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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?"
"This is Reddy Kilowatt, reporting a dangerous, overloaded octopus connection in sector five!"
"Flyin' in just a sweet place,
Never been known to fail..."
5 or 10 transformers, or 5 or 10 plugs on every outlet, one for each voltage?
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.
The device you're looking for is a power supply -- they're not just for computers. Just get one that will put out enough amps for peak demand on all your devices, mount some molex connectors onto a board of some sort, color code them by their voltages, and stick the whole shebang in an old PC case.
Of course you'll have moved from a bunch of smaller blocky transformers to a large honking thing with a fan, you'll have to wire up your own cables. Watch that you don't overload it, or you let out the magic smoke and none of your devices have power (and you'll be ventilating your room of noxious fumes). And none of it will be portable. It's going to be loud with the fan, and don't skimp on that, or it's magic smoke again.
This is probably even more misguided than the guy who wanted a raised floor.
Forget replacing wall warts with one very large wall wart.
Where is my wireless power?!
We wont be truly untethered until we have wireless power.
(Not entirely kidding. Is there any safe way to deliver wireless power? Or am I just asking to turn my house into a very large Microwave Oven?)
- For the complete works of Shakespeare: cat
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.
tasks(723) drafts(105) languages(484) examples(29106)
Instead of helping someone build the circuits they require and possibly learn something in the process, let's just remind them that they're only above average, and thus shouldn't even bother.
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./ SearchTool s/item-details.asp?EdpNo=392776&CatId=1284
"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
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.
I dub thee... Sir Phobos, Knight of Mars, Beater of Ass.
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?
It's designed for large scale server rooms, and as such won't particularly adapt to what you want, but this does show that others have had the same thoughts and are applying them to various niches. They do also explain what they see as the benefits of this arrangement.
http://www.rackable.com/products/dcpower.htm
...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
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!
Here's the correct link. http://www.securityideas.com/polipl.html
I swear reading most of these ask slashdot's are slowly killing me from the inside out.
e =CTLG&category_name=CTLG_009_001_003_000&product_i d=61-2755 , but if you want ONE DC converter with various voltages, you're just asking for trouble. An eyesore they may be, but they're quite safe for the most part and do their job properly.
If you're pissed that a block takes up like 3 ports on a surge protector, get a short extension cord like this: http://www.radioshack.com/product.asp?catalog_nam
-Adam
Get a normal PC power supply. It's got output voltages at 5 and 12 volts, which should cover most of your equipment (a lot of stuff that has a 6 volt wall brick works fine on 5 volts). It's also got a 5 volt line that's always on, if you've got something that you don't want controlled by the switch.
Others have posted similar devices elsewhere in this thread, but as an AC mine will get buried. The one I list is cheaper than the rest and is available at a place many of us have actually heard of:
Micro Center 10" Power Cord
Whew, finally somebody with some sense!
You're basically talking about a niche market application, which is not to say that it's unheard of, but if you did find it, it would be horrendously expensive.
Want to build one yourself? The easy way is to take apart a bunch of RadioShack universal wall warts, mount them in an enclosure, wire them up together with AC, add an AC plug, and do some cable management with the resulting output wires. Should take a couple of hours, and you wind up with a big box filled with tightly-packed transformers (watch out for ventilation).
Now, let's say you want to do it right. You'll need a single transformer to take the line voltage down to 32V, or 48V, a diode bridge, then some filtering caps (this is a basic, unregulated DC supply). From there, you will take this 32-48V rail, and use a variable switching converter on each output channel to bring the voltage down to the right level. If you need cleaner power, there are even circuits to take a variable switing converter, and use that to feed a variable linear converter for super clean power.
Some stock switching circuits are available in Linear Tech's Application note on switching regulator circuit collection. My favorite introduction to switching regs is Application Note 25, Switching Regultors for Poets, bless Jim William's heart and drawing abilities.
