Why I don't see the data for the rest of the channels?

I have a cyton board v3 with 8 channel configuration along with only 2 electrodes. When I connected my one electrode to SRB bottom pin and N5P bottom pin I dont see any data streaming from them but I when I connect the electrode N1P bottom pin I see some activity but I dont know if that's actually coming from the board or not but I can verify that that when both electrodes are placed on the surface of my forehead, I see that activity happening. Below is the screenshot of openbci GUI. Can you please let me know what I am doing wrong?

Comments

  • wjcroftwjcroft Mount Shasta, CA

    Lunar, hi.

    Since you are only using a couple channels, you might remove the Daisy, to simplify your setup. Are you following the Cyton tutorials?

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

    What electrodes, locations, and paste are you using? Where are the reference and Bias electrodes?

    William

  • lunarbrainlunarbrain India
    edited August 2022

    Hi Wjcroft,
    I did remove the daisy and run the board again this time again no change in the data. Now after reading the documentation, I also connected the Bias electrode injunction with the two electrodes that I was using previously, but no change in the output. I can only see data coming through on 1-4 channel 5-8 are still showing that "Data from the board doesn't change 0.00 uVrms".

  • wjcroftwjcroft Mount Shasta, CA

    @wjcroft said:
    ...
    What electrodes, locations, and paste are you using? Where are the reference and Bias electrodes?

  • Ops, sorry, I missed that one -

    A. **Electrodes Connection and Position - **
    1 electrode = SRB bottom pin : Near one ear
    1 electrode = BIAS bottom pin : Near another ear
    1 electrode = any pin between N1P - N8P bottom pin : Forehead ( I know I should connect based on 10-20 map but I just wanted to check, if my channels are working properly)

    B. **Paste: **No paste for now to make any contact between skin and gold cup electrodes for now.
    Sorry @wjcroft missing that in my previous reply. Let me know if you need anything else regarding this. I tested today again replaced all my electrode with new set of electrodes but still now luck.

  • wjcroftwjcroft Mount Shasta, CA

    Paste is a REQUIREMENT for the cup electrodes. You forgot to follow directions:

    https://docs.openbci.com/GettingStarted/Biosensing-Setups/EEGSetup/#2-connect-your-electrodes-to-your-head-and-body

    Why? Because such electrodes need the conductive electrolyte in the paste to complete the skin / electrode interface.

  • lunarbrainlunarbrain India
    edited August 2022

    Okay, Let me check and get back to you.
    But I have a question, can we use any kind of dry electrode?

  • wjcroftwjcroft Mount Shasta, CA

    The dry electrodes in the Shop, have a plastic base material, then plated with silver, then chlorided. These work for dry applications because of the silver chloride. (Gold is less effective.) But any dry electrode also requires significant pressure against the skin. The Shop kits include a velcro band that provides this pressure. If silver chloride is used on ear lobes, then typically there is a spring clip attached.

  • @wjcroft
    I think my board is faulty. I can't see any data beyond 4th channel. As mentioned in the documentation even running finger on the pins would allow you to see some noise in the GUI. One thing, I also noticed that when I run the impedance check, only 4 channels (1,2,3,4) shows some values which is not 0K ohm (5,6,7,8 channel).

  • wjcroftwjcroft Mount Shasta, CA

    So this has been going on for 5 months with no solution? Where and when did you purchase this Cyton? Did it EVER work correctly? Have you emailed (contact at openbci.com), customer support, to ask for assistance? Did you ever get the paste as suggested to use with your gold cups?

    William

  • @wjcroft
    Sadly yes :( I left this hardware unused for few months and picked up again until I got the electrode and t20 paste. I ordered the electrode from OpenBCI us and it took sometime to reach here in India. I bought the Cyton board from Aliexpress as I couldn't get in India because of high import taxes.

    Yes, I got the paste and electrode as suggested by you and used today but same result. Only 4 channels were working.

  • wjcroftwjcroft Mount Shasta, CA

    I'm sorry but the Cyton you have was not manufactured by OpenBCI. Therefore customer service will not be able to help you.

    Generally it's a good idea to test new products as soon as possible after purchase, so if something is wrong they can fix it. There is also usually a time limit on these new product defect replacements. Contact your supplier.

    If you have the 4 working channels, those are still usable. I hope they work well with your electrodes. Actually, EEG supply stores are in each country, so some items like this can avoid customs.

  • Thank you @wjcroft I guess I made a mistake buying from aliexpress.

  • lunarbrainlunarbrain India
    edited January 2023

    @wjcroft
    Just one last question. can you please help me understand when or why do I get the message on channel which has no data streaming -
    "Data from the board doesn't change 0.00 uVrms"

  • wjcroftwjcroft Mount Shasta, CA

    This appears to be a warning message that the data on that channel is unchanging. So as to alert the user the channel may be shorted out or damaged.

    https://github.com/OpenBCI/OpenBCI_GUI/blob/master/OpenBCI_GUI/Extras.pde#L511

    Have you carefully examined your physical board to ensure there are no foreign objects, particles, metal flakes, etc, that may be causing the shorted condition? Probably unlikely but worth a look. My guess is that your ADS1299 chip has suffered some type of internal failure. Does the writing on the top of the chip say ADS1299... ? There are some related chips in that family that do not actually have all 8 channels.

    https://www.ti.com/product/ADS1299
    https://www.ti.com/lit/ds/symlink/ads1299.pdf
    "ADS1299-x Low-Noise, 4-, 6-, 8-Channel, 24-Bit, Analog-to-Digital Converter for EEG..."

    If the ADS1299 is indeed a 4 or 6 channel version, then the part number on top of the chip will have a '-4' or '-6' suffix.

  • lunarbrainlunarbrain India
    edited January 2023

    @wjcroft
    Now that you have mentioned, I did look into the chip on the PCB. I basically got cheated. The chip on the board is ADS1299-4. I am freaking dumb. To check that further, I slapped the daisy board on top and voila, I get the same the behavior. Both main board and daisy board have only first 4 pin streaming the data. You are a genius. Thank you so much. o:)

    Now the final question :neutral: - how do I check/select the SRB and BIAS pin on the board. I mean, the board is setup in 8 channel configuration with all the pins annotated on it, but since they are using ads1299-4 channel chip on both board the rest 4 pins are useless so should I keep using the same SRB and BIAS pin as mentioned on the board or do I shift the electrode position?

  • wjcroftwjcroft Mount Shasta, CA

    I suggest you try to email or contact the original AliExpress seller. It's remotely possible that the PC fabrication company that assembled the boards had a screwup with ordering the proper parts. And they did not even check the boards for proper operation after assembly. Certainly deserves a refund or replacement.

    I would just turn off the unsupported channels by clicking on the GUI channel numbers on the time series graph. My guess is that the ADS1299 chip pinouts are the same, so your SRB2 and Bias will work as expected.

  • @wjcroft Thank you so much again for help. o:)

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