AC quite decisively won the battle of electric current. After all, whether your wall outlet is outputting 110 V or 230 V, 50 Hz or 60 Hz, the whole world agrees that the oscillation frequency should be strictly greater than zero. Technically speaking, AC won because of three intertwined facts. It is more economical to have a few large power plants than hundreds of thousands of small power plants. This means that electricity must be transmitted over a relatively long distance, which requires a higher voltage. At the time, AC transformers were the only feasible method of step-up and step-down.

But that was then. We are now on the cusp of a power generation revolution, at least if you believe in solar enthusiasts. This means two things: the local electricity that was originally generated as a DC. This completely eliminates two of the three factors that are beneficial to AC. (And an efficient DC-DC converter will kill the transformer.) No, we don’t think there will be a switch overnight, but if having two household electrical systems becomes more and more common, we won’t be surprised— -A remote high-voltage alternating current provided by a utility company and a locally-generated low-voltage direct current.

Why? Because most equipment now uses low-voltage direct current, with the exception of some large electrical appliances. The battery stores direct current. If more and more households have some local DC power generation capacity, it would not make sense to convert local DC to AC just to insert a wart on the wall and convert it back to DC again. Hackaday's [Jenny List] avoided many of these settings in her article "Where is my low-voltage DC wall socket?" and went straight to the point. And put forward some physical interconnection solutions. But we want to support it. When the low-voltage DC revolution comes, what voltage will it be?

The problem of low voltage wiring is a simple physical problem. For a given power demand, P=I*V, so a lower voltage means more current is driven. But instead of Ohm's law, more current also means that the resistance loss in the wire P=I^2*R is significantly higher. Reducing the resistance of the wires by using more copper is an option, but by focusing on the squared current term, you can get more benefits.

This is why, for example, Power over Ethernet (PoE) schemes use about 48 V to transmit about 30 W of power-these thin Ethernet cables can only transmit so much current without wasting most of the current as heat . Even at around 50 V, PoE solutions need to lose 3 to 5 watts in the wiring. Therefore, no matter what cable you use for the low-voltage DC part of your electrical system, it will be thicker than Cat-5.

But copper costs money, so there will always be some upward pressure on the voltage applied by the resistance heating effect.

The voltage of about 30-50 V is beginning to be dangerous to humans. This is where the current level that drives the resistance of the human body starts to become troublesome. But despite everyone saying "safety first!" It is also worth noting that you now have 110 or 230 volts AC on the wall. Obviously, this is "washing machine priority" in the real world. In other words, although less than 30 V DC will be safer, we suspect that safety will be designed into the connector or circuit breaker.

This brings us to the last question. Have you done arc welding? How much DC voltage is required to produce an arc? Voltages around 24 V are very common values ​​for professional equipment, but people have been able to use 20 V tool battery packs or even 12 V car batteries for welding. Some spot welder designs we have seen only use 2 or 3 volts, but they generate the required current by pressing the workpiece together very hard to form a low resistance path.

Have you ever seen a relay and noticed that it has ratings for DC and AC use? For example, these relays are rated at 10 A at 250 V AC, but only 10 A at 30 V DC. Where does this factor of ten come from? When two contacts are close, the relay contacts may spark, and they are easily welded together under a higher DC voltage, which is not the case with AC, because the AC arc will automatically extinguish 100 or 120 times per second.

Making a mechanical switch suitable for your DC home electrical system will be a problem, which will put downward pressure on the voltage. Normal cars contain a lot of relays, and they seem to be working most of the time, so 12 V might be a good choice here. However, don't believe me. This is an automotive engineer's view of home DC. It is a bit dated, but he complained of additional design issues when working on a 24 V diesel vehicle. We think this is a vote for lowering the voltage.

The X factor here is the advancement of MOSFET or IGBT manufacturing. Solid-state DC circuit breakers are not as cheap as mechanical (AC) circuit breakers, but they are already there at the internal voltage of the home we consider. The higher price may just reflect the current lower demand. Perhaps in the near future, the downward voltage pressure will disappear?

Now that we have reached the end of the article, let us see if we can understand all this. If solar energy is to play a role in our future energy demand, it is inefficient to go from DC to AC and back. It will be more efficient to maintain the direct current from the panel to the battery to the terminal equipment. In this process, you may only use an efficient DC-DC converter to change the voltage once or twice.

If there is a complementary DC standard, heating loss will push up the voltage level, and switching constraints will push down the voltage. We believe that safety is a baptism. Solar panels can basically be configured for high voltage or high current cost-free, and we think this means that newer installations tend to operate in the 24-50 V range. This fully illustrates the importance of heat loss. Batteries are also flexible, so there is no problem with matching them to the power source.

We will be attracted by DC power outlets and the devices plugged into them, all of which are powered by a medium-sized panel on the roof and stored in a medium-sized battery in the basement. Whether it is from the panel to the battery to the 48 V or 12 V plug, it will depend on the relative price of copper and large FETs, but we bet that FETs will become cheaper and copper will be more expensive. We personally want to see this relatively high voltage drop on the plug to ensure safety, such as 12 V, but we will not quibble. It will perfectly complement our existing communication infrastructure.

how do you say? What factors are we missing? Does any of you already have a DC side at home? What is the DC voltage?

At least one person got the reference.

Next, there is an article on a computer that will ask the right questions.

Then someone will ask this question, and the universe will unravel.

Golgafrinchans will mess it up somehow.

42 -20% is correct. Stay under the 50V "high voltage" PPE limit of UL and other things, and be compatible with existing DC power sources (such as PoE).

It may also be mandatory to require arc detection and interruption. (It is relatively easy to use DSP to detect the arc and shut down from there)

If you can strictly adjust, please choose 48V. This is already the standard.

If you can adjust less strictly, please choose 42V /-20%. This is also a standard.

There are already a large number of products designed to work at these voltages, so why reinvent the wheel?

48v is good for this because it is very suitable for battery configuration, and there is already a large platform available for stable and long MTBF inverters, converters, etc. I think this is a very good candidate for the DC family, but arcing is a problem with live circuits, so you need to plug in the device and control the device to engage with the circuit only after it is well connected.

Maybe it's a combination of something completely different from the standard AC outlet, and a 1-wire network instead of the ground pin, because it doesn't need to be grounded with the same capacity as the AC system. Then use the "smart" power bar to tell the panel what is the maximum current that can be sent from the socket to achieve load shedding and fault protection.

In addition, the currently selected 48v fuse and distribution are terrible and need to be replaced with something more durable. http://www.littelfuse.com/~/media/electronics/images/fuses/littelfuse_fuse_4​​81_image.jpg.jpg

As you may know, the MacBook MagSafe charger does exactly this.

For safety, grounding is still required. If this becomes a standard, there must be some metrics for reference (think GFCI). I am an electrician for 16 years. The ground connection in your home is the most important connection you have because it saves your life every day. We will never see the end of the ground pin on a safe power outlet with any voltage or oscillation.

AC always needs to be grounded. But DC power is inherently safer. Under the voltage we want, we can replace all appliances except for a few AC appliances such as refrigerators, stoves, laundry rooms, and microwave ovens. Easy to reach, thus reducing risk.

But on a socket or box dedicated to DC, the dedicated ground pin on the socket has no benefit. The low-voltage side return line has the same function as grounding, and the DC system will not have the risk of electric shock like the AC system. There are other risks, but they will be mitigated in different ways. You don't need to use GFCI type circuit breaker on the DC system, because there is no contact shock and transmission risk like AC.

1 wire network instead of the ground?

1-wire has its uses, but I found that its use in wired systems may go through many mating cycles, which is a problematic judgment at best. Much like a poorly designed USB connector, it has fewer plugs and unplugs and is installed next to a wall outlet with a high plug and pull. I will eventually replace the "hybrid" socket long before the AC side wears out. Don't worry about any electrical problems of the internal converter.

I think that if any new home technology wants to gain a foothold, then it needs to reduce the complexity of home wiring and improve reliability, even if it means increased complexity of terminal equipment.

I think that for reliability, there should be no necessary data connections or microcontrollers. I recommend using an additional (low power) control contact, which closes late in the mating cycle of the connector and opens early. In this way, the power connection has been established, and then the power source is turned on electronically, and no arc will occur on the power pin. Another possibility is a manually operated mechanical DC switch. When there is no plug in the socket, the switch is locked in the "off" position and the plug is locked in the "open" position.

"But DC is inherently safer,"

No, this is not right. DC can do a lot of nasty things, AC can't. It's like keeping the spark longer, or separating your blood through an electrical process.

You say "but on a socket or box dedicated to DC, the dedicated ground pin on the socket has no advantage. The low-voltage side return line has the same function as the ground." But there is no difference between AC and DC in this respect- In an AC system, which line is grounded is completely arbitrary, while in a DC system, the positive or negative ground is completely arbitrary. Grounding is necessary as a safety mechanism-otherwise an accidental ground connection will cause an electric shock hazard. This applies to any dangerous level of voltage, whether it is AC or DC. (If the *unintentional* ground connection can be completely eliminated, then without the *intentional* ground connection we are using now, the power distribution system will actually be safer).

In addition, for the sake of children, and because DC can sustain an arc, we will need a household DC power distribution system with a GFCI in the range of 42 to 48 volts. Please note that the DC GFCI is more complicated and more expensive than the AC GFCI, both in terms of the detection circuit involved, or because of the need for greater spacing between circuit breaker contacts.

