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Is RCA's Airnergy Snake Oil?
Ben Newman writes "Of all the tech that's come out of CES this week, nothing has gotten the blogosphere more excited then the RCA Airnergy. A lot of people love the thought of an ever-recharging cell phone, and the Airnergy promises to constantly charge its internal battery through 2.4GHz wireless signals. Neat idea, but as some commenters have pointed out the energy just isn't there to make this work — BOTECs for a full charge range from 100 days to 32 years. Plus, don't let the RCA brand fool you into thinking this must be from a legitimate company: RCA hasn't existed as anything more then a licensed brand name for a couple of decades. So what do Slashdotters think — real deal or 21st century hokum?"
Is totally gonna charge up your battery and run your cell phone for days.
The inverse square law and dBm being a logarithmic unit can all go to hell.
Let's say this RCA product isn't snake oil.
Do you know how much energy it must suck from the 2.4 GHz spectrum to keep it perpetually charged?
Multiply it by the hundreds to thousands of cellphones within one cell ... can you imagine how much power the cell tower much emit in order to charge all those phones?
And the effect of so much energy floating in the air --- what about the effect on human body?
Yes, when I am confronted with an RCA TV, the first thing I think is, "a legitimate company produced this."
...microwave it. :)
the mythbusters tried to get power from the em radiation from a high voltage line. That doesn't work nothing will.
Maybe we just need to remove all the shielding off our microwave ovens and run them on full. That should pollute the immediate vicinity with enough power to charge the devices.
YES
There's no -1 for "I don't get it."
Not necessarily, frequency is just as important as voltage and current.
While I am certainly no degree holder or scholar in this field, I often wondered about the following:
A coil of wire with a current running through it emits a magnetic force. From memory, a magnetic force applied to a coil generates a current. Seeing as the earth is covered in a huge magnetic shell, how come people don't actually generate power this way? Is the magnetic field simply too weak compared to what is needed to generate a current of any value?
Perhaps one of you smart folk here might help me out with this little "backburner" thought that I have had for a while?
Much appreciated,
- Fluffeh
Moved to http://soylentnews.org/. You are invited to join us too!
I don't think it was necessary to discredit RCA since you made no effort to back up that statement but I personally find the technology interesting.
I hold no misconceptions that this could keep any device perpetually charged however If the technology advances enough you could perhaps greatly extend battery life beyond its actual storage amount if it is always attempting to replenish itself to whatever is available as an energy source. It could turn your average 5 hour battery into a 6 hour battery, with no extra capacity. While I'm probably exaggerating the actual benefit of this current model, it could provide potential in the future.
It also has to do with a static field vs a moving field. Make a coil of wire, hold a magnet next to it, hook it to a voltmeter. Notice the coil doesn't have any induced voltage until you move the magnet. You can't get any energy out of a static field, no matter the strength of the field.
I think it is the _change_ in magnetic flux that generates a current in a conductor, not just the presence of magnetism.
They whose government reduces their essential liberties for temporary security, receive neither liberty nor security.
Yes. Solar power from visual light (EM radiation) works very well. We know that.
http://michaelsmith.id.au
but it will not be out for another 3 to 4 years. See it here: http://www.uberphones.com/2009/06/ambient_electromagnetic_radiation_to_charge_nokia_phones/
The purpose of writing is to inflate weak ideas, obscure poor reasoning, and inhibit clarity....Calvin
I'm sure we can look forward to a vigorous debate, where both sides bring up excellent points. I certainly cannot say where the slashdot community will land on this question, and the article certainly doesn't give any hints! Thanks, Ben, for your valuable question, and I hope you find the answers both challenging and enlightening.
That really should have worked, with a sufficiently long antenna. It'll be induction, but that ought to count too.
Finally! A year of moderation! Ready for 2019?
Assume a wireless router broadcasts at 1W, uniformly outward. Suppose the charger has an effective surface area of 4" * 2", or about 50cm^2. Assume the charger is 10m away fro the router; then the charger can receive no more than (1W) * (50cm^2) / (4 * pi * 1000cm * 1000cm) = 4 * 10^-6 W. A Blackberry battery on Bestbuy.com claims to store 1100 mAh @ 3.7V of energy, so the device could charge a powered-off Blackberry in (1100 mAh * 3.7V) / (4 * 10^-6 W) = 116 years... I'm wrong, or the device doesn't work as claimed.
Nasa HAS tried this.
http://en.wikipedia.org/wiki/Electrodynamic_tether
You can generate electricity as you move around the earth. Being in orbit, you are going fast enough to make worthwhile magnetic flux, and you are free of air resistance that would keep you from deploying the tether if you were lower in the atmosphere.
A *changing* magnetic field generates a current. If you just take a coil with some wires attached, and hook up a voltmeter, nothing will happen. Only when you start moving your coil through a magnetic field will you start to see volts. (Earth's field is extremely weak, but with a big coil and a sensitive meter you could see a small current.)
The reason this can't be used for infinite power generation is that the coil will resist movement. Any flow of current generates a magnetic field of its own, and if you do the math, it turns out that the induced current in your coil creates a field in opposition to the field it's moving through. It works against you like a kind of friction, or like air resistance. If you just give the coil an initial kick, it will quickly run down to a stop. In order to generate power you have to keep putting energy into the system.
In other words, you're not draining energy from the magnetic field, you're just converting the kinetic energy you put in.
This is in fact how generators work. A big conductive coil is spun around inside the field of some permanent magnets. If your generator is connected to a water turbine, you're converting the kinetic energy in falling water into the kinetic energy of a spinning coil and thence to electrical energy in a wire.
Obviously, you put this thing in the microwave, set it to High, and let it charge for 30 minutes.
(Please let it cool down before removing it from the oven.)
Well, we can't do much about the inverse square law, but we can easily switch to linear units. :-)
I am of the belief that yes, you can re-charge your 'phone's battery from an R.F. power source (after all, it works for RFID).
There are IMHO two caveats;
Your 'phone needs to be in standby, since when talking, you'll be using far more energy than the cell can provide.
Any active users will suffer reduced signal-strength due to all the passive users re-charging their 'phones. This power has to come from somewhere and that place will be the cell transmitter. Given enough 'phones re-charging and you won't be able to make/receive a call because your 'phone won't be able to hear the cell due to all the other 'phones sucking all the signal from it...
