Crazy, USA needs higher voltage AC, not DC...
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...
So Where’s My Low Voltage DC Wall Socket?
91–100 of 115 posts
Re: So Where’s My Low Voltage DC Wall Socket?
#92Earlier quoted context omitted.
Wait, that exists. USB is the standard. The UPS with standardized DC-outs is a USB power bank with integrated pass-through charging.
Slightly OT, but have you managed to actually find an acceptable quality USB power bank (PD/Type C or otherwise) that actually supports this "UPS mode" of operation? Most of the one I have tried cannot simultaneously output and input, or introduce a second of switching delay in between.
Some discussion about pass through charging on the Anker forum boards [1]. Pretty much everyone I know who carries a power bank only remembers to charge it at the same time they want to use it, so pass through charging capitalizes upon this consumer behavior to use the power banks more frequently.
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...
Re: So Where’s My Low Voltage DC Wall Socket?
#93It seems like USB A/C are going to be that. You can already buy outlets that have both mains and USB ports, there are even dual USB C outlets now, that can do 30 watts: https://www.amazon.com/dp/B07PTWG5DV
The author makes the valid point that USB-A is too low power, and USB-C requires active cables. (Translation: expensive or dangerous)
USB-C doesn't require active cables. Only 100W USB-PD and longer high speeds require active cables. The marker chip for 5A charging cables is cheap.
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.
Re: So Where’s My Low Voltage DC Wall Socket?
#94Earlier quoted context omitted.
They break easily. Spring loaded bits (actual springs). No properly defined standard and they vary a lot. Come out easily depending on quality. Easy to contact center pole to side poles on insertion. No ability to add earth.
12v plugs are indeed a standard, and can be quite robust. Other than size and cost, there are no such downsides. On DC there is seldom an 'earth', gound is analougous to dc negative/neutral depending on local standard. ANSI/SAE J563 and UL2089 https://en.m.wikipedia.org/wiki/Cigarette_lighter_receptacle shows the UL standard.
The case was made as a dc plug in general. Though 12V does definitely not require "earthing", you are correct about that. With earth in this case it is not the ground perse but some connection schemes (and standards) require either a third connector or open return path for DC which this connector cannot provide.
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).
Re: So Where’s My Low Voltage DC Wall Socket?
#95Is "Digital Electricity" a real thing? Its billed as an alternative to AC or DC. This may be as good a place as any to ask this question, but I am a hotel developer, and we've had a few people reaching out to us trying to sell "digital electricity" that sends high voltage over cat5 (up to 2000w per the Belden materials) by essentially sending high voltage for very brief blips with the ability to switch off before any…
Looks like buzzword marketing bullshit to me. Apparently they're just sending pulsed DC power over Ethernet cables? Nothing else in that article is as new or exciting as they dressed it up to be. GFCI outlets are standard in modern houses, they claim to be safely transmitting "high voltage" but 120V is not, and the "digital" buzzword stinks of marketing. >It transfers high levels of power over non-power cable You can…
It sounds like "digital electricity" is a more advanced sort of GFCI: instead of verifying that the two pins are carrying equal current, it verifies that the expected amount of power makes it all the way to the receiving end.
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.]
Re: So Where’s My Low Voltage DC Wall Socket?
#96Is "Digital Electricity" a real thing? Its billed as an alternative to AC or DC. This may be as good a place as any to ask this question, but I am a hotel developer, and we've had a few people reaching out to us trying to sell "digital electricity" that sends high voltage over cat5 (up to 2000w per the Belden materials) by essentially sending high voltage for very brief blips with the ability to switch off before any…
Looks like buzzword marketing bullshit to me. Apparently they're just sending pulsed DC power over Ethernet cables? Nothing else in that article is as new or exciting as they dressed it up to be. GFCI outlets are standard in modern houses, they claim to be safely transmitting "high voltage" but 120V is not, and the "digital" buzzword stinks of marketing. >It transfers high levels of power over non-power cable You can…
It's apparently a bit smarter than GFCI. [1] says it measures the loss in the wire to determine if a person or whatever is touching it. So that would protect people against shocks from touching both wires, which GFCI can't do.
[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.
Re: So Where’s My Low Voltage DC Wall Socket?
#97I don't see how going to 12 V would help simplifying devices. Most chips don't run on 12 V, so one will anyway need a switch-mode power supply or linear regulators with big heat sinks inside each device. The added expense of a rectifier and mains-capable transformer is minimal.
On the other hand, at least fewer people would be electrocuted by their crappy Amazon USB chargers.
Re: So Where’s My Low Voltage DC Wall Socket?
#98I always thought running low-voltage DC through a house from a single supply was doomed due to voltage drop over the distances required....
Well, there is less drop with more copper, so it's more about costs. Cost of cables, DC-DC converters, power supplies and their efficiency determine optimal configuration. Probably going as high as cheap mass market DC-DC converters and PSUs allow is good rule of thumb for low voltage, so like 20-24 V. Beyond that better to go with high voltage.
For some reason, I feel like 48V DC over super-chunky aluminum bus bars is the only way you could avoid making the DC whole-house wiring cost less than the entire rest of the house.
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.
Re: So Where’s My Low Voltage DC Wall Socket?
#99I have to deal with this problem constantly and I haven't figured out a good solution yet. I'm not sure this is particularly meaningful in a normal mains-connected environment but as someone who's base power source is a finite amount of 24v DC, I hate eating the inversion losses when I could save ~7-16% using switching supplies off the main bus.
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.
Re: So Where’s My Low Voltage DC Wall Socket?
#100Earlier quoted context omitted.
I was going to link to that exact product. I put in the USB A one a few weeks ago and love it. When the iPhone 12 is released I’ll switch to USB C.
Why wait for the iPhone 12? The current iPhone already charges significantly faster over USB-C than USB-A, as do all iPads released in the past ~3 years.
I read here recently that fast charging is bad for batteries.