We tend to rely more and more on our clever electronics these days – but here’s a timely, cautionary tale! My friend MAT over at NotEnoughTech has just TODAY written about the Tonga volcano and one of his Zigbee sensors which includes not only temperature but also a (generally) not entirely interesting barometric pressure sensor. I suggest a quick look at his blog entry if you are interested in the Tonga volcano disaster and how such events may or may not affect your sparkly new sensors.

Tonga volcano

But of course this is not new and it doesn’t need a massive, distant wayward volcano or other such events to reduce your sensors to a pile of poo – much less significant events much closer can of course achieve the similar results (hindsight is a wonderful thing). I left our home in Southern Spain for a trip to the UK back in November and will soon be heading back – hopefully all will be well (except for two sensors – read on…). It is in situations where the sensors are remote and inaccessible that the real problem lies with external interference.

Aqara sensors

Shortly after I arrived in the UK I checked the same Aqara sensor type back in Spain and I store (in Grafana) the readings for humidity and temperature but not pressure (not something I expected to change much in remote Southern Spain). Being Zigbee, the Aqara sensors tend to report mainly when there is a change (not a lot of point in wasting batteries to get repeats of the same data). I have an un-necessarily high number of all kinds of sensor around the house and can check the temperature in both bedrooms, the hall, outside, the living room and my office as well as my outside pergola.

I noted in December that both bedrooms seemed to be quite warm, but given the low heat losses of the building and reasonable temperatures in Southern spain even in late November/early December, I thought nothing more of it – I also had more severe problems due to power outages, one of which blew an internal fuse on teh PXU that charges my Pergola batteries, taking out my beautiful Imou Ranger camera until we got to the bottom of it.

Around Christmas I took a remote look and neither bedroom had shifted from 26c whereas the other sensors around the house were hovering around a more reasonable 10c. That’s when I went into more detail. There is nothing I can do about that until I get back to Spain. I SO now wish I’d added pressure sensing and battery state recording earlier as I took an intense interest in the La Palma volcano but it never occurred to me that there could be significant pressure effects in play so far away.

It was Mat’s article that got me thinking about the subject this evening, but it is worth pointing out that our home in Spain suffers the most attrociously noisy power failures – something like the one we had in the Northeast of England recently but of much shorter duration.

When I get back there as well as doing simple checks, I’m going to add pressure readings and while I’m on, the battery state to my list of stored sensor data in Grafana. I’d just assumed dead sensors for whatever reason but never thought that a significan number of out of the ordinary events could so affect the batteries – time will tell. I’m also planning to replace a single RCB with several RBBOs, cabinet size permitting.

Now I’m onto this general subject, expect updates when future disasters take place as, sadly they will. I’m already convinced the noisy power cut we had in December caused some electrical interference but maybe now I have to think about pressure variation taking out sensors (maybe future variations on the La Palma and Tonga disasters) and how that might come into play. As Mat rightly pointed out, the issues are utterly insignificant compared to the suffering such events cause – but may as well check to see if some sensors are more easily shut down by external influence than others and what those influences might be.

It is worth pointing out that unlike Mat’s setup, my sensors are all fairly new and so in normal use there’s no way those batteries would have given up. It’s unlikely I’ll get any great data now from past events but perhaps some alert on my mobile could let me know about any unusually long period of time with no events from a given sensor.

See earlier Aqara blog entries of mine here, here and here.
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