WAVE: A cell phone that charges battery with wifi signal. - Page 1
Forum section: electronics / general

author: rthorntn
author_rank: Frequent Contributor
timestamp: March 28, 2015, 05:57:56 am
content: Another one:https://www.kickstarter.com/projects/945803481/wave-a-cell-phone-that-charges-battery-with-wifi-s/descriptionA modest $300K target!

author: zapta
author_rank: Super Contributor
timestamp: March 28, 2015, 06:46:03 am
content: Three of the 4 rewards are very feasible.

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 28, 2015, 06:47:29 am
content: great! but $499 to get a working unit? i'll wait mass production $15/pop. since charging time is not stated, i must assume it will be infinity...

author: AlfBaz
author_rank: Super Contributor
timestamp: March 28, 2015, 06:53:35 am
content: He'll never get the research done if he's going to piss away valuable time cooking swirly pastry

author: rthorntn
author_rank: Frequent Contributor
timestamp: March 28, 2015, 07:15:11 am
content: The $300K will be used for the final stages of R&D, lawyer fees, and marketing:R&D $10KLawyer fees $280KMarketing $10KHe has factored in lots of legal action coming his way

author: Dubbie
author_rank: Unknown
timestamp: March 29, 2015, 09:21:34 am
content: Considering the limit for wifi power output is a watt if you're lucky, he's going to need to buy a u-current from Dave to measure the tiny amount of power this thing will collect. I wonder if he plans to add solar panels to collect the power from the LEDs on the wifi router as well?

author: Dubbie
author_rank: Unknown
timestamp: March 29, 2015, 09:42:55 am
content: Haha! Couldn't get more relevant.The thing that made me laugh on his site is how his prototype aerial is huge, yet he talks about building an IC version of the thing.

author: SaabFAN
author_rank: Frequent Contributor
timestamp: March 31, 2015, 03:01:13 am
content: All he has to do, is to chose a different frequency-band: Radio-Transmitters in the long-wave to short-wave band. Haven't done any math on it, but several Transmitters in the Kilowatt (87,5 to 108Mhz), and a few at about 4 Megawatts should provide a large enough energy density to acutally do stuff.I remember building a radio once with a Kosmos Electronics Learning Kit (probably 20 years ago), which was completely powered by the energy it received via the antenna.You probably couldn't market such a device on Kickstarter though, because you couldn't use such words as "WiFi" and "Bluetooth" in the advertising^^

author: AG6QR
author_rank: Frequent Contributor
timestamp: March 31, 2015, 04:08:29 am
content: Quote from: SaabFAN on March 31, 2015, 03:01:13 amOnly if you're really close. The inverse square law makes it tough to extract significant power at a distance, especially if you have an antenna of reasonable size. To a first approximation, the percentage of the transmitter's output power which you can receive is no greater than the percentage of a full sphere which your antenna would cover, as viewed from an observer at the transmitter's antenna site. Directional antennas pointed straight at you will change things a bit, but the inverse square law still causes serious problems if you're trying to harvest broadcast radio waves.QuoteYeah, crystal diode radios do work, but they only produce enough output power to drive a small and efficient earphone, and they normally require a pretty long wire antenna and a pretty powerful nearby station to do even that.

author: Nerull
author_rank: Frequent Contributor
timestamp: April 02, 2015, 12:00:26 am
content: Crystal radios operate on microwatts to nanowatts. Apparently a good modern one can receive at 50 picowatts. Good luck charging a phone with that. Unless you're standing next to it, even a MW transmitter isn't outputting useful amounts of energy into an area the size of a phone. Certainly not an IC.For a 4MW transmitter operating at 100MHz, you're looking at energy densities of under 1mW/cm2at a distance of only 400m. There are transmitter towers taller than that (not many, but some).FM transmitters are limited to 100kW in the US, unless grandfathered in. Digital TV is 1MW, and most don't that high.

author: Muxr
author_rank: Super Contributor
timestamp: April 05, 2015, 03:14:59 pm
content: The best part of the video is that he admits stealing his neighbor's Wifi haha.Trust me with your $300k funding folks!

