Hackaday Links: July 24, 2011

Plasma speakers

Apparently if you run AC and DC currents through a welding torch flame you can use the resulting plasma as a loudspeaker. [Thanks Cody]

Power metering

The Google Power Meter API is no longer in development but that didn’t stop [Pyrofer] from finishing his metering hardware. It uses a reflectance sensor to read the meter instead of using clamp-based current sensing.

Music videos from inside the instrument

Filming from inside of a guitar creates the camera effect seen above which looks like the waveform you’d see on an oscilloscope. [Thanks Philleb]

Hidden messages in audio files

GhostCoder lets you encrypt and hide audio files within other audio files. The thought is, you can piggyback your own data into Torrents that are circling the interwebs.

2×4 Chair

If you’re skilled with a Skill saw you can make a chair out of one 2 by 4. You can see the pattern you’ll have to cut out from the board in the image above, wow!

Monitor your home’s power usage on the cheap


[Paul] was pretty sure that he and his family used a lot of electricity throughout the day. Admittedly, he enjoys his creature comforts, but was wiling to try living a little greener. The problem was, he had no idea how much electricity he was using at a given time.

While some power companies offer devices allowing homeowners to monitor their energy usage, [Paul’s] did not. After a bit of research however, he was ready to build a power monitoring system of his own. He found that his meter emits a small infrared pulse every time a watt-hour of electricity is consumed, so his system counts how many flashes occur to measure usage.

The counting circuit is pretty simple consisting of only an AVR, a resistor, a capacitor, and a phototransistor. The data is fed to a computer where the results are graphed with gnuplot.

It’s quite a useful little hack, and undoubtedly far cheaper than purchasing a whole house power monitor.

Tweet-a-Watt now speaks to Google Power Meter

Hackaday’s own [Devlin Thyne] has been working with Adafruit to come up with a way to use the Tweet-a-Watt along with Google Power Meter. Back in March we put out the word that Google had unveiled the API for Power Meter and [Devlin] is the first we’ve heard of to come up with a way to use your own equipment with the service. You can build your own or use Adafruit’s kit and the data pulled from your energy use will be nicely displayed using the big G’s tools. Right now there’s only support for one Tweet-a-Watt but we’d image this will evolve fairly quickly into a much larger house solution. Head over to the Tweet-a-Watt code page to get the source files for this project.

[Thanks PT]

Tweet-a-Watt kits


[adafruit] wrote in to let us know that the Tweet-a-Watt is now available in kit form. While the plans have been available for a while, a kit is a welcomed addition. The kit doesn’t include the Kill-a-Watt monitor, but rather the XBee adapters and parts necessary to make it talk to your Arduino or computer. The kit is $90, while the Kill-a-Watt can be found for roughly $20.

Wattcher, twittering Kill A Watt plans posted


You probably saw [Phillip Torrone] and [Limor Fried]‘s twittering Kill A Watt earlier this week. It was an entry in the Core77/Greener Gadgets Design Competition. We saw a little bit about how it was assembled, but now they’ve posted a full guide to assembling the hardware. Each Kill A Watt gets an XBee radio that transmits back to a receiver that logs the power usage. The difficult part when putting this design together was the XBee required 50mA when transmitting. This is well above the Kill A Watt’s internal power supply. They remedied this by adding a 10,000uF supercap to act as a rechargeable battery. The daily twittering is just a side-effect of the project. The Kill A Watts transmit every 2 seconds, so you’ll get a very accurate report of your power usage. This is a great project for renters who can’t permanently modify their power infrastructure. Each Kill A Watt can support quite a few appliances since they’re rated for 15A, ~1800W.

Kill A Watt teardown


Come on, folks. If we keep tearing apart everything that’s handed to us, we’ll never get nice things. SparkFun got their mitts on two Kill A Watts and proceeded to plug them into everything and then dismantled them to see how they work. The Kill A Watt keeps track of how much power is used over time. The largest load they found was their soda machine using 500W (should probably add a motion sensor to that). They plugged a meter on either side of a UPS and found out that it uses 5W just to charge. On the inside of the meter, there isn’t anything too substantial. One unlabeled IC runs the whole show.


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