Thursday, June 22, 2017

EEV Blog takes on uBeam

Many readers of this blog will know the name EEVblog, it's a website and online forum for talking about  electronics run by Dave Jones, an Australian engineer. It's host to the uBeam FAQ, which puts together a lot of information on uBeam in one place. In addition to the forum, Dave makes videos where he delves into topics in a pretty entertaining manner, and for his 1000th video, he takes on uBeam.

Gotta say, he does a great job of covering the tech in an entertaining manner, not sure I could have done better myself.

An interesting point he makes is the difference between possible and practical, and it echoes a comment from one of my first posts a year ago that always seems to be missed:

"In theory, it can be done in limited cases, but in practice cost and efficiency issues will likely render it impractical." 

Enjoy the show.



Sunday, June 11, 2017

Arguing The Point


Someone on the internet is wrong. You wish to let that person know they are mistaken, as well as inform others to be sure they too do not mistakenly believe this to be true. How do you argue your point in an effective manner, disagreeing with someone, while maintaining civility? There's a good post on How to Disagree by Paul Graham which lays this out, and I'd like to touch on this, especially as it relates to science and engineering discussions.

We're living in a world where we are surrounded by incredibly complicated technology - sometimes the simpler that tech looks on the surface, the more complex it is. There's a large percentage of the population that would have a hard time explaining technology as old as the internal combustion engine in your car, and things get worse from there as you move through things we all use every day but barely know it - encryption and compression get the latest episode of 'House of Cards' onto your TV, but care to lay out how that happens for me? 

More importantly, how do you tell when someone is making false or exaggerated claims about technology? The facetious answer is "study for long enough to become an expert" however even then it's hard - there's a lot of technology out there, and only so many hours in the day. If you don't know the technology, and people are arguing about it, how do you evaluate the arguments they make? One way is to evaluate how they are arguing, even if you don't understand fully what they are saying.

The pyramid in the graphic above is an attempt to lay out Paul Graham's hierarchy (I have no idea where it's from, I'm not taking credit for it, thanks to whoever did it). The pyramid you see here contains the 'best' arguments at the top, the 'worst' at the bottom, and as you can see, it's wider at the base to represent that it's a lot easier to make the worst arguments than the best - 80% of everything, after all, is crap.

At the base it's fairly obvious - if one side is saying "the other guy is a doo-doo head" then they don't have much on their side. Sadly, you don't have to go to far above this for most people to lose critical thinking and an ability to evaluate what's being said. Ad Hominem is actually quite effective in discrediting a party with some audiences - for example saying "they're just a disgruntled former employee with an axe to grind" while ignoring any detailed points that person may have made, or whether they are even justified in being disgruntled. The most common form of argument is often simple Contradiction with no evidence to support it - "My client is innocent, and we're confident that the jury will agree." Frustratingly, we seem to be in a world where there's a media bias to he-said/she-said and placing the weight of argument 50/50, regardless of actual merit of the case.

I've never seen this fake-balance more brilliantly demonstrated than by John Oliver in this Daily Show segment on the Large Hadron Collider, and how there is a "50/50" chance the world would end when it was switched in. The part in question is at around 3:00, but I'd encourage you to watch the whole thing, it's John Oliver comic genius.


Dr Ellis is my hero here. Watch him start at the 'top of the pyramid' and refuse to be dragged down into what we're used to from media. He stays on topic, doesn't get tricked by Oliver (way harder than you might think), sticks to his point, and doesn't let himself be drawn into the arguments from the base of the pyramid. It's a short segment but really highlights how awful the media are in pushing junk science from those with limited understanding compared to those with deep knowledge - but where's the audience in that?

To further illustrate that point, and to show an example of an argument on a technical matter, let's take with this recent statement from uBeam 

uBeam is an innovation that will breed innovation. Ubiquitous wireless power will lead to a world with smaller batteries and thinner, lighter devices. With wires virtually eliminated, TVs can sit in the middle of a room cord-free and light fixtures will become “stick-on” without the need for routed power. uBeam is also a universal standard, making those bulky travel adapters a thing of the past. Imagine charging your phone, laptop or even your hearing aid virtually anywhere, without any effort. This is life powered by uBeam.

I'll take that one bolded point - that TVs can be powered wirelessly with ultrasound in the middle of a room and try and 'refute the central point'.

I'll begin by trying an argument against it:

"They're a bunch of stupid poopy heads" - No, that's bad, that would be Name-Calling

"They're just disgruntled current employees desperate to share their misery with the prospective employee and have no idea of the basics of physics" - No, that's Ad Hominem

"Powering a TV with ultrasound in the middle of a room is not a practical possibility, and is around one hundred times larger a problem than charging a phone in the same manner. While it is theoretically possible, the costs, inefficiency, and safety concerns are staggeringly high, while practical alternatives are low cost, and there is no economic demand to make this happen. Regulatory limits make it difficult in the US, and impossible outside the US." - OK, now we're doing somewhere between Contradiction and Counter Argument.

