Slashdot Mirror
Sensibly Powering DC Technology?
splatnet asks: "Having upgraded my PC to a Mac Mini all my IT kit is now DC. The Mini, my flatscreen, external USB HDD, USB DVD writer, JBL speakers, ADSL/Wireless Router. I have practically the same amount of space taken up for transformers as I do computer equipment! Has anyone found/invented a way to power multiple DC devices (all with slightly different power requirements)? I'm thinking in terms of space/convenience/running costs etc." It would be neat if there was a DC power source that could be tuned to a specific voltage, as well as modular plugs to fit your various devices. Is there anything out there that comes close?
1) Take power bricks and place in pile. 2) Cover in duct tape. 3) Continue wrapping of duck tape over cables. 4) Spray paint blue. Voila, a uni power brick... Seriously, i have this problem too, its even worse for traveling with devices. Most of the time the power brick is bigger than the gadget. I ended up building my powerbricks into my table, (underneath the desk) looks neater. Not much more functional. -tris me
This has been discussed before. That being said, good luck. Having read the last discussion, I think you'll need it.
Your typical PC AT power supply comes very close. It outputs 12V and 5V DC (most of what you need) and can handle a lot of current if it isn't a cheapo. Go to Radio Shack, get some plugs and some solder and have fun.
I've learned, the hard way, that the coaxial power plugs used on most devices these days will temporarily SHORT when you plug them it, which means, at a minimum, a separate current limited regulator for each plug.
Accept the things you cannot change, this is one of them.
--Mike--
A Froogle search for Universal Power Adapter found this: Coby CA-33 Universal 110-/220-Volt AC Power Adapter, but it only supplies one voltage at a time.
It would be great if these were available to supply multiple voltages. A problem, however, would be that all devices powered would need to have the same ground, a condition that might not exist. Deciding whether all devices had the same ground might be tricky.
If you don't know anything about power electronics, linear and switching supplies, and transformers and rectifiers you won't be able to pull this off. You will need to find all the different specs for power, produce switching supplies for each device, and make sure you provide very clean power. I've been thinking about doing this myself, but never doing it, partly out of lazyness with how much work it will take.
When houses will be wired for DC for just this reason. Imagine a nice plug that's secure in the wall like 110v so it won't be flopping around, and having a 12vdc and 5vdc wall plate. Any other requirements could be done by stepping voltage down.
The requirements seem to be:
* 5 output ports;
* for each port (or via a central control panel) configuration for output voltage on that port, continuously variable from 2 VDC to 24 VDC;
* each port capable of 50 watts without significant voltage drop;
* a handful of accessory connectors / converters including 1 plug male -> 4 plugs female, big diameter plug to small plug, extension cables, etc.
* silent power supply if possible / air cooled, or very, very quiet fan
I'd think that a sealed design with a large external heat sink is best. I have a cat and the cat hair ends up all over things on the floor, which is the power bricks and one of my PC's, making cleaning a regular (once / 2 months) thing to lengthen lifespan / prevent overheating).
I don't care about weight too much. It should be well grounded.
Another wonderful idea is the ability of it to use as input a 12VDC car/marine-deep-cycle battery, so if the power goes, I can still use my accessories.
Unitarian Church: Freethinkers Congregate!
Lots of guitarists use something similar to power multiple FX pedals on stage. However FX pedals tend to be fairly low power, and all at simialr voltages (as they mostly run on 9V square batteries).
Contact someone who puts together racks of FX for guitarists/stage musicians?
But there are plenty of peripherals that need voltages like 14.1v.
Generally, a voltage requirement like 14.1V means the peripheral will accept anything from 12V to 16V but they don't want you using a third-party adapter. Even switching adapters are usually off by half a volt or more, and regular transformer bricks are +/- 30% or more.
Also, you don't need heavy transformers to put out high currents. Read about switching power supplies sometime. With those, the transformer size depends mainly on switching frequency.
You do bring up a valid point. I think the main reason nobody makes such a device is because it's impossible to make idiot-proof. If someone doesn't set the voltage or polarity properly, they will be very pissed when they fry the device. When you have multiple outputs, this is extremely easy to do.
