Fed up with Fine Offset. I want to start from scratch?

[AllyCat]

Hi Scott,

Most of my information came from about page 22 of Gina's mammoth thread on spikes in the external data caused by Electric Fences.

I believe the capacitor is 4.7uF, the micro first charges this through a fixed resistor (10k?) taking about 50ms for calibration, then through the external temperature thermistor (also about 50ms at normal temperature) and finally through the wind vane, which takes from about 3ms up to 500ms. If the vane is disconnected it times out after about 1 second. The vane is so "lively" that reed switch bounce must be irrelevant, but if the micro reads a value that it doesn't recognise, then it (or maybe the console) appears to hold the previous reading for one cycle and then displays "--" subsequently.

But with a PIX(axe), for example, you can just feed the vane from the supply via a resistor of about 3k - 4k ohms and, even with only 8 bits A/D conversion, easily differentiates the values. My application indeed involves "processing" the raw vane data and re-encoding it into FO's A/D converter.

Cheers, Alan.

[rwilliam99]

It doesn't sound like this idea ever went anywhere, but it sounds like it might be the only way to get around the FO station lockup issues.

Has anyone made any progress on this? I know nothing about electronics, but am interested in this project. I don't even care about the base station, really - I just want the data to be logged by Cumulus.

[ScottM]

I've just recently restarted my weather station project. I'm using an Arduino, a wifi shield, and some one wire sensors, plus the rain gauge, wind vane and anemometer from the FO station. Not the cheapest solution, but I have the wifi and temperature working and it's been simple so far. I expect the wind vane to be the fussy part; the Arduino has an analog input and I'm hoping to use a simple voltage divider to measure it. We'll see...

[Gina]

I'm building an Arduino plus 1-wire based station. Arduino handles 1-wire with a library - I have another thread on it - though been too busy to progress it much lately.

[ScottM]

I've had success with the one wire library, though very occasionally one of the sensors decides not to report back. (It's possible the poor Arduino can't quite handle everything I'm throwing at it, but it's more likely my prototype's wiring isn't perfect, and things will improve when I use a real circuit board.) The wifi shield works well at the distance I have in mind, and the nice thing about real wifi is real TCP - so both the station and the receiving computer can tell when data isn't flowing, and take steps to restart the connection.

My plan is to put the rain gauge on one interrupt (debounced at 100ms - the rain gauge can't possibly tip faster than that), the anemometer on the other (debounced at 15ms? I guess - experimentation will tell me more), and the wind vane on A0, using the vane as a voltage divider against some fixed resistance. Everything else (light meter, temperature, humidity) is one wire. I don't have a solution for pressure yet, but then there's no reason why the pressure sensor can't be inside and a completely separate solution.

When I get a solution I like, I'll post schematics. There won't be much to them; it's just a few resistors needed to get lines pulled up and down as needed.

[ScottM]

I have everything "working" in the sense of electrical signals and software to process them; but I'm unhappy with the way I'm doing wind direction. I have a voltage divider with a constant 45k pulling up to +5v, and the wind vane's varying resistance pulling to ground. The Arduino only sees a 2 out of 1023 difference (18/1023, 20/1023) between 2 adjacent directions, in the worst case. That's too close. Is anyone using a value better than 45k?

Also, while I get windspeed numbers from a spinning anenometer, I don't believe the number I get.

[AllyCat]

Hi Scott,

45k is far too high to use with the FO wind vane. The resistance values (note that they do not run in sequence) vary from about 690 ohms up to 120 kohms. The "optimum" pull-up (or pull-down, as appropriate) resistor is about 4k (because there are three values of 0.69k, 0.89k and 1k at the "low" end, but only 65k and 120k to resolve at the "top" end).

In what way don't you believe/like the windspeed readings? Have you tried any "controlled" tests?

Cheers, Alan.

[ScottM]

I don't have any controlled tests available. In my ad hoc test, the peak windspeed and average windspeed seem too different, but I'll experiment more and check my math.

