Monitoring home electricity usage via a tidy wall display


[Janne Mäntyharju] wanted to get an idea as to how much electricity he consumed in his new home, mainly to see if using his fireplace for additional heat had any effect on his bill. Luckily his power meter was mounted in the utility room of his house, making it easy to keep tabs on his usage.

His meter features a small LED that blinks a fixed number of times per consumed Kilowatt hour, so he mounted a photoresistor and ATtiny2313 above it to detect the light pulses. [Janne’s] server polls the microcontroller every 5 minutes over an XBee connection, recording the power usage in an SQL database for further analysis. From this database, he generates graphs showing both the temperature in his home as well as the average electricity usage for the specified time period.

[Janne] also wanted to make the data easily accessible, so he constructed a wall-mounted display using a Beagleboard and digital picture frame. The display not only shows his electricity usage, but it toggles between the weather, calendar events, IRC logs, and pictures from his security camera.

We’ve certainly seen this sort of electric meter monitoring before, but it serves as a quick reminder that given the right tools, watching your power usage (among other things) can be as easy as taking a quick glance over at the wall.

16 thoughts on “Monitoring home electricity usage via a tidy wall display

    1. Your language aside, that is correct. Just because you didn’t actually change what the meter says, it’s still considered fraud to modify one.

      Another route you can take is to clamp a wrap-around ammeter to your supply cable where it goes into your breaker box. This way you can measure exactly the current flow, but you don’t have to cut into anything (good, because that’s dangerous)

    2. Not really sure what it’s that you are getting at, but there is no tampering with the meter here. Janne’s write up reveals that there is a light that can be easily seen, whose blinking can be used to determine consumption.

    3. My meter is in full sunlight if it has such a LED. it’s probably lost in the Sunlight. Where I own the boxw the meter is in I can mount anything I wast on the box to shade the meter so this could work, as long I don’t break the tamper seal, and leave door that the meter reader could open to read it. Bit that would require the meter reader to get out of the vehicle to read it instead of using field glasses to read it from the road. Unless the fireplace goes unused to gather baseline data, I’m not sure will or can be learned

      1. a black tube with a lens would work. you can play around with a visible red led. once the lens projects the led onto the photo resistor, you got it about right. if you still have problems with ambient light, add some exposed filmstrips to filter visible light.
        but first take your digital camera and try a 30 second recording, the ir led should be visibly blinking at some point in that recording.

      2. Try mounting two photo-transistors side by side: one pointed directly at this LED, and the other positioned as closely to the first as possible, but with the LED outside its field of vision.
        An IR blink should show up as an increased voltage differential between the two phototransistors.

  1. For data logging projects like these I’ve found that using RRDTool for data storage and graph rendering is a much better solution than using MySQL. RRDTool creates Round-Robin databases which won’t grow in an uncontrolled fashion like MySQL will if left unchecked, they simply overwrite the oldest data.

    And if you want to keep archives of data forever it’s easy enough to write a cron-job to dump xml of the rrd and compress it.

  2. Seeing as how it has the ir led, its bound to be a smart meter, iirc most of those use zigbee to report in, would it not be possible to listen for your meter to transmit and collect it from there? Anyone know of anyone working on that? Im not quite that skilled it such things yet. Seems a tad redundant to attach a second meter to your meter, or an extra unit to read and transmit what the meter is already reading and transmitting. Assuming one could listen to what it says.

    1. The Zigbee comms, if they are being used, are usually encrypted. The easiest way to pull data right off the meter without having to break into it, or somehow sniffing the wireless traffic and decrypting it, is definitely using a photoresistor to monitor the blips.

  3. I have one of these (warning: danish homepage):
    works like a charm, but it only logs a total for last hour, day, week and month. I would love to be able to log the signal in the same way this hacker does it. I’m not much use with building electronics, so my hope is that there’s some USB device that i can program to listen to the transmitters signal, and log it to my Linux box.
    Any ideas?

  4. Wattvision can sell just the IR sensors with pulse output, so you can wire to your own hardware, if you’re interested in that. Their sensors have been tested over the last several years since the company was founded in Jan 2009. The first version of Wattvision was arduino based.

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