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remote APRS WX station project

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RonVE8RT:
I've come to the WXForum looking for guidance, mentoring, and more for a project I'm interested in building.
Because of our range of temperatures, which will go colder than -40 several times during our winters, commercial stations which blank out the temperature at -40 and colder will not do.

The station hopefully will monitor temperature (humidity is optional) wind velocity, rainfall, and have a second temperature input for ground level (or a sub surface permafrost temperature sensor).  Air quality would be a nice feature, especially in summer when forest fire smoke is a problem.

Power would be battery, solar or wind charged.  The station would be remote using a VHF APRS link (it could be tens of kilometres into the bush).   Battery power budgeting and management are a concern.

Looking for help to make this work.   Thanks!  Ron VE8RT

Mattk:
I'll start by saying any gear running less than -40 measuring especially wind velocity, rainfall will require some serious de-icing (heater) capability and typically that will require 24VDC / 150-250 VA hence the power budget is going to be fairly high. Remote temperature probes to -40 are doable on some systems but typically the quality won't be found on hobby stations. Air quality is also something not commonly incorporated into basic systems.

What is your budget to achieve what you require including the APRS comms?               

RonVE8RT:
The rainfall / snowfall wouldn't valued data other than from spring through fall.  The data I'd most value would be that gathered/reported during forest fire season and related to fire threat and impact.  That is when the air quality would be wanted.  Year round temperature and to a lesser degree humidity (I don't know if typical humidity sensors would work in the cold).  My decades old experience goes back to Stevenson screens with wet dray and wet bulb thermometers. 

The power requirements you've mentioned are not achievable 24/7.  In winter of course near the solstice we have about three hours of dim low angle sunlight (we may have high winds).  In summer during bad fire years solar is compromised by the persistent (has been July through to the end of September or longer) thick layer of smoke.

The quality and types of data would be that which may be useful for fire progress monitoring, and/or permafrost monitoring, those are my goals.  It would be nice to have a basic station that could be replicated by school students or Maker Space groups in small communities.

RonVE8RT:
I'm at work and have a few minutes to answer your post.
Radios, to be determined.  Some handhelds have over the years worked well in the cold, I've used HTX202 for APRS and leave them in the car.  The displays may not like the cold but they work.  My Alinco DR-135T didn't work below the manufacturer's specified temperature range, some modifications I did extended the cold range a little.  The receive capability on the handhelds may be of no use, but they're affordable, obtainable, and easy (during winter) to cold test. Not wanting to, or able to I suppose, come up with something from scratch as this will end up as another never completed project. Using an antenna with some gain, and modes available on Direwolf such as FX.25 or IL2P, I'd like to do some range testing, hopefully will improve throughput and range.
Batteries, as there will be times when solar or wind will not be enough; I have a quantity of calendar life expired emergency locator lithium batteries.  They do work at temperatures below -40, as do the Energizer AA lithium cells in my trail cam.  The batteries packed in with the electronics should provide thermal ballast keeping everything from rapid temperature changes and extremes (inside a thermally insulated enclosure).
During winter the temperature, wind, and pressure are most important, I don't know how good humidity sensors are in the cold (haven't looked at a datasheet for one yet).  Air quality might be interesting if the station was located close to a zombie fire.
Additional summer data, it would be nice to also have air quality, and rainfall, and as a bonus a pyranometer (a rough indication of sunlight attenuation from smoke and cloud.
Maybe to start with, and add sensors later, a very basic WX station adapted to monitor sub surface temperatures in areas where permafrost melting is, or is expected to be, a concern.
The hardware is within my range of skills, interfacing, microprocessors, and programming are not.

TheBushPilot:
RonVE8RT,

A few things I ask myself before starting the design process of a weather station:

* Cost
* Performance requirements
* Power
* Battery CapacityGiven where you live and the requirements at hand, it sounds like you need something quite substantial.

From what I understand you would like this site to operate year round. It will be subject to temperatures at or below -40°C/F each winter on multiple occasions. And you would like it to report via APRS.

Probably go commercial instrument route if budget isn't an issue. To keep things simple, get an R. M. Young alpine wind monitor, temperature/relative humidity sensor (-50 to +50°C measurement range), Setra/Vaisala/Young barometer, and Texas Electronics or Young tipping bucket rain gauge. Apogee Instruments or Eppley Laboratory solar radiation sensor. Soil temperature can be measured with an epoxy sealed thermistor or PRT from Campbell Scientific or Apogee Instruments. Campbell Scientific data logger, more recent CRBasic variant that can be calibrated for a certified operating temperature range of -55 to +85°C.

Not sure what the current draw of the radio would be but optimizing the station battery usage could get it down to mere milliamps. Get a pair of 250Ah sealed lead-acid batteries and the capacity alone assuming no source of recharge would get you through the winter. 200 watt solar panel with an MPPT charge controller.

I know my suggested way may be the costliest and most involved but it would probably last the longest in those conditions. Silver lining here is you can often find all of these instruments on eBay for a fraction of what they cost originally. Most expensive on that list being the data logger.

Hope this helps.


Cheers

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