Home Power Monitoring Hack

dvogt writes "You think your power bill is bad? I built a power monitoring system to monitor every circuit in my house with three second resolution for over a year. And while I had to rewire all my electrical to do it, I can now reconcile my electricity bill down to the penny... Of course when my wife figured out most of the bill was because of my computer gear I had to build her a dome, so reader beware!" From the article: "About a year ago I developed a web based power monitoring application for data centers. The application was designed to monitor thousands of individual branch circuits using current transducers at the breaker panels. Among other things, the data logging requirements were to provide one year of min/max/mean measurement data with one minute resolution per circuit. Since I had all the hardware for testing, I figured what better way to test things than to install it in my own home."

Comments

Another way to do it: read the meter

[seanadams.com]

If you want to monitor the whole house (as opposed to individual circuits) you can do it for less than $20 in parts plus a Linux machine. I made a system to do this a couple years ago - unfortunately I never hooked it up again after I moved, but it worked just fine.

If you're lucky enough to have the kind of electric meter with a blinking LED on it, you could do this much more simply. Also if I had to do this again I would ditch the op-amp circuit and feed the signal from the photo-resistor straight into the sound card and then do the filtering in software (if the photo-resistor is exposed to sunlight it can be a little tricky to tune using this circuit - software could be smarter).

Re:Another way to do it: read the meter

[d2_m_viant]

Yes, but that won't do much if the power company is cheating you. The article's way, you'd be more able to catch the power company charging you for something you didn't use.

On a side note: Imagine trying to convince the customer service rep on the phone that you rewired your house with a homemade power monitoring system and your monthly audits of your electrical usage uncovered the error...me thinks you'd have better luck convincing a Slashdot reader to install the WeatherBug...

Re:Another way to do it: read the meter

[seanadams.com]

If you can read the wheel then you can test its accuracy. Just turn a known load on and off and measure the change.

You can do that with just a stop watch and some math.

Re:Another way to do it: read the meter

[skids]

Good hack. You can also get readings of the mains post-power-meter with nothing more than a couple of ferrite toriod cores and some resistor divider bridges, feeding voltage and induced voltage (which is proportional to current) into a sound card's mic and line in inputs. I have that working downstairs, though I haven't bothered to calibrate it.

The toriods can be split carefully with a chisel, and need 70 to 200 turns on them, evenly spaced. They might saturate, but that can be fixed either through using a different core/winding or by software post-correction.

The original post is, well, for people who really want to go overboard and drop a lot of cash.

Re:Another way to do it: read the meter

[MyLongNickName]

Possible. I tried this method, but was coming up with irratic results. I found out that my fridge uses electricity almost continuously, but uses a variable amont of electricity. I was very surprised by this. I think you will find the same thing with your PC as well.

So, for many applications, your method works. But if you want to measure your average PC's power usage over a period for days.... ain't gonna happen.

Plus this IS slashdot. If it ain't a geek implementation, it ain't worth doing ;)

Re:Another way to do it: read the meter

[chris_eineke]

Also if I had to do this again I would ditch the op-amp circuit and feed the signal from the photo-resistor straight into the sound card and then do the filtering in software (if the photo-resistor is exposed to sunlight it can be a little tricky to tune using this circuit - software could be smarter).

I tried to read this sentence to my mother. She combusted halfways through.

Re:Another way to do it: read the meter

[anthony_dipierro]

I remember reading somewhere about someone who did something similar but hooked it up to individual circuits by acquiring spare meters and hooking them up through the circuit breaker.

Re:Another way to do it: read the meter

[The Slaughter]

Speaking as a customer service rep at a electrical utility, I think it would be one of my more NORMAL calls.
Typically speaking though, meters do not 'speed up.' With age, they slow down which does not work in the utility's favor, which is why they usually have a periodic meter replacement program, ie every 5 years.
I haven't ever sent out a service order on a meter that's ever tested too fast.
Many utility companies (like the one I work for) have automated metering, with meters transmitting at 917mhz back to a poletop box every 5 minutes for a second or so. (Like a cordless phone). What that means is that a lot of companies now have on their website a means for you to view your usage every day, so you can go online the next day after running your hot tub for a few hours and see how much extra you used in number and graph form.
But back to accuracy, typically, on a service order when a field rep goes out to test a meter, they will find the cause of the increased usage... like a new hot tub that was just installed :)
Meters all have to be tested to NIST standards... (from here: http://www.nist.gov/public_affairs/nhouse/watt.htm "NIST and Your Electricity Bill") No one needs reminding about those meters with little turning wheels that the power company uses for determining your monthly electricity bills. It may be of some solace to know there is a third party out there who is helping to make sure those watt-hour meters, as they are known, accurately record the amount of power you are using. That way you don't pay for more electricity than you actually use, and, in all fairness, the power company doesn't end up giving away its products for free.
This two-way assurance rests upon a short chain of calibrations anchored at the National Institute of Standards and Technology (NIST) where the ultimate power meter lives. The accuracy of every watt-hour meter in the country ultimately is traceable to the Electricity Division of NIST's Electronics and Electrical Engineering Laboratory. Most watt-hour meters are electromechanical devices in which a tiny portion of the electrical power going through it is converted into the mechanical clock-like motions that move the meter's dials. Just as clocks can be fast or slow, so too can watt-hour meters be off. That is why state public utility commissions (PUCs) own and maintain standard watt-hour meters with which they can certify the accuracy of mass-manufactured meters. Meters pass when they produce the same power reading as the standard meter when the same amount of current passes through them.
NIST provides the ultimate basis for these measurements because the standard meters of the PUCs go through periodic calibrations at NIST in which the amount of electricity going through a meter can be more accurately and confidently measured than anywhere else in the country. Once the standard watt-hour meters pass muster at NIST, they can serve as genuine gatekeepers for the much larger population of residential and business watt-hour meters.

Re:Another way to do it: read the meter

[Wolfrider]

+1 Mothercombuster
;-b

Re:Another way to do it: read the meter

[scottv67]

If you want to have a bit of fun while at the meter try out this game; Turn off all electrical devices. One person then runs though the house turning on all the power they can while another counts the meters rotation for a set time. The person who can turn the meter the most wins :)

This is just plain stupid (in addition to being wasteful).

How long did it take you to figure out that "electric oven + electric clothes dryer + central air" (or whatever hi-draw appliances you have in your home) is the quickest way to make the pretty little wheel spin?

Automatic Marriage Conflict Device

[DanielMarkham]

This doesn't seem like much of a practical thing to me. After all, most marriages have difficutly when it comes to spending money -- do you really want minute-by-minute graphs of who uses what in the house? After all, the writer admitted that at the end of this whole adventure he managed to show that his computers were using more electricity than his wife's stuff. FTA

Keep in mind that when it comes to friends and family, 'informative' is a relative term. Although you might find it very 'informative' to know that your wife left the lights on in the living room three out of four nights last week, she will probably not think so. I've found it better to save my geek points for things like "honey, don't you think we should have a raid server?"

I don't find any of that informative. Or rather, I find it detailed information about something that is trivial. Even if you have very tight budget, do you really want to argue about who leaves the lights on the most? What's next, sensors to monitor where people are at all times, and correlate electricity usage? No. Count me out on this one. But I got to admit -- the software looks cool!

NASA: Beats us

Re:Automatic Marriage Conflict Device

[Anonymous Coward]

After all, most marriages have difficutly when it comes to spending money

Yeah, tell me about it! My girl gets absolutely furious when I spend all our money on working girls. Stingy bitch.

Re:Automatic Marriage Conflict Device

[ImaLamer]

After all, most marriages have difficutly when it comes to spending money -- do you really want minute-by-minute graphs of who uses what in the house?

I've always said that two people who keep score lose...

Re:Automatic Marriage Conflict Device

[syukton]

You don't find it informative to know which lights are left on most frequently? Think outside the box. Don't think about pointing the finger, think about problem resolution.

Lights being left on wastes energy. Perhaps that room needs timed light switches that switch off automatically after 4 hours' time? Perhaps that room needs Compact Fluorescent Lamps instead of Incandescant in order to save power when they do get left on? Maybe both? It isn't about arguing over who is using more power, it's acknowledging everyone's power usage and looking at ways to eliminate unneccessary consumption.

What's next, sensors that monitor peoples' position and only turn on lights / apply electricity to the devices near them? Hey, that's a thought...

It isn't about guilt or accountability, it's about getting a fuller picture of the scenario so that one can navigate that scenario responsibly. Finger-pointing and blame-placing does not a solution make.

Re:Automatic Marriage Conflict Device

[dvogt]

Syukton, you make an excellent point. The other thing to think about is all the heat generated by that electricity. I live in a small house with no AC (except for the servers in the attic) and in a warm climate. While electricity consumption can be viewed as simply an economic cost you're willing to bear (ie. you cut back when it costs too much), another impact (which I notice more on a day to day level) is the discomfort caused by the additional heat build up. In this sense it's really handy to know where in the house that electricity is being dissipated.

Does your home still meet safety codes?

[CyricZ]

"while I had to rewire all my electrical to do it"

Most areas have municipal safety codes when it comes to stuff such as wiring. Are you sure your wiring is compliant with such standards? Has it been approved by your local building inspector?

Re:Does your home still meet safety codes?

[Naikrovek]

he rewired his house without killing himself, which proves to me he's smart enough to know to get it all inspected.