Just a thought.
C:\>
If all you have is a hammer, everything looks like a thumb.
This is embarrassing. Embarrassing for Thompson, which owns the RCA brand. Embarrassing for press who took it seriously. Serious career trouble for whomever authorized licensing the name to the clowns behind this.
We'll probably hear some disclaimer from Thompson shortly.
Much earlier than the mythbusters a german tv-show for kids, the "Sendung mit der Maus" ("program with the mouse") made the point: they held up a neon tube next to a state radio-transmitter and it began to glow. And they explained to the kids, that it will work next to such a high energy radio transmitter, but it is also robbery according to german law. So don't try, kids, unless you don't mind being a thief.
Tesla seemed to think this idea was workable. Can't say about RCA's product but I'll trust Tesla.
At what price learning? At what cost wisdom? The price is a man's peace of mind, and the cost is his life.
I'll get more energy with a hand-crank generator...
How can you steal that what is freely given? Laws are weird.
Not enough energy available. Would probably not even offset self-discharging unless a pretty large antenna is used. You can fake a demo though with a highly directional antenna to beam in a wireless signal. Not realistic at all and inefficient as hell.
I am constantly amazed at what people are willing to believe.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
2.4Ghz waves aren't small enough to damage DNA.
You're blocking the signal by absorbing large amounts of it. A shared resource should be shared, and not abused.
I see your point, and you are dead on - today!
I remember an episode of Star Trek where the Captain and Spock admire a source of lighting that "produces light, but no heat! - How advanced!" yet, compared to incandescent bulbs, that's an apt description of LED lights, especially those designed for high efficiency!
Let's talk now about Cell Phones - I almost bought a cheapie cell phone for $29 that was about the depth/width/length of a hershey chocolate bar. It sported 2 days of battery life, unlimited text/picture messaging, and (get this!) NO CONTRACT. Compared to the "brick" 1980s cell phone, we have at LEAST an order of magnitude reduction in power consumption and possibly two, by using such techniques and digital packet switching, variable power output, and the like. And this trend is set to continue into the indefinite future - we are *still* spending far too much in resources to get what we want.
Now, if you figure that we can improve power conductivity by, oh say, 50%, and can cut power utilization by 100x, (1/10th the amount claimed by Bell Labs) then suddenly, the charge rates from a 150 mw 802.11 radio source 5 meters away actually seems reasonable!
It won't happen today, or tomorrow. But in a few years? Not only possible, but likely!
I have no problem with your religion until you decide it's reason to deprive others of the truth.
If you read the article:
"Airnergy takes the energy created by wi-fi signals and stores it in a rechargeable battery. At CES, the device's battery, which I believe was precharged with Wi-Fi power, was able to charge"
The key words are "the devices battery, which I believe", if he can charge a mobile battery from another battery then this is nothing new, however the charging of the "devices battery" is what is questionable in my mind, fooling yourself into thinking that the guy was sat in McDonalds or at home and powered if off his neighbours wifi is stupid.
bingo. it's flux (change in magnetic field), not the magnetic field itself, that produces a current.
Beware the Jubjub bird, and shun the frumious Bandersnatch.
Not necessarily, frequency is just as important as voltage and current.
You just failed physics 101. Frequency has absolutely no impact on energy in a signal.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
Plus, don't let the RCA brand fool you into thinking this must be from a legitimate company: RCA hasn't existed as anything more then a licensed brand name for a couple of decades.
You got that right. Neutron Jack cannibalized RCA in the late 80s, selling the consumer electronics division to Thompson. About 12 years ago, they sold chinese company TCL the right to use the RCA name on TVs and other products.
They ought to replace Nipper with one of those chinese hounds with all the extra folds of skin. HIs master's voice is in chinese.
Wansu, th' chinese sailor
As others have pointed out, you need a change in the field to generate current, either by moving through it or moving the thing making the field. You can observe this effect on a high speed aircraft, where there is a measurable potential difference between the wingtips as it flies though the earth's magnetic field. It's not really strong enough to extract anything useful out of it - you couldn't hook it up to a motor and power the plane, for instance. You'd do better bolting PV panels on every exposed surface.
A coil of wire with a current running through it emits a magnetic force. From memory, a magnetic force applied to a coil generates a current. Seeing as the earth is covered in a huge magnetic shell, how come people don't actually generate power this way? Is the magnetic field simply too weak compared to what is needed to generate a current of any value?
Perhaps one of you smart folk here might help me out with this little "backburner" thought that I have had for a while?
You have something wrong here: Only a changing magnetic force induces a current, a constant one does not. (Well, technically it does, but at zero Volt, so no current flows.)
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
Sorry, but you fail: E=hv . frequency is proportional to energy!
Now, if you figure that we can improve power conductivity by, oh say, 50%, and can cut power utilization by 100x, (1/10th the amount claimed by Bell Labs) then suddenly, the charge rates from a 150 mw 802.11 radio source 5 meters away actually seems reasonable!
It won't happen today, or tomorrow. But in a few years? Not only possible, but likely!
Not at all. Cellphones need something like 100mW...2W RF output to cut though background static and get a signal to the cell tower. And by conservation of energy that means even if nothing at all besides the RF emitter consumes energy, the power consumption will be at least 100mW...2W.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
If it does, i'd imagine CES to be the _perfect_ testing ground for such a product. Elsewhere? Not so sure..
Frequency effects your ability to absorb the energy. I can only pick up NSA broadcasts on my dentalwork, for example.
If you were blocking sigs, you wouldn't have to read this.
But it has an big impact on the antenna design.
Nokia proposed a power-harvesting (and power-sipping) handset over the summer last year, to derive its power from cellular signals rather than wi-fi. Although their target amount of 50mW is way off, they claim to have a prototype that can pull in a few milliwatts, which inspired a mixture of scepticism and existential terror from researchers in the field.
No kidding!!! What do you say at this point?
1) Note that Tesla never got wireless power working. He liked the idea, but he couldn't make it work. Also note that to this day we still don't have it. That should tell you something. The problem, it turns out, is that EM power decays logarithmically with distance. So a little more distance translates to large losses in power. You have a 1 watt transmitter and it is only a few milliwatts when you get a bit away from it. It would be extremely inefficient to transmit power through the air, even ignoring other problems.
