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1214Re: [buildcheapeeg] Re: comADC-EEG

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  • Joerg Hansmann
    Oct 5, 2001
      Hi Vladimir,

      ----- Original Message -----
      From: Vladimir.K <gogol101@...>
      To: <buildcheapeeg@yahoogroups.com>
      Sent: Thursday, October 04, 2001 6:20 PM
      Subject: [buildcheapeeg] Re: comADC-EEG

      > I've finished older variant of comADC-EEG , the gameport.
      > ( I used TLC272 and 9V Battery).
      > Now, I am reading gameport on old Linux box and sending to
      > other machine (W98) to Electric Guru.
      > Even some experiment with kernel Real Time extension ( KURT ) and
      > altering parameters in joystick driver, results are not perfect.

      What sample rate and how many bits resolution do you get ?

      > It's
      > only 120MHz Pentium.
      > I would like to try your code for DOS, so if you can, send me, please
      > it. (gogol101@...)

      I will send it via email.
      However it is for the comADC02 hardware.

      > One curiosity:
      > I didnt think that 9V is dangerous, but when I mesured resitance of
      > EEG electrod ( home made saline type ) I got el. shock and becaus
      > I had electrode on forehead near eye so I saw light flash.
      > ( I have 9V battery in Ohmmeter).

      A normal ohmmeter is not very suitable for measuring electrode
      impedance, because it uses DC (resulting in electrode
      polarization) and probably exceeds the limits of IEC601-1
      (therefore you got the electric shock and the light-effects)

      > If I remember, you said that RS232EEG is limited to 8( or 6 ) channels

      6 channels, because the AT90S4433 has only 6 analog multiplexer inputs.

      > for limited bandwith on RS232 ( 115 kbaud).

      There are other limiting factors too like ADC conversion speed.

      > I was suprised when I saw on Linux possible setting for 230 and 460
      > kbaud. I am curious if so high speed is real.

      If the UART chip on the mainboard can handle that speed, I see no
      reason why such settings should not work.
      For RS232EEG however the upper limit is 115200 baud due to
      xtal-frequency and minimum possible baudrate divider factor.


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