Re:Does your home still meet safety codes?

[CyricZ]

Just because it is working now does not mean that it will be in several weeks, months or years. Such codes are in place to prevent home hackery like this, especially in the case of electrical wiring. The potential for his modifications to fail are astronomical. And if he did such modifications without proper inspections, then the situation could get very hairy were things to go wrong.

Perhaps his insurance company would not pay him if it was found that his uninspected electrical modifications were the cause of his house burning down, for instance.

Re:Does your home still meet safety codes?

[Fallen_Knight]

i thinkt he parent was suggesting that because he managed to rewire it all himself he cna't be stupid enough to not do it right with permits and the like.

Re:Does your home still meet safety codes?

[CyricZ]

While his site is now completely slashdotted and I thus cannot double check it now, I do not recall seeing any mention of such inspections while reading it. That is a pretty integral part of the plan, or at least would be if performed by somebody who is alert to such safety codes.

I would have expected him to brag about how the local safety inspector was impressed by his system, or perhaps even how the safety inspector pointed out potential flaws that needed to be fixed. Indeed, I recall reading about neither possibility.

Re:Does your home still meet safety codes?

[CyricZ]

An engineer who disregards the law will be in for one hell of a surprise when his disregard of the law kills someone (if not himself, as is possible in this case, God forbid).

Re:Does your home still meet safety codes?

[zxnos]

i know plenty of smart people who dont bother with permits/inspections when it comes to home improvements. it can be a hassle to learn code (if you dont know it) and to get someone down from the county that isnt going to say, "you did what with your wiring?" being said, you still should get those things sign off on.

Re:Does your home still meet safety codes?

[ErikZ]

Such codes are in place to prevent home hackery like this, especially in the case of electrical wiring. The potential for his modifications to fail are astronomical.

I agree! Think of the dangers of brewing your own beer, working on your car, or even programming! Almost all viruses were programmed without any kind of government oversight.

There should be codes that are enforced by the governemnt that touch upon everything you can possibly do. To protect you, and others, from yourself.

Seriously, the codes are there to protect people from substandard wiring. But to insist that you have no right to modify the wiring in your own house is too "Big Brother" for me.

Re:Does your home still meet safety codes?

[CyricZ]

Sure he has the right to rewire his own house. In case you failed to notice, that is exactly what he did.

Indeed, the safety codes are there to protect people from substandard or faulty wiring. That is why he should have gotten the local inspector in to check on it, and to verify that the modifications he has made are safe. It's not only the financially prduent thing to do (ie. in terms of insurance and preventing the loss of his hard-earned property), it is also the socially responsible thing to do. Not only for his own safety, but for the safety of his wife, housekeeper, children, guests, and others.

His house burning down because of faulty wiring could have devastating effects on his neighbors. His neighbors should demand that his house be checked by the local inspector for the safety of their own homes, family and other property. Fires can spread between houses rather quickly, you know.

Nobody is taking away this fellow's right to wire his house, or your right to brew your own beer, or Torvald's right to develop his own software. Inspections of his wiring would be to help guarantee that his modifications do not lead to the untimely death or injury of himself and others.

Re:Does your home still meet safety codes?

[cyb97]

getting off topic here, but what happens to your "modifications" when you sell your house?

Caveat emperor?

Re:Does your home still meet safety codes?

[kent_eh]

From TFA:

The current transducers are actually really small and they clip on to the wiring

The power monitoring system is not connected dsirectly to the wiring. It is using inductive sampling.

I serioisly doubt that having an inductive device near the conductor (outside the insulation) has any impact on the overall safety of his house's wiring.

Re:Does your home still meet safety codes?

[Gothmolly]

MoD PaReNt UP, +1 Individualist

Re:Does your home still meet safety codes?

[ArsSineArtificio]

getting off topic here, but what happens to your "modifications" when you sell your house?

Caveat emperor?

I think that if an emperor were to buy your house, he could afford to perform his own inspections and rewiring.

Perhaps you meant "caveat emptor".

Re:Does your home still meet safety codes?

[runner_one]

PERMITS? We don't need no STINKING PERMITS
SCREW THE CODES AND ANAL-RETENTIVE CODES INSPECTORS!
It's my house and my property I will do WHATEVER I want with it!
In fact I Do! I have added on about 40% to the size of my house since I moved in about 16 years ago. I have done much indoor and outdoor wiring as well as plumbing. Installed a pool and Solar heater, as well as miscellaneous outbuildings. ALL without one single permit or inspection. Granted I live in Tennessee where freedom is still more than ancient history to us. The local government tends to take a "If you are not bothering anyone we won't bother you." attitude in most circumstances except on drugs. In addition to the fact that the area I live in there is NO zoning of any kind. A couple of years ago an investor started to put in a dirt racing track near the county line and a few adjoining farmers and residents started raising holy hell about the noise and traffic it would cause. They went to the local county board and said "Can't you do anything to stop him?" Their answer was " Yes we can adopt a county-wide zoning plan, but then every time you want to build something it would have to go through the zoning board." That Idea was dropped like a hot potato and the race track went in. County-wide zoning will not happen anytime soon in this area.

Re:Does your home still meet safety codes?

[plover]

Well, there's an awful lot of stuff in the NEC these days. As the technology of the components changes, and as best practices are improved upon by the industry, these are adopted into the modern electrical code.

Smart people aren't always knowledgeable about other fields. As in computers, there are ways to make it work that don't necessarily mean they're done correctly. I was almost zapped earlier this year because I was working on some wiring in my sister's basement that had been put up by a previous owner. I discovered through the "spark method" that the guy had two separate circuits operating in the same box, coming in different sides and both on black wires. This made me extremely wary of anything the guy had touched, so I pulled the main breaker before continuing. As I ripped out his dangerous connections in order to put them together correctly I found other places where he used white wires to carry the hot side without marking them with black tape (as required.) I also found a case where he switched the neutral wire instead of the hot wire. Yes, the light was operated by the thing on the wall as you might expect, but no, it was not done correctly nor safely.

Also, what your smart friends may have learned in the 1970s and 1980s may no longer be legal for wiring today. For example, in the 1970s aluminium wire was legal for use in residential wiring, but it was later discovered that its coefficient of expansion was greater than that of copper, and that after years of expansion and contraction the wires could escape from underneath the screws that held them, causing arcing and fires. The code has been modified to explain how to handle existing aluminium wiring.

Does that mean your friends did anything wrong? Not at all -- they could have been very careful and safe, and put everything together correctly. Would they have benefited from an inspection? Think of an inspector more like pair programming, where you have a second pair of eyes to make sure you did things right.

Re:Does your home still meet safety codes?

[bill_mcgonigle]

And if he did such modifications without proper inspections, then the situation could get very hairy were things to go wrong.

I agree with you on codes - they are there to demonstrate good building practice and any smart person will consult them like a good reference book.

But inspections - these are for the municipality to justify their permitting process, which is really to increase their tax revenue.

The previous owners of my house were an old couple, by-the-books, they hired out everything and pulled every applicable permit and followed ever requirement. I've still had a flooded basement from improperly soldered water pipes, a boiler that blew up because the vent was installed on the windward side of the house (the high-efficiency POS rusted out from collected rain water) and a light switch box that caught fire from improperly stripped wire and could have burned the house down if I didn't notice 'that smell'.

Now you might argue, "that's just a bad inspector at work." But that's exactly the problem. Because municipalities mandate it and provide the inspector they're screwing the market. There should be independent inspectors who have some kind of certification like an engineer who can get their license pulled like an engineer and who will gain a reputation among the trades for the quality of his work. Most importantly he needs to work for the owner, not the general, as there's too much conflict of interest there. If the municipality wants to require a licensed stamp on the permit, fine.

But as long as the they require their own inspector this isn't going to happen. I wonder when they'll start requiring the use of their own engineers.

Re:Does your home still meet safety codes?

[LittleRedStar]

What is with this local inspector stuff? Do you know for a fact that the inspector(s) have a clue themselves?

If you can learn how to write the programming code to interface with power monitoring devices you can master the friggin electrical code!

I have rewired nearly my entire house. It is a local requirement when upgrading or changing the main feed (I went from 100A to 200A panel) that the local inspector sign off before the power company will finish the final meter changes.

I had every wire neatly placed in the panel, correctly sized, etc. This is not rocket science. But you know what the inspector question? A GFI breaker in the panel was not clearly mark as to what brand it was. He claimed that not being the same brand as the panel mfg it was not 'right'. BS, not only is he wrong, but when I pulled the breaker out I showed him it was in fact a Cutler Hammer, same as the panel.

So much for intelligent inspectors.

Re:Does your home still meet safety codes?

[SydShamino]

You pull your house off of the grid, and you can do whatever you want to with the wiring in your house.

As long as you choose to attach to the public electric grid (privately owned or not, there is public interest in its upkeep), you have to accept some level of oversight of the things you do in your house. For example, if you chose to use equipment that had a really bad power factor (i.e. voltage and current were out of phase), the power company could and would order you to adjust your load. Or, if your tweakings injected noise back onto the grid, they would make you fix it or cut you off.

Re:Does your home still meet safety codes?

[CyricZ]

A second set of eyes never hurts. That goes for electrical wiring just as much as it goes for peer programming or unit testing.

People make errors. That is why it is helpful to have other people check over your work, to make sure it was done correctly. In a case like this, that person could be the difference between a safe and useful modification to the existing power system and a house that burns down.

