Re: Openeeg-list Digest, Vol 133, Issue 4

If you leave the inputs floating or connect to a subject (i.e. via
electrodes to your scalp) you get a signal and mains noise, then connecting
the DRL you get nothing?   Is that what happens?

It sounds as if your DRL circuit is not working properly and the output of
IC4B saturates at the top or bottom supply rail.  This would then move
CH1+, CH1-, Ch2+ & CH2- also against the rail.  Your instrumentation
amplifier cannot work with it's inputs at, or close to the supply rails and
it too will saturate and the AC coupled output will flat-line.

Make sure that the output of IC4B is close to the virtual ground (V_REF).
A voltage of up to about +/- 1V away from virtual ground is fine.

Perhaps you have only been using one channel (connected to a subject) and
left the 2nd channel unused.  Any unused channels must "normally" be tied
together to ground.  I say normally, meaning for an amplifier that uses DIN
or some other input connectors.  However, these stereo headphone type
mini-jack plugs on EEG-SMT should automatically do so.  BUT only if no plug
is inserted.  Don't plug a cable in, and then leave it unused.

SJ








On Fri, Feb 2, 2018 at 5:52 PM, <[email protected]>
wrote:

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>    1. Re: Openeeg-list Digest, Vol 133, Issue 1 (Dami?n Filo)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 2 Feb 2018 16:52:24 +0100
> From: Dami?n Filo <[email protected]>
> To: "Discussion of EEG hardware, software, training protocols, NFB
>         theory - for developers and users."
>         <[email protected]>
> Subject: Re: [Openeeg-list] Openeeg-list Digest, Vol 133, Issue 1
> Message-ID:
>         <CALPZnbH6eNF2_HttRJ=EbNnkhAUb7fC6Z9Hxzjgcbr16Nacibw@mail.
> gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> At first, let me thank you for your e-mail.
> About the filter, I agree it would probably be the best, if I leave it as
> is. But I am facing another problem. After connecting the drl to the body I
> get 0 signal, nothing. What could cause it? Should I add the third trimmer
> for the drl? Is there any difference between INA114 and INA128 that I used
> that would be causing it? Currently I don't have my EEG with me, on Monday
> I would be able to show you.
> But if you don't have much time, wouldn't there be someone, who will be
> able to help me?
> Again, thank you.
> And as I said, as soon as I will finish the EEG, I will share everything,
> even documentation in slovak language.
>
> 2018-02-01 13:55 GMT+01:00 Stefan Jung <[email protected]>:
>
> > Hi Dami
> >
> > I have no time to check the design and look at calculations, but I would
> > recommend that you stay with the original filter design for the following
> > reasons.
> >
> > 1. No filter is a brick wall.  A 3rd order filter is really not very
> > sharp, so if you choose a 49.5 Hz cut-off, your 50Hz mains noise will
> only
> > see a bit more than 3db reduction, which will not help you.
> >
> > 2. If you reduce the cutoff point as you intend, your filter pass-band
> > will be negatively effected.  I.e. your higher frequency EEG signal will
> > start to be attenuated and your processed data will be inaccurate.  No
> EEG
> > amplifier has a perfectly flat transfer function, simply because filters
> > are far from ideal.  High order filters produce all sorts of phase delay
> > and other problems and are thus also not a solution (not to mention the
> > cost).  We all need to accept we live in an in-perfect world.  You should
> > not act in a way to further compromise the accuracy for reasons that are
> > not that important.
> >
> > 3. From all my readings about neurofeedback, I have learned that everyone
> > has 50 or 60Hz interference and that most people use it to judge their
> > electrode conductivity.  If they have high 50/60 Hz, they know that their
> > electrode is not well seated, or the electrolyte has started to dry out,
> or
> > whatever.  If the mains is fairly suppressed, they know the electrode
> > contact is sound.  There will always be some mains hum, and they simply
> > learn to ignore it.
> >
> > 4. I think the original design team spend many 100s of hours analysing
> the
> > filter response and carefully considered where best to position the
> > -3db filter cut-off point.
> >
> > I KNOW you want to understand the design.  And that is good.  You should
> > find discussions and explanations in old openeeg forum messages.  This
> msg
> > will not help you with the filter analysis, but I just want to make you
> > aware that the openEEG design does not need to be changed for EU mains.
> In
> > fact, the design team was mainly from Europe.   Joerge, one of the
