Hall effect sensor for wind vane, or ultrasonic sensors

[Irish Steve]

OK, here we go. I have an (Maplin) FO 1080 station that's been on the roof for a couple of years, and it recently stopped recording rain, which is the main reason I need the station, as it's my early warning of the danger of flooding. I've also been casting roung the threads here recently, and come across several areas that have been thought provoking,

The thing that got me going on this is that I've had to take the external devices off the pole on the chimney to fix the rain recorder, and when I did eventually get it down to investigate, it wasn't spiders, which was the main suspect, but the reed switch had failed. It's been up there for a couple of years unattended, I don't use batteries in the unit, it's powered by a battery backed regulated PSU at ground level, the batteries are there to provide cover for power outages, so that I don't lose the signal if there's a cut.

As part of the whole exercise, I'm putting up a higher pole to get the wind sensors out of the turbulence that's thrown up by the dormer roof. We're not in a good location from that aspect, there's a lot close to us that messes the wind flow up, so a higher pole will help. Anyway, I've also been looking at the wind vane, it had a fin on it made from corrie board, the plastic cardboard that Estate Agents use for house sale signs, and it lasted quite well, until the wet got behind the duck tape holding it to the fin, so that's getting an upgrade as well,

The rain measure is also sheathed in some more of the same "cardboard", to prevent spiders from getting in to it, and to stop strong winds from getting into the holes at the bottom and triggering false rain detects, and so far, it's worked well.

The main transmitter is shrouded, a simple shield, a piece of 4" plastic drainpipe, covered with White Vinyl to help reflect the heat, and it too seems to work well, and has the advantage of being real cheap to do.

So, while I'm doing all this, Im also adding a second base station so that I can capture all the readings to a PC and still have an immediate view station in a location where a USB connect is not viable, ( Maplin have the stations real cheap at the moment, and this way, I get a full set of spare sensors) so a second base in the office connected to a permanently live PC is a much easier solution

In among all the fiddling, the pole is going up an additional 6 Metres, I got to thinking about and reading some of the threads here, and that triggered some Google searches, mainly looking at the areas we have problems with on the FO stations


I have seen 2 possible options for the wind vane, the first is a small potentiometer that's not mechanical, and can cope with continuous rotation, gives a variable output based on input voltage, the other, which is even more appealing, is a solid state device that can recognise the rotational position of a magnet above it, and does not require a "home" position device to work out where it is. The other option that was interesting, but horribly expensive in the commercial form is a device that's using 3 or 4 ultrasonic sensors to measure both wind speed and direction in the one device, and there are no moving parts with it, which has to be attractive.

For our purposes, the factors to consider are accuracy, cost and reliability. At present, I don't know what resolution we're looking for in terms of direction and speed, but I would reckon that the devices I've been looking at will more than meet the requirements.

The devices I'm looking at here won't work with the FO station, but with the hardware that's available now, that's not an issue, licence free TX & RX devices that would be suitable for weather stations are disgustingly cheap now, and available from many sources, so that side of the station is not an issue, and Arduino micro processors to collect the raw data and forward it to a central receiver are also not going to be an issue. I am also active in a Radio model forum, and there are some very interesting things happening in that market place, and some of that hardware would be ideal for weather stations as well.

With me so far? Good,

Now, the questions. Has anyone else thought of going down this road, or even making an interface that could connect some or all of these devices to the existing FO station that we're using.

If we were to start looking at a home brew station, ( This bit's for Steve), what format would the captured data need to be in to make it viable to interface to Cumulus. If we went that route, the absence of a dedicated display station may not be an issue, in that the Cumulus display covers the items that need reporting, and something like a tablet, or even an App capable phone type device might be suitable. The other option is an old, cheap PC that could be used as the capture and recording station. A Netbook would also work,

So, am I barking up the wrong tree, or reinventing the wheel?

Cheers

Steve

[steve]

The other option that was interesting, but horribly expensive in the commercial form is a device that's using 3 or 4 ultrasonic sensors to measure both wind speed and direction in the one device, and there are no moving parts with it, which has to be attractive.

I'd like one of these. No, I don't want to know how much they cost...

If we were to start looking at a home brew station, ( This bit's for Steve), what format would the captured data need to be in to make it viable to interface to Cumulus.

See the thread just below: https://cumulus.hosiene.co.uk/viewtopic.php?f=16&t=6533

[Irish Steve]

The other option that was interesting, but horribly expensive in the commercial form is a device that's using 3 or 4 ultrasonic sensors to measure both wind speed and direction in the one device, and there are no moving parts with it, which has to be attractive.

I'd like one of these. No, I don't want to know how much they cost...

If we were to start looking at a home brew station, ( This bit's for Steve), what format would the captured data need to be in to make it viable to interface to Cumulus.