In your particular case the inspector did the right thing. He noticed a discrepancy, and he brought it up. You showed him that the situation was not problematic, and everything was fine. That is the system working. Much like you making a modification to a piece of Java software, and then running your JUnit testcases just to ensure that everything is working fine.

Re:Does your home still meet safety codes?

[poopdeville]

PERMITS? We don't need no STINKING PERMITS SCREW THE CODES AND ANAL-RETENTIVE CODES INSPECTORS! It's my house and my property I will do WHATEVER I want with it!

That's great. But once you move into an urban area, where what you do affects others, you'll have to comply with permits and inspectors.

Re:Does your home still meet safety codes?

[0111 1110]

Such codes are in place to prevent home hackery like this, especially in the case of electrical wiring.

Actually building codes are mainly intended to guard against shoddy work by contractors trying to save a few bucks. The only enforcement focuses on getting occupancy permits and the like. Most building departments don't worry too much about stuff like this.

I've done quite a bit of home electrical wiring, and I'm familiar with a lot of the code. It's mostly common sense stuff. While I can't speak for the building inspectors in his locale, I don't think he would have a problem in my area. In construction there are two ways to do things: the easy way and the right way. The author doesn't strike me as an 'easy way' kind of guy.

OTOH, where I live you have to be a licensed electrician to legally do this kind of work. And even then you need to get a permit from the town before you go ahead with it. So it may not be advisable for him to call the building department to come and admire his work.

Re:Does your home still meet safety codes?

[ldm314]

I seriously doubt that you actually read the article. Clipping on transducers wasn't the only thing he did. He also wired up another breaker panel on the inside of the garage.

Re:Does your home still meet safety codes?

[modecx]

No zoning? Holy crap. I thought I liked Tennessee before, but that's just awesome.

Stupid zoning...

Re:Does your home still meet safety codes?

[kent_eh]

Yeah, he replaced the panel with a larger one. And he said more than once don't do this unless you know exactly what you are doing
It seems that he feels that he does know what he is doing.

As someone who has installed/replaced considerable amounts of home and industrial wiring, I don't see anything in what he wrote that is inconsistant with him "knowing what he is doing".

Re:Does your home still meet safety codes?

[TClevenger]

Exactly. Some municipalities impose fines for doing work without permits and inspections, and calling out an inspector sounds like a good way to get your power shut off until you undo all your changes and start with the permitting process from the beginning.

I would pay a licensed electrician for an hour of his time to come out and inspect the work. While he wouldn't 'officially' sign off on it, he would be able to point out any glaring safety issues or code violations.

Re:Does your home still meet safety codes?

[jrockway]

Your point still holds: the emptor should have an inspection performed.

It's my right as an American to burn down my house if I want to. Besides, what's the difference between faulty wiring burning down my house and a carelessly discarded cigarette doing the same? Should inspectors come by your house every night to make sure you're not smoking in bed?

Re:Does your home still meet safety codes?

[unitron]

"Most areas have municipal safety codes when it comes to stuff such as wiring. Are you sure your wiring is compliant with such standards? Has it been approved by your local building inspector?"

Well, I'm 99 and 44/100 % certain that he no longer has valid insurance coverage, even though he might think that he still does, and that the inspector would probably have a conniption fit if he ever actually saw that installation.

If he just went out and bought a new panelboard because it was rated for enough amperage and was physically large enough to include the inductive sensors and the circuit board, then he's definitely screwed, because the manufacturer of the panel board never submitted the board with all that extra crap wired in to Underwriter's Laboratories for certification, so any UL certification the panelboard had when it was sitting in the store is moot. Also, the inclusion of low-voltage wiring and that circuit board inside the board means a violation of the National Electrical Code, which usually has the force of law local ordinance wise. I'm sure his homeowner's policy is worded so that they can just laugh at him if he ever submits a claim. When it comes to house wiring you can be your own installer but you can't be your own manufacturer, at least not the way he was.

Re:Does your home still meet safety codes?

[CyricZ]

It's not your right as an American to burn your house down, at the same time possibly killing your wife, your housekeeper, your children and potentially others (ie. neighbors, guests).

Re:Does your home still meet safety codes?

[CyricZ]

Remind me never to move to Tennessee (not that I ever would, mind you). I'd much rather live in a city or township where inspections of homeowner (ie. non-professional) renovations, especially to potentially hazardous systems like the electrical system, are mandatory. I don't trust redneck cowboys to properly wire anything safely, let alone a house. It isn't a matter of "freedom" to get your wiring inspected; it's a matter of common sense dictating that any avoidable disaster should be avoided.

Re:Does your home still meet safety codes?

[anthony_dipierro]

Those safety codes usually don't apply to people doing work on their personal residence. If you rent out the house, or if you charge for the work, fine, but if you're just working on your own home you usually have the right to do whatever you want.

Re:Does your home still meet safety codes?

[anthony_dipierro]

A second set of eyes never hurts.

Even if that were true, something not hurting and something being legally mandated are two very different things.

Re:Does your home still meet safety codes?

[anthony_dipierro]

The new occupant is going to have to get a certificate of occupancy, where the electrical wiring (along with lots of other things) will be inspected. If the house was sold as is, then it's up to the new occupant to fix the problems. If not, then it's up to him to fix them. Either way, without a CO, the buyer isn't supposed to live in the house.

Re:Does your home still meet safety codes?

[anthony_dipierro]

That's a pretty naiive way to look at things. There are lots of things which aren't wrong which are still prudent to hide. Some of them are illegal. Some of them are just frowned upon by a segment of society.

Re:Does your home still meet safety codes?

[runderwo]

The difference is intent. Did you intend to burn down your house or not? Did you know that your actions would reasonably lead to the conclusion, or are you willing to admit publicly that you are just *that stupid*? Once having done that, then if you do the same thing again expecting a different outcome, you could be committed for insanity - if you manage to convince a jury that you were in fact not acting maliciously even with prior knowledge of the likely outcome on the record, which would suffice in many areas to provide intent.

By the way, the amount of pollution and cleanup work that a burning house produces ensures that you have no right at all to deliberately burn it down unless you can contain the pollution and perform the cleanup yourself.

Re:Does your home still meet safety codes?

[makomk]

For example, in the 1970s aluminium wire was legal for use in residential wiring, but it was later discovered that its coefficient of expansion was greater than that of copper, and that after years of expansion and contraction the wires could escape from underneath the screws that held them, causing arcing and fires. The code has been modified to explain how to handle existing aluminium wiring.

In the US, at least. (The UK, for examlpe, never had this in homes). Of course, none of this applies to non-US countries anyway, variations in electrical standards, wiring techniques and conventions, etc being what they are.

Re:Does your home still meet safety codes?

[/dev/trash]

I hope you never need to file an insurance claim.

+++
http://www.drudgereport.com for the truth.

Re:Does your home still meet safety codes?

[runner_one]

My policy makes no mention of codes or inspections.
Then again it's not a large national company but a small local Farmers insurance CoOp.

Re:Does your home still meet safety codes?

[plover]

Actually, it pretty much applies equally everywhere (that was a specific example of why the code changes, not of what you might have done wrong today.) Not that I'm an expert in British wiring, but I expect you have an electric code, and that it is revised periodically, and that you have electrical inspectors for exactly the same reasons we have them here in the U.S. If you have wiring done, you should have an inspector verify that it was done in a safe and prudent manner, following local best practices that were current as of the time of the inspection. That's pretty much universal, (although I suspect that in some countries the electrical inspector is little more than yet another corrupt official requiring a bribe.)

When visiting friends on the isle of Arran, Scotland, I remember seeing the "fuse box" and being quite frightened at all the exposed, uninsulated 220V hot wiring. It certainly made me appreciate the U.S.'s NEC all the more.

electrical bill now?

[AmigaAvenger]

great, you do all this to minimize your bill, then post on slashdot?!?! server is already slow, I imagine the meter is spinning like a top right now...

Re:electrical bill now?

[Alwin Henseler]

server is already slow, I imagine the meter is spinning like a top right now...

It's not as bad as you think, he's just using his white-hot CPU for heating, cooking and lighting now.

Re:electrical bill now?

[self assembled struc]

if you'd bothered to look at the URLs you'll noticed he used The Corel Content Distribution Network.

His server isn't really doing anything.

From the article...

[Toasty16]

"About nine months ago the motor overheated on our dryer while the house cleaner was here. I asked her how many loads of landry she had done that morning and she said three. I took her back to my office and fired up the software and told her she had done four and wow, there was a significant current surge when the motor gave out. She was also not particularly impressed and she now asks me every time she wants to use something in the house (not a good thing)."

Uh, can someone say backfired? Women.

Re:From the article...

[BrK]

A passive current monitor isn't going to have any effect on the dryer motor.

Re:From the article...

[sleeper0]

I didn't get to read the article, but this quote sure does have some insight into the type of mind that goes ahead and builds a comprehensive home power monitioring solution. Can you imagine being quizzed by yourhusband about how many loads of laundry you did a certain day and then having him insist you come with him to see on the computers about how you were WRONG and you were OFF BY ONE? Jesus that would drive me crazy.

Re:From the article...

[gkuz]

Can you imagine being quizzed by yourhusband about how many loads of laundry you did a certain day and then having him insist you come with him to see on the computers about how you were WRONG and you were OFF BY ONE?