Hope this helps
This would be entirely possible thanks to modern power electronics, if you really want to. Honestly I'm not sure it's worth the bother, but here you go:
Get a normal DC power supply that will supply the largest voltage you need and more current than you need. Or build one. Whatever.
Go to some electronics shop (If you're in the UK, Maplin are good) and get some Voltage Regulators. These are basically integrated circuits that can take in a wide range of voltages and output a fixed voltage.
Connect the voltage regulators' inputs to the output of the main power supply.
Connect the voltage regulators' outputs to your devices.
NOTE: Lots of external computer bits ask for unusual voltages. That might be a bother.
NOTE 2: There will be lots of books availiable on this topic. Look for 'Power Electronics' on Amazon - or in a local university's library (since textbooks are expensive). Don't get a book that's too old - some of this stuff is pretty recent technology.
NOTE 3: I am no expert. While I believe my design would work (and be pretty efficent), I can't promise anything.
Michael
"Goodness me, how unlike the FBI to abuse the trust of the American public." -- The Onion
DC power distribution is used in telecomm applications. They use a 48V bus and use DC/DC converters to get the required voltages. The DC/DC converters are expensive, and the AC->48V converter is also expensive.
You could just get auto-adapters for all your crap and then use an AC->12V converter. However, I imagine that this is more work than it's worth.
Why not just do what everybody else does and get more outlet strips?
You already have all of these transformers in the original plugs right? Why not just find a suitable container to put a power strip or two in and have all of the transformers plugged into that? You could even change the connectors on the end of each transformer so that you could just build the jack into the box and just plug your device into this box that way it wouldn't be just a box with wires coming out of random holes.
I recently cleaned up my computer rats-nest at home and located no less than five wall-warts plugged in but with no equipment connected to them. Some I could remember; the old linksys router I bricked with a firmware idea, the DSL modem I replaced with cable a few months ago, and several others I just have no clue about. They join the existing crate full of cables in the garage.
Some accessory manufacturer will catch on and start building devices that don't each have a different shaped (linksys), voltage (belkin) or design (DELL!!!!) power brick, and they will clean up - moneywise, too.
ICs like this should step down 110V to 12V, and a bridge of diodes and eeny weeny capacitor should make it DC. I just dont see why would anyone need big coils. I've increasingly been seeing 3-pin ICs that are power regulators, some that can handle plenty of wattage with a heatsink, and are TINY. I fail to understand why manufacturers are still packaging the ugly adapter. My new voip device from linksys, a PAP2, is small sleek, and comes with a giant unslightly adapter. Its the stereotypical engineer thinking... input=12V and design the rest of the PCB from there. Marketing just looks away.
"Give orange me give eat orange me eat orange give me eat orange give me you." -Nim Chimpsky
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.
Mod a computer power supply. I got my 550 Watt power supply for $10 plus shipping, and it works great. (Was supposed to be free shipping, but with that good of a deal I wasn't going to bother with it).
I hate grammar Nazi's.
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.
I was going to mod you a troll, but since you're other posts in here are reasonable, you must honestly be missing the point.
I believe the original poster's point is that if the converter is built in, then you will end up having to convert the energy twice. If you use solar, and get DC current from it, then you could convert from DC to DC with acceptable power loss. However, if there is a converter built into the device, then you have to convert from DC to AC simply to power the device that will convert back from AC to a different voltage of DC. This means you had to convert twice and experience power loss twice.
-> Fritz
Spooooon!!!!!
I used to have a 1-rack space device that did just that... it was marketed for musicians to power rack gear. I think it was made by Furman, but I'm not sure.
Here is my 2c worth.
b ar |
Buy a bunch of little extension chords (or shornten them yourself). You take your chord, plug one device in on either side of the end, and the other end into the wall/powerbar. You can now hide the worts in a big clump out of sight, and can also free up space in your power bars.
