/transmitters-and-sensors/#block1)?
--- End quote ---

Not in the sense you mean. The 6332 box does indeed convert the anemometer output into a digital format but then transmits it over proprietary wireless. So you need a suitable receiver and then to understand the data format. You could certainly use a receiver like Meteostick (or indeed a Davis Vue console plus logger or a Weatherlink Live unit). That could certainly work but would be substantial overkill. But obviously your call.


--- Quote ---Or maybe this https://www.scaledinstruments.com/shop/ocean-controls/ocean-controls-ktl-250-12v-anemometer-modbus-interface-with-lcd/?
--- End quote ---

OC KTA250 would be another option, but the outputs aren't directly compatible with a Pi**. There is a Modbus HAT available I believe, though I've never used it, which would be one option for a digital interface. Or you could use the analogue outputs but then you hit the snag that the Pi doesn't have onboard A/D converters AFAIK. But again there are several A/D HATs on the market. But then if you're going to use an A/D HAT you could interface the 6410 direction direct to the HAT and use a Pi GPIO pin to connect to an interrupt for pulse counting. Not sure how reliable that is on a Pi, but assuming the Pi is dedicated and not doing much else then I guess it would be OK. But that's the reason that a microcontroller like an Arduino is often used for the primary sensor connection - there's no operating system to get in the way of timings and the MC can be dedicated to its task, while a downstream computer like a Pi can do the more complicated data manipulation etc.

All that said, and depending on the downstream application (you haven't said what you need to do with the data in detail) I'd personally be wondering whether a Raspberry Pi Pico maybe programmed in MicroPython or CircuitPython couldn't handle the whole job.

** Edit: Actually, I see that the latest KTA250 versions do seem to have a Modbus over USB option as well as Modbus over RS485 (but not Modbus over Ethernet AFAICS), so maybe a direct Pi connection via USB is possible. Presumably this is simply a serial Modbus connection delivered over USB via a virtual com port, but you'd need to work out how to speak Modbus across the interface (which might be trivial to do, but I've never tried).

mcrossley:
There are a few anemometers targeted for boats that output a NMEA data stream - I don't know much about them, nor if they have replaceable bearings, but they are designed for one of the harshest environments!

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