I've been married for 28 years, largely by studiously avoiding that sort of behavior. I'm frankly surprised the guy is still alive, let alone still married.

Have to say

[zegebbers]

Since I had all the hardware for testing, I figured what better way to test things than to install it in my own home.

That's an awesome attitude that we don't get enough of on slashdot these days :(

Re:Have to say

[elmegil]

You're not really getting it on slashdot today either. This is basically horked from the Make Magazine blog. If you really are interested in that kind of attitude, you should read it instead of slashdot.

Re:Have to say

[the pickle]

Not sure what your point is. If you're saying that Slashdot was six days late to the party, well, yeah, surprise surprise. But if you're saying the guy just aped a Make hack and then got it posted on Slashdot, no. The guy who wrote the article Make blogged is the same guy who wrote the Slashdot story you're reading right now. Both link to

http://www.kondra.com/circuit/circuit.html

p

Re:Have to say

[babyrat]

Why is this 'horked'?

Sounds like David posted to both places...which is well within his rights to do. Seems like it was interesting enough for both places to post.

Re:Have to say

[noidentity]

Maybe the "I'll try it in my home" results in lots houses burned to the ground? Kind of like posting a link to your home page in a Slashdot article.

Very cool, but a potentially dangerous area

[Sv-Manowar]

The screenshots of the monitoring software in use and everything make this seem extremely cool, but the potential risks seem huge. Obviously from the article this guy has done this kind of thing for work and had all the right equipment. I'd hate to see the results of someone lacking these vital elements 'hacking' their mains power system to get pretty graphs. The website says as much in its disclaimers too.

his project will come in very handy now

[Anonymous Coward]

He'll know exactly what his electric bills will be after this slashdotting!

This "conflict device" is "information-based" ...

[benji fr]

Informative, informative ...

I just read an article (in french) ( Subversiv ) about "information" ...

There is a very interesting example in it : In the bible (Genesis, IX, 20-25), Cham, son of Noe, found his father drunk and naked. Instead of helping him wearing clothes and go to bed, the son told it to his brothers.

It was the first journalist, and he was doomed for that ! ...

Informative you said ?

Dome? What dome?

[jfengel]

With the server already grinding to a halt and the "dome" left unexplained in the summary (is it some sort of euphemism?), I'll spoil the ending:

His wife got ticked off, so to apologize he built her a ceiling dome (a recessed dome built into the ceiling, with a light fixture suspended from the peak). It looks nice.

I would love to see screenshots of the effect.

[CyricZ]

I would love to see screenshots from the program he is using showing the power consumption of his web servers during this slashdotting. Indeed, it would be beneficial to know more about his hardware setup, too. It would be very interesting to correlate the number of hits/minute with the minute-by-minute power usage of his server(s).

Re:I would love to see screenshots of the effect.

[dvogt]

Here is a screenshot for the last few hours: http://209.10.40.245/circuit/status.jpg

Oh great....

[qwave54]

another piece of hardware looking to kill the meter reading industry!

- Meter Reader

Network Power

[Doc Ruby]

Seems to me that this kind of application should be integrated with "Power Over Ethernet" (PoE). Since every node on the network gets its power from the network, the adapter should collect this kind of data, perhaps in an embedded device with its own IP#. The same design logic for DC PoE seems like it should be true about AC "BPL", Broadband over Power Lines. In fact, those power/packet sockets should have cheap little embedded devices that not only report power consumption, but allow control of it via TCP/IP. Isn't there such a network/power platform available COTS?

Re:FTA?

[lastchance_000]

From the article. But your version is more amusing.

Re:Already slashdotted

[SisyphusShrugged]

http://www.kondra.com.nyud.net:8090/circuit/circui t.html http://www.kondra.com.nyud.net:8090/dome/dome.html

coral cache links

[AMystery]

Since I had to go look for caches, i thought I'd share.

The article on house wiring. http://www.kondra.com.nyud.net:8090/circuit/circui t.html

Another popular article from the site on building a ceiling dome. http://www.kondra.com.nyud.net:8090/dome/dome.html

Re:SAD TWAT

[joelsanda]

So assuming he did it to try and save money, after all what is any other point of doing it...

Maybe he did because he was interested in doing it? Which would make him a fairly clever bastard; because I'm sure there are more people who would criticize's another interest than actually do the work (the interesting part?) themselves.

Yeah

[cynical kane]

You don't mess with a woman with a Power Management System...

(ducks)

Money isn't a problem for him.

[CyricZ]

It doesn't look like money matters much to him.

From the article:
"About nine months ago the motor overheated on our dryer while the house cleaner was here. I asked her how many loads of landry she had done that morning and she said three. I took her back to my office and fired up the software and told her she had done four and wow, there was a significant current surge when the motor gave out. She was also not particularly impressed and she now asks me every time she wants to use something in the house (not a good thing)."www.kondra.com

If he can afford to hire a housecleaner (one who does his laundry, not just clean the floors and bathrooms), then some wiring is the least of his financial worries.

Re:Money isn't a problem for him.

[BrK]

Wow, you could make Conclusion Jumping an Olympic sport with your talents!

Re:Money isn't a problem for him.

[CyricZ]

People who worry about their financial situation do not waste money on luxuries like housecleaners. Especially housecleaners who do their laundry for them.

power monitoring

[unix_geek_512]

Geeks unite!

Why not take this further? Instead of just monitoring let's modify the system so that we can turn circuits on and off remotely as well as being able to monitor usage. In fact why not wire the whole house so that the lights turn off automatically if there is no one in the room unless the system is manually overridden?

We all need to think about energy conservation and energy security which is a big part of our national security.

I would encourage everyone here to build a system with occupancy sensors so that lights, appliances and devices are not left on unnecessarily.

The occupancy sensor module could include PIR sensors, temperature/humidity sensors, smoke detector, CO detector, intrusion detector and perhaps a CCD camera all linked to a GNU/Linux system capable of controlling energy usage as well as calling the Police or Fire Dept. in case of an emergency.

Live long and prosper

Re:power monitoring

[NoMoreNicksLeft]

X10 sucks. It can only turn on and off.

Would require an entirely new protocol, to do bidirectional data. I've considered such, but it's doubtful that the things would have any mass market appeal. I'm thinking a board the size of a deck of cards. z80 cpu, 32k static ram, 32k eeprom. Tcp/ip stack, over daisy-chained serial. You'd have a single cat running from your computer to the first module, and then another chained off the first, etc. Could even do power over the cat5, reduce wirepulling.

Now, put 3 or 4 slots on the thing. Make it a simple, cheap connector. The 2x20 headers you see on a hd, for instace. The slots would need an innterrupt, 8 data, and just a few address pins.

Give it to the slashdot crowd, and let them make their own sensor/activator cards for the things. Put one in your fridge, have one module wired to the door switch, so you know if its closed or not, slot 2 would be a photosensor, to see if the lights on or off. If the door is open, but still dark, have the damn thing add "fridge lightbulb" to next weeks automated grocery list printout.

Who can come up with the weirdest (cheap) sensor you might build for such a thing? I'm thinking geiger counter myself, but I can imagine some college physics student building a cosmic ray detector for the back yard...

PS I would not trust a system that I couldn't test, to call the fire dept. for me. False alarms can get you in trouble... maybe have the thing use your asterisk card to call you on your camera phone with a inside pic, so you can confirm for it?

Or maybe smoke + extreme heat sensors going off in multiple rooms is conclusive enough?

Re:power monitoring

[noidentity]

The occupancy sensor module could include PIR sensors, temperature/humidity sensors, smoke detector, CO detector, intrusion detector and perhaps a CCD camera all linked to a GNU/Linux system capable of controlling energy usage as well as calling the Police or Fire Dept. in case of an emergency.

Be sure to factor in the cost and labor of of installing and maintaining all this equipment (including cost of false calls to emergency services).

Re:power monitoring

[JNighthawk]

My high school (freshly built in 2003) had automatic light sensers like that. It was fun when the lights would go out in the middle of class when the teacher was giving a lecture, or after-school when the teacher was the only one in the room.

Re:power monitoring

[nwf]

X10 sucks. It can only turn on and off.

Would require an entirely new protocol, to do bidirectional data.

X10 can do bidirectional traffic. I have several X10 devices that will confirm their status back to the controller so it knows when things are really on. Check SmartHome.com for all kinds of X10 devices to do both control and monitoring.

However, X10 is very unreliable and prone to data loss. It's a major pain to get it working for anything larger than a few units. Signals get lost and garbled regularly by all kinds of things. The bidirectional capability helps somewhat, but can only do so much.

Re:power monitoring

[evilviper]

Instead of just monitoring let's modify the system so that we can turn circuits on and off remotely as well as being able to monitor usage.

You've clearly never tried to do this, because it is massively difficult.

Nobody would ever suggest doing this for a private home, because the huge cost, time, hassle, and minor savings aren't worth it. (A large office building is a different case.)

If you want to save energy, use (good) fluorescent light bulbs instead. They use as little as 1/10th as much power, and lights are usually the single biggest power drain in a home.

Beyond that, just train the people in your home to start shutting off the lights when they leave the room. It works far better than any automated system could.

as well as calling the Police or Fire Dept. in case of an emergency.

This is an incredibly bad idea. One faulty smoke detector and you could be paying several hundred dollars to the emergency services.