For the same reason, I plan to say 48 volts. As far as I know, this is why the POTS line runs at 48 vdc.

About 50 volts, 90 volts ringing (20Hz AC signal) and 6-12VDC during a call...

A voltage higher than 120Vdc or 50Vac (up to 1kV) is appropriately called a low voltage. Anything lower is an ultra-low voltage.

However, given the quotation marks, you may know this.

It also happens to be around three 12V lead-acid batteries connected in series, nominal 36V-charging ~42V

Very good answer, because it is lower than 50V ;-). In the United States, most states do not require a licensed electrician to work on circuits below 50 volts. This is one of the reasons why TelCo uses 48V

Or, is the telecommunications company the reason for the electrical regulations to set the limit to 50V? The phone has been around for longer than the national electrical code.

maybe. For a long time, consumers were not allowed to install their own phones. I was too young at the time, so I was not sure about the logistics behind it. In any case, I think the first change in the rules occurred in 1969 or 1974. As a child, I remember seeing piles of old Formica(?) telecom connectors in my father’s recycling business.

I think NEC was first released in 1987, even though Google showed some dates cited as early as 1983.

This has more to do with the monopoly of the Bell system than with security.

NEC was first released in 1897. Telephone installation restrictions stem from the fact that Bell has a monopoly and actually owns the lines and equipment in your home.

NEC was first published in 1897. Bill's statement about telecommunications monopolies is correct.

People have been killed by 40 VDC.

This makes many of us do not have permission to install some ptz camera systems. They are 54v PoE devices.

Oregon doesn't care about these cumbersome details. If it is wiring and you pay someone else to run it, then someone else must obtain permission for this type of wire. If you are an electrician who wants to run a network cable, then you must also obtain a license. The union governs Oregon with a very strict iron fist.

Thankfully, I don't live in Oregon, so many bolshoi are not applicable.

I think 110vdc is a good balance of safety and efficiency. Most modern appliances have a switch-mode power supply that can work happily under AC and DC (no inverter required). I have tested it with battery packs, mobile phone chargers, laptop chargers, LCD/LED TVs and everything is normal! And because the device can work in different countries, the voltage can be from 100-240v! Most LED bulbs (but not all) will work properly! Some new refrigerators and washing machines have built-in variable frequency drive motors, so they can effectively use DC power inside the equipment!

"Because most equipment now uses low-voltage direct current, except for some large appliances."-This is your answer. Most POWER is consumed by equipment that runs happily on AC. Especially asynchronous motors are very suitable for communication.

So this will not happen because the infrastructure costs are, to put it mildly, huge.

OTOH, the company that promotes the DC/DC conversion will tell you that this is the future. Follow $ as always.

For heavy users, yes, but for residential? The only thing in my house that needs air conditioning is the refrigerator...

air conditioner? Vacuum cleaner? dishwasher? Garbage disposal?

Most modern household machines (refrigerators, air conditioners, washing machines) that use AC motors now use some kind of inverter to better control the speed and make the bees "greener." Some kind of DC power is already cut off somewhere inside, so it's not that far to jump to DC-powered household items.

From a purely physics point of view, I agree to jump to homes that are mainly powered by DC. From the perspective of most families now, they only have AC power installed on their walls. I find it difficult for manufacturers to start manufacturing DC-only electrical appliances, even when the market is such a scale, they don’t even bother to manufacture AC or DC electrical appliances, um, It is basically 0 now.

The chicken and egg problem. Who wants to double their SKU and deal with customer confusion?

This is the same reason why the United States still has very poorly designed electrical plugs. Metal exposed during partial insertion? Check. No fuse? Check. The bottom is grounded (sometimes)? Check. Oops, even polarized plugs are not always certain. But this is how things are done. This is something that is cheap, available, and code-compliant, so we must continue to do so.

But you can't run large appliances on 48V, so you might as well keep the current AC system for those and add an extra low-voltage DC for the small things.

Inverters of large motors cannot operate at low voltage... They rectify high-voltage alternating current and then cut it off at the required frequency... Even if there is a small section of rectified high-voltage direct current, it will eventually be high-voltage alternating current in the middle ( Note that this is a small part of minimizing losses).

air conditioner? – Not half the world... a vacuum cleaner? – Can it run on a battery dishwasher? – If it’s just for heating... why? Garbage disposal? -We have a trash can outside...

So the United States may be left behind, but the rest of the world can praise our new DC overlord!

Dishwashers have a pump motor, which usually requires alternating current.

DC may be the appropriate voltage type, but higher voltage lines are still required. Because there, at least in Northern Europe, the energy for many houses is only electricity, and many kilowatts are used in heating, cooking, etc., I did not see the 48V DC line output and the 400V AC power line will be the same soon :)

A typical dishwasher requires 2 to 3 kilowatts of heating power. This will be in the 50 amp range on 48V. Then there are other high-power appliances, such as hair dryers, washing machines, toasters, coffee machines, etc. Have fun with proper wiring and a 50-amp rated plug. Imagine the buck converter you need...

In 230V-Land, all these appliances can run on ordinary sockets anywhere you own. If I want, I can use the hair dryer in the living room. It can be said that almost all household appliances use a socket. The only exception is usually the oven/stove, and if available, there is also a fast heater for hot water (usually rated for 3-phase, 32A). I really don't want to give up.

@Gerrit: Actually, most ovens/ranges nowadays operate on single phase-standard models with ovens and four hot plates (?) put the oven in a dedicated stage and use two plates in other stages. As long as you don't turn on all the power immediately, they will run happily on regular 230V/32A or even 16A sockets. Okay, you don’t want to show it to your electrical safety inspector;)

dishwasher? Because it is heating up! 2kW @50V is 40A! @24V is greater than 80A. If you have a car, check the wires connected to the starter. Do you think it is a good idea to lay busbars like wires at home? This can be very expensive on copper, and in the event of a short circuit, you can make light-emitting connections very quickly.

Vacuum cleaner: I have a battery-powered Dyson. Its size is good, but you can't compare it to AC power, and the battery can't continuously clean the entire apartment. Well, for me, garbage disposal also means going downstairs with a bag on my back. I don't have air conditioning in my house. Fortunately, in the office.

I don’t know about air conditioners and dishwashers, but vacuum cleaners and garbage disposal can also work on torque DC motors. Especially if it is powered by a 48V line, then the current is not large at all...

But yes. I totally agree that only DC houses will appear for a long time, if any. I am more interested in the middle half.

If your vacuum cleaner uses 1100W on AC power today, it will also use 1100W on DC power.

At 48V, you need to provide it with about 23A of current.

The household DC power supply cannot work below about 300V. It needs to be higher because the current needs to be reduced. The wall sockets will be smart DC-DC converters, and the devices will specify the voltage and power they require. Plug in a 6-port USB-C hub, it will require 600W of power, about 120V@5A, and then down-convert to 20V@5A for each USB-C port. As the battery charges, the USB-C hub will renegotiate power, 120V@4A, then 3A, and so on.

As for the vacuum cleaner, it will require 300V@4A. Due to resistance loss, smaller current means less heat, so the heat exchanger only needs to dissipate the remaining heat in actual work.

Further run Alex's scene:

For an average vacuum cleaner cord length of 25 feet, 48 volts, and 23 amps, assuming 2% loss is acceptable over its length, 8-9 AWG cable is required.

Your ordinary vacuum wire is connected with 17 AWG wire.

It would be foolish and wasteful to add more copper to absolutely everything to make up for the loss.

@Alex: You are right about voltage. Therefore, I think DC home wiring is useless. 300VDC is not safer than AC, and the switch becomes more expensive (the arc must be extinguished). And the bridge rectifier is quite cheap. Yes, you can avoid PFC and large electrolyte. But the most common failure is the low-voltage electrolyte on the output side of the DC/DC converter.

In fact, my name is Alex. I also recommend 300 Vdc. In fact, 300 Vdc -10% is on the supply side and -20% is on the user side, because there can be a long cable between them and it needs to be consumed. Electricity or injection. I come from Belgium and Europe, so we are used to 230V, and the tolerance on the instrument is -10%. (Industry may be -300V = 600V). Only hackers know that DELL computer power supplies also accept 110Vdc to 370Vdc. 300V -20% is 240-360V, perfect compatibility. So, if your photovoltaic panel happens to be in this range and can provide 70W or higher at the moment the computer can work in it, I will do this many times. Many SMPS can use PV directly. In fact, the battery voltage may have a tolerance of -10%. However, commonly used switches (such as thermostats) for controlling resistance are not made for DC. Actual use stops at 40 Vdc of a single tag switch. For a single tag switch, 48V may be too large, and the wall plug seems to be no problem. On the other hand, the power transistor has no problem at all to switch DC! There are still many things that need to be developed to work properly and safely. However, for the same power, a large current short circuit of 48V may be more dangerous than a higher voltage. Higher than 370Vdc may have a high risk of damage to household equipment. In Japan, a 100Vac grid voltage of 50 or 60 Hz is used, with a peak value of 140V, a tolerance of -15% and a capacitor ripple of 15%, which means that many wide input voltage devices even form about 100 Vdc in actual work.

