DC Power distribution - Nix the Transformers?

MailtoDelete asks: "I have most of my electronic gear plugged into a couple power strips hanging off a UPS. Most of these devices have big block-type transformers which, besides being bulky, are a bit of an eyesore. I have been trying to find a product out there somewhere that would allow me to have one central transformer that would distribute DC power at variable voltages, depending on what devices I wish to plug into it (think one AC input and 9 or so DC outputs individually adjustable). I found this device that resembles what I have in mind, but it does not have sufficient output for my router, switches, and various other devices. Is there a product on the market already that would do this? Can I build one with my marginally above average soldering and electrical schematic skills? Have any of you found a better way to eliminate these blocky plug-hogs?"

Marginally?

[Anonymous Coward]

If the true measure of your skills is "marginally above average" then the simpile answer is "No" However, if you actually have electrical design skills and have a good feeling for circuit protection, filtration etc. then you should already have built it.

Why?

[Guspaz]

Why bother? If each device has it's own power brick, it's safer. If one fails, the others won't.

If you combine all of them into a single point of failure, you might reduce what you think is an "eye sore" but at the cost of a higher risk of failure.

Is making your setup less sturdy worth a cosmetic fix?

Re:Why?

[voisine]

never had a wall wort fail... ever. ac's gone out many times. I think the dc power supply is not the weak link in the chain unless you've got a battery backedup generator backed up ups at an earthquake/hurricane/tornado proof co-lo somewhere.

Also...

[Yobgod Ababua]

...now that I think about it, so could just obtain a hobbyist DC power supply of sufficient amperage and hook all your devices up to the appropriate voltages.

It's possible that a spare PC power supply might even suffice, but be careful that you get one that doesn't detect and auto-off when a motherboard isn't plugged in.

Lots of power supplies from somewhere like this: http://www.kepcopower.com/prodmod.htm

Re:Power supply

[alienw]

There is absolutely no reason a power supply has to be large or needs a fan. It's possible to make one the size of a notebook adapter.

Re:No.

[alienw]

You don't need a winding for every voltage. One winding with multiple taps should work just fine. As far as current draw: a circuit breaker or fuse on the primary will do the job.

Re:Wireless power!

[raider_red]

We could probably set up a wireless power system, but you can forget about the "safe" part. You could also give up any hope of ever having children.

Re:Why?

[Guspaz]

All the more reason to continue using wall worts. You're moving from a simple wall wort to a much more complex system. One that is akin to a computer power supply. And I've had MANY computer power supplies fail.

Re:Use the IC, dammit

[robert bitchin']

The coils are there to provide electrical isolation. If they were left off then you'd be exposed to at least one side of the 120VAC in what may be a poorly isolated unit. The coils are large because electromagnetic inductive efficiency drops with the input frequency. Efficiency is the major reason why the switching frequency in PC switching power supplies are so high, most can get away with just using air cores rather than metallic cores.

The IC you mention is useful for completely isolated devices (no external connections) such as night lights.

Re:Use the IC, dammit

[LordEd]

The problem is efficiency. You can drop 120V to 12V on this, but that means that the regulator has to burn up 108 V. If you're drawing 1A, then that's 108W being wasted just to step down the voltage, and 12W actually being used by the device (90% wasted).

However, a transformer can step down voltage with a very high efficiency (google says 80 - 90% efficient).

A stepped down signal of 12V and 1A means an input of 120V and 0.1A, plus loss due to resistance. With 90% efficiency, that means an input of about 13W for the same output as the regulator alone.

Of course, there will be some loss due to using a DC regulator after the transformer, but nowhere near the 108W lost above.

Re:Make device transformers external, easy convers

[alienw]

Please, if you don't know anything, shut up. Converting from DC to AC is just as efficient as converting from DC to DC. Unless your solar cells happen to put out the exact voltage your device requires (they don't), you still need some kind of switching power supply. Whether it takes in or puts out DC or AC is almost completely irrelevant.

Re:Hardware Wars

[who's got my nicknam]

True dat. Tesla was the real inventor back then, which is why we wound up using AC polyphase instead of Edison & Co.'s DC system. Many bitter exchanges between the two camps, with Edison's side performing their famous "Westinghousing" of dogs and such to prove AC's danger. (The name comes from the fact that George Westinghouse had bought/leased/stolen Tesla's patents for AC production/distribution.) Fortunately the science of Economics won out when it was shown that AC would be far cheaper to produce and transmit. Tesla often mocked Edison's lab techniques for being too laborious; Edison would produce dozens or hundreds of prototypes for a product (the light bulb being a prime case), whereas Tesla figured it out in his head, made the drawings and had his engineers build the working product. Unlike Edison, Tesla was an absolutely dismal businessman who died broke and senile, forgotten and abandoned by those he helped to make rich (like Westinghouse). There. I've had my Rant. Hail Tesla!