Low Voltage Power Distribution? 237
thesp asks: "As I look around my apartment, I am continually struck by the plethora of high-voltage AC to low-voltage DC power adapters I use to power my various devices. At a recent estimate, around 30% of the power consumed in my house is via these adapters. From my laptop to my digital music player, and from my mobile telephone to my PDA, each device is down-converting its own power through its own adapter. Double this number to include my partner's devices. Many of these run hot, and are inconvenient to remove/replug to conserve power and outlets. Does Slashdot know of any moves to standardize power delivery to such devices, or of hobby/home-brew projects to distribute low-voltage power from a central power converter? Alternatively, are there reasons as to why this would not be a simple and effective solution to the proliferation of wall-warts."
"On closer examination, these adapters seem to fall into four major categories, 7V, 5V and 3V, with the most common being 5V. Despite this, each device uses a different DC plug configuration, which makes efficient use of adapters difficult. It seems to me that, just as AC power is standardised, portable electronics power requirements should be also be standardised, with a standard wall outlet and car outlet at, say, 5V, and a standard device cable and interface. Electronics manufacturers would save money on power adapters, and the consumer would have the cost of the converter written in to home construction or automobile construction costs. No longer would we have to lug 4 separate power adapters with us on an overnight business stay to power our various equipment."
Low Voltage DUPE distribution? (Score:4, Informative)
Article is a dupe...original discussion can be found here [slashdot.org], which amusingly enough, is itself a dupe of this [slashdot.org] discussion. Even more amusing is the fact that all of these submissions share the same editor.
Way to go, Cliff...a dupe hat trick. Zonk has nothing on you.
Re:Low Voltage DUPE distribution? (Score:5, Insightful)
Just about every device needs power in the 5 to 20 volt DC range to operate. No matter if it is 25 days old, or 25 years old.
In the old days there was a transformer and an AC/DC rig to achieve this. And a big fat Power switch, to connect the transformer to the high voltage AC supply.
This used to be all built into the device - think: big old fat radio, stereo, or TV. Because it was easy and convenient, because it was a big fat apparatus anyway.
And ON really meant ON, and OFF meant OFF.
Then came Stand-by mode. OFF suddenly meant: a little bit ON.
Goodbye to the big fat Power switch. Enter the apparatus that consumes power all day long.
Then, everything started shrinking, to become portable, "personal", etc.
So now we have the i-Pod, mobile phone, MP3 player, laptop computer, Discman, PDA, GPS. "We" want to take them wherever we go, so they have to be light, Battery powered, nobody wants a big heavy transformer inside of course. Enter thousands of battery chargers. And because we are lazy, we keep the chargers plugged in, all year long.
It's a trend. Not one that I necessarily like.
Why are there no chargers that we can keep plugged in, with true mechanical ON/OFF switches?
Re:Low Voltage DUPE distribution? (Score:2)
Re:Low Voltage DUPE distribution? (Score:3, Insightful)
Re:Low Voltage DUPE distribution? (Score:2)
Re:Low Voltage DUPE distribution? (Score:2)
Re:Low Voltage DUPE distribution? (Score:2)
Re:Low Voltage DUPE distribution? (Score:2)
It could *appear* to be timezone related,
but it could be due to geography (via subnets).
At minimum, you could blame it on a bug.
Alternatively, it could be a feature.
Are you sure you trust what you see on the Internet?
Are you really sure?
Re:Low Voltage DUPE distribution? (Score:2)
It could *appear* to be timezone related,
but it could be due to geography (via subnets)."
Silly me. I thought time zones *were* due to geography.
Or were you trying to say that vsprintf was posting from the mysterious future (or past, depending on your point of view)?
Re:Low Voltage DUPE distribution? (Score:5, Insightful)
% Power loss = Power * Resistance / Voltage Squared
So, with a length of wire that has a resistance of 10 Ohm, with 120V at 1 amp (120W), you lose
%P = 120W * 10 Ohm / 120V^2
or 8.3% of the total power, about 10W.