A typical refrigerator uses about 60 to 120W, and some efficient ones are even lower. This is easy to do with DC. You can already use DC refrigerator compressors, such as 12V/24V for camping/off-grid use, although they are more expensive than traditional ones. They use BLDC motors with soft start. The use of a traditional refrigerator on the inverter requires a refrigerator that seriously exceeds the standard, because the asynchronous motor requires about 10 times the rated current when starting. My 220W/600W peak inverter cannot start the 95W refrigerator, it just blows the fuse (30A@12V). But any type of electric heating (washing machine, dishwasher, coffee machine, hot water, microwave oven...) basically anything with a power consumption greater than 100W, or depending on the DC voltage used, 10 to 20A, I think it is not suitable for one ( Additional) low voltage DC system. LED lights, computers, LCD monitors, and battery chargers will be a suitable use.

Could someone please talk about the multi-12V DC bus system. 12V is good, the loss of short house distance or low watt and plug usage is not high. Combine multiple 12V lines to get a higher voltage; maybe think of a way to increase the wattage of these combinations? 5-pin combination plug? (1 ground, 2 bus.. remember that USB has more than 5 contacts)

In order to solve the danger of high-power DC (A or V), what about pulsed DC? It's like a simple rectified alternating current-it never reverses polarity. That should make the arc safer, right? (Regardless of polarity, an arc is an arc? Its on/off makes AC safer.) Household pulse generators for high-power DC can be tricky... I don't know. Does DC generate pulses similar to AC but output 2 DC buses from AC like generators? Will the AC and ground capacitance loss occur in pulsed DC?

Divide it into two parts: getting electricity from the grid (I think this is the current alternating current we have) and self-generated direct current (12/24/48V DC). Later I saw that local battery technology came into play. The thing is that some government agencies need to find standards, because Big Grid and Big Battery won't work well together until someone makes a decision for them. I'm not sure this is a good thing.

Although I agree that the cost will be huge and follow the money, because it clearly shows whose benefit it is. I can see where the newer battery technology can be used to transform the house. You can use a DC to AC converter (you can also add grid AC to DC), but I wouldn't be surprised to see the USB port directly on the battery for charging. Now, how to transfer DC around the house without AC conversion is an interesting problem. What is considered the cheapest method, and what is considered a reasonable power loss.

The USB port on the battery is not very useful. Usually you want to charge your mobile phone in the living room, and the battery is placed in the basement or some storage room. Although I have seen 100Ah lead-acid batteries in the living room: In India, there are so many power outages that inverters with backup batteries (for lights and ceiling fans in every room) are installed in many places.

The stupidity of the whole argument is that the DC-DC converter is internally a DC-AC-DC converter.

If you have a DC power supply like solar panels and batteries, and you are running DC appliances, these appliances will inevitably have their own internal DC-DC converters, because you can’t charge your phone at 48 volts. Then the power path gets (DC-AC-DC)-(AC-DC) conversion from the power supply to the device. If your inverter provides AC power to your house wiring, the power conversion path will become (DC-AC)-(DC-AC-DC).

You may notice that the number of conversion steps is the same in both cases. There is no benefit to using DC wiring at home.

Well, if I have ever had an idea you didn't know before, then your post just now must have cleared all the doubts.

Except for the smallest charge pump and boost converter, everything will be some kind of topology, essentially an inverter, a transformer, and a rectifier.

I’m just thinking about this, and then browse the comments about it... My idea is more, if the wire resistance is very large, but the inverter is very cheap, then why not let the wiring in the wall continue to use AC power... And you The house power supply may be different (if AC power is used on the old grid, DC power is used if it is generated by photovoltaic power, and AC power is used if it comes from wind/water turbines, etc.). Now maybe switching losses may be a problem, but as Dax mentioned, most of these inverters pass through the AC stage (even if it is only single-ended, the skin effect still looks the same, right?).. .... If anyone is worried about vampires/leakage current, installing a simple "smart grid" for your house seems to be a solution.

Technically speaking, most low voltages (the difference between Uin-Uout <50V) use simple inductors instead of transformers: P

Explain this in detail: flyback, boost, buck-boost, sepic, etc. cannot use magnetic cores very effectively or have other problems that limit power density. The remaining options are push-pull, half-bridge, and full-bridge, which are what you need when converting power to your house, such as 1 kW. When you have a full-bridge topology, what you actually have is a DC-AC inverter—albeit a high-frequency inverter. Then you add a rectifier and you will get direct current.

http://powerelectronics.com/dc-dc-converters/topology-key-power-density-isolated-dc-dc-converters

Yours is right, but yours is wrong. You only see the trees but not the forest. The real stupidity of the whole debate is that this is a solution to the problem. When something is not damaged, there is no need to repair it. The current system is not damaged. It fulfilled its purpose well, and our whole argument that we are now on the cusp of the power generation revolution is pure fantasy. The ideas discussed here will add a lot of cost to each house and building constructed, and for 99.9% of consumers, it will not bring any benefits. This does not even take into account that it will increase the cost of new household appliances, which means that people will face the cost of replacing all existing appliances, buying some kind of adapter for them, or keeping at least one or more old circuits in their home wiring to maintain them . When you see all this, you have to ask why? Why do ordinary consumers endure all these additional costs and inconveniences for things that will not bring them any benefit? This is why this is a stupid idea.

If someone wants a DC wall socket, just build a socket with a DC power supply inside. I bet the solution already exists. I have seen wall sockets with USB power ports. For most people who just want to use such a socket to charge a mobile phone or tablet, this is enough.

Yes, this topic has always been on HaD, and its presentation is just a pipe dream.

What you can do with something is not important, what you *cannot* do.

How does my 2kW space heater work and draw 83amps at 24v?

I think we might move to a DC home, where some parts of the highly developed world seldom draw power from your AC, and the rest of us will stick to AC.

Just like Bhutan, which got TV in 1999.

Simply plug the short circuit into a DC power outlet and the house wiring will heat the room.

The dollar will be the decider, and it will decide AC. How much do I need to pay for the AC outlet? Can be as low as $5, fully approved. How much do I have to pay for the wall USB socket? It is currently about $30, and all are 2 amps (10 watts). It may be convenient to charge my phone, but it's certainly not cost-effective. I can buy sockets and wall-mounted sockets for less than one-third of the cost of "USB export".

Even if people are really fascinated by efficiency, as Dax pointed out, when the "DC to DC" converter is scattered around the house, the efficiency will not be better and the reliability will be much worse; and due to poor reliability, replacement and therefore The impact on the environment will increase.

This topic has been proposed (pushed?) by HAD many times, and I think they have no suitable cool hackers to talk about.

In the United States, standard load 15-amp sockets and light switches can be purchased for the first batch for as little as 50 cents. A construction company will buy so many houses that the cost of the entire house is only a few dollars.

The "smart" DC socket can adapt its output to various devices and make the device "smart" to convey its power needs to the socket-while preventing incidents such as children inserting hairpins into the socket from causing deaths, fires and other incidents or malfunctions Equipment-unlikely to happen.

What we have are things like tablets and smartphones and their AC adapters. They are semi-smart because adapters have a rather crude way to communicate how much power they can provide at a fixed 5 volt voltage, and the device It will detect and adjust the power consumption accordingly when using the internal circuit to change the voltage as needed. This works even though OEM AC adapters are often overpriced.

For appliances such as vacuum cleaners and leaf blowers, having such "smartness" is not so smart. You flip a switch and they will work. When finished, close them. Many of them have used DC motors and simple bridge rectifiers, or four diodes welded together as bridge rectifiers. They can run DC power directly by turning off the rectifier, but it is impossible to have 110~120 or 220~240 volt DC indoor wiring. This will require soldering cables to the wall.

Those 50-cent sockets and switches have astronomically low mating cycles. About five years later, I have replaced most of the sockets and switches in my 2000 home with more expensive "industrial" rated sockets. Each IIRC is about US$3 or US$4.

Damn it, the socket in my 1940s house was more durable than the aluminum wire I tore off. Yes...I turned off the socket. But I kept the cool art deco wall panels.

I can't imagine that a $30 USB socket will last longer than the smartphone I plugged in.

In fact, there is a German who uses a 12V 100A water heater to run something similar... http://www.dasgleichstromhaus.de/?page_id=5268

Try using flash heaters...they are usually rated at 230V, 3 phases, 32A per phase (about 22KW). This is what you need to get enough water flow for a hot shower.

For hot water, I will use a collector. However, if I want more solar energy usage than small lighting and music, I will use a voltage above 12V.

The current consumed by the space heater is largely irrelevant, because the I^2R loss only transfers a little bit of heat to the wall-the house is still heated. For the 41-amp 48v (the most supported house voltage in the international market), 2kw is quite moderate. 48v/5kw inverters are more high-end in the market and have now become widely used standard commercial products. House wiring of the right size is slightly heavier than high-voltage wires. An ostrich who claims that something cannot be done may profit by glancing at many people who have been doing it for years.

But in Australia, electric heating only pollutes coal heating. I just split and stacked the first 9 cubic meters of firewood for the coming winter. Heating does not add any carbon dioxide to the biosphere, thereby keeping millions of carbon stored for millions of years away from it. (Well, I have my own forest, so _know_ it is being replaced-spades.)

What will improve the practicality of DC houses is the range of improvements in DC appliances and workshop tools. For example, there are small DC refrigerators that contain state-change thermal storage, so they do not need to be powered overnight. (Heat storage is much cheaper than electricity.)

> "There is still heating in the house."

This is a dangerous proposal. You are fraying the insulation in the wire and creating a fire hazard by absorbing a lot of power in the wire.

