Author Topic: Remote weather monitoring  (Read 7107 times)

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Offline johnd

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Remote weather monitoring
« on: March 13, 2011, 01:10:21 PM »
I guess I'm the guilty party for suggesting this new forum section, so maybe I should just outline why I believe this new section could be valuable:

Many people people here will be hobbyists who monitor weather from their own home, where there will usually be services available like mains power and a broadband Internet link. But some users may also be able to site stations at locations which are distant from towns and other properties. These 'remote' locations can be excellent for weather monitoring either because the site is very open and so sensor exposure can approach the ideal much more easily or because the weather at the site may be plain interesting, like a hilltop site or perhaps a vacation home or cabin that you have.

The weather sensors at a remote site don't usually need to be any different from usual, so the standard Davis, Oregon etc stations should still be perfectly suitable. But what very often does have to be different is how you get access to the weather data. Actually, if you're able to visit the site with a laptop at eg weekly or monthly intervals simply to download blocks of logged data to the laptop, then there are no special issues involved. But what if you want live weather data from the remote location or daily downloads or you just can't get to the site very often? Then you need some sort of data link to the remote site and issues around how best to set up these links will I guess be the staple diet for this forum section.

I'd suggest that weather data links from remote sites set two main types of challenge:

1. Electrical power: Although the weather sensors and loggers can usually run pretty well on batteries and/or small solar panels, data links typically create a challenge of a different magnitude. A Davis VP2 system plus USB logger will run quite happily on about 24mAh a day. But introduce a cellular modem into the setup to stream live weather data back to base and the power requirement can rise to 5-10Ah/day. And while it's not too difficult to generate this amount of power from eg a solar panel in summer, what can be much more tricky - especially if you live in more northerly or southerly latitudes - is to keep the system running over the winter when the available solar energy may be only 5-10% of the summertime level. Wind power is obviously another option but a combined solar/wind installation can start to become expensive.

2. The nature of the data link back to base, which will typically take some form of cellular, other wireless or satellite connectivity.

Of course, professional wx station installers have been grappling with these various issues of remote installations for many years now, but typically their solutions are expensive and often don't offer live data. I think what many of us here are interested in are solutions that are as affordable and cost-effective as possible and, where feasible, do offer live weather data. Hopefully this forum section will offer some ideas and answers for affordable remote weather monitoring.
Prodata Weather Systems
Prodata's dedicated Davis EnviroMonitor website
UK Davis Premier Dealer - All Davis stations, accessories and spares
Littleport, Ely, Cambs UK

Offline d_l

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Re: Remote weather monitoring
« Reply #1 on: March 13, 2011, 01:36:24 PM »
The 6620 Vantage Connect appears to solve all these problems providing the Davis system is within range of a cell tower.
--Dave--

Wireless VP2 w/ solar, 24hr FARS, Heater, (Envoy-WLIP)*3-Meteohub, plus custom VP2 @ 26', WL 6.0.3, WU & W4U=KNVRENO37 NetcamXL

People always talk about the weather, but they never do anything about it.  Not me.  I'm gonna measure it.  https://www.tceweather.com

Offline Bushman

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Re: Remote weather monitoring
« Reply #2 on: March 13, 2011, 01:46:51 PM »
The 6620 Vantage Connect appears to solve all these problems providing the Davis system is within range of a cell tower.

But is is $895 MSRP and you need a cell plan etc.  That  will limit the market IMO except for  the really, really remote (within range of a cell tower).   Likely better cost effectiveness to run a wifi stick on  a netbook.
Need low cost IP monitoring?  http://wirelesstag.net/wta.aspx?link=NisJxz6FhUa4V67/cwCRWA or PM me for 50% off Wirelesstags!!

Offline johnd

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Re: Remote weather monitoring
« Reply #3 on: March 13, 2011, 01:59:06 PM »
The 6620 Vantage Connect appears to solve all these problems providing the Davis system is within range of a cell tower.

