So Where’s My Low Voltage DC Wall Socket?
hackaday.com
hackaday.com
A better solution would be to get everyone on board with a single DC voltage and connector. Then we can buy larger multi socket bricks that are just AC-DC power strips. You can then add batteries and give it UPS functionality. But good luck getting everyone to agree on a single standard.
Why? For many things 6V is enough as it will downscale without too much loss to 5V/3V3 which is what most electronics run on... but everything that draws a boatload of power (computers, laptops, LED strips, ...) will go on 12V up to 24V, so if you want a standard it's either 12 or 24V which will introduce a lot of regulation waste in the form of heat in the device.
5-6V is fine for small loads of around 10 watts but you then have to deal with line losses. A 5 m / 16 foot 24 AWG usb cable will lose 38.5% of its power from line losses at 5V, 2.5A (a measly 15 watts). If you wanted to get a low 2-3% loss for 5V, 2.5A at 5m cable length you would need 12 AWG which is massive. 24V does better but if you wanted 50+ watts you again have voltage drop issues.
So in conclusion, low DC voltages are not very practical for power cable runs of over 2 meters. Though it would be nice if the last meter could be more unified with a single DC voltage and connector (my vote is for 24V). Then we can consolidate multiple devices to one strip/brick and call it a day.
So I thought, why not, opened the router,and lo and behold, the DC circuit is perfectly happy with 5V and 1.2A or so, and converts it down to I believe 3.3V.
So I drilled a hole in the router and soldered the working end of the damaged cable to the power input. Other end is pluggend into the useless USB TV port. Has been working fine ever since. Neither TV nor router runs hot, which I couldn't say about the old wall wart.
In theory, USB should negotiate the required amount of power It turns out the TV manufacturer decided to simply wire the port directly to the internal 5V rail connected to both USB ports, so it should be able to give at least 2x2A.
Yeah, it was probably cheaper to just buy a new router. Got a bit nerd-sniped there I guess ;-) .
Or, you know, have better silicon components give us SDVC (Software Defined Voltage Control). I'm joking, but I also don't think you will save what you thik you will in TCO - Energy Savings + Device Cost differential.
I could be wrong. I have been before. And I am operating on almost zero sleep for over a day, so odds are, I could be doing to again at greater than my average error rate.
It’s really easiest to just keep everything AC until the point of use, putting a transformer and a bridge rectifier in most devices is a better solution than needing switching power supplies everywhere to convert DC voltages (or wise options like linear regulators).
Switched mode power supplies also have EMI to deal with due to the higher switching frequencies, an AC transformer runs at line frequency (50/60Hz).
Switchers, for all their complexity, are pretty damn clean in terms of output and input PF correction. Even in audio and sensitive analog applications where dumb supplies were preferred have been replaced by switchers. A good design goes a long way and it's unfortunately easy to design junk switchers because of the complexity involved.
Yes, and cheaper to build!
You can achieve the same efficiency with DC and AC do not directly effect efficiency across the line contrary to popular belief. It is simple about what the voltage across the line is.
AC was in because it allowed us to build transformers to up and down voltages to provide efficient across the line.
Nowadays, we can build DC transformers with Power MOSFETs which are cheaper, and more efficient then there AC counter parts (old [magnets and inductors] and new [You can do AC transformers with MOSFETS with some extra steps/components]).
Additionally, since most consumer appliances first step is to rectify the voltages most build in the past two decades are DC compatible. Additionally, newer ones could then drop the rectifier stage and become cheaper and more efficient.
In fact there are higher loses with AC power transport (specially in long distances) due to the parasitic capacitance of the lines, that’s why some countries use DC power transport lines now.
The problem with calling USB a DC power standard is that it often doesn't work. I have a lot of trouble trying to charge my PS4 controller using random USB cables when it's attached to my PS4--I'm not even introducing an a/c adapter. I've had things like Qi chargers where I had an insufficient a/c adapter so they behaved poorly. If I'm at an airport and need a quick charge on my phone I'm definitely not going to use their USB port because if it works it'll likely charge slowly.
