EEVblog Electronics Community Forum
EEVblog => EEVblog Specific => Topic started by: EEVblog on January 30, 2021, 01:44:53 pm
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Dave debunks the Xiaomi Mi Air wireless charging system that claims to be able to charge at 5W up the several meters using mm wave RF beam steering technology.
Where have we heard this before?
https://www.youtube.com/watch?v=X6JDOXjvKAI (https://www.youtube.com/watch?v=X6JDOXjvKAI)
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Indeed - RF interference generators. Hopelessly inefficient. No doubt inventors have some magic new law of physics they are exploiting - like near-field optimal coupling or electromagnetic missiles or something.
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That much power is not safe. It will burn your cornea.
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This Xiaomi thing is so mind-boggingly stupid that it hurts.
The main points you're making are all good points, and they basically converge to this device being completely unpractical.
Still something that tickles me here. You're saying that this thing can be made safe. That, IMHO, remains to be seen. Do you really want a several-hundred Watts 5GHz emitter in your own home? That's crazy.
I suggest the following reading: https://pubmed.ncbi.nlm.nih.gov/17929264/
Penetration @5GHz may look marginal, but it still seems enough to penetrate the dermis layer. With such high-power emitters a couple away from you for extended periods of time, I would personally not sign if I had to take responsibility for the consequences. I just don't know, and from the last studies about this, it still seems unconclusive, which means we don't know. Hundreds of Watts is a fricking lot of power.
Beyond safety issues, I'm also curious how you can design such a device, again for "home" use, while passing all correspondingl EMI and RF regulations. That's probably very tricky. Managing that would look like a feat of engineering.
Now I can see why this is the holy grail of electricity distribution. Many people probably see the future of that as houses with only wireless electricity transfer, and no plugs, for which this thing is just a preamble. Tesla envisioned the exact same thing a century ago, and it didn't really end up well. Sure technology has dramatically improved, but the laws of physics look stubborn.
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Still something that tickles me here. You're saying that this thing can be made safe. That, IMHO, remains to be seen. Do you really want a several-hundred Watts 5GHz emitter in your own home? That's crazy.
It was Shahriar that said it could potentially be made safe, and he's a world expert on this stuff. So I was willing to give them that concession that's it's possible.
As I said in the video, personally I don't think that's possible, and I wouldn't use it even if they did.
It's almost certain that for it to be made safe you'd have to cripple it so much it would be useless in all but the most ideal scenarios, which is doomed to be the case anyway regardless of the safety issue.
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This is technology tragicomedy...
Don't sell your copper stocks just yet. :(
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I don't know, but I think this has nothing to do with Xiaomi, but somebody impersonating them.
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I don't know, but I think this has nothing to do with Xiaomi, but somebody impersonating them.
It is also on -what seems to be- the official Xiaomi website. In a different thread forum member Blueskull predicts that this is a product which will be for sale soon because Xiaomi is not the type of firm to announce a product they don't have ready for sale.
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Entirely possible, beside two side effects : electricity bills and fried cats.
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Sorry for being Cpt. Obvious, but...
Free-running 500W radiation source kind of makes me worried or should I say horrified.
Imagine what it does to all things and living beings around besides specially designed phone charger. :palm:
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Maybe it would be more practical to make a "recharge drone" that follows you around, with a charging cable dangling down to your phone. When its battery is done, it would automatically fly back to its own charger.
:-DD
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Why would one want a wireless slow charger:
I see mainly 2 scenarios for charging:
A) slow over night with phone a fixed place
B) fast charging because the battery is empty due to unusual use - than it is usually about getting energy in as fast as possible.
One may even need external cooling for the phone than - no extra 50% of extra loss for a RF retifier.
Usually this happens rarely - so not about compfort.
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Why would one want a wireless slow charger:
I see mainly 2 scenarios for charging:
A) slow over night with phone a fixed place
B) fast charging because the battery is empty due to unusual use - than it is usually about getting energy in as fast as possible.