Let's move this to an argument from the 'top of the pyramid' by Refuting the Central Point

I'll begin by stating my assumptions:

We're talking about a large screen TV, not a small hand held. The TV is in a room you have some control over the infrastructure. The TV does not have a battery and needs a constant supply of power to work that can't be interrupted. From Energy Use Calculator I'm going to take 100 Watts as the power requirement for a 50 inch LED TV. We'll be assuming this is in the USA, and that the pre-2015 OSHA safety regulations are in effect and that in no location is sound over 145 dB used. Outside the USA the 115 dB limit give a transmitter and receiver 1000x area increase requirement. Note this will also apply within the USA should current OSHA limits restrict usage to 115 dB.

I will assume a generous 33% efficiency on receive, with 50% efficiency from transmitter to receiver incorporating both distance and angle of incidence. I will assume there is infinite power available into the transmitter and that efficiency from the wall socket to the ultrasound conversion is also 50%.

I assume each phone case sized receiver, at 5 by 10cm, uses $10 in parts, and we need to sell at 3x BOM to make money.

I'll ignore nonlinearity for the sake of simplicity, even though that's likely to become an issue, and limit the separation of transmitter and receiver to no more than a meter.

Now my calculations:

100 Watts powered means 300 Watts acoustic needs to be received. (100 Watts at 33% efficiency). This compares to around 0.5 Watts requirement for a phone, hence the "hundred times larger" comment. At 145 dB ultrasound is around 300 Watts/m2, meaning the receiver will need to be 1 m2 in size, that is a square of 1 meter on each side, or equivalent. A 50 inch TV is around 25 by 44 inches in size, (64 by 112cm or 0.72 m2)  so as a meter is around 40 inches, that means the receiver will be around 1.5 times the size of the TV. Ooops, better get to work on that efficiency.

Now a panel that's 1m2 is about the size of 200 phone cases, so around $2000 in parts, or $6000 in cost to sell and attach to that 50 inch TV, that costs around $500 right now.

The Transmitter needs to be twice the size of the receiver to take into account that 50% efficiency, so it's 2m2, and from the above calculation that means $12,000 for the transmitter.

Note that if the regulatory limit is 115 dB then the area scales by a factor of 1000 and the transmitter and receiver are each larger than the room.

For power supply, going with the efficiencies, the wall socket needs to provide 100 Watts, times 3 for the receiver efficiency, times 2 for the transmit efficiency, times 2 for the conversion efficiency, for a total of 1200 Watts. Fortunately this is (just) what a 110 volt 15 amp circuit can provide at 80% max load regulations allow (1300 Watts).

At 5 hours usage per day, and 12 cents/kWh average power cost in the USA, that's 72 cents per day to run, or $262, of which $22 is the actual TV use, the rest the wireless power system.

The additional 1100 Watts to use the wireless power system will be lost as heat (it's about a one bar electric fire equivalent), so in the winter that will save money, in the summer you'll need AC. I'll call it a wash to simplify this.

Summarizing the Argument:

Given the above, to power a TV wirelessly with ultrasound, it will cost $18,000 in the transmitter and receiver, with an additional $240 per year in running costs. Assuming efficiencies are as high as stated. And that no-one walks into the beam, since any interruption will make the TV switch off. And that you don't mind a receiver that's larger than the TV. And a transmitter that's twice that size and isn't too far from the TV. And that the room gets a bit warm. And that it's in the USA and the OSHA limits don't change to match the rest of the world.

But other than all that, isn't that much more awesome than running a $5 cord to the nearest outlet or paying someone to run a cable under your floorboards?

I think I'm going to call this "impractical".

OK, sarcasm over - I've run my calculations, providing all assumptions, workings, references etc so that anyone who disagrees can say "Your assumptions are faulty, here's what they should be" and then it's simple job to rerun those calculations get the new numbers, and judge from there. If anyone who is an advocate of wireless power would like to argue with these, feel free to correct me, and let's see where it takes the numbers. Or argue that my methodology is incorrect, I'm happy to do so - but like every other time in this blog where I have presented numbers, equations, and physics as core to my argument, I expect I'll be met with silence or more questions as to my motives. The top of the pyramid meeting with a response from the bottom.

My point to most people is this - if you don't understand the physics or details of a technical discussion like this, look to those presenting actual data, references, and their methodology and assumptions. If there is one side doing that, and the other calling names and questioning character, then you should likely consider one side's argument as superior to the other. If both are arguing methodology and data, then you may be watching a genuine scientific debate, which is good and healthy, it's what we want. If both are calling names, they're both idiots.