USB-c is worse with all of this. With a/c power it's only an issue when traveling to other countries and in many cases a physical adapter is good enough.
The possible dark pattern I see operating instead is manufacturers are opting to ship power banks charged up to the retail shelves, and likely don't mind if people keep buying more new units because they can't wait for the units they already have to charge up?
I tend to keep all my gear plugged into chargers whenever I'm stationary because I know all of them have charge protection circuits and I have a work profile closer to that of a digital nomad than an office-worker, so I'm an outlier with that common consumer behavior of only charging when one must.
[1] http://community.anker.com/t/any-powerbanks-that-allow-drain...
When current manufacturers claim USB-PD they mean PD 2.0 which requires the CC line (Only included in usb-c to usb-c) to signal and set the voltage. When PD 3.0 is included, they usually call it quickcharge 4.0 or PPS.
Otherwise every single cable would have to be built to handle the highest possible power delivery rate (100W for USB-C).
I'd be impressed if you could cause a short on purpose with significant force let alone fumbling in the dark.
It's really easy to buy some substandard USB-C cable that lies about it's capability.
Both USB-A and USB-C chargers require active logic. USB-C is more complicated because includes both USB-C and legacy USB logic. USB-PD is the most complexity.
Depending on what standards your existing ports support and what power input the iDevice can accept, you may find that a simple A->C adaptor will suffice. You may not get the fastest charge possible so in that case will want to move over sooner rather than later, but this may be an inexpensive (in terms of money and effort) stop-gap measure.
Also, fast charging your battery more often could be better since you're not fully discharging and recharging your battery.
What actually worries me about this is that they are all backed by tiny switch mode power supplies, and if not designed and built correctly they have a habit of exploding. So now your hotel has hundreds of potentially explody boxes hidden in the walls.
https://www.belden.com/blog/smart-building/digital-electrici...
No idea how this would be more efficient. Bursting voltage will lead to higher loses versus a continuous voltage. Are they claiming efficiency thanks to a centralized AC->DC converter?
>It transfers high levels of power over non-power cable
You can't beat physics. Wires heat up from current, regardless of whether it's AC, DC, or "digital" pulsed DC. I doubt Ethernet cable is rated for any significant amount of power, but searching for "cat6 max power" doesn't return any relevant results because search is broken in 2019.
It's also likely to be rather inneffecient, as they are converting from AC to DC and then potentially back to AC? There may be an advantage to pulsing DC but I'm not sure, typically AC is more efficient for power transmission because of lower losses for the same power over distance and higher transformer efficiency (no need for an inverter).
Normally, running high voltage through a wire is dangerous because a fault can dump power into the middle of the wire (starting a fire) or into a person (stopping their heart), but perhaps with end-to-end active monitoring, it's possible to operate safely at much higher voltages?
If this technology works, I think it would also be useful for powering a tethered drone from the ground.
[Edit: according to lopmotr's link, they are using this for drones and balloons already.]
[1] http://magazine.connectedremag.com/publication/?i=488126#{%2...
I think this is a pretty nice idea except for the patents and only having one or two suppliers and lack of technical details.
That said...Belden is reputable, but this doesn't sound like it's fully baked.
CAT6 cabling uses 4 pairs of AWG 24 wire. This type of wire typically comes with two options for insulation 250V and 600V, Let's be optimistic and use the latter. The maximum recommended current for AWG 24 wiring is 0.577A [1], as a reference PoE specs use 0.3A (if I remember correctly). Using these assumptions our maximum power transmission would be 4 (pairs of wire) * 600V * 0.577A = 1384.8W, this doesn't include power losses inside the wire itself. Belden's descriptions seem to indicate that power transmission is multiplexed in the time domain, which would reduce the power transmission capability even further.
Current limits on wiring are semi-arbitrary, what it really comes down to is how much heat generation is tolerable in the wires and the environment in which they reside. If we were to ignore the suggested current limit of 0.577A per core then it is possible to transmit 2000W. More specifically you would need 0.833A at 600V in 4 pairs of wire to get 2000W.
