Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Batteries Not Included, or Required, for These Smart Home Sensors

coe.gatech.edu

Post reply on HN
Print view View original

41–50 of 100 posts

Re: Batteries Not Included, or Required, for These Smart Home Sensors

#41

Post by nh2 »

Terr_ wrote: post #21
harg wrote: post #13

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…

> for detecting other events like doors opening/closing etc. If any of those doors are important for security, then I'd want something an intruder can't easily jam or spoof.

A big benefit of piezo-powered electronics is that they can do all the usual stuff, such storing state, or cryptography to prevent spoofing, which the ultrasonic approach from the article cannot do.

Re: Batteries Not Included, or Required, for These Smart Home Sensors

#42

Post by ranger_danger »

taco_emoji wrote: post #37
buescher wrote: post #15

Earlier quoted context omitted.

Piezo harvesting switches and similar (I think there’s a flywheel design out there too) are quite expensive, not terribly reliable or consistent, and require substantial activation force. Conventional switches and batteries that can last for years in remote push buttons and sensors are extremely inexpensive in volume.

The ones I have in my house [0] were not that expensive and have been quite reliable for years now. [0] https://www.amazon.com/dp/B09MHL8QTC

Do you know of any where the receiver plugs into an existing outlet and has an inline receptacle for the controlling device already wired up?

Re: Batteries Not Included, or Required, for These Smart Home Sensors

#43

Post by mschuster91 »

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.

Re: Batteries Not Included, or Required, for These Smart Home Sensors

#44

Post by fennecfoxy »

buescher wrote: post #15
harg wrote: post #13

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…

Piezo harvesting switches and similar (I think there’s a flywheel design out there too) are quite expensive, not terribly reliable or consistent, and require substantial activation force. Conventional switches and batteries that can last for years in remote push buttons and sensors are extremely inexpensive in volume.

Lmao no, my doorbell is one (doesn't have a battery at) and has been going for 7 years strong, as long as I've lived in this place.

Sure you have to press it very slightly harder than a regular switch and the travel is a little more, but not by much.

I think the doorbell cost like £20 in 2020, actually lemme check Amazon...ah in fact it was 15.99£ (now it's £20.99 hmmm) "TECKNET self powered doorbell".

Re: Batteries Not Included, or Required, for These Smart Home Sensors

#47

Post by simpleintheory »

dn3500 wrote: post #25
xoa wrote: post #24

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 senso…

Children too. My own hearing extended to about 23 kHz until I was in my early 20s, and I don't think I was exceptional. There was a jewelry store in my town that I couldn't go in to because the "ultrasonic" motion detector was so painfully loud. But I doubt these devices would be a problem for children or pets because the pulse is so short.

Are you sure it wasn’t one of these? https://en.wikipedia.org/wiki/The_Mosquito

Re: Batteries Not Included, or Required, for These Smart Home Sensors

#49

Post by fleventynine »

xoa wrote: post #24

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 senso…

PoE is lousy for sensors. The switch will cut the power if you draw less than 10mA (480 mW), so regardless of PHY efficiency (which is terrible compared to most RS-485, CAN, or even radio ICs), you are REQUIRED by the spec to generate heat that will mess up your sensor measurements.

Re: Batteries Not Included, or Required, for These Smart Home Sensors

#50

Post by itissid »

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.
Post reply on HN