Home Power Monitoring

[Talguy]

I just thought of an idea to monitor my homes power usage. I am not the most experienced circuits hobbyist but I am learn and quick. Basically I want to modify all my outlets in my house to a custom smart outlet that will monitor the power usage at the outlet and send the information to a server for further processing. I would also like to use power the microcontroller over ethernet. My question does anyone know where I can find a rogowski coil that is small enough to fit in an existing electrical outlet box with little or no modification for it an the uC? I don't know a whole lot about uC and would like to go the pic route. What would be the smallest footprint C based chip that could handle the measuring of the coil and Tx/Rx on ethernet? Also, if I stuck everything into the outlet box (modified or not) do you think I would have a lot of interference from the powerlines.

 

[MikeMl]

Are you planning to wire all the modified outlets to an isolated (from the AC line) low-voltage cable that communicates with the central server, or are you trying to send ethernet protocol using some sort of RF modulation on the AC line?

 

[bychon]

If you get it working, please don't tell the government. If they find out about this capability, they will start monitoring how many times I open the refrigerator or turn the light on in the bathroom. **broken link removed** All in the name of stopping terrorists, of course.




(Does anybody on this forum have a sense of humor?)

 

[Talguy]

MikeMI, I plan on having the a ethernet plug on the side of the outlet to send out the information. I also want to power my monitoring circuit over the ethernet cable.

 

[MikeMl]

So does that mean that you will have all of this cat5 cable running around the floors of your house, or are you going to run wires in the walls?

So all you have to do is to monitor the voltage Between Line1 and Neutral and Line2 and Neutral at one place in the house, and then monitor the current(s) to the respective branch circuits. You can do the vector multiplication (V*I) to compute the power in the central server, rather than doing in each outlet.

If I were doing this, I would put about 20 CTs (current transformers) in the central electrical panel (not in the outlets). There you can undo a single screw, pull the wire out of the breaker, thread it through the CT, and then reconnect the wire to the breaker. A single high-end PIC placed there could monitor the whole house without touching the outlets or walls.

You give up monitoring each individual appliance, but there are usually only two or three things plugged into each circuit controlled by any given circuit breaker.

Hey, I should patent this idea.

 

[nickelflippr]

Hey, I should patent this idea.

You could, but I remember installing just such a device in a house built back in the energy crisis of the late 70's, early 80's. The power company was threatening to change everyone to a time of demand use billing, so everyone was freaking out. As it was, they never followed through, and I was out $500 for something I didn't need.

The device installed as a sub panel to the main breaker box. It had 4-5 (or more?) ct's installed on the major appliance and heating circuits (I had electric baseboard heat), which will always have a dedicated circuit. You set the time period, max load for that period, and a priority for load shedding. Go over your power budget, and it would start de-energizing your low priority circuits first, like the clothes dryer, then the bedroom heat, and so forth.

 

[RCinFLA]

You should do a preliminary survey to prioritize your plan. Measuring outlets will likely only cover a minority portion of your consumption.

General order of power consumption is:

Heating (if electric)/Cooling -- Air conditioners are usually always greatest.

Hot water heater (if electric)

Refrig.

Cooking (if electric)

Washer/drier.

lights

TV's / electronics.

There is an inexpensive unit called 'Kill-A-Watt' meter that can plug into outlets that gives power and power factor measurements. You can buy them for about $25.

 

[canadaelk]

Bychon re post #3:
You turn the light on? Why?
And to your Q: I like to think so!

 

[bychon]

The exhaust fan is connected to the light switch and it makes enough noise to cover the other sounds. **broken link removed**

 

[Talguy]

My main goal for this idea is to find the highest power consumption zones in my home and measure the total power my home consumes. This information is then transmitted to a server for further processing and/or graphical rendering. Right now I am focusing on the amount of power my home theater system consumes. I don't know a whole lot of about power factor but was reading up about it a little. If i was plugging and unplugging device on a outlet I was measuring would that cause accuracy problems when meauring the amount of watts consumed.

 

[Nigel Goodwin]

The exhaust fan is connected to the light switch and it makes enough noise to cover the other sounds. **broken link removed**

Assuming there's no natural ventilation in the bathroom it's a legal requirement in the UK to have a working fan, which also has to stay on for a certain time after the light is turned off.

 

[bychon]

Apparently the manufacturer of fan-staying-on timers hasn't bribed enough congressmen to make that a law in the U.S....yet.

 

[Sceadwian]

Talguy, there is absolutely no rational for modifying every outlet in the house to determine your general power usage patterns. You can guesstimate and figure bulk power usage simply by looking at the nameplate on any device and determining it's ontime vs offtime. In the day it would take you to figure this out it would take you a month or three to learn the programming and electronics required to create a power monitor. If you want detailed information about a specific devices ACTUAL real world power usage you can buy modules that plug into the wall that you plug the appliance into that will give you this information. Hardwiring an entire house to a centralized server for this information is... overkill. Much more can be done much less complexly by simply thinking about your energy usage rather than looking for a technology to solve the problem.

 

[foobillious]

It might be worthwhile checking out the tweet-a-watt project. google is your friend.

 

[nickelflippr]

There is an inexpensive unit called 'Kill-A-Watt' meter that can plug into outlets that gives power and power factor measurements. You can buy them for about $25.

The Kill-a-Watt is a great tool. Stick that on a 20 year old fridge for a day, and the energy savings light bulb comes on rather quickly.

 

[bryan1]

The Kill-a-Watt is a great tool. Stick that on a 20 year old fridge for a day, and the energy savings light bulb comes on rather quickly.

Well my 40 yr old shed fridge which used to be the house fridge was put along side 14 other much newer fridges for testing, the old fridge came out way in front on power usage/coldness and the one that came last was the most expensive new fridge. I've since had a 24 volt DC 540 litre fridge/freezer custom made for the house which runs off it's own RE system and the 40 yr old fridge is on my shed RE system keeping my beers cold.

As far as power saving goes try living off the grid for over 7 years and using power like we normally would on the grid but with less power hogs of appliances. Back 7 years ago people thought we living in 3rd world conditions not having the grid now they come knocking asking how they can do it.

I must admit those kill-a-watt meters are perfect when shopping for new appliances as I hook one up to the item I'm looking at and get the real figures on it not the advertising crap on the front.

Cheers Bryan

 

[nickelflippr]

Well my 40 yr old shed fridge which used to be the house fridge was put along side 14 other much newer fridges for testing, the old fridge came out way in front on power usage/coldness and the one that came last was the most expensive new fridge. I've since had a 24 volt DC 540 litre fridge/freezer custom made for the house which runs off it's own RE system and the 40 yr old fridge is on my shed RE system keeping my beers cold.
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Cheers Bryan

Yes, making general statements is fraught with exceptions. That old fridge of yours must have an outstanding compressor and insulation package. What brand and model is it? Link? It must have been a remnant from a bygone era, when quality and serviceability was a virtue.

In my case, going with a new energy star refrigerator was like 2.5-3 times more efficient than a crummy energy hog from the early 90's.

 

[RCinFLA]

Adding a Zigbee wireless data module to a Kill-A-Watt meter.

Tweet-a-Watt! A safe and simple wireless power monitor

 

[kuthubu.niyas]

hmmmm...why do this happening to me

 

[kuthubu.niyas]

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