The minor rants thread.
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Actually, there will be degradation to the power/range of the router. Will it be enough to notice? I'm not sure, I've never played around with a rectenna. But you can't just stick unlimited rectennas around a wifi router and expect a usable signal to still get out while also harvesting an unlimited amount of electricity from the electromagnetic waves the router is putting out.
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I suppose that you could reason like this if, for example, one side of your router is facing the street so you have no need for any signal there anyway.
But if you deploy this as a stationary energy-harvest-technique I think it sort of defeats the purpose. Get one of these:
and blow instead.
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Supposedly you could also use a rectenna ~3 feet long to power a light bulb if you live next to power lines.
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It does sound counter intuitive. There is the inverse square law that dictates that the signal will get weaker with distance. But here is the empirical evidence:
You have a broadcast tower emitting radio waves for, say, TV. That tower is surrounded by houses with TV aerials. Allowing for the signal to not be physically blocked, and even then you get attenuation rather "no signal", house further out can still receive the signal. Yes, up real close they are receiving at a different angle, but there comes a point where line of sight is virtually flat.
The above conditions not withstanding, however many closer house then receive the signal, the outer houses still get it. It is similar with cable, but the attenuation rate is higher.
In short: because of the way that radio waves are propagated, total Output Power is not equal to the sum of the Received Power. In fact the only effect the Output Power has is in the amount of energy it can transfer to wave propagation.
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It does sound counter intuitive. There is the inverse square law that dictates that the signal will get weaker with distance. But here is the empirical evidence:
You have a broadcast tower emitting radio waves for, say, TV. That tower is surrounded by houses with TV aerials. Allowing for the signal to not be physically blocked, and even then you get attenuation rather "no signal", house further out can still receive the signal. Yes, up real close they are receiving at a different angle, but there comes a point where line of sight is virtually flat.
The above conditions not withstanding, however many closer house then receive the signal, the outer houses still get it. It is similar with cable, but the attenuation rate is higher.
In short: because of the way that radio waves are propagated, total Output Power is not equal to the sum of the Received Power. In fact the only effect the Output Power has is in the amount of energy it can transfer to wave propagation.
Because the signal's being absorbed by small antennas, not the entire houses. If you stick a shitton of small antennas all over a broadcast tower, the signal's going to be affected, because they're going to be absorbing the signal and converting it to electrical energy.
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@Mikael_Svahnberg Or get a hamster.
@Fox Been there, done that. Get a simple bare neon bulb
fix to a stick and wave it around. If it glows at all you are surrounded by RF; If it glows brightly you are in a strong RF field; if it explodes, your kidneys or eyeballs are sure to follow.
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And now you're talking about magnetic flux
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What's the emoji for "I give up"?
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Rectennas don't require motion, just radio waves. Magnetic flux requires motion, and magnetic fields. There's a very important difference between the two.
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nail the fucker to a radio mast and watch it glow, only don't choose a mast attached to a moving vehicle because it will provide evidence to support your thesis.
No... wait.... the Earth is moving about its own axis of rotation, and is moving in a orbit around its Sun, which is in orbit in its Galexy, which is moving (or not) in it's Universe.
Damn! an Bugger!
Dear King Canute,
I empathise with your feeling of helplessness in the face of the inevitable tide.
Yours, Loose.
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relative motion is what drives magnetic flux, not absolute motion.
edit: actually, it does appear that neon bulbs on their own do act like very small rectennas. my apologies, I'd never fiddled with them before, either.
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magnetic flux
If you're getting power out, you're talking about varying magnetic flux, and so there will also be a varying electric field. Can't have one without the other.
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The thing about broadcast power is: If I deploy something like this near my router I will have 100 µW of free power (not what they claim, but for the purposes of illustration). If I deploy 10 of them, I will have 1 mW of free power. WITHOUT any degradation to the power / range of the router. Buttuming, I don't block the signal.
INB4: Again for the purposes of illustration, I am buttuming a 100% lossless environment
You do block/degrade the signal. Where exactly do you think the energy you siphoned off comes from? The electrons you just pushed into moving will create a counteracting EM field.