One may even need external cooling for the phone than - no extra 50% of extra loss for a RF retifier.
Usually this happens rarely - so not about compfort.
For the slow overnight charge, it could be a Qi charger in the bedroom or whatever...
Why not try a different approach: a charging cable that is much easier to plug and unplug than a USB cable? I have never understood why phones have to have the fiddliest possible connector for charging... just so they can save the cost of one extra jack? Really? .... :palm:
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Why not try a different approach: a charging cable that is much easier to plug and unplug than a USB cable? I have never understood why phones have to have the fiddliest possible connector for charging... just so they can save the cost of one extra jack? Really? .... :palm:
IMHO USB-C is easier to plug/unplug compared to micro-USB. The connector is bigger and there is no up or down side of the connector.
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Why not try a different approach: a charging cable that is much easier to plug and unplug than a USB cable? I have never understood why phones have to have the fiddliest possible connector for charging... just so they can save the cost of one extra jack? Really? .... :palm:
IMHO USB-C is easier to plug/unplug compared to micro-USB. The connector is bigger and there is no up or down side of the connector.
You still have to hold it at an exact zero or 180 degree angle to insert... Unlike a round power connector, for example.
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The usual round connectors are a bit large for the usual thin phones. The time when they decided to use USB for charging was just when the phones got thinner. It also made sense to use USB, as it was a common standard also for data transfer - now data can go wireless, but this does not mean power also has to go wireless.
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The usual round connectors are a bit large for the usual thin phones. The time when they decided to use USB for charging was just when the phones got thinner. It also made sense to use USB, as it was a common standard also for data transfer - now data can go wireless, but this does not mean power also has to go wireless.
I'd buy a somewhat thicker phone with a significantly bigger battery and a round charger jack... and an external SD card slot too, for good measure!
But that is not on offer from any of the manufacturers, their focus groups all ended up on paper thin phones as being super cool. Which they are, but I don't like the price (in terms of battery life, lack of ports, fiddly connectors, and the rest of it).
I have put a larger capacity battery on an old Samsung S5, which now runs for 5 days on a charge - it is now twice as thick - but it is the best phone I've ever had!
I'm going to try to rig up a Qi charger for this setup, that would make it 'Perfect'!
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Having made some wireless power transfer products myself for centimeter distances I was interested in whether a longer range is feasible. And this seems to be the case. This paper https://www.researchgate.net/publication/304372625_Magnetic_beamforming_for_wireless_power_transfer (https://www.researchgate.net/publication/304372625_Magnetic_beamforming_for_wireless_power_transfer) discusses the results of an experimental magnetic beamforming setup where they transfer 25W over a distance of 1 meter while achieving an efficiency of over 75% and power levels of up to 35W (but at lower efficiency; IMO probably due to copper and switching losses).
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Just waiting for the day when lawmakers make replaceable batteries compulsary. Or the day when fat batteries become common again. I hate the camera nipples. It make the lens get scratched up easier and it'll make cameras be recessed again
I wonder if and why, no one does "back of the envelope" calculations before thinking of making such stuff.
They can make a fully functioning phone but somehow they can't do that, is surprising.
Ideally, companies don't do anything, that they can't make money out of.
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How is it with lower wattage, e.g. 0.5 or even 3 W. If you use different electronic parts to amplify the low wattage (and some other heavy engineering), using one or two bigger patch antennas (with bigger I mean around 20x20 cm something maybe), and use a lower frequency than the 5 GHz you mentioned, can't it be possible to charge a phone (as an example) over about 0.5-1 meter, maybe more/less ??? Isn't there a way to improve this technology because it is an interesting method but does have some limitations, which I realised after watching your video.
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You still have to hold it at an exact zero or 180 degree angle to insert... Unlike a round power connector, for example.
There is some crazy invention available: magnetic USB-plugs (available e.g. as USB C) and magnetic cable, rotating. A bit like Apples Magsafe, but only 2-wires. Downside would be no highspeed charging.
Just google for "magnetic usb adapter".