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More ubiquitous than an induction recharger is the microwave oven: every home and office has at least one.
The idea is to build the covers of portable devices, such as cellphones, PDA's, media-players etc, with an embedded rectenna, arranged as a Faraday cage around the circuitry, which will not
only soak up the microwaves to recharge the batteries, but simultaneously protect the delicate'ish electronics inside.
Power Microwave Diode
http://www.google.c...fp=ea5733a97aebfa72
Rudimentary search [csea, Jan 08 2011]
Campfire Cellphone Charger
http://boards.strai...x.php/t-559862.html
Similar thought... [csea, Jan 08 2011]
Wireless charging via microwave energy
http://www.seminarp...rowaves-full-report
.pdf requires account [csea, Jan 08 2011]
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This is either an outstandingly brilliant idea or a very very
bad one, but I'm going with the first option. [+] |
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/Ian/
when he got to the quit in ubiquitous, he did. |
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Yes, [Voice], had it not been in text it would have been cause for concern. As it was in text it is instead a rather funny comment. And then [bungston] came through with the zinger. |
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Won't the process of charging the phone reduce the
faraday effect and subsequently shit the phone? I'm
guessing there's a safe middle ground and it just may
be worth it. + |
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The phone wouldn't actually be bothered by the electric field (or else induction charging would hardly work), and microwave transmission method efficiency is listed as 95% so there wouldn't be enough microwaves getting through to poach it. (As a sidenote, induction charging has an efficiency of ~85% at best.) |
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[csea] relevance of your link ? [edit: oh I get it] |
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Sounded fairly simple, just provide a tuned antenna and a microwave diode to rectify the energy to dc. (+) |
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But I'm quite skeptical that this could work. ( I did a preliminary search for an appropriate microwave diode to rectify the oven field. [link]
-Not much success.) |
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I'm fairly sure you'd be better off converting uwave radiation to thermal energy (heat) and then converting to electrical current. Protecting the phone via Faraday cage might upset the oven's field. |
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Efficiency shouldn't be a concern; even low-powered uwave ovens deliver a few hundred Watts, and a phone charger only needs maybe 10W. |
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A thermally-based charger would work with [IT]'s ubqwtrr-whatever kettle. [and campfires! -link] |
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A bit outside my expertise, would be glad to learn more. |
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But efficiency *is* the concern, not from a cost/kWh perspective, but from the perspective of: whatever power *isn't* being sopped up is going places you don't want it to, ie: frying the guts of the phone or, as you mentioned, upsetting the microwave oven itself. That's where the "95% efficiency"(WP) comes in handy. |
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That being said, I wonder if you could make a charger-free cellphone, utilizing ambient celltower radiation to power transmission and for receiving go unpowered... nah, probably not, you have to have power for AD/DA stuff and en/decoding. § x1 |
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Which is why a thermally-based product may be the solution - i.e. let the oven do what it is designed to do (produce heat) and let the charger take an inefficient fraction and convert to charging current. |
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Sometimes, it's best to let stuff do what it was designed to do... |
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[csea] Thermal charging sounds neat too except you'd have to worry about overloading the thermal capacity of the cellphone construction materials. Given an efficiency of 95%, a "beamed power" method is going to take less magnatron on-time = less heat/emf to dissipate. So thermal charging is probably not a good idea in a microwave. |
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On the other hand if it was strictly thermal, you could dunk your cellphone in your coffee to recharge... but thermal recharging requires a cold side, so that won't work unless you have someplace to dissipate the heat. |
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//Sometimes, it's best to let stuff do what it was designed to do...// [marked-for-tagline] |
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The inside of the oven would be a suitable heat sink for the few Watts needed. (Not my bone.) |
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Another approach would be to drill a suitably sized hole in the microwave, and use a "2.45GHz slotted wave guide antenna" and presumably a suitable rectifier. (Don't try this at home!) [link] |
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//and use a "2.45GHz slotted wavelength antenna// which is what we'll be using as a Faraday cage in this Idea. (okay, it's a pretty special Faraday cage since the wires aren't joined to each other as a mesh). Sry about the autobone accusation. |
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[21Q] The Idea uses a rectenna which is folded through the cover such that it also acts like a Faraday cage, ie: the wires are spaced closely together. |
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The "metal in microwave" thing won't happen: these wires *absorb* the uwaves because they're a microwave antenna: that's what they do. So there's no bouncing the uwaves back to the magnetron. |
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because I thought I'd be cute and push "Faraday Cage" as an easy visual aid... consider me chastised, post amended. |
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There's a shop in East Anglia that sells batteries. |
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I've heard of that place: do they deliver ? |
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