If you were to run the same amount of power over a 5V line (120W, or 24A), you would lose
%P = 120W * 10 Ohm / 5V^2
or a whopping 48% of your power, about 58 Watts. So you see, having all those transformers is actually more efficient. This is the reason why we have high voltage lines. The power that comes into your house is 120V, but if it were to be 120V all the way from the power plant 20 miles away, most of the power would be lost. So, power is sent on high tension wire at about 200,000V, then steped down to several thousand volts on main streets, then to less than 1,000V for your side street, then finally transformed down to 120V (or 240V if you live in some countries) right before it goes to your house. This minimizes loss.
On the other hand, if you have lots of devices that all use the same voltages right next to eachother, it can be efficient to get a single transformer. Musicians (like me), who have dozens of effects pedals that run on 9V, can buy special power bricks that power up to 6 devices. You can buy these from musician's supply stores (like musiciansfriend.com). You can even make one from parts at radioshack. You have to make sure you have a beefy transformer, then wire on several plugs in parallel.
If you want more info about power line waste, there is good info at:
http://www.bsharp.org/physics/stuff/xmission
Re:Low Voltage DUPE distribution? (Score:2, Interesting)
Ok, that's all well and good, but why not use a higher voltage DC to the outlet then? Say 50-100 volts.
Perform this conversion where service enters, along with stabilizing the power, filtering any noise, to protect sensitive electronics, etc, the resistance down the household wiring should be low enough that the heat waste on the wire is small, so that the convenience matters, and high voltage offers some flexibility.
Then have each kind of wall outlet include components to reduce the voltage to fit
Re:Low Voltage DUPE distribution? (Score:5, Interesting)
actually that is not entirely correct. 10ma of current across your heart period will cause serious issues be it DC or AC. In fact, DC is actually safer then AC when it comes to turning yourself into a light bulb. When the power grid was first being created, DC proponents used to fry small animals to prove that AC was unsafe while DC would do no damage. Granted, a DC power grid would need a power generation station almost every 3 blocks.
As a side, don't be fooled, 110v AC can kill you dead just like 400v AC can. It's all about your bodies internal resistance mostly due to moisture and the path the power takes.
Re:Low Voltage DUPE distribution? (Score:2)
OT here but good info nonetheless:
DC used to be distributed locally to homes and businesses. It was only good for short runs (no more then 2 miles) from the dynamo. It is difficult to easily transmit because DC voltage cannot be easily varied by using transformers like AC. They wound up transmitting
Re:Low Voltage DUPE distribution? (Score:3, Insightful)
Pardon me, but saying something like this just makes you sound ignorant.
It's not like you can a current "by itself". It's directly related to voltage. The higher the voltage, the more current will flow through a given resistance. So, arguing which one of the two kills you is like saying that the speed of a car hitting you doesn't matter, it's the weight.
DC Vs AC Safety (Score:3, Informative)
Edison, for some unknown reason, hated Tesla and tried to kill his ideas of AC power distribution. He apparently had the (AC-powered) electric chair created as a PR stunt so that people would know that AC power was being used to kill people -- but it turned out to be relatively difficult to reliably kill people with AC power because an AC charge turns out to be an impro
Re:Low Voltage DUPE distribution? (Score:2, Informative)
You have got that backwards. It's hard and expensive to change 120 down to low voltage DC with any decent efficiency, whereas efficient (>90%) DC-to-DC is cheap and straightforward. Transformers are expensive, as are high-voltage rated components.
Re:Low Voltage DUPE distribution? (Score:2)
Um.... how?
There are 2 ways to change a DC voltage. Use a mechanical machine like a dynamotor or a motor generator. Or you can use a solid state switching power supply. Most AC wall warts I see today are switchers. The DC-DC inverters you are talking about are nothing more then switching po
Re:Low Voltage DUPE distribution? (Score:2)
Which do you suppose was used in vacuum tube automobile radios? Unless you're defining your terms very broadly the answer is neither.
You've also left out resistive voltage dividers.
Re:Low Voltage DUPE distribution? (Score:4, Informative)
Not true. DC-DC converters have existed for years, and they are highly efficient. Take, for example, the DC-DC convertor on your motherboard - if it were only 30% efficient, it would be dissipating more heat than the CPU. Fortunately, DC-DC converters are generally closer to 90-95% efficient.