Monday, June 5, 2017

What Does It Take To Switch a "Phone Charging" Light On? Pt II

Following uBeam's demo, EEV Blog contributor Howard Long made a very interesting video showing how you can turn on a phone charge light with ultrasound. It's about 4 minutes long, with audio commentary, and gives more info in that 4 minutes than in the entirety of uBeam's demo. If this subject interests you at all, I encourage you to watch this.



From his comments (edited for brevity, read the whole thing here):

I could get it to light visibly with about 1mA at a distance of 2cm ... At 2cm distance, I had about 2mW, giving it a 2% efficiency. However, ... perhaps only 15-20% of the transmitted power appears at the rx anyway. So beam forming and reasoanably sized apertures on the receiver are essential facets for this to work.

... That camera thing is an Nvidia Jetson which looks like it's for visual device tracking. ... If it needs visual indication of where the target device is, and the sensors are on the rear of the phone, the phone will have to be used face down for a ceiling arrangement, and you won't be able to hold it in a normal fashion to make a call or use the screen. Even wall mounted, assuming nothing's in the way, you'll have to figure out new ways to hold your phone.

In its current form and key use, as a phone charger, this remains practically speaking a non-starter.

It seems an engineer reproduced a basic version of the uBeam demo in a day with about $20 in parts.

The phone charge indicator lights at 1mA, which implies 5mW (5 Volts supply) and so would take about 1000 hours (~6 weeks) to charge the phone - if it weren't for the pesky fact that a phone requires around 500mW to operate, on average, so it would make no appreciable charge effect at all. 

Now of course there's only a single element here, not a full array which could emit more power, but the key point is that a charging symbol tells you nothing about whether it is practically charging. You need voltage and current to know the actual power, and you need it at both transmitter and receiver to get efficiency (which he's calculating as 2% in this setup, pretty good actually for through air). Those are key numbers you need to have. From Howard's numbers 100 transmitters will get you that 500mW and maintain charge at a constant level, in an ideal world setup - possible but very large and introduce many questions on practicality and cost.

I like the way Howard also brings out a key point in this video - of course you can send power through the air by ultrasound. That's never been doubted or questioned, here or on the EEV Blog. What is questioned is how much power can be received, the efficiency of that, the safety aspect, the cost of transmitter and receiver, and the practicality for the user.

None of those points were addressed by uBeam, other than the emphasis on slow "trickle charging", implying the "faster than a wire" claims of 2015 aren't going to be happening.

Anyway, bravo to Howard Long for showing how to put together a short, clear, technically accurate demo from which you can actually learn something.

Friday, June 2, 2017

What Does It Take To Switch a "Phone Charging" Light On?

A few follow up points on the post from yesterday on the uBeam wireless charging.

I did like seeing this quote from the journalist:

Asked why the battery percentage didn’t appear to increase rapidly, Perry shakes her head.

“You’re thinking about it the wrong way, this is about a paradigm shift,” she says. “If you’re moving from your car to a coffee shop to work and your phone is charging while you’re using it, it’s no long about what percentage you’re at. You could stay at 1% all day.”

So it's an artful dodge of the question (that the journalist didn't press on), and perhaps an admission that the charge rate is not 'faster than a wire' as has been stated before by uBeam. It's more the "trickle charge" route, where you get tiny amounts of power over a long period of time. That "faster than a wire" claim was made at a time when the company was stating 1.5 Watts minimum charging which is much more than "trickle charge", and would fully fill your phone in 3 to 4 hours. Saying you stay at the same charge rate all day implies you are charging at an overall average of around 0.5 Watts, including all the times you are not around any uBeam transmitters, but if the charge rate is much greater than 0.5 Watts, why not say?

I noticed in that article the transmitter and receiver 'prototypes' back then in November 2015 were much smaller as well.


If there is actually a "trickle charge" regime, then the phones need charged as they are in use, and most use is a person standing or sitting holding the phone, fingers around the back, at around 45 degrees. Given line of sight, and assuming the 'bezel free front' of most modern phones, this implies the transmitters will need to be on the floor or base of the wall to get access, but will also likely be cluttered. Fingers on the phone case will prevent charging - unless of course you want to hold your phone by the edges as you use it (unlike in the picture above). I'm not seeing how trickle charge works with a mobile user, you need rapid charge in such circumstances. The practicality here, I'm not seeing. Maybe uBeam can layout the actual use-case scenarios they envision?

Also interesting was the quote from technical adviser Matt O'Donnell:

“When Meredith called me in 2015, I was curious and skeptical as hell, because you just hadn’t seen efficient airborne transducers,” says O’Donnell, dean emeritus at the University of Washington’s college of engineering, who now serves as uBeam’s chief technology advisor. “But holy moly, the leaps they’ve made in the past 18 months have been impressive.”