Your typical PC AT or ATX power supply will fall on its face if your power network doesn't resemble a PC's. In my lab, we power a lot of 3.3V and 5V systems with COTS ATX supplies. We have to put big resistive loads on the 12V lines to get adequate current.
The electrical aspect of this problem makes it, shall we say, untenable. So, I suggest solving the problem in an architectural way. Suppose you develop a form factor for transformers, where the plug from the transformer to the AC source is not attached directly to the transformer, something common on laptop ac adapters. The plug itself is removable and OEM's can provide varying sizes for your needs. And the connector on the transformer for the power cable (AC Source) is standardized so that someone could make a 'rack' of sorts to plug that transformer into directly (with cooling space and so forth). Size variation needed by larger applications would work just like rackmount cases, in unit format i.e. 1u for your mac mini, 3u for your 500 watt 7.1 digital surround processor and receiver.
The problem I have is with the powerstrips and their utter lack of a good transformer solution. I'll get around to this one day but I intend to get a series of short (3-6") extension cables to make it so one power strip will hold all of my various transformers. Then I'll probably just hang them somewhere on the side of my desk or tie them together with those nifty little velcro strips.
Another wish of mine is that everyone would use the same stupid form factor for transformers. If you look at Apple's transformer it's perfect for the usual powerstrip configuration, same thing with Nokia's latest charger adapters. They are no wider than the regular plugs out there and they grow in such a direction that you can put them side by side without issue. Now one example where they came close but completely screwed up is Linksys. At least some of their products have this thin power adapter that looks a lot like it would be great on powerstrips but it's turned 90 degrees. This provides excellent wall plug support but that's really not where you should be plugging these in! Now, if they used this format and made it so the blades could be rotated 90 degrees then it would probably be my favorite.
*sigh* sorry for the book.
I read the script, and I think it would help my character's motivation if he was on fire. -Bender
is the iGo power adapters. To really meet your needs you would have to reverse-engineer something, though.
What makes the iGo solution work is the "tips" which apparently provide feedback to the DC-DC voltage regulators as to what the desired voltage for that tip is.
What makes it suck is that you can only have two "tips", and it has so many cords that it is almost worse than the original two wall warts you had to carry around.
My solution would be to reverse-engineer an iGo system, have a common high voltage DC bus and modular DC-DC regulators that can stack, with integrated ports for additional cords and "tips". It isn't perfect; you still have way more cords than a sane person would want, and if your device requires multiple voltages (I think the mac mini is in this category) you will need to do something fancier...
Get a big tesla coil and broadcast the power wirelessly to your devices. Try not to worry about the side effects.
...But I digress. TREMBLE PUNY HUMANS!ONE DAY MY SPECIES WILL DESTROY YOU ALL!
Someday we will have devices that - IF they need to be plugged in - will communicate with the power supply its needs in terms of power handling, voltage, and ripple requirements (or desires). While adapters could provide a means for some time to power the devices that will not communicate (use a switch to manually select), eventually things should be plugNplay - just like your USB mouse. (It's too bad USB can't handle more power at this point....)
:) to start however. Happy 420!
This power supply could provide a few hundred watts, run off any voltage (AC or DC) to step (buck or boost) and switch (provided the current on the supply side is available) to the proper output voltage. 3-6 wires and some sort of universal plug would be sufficient to provide a serial comms link and power/ground for a few different supplies to a number of devices.
I can imagine having to buy a large one for your computer desk, and maybe a smaller one for your phone/answering machine/etc. (If they're still around).
The connectors should be bisexual so you can connect a number of cords together without worrying about which end is which (or having to buy matched pairs and end up with extras for DIYers) to get to your device. Feedback from the device on power quality or voltage drop would be nice (expensive however) to compensate at the supply for bad contacts or extra long runs.
NatSemi will eventually come out with an integrated controller that takes care of the signaling (including PHY), all control functions, and the kitchen sink - all somebody has to do is provide the transformer, diodes, filter caps, and case. This will make these easy to manufacture and then companies can compete on form factor, efficiency and cost rather than trying to get you to buy their proprietary cables and yet another wall wart for your [whatever].