Go look up Lenz's law.
And to think that I even predicted that he'd fall for this when I mentioned "Free Energy".
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Rectennas don't require motion, just radio waves. Magnetic flux requires motion, and magnetic fields.
It does not (necessarily) require motion, just a change in the field. A changing magnetic field induces a changing electric field, and vice versa. The change in the field may be due to motion, as in the moving parts of a generator or alternator, or it may be due to changing current in a conductor (which is what causes an antenna to radiate radio waves). As @dkf wrote, you can't have one without the other.
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Electricity from the air - Drayson's big idea
Free energy from the air. It sounds like a fantasy but that is what entrepreneur Lord Drayson has just unveiled at London's Royal Institution.
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Which part of "the energy density is way too low" did you not grasp?
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"it's recycling the energy which isn't being used at the moment"
- That article
The article itself even points out that it uses energy. This isn't an unlimited energy source, and if a bunch of people start using it, it probably will have a significant effect on wifi signals, 4G, radio, etc.
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You're talking to someone who seriously proposed that this checkcard sized thing, even if he used ten of them, would not reduce the signal strength of his router in any way.
Fun experiment: Take a strong, rod-shaped magnet (Neodymium based ones work just fine) and let it fall through a copper tube. You'll wait quite a bit until it reaches the bottom.
He'd probably insist that this is magic because the energy to brake the magnet comes from seemingly nowhere :)
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Fucking magnets, how do they work?!
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Indeed. I'd link a video I made where I used a bunch of n=1600 induction coils and LEDs to show the induction current created by the falling magnet - but a) I'm "starring" in it and b) it has my real name tacked on it ;)
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Hah, on this forum, I don't blame you there.
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Strip the identifying info ? i want to see this now...
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Will see. Not today, though, getting a bit late :)
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Ach, damn it. Here it is in all its glory:
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This isn't an unlimited energy source, and if a bunch of people start using it, it probably will have a significant effect on wifi signals, 4G, radio, etc
No, not really. The thing with these devices is they radiate the power in all directions, more or less, and radiate the same power whether or not a device is actually listening--or gathering.
Suppose his device is 100' from a WiFi, at 0°. His device can't gather the power radiated in the 3° direction or even the -3° direction; it can only harvest that energy that comes directly to its antenna. It's not a broom that can sweep in radio waves, it's a dustpan that captures whatever radio wave slides in the opening.
So his system won't affect other devices--unless possibly the device is directly shaded by his device--but that can happen if you stand between the WiFi and a device, too.
It's an interesting approach, but the powered device has to have very low power operation to take advantage of it. Here's a story on a similar invention from 2013: the five cells run together capture about 750 milliwatts. They're about 2 square inches each; the whole 10 square inches probably won't recharge your cellphone (chargers today are 2 amps x 5 volts = 10,000 milliwatts).
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But it could power a small soft circuit built into your outfit...
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But it could power a small soft circuit built into your outfit...
Sure, and they've already shown that.
I would expect the biggest problem over the long haul would be the decreasing power of radio waves: all of our devices like WiFi are broadcasting less and less power as time goes on, so it'll get harder and harder to collect usable power. Then, if you're out of a city...even now, go to my old stomping grounds in northern Wyoming, and I doubt if his fancy collector could pull in enough to run a watch.
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Where do you get the 750 milliWatt from? That would be really impressive, considering that my own router only goes up to 500 mW signal strength (and is at 100 mW factory default for 2.4 GHz and at 200 mW in the 5 GHz band) and a UMTS phone only goes up to 2 W. That's the broadcast power sent into all directions. It's also sent in packets and not continuously. And before you say "oh, but it's multiple routers and cellphones", consider how the radio protocols work and that there are only so many channels.
Are you sure you meant to write "milli"? Because I'm pretty sure it should be "micro".
