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Re: [buildcheapeeg] question about safety testing

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  • Joerg Hansmann
    Hi, ... From: To: Sent: Sunday, December 31, 2000 7:09 AM Subject: [buildcheapeeg] question about safety
    Message 1 of 3 , Jan 1, 2001
      Hi,

      ----- Original Message -----
      From: <yaniv_vi@...>
      To: <buildcheapeeg@egroups.com>
      Sent: Sunday, December 31, 2000 7:09 AM
      Subject: [buildcheapeeg] question about safety testing


      > --- In buildcheapeeg@egroups.com, "Joerg Hansmann" <jhansmann@g...>
      > wrote:
      > hi jeorg
      > if i understand correctly you have to test every unit that comes out
      > of the factory with tests according to the iec601 ?

      If IEC601-1 is applicable , I would say: Yes. In series production
      probably random samples will be enough after an initial phase.

      > one thing about irda versus cable -
      > we can use a very simple not irda - infrared comm , that we'll
      > specially design with full duplex

      For full duplex the forward and the backward channel have
      to be designed in a way that they will not interfere with each other.

      This could be done with multiplexing (e.g. time-multiplex,
      frequency-multiplex etc.) or physically isolated channels
      (fibre optics, etc.)

      IRDA transceivers simply suffer from scattered light that goes
      from the IR-emitter to the IR-receiver in the same device.
      IRDA transceivers block their input while transmitting in order
      to not receive their own data and to keep the AGC of the
      receiver adjusted to the remote device.
      Scattered light could be avoided with tubes and lenses and
      precise alignment of the two devices.
      However the cost-benefit comparison seems unfavourable to me.


      > , 115000 baud , and because we have
      > to build reciever card - we can build it to connect to printer port
      > throught long 5meter cable . this could be very simple little card ,
      > that can be put near the device , and he'll get he's power from
      > the printer port .

      Why printer port ? What advantages do you see over com-port ?

      The com-port seems better to me, because
      it has windows driver support and is supported by
      existing software like Rob's ElectricGuru.

      > i think this interface design could be very simple one .

      > it's seems o.k. with you ?

      Hm, yes... as long as I am not the one, who has to build it ;-)

      My current approach to solve the isolation problem
      is two optocouplers _inside_ the RS232EEG that are
      built of discrete IR-Emitters and Phototransistors and
      have an isolation distance of 2cm (that will give protection
      of about 20kV ).
      For such short distances and fixed alignment there should
      not be greater problems and the costs and development
      time will be sufficiently low.

      Regards,

      Joerg
    • yaniv_vi@yahoo.com
      ... wrote: o.k. i get your point about the interface - you did alot of good work for this project and i really appreciate youre willingness to work and share
      Message 2 of 3 , Jan 3, 2001
        --- In buildcheapeeg@egroups.com, "Joerg Hansmann" <jhansmann@g...>
        wrote:
        o.k. i get your point about the interface - you did alot of good work
        for this project and i really appreciate youre willingness to work
        and share the design , so sorry about the irda stuff .

        so now you're current problem is 10UA current .
        i remember in design of the brainmaster the input stage is the
        instrumentation amplifier . and it's suppose to be safe enough .
        (to collura who designed it does it for his living)
        when i look at your first design - i guess the only 2 things
        that can make a leakage current are :
        1.the diodes (esd protection )
        2.the amplifier
        my guess is the diodes will make the noise .
        and i don't remeber i came across diodes in any eeg design
        that i saw .
        maybe the design will be good also with out them ?
        i'll start checking this on the net .
        can you please tell what's the leakage current of input amp ?

        by the way - how's you re desig change for 10UA ?is it working ?
        what the preformance changes ?

        and to another subject :
        are you sure the in mass production we only do sample tresting for
        iec ?
        because on every chip i know there's a disclaimer agains medical
        warranty - so i don't know if what enough for plain electronic device
        (sample testing) is enough for medical device .
        and are first quantities will be small - 100 max i think .
        and another thing - one of the ways to market and sell is by third
        part kit assembly - this is done by hand assembly , doesn't it matter
        for sample testing ?
        i'll try to get some info about the question here , and also please
        send me your opinion .

