Author Topic: The uBeam FAQ  (Read 268119 times)

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Offline Dubbie

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Re: The uBeam FAQ
« Reply #950 on: July 31, 2017, 06:46:29 am »
Being fat nullifies the advantage of being blonde.

Comments like this make you look like a cruel ignorant dick.

There are plenty of legitimate reasons to critique uBeam. Stick to those.

R
 

Online Howardlong

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Re: The uBeam FAQ
« Reply #951 on: July 31, 2017, 06:59:57 am »
Where were they intending to use the ASIC(s)? I assume just in the handset receiver. I remember thinking they were trying to run before they could walk by jumping straight in with ASICs as soon as they'd received funding. The same applies to the production and operations call centre appointment, that must've been a busy role.
 

Offline brainwash

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Re: The uBeam FAQ
« Reply #952 on: July 31, 2017, 07:17:20 am »
I think the project has been debunked in every possible way. But assuming it would be feasible, could you take e-car batteries to a rock concert and charge them? Or just buy a couple of pairs of these devices and hook one up in your house and take another one to the concert - then you can power your home remotely! It would be a bit difficult for the receiver to track you but you can activate the Google location service. There's a new idea for those indiegogo campaign videos!

On a more serious note, my 2.4GHz band is overwhelmed now, I can count at least 20 routers at all times, probably at least 100 devices, and that's just on WiFi. If I turn my Bluetooth on I can see a dozen Samsung TVs at the top of the list, haven't scrolled down yet. Unfortunately, a lot of my 802.11 devices are stuck on 2.4GHz. Really, any new wireless innovation has to think this contention through.
I set up a 433Mhz receiver to feed decoded signals into my rPi, but I shut it down as soon as the database got to a few hundred megabytes (one week). Wonder how many remote sockets and thermostats I can control just by replaying those signals.
 
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Online Howardlong

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Re: The uBeam FAQ
« Reply #953 on: July 31, 2017, 07:39:13 am »
The only way I've reliably defeated 2.4GHz noise floor increase in-spectrum is to increase the number of APs and let devices roam between them. I use the same SSID and access on all my APs for this purpose.

This takes us back to the interesting "r^2" comment in the recent twitter spat (#913). Perry was correct in my view, to point out 1/r^2, and Matthew Ocko made quite the dick of himself trying to explain it away as Twitter-speak, a bit of a "covfefe" moment. Maybe it is Twitter-speak, but I don't see any other reference to it. Either way, clearly this spat wasn't his finest hour, not least by trying to erase it ever happened.
 

Offline coppice

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Re: The uBeam FAQ
« Reply #954 on: July 31, 2017, 08:11:45 am »
This takes us back to the interesting "r^2" comment in the recent twitter spat (#913). Perry was correct in my view, to point out 1/r^2, and Matthew Ocko made quite the dick of himself trying to explain it away as Twitter-speak, a bit of a "covfefe" moment. Maybe it is Twitter-speak, but I don't see any other reference to it. Either way, clearly this spat wasn't his finest hour, not least by trying to erase it ever happened.
Engineers generally refer to r-squared loses, not 1/r^2. What Perry said makes no sense. She said the r-squared issue doesn't matter with a tightly focussed beam, but r-squared loses apply regardless of the beam width.
 

Offline StillTrying

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Re: The uBeam FAQ
« Reply #955 on: July 31, 2017, 08:27:21 am »
Perry was correct in my view, to point out 1/r^2,

She might have been correct in saying 1/r^2 doesn't count much for tightly focused beams, but she didn't say that uBeen were producing tightly focused beams.
Reminds me of the 2 or 3 last videos with the 2 prototypes, it was her that described all the conclusions, and told the reporter what he had seen, just like a magician.