Take, for example, the picoPSU [mini-box.com] - it outputs 120W at various voltages (from a DC source) and it doesn't even have a heatsink.
Re:Low Voltage DUPE distribution? (Score:3, Informative)
At the EXACT current output they were designed for.
Sure, you can get tons of efficiency if you're designing with a known load that doesn't vary too much. This is not the siutation we're talking about here. One minute you might be drawing 10mA, the next minute you might want 10 A, the supply is not going to maintain 95% efficiency over that range and maintain a reasonable cost.
Re:Low Voltage DUPE distribution? (Score:2, Insightful)
AC and DC have different characteristics, too. Depending on the properties of the wire, the same piece of wire may have a noticeably higher resistance when AC flows through it than that some wire would have when AC were flowing through it, because high frequencies of AC avoid travel through most of the wire's cross-sectional area. This can be a substantial increase in resistance, one disadvantage of using AC.
See Wikipedia: Skin Effect [wikipedia.org]
Re:Low Voltage DUPE distribution? (Score:2, Informative)
BTW, Tesla was the oddball, he was all for wireless electricity. Sadly, his proposed wireless transmission device, the tesl
Re:Low Voltage DUPE distribution? (Score:2)
Dupe complaints are hypocrisy.
Ohm's law (Score:3, Insightful)
Re:Ohm's law (Score:5, Informative)
Depends on your current draw. Check out this table [windsun.com]. Remember that by time you wire your entire house, there will be several hundred feet of wire.
There's a reason we feed houses with AC.
Re:Ohm's law (Score:3, Interesting)
If you wire your house intelligently - converting your A/C to D/C in a central location and radiating each a line to each room from there - only very large houses will have a throw distance
Re:Ohm's law (Score:3, Informative)
You might note that that applies at 120 Volts, not 12V - at the lower voltage your #10 gets you a whopping 22 feet. For 200 feet at 12V you need 1/0 gauge wire, which is ten times the cross-section, and three-and-a-half times the diameter...
Again, not huge in real-world terms, but bigger than you imagine...
I think the biggest pitfall is making sure you don't d
Re:Ohm's law (Score:2)
Re:Ohm's law (Score:2)
I believe that's also known as an arc welder. How do you think your mp3 player with in-ear headphones would behave in the (very common) dead-short failure mode?
Probably not likely to obtain UL certification for powering consumer electronics anytime soon.
Re:Ohm's law (Score:2)
Is the loss of converting to DC centrally with a beefy power supply that can handle enough amperage to run all the houses devices and distributing via wires a few hundred feet more or less than distributing via AC and then converting it into DC with lots of little AC to DC converters?
Besides, sure you will have several hundred feet in a wired house, but... what if you say... put AC/DC converters in several places in the house to keep wire runs small? Or plan for more circu
Re:Ohm's law (Score:2)
1) simple power production: rotate a magnetized rotor in a multi-pole stator, completely brushless for reliability
2) simple power distribution: simple, relatively inexpensive and reliable laminated iron-core transformers (multi-megawatt DC-DC conversion was practical 30+ years ago anyway... and is rarely so even today)
3) compatibility: transformers cannot be plugged on a DC bus and many AC-DC converters have a voltage-doubling input topology that would be incompatible with DC
Converters in outlets (Score:2)
Re:Converters in outlets (Score:2)
And exactly how long will it take till someone sues whoever installed the outlets because he fried his expensive gizmo by using the wrong voltage, polarity, connector,
Greetings from 230V-AC-land.
IMHO, USB will become the de facto power standard. (Score:4, Insightful)
The natural next step is for more devices to switch to USB power. Routers and hubs and other things that are typically "near" a computer come to mind.
Re:IMHO, USB will become the de facto power standa (Score:2)
Re:IMHO, USB will become the de facto power standa (Score:2)
> that plugs directly into the wall and supplies power only,
> and no serial connection, but if you're going to go to
> those lengths, why not create a new standard and design it
> for powering things, instead of re-using an old standard?
