Read more.Highly sensitive diodes have been developed by Fujitsu, JSP and TMU for IoT devices.
Read more.Highly sensitive diodes have been developed by Fujitsu, JSP and TMU for IoT devices.
Didn't fully understand a word of that, but it sounds something like "stuff what dun't need batt'ries"...?
If so, then that sounds really quite cool.
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Originally Posted by Mark Tyson
Oooooh, now this is exciting!
I can imagine entire digital farmlands with sensors powered by the local radio mast and other benign stuff!
Will this not have an adverse effect on the waves it takes power from? Those microwaves are being used to transmit data, so won't this lower the effectiveness of the wifi/data coverage in that area as it's being absorbed?
By taking power from one part of the wave it does not affect the rest of the wave. What could happen is any devices behind a device between it and the antenna would have a dramatically reduce signal strength.
But this technology is not a sinkhole for the whole signal, it only picks up from the wave at the part it has been hit by.
In short, no, it would not have an adverse affect as a whole.
Good explanation. I think one way to look at it is like how a dark rug placed in a room doesn't absorb all the light emitted from a light bulb in the ceiling. The room might be a tad darker as a whole (compared to if the rug was white) but you'd still be able to read your book fine.
I dare say an RF engineer will correct me, but I think that the diode in the setup will tend to rectify the incoming radio signal, and re-broadcast it at double the frequency.
eg: if the IoT device is tuned to harvest power from the 2.4 GHz band, then we could start seeing lots of RF noise at 4.8 GHz
(This effect is used by a nonlinear junction detector to detect covert listening devices, as all electronics contain diodes, so if you broadcast at one frequency and get noise back at double the frequency, you know that there is some electronics nearby).
Devices powered entirely by incoming radio waves are nothing new, crystal radios have been around since the 1920s. I was given a crystal radio kit, as a small boy in the late 60s.
Indeed, I built one as a kid. The difference is that they want to take this stuff and, instead of just sending waves to a speaker at low power, generate power and use it to power a low power device. This kind of thing is everywhere, in RFID tags and was even used in bugs that were powered by directed, modified radar kit. The idea here is to use ambient ~RF stuff to generate useful power which can run an IC and associated stuff.
I call utter tripe. The maths is doable on the back of an envelope and so far has never been viable. It's a lovely idea but it's almost like free energy in how idealistic it is.
I'm actually quite sure there will be a place for this kind of stuff and R&D is worthwhile but it's gonna stay in the lab for a very long time until power consumption seriously drops. The idea that you can use ambient RF to power a current or even near-future generation RF Tx device at any useful range is, at the moment, trying to break the laws of thermodynamics. You're always asking for more power than you can put in if you want the thing to be of any use.
If someone can show me maths that proves this can work in the real world, I'm happy to read it. Everything I've seen so far just says no chance.
They say in the article a "power source for sensors". You may be able to power your sensor, but how are you going to do anything useful with that? The processor and the ability to transfer or write the data will not be practically powerable by this. If you're going to write it to NAND then you'll have to access the device to get the data off it and then you might as well replace the battery. You're seriously better off using a button cell battery which can last years in these low powered applications and given you have to have these units exposed (inaccessible usually means attenuated waves and therefore no useful harvesting and also a high transmission power requirement which will exceed the capabilities of this kind of device), you might as well have them serviceable every couple of years... which they'll probably need anyway. There will be no way of powering an inaccessible device to an extent that allows it to broadcast a useful distance / through materials using this kind of thing. Short range, yes. Maybe, in future, directional stuff with lower requirements. Right now? Just no.
Please, feel free to cut me down and tell me I'm an idiot if you have the maths to back it up. I am an idiot and I'm more than willing to accept that. I've got a crazy Auzzie electronics engineer who did the maths on this and always seems to be proven right.
Am I going mad?
EDIT:
https://www.youtube.com/watch?v=P8s3Xjeg0sk
Remember that they're saying 10% of the coverage area of a mast will be usable.... so what do you not have around masts? Obstructions. They're up high away from anything which could get in the way. They are up high and if that 10% is area and not actual distance...... it just can't work.