And I don't think any of the 'steerable beams' we saw in the videos were outside the normal beam of a US transducer, and as they're quite directional it's a problem.
« Last Edit: July 31, 2017, 01:03:16 pm by StillTrying »
 

Online EEVblog

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Re: The uBeam FAQ
« Reply #956 on: July 31, 2017, 08:51:21 am »
Perry was correct in my view, to point out 1/r^2,
She might have been correct in saying 1/r^2 doesn't count much for tightly focused beams, but she didn't say that uBeen were producing tightly focused beams.
Reminds me of the 2 or 3 last videos with the 2 prototypes, it was her that described all the conclusions, and told the reported what he had seen, just like a magician.
And I don't think any of the 'steerable beams' we saw in the videos were outside the normal beam of a US transducer, and as they're quite directional it's a problem.

Let's just assume for kicks that have a perfectly steerable beam (they do have some beam forming in the huge basement model, done by the custom ASIC) that is 100% focused.
You still have the show-stopping problems of efficiency, cost, safety, and receiver angle alignment in practical usage.
Is there any product idea that's possible "in principle" and yet has so many show-stopping problems?
Even Hyperloop has fewer show-stoppers, and that's saying something.
 

Offline brainwash

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Re: The uBeam FAQ
« Reply #957 on: July 31, 2017, 09:35:40 am »
As a theoretical question, I've seen some papers where the ultrasonic power transfer efficiency at 20kHz is 70-90%, but I cannot find any data on the efficiency of a phased array setup, even for radio. I can instinctively think that there is some power loss in the side lobes as well as some loss because there isn't an infinite number of radiators, but what's the ballpark we are talking about? Assuming a 16x16 or maybe 64x64 array, I doubt anything consumer-related can go higher than this.
 

Online EEVblog

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Re: The uBeam FAQ
« Reply #958 on: July 31, 2017, 09:45:14 am »
As a theoretical question, I've seen some papers where the ultrasonic power transfer efficiency at 20kHz is 70-90%

Through what medium and what range?
There is a paper that shows about 3dB loss (i.e half power, 50%) per meter in air. Worse at higher levels due to saturation.
 

Online Fungus

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Re: The uBeam FAQ
« Reply #959 on: July 31, 2017, 09:53:04 am »
As a theoretical question, I've seen some papers where the ultrasonic power transfer efficiency at 20kHz is 70-90%

Sure, but:
* How much power were they transmitting?
* Over what distance?
* How big were the transducers?
 

Offline coppice

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Re: The uBeam FAQ
« Reply #960 on: July 31, 2017, 09:59:06 am »
As a theoretical question, I've seen some papers where the ultrasonic power transfer efficiency at 20kHz is 70-90%
That sounds high for for the efficiency transferring into air. You can get pretty high efficiency transferring into liquids, but getting high efficiency into gases is more of a challenge. Loses within liquids are generally much lower, too.
 

Offline amspire

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Re: The uBeam FAQ
« Reply #961 on: July 31, 2017, 10:04:34 am »
Assuming a 16x16 or maybe 64x64 array, I doubt anything consumer-related can go higher than this.
UBeam have been working towards a way to make arrays with thousands of elements "economical" but it hardly makes sense talking about what is economical in a consumer environment when they do not seem to have any technology that is practical in a consumer environment. This has always been a concept that needs the phone manufacturers lining up to integrate into their products and given that UBeam are now talking about maintaining the charge rather then boosting the charge, I cannot see why any manufacturer would even start to look at it.
 

Offline brainwash

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Re: The uBeam FAQ
« Reply #962 on: July 31, 2017, 10:17:00 am »
I don't know where I got the 70-90% figures from, it was a table inside a scientific paper, I think they were determining the efficiency for cleaning (so liquid medium). Does not matter much, I'm sure there are plenty of studies on that.
My question was about the phased array efficiency, I can't find any data on that, much less on ultrasonic ones (used in medical equipment). Just as a ballpark, for example: 90% at 90 degrees (head-on) in vacuum, 70% at 45 degrees, with an array of 64x64. Celsius degrees, of course (joking).
 