2) Tesla was nuts, like "lock him in a soft room" crazy. He was brilliant, don't get me wrong, but he was also crazy. The guy had some really wacky ideas, along with some extremely genius ones. Just because Tesla thought something would work, doesn't mean it would.
Well it has been on techcrunch, techMeme, engadet, gizmodo, ycombinator and many more.
Not sure what you are following?
The crux is to use "Magnetically coupled resonance" to achieve efficient power transfer to prevent the vast majority of power from being broadcast into space (read wasted) when no receiver is present to absorb it. Unfortunately that very feature seems to severely limit the transmission range.
So I wouldn't worry about long-distance power transmission through the air just yet.
I'm more worried about plans for space-based power transmission which were recently green-lighted in California. For example, what happens when the beam from such satellites shifts from the intended receiver area to, say, a residential block?
According to http://en.wikipedia.org/wiki/Space-based_solar_power#cite_note-intensity-41 at the center of the downward beam, we would be looking at 23 mW/cm2 (and 1 mW/cm2 outside the center), compared to OSHA workplace exposure limits for microwaves, which are 10 mW/cm2. Not bad, but not good either. Suppose someone goofs and directs the beam onto a kindergarten and leaves it there for a week. What then?
Those 23 mW might not look like much, but it's still 230 W/m2, and it's radio-frequency which penetrates far deeper than visible light. I simply don't know how detrimental that is, but I'd like to be sure of the potential long-term effects before anything like that is built, let alone switched on. I'm certainly no Luddite, but in the light of e.g. findings like these (see http://www.isracast.com/article.aspx?id=57) about the detrimental effects of 2mW of 1.1GHz radiation on eye lenses I feel we ought to be careful. Signal-level transmission at 2mW is one thing, but power level transmission at 23mW/cm2 is something else.
That sounds cool. It might actually work!
Diet pills | Penis enlargement
You just failed physics 101. Frequency has absolutely no impact on energy in a signal.
Indeed, That's Why the the GHz Barrier was a myth, in fact we should have Thz machines if it weren't for the man keeping them down.
*cough*E = h*(c/lambda)*cough*
You are not considering the possibility that this device is not intended for your average user.
Maybe it was envisioned with a more... active crowd in mind.
You know... the kind of people who would find the prospect of running up to one of these a valid possibility.
Also, it would make a GREAT plausible denial device for the active denial system (PDDfADS).
Hang one of those around your neck and you can claim that you were just trying to charge your phone (and not the ADS), when you are arrested for whatever activity it may be that required the use of the ADS on you in the first place.
Mit der Dummheit kämpfen Götter selbst vergebens
I tried it with a 500mW power source on 460MHz using a pair of resonant quarter-wave aerials. At about one metre separation, it was receiving around -6dBm, or about 250uW. So that's ten times the power, ten times closer, on a lower frequency with better propagation. Ten metres away and 50mW would give -26dBm which my meter won't measure, but is one hundredth the power - 2.5uW. Good luck charging a battery with that.
Gordon MM0YEQ
Look again into that physics text. Frequency is denoted by "f", not "ny" (no, that is not a lowercase v). The formula you quote relates to the energy of a single photon, no voltage or current in there anywhere and is completely irrelevant to the discussion at hand.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
As I said above, that would be the energy of a single photon. Not relevant to energy transmission on the scale we are talking here. Looking up a formula that has energy and wavelength in it is not enough to understand where this formula is actually relevant. Now, if we were talking about single photon detectors, that would be something different. But we are not.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
The inverse square law and dBm being a logarithmic unit can all go to hell.
What makes you think it's got to be an inverse square law? An inverse square law would apply to something emitted radially, but in the case of a charger, it need not be.
I suspect the sun is putting out slightly more than 50mW, though...
maybe I can run my 3g wireless access point on them?
If I place them close enough I might not even need any other wifi signals..
The greek nu is the standard notation for frequency in physics, or at least it generally was when I did that kind of thing. f is sometimes used, though less commonly. However, photons are not relevant for RF - the photon energy is so small that the quantum nature of the radiation is not apparent, and it behaves for all practical purposes as a classical wave.
Frequency plays a massive difference in EM radiation and magnetic induction.
For EM, you really need an antenna that's close to the wavelength, and for 50Hz that's 6000km. For 2.4GHz it's about 12cm.
For induction, frequency affects the overall number of turns required. A 50Hz transformer that copes with 300W is the size of a shoe box, but for a switchmode power supply at 100KHz it's the size of a match box.
Sure it will recharge your battery...
over the next few years. :P
Moderate sunlight will burn my skin. Radio waves don't come anywhere near doing that.
Meh, according to the German broadcasting agency I'm already stealing radio waves by owning a computer.
I'm not kidding.
and the fact that wifi has a very low max emmited power (which the FCC is strict about) in most aplications, in point to point you can go to a massive 4W but as this will be on top of a builiding/tower in a very directional beam even thats not any good.
Take any solar collector and place it in a dark room with an LED nightlight on the other side of the room or down the hallway and let me know how much output you plan to produce.
If you are near a wifi hotspot, charge off the USB port of a laptop instead. It is several orders of magnitude stronger. Is it April first already?
The truth shall set you free!
Well, try standing next to a microwave antenna.
Instead of using wifi why don't they grab the power from mobile phone transmissions and use the power transmitted from the mobile phone instead. They can build the device right next to the phone then so they can get *much* more power. In fact the inverse square law states that the closer you get to the source the power increases. If you are building this into a phone then you can put the device right inside the transmitter and be at ZERO distance and so the inverse square law tells me that would generate an INFINITE amount of power! That should be enough to power a cellphone, right? /not serious...
Are you saying they failed?
I *know* someone who ran his entire house from a coil in his loft, a few meters under a power line which passed directly overhead.
AC coupling is no myth. The only thing that was busted in this case was his ass, when the power company figured out where their drain was coming from.
If I climb onto the roof of my local shopping mall and stand next to the cell phone mast, maybe it will burn me, but down on the ground it certainly doesn't. I suppose it is about the same as having an electric heater element up on the roof of my shopping mall.