author: codeboy2k
author_rank: Super Contributor
timestamp: April 06, 2015, 06:28:37 am
content: The thing is with many of these guys doing similar things (including all the free energy guys) is they do something that harvests some volts from the sky (or some spinning device), and when they see the volts they think they can do meaningful work with it, without understanding the power equation.The problem is, 90% of the world also doesn't understand the power equation, so their willing to throw money at these guys.Kickstarter needs independant review teams that can comment directly on the project page, regarding the viability of a project and the risks of completion or non-completion, especially the technical ones. Of course, that won't happen, since KS would not get as much income then.

author: Gavin Melville
author_rank: Contributor
timestamp: April 13, 2015, 04:41:30 am
content: I invested $5 to become a backer. The guy is a little sensitive to any suggestion it's not going to work.Ty Williams says:Ok, so what's the point of your spam? And why would you pledge to back a project if you think it's a scam? I have clearly stated I'm in beginning R&D, and posted a video of the project. Time us too valuable to waste. If you don't like a project, that's why there is the option to not back it.

author: BlueBill
author_rank: Regular Contributor
timestamp: April 13, 2015, 04:53:05 am
content: Quote from: Gavin Melville on April 13, 2015, 04:41:30 amNice. Kickstarter is becoming a joke.

author: rthorntn
author_rank: Frequent Contributor
timestamp: April 13, 2015, 05:05:06 am
content: Where did he "pluck" the $300,000 figure from, I wonder

author: BlueBill
author_rank: Regular Contributor
timestamp: April 13, 2015, 02:13:21 pm
content: Quote from: rthorntn on April 13, 2015, 05:05:06 amMaybe more financial sense than electronic savvy.

author: Gavin Melville
author_rank: Contributor
timestamp: April 13, 2015, 10:55:55 pm
content: The other little issue that he has not considered, is that most Wifi versions are DSSS. You can't even see the signal without reversing (demodulating) the spreading process - it just looks like noise. The coding gain for 802.11b (for example) is 10 odd dB. 802.11n is OFDM, but spreading the TX power across many low powered carriers is making recovering energy harder, not easier. Those little carriers are not in phase....While recovering usable power from a non modulated single frequency RF source is hard, it might, with gain antennas, short range and careful management of losses be possible to get a little power transmitted.Spread spectrum, 2.4 GHz, low gain transmit antennas (you can't choose that one) and all sorts of path losses, simply impossible.There's possibly a reason that all wireless charging schemes use modulated magnetic fields.

author: zerorisers
author_rank: Regular Contributor
timestamp: April 15, 2015, 04:13:30 pm
content: Quote from: Muxr on April 05, 2015, 03:14:59 pmMaybe thats what his mass lawer budget is for!

author: Gavin Melville
author_rank: Contributor
timestamp: April 20, 2015, 10:11:50 pm
content: Yes!!This is a message from Kickstarter’s Integrity team. We’re writing to notify you that the WAVE: A cell phone that charges itself, using wifi signal., project has been suspended, and your $5.00 USD pledge has been canceled. A review of the project uncovered evidence that it broke Kickstarter's rules. We may suspend projects when they demonstrate one or more of the following:Accordingly, all funding has been stopped and backers will not be charged for their pledges. No further action is required on your part.We take the integrity of the Kickstarter system very seriously. We only suspend projects when we find strong evidence that they are misrepresenting themselves or otherwise violating the letter or spirit of Kickstarter's rules. As a policy, we do not offer comment on project suspensions beyond what is stated in this message.

author: rthorntn
author_rank: Frequent Contributor
timestamp: April 21, 2015, 06:40:33 am
content: Cool at least one example of common sense at play in the Kickstarter integrity team!

author: codeboy2k
author_rank: Super Contributor
timestamp: April 21, 2015, 03:48:42 pm
content: Quote from: Gavin Melville on April 20, 2015, 10:11:50 pmJust for kicks, they should change their group name to theThe Kickstarter Gravity Integrity Team. It would be so much more applicable to the free energy guys... Keeping the world safe from violations of the Laws of Physics and the inadvertent and untimely creation of large, scary black holes.

author: bitwelder
author_rank: Super Contributor
timestamp: April 21, 2015, 05:27:45 pm
content: Quote from: mojo-chan on April 21, 2015, 09:00:21 amI've done the same. As I backed so far on 3 IGG campaigns, I received as many request for feedback to IGG.In every one of them I replied my wish that IGG would not accept campaigns for freaking solar roadways and the likes, as they reduce their own reputation and those of seriously designed projects. I doubt it will have an effect but anyway...