Basically, you want to just move the plug onto a smaller footprint, so, extend the plug a bit
|device|----wire----|wort|---minichord---|power
hope that helps
Rather than an ATX PSU that require special wiring to keep it alive, bust out your old 486 and steal the AT powersupply. It has a real power switch and enough kick to run plenty of 12v cameras and DAs (from experience). Smaller supplies can be lifted from old external HDD cases. I have one from a 20meg Mac SCSI drive that I use all the time (it is not an open frame unit).
SD
âoeWho knew something as harmless as willful ignorance could end up having real consequences?â
Is it true that DC-to-DC is just a combination of DC-AC and AC-DC? In that case, then there are still two conversion steps. (Still more efficient than when separate, but not by half).
Tsunami -- You can't bring a good wave down!
It's pretty easy to build. Just need one multiple-voltage power supply that can handle the entire load. Most equipment powered by wall warts will be fine with 9-12VDC, or 24VDC. If not, you can use a bunch of adjustable voltage regulators, but each one will consume power and waste more than an equivalent wall wart. Add a bunch of cables, jacks and probably a fuse on each output and you're done.
But is it really worth this effort just to avoid an eyesore? Just hide it behind a desk somewhere.
Mod a computer PS or do what I did. Run wires into your computer. I have several wires that have coax power plugs on one end and all run into one molex power connector in my computer which is then connected to a spare power connector on my PS. So, my linux server powers my cable modem, router, and access point. This gets rid of all the power bricks and I think uses less power overall because the switching power supply in the computer is more efficient than all those bricks. It also gets rid of the need to have a power strip in between my UPS and my server, so it's a much cleaner setup.
Also, a small tip here. I have found that many devices that come with 7.5V or 9V or 12V power bricks run just fine on the 5V output of the computer PS. This is the case for all three of the devices I mentioned above. They run much cooler and consequently use less power. Just don't do it backwards and use the 12V supply to power a device rated for less than 12V.
Many others have posted about the short cords that go from the wart to the plug. Another solution is a power strip like this one which has a special section for wall warts where they won't cover other outlets.
I have an iGo Juice power supply for my laptop that uses various tips to power different laptops, and has a splitter that uses its own set of tips for low-power devices like cell phones and such. The Juice can handle up to 70 watts, so if you don't try to power a laptop, too, I'd think you should be able to split the non-laptop side several times. Then you could use the standard tips to provide the final output voltages you need.
"We have nothing in common, your attitude annoys me, and your political views are appalling."
Sure - Edison lost to Westinghouse.
The issue was how to get energy from the Niagra falls. People discussed compressed air, DC, and AC, and Westinghouse showed that by jacking up the voltage, he could use a small(er) guage wire.
DC is fine, but at the time, there wasn't any good way to increase the voltage.
Ironically, 50-60 hertz is fairly slow, and not the most effeceint frequency.
Now - with semiconductors, transformers, and high speed transformers (switching Power supplies) we could do better - but there is so much built around 120/60Hz, it would take a revolution to convert.
AIK
I was thinking about all the power consumed by idle wall warts around the house. The average wall wart wastes 1-3 watts or 9-27kwh a year. Not much, but multipled by the several dozen I have in operation its a lot. (Some studies have shown that "idle" electronics consume 11% of a home's average power usage)
Most of this is becuase cheap low powered power supplies are really inefficient, often wasting more power than the device uses.
My idea was to modify most of my devices to run on 48VDC using DC/DC converters. Then use my many ethernet jacks to send power over ethernet to each device, supplied from one large efficient (battery backed) 48v supply. I got a few prototypes done: the alarm clock (now it needs ntp support) cordless phone and cell phone charger but got bored and overwhelmed by the sheer number of devices.
I know I'm coming in late on this, but hey, it's an idea that's been kicking about in my head for quite some time
You have a SLA battery bank, ok, 1.2v between each of the cells. Your charging mechanism puts out 24 volts, so you have 20 SLA cells in series.
Follow me so far?
You need 6v, 9v, 4v, and 12v.
For 6v you tap off of 5 of the cells
for 9v you tap off of . . . hrmm, 8 cells gives you 9.6, so you waste some current there or overvolt the eq.
