Piezoelectric Transformers

behoward writes "Tired of those big honking power adapters needed for all your portable toys? Me too! So far the best solution I've seen is the AC adapter for my G4 Powerbook, a sleek combo yoyo/flying saucer; but while it looks good on the desktop, it still makes too big of a bulge in my case when I travel. Now engineers at Penn State are working on a real solution. Hope Apple gets this technology in place in time for the G5 Powerbook."

Comments

Merry GNAAMAS !

[Anonymous Coward]

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DID I GET TEH XMAS FROSTY PISS?!?!

[Anonymous Coward]

LOVE, AKEDIA

HO HO HO MERRY REICHMAS

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Current products DONT use transformers

[Chmarr]

The current power adaptors don't use transformers. They're switch-mode power supplies, which use a small inductor and a bunch of circuitry to control switching and regulating.

So, yes, the article states that the new piezoelectric transformer will be smaller than regular transformers, but the current laptop power supplies DONT use regular transformers!

So, the real question is, will the piezoelectric transformer be SMALLER than a switch-mode supply, AND, will it be more efficient?

Re:Current products DONT use transformers

[FreeMars]

That's going to be a big surprise to the folks who manufacture transformers for switching mode power supplies.

Yes, they are smaller than the transformers needed for non-switching power supplies, but they are there.

Re:Current products DONT use transformers

[jabuzz]

You have not the faintest clue what you are talking about do you.

They may not use regular transformers, but they still use transformers. All offline (i.e. connected to mains) SMPS use a transformer. They have to for safety reasons. The transformer provides galvanic isolation so if there is a failure in the electronics somewhere you don't end up with live mains on the output.

Low voltage DC-DC SMPS do indeed use a small inductor as a charge storage device, and you could even do the same with rectified mains, it is however just not safe.

Re:Current products DONT use transformers

[smokin_juan]

dc-dc ac-dc switching power supplies may not use transformers (besides isolation as mentioned below), but they're chocked full of electronic components. Reduction of components count reduces failure points, manufacturing cost and price.

Re:Current products DONT use transformers

[kfg]

http://www.smpstech.com/tutorial/t01int.htm#SMPSDE F

Please note the inclusion of transformers as a componant of ac/dc switch mode power supplies.

KFG

Re:Current products DONT use transformers

[smokin_juan]

Eh so i screwed up. price probably won't come down. The manufacturers will probably leave the price as ac-dc converters or jack it up due to the "convenience" of having a smaller lighter power supply. all hail capitalizm.

Re:Current products DONT use transformers

[Chmarr]

Is having a clue a requirement for posting on slashdot?? :)

Thanks for the information, though! I still believe the article is referring to transformers for the purpose of voltage conversion, not isolation... but... we'll see when products start using it :)

Re:Current products DONT use transformers

[Anonymous Coward]

In a typical AC-DC switching power supply the line voltage is recitfied and then chopped up (switched) at a high frequency). This high-frequency AC is then fed through a *transformer* and rectified to produce low-voltage DC.

The only difference is that instead of a big, bulky 50/60Hz transformer we have a small 100Khz transformer. It is possible to build a switching power supply without any transformer, but that would mean no isolation between the power grid and the powered device so I don't think that would be legal in most cases. I certainly don't want my laptop headphone jack at 220V AC!

Re:Current products DONT use transformers

[sfe_software]

Yes, they are smaller than the transformers needed for non-switching power supplies, but they are there.

Adding to this is the fact that switch-mode power supplies are the main culprits for RF/EMI problems. A simple 60-Hz transformer (unless in very bad shape) emits very little of anything in the RF spectrum.

I assumed that the article was in fact referring to switching supplies, since they mentioned the EMI issue as one of the problems that their idea solves.

The only thing I wonder about is decoupling. Not knowing exactly how they work (the article isn't all that technical), I wonder how well decoupled the output is from the input. I recall a laptop being recalled over poorly decoupled modems, causing a shock in some circumstances; with 110 to 220 VAC, I think the problem would be worse, but it's possible that there is a good degree of isolation in these things.

Re:Current products DONT use transformers

[Animats]

Some wall transformers use switching power supplies, with a small high-frequency transformer after the chopper, and some are linear, with a front-end transformer running at 50/60Hz.

Worth mentioning is the forged UL safety label problem. If a power supply doesn't have a UL or CSA label, don't buy it. It will probably catch fire if shorted or even heavily loaded. A UL label must have the UL logo and a certification number. UL certifications can be looked up here. This is worth doing for desktop computer power supplies, for which forged certifications are a big problem. The ones that catch fire are almost invariably uncertified. UL requires that no single component failure can cause a fire.

Re:Current products DONT use transformers

[jabuzz]

The transformers in a offline SMPS also step the voltage down as well as provide the galvanic isolation required for safety purposes

Re:Current products DONT use transformers

[albeit unknown]

Totally wrong.

Most electronic products, especially those using switch-mode DC power supplies, do use transformers. The reason is that the transformer provides galvanic isolation from the AC mains. This helps prevent transients like lightning strikes from propagating through the device. Also, it prevents the wrong parts from becoming "hot" because the cord is plugged in backwards.

Products that do not have transformers have much more stringent requirements for creepage and clearance distances, and are usually simple devices. A drill, for example. Hard to do with an electronic device with lots of buttons and slots.

The high-frequency operation of a switch-mode power supply does allow the magnetics (transformers and inductors) to be much smaller than their 60 Hz linear counterparts, but they are still there.

Please refrain from commenting about something you know nothing about, as someone may read your post and build something lacking the necessary safety features and hurt themselves.

Re:Current products DONT use transformers

[Patrik_AKA_RedX]

The reason is that the transformer provides galvanic isolation from the AC mains. This helps prevent transients like lightning strikes from propagating through the device.

You're not serious, are you? A lightning strike would pass easy trough a transformer. Take a good look on a transformer and see how much isolation there really is between the mains and the secundairy coil. They can handle (at least) 4KV, but they can't handle a lightning strike.

There are numerouse designs from SMPS, and many of these don't have a transformer in them. Some have a small one in the regelation circuit. Most of them aren't isolated from the mains. Even those which have a transformer, may have a path between the mains and the output via the feedback circuit.

Re:Current products DONT use transformers

[MemoryAid]

And a surge protector can get blown out by a lightning strike, too, but surges that are stoppable by the same surge protector can have been created by a lightning strike. It was just farther away.

Isolating transformers really do work for many things, even if thesis-level detail wasn't included in some specific post on Slashdot.

Re:Current products DONT use transformers

[Anonymous Coward]

in short

1. Peizo will be smaller than both switch mode psu and other's. Sizewize a mobile phone charger will be able to be buildt into the phone.

2. One thing they forget to mention is the total lack of switching noise - which means the applications where it will benefit the most is medical etc - plus no need for HF/RF shielding

3. There are a few Peizo generators out there but the problem is producing a stabel uniform output. That requires a DSP or ASIC solution addon chip. ;-)

best

Re:Current products DONT use transformers

[robhancock]

It's certainly possible to have an SMPS where the output is not isolated from the AC line. However, that would most likely not be considered safe (i.e. for regulatory purposes) for a device that is has external connectors on it, because of the potential shock hazard. So such a design is really not applicable for a device such as a laptop.

Re:Current products DONT use transformers

[GORby_]

I can't really say whether they will be smaller or not (having read the article), since you have a point here about the power supplies not containing transformers...

They are saying that heat won't be an issue, as it is with current laptops, so we can conclude from that that the conversion will be more efficient than the current power supplies.

On the other hand the article mentions laptops that typically use only 15 watts of power. While these may exist (not sure about that), I think these will be quite rare. The laptop (AMD XP-M 2500+) I'm now typing this on mentions 20V - 6A as it's specs, which is almost 10 times what they say.

Another thing they are forgetting is that the power supplies aren't only used to power the laptop, but also to charge the battery, even when the laptop is powered on.

Anyway... that's just my humble opinion.

Piezoelectric Transformers

[Anonymous Coward]

More than meets the i...Book.

Re:Piezoelectric Transformers

[Anonymous Coward]

I never realised that electroactive crystals could deliver any kind of current. Piezos are already well established for high voltage supplies, and show up in electronic gas lighters to make the spark.

I still don't quite see how something of such high impedence can deliver any current, but its a good development.

Mind you these will drive pets crazy. To a dog a house full of these would sound like a rock concert.

Re:Piezoelectric Transformers

[wirelessbuzzers]

Then you should be able to answer the obvious questions that people on these forums have posed: what's the efficiency, and will it drive pets insane?

Re:Piezoelectric Transformers

[Malor]

Ok, so here's a couple of questions..... the piezoelectric effect is based on physical vibration. In essence, we are introducing moving parts into a power supply. This prompts the questions:

1. Do they wear out?

2. Will other motion or vibration cause voltage spikes or sags?

Re:Piezoelectric Transformers

[smokin_juan]

First thing that comes to mind is a potentiometer where a voltage is applied to the ends and the wiper is adjusted to get a voltage (i guess you could also use a multitap transformer analogy).
If this is the case it sounds like concerns about selectable input (120 / 240 vac) can be resolved by tapping into the crystal at different points for different voltage inputs, not to mention varying different taps for differnt voltage outputs.
The thing that baffles me is how it works in the ultrasonic range. is the 60hz line frequency being multiplied first or is it just the size/thickness of the crystal, standing waves and all that?

Re:Piezoelectric Transformers

[sfe_software]

I am doing some graduate studies in this field, so here's a quick breakdown. ...

So if I'm understanding correctly, this is roughly equal to driving a speaker with a high voltage, and picking up the sound on a dynamic mic... resulting in a low voltage output from the mic. Accoustic coupling, only at a miniature and inaudible scale in a self-contained unit.

Cool!