Yes it's an interesting product certainly with a huge amount of potential, though not due for launch for another 3-6 months AIUI. I foresee four challenges for the VC:

1. The maximum update frequency is going to be 5 minutes, and so anyone that wants literally live data (eg individual wind gusts with eg 3sec (or even 10- or 60-sec updates) is going to be disappointed. But I agree that a 5-min frequency is plenty enough for many purposes.

2. Although the details aren't clear yet, I'm not sure whether there will be a free choice of network. In any event, I'm guessing that the price won't be the same for each network. And the price, especially if you opt for the more costly 5min rather than 15min or 60min updates, may not appeal to everyone.

3. I hope that the solar panel has been specified as large enough to carry the VC through a gloomy winter at say 55N latitude, but I'm a little concerned about this part of the specification - I hope unnecessarily.

4. I suspect that the data will be in WL-only format and won't be easily compatible with 3rd-party software (or at least any software that doesn't use the Davis WL DLL).

I could be wrong about all of these points - time will tell of course.
Prodata Weather Systems
Prodata's dedicated Davis EnviroMonitor website
UK Davis Premier Dealer - All Davis stations, accessories and spares
Littleport, Ely, Cambs UK

Offline d_l

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Re: Remote weather monitoring
« Reply #4 on: March 13, 2011, 02:54:59 PM »
1. The update intervals are not necessarily the same as the archive intervals because the Vantage Connect stores data between updates.  So archival granularity apparently can be at more frequent intervals than the update frequency.  Admittedly there will not be real-time capabilities for the data; however, alarms are real time.

2. Using the Davis catalog as a source, there is only one monthly price listed for the Vantage Connect service at each update interval.  It is possible that Davis will only contract with one cell service provider for their connections and this might preclude the use of this service outside of the US.

3. It looks as though they have re-purposed the 7707 Solar Power Kit for Cabled Vantage Pro to house and power the cell transmitter.  They have a recommended tilt angle for the various latitude ranges.

The kit's solar cell is rated at 2.5 Watts. It provides about 300 mA of current in bright sunshine (1000 W/m2). In 2 hours it will provide enough power to operate a cabled console or Envoy station for 48 hours.

The kit is designed to use the 12 Amp-Hour battery provided, but any 6-volt rechargeable battery may be used. The 12-Amp-Hour battery, when fully charged, can supply power to a cabled Vantage Pro2 station or Weather Envoy station for 12 months assuming an average temperature of 68F (20C), or 10 months at 32F (0C), or 8 months at -4F (-20C).

In order to increase the efficiency and life of the battery, the kit's regulator circuit limits the voltage to which the battery is charged, and it adjusts this voltage according to the temperature at the rate of negative 7.5 mV per C. This ensures that the battery is fully charged for the conditions, but never over-charged.

4. Each Vantage Connect subscription will include a WeatherLinkIP account.  Because the Vantage Connect will use the WeatherlinkIP's servers as a storage medium, it is almost a certainty that the data format will be Weatherlink standard.

One thing I find interesting is that the Vantage Connect is apparently not attached by cable to the various Davis sensing devices, i.e., ISS, etc.  I guess this means that the Connect can be optimally sited to connect to the nearest cell tower even to the point of having relay repeaters between it and the Davis sensors.
--Dave--

Wireless VP2 w/ solar, 24hr FARS, Heater, (Envoy-WLIP)*3-Meteohub, plus custom VP2 @ 26', WL 6.0.3, WU & W4U=KNVRENO37 NetcamXL

People always talk about the weather, but they never do anything about it.  Not me.  I'm gonna measure it.  https://www.tceweather.com

Offline johnd

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Re: Remote weather monitoring
« Reply #5 on: March 13, 2011, 03:17:56 PM »
@d_l

1. Yes - of course. I'm not sure that there would be much point in having 1 minute granularity with 5min uploads, but yes 5- or 10-min granularity with 60-min uploads would make sense. I don't disagree in the slightest that these regimes will satisfy quite a lot of VC customers but, as you say, it won't be real-time data, or close to it. So there will still be a significant constituency of potential users interested in real-time data who won't be fully served by VC.

2. VC will AIUI definitely be available outside the US, but plans still need to be agreed in each OV territory. And exact details, costing etc remain to be seen.

