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1628265 No.1628265 [Reply] [Original] [archived.moe]

EEG/Eletronics general thread
Has anyone here done any project involving EEG? Since it is a somewhat uncommom type of project anything is welcome ( Articles, Information, Sci.Papers you find interesting or important when making such project )

•Eletronics focus: Information on analog filters is welcome ( tips on how to make a good filter and improve performance ***Points on info about performance of diferent types of capacitor on low freq filters (specially but not limited to 0.1~100Hz) and butterworth filters ( bandpass highpass and lowpass )***

>I need help with butterworth filters In the 0.1~100Hz (If you have send in filters designs). Im somewhat inexperient with eletronics and I am failing to *test performance of diferent types of capacitor ( and parasitic effecs )* on butterworth active filters using LTspice

>> No.1628282

>2018 + 1
>analog filters
If you'll be digitizing your signal at some point why not make filter in software? It'll be much simpler and more stable.
>In the 0.1~100Hz
This is so slow that even cheapest micro could handle it. As it says on wiki:
>Most EEG systems these days, however, are digital, and the amplified signal is digitized via an analog-to-digital converter, after being passed through an anti-aliasing filter. Analog-to-digital sampling typically occurs at 256–512 Hz in clinical scalp EEG; sampling rates of up to 20 kHz are used in some research applications.
Since you're dealing with such low frequencies you could maybe even use your PC's sound card. It should be more than capable of sampling input from differential amplifier, then just do your filtering in software. Only problem is if there are enough channels for your application.

>> No.1628295

Indeed it is true that digital is much more pratical and simple, in fact i have already been able to process the signal and get multiple bands using mathlab.
Since I already got what I wanted from functional part done Im using this project to learn more about eletronics in general, so practicality is not my main objective
As I already started a thread and started working on the project again might as well learn more about

>> No.1628299

And I cant use my PC Input because it has a cut off freq (about ~20Hz) so I would lose most of the strongest signals that are between 10~35Hz

>> No.1628302

I have been looking for a low noise affordable single sided op amp for this application

>> No.1628467

Filtering or obtaining signal? I use an AD620AN instrumental to amp. signals then 2 TL084CN chips to cut off 60Hz ( power line freq in my place ) and I use an arduino to get the analog signal in my PC so I can process it on mathlab. Works fine but I want to "make the software filters" on the pcb

>> No.1628490

Measurement and Control Circuit Collection
google dis and scroll down to da sources

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