4 volts much the same. Except you can choose to run at 3.6 instead..
12 volts needs 10 cells.
It's the same principal as a multi-tap transformer. You just have to watch the grounds(if any) because you have a maximum potential of 24 volts.
IANAEE, IHNTTB4(I am not an electrical engineer, I have not tried this before)
On the plus side, if the power goes out, your system still works.
The previous has been a secret message to my comrades.
That is not a good idea. It would sort of work, but you would discharge your batteries at different rates. This is really bad for your battery pack and will kill it in no time.
In all honesty, I have no idea. An interesting question though. . .
-> Fritz
Spooooon!!!!!
In the Army we used DC power for some applications, it's an nasty problematic way of distributing power and tends to be unreliable, if at all possible avoid it. If you are wondering why, it reinforces the fact you don't know enough about real-world power distribution to do it with out it cause more problems than it creates.
DC is dangerous, if you get shocked by it it holds on to you more, there is no pauses in the current to allow you to get off the conductor. DC is dangerous, generaly it needs much more current for a give power because the voltage is lower, short curcuits tend to arc-weld together; Avoid DC power distribution when ever possible.
Apocalypse Cancelled, Sorry, No Ticket Refunds
With an old/cheap PC power supply, a project box from Radio Shack, and some voltage regulators, and few barrel plugs. You can regulate the 12v to 9v, the 5v down to 3v, 13.8v might be hard to get. A little bit of soildering later, and you should have more than you need.
Is it true that DC-to-DC is just a combination of DC-AC and AC-DC?
No.
In that case, then there are still two conversion steps. (Still more efficient than when separate, but not by half).
For DC-DC, you get 90-95% efficient. For AC-DC and vice-versa, you can get into the 90% range, but much more commonly see 80% and below.
But, for argument's sake, let's take each as 90% (the low end of DC-DC and the high end of AC<->DC) efficent. For DC-DC, you do it once, giving 90% overall. For AC->DC->AC, you need two steps, giving 90% * 90% = 81% total. So, you'd still do better to use DC-DC conversion.
Also, the above assumes an arbitrary DC voltage to another arbitrary DC voltage. If you have a starting voltage very slightly higher than your desired voltage (say, 9.2V to 9V), you can "perfectly" throw away the excess, giving only the drop as your overall loss (so 9.2V to 9V would mean 98% efficient).
Selectable voltage is a feature on many computer supplies, though I suspect 99 percent of desktop computers in the US run on somewhere around 110-120 volts. Many newer supplies even make it easier, and autodetect the voltage for you. I purchased a used supply to try and resurrect an old 486 host PC used as a user interface on a large machine, and KABLAMO! I momentarily forgot that the computers on the machine run on 230 volts, not 115. DOH!! (It was time to upgrade anyway).
This, in fact, is what's happening when you have devices powered off USB, FireWire, or Ethernet. Read this discussion of how USB power distribution works.
So the parts exist to do what the original poster wants to do. But they're not typically packaged for the end user.
We get a lot of those at work. Last time it was in a lab, there was apparently a "kerpow" and the computer died. Kid tried reaching around the back of the PC for the power and got a little zap... I found the shredded remains of a capacitor blown partway out the fan slot.
I have a device that sort of does what you want, the Dunlop DC Brick Power Supply, but it's designed for effects pedals, not computer equipment, and it only offers two voltages, 9V and 18V. The design specs might give you some ideas for building your own. http://www.musiciansfriend.com/srs7/g=home/search/ detail/base_id/42909
"If it's real, then it gets more interesting the closer you examine it. If it's not real, just the opposite is true." -
I had the same problem and decided to test my Electronic skills. I used a power supply from an old apple (see they are good for something) and rated all the wires with a multi-meter. Then I looked at all the watt ratings of my various devices (yes watt not volt) to make sure I would not overload my 250 watt Power supply. Since the output of the power supply was mainly 12 volt, I hit radio shack for some resistors (and even remembered the color coding correctly). The DC plugs I salvaged from my junk drawer and the wire I used was 20Ga. copper. I soldered all the joints, tested the output and load, made sure it wasn't going to burn down the house and stuffed it all in a radio shack project box. I even tore apart an old Isobar surge protector and integrated it into the mix. All in all it works pretty well, but I cannot move my stuff around much, because it all has to be located around my power source.
