>> I currently don't have access to fancy lab equipment, either, and I was >> thinking about using a sound card (an external USB one to not damage the >> computer in case something goes wrong) as a replacement for an >> oscilloscope. What do you think of this idea? > > It is very interesting. I'm curious to see your implementation. How do > you replicate it?
I have not tried this yet, I am just thinking about it. Here is a link with a summary of different Oscilloscope replacements: http://opencircuits.com/Oscilloscope There is an open-source application called "xscope" for Linux: http://xoscope.sourceforge.net/ Apparently, sound cards have an input range on the line-in from -1V to 1V. Most sound cards should support a sampling rate of >40kHz and a sampling depth of 16 bits. The biggest unknown (to me) is whether the sound cards filter out the DC component (e.g. you cannot measure voltage, but only changes in voltage). If this is the case, I would need to find a different solution. Otherwise we can probably expect something like this: The sound card might have an antialiasing filter with a cut-off frequency of 20kHz, so we should get a temporal resolution of around (1s / 20'000 =) 50us (I think even 100us is good enough for me). We might have to amplify/attenuate the signal from the mote. If we make a simple input circuit to measure current in the range of 0-50mA (a typical MicaZ or Iris mote with the radio, CPU and all LEDs on and also writing to the Flash should not draw more current) and in order to keep the circuit simple map this to 0-1V (we loose half of the input range), we should get a resolution <2uV. Considering noise and imperfections in the circuit the accuracy is probably more around 10uV, but even 100uV are probably good enough for me. _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