TLDR: The claims seem dubious. It is possible if the current limits for AWG 24 wire are are exceeded by about 2x.
The other advantage it that solves a lot of the IoT last 25 feet problem. Because it's both power and a data link.
[1] https://www.belden.com/products/enterprise/copper/cable/de-c...
4 * 300V * 2.3A = 2.76kW
It looks like it's totally doable with those cables! But if they're running 300V DC through there... may as well just run 120Vac. The only benefit I see is that they can detect faults on the transmitting end in a sophisticated manner.
As I understand it, the problems that make aluminum wire strictly inferior to copper wire--expansion coefficient, heat dissipation, non-conductive oxide, and strand breakage--are less significant in bus bars. The remaining concerns would then be bimetallic junction corrosion and work hardening.
Maybe a bus duct with polybenzimidazole spacers and insulation? Still sounds expensive and inefficient, though.
Ideally to me every led lamp, settop box, alarm clock, phone, laptop would not come with a power supply box. It would just take a USB cable or similar standard. Then you could buy a good quality power supply adapter that you can reuse for lots of products - and avoid the abundance of random adapters everywhere.
I suspect that with PD, that allows even lamps to negotiate that they need more power, maybe?
You would also still need something similar to a wall-wart to step down the voltage to whatever your device actually uses (e.g. from 12 V to 5 V to charge your phone), so its not clear how much benefit there would really be from such a system.
Whatever specs we adopted would probably also end up not being appropriate for some future devices, so we'd probably go back to a substantial number of devices bundling their own PSUs anyway.
Interesting idea, unlikely to ever be worth the cost. If wall-warts really bother you, then just invest in some wall outlets with integrated USB sockets - there are many good options on the market.
Otherwise the voltage sag and resistance makes it cheaper and more efficient to do normal 120/240 voltage with device-specific converters. (For example, if I had to run 0-gauge cable from my breaker box throughout my house to support 12v, the cost of copper alone would be prohibitive.)
I honestly think standardizing on USB for devices that can use it is the best approach, given that we already have tiny AC->USB converters that don't block other plugs, and outlets with USB built-in are on the market. Furthermore, I wonder just how much we can shrink the typical wall-wart so it won't cover other plugs?
(I also think we're better off trying to do a global domestic 200 or 400 volt DC standard.)
12V DC is fantastic for a solar setup (vacation cabin, off-grid home, or whatever). You can still have some standard AC outlets using an inverter, but there's no reason to have lights running off of AC -- especially if you have LEDs! Since inverters cause a slow but constant power drain, it makes sense to leave them off most of the time.
Edit: I also wanted to mention the amazing "3-way" fridges, which I was not aware of until looking into solar a few years ago. They can run on AC, DC, and propane, giving you an alternative if the power goes out. The RV world has tons of this stuff, and the appliances usually aren't that much more expensive. Some are even cheaper than regular appliances since they are usually more compact.
Propane-based refrigerators use an absorption cycle which depends on heat produced by burning the propane; in electric mode they just substitute resistive heating. A pure electric refrigerator would use a compressor-driven heat pump, which is considerably more efficient.
Amateur radio has standardized on the Powerpole connector for 12V DC. Powerpole is hermaphroditic so don't have to worry about which end is plug or socket, and uses color coding for polarity.
I have a friend who installed 12V in parts of his house, backed by a solar charged battery system. See my previous comment for some details:
https://news.ycombinator.com/item?id=21109247
Talking to this friend, we discussed the same problem as the OP. In RVs that are wired for battery power, they use wall-mounted cigarette lighter plugs, and you can buy some small appliances that use them. They are ugly and take up too much space, it would be so much better to have a plug of a regular shape and size. Of course it has to be polarized for DC, so something like ( - | ).
There is also the problem of breaking the arc in DC, so one prong needs to be longer and making contact further in so it can't arc outside the plug. Or maybe it needs some internal mechanism such as plastic slot covers that close and break the ark (like child-protected sockets have now). Anyway it definitely needs some research and design, but I think it would be cool to have a new 12VDC standard plug, then people could start designing products that use it to get the whole ecosystem started.
