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Researchers Power a Security Camera With Wi-Fi Signals
Kristine Lofgren writes: Nikola Tesla dreamed of a world full of free, wireless power. While he never accomplished that dream during his lifetime, researchers at the University of Washington are doing their part to make it a reality with a breakthrough in wi-fi powered electronics. Dubbed PoWi-Fi, the team led by Vamsi Talla were able to recharge and maintain consistent low-level power over a number of different devices at distances of up to 28 feet.
Nothing new to see, move on...
RF back-scatter energy collection has been used since Tesla (not the company, the scientist) invented it nearly 100 years ago.... So now you can park your web camera near a WiFi RF source and get some images out of it? Color me surprised. How quaint...
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
WTF do you consider "digital wifi"? It's RF. It's analog, modulated to carry digital information.
"National Security is the chief cause of national insecurity." - Celine's First Law
If you RTFA, they didn't just use a regular WiFi access point. They modified the AP so that in addition to one channel carrying data, there were another two radios on non-overlapping channels transmitting noise. Great for powering your thermostat, but horrible for your neighbors.
The spectrum is already crowded with most homes transmitting one channel - imagine if everyone stated transmitting three. The noise floor would go up drastically and WiFi would be rendered near inoperable.
well now there will soon be spy cameras everywhere
It's not a typo if you understood the meaning!
Like my digital circuits instructor was fond of saying... "Digital circuits are just Analogue circuits that spend most of their time on or off. The fun begins when they start switching states".
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
I mean seriously, if you dont think this site has gone downhill just take a look at the questions here.
Don't RFIDs already work this way? They don't continuously power those, not because they can't but because it's wasteful. I wonder if they considered energy use during their test?
As someone with a reputation of knowing how electronics work among friends and relatives I am often asked to fix issues of interference on wireless devices. What is often the case is the baby monitor, Wi-FI, cordless phone, and microwave oven all operate on the same frequency. Now we get someone that wants to power his toys by transmitting noise in that band.
The article claims that the test subjects saw no drop in their Wi-Fi access from the use of this device. I don't doubt the report, I just expect that this was not a real world test by having other common wireless devices operating at the same time.
I wonder if the "greenies" will latch onto this. Given the unrealistic claims of energy sources and power distribution systems from these people I expect someone will read this report and expect to see all the power lines in the world disappear and be replaced with antennas.
I am armed because I am free. I am free because I am armed.
There is an article over at New Scientist where they power devices with a hardware-modified router that delivers an extra 20 Watts on an unused channel. They claim to get around the FCC's 1 Watt limit by transmitting only a carrier wave.
Is that really how the regulation works? If I don't put any information in the signal, I can use all of the power that I want?
http://www.newscientist.com/ar...
According to the article referred to by this Slash Dot story, the received power is on the order of microwatts, while the camera requires milliwatts. Because of this, you need to wait many minutes between camera frames.
I think that if we are going to broadcast noise for the purpose of powering gadgets, we should dedicate some unused spectrum for this and not interfere with existing signals.
On another subject, I used to live within sight of a 50,000 Watt AM radio station. The signal used to get into the band's amplifiers. I bet that you could power a lot of gadgets from that monster.
Conversely, all analog circuits are digital, just different levels of quanta.
"National Security is the chief cause of national insecurity." - Celine's First Law
I think you are full of shit. Supply relavant FCC rules to redeem yourself.
As I recall they achieved this by "cheating" and broadcasting noise on the channels in order to generate more RF energy (i.e. there wasn't enough power because unless you probably aren't transmitting 100% of the time)
Evolution: love it or leave it
Health concerns?
"If any question why we died, Tell them because our fathers lied."
I wonder if the "greenies" will latch onto this. Given the unrealistic claims of energy sources and power distribution systems from these people I expect someone will read this report and expect to see all the power lines in the world disappear and be replaced with antennas.
General ignorance of inverse-square law and the order of magnitude between a fun experiment and practical applications.
Let's build central humidifiers in the home and sell wireless water systems to bring up the humidity to the point where little condensers installed in each faucet can deliver a steady stream of life-giving water from a series of packets called 'drips' --- enough to sustain an adult grasshopper. Since our wireless plumbing will be a tough sell, there is no escape from the scaling problem, we'll go on the offensive. We'll launch an ad campaign with a cute cartoon grasshopper that portrays him as the one true environmentalist living among a teeming mass of wasteful cartoon humans always drawn with their gaping gullets demanding a raging torrent of precious water, even as they're pissing it out the other end. To personify the grasshopper and dehumanize the people we'll give the little fellow expressive eyes, a top hat and cane, and the humans' eyes will be expressionless and button-like. The first market goal is to get folks to install at least one 'water base station' and wireless faucet in the home to prove their commitment to the environment.
Tesla was a bloomin' genius but his tech was noisier than hell and the global power concept unscalable and even IF we had a Krell technology generator at the top of the world , irresponsibly dangerous chemically and inductively. Tesla lived in a radio-quiet world that is not our world. We made this choice, to deliver energy in pipes, wires and tanks, leaving the ether quiet enough for true distance communication. It was a good choice.
This WiFi/Radio free-power-all-around-you idea is a parasitic vulture-culture where someone wants to get rich on a little idea whose unintended consequences exceed the benefits. Never mind the unworkable engineering, even the concept is creepy, sociopathic. If Walmarts were built with Faraday Shields that block communications from the outside people would consider it inconvenient to shop there. But the folks who want to fill the world with tiny parasitic power systems want them to become so ubiquitous that they are woven into the clothing and all, is an actual direct affront to that decision we have made to preserve the airwaves for communication.
A woman trapped in her vehicle, fatally injured and bloody after an automobile crash is attempting to dial 911. She is down in a ditch and at the extreme end of cell range, but she cannot manage to get a reliable connection. Finally she gives up and writes in her own blood on the dashboard her last message to the world. The headlights and shorted wires quickly drain the car's battery and all goes dark, except for a dim mesmerizing pattern of tiny LEDs dancing across her shirt. The shirt's designers needed to incorporate several band resonators into it to make it practical, and even bragged in their advertising that it became brighter every time you were on your cell phone, speaking to the one you love.
<blink>down the rabbit hole</blink>
Well, in theory, yes. Because an unmodulated carrier wave has zero bandwidth. The instant you modulate it (with any modulation type - AM, FM, other modes) it takes up a non-zero amount of bandwidth.
AM transmissions are an illustration of this - the standard AM transmitted over MW broadcast, or aircraft is known as double-sideband non-suppressed carrier - the carrier frequency consumes almost 75% of the power in an AM signal not doing anything useful (other than providing a trivially easy signal to lock onto for the tuner, which is why they transmit it). Single-sideband eliminates the carrier (suppressed-carrier) and half of the sideband (either upper or lower, referring to the frequency of the sideband compared to the carrier). This lets you use all the amplifer power for useful modulation, and halves bandwidth, at the expense of more complex receivers (which usually work by regenerating a local carrier and the other sideband, then doing a traditional demodulation).
Of course, it's all theoretical since to generate a perfect zero bandwidth carrier requires generating a perfect sinewave - practically impossible. Any distortions to the sinewave result in sidelobes and now make your signal not zero bandwidth.
Yeah, because all those things that need automating in a home are never connected to a power source and all those things doing the automating cannot possibly draw any power from the lines they are installed to switch on and off.