In an unair-conditioned house on the east coast of Australia, there is hot water and stove (and battery vacuum cleaner) with immediate gas demand. It seems that only the washing machine needs AC power. 12V refrigerators are very common here (although there are caravan and motorhome types; I have not searched for 12V household models). I am happy to run inverters for refrigerators/freezers/washing machines; today, the best efficiency is over 90%.

We use gas to boil water and cook, and use wood for heating in winter is what we do here. With the privatization of utility companies and rising electricity prices, 12V systems that are off-grid and powered by batteries have become increasingly attractive.

24V. Because this is running on my battery pack configuration, and because some cheap 12v regulators cannot accept input voltages higher than 50v, if you want to finally drop to 12v, this excludes the nominal 48v battery.

I chose 12V myself-mainly because I don't want to deal with the link battery and can use off-the-shelf 12V car power. I thought about 24V, but some of my laptop car PSUs don't support anything above 15V, and it needs additional control instead of just pushing cheap 12V LED strips onto the line. In the past few years, I have converted most things to DC, and I guess that now about 50% of the electricity is consumed on it. One problem I had to work hard to solve was protection-most of the larger and cheaper car fuses are for enthusiasts, and if you really try to use the current rating printed on them, there is no chance. I ended up with oversized ANL fuses and some off-the-shelf circuit breakers. Fortunately, these circuit breakers received DC usage ratings from the manufacturer I purchased. I even started to deploy RCD, but because many devices are not properly isolated after leaving the PSU, it is not so easy. For the plug, I use the British plug-cheap, fuse, reasonable power, polarization and no one here knows what the plug does ;) The problem is of course the wiring, but for me, throwing some money is still cheaper than Instead of getting a higher rated voltage PSU on heavy wires. I think I will deploy some "transmission lines" in the future to use higher voltages to connect local power distribution units and allow longer cables to run without causing too much voltage drop.

Another side note: If the voltage is large enough, most AC devices with a universal switch-mode PSU will happily run on DC-40 to 75V should be the lower limit of these devices. This will open up another way of doing this kind of thing and allow a smooth transition.

For the plug, I use the British plug-cheap, fusion, reasonable power, polarization, no one here knows what the plug does;)

What is a British plug? If I search for "britisch", I will get pictures of cats... If I add the word "plug", I will get BS 1363.

BS1363 sounds good-my cat does not provide enough power;)

A true catatonic power source.

In winter (dry air), my cat provides more electricity than I or he wants. :-)

I hope you use a wire nut to fix the connection, not sure if anyone outside the UK can handle the safety of our excellent plug, you need to counteract it with dangerous things :)

One design flaw is that when you stand on the prongs when you unplug the plug barefoot, there is no such pain. Besides, when I see other plugs in other countries, they look dangerous compared to our plugs.

Interestingly, I looked at British plugs and wondered if they were serious about designing them for the electrical current used around the home. I think I can push 100 amps through one of the pins! At 220v, this will exceed 20kW. Good for heating, but I believe it is very much needed in the UK...

I think the pins can be tolerated, but there is no problem and some thick wiring is required. British homes *usually* have 80-100 amp power fuses @ 240v, so I don't think I will try, but the pins are really strong.

I'm sure that ordinary people in the UK cannot afford 20 kilowatts of electric heating. Electricity prices in Europe are not the lowest for ordinary consumers. As far as I know, it is 5 times higher than the United States in many countries.

Those British super safety plugs should be excellent melee weapons. Cut the power cord from the hair dryer, tie a loop at the end, and rotate it so that it has enough power to achieve a good THWACK.

I have heard stories of people doing this in prison, and I certainly don’t want to be hit in the head by a certain person.

I will insist on using AC to wire my house, thank you. I would rather get a short AC vibration to get my fingers out of the line of fire than a short live DC vibration, which can lock my fingers on the line of fire. In this regard, I have a strong preference in my heart. :)

The entire article is centered on DC voltage that does not cause any risk of electric shock.

You can shock yourself with a 9 V battery. Just place the terminal on the tongue.

That's not shock, it's entertainment.

Electricity is not your friend, especially when you happen to come into contact with a live wire with a low-resistance body.

I worry about the assumption that AC voltage will "throw" your fingers off the wires.

Throwing/triggering your nerve spasm and release (not DC can trigger spasm and hold)... This is a muscular response, but a bit unconscious, depending on how you look at it.

Still went the wrong way. AC causes muscles to lock up because it triggers nerves repeatedly. DC just polarizes the nerves in one way, and then they stop working, which causes the muscles to pull once and then become limp.

The current required to obtain a grip from direct current is four times that of alternating current, and with direct current, muscles relax after spasm.

http://emedicine.medscape.com/article/770179-overview#a5

"High-voltage direct current usually causes a large single muscle contraction, which moves the victim away from the source, resulting in short-term contact with the source. In contrast, alternating current of the same voltage is considered to be about three times more dangerous than direct current because the circulation of electrons will Causes muscle twitching, which prolongs the victim’s exposure to the power source. Muscle twitching occurs when the fiber is stimulated at a frequency of 40-110 Hz."

Therefore, we only have the "correct" power frequency to make this happen:-( But the whining sound of 400Hz will not be very good, and the loss will be higher, and the really big transformer (16,7Hz) required for railway power supply is also Very expensive.

The danger level of DC is the commutator noise from the motor and other switching ripples at the top of the DC. This has the same effect as AC because it allows you to grasp the wire without letting go.

There must be a critical point where the low efficiency of using AC inverters is overcome by the efficiency of using AC appliances and wiring. As Miroslav pointed out, if you strictly adopt DC, there will be many things that require DC-DC conversion, which means you can use the AC power from the inverter effectively.

Two things can be defined as "efficiency"-the cost efficiency of investing in necessary upgrades, and the purely physically related efficiency of energy transfer between the two systems. I can already hear purists praise the efficiency directly from the battery to the appliance, but if the cost of a DC appliance is five times that of an AC appliance, there is still a loss of efficiency. It just makes humans work harder to make money to pay for it.

The DC-DC converter is an internal inverter with an additional rectifier and filter that can convert it back to direct current.

Deciphering a book Dax... This is definitely not true. The buck converter is essentially a PWM circuit, which feeds the back-end LC filter. There is a feedback path through the error amplifier to control the on/off frequency of the PWM load switch relative to a fixed voltage reference (such as the band gap) to maintain the target output level. The boost converter switches the inductor to ground to charge it, and then returns to the series path with a slot cap to release energy and build a voltage. In any design, there will not be any polarity reversal with respect to the ground reference. Nothing is closer than AC.

Try to make a 1 kW step-down converter.

Sorry, Dax and I are together. Switching DC is AC, there is absolutely no dispute. Even if the PWM changes from 0 volts to 48 volts, it is also biased at 48v pp AC and 24v DC. You should take a look at some Fourier.

This is probably the answer we are looking for. 170V or 340V DC pulses at a frequency of about 100Hz, with a controlled rise/fall rate and a duty cycle of about 80%. Pulse interruption of arc is like alternating current, but it is much simpler to go from direct direct current to pulsed direct current than all the way to alternating current.

"But going from direct DC to pulsed DC is much simpler than all the way to AC."

A large DC-DC converter that provides several kilowatts of capacity for house wiring will be a full-bridge switch that provides alternating current to the transformer and then rectifies it back to direct current. In this case, having AC is actually simpler.

Of course, the circuit needs to be redesigned for 60 Hz operation, but this is not the point.

In addition, 80% duty cycle PWM will generate a large number of harmonics, which will be radiated everywhere in the form of EMI.

You can describe it like this. But of course, the voltage on the coil will change the polarity between the two parts of the PWM cycle. In a buck converter, the input of the coil switches between battery voltage and ground (switching to ground can be done through a diode or MOSFET (synchronous rectifier). The output is connected to the output, and the output has an intermediate voltage, so the polarity In a boost converter, the coil voltage also changes polarity.

The battery storage efficiency is about 80-90%...The efficiency of the grid-connected inverter is about 90%

Grid-connected solar cell arrays solve the problem.

The problem with grid-connected inverters is that if the grid fails, they must be shut down—at least in my area. And because I see how much money has been cut from infrastructure maintenance, I prefer to have a backup...

SunnyBoy has a new feature. They have a socket on the inverter, which stays on during a grid outage. I think this is a big selling point for places where power outages may occur for multiple days due to weather or other reasons. Where I live, according to my estimation, the AC power is about four 9s-beyond the acceptable range.

I think the newer inverters are designed to cut off the power supply from the grid in this case, but still deliver pipeline power to the house (provided that the solar array generates enough power to power the house.) Then when the grid is restored...​​ ​...They will adjust their sine waves to match the grid and start pumping electricity back.

I thought I had read that it was the way they built it now... I might be wrong.

Depends on the method of connecting to the panel. Different countries/towns deal with these things differently.

My system has a "smart" meter that can sense power outages from the grid and cut off outbound traffic. Therefore, my panels continue to plug the power supply into the panel legs to which they are connected.

Others need to be completely cut off manually.

In these situations, there are multiple ways to isolate your home from the grid, and this is the only way I plan your home. If the grid fails, investing in an idle solar system is a huge waste, because my house still needs electricity, and I don't want to rely on the power company's incompetence.

Most solutions include a grid-aware inverter or a transfer switch before the inverter. If the control panel is located on the side of the inverter's house, the solution can even be used in conjunction with the micro-inverter solution and will continue to operate in the event of a grid failure.