If there was any chance of this to happen then it would have already happened one or two decades ago. I see the obvious absence of such a standard as a very good proof that creating such a standard is not
Re:IMHO, USB will become the de facto power standa (Score:2)
Technically USB was designed to provide power, however, the limitations do preclude supporting many devices, since there is a 500mA limit for "high power" devices. Many devices need more than that. A group of devices would likely draw more than the source could provide, in any event. So, I agree USB is not a viable power distribution option.
http://www.usbdeveloper.com/UnderstandUSB/understa ndusb.htm#Power%20Distribution [usbdeveloper.com]
USB PlusPower would be a good alternative (Score:2)
USB PlusPower was developed in the late 1990s by IBM, Fujitsu and NCR in response to retailers' demands for self-powered cash register peripherals. Cash registers have several peripherals that require more pow
Technically true... but my bet is still on USB. (Score:2)
A few reasons... (Score:4, Informative)
2. Low voltage == High losses, esp. with DC.
Re:A few reasons... (Score:2)
Re:A few reasons... (Score:2)
The thing you are noticing (adapters getting warm) is losses from inefficient transformers. A switcher is less efficient when it's on, but it can shut off completely with no load. A cheap transformer will waste a lot of p
Re:A few reasons... (Score:3, Informative)
Actually transforming DC is way cheaper and more efficient than transforming AC...
The 120v to 5V (or whatever) in your power supply is done before the AC is rectified to DC.
The 120V to 5V transformation is done by treating the AC as a fluctuating DC signal, and doing DC conversion. It is less efficient than proper DC to DC conversion, but not much, and it's way more efficient than using a traditional transformer.
It would be very nice t
Re:A few reasons... (Score:5, Interesting)
Parent comment: Actually transforming DC is way cheaper and more efficient than transforming AC...
You can simply transform AC voltage using the simple and low-tech electronic device called a transformer. Just a bounce of wire wound a metal core.
I assume you are referring to solid state DC-DC converters which can be (far) more efficient (less waste, less heat) than a linear power convert, but they are not simplier.
Distribution to businesses and houses will remain AC because AC is easier to distribute over long distance. High power (wattage) is easier (more efficient) to distribute (power transmission) with a high AC voltage than high voltage DC. This goes back to the famouse Edision vs. Telsa fight over DC / AC power distribution near the previous turn of the century.
It is possible to distribute low voltage AC (say 12 VAC) within a house for electronic usage. Using high efficiency power supplies (i.e.: don't waste a lot of engery producing wasted heat as a by-product of the conversion process) such as found in newer laptop power supplies would be another positive step. Otherwise I don't know if we'll see the elimimation of inefficient wall-warts.
To the submitter: Don't forget about electric applicants that are high power (e.g. 1000W or higher), in my case that includes: electric force air heating, electric stove (aka range/oven) for cooking, air conditioning, refridgerator, microwave, toaster, hair dryer, and coffee maker. These devices would not work (easily) at a lower voltage without a large increase of current. Remember or learn Ohm's Law: Power (Watts) = Voltage (Volts) times Current (Amperes).
Re:A few reasons... (Score:2)
Re:A few reasons... (Score:2)
Well, that pretty much defines the Power over Ethernet niche (at least for smallish values of Power).
Re:A few reasons... (Score:2)
1. Small form factor devices. A cell phone WITHOUT a high-ratio DC-DC converter will always be smaller, lighter, and generate less heat than one WITH a high-ratio DC-DC converter. This is obvious. Therefore, under the suggested plan will either r
Re:A few reasons... (Score:2)
Re:A few reasons... (Score:2)
Re:A few reasons... (Score:2)
That is pure nonsense. You are perhaps confused with power transmission; DC transmission over long distances is inefficient compared to AC.
Re:A few reasons... (Score:2)
PS: and the reason why is because it's easier to step AC voltages up, and higher voltages have lower losses due to lower current.
Wrong! (Score:2)
Re:Wrong! (Score:2)
HVDC is only used in rare situations, such as undersea power cables where capacitance works against AC. Power transmission across land is almost without exception HVAC.