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 21, 2015, 05:32:52 pm
content: Now if only someone would invent a car that would re-fuel by driving by a gas station (or a gasoline truck).

author: JimRemington
author_rank: Regular Contributor
timestamp: April 21, 2015, 06:02:35 pm
content: Funding was suspended for this project a few hours ago!https://www.kickstarter.com/projects/945803481/wave-a-cell-phone-that-charges-battery-with-wifi-s/descriptionDoes anyone know if it is possible to learn the reasons?

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 21, 2015, 06:08:07 pm
content: Quote from: JimRemington on April 21, 2015, 06:02:35 pmYes, @Gavin Melville posted the suspension news yesterday (in case you missed it).In the message he quoted from KS, they said (in part): "As a policy, we do not offer comment on project suspensions beyond what is stated in this message." q.v.

author: PeterFW
author_rank: Frequent Contributor
timestamp: April 21, 2015, 08:23:36 pm
content: Quote from: JimRemington on April 21, 2015, 06:02:35 pmHow much more reasond do you need besides this:It was allready linked in this thread.

author: rickey1990
author_rank: Regular Contributor
timestamp: April 21, 2015, 08:33:59 pm
content: The project has been stopped, id just like to say to the guy doing this project not to give up on it, im no free energy nut, but i understand the importance of taking something useless and making it into something useful.So here is some information and some other stuff which might be helpful to you or anyone wanting to per sue something similar, In which you could make a product for a dollar and them sell cheap and in big numbers.Heres a pdf of a microwave energy collector by Dukes University, may look a little overwhelming but all a Meta material is, is a piece of fibreglass with copper tracings on top.http://dukespace.lib.duke.edu/dspace/handle/10161/8006I have also attached a picture of the simplified circuit and would also recommend looking up fractal antenna design as this will increase the range of signals the board can collect. (Also just a fort, there's all that microwave background radiation floating around from the big bang)https://www.google.co.uk/search?q=fractal+antenna&espv=2&biw=1517&bih=692&source=lnms&tbm=isch&sa=X&ei=HrI2VfrVJ8PT7QbMw4CgAg&ved=0CAYQ_AUoAQ&dpr=0.9Hope this helps,Rickey

author: tom66
author_rank: Super Contributor
timestamp: April 21, 2015, 08:39:43 pm
content: This is simply a case of the laws of physics. "If you open your mind too much your brain may fall out." This product cannot harvest ausefulamount of power. No one is denying it may harvest some power.For example, a typical wifi base station has an output power of ~100mW when transmitting and the power is spread quite well over the transmit bandwidth. A typical phone charger is rated at 5W. Minimum USB charge supported by most phones is 0.45A @ 5V, i.e. ~2W. So even if you could harvest 100% most phones would not charge and the self-discharge rate (my phone lasts ~1.5days between charges if unused) would likely exceed this for any modern phone. It gets worse when you introduce the inverse square law, the power received at just 1m will be measured in milliwatts, essentially useless.

author: Nerull
author_rank: Frequent Contributor
timestamp: April 24, 2015, 11:42:37 pm
content: Quote from: rickey1990 on April 21, 2015, 08:33:59 pmIf you come up with a super meta material antenna able to harvest 100% of RF-energy passing through it...it still won't harvest enough power to charge a phone unless you literally wrap it around the TX antenna of a over-legal-limit router. Harvesting the RF energy isn't the problem, there just isn't enough of it to be useful.

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 25, 2015, 12:04:51 am
content: Quote from: rickey1990 on April 21, 2015, 08:33:59 pmYou (and Mr. Williams) really don't seem to grasp the orders-of-magnitude difference between what it takes to charge a cell phone battery and what you can reasonably expect to harvest in an average urban environment. If you spent the rest of your life and never turned on your phone, you MIGHT "harvest" enough energy to keep up with the self-drain rate of the battery. And do you really want to carry around an antenna the size of a giant pizza box?Anyone who understands the actual numbers can see in a glance that this is just pure fantasy. Sorry to burst your bubble. Do you really think that if this were possible the billions of dollars available for R&D from the big cellphone makers wouldn't already be at work? If something seems too good to be true, that is usually because it IS.