A large contactor on the house input should solve this problem ;-)

"With grid-connected solar arrays, the problem is solved."

That is another way. Grid helps a) centralized storage is more efficient than distributed storage or b) the problem is to balance the load over distance rather than time. The local area is also more capital intensive and may require more maintenance by the end user.

However, especially for solar power, the electricity that will be used overnight must be stored somewhere, so the problem is only concentration (plus distribution) and local. If local DC storage is as efficient as centralized storage (not yet), then the equation will be reversed, and we may see this in our lives.

What makes you think that local storage will be more efficient than centralized storage ("not yet" commented)? Local storage is limited to batteries-I really can't think of anything else. Centralized storage can use anything, from heat (molten salt/metal/silicon) to hydraulic systems for pumping and generating electricity, or esoteric battery systems (for example, redox flow batteries). When talking about MW and even GW, all of this becomes economically viable. Traditional batteries cannot compete on these scales.

In Australia, burning more coal is cheaper than storing energy, mainly because of government subsidies to the coal industry. But there are still people bucking the trend, thank goodness.

The thermal mass is much cheaper than batteries, can basically be used continuously, and is suitable for the three major energy users in most households-HVAC, hot water and refrigeration.

@Fred: When comparing directly, I think local storage will never be more efficient than centralized storage. However, the wedge between them is the round trip from solar energy to low-voltage DC, and its cost is about 7-15%: inverter, transmission, storage center, transmission, conversion, rectification.

Home storage (battery part) only needs to account for 7-15% of remote storage ("battery" part) to make sense.

But there will be great difficulties for you. For example, just manufacturing lithium batteries is equivalent to about 10% of its life storage capacity, which put this idea at risk from the beginning. Check the "ESOEI" concept of different battery types.

The entire storage business is a huge "IF" because no good storage solution will not double or triple the basic cost of electricity-whether remotely or locally.

The touring caravan already operates in this way; 230V AC is used for heating and high-power electrical appliances. 12V DC is used for lighting and low-power applications, usually powered by photovoltaic solar energy.

Exactly. Who would want to live in an upgraded caravan? !

I would choose 42VDC for one terminal and -42VDC for the other terminal. This is similar to a center-tapped power supply, so if any terminal is subjected to a voltage lower than 50V, but the combined voltage is 84V.ji

What if you manage to touch both?

"So no matter what cable you use for the low-voltage DC part of your electrical system, it will be thicker than Cat-5."

However, this is a bit misleading because there are 8 wires in CAT-5, and each wire has a maximum of 22 gauge. A single No. 14 solid wire is much thinner than the entire set of UTP wrapped in CAT-5.

Fortunately, the metric system has not yet been invented, because every farmer knows that 8 times 22 rails are obviously better than solid 14 rails.

In this "meter" system, the lower number is the larger wire, so the 8 parallel #22 must be similar to 22/8 or ~#2 or #3 :-) but it seems to be more similar to the dB equivalent Number scale.

The "Units" utility can classify them effortlessly:

$ Unit-1 You have: awg(22) You want: mm * 0.6438033

The diameter of the area increased by 8 times will be sqrt(8) ~ 2.83, and

You have: awg(22) * 2.83 You want: awg 13.027711

That is about half of the gauge, which is almost 3 times the diameter. To read the formula, type "help awg" at the prompt:

Then click ^B (control-B) to return to the help page. There is history there, if you are thinking of BSW, not AWG, then brwiregauge.

(If there is no easy-to-use linux command line-we hope that functionality will be restored soon. ;-) ($ man units # is worth reading.)

The standard is a multiple of 12v. I have some refurbished batteries (we have some heavy equipment, if someone discharges the batteries-1700Ah-it takes too long, so local places refurbish them as half price).

I have an Outback 80A charge controller. Please note that for the above reasons, ampere is important, but even worse, P=I**2*R, so halving the current will reduce the loss by 4 times. If you only have a few solar panels or windmills within a short distance, you can feed them in at low voltage and high ampere. 80A at any voltage (although there is a wattage limit), this means that 24V 100A needs to be reconfigured to 36v, or 48V 50A to use the 80A charge controller.

The FET is limited (at the top) to about 150V, so this is the upper limit for series solar panels.

12V-All your car accessories can work, including larger inverters, but you will see the same amperage problem. Cars and trucks are often limited in size, so the wiring may be short at 12V. Check out winches that can withstand more than 10,000 pounds to understand their wiring requirements. Similar high-capacity inverters.

A 100W amateur radio usually works at 12v, but you won't let 1500W work linearly. (Think about the live day).

24V seems to be very common too. I have a 24V pure sine inverter and a larger step inverter. Due to the length of the wires and current, my battery pack is 24v. There are fairly cheap 24V switches and high-efficiency DC-DC converters that can reduce the voltage from 24V to 12V.

The relay was mentioned, but you are looking at (car starter) relays to switch things. In addition, if you have tiered pricing, you may want to use AC to charge DC power during cheap hours.

Another consideration is that when your battery is fully charged, you may need to connect to the grid to "push" the inverter to move the meter backwards. I'm not in a place where they will pay for my electricity, but by pushing the electricity back to the grid, I can pay less. These also have 12V/24V variations.

FET can work normally to medium voltage (IXTL2N450 is the part I have used recently. 4.5kV, 2A). Most PFC products use low power (<300W or so) 650V super junction FET. When you reach about 200V and a few amperes or more, although IGBTs usually reduce losses at least in silicon. If you use GaN or SiC, it will get better.

"If you use GaN or SiC, it will get better" In addition to pricing: P

5, 9, 15 or 20 V. USB PD is very good.

Just right.. Up to 100W, there is a USB-C socket on the wall. All toothbrushes, shaving machines, etc. are beginning to use USB-C plugs instead... (this makes sense anyway). For households without local DC voltage wiring, usc-c wall warts or sockets that convert AC to DC ensure that the product is not limited to DC households.

It would be interesting if the DC wiring in the wall is as smart as the USB PD, requesting different voltages directly from the battery as needed...maybe even AC. This will reduce the number of required DC-DC conversions, and unless necessary, keep the AC power away from the socket.

Yes, it will be a dream. I recommend watching the Cypress video tutorial on USB PD: http://www.cypress.com/products/usb-type-c-and-power-delivery

Is anyone willing to make an open hardware USB type-C PD wall socket? For example, an idea could be a central converter that extends the 48V bus to a wall that exposes multiple USB Type-C sockets.

I would choose a dual voltage system, there may be 48V and 12V taps on the system.

Most wallwart drives need to be below 12V, and heavier loads can be connected to a 48V system.

In addition, there are already many 12V products used in cars and RVs, such as water boilers, microwave ovens, coffee machines, refrigerators, audio systems, TVs, etc. (Of course there are also 24V products for trucks)

Then you can have 4 different taps on the battery pack, with smart balance system, and connect solar panels for the 48V system

Computers and many other household electronic products usually run at 12v and 5v (some are 3.3v), but if you use 12VDC, the resistance loss around the house will be huge. Even at the 50VDC recommended above, the loss will be greater than your 230VAC. I think the problem that this article does not completely solve is that reducing the higher DC voltage to something more useful will have a DC-to-DC stage, which is not more efficient than the AC-to-DC stage currently used-so I really No advantage is seen.

There is a trend that old electric car batteries will enter the home as "instrument storage" to smooth utility demand and create a smart grid with dynamic pricing. Perhaps there is a way to use photovoltaic panels to directly charge the battery packs stored in the "post-meter" storage (without voltage conversion), instead of replacing a house full of traditional wiring?

48v is a good compromise between safety and efficiency, and there are many off-the-shelf converters. Circuit protection is still important-a large 48V PSU is not much different from an arc welder. Another problem is to maintain the efficiency of input mains to low voltage conversion in a wide load range.

My arc welding machine works around 20-24V: P

Use automotive standards, whether it is 12v or the newer 42v (or .mil 24v). There are already many components.

Some people say that the DC loss is too great, but this is only the route to and from your home, and the operation in the house is close to that of a large RV. We need to develop a standard plug as soon as possible. HAM is informally standardized on PowerPoles, so this may be an option. But we need to develop a standard so that before the 120v is phased out, it can be combined with the 120v into newer houses.

What about high-power appliances like 2400W air conditioners? The wiring needs to be thicker than the car jumper, and copper is not cheap.

The reason why we have a 120V / 240V system is simple.

Industrial applications generally use three phases of 415 volts (Australia) and 380 volts (EU and other countries). Don't know the United States. In short, compared to thinner wires that are cheaper, faster/easier to install, there is less power loss, so you save money in every way. The dollar will be the decider, not the idealist.

The European Union standardized as 230V/400V many years ago. It is basically the average value between 220V in continental Europe and 240V in the UK. Maybe 415V is the incremental voltage of a 240V system?

The Y voltage of 240 volts is 240 * sqrt(3) = 415.69 volts.

Well, if it's not because of the high voltage, I think you can switch from AC to DC by flicking the switch, just like switching from explosives to TNT, they will all "blow up your video". But it takes the persuasive power of some tie-wife to work on the contract to get back into trouble (but I'm happy to be a fly on the wall during these meetings). This is not like the jailbroken phone here. This is not a dirty act, it is done very cheaply. Money can push the ghosts. BS walks. Just thinking about it all makes me thunderous. I have been on this highway to hell before. Not to mention once encountered a wire that shocked me all night. You must have a big ball to mess up this kind of thing. Really skate on Razors Edge or Black Ice. You must maintain a rigid upper lip in the energy field. I think you all need to calm down and have a drink with me. I know some of you are saying "let rock", so I think to those who are about to rock, do I pay tribute to you?