Is totally gonna charge up your battery and run your cell phone for days.
Why not have a phone which works like self winding/powered watches? Something which extracts mechanical energy from body movement. Indeed with a phone such a mechanism could be put entirely inside the "battery" so no need to modify anything else.
The inverse square law and dBm being a logarithmic unit can all go to hell.
You might do better by covering the thing in photovoltaic cells. Given that there are likely to be more visible light photons around to capture.
Not necessarily, frequency is just as important as voltage and current.
:)
In the case of a power line the frequency is likely to be 50, 60 or 0 Hz. Which there not being that many which are DC
Much earlier than the mythbusters a german tv-show for kids, the "Sendung mit der Maus" ("program with the mouse") made the point: they held up a neon tube next to a state radio-transmitter and it began to glow. And they explained to the kids, that it will work next to such a high energy radio transmitter, but it is also robbery according to german law.
AFAIK "crystal" sets are legal in Germany...
The calculations posted here and elsewhere are based on the assumption that the device uses standard transverse electro-magnetic waves for the energy transport. In principle, it could also be possible to use longitudinal electric waves, even though this is generally assumed to be impossible, because it is assumed there are no free charge carriers in vacuum that could support longitudinal electric waves.
However, the Maxwell equations are based on Faradays experiments and while Faraday was a physicist, Maxwell was a mathematician. Maxwell postulated the concept of charge carriers as causing the electro-magnetic field, while at the present day it is known that EM waves cause matter to exist and not the other way around. So, one can certainly not rule out the possibility that longitudinal electric waves are possible after all.
This is exactly what the German Professor Meyl points out:
http://www.k-meyl.de/go/60_Primaerliteratur/Scalar-Waves.pdf
http://www.energeticforum.com/renewable-energy/3545-konstantin-meyl-scalar-faraday-vs-maxwell.html
According to Meyl, one can achieve a very thight coupling between transmitter and reciever and achieve almost 100% efficiency in the transmission of energy.
This means that if this thing works, one will have consider the existence of longitudinal waves a very serious possibility.
"don't think of conspiracies, think of sharks swimming in parallel lines." - John Loftus
You use the "nu" when dealing with particles. For waves it is f. In electronics it is practically always f.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
Wireless Power Calculator
http://powercastco.com/wireless-power-calculator.xls
http://www.powercastco.com/resources/
Doing a simple calc with the above spreadsheet at 2.4 Ghz, 1W of radiated power, patch antenna, and five meters distance from the radiated power source, you would have just 0.040 mW of usable power, and at that, not enough to light even an average LED (30-150 mW req). So, don't be looking for that 'power on' indicator on this device. At that 'available power density' the charger might almost make up for its own internal losses from the battery charging circuitry.
For any device of this kind to be useful it needs to be broad spectrum and not limited to a single frequency band such as the 2.4Ghz band stated here. If you could capture all available RF in a large enough swath of spectrum then this bulky device might have enough power to be competitive with a teeny tiny button battery.
We're talking about energy transmission here, not just the total energy in the system ;-) Frequency is very important in that regard.
so depending on where you are in that 100mn..2W you can talk for some % of the time and have it charging the whole (or possibly only remaining non talk, depending on setup).
but yes by conservation of energy if you want to talk constantly then you need equal power charging
Tesla was a very clever man, but his experiments (tesla coil etc) were based on something quite different than "broadcast energy".
Tesla played with "harmonic" or "tuned" energy, eg take two tuning forks tuned to the same frequency, tap one to set it going, and hold it three inches away from the second one, the second one will start to vibrate, you just transferred energy.
The primary and secondary circuits in a tesla coil works the same way, not with sound, but with tuned electromagnetic force, it is a tuned step up transformer.
The SINGLE wireless power experiment that worked recently worked on the same principle, tuned magnetic coupling.
***This*** device is about simple absorbtion, so yes, it *will* absorb power, and yes it will *charge* a battery, technically speaking, so will your old external TV antenna, satellite dish, ham radio antenna, and indeed how the hell do you think the old crystal / cats whisker radios worked without a battery? It works for RFID too.
But *practically* the rate of "charge" you get out of this is going to be less than the rate of self discharge, even for s single AAA size rechargeable battery.
The physical analogy is a steel plate placed in the bottom of an empty swimming pool with indeed grab water condensation from the air overnight and "charge" the swimming pool with water.
It will NEVER fill the pool though, the self discharge (evaporation) is a faster and more robust process.
I though slashdotters were supposed to be educated?
http://slashdot.org/~GuyFawkes/journal
what if the phone is designed so you can only talk some % of the time not 100% as everyone mentioning conservation is implying.
with this thinking.. it can certainly be done and may be useful. say for emergency scenarios like say a mobile phone out at a public camp in the bush or mountains, it can receive a signal from towers 10 km away but they dont need solar or similar to keep the phone battery charged it just gets trickle charged from the ambient waves and can support being used for 1% of the time which would be 15min of talk time a day on average (not only 15min at one go, if nobodys used it for several days there would be more available)
so i think this idea is possible but the relevant question is, providing what % talk time?
Well, in switzerland it's about the same thing, you have to pay for TV reception on any computer, even if you have no internet/tv-tuner.
you can't suck radio waves out of the air like that.
But it would work, right? It just wouldn't be enough for an indefinite charge. I think it's enough that you extend unplugged lifetime, surely. It's not necessary to have an everlasting charge so much as a longer-lasting charge, offsetting the energy consumption by continual recharging. Isn't that the idea?
I want my Cowboyneal
Or directly under a microwave satellite...
stealing the battery out of your friend's cell phone when he isn't looking. Simply say, "Hey look over there! Free WiFi!" and when he is distracted, exchange batteries. This proves cell phones can be recharged wirelessly.
Sorry, but gray text on gray background is making my eyes bleed.
You use the "nu" when dealing with particles. For waves it is f. In electronics it is practically always f.
But since all particles are waves, which should one use?
WARNING! This girl exceeds the MAXIMUM SAFE standards established by the FDA for BRATTINESS
The inverse square law and dBm being a logarithmic unit can all go to hell.
