I have an IoT application where, ideally, I’d like to use the three Ruuvis I bought to measure:
#1 - water temperatures in multiple locations, so the Ruuvi would remain in roughly 1" (25mm) of water for extended periods of time #2 - temperature and humidity for an Aerated Static Pile, a type of compost pile, where one or more Ruuvi devices would be placed about 24"-36" (600mm-900mm) deep in poultry litter. #3 - temperature and humidity in points of a greenhouse
In #1 above, temperature range would be roughly 32-180F (0-82C) with 50-130F (10-55C) being “normal”. Beacons would ideally measure in water (1" deep) and air. The application of the “hot” upper limits are a solar thermal collector tank and a the top of solar PV panel
In #2 above, the device can be placed in the middle of a “ball” of wood chips. I can take a picture, but the wood chips are meant to provide some air space between the Ruuvi and composted material. As an experiment, I have placed the Ruuvi in the pile in a plastic bag at about 10"-12" (25mm-30mm) and I can receive the beacon at about 20’(6 meters) direct line of sight but not through a wall or door. I can place the receiving RPi close to the pile, but not sure if the data will be reliable or if the Ruuvi will survive.
In #3 above, multiple devices will be placed throughout the grow house and the beacon data will be used to switch on/off (e.g. sonoff) environmental control systems (e.g. fans, pumps, etc.)
Of the above, I think #3 is very realistic for the Ruuvi. I have not tried #1 or #2 yet because I don’t want to ruin them. I wanted to ask this question before looking for other solutions. If I can get this to work, I’ll standardize on Ruuvis,
#1 2.4GHz radio waves don’t travel well in water but one inch can be doable if your receiver is close. Tape or glue the breathing hole on top of the RuuviTag to make perfectly waterproof. Even the sticker is IP67 specified, it may not tolerate long times under water.
The default battery RuuviTag ships with is specified to work up to 65 celsius degrees. Electronics are rated up to 85 celsius degrees. Extremely high temp (up to 115C or so) batteries are also available but sometimes hard to find.
I think this something you just need to try and see if it works.
#1 as Lauri mentioned, the biggest challenge is the water, as it absorbs 2.4Ghz really well, I’ve observed a noticeable drop in signal with my “outdoor” tag just during rain. Also, from certification point of view, IP67 assures just that “it’s watertight enough for 1 meter depth for 30 minutes”, even though usually the realistic case is longer, but definitely not infinite, especially with the sticker, so definitely tape/glue the breathing hole when using “permanently” in water
#2 Should work just fine, as long as no condensation happens, ie. humidity reaching 99-100% and then temperature dropping. A bit more than a year ago I buried one of my ruuvitags underground (about 10cm, or 4" deep), and as one might expect, the air humidity in the small cavity underground just goes up, but never really down as the humidity has nowhere to as the air never changes there. Long story short, the humidity climbed relatively steadily to 100% in just two weeks and stayed there with occasional variation between 95-100%. After 2 months the humidity never went below 100%. After 4 months the tag stopped transmitting sensible data and I had to dig it up, and found out that there were a few water droplets condensed inside the tag, short-circuiting something. (the tag worked fine after letting it dry without the battery for a few days)
#3 Definitely should work, I’ve actually seen a setup where there’s a ruuvitag in a greenhouse.
@Scrin I know this is an old post, but I wonder if Ruuvi has considered doing a waterproof coating for the board? I suppose something special would need to be done to keep the humidity sensor hole from getting plugged, or at least to keep the coating from going inside and spoiling the sensor. Have there been any thoughts about this?
I like to use the tags to monitor cell-culture incubators (37 C and 100% RH), and I have had a similar experience as you had regarding prolonged high humidity. In one case after a few months condensation built up to short something out, so the whole sensor was spoiled. In another case the battery seemed to have drained through the water film, and I was able to simply clean off the contacts and go again for a while. But even in the latter case you could see that corrosion was happening on some of the traces and contacts elsewhere on the board.
We do have enclosures without the breathing hole, if you need to monitor only the temperature adding some desiccant inside fully sealed enclosure might work.
If you need to measure humidity and pressure too, this becomes a lot more complicated. The BME280 might survive 100% pure distilled water, but in a practical environment there’s always some contaminants in water which end up degrading the sensing element.
Conformal coating cannot really protect the humidity sensor, but masking the sensor and battery contacts with tape and spraying the board with coating would probably be doable, I have sprayed some of my hobby PCBs and have always been happy with the result. If you need a large batch of tags, we can look into doing it industrially.
Please contact sales@ruuvi.com if you’re interested in fully sealed enclosures or want to discuss about the industrial conformal coating for a special batch.