Sounds drunk-or you have taken the wrong medicine. :-(

Consider another factor at work—how about AC power used for "centralized coordination" consumption and DC power used for on-demand consumption?

Dishwashers, air conditioners, etc.-They can be operated almost any time, including the time the grid provides baseline load. I think that if the spot price is above a certain threshold, the meter/contract will be disconnected, which may become attractive. For what we need now-we have direct current and batteries!

My answer is 12-48V. Electrical appliances should be able to accept voltages as low as 12V (most of them should only be used for step-down DC/DC anyway), and buildings can choose to generate voltages as high as 48V-the additional cost of electrical appliances is very small, and it allows people to choose what they think Appropriate local voltage.

The only problem is stupid (resistive) electrical appliances-LED strips, etc. Due to heat, they may just be high frequency switches.

Seeing how many dishwashers have caused fires near me, I prefer to run these dishwashers only when I am around...

The old Wincharger runs at 12 and 32 volts. There are still some Winchargers on the farm and there are still parts available.

I voted for the wall plug to be a USB type-c wiring system with QC3.0. This allows the receiving device to determine the wall voltage. From the wall plug to the back end of the circuit breaker box, a similar method can be used so that the entire circuit coordinately adjusts the line voltage. In the circuit breaker box, we will consider the generation voltage, the conversion cost, the time of year (is the environment heat bad in winter?) and the overall wattage requirement of the circuit. Maybe think of a timing system with a stepped voltage, where each plug will choose their alternating voltage.

No, please don't let Qualcomm have so much power in our lives. PD is an open standard, let's use it instead.

Am I the only one who thinks the basic premise here is flawed?

Due to the number of electrical appliances and possible loads, an ordinary family home may be lower than I think there must be too many circuits or wires will have to be too thick and uneconomical.

Even if you take away large built-in appliances such as washing machines, dryers, dishwashers, ovens, microwaves, etc., there are still many possible uses anywhere in the house, a few TVs and computers, the infrastructure to run them, plus permission The usable capacity of household tools such as electric hand drills still requires your DC system to handle at least one kilowatt, and more likely 3 kilowatts to be useful. Even at 50 volts, people will see the conservative side of 20 amps, you need 3mm A square conductor can safely transmit 1kw at 50v.

Sorry it is not 3mm square, 3mm in diameter.

But the 3 mm (1/8 inch in the old currency) conductor is very thin. The diameter of all solar panel wiring starts from 4 millimeters. It is cheap and easy to run several in parallel to obtain higher current within a range of only tens of meters around the house. When the current of each wire is half, the loss is 1/4, and the three losses are 1/9. In any case, how far is it from the battery to the air conditioner?

Well, I think it all depends on your lifestyle. Dryer-well, it can dry on its own. dishwasher? It takes more time to load, instead of just washing off something. Most of the ovens here run on gas. Computers nowadays are usually tablets or laptops for advanced users-not very power hungry and TVs? Does anyone still use these? You will see: Power consumption will vary greatly depending on your location and identity...

This is why AC is still the standard. It applies to all people in all regions and climates.

So, because it works, I have to add a brick between the socket and most devices, right?

Unless there are universal standard bricks, they are needed anyway.

However, for those who cannot afford affordable AC services, AC is not the standard. You want the AC to stay away from the grid, and you pay for installation and maintenance from the grid to the selected location. People living in rural areas may find it cheaper to use the DC power they provide for themselves and still be able to live comfortably.

This is my point of view, one system is suitable for everyone, reflecting economies of scale in different ways. It also makes it easy for people on the other end to design for their customers. In many devices, the voltage requirements are quite strict, ensuring that in most cases 10-20% will not make much difference, but start the device from the 12v rated voltage To 42v? What are the conductor sizes, should they be overused so that you know they will not burn out, or should we provide several different sockets for different wattages and voltages, how many sockets do we really want?

Make sure we can make them smart, but each product needs to be compatible with that particular protocol and any legacy protocols that have evolved over time.

A simple kettle itself may only have a few kilowatts. Everything adds up. The real problem is that for this concept to work, it must not only be more efficient or economical, but it must also justify the cost of change. The cost of standardization and compliance design is just like today. If I make a small low-voltage device that I want to sell, I can buy a certified power brick. I only need to deal with the less stringent low-voltage certification, and I don’t I will have to include a wide-range voltage converter in my device, a portable device that is important for every square millimeter.

In short, I think there are many reasons why DC will not become the de facto standard. Of course, there are some niche use cases that are completely reasonable, but there are still many issues to deal with around the house before DC power distribution is practical.

As others have pointed out, separate the problem and use DC for lighting and other connected low-current devices, the rest may have to wait. One thing about the motor is the starting and running power, maybe putting a supercapacitor in the appliance will help? Some people tend to design the house and then study how to operate the power supply. Maybe we need to make the power efficiency consideration more affect the floor layout? Get it right, you might find a larger, low-resistance DC bus between areas, and then become economically viable?

"Converting local direct current to alternating current is just to insert the wart on the wall and convert it back to direct current again. This has no meaning."

But this is exactly how the DC/DC converter works! It converts direct current to alternating current at a predetermined frequency to generate the largest possible RFI on all frequency bands, runs through a transformer, and then rectifies it back to direct current, usually leaving all harmonics intact for use in other parts of the world. , TV and telephone reception. Very stupid.

I don't know if you are joking or "very stupid"! :)

As a practical matter, the current 12 volts will be the choice for anyone who decides to live off-grid for any reason and intends to use direct current. Many devices that you want to use use 12 or 5 VDC. Their current demand is low enough, even if more circuits may need to be installed, line 14 or 12 is sufficient. Of course, projects such as central heating, ventilation and air conditioning, electric hot water, kitchen stoves and clothes dryers are impossible. Bottled gas can be easily transported to most areas, enough to provide hot water in the kitchen, and even run an absorption cycle reference and supplement heat when needed. If a water well pump is used, an inverter may have to be included. I believe there are 12 VCs available, but they are very expensive. Although they are things that the store keeps in stock, people must buy their own spare equipment. Regarding becoming your own utility company, it depends on whether you have a stock of spare components so that you can repair it yourself, or if you can't do the repair, you can hire someone else to do the repair. Only if you are unwilling to change a simple and convenient way of life, you must use more than 12 VDC to provide enough power to live better than most people on the planet.

No, I don't want to change my lifestyle, I hope it is similar (or better) to other people in my country (Central Europe). "It's better than most people on earth." It's not enough. I sometimes do things like what you describe on weekends. Used for camping, festivals or gardens. There I only have a small 12V solar system for some LED lights or music, because I don't want to invest in grid connection because I don't have a house there. So I know the limitations of the 12V system. Even a 12V compressor refrigerator will run out of battery power within a few hours. Heating and hot water can be done with gas. If you want, you can do without the dryer, but to dry the clothes, you must wash them first. A 12V DC washing machine will not work.

No indication of humor or satirical intent. IMHO, it is best to be very ignorant, and it is recommended that the buck-boost converter is specifically designed to generate as much RFI as possible.

Have you seen some of them on a spectrum analyzer? I have, and I haven't found a single switch mode device with a clean output, and most of the cheap devices that flood the market have almost no filtering.

Has anyone ever been in an RV?

We once had a Winnebago from 1978.

When the device is plugged into AC power, everything is normal. At 5 MPG, Dad parked his car by the pond where we were fishing in the countryside. Electric poles are installed.

I believe that all the lights have turned off the inverter, which is about 220VAC to about 12.5VDC.

The refrigerator is very satisfied with 110 VAC, 12 VDC or propane (the RV must be level, not hard, hope I know how many BTUs

In August 2016, my approximately 1,900 square foot home was recently flooded by 6 feet 4 inches of dirty and unsanitary water. I have been thinking about lighting, removing wall switches, and removing copper wires; replacing them with momentary switches connected to Raspberry Pi, Adriuno, etc. Not sure, because I am not familiar enough with different manufacturers. Perhaps no visible switch will work as a sensor behind the STD light switch position. With LED lighting, relay 4 power supply or transistor.

What I know is that I prefer that the whole system is based on open source hardware and software.

Does anyone know the way to find the correct LED that is not needed: fan/heat sink. 5,000 Candle Power (one or a combination) 180° 3-D light dispersion at no cost. The industry is changing so fast, lighter, less heat, less power, and lasting.

About a month ago, I saw a 5k candle power LED with a fan and a heat sink for $20.

Don't know how to find its old cousins, such as 1K candle power, each has good temperature (close to full color spectrum, good light dispersion (installed on the ceiling). The price is about $1.00. EA.?

Or any known open source home control hardware/software suggestions.

Need to be able to have several electronically controlled water valves.

#1 The residential energy pig is an electric water heater that we insist on supplying cold groundwater. I will disassemble the system before entering my home, do everything possible to preheat 40 gallons, such as a roof-mounted water tank/radiator, and try to put it in a glass or transparent plastic container, which may be painted black (if I need it) A new roof), but if there is a way for water to remove heat from a 100% metal roof, then every BTU is important.

