Memo on Plug Experiment

Project Page for MAS961

Yasuhiro Ono <ono_at_media.mit.edu>, Visiting Researcher, MIT Media Lab

Posted on 11.8.2005

Notes on plug experiments conducted (1) to be familiar with the data-extraction process, and (2) to know the difference of current waveform among devices. Tested devices are;

- Light

- Fan of a humidifier

- Cell phone charger

- Toaster

- Finger Tap

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Memo

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1. PC:

-Windows XP SP2

-Python Enthought edition (contains python2.3.5, wxpython2.6.1.0, scipy0.3)

http://www.enthought.com/python/

-Matplotlib (matplotlib-0.84.win32-py2.3.exe)

http://matplotlib.sourceforge.net/

Scipy’s graph didn’t work, which is the reason I installed matplotlib.

2. Connection

If the right firmware was on the plug, green light responds to vibration after usb cable plugged to the plug.

3. Communication between PC-Plug

On the linux(ubunto) box in resenv, type; “sudo python –i PlugUSB.py log temp.dat“.

To parse data, the option is ‘parse’, instead of ‘log’. Note that this doesn’t require pyUSB, which seems fairly unstable. After parsing, draw graph with matplotlib. It’s very slow. Maybe something is wrong on the code.

4. Graphing

The 7 sensor data value, without vibration, is the output of ADC, 0-255. The vibration data is timings when the voltage output change with microcontroller’s interruption. The timestamp is done by PC, and it’s a “unix time”, where the unit is second. The interval is almost 2ms, with some variation.

Savefig command can save the figure, such as savefig(‘xxx.png’, dpi=300). 300 dpi seems good in resolution and file size (138KB for an example). Note that show() command should follow savefig, otherwise no image is saved, and show command blocks the code.

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. Light

ono_lightonoff_11042005.dat:1.3MB, 26756 sample points, 58seconds

The light, found in the lab “Electrix k909 20W”, has a button to turn on/off. I plugged it, and turn it on/off several times.