Temperature Logging On The Last Frontier

In Alaska, the impact of climate change is easy to see. Already the melting permafrost is shifting foundations and rocking roads. Hotter summers are also turning food caches from refrigerators into ovens.

A permanent food cache. Via Wikipedia

[rabbitcreek]’s friend builds food caches with kids as part of a program to teach them traditional native activities. Food caches are usually inside buried boxes or small cabins raised on poles. Both are designed to keep hangry bears out. As you might expect, monitoring the temperature at these remote sites is crucial, so the food doesn’t spoil. His friend wanted a set-and-forget temperature monitoring system that could collect data for eight months over the winter.

The Alaska Datalogger carried a pretty serious list of requirements. It has to be waterproof, especially as ice and snow turn to water. Ideally, it should sip power and have a long battery life anyway. Most importantly, it has to be cheap and relatively easy for kids to build.

This awesome little data spaceship is designed around an O-ring used in domestic water purifiers. The greased up O-ring fits between two 3D printed enclosure halves that are shut tight with nylon bolts. Two waterproof temperature probes extend from the case—one inside the cache and the other outside in the elements. It’s built around an Adafruit Feather Adalogger and powered by an 18650 cell. The data is collected by visiting the site and pulling the SD card to extract the text file. There’s really no other way because the sites are far out of cell coverage. Or is there?

Though it probably wouldn’t survive the last frontier, this self-sufficient weather station is a simple solution for sunnier situations.

36 thoughts on “Temperature Logging On The Last Frontier

  1. Have I missed something? There are a number of penetrations (around the bolts) that are inside the o-ring. surely this makes the o-ring a waste of time. I am interested in making waterproof enclosures but I still have a lot to learn

  2. “Builds food caches with kids” — W.C Fields: The actual quote, from a film – The actress asks him, “Do you like children?” and Fields responds, “I do if they’re properly cooked.” (from Tillie and Gus )

  3. I wonder what the feasibility of solar power and low power radio would be for data retrieval? Once a day or twice a day send the temp via Morse code with a QTH type transmitter?

      1. He may have meant QRP operation, which refers to transmitting at reduced power while attempting to maximize one’s effective range. The term QRP derives from the standard Q code used in radio communications. QTH refers to ones location !

  4. LoRa could indeed be worth checking -especially Semtech’s new SX126x based LoRa modules. Enhanced features abound when compared with existing SX127x based LoRa modules – check the likes of Chengdu EBYTE’s SX126x E22 range –

    * cheaper (< US$10 for UART), smaller, lighter
    * wide supply range
    * allow remote config.
    * RSSI
    * channel "listen before talk" carrier sense
    * WOR (Wake On Radio -greatly enhances battery life !)
    * relay feature – could ENORMOUSLY boost range.
    * low RX current drain (~half that of SX127x)
    * config. over a wider freq. range. "400" apparently 410-493MHz @1MHz spaced
    * simple UART or SPI
    * GUI setup
    * AT command friendly
    * work with SX127x

    Several of these features look "smell of an oily electron" goldmines for energy sniffing IoT applications!

    Stan. (ZL2APS- since 1967 )

  5. For those suggesting LoRa: it’s an amazing technology, but remember it’s still UHF and so essentially line-of-sight. Either you stick it way up high on a tower to get the “long” range (of maybe 10-20 km if you’re doing things right), or you’re at ground level and subject to the usual obstacles and ending up with 1-2 km range on a good day.

    Maybe 1 km is enough for these kids. Or maybe Alaska is someplace big and “scattered around the state” implies slightly longer range is needed if daily reports are desired.

    1. yea alaska is huge. hundreds of miles separate sparse smatterings of civilization and equally sparse cell towers. and that’s down here where the people are. out in the bush you better bring your sat phone.

    2. Yeah, but even just driving somewhere near the site and getting a data dump, even just a hundred feet away, saves a lot of time compared to scaling the tower and opening a door and unscrewing a bunch of bolts and pulling an SD card and popping the card into a laptop and transferring the data.

      If the towers could form a mesh with each other and opportunistically relay each other’s data as RF conditions allow, you might not need much range either. I don’t know how densely these caches are spaced, but there is more than one of them.

  6. I thought this was for traditional native activities. Anybody can build a temperature logger with modern devices and materials. Now go back to the drawing bard and come up with a solution that uses twigs, rocks, and bear scat. That would be an achievement.

  7. I have worked on several projects that have been deployed down in Antartica, one of the issues with 3D printed stuff is no matter what you try moisture gets in to the 3D printed housing, then freezes. The expansion of the ice causes the 3D print to crack. The work around I found was to use zero infil and use acetone to better bond the layers.

    The project I am working on at the moment is heading down there at the end of the year, Each node has 60 teperature sensors and needs to mesh back to a master unit that will record the temperature. Power is a real pain as 18650’s will not charge below 0 degrees. Wind generators get ripped appart in the 200+kmh winds and solar pannels end up covered in ice.

