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Author Topic: network enabled home power monitor.  (Read 3281 times)
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Hello,

I am new to the whole Arduino experience, and I want to construct a reliable home power monitoring system.
I've been researching on the web and practicing basic stuff with actual arduino.
The power monitoring system will be non-invasive, and it will measure 110V/50HZ/Single phase, 2 wire(United States). Also, I want it to be network enabled, so I can monitor the real-time power usage and history with my computer and phone.
I have no idea where to start except that I need to use current transformer with arduino.

Anyone has successfully completed a project like this?
any advice on safety with current transformer(i am new to this whole electrical engineering)?

thanks.
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I don't think you connected the grounds, Dave.
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any advice on safety with current transformer(i am new to this whole electrical engineering)?
Don't.
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Chester, UK
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I've seen projects where people have detected the flash of an LED on their meter that indicates an amount of energy has been used.  I'm not sure that a current transformer is a good idea for a first project as I'm led to believe that they can pose dangers if used incorrectly.
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If your system involves lethal voltages/life critical/flamable elements - you probably shouldn't need to ask.
The Arduino != PC.

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I have no idea where to start
Start with posting a picture of your KWH meter ...

Are there moving parts to be seen that for example could reflect light (black/white disc), or a blinking led or ...
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Seattle, WA USA
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and it will measure 110V/50HZ/Single phase, 2 wire(United States).
Where, in the United States, are you finding 50Hz power?

As Grumpy_Mike says, don't.
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I don't think you connected the grounds, Dave.
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sp. "Grumpy AWOL"
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sp. "Grumpy AWOL"
Oops. Sorry about that. The advice sounded so much like Grumpy_Mike that I didn't scroll back to double check. It's still good advice if you have to ask how to do it.
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If you do decide to proceed , here is a project like you describe using current transformers and a WiShield on the Asynclabs forum.
http://asynclabs.com/forums/viewtopic.php?f=18&t=78&sid=fd36d59fad1ebf0ad977579f6312e407

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Topsham, Vermont USA
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Hundreds of people were using GooglePowerMeter stuff.. the Google part is being retired as a project but there's lots of hardware out there.

See: http://www.google.com/powermeter/about/index.html

I'll post some hardware stuff when I find it...

The "sense your power meter without opening anything" approach is a good start.

But MANY people and projects are doing this, so calm down the Fear Factor.  Just follow Universal Rule #1:

Don't Be Stupid!

Regards, Terry King
...In The Woods In Vermont
terry@yourduino.com
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I have done exactly what you're describing and so have many others.  Current transformers are extremely easy to install and safe, provided you simply turn off the power when you install them.  They are low voltage so getting the wires out of the mains box is easy.  And, then, this is almost the only place you deal with wall level power.

Personally, I put the current transformers in myself while the box was live (you don't have to disconnect anything) and it took about 15 minutes from walking up to the box to walking away with the wires already run inside the house where I put the electronics.  I used a wishield, which isn't produced anymore and later switched it to an XBee and did the web interface on another Arduino inside my house.  My mains box is on the side of the garage about 50 feet from the Arduino that interfaces with the web.

I used a wall wart to power the arduino and have another step down transformer to measure the mains voltage.  I have the project posted and the code I am running to measure the power.  There is also a link there to other folk that are doing similar things at an open energy project in Wales.  They have created a library for the Arduino IDE that does most of the work for you.  I don't currently use the library because it didn't exist when I started the project and why fix something that is working?

How easy it is to do depends on your skill level and interest.  It took me a month or so to get the various parts and have a prototype running on my kitchen table.  I split an extension cord and put the current transformers on it to test.  I used a toaster (1500 watt) to create a load I could turn on and off for measuring power; comparing the various readings to a kill-a-watt I picked up at Home Depot.

So, what amperage drop do you have to your house?  Mine is 400 watts, split in the box to two 200 watt feeds and I am only using one of them currently.  It was the biggest drop I could get in a residential area and I didn't want to come back in a few years and have to upgrade.  This number will determine which current transformer you need.

Of course, this got me started on handling devices around the house.  Originally, I simply showed the power level on a web page.  Then, I wanted to be able to see it any time so I made a display that would show the power and mounted it on a wall.  Then I wanted to record it over time so I put in an interface to Pachube.  Then I ........  Needless to say, I'm still working on it and incorporating lots of things around the house.  I even went so far as to replace the heat pump thermostats in the house with arduinos and have full control of my heat and A/C over a web interface.  Once I could measure the power and see what was actually going on, I installed a solar hot water heater for the house water, solar heater for the swimming pool, inside and outside temperature sensors. 