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.
Several posters here have made good suggestions. The 7805, 7809, 7812 regulators all require a heatsink if you plan to draw more than 50 milliamps from them. Been there, done that. Even with a good heatsink, the limit is about 1 amp, each.
I've seen plenty of discussion here about volatge, but very little about CURRENT. Look at the wall warts you are planning to replace, or the device. One or the other (or both) will clearly indicate the voltage AND CURRENT that the device requires.
Let's say, for example, that you had three devices that all require 9 volts. One is 500ma, one is 800, and another is 300. That adds up to 1.6 amps. (1600ma) Your 7809 regulator can only SAFELY handle about 1100ma (1.1 amps) *with a good heatsink*. You would need two regulators, one for the 800ma load, and the other could handle the 300 & 500 together.
It is not a difficult project, but you must consider the total current that all of your "wall-wart" devices will need in order to decide what to use as a "master power supply".
DigiKey is a good source for parts like voltage regulators. You can start with a "12v" power supply (usually, a "12v" supply is regulated to 13.8v) that is rated to deliver at LEAST 1.5 times the total current of all your devices running at once. You always want to keep things at LEAST 20% below maximum ratings, preferably, 30% below if it's continuous duty. (REMEMBER: You DON'T want to let that magic smoke out!)
I've been a tinkerer for years, and work as a Broadcast Engineer. I have plenty of experience with power supplies and homebrew projects, so I can say that if done carefully and properly, this is a very feasable concept.
Willie...
The other DC-distribution system design exercises remain impractical for a couple other reasons that I can easily pull off the tip of my tongue.
First reason: Voltage, and power variations. Around here I have various kit with power-supplies rated for voltages from 3.7V DC, 5 V DC, 7.5V DC, 2x8V AC (16 V center-tapped), 9V AC, 12 V AC, 12 V DC, 19 V DC and 21 V DC. I would suspect most other installations have a similar variety.
OK, so the various DC voltages could be hacked using a variety of linear or switching regulators off an ex-equipment PSU, though the 19 V and 21 V might present an educational challenge. Besides the fact that that this is likely to be at least as unsightly as the handful of wall-warts it replaces, this does absolutely nothing for the AC supplies, which wall-warts are simple transformers and rather efficient anyways. (the dual 8V unit has its own power cord and isn't even a wall-wart). Implementing DC-AC conversion for these purposes while regular mains AC is right there seems to be way overkill.
The second reason is reliability, as in "everything put together sooner or later falls apart".
In recognition of this, for all their cheapness and nastyness, these wall warts are going to be one or more of UL, CSA, GS, VDE, CE, etc., approved and marked, lest they be illegal to sell to the general public. That does not mean that they will last any longer than the warranty plus one day, but it does mean that if one of these guys should catch fire or fail violently in other ways, there may be some recourse from the manufacturer, and your insurance company has one less reason to withhold damage payments. Perhaps more important is that the warranty on the connected equipment isn't voided because a nonstandard power supply was used. Sometimes this can be nice, or it may be irrelevant, YMMV.
Beyond all this, the fact remains that if this common power-supply fails, all of the devices powered from it will stop working, temporarily or permanently depending on the nature of the failure... but with individual power warts, only the device feeding off the failed unit will be in jeopardy. Then there is the matter of moving things around and having to lay fat low-voltage cables following, and having to worry about power quality issues and fire hazards (a PSU delivering 12 V and 25 A DC can sustain some impressive arcs!) All of this instead of just plugging it into the everpresent mains and just have it work?
No way, I'd use time on more fun things.
SIGBUS @ NO-07.308