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 25, 2015, 12:08:37 am
content: Quote from: mojo-chan on April 22, 2015, 09:14:00 amNot clear how that has anything to do with wireless charging (much less "energy harvesting").QuoteHave you not followed all the other discussions about wireless charging? It is typically not efficient enough to charge little cell phone batteries. Can you even imagine how much power would be wasted charging a big vehicle battery? Don't let any of the green/ecology/tree-huggers hear you talking about this!

author: helius
author_rank: Super Contributor
timestamp: April 25, 2015, 12:43:52 am
content: He's talking about inductive power transfer, which is widely used in different applications. The idea is that the car's automatic parking feature would be slaved to the inductive pad in such a way that it can drive over it exactly, since the inductive transfer is best when the two coils directly face each other.Inductive power transfer can be made highly efficient by matching the Q of the two inductors and putting them fairly close together. This has nothing to do with RF energy.

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 25, 2015, 12:53:06 am
content: Quote from: helius on April 25, 2015, 12:43:52 amI never mentioned "RF energy". Perhaps you are responding to someone else. When they are mandating near-zero quiescent current drain for cell chargers, do you really think that "highly efficient" resonant charging is even within 2 or 3 orders of magnitude? Got any actual numbers in mind?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 25, 2015, 02:12:23 am
content: Maybe another business opportunity. Kickstarter evaluator. Scores from 1 to -1. -1 is clearly violates laws of physics. Scores less than zero for things like this that don't directly violate physics, but the numbers don't come close to working. Small positive scores for things which might work, but aren't a slam dunk.Charge actual time spent evaluating. These stupid ideas can be evaluated in only a couple of minutes, so even a high hourly rate would only cost a few bucks. Could even try to cut a deal with Kickstarter which allowed sending a query to you with a mouseclick (percentage of your take or something like that).Might save a few idiots from losing their money, and reduce the number of idiots and scammers clogging up Kickstarter and other similar venues.

author: helius
author_rank: Super Contributor
timestamp: April 25, 2015, 06:36:41 pm
content: Quote from: Richard Crowley on April 25, 2015, 12:53:06 amYes, the efficiency is about the same as a galvanic connection when you control eddy currents in nearby objects.http://www.hybridcars.com/momentum-dynamics-wireless-charging-could-relegate-plugs-to-history/

author: gildasd
author_rank: Frequent Contributor
timestamp: May 08, 2015, 12:56:32 pm
content: In the free rag:Nikolalabs instead of Wave, but the same bullcrap...

author: rickey1990
author_rank: Regular Contributor
timestamp: May 08, 2015, 08:16:46 pm
content: QuoteMmm.... Well call me crazy, am I crazy :/ but i wasn't on about RF, But on that subject:I designed this device to capture radio waves, It gives me a constant 48V's @ 200ma Day and night 7 days a week (1 antenna) . 4 Antenna's can be attached to the device. increasing output. So its producing just under 10watts.Here is a example,"The iPhone 6 takes one hour 50 minutes using a 12 watt usb power adapter and the iPhone 6 Plus took 2 hours and 30 minutes. The iPhone 5, by comparison, took a similar amount of time to the iPhone 6"The question id like to leave to you, is can radio waves charge a cell phone?.But i will argue that radio-waves are not free sources of energy, so i am more for electrostatics.Check me out @http://empjammer.blogspot.co.uk/http://beambuilder.blogspot.co.uk/

author: Howardlong
author_rank: Super Contributor
timestamp: May 08, 2015, 08:28:17 pm
content: Quote from: rickey1990 on May 08, 2015, 08:16:46 pmWhat do you do to make it do that? Put it in the microwave?QuoteYes, if you have a microwave handy.

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 08, 2015, 08:31:11 pm
content: Sorry, @rickey1990, but I don't believe a word of it. Show us the demonstration.Even the USPTO requires a working model before they will issue a patent for a perpetual motion machine.

author: SeanB
author_rank: Super Contributor
timestamp: May 08, 2015, 10:11:55 pm
content: He probably is living 200m from a high power FM transmitter, in the near field that is probably strong enough to light a fluorescent lamp without the mains connected.

author: gildasd
author_rank: Frequent Contributor
timestamp: May 08, 2015, 10:37:23 pm
content: Quote from: SeanB on May 08, 2015, 10:11:55 pmOr his residential heating is microwave based.He should be careful about putting metal spoons in his coffee during winter.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: May 08, 2015, 10:56:24 pm
content: Quote from: rickey1990 on May 08, 2015, 08:16:46 pmNo, it doesn't. And if it does, you need to pack up and move to another home immediately because your innards are being cooked.Either that, or your antenna is the size of an office building.