Maybe some cooling technology based on computers. My dream is to repeat the cooling system for a generator without a water pump. Use water or coolant for off-grid daily necessities. The hot water flows from the generator (closed loop), and there is a water tank with enough water to ensure that Genny will never It will overheat.

Now, we have self-sufficient chains of plastic blocks that use zero load, float in the ocean, introduce bacteria into the interior, and generate more unit power than solar energy. I may have a few words wrong, please check Nasa Tech Briefs.

They also have a closed cooling system, and the refrigerant does not require a compressor. I intend to apply for a patent for this idea, and have been thinking about it since the 10th grade, and then I won the first place in the annual National Science Fair Competition of the Mississippi Private School Education Association. Without my knowledge, they contacted the equivalent state of the MS entity on my behalf and asked me to be allowed to participate in the competition with the public school students who won first place in their respective states so that I could participate in the national competition. Basically, "Yes, yes...When hell freezes, your "boy" may have the same chance as the snowball before hell freezes.". That was more than 30 years ago. I saw my project based on aligning the solar panel at the sun when the sun passes overhead, and when it is below a preset threshold, returning to the initial AM recording position to adjust for the next AM.

Anyway, suggestions are welcome. TG nospam7350@yahoo.com

I would like to see DC wall sockets with multiple voltages (such as 5, 12 and 19V) or sockets that allow the device to select the desired voltage, just like some psu bricks with resistor selectors. The problem is that almost all DC devices use internal regulators or DC/DC converters to change the voltage again, and even cascade multiple times. It is possible to save a lot of power by eliminating one or more conversions, and it will increase rapidly. Centralized converters may be easier to improve efficiency, and easier to replace when a defective or more efficient design becomes available.

As for the DC power used only for solar power circuits, it may use much more power than the usual small current DC equipment, so if it is not pumped back to the grid, what will happen to the excess power? Your neighbors are likely to use it, so the distance covered by the power you provide is much lower than the distance of the power station.

Standard plugs and connectors for low-voltage DC-Stuff provide more benefits to the DC-network in the home.

Hi everyone, I think you all know the following:

* Series arc faults and arc fault risks in DC systems* Thermionic emission and field emission of electrons and ion currents* How to solve nonlinear equations to find DC arc resistance

For those who don't: This is related to all DC voltages above 30 volts, give or accept. Google "Serial Arc Faults in DC Systems" will let you know the issues involved.

Even though high voltage is required to ignite an arc within a certain distance, if you separate the two contacts, the arc cannot be maintained. For example, when the switch is turned on or the contact is loose.

Unless the system is specifically designed to handle series arc faults, do not use voltages greater than 24V. If it were that simple, the automotive industry would have used more than 24 volts a long time ago.

Unless you want to build an arc welding system for yourself instead of a power system.

==> Use 24 volts and 15 amps to fuse the circuit. ==> Or use 12 volts and use 30 amps to fuse the circuit.

Unless you have proper DC arc fault protection.

Of course, the circuit should not be fuse according to the power supply voltage. The current carrying capacity of the protected conductor determines the fuse used. The fuse panel in the car has a variety of fuse values. There is a reason that the current requirements of the equipment determine the size of the conductor used and the value of the fuse used.

I will choose the dual output standard. 500W 60V is suitable for notebook computers, garden lights, small computers, mobile phone chargers, flat-screen TVs and stereo speakers. 4kW 400VDC is used for charging gaming computers, large flat screens, air conditioners, vacuum cleaners, dishwashers, welding equipment, dryers, and electric cars.

60V means that it can be easily integrated into almost all low-power systems. It is not self-voltage, so all equipment must still pass conventional electrical safety/regulatory standards. (We should flood our home with dangerous equipment)

400V means you can remove the entire PFC section of approximately all power supplies. All sockets need a relay or mosfet to disable output pins to save connection establishment/disconnection. Some kind of power request communication may be needed to prevent severe overload of the x-kW PFC. Smart grid/solar panel balancing should also be easy!

Have you compared the cost of a 4kW 400V DC relay with the cost of a mains AC switch?

It is not a good idea to be just above the SELV voltage. Or do you work for some kind of regulatory agency and want to generate more business (or worry about losing business)? Therefore, if it is a low voltage, set it to SELV. In addition, I don't think it would be very efficient to install a "Mega PFC" at the entrance of a house that is under light load operation most of the time.

If you check, I think you will find 60v _is_ SELV in Australia. Keep in mind that 4x12v lead-acid batteries have been used in telephone exchanges (US Central Office) for a century, most of the time they are above 50v, and are close to 60v when charging.

If your neck only allows 50Vdc for SELV, then you can only have 3x12v (nominal) batteries. That would be very stupid.

Yes, it must be connected to the battery pack through HRC fuses and rated isolators. (HRC fuse is usually ceramic body and filled with sand. It is very good at extinguishing rupture arc.)

1. RFI is a very real issue. 2. The cost of components will plummet with usage. Namely LED bulbs. 3. The microwave oven is an electric pig. 4. My yurt runs well under 12V (but its diameter is only 16 feet.) 5. In the north, mountainous areas and other places, backup power is very important. Most generators do not have a high DC output. 6. The DC vacuum sweeper is a coward.

By the way, for DC systems above tens of volts, another serious cost issue is that in addition to individual MOSFET/DC contactors for each load point, you also need a newly developed electrical/mechanical interlock and / Or a plug with dual lead contacts. If the voltage is unbalanced and the current is interrupted first, you really cannot plug or unplug the DC load.

Not sure what "tens of volts" means, but most of this article deals with >50 VDC and relatively low currents. It is equivalent to the current level of each switch in a motor vehicle.

IEEE Spectrum has published several very interesting articles about the deployment of real-world DC microgrids in very remote locations. Through the microgrid, they mean about 1-4 houses. The power source is solar (battery used at night), and the area is remote enough that even if a grid connection does exist, it is difficult, expensive, and unreliable. In these cases, the "last mile" (or 10 miles) is actually determined by the social animals and feet.

The system uses a 48V DC system in the house: http://spectrum.ieee.org/energy/renewables/innovative-direct-current-microgrids-to-solve-indias-power-woes

This seems to be 12 or 24 volts: http://spectrum.ieee.org/green-tech/solar/lights-for-the-enlightened-an-engineering-trek-in-the-himalayas

Obviously, according to the standards of developed countries, solar power generation in the 125-250W range is small, but a system of this size can power TVs, computers, mobile phone chargers, ceiling lights, work lights, and fans to provide more comfortable power. Sleep environment.

How about the PoE of the whole house. 48V plus Ethernet connection. We already have the technology.

Me too, I have been thinking about this topic recently. About a year ago, I bought a bunch of extra solar panels. Converting DC to AC seems silly to me, because most things I want to run can run on AC or DC. The light bulb does not matter. Even most LED bulbs rectify AC power before being applied to LEDs. Even most of the switching power supplies that we all use to charge mobile phones, and most of the electrical appliances will run on 100-240 AC or DC. I will use 120VDC in my application because, of course, with the right filtering, most of the things I want to run (lighting, phone and even my LED TV) can run normally on DC, so use a voltage It is meaningful to those things that are acceptable.

I voted for SMART VOLTAGE SYSTEM, which can change its voltage by negotiating connected devices. Hey, it's 2017! Why must we only use ONE? Think like Quick Charge 3.0 or USB-IF...

For old-fashioned people, I recommend DC V400 because of compatibility. In fact, almost all equipment we use now (not including replacement motors of course) are compatible with it. Your TV, laptop, PC, printer, scanner, Powersave CFL or Led bulb, boiler, and modern {AC, refrigerator, dishwasher} with a DC motor or drive can all use DC400V. Because this machine has converted AC220 to DC 400 before use. They have DC 400V rated capacitance and bridge diodes.

No, I prefer a reliable power system. Without SMART, there are as few attack areas and failure modes as possible for malicious hackers. If this "smart" garbage fails, it can easily damage connected devices due to overvoltage. So keep the system simple, with a fixed voltage on the wall socket, and a (wide input range) PSU in the device. I also have many wall sockets in my house or apartment, and they are not used at the same time. So there should be no electronic equipment in the socket, which will increase the cost and standby loss

Dual 12V (12V GND -12V). When I was doing reno at home, I ran 12V for the light, and now I regret not running the dual setup. Just an extra wire, plus the option of running a 24V load, can provide twice the power. The 14-3 line is cheap and gives you 360W of power. It is sufficient for the most common loads. Air conditioners, refrigerators and stoves operate at 120V/230V.

Remember this person? http://300mpg.org/projects/smartgrid/ Use cheap existing technology

48V is already a widely used standard in photovoltaics, PoE, and enterprise data centers. At 50VDC, it is still under the typical regulatory limits of ELV/SELV, but still as high as possible, thus minimizing ohmic losses.

In Australia, IIRC and SELV are as high as 60 Vdc. This is still only 4 x 12v lead-acid batteries, because they usually require 14.2v to charge, and each requires 15v for equalization. That is, the 48v (nominal) battery can withstand up to 60v exposure. The important thing is that if I have the proper experience, I can legally wire without an electrician license.

As for another consideration-arc extinguishing (and the accompanying fire hazard), the battery pack must be equipped with an HRC fuse and an isolator capable of extinguishing the arc. (I have an isolator with a built-in HRC fuse.) I am not very inclined to use a relay to switch high-current DC loads, because MOSFETs will not produce arcs. If 5 milliohm RDSon is not good enough, just connect two in parallel. (I recommend using a separate series gate resistor.)