Re:Piezoelectric Transformers

[sfe_software]

Sorry to reply again, but something occurred to me. In a normal power supply, a load on the output side directly affects the current draw on the input side. How does that work here? Other than having some kind of input-side regulation and feedback (opto-coupler?), similar to what we have now with switch-mode supplies, I'm not sure how this would work.

By itself it seems that this technology would draw about the same amount of input current, regardless of load. Of course it's possible that it's exactly a "normal" switching supply, with the transformer swapped out in favor of a Piezo device -- in which case the other problems have already been solved.

Any insight?

Re:Piezoelectric Transformers

[aaarrrgggh]

The biggest obvious problem with this technology is the fact that you can no longer have universal power supplies, since the voltage ratio is a function of distance.

Nice to remove the inductors and other compensating components, but it seems like there is still a HUGE trade-off.

Re:Piezoelectric Transformers

[Anonymous Coward]

So if I'm understanding correctly, this is roughly equal to driving a speaker with a high voltage, and picking up the sound on a dynamic mic... resulting in a low voltage output from the mic. Accoustic coupling, only at a miniature and inaudible scale in a self-contained unit.

You're right on the account of acoustic coupling, but your example is awfully inefficient. Speakers require high voltage*high current, while the mics produce low voltage*low current. Just how much energy is wasted? Considering that over 90dB of amplification is required for most mics, I'd say the mic pics up fraction of a percent of the power going to the speakers. That's awful when you consider that most toroid transformers will get you over 90% efficiency.

Re:Piezoelectric Transformers

[robhancock]

I can't see either of those being a problem. Devices of this type aren't entirely new to electronics - lots of devices like TVs have types of delay lines or SAW (Surface Acoustic Wave) filters which work on a somewhat similar principle.

Re:Piezoelectric Transformers

[DrJimbo]

... By itself it seems that this technology would draw about the same amount of input current, regardless of load. ...

A load on the output side a piezoelectric transformer will affect the current draw on the input side just like a magnetic transformer or any other resonating circuit.

The important thing is not the current but the power. Since this is an AC system the power flow depends upon more than just the magnitude of the voltage and current it also depends upon their relative phase. As more power is used on the output side, the current and the relative phase change on the input side to supply more power to the piezoelectric resonator.

The less technical but perhaps over-simple analogy is pushing a child on a swing. Once the child gets up to a certain height, you need to give a fixed amount of push to keep them swinging up to that same height. But if the child starts dragging her feet on the ground or using up her energy some other way then you will need to give her bigger pushes to keep her swinging to the same height.

Re:Piezoelectric Transformers

[Muad'Dave]

From the article:

Transformers are made from piezoelectric materials by applying a chopped electric voltage to one side of a piezoelectric wafer.

It seems that they are still using some sort of line-side switch to manipulate the input to the piezo crystal. This means that having a large input voltage range is still quite possible by varying the duty cycle or turn-on phase point of the input waveform.

Re:Piezoelectric Transformers

[bar-agent]

Increasing or decreasing the piezo separation is easy enough mechanically.

Re:Piezoelectric Transformers

[InfoVore]

The important thing is not the current but the power...As more power is used on the output side, the current and the relative phase change on the input side to supply more power to the piezoelectric resonator.

Exactly right. I think sfe_software's confusion may come from not being able to visualize the mechanisms which cause power draw on the output side of the piezo to affect power draw on the input side.

IANAP, but here goes:

The piezo element is sitting there with no input power applied and nothing connected to the output side. You connect a voltage pulse to the input side. The piezo element starts to vibrate from the pulsing voltage due to piezo-electric effect. The element hasn't reached its natural capacity to store mechanical power yet (eg its resonance frequency), so the current flowing from the power source increases due to the power draw by the piezo element.

When the piezo element can absorb no more power (eg it is at resonance), the current draw from the input drops off. The voltage pulse is still driving the piezo element, but much less power is being transfered now.

The piezo element is now vibrating at its natural resonance frequency and a small amount of power is being lost from friction (heat) and natural emission (heat/light/sound). The piezo element requires some power from the input side to maintain its present vibrational resonance. If you pulled the plug on the input side, the resonance vibrations in the piezo element would quickly decay away to nothing due to friction.

Now see what happens when you connect an electric load across the output side of the piezo element:

The vibrations in the piezo element are creating a voltage across the element's output side due again to the piezo electric effect. No power is being consumed at the output, because no current is flowing. Now connect a load to element's output side. The load sees a voltage and draws power as a result. Vibrational energy in the the piezo element is now being transformed into current in the load. Since there is now less vibrational energy in the piezo element (it is not at resonance anymore), the element starts pulling in power from the input side. The more power that gets sucked out of the element by the load, the more that the piezo element sucks out of its input. So power is transfered from the element's input side to the load on its output side.

So the more power you draw from the piezo element, the more gets pulled in from the input source.

That's a simple step-by-step summary of the process. I know its more complicated than what I described, but I think the description hits the high points.

Hope it helps, sfe_software visualize it.

Cheers,
I.V.

Apple?

[Anonymous Coward]

Apple get it in time for the G5 powerbook? Some hope - since when have Apple ever done anything other than slavishly copy other company's ideas?

for Apple users

[Anonymous Coward]

the best option would be a dual purpose device - like a charger that acts as a spiked dildo.

In disguise!

[Scrameustache]

Who is this new Piezoelectric transformer aligned with?

Will Megatron get his alligeance and collect enough energon with his help to conquer earth and Cybertron, or will Optimus Prime woo him to the side of good and save us all? ;- )

Re:In disguise!

[azuretek]

I'm glad I wasn't the only one that pictured a truck transforming into a giant robot...

Re:In disguise!

[fraudrogic]

When I read this headline, I really thought someone modded a transformer toy to transform by itself or something to that effect.

On that note, this probably could be an Ask Slashdot question, but does anyone know who to go to, to create a Decepticon icon replacement for my honda symbol on my prelude? I always thought that would be a real subtle, cool thing...(since they look similar)

Re:In disguise!

[Anonymous Coward]

You could try extruding some super sculpey in the shape of the decepticon icon, baking it, sanding it down smooth, and applying silver leaf. Buff the leaf down, apply shellac or other sealer, and try mounting that in place of the Honda symbol. Make sure you leave attachments for the holes that the Honda symbol goes.

Heh, if you do this, please post to Slashdot so we can all see (and slashdot your server to boot) :)

Re:In disguise!

[John Courtland]

Get a dremel tool and make a template by printing off a image to the size you want it. Get some fiberglass (REAL cheap, like $4/yd) and some epoxy resin. You COULD use Carbon Fiber, and make it invincible and very very sharp-looking, but that shit is quite expensive ($50/yd), but it works the same as the fiberglass fabric. Lay the fiberglass sheet down and apply the resin. Do this a few times to give it some thickness and integrity. Check out some fiberglass sites to tell you the exact procedure, it's pretty simple, but it takes some waiting and making sure you don't over or under soak the fabric with the resin.

Now, after it has dried completely, AND WHILE WEARING A RESPIRATOR, cut the thing to the desired size. Bore out the eyes and the intricate designs via your properly sized template, sand to a rough smoothness (paint needs to stick) paint purple with a good automotive paint, sand, paint, sand, paint. Until it looks like glass, you aren't done. Use proceedingly higher grits of sandpaper, probably 220 up to 2000. And don't sand the paint off or anything, that's too much, you just want to give it some depth, so just scuff the surface. And wear the respirator this whole time too, fiberglass dust is not good for your respiratory tract. And goggles and gloves, but you should know that.

Re:In disguise!

[fraudrogic]

wow. I'm going to see those lame tasks they show in the dremel commercials in a whole new light. Thanks, I'll do some research on this.

Re:In disguise!

[__aafutm5472]

I'm so glad I'm not the only one who read the title to the article and immediately thought of the toys from my childhood...

Re:CHESTNUTZ

[Anonymous Coward]

my nutz, on your chest, by an open source fire.

we'll call it:

kmynutzonyourchestbyanopenfire 2.1.0.0.0.1-3.3.4 stable release.

Do Not UpMod Anything From RKZ

[Anonymous Coward]

RKZ puts horrible porn redirect links in his sig. He Karma Whores to get people to up-mod him and his sig link.

He is slime.

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Re:Do Not UpMod Anything From RKZ

[Anonymous Coward]

Whats the matter? Can't troll better yourself?
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As long as the stimulation remains outside the body on the perineum, any type of lubricant (petroleum-base or water-base) will do.

However, because this kind of stimulation is often associated with insertion of the finger into the vagina or anus, or both, a water-base lubricant is recommended and preferred.

The anus is rich in nerve endings & participates with your genitals in the contractions of sexual arousal & orgasm. Anal stimulation greatly enhances & intensifies masturbation, oral sex, or intercourse. A good rule of thumb, when experimenting with anal play, is relax, use plenty of lube (the anus & rectum do not produce any lubrication of their own), and enjoy.

Because the perineum is so rich in nerve endings it often feels pleasing to have it touched or stroked. If one is comfortable with being touched on the perineum, its stimulation can be incorporated into a couple's lovemaking to further enhance sexual arousal.

The vagina is rich in vulvatic sensor spots & cooperates with your clitoral system in the up and down movements of sexual arousal & orgasm. Vaginal stimulation greatly enhances & multiplies masturbation, perienium stimulation, and orgies. A good rule of thumb, when experimenting with vaginal stimulation, is to relax, and use one quart of 10W30 (the vagina produces no lubrication of its own during normal stimulation), and enjoy.

However, because this kind of stimulation is often associated with insertion of the finger into the vagina or anus, or both, a water-base lubricant is recommended and preferred.

[ Reply to This ]

• Re: What the hell are you thinking? by JJahn (Score:2) Friday May 30, @09:06AM

1 re

ultrasonic

[spoonist]

"Piezoelectric power adapters operate in the ultrasonic range so humans cannot hear any sound produced..."