author: djQUAN
author_rank: Frequent Contributor
timestamp: May 16, 2015, 05:31:39 pm
content: Stumbled across this on FB. Not sure if it is the same thing.http://www.sciencealert.com/iphone-case-chargers-the-phone-from-the-air

author: wraper
author_rank: Unknown
timestamp: May 16, 2015, 06:14:29 pm
content: Quote from: suicidaleggroll on May 08, 2015, 10:56:24 pmMaybe he lives in the front of powerful military radar

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 16, 2015, 09:55:03 pm
content: I propose that just as there is a "Godwin's Law" (http://en.wikipedia.org/wiki/Godwin%27s_law), there should be a "Tesla's Law" for discussions about "free energy" and "wireless power" and other such frivolities.

author: rthorntn
author_rank: Frequent Contributor
timestamp: June 01, 2015, 11:12:05 pm
content: http://www.newscientist.com/article/dn27633-gadgets-powered-wirelessly-at-home-with-a-simple-wifi-router.htmltl;dr"With Wi-Fi for communications, you only want to transmit when you have data to send," Talla says. "But for power delivery, you want to transmit something all the time. There's a clear mismatch."To get around this, the team designed software that broadcasts meaningless data across several Wi-Fi channels when no one is using the internet.Small devices could use this as part of an internet of things, says Ben Potter at the University of Reading, UK.

author: retrolefty
author_rank: Super Contributor
timestamp: June 01, 2015, 11:39:44 pm
content: Quote from: Richard Crowley on May 16, 2015, 09:55:03 pmAdd super caps to that new law and that would be worth having.

author: tom66
author_rank: Super Contributor
timestamp: June 02, 2015, 11:39:45 am
content: Quote from: retrolefty on June 01, 2015, 11:39:44 pmDon't forget graphene.

author: tom66
author_rank: Super Contributor
timestamp: June 02, 2015, 11:41:49 am
content: Quote from: rthorntn on June 01, 2015, 11:12:05 pmWat. So... We needlessly clutter the already cluttered 2.4GHz space so that people can gather a few mW to charge their phones. Not to mention the dreadful inefficiency of most 2.4GHz wifi routers (mine pulls 9W when active.)

author: edy
author_rank: Super Contributor
timestamp: June 02, 2015, 04:22:45 pm
content: I think we should use a hand-crank to charge the phone.... Like this idea....(photo3.jpg). Or maybe just a very big antenna to capture the WiFi radio waves...(photo4.jpg). Or even better a repurposed satellite dish to concentrate a larger reception field for radio waves to be captured by the phone which as you can see is held at the focal-point in this rig (photo5.jpg).

author: mikerj
author_rank: Super Contributor
timestamp: June 03, 2015, 11:32:09 am
content: Quote from: rthorntn on June 01, 2015, 11:12:05 pmThe University of Reading; that makes sense. I suspect they have some kind of cloning device for their academic staff which has been seeded with DNA from Kevin Warwick.

author: edy
author_rank: Super Contributor
timestamp: June 03, 2015, 01:09:41 pm
content: The surface area of a sphere is 4 x pi x radius^2. So even 1 meter out from a WiFi source the output would be spread across a sphere of 4pi.... 100 W source spread over an area of 12.57 meter squared. 1 meter Sq. Is 10,000 cm Sq. So the surface of a sphere 1 meter radius is 125700 cm squared. The 100 W is now 1/1257 or 0.8 mW per cm square.Let's round it to 1 mW per sq cm. Imagine a phone or let's be generous a tablet of 10 x 20 cm size. That is 200 cm sq so at 1 meter it will have 200 mW falling on it from the 100 W source.If we are 2 meters out we will have 1/4 the power per unit area than at 1 meter out (inverse square law). So at 2 meters the power capture is 50 mW on our huge phablet. At 3 meter it is 12.5 mW.... and so on.What is the FCC limit and what is the typical power of WiFi? Are these crude calculations valid? My understanding is WiFi cannot be over 1 W so we can already reduce the power by a factor of 100x.In the scenario above, 1 W source would provide a 10x20 cm area about 2 mW at 1 meter away. Phones are smaller than that. Nobody sits 1 meter from the WiFi. You may as well put it on an inductive charging pad. At 2 meters it is 0.5 mW. This is a factor of 1000x less than what is needed just to keep up with standby power consumption.Maybe these WiFi power sources need to be massively scaled up in power and used for very energy efficient sensor modules (not phones). To call it WiFi even is a joke because by the time it is implemented they aren't even using it for data transmission. They need it on full power all the time and maybe just in the WiFi spectrum. It is just a bad idea all around and trying to solve a problem that is not really a problem, only risking more of our health.

