Future of DC circuits in the home

alan4cult

Not sure if this has been discussed here before but what do people think is the future of DC circuits in the home?

We run probably more transformers in the home than ever e.g. smart bulbs, smoke alarms, sensors, routers. Of course the core items oven, fridge, electric heaters are running 230V but are DC circuits possible in the home?

I guess an AC doorbell transformer has been around a long time but are other low voltage circuits a good idea?

omegab

Low Voltage DC power losses over long distances (within a house) would mean much thicker cables. And if you have one central DC power supply how do you size it?

alan4cult

Yes good point and also 3V/5V/12V would need to be available and would make it quite complicated.

Good point about the central transformer and of course the power loss on the cables.

POE across CAT6 seems to be used a lot as a bit of a DC circuit at the moment, I wonder could network ports begin to double up as this.

Stoner

Poe has been around for a long time.

It's still expensive to terminate a data cable at both ends.

Many of the poe systems just use cat6 cable, they have their own network cabled alongside the data network.

10-10-20

Transformers. per sey, are a rare thing these days; you mean SMPS power supplies devices. They are typically far more efficient, less bulky and have cheaper component cost and can be tuned better for power-factor than wire-wound transformers.
Those loads are everywhere. In the time of transformers, had there not been a move to SMPS, there would have been a greater need for a DC supply now, but power-supply efficiency has probably leapt ahead and the need isn't so much now.

I've always wanted a 12v/24v DC circuit in my house, but it's impractical to retro-fit.
It would be ideal for those loads you describe where a small switch-mode circuit is converting down from 230v AC to 12v / 5v / 3.3v DC, but you would need a connector which is more flexible than a USB B/C socket to deliver that power (USB is physically insecure and gets damaged easily). Safety is also a concern; I have had two USB cables start to burn at the device end-connector from over-flexing, so some better overcurrent protection would be needed given that some USB plugs now provide up to 3A at 9v (27w).

I suppose, in consideration, one of the best possibilities of DC distribution in the home is now PoE. Right now infrastructure-wise, PoE is not an ideal distribution architecture as it's switch-centric (all cables must home-run to the switch), but with some smart design of electrical sockets they could become Ethernet hubs and power injectors allowing only one Ethernet cable to be used to transport the data while the plug delivers the PoE power.

But perhaps Brexit is an opportunity for us to review what the alignment with the BS standards have given us, and what we are missing, and possibly make a clean break from the BS and take a more European approach to our electrical standardisation, and maybe DC distribution can have a part here. I say that as I look at many purchases which will be made on European websites and won't come with a BS-1363 (UK) plug and won't be fused or even have valid CE testing certs (China Export?).

10-10-20

Oh and I might add, you don't need to have different sockets for each voltage. With USB C the voltage selection is included in the protocol and can be selected by the device from 5v, 12 up to 20v at 5A (100W).
Very good video on it here:
https://www.youtube.com/watch?v=aIHj3qMRqqE

Plus I also see that it has some overcurrent protection too:
https://en.wikipedia.org/wiki/USB-C#Power_issues_with_cables

omegab

In this case you need a separate USB Qualcomm controller for each device to negotiate. Again the Current required starts to add up very quickly. POE is 48V and still essentially needs a Buck regulator at the destination device to step down the voltage to suit so you are not gaining. It's impractical to serve 3.3V or 5V from a remote part of the house, you see quite a lot of Voltage drop even at 4 metres over 1.5mm2 cable (I've a few sets of WS2812B LEDs fed from a central source.

Stoner

True , even in some of the new motherboard specs, the psu only needs to provide 12V the lower voltages are all produced locally on the motherboard, inexpensively.
Generally speaking flooding places with cables is expensive, particularly cables that often require a point to point certification.

Many of the poe lighting systems have distribution boxes that require 230V 10 to 20 amp supplies, the light fitting are fed from these boxes with cat6 cabling. From a power perspective the cables have little power flexibility, they feed the light and that's it.

The control and iot integration with multi sensors have some great information and control features