The code, hardware and techniques are all documented on my blog at http://draythomp.blogspot.com/, the tabs at the top link to the various projects.  It isn't hard, it isn't any more dangerous than any other project around the house and it's a heck of a lot of fun.  Currently, I'm saving over U$100 bucks a month in power bills, but I use electricity for everything here in the desert.
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Oh, every time you talk about touching the mains, it sets off an immediate reaction in folk.  You start getting replies that tell you how horribly dangerous it is and how you'll kill yourself and void your home warranty or insurance.  While you may kill yourself, it probably won't be from messing with the current transformers and when I checked with the home insurance folk, they said that it was a problem only if it didn't meet code.  Since there is no code on low voltage wiring where I live, no problem.  It's roughly the same thing as putting in a new doorbell transformer, except much safer since you never actually have to touch any of the wires.

And, the cardinal rule, if it scares you, turn off the breaker.
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Oh, every time you talk about touching the mains, it sets off an immediate reaction in folk.  You start getting replies that tell you how horribly dangerous it is and how you'll kill yourself and void your home warranty or insurance.  While you may kill yourself, it probably won't be from messing with the current transformers and when I checked with the home insurance folk, they said that it was a problem only if it didn't meet code.  Since there is no code on low voltage wiring where I live, no problem.  It's roughly the same thing as putting in a new doorbell transformer, except much safer since you never actually have to touch any of the wires.

And, the cardinal rule, if it scares you, turn off the breaker.

Your entitled to your opinion. My policy is that anyone asking questions about working with or around AC power gets some version of "If you have to ask, then you shouldn't mess with it, get professional assistance".

Lefty
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I don't think you connected the grounds, Dave.
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And, the cardinal rule, if it scares you, turn off the breaker.
There is no breaker from the utility supply here in the UK, just a fuse with a seal.
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And you folks accuse me of evangelizing?   First, in any legal mains installation in the US (where the OP said he was), there is a main cutoff between the meter and the house supply rails.  Here is mine:



See the 200A breaker at the top and the house supply breakers underneath?  Notice also that the circuit transformers wrap around the insulated wires from the main breaker to the house rails.  They snap around the wires and nothing, absolutely nothing has to be disconnected.  I had to put a couple of plastic ties on them so they wouldn't slide down the wires.  Those wires are in excess of a half inch with about a sixteenth of kynar insulation on them.  If you turn off the 200A breaker, there is no power down there to worry about.  Electricians do this all day, every day, a reasonably intelligent person can be expected to do it once or twice.  Other boxes have slightly different configurations, but this is the general idea.

So, no meter removal, no calling the power company, no need for a U$100 an hour electrician that will turn off the breaker for you.  If one has concerns in this area, just look at it and use a little common sense.  Maybe the OP needs to call an electrician in his particular instance, but I'm certainly not going to rant at him about how unsafe it is without seeing it.  I've installed a large number of electric water heaters and they are exactly as unsafe as this situation.  Turn the breaker off, do the job, turn it back on.  Turn off the switch, change the light bulb, turn it on.  The wires are bigger and scarier, but the voltage is the same, enough to kill you if you don't pay attention.  I only know a few old ladies that call an electrician for a light bulb even a broken one.

As for my experience, how the heck can anyone determine that?  Maybe, I am an electrician, maybe not.  And, the reason I don't have a ton of bad experiences is simply because I take precautions and pay attention to what I'm doing.

And lastly, people do die of electrocution.  But we can all look up the stats on that to see what the odds are.  We can also look up the stats on every other way people die and compare them.   McDonald's represents a more significant threat to people if we want to look at the stats.

But telling someone not to do it because you won't is just silly.  Give them the information on what is going on and let them make an informed decision for themselves.  They may come up with a new, better way that none of us thought of.
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I don't think you connected the grounds, Dave.
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But telling someone not to do it because you won't is just silly
So is suggesting that you're in the US, and the supply is 50Hz.

You may not die from electric shock from wimpy US 110V, but the current is quite enough to give you severe flash burns (or worse) from your vapourising screwdriver or pliers.
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Do not send technical questions via personal messaging - they will be ignored.

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