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Comment: Re:Too much current (Score 1) 199

by tibit (#43768883) Attached to: Charge Your Cellphone In 20 Seconds (Eventually)

Nope, not even close. Continuous-rated contacts are way bigger than those would be. They only need to carry the current for a minute, and at that point they can reach the maximum operating temperature. I could stuff one 50A Molex Mini-Fit Sr contact in a USB Type A shell, and that would be continuous duty.

Comment: Re:Too much current (Score 1) 199

by tibit (#43767655) Attached to: Charge Your Cellphone In 20 Seconds (Eventually)

Again, nobody advocates pushing 380A to the device. You push 10x less to the device, and an on-board power converter steps-down the voltage. That's like power distribution engineering 101. Since the "charging equipment" on your typical motherboards and GPU cards routinely supplies in excess of 100A, I think it's a non-issue. Just because legacy technology is huge doesn't mean modern techniques can't pack it in a very small volume.

Comment: Re:Too much current (Score 2) 199

by tibit (#43767629) Attached to: Charge Your Cellphone In 20 Seconds (Eventually)

Sigh. This is 8th grade physics stuff. Power = Voltage * Current (DC values). If the cells are at 3.5V, what you do is supply the thing with an off-the-shelf telecom supply at 48V, and even with losses you only need to push 30A or so if the cells need 380A charging current. Since the plug only needs to handle that current for a short time, it can be much smaller than already-small 30A-capable contacts. It'd easily fit in the envelope of a full-size USB type A connector.

Comment: Re:supercapacitors are cool (Score 2) 199

by tibit (#43767595) Attached to: Charge Your Cellphone In 20 Seconds (Eventually)

I don't know where you got your numbers from, but the energy density this supercap has is on par with batteries: 20Wh/kg. Now look at the size of the caps she has. Those are samples that weigh grams. Whatever fits in a cellphone will weigh probably on the order of 100g, and will store on the order of 1 Wh. I don't see kilowatts for charging, never mind that you absolutely don't have to charge in 20s. A one minute charge cuts the power by a factor of 5, and anyone sane will go with what's economical and makes business sense, not with what was put on a headline somewhere.

Never mind that it doesn't matter much what the energy rate (power) is, what matters is the stored energy. 1 Watt-hour is 0.86 kg*Kelvin for water. Assuming whatever the phone and battery are made out of have the heat capacity comparable to water, releasing 1 W-h will heat things up by 10 degrees C.

In other words: yes, it's as harmless as any current battery technology. Get over it.

My other gripe: couldn't that girl publish this stuff like everyone else out there? All we have is stupid news articles and a single-page PDF summary. Weren't they supposed to have write-ups submitted with the project? WTF is all this stuff? To me it's not $5k-worthy science if it's secret.

Comment: Re:This thought crosses my mind a lot. (Score 1) 793

by tibit (#43751695) Attached to: Rice Professor Predicts Humans Out of Work In 30 Years

It is the basis of property law - the idea that raw land becomes valuable property only after some form of human labour is involved

I don't know what planet in what solar system you're talking about here, because certainly it's not the basis of the property law here on Earth. Unimproved land prices depend on zoning and desirability for given use, sometimes they are also influenced by speculators.

Comment: Re:pfftt... (Score 1) 544

by tibit (#43743703) Attached to: A Computer-based Smart Rifle With Incredible Accuracy, Now On Sale

Whoa, whoa, not so fast. I'm talking about small freshwater post-glacial inland lakes. The ones I like are usually between an acre and 50 or so. No whales, no real bottom "features" (it's just silt deposited from whatever stream happens to run through the lake), I don't see much net use in those places either. I'm not saying I'm using dynamite, just that if I was there and was forced to feed a big group and it was legal to use, I'd do so.

Comment: Re:Good Training for embedded systems (Score 1) 143

by tibit (#43736859) Attached to: Interactive Raycaster For the Commodore 64 Under 256 Bytes

Division operations for line drawing? Ever heard of Bresenham's algorithm? It can be further tweaked based on the organization of the frame buffer.

There are many state-of-the-art designs that are memory constrained. Parallax's Propeller has 512 32-bit words for high-speed cog memory. Their new Propeller II adds a third memory space (besides cog and hub memories), but the basic 512 word limit remains unchanged. XMOS XS1 architecture has 64 kbytes of RAM shared between code and data for a multi-core CPU tile. Each tile has at least 4 cores running at 125Mips, from that shared memory. All are quite capable chips, each in its own way (Prop II only exists as an FPGA testbed at the moment).

Comment: Re:The harddisks are much slower (Score 1) 184

by tibit (#43733903) Attached to: Has Supercomputing Hit a Brick Wall?

Recently on eBay I saw a bunch (like 500 or so) of HP Xeon servers with 72GB of DDR3 RAM each, each for under $500 shipped buy-it-now, with some sort of a volume discount, too. Since that's likely registered server RAM that IIRC costs more than non-registered consumer stuff, it seems like a steal. I'm not sure what sort of memory bandwidth requirements do modern compute nodes have, perhaps DDR3 isn't enough, but still - RAM is cheap, it may be cheaper than pushing data via a custom interface to a fast hard drive array.

If you are going to walk on thin ice, you may as well dance.

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