That's nice and all, but what about our pets (cats, dogs, etc)? Are they going to be driven nuts by a high pitched whine?

Re:ultrasonic

[Seahawk]

Well - me reading slashdot havent driven my cat nuts yet - and slashdot definately creates a high pitched whine once in a while...

Re:ultrasonic

[gregorious]

Hmm, a power supply that repels flying insects. Or, attracts 'em.

With other piezo devices I sometimes hear an irritating mosquito-like whine. I've wondered if this is due to interaction with casing, or resonance with other components. Two piezo components could set up beat frequencies. Gaaah. Jbecause we can't hear its dominant frequency doesn't mean a sound-generating device is Goodness on a Bun.

Re:ultrasonic

[Flavio]

Regular switching power supplies also operate in the ultrasonic range.

Well designed supplies are reasonably quiet (as one can verify by making them operate in lower frequencies), so pets tolerate them.

Likewise, badly designed supplies really pollute the airwaves. It's usually impossible to tune an AM radio within 20 meters of a cheap desktop computer PSU.

Re:ultrasonic

[Anonymous Coward]

But energy increases with frequency, so the higher the frequency the louder the noise (even if it's too high to hear). A 3" throw on a subwoofer is great at 30 Hz, but a 3" throw at 10 KHz will quickly send you out to buy new windows.

Re:ultrasonic

[The_REAL_DZA]

I can tell you from personal experience you don't have to be of canine or feline ancestry to be bothered by poorly-designed (or poorly-tuned) electronics; the ultrasonic "pest repellers", the car sensor at McDonald's (look for the little hockey-puck shaped thingie mounted outside and below the drive-up window), and televisions with misadjusted horizontal hold bug the daylights out of me (no pun intended...) -- In my hometown there used to be a department that had their electronics department at the front of the store; I had to cover my ears with my hands when we went through the doors because of all the televisions with their horiz. holds just a little out of tune. If you get a headache nearly every time you go into department stores, don't automatically assume it's the crowds or the prices!

What's really interesting is that my wife's voice, while definitely feminine, must not register anywhere near ultrasonic; she's always complaining that I'm not listening but I swear I just didn't hear what she said...

your trolling abilities are lacking, son

[Anonymous Coward]

RKZ > YOU
*_g_o_a_t_s_e_x_*_g_o_a_t_s_e_x_*_g_o_a_t_s_e_x_*
g_______________________________________________g
o_/_____\_____________\____________/____\_______o
a|_______|_____________\__________|______|______a
t|_______`._____________|_________|_______:_____t
s`________|_____________|________\|_______|_____s
e_\_______|_/_______/__\\\___--___\\_______:____e
x__\______\/____--~~__________~--__|_\_____|____x
*___\______\_-~____________________~-_\____|____*
g____\______\_________.--------.______\|___|____g
o______\_____\______//_________(_(__>_\___|_____o
a_______\___.__C____)_________(_(____>_|__/_____a
t_______/\_|___C_____)/______\_(_____>_|_/______t
s______/_/\|___C_____)_______|__(___>_/__\______s
e_____|___(____C_____)\______/__//__/_/_____\___e
x_____|____\__|_____\\_________//_(__/_______|__x
*____|_\____\____)___`----___--'_____________|__*
g____|__\______________\_______/____________/_|_g
o___|______________/____|_____|__\____________|_o
a___|_____________|____/_______\__\___________|_a
t___|__________/_/____|_________|__\___________|t
s___|_________/_/______\__/\___/____|__________|s
e__|_________/_/________|____|_______|_________|e
x__|__________|_________|____|_______|_________|x
*_g_o_a_t_s_e_x_*_g_o_a_t_s_e_x_*_g_o_a_t_s_e_x_*


The perineum is the area of skin rich in nerve endings that is located below the anus (the opening for bowel movements). For men, the perineum extends to the vaginal opening; for women it extends to the base of the testicles.

Because the perineum is so rich in nerve endings it often feels pleasing to have it touched or stroked. If one is comfortable with being touched on the perineum, its stimulation can be incorporated into a couple's lovemaking to further enhance sexual arousal.

To make stimulation smoother and more comfortable, it is often helpful to lubricate your fingers before stroking the perineum during lovemaking.

As long as the stimulation remains outside the body on the perineum, any type of lubricant (petroleum-base or water-base) will do.

However, because this kind of stimulation is often associated with insertion of the finger into the vagina or anus, or both, a water-base lubricant is recommended and preferred.

The anus is rich in nerve endings & participates with your genitals in the contractions of sexual arousal & orgasm. Anal stimulation greatly enhances & intensifies masturbation, oral sex, or intercourse. A good rule of thumb, when experimenting with anal play, is relax, use plenty of lube (the anus & rectum do not produce any lubrication of their own), and enjoy.

Because the perineum is so rich in nerve endings it often feels pleasing to have it touched or stroked. If one is comfortable with being touched on the perineum, its stimulation can be incorporated into a couple's lovemaking to further enhance sexual arousal.

The vagina is rich in vulvatic sensor spots & cooperates with your clitoral system in the up and down movements of sexual arousal & orgasm. Vaginal stimulation greatly enhances & multiplies masturbation, perienium stimulation, and orgies. A good rule of thumb, when experimenting with vaginal stimulation, is to relax, and use one quart of 10W30 (the vagina produces no lubrication of its own during normal stimulation), and enjoy.

However, because this kind of stimulation is often associated with insertion of the finger into the vagina or anus, or both, a water-base lubricant is recommended and preferred.

[ Reply to This ]

• Re: What the hell are you thinking? by JJahn (Score:2) Friday May 30, @09:06AM

1 reply beneath your current thres

Different adapters for 110 and 220V?

[rduke15]

The article mentions plans to develop 220V. versions. That seems to imply they cannot make adapters taking any voltage between 90 and 240 volts, like the current notebook adapters.

In other words, it would be a big step backwards if you need to carry around two adapters with your notebook!

Or can these be made universal like the current standard adapters?

Re:Different adapters for 110 and 220V?

[carndearg]

Why cant they produce a dual voltage version? This mystifies me.

In a dual voltage switch mode power supply the AC input is rectified to form a high voltage DC which is then switched at high frequency(tens of kHz or so) and passed through a ferrite transformer to step down the voltage. The dual voltage bit comes from the rectifier being a bridge rectifier when you set the switch to "240" and a voltage doubler when you set the switch to "110", both giving a DC voltage to the switch somewhere around 300V.

I would be extremely surprised to find these piezo transformers work at line frequency, i.e. 50 or 60 Hz, I'd expect this to have a detrimental effect on the size of the thing. So I'd expect that the circuit would be surprisingly similar to a conventional switch mode PSU with a rectifier and high frequency switch driving the high voltage side of the piezo transformer. Hence you could use the same bridge rec/voltage doubler arangement I described earlier to give you a dual voltage PSU.

If there's a piezo expert around to explain whether the piezo transformer will work at 50/60 Hz, I'd love to hear an answer to this one.

Re:Different adapters for 110 and 220V?

[Anonymous Coward]

The article mentions plans to develop 220V. versions. That seems to imply they cannot make adapters taking any voltage between 90 and 240 volts, like the current notebook adapters.

Where are you that you're plugging into a 220V line?? All my outlets are 110V. Is that a European thing?

Re:Different adapters for 110 and 220V?

[The Wicked Priest]

The article says the adapters are 1/4 the size of current models. So you could bundle two together (perhaps in a single case, with a switch) and it would still be only half the size.

Re:Different adapters for 110 and 220V?

[Anonymous Coward]

It's a European, African, Australian, Asian and South-American thing. See here.

Re:Different adapters for 110 and 220V?

[sfe_software]

The dual voltage bit comes from the rectifier being a bridge rectifier when you set the switch to "240" and a voltage doubler when you set the switch to "110", both giving a DC voltage to the switch somewhere around 300V.

That's one way, but most notebook adapters don't have such a switch. Rather, they accept a very wide range of input voltages. They work by simply being able to regulate and handle the full range of voltages; at 90v input the regulator would be passing quite a bit more current through, where at 240v the duty-cycle would be dropped significantly.

The piezo supplies, from what I gathered from the article, are more along the lines of a basic 60-Hz transformer; eg, you get some specific ratio of input/output voltage, without regulation. I'm sure these could be easily regulated, and I'm sure a future version will be.

It's (AFAIK) brand-new tech, so more features will come I'm sure, if the technology takes off.

Re:Different adapters for 110 and 220V?

[rduke15]

All my outlets are 110V

So you are in one of the rare countries with the old cumbersome 110V., and apparently never went out into the world :-)

Re:Different adapters for 110 and 220V?

[TheMidget]

And, until recently, it used to be Iraqi too...

Re:Different adapters for 110 and 220V?

[alienw]

They are just a transformer replacement, so I would think it would still need most of the regulator electronics that a normal SMPS (switch mode power supply) has. Not sure the size will be significantly smaller, though. SMPS transformers are small.

Re:Different adapters for 110 and 220V?

[Anonymous Coward]

As quoted from the article:

"Piezoelectric power adapters operate in the ultrasonic range so humans cannot hear any sound produced and they do not produce electromagnetic interference".

So there is something inside the box which converts 60 Hz to the 20+Khz required for the ultrasonic part.

Re:Different adapters for 110 and 220V?

[bedessen]

I would tend to think not. The physical geometry of the piezoelectric ceramic is what determines the voltage ratio. It might be possible to package several different configurations in one enclosure, but at its core it's a fixed ratio.

In contrast, the switch-mode powersuppy you're using now rectifies line AC and then switches it at a very high frequency (around 40kHz) and uses the duty cycle of this switching to regulate the output. Through a closed-loop controller it regulates the output to a constant level regardless of the input, which is why it can take such a large input range.

