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DIY Circuit Monitoring

kondra.jpgOne rule of thumb is that it's easier to make changes when you know what you're changing -- that's one of the goals of "making the invisible visible." In particular, if you want to figure out how to reduce the amount of power you use in your home, you need to know where the power is going. In the past, we pointed to the Kill-A-Watt as a handy device for measuring the power consumption at a single outlet -- but what if you want more information than that?

David Vogt at Kondra Systems decided to test a power usage monitoring system he was going to implement for a corporate client by installing it in his own home. He took abundant pictures and chronicled his efforts at his website. The project required essentially rewiring his home -- but as a result, he ended up with a system that could track power consumption along every circuit, with usage graphs and over-consumption alarms.

His project may be too complex for most of us, but it does suggest an interesting alternative.

If you don't know what you're doing, duplicating the Kondra home rewiring project could electrocute someone or burn down the house. So where's the home power monitoring that's more sophisticated than a Kill-A-Watt but less complex (and potentially deadly) than the Kondra example? A quick googling didn't come up with anything suitable, so here's a proposal:

I'd like to see "smart" power outlet units able to track usage and report that to a recording device. The smart outlets would require a fairly simple (and probably fairly inexpensive) chip, and could send the data to the main monitor using "in-building broadband-over-power-line" technology. In-building BPL is able to run IP networking over existing electricity wiring; the monitor device could therefore function plugged into any outlet in the house. The recording device could have a data link (USB, ethernet, WiFi) to hook up to a computer for data display and analysis.

This would then allow for monitoring over time of every smart outlet in the house, making it possible to identify points of excessive use (whether for controlling overall consumption or avoiding overloading a circuit). More advanced versions could even allow for remote control of power throughput, turning the power on or off as needed (with a timer, or as a way of controlling "phantom use").

So, what do you think? Is this plausible? Useful? Has someone already done it?


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Comments (9)

Its a great idea (much like monitoring fuel consumption in cars) and I'm sure its technically feasible.

One extra element I'd like to see (which you've touched on in some of your "smart grids" type posts before I think) is the ability to show how much money (as well as power) the building is consuming, which would really help people get the feedback needed to adjust their consumption intelligently.

Where power usage is charged at variable rates depending on peak / off peak time bands, this can be a bit of a challenge, as you then depend on data from outside the closed system you are talking about in the post.

I'm not sure if anyone is doing this but one friend of mine here did have discussions with a power company about smart meters that both tell the homeowner how much power the house is consuming and also send the meter data to the power company.

This would be a great solution from a techie point of view but the basic economics make no sense to the company - manual meter reading is pretty cheap compared to the hardware costs and the companies don't have much incentive to encourage users to reduce their consmption either (though that may change as the system struggles to handle the increasing peak loads we are seeing).

Off thread:

Not a big deal, but in IE what is supposed to go in the right hand column is being dropped all the way down to the bottom.

I think I mentioned this before and I think you had at one point fixed it, but the problem appears to be back.

Just wanted to give you a heads up. Post on.

Jason Trout

Hmmm: reading this post together with the CUWin post (http://www.worldchanging.com/archives/003133.html), and as I'm currently working on whole-of-community ideas for next generation energy solutions, is it possible to see old computers being used as smart networking and grid agents, connecting the idea of a wireless community with community energy management?

I agree it is very helpful to change by "making the invisible visible". One thing I like to see is a meter on every car showing the fuel cost for every trip.

The formula of fuel cost is just simple math:

fuel price x gas mileage x distance travel

When I suggest to people to buy a car with better mileage or make a shorter trip instead of driving around town to save cost, I find people usually think very little of money. So I resign to the fact that people just want to drive their big SUV wherever they want and money is just no subject. On the other hand I am surpirse to find people react very strongly to gas prices. Small price increase are enough make drivers furious and makes talk of the town. When you notice gas price are often quoted in cents, you'd find people are literally pinching pennies.

So what make the difference? Posting gas prices prominently invite people to compare and shop around. So perhaps a trip cost meter would help inform people and hopefully them to make smarter decision. Let every car has a meter and clicks like a taxi would. The further one drives the more money one realize spending. It should also help avoid illogical decision liking making a long trip to some gas station for slightly cheaper fuel. Hopefully that would help them to react to fuel economoy like they would react to gas price increase.


Regarding the comment about showing actual price information, I wrote software to do that as well (although not in the product I wrote the article about). I takes into account all the variable pricing informaiton along with all the penalty factors and limits. It was setup as a budget based system so you would enter how much you wanted to spend that month and it gave you a daily budget (which adjusted in real time). If you went over one day, it would adjust your budget for the remainder of the month, etc... It had a running total, but more interestingly, the graphs (similar to the ones in the article) could be switched to dollars instead of amps. Very interesting stuff as you start taking into account variable pricing. A flat line in amps view looks much different in dollars view. Even without variable pricing it goes up and up at the end of the month as you progress into the penalty phases of the pricing structure, etc.

Nick Lombardi:

Interesting post, and in fact, I believe I have a friend who is about to work for a new company that essentially is developing Intelligent Energy Management systems. I haven't gotten the nuts and bolts from him yet, but the website has a lot of information about what they are trying to do.



An aside: one of the nasty side effects of BPL is the interference it creates in the radio spectrum for everyone from amateur radio operators to emergency/first response teams.

Ack -- that's not good. Is that a characteristic of all BPL, or is it something that occurs just with some implementations?

Would it not be easier to make replacement modules for standard RCD fuses as this would let you easily monitor the state of the individual rings in your house rather than needing to apply filters to every single device. Could even monitor the state of the fuse as well and enable a remote reset of flipped fuses. This could then be easily extended with individual outlet based filters at a later date if required.

It would also be quite interesting to let the devices monitor the quality of the current that is being supplied - spike analysis and average voltage monitoring?

Finally if you wanted to run a wind generator or solar panel system then this should integrate into the network as well so that the system is aware of how much power is being input into the system from different locations. This could all tie together into something that can make quite sensible informed judgements about when to switch on or off power to optional appliances.


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