noise signals in tests with Ultracortex and Ganglion

CarolRamMoCarolRamMo México
edited December 2021 in Ganglion

Hey OpenBCI forum!
We are STEM students from Mexico working on a project related to Brain-Computer Interface. We considered the Ultracortex "Mark IV" EEG Headset and the Ganglion Board like the best option for us because the price was right for our very limited budget, and we just bought them 2 months ago. We assembled the 3D-printable headset just like in the Open BCI tutorials, we did some trials in the OpenBCI GUI but we didn't get the same signals like in the tutorials. The tests were carried out in a head and we also tried directly touching the sensors with our fingers, but still the signals didn't change, only nonsense periodical signals.
That's why we suspect that the Ganglion Board has a problem. Could you help us to figure out what is going on and what can we do about it?
We add an screenshot from OpenBCI GUI to show our signals.

Comments

  • wjcroftwjcroft Mount Shasta, CA

    Hi Carol,

    The default switch positions on Ganglion are setup for 'differential' mode, such as with ECG, EMG. Where each channel uses both the plus and minus electrodes pins. DId you flip all the switches to 'common reference' position, which is DOWN, when holding the board upright. This then uses the REF pin as common reference, typically connected to an ear lobe.

    https://docs.openbci.com/Ganglion/GanglionSpecs/#inverting-input-select-switches

    Did any of the other tutorial steps work? Do you have cups and paste?

    https://docs.openbci.com/GettingStarted/Boards/GanglionGS/
    https://docs.openbci.com/GettingStarted/Biosensing-Setups/EEGSetup/

    William

  • Hi!
    Yeah, our Switch position is in mode “common reference”, and we are using the electrodes that come with the headset.
    We followed this tutorial after to prove your videos, but the result is the same.
    http://brainwaves.io/wp/blog/2017/04/26/openbci-ganglion-windows-10-part-4-electrodes/
    And we don’t have golden cups, we only have the Ultracortex electrodes.

  • wjcroftwjcroft Mount Shasta, CA

    Carol, this looks to me like some type of electrical noise in your environment. Have you tried running your tests in another location, that may be more free of electromagnetic signals?

    https://docs.openbci.com/Troubleshooting/minimizingNoise/

    It would be good to try another type of bio-measurement besides EEG, such as ECG or EMG. Would you have any electrodes you could do that with? This would confirm that the board is working with those signals.

    However your statement:

    "... The tests were carried out in a head and we also tried directly touching the sensors with our fingers, but still the signals didn't change, only nonsense periodical signals. That's why we suspect that the Ganglion Board has a problem..."

    This seems to implicate the Ganglion board, if nothing changes when pins or electrodes are touched. Normally contact like that should result in large time series swings in the GUI. Have you been in touch with OpenBCI support? That can be done by emailing contact at openbci.com. There may be other tests suggested.

    William

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