What makes you think it's got to be an inverse square law? An inverse square law would apply to something emitted radially, but in the case of a charger, it need not be.
True, but that's not what this charger is. It's meant to scavenge from 2.4GHz WiFi, which emits radially, and therefor follows the inverse square law.
Write your representatives! Repeal the 2nd Law of Thermodynamics!
I think somewhere south of zero.
Seriously, especially in your case of being "out in the sticks", you'll get maybe -90db of signal, which isn't going to be sufficient to power the radio receiver, much less send the occasional blip back to the tower using the transmitter. You might extend the 2-day battery life of your phone by, possibly, about 10 minutes. And I'm being generous.
I suppose you could leave the charger battery at camp and have enough to charge/power the phone there for occasional visits, but you're talking about a long charge time, probably measured in months.
It's an expensive and inefficient way to collect energy. For a camp, you're better off with a larger-capacity battery and a solar panel. You'll collect more power, you aren't dependent on a WiFi transmitter, and it's probably cheaper. I imagine a 2" square solar panel would collect more power than this thing could possibly do, especially in areas far from the nearest cell tower.
"This post contains words, known to the State of California to cause thought. Wash brain thoroughly after reading."
It's meant to scavenge from 2.4GHz WiFi, which emits radially, and therefor follows the inverse square law.
Luckily for me I have a parabolic dish behind all my wifi base stations ;)
...highly refined snake oil! Just look at that sleek case!
There is no way this can work as described. The device itself isn't large enough to gather power at anything near the required rate (you'd need a sizeable antenna to do that). The internal leakage current of the rechargeable batteries it supposedly contains is probably greater than the amount of power it could gather; even disregarding this, it would take so long to charge from WiFi signals alone that it would not be useful.
trouble is, that earths magnetic field seems to not be as even as we had imagined it, and you tend to get surges that ruin the equipment. (weld the tether reel solid, foul up electronics and my personal favorite, snap the tether like a fuse)
I've decided to Diversify my Holdings. I've divided my cash between my left and right pockets, instead of all in one.
What's so special about buying a phone without a contract?
Particles are not waves, they can be thought of as waves OR as particles, and vice-versa.
The new physics fashions for frequency range from: omega or 2pi/T (University Physics. Young and Freedman. 11th ed.) or theta dot (Classical Dynamics. Greenwood. Dover).
GO BLUE!
Particles are not waves, they can be thought of as waves OR as particles, and vice-versa.
If I can think of them as either waves or particles, then they exist in a superposition before I decide where they are both a wave and a particle at the same time.
WARNING! This girl exceeds the MAXIMUM SAFE standards established by the FDA for BRATTINESS
Mythbusters isn't always right. For example, they busted the "myth" of an ancient Greek "Death Ray" by making one that didn't work. Some MIT kids showed it was possible (this was discussed on slashdot last year).
They had busted the "myth" of a sniper shooting another sniper through the second sniper's scope, and the US Army showed they were wrong, by giving them some better ammo. They covered this on the show itself.
I saw the episode you refer to, IIRC they used a device they bought from the internet. Just because that device wouldn't work doesn't mean none would. You should be able to get voltage from stray EMF from your house current; a crystal radio has no power source and is powered only by the transmitter's signal. But it takes tiny amounts of current for headphones to work, a phone takes quite a bit of juice.
So I'm skeptical. I'll believe it when I see one. I do think you could probably make an LCD clock without a power source, you can run an LCD watch from a potato battery.
Free Martian Whores!
It's not a vacuum; it's more like a stationary scoop. Someone standing right next to you will still get approximately the same amount of signal whether your scoop is there or not.
Look up the mathematical definition of flux (integrate the scalar product of the vector field with the differential area vector normal to the surface). You and the GP are saying two different things. The GP is correct, and you are not, although I think you have the right idea, just the wrong words. The change (over time) of the magnetic flux (think "the amount of magnetic field") passing through a conducting loop is proportional to the current generated around the loop.
SIGSEGV caught, terminating
wait... not that kind of sig.
I'm less interested in the technology's ability to charge mobile devices - I agree with other posters that it seems unlikely to work in a reasonable time frame. I do think it could have potential for powering wireless sensor networks though. Some of these devices require relatively little power, but the present need for batteries (and replacing them) is a show stopper for realistic deployment.
It's the differential in potential that makes electrons flow one way or the other, or in an alternation. A static relationship produces nothing. The waveguide charging theory isn't going to be too productive because the available amount of electrons available at the frequency drops inverse-square from the source. A one watt 2.4ghz access point radiates that energy in all directions at once if it has an omni-directional antenna. Move a few feet away and the energy gets really small, in terms of charging something-- then you can add-in the inefficiencies of the conversion electronics to further stanch the flow going to a battery. Nonetheless, there is a bit left over to charge a cell. How much? I'm thinking not very much at all.
---- Teach Peace. It's Cheaper Than War.
You can't stop your own EM radiation to go out for only a SPECIFIC purpose (radio) and forbid all other purpose. It is freely give if your radio receptor only gets a few microwatt from the antenna or at least low enough not to be a disturbance. But as soon as you get the power for another purpose not forseen, and this is a huge drain, then you break the system if it is allowed, and nobody would really have any radio antenna. Therefor the law forbid it. As far as I can tell , same problem if you put Neon tube udner high voltage cable.
C. Sagan : A demon haunted world:
http://www.amazon.com/gp/product/0345409469/
visit randi.org
Schrodinger's Cat. From the interpretation I was given, although it can be thought of as either/or, the particle exists in either the particle state or wave state (or in between), but it cannot be in both simultaneously. It is only the information an observer has that changes the perceived state.
GO BLUE!
my phone has wifi, so it can charge itself!
You use the "nu" when dealing with particles. For waves it is f. In electronics it is practically always f.
I'm sorry, but the correct answer is w (lower case Omega). No point in having to keep a 2pi hanging around in all your equations.
"Educate the mind but never at the expense of the soul."~Blessed Basil Moreau
Maybe "theft". Definitely not "robbery".
Theft is when I take your wallet out of your pocket.
Robbery is when I scream at you, shake my fists and threaten to punch you in the face and take your wallet.
Somehow I can't imagine Armin Maiwald threatening the radio people in any way. ;-P
Ha!!!
