Item — HN Reader

You really don't want to use DC for distribution in your home. Go price out telcoflex copper cabling (from 0000 up to 4 gauge) for -48VDC datacenter use. Voltage drop over distance and losses to heat make it impractical in homes. You really want to pay the extra money to wire your home with 6AWG cable in the walls? That's a lot of copper.

Centralizing an AC to DC transformer is pointless for consumer stuff since things run on DIFFERENT voltages. A lot of consumer grade stuff is 5VDC internally. Or 12VDC. Or 17.5VDC. Or 19.2VDC laptops. Or 24VDC. Or 48VDC.

That's before we even get into the problem of "everything in the world is already standardized to run from 110-240VAC 50/60Hz".

If you really want to do DC distribution in your home, do it with 802.3af/802.3at switches (or "dumb" midspan injectors") and cat5e/cat6 cable. You can get LED lightings and other things that will run off PoE voltages and amperages now.

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Also, with the new USB standard, its no longer only 5v, you can now use up to 20v @5A [1]. My laptop that has a USB-C port to charge uses the full 20v.

120/240VAC 50/60hz @ ~12A (steady state draw) is pretty much the only thing people agree on when it comes to consumer power.

[1]: http://www.usb.org/developers/docs/

I'm waiting for the first news stories about house fires caused by USB-C chargers. A faulty 5Vx1A charger will melt, 20Vx5A will be a bit more lively.

The tests by people like Benson Leung [1] haven't given me any faith that manufacturers will actually care about getting the specs right.

[1]: https://plus.google.com/collection/s0Inv

Also, the specs themselves are non-ideal. What they really need instead of the cable DRM/smarts (USB Authentication [1]) is to standardize V-Droop (Voltage drop from no-load) detection and behavior.

They need to make part of the spec a current ramp and monitoring of the voltage while doing so. If the voltage sags too much or ripple increases that means the cable or power source can't handle the load and the device needs to back off. There is very little a non-compliant power supply or cable can do to fake conformance without costing more than doing a conformant implementation. Some phones monitor V-Droop already as there are too many bad power-supplies and undersized cables out there. The downside is that it isn't as sexy to implement this.

[1]: USB Authentication section of http://www.usb.org/developers/docs/

Oddly i think the original charging spec do it that way when dealing with dumb chargers.

wait until we have USB-C charged hoverboards (and similar products), where not only can the charger and cable catch fire, but so will the low budget Li-Ion battery pack/charge controller/battery management system.