    Speaking of Ice the other issue is that the communications needs to be pushed over about 30Km and antennas also turn in to awesome looking iceblocks on the mast.

    Working in these enviroments is a real challange and my hats off to rabbitcreek for such a cool little design.

    1. Thanks for the experience lesson. It settles the doubt in my mind whether I can trust a 3D printed enclosure to survive a mast top in +50/-30C conditions for a decade or more. I’ll be going with a commercial NEMA 4 now, even though it’s ugly and expensive.

      1. Even the NEMA cases have issues as I found up some of my masts.

        I had some that were sealed with a rubber gland around them, all the cable holes had really nice metal cable glands with rubber gromets that sinched up around the LMR400. After a year or so one of the nodes stopped working. When i went up to take a look the case had a pile of water inside.

        What was happening is as the rain, condensation etc was hanging around rown the bottom of the case and the case was heating up the expansion and contraction of the case would suck the water in. Happend on all the units. So i ended up drilling some little holes in the bottom and sticking silica gell packs inside.

        Lol, then came the next problem, where there is a hole you can guarentee bugs will get in and sure enough they did.

        My final fix was to cast up some solid aluminium cases. they had a 4mm wide rubber seal around the edge and 4 M6 socket head bolts that would crank down holding the lid on. Not exactly a lightweight solution but I never had any issues after that. Some of the untis were still opperational after about 8 years without ever being opened.

        1. When I was a radio field tech some time in the last century we called that class of enclosure “Railway Grade” – a notch or two above the toughest Mil Spec standards. The state railway we contracted to had very strict equipment standards. Some dating back to the Victorian era, I’m sure, but you can’t fault them for demanding high reliability in awful conditions, given their mandate. I’m sure it came in well over 10x the cost of the COTS stuff, but as the resident peon I didn’t see the numbers.

          1. Haha, I like the term “Railway Grade” :) and can see why it would be a notch or two above Mil Spec.
            The custom boxes I built did not end up being overly expensive when compared to the equivilent NEMA plastic casing. From memory the plastic boxes ended up costing me about $42.00NZ each and the custom Alu cases ended up around the $60.00nz mark. The bonus was that I also got to design all the custom mounting etc inside the case so when it came to assembly it was nice and simple and im prety sure that ended up saving me money.
            There was also the benifit of not having to paint the inside of the box to create an RF shelild. Copper/Silver conductive paint was not cheap.

            Mind you duting the several years designing and setting up the system in one year I lost 2 laptops, 1 tablet due to either dropping them or rain/weather so I opted to purchase a Panasonic Toughbook that was Mil Spec. dropped it off the roof of a house more than once, Used it as an improvised step stool so i could reach the top of a 42U rack more than once, was rained on and keyboard was saturated and the beast is still running to this day (some 10+ years later).

        2. Sounds like you need gore-tex hydrophobic breather vents. They allow air in and out to equalize pressure, but exclude water so you don’t get condensation. Tap an M12 hole in your housing, screw the vent into it, and call it a day.

          Not a shill, I just see these things on a lot of fancy electronics and I figure they must be there for a reason. I’ve done some datasheet reading and they look fascinating. Never seen a drop of condsensation in any of the housings I’ve opened.

          1. Nate, I’ve been impressed at how well this concept works on my Pelican cases that come equipped with them, but have not been able to find vent parts that screw in like you describe. Do you have a supplier or part you can spell out for those of us who’s google-fu isn’t so strong?

  8. I appriate the intiative, why not enlist teachers and kids in the 48 to construct a network to get the bugs worked out, beford deployment in a harsh environment. even at minuscule power levels, can to things that would bite you in the butt, creating interference to others.. Watch dog timers for the digital board and any transmitter can sap away power reserves. A great project for places where year around access is generally normal.

  9. “In Alaska, the impact of climate change is easy to see. Already the melting permafrost is shifting foundations and rocking roads. Hotter summers are also turning food caches from refrigerators into ovens.”

    Wow, refrigerators to ovens. How many hundreds of degrees of climate change has Alaska experienced? And it doesn’t have anything to do with food caches being intended for the winter, but complained about in summer?

    1. Yeah, I kind of wonder why you would be storing perishables in a cache, and during the summer no less. My understanding, was that a cache was more of a backup plan, in case you lose, or use up your planned supplies. Stores can be a few miles away, and weather doesn’t cooperate all the time.

      Other than not being equipped for long periods of warm weather, I get the impression most of the people, and wildlife are enjoying the warm weather, while it lasts. It also means they are going to have a surplus of food, since everything grew well this year, and plenty of time to harvest and preserve. They don’t get summers like this every year, it’s still a rare treat. Seems odd, since for the past 30 years or more, we’ve been warned it’s going to get really hot. Should they already have been needing air conditioners and refrigeration every year by now?

  10. Use NVIS (WSPR with 100mW in an inverted V at 5 MHz or so).
    There is plenty of room to set up an antenna as I can see from the example picture
    You don’t want to spoil battery power on an inefficient VHF system that is unlikely to work anyway.

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