Hmmm, so all this advancement was made in the last 18 months, they had much, much less back then. But I'm confused because in September 2015 uBeam made this statement (among others):

“We’re at a massive inflection point,” said 26-year old uBeam co-founder and Chief Executive Meredith Perry. “We are about to head into a completely new phase of growth.”...In order to ease the transition into production, uBeam said today it has hired former Cisco Vice President of Supply Chain Management Jeff Devine as chief operating officer...“When we were seeking out an operations candidate we were looking at someone with decades of experience from taking a product from prototype to production,” said Perry. “He’s going to be the one that’s going to help us take this from our small shop to what will become our massive multi-million (unit) production next year.”

So which of those is true? Production ready in September 2015, or not? As with the "faster than a wire" claims from 2015 there are some implications as to 'perception vs reality' over the last few years if what Prof O'Donnell says is accurate. (COO Devine left his role at uBeam earlier this year before 'inflection' happened). For a further point of reference, I left the company at roughly the time these claims were being made.

The current receiver case is pretty interesting too. Looking at it, I'd guess 6 by 11 by 1.5cm which is larger than the phone itself, for around 100 cm^3 of volume. A standard battery for a Galaxy S5 is about 15cm^3 so you could have around 7 of those packed into that volume, giving you around 4 days of continuous use before recharging, and would cost about $70. If uBeam are using Murata (or Murata style) transducers in that case, there's around 60 of them at $3 each, so $180 just in transducers there. I'm not seeing the practicality or economics here.

(For those wondering - Murata are the primary maker of the parking sensors that are used in many cars, using ultrasound as the detection method. They're the small circles you see on bumpers, and individually look like cylinders about 1 cm each in diameter and height. They sell millions of them every years to the auto industry, and are around $3 each in bulk. You can go buy them yourself if you like.)

I did notice they have two different arrays that are used at different times, and I wonder if they are operating in the same manner, or if they are specced to handle different test conditions, and what is seen in these demos can't all be done on the one demo system. It's a little hard to tell from the videos as shown.

Now I could make a few more comments, especially on the posters in the background of the video and what they give away, but that's just going way too detailed even for my blog. 


Last point for now - the above picture shows a Kindle Fire on the right, and if you look in the bottom it's indicating "charging", but what rate is it charging at? 4.62 volts and 10 mAmps - basically  under 50 mW. To give you an idea of what that amount is, a typical phone batter is in the 5 to 6 Wh range, which means at this rate it would take over 100 hours to charge your phone at that rate. That's also assuming the phone is switched off, as it's typically consuming at around 500 mW so without that level of 'charging' it's consuming power faster than it's receiving it. I'm not seeing the practicality if that's the case. (A demo of a charging indicator coming on can be found in a newer post, here)

All this indicates is that the floor to show a device charge light come on is not the same as actually charging it - you need to see something like the screen on the left with voltage and current to know actual charging rate. This floor varies by device (iPhone seems to trigger at a higher floor than Android, and the floor varies with charge level IIRC), it's possible it's charging much faster (faster than a wire even?), but if it is, why not say?

As has been said before - physics doesn't prevent you sending power via ultrasound, or RF like Energous does, but can you send enough power to be useful, safely, efficiently, simply, and cost effectively?

Thursday, June 1, 2017

Someone was paying attention

Almost immediately after my article yesterday, it looks like someone at uBeam was paying attention and actually did a proper, adult, professional PR piece and got the company onto the front page of USA Today. Much less embarrassing! :) It does also show part of my article was wrong - at least some people care!

To very quickly give a summary:

Reporters buy a phone at a local outlet to use charging (shows phone isn't tampered with, well done), put it in the brick case, and get the charge light to come on. Shows a device with an IR camera for tracking. Done with more than one phone at around 4 feet. They go on to say:

The technology is at least a year away from commercialization, and it faces significant hurdles from ever getting out the door of this 30-person start-up. Even though it can at present power a handful of phones, it's not clear what leaps need to be made to charge a busy coffee shop. And consumer questions will linger about safety as well as cost.

So at least they maintain some skepticism.

In the short time I have available this morning, and I'll update later tonight, I'll make the following comments:

In all this time, have reporters still not learned to press on the key questions? "How much power is being received?", "How much is being sent?", "What's the efficiency?", "How much does it cost?", "Have you proved it safe?", and "If this is what you have now, what were all those 'prototypes' you were talking about 2 years ago?". But those are actual questions that matter, and basically we know the same today as we did yesterday (which indicates it was an awesome PR piece, lots of coverage with no actual info).

Technically, it's still hard to say exactly what's being done, and there's not much to add beyond my earlier articles. The video does make it look like off-the-shelf Murata devices are being used and focused into a tight beam straightforward. Efficiency and safety questions are dodged.

Is this enough to convince someone to put more money in? Most likely, so let's see if someone big enough to price a round steps up or if it's smaller less sophisticated investors again.