Re:Different adapters for 110 and 220V?

[MemoryAid]

I smell Troll...

Apple might use it in their new products...

[Anonymous Coward]

...but eighteen months later you'll need to get a new one.

Transforming cuurent events!

[niko9]

Sounds electrifying! We need to rectify this alternating situation. We currently need to take a more direct approach. Let's hope they can induct some more engineers, and they can harness the capacitance of their talents and rectify the situation.

We shall now meditate, repeat after me:

Ohm
Ohm
Ohm

Re:Transforming cuurent events!

[Anonymous Coward]

Great zombie jesus, you are a NERD!

Re:Transforming cuurent events!

[Salamander]

That was revolting.

Re:Transforming cuurent events!

[Anonymous Coward]

Hey, don't blow a fuse!

Re:Transforming cuurent events!

[Anonymous Coward]

Not sure what's funnier... the parent, or the fact that someone modded it "Interesting"... :p

Re:Transforming cuurent events!

[Anonymous Coward]

OK ... who the *fuck* modded that Interesting?

Re:Transforming cuurent events!

[tonydiesel]

Shocking... I was positive that post would get a negative reaction. At least some of us seem to have gotten a charge out of it...

Not really

[Anonymous Coward]

They typically have small flyback transformers. Making them smaller wouldn't allow us to redesign adaptors (or fit them into a pen).

The whole idea of a switching power supply is that it gives a regulated output. A transformer would still give you an AC output, which is useless by itself.

Re:Not really

[Anonymous Coward]

Well, you are wrong too. You can regulate the output of a transformer, but
that doesn't make it a switch-mode supply. The really bulky (non-switching) supplies are
called linear supplies and are only about 1/4 efficient.

Power is the biggest trouble of portables.

[GNUALMAFUERTE]

And this seems to be a preety elegant solution (I still want to know how much they are going to cost.)
Another important point is that the only amazing feature doesn't seem to be the size, but also they seem to eliminate other problems of standard AC/DC adapters, for example, magnetic interference with other devices.

Piezoelectric Transformers

[Gary Whittles]

I am doing some graduate studies in this field, so here's a quick breakdown.

Power electronic circuits have traditionally been based on magnetic technology, and until recently, have not been part of the tide of miniaturization and integration advances from which signal-processing integrated circuits have benefited. In an effort to miniaturize power components, acoustic rather than inductive coupling can be used as the basis for a transformer. Note that acoustic coupling can be achieved through piezoelectric *or* magnetostrictive means.

In a piezoelectric transformer, the direct and converse piezoelectric effects are used to acoustically transform power from one voltage and current level to another through a vibrating structure. The converse piezoelectric effect, in which an applied electric field produces a resulting strain in a body, is used to convert an oscillating electric field applied to the left half of a structure, such as a bar, into a vibrational mode of the entire bar. If driven at resonance, standing-wave distributions of large amplitudes of stress and strain result. The resonantly amplified strain in the right half of each bar is converted to a voltage across the output terminals by the direct piezoelectric effect. Depending upon geometry and materials parameters, you can obtain voltage amplifications of various magnitudes, with associated step-downs in current level.

The unique nature of the piezoelectric transformer offers the opportunity for innovative circuit design such as operating above resonance for inductive behavior to achieve soft-switching without compensating inductors.

Old news...

[Nimloth]

Big deal. I've had these Starcom toys for years with no batteries or adapters.

Only question I haven't yet answered is... could they run Linux?

Mod Parent Up

[toxic666]

This guy knows electro crystal chem.

Why marked a troll?

[Anonymous Coward]

or are moderators protecting Apple from the truth?

Re:Why marked a troll?

[Anonymous Coward]

It was marked as a troll because certain computer users are unhappy with anything short of dewy-eyed admiration of their platform. I'm not mentioning any names so perhaps this will escape their notice.

Simple solution.

[Anonymous Coward]

it still makes too big of a bulge in my case when I travel.

Simple solution. Don't carry the transformer in your case. Place it down the front of your pants.

(BTW, these transformers are already being used in laptops, they are what help step up the voltage in the backlight in some designs)

The rectification will still kill you

[Anonymous Coward]

The problem is not the transformers, you can make them much smaller than the standard wire wound ones with planar magnetics.

The real problem is the rectification of the output of the transformer to get DC again. You still have to use diodes, and the very best ones still have a significant forward voltage drop. As a result the generate heat and need cooling.

Open up any ATX PSU, and the main heatsinked components are the output rectification diodes. It is cooling these that limits power supply size. It is also the main inefficency in the PSU.

To those that think that all three legged TO220 packages are MOSFET's think again, because they are not!!!

Re:The rectification will still kill you

[aXis100]

You can (and many people do) make a much more efficient power supply (98%) by replacing diodes with transistors. Sure, it takes more control, but these have excellent forward conductivity (eg mosfets with 0.01ohm on resistance).

Re:The rectification will still kill you

[Brians256]

Can you link to any examples of this modification? I'd like to modify a PC SMPS to lower the heat so that I can reduce the fan noise, so this is an attractive notion.

I didn't think that you could make the switch to MOSFETs from the standard diodes because of leakage during the reverse cycle.

Re:The rectification will still kill you

[ChrisMaple]

The power supply has to be designed "from the ground up" to do this. Modifying an existing supply is difficult and dangerous for anyone but an electrical engineer who specializes in switching power supplies.

No YoYo.

[Anonymous Coward]

The YoYo shaped adapters for Apple's PowerBooks have already been replaced by small lightweight adapters. The current ones are tiny and I carry it everywhere without noticing it at all. It looks like the iPod power adapter only slightly larger. Take the current Apple power adapter and compare it to some other laptop manufacturer's power supply and the difference is clear.

Too Much of a Bulge

[Anonymous Coward]

Yeah, I'm familiar with that problem.

Apple's YoYo transformer is crap...

[Anonymous Coward]

It is unreliable, it is unwieldy, it is hard to pack (sure, the cord that plugs into the powerbook wraps up nice, but the power cord doesn't). It is poorly designed and in fact Apple doesn't use them anymore. They have a much more sensible design with the newer PowerBooks.

The design previous to the yo-yo was better, other than its propensity to short out and cause fires. Hmmm, is there a trend? Why yes, when I was at Apple I replace a lot of PowerBook transformers where the tip's plastic had crumbled.

Is there a portable maker that has good transformers and good quality and good service? I'm sick of Apple's mediocre quality and their horseshit service on portables (mine came back from service WORSE than I sent it in! And don't get me started on their phone reps, they are mindless script reading monkeys).

This will be a signifigant breakthrough

[vmalloc_]

I for one am looking forward to seeing this technology develop, and let me tell you this is signifigant! As an electrical engineer that builds transmitters for an income, I can tell you just how signifigant.

There are basically two ways to transform voltage right now. The first way is to use an electromagnetic transformer, which is a very bulky solution. A 2A 125v-24v power transformer can be the size of my fist, and will generate a lot of heat at even half that amperage max.

The second way is to use a type of switching power supply that basically uses a step-up transformer to convert the voltage and then filters it down through a series of circuits. This is the system used by most power supplies nowadays because it is cheaper and smaller, but there are many disadvantages to this method as well, most importantly SAFETY. The voltages that run through these can be thousands of volts, and also the circuits can be complicated (it's easier with a transformer, because all you need is a recitifer bridge and a filter capacitor).

This method, on the other hand, uses a peizoelectric method, which (if I'm understanding it correctly) is very cool. If you need an analogy, this method basically acts like a quartz crystal does, like in radio transmitters and those little RC cars you probably got for christmas.

If these aren't too expensive and can handle at least a few amps, I can see these being adopted widely in the market, not just in laptops. These things are a potental goldmine, for the improved efficiency alone (heat loss = energy loss).

ho ho ho niggerz

[Anonymous Coward]

Troll-O-Meter [The Jargon Dictionary] The Jargon Dictionary - http://info.astrian.net/jargon/terms/t/Troll-O-Met er.html The Jargon Dictionary : Terms : The T Terms : Troll-O-Meter
Troll-O-Meter Troll-O-Meter n. Common Usenet jargon for a notional instrument used to measure the quality of a Usenet troll. "Come on, everyone! If the above doesn't set off the Troll-O-Meter, we're going to have to get him to run around with a big blinking sign saying `I am a troll, I'm only in it for the controversy and flames' and shooting random gobs of Jell-O(tm) at us before the point is proven." Mentions of the Troll-O-Meter are often accompanied by an ASCII picture of an arrow pointing at a numeric scale. Compare bogometer. troll <<< Troll-O-Meter >>> tron

bad modding

[Anonymous Coward]

What silly person moderated the parent Interesting instead of Funny?

The ultimate solution...

[Anonymous Coward]

...would be a transformer that shot lightening bolts at any passing Mac zealots.

The Current Powerbook Adapter is Excellent

[Qweezle]

I have a 12" Powerbook G4(original model), and let me tell you, the AC adapter is just excellent. It is very solidly built, and unlike some of my Apple AC adapters of the past, the wire has not frayed at all. I wrap and unrwap it every day, too, so this is even more impressive.

The small prongs that flip out from the brick are very handy for winding the wire around, and the design is simple, small, and much more durable than other companies' adapters I've used/seen.

But for this fellow to say the yo-yo design was "great" is just silly. The design was good for its time, but I have one, and the wire frayed eventually, and compared to the current white-brick adapter I own, it is a piece of crap.

Re:The Current Powerbook Adapter is Excellent

[iotaborg]

Really, I much prefered the yoyo model, or the older models with the molded plug, as I don't find the current white brick models that stable. I've had my mother's ibook's AC adapter replaced twice and mine once as the end of the plug kept loosening and eventually fraying and dying, as the ends of the current white brick adapters are not fully molded but can be disassembled quite easily.

