MIT engineers build a battery-free, wireless underwater camera | Hacker News Reader

MIT engineers build a battery-free, wireless underwater camera

news.mit.edu

88 pointskungfudoi32 comments

This was posted here earlier this month, and while it's a cool invention and worthwhile endeavor, it must be noted that this is battery-free because it's powered by sound. The reporting is kind of disingenuous because only the transmission back to the surface is energy-efficient.

In practice, powering this means blasting ~ 180 dB of acoustic power downwards to the device.

https://news.ycombinator.com/item?id=32983264

> This was posted here earlier this month, and while it's a cool invention and worthwhile endeavor, it must be noted that this is battery-free because it's powered by sound. The reporting is kind of disingenuous because only the transmission back to the surface is energy-efficient.

And it's also disingenuous because the battery is literally described in the article as well:

> Those sound waves could come from any source, like a passing ship or marine life. The camera stores harvested energy until it has built up enough to power the electronics that take photos and communicate data.

I guess what they meant to say is that it doesn't require manually recharging of the battery it has, or that it can recharge itself underwater.

Storing energy is quite literally what a battery is, and it has a device that does just that.

180 dB seems terrifyingly loud to me. Is that not true because of submersion or is it still super loud?

Still super loud. They should also note that this would have devastating effects on marine mammals.

Sonar is a likely cause for whales beaching themselves, using sound to transmit the image data underwater may do more harm than good.

The authors discuss the impact on wildlife:

> In the Keyser Pod experiment, the cumulative sound exposure level (SELcum) value was 191.29 dB re 1 μPa2s at a distance of 10 meters from the transmitter. Note that this value is within the limits defined by Marine Mammal Protection Act (MMPA) for all marine mammals except for mammals that lie within high-frequency cetacean hearing group. However, there were no mammals from this group (or any other group) within the 10-meter radius of the transmitter.

190 dB ???!? Is that different under water, and how much is left after 10m?

I mean 130-140 dB is the jet engine and the range were exposure without plugs is painful and longer than few seconds causes damage. This is 6 magnitudes higher, how can this be a good idea?

(Sounds like microwave wireless energy transmission: it's great, unless you care for birds which just get roasted if they fly through the beam?!).

Sound pressure readings under water are different than in the air. They're measured at 1µPa instead of 20, and water has a higher impedance.

Most legit scientists agree that loud, low frequency sonar have negative impact. But this is not that. It’s high frequency and low power.

> Sonar is a likely cause for whales beaching themselves

While I join the outrage, evidence of whale beachings predate the development of sonar by some 14K years.

And evidence of bison killings predate bison being nearly killed off. It's more about sonar causing more whales to beach themselves, not that it didn't happen ever in nature, but that our actions cause it to happen way too often. This is a weird argument.

It was not an argument, thus the qualifying first 5 words of my comment. I hate sonar, in anger accept that it beaches whales, but acknowledge that whale beachings predate sonar.

the earth makes all sorts of horrible noises across the spectrum.

I think that it's unfair to use that as a defense of sonar unless you're certain that the number hasn't been trending upwards since the beginning of sonar usage.

if whale navigation is somehow affected by strange very high or very low noises it's not outside the realm of possibility that there have been plenty of whales beached simply due to tectonic/planetary movement inducing confusion.

You're preaching to the choir. I think there should be a century-long moratorium on all commercial, industrial and military activity in the oceans.

It’s a cause. Likewise, people have been dying long before the development of guns.

They likely weren't dying from gunshot wounds.

They were, however, dying from organ failure and blood loss.

Also, some drowned, some burned to death, some fell from a great height, some were trampled, some buried alive. Hardly any were killed by metaphor.

As it happens with us, whales can die by several different reasons.

I wonder if you could use free space optics or mm wave radio (above the absorption spectrum of water) to do this without the environmental externalities. Dispersion is still a problem underwater with these high frequency EM waves, but presumably a researcher could deploy some relays along with the cameras.

Passive sound absorption for power could also work without any sort of active sonar pinging.

There are some videos of divers experiencing sonar underwater on YouTube. Seems like a weird experience.

https://m.youtube.com/watch?v=sCmyZYYR7_s

Does not seem very compatible with monitoring aquaculture systems without damaging the fishes skeleton.

But it looks damn sexy

Most of the world's oceans remain unexplored. Underwater cave systems in particular have a lot of uncharted territory. It's dangerous work, but explorers are still finding new caves and naming them.

Underwater robotics makes this task a lot easier. It's interesting to think that most of the planet's surface is abyssal plain, the largest habitat on Earth, flat surfaces on the sea floor beyond the reach of sunlight.

Ocean exploration really sparks curiosity. We are in such a rush to leave our beloved blue planet and send people to uncharted frontiers, but we still have an unfinished frontier right below our noses. Marine exploration also coincides with environmental preservation, as oceans are made of the most vital, life-giving resource on the planet.

Something interesting you learn in SCUBA diving is that sound waves travel faster in water than in air. This makes it difficult for humans to discern the source of audio while underwater, but machines like this seem to emulate the sonar capabilities of underwater creatures.

Always fascinated by what the minds at MIT are working on.

This is absolutely fascinating. We are coming for you, Atlantis!

>The autonomous camera is powered by sound. It converts mechanical energy from sound waves traveling through water into electrical energy that powers its imaging and communications equipment. After capturing and encoding image data, the camera also uses sound waves to transmit that data.

That reflective data transmission technique has been discussed around the barely-possible-but-plausible Venus surface rover demonstrators, but using radar. I really like seeing seeing projects like these that clash hypothetical technologies against real-world constraints, if only to better map out where to look next.

Wouldn't many cameras already be able to run weeks on end with just a large battery?

I really like this. I think a lot about ultralight versions of things I'm trying to do and try to angle towards them. I'm not in an academic research lab and I'm also a certified idiot but that meditation has served me well. I think the maxmimalist, disposable culture we find ourselves in often misses some of the best things we can do with our technology and I think this project does a great job of embodying that. I would really like to see more about their system but I get the feeling it's pretty off the shelf stuff too. Maybe not the exact peizo pads that I got for $0.10 per that I use for cigar box guitars but probably in the same line. It works well because of how sound works in the ocean. That shit is cooool.

Meanwhile, my new multi thousand dollar iphone sucks more than ever at apps I've been running for over a decade. It's got some really cool laser scanners and shit but is mostly just a disgusting embarrassment. The Wright Brothers were first-ish in flight because they were bicycle mechanics.

A very cool idea, but two things are a bit worrying:

1. “the camera could run for weeks on end” — i hoped it would run for years instead

2. It can transfer audio only 40 meters currently. They say they work on extending range, though. Would be really cool to make a mesh network with on-surface radio repeaters

I think that any camera device being underwater needs some cleaning after few weeks.

Some really clever problem solving going on with this. Watch this space!

A whale clicking it’s tongue is worth a picture is worth a thousand words.

Maybe useful to protect underwater gas pipelines?

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