4 ms·

It's Big Wallwart, keeping us all down to prop up the transformer industry! More seriously, would there be any electrical or interference issues with running u

It's Big Wallwart, keeping us all down to prop up the transformer industry! More seriously, would there be any electrical or interference issues with running usb-c power delivery cables everywhere?

bombcar 3y ago
The problem with low-voltage is lengths. I don't know how far USB-C as such can reasonably go. PoE, of course, can go as far as the ethernet (usually) and so any future low-voltage system in homes will probably be based on it (it's already used in some commercial setups).
- mtreis86 3y ago
  The other problem is wire size, since the amps go up as volts go down, and the heat generated in the wire is proportional to the amps, not the watts. So to carry the same power, a lower voltage wire has to be thicker.
  - bombcar 3y ago
    Yeah, the advantage is when the power usages is way below normal mains. We already see it (I have lights in my kitchen that have one transformer connected to the mains, and then all the rest of the wiring is low-voltage).
vetinari 3y ago
There's a reason why you want higher voltages: to minimize losses in conduits; i.e. you can move more effectively 12W in 120V/0.1A rather than 12V/1A -- the lower current, the lower resistance. There are no 12V standards for wiring buildings, because effectivity-wise, it make no sense. Even the above-mentioned PoE is 48-56V (56V, so it can be 48V at the other end of up to the 100m long cable). The 5-12-20V USB PD is for relatively short cables, not for something that goes around your house.
- dreamcompiler 3y ago
  > the lower current, the lower resistance The lower the current, the lower the losses. Resistance doesn't change. I^2*R is what decreases with current.
- bloopernova 3y ago
  Thank you for the informative reply, Lord Patrician! Is it straightforward to step down the voltage from PoE to something that USB-C can use? My Forest M Mims Electronics book sits unread and dusty in a box somewhere so I'm not really able to interpret the schematics google is showing me :/ (apologies for extra questions)
  - vetinari 3y ago
    There are PoE-to-USBC adapters available; random pick on Amazon: https://www.amazon.com/dp/B087F4QCTR https://www.amazon.com/dp/B087F4QCTR (this one is af, 5V/12W and plain USB; no at, no QC or PD. If you need that, you will surely find it). For DYI, there are dc-to-dc convertors available. Or do you intent to build your own?
    - bloopernova 3y ago
      It was more for curiosity's sake, but it's really cool that there's already converters. My project is very much in the "hey it would be nice if" stage right now, but I'm on the Python track at Exercism and want some "small" projects lined up once I'm finished there. The idea is: pull in a quick 3D sketch of a home. Place (USB-C via PoE-power?) ESP32/Pi/Other devices at specific points with very precise measurements between them. Use them to determine the exact position in 3D house-space of Bluetooth low energy beacons. Use that info to help my very ADD wife find the things she loses. (because Tiles often fail) A lot of the code to calculate position from timings already seems to be out there so I can cargo-cult things over. In a far-too-roundabout way, that sorta kinda answers your question.
  - dylan604 3y ago
    what's the difference in having a 120v->5v wall wart vs 48v->5v one?

It's Big Wallwart, keeping us all down to prop up the transformer industry! More seriously, would there be any electrical or interference issues with running usb-c power delivery cables everywhere?

bombcar 3y ago

The problem with low-voltage is lengths. I don't know how far USB-C as such can reasonably go. PoE, of course, can go as far as the ethernet (usually) and so any future low-voltage system in homes will probably be based on it (it's already used in some commercial setups).

mtreis86 3y ago
The other problem is wire size, since the amps go up as volts go down, and the heat generated in the wire is proportional to the amps, not the watts. So to carry the same power, a lower voltage wire has to be thicker.
- bombcar 3y ago
  Yeah, the advantage is when the power usages is way below normal mains. We already see it (I have lights in my kitchen that have one transformer connected to the mains, and then all the rest of the wiring is low-voltage).

vetinari 3y ago

There's a reason why you want higher voltages: to minimize losses in conduits; i.e. you can move more effectively 12W in 120V/0.1A rather than 12V/1A -- the lower current, the lower resistance. There are no 12V standards for wiring buildings, because effectivity-wise, it make no sense. Even the above-mentioned PoE is 48-56V (56V, so it can be 48V at the other end of up to the 100m long cable). The 5-12-20V USB PD is for relatively short cables, not for something that goes around your house.

dreamcompiler 3y ago
> the lower current, the lower resistance The lower the current, the lower the losses. Resistance doesn't change. I^2*R is what decreases with current.
bloopernova 3y ago
Thank you for the informative reply, Lord Patrician! Is it straightforward to step down the voltage from PoE to something that USB-C can use? My Forest M Mims Electronics book sits unread and dusty in a box somewhere so I'm not really able to interpret the schematics google is showing me :/ (apologies for extra questions)
- vetinari 3y ago
  There are PoE-to-USBC adapters available; random pick on Amazon: https://www.amazon.com/dp/B087F4QCTR https://www.amazon.com/dp/B087F4QCTR (this one is af, 5V/12W and plain USB; no at, no QC or PD. If you need that, you will surely find it). For DYI, there are dc-to-dc convertors available. Or do you intent to build your own?
  - bloopernova 3y ago
    It was more for curiosity's sake, but it's really cool that there's already converters. My project is very much in the "hey it would be nice if" stage right now, but I'm on the Python track at Exercism and want some "small" projects lined up once I'm finished there. The idea is: pull in a quick 3D sketch of a home. Place (USB-C via PoE-power?) ESP32/Pi/Other devices at specific points with very precise measurements between them. Use them to determine the exact position in 3D house-space of Bluetooth low energy beacons. Use that info to help my very ADD wife find the things she loses. (because Tiles often fail) A lot of the code to calculate position from timings already seems to be out there so I can cargo-cult things over. In a far-too-roundabout way, that sorta kinda answers your question.
- dylan604 3y ago
  what's the difference in having a 120v->5v wall wart vs 48v->5v one?