This only works for alarm systems because you have a phone-bank of waiting personell to read what the automated system is saying, sanity-check the results, call-back the occupants of the home to verify the issue, and only then call the emergency services.

Re:SAD TWAT

[msimm]

FTFA:

About a year ago I developed a web based power monitoring application for data centers. The application was designed to monitor thousands of individual branch circuits using current transducers at the breaker panels. Among other things, the data logging requirments were to provide one year of min/max/mean measurement data with one minute resolution per circuit. Since I had all the hardware for testing, I figured what better way to test things than to install it in my own home.

Sounds like a clever bastard to me.

Not necessary, use the TCP/IP stack for power

[CrystalFalcon]

Power over Ethernet is not necessary, use the electricity in the TCP/IP connectivity.

See RFC3251, Electricity over TCP/IP. It's a very interesting read if you're not familiar with it.

Re:Not necessary, use the TCP/IP stack for power

[Doc Ruby]

Yes, that's even better. I wonder when we'll start seeing "PoT" (Power over TCP/IP) spec'd for very low power apps, like millivolts, as simple embedded chips get nano. Hell, what about "PoW", Power over WiFi? How low power would that have to be?

1 minute resolution is not enough

[zippthorne]

In fact he must sample at greater than 120hz* to get meaningful results. He has neglected the possibility that voltage and current can and will be out of phase for each of the loads in his house. Without determining the phase difference, there is no way to accurately deterimne the average power over any interval.

There are quite a few meters that measure RMS voltage and RMS current, (though most of the cheap ones actually measure peak values and multiply by .707), there are fewer still that accurately resolve power factor

This is a common mistake to make for first year EE students and "over-unity" power converter proponants.

As I understand it, the Kill-A-Watt, http://www.professionalequipment.com/xq/ASP/Produc tID.3375/id.5/subID.57/qx/default.htm makes a pretty good approximation. In fact, it even does the integration for you. You could pepper every outlet with these things or just move them around as needed.

*I know you need 2f according to nyquist to resolve the frequency, but I'm not sure what you need to gather the phase information**

** There are other ways to obtain the phase information involving bridge circuits and such, It does not appear that the boards in question provide that information.

Re:1 minute resolution is not enough

[dougmc]

[disclaimer: the original site is down, so I haven't read the article ]

In fact he must sample at greater than 120hz* to get meaningful results.

Well, he could sample 120 times a second, but then only keep one data point for each three seconds, with that one data point being calculated from the 360 readings taken before it. It could save a lot of disk space ...

He has neglected the possibility that voltage and current can and will be out of phase for each of the loads in his house.

And you've neglected the possiblity that there may not be a phase shift at all (go down to `It ain't necessarily so!').

(Granted, in practice it's almost never a signifigant issue, but still ...)

Without determining the phase difference, there is no way to accurately deterimne the average power over any interval.

Ultimately, if you can't figure things out any other way (for example, the current used may be essentially random, but varying so you can't just take the average), you could measure the heat produced by the device and calculate the power usage that way. (Though this probably wouldn't qualify as accurate ...)

That method is sometimes used in radio work -- send your complicated signal into a dummy load, and see how much the temperature of the load changes. Sure, there's more accurate ways to do it, but low tech ways are often a lot cheaper. :)

the Kill-A-Watt

I've got two of these -- they were on clearance at Radio Shack for $20. Nice devices. They do tell you the power factor of a given item (in addition to the power used and some other things), though I've never tried to determine how accurate they were.

Re:1 minute resolution is not enough

[domefreak]

I did my undergrad thesis in home power metering, and used 2 different models of Brand power meters. They sample current and voltage at 4kHz to accurately measure true power factor (see their description). Single circuit "plug-through" meters are $150-350; the higher-end ones have computer connectivity and datalogging.

Another option for those interested in exploring home power use--and not ignoring power factor--is the Watt's Up? meter (also plug-through, $100-150, with computer connectivity at the high-end). I believe both this and the Brand meter will show you the instantaneous power factor of the load you're metering if you cycle through the display.

While power factor might be irrelevant for simple inductive loads, I agree with the parent that this is an oversight (if it's true that the hardware in question doesn't do more than measure volts * amps), particularly if you want to check usage against your power bill. Power factor is more of issue for commercial electricity customers, who are billed for non-unity power factor and often install huge banks of capacitors to correct it (though i forget exactly how this helps).

Re:1 minute resolution is not enough

[Anonymous Coward]

Everything (except capacitors) is a resistive or inductive load. Since everything that turns is an inductive load (motors) the bank of capacitors provides a negative inductive (not real) load to keep the power factor sane. However, at home, the inductive load is trivial. The parent just cut and pasted a comment from the windmill post, where it was relevant.

Re:1 minute resolution is not enough

[dan42]

I believe the 1 minute resolution was for the reported data and not the actual analog sampling rate. The 1 minute data may (should) be the RMS of the all the samples collected during that minute.
His device seems to be a prototype version of the Veris H663. The released version of the device apparently samples at 1280Hz and reports data every second.
The "phase information" you mention is good to have, but only if the power is at just one frequency. The fact is that computers (as with most devices running of a switching power supply) draw current as a short pulse during the peaks of the input voltage waveform (with no phase angle between voltage and current at the fundamental frequency). Often the 60Hz component (or whatever the fundamental frequency) makes up only half the RMS current. And since these harmonics are only dominant in the current and not the voltage waveform, the real power consumed by a computer will typically be ~50% x RMScurrent x RMSvoltage (even though the phase angle is zero).

Re:1 minute resolution is not enough

[calidoscope]

Everything (except capacitors) is a resistive or inductive load.

Over simplified.

You're forgetting about linear vs non-linear loads (think capacitor input power supplies for the latter). I would guess the current waveform in a modern home will look pretty ugly.

The real way to do power monitoring is to sample the current at 4kSamples/sec as well as sample at least one of the voltage wavefforms. Data processing would be taking the average of the instaneous power and recording that average every few seconds.

BTW, watt-hour meters do measure power and not simply current.

Re:1 minute resolution is not enough

[hernick]

You are wrong about the resolution. He's sampling every 3 seconds and making a min/max/mean database entry out of 20 samples, every minute.

You are wrong about the importance of the power factor. It is not even measured by the power companiesl; they ignore it in their billing. He cares about the bill, not some unmeasurable factor.

This is a common mistake to make for young scientists who fancy themselves engineers, electrical or otherwise.

Once upon a time, a young scientist learned of an home power monitoring system. It worked well, produced numbers that could be renconciled with the bills, was automated and not too expensive.

So the young scientist said: "Heresy ! This system does not meet the holy five-nines precision! Operating is is akin to spitting on the tomb of Nyquist while claiming that phase information is more of a theory than evolution ! The readouts are meaningless and design negligent !"

But he had a solution: "You will buy 15 of these meters and spread them around your house !" As for the automation, he figured you'd put a couple grad students on shifts for readout collection duty.

Re:1 minute resolution is not enough

[zippthorne]

Vrms*Irms = | Pre - j*Pim |

In other words, (Vrms*Irms)^2 = Pre^2 + Pim^2
It is not the real power.

the real power is equal to Vrms*Irms*cos(theta) where theta is the phase angle. between V and I.

You can also calculate the real power by the integrating square of the instantaneous product of V and I over one full cycle

Prms = 1/T*sqrt(int(t0->(t0+T),V(t)^2I(t)^2dt))

It appears from the article that he is measuring V and I (rms? average? sample? doesn't say) of one-minute intervals. Since he appears to be close to the actual power recorded by the meter reader at the end of a month, we can assume that the sum of the reactive loads in his house is small. I'm sure the power companies are happy about that.

Re:1 minute resolution is not enough

[bMuZal]

Looks like you have missed the point. Yes, Residential meters measure real power. However the question is if the clip on system measures Real Power or simply Volt-Amps. If it is the case that the clip on system just measures VA, then its measurements may or may not match well with measurement by the official power meter. Some industrial meters certainly do have the capability of measuring both real power and VA (And a whole lot of other things as well). It depends on the electricity provider on how the bill is calculated.

Re:1 minute resolution is not enough

[bMuZal]

Not to mention that residential meters only have to be within 0.5% at "normal" temperatures and loads.

Re:1 minute resolution is not enough

[Technician]

Power factor is more of issue for commercial electricity customers, who are billed for non-unity power factor and often install huge banks of capacitors to correct it

Here is a brief rundown and how it helps.
In DC Volts times Amps = Watts.
In AC Volta times Amps times Power factor = Watts.
Volts times Amps minus Watts = VAR's (Volt Amps Reactive) Power Factor is always between 0 and 1.0 and is either inductive or capacitive. 1.0 = no reactive current.

How does reactive power affect the power company?
Take for example an air conditioner. It's electric motor has windings that are inductive. The current is not directly in phase with the applied voltage. The current lags. The AC may draw 15 Amps, but on a 120 Volt circuit only consume 1200 Watts. 15 * 120 = 1800 Volt-Amps. 1200 Watts is the power used. 120 Volts * 15 Amps * 0.66667 PF = 1200 Watts. This leaves a component of 600 VAR's or 5 Amps of reactive current and a Power Factor of 0.66667 inductive. Drawing 5 Amps seems like no big deal to an end consumer. However for the power company, it means the transformer has an extra 5 amps as well as it's circuit breaker and wires. All wire has resiance. A current flowing in a wire will turn some of that voltage caused by the current to produce real Watts (heat) in the wire, transformer and circuit breakers. Your 5 Amps of 0 Watts costs the power company money to heat their lines and reduce their capicity.