The small 24V system is suitable for LED lighting, running computers, modems and soldering irons, and 24V DC pressure pumps for off-grid holiday homes, but nothing more.

The deciding factor for the replacement of the off-grid tree I am pending is that 48v battery inverters are very common and inexpensive. Most appliances still need to convert battery energy to 240 Vac, even though 48 Vdc air conditioners can now be used.

The voltage standards for telephone exchanges a few decades ago (the "central office" in the United States?) seem to have some vitality.

If 5mOhm is not good enough, then there are 1 and 2 mOhm types. But I don't know how to get it easily.

Oh, come on. Those bad humans can't even agree to open a hole of the same type in the wall to power you. Do you now want to replace the entire infrastructure with something else? (Actually this may be an opportunity for universal plug type)

No matter what voltage you use, which may be a multiple of 12 volts, I recommend using Anderson Powerpole connectors:

https://en.wikipedia.org/wiki/Anderson_Powerpole

They are versatile and beautifully designed. There is even a version suitable for standard household appliance boxes:

Good luck with your plan and let us hear from you.

For lower currents, I like the DIN ISO 4165 https://en.wikipedia.org/wiki/ISO_4165 power socket. It is a bit smaller (12 mm) than the cigarette lighter socket, but has better contact because the center pin does not try to push the plug out of the socket, but is connected and secured by spring contacts on the side. Unfortunately, it is not widely used, and I have not found it from cheap Chinese suppliers like AliExpress.

If you search for "hella plug socket" on eBay, you will find, for example, two for 25 Australian dollars each. This may be as good as what is used for boats and caravans. For Chinese suppliers, the number may be too small.

In the 1970s and 1980s, I lived in a 114V DC home for many years. The home had Dunlite wind turbines and 19-6V golf cart batteries. We ran everything, lights, vacuums, tools, flat irons, etc. Class "F" switches work normally, wiring works normally, and general-purpose motors are running. The switches in some electrical appliances require a capacitor to prevent sparks when the contacts are opened, just like our kitchen utensil mixers and vacuum cleaners. It's easy. In my RV, I use 12 volts because there are many things available, such as TVs, computer chargers, etc. Now we have many DC to DC voltage converters and electronic inverters. These converters and electronic inverters did not exist at the time or were too expensive for common use.

No no no. This will never happen. The future will be the way of Nicholas Tesla, and it has already begun. Your wireless mobile phone charger generates a magnetic field, which is converted to direct current by the mobile phone through a simple coil. All you have to do is to make the magnetic field as big as your house. Everything will run, no wires are needed.

The magnetic field sufficient to wirelessly power the entire house will be so strong that it will be dangerous. Especially for people with metal implants, braces, earrings, etc. In addition, the RFI will be large.

I will go with the "48V is already standard" crowd. If you are talking about modern electronics, the story of the end of the world DC arc is nonsense. Should you connect the 48V battery directly to some wires and pass it through the walls of the house? No, this is not the best idea. Each office building and many data centers use 48V PoE for internal and external wiring. It uses dark and mysterious magic voodoo to determine when a malfunction occurs and immediately stop the power supply. This is called...resistance. The voltage is known, the maximum power capacity of the device is negotiated, and if the current exceeds the negotiated limit, the load is disconnected. If you only have a PoE chipset, even if there is no network, you can still get the power management advantage. In addition, if you want to use it, you can still use Ethernet. One disadvantage of this is that each outlet needs to go back to the switchboard by itself. Although in this case each room can have its own panel.

These people came to our makerspace last year and I helped them 3D print some parts of the prototype. They have a lot of interesting ideas on this topic, and they have basically completed what I described. They have a good DC panel design, and there are various PoE-like modules that can be inserted like a circuit breaker in an AC panel. It can provide Ethernet and other "functions" for sockets. (Not particularly fanatical, but I have some experience with 48V systems and PoE, and usually like their ideas.) http://lumencache.lighting/

"Because most equipment nowadays uses low-voltage direct current, with the exception of some large appliances. Batteries store direct current. If more and more households have some local direct current generation capacity, then the local direct current is converted to alternating current just to plug the wart on the wall. It doesn't make sense to convert it back to direct current again."

"Battery storage DC" In order to provide useful power without causing excessive I^2R loss, you need at least a 24V battery pack, which may be 36V or 48V.

"Most devices now use low-voltage DC" low-voltage DC of various voltages, 3.3V, 3.6V, 5V, 12V, 19V [and quite a lot of 5V and higher devices will drop to a lower voltage internally)] . You will not find many devices that use 24V DC or higher voltage, so "battery storage DC", "equipment uses DC"... profit! is fake.

The reality is that household power supplies need to be able to power high-power [kW range] devices as well as a large number of low-power devices that require a wide range of input voltages. AC did a great job. Switching to DC only means that devices that do not match your mesh DC voltage require additional DC/DC conversion.

One place you *can* improve efficiency is to switch to 400Hz AC, if you can buy appliances that can handle it.

I'm not sure if this is a good idea in the family. 400Hz is much more audible than 50Hz (or 60Hz). Therefore, if the equipment is not well constructed, the noise can be annoying. 400Hz AC will also cause more capacitance loss in the transmission of power to the house, I am not sure about transformers-they have more hysteresis loss per kilogram of iron, but require less iron.

In Argentina, many houses in rural areas do not have electricity service, so the rated voltage of generators or solar panels is 36V. This has been the case since around the 1950s. I went to a house and there was a very old diesel generator in it. It can still work for a few days, and the light bulb and refrigerator are 36v (you can also find 12v)

My home uses a time slice DC system.

The DC voltage in the wire starts at zero volts (useful for devices that are turned off), then it takes a short time for each voltage to rise to about 160 volts, and then drops to zero. It does the same thing with negative voltages, which is useful if you plug your device upside down (USB should learn from it). The whole process takes about 16.7 milliseconds, so you don't need to wait a long time to get the proper voltage.

There seems to be a divergent consensus on what DC voltage to choose.

High-power equipment must remain on the AC grid. We don't have enough copper for high-wattage low-voltage direct current, so I won't go there.

"42" is more consistent than any other answer. The history is humorous (thank you!) and interesting, and attractive to the low end of the copper cost range.

It is recommended to use a multiple of 12v, and it seems that it is convenient to use the ready-made inventory to allow commuters to convert more gasoline into energy, at the expense of your alternator life, to charge the battery to run the home... actually Installing a windmill is roughly the same as a car to charge the battery. I believe this has been tried... There is an episode in the red and green show. In any case, this is meaningless, because soon we will charge the car from home.

Suggest that I have tried the solar cell option. Due to degassing, the code here does not allow such batteries to be used in living spaces, so there is a shed or an outdoor box. You water the solar panels to clean them, and the dead lawn below will cause dirt to enter the house. The fallen leaves must be swept every day, and then the dead lawn must be raked away. This is solved by placing the panels on the roof, but now when hail storms come twice a year, they cannot be flipped/covered quickly.

I want direct current for lighting...maybe a small fan or two...a laptop...a ​​router and a modem...an alarm clock...a weather radio...and two battery chargers.

All of this is to get rid of wall warts?

The 0.02 Euro DC in my home is a stupid idea. Perhaps a few decades ago, when low-power power supplies were messy and inefficient, this might make sense. Nowadays, modern switching power supplies hardly care whether the power supply is direct current or alternating current. They use alternating current and use direct current as a power source with similar efficiency.

Switching to DC will only cost us all the benefits of AC. Transformers is the same thing! It would be naive to say otherwise. Even if they are only used for galvanic isolation.

Interesting mental exercise...but it's far from a thing for most of us.

I can see that a certain standard surrounding the residential “secondary” DC sub-circuit is being developed, which may be used for LED lighting, as we are currently talking about when using 12-volt lamps for under-cabinet lighting, but I don’t have See too much practicality. Whole house DC standards with sockets will replace AC wiring.

If so, the next step may be the system's general PSU—for example, having a DC power supply to power everything in your computer system—PC, monitor, printer, speakers, etc. Or equip your home theater with a DC power supply for tuners, power amplifiers, large displays, etc.

If you are off the grid or the power supply is unstable, make sure you can design for DC power distribution. In RVs and boats, 12v is the standard, and there are many hardware and components that can be used for this purpose. Although "cigarette lighter" is not a good export standard.

Our 19-foot boat has two 12-volt sockets, some built-in 12-volt LED lights and six USB sockets driven by a cheap step-down converter for IKEA gooseneck lights and equipment charging.

I know I am not the first to mention it... but for my money, the 12V DC on the socket is the way to go. The entertainment market already has a large number of devices manufactured for this voltage, which are family friendly and do not bring great danger.

Depending on how many banks I have when building the house and the cost of things like DC-DC converters, I may use a straight 12V system (maybe rectified to 13.4V in the power box, at the jack), or use 48V internal and Drop the pressure at the jack. As mentioned in the article, if I'm doing solar energy, I can still make this choice...Because DC power is used, the final voltage depends more on the wiring rather than the power source (because solar cells are usually about 1.2V alone, So unless this is what you are running, you will link them together somehow).

If it is a small system, I would choose 24V because there are a lot of low-cost hardware, such as DC-DC converters used in some heavy trucks and airplanes. A large 48-volt system, but you want to pay more for the inverter, although you may make up for the cost by being able to use thinner wires.

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