EDITEDIT: Also, the order of tens of microwatts are what I work in with pacemakers which are minature computers these days and can transmit short distances and so on. The batteries in these things are around 3000mAH. This generation are currently looking at lasting nearly 20 years... This product just isn't useful when you can do that reliably.
Last edited by philehidiot; 24-09-2019 at 09:56 PM. Reason: adding invitation to squish my idiocy.
There is no maths yet because they haven't released the soecifications of how their nanowire filaments work.
I do feel you are unjustly flaming a potential breakthrough in tech because you are basing your assumptions on current tech and how unviable that is right now across long distances without specialised hardware.
Also, you are forgetting that a lot of sensors that are solar powered go into deep sleep while the battery charges, wake up, take reading then deep sleep again. This power tech will take a similar focus.
This technology was proven as far back as the sixties but that was with dedicated power transfer microwave emitters. The tech in this article focuses on harvesting the power from much much lower power radio waves down to as much as 100nw. Wifi broadcasts at around 4/1W so having a sensitivity 2 orders of magnitude lower than a broadcasting source means the sensitivity and efficiency allows for a much high broadcast power conversion.
Cursory googling found the university of washington were able to power battery less tempersture sensors and cameras in 2015 up to 20 feet from general wifi. That means they were within quite a high wattage space in line of sight.
Again, this tech is to allow harvesting of energy when the waves have degraded through obstructions, air, weather etc.
I'm not sure your need for mathematics is quantifiable because the tech is proven it just needs to be drastically improved.
I wouldn't say I'm flaming it, I did say I can see a use in future.
The maths I've seen doesn't require a specific antennae. You look at the energy available at a given distance from a source / multiple sources and then you look at what is required to do something useful. You can absolutely mess with the antennae and so on to make it more efficient but at the moment I am unaware of anything that can transmit a useful distance with the energy that can be harvested from even an ideal source with an ideal 10cmx10cm antenna. Going beyond that isn't required as you can't take more energy out than is available to harvest. It's flaw at that level, you don't need to go beyond that because the ballpark figures tell you all you need to know. Yes it can work, absolutely and as you say, it was used in the 60s with that utterly awesome bug. The question isn't so much can it work, it's a matter of can you do anything useful with it.
At the moment, I'd say the limitations of the technology mean that you're better off just using a battery for almost every application. I do absolutely see a use for this in future and in limited applications. I expect that we may end up using something like this for active tagging. Imagine if you had a room full of perishable stock, all tagged and you could send a robot past each shelf, broadcasting a signal and get useful data back from a sensor in the packaging that monitored the condition of the food. You'd prefer that over a battery as there are no risks with contamination or temperatures ruining the battery or transport of lithium batteries. Make it cheap and convenient enough and that could make a big difference to food longevity. Add in beam forming - why not. Scale it up and take it domestic and replacing best before / use by dates with a phone type device would be a great way to reduce waste.
The way it's being pushed however, does not say to me this is a niche product with limited scope. I think it's one of those things which is genuinely awesome in some applications but is being pushed into greater service for marketing, investment and job protection.
How does it work in noob terms... as in within one or two sentences?
I'm imagining microwaves hitting and wiggling/vibrating this nanowire, which then generates power from the back and forth motion or perhaps turning a teeny tiny turbine, similar to how wave power works?
Obviously a long way off powering our electric vehicles and the like, but what would it take to power, say, my Casio DB36 watch?
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Originally Posted by Mark Tyson
Back in the '60s, I remember a transistor circuit using power from a strong radio station to drive a tuneable AM radio. Still using a sensitive crystal earpiece. Probably required an aerial the length of the garden though..
This circuit was along with ones like the matchbox/wristwatch radio. Early thoughts on miniaturisation. The long AM aerial required was a problem. (PP3 battery powered?) I find it a neat idea that mobiles now double up the headset lead as an FM aerial.
Indeed, but the recovery (switching) time limited the frequency response and increased power loss within the dive. Shortly diodes have a much faster switching speed and so the pier recovery is more efficient and possible at higher frequencies.
This new diode represents the next generation of device permitting operation at still higher frequencies and efficiencies.
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