Researchers Power a Security Camera With Wi-Fi Signals 59
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.
Mo bettah! (Score:1, Troll)
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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.
Gee this AGAIN? (Score:3, Informative)
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...
Re:Gee this AGAIN? (Score:4, Interesting)
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So, how are the CCD pixels supposed to be charged? By magic?
maybe your CCD pixels can use power from the CMOS sensors thats capturing the image? .. not sure why you would also put in CCD's sensors tho... seems wasteful.
Re:Gee this AGAIN? (Score:5, Insightful)
Cameras actually used to work like that! Of course, they used chemicals instead of electricity and each 'sensor' only worked for one image...
Re:Gee this AGAIN? (Score:5, Informative)
It's still in the early stages of research, but yes [columbia.edu] you can power a camera from light entering the lens.
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Do note that that only works when you have an external light source. Most security cameras have infrared LEDs to light up whatever they're supposed to be recording at night, when there isn't enough ambient light to record an image, much less power the camera. On top of that, any security camera recording anything important is going to be wired. If it's wireless, any burglar can defeat it with an RF no
RFIDs? (Score:2)
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?
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Smart RFID's harvest power from the radio signal, dumb RFID's just modulate the existing feild. Either way the distances involved are tiny - several centimeters, not meters.
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Smart RFID's harvest power from the radio signal, dumb RFID's just modulate the existing feild. Either way the distances involved are tiny - several centimeters, not meters.
Actually you would be wrong on the point about distance. UHF back-scatter RFID tags that are considered long-range with a 1-Watt 900MHz transmitter can achieve distances of several meters.
http://en.wikipedia.org/wiki/Radio-frequency_identification
From a table in the link:
433 MHz (UHF) Short Range Devices 1–100 m Moderate Part 7 Defense applications, with active tags $5
865-868 MHz (Europe)
902-928 MHz (North America) UHF ISM band 1–12 m Moderate to high Pa
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Agree. I've personally read 900MHz backscatter tags at more than 10m. I _think_ we used a 1W transmitter with a legal-limit (6 dBi) antenna, but it might've been a lower-power transmitter with a higher gain (narrower beamwidth) antenna. These were GEN-I tags from 10 years ago.
Title 47 Part 15 15.247(b)(3) and (4) [ecfr.gov]
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Build one or shut up.
Did when I was a kid.
http://en.wikipedia.org/wiki/C... [wikipedia.org]
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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".
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I mean seriously, if you dont think this site has gone downhill just take a look at the questions here.
Interesting experiment but deeply flawed (Score:5, Informative)
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.
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Great for powering your thermostat, but horrible for your neighbors.
If its great for me and my thermostat, I'm sure that they wouldnt mind that their thermostat also gets some free power on my dime.
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Unless they are trying to find a free channel for data and there just isn't one because 6 people around you are doing this all on different channels. Allocation of another part of the spectrum for power transmission: much better idea than trying to use the same ones as for data.
Using incidental energy that is being used for data transmission anyway - nothing wrong with that. Flooding data channels with noise, not so nice for other people around you.
If you think that is bad, check out this other one (Score:2)
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... [newscientist.com]
According to the article referred to by this Slash Dot story, the received power is on the order of microw
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I think you are full of shit. Supply relavant FCC rules to redeem yourself.
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Well, in theory, yes. Because an unmodulated carrier wave has zero bandwidth. The instant you modulate it (with any modulation type - AM, FM
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I did RTFA, and they did test the effect on their own and other networks and found it to be negligible. I'm a little sceptical because of the hidden transmitter problem, but they did at least consider it. Also, in an area where there is wifi congestion, you wouldn't need to transmit anything yourself anyway. For example, where I live the 2.4GHz band is pretty much saturated just by the beacon packets of all the APs in range, let alone traffic on top.
The main problem is that the amount of power they got is t
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this would suck on 2.4GHz, but the 5GHz range has more channels and less penetration, so it would seem like it'd be easier to find spectrum not in use without bothering the neighbors.
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Spy Cams (Score:2)
Re:Spy Cams (Score:5, Informative)
You'd be able to detect them, since all other WIFI signals in the vicinity would be horribly degraded by the modified AP spewing continuous noise on several channels.
They managed to take one 174x144 pixel black and white picture every 35 minutes at a distance of 5 metres. No transmitting of the image anywhere, it's stored locally.
You'd probably be able to do much better with one of those small solar cells from a calculator.
Great! More noise on ISM frequencies! (Score:2)
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 tha
Great! Let's move on to Wireless Plumbing! (Score:2)
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 [wikipedia.org] 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
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Nah, the greenies and crystal-suckers already claim that WiFi causes all sorts of diseases and conditions [google.com] - do you think they'll endorse even higher power Wifi transmitters? It might start interfering with their 'aura'.
fill in the blanks with noise.... (Score:2)
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)
Hmm (Score:1)
Health concerns?
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Let's be real here. Radio waves _can_ be harmful. They may seem magical but they really can be damaging if they deposit too much energy into living tissue. For 2450 MHz into a 9 dBi antenna [wirelessconnections.net], the 'safe' distance for a controlled environment is 0.518 meters (1.700 feet) - that's an environment where everyone is aware of the radiation and the public is not allowed. In an uncontrolled environment (where the public may be exposed) the 'safe' distance is 1.140 meters (3.739 feet). I put safe in quotes because the