Online EEVblog

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Re: The uBeam FAQ
« Reply #963 on: July 31, 2017, 11:11:41 am »
Assuming a 16x16 or maybe 64x64 array, I doubt anything consumer-related can go higher than this.
UBeam have been working towards a way to make arrays with thousands of elements "economical" but it hardly makes sense talking about what is economical in a consumer environment when they do not seem to have any technology that is practical in a consumer environment. This has always been a concept that needs the phone manufacturers lining up to integrate into their products and given that UBeam are now talking about maintaining the charge rather then boosting the charge, I cannot see why any manufacturer would even start to look at it.

They won't, their engineers will laugh their arses off.
 

Offline StillTrying

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Re: The uBeam FAQ
« Reply #964 on: July 31, 2017, 12:56:25 pm »
My question was about the phased array efficiency, I can't find any data on that, much less on ultrasonic ones

Including the word radar helps, there's quite a few old pdfs out there, which don't help much, there's nothing I've found on ultrasonic arrays efficiency, probably because it's a stupid way to try to transfer leccy power!

I still think uBeen's efficiency is about the same as it's practicability, < 0.1%
« Last Edit: July 31, 2017, 01:04:26 pm by StillTrying »
 

Online Howardlong

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Re: The uBeam FAQ
« Reply #965 on: August 01, 2017, 12:50:46 am »
This takes us back to the interesting "r^2" comment in the recent twitter spat (#913). Perry was correct in my view, to point out 1/r^2, and Matthew Ocko made quite the dick of himself trying to explain it away as Twitter-speak, a bit of a "covfefe" moment. Maybe it is Twitter-speak, but I don't see any other reference to it. Either way, clearly this spat wasn't his finest hour, not least by trying to erase it ever happened.
Engineers generally refer to r-squared loses, not 1/r^2. What Perry said makes no sense. She said the r-squared issue doesn't matter with a tightly focussed beam, but r-squared loses apply regardless of the beam width.

Ocko didn't say "R^2 losses", he said "R^2 math" and then said it was Twitter-speak. Had he said "R^2 losses" I'd agree.

On the point of the tightly focussed beam, in the far field, I agree 1/r^2 applies, but considering the aperture size, this is still in the Fresnel near field.
 

Offline coppice

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Re: The uBeam FAQ
« Reply #966 on: August 01, 2017, 05:11:00 am »
This takes us back to the interesting "r^2" comment in the recent twitter spat (#913). Perry was correct in my view, to point out 1/r^2, and Matthew Ocko made quite the dick of himself trying to explain it away as Twitter-speak, a bit of a "covfefe" moment. Maybe it is Twitter-speak, but I don't see any other reference to it. Either way, clearly this spat wasn't his finest hour, not least by trying to erase it ever happened.
Engineers generally refer to r-squared loses, not 1/r^2. What Perry said makes no sense. She said the r-squared issue doesn't matter with a tightly focussed beam, but r-squared loses apply regardless of the beam width.

Ocko didn't say "R^2 losses", he said "R^2 math" and then said it was Twitter-speak. Had he said "R^2 losses" I'd agree.

On the point of the tightly focussed beam, in the far field, I agree 1/r^2 applies, but considering the aperture size, this is still in the Fresnel near field.
I don't think we know the frequency yet, but it has to be at least 40 or 50kHz. Let's say 50kHz. That means the wavelength is <7mm. How many wavelengths of near field do you think you will get? This is not a large emitter trying to produce a plane wavefront, where only the ends of the wavefront lead to divergence. Its an array trying to produce the tightest beam it can. It will diverge in an r^2 manner from a couple of wavelengths out.
 

Offline HackedFridgeMagnet

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Re: The uBeam FAQ
« Reply #967 on: August 01, 2017, 09:11:30 am »
But it is not a point source. covfefe.
 

Online Howardlong

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Re: The uBeam FAQ
« Reply #968 on: August 01, 2017, 05:29:33 pm »
This takes us back to the interesting "r^2" comment in the recent twitter spat (#913). Perry was correct in my view, to point out 1/r^2, and Matthew Ocko made quite the dick of himself trying to explain it away as Twitter-speak, a bit of a "covfefe" moment. Maybe it is Twitter-speak, but I don't see any other reference to it. Either way, clearly this spat wasn't his finest hour, not least by trying to erase it ever happened.
Engineers generally refer to r-squared loses, not 1/r^2. What Perry said makes no sense. She said the r-squared issue doesn't matter with a tightly focussed beam, but r-squared loses apply regardless of the beam width.

