leka0024
leka0024
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Comments
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Appreciate your comments (and links especially), as always. Thank you
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Thanks for the links on the tri-polar. Active "just" means that the amplifier is sitting on top of the electrode, instead of being back at the board/box, right? (I put just in quotations, because that's not trivial or cheap, I'm sure) I've only bee…
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And so, I wonder just how good of a "stadium microphone" the spiky dry electrodes are, compared to the flat rings (using gel to remove air/hair gap). Or like I mentioned before, the guy at URI uses concentric rings to obtain even higher performance.
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Thanks for the link to VC. It seems to confirm what I thought, that EEG working first principles are fields, not direct electricity. That makes sense to me.
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"No, good conductivity is all that is required." That doesn't seem right, to me. I doubt that the neurons are directly supplying charges to the conductors, through the skull. If that were the case, then what you said would make sense. Rather, I thi…
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Quick question about the paper you posted in the discussion 84 link (http://www.csi.uoregon.edu/members/ferree/pubs/EEG2001.pdf) It says "the required procedure was to abrade the skin to achieve a scalp-electrode impedance of less than 5 kΩ. To ach…
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Great! Thank you!
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Thanks for the reply. Makes sense to me!
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Thanks for the info about the clock drift. Lo and behold, you were right after all. I will swear to you that the GUI ran smoothly when I first came over to this station, but indeed when I just ran it now it was only updating roughly twice per seco…
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I already know that the GUI does indeed plot smoothly, as I ran it when I first moved the hardware to our Win7 station. But again, that could simply be it assuming the timing and having enough data to update the graph on a timely/smooth manner. For …
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Why would OpenBCI's GUI know the "true" timing of the samples?? Unless the hardware is also sending timing information in the packet (and nothing I've read so far shows that it is), then the GUI is making the same assumption. My guess is the radio…
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Hi @wjcroft I'm not actually losing the packets. I'm getting all the sample.id numbers (in sequence). The issue I'm facing is that when I use Python's time modules to time all the function calls, then the timing of when the samples are recording is…
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Perhaps it would be easier to just ask this: is it a fair assumption to just set the timestamps based off the sample.id number (a continuous version, not the one that loops around every 255)?? Like, if the sample.id numbers are [0,1,3,5,8,9], then…
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Update: the headset continued to run without any problems all the way down to 3.3V on the batt. In fact, I even switched workstations and am now working on a Win 7 machine. Never ran into the problem again ... until today. Voltage is 100% not the i…
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I'll contact Cortech and see what they have to say. Given the discomfort of the Mark III headset electrodes, I'm cautious about using "comb"-style dry electrodes. I'd be quite fine squirting or injecting gel, however that is done, into a flat/cup e…
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@wjcroft , that sounds like a potentially great improvement for the next 3D printed Mark XX headset design. Especially if it could have 10-10 spatial resolution. In looking at the g.tec product line, it looks like the only passive electrode they ha…
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@wjcroft There was nothing special about the Geo Desic design that interested me, or saline electrodes for that matter. Ideally what I want in a headset/cap is: 1) 10-10 spatial resolution, 2) comfort and ease of use for the electrodes and 3) high …
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@wjcroft I believe it, for a whole setup. I think the electronics are what really cost a ton on the commercial setups. But I think the cap is "only" $2k. In regards to having a proprietary connector on the end of the cable/wire from the sensor ...…
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@wjcroft (or anyone ...) Is there any reason that if we purchased a 64 ch cap like this: http://www.egi.com/research-division/geodesic-eeg-system-components/geodesic-sensor-nets that we wouldn't be able to plug 16 of the cables into the OBCI boa…
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Reason I thought it was broke is I did a run with the headset off and the FFT results I got looked like everything else I was getting. But now I think that was because of the time response of the filter output. I looked at the raw channel time serie…
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Well, I don't doubt you. But we need Mu waves. Alpha doesn't do anything for us.
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Trying to detect Mu waves, actually. Now I *think* the problem is the filter I was using on the raw sample values (time series) for the electrodes. I took that off -- obviously the FFT blew up closer to DC, but I just zoomed the graph in on the 8-12…
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@wjcroft , thanks again for your continued responses. You must work for OBCI?? Otherwise, you're incredibly dedicated. Anyhow, I'll try the tutorial to see if I can get Alpha waves. However, I suspect (but may well be proven wrong) that the problem…
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@wjcroft , ran the headset several times today and got the failure mode to appear. Batt voltage was down to 3.95V. However, the sequence of powering down main board, unplugging dongle, replugging dongle and powering up the main board allowed normal …
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@wjcroft My failure mode would never recover when toggling the power switch between OFF/PC. But I also did not let it sit for 5-10mins before trying again. No failure mode today after 12 runs. Battery got down to 3.97V. But in light of your commen…
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@wjcroft My apologies, the sentence "It has happened for two straight days, after working just fine for a couple hours." was poorly worded. Let me attempt to reword, as follows. The previous two days, the same thing has happened: the system works …
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[Original thread title: COMM between dongle and main board dying, for no reason??] Recording 16-channel EEG using the main board + daisy board. I import the open_bci_v3 code module in my python code. It works perfectly, but then for no apparent …
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@wjcroft, Thanks for the link, I should've known there was already a thread on this. Doh! From your link, it's definitely the mode "2" version. In other words, once the failure occurs then it doesn't matter how many times I run my python code…
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@wjcroft Thanks again for all the info in this thread! The Mark3 headset only has midline locations at FpZ and OZ, beyond the FZ,CZ,PZ locations that we're using for signals. So it would have to be one of those. Hence I was just wondering if tying…
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@wjcroft Interesting idea! Thanks for sharing that. I just assumed that using A1/A2 (either or) as reference and bias was the standard way. But I like the idea of using a midline electrode as the bias, to be physically closer to the 15 electrode si…