> original
> > team members, later made certain modifications regarding safety, leakage,
> > etc. to pass/qualify EU medical grade standards for a commercial spinoff
> > for a student start-up (based in Berlin, if I remember correctly).
> >
> > Regards
> > Stefan
> >
> > On Thu, Feb 1, 2018 at 2:02 PM, <openeeg-list-request@lists.
> > sourceforge.net> wrote:
> >
> >> Send Openeeg-list mailing list submissions to
> >>         [email protected]
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> >>         https://lists.sourceforge.net/lists/listinfo/openeeg-list
> >> or, via email, send a message with subject or body 'help' to
> >>         [email protected]
> >>
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> >>
> >> When replying, please edit your Subject line so it is more specific
> >> than "Re: Contents of Openeeg-list digest..."
> >>
> >>
> >> Today's Topics:
> >>
> >>    1. Low.pass filter (Dami?n Filo)
> >>    2. Re: Low.pass filter (salsero)
> >>    3. Re: Low.pass filter (Dami?n Filo)
> >>
> >>
> >> ----------------------------------------------------------------------
> >>
> >> Message: 1
> >> Date: Wed, 31 Jan 2018 16:58:39 +0100
> >> From: Dami?n Filo <[email protected]>
> >> To: "Discussion of EEG hardware, software, training protocols, NFB
> >>         theory - for developers and users."
> >>         <[email protected]>
> >> Subject: [Openeeg-list] Low.pass filter
> >> Message-ID:
> >>         <CALPZnbFYtf2_D0XqJArAUOJ-tGUENbKi0258N05DkWj2Q_0cyA@mail.
> >> gmail.com>
> >> Content-Type: text/plain; charset="utf-8"
> >>
> >> Hello everybody.
> >> As I am finishing up my project of customizing EEG-SMT I encountered
> some
> >> things I can't seem to understand about the OpenEEG. One of those things
> >> is
> >> the 3rd order besselworth filter which I cannot successfully
> >> reverse-engineer in several Bessel filter calculators. Every time when I
> >> enter the provided values of cutoff frequency, order... I get really
> >> different values of the parts used. It is really important to me,  I'd
> >> like
> >> to set it to 49Hz cutoff because of european electric network of 50Hz.
> >> That's why I get too much 50Hz ripple. I will share the schematics,
> board
> >> and electrode designs, but at first I need to understand the filter. Is
> >> there someone, who will be able to explain the value selection and
> >> formulas
> >> used for this filter? I'd be really thankful. I spent hours maybe days
> >> figuring it out, but I can't seem to understand it. I used multiple
> >> calculators, but this one looks the best:
> >> http://www.beis.de/Elektronik/Filter/ActiveLPFilter.html
> >>
> >> Thank you in advance.
> >> --
> >> Dami?n Filo
> >> -------------- next part --------------
> >> An HTML attachment was scrubbed...
> >>
> >> ------------------------------
> >>
> >> Message: 2
> >> Date: Thu, 01 Feb 2018 11:38:58 +0100
> >> From: salsero <[email protected]>
> >> To: "Discussion of EEG hardware, software, training protocols, NFB
> >>         theory - for developers and users."
> >>         <[email protected]>
> >> Subject: Re: [Openeeg-list] Low.pass filter
> >> Message-ID: <[email protected]>
> >> Content-Type: text/plain; charset=UTF-8; format=flowed
> >>
> >>
> >> Hi Damian,
> >>
> >> Did you try a twin-T notch filter? An RC low pass filter is not really
> >> that sharp. May these articles will help you:
> >>
> >> http://www.g3ynh.info/circuits/Bob_Batey/LB-5.pdf
> >> http://fourier.eng.hmc.edu/e84/lectures/ActiveFilters/node4.html
> >>
> >> Hope this helps a bit,
> >>
> >> Leo.
> >>
> >>
> >>
> >>
> >>
> >> Dami?n Filo schreef op 2018-01-31 16:58:
> >> > Hello everybody.
> >> >
> >> > As I am finishing up my project of customizing EEG-SMT I encountered
> >> > some things I can't seem to understand about the OpenEEG. One of those
> >> > things is the 3rd order besselworth filter which I cannot successfully
> >> > reverse-engineer in several Bessel filter calculators. Every time when
> >> > I enter the provided values of cutoff frequency, order... I get really
> >> > different values of the parts used. It is really important to me,  I'd
> >> > like to set it to 49Hz cutoff because of european electric network of
> >> > 50Hz. That's why I get too much 50Hz ripple. I will share the
> >> > schematics, board and electrode designs, but at first I need to
> >> > understand the filter. Is there someone, who will be able to explain
> >> > the value selection and formulas used for this filter? I'd be really
> >> > thankful. I spent hours maybe days figuring it out, but I can't seem
> >> > to understand it. I used multiple calculators, but this one looks the
> >> > best: http://www.beis.de/Elektronik/Filter/ActiveLPFilter.html [1]