Re:The Current Powerbook Adapter is Excellent

[fermion]

I like the white rectagle thing. The original was not so well built, but still lasted a year. I just purchased the new model, and it much better. Thicker power cord for home use and an extra grommit on the output.

The form fact is not noticible. The reason I prefer this to the saucer adapter is the interchangable power cord. It is usually unnecesary for me to carry the cord, so it is nice to have the small adapter.

Re:The Current Powerbook Adapter is Excellent

[Spyky]

There are at least two versions of the white brick adaptor. I have a new 1.25 15" and I have a later version than my girlfriend's 800 TiBook 15". They look the same, but on closer inspection, the cord connection is a little different the new one has a stronger rubber connection, the old one had a rounded surface so the cord wouldn't rub. This is hard to explain, you'd probably need to see both to understand what I am talking about. Also, the new version seems to carry a ground connection through the heavy duty cable (the pin on the removable plug is now metal). Also, the power rating of the new version is slightly higher, and it is a tad heavier.

My favorite feature of this adaptor design is clearly the removable extension cable. When I am making day trips to school or whatever, I don't bother to carry the cable. Only on longer trips or specific occasions do I even need to carry the (bulky) heavy duty cable. Most other adaptors I've seen for Dell or other notebooks are much larger to begin with, but also require the heavy duty power cable to be carried along with it.

-Spyky

Re:The Current Powerbook Adapter is Excellent

[curious.corn]

Don't just trust the damn thing, if it's the model where the DC cable enters the plastic brick without the classical grommet but straight into a trench you've had it... it'll break and badly too! Mine died the day I was showing off the beauties of Os X to a chap I had just convinced to get an iBook; and a bad death was it too! The flimsy cheap wire (Apple must have noticed since it changed the design and the wire gauge) shorted on the laptop plug side and the circuitry cooked itself destroying the whole adapter. Now:
1. Ok Apple, you tried to pull a cheap one... the first device went offline on it's own, the second shorted... change design and manufacturer
2. Apple has grown a tad too much for it's current logistics? My dealer was extraoridarily kind and pulled an extra one while the Apple bureaucracy decided my adapter was dead, under warranty, it was their fault after all and replace it. What was I supposed to do in the meantime... BUY A NEW ONE? Well, the dealer made it clear it was a favour since Apple didn't provide for extra "courtesy" stock... it's been past two weeks...
3. For hell's sake, put a short breakout in the silly thing! Not a fuse no, the whole thing is a switching, electronically controlled AC/DC converter; so why on earth didn't Apple put a transistor on the output load to shut off the input stage in case it shorted for some reason?

Now, listen up Apple... I like OS X, the HW and all... but you pull another one of there cheap tricks on me and you won't see another cent... with the money I spent I could have bought 2 shitty Dells... I haven't so I don't expect to be treated as if I had. Rant and bitterness aside, I'm pretty happy with my mac... looking forward to a portable G5.

Re:The Current Powerbook Adapter is Excellent

[myov]

The removable cord/travel prongs - great.
Having to replace my p/s 5 times in the last 18 months - really poor design. In almost all cases, the strain relief at the notebook end broke, and within 2 weeks or so, it was dead. (once, the brick itself died. hacked something together using the dead ones).

Yes, it's under warranty, but still a stupid design. And I've had a few clients with the same problem (not realizing that it was under warranty too - $150 for a new one)

boring

[Anonymous Coward]

not even amusing

*MOD ABUSE ALERT*

[Anonymous Coward]

This is a legimiate and on-topic post, yet it was censored beacuse a moderator with an agenda (read: a Mac zealot) decided that the truth should not be read by others.

Transformerless adapters of yesteryear

[ortholattice]

Does anyone remember those cheap transformerless adapters you could buy around 1970? They replaced a 9-V transistor radio battery and were the same size, with a cord coming out that plugged into 110V. I opened one up, and there were 4 parts: a capacitor in series with the AC line, a rectifier diode, a 9V zener diode, and an electrolytic filter capacitor. I wonder if anyone got electrocuted by them, and when they were (as I assume) banned.

Here's a previous rant of mine on AC adapters.

Re:Transformerless adapters of yesteryear

[alienw]

The main problem with those is that with a zener diode you can only get a tiny amount of current. Enough to power a small transistor radio, not enough to power anything else. Not to mention that the regulation is total crap. Those devices are cheap and that's their only positive side. You could make a transformer brick that's smaller and more efficient.

Re:Transformerless adapters of yesteryear

[Hirsto]

Sure, this device is a half wave charge pump running at the frequency of the AC power source. During the negative half cycle the pump capacitor charges to -170Vpeak and the charge is then pumped to the electrolytic as the input AC voltage swings from -170Vpeak to +170Vpeak. The total charge pumped on every full cycle is q=c*deltaV where deltaV is 340V for 120VAC. The average current supplied is i=q*f. So for a 120V 60Hz source with a 0.1uF pump capacitor you can draw an average of i=120*2*1.414.60Hz*0.5uF or 10mA! The zener is used to limit maximum voltage at no load conditions. For very low power loads this can be extremely efficient (>97%) The output voltage starts to collapse once the average current drawn by the device exceeds the average current that can be supplied by the charge pump.

Re:Transformerless adapters of yesteryear

[NoMaster]

But the biggest problem with these things? They're not isolated from the 110v / 240v mains supply.

Effectively the output is floating at mains potential, with the current only limited by the capacitive reactance + resistance. So, while the V between the + & - terminals may be 9V or whatever, the V from the output to earth is is basically the peak of the 110v / 240v mains - at 240V, that's nearly 340V!

Not to mention that *all* the components need to be rated to withstand this full mains V - generally they're not, because most capacitors (excepting poly & some ceramics) aren't, and the miniature metal-film or carbon-deposited resistors certainly aren't...

Of course, that's only at a very low current, further limited by the turn-on I of the zener - but, it's still there. 340V DC at a small handful of mA is still dangerous applied to the wrong places...

Re:Transformerless adapters of yesteryear

[Hirsto]

Well, in most designs the output is referenced to the AC neutral which still isn't safe for most consumer devices. In these designs the only devices that need to be rated for full mains voltage are the charge pump capacitor and the diode. The electrolytic can be rated at just slightly above the zener voltage, i.e. 15V electrolytic with a 12V zener. To further eliminate shock hazard a series resistor of about 1k ohm can be added in both the line and neutral lines and an additional series capacitor (10x larger than the pump capacitor) is placed serially in the neutral line to give DC isolation. So the final circuit would consist of two resistors on the Line and Neutral connections, a charge pump capacitor, two diodes for the half wave charge pump, a zener, an electrolytic capacitor, and the Neutral isolation capacitor. I only use these types of designs in primary side circuits which are isolated from secondary circuits.

Re:Transformerless adapters of yesteryear

[samjam]

Nice closing comment, but in 1970's you couldn't make a transformer brick smaller OR more efficient.

The electrolytic only charges up in one cycle (current is only drawn from mains on one cycle) and THEN only insofar as the electrolytic capacitor has been discharged. No discharge means do mains current used (except to cover leakage).

And lots of modern plug-in timers and light sensitive switches worked the same way.

I converted such a light sensitive switch to a radio-control mains switch by combining it with a wireless door-chime.

Sam

way to go PSU

[Anonymous Coward]

Wow, I am glad somebody is doing something at school, (I made the deans list!)now all PSU has to do is fire Joe Paterno and they will be set.

Bulge?

[donutz]

the best solution I've seen is the AC adapter for my G4 Powerbook, a sleek combo yoyo/flying saucer; but while it looks good on the desktop, it still makes too big of a bulge in my case when I travel

Well stick that adapter in the front of your pants -- then you won't hear any complaining about the bulge being too big.

Re:Bulge?

[behoward]

There isn't any room left, and I bought the baggiest pants available! HeHe.

Re:Bulge?

[Anonymous Coward]

... is that your AC adapter, or are you just happy to see me?

Re:Bulge?

[Anonymous Coward]

Well stick that adapter in the front of your pants -- then you won't hear any complaining about the bulge being too big.

I'm female, you insensitive clod!

not thousands

[Anonymous Coward]

The voltages that run through these can be thousands of volts, and also the circuits can be complicated (it's easier with a transformer, because all you need is a recitifer bridge and a filter capacitor).

I thought that (at least in the computer PS) the highest voltage is actually the rectified input voltage stored in the main capacitor so maybe it will go to 150V but not thousands of volts. The capacitors themselves (when I opened one of those ATX power supplies) were rated to only a few hundred volts AFAIK.

stupid problem in the first place

[treat]

The real problem is that there is no standard connector for low DC voltage. Why isn't there one? This would benefit everyone. This isn't a very difficult problem, except that it needs support of big businesses. But it seems that it would even benefit them.

When I travel I have to bring 9 power supplies (2 laptops, mp3 player, still camera, video camera, 2 cellphones, razor, toothbrush). This is insane! Of course I don't always bring all these devices. I often leave them behind not because of the device itself but because of the weight and volume from the power supply.

Re:stupid problem in the first place

[Dun Malg]

The real problem is that there is no standard connector for low DC voltage. Why isn't there one? When I travel I have to bring 9 power supplies (2 laptops, mp3 player, still camera, video camera, 2 cellphones, razor, toothbrush).

Because there's no standard for low voltage. How many of those items use the same voltage? How many of them are even DC? Some devices are sensitive to as little as 2 volts difference plus or minus, and "low voltage" will generally be anything from 3 to 24 volts, plus they can be AC or DC. The connector isn't your problem-- it's the power your devices require.

Re:stupid problem in the first place

[Anonymous Coward]

but if you had a standard 'low' DC voltage, you could just design devices with a regulator to reduce the voltage to the desired level

Re:stupid problem in the first place

[Anonymous Coward]

Nice lifestyle, dude. Try consolidating your TWO laptops into one. And your TWO cellphones. (Hint: One nice phone and several SIM cards work well.)