Now the neat way to fix it. Capacitors don't heat (except for some small losses) Add some capacitors so the capacitive reactance = the inductive reactance on the line. In the above example 5 Amps is needed.

When done, the 5 Amps of capacitive reactance is out of phase with the inductive reactance by 180 degrees (90 degrees to the resitive load) and thus the 600 VAR's (5 Amps Inductive) from the AC is balanced with 600 VAR's (5 Amps Capacitive) from the capacitors. The nice thing is now the AC gets the current for the VAR's from the capacitors, not the power company. Now the AC uses only 10 Amps from the power company, not the 15 it used to. (The AC still draws 15 Amps, but the combined load of the AC and Capacitors is now 10 Amps and still 1200 Watts.) This is why the power company would like you to adjust your VAR's. If the power company tried to adjust it, (sometimes they do) by adding capacitors, then they may be unbalanced the other way (capacitive) when your AC shuts down but the capacitors don't.)

Re:1 minute resolution is not enough

[elgatozorbas]

*I know you need 2f according to nyquist to resolve the frequency, but I'm not sure what you need to gather the phase information**

The same of course. Nyquist sampling allows for perfect reconstruction of ALL info, hence also phase info.

Re:1 minute resolution is not enough

[evilviper]

As I understand it, the Kill-A-Watt, http://www.professionalequipment.com/xq/ASP/Produc tID.3375/id.5/subID.57/qx/default.htm makes a pretty good approximation. In fact, it even does the integration for you. You could pepper every outlet with these things or just move them around as needed.

Very nice... I was going to mention the Kill-A-Watt here if nobody else did.

I only have one ($30) and it's all I've ever needed. Plug it in to a device for a day/week/month and it will tell you exactly how much power it has used over that period of time, the power factor, the average voltage level, etc.

Until you've used a power meter, your guesses as to how much power each device uses will be very far off the mark.

I've learned all sorts of interesting things. Like how newer northbridges are using as much as 30watts more power than than older northbridges driving the same CPU/RAM. How that single issue causes newer motherboards (for 32bit AMD CPUs) with S2K/Bus Disconnect support to actually use up more power AT IDLE than older motherboards without S2K support. Of course, the meter is also how I got involved in S2K support in the first place, realizing that the power difference in an AMD system at IDLE/LOAD was nominal (eg. 5WATTS on a 90WATT system).

I also learned that, despite people saying how much lower-power swamp coolers are, that a medium-sized swamp-cooler will still use about 40% as much power as a small air conditioner, that will cool the same area. Perhaps this is an issue of people having old or ineffecient air conditioners that need to be recharged? Never the less, urban legends about power usage abound.

I was equally amazed that my new (fairly large) energy effecient refridgerator is using up an average of about 500watts continually, more than all my computers would if left running constantly (about half are usually off).

And finally, lightbulbs were a surprise. One fluorescent screw-type bulb can use 4Xs as much power as a different brand. The worst (cheapest) fluorescent bulbs use about 1/2rd as much power as equivalent incandescent bulbs.

Re:1 minute resolution is not enough

[zippthorne]

Yes, I failed to mention the effects of DC converters and such.

The board may sample at a million hz and report data every second, but if he just takes average |V| and average |I|, the million hz is useless. If the board is calculating the power at every sample and reporting it to his machine, that's a different story altogether.

From my reading of TFA, it appeared he was only sampling and and multiplying them in his computer to determine the

over the interval. No mention is made of whether the board is capable of a calculation.

I'm still a little unclear on that point: The board has current transducers, but where is it getting voltage information?

Re:1 minute resolution is not enough

[dvogt]

Great discussion! I am of course limited by the capabilities of the board and the board I'm using doesn't provide voltage so I actually pull that in through a different feed (not documented in the article) and compute some of the data in software (with some of the previously discussed limitations). The guys at TrendPoint Systems (the company I wrote the software for) are building their own board that has all of this integrated (including power factor, instantaneous kwh, etc.) The software was designed to have these real feeds available so it will be nice to be able to use them.

As has been pointed out, things 'happen' to work well because most stuff in a house has unity power factor (at least by percentage of total consumption in my case).

Re:1 minute resolution is not enough

[hubie]

Well, he could sample 120 times a second, but then only keep one data point for each three seconds, with that one data point being calculated from the 360 readings taken before it.

I'm not quite sure I understand you. Doing this you'd only be sampling at 0.3 Hz. To satisfy Nyquist, as the other guy said, you'd need to make sure you sample at least 240 Hz to make sure you don't get lots of aliasing and mistake something measured at low frequencies that is really happening at high frequencies.

Re:1 minute resolution is not enough

[dougmc]

I'm not quite sure I understand you.

Ok, let me explain.

Your goal is to calculate the correct amount of power consumed, and to keep some sort of historical information.

You know that measuring the average current and using that is not going to be accurate when the power factor is something other than one (which is most of the time), so what you do instead is measure the current and voltage 120 (or 240 or 4800 or whatever you like) times per second, and then do that for three seconds, and then use those 360/720/whatever datapoints to calculate the average power used during the last three seconds, and then write one row to your database.

So, you've taken hundreds of readings in that three seconds, but only stored one value into your database. After all, do you really need historical data accurate to the 1/10th or more of the second?

This way, you can make Nyquist happy, and yet not give your DBA fits.

(To be fair, I don't think even 120 Hz sampling would be adequate. Apparantly some commercial units do 4800 Hz, which should be adequate.)

Re:Dome? What dome?

[thebigmacd]

I dunno about you, but here in urban Ontario electricity is the most expensive bill lots of us have.

Holy crap!

[pr0nbot]

Surely the next news item has to be "slashdot editor reads TFA"!

Try designing an entire power network (off-grid)

[JimMarch(equalccw)]

That's a whole 'nuther thing.

http://www.equalccw.com/wiringdiagram.gif/

This is all going into the older motorhome I'm renovating :).

Every watt going into and out of that monster 650lb battery (all $1800 worth) will be measured by the Bogart Engineering "Trimetric" device. It sits in-line with the battery negative terminal.

http://bogartengineering.com/trimetric.htm/

The solar charge controller has it's own measuring system as does the inverter/charger but those can be mostly ignored - it's the Trimetric that matters.

Note: "inverters" take 12v DC (or 24v or whatever size battery bank you're running) and convert that to 110v wall juice. Good ones deliver "pure sine wave" power like a very clean electrical outlet. An "inverter charger with pass-through" like my Outback 2812 will take any amount of incoming AC (utility grid, generator, whatever) and pass it through while also charging the battery at 12v in my case. When the utility grid or generator is cut off, it works in reverse, delivering 110v from the battery bank.

My main inverter is this sort of inverter/charger. My secondary inverter is "just an inverter" and smaller at 1100watt, but it's completely isolated from what's going on at the other inverter - a major load like air conditioning or the washer/dryer combo can spectacularly puke and die over on the 2800w main inverter and it'll cause not a single glitchy on the 1100 inverter powering the computer gear, satellite internet, etc.

Anyways. If I wanted to monitor all this with a PC I'd get the Bogart "Pentametric" with PC interface:

http://bogartengineering.com/pentametric.htm/ ...but...why? :)

Re:Try designing an entire power network (off-grid

[JimMarch(equalccw)]

Sigh...remove the "/" on the first link...sorry.

http://www.equalccw.com/wiringdiagram.gif

Rating houses

[typical]

It would be kind of interesting to rate housing/apartments by power cleanliness.

Hoax?

[JeffMagnus]

Maybe I was just burnt too hard on the Alek's Christmas Lights scam, but this description reads like a hoax to me.

I saw this the other day....

[The Slashdolt]

I saw this the other day as a reference from Make magazine. I looked into the hardware and that circuit monitor alone is over $2000 USD. Be aware that this setup is quite costly. Notice the update on the first page that says he is trying to get the company to provide a lower cost version.

Neat idea for Saving Power

[standards]

It would be great if appliances and lamps summed up their own electricity usage over time. All that electricity comes to us by giving a ton of cash to those people who'd prefer to bomb us or raise our oil prices. Minimizing electricity usage is a good idea.

I've significantly used my electricity costs over the past year just by changing my habits. This guy went a bit further and saved even way more than I did. Impressive.

Re:Dome? What dome?

[thebigmacd]

I think I would rather consult the bills of me and my acquaintances than google in this case.

Obligatory

[Safiiru]

Of course when my wife figured out most of the bill was because of my computer gear I had to build her a dome

So what he's saying is that if anyone needs her she'll be in the angry dome?

Is there a difference between...

[qualico]

...the meter and the collected data?
I'm interested in any discrepencies and did not find the information in the article.

I can see doing this if I don't have to pull my panel apart.
Looks like he did that for space reasons.
Do the transducers have to be so close to the breaker?
Can you install them on the outside of the panel?

Anyway, great job.

Re:Is there a difference between...

[Cecil]

No, he did that for getting-a-reading reasons. As he says in the article, if you simply wrap the coils around the cables coming out of the box, you're wrapping them around both the hot and neutral cable at once, so the voltage going one direction cancels out the voltage going the other direction and you get no reading. You'd have to split the cables outside the box, then splice them back together again with the coil around just the hot or neutral wire, and that would look mighty ugly, especially done 8 or more times.