> >> >
> >> > Thank you in advance.
> >> >
> >> > --
> >> >
> >> > Dami?n Filo
> >> >
> >> > Links:
> >> > ------
> >> > [1] http://www.beis.de/Elektronik/Filter/ActiveLPFilter.html
> >> >
> >> > ------------------------------------------------------------
> >> ------------------
> >> > Check out the vibrant tech community on one of the world's most
> >> > engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> >> >
> >> > _______________________________________________
> >> > Openeeg-list mailing list
> >> > [email protected]
> >> > https://lists.sourceforge.net/lists/listinfo/openeeg-list
> >> > Go to the above address to change your
> >> > subscription options, e.g unsubscribe.
> >>
> >>
> >>
> >>
> >>
> >>
> >> ------------------------------
> >>
> >> Message: 3
> >> Date: Thu, 1 Feb 2018 12:54:03 +0100
> >> From: Dami?n Filo <[email protected]>
> >> To: "Discussion of EEG hardware, software, training protocols, NFB
> >>         theory - for developers and users."
> >>         <[email protected]>
> >> Subject: Re: [Openeeg-list] Low.pass filter
> >> Message-ID:
> >>         <CALPZnbF9AUmUqFrGx6+c8+sXufd2yvTp=XyLDpKDLmDOWPfRpw@mail.
> >> gmail.com>
> >> Content-Type: text/plain; charset="utf-8"
> >>
> >> Thank you for your reply, but as I am using the original
> filter/amplifier
> >> design it would be really time consuming to modify it to another type of
> >> filter. I just need to get to understand what have been used
> >>  in the original design. The original design is here:
> >> https://imgur.com/a/MzSs2
> >>
> >> If you would be able to point me to the right direction I'd be really
> >> grateful.
> >>
> >> 2018-02-01 11:38 GMT+01:00 salsero <[email protected]>:
> >>
> >> >
> >> > Hi Damian,
> >> >
> >> > Did you try a twin-T notch filter? An RC low pass filter is not really
> >> > that sharp. May these articles will help you:
> >> >
> >> > http://www.g3ynh.info/circuits/Bob_Batey/LB-5.pdf
> >> > http://fourier.eng.hmc.edu/e84/lectures/ActiveFilters/node4.html
> >> >
> >> > Hope this helps a bit,
> >> >
> >> > Leo.
> >> >
> >> >
> >> >
> >> >
> >> >
> >> > Dami?n Filo schreef op 2018-01-31 16:58:
> >> >
> >> >> Hello everybody.
> >> >>
> >> >> As I am finishing up my project of customizing EEG-SMT I encountered
> >> >> some things I can't seem to understand about the OpenEEG. One of
> those
> >> >> things is the 3rd order besselworth filter which I cannot
> successfully
> >> >> reverse-engineer in several Bessel filter calculators. Every time
> when
> >> >> I enter the provided values of cutoff frequency, order... I get
> really
> >> >> different values of the parts used. It is really important to me,
> I'd
> >> >> like to set it to 49Hz cutoff because of european electric network of
> >> >> 50Hz. That's why I get too much 50Hz ripple. I will share the
> >> >> schematics, board and electrode designs, but at first I need to
> >> >> understand the filter. Is there someone, who will be able to explain
> >> >> the value selection and formulas used for this filter? I'd be really
> >> >> thankful. I spent hours maybe days figuring it out, but I can't seem
> >> >> to understand it. I used multiple calculators, but this one looks the
> >> >> best: http://www.beis.de/Elektronik/Filter/ActiveLPFilter.html [1]
> >> >>
> >> >> Thank you in advance.
> >> >>
> >> >> --
> >> >>
> >> >> Dami?n Filo
> >> >>
> >> >> Links:
> >> >> ------
> >> >> [1] http://www.beis.de/Elektronik/Filter/ActiveLPFilter.html
> >> >>
> >> >> ------------------------------------------------------------
> >> >> ------------------
> >> >> Check out the vibrant tech community on one of the world's most
> >> >> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> >> >>
> >> >> _______________________________________________
> >> >> Openeeg-list mailing list
> >> >> [email protected]
> >> >> https://lists.sourceforge.net/lists/listinfo/openeeg-list
> >> >> Go to the above address to change your
> >> >> subscription options, e.g unsubscribe.
> >> >>
> >> >
> >> >
> >> >
> >> >
> >> > ------------------------------------------------------------
> >> > ------------------
> >> > Check out the vibrant tech community on one of the world's most
> >> > engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> >> > _______________________________________________
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> >> > Go to the above address to change your
> >> > subscription options, e.g unsubscribe.
> >> >
> >>
> >>
> >>
> >> --
> >> Dami?n Filo
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> >
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> Dami?n Filo
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