*Runs of to the patent office to patent the potato-powered cellphone*
If you run out of potatoes in an emergency you could probably also run it using the bloody flesh of your own wounds.
As I said above, that would be the energy of a single photon. Not relevant to energy transmission on the scale we are talking here. Looking up a formula that has energy and wavelength in it is not enough to understand where this formula is actually relevant. Now, if we were talking about single photon detectors, that would be something different. But we are not.
yet you ignore the other half of my post about the GHz Barrier?
He had this idea way back. He's laughing because everybody thinks it's a new idea.
I read Slashdot for the headlines, because the headlines, unlike the articles, are usually original and never duplicated
As some others have said, either the coil or the magnet have to be moving. Interestingly, though, my now-retired father used to construct high voltage transmission towers. He says that before the transmission line was finished, before any power was applied, he could (and would) wrap a coil of wire around the cable and weld his initials into the tower.
He couldn't figure out how that could work, but it seemed simple to me. The swaying of the cables in the wind generated current by interacting with the earth's magnetic field.
Free Martian Whores!
If the mythbusters didn't get that to work, they were probably doing it wrong. It does work for other people
Actually you only need about 1/4 of the wavelength to get a good antenna. A full wave antenna doesn't provide a good match for real work situations.
It's easier to fight for one's principles than to live up to them.
The radio of a cellphone isn't on all the time. For GSM phones, the transmitter is probably off for at least 100 times as long as it's on while it is idle. Even when it's sending, it's on for only 1/8 of the time.
Tesla's work involved magnetically coupling the receiver with the transmitter. Recently MIT even used it over short range to provide useful amounts of power with reasonable efficiency. (Witricity is a spinoff from this effort. Their first predicted application is indeed wireless small-device charging.)
Pointedly, the wireless power transmission isn't using radiative broadcast for this; they are using magnetic fields.
You can transmit useful power using 2.4GHz signals, but it is either directional or it is contained (like your kitchen microwave.)
SirWired
It's meant to scavenge from 2.4GHz WiFi, which emits radially, and therefor follows the inverse square law.
Luckily for me I have a parabolic dish behind all my wifi base stations ;)
1) Too bad you will have to leave your device in the path of that directional beam.
2) If you're in your own house, is this supremely more useful than charging from the wall?
3) Still doesn't make it useful as soon as you leave your house, which is the idea.
Write your representatives! Repeal the 2nd Law of Thermodynamics!
1) Too bad you will have to leave your device in the path of that directional beam.
Why does it have to be a directional beam? It can be anything from a beam to a pretty decent cone.
2) If you're in your own house, is this supremely more useful than charging from the wall?
Absolutely! It means I can charge outside people's houses. I don't even need to get their WEP key! Only problem is I'd need to break into their houses to put a parabolic dish behind their router.
Actually, you should try this with an ammeter instead. You can use a voltmeter across a load resistor placed in series with a coil. In some cases, though, you could use a voltmeter in series with a coil, letting the coil itself be the load resistor - depends on the coil and the delta-B available.
Well I have not seen the Myth buster film at all so I cant know what they did or what they did wrong or what they left out. What i know is that Power (excuse my bad english) is P=UI*cos(). So if U is 100000000000 kV and current is 1A but cos() is 0, you get 0W and that is 0 power. But still an experiment I really would like to be done, I've had this in mind for almost 15 years I'm 31 now. Place a isolated copper cable under a high voltage line that is exactly 1 wave length long. This should cause resonance in the cable but I have no idea what the outcome would be. And no one has been able to explain theoretically what would happen. Would the Voltage increase towards ? Or what would go towards ? If not, why not, the resonance should have some effect in this direction?
How does this not sap energy from your orbit? Is it basically a roundabout way of converting reaction mass into electricity?
I read the internet for the articles.
https://www.shakeweight.com/ver4/index.asp
Not at all. Cellphones need something like 100mW...2W RF output to cut though background static and get a signal to the cell tower. And by conservation of energy that means even if nothing at all besides the RF emitter consumes energy, the power consumption will be at least 100mW...2W.
I may be missing something here, but can't you use this power to trickle charge a battery? You don't necessarily need to collect the exact amount you are expending at the same time, you only need to collect at a rate which equals the average amount you use in the same amount of time. (assuming you start with a dead battery)
Out of modpoints but really liked a post? 1BDkF6TtmmeZ3yqXbz9yhdYVqRYnwFoXDj
I believe the standard rule of thumb is ~ 1 kW / meter^2.
I've always had a special little place in my heart for Faraday's law. Ahh, EMF=dPhi/dt, how I cherish you ;D
The frequency is irrelevant; the power just isn't there. Even if you captured ALL energy from the wifi device and converted it into electricity with 100% efficiency, it would still take more than a month to charge a laptop battery. A foot from the device, it would take decades.
Less. Typical cell towers are 30-45W average power.
The el cheapo heaters in Wally World/Target/etc. are usually 1500W at full power.
I wouldn't directly touch the antenna though, just like touching the heating element of above heater directly is probably a bad idea.
retrorocket.o not found, launch anyway?
Yes it would sap the orbit. The current induced into the satellite would create an opposing field which would react with the Earth's field and degrade the orbit. The question is; what is the intensity of that effect? It's probably very small.
You are lucky... I pick up the 24 hour all Polka all the time station on my dental work.
If I were God, wouldn't I protect my churches from acts of me?
yeah... you're right.
this is why I'm a bio major.
Beware the Jubjub bird, and shun the frumious Bandersnatch.
Yes, but this discussion is about low frequency high voltage lines, not the RCA WiFi boondoggle.
Look up the mathematical definition of flux...
That we get to have FLUX CAPACITORS????
AMERICA, FUCK YEAH!
Over-the-top Response Guy! Giving "Over-the-Top Responses" since 1970.
1) Too bad you will have to leave your device in the path of that directional beam.
Why does it have to be a directional beam? It can be anything from a beam to a pretty decent cone.
Even a cone diminishes at an inverse-squared rate, it just starts more powerful. The measurement of an antenna reflects this, as it is simply a dB ratio of the power compared to a spherical-radiating antenna.