Ocko didn't say "R^2 losses", he said "R^2 math" and then said it was Twitter-speak. Had he said "R^2 losses" I'd agree.

On the point of the tightly focussed beam, in the far field, I agree 1/r^2 applies, but considering the aperture size, this is still in the Fresnel near field.
I don't think we know the frequency yet, but it has to be at least 40 or 50kHz. Let's say 50kHz. That means the wavelength is <7mm. How many wavelengths of near field do you think you will get? This is not a large emitter trying to produce a plane wavefront, where only the ends of the wavefront lead to divergence. Its an array trying to produce the tightest beam it can. It will diverge in an r^2 manner from a couple of wavelengths out.

You're assuming a single point source, this is a phased array, so there are interference effects dependent on both wavelength, as you say, but also the aperture size.

Consider the complex interference patterns of the ~ 1,000 element radiator, when phased appropriately there are going to be some very hot spots where the wavefronts interfere constructively by design, and where they converge it will also depend on the distance from the radiator.

Although there is a transition region where both near field and far field effects are considered relevant, the near field is typically defined as the Fraunhofer distance, 2*D^2/L where D is the largest dimension of the radiator and L is the wavelength.

Given your frequency, and a maximum linear aperture dimension of, say, 0.5m:

c=340 (speed of sound m/s)
D=0.5 (maximum aperture dimension)
f=50000 (frequency)
L=0.0068 (wavelength)

gives the extent of the near field as 73.5m, so I'd suggest for this application's use cases, and in the demonstrations given, we're well inside the near field where we should be considering interference effects well ahead of far field concerns.

Edit: My experience is in RF, it looks like acoustics refer the the near field differently, i.e. D^2/(4L). This gives a near field distance of 9.2m, so the use cases are still well within the near field with the amended definition (from https://en.wikipedia.org/wiki/Phased_array_ultrasonics)
« Last Edit: August 01, 2017, 06:02:42 pm by Howardlong »
 

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Re: The uBeam FAQ
« Reply #969 on: August 01, 2017, 07:14:28 pm »
I don't think we know the frequency yet, but it has to be at least 40 or 50kHz.

We do know:
https://techcrunch.com/2015/11/07/wireless-power-charger/

Quote
45kHz to 75kHz with an output of 145dB to 155dB (or 316 W/m2 – 3kW/m2)
 

Offline JimRemington

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Hearing loss, U.S. diplomats in Havana
« Reply #970 on: August 10, 2017, 12:51:26 pm »
Quote
The two-year-old U.S. diplomatic relationship with Cuba was roiled Wednesday by what U.S. officials say was a string of bizarre incidents that left a group of American diplomats in Havana with severe hearing loss attributed to a covert sonic device.

https://www.washingtonpost.com/world/national-security/us-expels-2-cuban-diplomats-after-incidents-in-cuba/2017/08/09/

I wonder: intense ultrasonic beams?
 

Offline StillTrying

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Re: The uBeam FAQ
« Reply #971 on: August 11, 2017, 01:15:51 am »
Ubeen are very quiet, they must all be heads down hard at work gearing up for mass production, arranging mass distribution and marketing networks.  :horse:

http://www.olympus-ims.com/en/ndt-tutorials/transducers/focusing/

Online EEVblog

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Re: The uBeam FAQ
« Reply #972 on: August 11, 2017, 07:48:26 am »
Some idiot gave her more money?  :-//

 

Offline StillTrying

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Re: The uBeam FAQ
« Reply #973 on: August 11, 2017, 07:51:36 am »
Looks like she reads this thread!  :horse:

Offline djos

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Re: The uBeam FAQ
« Reply #974 on: August 11, 2017, 08:17:19 am »
Some idiot gave her more money?  :-//



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The impossible often has a kind of integrity which the merely improbable lacks.
 


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