Re:Is there a difference between...

[cr0sh]

Actually, no - reread the article. He does mention that you can read the levels by simply putting the device around the romex, as the hot and neutral return would cancel each other out. So, you have to put the coils on the individual wires. Every breaker box *already* has the wires broken out to each breaker, but in the original 100 amp box he had, where there was scant room for anything, he tried a "dry run" with mounting the coils and could only get 8 mounted before he ran out of room. So, he simply got a bigger panel, and moved the 100 amp service coming from the original breaker box (so now it is basically only serving as a box to hold the meter) to the new breaker box, which has tons more room to allow him to monitor all the circuits. This, however, did require him to move all the circuits over and rewire the new box. He should have, while he was at it, tried to get a bigger service than 100 amps - that is a small service for today's needs. It looks like his house is 1940-1950's vintage, hence the smaller amperage box - today's houses, IIRC, tend to have 150-200 amp or greater service - simply because of all the extra appliances today's houses are likely to have.

Re:Is there a difference between...

[Cecil]

Um, I realize all that. That's basically what I was saying. "Can you install them on the outside of the panel?" is specifically the question I was answering. I was saying yes, you did have to install them inside the breaker box, because doing it outside like I suggested would be stupid. I agree that it's stupid. That's why I described it, in the hopes that it would appear stupid and he would decide that yes, it is better to put them inside the breaker box.

Incidentally, the breaker box is not nearly so scary as some people believe. Most breaker boxes I've ever seen have had seperate compartments for the main breaker and the circuit breakers. As long as you leave the main breaker panel covered and closed and the main breaker itself turned off, (and you MAKE SURE YOU TEST THAT IT'S ACTUALLY POWERED DOWN using a voltmeter on the circuit breakers) then as long as you keep your wiring confined to the circuit section of the box, you have no chance of accidentally touching hot wire. They are specifically designed this way to make it possible for homeowners who take the proper precautions to add new circuits and change circuit breakers in relative safety.

Shunt Trips, Contactors, Opinion and CircuitView

[wintermute1974]

Instead of just monitoring let's modify the system so that we can turn circuits on and off remotely as well as being able to monitor usage.

This is already possible. Many breakers can be bought with a shunt trip mechanism. Essentially, you provide a small current into the shunt trip, and it will cause the breaker to trip. So yes, you can turn the power off. If you want to turn it back on, you have to walk over to the panel.

Are there breakers with two shunt trips, one to turn it on, another to turn it off? I have not seen them, but they might exist.

Another solution would be to put a bistable AC contactor in series with breaker. Then you could energize the contactor to turn power off and on each individual circuit without using the breaker.

Most slashdotters could use a trip to a power plant or an electrical utility. After seeing battery chargers the size of refridgerators, it would help put the piddling amount of AC trickling through house plugs into perspective.

Incidentally, that software looks amazing. I want to wire my house now, just to watch my power consumption graphs wiggle by in real time. With help of a close personal friend (Google), I was able to find the company, called TrendPoint which makes CircuitView.

Re:From my knowledge....

[Craigj0]

How does this passive device mesaure the current with out affecting it?
1) Is is magical, no it creates a samll load on the circuit
2) this can change the pwoer factor
3) the motor could be an induction motor
4) a change in power factor could change the efficiency of the motor causing it (or the wiring) to heat up more than usual.

Unlikely but it could make a difference.

Re:Joists (a little OT - about dome)?

[gregm]

He probably only cut one joist and he probably put in 2 short joists between the adjacent joists and attached the ends of the joist he cut to these little joists. This spread the load from the joist he cut to the adjacent joists. Not a perfect soltuion but it's done all time. To use the terminlogy around here 10 years ago... He boxed it in. I used to do remodeling for a living.

Re:From my knowledge....

[Anonymous Coward]

1. Is is magical, no it creates a samll load on the circuit

   It creates a very small additional inductance in the line. Putting your DVM onto a circuit creates a very small additional conductance in the circuit. Both have very small effects if you are using them appropriately; you cannot insert a sensor and have zero effect.

2. this can change the pwoer factor

   I'm certain that it does. I'm also certain that you'd need sensitive equipment to measure the difference.

3. the motor could be an induction motor

   COULD be? Certainly is, and it's a capacitor-start unit to boot. Might not have a running capacitor, but I'm not up on what's in dryers these days - I suspect it did (see below).

4. a change in power factor could change the efficiency of the motor causing it (or the wiring) to heat up more than usual.

   Two things wrong with that hypothesis:

   • If the sensor caused the motor to overheat, it was way too close to its ratings anyway.
   • An overheating motor is inconsistent with the failure, which would have shown a very slow change due to increasing winding resistance until the thermal cutout opened. The failure of the motor showed marked abnormalities in power consumption until final failure, more consistent with progressive breakdown of a run capacitor.

If you have any speculations based on the available evidence, go ahead and post - I personally think you're just another bloviator.

re:Another way to do it: read the meter: + or - ?

[Locutus]

But how would you tell if your meter is going backwards or forward? ;-) Great hack but it won't work for systems with grid tied solar electric systems. It's too bad because I liked that your system actually reads the power companies measured usage.

If I could tell the direction, then I could take the difference between the solar generation and the amount of negative power usage on the meter. That would then be the actual energy usage.

LoB

mandatory wtf....

[Anonymous Coward]

Hardware: Zero dollars
Software: Zero dollars
Linux box: Zero dollars

Explaining to your wife that after hours of development you've built a device that proves the most power hungry appliance in your house is the damn power monitoring system itself: Priceless

Re:mandatory wtf....

[CFMLSpecialist]

Haha, thats great. Either way, she will be happy as long as you don't accuse her blowdryer of anything...

Seperation of High Voltage/Amperage from Low

[MonkeyBoyo]

I am not expert on the details of various building codes, but I am familiar with the intent of electrical codes that try to prevent high voltage/amperage wiring from being in the same enclosure as low stuff. For example, codes encourage 120 V wiring to run through conduits but prohibit running low power lines (such as phone) to run through the same conduits. Why? Because some stupid accident might cause the wires to become cross connected and blow out devices or start a fire.

Mounting an uncovered PCB (printed circuit board) that communicates with a computer within a 120 V distribution panel is a very big no-no. What if geek hubby is out of town and wifey experiences a power problem and calls in a yellow page electrician to fix the problem? In the worse case the "electrician" accidently drops a tool that winds up connecting 120 V to the computer circuits and starts a fire in the server room.

Building codes are designed as protection from stupidity - not only the stupidity of the the original builders but from the stupidity of those called in to fix problems.

To anybody who wants to do anything similar - it makes sense to put the current sensors in the distribution panel, but please rout them out to a seperate box that sends their info to a computer.

Re:Power Monitoring is cool, but...

[belg4mit]

Yup, that's why in places with a mixed power supply and deregulation your "battery bank" is the grid...
you're credited for your excess and you can consume
it in proxy as dirty-power later.

Resolution of graphs

[eXocomp]

This is pretty cool... it'd be interesting to have graphs like this for my own home, and might even encourage conservation if I could see how much each thing was using. Too bad it's only of achedemic interest (I'm not about to go and install this, but it's impressive what this guy has done).

One thing I'm kinda puzzled about is the resolution of the graphs. If the hardware has a 3 second resolution, why only take averages at 1 minute fixed intervals? A shifting average (like in this experiment of mine) would make for prettier graphs and I doubt it would take much computation power (and might even reveal details that would otherwise go unnoticed).

I noticed that the graphs shown in the article don't even have a 1 minute resolution; for some reason they are limited to a 4 minute resolution. Seems silly to have such fine measurement resolution and throw it away in the graphs. :-\

Re:Resolution of graphs

[dvogt]

I noticed that the graphs shown in the article don't even have a 1 minute resolution; for some reason they are limited to a 4 minute resolution. Seems silly to have such fine measurement resolution and throw it away in the graphs.

Yeah, I didn't really explain that since I didn't want to bog down too much in the software description. The circuit view has two graphs... the one on the top represents the data in the dark grey section of the bottom graph. This makes it easier to navigate (by dragging the grey area) and not have to zoom in and out all the time. The magifying glass buttons are for zooming in and out (which obviously changes the resolution of the view). However, as I think someone else guessed correctly, the data is sampled every 3 seconds and then min/max/mean is rolled up for that minute and stored for a year. All the graphs are derived from this data (although obviously there are other rollup tables for performance reasons as you get to viewing months at a time). The view in the screenshot is not zoomed in completely.

Re:Resolution of graphs

[eXocomp]

I didn't realize you'd be replying here yourself. :) Thanks. The ability to browse the data at two zooms simultaneously indeed looks useful. But that doesn't answer my question...

I don't understand why the top graph doesn't make full use of pixel resolution. In the 6 hour view, every 2 pixel interval could represent 1 minute. But instead, every 7.8 pixel interval represents 4 minutes. Wouldn't the medium-zoomed rendering still be acceptibly fast if done at maximum resolution?

Re:Resolution of graphs

[dvogt]

I see what you're asking... good question. There are two reasons for this:

1. The interface is a java applet launched from a web browser. It is commonly used over home dsl + vpn for network administrators to remotely monitor data centers, etc... so we made an effort to minimize the network payload associated with opening multiple concurrent graphs. By fixing the number of data points in a view (regardless of pixel resolution) we can greatly control the network overhead (which is good since they all update in real time).

