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I want universal DC power


I went around and counted that we seem to have around 30 birick and wall-wart DC power supplies plugged in around the house, and many more that are not plugged in which charge or power various devices. More and more of what we buy is getting to be more efficient and lower power, which is good.

But it's time for standardization in DC power and battery charging. In fact, I would like to move to a world where DC devices don't come with a power supply by default, because you are expected to be able to power them at one of the standard voltage/current settings.

One early experiment is on airplanes. I have an adapter that takes the 12v from the airplane, and has many tips which put out different voltages for different laptops. These are expensive right now, but on the right track.

Our other early venture is USB, which provides up to 500ma at 5 volts. Many small devices now use USB for power if that's all they need. There are devices that plug in to USB only for power, they don't use the data lines. Some come with a small cigarette lighter plug that has a USB socket on it for car use. This includes cellular chargers, lights etc.

I think a good goal would be a standardized data+power bus with a small number of standard plugs. One would be very tiny for small devices and only provide minimal USB-level power, a couple of watts. Another would handle mid-level devices, up to a couple of amps. A third would be large and handle heavy duty devices up to say 20 amps, replacing our wall plugs eventually. There might be a 4th for industrial use.

In full form, the data bus would be used for the components to exchange just what power they want and have. Years ago that would have been ridiculous overkill, today such parts are cheap. However, to make it simple there would be a basic passive system -- perhaps as simple as a finely tuned resistor in place of the data components -- to make it easy and cheap to adapt today's components.

A fully smart component would plug into the smart power and get a small "carrier" voltage designed to run the power electronics only. A protocol would establish what power the supply can provide and what the component wants, and then that power would be provided.

To plug older components into smart power sources, a small dongle would be
available hardwired to simply say the device wants the power it wants. This could be as simple as a finely tuned resistor over the data pins, the exact resistence defining the desired voltage and expected current.

Likewise a mass produced cheap component would go on the end of existing fixed-voltage supplies to handle their end of the transaction. This has to be slightly active, to at least listen to the component.

I haven't worked on this enough to figure if you can do all this with 2 wires, but that of course would be great. However, I suspect 3 to 4 wires is more likely.

In addition, an extension of the system would be needed for devices that need multiple voltages. These are almost all in the middle-power need (2 to 20 watts.)
In that case you would define multi-pin plugs and the data protocol would define the voltages on all pins.

Of course, you could ask for AC or DC, and even wall plugs with 120v AC or 220v could speak this protocol. This would actually be a great safety feature, in that the plugs would not provide power until a device was plugged in to ask for it.

The result of all this is that people would buy a DC switching power supply with multiple outputs. Each output would be tunable on the command of the device plugged into it. This would power all the low voltage devices in one place.

Even with such general supplies, it would also make sense to standardize voltages needed. This could allow for even simpler design. If everybody who needed between 3 and 6 volts settled on 5v, one could make block 5v supplies that run many components without having to adjust each output.

This would also be good for homes that run on solar which like to have DC appliances.

Of course, the data bus would not be speed limited. In the end, it would be a replacement for USB 2.0. USB was about data, with a bit of power for very low power devices. This proposal is about data and power together. It could work at low data rates for devices that just need a power negotiation, but it could also provide high data rates so a digital TV could plug in with one plug and get power and TV station digital streams on the same wire. Ideally an IP like P2P bus rather than a master/slave bus as USB is. (See earlier entry on ideal AV system.)


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As a frequent traveller, I'd love not having to carry notebook and mobile phone chargers on my trips, since the hotel could provide a cable with a standardized connector coming out of a jack something along the lines you've described.

I am carrying the iGo Juice now for charging notebook and mobile phone via one device, which helps, but I love the vision of life without AC adapters.

Yeah, you're right, and that's all there is to it.

I have worked for some years on modularity and standardization and e-waste cutting, and having a lot fewer power supplies and disposable batteries sure would help. USB is probably the right way to go for computing and telecom gear, since it exists as a standard and low power equipment is the way of the future. I would advise that as part of a general strategy of "healthy telecom"
(lots of other ways to mature the industry there)

12V is important for fuel cells and solar power and replacing our 110-125-220V systems that need wasteful power grids to distribute power. The more you can do on 12V, the better. We should be charging cars with power at an efficient central generation point, driving them home, and hooking them up as 12V or higher supply to our homes. It is the most practical way to move hydrogen power, since pipelines are not a good plan, and neither is powerline transmission beyond the "gas station". Jeremy Rifkin talks about this a lot.

Probably biodieselectric cars must come first as the stopgap, though. These are already around... and they might also be good 12V power sources, and decent generators, but they aren't batteries.

Actually rather than 5V, a standard should be established that can be delivered easily with some multiple of cells... such as 3, 6, 12 or some such, so for the need of totally portable power one could resort to batteries. 5V is pretty arbitrary these days... held over from TTL. Current cell phone tech is running on 4.5 and 3.2V...

Any voltage can be regulated to deliver what ever a device needs, so why not use a 1.5V cell multiple as a starting point.

"In some cases, a device will use only part of the USB spec. Nintendo Gameboy SP is rechargeable -- and a third party sells a USB charging cable for it. This uses the physical spec and power, but doesn't even show up as a device. The protocol is ignored entirely. This is common enough that some car and airplane AC adapters now offer a "dumb" USB port which just provides power for rechargeable devices. "

I'm fed up with carting transformer bricks around and have been thinking for a couple of years about ways out of the mess. There are only two widespread low voltage DC "standards": car cigarette lighters and USB.

Any ideas how to promote and publicise USB as a power standard?

i have a big question. Why does the telecommunications systems use negative voltages for their power supplies?

totaly agree. having a bulk of DC adapters is redicilous.
some standartization needs to be done

it looks like a promising replacement to power all my home's DC devices.

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