Re:Wrong! (Score:2)
Re:A few reasons... (Score:2)
http://en.wikipedia.org/wiki/Switched-mode_power_s upply [wikipedia.org]
DC is more efficient and more useful over long distances because you don't have a) inductive losses, b) capacitive losses, c) no need to synchronise phases at both ends. On the downside, you need an inverter at each end. AC wins in the co
Re:A few reasons... (Score:3, Informative)
2. Losses have nothing to do with AC or DC, it's just a function of current.
Let's say you've got 12 AWG wire in your house
Re:A few reasons... (Score:3, Informative)
There are still some nearly unsolvable problems with higher voltage DC as a distribution system. For one, arcs start easier on a 48VDC system, and arcs are harder to break because current can just follow the ionized trail and is easily sustained. T
Re:A few reasons... (Score:2)
Re:A few reasons... (Score:2)
The advantage of AC is the ability to use a simple transformer to change the ratio between the voltage and the current as well as it's generation and use in polyphase alternators and motors.
High voltage (Score:2, Insightful)
Re:High voltage (Score:2)
True, but this is about distributing low-voltage DC throughout the house, NOT transmitting it long distances. You'd still want high-voltage in the house for high-power applications (electric dryer, AC, electric stove), but low voltage DC would be better for most electronics, maybe even for lighting if you switch over to LEDs or other "cold" lighting, where you don't need all that excess power to produce heat.
I've wondered about whether it would be possible to create a low-power converter that would take i
Re:High voltage (Score:3, Informative)
P = power dissipation
I = current
R = resistance
V = potential difference (voltage)
We know that power is a function of power and current. For direct current,
(1) P = V * I
By Ohm's Law,
(2) V = I * R
Therefore
(3) P = I ** R
So power dissipation is proportional to the square of the current. Given a requirement to deliver some arbitrary amount of usable power to the devices you have plugged in, by (1) you know that if you halve the voltage you must double the current to deliver the same amount of power. But, by (
Re:High voltage (Score:2)
Standardised DC Power (Score:3, Interesting)
The 12VDC cigarette lighter plug is a de-facto standard. Redo all your devices to use 12VDC with a simple voltage leveller - eg, a zener diode followed by a 5V regulator IC - and then standardise on cigarette lighter sockets throughout the house.
Re:Standardised DC Power (Score:2)
While that sounds like a nice idea, it's extremely wasteful.
If your global supply is 12V, and you want to run a 5V device, you need to blow off 7 volts.. that's more power wasted than actually delivered to the load. Kirchoff's & Watt's laws will get you everytime.
Re:Standardised DC Power (Score:2)
Good idea, but it'll never happen (Score:2)
I like the idea, but forget about it ever happening. Manufacturers have no incentive to standardize. I
Re:Good idea, but it'll never happen (Score:2)
Re:Good idea, but it'll never happen (Score:2)
Re:Good idea, but it'll never happen (Score:2)
Re:Good idea, but it'll never happen (Score:2)
30 Percent? (Score:2, Troll)
You're new here, aren't you. By "new", I mean, new to this planet. Apparently you have no idea how much a TV uses, or how much a refridgerator or microwave uses.
So this article is a "tripe", and also has a stupider premise than the others. Thanks, "editors".
I'd gladly settle for.. (Score:3, Insightful)
Standardized connectors. It's one thing to have a variety of devices that use different voltages, but having a variety of 5V devices each of which uses its own style of plug & jack defies all common sense.
For that matter, even on devices that use the same voltages and connectors, there is no standardization for polarity! Is it really that difficult to agree that ring is negative, and tip is positive, or even vice-versa?
Adaptor lock-in is just plain obnoxious.
Re:I'd gladly settle for.. (Score:2)
Multiphase power (Score:2, Insightful)
3-phase AC is much more easily converted to DC, and also allows for simpler and more efficient motors. (So it is also ideal for things like air conditioners, refrigerators, furnaces, and such.) Overall, I think the advantages far outweigh the cost of an extra conductor, and it is unfortunate that it isn't mor
Re:Multiphase power (Score:3, Informative)
DC does not require any larger conductors than AC does, for the same voltage and current. You must be assuming low voltage in reference to DC.
Three phase is only marginally better than single phase for converting AC to DC. And unless the power supply is a very complex and expensive type, it will result in a high level of harmonics and a low power factor on the AC source due to the rectification cycles. On a large scale this could also overload the neutral conductor.
