Whole house "battery" wiring/power...

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TDD

Reply to
The Daring Dufas
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My suggestion would be for a 48 volt DC system. Plain old telephone service uses 48 volts DC for battery and PoE, power over Ethernet is usually 48 volts DC. The wire size could be smaller than that for a lower voltage system and the 78xx type regulators are very inexpensive and come in a variety of wattage ratings for stepping down the voltages. The technology to pull it off is not exotic and can be done with all off the shelf parts. Solar and wind power could integrate quite easily with such a system.

TDD

Reply to
The Daring Dufas

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Think "transformer".

The maximum "safe" voltage. There is a reason power transmission is in the hundreds of KV. AC.

You really want to waste power, don't you?

Not everyone wants to waste ten times the power they use.

Reply to
krw

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Do you have the slightest clue of what the discussion is about? It's a hypothetical discussion about a DC power distribution system for a home. I neither seek to impose a standard or ridicule the ideas of others. I do have about four decades of experience with all things electrical and electronic but sadly, I don't know everything. I wish I did.

TDD

Reply to
The Daring Dufas

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Pretty impractical because there is a single point of failure.

You can consolidate a lot of it for a good start. For example in our house we have an alarm panel which powers all of the smoke and CO alarms and of course the security system.

What does a phone answering machine do?

Reply to
George

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I am guessing his point was that linear regulators such as the 78xx series are quite inefficient.

Reply to
George

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and have a 35 volt limit on the input voltage. Even if one could handle 48 VDC at the input, a 7805 with a 1 amp load would waste 43 watts as heat just to power a 5 watt load.

Reply to
Michael A. Terrell

And what would be the advantage? The 78xx series are linear regulators, they are in effect a regulated resistor that burns up the excess voltage in the form of heat. On top of that, they max out at 37V input at which point a substantial heatsink is required to dissipate the heat. The end result is FAR less efficient than even the lousy iron class II transformers found in most wall warts and small appliances.

You could use a switchmode regulator to get decent efficiency, but once you've gone that route, you may as well just use 120V or 240VAC since the additional components required are trivial.

Solar and wind power can easily integrate with the existing grid, with the additional advantage of being able to sell excess capacity back to the utility. The cost of the special inverter is low compared to what the panels cost, and dropping all the time. This proposed DC system is just reinventing the wheel with something inferior to what we already have.

Reply to
James Sweet

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DO you have the *slightest* clue about electronics? No, I didn't think so. To answer your question, yes, I can read and understand your post quite well. ...well enough to know you're clueless.

Think before posting in an electrical engineering (science) group.

You clearly haven't and don't.

The short story is that linear regulators waste tremendous power, particularly in this application (large voltage drops), making your idea worthy of ridicule.

There is a very good reason AC is used to transmit power. Thinking that your brainchild throws out a hundred years of practice is another reason it's worthy of ridicule.

Reply to
krw

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I was thinking about the 35 volt limit and the fact that the

78xx regulators are linear regulators but for low power needs what's a power resister and a 78xx regulator going to waste? DC to DC converters are a lot cheaper than they used to be and for a heavy load like a laptop I would use something like that. A "greenish" home with things like LED lighting and thermoelectric refrigeration could be an interesting use for a 48 volt DC system in a home. An LCD TV, a surround sound system and all manner of the electronic gizmos that we can't live without these days could be adapted to a 48 volt DC system. I don't remember the part numbers but I remember a line of controllers made by Linear Technology Corporation that have input voltages that can range up to 60 volts DC and provide a constant DC output regardless of the varying DC input. There are some interesting developments with thermo- electric air conditioning and I think that a 48 volt DC power source would be great for that. For someone living off the grid, a 48 volt system could use 12-2 Romex instead of a large wire size needed for a 12 volt system to carry the increased current. I find it an interesting concept.

TDD

Reply to
The Daring Dufas

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Well professor, I would only use the damn things for low power applications. For any kind of load, a DC-DC converter would be the way to go. Remember, it's just a discussion about possibilities. Good grief, 78xx regulators are very inexpensive and DC-DC controllers are getting that way too. Ridicule bothers me not because as a small boy I had Irish nuns for teachers. That's also why I have no fear of terrorists. I'll take Tesla's power distribution system over Edison's any day. Darn, now I'm gonna have to go out in the back yard and try to build one of those power transmitting towers that Nikola used to play around with. Do you scream at your TV too?

