threshold value off scale (-32766) with Brainbay

afliu · September 2015

maybe this questions is relevant to BrainBay, not the OpenBCI, but I pasted here if someone has the comments.

Recently, I am trying to make focus neuro-feedback practise with SMR based BrainBay+OpenBCI. So far, all looks well except SMR or Theta, even Beta Threshold value displayed -32766 sometimes. Moreover, I was confused is that the ratio between SMR and Beta looks correct, even SMR value is invalid(-32766)

I shared the configuration and reutls snapshot below. Any comments are welcome.

http://pan.baidu.com/s/1o6N6ViU

BTW: does anyone has the focus-neurofeedback suggestions or document to share?

-Anfeng

wjcroft · September 2015

Anfeng, nothing is coming through on that Baidu link. Can you upload a screenshot to Google Drive instead? I know others have tried posting Baidu links in the past and it's not reliable for some reason.

Are you certain that you are bandpass filtering the signal going into your main element blocks? If you don't remove the DC offset below .5 hz, you'll get these kinds of overflows. Your first element after the channel should be a bandpass filter, say from .5 to 40 hz. Then connect that to other elements. The tutorial mentions this.

http://openbci.com/forum/index.php?p=/discussion/90/brainbay-install-neurofeedback-tutorial

https://sites.google.com/site/biofeedbackpages/brainbay-openbci

Another approach would be to try some tests with neuromore.

http://openbci.com/forum/index.php?p=/discussion/469/neuromore-studio-new-free-visual-programming-language-vpl-for-openbci

William

wjcroft · September 2015

OK, I retried the Baidu download and got the picture of your circuit. Please see the tutorial link in previous post. The MAG (Magnitude) element blocks will not function correctly unless they are preceded by a bandpass filter that removes the DC component. That's why your thresholds are misbehaving.

In general it's a good idea to pre-filter the channels to say .5 to 40 hz before routing to other elements.

afliu · September 2015

thanks William. I will follow your suggestion to update the configuraiton and re-run the testing, then let you let know the result.

For the google stuff, by the way, we could not access it offically from China :-(. Need to "firewallwall break" by VPN.

Thanks again.
-Anfeng(Andy)

afliu · September 2015

Hi William,

After filter 0.5~40Hz first, then routing to MAG and other elements, the result looks good, here is the snapshot for the reference.
http://pan.baidu.com/s/1hqIZAoW
http://pan.baidu.com/s/1kT90eV1

At the same time, I shared my configuraiton in case someone is interested in it.
http://pan.baidu.com/s/1sjssOqD

Regards,
-Anfeng(Andy)

threshold value off scale (-32766) with Brainbay

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