        and again sorry for the irda issue .
        sincrerly yaniv v.
        > Hi,
        >
        > ----- Original Message -----
        > From: <yaniv_vi@y...>
        > To: <buildcheapeeg@egroups.com>
        > Sent: Sunday, December 31, 2000 7:09 AM
        > Subject: [buildcheapeeg] question about safety testing
        >
        >
        > > --- In buildcheapeeg@egroups.com, "Joerg Hansmann"
        <jhansmann@g...>
        > > wrote:
        > > hi jeorg
        > > if i understand correctly you have to test every unit that comes
        out
        > > of the factory with tests according to the iec601 ?
        >
        > If IEC601-1 is applicable , I would say: Yes. In series production
        > probably random samples will be enough after an initial phase.
        >
        > > one thing about irda versus cable -
        > > we can use a very simple not irda - infrared comm , that we'll
        > > specially design with full duplex
        >
        > For full duplex the forward and the backward channel have
        > to be designed in a way that they will not interfere with each
        other.
        >
        > This could be done with multiplexing (e.g. time-multiplex,
        > frequency-multiplex etc.) or physically isolated channels
        > (fibre optics, etc.)
        >
        > IRDA transceivers simply suffer from scattered light that goes
        > from the IR-emitter to the IR-receiver in the same device.
        > IRDA transceivers block their input while transmitting in order
        > to not receive their own data and to keep the AGC of the
        > receiver adjusted to the remote device.
        > Scattered light could be avoided with tubes and lenses and
        > precise alignment of the two devices.
        > However the cost-benefit comparison seems unfavourable to me.
        >
        >
        > > , 115000 baud , and because we have
        > > to build reciever card - we can build it to connect to printer
        port
        > > throught long 5meter cable . this could be very simple little
        card ,
        > > that can be put near the device , and he'll get he's power from
        > > the printer port .
        >
        > Why printer port ? What advantages do you see over com-port ?
        >
        > The com-port seems better to me, because
        > it has windows driver support and is supported by
        > existing software like Rob's ElectricGuru.
        >
        > > i think this interface design could be very simple one .
        >
        > > it's seems o.k. with you ?
        >
        > Hm, yes... as long as I am not the one, who has to build it ;-)
        >
        > My current approach to solve the isolation problem
        > is two optocouplers _inside_ the RS232EEG that are
        > built of discrete IR-Emitters and Phototransistors and
        > have an isolation distance of 2cm (that will give protection
        > of about 20kV ).
        > For such short distances and fixed alignment there should
        > not be greater problems and the costs and development
        > time will be sufficiently low.
        >
        > Regards,
        >
        > Joerg
      • Max Kargl
        Note:the first part of this message is kept in german, as no project-related things are mentioned. Hi Jörg, 1) da ich jetzt endlich etwas Zeit finde, möchte
        Message 3 of 3 , Jan 17, 2001
          Note:the first part of this message is kept in german,
          as no project-related things are mentioned.

          Hi Jörg,

          1) da ich jetzt endlich etwas Zeit finde, möchte ich gern an den
          Nachbau der EEG-Schaltung gehen.Dazu hätte ich folgende Fragen:
          a) welches der vorliegenden(Egroups ?) Designs empfiehlst Du?
          b) hast Du EINE günstige Bezugsquelle für ALLE Komponenten, vor
          Allem aber für INA114 (von Deutschland nach Östereich pflegt
          man
          bis zu 40 DM Versandkosten zu berechnen!)?
          c) muß für die In-Circuit-Programmierung des Controllers das
          Board-
          Design modifiziert werden,welche Software ist verwendbar?
          d) Ist PC-seitig(Windows95,98,NT,Linux) schon irgendeine
          rudimentäre
          Software(Dll) vorhanden ?

          2) Cheap Electrodes:
          As my grandfather bought a PCE-Trainer (standalone
          biofeedback-device,measuring ultra slow (brain) potentials)with a

          set of headband electrodes included,which I was told on request
          was
          also used
          for EEG-measurements, it showed up that these are very simple made:
          the set consists of a 5cm rubber band which can be adjusted to fit
          any headsize.There are four 4 polished steel (nirosta) electrodes
          attached which are made of simple PRYM Snap-Buttons.On the

          outside the unshielded electrode cables which are bundled into
          a (bajonett-locked) 5 pin Din-Plug,can be clipped in.
          The set costs about 100 $ and can be easily rebuilt for about 5$.
          The electrode placement (for the purpose of ULP-measurement)
          is as follows 2 (GND)dorsal,distance about 10 cm at height of eyes,
          2 ventral,same distance,at temple-height.
          I guess for the EEG-Amplifier the AGND electrodes would be
          attached
          to the ears (with clips).
          Contact to the skin is established by applying saltless
          electrode-gel.

          (.Would it make sense to solder sheet silver to the electrode
          surfaces (and after that,chloriding them) for better results ?
          (.By the way,the cheap one-way electrode set (3M) of the same
          distributor is ment for EKG usage only.

          (.Also by the way- As the units case is sealed with superglue,
          I won't be able to take an analyzing glimpse at the circuit
          for the time it is under warranty (6 months), although I am
          eager
          to learn some secrets of DC-measurement.

          3) This point has also been discussed (but not answered) in the
          brainmaster newsgroup:

          Have you ever thought of using the pc's soundcard
          as high quality (16 Bit !) AD-converter ?

          I can imagine several obstacles:
          (a optical insulation would have to deal with analogue signals.
          (b don't know how much aditional noise will be produced.
          (c input decoupling of the soundcard could cut off low frequencies.
          (d As far as I understand (most?) SCs have a minimum
          adjustable sample frequency of about 8kHz,
          so maybe one would have to take only samples of the sample.
          (e the only DLL I know offers only a call which can not

          execute in the background.There exist several

          programs(shareware), which utilize the soundcard as realtime-
          oscilloscope but without sourcecode...
          I guess one would need some DMA-Coding(of which I have no idea)
          (f I don't think MS-DirectSound supports the required tasks.

          Greetings, Max
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