Three phase is generally good for mot
Re:Multiphase power (Score:2)
Low voltage as in safe DC voltage. 120VDC is unsafe for home use. Start an arc and you can't stop it short of tripping a circuit breaker. The same arc on an AC system, 120VAC RMS, the arc dies before the zero crossing.
Cable thickness (Score:3, Interesting)
There's also neat experiments you can do in school with transformators - put a coil with, say, 5000 windings opposite of one with, say, 5, and you'll be able to quite literally melt nails.
Issues in low voltage power distribution (Score:3, Informative)
If you have a cluster of devices of all the same voltage at the same location, then it would make sense to have a common power supply. Otherwise, it makes more sense to use a higher voltage for distribution purposes. The electric utility generally brings power down to your street in the 11kv to 14kv range, and a permanent transformer drops it down to the 120 to 240 volt range you get into your home. Distributing power at 240 volts would not even be considered beyond at most 100 to 200 meters. Every time the voltage goes up by 2, the distant can go up by 4 since the current is cut in half, which means the voltage drop is cut in half, which has even less effect on twice the voltage. When they run the voltage at 50 to 100 times as much, they can deliver power over substantial distances. Cutting voltage to 1/10 as much means you can deliver the same amount power to only 1/100 the distance.
Incandescent lights actually work better at lower voltage, especially for bulbs of lower wattage. Normally a low wattage bulb requires greater resistance in the filament. That means the filament must be longer and/or thinner. That means it is more prone to mechanical shock damage. It also has to run at a lower temperature, producing a more orange light (which in some cases is what is desired). The lower temperature wastes power since more is emitted as infrared instead of usable light. By changing the bulb design to a low voltage like 12 volts, the same power level can have a shorter, thicker, hotter filament, which can run more efficiently, even making up for the loss involved in having a transformer converting the voltage.
The reason I mention low voltage lights is to point out that they are rather standard at 12 volts (a few use 24 volts), yet transformers are generally located close to where the lights are, rather than in a central location which would require the power be distributed in low voltage form. If a central low voltage source were practical, low voltage lighting would be the first to use it. But with very few exceptions, they don't do it this way.
I once considered running lots of stuff in my house on lo
low voltage power distribution answers (Score:2)
The Pessimist (Score:3, Insightful)
Have we all forgotten what companies charge for $2 wall warts? I've even seen a Brother label maker wall adapter that has an odd voltage (7.3v), odd amperage, a non-uniform center pin, and inverse polarity. They go overboard with the accessory business. This particular wall wart costs $24 at OfficeMax [officemax.com]. Then another $18 for the label cartriges. Then there are the power-hungry devices like cameras that don't come with a wall wart at all (computer controlled, time interval shots). Us mere mortals have to guess when we go down to the store what size connector to use. Face it, the money is in the connectors. If they can find a cheap way to make you use a new connector and charge outrageous amounts of money for adapters, they will. Cheer up. Atleast your iPod doesn't have any custom connector on it. Oh, wait. Never mind.
So maybe a better solution would be a single brick with different connectors for different voltages - this would conform to ISO standards. Then they could just pull the old printer "this box contains no cables" trick, and it would reduce the number of unused transformers out there eating away at copper supplies [foxnews.com].
