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?"

Comments

No.

[Short Circuit]

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?

Sure, but you'd need a transformer with multiple sets of windings, one for each voltage you want to put out, and one for your line input... But you're not likely to find one that fits your exact needs.

Nevermind concerns about drawing too much current from your device, and failing gracefully.

Re:No.

[harrkev]

What the parent poster said! I design boards for a living (along with doing some VHDL stuff in FPGAs). My expertise is digital, but I do have an Electrical Engineering degree -- and I could not properly design a switching power supply -- at least that what what I was told by my power supply guy after I tried laying out his circuit on the board.

I have also tried my own experiments in this area. I had an old Celeron 466 system, and my scanner, speakers, and force-feedback joystick all ran off of 12V. So I hooked up my computer's 12V rail to some connectors on the back (with caps attached to help reduce noise). Here were the results:

1) Scanner - worked like a charm. But you had to plug in the power while the computer was off. Otherwise, the whole computer would reset iself. This was my one success.

2) Speakers - Worked, but you could hear the hard drive heads moving. The amount of noise was too much, so I had to go back to a separate wall-wart.

3) Force Feedback Joystick - This was a Microsoft model, which connected to the Game port (not a USB model). Apparently, this stick did not like sharing its power ground with its signal ground. The computer shut off instantly, and the joystick was fried. This goes to show that you need to have FLOATING power supplies in any scheme like this.

In the end, my grand experiment was not really worth it, as I spend a couple of hours soldering and drilling, and all I did was to remove one power supply.

But if somebody DID make a power supply box that had the following: 3x12V, 2x9V, 2x6V, 3x5V, all at 2A each, and they could do it for under $100, then I would be very tempted to buy one. Unfortunately, I suspect that this type of supply would go for a lot mroe than $100.

Re:Hardware Wars

[snorklewacker]

Wasn't it Thomas Edison who tried to prove that Tesla's 3 phase AC power distribution was dangerous by electrocuting frogs with it and showing how they thrash about vioilently before they died?

Not Tesla, Westinghouse. The whole frog twitching thing was a sideshow trick when electricity was first discovered, and could be done with DC. Edison went all the way up to electrocuting horses, and advertised it could be done on people with "Westinghouse's Electric Chair". He thought people would be horrified. In the last bit of irony, several states loved it and actually ordered these things, using them for capital punishment for many decades afterward.

Edison may have been quite an inventor, but he was rather a ruthless man not above gross distortions and character assassination.

Liberator

[Zakir]

This doesn't fit what you're looking for exactly, but it fill help the problem of having to plug wall worts into your power strip. It is basically a 12 inch extension cord that plugs into your power strip so that the transformer doesn't take more than one outlet up.
"Get full use of your power strips and UPS outlets with this premium power cable from Cables Unlimited! Just plug this cable between your bulky power adapter and any unused outlet and this revolutionary designed space saving cable acts as a 1' extension, giving you a little extra length to get into hard to reach places."
http://www.tigerdirect.com/applications/ SearchTool s/item-details.asp?EdpNo=392776&CatId=1284

Re:Liberator

[MarkGriz]

"I'm actually kinda partial to Dr. Ferd's Wart Remover"

Seems a bit overpriced at $6.99

The cheapest source for these I've come across is here $8.99 for a 5 pack.

They have tons of variations on this item too, including dual plugs, flat plugs (so you can put furniture up against them), etc.

Your link.

[Murphy Murph]

The link you provided to the "ELK-PD9 Power Distribution Module" is telling.

Do you understand why devices such as that are used?

A power distribution module such as that is used to power devices like remote video cameras, remote security sensors, and other remote monitoring devices.

Key word being remote.

Devices such as these use structured wiring with data (video) and power coming in to the device over one cable bundle. This is done for ease of installation to the remote site, and because the security camera on your neighborhood Target store being 100 feet from the nearest power outlet makes a wall-wart is unfeasible not unsightly.

Watch out for unexpected shorts!

[RandomJoe]

If you do this, be sure to check for unexpected shorts. A piece of equipment we install at work has a big warning to only use it with its own power supply. Of course, it's so much easier to tie it to the beefier supply running the other panels it associates with, so many techs do just that. And it works just fine. Until...

Turns out, due to some wierd design decision, the common pin for the serial port isn't really "common". If we plug into it with our laptops, and then plug the laptop into AC power (with ground pin intact on the PS) it shorts the power supply through the serial port, the laptop ground, back to the grounded power supply on the main panel. (This little panel "doesn't require" grounding - wonder why...)

So, if your devices all connect to each other in some way make sure this sort of loop doesn't occur. Especially if you use a single beefy supply - you might be in for fireworks!

Make device transformers external, easy conversion

[Eravnrekaree]

As far as the things we plug into wall outlets, I think it would be very wise for all electric devices that uses a transformer to use an external transformer rather than build it directly into the device. this way, if you later switch to solar you can run the device directly off the DC from the solar panel, only perhaps having to adjust the voltage. DC is preferable with solar technology, which produces DC output, whenever possible, since an invertor to convert from DC to AC cuases you to lose energy and are somewhat innefficient. DC works best with short runs as well, such as from the panels into your house. AC for distribution was chosen since the voltages can be easily stepped down after high voltage runs, since high voltage carries better over long distances. It would be great if we could find clean, renewable, safe, practical, non-toxic energy sources, like improved solar, so we could get rid of AC and its EMF fields and all of those ugly high voltage power lines crossing the country.

All devices could use Power Over Ethernet or USB

[metoc]

IEEE 802.3af aka Power-over-Ethernet and USB 2.0 both provide DC power in a standardized form factor.

USB 2.0 is good for 5.0 volts and a max of 500ma (2.5 watts) for the bus.

IEEE 802.3af is good for 44-57 volts and a max of 15.4 watts.

Many devices currently on the market, such as PDAs, iPODs, and a few cell phones will charge from USB ports.