HomeNewsTonga volcano killed my Aqara sensor

Tonga volcano killed my Aqara sensor

This was a shocking discovery!

As far as clickbait titles go – this one is pretty awesome. And it’s not entirely misleading, so keep on reading. You are probably aware of a massive volcano eruption on the other side of the globe (to me). Hunga Tonga-Hunga Ha‘apai exploded on 15th Jan at 5:20 PM local time throwing a lot of dust and causing a deadly tsunami which no doubt will affect a lot of people.

You can observe the eruption and the following shockwave

In the more calm parts of the world (UK), I discovered that one of my sensors stopped submitting data to my home automation system. I know the scale of that disaster simply cannot compare to a Tonga volcano eruption, but we all deal with our own problems. I had all of my temperature sensors hooked up for my overview of the best ZigBee temperature and humidity sensors. While the pressure metrics didn’t make the cut, I carefully logged everything sensors were able to supply to my server. Just in case, and just because I could. I guess we all know why every company is harvesting your data!


Aqara Temperature/Humidity/Pressure sensor

The Aqara sensors are able to submit barometric pressure as well as temperature and humidity. It’s not a big deal as watching the air pressure graphs is as interesting as watching the paint dry. At least I thoughts so. As my sensor stopped reporting, I decided to check back to see what happened to it. It turned out, that the sensor decided to flatline (Grafana is set to retain the last value) on the 15th of Jan around 9:30 PM – there was nothing particularly special about this date until you look at the pressure graph.

Tonga volcano explosion (the big one) occurred at 4 am GMT time on 15th of Jan. A quick Google Map lookup reveals that the volcano is approx 16.300km away from me. While I don’t anticipate rocks falling from the sky any time soon, a quick google search revealed that shockwaves travel at 340m/s.

16300*1000/340/60/60 = roughly 13h

This confirms that should the shockwave reach my humble abode it would place it there around 7PM-ish GMT time. I could not believe that the cheap Aqara sensor with far from ideal measurement resolution could pick this up. Normally, these sensors report every 1-3 minutes, but upon sudden condition change, the reports are more frequent. It corresponds with the increased number of updates sensor provided for that short period of time.

A significant increase in the update count

The Aqara sensor has recorded an explosion of a volcano 16.300km away and that’s mind-blowing. I’m not 100% sure why the sensor stopped responding (I suspect the battery finally gave in, due to an old battery and increased payload count), but the timing couldn’t be better. Causation isn’t a great headline maker, but correlation can work wonders.

Have your sensors recorded the explosion? Let me know in this Reddit thread.


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