My biggest immediately question though and one I'm a little surprised not see addressed, even at the research stage, is any mention of other animals. There is a bunch there about the ultrasonic frequency being well above the human limit of ~20 kHz. But IIRC for example dogs can hear up to like 45-60 kHz, and cats all the way to 65-85 kHz. I assume lots and lots of other animals also can perceive sounds well beyond human senses. Noise pollution is already a somewhat unrecognized but big problem for all sorts of life around us (not that it's irrelevant to human health either), so if more use of ultrasonics made that worse that's a concern. And as a practical matter the product market is probably going to shrink pretty dramatically if it drives pets mad, a lot of people have pets nowadays they care about a great deal. For that matter even in public environments if it messed with service dogs that might have ADA or equivalent implications.
Still, good reminder of various side channels one doesn't always think about.
There's probably no reason why these kinetic switches can't also be used for detecting other events like doors opening/closing etc. I feel like a radio signal is a bit more reliable and easier to detect than high frequency sound.
I also think calling these a "sensor" is a bit of a stretch. They detect events but have no knowledge of the current state of the thing they're sensing. E.g. the can detect a door opening/closing, but have no idea if the door is open or closed at a given time
1) 93.75% success rate in controlled conditions, 92.1% in a somewhat-realistic deployment scenario - too low for reliability. I wouldn't use something like that to trigger smart home automations.
2) Range hardcapped at ~1m due to how ultrasound works, you can't centralize detection. Their answer is to give everyone in the household a wearable receiver, which is eeeeeeeh idk, doesn't look consumer-friendly to me.
3) Paper suggests a mix of durable and consumable parts for the transmitter. Their numbers show that the 3d-printed PLA cantilever needs to be replaced every 900 cycles or so. Should work fine, but...
4) ...every transmitter pair needs to be tuned per-setup, every time. Not a plug&play in the consumer sense.
The linked Instagram video was really useful and understanding the applications. I highly recommend watching that too. In addition to reading the article.
Personally, I would not find it useful as they seem relatively fragile and if the receiver is not bulletproof and VERY sensitive then it could miss state changes.
However, it would be interesting to see how it would work if you were able to have different ones on different frequencies with one main receiver. That would make a cost effective way to track cabinets, doors, etc in the same room.
Ultrasonic is DOA, sorry, but that just won't do. It's already a nuisance to have all these switching supplies that mess up your hearing (and some can be surprisingly loud), using it for power delivery is really a non-starter.
There was a company that planned on using ultrasonic for power delivery to smart phones, every engineer with some ultrasonic experience said it wasn't going to work and they just kept going until they - predictably - went out of business.
https://en.wikipedia.org/wiki/SonicEnergy (formerly Ubeam).
Just wishing it exists does not mean it is possible or practical, that's right up there with Theranos (and I think Theranos actually had a better chance of working even though that chance was extremely slim).
There are interesting start-ups around the theme of energy scavenging though, that's a far more realistic but still extremely challenging proposition.
This isn't a smart home sensor.
Now companies are desperately trying to figure out how to jack up the price to $10.00 each without us knowing they are ripping us off.
People need smart devices to count their reps !?
Also I guess this might be annoying for pets that can hear well beyond 20 kHz.
If so, will it penetrate through walls?
Most common one - kiddo smashes it 5 times which kicks it into pairing mode...
Unfortunately... I see issues:
> Those frequencies are above 20 kilohertz, which is the upper limit of sounds humans can hear.
Yeah. Humans' range ends there, at least in adulthood. But what about pets? Wildlife? Children and toddlers? Or just people that take care of their hearing by not frying their ears with too much exposure to loudness? It's already an issue with "mosquito teenager repellant" devices.
Sensors must be using batteries, wear out in a month or so, tied to an oppressive cloud seevice, and regular up-sells of things that would be standard but we stratified types of paying users.
For a dotedu, this is perfectly fine. But this wouldn't pass muster as a real product. You can't do all the HorribleUsesAsAService like almost all IoT hardware is.