A controller that could plug into a spare ATX power supply that would properly load it and provide a number of different voltages and a cabling system with converters to a number of different barrel connector sizes and polarities would be nice
If you...solder yourself ... and it subsequently burns your house down, you will get $0 from your insurance company when they figure it out.
.8 = $300. Extend that to underwear, ties, shoes, etc. and you end up with huge dollars involved in just replacing what you have.
The insurance industry doesn't quite work that way.
You can burn down your house by misusing matches (or a propane torch, or a hand grenade) and you'll still get your insurance adjustment. As long as you don't do it ON PURPOSE you're covered. That means if you accidentally knock the lit candle into the paper-shredder-basket, it's covered. If you trip over the cat and do the same thing, you're still covered. But if you decide, "Hey, I don't like my stuff anymore!" and do it on purpose, you're not covered.
This leaves aside the stupidity of purposefully burning down your own house. Most policies cover 80% of actual (demonstrated) losses, with some very-much-higher priced policies covering 80% of replacement costs. In both cases you have to prove what you owned. This is usually quite difficult to reconstruct from ashes. One good trip 30-minute around the house with a video recorder and sending the tape to your favorite sibling/parent/safe-deposit-box supposedly means the difference between getting bubkus and actually being able to state (and prove!) you owned relatively new 25 button-down shirts at 50% of their expected lifespan at $30 each = $15 * 25 *
Remember the reimbursement price for lots of things is basically garage-sale prices, which isn't much considering you'll have to go out and actually find it all again.
Fires suck. Insurance sucks, too, except when you need it, and then it's the best thing there ever was. I dated a gal a long time ago that lost everything in a tornado. She got new stuff, but not very much of it, and she lost all the pics she'd ever taken, etc.
So: It's okay to solder your own Power Supply. It's okay with your insurance company (probably, IIRC) to use it. But, it's wise to test the sucker and probably leave it plugged in for a couple of days on a concrete floor with no combustibles around and a good circuit breaker protecting things.
My advice: Simplify things. Buy a set of 5 outlet strips, use the provided screws to affix them to a piece of plywood, plug them into each other (cascade them; they have built in circuit breakers themselves), plug all your bricks into this arrangement, and put a very nice smoke detector right over the whole thing.
Unitarian Church: Freethinkers Congregate!
Certain types of basic switching regulators actually have a MINIMUM load that allows them to maintain regulation.
Many ATX-type switchers use a flyback-style arrangement, where each of the voltages is obtained from a tapped transformer. Regulation is often performed by monitoring the voltage on one line, and if the loads on the other lines are within the design specifications of the supply then the other lines are guaranteed to be regulated if one is.
In any PC, it's pretty easy to guarantee that the loads are within specs, as the load ranges of a properly designed supply are quite wide. Unfortunately, it is basically impossible to maintain regulation in these designs if some of the lines have zero load, ESPECIALLY the line that is monitored.
Higher-end PC power supplies (Such as some of the top-end Thermaltake and Antec units) use independently controlled switching supplies for each output, and will run fine with zero load on some of their lines, but 90%+ of ATX supplies are not built this way because it's significantly more expensive.
If this doesn't make sense, I suggest reading up on switching power supply theory. For optimum operation, switching power supplies depend on there ALWAYS being current flowing through an inductor. Whether this happens is dependent on switching frequency, inductor size, and the value of the load resistance. The higher the load resistance is, the higher the inductor size and frequency needed to keep current always flowing in the correct direction. If an ideal (no resistive losses) power supply is operated within this region, its output voltage will always be a direct function of the input voltage and the ratio of on/off times of the switching element. If the load resistance is too high, this no longer holds true and the switching circuit is no longer regulated. In non-ideal circuits, resistive losses in the inductor and switching element will impose a maximum load in addition to minimum load.