And a question: Does your razor really have an external power supply? Or are you just referring to the small AC cord to plug it into the wall? All razors I've seen take mains AC power and don't require any power supply.

I predict if you travelled with less dependency on electronic posessions, you'd whine less.

Re:stupid problem in the first place

[bsmoor01]

But they are POWER supplies, not voltage supplies. A cell phone needs much less power than a PowerBook. Thus it would be absurd to make power supplies standard. (I personally don't want to carry around a 65 W brick for my mp3 player).

Re:stupid problem in the first place

[Anonymous Coward]

Then the regulator would be a power supply in itself integrated in the device, generating heat and generally kind of defeating the purpose of having a separate power supply in the first place.

Re:stupid problem in the first place

[treat]

My point is that if it was a standard, you won't need to carry it around, just like how you don't carry around a 22kv to 110v transformer.

Re:stupid problem in the first place

[treat]

Have the connector select the voltage(s) and AC or DC by jumpering different sets of pins.

Re:stupid problem in the first place

[treat]

Nice lifestyle, dude. Try consolidating your TWO laptops into one. And your TWO cellphones. (Hint: One nice phone and several SIM cards work well.)

I need two laptops because one is work and one is personal. I'm forbidden to use the work laptop for personal use and I'm forbidden (both by the company and by software licenses) to use the personal laptop for work use. There's nothing I can do about this until the economy recovers and it is safe to get a better job.

I live in the US and most cellphones don't have SIM cards. Also I need both to be on at the same time. And it's the same issue as the laptops, one is work and one is personal and while it's not expressly forbidden to use the personal phone for business, it certainly is forbidden to use the business phone for personal calls.

Re:stupid problem in the first place

[jungd]

Unless you can think of a way for the companies to make up the lost profit made from selling the power supply to you - you won't see it.

Re:stupid problem in the first place

[Jman314]

I agree. There are far too many power "bricks" in our house doing nothing but inefficiently converting 120 V AC into 3 or 6 V DC. There has got to be two dozen or more. All those power supplies feel warm because they lose energy due to heat.

It would be interesting to try to standardize a different connector: low volt DC. Power from the grid could be converted to maybe 10 V DC before being used all over a building by devices with special connectors. Most of the conversion could be done in one box by the main ciruit panel, which should be more efficient than converting for every device.

There are a couple obstacles: getting the devices installed and then standardized. Maybe the existing plugs the current power bricks use could be copied. Anything to reduce dependence on power bricks.

Re:This will be a significant breakthrough

[SteveAstro]

For an electrical engineer you don't know a lot do you ? A decent transformer of 48VA (2A, 24V) will run barely warm if its designed right. Increasingly transformer designers are using cheaper and cheaper techniques which has reduced the regulation of small transformers to as much as 75%. A 48VA TOROIDAL transformer runs basically cold, and is smaller than a clenched fist.

A an on-line (90-280 V AC In) SMPSU DOES NOT work in the way you describe. The input stage rectifies the incoming AC to high voltage DC (110 x root(2) )The High direct voltage (500 volts) is then chopped at very high frequency and transformed and isolated by a very small high frequency core.

The piezo electric method is interesting, but TANSTAAFL, and the catch is that piezo materials suffer from hysteresis loss, which results in, you guessed it, heat generation.

Electromagnetic transformers are close to perfect machines, particularly as the size increases.

Steve

What's Old Is New Again

[Hirsto]

While I'm glad to see that someone is actively working in the area, this idea is many decades old. About 20 years ago I obtained a sample kit from a vendor of the PZT and kynar type piezo films and the technical materials with the films gave formulas for computing the width, length and thickness of the films for creating voltage transormers. They gave many construction hints for increasing the output current and suggested operating at frequenccies greater than 500kHz. BTW, they are wonderful tweeters when connected to an audio amplifier. Here is a link to an IEEE artical on the history of Piezo ceramic transformers and filters. http://www.ieee-uffc.org/ultrasonics/jan1.pdf Doesn't mention the film based transformers though. Here is another link to an IBM text article describing kynar voltage tranformers from the late 60's. http://www.research.ibm.com/journal/sj/mit/section c/paradiso.txt

Re:What's Old Is New Again

[Anonymous Coward]

So are the old power Vibrator's in old valve sets from the 40's using springsteel. Selinium rectifiers- what happened to them?

So will the rubber or neoprene dampners wear out in this new fangled stuff. Anything ultrasonic fatigues material.

Neat addy

[Handpaper]

If you're building power supplies, it can't hurt to have your email address end in @psu.edu

Laptops use more power than that

[Anonymous Coward]

My laptop is currently using 15W (with a crappy power factor of 0.5!) and it isn't even charging. When charging or when the HD is on, it takes over 25W. The current Apple laptop power supplies are rated at 65W.

So where does this article get the 12W figure from?

I also question the likelihood of ever using these things. Current laptop power supplies are the size they are largely as a heat dissapation and safety issue (have you seen the requirements for computer power supplies?). They are switch mode supplies and very efficient.

To be smaller, these piezo power supplies will have to be more efficient and thus produce less heat. Then they can be smaller without overheating.

article is full of bad information

[frovingslosh]

Yes, your point was the first thought that struck me as I read the article. Then I came across this gem: Most laptops require about 15 volts direct current with less than one amp of current and about 12 watts of power.

Most laptops use about 12 watts?????? If these guys are working towards making their pizo suppkies reach a target of 12 watts of power, then it's going to be a long time before we'll ever be able to use them with real laptops, which can draw 75 watts or more. The article seems high on hype and low on anything meaningful.

Look to Japan?

[Anonymous Coward]

Thanks to the grad student for the more detailed view of this field. My first question upon reading this headline though was,

what do the Japanese know that we don't? As someone that travels to Japan extensively, I've become enamored with their electronic consumer goods market. One of their many nice touches -- very small transformers/power adapters for their phones/computers/you name it. Easily half the size of their American counterparts.

So what gives?

Re:Look to Japan?

[Anonymous Coward]

All electrical devices sold in the US are required to have a "built in" safety factor. usually 5%-10% which means that the transformers are wound with wire that can handle 5%-10% more current than what is rated on the label.

In contrast, Japan does not have the same standard as the US. They build their transformers to handle the maximum current with no overcurrent protection.

This not to say that the US is better, as it means that more resources are expended building out that 5%-10% protection, but we expect things to fail whereas Japan expects things to work.

Re:Look to Japan?

[Anonymous Coward]

I believe that Americans don't care yet to use resources efficiently. All we optimize is money. A bulky transformer is cheaper to build than a small switching power supply. A big displacement V8 is simpler to build and maintain than a high-tech four or six. To hell with oil and tress and whatnot.

Re:Look to Japan?

[Anonymous Coward]

I find that reasoning hard to believe. All electronics are built with a significant safety margin into them, if for no other reason than to reduce premature failures due to wear if they were to run at 100% load.

Re:Look to Japan?

[Anonymous Coward]

yeah we're big dumb brutes, move along

Re:Look to Japan?

[Anonymous Coward]

Not necessarily, a devices current draw could be say 100mA at startup but consume 80mA running.

In the US, (if using the 10% rule) the device would be required to be rated at 110mA and the transformer would be required to be capable of outputting 121mA (10% of 110mA) even though it only consumes 80mA.

In Japan this would be different. The transformer would be rated to handle the 100mA startup current with a net savings of 21mA worth of resources (Larger wire, Diodes, Cases, etc..). Even a 100mA transformer will still handle a higher surge current for a short period of time.

Ok, you are saying big deal, it's just 21mA, until you take into account that the average generic transformer is only 80% efficient.

DC Power Distribution.

[Grendel Drago]

Speaking of DC power conversion technologies...

I know that DC power transmission went out with Westinghouse's AC transmission, mostly because DC doesn't really work over significant distances. Would it still work over small distances, say in a house or apartment? (For the sake of argument, say that cable runs could be kept to a maximum of a hundred feet.)

Assuming that it can work like that, why isn't there DC power distribution alongside AC in many situations? We have so many damned wall warts that it'd be worth it to distribute, say, 24VDC and step it down to 12, 9 or 4.8124VDC. (Whatever's popular.)

Wouldn't it be more convenient to replace those clunky wall warts with cables designed to step down DC voltage?

Question is, what exactly is the hardware required to shift DC voltage? I know AC can use a pair of coils with differing winding counts (that's a transformer), but how do you step down DC voltage? And can it be done on the cheap-cheap, and in a small footprint?

--grendel drago

Re:DC Power Distribution.

[eriksarcade]

its called the 78XX series of voltage regulators. where XX is the desired output voltage. a lot of electronics that use 6v in use a 7805 to regulate the voltage to 5v.

Re:DC Power Distribution.

[Anonymous Coward]

it's called a voltage regulator.

Re:DC Power Distribution.

[enosys]

Linear voltage regulators like the 7805 are cheap, easy to use and amazingly resilient (eg. protected against short circuits and overheating) but they have their disadvantages.

The main disadvantage is heat. If you want a lot of power, especially if there is a large voltage drop, you'll need heat sink bigger and much heavier than a small switch mode converter you could use instead.

You also couldn't get 5V from 6V with a 7805. The dropout voltage is 2V, meaning you need at least 7V to get 5V. There are special low-dropout alternatives that can get 5V off 6V or even less.

Re:DC Power Distribution.

[TeknoHog]

Regulators are very much not the equivalent of transformers. They can only give a voltage drop, but the current is kept constant, which is why some energy is wasted.

For example, converting from 6 V to 5 V at a current of 1 A means a voltage drop of 1 V. Input power is 6V * 1A = 6 W, whereas output power is 5V * 1A = 5 W. The difference is wasted heat, and you can always calculate this as voltage drop times current. You need to choose a suitable heatsink to accommodate the heat. For many electronic gadgets the current is small enough that the waste is not a concern, but with computers you need several amps, so a regulator would be out of the question.