TDD

Reply to
The Daring Dufas

I was thinking about it as an off the grid system. I would imagine that a single high current DC to AC converter in the battery room putting out standard AC power to a home would be more practical than trying to reinvent all the appliances and gadgetry. Tesla won the battle for the power distribution system and I'm glad of it. There are those very high voltage DC power transmission lines. I'm going to have to read up on them and find out why they're using DC. It's been 20 years since I worked on any high voltage power distribution systems. Have you ever used a wooden hot stick? Make sure it's dry.

TDD

Reply to
The Daring Dufas

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My house has outlets all around that do not use any power at all unless I attach a device to one, and then it only uses what that device needs to operate.

Your long line, low voltage "idea" is wasteful from the get go, regardless of the regulation device you should choose. Since you are unable to grasp why it is wasteful, you are unable to handle any of the advice you get about it here, and you are ridiculed, by your own hand.

Your "idea" is an old one, and the facts were ironed out decades ago. So take your idea and use it to stuff the obviously vast empty space between your ears.

Reply to
StickThatInYourPipeAndSmokeIt

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The same as the ratio of the voltages. For a 5V device, you're wasting 7 times as much as you use. Most people don't consider that smart.

Could be smart.

Reply to
krw

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So you're going to add another level of wiring into homes. Real smart.

Why not stay with the AC distribution we have and use a small power supply for those things that need low power. Oh, that's what we are doing.

They're *very* wasteful too. I don't want my power bills to go up 7x.

IOW, you're simply stupid as a stone.

Reply to
krw

In all fairness, DC-DC converters can exceed 95% efficiency, and 85% is common. They're really not too bad.

The class II transformers used to power most small stuff are down around

50%. It's one reason switchmode power supplies have become popular for those applications. A SMPS is nothing but a DC-DC converter that first rectifies the AC line to DC.
Reply to
James Sweet

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You still don't get it, it's only an exercise in what's possible. Look at all the replies on how and why this or that won't work. That's what a discussion is all about. Good grief, you've no idea what the term "thought provoking" means. You get your pointy little head tweaked and result to name calling? You point out what's wrong with an idea and that's a good thing. When I ran a crew on a project, I would deliberately tell them to do something that was wrong. After having to stop them a few times, the really smart ones caught on and challenged me. I told them that if they even had a feeling something was wrong, speak up but be prepared to explain why. A crew like that can save a company a lot of money. I once installed a Halon fire suppression system in a mission control center and the prints I was given made no sense to me. I argued with the HMFIC and was told it's on the print, DO IT. The prints had been prepared by my employer not The Core of Engineers. The cost of a mistake like that falls on those who supply the prints. When the manufacturer's rep arrived, he exclaimed, "These prints are wrong! It's a good thing you didn't go by this!". Even though I saved the company a great deal of money, it put a bug up the tailpipe of the HMFIC. Something about loss of face. Being an agent provocateur is a lot of fun, keep those ideas coming.

TDD

Reply to
The Daring Dufas

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Reply to
tnom

78xx switch mode DC-DC.

95% efficiency is a bit optimistic for the real world. 85%, perhaps. I still don't want to increase my power bill by even 10%, though it's better than 10x.

Most power supplies are more or less the same thing. That said, there is still no advantage to DC distribution and a *LOT* of disadvantages.

You still haven't identified *ONE* reason to go through this crap.

Reply to
krw

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No, Dufus, it is you who doesn't "get it". What is possible is irrelevant, if the dream is worse than what is.

Yes, all telling you that your idea is stupid.

I agree. Everyone agrees that your idea is stupid.

You have to have some thoughts before they can be provoking. Try it.

You are what you are. I've simply told you what you are. Grow up and deal with it.

Something that should be immediately obvious to anyone posting in a science/engineering group.

Ah, so you're testing us? You're not just stupid, but a stupid liar.

Do keep the really stupid ones to yourself.

Reply to
krw

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