author: Howardlong
author_rank: Super Contributor
timestamp: June 05, 2015, 12:17:45 am
content: Before we all write the idea off as cranky, take a look at this POWIFI paperhttp://arxiv.org/pdf/1505.06815v1.pdfIt seems to have been covered in a number of popular news outlets, including several mainstream ones, over the past two or three days. I was on the tube this morning and noticed it in the Metro's pop sci section overlooking someone's shoulders. Brain said "bollocks", but I thought I'd look at the underlying details, from both what they're claiming it can do, and how they apparently achieve it.Once you get beyond the media hyperbole, the actual claims are rather more sensible. Furthermore, I spent half an hour or so with the back of an envelope and, against my gut feel, it does seem workable.Key to this is that the router needs modifying to transmit almost continuously at full power on multiple channels at times when the channels are not utilised for real traffic. The harvester end itself is actually quite simple but there have been some rather careful parts selections.But no, charging a mobile phone over WiFI, it's not going to happen unless you're prepared to wait an awfully long time and it's switched off while you do it.

author: Richard Crowley
author_rank: Super Contributor
timestamp: June 05, 2015, 03:15:36 am
content: Quote from: Howardlong on June 05, 2015, 12:17:45 amThat is a pretty good definition of the bad old days practices of the Communist-era jammers.A 2.4 GHz users that does anything resembling that will be VERY unpopular with their neigibors who are trying to use WiFi (or Bluetooth, etc.)Wishing something would work is not a viable alternative to understanding the laws of physics as we know them on this planet.We seem to be losing our grip on reality here, folks.

author: Howardlong
author_rank: Super Contributor
timestamp: June 05, 2015, 05:22:34 am
content: Quote from: Richard Crowley on June 05, 2015, 03:15:36 amDid you read the paper? That, and many other possible problems are specifically addressed in there, including its effects on channel bandwidth.Seriously, Istronglysuggest you read it before jumping to conclusions as I indeed did.http://arxiv.org/pdf/1505.06815v1.pdf

author: Richard Crowley
author_rank: Super Contributor
timestamp: June 05, 2015, 05:27:56 am
content: Quote from: Howardlong on June 05, 2015, 05:22:34 amIt wasn't my conclusion. It was yours.

author: Delta
author_rank: Super Contributor
timestamp: June 05, 2015, 11:16:26 am
content: Quote from: Howardlong on June 05, 2015, 12:17:45 amI've not yet read the paper, but surely you are always going to be limited by the max legally allowed ERP of the Tx, and the old bastard of the inverse square law...?

author: Howardlong
author_rank: Super Contributor
timestamp: June 05, 2015, 11:51:42 am
content: Quote from: Richard Crowley on June 05, 2015, 05:27:56 amCorrect, but I don't understand how you would have come to all of your conclusions had you read it in toto?

