FCC Approves WattUp Long-Range Wireless Charging

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#1 This isn't Net Neutrality, but I'm angry about that too.
#2 What is this fear of the device based on? Basically, anything will vibrate when excited at its resonance frequency and ignore other frequencies. You can have a building that safely wobbles through one terrible earthquake, then crumbles after another earthquake--all because each earthquake hits at its own frequency (which does vary by direction measured). If you hit a building at it's natural frequency, it can shake worse and worse until it falls down. Earthquake engineering damps out repetitive motions or creates structures with no single natural frequency (i.e., different parts of a structure that all want to vibrate differently).

So you can have a coil put in a charger that vibrates when hit with a resonant frequency of 5.8GHz, in this case, (I read about this in PopSci about 9 years back.) and then the vibration in that coil can be converted to an electric current and charge the battery in the receiver). It's only dangerous if your body is made of coils that vibrate at 5.8GHz...and your body isn't or the sun would have destroyed all living things eons ago.

UPDATE: I guess if they decided to make a device powerful enough to cook you with high-amplitude radiowaves, it's mathematically possible. But I would also guess that such a device would trip your circuit breaker. I suppose someone could deviously plot to slowly cook you in your sleep, but that wouldn't even give you cancer (due to the non-ionizing thing). It might be a lot more like sleeping in a room that's a bit too hot.
 
I teach physics. Your response totally made sense. Most people do not teach physics. Therefore, your response made about as much sense for most people as French...which is more than Chinese and MUCH MORE than Swahili.
Electromagnetic radiation (EMR) has and amplitude and frequency. Think of this like sound in terms of volume (amplitude) and pitch (frequency). EM radiation is what we are most familiar with as visible light, but when it's at a lower frequency (think of sounds too deep to hear), you get microwaves, and even lower, you get radiowaves. If you go higher frequency (think of high pitches dogs can hear, but you can't), you get UV light, X-rays, and gamma rays. Gamma rays kill stuff fast--and in higher amplitude are the most powerful energy sources in the Universe.

So you can have dim green light or bright green light. Either way it's the same frequency. Now a 4W laser is referring to using 4 Joules (of energy) per second, so watts work perfectly adequately for talking about the amount of energy being transferred. A bright enough green light CAN hurt you. But we're not talking about that bright of a green light. We're talking about things in the range of 5W chargers...probably lower. And we're not talking about green light, we're talking about something a lot more innocuous.
 

bit_user

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Another generic non-answer.

How about this: microwave ovens allegedly use 2.45 GHz, yet their wireless power uses 5.8 GHz. While an oven's output is something like 10x to 100x what you'd need to deliver a meaningful phone charge, the phone is at a much greater distance than food in a microwave. So, their emitter should still be running hot enough that I wouldn't want to sit next to it for any extended period of time. Either that, or it's useless as a charging technology.
 

bit_user

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My point was that I didn't ask for an explanation of electromagnetic radiation - I asked specifically why we think this is safe.

Read the question. Now, read it again. The answer should reference specific mechanisms of damage caused at this frequency, as well as the exposure conditions (i.e. power density and exposure times) required for the lowest detectable signs of damage.

If we're using Wikipedia, neither of you referenced the obvious entry (and the only one I've found particularly relevant):

https://en.wikipedia.org/wiki/Microwave_burn


Do you give your students credit for such politicians' answers? How would you grade a word problem about whether it's safe for two trains with specific initial conditions and destinations to use the same track and someone answers with a treatise on modern ground transportation infrastructure?
 
Dude. You're kind of aggressive. The fact is, your question was vague. If my question was vague, I'd have to give them credit in class. Also, I teach non-AP high school physics, so my questions are pretty straightforward this year and analogous to questions that occur in homework. Given no frame of reference or context, your question was hard to interpret. Remember, we're not responding to you to be jerks. We're actually attempting to provide helpful discussion.

"I'm open-minded, but skeptical. Can anyone explain (with references, if possible) why we think this is safe?"

Your responses seem to indicate that you are not half as open-minded as you implied in your initial post. The challenge should be to prove that something that has not been measured to cause harm would cause harm, not to prove that something can't cause harm so long as we're just discussing if the idea is feasible. I think our previous discussion has already confirmed that, properly regulated and prepared, this concept is feasible and could be safe.