Plus, the morons of Duke University aren't even capable of using the proper terms:
They used a series of five fiberglass and copper energy conductors wired together on a circuit board to convert microwaves into 7.3V of electrical energy. By comparison, Universal Serial Bus (USB) chargers for small electronic devices provide about 5V of power. Link
"7.3 V of electrical energy". "5 V of power".
Geeze. Those guys are the reason I have to chase my pupils around with a big stick so they don't use voltage, current, power and energy without rhyme or reason.
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"7.3 V of electrical energy". "5 V of power".
Geeze. Those guys are the reason I have to chase my pupils around with a big stick so they don't use voltage, current, power and energy without rhyme or reason.
Next thing you know, they're bragging about how they made the Kessel run in under twelve parsecs.
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Where do you get the 750 milliWatt from?
It's probably powered by the misunderstanding of the difference between mW and microwatts. “But ‘m’ is for micro, right?”
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Nice play of words.
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Neat little table of prefixes in the article
INB4: Unless, of course, you would want to discredit the information because it comes from wikipedia. In which case try:
The information is in Section 4.3 (Page 7 - about 19 pages into the document)
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Much sense, your post it does not make.
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Then maybe you can explain where 750 mW of power are supposed to come from when a router only has a power output of 200 mW?
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I don't have to explain anything. I have made no claims. You initiated this by asking if a scientific claim is a scam. All I have done is state that the principle behind it is valid. If you want somebody to tell you it is a scam, then yeah, It is a scam.
No go and crawl back under under the slimy little rock you emerged from and take your ignorance and bigotry with you. In the UK we have a term for the likes of you: It is Luddite.
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And I NEVER stated that the scientific principles are invalid. Hell, I used those myself in the experiment I linked a video to!
I stated that the ECONOMIC principles behind the proposed applications are invalid.
Good grief. And we have an equal term for you: Ignorant moron who is incapable of reading.
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Congratulations. You are going to be the first forum member (of any forum) I have ever "muted". I am not doing this because you have chosen me, but because you choose others as well. You argue, reason and justify like a small child, and children should be seen and not heard. You need to grow up and grow a pair.
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Moron. There is no ignore function on this forum. You can only mute a thread.
And considering your willful ignorance of physics, good riddance. I'll weep with joy when you inevitably succumb to one free energy scam or another.
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You are going to be the first forum member (of any forum) I have ever "muted"
Man, you're going to be disappointed by muting someone on Discourse.
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This post is deleted!
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Where do you get the 750 milliWatt from?
Sorry, it was from another article that I decided not to link, based on the article I did link. They computed it by 7.3 V x 0.1 amperes. But now, of course, I find that there is no current figure in the article I did link, and, of course, I can't find the other article.I am sure it said milliwatts, but in retrospect, I think you're probably right: they probably meant 0.1 microamps.
Which makes this a mea culpa since, also in retrospect, I should have considered any such massive figure suspect.
Still, you can do a lot with .1 microamp these days, with ultra-low power circuitry targeting down to the 5nA regions.
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This post is deleted!
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While that is certainly true, I was ranting against the linked applications. I mean, they displayed a wristwatch (with an active display) and a security camera on a movable head. That's something well beyond the power of those siphoning devices, particularly considering that it has to be checkcard-sized which makes it a bit of a no-go in case of the watch.
And the other application they proposed, the smoke detector: While that may work, a smoke detector has to be reliable. This device does not provide a reliable source of energy. Which means you need to include a buffer which in turn means that you can use a battery which makes the whole thing useless.
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Job site for IT professionals done wrong:
Also, there's an editor box to add a "message" (cover letter, I assume) to a specific application — that has copy/cut/paste from both keyboard and right-click disabled. However, the editor has a clipboard button. Does it paste the text on your clipboard? No, but it pops up an alert that Ctrl+V is now enabled.
?
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Rectennas don't require motion, just radio waves. Magnetic flux requires motion, and magnetic fields.
just out of curiosity. what do you think "radio waves" are?
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Great video!
we need more physics teachers doing this kind of things
Metric prefix - Wikipedia