Lots of car barrel connectors have fuses inside. I'm not seeing much reasoning behind not using the car barrel connectors, aside from 'it was designed for cars, not as a general purpose connector'.
ANSI/SAE J563 and UL2089
https://en.m.wikipedia.org/wiki/Cigarette_lighter_receptacle shows the UL standard.
Apparently they decided to make it a standard in 1994 after years of mismatching equipment all over the world, which is longer than I would have ever guessed. Interesting to see. Apparently UL "standard" does not translate well to actual standard. My experience is that most devices fail on the spring center contact, and do not fit for all cars. Anecdotal but still: even the expensive charger I have doesn't work in one car I've owned (opel) due to the misalignment of the outer contacts and it jumps out too much). It says it's UL2089 compatible though so I guess opel was at fault. There are so many "extension cords" out in the wild which hardly work or go lose after time due to bad design or because they are just a bit too wide. I own several of them and have thrown most away.
The funny thing is the standard describes two sockets with differing size which is not helpful in any way and looks like a legacy of some manufacturers made into the standard.
The article also mentions other bad characteristics about the connector and plug like bad contact causing high resistance which is simple due to the design but might also be present with other designs of course.
I mean, it's nice it became a standard as it was in every car anyway since everybody smoked in them but there are way better solutions which do not have the problems I already mentioned and are way better solution for home appliances. If there is not yet a proper standard, why chose one which is not designed for this usage and most definitely was never designed for what it is used for today with all kinds of side effects (good or bad).
People in the 240V world get to pull 3KW from their wall sockets, I'm jealous.
http://wordpress.mrreid.org/2012/04/16/why-kettles-boil-slow...
According to that table, the latest standard, 802.3bt Type 4, can provide 71 W to the device at the end of the cable (and inject 100W into the otherside).
Unifi is selling LED panels, that are powered over PoE and controlled over Ethernet.
Currently everything I have is connected up with a hodgepodge of those green pluggable terminal blocks. It's not an elegant solution but it's hard to standardize on something, especially when I have devices that run off 5, 9, 12, 24 and 48 volts. I still run an inverter most of the time (I have two, pure and modified depending on the load).
I think it's possible to devise a decent solution here, I like the XLR based designs but I'm afraid of plugging things into the wrong voltage. I think maybe the good solution is to make a color-mapping for the common voltages up to 48v (past that you require an electrician to do wiring in the US iirc) and then make cables that are XLR on one end, and whatever-plug on the other end with an LED that lights up corresponding to the voltage. That way you know if your barrel jack is 12 or 5. It doesn't have to be foolproof, or even customer friendly really. People setting up DC buses to run all their electronics should be able to accept the responsibility of frying something if they give it too much juice.
Thus you see daisy chains of mechanical adaptors in telecom closets.
What there never was was a connection standard safe enough to put in a house, made to be (ab)used by normal people. 48v DC as it lives in the telco world is flat out dangerous if you aren't careful.
Having both ethernet and low power from one socket would be perfect for IoT devices, save people from having to run Ethernet wiring themselves afterwards, and cut down on wireless spectrum use.
And your 'smart fridge' would just plug into both outlets and use a relay to cut 230V if the motor doesn't need to run.
My perspective is just that of someone who's run a bit of both at an amateur level through my house, and finds terminating stupid-simple 120v wiring much, much easier than ethernet.
Heck, I don't know that there is even much need for high power ceiling lighting any more. Everything that people want to see with any detail is self illuminated these days. Just scatter some low power LEDs around (you don't even have to provide a way to turn them off) and you are done. If you actually want to read a paper book or do some knitting then an appropriate lamp is not going to take hardly any power as it would only have to illuminate a small area.
x10 speaks a protocol designed for this purpose and requires a base station.
Passive USB-C cables should be fine up to 60 watts. Beyond that you need a chip to certify safe construction but that's a good thing.
That's aside from the environmental costs of making & disposing of these pernicioius devices. Time for that decades-old solution to retire.
On the other hand, at least fewer people would be electrocuted by their crappy Amazon USB chargers.