3. I'm not sure where you're taking those capacity/consumption figures from. Are those just the standard Davis figures for the 7707 panel or have you also factored in the modem demand which, even if it sleeps most of the time - as I guess it will - will be quite significant. And the 7707 can be marginal in northerly latitudes - here in the UK it's not uncommon in midwinter to get 5 or 6 consecutive days of 5-6 hours of useful sunlight pre day of no more than maybe 100W/sqm. Possibly Davis might need to reintroduce the 7705 supplementary panel, which IIRC was discontinued some while back.

4. Agreed
Prodata Weather Systems
Prodata's dedicated Davis EnviroMonitor website
UK Davis Premier Dealer - All Davis stations, accessories and spares
Littleport, Ely, Cambs UK

Offline d_l

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Re: Remote weather monitoring
« Reply #6 on: March 13, 2011, 03:53:15 PM »
3. Those are stated 7707 power output capabilities.  I have no idea what the cell modem's power draw will be, but perhaps Davis will make power connection provisions to add an auxiliary 7707 to the VC for northern latitudes.
--Dave--

Wireless VP2 w/ solar, 24hr FARS, Heater, (Envoy-WLIP)*3-Meteohub, plus custom VP2 @ 26', WL 6.0.3, WU & W4U=KNVRENO37 NetcamXL

People always talk about the weather, but they never do anything about it.  Not me.  I'm gonna measure it.  https://www.tceweather.com

Offline SLOweather

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Re: Remote weather monitoring
« Reply #7 on: March 13, 2011, 04:28:18 PM »

2. Although the details aren't clear yet, I'm not sure whether there will be a free choice of network. In any event, I'm guessing that the price won't be the same for each network. And the price, especially if you opt for the more costly 5min rather than 15min or 60min updates, may not appeal to everyone.

Based on the catalog pricing, I'd say there's no choice on network. Davis will have had to negotiate a bulk deal to get that kind of pricing, they own the plan, and you pay them for the service, and it's clearly bandwidth dependent. It may well work on many networks. We have a RACO Alarm Agent for our water company controls. It's similarly priced, and RACO didn't even ask which carriers we had around here. I set it up and it just works. It's interface is similarly web based.

The cheapest data only plan I could get for development from Verizon was $40/month for 250 megabytes. My solar station uses about half that at 30 second updates.
 
Davis probably compresses the data upload to conserve bandwidth even more.

Offline d_l

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Re: Remote weather monitoring
« Reply #8 on: March 13, 2011, 04:56:47 PM »
Davis probably compresses the data upload to conserve bandwidth even more.

Why bother?  A monthly WLK file at 5-min interval is only 775 KB in size.  I doubt that the total monthly bandwidth at a 5-minute data collection rate would be very much larger than that even allowing for inclusion of the WLIP account ID and PW, and CRC checks of the uploads.
--Dave--

Wireless VP2 w/ solar, 24hr FARS, Heater, (Envoy-WLIP)*3-Meteohub, plus custom VP2 @ 26', WL 6.0.3, WU & W4U=KNVRENO37 NetcamXL

People always talk about the weather, but they never do anything about it.  Not me.  I'm gonna measure it.  https://www.tceweather.com

Offline johnd

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Re: Remote weather monitoring
« Reply #9 on: March 14, 2011, 04:15:46 AM »
Davis probably compresses the data upload to conserve bandwidth even more.

Why bother?

I'm not sure that it actually is compressible. Assuming that the WLIP data format is like a loop or archive data packet then it will already be in a dense packed binary format and not a compressible format like text. I think that the only way of compressing this further would be to delete certain of the data fields.
Prodata Weather Systems
Prodata's dedicated Davis EnviroMonitor website
UK Davis Premier Dealer - All Davis stations, accessories and spares
Littleport, Ely, Cambs UK

Offline Flag

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Re: Remote weather monitoring
« Reply #10 on: March 14, 2011, 07:34:25 AM »
3. It looks as though they have re-purposed the 7707 Solar Power Kit for Cabled Vantage Pro to house and power the cell transmitter.  They have a recommended tilt angle for the various latitude ranges.