author: Howardlong
author_rank: Super Contributor
timestamp: June 05, 2015, 12:27:25 pm
content: Quote from: Delta on June 05, 2015, 11:16:26 amAll of this is dealt with in the paper if you read it, it is a good read, and, as I said I was most sceptical until I'd read it and done a few back of envelope calculations.The only thing glossed over in the paper as far as I can see is the energy harvesting matching network, although it appears to match reasonably well from their graphs. I can't see how it achieves this considering the rectifier after the matching network and the matching network itself.To reiterate, I smelt bullshit, tons of it, but there's little I can question having read it and run the numbers.Assume 3W* output (34.7dBm) aggregate across three non-overlapping channels and a 4dBi tx antenna and 0dBi receive antenna. Path loss over 17' is 54.5dB giving net -15.8dBm or 26.3uW at the receiver.At 50 ohm that is 0.036V rms or 0.10Vpp, the rectifier doubler gets that to 0.20V at 131uA peak so you're now well within the territory for energy harvesting capabilities of the BQ25570 (100mV min, operating quiescent current <500nA).So, in 30 minutes you can accumulate 26.3 x 60 x 30 = 47mJ.Alternatively, that's 47mW for 1 second, that's quite a lot of MCU processing these days.While my calculations assume 100% efficiency, they are there to show that this doesn't appear to be complete baloney.* edit: I would question the legality of running 3W from a single unit as a use case under FCC regs which specify 1W max. That does not stop the end user from deploying three 1W units themselves.Edit 2: To put this into perspective, this means it takes 10.6 hours to generate 1J. A typical phone battery is 5Wh, or 18kJ. It will take about 21 years to charge that battery assuming 100% efficiency and no self-discharge at a distance of 17'.On the other hand, if we place the energy harvester 2" away, the path loss is only 14dB, giving a power of 290mW. This would take 17.2 hours to charge a 5Wh battery assuming 100% efficiency.But then unlike other "products" the POWIFI is not claiming to be a phone charger.

author: Delta
author_rank: Super Contributor
timestamp: June 06, 2015, 09:27:48 pm
content: Quote from: Howardlong on June 05, 2015, 12:27:25 pmBollocks. Gain antennas on a bog standard wifi router? 3 Routers blasting illegal power? Zero losses in the whole system?Bollocks.

author: Richard Crowley
author_rank: Super Contributor
timestamp: June 06, 2015, 11:43:55 pm
content: Quote from: Delta on June 06, 2015, 09:27:48 pmAgree 1000%. You don't have to read the document to know that it is pure fiction.But apparently written well enough to fool many people who ought to know better.

author: Howardlong
author_rank: Super Contributor
timestamp: June 07, 2015, 02:46:27 pm
content: I am not saying there are zero losses in a real system.What I am stating is that the POWIFI thing is not complete baloney, they are in the ball park, well within an order of magnitude.Again, unlike other systems that are several orders of magnitude out, the POWIFI lot are not claiming they can charge a phone from 17'. They are claiming something very different. I hope that was clear.Where do you think the losses are, and of what magnitude do you think those losses are? RF magnitude losses are easily calculated, but I doubt that's the main source of loss* once path loss (54.5dB) is already accounted for: I would suggest that the rectifier and energy harvesting process will provide the largest losses in the system. Remember too that in real RF situations once in the ether there is both constructive and destructive interference particularly from reflections.I am a little surprised at the response considering I've done the figures in an open and objective manner. The reason I did it was because my gut feel said "bollocks" too. If you want to debunk it, please give it objective due consideration with reasonable and representative calculations.Regarding the gain antenna on the router, 4dBi is not at all unreasonable. Why do you think otherwise? Antenna theory and practice are well understood, and this is easily achievable, even a lambda/2 dipole gives you 2.15 dBi. All you're doing is taking a spherical radiation pattern and squashing it in the horizontal plane into a doughnut with the same volume, thus giving gain horizontally. In fact if anything, I'd say 4dBi is on the low side, 6dBi is the maximum legally allowed assuming 30dBm transmit power at the feedpoint giving an EIRP of 36dBm.So please, let's have your reasonable and representative figures debunking this! Without numbers, it's just a subjective opinion, and one that I shared originally too. It's not like I have a history of supporting these kinds of claims, quite the opposite in fact, I'm often the one debunking them myself, which is why I spent time looking at it in the first place!*edit to add: "once path loss (54.5dB) is already accounted for".

author: Richard Crowley
author_rank: Super Contributor
timestamp: June 07, 2015, 02:50:36 pm
content: Even "optimized" wireless charging with specially-made charging antennas on the devices, and placed INSIDE a "charging bowl" where a high-power signal is blasted into the bowl using an OUT-OF-BAND frequency (to not interfere with the primary communication channels) are having a hard time getting started. And even with massive funding by the big names in technology and consumer electronics. This IN-BAND "charging" scheme just fails on so many levels it is a waste of time to even discuss it.