See the thread just below: https://cumulus.hosiene.co.uk/viewtopic.php?f=16&t=6533

Thanks Steve, The price of the "professional" units is several hundred each, and I can't see the value there at the moment, so I am going to do some experimenting with some smaller units and an arduino, and see what happens. It's apparently very simple, 3 or 4 sensors, and 4 is easiest to describe, ping (for lack of a better word) A to B, (opposite each other) and get the time, then ping B to A, and depending on the wind speed and direction, the time is different, Do the same C to D, (90 degree opposing A & B) and D to C, and the math of the vectors gives speed and direction. Sounds horribly simple in terms of the hardware, and the math is not that bad from the reading I've done. Calibration is done by putting the thing in a "can" so there is no wind, and then any minor sensor differences can be factored out in the micro code.

Don't know yet what the max speed it can resolve is, but they are being used widely, and have be be better than the cheapo mechanical devices we're using at the moment.

From the comments I've seen her make, I am guessing that Gina will be more than a little interested in this as well.


I will have a closer look at the file formats, with any luck, it might be as easy as using 2 programs to write the data, let the FO station write the original record, and then update the fields that the FO station is not capturing, or even, having now seen the comments, maybe even look at using the Davis station file layout, in the scale of things, that won't be an issue as such, if I start writing code, then we'll go for it properly, and maybe have options for other sensors that will improve the quality of what's being recorded.

I shall have to start building a database of the relevant specs, like gust measuring specs, in terms of duration and variance used to determine if it is a gust, stuff like that.

First thing is to get my FO station back on line, then I can do some more research on this, there are already some very capable add on boards for the Arduino that are being used for things like autopilots, and they carry a lot of the sensors that we'd be interested in, like pressure, and temperature, they call them shields.

When I get the FO back on line, it will be onto a web site or similar this time, and then I've something to work with for comparison and testing.

I suspect I will be back to annoy you again at some stage

Cheers

Steve

[gemini06720]

Indeed, as Steve (Loft) pointed out, those ultrasonic wind (anemometer/wind direction) sensors are, on average, the price (or above the price) of a good/high quality complete weather station...

Steve (the Irish Steve ), during my searches to find additional information about ultrasonic wind sensors, I came across this Ultrasonic Anemometer page describing the development of a precision measuring ultrasonic anemometer - might be an interesting document to have around if you do decide to build your own.

[Irish Steve]

Indeed, as Steve (Loft) pointed out, those ultrasonic wind (anemometer/wind direction) sensors are, on average, the price (or above the price) of a good/high quality complete weather station...

Steve (the Irish Steve ), during my searches to find additional information about ultrasonic wind sensors, I came across this Ultrasonic Anemometer page describing the development of a precision measuring ultrasonic anemometer - might be an interesting document to have around if you do decide to build your own.

Sheesh, that's some document, and there are "issues" with the ultrasonics that are a lot more complex than I'd realised were there. It might be a while before this sees the light of day, though with the way that chips are developing, something will turn up to make things easier, in the same way that they are for other areas.

Thanks for the pointer, and that document is indeed bookmarked, though I suspect it will be quite some time before I can get access to the sort of facilities that the builder of that device had. It will be a test of our collective imagination and skills, but that's where web communities are sometimes so powerful, the right combination of people can sometimes achieve results that are way beyond what was thought possible

Cheers

Steve (The Irish one )

[gemini06720]

It might be a while before this sees the light of day...

Ah, I am quite perturbed by that statement ... I was expecting a home-made ultrasonic anemometer sometimes in January...

[daedalusminos]

If you're interested in non-contact hall effect sensor for the windvane then the one I started to develop is described in this thread and may be useful:

https://cumulus.hosiene.co.uk/viewtopic.php?f=16&t=4570

Jonathan

[sanramonrover]

I know it has been a while since this thread has been visited, but perhaps here is a little more info someone can use.
I recently acquired part of a Nexxtek system and dismantled the weather vane and anemometer. The anemometer uses a simple tiny ring magnet on the cups' shaft to operate a reed switch - same idea as Easy Weather, et al.

But, the direction vane uses a 4 place optical encoder disk.
There is a small LED at the lower edge of the PCB (IR or visible light I don't know) which spreads light via a clear plastic piece (mounted in the case, not shown) towards the centre of the PCB. Visible above the clear LED are 4 light 'receivers' (LDR's?) in a vertical line.

To the right in the photo is the encoder disk, keyed to the wind vane shaft. It sits between the clear plastic piece (not shown) and the 4 light receivers. From the slots I determined it is using Gray Code encoding. However it appears that the LSB (least significant bit) is the 3rd ring from the outside, the 2nd bit is 2nd from outside. The 3rd and 4th bits are either the inside/outside ring, or reversed (outside/inside).

This design gives a very accurate 16 point wind direction, unlike the Easy Weather 1080 system.

I didn't dig into the electronics as it is all microscopically small, surface mount components.
Hope this is of interest to someone.

[mcrossley]

How about this variation on the FO reed switch system? I guess reed switches have the advantage over LEDs etc to power requirements...

http://www.google.co.uk/patents?id=O0Yw ... &q&f=false