The kit's solar cell is rated at 2.5 Watts. It provides about 300 mA of current in bright sunshine (1000 W/m2). In 2 hours it will provide enough power to operate a cabled console or Envoy station for 48 hours.

The kit is designed to use the 12 Amp-Hour battery provided, but any 6-volt rechargeable battery may be used. The 12-Amp-Hour battery, when fully charged, can supply power to a cabled Vantage Pro2 station or Weather Envoy station for 12 months assuming an average temperature of 68F (20C), or 10 months at 32F (0C), or 8 months at -4F (-20C).

"Cabled Vantage Pro2 station or Weather Envoy for 12 months"

I assume that would be without a WeatherLink logger? 

Offline d_l

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Re: Remote weather monitoring
« Reply #11 on: March 14, 2011, 09:15:27 AM »
I don't think there is much purpose for connecting a cabled Envoy without a WL logger so I would guess that one was included in the power draw calculations.
--Dave--

Wireless VP2 w/ solar, 24hr FARS, Heater, (Envoy-WLIP)*3-Meteohub, plus custom VP2 @ 26', WL 6.0.3, WU & W4U=KNVRENO37 NetcamXL

People always talk about the weather, but they never do anything about it.  Not me.  I'm gonna measure it.  https://www.tceweather.com

Offline Flag

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Re: Remote weather monitoring
« Reply #12 on: March 15, 2011, 06:24:59 AM »
Quote
The kit is designed to use the 12 Amp-Hour battery provided, but any 6-volt rechargeable battery may be used. The 12-Amp-Hour battery, when fully charged, can supply power to a cabled Vantage Pro2 station or Weather Envoy station for 12 months assuming an average temperature of 68F (20C), or 10 months at 32F (0C), or 8 months at -4F (-20C).

Did a bit more checking on this as from my experience I really doubt a 12-amp hour battery would run a cabled VP2 for 12 months and even Davis condradict themselves on this one.

Ok a data logger (WLIP is obviously exempt from this statement) makes no difference be it a cabled or wireless VP2. According to Davis (at normal temperatures) an 80Ah car battery will power a wireless VP2 for more than 4 years and a cabled VP2 for 14 months.

From tests I have done the 80Ah/14 months sounds about right the 12Ah/12 months is quite a way off the mark and more like between 1-2 months.

A 12Ah battery probably wouldn't run a wireless VP2 for 12 months?   


Offline SLOweather

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Re: Remote weather monitoring
« Reply #13 on: March 15, 2011, 11:48:05 AM »

A 12Ah battery probably wouldn't run a wireless VP2 for 12 months?   


Heck, they run on 3 C cells for months... Interesting how they break down the current draw by individual wireless sensors.

From http://www.davisnet.com/product_documents/weather/spec_sheets/6152-62-53-63_VP2Spec_C.pdf ...

Current Draw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.90 mA average, 20 mA peak, (plus 120 mA for display lamps, plus
0.125 mA for each optional wireless transmitter received by the
console) at 4 to 6 VDC
AC Power Adapter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 VDC, 900 mA, regulated
Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 C-cells
Battery Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . up to 9 months

Offline johnd

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Re: Remote weather monitoring
« Reply #14 on: March 15, 2011, 01:16:31 PM »
A 12Ah battery probably wouldn't run a wireless VP2 for 12 months?   

I suspect that it would be marginal - depends really on self-discharge rates. A wireless VP2+logger would use around 1mA continuously (assuming that it wasn't archiving data too often - with a 1min archive interval, the current draw would likely be significantly higher). So with a bit of self-discharge that would be roughly 1Ah/month, ie about 12 months total capacity if there was no interim recharging. But self-discharge might be higher than I'm assuming?

Cabled VP2 current draw is around 10x higher.
Prodata Weather Systems
Prodata's dedicated Davis EnviroMonitor website
UK Davis Premier Dealer - All Davis stations, accessories and spares
Littleport, Ely, Cambs UK

Offline Flag

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Re: Remote weather monitoring
« Reply #15 on: March 15, 2011, 08:59:45 PM »
What we can be sure of is that the 12A/h 7707 will not run a cabled VP2 for 12 months.   

 

anything