I actually did mention that lower frequency, high-amplitude weapon that cooked you in your sleep from a distance. But as stated in your microwave burn link, we're not talking about incidence of cancer, we're literally talking about heat. You can move if there's any discomfort you experience when sitting directly in front of the charger--much like people move when they sit in front of a heating vent. However, I doubt that a charger operating at maybe ~10W would cause heat that a body would have any trouble dissipating (remember microwaves and heaters operate at the 1000W range). But you are right that you shouldn't sit directly in front of it--so it's good that it turns off. Portable space heaters have auto-off features for when they get knocked over.

Mathematically, this could not charge a cell phone while running at full discharge rate. It could charge a potential future cell phone at a low power hibernation state during the day while it sits on your coffee table. There's no way it replaces proximity charging of high-draw devices.

It could also charge a low-draw device like a keyboard, mouse, or TV remote more easily. Note that they actually recommend a 3ft range though. So we're talking about 3ft for this charger vs 0.5 ft for a microwave. That's actually comparable. That would follow the inverse square law, so that a 6x increase in distance relates to a 36x decrease in power. So if you want to cook someone like you're using a really slow (but still dangerous) 100W microwave, it would not do much damage from 3 feet (roughly the damage of a 3W microwave). Maybe it could cause discomfort if the power signal was that high? But I'm ignoring inefficiency between microwaves, signals, and received signal strength.

That doesn't leave much power to charge--which is the rate we'd really want to be looking at. The efficiency would be terrible. (50W signal to charge at 1W rate at best probably?). There's a lot of criteria that we don't have here for trying to prove safety. But there's definitely a significant realm of feasibility and safety.

And no, politicians don't use math that actually works, science, or references of any sort. They use "facts".

You asked for references, if possible. I generally referenced the formulas and theory as that's what's most relevant. If you want "tests", those are rarely scientific or valid, sadly, and I don't have that. I'd have to Google it.
 

wandurr

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Anyone remember when CPU Mag got "April fools'd" about 10 years ago and they covered (with a small blip) a fake wireless charging product in their magazine like it actually existed? And now it does.
 
I seriously read about this in PopSci in like 2009. It wasn't a product yet, but they were playing with it in a lab. It required coils of particular resonance frequencies, which is why I was discussing that earlier.
 

bit_user

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If that's what it takes to disabuse someone of the notion that a bad answer is at all helpful, so be it. Bad answers just waste everyone's time.


Then ask for clarification.


I get that, but what matters isn't your intent. If you waste my time with a post that doesn't answer my question, then you're still wasting my time. Sure, trolling would be worse, but a well-intentioned but sloppy answer is still a bad answer.

The point is people should try to be more discerning and not waste their time & others' when they don't actually know the answer and don't intend to do the work of trying to find it. This isn't some quiz where you get partial credit for putting down something sort of related. That kind of sloppy thinking just needs to be unlearned when people actually enter the STEM workforce. Best not to sew the seeds of it, during their education.


Really? I meant what said - I'm skeptical, but willing to consider the evidence with merit.

If someone presents a weak case, should I simply say "gee, he meant well so I'll just plunk one of these chargers on my bed-side table and assume the best?" No, I'm looking to be convinced. Unless someone can make a pretty good case that it's safe, the prudent thing to assume is that it's not.


We're not talking about string theory and dark energy. The safety of microwaves has been studied to a considerable degree, so it shouldn't be that hard to make the case that the tolerable upper limit of exposure is X, which this cannot be anywhere near. Or, if it can be, then say so.


You're looking at it backwards. In order to work as a charger at the recommended distance of 3', what would have to be the amplitude at the closest possible distance someone could get to the emitter?

@tigerwild already used a similar example:
Imagine the average person putting their charger base station 6 inches from their arm chair to charge a device 15 feet away
You seemed to answer a different question.
 
I think I meant something else, but I was definitely explaining that 36x thing backwards. I'm still pretty sure that the maximum potential danger is similar to a space heater...which has been the cause of fires.

As far as microwaves...there can't really be a tolerable limit because it's just heating things up. There's a maximum safe body flesh temperature, which depends on the part of the body, but how things heat depend on so many factors that arbitrary standards would have to be determined. That's fine, I suppose, as it would end up with a safety factor of maybe 10. That is, you'd have to answer the question, "How much heat would be transferred to a 30lb toddler's head if they were to leave it on the charging emitter indefinitely?" Then you would need to solve for about a dozen other assumed variables.

Well so long as this isn't an actual product with specs, I guess none of this really matters.
 
So is your skepticism whether this CAN be implemented safely or whether it's safe to assume that it's implemented safely? I think this tech is cool, but after looking some of these numbers, I can't see it helping charge a phone, let alone power a monitor or camera, in the next five years.

I would expect it to work for long-term powering of certain remote controls.
 

photon123

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It is still fake.
 
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