However, a transformer from 6 V to 5 V would have ideally equal input and output power. Keeping the input at 6 V, 1 A, the output would be 5 V at 1.2 A, i.e. the same power, no waste. However, "DC transformers" are always a little complicated (basically inverter+transformer+rectifier) and there are other losses.

Re:DC Power Distribution.

[Dun Malg]

I know that DC power transmission went out with Westinghouse's AC transmission, mostly because DC doesn't really work over significant distances.

Actually, DC is more efficient than AC over long distances. The problems with loss have more to do with the voltage. The reason DC lost to AC early on was that AC is easily stepped up to high voltages for transmission, then dropped to "safe" voltages for local distribution. 100+ years ago, all they had were regular copper-wound inductive transformers, and they only work with AC.The problem we have now is that all our DC devices are slaves to their wall-warts, most of which are copper-wound inductive transformers and require AC power. Being that they all had their own power supplies anyway, all those DC devices have different voltage requirements, usually dictated by the "power-hungriest" component in the device. Thus we have no standard for low voltage devices, and no real hope of seeing a standard anytime soon. The closest we have is 12VDC, but only for devices you could conceivably use in a car! You could set up your own home DC power system, but how much will you end up paying for all the DC-DC converters to match the voltage to the device?

Re:DC Power Distribution.

[Avian visitor]

I know that DC power transmission went out with Westinghouse's AC transmission, mostly because DC doesn't really work over significant distances.

Actually DC power transmission becomes more efficient than AC at very large distances.

There is a certain threshold distance where capacitive losses in transmission lines become greater than losses in rectifiers and inverters.

For example electricity from the Itaipu power plant in Brazil is transformed to high voltages with regular transformers, then rectified to direct current. On the other side of the long transmission lines is a large inverter that turns DC back to AC that can then be transformed to lower voltages.

Re:DC Power Distribution.

[calidoscope]

I know that DC power transmission went out with Westinghouse's AC transmission, mostly because DC doesn't really work over significant distances.

That's true of the low voltage DC used in Edison's distribution system (which, by the way, is why American homes have 120/240V single phase service). High voltage DC (+/- 400 KV or so) is actually better than AC for long distance power transmission - due to lower losses and not having to keep the neds in synchronism.

Assuming that it can work like that, why isn't there DC power distribution alongside AC in many situations?

Hmmm, the Edison system was still in active use in some cities until recently, that is you could get 120V DC power from the utility.

Seriously, a DC power distribution does have a lot of merit (power over ethernet??) - it would make a hell of a lot more sense for a UPS to put out DC instead of having to convert the battery voltage from DC to AC. Even if a voltage conversion step is necessary, it would be more effiecient than a wall wart. It would also make sense for those living "off grid".

If you turn the clock on your DeLorean back to the 1930's - a lot of the ranch and farm houses would have a windcharger for the lights and would have a collection of 32 volt appliances. 32 volts was also common lighting voltage used in railroad passenger cars of that era.

Question is, what exactly is the hardware required to shift DC voltage?

If no galvanic isolation is needed, a chopper works fine. Voltage step-down or step-up is adjusted by varying the duty cycle of the switch and free-wheeling diode.

Re:DC Power Distribution.

[anakin876]

also in the US in the state of Utah there is a HUGE power plant called IPP (Intermountain Power Plant) that provides a great deal of the power for Los Angeles. The cables that transfer all the power run DC from Delta, Utah to Los Angeles. Supposedly the cables are actually the right length to produce harmonics that would pretty much overpower any radio signal on the earth if the power was transferred via AC as opposed to DC. Not sure I believe my University Physics professor on that one though.

Re:DC Power Distribution.

[Anonymous Coward]

I've tried it, for low voltage DC, you'd need some thick cables, and you couldn't draw much current. (Look at the battery cable in your car, particularly the solenoid(s) to see what I mean)

From what I understand (and maybe some engineers will correct me) the trouble with DC is that it builds a magnetic field around the wire wich impedes the flow of current.

In my case, I switched to sending low voltage AC through the same wires and installing a rectifier next to the device I needed the power for, and it worked.

Personally, what I think is needed is some sort of ANSI standard for "plug-n-play" voltage and current requirements. Plug a device in to a magic box, it reports it's required voltage and current. The box provides it. 1 transformer (with several secondary tappings and support circuitry I'd imagine) provides the required voltage. The output from the black-box would be lower voltage AC, it would still be up to the individual device to regulate and convert it to DC. (if the original voltage is "near" what you actually need, you can lower it with regulaters and such.)

I for one am fed up with the spiderweb of cables I have mostly involving cube-taps for those annoying walwart transformers.

Re:DC Power Distribution.

[Anonymous Coward]

Blah, blah, blah.... Eddison was a troll and you know it. Long live Tesla's AC power distribution!

Overlord...

[Reaper9889]

And I, for one, welcome our new 1/4-of-standard-lightwhight-complex-supersonic-low heat-100-to-125volts-powerconductor overlords.

A _Real_ Solution...

[John Hasler]

... would be to move the power supply inside the computer. However, that would require that the computer meet UL safety requirements.

Re:A _Real_ Solution...

[geirt]

A Real Solution would be to move the power supply inside the computer. However, that would require that the computer meet UL safety requirements.

Please moderate this as +5, Brilliant ...

voltage

[Anonymous Coward]

European standard is 230V, _not_ 220V.

Re:voltage

[puffing_billy69]

In New Zealand it's anywhere between 220-245VAC.

I've not idea what it is in Soviet Russia.

A few questions to the expert :)

[Anonymous Coward]

What is the frequency range that you can tap power from ?

How many eigenfrequencies does that correspond to?

How much do you have to rattle the notebook to generate a reasonable power?

What is the ratio between the generated voltage, and the voltage of the thermal (Nyquist) noise in the piezoelectric crystal?

But will the cheaper PC makers use it...

[Anonymous Coward]

Does any know why my Sony laptop's AC/DC converter is about twice as big as my powerbooks. The Sony is newer. Sony just trying to save a buck or two on the larger unit?

Power supply in the cable

[|>>?]

When I visited IBM's Almadden Research Centre in 1997 I recall seeing a cable that looked just like a power lead, but it had the power supply built into the cable. You plugged it into AC power at one end and DC came out the other.

They were having problems getting aproval from the power company as I recall...

My memory is getting poor at my old age, so perhaps I'm retelling a story of a friend-of-a-friend who thought about this idea, but I'm pretty sure I saw it - lots of geek magic happened on that trip in 1997.

Re:Power supply in the cable

[Dun Malg]

You plugged it into AC power at one end and DC came out the other.

Gimme four appropriate diodes and a power cord and I'll build you one. Unless, that is, you're expecting something other than dirty 110VDC....
Getting to DC it the easy part-- it's the voltage conversion that thakes up all the space.

Re:Power supply in the cable

[|>>?]

it's the voltage conversion that thakes up all the space.

As I said, my memory is hazy on the subject, but I'm pretty sure that the voltage conversion was also included in that cable. That's what made it so sexy...

Re:Power supply in the cable

[ChrisMaple]

It's possible that a low-power switching power supply was built into either the plug or socket end.

Another possibilty is that the power cord was made of a moderately resistive material to drop voltage in a lossy manner. This is an old (and poor) technique.

Ideas

[enosys]

Don't increased frequencies allow shrinking of electromagnetic components? Why not just increase the frequency?

What about non-line-isolated battery chargers? When you're supplying power to the laptop you need isolation, but you don't if you're just charging the battery. These could be extremely small and light.

Re:Ideas

[Anonymous Coward]

You are right; the electrical systems of airplanes operate at a few hundred
Hz so that smaller transformers can be used, IIRC. However, are you
suggesting that the frequency that the power plant sends out be
dramatically altered just to suit the needs of laptop users?

Re:Ideas

[enosys]

No, this has nothing to do with the frequency the power plant sends. I mean make the switching mode power supply run at a higher frequencies, MHz instead of KHz perhaps

Re:Ideas

[aXis100]

They allready do that - you'll probably find all laptop power supplies are switch mode, operating in the order of 100's of kHz.

This does shrink the transformers (# windings is proportional to frequency), however there are limits.

Optocoupler

[Anonymous Coward]

From my experience, most switch-mode power supplies use an optocoupler to isolate the feedback loop from the output.

Aluminum Wireing?

[lhaeh]

Aluminum wire instead of copper for winding the transformer coil would reduce the weight, although the size would remain the same.

The reason copper wire is more common then aluminum is that aluminum is not as malleable (breaks when its bent back and forth) so it is not practical for things like household wiring.

Since coil windings are stationary the only time they could break is during manufacturing, increasing the cost of the final product. From what I gather that's why aluminum is not used.

Re:Aluminum Wireing?

[Avian visitor]

Aluminum wire instead of copper for winding the transformer coil would reduce the weight, although the size would remain the same.

An aluminum wire has higher resistance than a copper wire with the same cross section. Because of this, transformers would have to be made out of a thicker wire which would mean bigger and (probably) heavier transformers.

Also aluminum is a lot cheaper than copper so I don't think cost would be a problem.

Re:Aluminum Wireing?

[Anonymous Coward]

Actually, aluminum was widely used for household wiring in homes build around the time of WWII (including my parents' old house). Since, as you say, aluminum is more brittle and has higher resistance than copper, homes with aluminum wiring are at greater risk for house fires than those with copper wiring. This is one reason why electrical codes these days forbid aluminum wiring.

Re:Aluminum Wireing?

[lhaeh]

Good point. For some reason I thought aluminum was a better conductor.

