Periodic noise peaks in Ganglion board with native bluetooth

Hi! We're students making a final project with EMG signals for our university and we're using a Ganglion board that the university gave us to do it. Until now we were using only the channel1 for testing purposes and everything went ok but now we are trying to use all 4 channels to amplify our muscle signal but we discovered that channel 2 and 3 have periodic noise peaks with and without the electrode cables connected to it. Channel 1 and 4 seems to work fine for now. It seems that the noise peaks are time synched with some packets lost (we saw 2 packet loses for each noise peak involving channel 2 and 3). We searched in the OpenBCI page and forum for answers but we couldn't solve the problem. The only big issue that we think could be the problem is that we are using the native bluetooth option because we don't have the BLE dongle that is mentioned in the official page, could it be that the native bluetooth connection with the Ganglion board is causing these big periodic noises in channel 2 and 3? We also used different computers and operating systems, we updated the software version to the latest (3.0.2) and always used the last version of the GUI.
Here there is a video of the noises we're facing with, the board has no cables connected to ir, only the battery: https://drive.google.com/file/d/1I_bYgbaa_-fr26ljIqFEcgTEda7HCiZV/view?usp=sharing

The initial setup is this:

Comments

  • wjcroftwjcroft Mount Shasta, CA

    Hi Katuto,

    I suggest you email (contact at openbci.com), which is customer support and ask if they have any insights.

    Normally you cannot infer anything from channels that are free floating / unconnected. The EMF Electromagnetic Field noise in the room can couple into such floating channels and produce spurious results. However you say that the noise is also present when attached to your subject. So that is a valid point. One thing to try is to swap out the cables / connectors / electrodes to see if the situation changes.

    Is this a new purchase or older? Has it EVER worked correctly?

    The 'native Bluetooth' should normally work fine. But it's possible there could be issues with your specific model of Mac and macOS. State these on your customer support request.

    You could actually obtain easily the BLED112 dongle there in Argentina,

    https://ar.mouser.com/ProductDetail/Silicon-Labs/BLED112-V1C?qs=8HqIXBaaO6zjZ6K0tFUm5w==

    So might be worth trying with that to see if any changes.

    William

  • katuto03katuto03 Argentina

    Thank you for the fast reply, we will reach OpenBCI by email to see if they have another guess on this. As far as we know, we think that these periodic noises is purely a board failure or a connection failure (guessing this by the packet loses sync with the noise peaks) because we tried with different cables and electrodes combinations and it's always channel 2 and 3 that have this issue (1 and 4 work just fine). The board it's not ours as I mentioned, it's from our university but they gave it to us closed and it seemed to be new and unused. We just bought the official OpenBCI dongle from the shop and we hope to get it soon via FedEx in Argentina to see if this could be the issue (we bought many dongles here months before but we always had compatibility errors with Mac so we're trying with the official one now). The thing is that now that you are telling us that the native bluetooth should work fine I guess the probability of the board being the problem is higher. Until now we were discovering the GUI features and just working with the first channel (everything was ok until this point) so we can't know for sure if the error is old or recent, the board from outside seems fine and it never had any hits or broken things. The macOS version that we are using theoretically doesn't have any trouble, and for the packet loss problems in Ganglion they only say this
    In all OpenBCI API, troubleshooting and guides it says that the dongle is a MUST have and that there should be no problem with it, also everybody seems to use the dongle with the ganglion board so it's hard to find someone with the same problem that we're facing. We're hoping that the problem is only a connection problem and it will be solved with the dongle... Anyways, thank you very much and if you ever find something or someone that had a similar problem with ganglion please let us now.

  • wjcroftwjcroft Mount Shasta, CA

    If you are seeing packet loss with the native bluetooth, that is a clear red flag. One common strategy with the dongle is to put it on a usb extension cord to get it up off the table or bench you are working on. Some people drape the end of the extension cable (with dongle) over the top of a nearby monitor to get it higher in the air.

  • katuto03katuto03 Argentina

    As you can see in the end of the video I shared (https://drive.google.com/file/d/1I_bYgbaa_-fr26ljIqFEcgTEda7HCiZV/view?usp=sharing ) there is a 1% packet loss detected that matches with the peaks in channels 2 and 3. The red flag is because there is something wrong with our Ganglion board or is it maybe that the native bluetooth connection is not working well? We will try that strategy that you're mentioning once we get the dongle, thanks for the advise. Just let me ask you why should we put the dongle higher in the air? Isn't it best to keep it the closer as possible to the board?

  • wjcroftwjcroft Mount Shasta, CA

    It's not necessary to position the dongle directly next to the Ganglion mainboard. Some tables or cabinets are metallic and tend to block radio signals. Especially if the dongle is close to the metallic surface. The suggestion of draping the cable over the monitor gets it off any metallic surfaces / objects, and more in a direct line of sight to the Ganglion.

    The other tip I think already mentioned, is that other Bluetooh or wireless devices in the vicinity may be interfering / causing the packet loss. So you may experiment with trying other locations, rooms.

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