Even if you have a 4W transmitter focused onto 1m^2, this receiver is no bigger than 10cm^2. You'd still only receive 1% of the power (40mW), and only if the receiver stays within that 1m^2 area, and that's also your WiFi signal. The point of WiFi is to let you access the internet in a way that lets you move more than 1m, so the idea is bunk anyway.
You're still starting with too small of an initial power and losing too much of it to be of any practical use even if you design the system to take advantage of it, let alone in a random public location.
Write your representatives! Repeal the 2nd Law of Thermodynamics!
I've been thinking a lot lately about the dangers of EM radiation around us.
If this is true, energy can be created from those signals in the sky ; one might wonder which effect this has on the human body, DNA and the brains.
Daily signals get added with watts/megawatts of power behind it. It's already proven DECT could create medical problems.
So, how safe are we really inbetween this vast space of electromagnetic radiation? And how does this affect our lives with all those signals combined bouncing off and through our bodies by the second, mostly for commercial gain?
--- I am known for the ones who want to find me on the net. Is that a privacy risk or a privilege? One might wonder..
Why do you say I have blood in me?
Don't oppress my people bu** f%#ker!
I drank what? -- Socrates
So, if you raise the generator plant above the surface of the earth, and let the earth spin below it, it should generate current from the magnetic field passing by?
If only we had a spinning neutron star near by...
I drank what? -- Socrates
You are lucky... I pick up the 24 hour all Polka all the time station on my dental work.
Those are the same station.
LED lighting only produces light with no heat in comparison to incandescent. High-power LEDs actually have fairly impressive cooling requirements if you don't want them to cook themselves to death from the heat produced.
yet you ignore the other half of my post about the GHz Barrier?
And what mythical GHz barrier would that be? AFAIK there is no such thing. Maybe a marketing invention.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
The death-ray myth was re-busted, despite the brave efforts of the MIT team. And the sniper incident got upgraded to "plausible", which is quite a bit different than "HA, YOU WERE WRONG!!!". I find the sniper thing particularly annoying because, even if it's true, it isn't indicative of any exceptional skill - such a shot would be a complete fluke.
On the other hand, sure, they've made mistakes. Who hasn't? I'm not sure why you'd bring that up. Are you trying to suggest that because they were wrong before, they must be wrong about this particular myth also? Or that they're not a reliable source of information? ... ?????
You have heard of solar panels, and how they work, have you? ;)
Any sufficiently advanced intelligence is indistinguishable from stupidity.
Isn't omega used for angle/rotation speed, as in 2pi/T, radians per time unit? Nu or f is for frequency, as in 1/T.
It would do that, you are right. Lets look at the numbers. Wikipedia states something like 5-10% self-discharge for Li-Ion batteries a month. Lets assume that a typical commercial phone battery has about 5%. Now my phone has a 3.6V 0.6Ah battery, which comes down to about 2.2Wh. 5% of that are 110mWh. Assume 1mW gotten from the RF collector, that means it actually delivers 0.72Wh per month. That means you are right, this technology can keep the battery of a phone that is completely off topped off. It does however need something like 3-4 months to charge an empty battery.
A second number: My phone has 300h standby time. That means in standby it takes around 7.5mW and will discharge the battery about as fast with the magic RF charger as without.
So the RCA device can keep a Li-Ion battery topped off, but only if the attached device is off or takes less than 1mW in power. For specialty situations (emergency phone stashed somewhere, but keep in mind that Li-Ion only lasts about 5 years until dead, see below) this may actually work. It is also can keep the internal battery of the thing by RCA topped off, but only in an emergency use and manually charge after use scenario. This means it is not something that has general usefullness as was implied by the manufacturer, but really is only useful to have a long-term automatically maintained power reserve that you very rarely use.
Whether 5 years is long-term is reallty up for debate. Let us take a long-endurance battery technology, i.e. Lithium button cells as comparison. A CR2477 Lithium cell, which holds about 3Wh, i.e. more than my phone battery, has a self-discharge below 1%/year and costs around 5USD/3EUR when bying in small numbers. So how often are you going to need the emergency charger? Say every 3 months. Then the self-discharge of Li-Ion is about 15%, you don't need the topping off by RF power. Say once every 6 months, which means it is down to 70%, still no need for topping off. Say once a year, ok, then you want the RF topping off. Keeping a bunch CR2477 around and using one per year would now cost you about 5USD/3EUR per year. From then one the CR2477 option costs you 5USD/3EUR per use. If this device is $40, it breaks even with the Lithium batteries after you had 8 charge emergencies, but only if they were something like a year apart and you used the full Lithium battery charge in each emergency.
A single CR2477 would give me about 10 hours speaking time on my phone. If each emergency only requires an average of 1 hour speaking time, the 5USD/3EUR CR2477 gives me 5-10 years emergency reserves (at 1 emergency every 6-12 months). Since Li-Ion batteries do not have an infinite shelf life (Wikipedia says 20% capacity loss per year for a fully charged battery), the RCA device will likely last even shorter (3 years for down to less than 50% capacity) at a considerably higher price. And you need to charge it.
Do you see where I am going? The use-case is just badly off and the ecconomics do not make sense at all.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
You're naive. Radio waves don't burn your skin because they go right through it to burn your DNA instead.
I can feel the energy from the sun on my hand. I can't feel the energy from a router. Not even with my EM allergies :-)
This was demonstrated some time ago .... however not using wifi.....
http://www.ted.com/talks/lang/eng/eric_giler_demos_wireless_electricity.html
I look at it like this... There's no doubt it can harvest "some" energy but it is the equivalent of trying to harvest a field with a sickle when you're trying to feed China and what you really need is a combine harvester.
No, I only suggest that they COULD be wrong about this particular myth.
Free Martian Whores!
I know they don't work at radio frequencies (RF).
Schrodinger's Cat. From the interpretation I was given, although it can be thought of as either/or, the particle exists in either the particle state or wave state (or in between), but it cannot be in both simultaneously. It is only the information an observer has that changes the perceived state.
The math works for either at any time. From the quantum mechanics standpoint, from a practical standpoint it should be treated mathematically as if it were both... your interpretation of why this works however, is entirely up to you.
