Batteries Not Included, or Required, for These Smart Home Sensors (opens in new tab)

For a brief, beautiful moment from the headline I thought "oh good, more PoE sensors finally happening!" doho. But no not just about battery but any power at all, and an interesting approach for further research. Of course to actually get data from still requires powered devices but in a lot of cases it'd be much easier to have that be a single or small number of more easily placed central units vs every single sensor tag separately. Ultra low cost and simplicity are values all their own in terms of applications.

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 already exists "kinetic" switches for lights etc whose switch contains some passive electronics that when actuated produces enough energy to emit a radio signal that can be read by a relay module. They're pretty handy as you can basically place the switch anywhere you want without the need for the wires to be there. The relay can live in the light fitting or somewhere else convenient.

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

It's research, not a product. Even with that, framing it as a smart home sensor in the press release is a stretch.

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.

My father was an engineer at Zenith when they were developing the Space Command TV remote control. This was a couple years before I was born, so by the time I got interested in hacking, Zenith TVs with this remote were commonplace. When visiting my friends homes I would prank them by jangling my keys and making the TV louder or quieter and randomly change channels. This presents new opportunities.

What a brilliant concept, useful for so many applications!

The linked Instagram video was really useful and understanding the applications. I highly recommend watching that too. In addition to reading the article.

This is a neat idea.

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.

So, in the true spirit of the HN dismissive comment, but this time I think it really does have its place.

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.

Same for EnOcean (energy harvesting ones). But most of them are too expensive for wide adoption (€50 for a temperature+humidity sensor is bit too much).

This is a very clever idea. However i think almost all smartphone microphone recorders cap out at 44.1khz or 48khz sample rate. Some have 96khz, but im not sure what is compatible with modern devices. That's going to limit how much frequency spectrum these fingerprints have to work with.

We've come full circle; one of first TV remotes used tuned pipes to generate sound driving the circuitry

Would these maintain their signature under repeated use? Or regular wear and tear?

Wonderful. ultrasonic range emission having high S/N is amazing too. My hero usecase for this is to use these for behavioral therapy: Have a ring or a bracelet, thus without reaching for a phone or a notepad, record when a negative thought happens, i.e. a counter, or generate a sequence of ultrasonic sounds to map to specific kinds of thoughts. Have a sensor record and log them. I would then analyze the data across multiple days. My current method is recording them in obsidian.

range of barely 3 meters, doesn't mesh, purely unidirectional, only applicable as a sensor for collision detection, still needs a powered microphone on the receiving side, most likely wears out.

This isn't a smart home sensor.

> "and cost only a few cents each"

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.

Finally, we are making the smart surveillance dust from the famous "Don't Make Smart Surveillance Dust" novel!

> ... and counting reps in the gym

People need smart devices to count their reps !?

What about durability? They are mechanical metal pieces, so would eventually wear down or change tone.

It's a unique idea that I could see being useful in select situations. The reliance on wearable microphones sounds like a downside.

Also I guess this might be annoying for pets that can hear well beyond 20 kHz.

Im not sure I got it. It generates acoustic signals and a microphone server picks them up.

If so, will it penetrate through walls?

Bought my house almost 3 years ago and put bunch of battery operated sensors, lights, switches. None of them died yet. None of the problems were due to batteries.

Most common one - kiddo smashes it 5 times which kicks it into pairing mode...

Trivia time! The first practical wireless remote control for TVs also used ultrasound: https://www.youtube.com/watch?v=MLPk1Us62xQ

Titlegore

Interesting idea and reminds me of the German train security system PZB which acts completely electricity-free at the signal - a mechanical switch connects a capacitor to de-tune a magnetic resonance circuit, which is then detected by a passing train's magloop transmitter.

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.

Get an SDR, tune into the frequency, and troll the home automation system! Given that it’s not of a high frequency, the attack can be done from a distance with proper antenna, and the frequencies use a hardcoded algorithm. Hell, I wouldn’t be surprised to see flipper zero addon to that (hardware through GPIO and software) for portability.

Where the profit in acoustic tuned sensors?

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.

I can see some uses, but calling this system batteries free seems a stretch. A sensor is worth nothing if it can't be read, and to read this you need a powered microphone and computing. Some already common magnetic door systems do the same; door plate and magnet movement is enough to create a detectable current, (using no external power), then that signal is read and computed by an electronic/digital system (using power).