Author Topic: Open source anemometer with replaceable bearing  (Read 1209 times)

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Offline LR

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Open source anemometer with replaceable bearing
« on: May 14, 2021, 02:42:34 AM »
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.

Offline johnd

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Re: Open source anemometer with replaceable bearing
« Reply #1 on: May 14, 2021, 04:23:49 AM »
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.
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Offline LR

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Re: Open source anemometer with replaceable bearing
« Reply #2 on: May 14, 2021, 05:08:53 AM »
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?

Offline johnd

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Re: Open source anemometer with replaceable bearing
« Reply #3 on: May 14, 2021, 05:40:25 AM »
So if I understand this correcly, I can calculate the rpm using the equations you gave me from the wind speed?

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.

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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)?

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/?

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).
« Last Edit: May 14, 2021, 06:22:59 AM by johnd »
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Prodata's FAQ/support site for Davis stations
Includes many details on 6313 Weatherlink console.
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Cambridge UK

Sorry, but I don't usually have time to help with individual issues by email unless you are a Prodata customer. Please post your issue in the relevant forum section here & I will comment there if I have anything useful to add.

Offline mcrossley

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Re: Open source anemometer with replaceable bearing
« Reply #4 on: May 14, 2021, 08:56:22 AM »
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!
Mark

Offline davidmc36

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Re: Open source anemometer with replaceable bearing
« Reply #5 on: May 14, 2021, 10:11:57 AM »
Could this type give any advantage to your needs vs the resistor type wind vaneunits?

https://www.peetbros.com/shop/category.aspx?catid=35

I wish Davis used this tech.

Offline LR

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Re: Open source anemometer with replaceable bearing
« Reply #6 on: May 14, 2021, 10:42:00 AM »
Sticking to the davis anemometer + arduino / raspberry seems the best approach in the end.

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.

I just found this guide that shows what I think you are referring to (https://blog.towerup.com/wind-speed-measurements-with-anemometer-and-a-raspberry-pi/). The guide talks about the 4 wires of the rj-11 cable (GND, 5v, wind speed, wind direction) but in the pictures I can see more then 4 wires connected in the GPIO. I suppose the rest are for an A/D converter?
Electronics isn't my field, if it wasn't for you I wouldn't have assumed that a converter was needed ahah

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.

The raspberry has only to send the data from the anemometer and from the vibration sensor online (and read the data if I'm not using an arduino). That data will be filtered and processed by a neural network in a remote server.

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!

Thanks I'll have a look, do you suggest one in particular?

Could this type give any advantage to your needs vs the resistor type wind vaneunits?

I'll look into it. Thanks for the suggestion!


Offline johnd

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Re: Open source anemometer with replaceable bearing
« Reply #7 on: May 14, 2021, 10:44:12 AM »
I wish Davis used this tech.

Why, just out of curiosity? The direction potentiometers typically last many years, very possibly longer than a traditional reed switch, especially if your design uses multiple switches. I suspect that Peet are simply trying to claim a virtue out of their design choice. It's an interesting idea certainly but not sure that it has any real-world advantage over using a pot. And it doesn't appear to have an easily replaceable speed bearing.
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Includes many details on 6313 Weatherlink console.
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Offline davidmc36

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Re: Open source anemometer with replaceable bearing
« Reply #8 on: May 14, 2021, 11:02:09 AM »
The bearing is an unknown as far as the original requirements, yes. If that could be found out......even if not "User" replaceable it can't be much harder than old style Davis.

I find there to be very inconsistent friction on the Davis pot once it ages a bit. True action is what drew me to that idea.

Offline johnd

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Re: Open source anemometer with replaceable bearing
« Reply #9 on: May 14, 2021, 12:05:08 PM »
I find there to be very inconsistent friction on the Davis pot once it ages a bit. True action is what drew me to that idea.

Maybe you have/had a bad anemometer? We provide support for literally many thousands of 6410 anemometers and honestly can't say that it's reported as a common issue. The anemometer is a mechanical unit and inevitably wears over time, with a useful lifespan of maybe 5-10 years. But before the revised 6410 version was released, a few years back now, with its solid state speed sensor, a defective reed switch was always the commonest 7911/6410 fault. I don't hold much love for reed switches as a durable item on a unit like an anemometer exposed to marked diurnal/seasonal temperature swings and various vibrations due to wind and mounting poles etc. The Vue ISS of course has a Hall Effect direction sensor though inevitably the cups/spindle still has a mechanical bearing.
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Prodata's FAQ/support site for Davis stations
Includes many details on 6313 Weatherlink console.
UK Davis Premier Dealer - All Davis stations, accessories and spares
Cambridge UK

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Offline davidmc36

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Re: Open source anemometer with replaceable bearing
« Reply #10 on: May 14, 2021, 03:50:28 PM »
Reed switches sure can be non-durable. But cheap and usually easy to replace. Be nice to see under hood of Peet.

https://blog.towerup.com/wind-speed-measurements-with-anemometer-and-a-raspberry-pi/

That has other attachments since it has temp and humidity also.

Offline doubleohwhatever

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Re: Open source anemometer with replaceable bearing
« Reply #11 on: May 15, 2021, 10:38:41 PM »
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.

Proprietary but known and documented:
https://github.com/kobuki/VPTools

Offline johnd

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Re: Open source anemometer with replaceable bearing
« Reply #12 on: May 16, 2021, 08:37:27 AM »
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.

Proprietary but known and documented:
https://github.com/kobuki/VPTools

Certainly, and has been for quite a few years. It's an excellent project, but for this particular project I'm not sure that the extra cost and complication is worth it compared to connecting the anemometer direct to a Pi with an A/D HAT. And I still suspect that a $4 Pi Pico would do all that the OP wants and also has A/D built in. But sure, it's certainly another option.
Prodata Weather Systems
Prodata's FAQ/support site for Davis stations
Includes many details on 6313 Weatherlink console.
UK Davis Premier Dealer - All Davis stations, accessories and spares
Cambridge UK

Sorry, but I don't usually have time to help with individual issues by email unless you are a Prodata customer. Please post your issue in the relevant forum section here & I will comment there if I have anything useful to add.

 

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