I did a quick check and found out that aluminum only has about 65% of the conductivity of copper, which would mean a 35% size increase. Copper weighs 2.35 times more then aluminum. So it would be 15% lighter? I personally would prefer my adapter to be lighter rather then smaller, but that's just me.

Also aluminum is a lot cheaper than copper so I don't think cost would be a problem.

I should clarify, I meant it would cost more to manufacture in terms of re-tooling to work with aluminum.

The size of laptop power supplys isn't much of an issue as it once was I'm seeing a lot of those small, thin, light ones that are about the size of an original palm pilot. Personally I would like to see laptops that I can plug a molex power connector into, anytime Im around someone's computer I can just plug it right in, I wouldn't even have to carry anything with me besides maybe a small cable.

Re:Aluminum Wireing?

[NoMaster]

Aluminium wire has only ~ 2/3 the current capacity of equivalently-sized copper.

Transformer windings aren't perfectly stationary - they do vibrate (abeit only microscopically in a well-made transformer). Aluminium is much more brittle than copper.

Aluminium is an absolute bitch to join electrically and mechanically to anything else - it's extremely reactive, and tends to form a very good dielectric as it oxidises. For some examples, ask a boatbuilder / guttering expert, or look in your car engine in a few years...

Re:Aluminum Wireing?

[Anonymous Coward]

Aluminum is more expensive as it's produced via electrolysis.

Re:Aluminum Wireing?

[robhancock]

Personally I would like to see laptops that I can plug a molex power connector into That would mean putting that connector on something that didn't already use it, however, which I think would be a bad thing. I think the guy that decided to use those things for PC peripherals should be shot, given their propensity to become stuck so tight they require pliers to remove..

Re:Aluminum Wireing?

[Brians256]

This is what a local electrician told me (IANAE, of course):

It is not the intrinsic resistance of aluminum that causes the greater fire risk. It is the thermal expansion/contraction of aluminum. As the wiring goes through cycles of being used (gets hot) then not used (gets cool), it can cause crystalization (it gets brittle) of itself and changes that make it into a higher resistance material. So, as it ages, it turns into a higher resistance and higher temperature wire. Then, when you run your nifty 15A vacuum cleaner, the wiring in the walls starts a fire.

repair those servers please NOW

[Anonymous Coward]

Please repair the damn servers, it's getting unbearable...

500 Internal Server Error An internal server error occurred. Please try again later.

500 Internal Server Error An internal server error occurred. Please try again later.

500 Internal Server Error An internal server error occurred. Please try again later.

500 Internal Server Error An internal server error occurred. Please try again later.

500 Internal Server Error An internal server error occurred. Please try again later.

Effects on the power distribution network

[Avian visitor]

Almost all power supplies for consumer electronics, together with so-called energy saving light bulbs, LED lights, etc. cause significant losses in the power distribution networks. Why? Because they draw current only on the top of the sine wave.

Think about it. The first stage of most power supplies is a simple rectifier circuit. A capacitor that is charged through a couple of diodes. Diodes are open only when the line voltage is grater than the capacitor voltage. And that happens only on the top of the sine wave.

Why is this a Bad Thing? Because if you make a Fourier analysis of the current you will see that a large part of the current has a higher frequency than the normal 50/60 Hz. This is called higher harmonic current and the transformers in the power distribution networks really suck at transforming it (the losses in the ferromagnetic core of the transformer rise with the square of the frequency!).

Everyone that talks how LED lights and those fluorescent light bulbs will save environment doesn't know what he is talking about. The losses only move from your house to the nearby transformer (But of course, you do not care about that, do you? You only care how much you pay for your electricity bill).

I really hope that this new kind of a power supply doesn't have these drawbacks. It would really make life easier for folks that take care of the distribution network.

Re:Effects on the power distribution network

[Anonymous Coward]

You're going to have to explain that further before I believe it!

Re:Effects on the power distribution network

[Loosewire]

can yo u provide some links / elaboration?

Re:Effects on the power distribution network

[aXis100]

This is why utilities put limits on power factor, and why some consumer electronics (PC Power supplies) are starting to include power factor correction. Big industrial loads have been doing it for a long time.

We can correct for it, but sometimes the effort is not worth it.

Re:Effects on the power distribution network

[Avian visitor]

I am not talking about power factor here. Power factor is not such a problem, because it does not affect the losses in the transformers or the power plants. The effect I mentioned can be measured with the klirr factor (RMS value of the higher harmonic currents over RMS value of the entire current).

If a machine has power factor != 1 it only means that the current and voltage are not in phase with each other.

This is not such a big problem because power plants with synchronous generators can compensate for this effect. But there is absolutely nothing you can do against higher harmonic currents on the power plant side.

Re:Effects on the power distribution network

[^Z]

How come that a typical 4-diode rectifier bridge is not used there? It accepts AC on both half-waves.

Re:Effects on the power distribution network

[Avian visitor]

Graetz bridge is indeed used in power supplies, but it still draws current only when the absolute value of AC voltage is greater than the voltage on the capacitor. And that happens only on the top and the bottom of the sine wave.

BUUUZZZZZ...

[autopr0n]

Unless they can make these thing small enough so that the frequency is inaudible, or include lots and lots of sound dampening, you're going to be hearing an annoying buzz all the time.

Poor "technical" article

[serbanp]

It's simply full of inaccuracies. The piezo transformer is not a new idea. You take a piece of piezo-electric material, excite it in AC (thus making it vibrate) and, with electrodes placed properly on the same piece of material, you get back electric signal from the vibration.

This stuff is already used in low-to-high voltage converters (e.g. the inverter in the laptop panel - its job is to produce high AC voltage for driving the backplane CCFL). However there are tremendous shortcomings when comparing to the mature magnetic energy conversion:
1) LOWER efficiency - if you can get 84% you've got a lucky day. Magnetic-based conversion can easily achieve 90-95%.
2) to work properly, these things must be driven at resonance, i.e. the AC input signal must match the resonating frequency of the piezo-transformer. This is much more difficult (think dynamic frequency tuning) than driving the wide bandwidth magnetic transformer.
3) derived from 2), the driving signal must be sinus (the energy confined in a narrow spectrum). This is very difficult. A magnetic transformer is usually driven in switching-mode - certainly all AC-adaptors (off-line AC/DC converters) for laptops are.
4) the input/output voltage ratio is fixed by the piezotransformer geometry. A ratio higher than 1:10 was very unusual back in 2001 when I designed back-light inverters with them. In contrast, the magnetic transformer is very versatile and, when controlling the insulation between the primary and secondary(ies), you can easily achieve factors of 100s.
5) present piezo materials have much lower power density ratings than the better magnetic cores. This means that for the same 80W AC-adaptor you'll need a much bulkier piezo-transformer than a magnetic transformer to transfer that power.

Did you see any of these major setbacks mentioned in the article? What a piece of crap!

B.t.w. it makes no sense to integrate the AC adaptor in the laptop as it limits its portability. When you're on batteries and you can't use the AC outlet, you don't want to carry with you the extra weight of an useless AC adaptor, do you?

Serban

Re:Poor "technical" article

[TeknoHog]

the driving signal must be sinus (the energy confined in a narrow spectrum). This is very difficult. A magnetic transformer is usually driven in switching-mode - certainly all AC-adaptors (off-line AC/DC converters) for laptops are.

Add to this the point made in another post: DC appliances require those higher harmonics.

Re:Poor "technical" article

[b0rken]

Thanks -- I was wondering about the efficiency issue.

let's calculate

[Anonymous Coward]

Let's say that:
#4 gauge wire has a resistance of 0.3ohm/1000ft
100ft of that has a resistance of 0.03 ohm
(remember both wires count so that's 50ft away).
You have a load of 1000W powered from 24V DC.
That means the current is 1000/24 ~ 42A
Let's assume the wire can take it
42A through 0.03 ohm causes a voltage drop of 42*0.03 ~ 1.25V
1.25V at 42A means a power dissipation of 42*1.25 = 52W

(redoing at 12V would yield 200W!)
That is all heat (joule effect).
Inside the wall (which is designed to not transmit heat).
There is also a domino effect because the devices getting less voltage will tend to draw more current in turn.

And this does not take into account:
- high-amperage connectors (regular power sockets would melt because they don't have enough contact conductivity)
- spliced wires etc (very difficult with heavy gauge)
- expensive heavy gauge wires in the walls

So a relatively high voltage (48 or 24V) is probably feasible over short distances and light load, but a low-voltage system for a small community is not possible until we have cheap superconductors.

PS. Try the above calculation for #18 to see just how fast it would melt.

Re:let's calculate

[calidoscope]

My impression is that the OP was thinking about distribution for all of the low power devices that currently use wall warts - you might be looking at 200W for a typical house.

If I was going to pick a distribution voltage - I'd go for 42V. Why? Because that is going to be the new standard voltage for cars and there should be lots of stuff that will run off that voltage. Other issue is that it is comfortably below the cut-off for low-voltage safety issues.

Trannys can draw infinite current though...

[caveat]

I always understood we used plain transformers because if you increase current drain on the output, the current in will increase to compensate. Something about the field in the tranny becoming unbalanced and the flux pulling more I into the primary...something like that. If you analogy is right, you can't draw more current from the secondary than is fed into the primary - useful for some applications, horrid for anything you'd want a transformer for.

The article was a sales pitch

[Anonymous Coward]

It was a Penn State article about a Penn State product, not a technical article.

"The piezoelectric PC power adapter was developed at Penn State in collaboration with Face Electronics of Virginia and Taiheiyo Cement Corporation, Japan. Taiheiyo is planning to mass-produce the devices in 2004."

They should have used Power Point.

Re: Why electric outlets are the way they are

[A55M0NKEY]

See this article

I, for one, ...

[Anonymous Coward]

... welcome our Piezoelectric overlords.

Me too...

[Anonymous Coward]

...but I don't call mine a Powerbook ;)