If you add circuitry that monitors the output of the switching circuit and changes the switching waveform appropriately if it is out of tolerance, you can maintain regulation outside of the aforementioned regions of operation (specifically the low-load conditions), although efficiency will often suffer in these regimes. As I mentioned before, most PC power supplies do not implement this independently for each output simply because it is not necessary, in any situation the PS was designed for, regulation on one line will imply regulation on all lines because of the way the loads are balanced. But if you leave one line totally unloaded, regulation is no longer guaranteed.
retrorocket.o not found, launch anyway?
If someone comes up with a workable solution, there are probably any number of solar power enthusiasts who would pay $$$ for a working product that would allow them to wire a circuit their house with DC of a fixed voltage which could then be converted for each device. Wall warts (and many other transformers) leak current due to their design (and usually also to their generally cheap components). This is a parasitic load- it does nothing for you and is using power even when the wall wart is disconnected. So, those of you who have the right background and ideas, consider this: A single, ultra-high efficiency transformer that generates,say, a clean 24 VDC with a stable ground. Low resistance (say 10-gauge?) wiring throughout the house with special outlets. Universal adapters (similar to RV or Car adapters) that plug in to these special outlets, then into the appliance. These could be quite small, because there would be no need for a lossy/bulky step-down transformer. Something to think about, anyway...
Any generalization is a stupid one.
One problem here is that it is impossible to provide a fool-proof way to get the right of power to the right devices given stupid consumers. You likely have two devices that have the same plug. Are they the same polarity? Same voltage? Do they have special needs such as inrush current limiting, special filtering, etc? Can you trust yourself to program a "universal power brick" to do everything correctly when the laptop manufacturer won't give you complete information? Can you trust joe average? Do you want to pay a lot of money up front to include every kind of connector that there exists, or do you want to special order each connector for $5 each after spending $300 on this power supply? When the manufacturer stops supporting your model with the latest connectors, are you going to swallow another $300 unit, or complain again?
No manufacturer is going to take this on because of the customer service issues, even if liability wasn't a problem.
Further, it would have to be mass produced to even approach the cost of buying seperate bricks, and many, if not most, consumers would rather save the 20% increase and deal with a few extra bricks.
Finally, such a supply could not be nearly as efficient as seperate bricks and still be remotely cost effective. The most efficient supplies are switching power supplies. The most efficient switching power supplies are fixed voltage, and have a peak efficiency at a particular current. Each brick is designed for the device it powers. While one can design an adjustable output supply it is optimizable for one voltage and one current - the rest of the range is very poor. This makes for a hotter brick, nevermind the cost of the additional electricity.
The best option is to have a universal supply at one voltage which can easily be converted by the target device into the power that it needs.
This is called AC distribution, and works quite well.
The real problems are consumers who complain to manufacturers that they want light/smaller/portable devices, and manufacturers who fulfill those requests by taking the AC power converter out of the device.
No, we're not going to run DC around the house because you either need high DC voltages (which can be more dangerous than AC due to muscle dynamics) or high currents which are a greater fire hazard.
No, we're not going to create a 'universal power supply' because universal for you is not universal for joe average, and even if you would be willing to pay $300 to power 5 devices, it's not a mass market item.
No, manufacturers aren't going to put the power supply back in the laptop/cellphone/monitor/etc. It's cheaper with the bricks, and they can sell worldwide with different bricks instead of completely different parts.
-Adam
Check a ham radio supplier, any decent shop will carry many different power supply units that are designed to address this precise problem.
For example, I googled and the first entry under "ham radio supplies" was aesham.com, their catalog is downloadable as a PDF. On page 82, they have power supplies from Astron, Daiwa, Diamond, AIM, etc. Most of them only output a single voltage but are adjustable, however a few units have multiple voltage outputs. Many of these units have big geeky analog gauges on the front indicating the power draw, for extra nerd appeal.
A few pages later (pg 84) they have power distribution busses, for feeding multiple units from the same voltage. Just what you're looking for. And Hams are totally obsessed with clean power, so you can set up rigs with pure, clean power and no grounding problems.
Check out some other Amateur Radio suppliers and gaze through the catalogs, and stand in awe at true hardware geeks that have been doing this for about 3 times as long as computers have even existed. I learned more about electronics from Ham Radio catalogs than anywhere else.