If you want a real trip, check out Phonons. :)
WARNING! This girl exceeds the MAXIMUM SAFE standards established by the FDA for BRATTINESS
Excellent so it's only a 1500km I need for me to get wireless power from power line emissions :)
Well actually the magnet doesn't HAVE to move. In order for a current to be induced into a conductor magnetic 'waves of flux' must cut through that conductor. This can be achieved by moving a magnet OR having a pulsating magnetic field such as an alternating voltage (frequency)passing through an electomagnet, creating waves of magnetism. This will induced a current in the conductor(s). A coil with thousands of turns will produce a current if you stood under high voltage overhead pylon cables if a neutral cable is not used, as many power producers use the earth for this purpose in order to save on cable.
It's not a neon tube (which requires thousands of volts) but a FLOURESCENT tube.
Its sad to see the lack of basic English skills from these Slashdot geeks. As a geek, I am personally offended by the lack of basic English skills. If a writer can understand one-tenth of the science discussed on Slashdot, one would think the writer would be able to grasp the difference between "then" and "than"
Tesla proposed this back in the 1800's, and now somebody is bringing it into reality. +8 to the genius who proposed it.
You are entirely wrong on that point. The more dense the "peaks" in a wave of electromagnetic energy is, the more energy is in that electromagnetic wave. The speed of this charger depends both on the wavelength (which is what i think is called a negative inverse correlation to frequency, 2.4 gHz has a wavelength of about 5 inches, or 125.4 mm, which is about 1000000 times longer then ultraviolet light.
How 'bout electric cars with similar method?
Omega is the angular frequency. 1 Hz = 2pi rad. If you're computing electrical admittance you're going to want the angular frequency.
"Educate the mind but never at the expense of the soul."~Blessed Basil Moreau
Nobody here knows WTF they are talking about, so let's take this from another approach.
Scenario: You develop a miracle product which can suck electricity out of thin air. It's a killer app and you'll sell millions of them. So you start your company, get the product manufactured in China and get ready to sell it. After doing all of this, you for some reason license the trademark of the long-defunct Radio Corporation of America -- a trademark you don't control and is mostly used to sell universal remote controls and cheap stereo cable.
Why would you do that? Why build a brand that nobody remembers and that you don't own? It makes no sense.
Conformity is the jailer of freedom and enemy of growth. -JFK
Well they would supply enough power to last your lifetime and your childrens' ;-)
All cows eat grass!
Well, here is yet more of Tesla Technology "finally" being tapped into.
I think we are missing the point about is that perhaps the RCA device is not so impressive in terms of performance, the bigger picture is that we can have wireless transmission of electric power for various devices. This has been possible for some time, but perhaps this is the entry into the mainstream.
Essentially, you could have a single point of distribution of power in your home and power all "low energy requirement devices from it", i.e. LED lighting, battery chargers for cell phone, remotes, pda's etc.
Kids rechargable games, Wii remotes, etc. all could be powered by transmitted energy.
As the energy and data are in teh same transmission, this really would add a great deal of flexibility to the "ipod" type devices, or other media devices.
Hard power lines could be wired to large energy absorbing applications (ovens, AC, Refrigerator, etc) but the control circuitry for these systems could be wireless and controlled devices with essentially always charged batteries.
There are many interesting applications of thsi technology including the ability for example to power devices inside the body from external sources, or to recharge same without connections.
Pacemakers, defibrulators, coclear implants, etc. anything requiring relatively small amounts of power need not have replacement batteries.
This technology could also be used to incorporate data encryption to only allow 'registered devices" to use the power transmitted.
Only in the daytime
For induction, frequency affects the overall number of turns required. A 50Hz transformer that copes with 300W is the size of a shoe box, but for a switchmode power supply at 100KHz it's the size of a match box.
It's not so much the number of turns as it is how much metal you need as the transformer's core. That's why aircraft used 400 Hz generators and/or alternators instead of 50 or 60 Hz, because transformers and inductive filters could be made with less metal, which meant not just cheaper, but, of prime importance, lighter.
I see even classic Slashdot is now pretty much unusable on dial up anymore.
Current moving along (or through) a wire generates a magnetic field. If you coil up the wire you increase its inductance and that makes the field stronger by concentrating it in a smaller area.
If you move a magnetic field along that wire you generate a current in it. If you hold the field still and move the wire, same thing.
If I were looking to invent something I might look into how much current I could get by having a person carry a coil in their pocket as they move relative to the earth's magnetic field. In other words, moving around would recharge your cell phone. The question is how much moving around in how a long a period of time would be necessary.
I see even classic Slashdot is now pretty much unusable on dial up anymore.
My DC electricity instructor from decades ago was a radar technician for WW2 era radars, so periodically they would have to tune the antennas because frequency drift would induce standing-waves on the feed-lines. He told us that they would fire-up the radar transmitter, climb up the ladder and prune each dipole to null and that in the winter it would keep them warm enough to work in shirt-sleeves, well at least in England where the winters are usually milder . My guess is that this gismo might pull enough energy to keep an already charged Li-ion or a NiMH cell from discharging due to internal leakage, but if you expect more than that your going to be disappointed. Being able to charge a battery, put it on a shelf and having it still charged a week later is useful but not earth-shattering.
Apocalypse Cancelled, Sorry, No Ticket Refunds
A 50Hz transformer that copes with 300W is the size of a shoe box, but for a switchmode power supply at 100KHz it's the size of a match box.
That's because the transformer's core magnetic saturation level is inversely functional to the frequency, so the lower the frequency the more metal you need, the number of turns isn't affected to a significant degree unless your using tuned coils. 50Hz transformers don't get as big as a shoe box until your at a 1KW or better
Apocalypse Cancelled, Sorry, No Ticket Refunds
I have a Lith-Ion cell batter right here rated for 800mAh. So with an output of 50mW. We could say 5V at 10mA for the charger, 80 hours.
Yet it wouldn't take much more power to drastically decrease that time and I am fairly confident that is possible as I'm reading this book from 1983, Chapter 14 is all about wireless energy transmission via a DIY device capable of powering a 20 watt florescent tube from several feet away.
Seems perfectly reasonable that we could achieve USB level output (500mA) from a wireless charger.
On the Oregon Cost born and raised, On the beach is where I spent most of my days