I'm trying a 5k resistor, but ENE and E are still very close together for a ten bit A/D, even with that. Not that big a deal, really; just annoying.

[AllyCat]

Hi Scott,

Yes, FO didn't do a very good job in "designing" the Wind Vane resistor values. There are two positions where the nominal difference between adjacent positions is only about 12% (one is where the 8k2 comes in parallel with 1k to make 0.89k, and diametrically opposite 120k comes in parallel with 16k to make 14.1k). If 5% tolerance resistors are used then the differential may be very small. So the "optimum" series resistance could be as low as about 3k.

For amusement, I designed my own set of 8 preferred (E12) values which spans a smaller resistance range but still gives a nominal minimum 20% separation between the 16 adjacent positions, e.g. 1k5, 6.8, 12, 56, 82, 18, 8.2 and 3.3 (but easily scaled up or down as required). However, not much use unless you're building/modifying your own vane (and decoder).

Cheers, Alan.

[Gina]

The F.O. resistors are 1% tolerance and my measurements show them as actually being much closer than that. But my measuring equipment is only accurate to 0.1% so can't say closer than that.

[ScottM]

I've gotten usable results with a 5k resistor pulling up to 5v, the wind vane resistor array pulling to ground, and the Arduino's analog input reading the result, providing a 10 bit value. How stable it's going to be when it's outside, facing a 110 degree temperature range over a year, I don't know. It works well inside, on my desk.

Calculating the comparison values for the A/D output was annoying, so if someone else does this, feel free to steal this C/C++ code. u is the value from the 10-bit A/D (0..1023) and w.windDir is the result, such that 0 is N, 1 is NNE, ... 15 is NNW, and 16 and 17 are "failure" values for too high and too low.

if (u < 100)
w.windDir = 17;
#define dirv(d, v) else if (u <= (v)) w.windDir = d;
dirv(5, 139)
dirv(3, 163)
dirv(4, 197)
dirv(7, 269)
dirv(6, 353)
dirv(9, 421)
dirv(8, 515)
dirv(1, 608)
dirv(2, 695)
dirv(11,767)
dirv(10,806)
dirv(15,861)
dirv(0, 901)
dirv(13,932)
dirv(14,966)
dirv(12,999)
else w.windDir = 16;

[rwilliam99]

Did this project ever go anywhere? It is 2 years old now, but it never seemed to have much success.

As several have said, I am looking for a way to read the data from the Fine Offset (WS-2080) station. The station works fine, but I've had numerous problems with the base station. The base station now seems to have gotten really flaky (after changing the batteries), and it is $50 for a new base station.

Suggestions? I could care less about the base station - I just want the data logged - Cumulus is what I'm not willing to go without. It is a GREAT piece of software!

[uncle_bob]

I too was totally over the communication and corrupted data issues with my Fine Offset.
I ended up making a WeatherDuino Pro2 and it's been brilliant!
You can read about it, if you're interested, here: http://www.meteocercal.info/forum/Threa ... Duino-Pro2

[ScottM]

In the end I got something working, using a microprocessor and wifi chip. It was very reliable, but it cost too much, and less than a year later a lightning storm destroyed it. (Lesson learned: you do not power a weather station with household current; nearby lightning induces currents relative to ground that fry hardware).

I plan to replace it someday, but if I can find something solar powered that does wifi, I will buy, not build. Building was a fun project and I learned a lot, but mostly I learned that building gear that works reliably outside for years is not trivial or cheap.

[rwilliam99]

I too was totally over the communication and corrupted data issues with my Fine Offset.
I ended up making a WeatherDuino Pro2 and it's been brilliant!
You can read about it, if you're interested, here: http://www.meteocercal.info/forum/Threa ... Duino-Pro2

That looks really interesting, but I'm not much of a hardware guy (other than assembling off the shelf parts). I think that is above my skills to assemble something like that. I was hoping for just a receiver unit as well - hoping to use the existing transmitter from the weather station.