Re:The Pessimist (Score:2)
Re:The Pessimist (Score:2)
None of which should pose any trouble at all for a universal AC adapter. I run 6V devices at 4.5V, and vice versa with few side-effects. Any universal AC adapter will have a setting for 7.5V. Ditto for the amperage... it really doesn't matter as long as it's close, preferably slightly above what's necessary. Polarity is a complete non-issue. Finally, the connec
Here is what I'd do (Score:2)
Re:Here is what I'd do (Score:2)
Just so you know, this is precisely why engi
Three major categories eh? (Score:2)
I envy you if your devices fall into three major categories. I've been toying with the idea of building an equiptment rack with a few DC power buses for things like my DSL modem, TV antenna amplifier, mic preamp, router, various chargeable devices, etc. In addition to power, the rack would provide real power switches; many of my devices lack power switches. Since all the equipment will be in the same rack, transmission losses should not be great. Now, it may be the case that most of these devices can han
Re:Three major categories eh? (Score:2)
15v DC, proprietary connector (iSub USB subwoofer)
12v and 5v DC, proprietary connector (USB hard drive)
12v DC, tip positive (speakers, ionic air purifier thing, wireless router, Ethernet switch)
12v DC, ring positive (speakers)
9v DC, tip positive (cordless phone)
9v DC, ring positive (speakers)
9v AC (original old-school Nintendo)
7.5v DC, tip positive (USB hub, cordless screwdriver, Ethernet switch)
6.22v AC, hard-wired (Dust Devil mini vacuum cleaner)
5.9v AC,
Not for the house, but maybe for the rack (Score:2, Interesting)
I've been considering this since the last time this was on slashdot. While over any real distance DC is inefficient for power transmission, the inside of a rack might benefit. I figure with a large UPS and some sort of redundant power-supply, you could feed a number of computers with 12V lines and a picoPSU-120 12V DC-DC ATX power supply [mini-box.com]. Has anyone tried this yet? I've never worked with high-density hardware (like blades) but I'd imagine that each blade is certainly not using its own PSU.
Re:Not for the house, but maybe for the rack (Score:3, Informative)
Check out the specs on telco equipment. A lot of them run on 48 vdc with special 48vdc power supplies. You can get a lot of networking gear that come with 48vdc power supplies. I think there
A proposal for 48V distribution (Score:2, Insightful)
As some may know, this standard provides for approximately 15W of power at a nominal 48V. See http://en.wikipedia.org/wiki/Power_over_Ethernet [wikipedia.org] for an introduction.
We can reuse and/or extend the probe/negotiation phase to provide additional power levels, let's say up to 150W (approximately 4A max).
Advantages
Keep it simple (Score:2)
When you leave home, hit the switch. When you go to bed, hit another switch. When you're getting busy in the bedroom...oh wait
Power Pole (Score:2)
Distance is still a problem.. why do you think that you have a big fat wire on your car battery? A lot of car manufactures are looking at using 47v or something for cars in the near future to reduce the weight of wire in cars.
My own centralization attempt (Score:4, Interesting)
I wired it all up and: 16 watts again.
It was exactly the same between using all the individual supplies and using the centralized PC supply. Admittedly, 16 watts isn't exactly ideal for a 90-watt supply (hmm ... maybe I'll try a smaller source supply ...) but at least I get a nice solid 5 volts going to the USB hubs.
If you get one of those Kill-A-Watt (or equivalent) meters, it's a great help in figuring out what you might want to put on a power strip and switch off manually. My stereo components when off drew a total of about 50 watts so I started switching them all off. The battery chargers in the basement used about 10 watts total, but since I was only using them to keep batteries topped-off, I could reduce it by putting them on a timer and running them an hour a day instead.
In essence, do your experiments and figure out how much you'll really save.
Forget low voltage DC, low voltage AC is a path (Score:5, Interesting)
Unlike DC or 50/60Hz AC, 35kHz (or even more) AC requires a lot cheaper wiring, very small transformers and have very little losses.
Roll your own - I'm doing it (Score:2)
http://ecloud.org/index.php?title=DC_power_system [ecloud.org]
Re:A real problem (Score:3, Informative)
Re:Surety you crave! Reality gives you none! (Score:3, Funny)
Like that one time, Satan decided that all railroad tracks should be the same distance apart, so that every train could work on every track, so people would ride around on the trains, which sucked out their immortal souls.
Oh, and then they standardized screws and bolts, so that you didn't need to carry around one screwdriver for each screw manufacturer, which put some screwdriver makers out of business. Their children were thrown out to starve in the stree
Re:Surety you crave! Reality gives you none! (Score:2)
-russ
Re:Surety you crave! Reality gives you none! (Score:2)
We all owe a debt of gratitude to the USSR for fighting Satan on that one...
Really? I was confused by the fact that I need 20 different screwdrivers to disassemble a damn stereo...
Re:How many devices need 110V anyway? (Score:3, Informative)
Yes there is. A 1200W microwave draws 10 amps at 120V. At 12V it would draw 100A. You have any idea how thick the wire has to be to handle 100A?