author: Howardlong
author_rank: Super Contributor
timestamp: June 07, 2015, 03:24:52 pm
content: Quote from: Richard Crowley on June 07, 2015, 02:50:36 pmLook, I have a lot of respect for you, you have a proven career, but in this regard I really don't understand your blinkered stance. The figures are there. I am not sure whether it's because you are misunderstanding what the POWIFI folks are claiming, or if it's something else, but to just reject the claims, and not give an objective basis for that rejection doesn't stand up to scrutiny.I have no agenda to support their claims, in fact the whole point of me running the numbers to begin with was to discount them!Refusing to discuss it because "it fails on so many levels" and then not identifying what those failing levels are is no proof of failure. So far, the few objections raised have already been covered in the paper cited. For example, the DoS of the channels that was raised is a very valid concern, and it is very heavily addressed in the paper in terms of detailing the mitigation algorithms that are subsequently shown to work both quantitatively and qualitatively in empirical testing. No laws of physics have been broken, either. The math(s) is there, but please, if you think I've made a fundamental mistake in my calculations, let me know where that is and I'll re-run them and prove myself wrong.

author: Richard Crowley
author_rank: Super Contributor
timestamp: June 07, 2015, 04:23:51 pm
content: I gotta hand it to U-dub. If they are training their students in modern hand-waving they are doing an excellent job.A 24-hour "test" in their private homes is hardly a "real world" evaluation of the technique's impact on WiFi traffic. Lets see them install it for a couple months in six Starbucks coffee shops or some other high-traffic WiFi environment. The 2.4GHz ISM band is already becoming overloaded with users and adding communication-blocking wireless charging to the load just seems to me wildly abusive to a scarce resource.I admit that they could have a scheme for reducing the impacting blocking legitimate use of the bandwidth, but I can't see how they could ever make it transparent and zero-impact. And they could implement the scheme with only a change to the WiFi protocol and re-writing the firmware on the routers.But the biggest barrier to the scheme IMHO is the minuscule efficiency. Their examples show very low power, intermittently-operating devices or offline applications like trickle-charging batteries, etc. And in an age when the EC is demanding that even wall-wart chargers have near-zero power consumption when not in use, I can't see how this PoWiFi scheme could ever be practical for real-world high-power gadgets like cell phones.Why do you suppose that Tesla's wireless power schemes never got anywhere? There are reports that the Russians are trying to revive the scheme. Lets see how far they get.

author: gildasd
author_rank: Frequent Contributor
timestamp: June 07, 2015, 04:51:18 pm
content: I agree with Mr Crowley.Unless a radical new technology is brought to the table, these RF charging systems are not going anywhere.In military applications, using AESA antennas, it is possible to focus emission on another antenna to jam it.So, why not do one to charge our Iphones, golly gee!?But we are talking about systems that cost in the millions, use kWs of power, active cooling and would fry your brain if you were to step in front at close range...I'm pretty sure that if you manage to build an AESAish system in your shed, for a few thousand Euros, that manages to follow AND charge your Iphone in real time...While not burning you leg or dimming your neighbourhoods lights - of course.Then you won't need no kickstarter! THales, Hugues or BAE will shovel money at you and make you a job offer that you will simply not be able to refuse.edit:Looks rather more complex than a Wifi base station.

author: Howardlong
author_rank: Super Contributor
timestamp: June 07, 2015, 06:11:09 pm
content: Quote from: Richard Crowley on June 07, 2015, 04:23:51 pmWell, I don't think there's anything there I would disagree with. It is a wildly inefficient way of powering anything, the loss budget alone is already 50.5dB, or 0.0009% efficient, you are already better off with solar panel derived power and battery charging, using room lighting is going to generate more power than that from ISM 2.4GHz unless you leave your microwave oven's door open, and that technology has been successfully powering ultra low power devices like LCD calculators and watches for decades now.The key difference I've been reiterating which seems to have been lost is that unlike so many other schemes POWIFI were not claiming to be charging phones or breaking the laws of physics, they were just powering small ultra low power devices.But precisely as you say it's difficult to see where this technology would apply where, for example, something solar wouldn't be better, even indoors.

author: Howardlong
author_rank: Super Contributor
timestamp: June 07, 2015, 07:19:13 pm
content: Quote from: gildasd on June 07, 2015, 04:51:18 pmI saw one of those radar phased arrays in action at Lockheed Martin in Fort Worth, they had a permanent installation that pointed to DFW and used the commercial air transports as their test chickens a few miles away. There was a perimeter zone to avoid wondering into about 100' radius from the antenna. Serious hardware indeed.