2. I've been building stuff like this for a while and more often than not the users get confused by the apparent 'fuzziness' of a full dataset graph. Not that this is my preference, just a common thing we run into. Which is fine since it makes the first problem easier to solve but obviously results in some intersting visual artifacts (which no one ever seems to complain about).

Re:Resolution of graphs

[eXocomp]

Thanks, it makes perfect sense now. :-) Even if a user had broadband, there'd still be #2. Though if I were using your software I'd request a "maximum fuzziness" toggle. ;-)

Sadly your "how to" link is broken

[waferhead]

Results in a 404. /. effect already?

Re:Sadly your "how to" link is broken

[dvogt]

Thanks for letting me know... Someone out there should write an article about what it's like to get slashdotted... I know I didn't know what to expect. I had to do a bit of live editing of the site to push things through Coral Cache because things were bogging down. This link had a typo (but it's fixed... thanks again).

Oh my Lord.

[CyricZ]

That is sickening what you encountered in your sister's home. Indeed, I hope the future owners of this particular fellow's home do not fall victim to his electrical hackery.

Re:Oh my Lord.

[plover]

My sister bought the house from a widow in the mid 1990s. I don't know if the late husband was the perpetrator of the wiring I encountered, but if so at least the rest of humanity should rest a little safer knowing this was the last house he threatened. As I recall, the existing dangerous wiring I was working with was Romex that was date-coded 1989, making it quite likely he was the guy.

Actually, given the state of the wiring, I wouldn't be surprised to learn he died from electric shock! :-)

Codes come from where you live, not the utlity.

[cbelt3]

"ou pull your house off of the grid, and you can do whatever you want to with the wiring in your house.
"
Well, no. Your connection to the grid has nothing to do with electrical codes, zoning laws, inspections, building permits, etc. Those rules are all established by your local despotic government. The more despotic, the more the rules. The more unionized the area, the less likely you are going to be able to do any work other than plug in a UL certified extension cord in your own domicile.

Oh, and the 'safety codes' ? They come from the Insurance Industry, NOT government or the Electrical Power industry. Governments can choose to accept the codes or not. Or take the code and then add all kinds of spiffy crap to it to make sure their idiot brother-in-law who invented the lefthanded wattsamatteru switch gets money out of the deal.

Just thought you oughta know, before you go and do something that will get your house condemned.

Ooops, something STOPPED running!

[martio]

An alarm that can detect when something ISN'T functioning properly (such as a 'fridge or freezer, or computer room A/C circuit) might be a more solid justification for the investment. Seems to me you could make a transducer pretty easily, though; get some small ferrite cores and thread 'em up. You'd need to calibrate them against whatever A-D device you're using (PIC's a good choice). Anyway, this is bitchin'. The raw data becomes interesting when you can compare it at a circuit level to similar circuits in other similar structures. "Am I paying more than average to run my 'fridge?" "How does running ceiling fans affect A/C power consumption in a house of this size?"

Re:Ooops, something STOPPED running!

[dvogt]

I've often wondered how hard it would be to determine which devices in your house were turned on based on the overall circuit data. Certain types of devices have very unique signatures (fridge, dryer, etc...) It would be neat to be able to 'guess' which device is on or off (or failed as you point out) based on analyzing the raw data.

Here is a shot of my fridge: http://209.10.40.245/circuit/fridge.jpg

As you can see it's very easy to find this within the data. As you can see from the image I've used cursors to determine the frequency of the compressor cycles. If you look at the cycles over a day however you can see them compress and expand based on the outside temperature.

I suppose this would lead to the next level which is to pre-cool in the morning when cycles aren't so long and electricity is cheaper (depending on where you live) and run less during the day. Overall I would guess that you could save additional energy (certianly extra money) if you could control stuff like this.

Re:Ooops, something STOPPED running!

[vthome]

Jeez, man, you'll definitely find a sympathetic soul here...

This is one of the coolest things I have ever seen

[multiplexo]

on /. It's so fucking great. I have to do this at my house. Seriously though I think that this guy is onto something. If you had some kind of standardized panel you could build the CTs right into the circuit panel. Then you could hook them up to a dedicated controller to give you the information. Or perhaps you could build smart outlets that had a built in TCs in them like a smarter X10 outlet. I think people would buy this, energy consumption is becoming more of a concern for many homeowners.

Re:Joists (a little OT - about dome)?

[ouphd]

If you study the first pic in the article where he shows the installed dome from above, you can see that this is exactly what he did. See http://209.10.40.245/dome/images/IMG_1244c.jpg

Re:From my knowledge....

[crucini]

I'm not saying the current sensors caused a problem. But:

For that matter, how could he screw up the circuit in such a way as to blow the motor without blowing it up immediately? You sure can't wire the circuit to 220 volts without doing something very funny with the common wire.

Imagine a long run of conduit from a panel to a room. In the conduit are one netural and two hots, on opposite phases. In the room are two machines - one, on the first phase, draws 20 amps. The other, on the second phase, draws 1 amp.

If the neutral wire has 1 ohm resistance, the first machine sees 101 volts and the second sees 139. Many variations on this ideas are possible.

Re:From my knowledge....

[dvogt]

Normally I stay out of these but the article had a typo so I'll clarify. It was actually the washing machine not the dryer that failed. In addition the motor had failed several times before (thermal shutdown) prior to installing the monitoring system. The repair guy I kept calling out said it was fine (since by the time he got there it had cooled and started again). Anyways, the last time it didn't start back up.

Re:Joists (a little OT - about dome)?

[pocopoco]

Be very careful doing this sort of thing if you ever want to resell your home. I sold a home I inherited recently that had a small pull down stair installed in the ceiling to the attic. This meant a joist was cut and the opening boxed in.

The buyer's inspector was claiming this counted as something like 5-10k damage as it violated the engineering plans/inspections/whatever for the house. God knows what my real estate agent did about it, but that number dwarfs the 50$ cost of the dome mentioned in the article.

low cost circuit monitoring using the micrometer

[n3r3us]

I had a similar goal to the author in monitoring the circuits of our house (we wanted to gauge production - solar panels against consumption - branch circuits to understand areas in need of optimization). After much research, we ended up installing two micrometer units - http://www.micrometer.com/

Chris Clements aka mr. micrometer - has done a great job of putting together a reasonable priced solution for power monitoring.

As a bonus, the micrometer have a straightforward ASCII interface which makes integrating the data a snap. LMK if you want any additional info, I'm very satisfied with ours.

cheers.

-Ophir

Re:From my knowledge....

[crucini]

OK, thanks. I really wasn't accusing you of anything - just trying to explain to grandparent that yes, a wiring error can result in overvoltage as well as undervoltage, and that it can be more subtle than sending 240 to a 120v device.

Separate Voltage Measurement

[zippthorne]

So have you noticed the average voltage to vary significantly from the expected 120V?

as an electrician ...

[freaker_TuC]

I studied for electricity and the way he build this setup is quite nice, only the controller board would not be legal in the same circuit-breaker-board, in Europe...

We got strict rules what can be and what cannot be in such boards, and putting a low-voltage board with a high-voltage circuit would not be approved by our electric companies.

Although, if this would be hanging seperately, with exceptions to the Ampere clamps, it would be a nice setup or even a nice addition to check the usage of your entire house, although I think about 12 circuits would already be enough ...

I wonder if this equipment is for sale in europe. I used to use my own tools together with the K8000 of Velleman to measure humidity, temperature and load; although the board is a little bit too big to use + its slow.

Any tips to get this kind of system in Europe?

Re:Another way to do it: read the meter: + or - ?

[Woody77]

If you're gride-tied solar, doesn't your inverter track this for you anyway?

The Trace units I've been looking at have computer connections (IIRC).

Re:Another way to do it: read the meter: + or - ?

[Locutus]

The SunnyBoy unit I have has an RS232 opto-isolated interface that I built for it and either way, it only measures what gets put INTO the system. What somes in off the electric lines, or goes out is not measured or measurable at this time.

Are you saying that the Trace systems wire in between the grid and the home? I wouldn't think they would do that just for installation simplicity and/or dealing with the loads the existing system must support.

LoB

Re:Another way to do it: read the meter: + or - ?

[Woody77]

Yeah, they do. They're not cheap, either. Basically, you hook up your feed from your battery bank, and your mains connection from the power company (and optionally a generator), and then it figures it all out. Runs off the panels when it's bright out, as the panels are connected to the batteries, so as long as the panels are charging the batteries, it can supply current to the house from the panels, once the panels can't supply enough current to charge the batteries, the batteries start draining to the inverter (this is all controlled by the battery manager). Then the inverter drains down the batteries, and when they fall below a threshold, it starts pulling from the A/C mains to supplement, and recharges the batteries.

The inverter keeps itself fully synchronized off the A/C mains when they're present, and when they go away (as they often do in my area), then it uses it's own internal clock to keep the waveform correct. When mains is down, it stops backfeeding the mains (for safety of everything involved), and will recharge the batteries off the generator, if needed.

When mains comes back up, it slowly adjusts it's clock to match, and then switches over to running off the mains until the batteries are fully charged.

Re:Another way to do it: read the meter: + or - ?

[Locutus]

Wow, sounds like a nice setup but if a basic SunnyBoy goes for around $2k, I'm guessing the unit you're talking about is in the $5k-$10k range. Nice but definately overkill for Panel-only grid tied systems.

LoB