From: Jim Meissner (jpmeissner_at_mindspring.com)
Date: 2001-12-19 16:30:28
Dear Joerg:
I would like to help. I solved these problems many years ago. After my move it is very frustrating to know that you have something and cannot find it. But, I have found most of the hardware including the input stage but not the schematics. How would you suggest I get the information to you. I do not want to tell you how to do your design. But, I can tell you how I solved the various problems you are running into.
I posted the source code for the opto isolated HC11 module on my webpage. There are some EEG test files and some real EEG data that you can download look at using the slink12r program.
Juergen P. (Jim) Meissner
Check out my Website at www.MeissnerResearch.com
Read about the benefits of the Brain State Synchronizer sounds for improving your life and health.
----- Original Message -----
From: Joerg Hansmann
To: buildcheapeeg_at_yahoogroups.com
Sent: Wednesday, December 19, 2001 10:08 AM
Subject: Re: [buildcheapeeg] Re: modularEEG input stage prototype
Hi Andreas,
----- Original Message -----
From: sleeper75se <sleeper75se_at_yahoo.se>
To: <buildcheapeeg_at_yahoogroups.com>
Sent: Wednesday, December 19, 2001 3:55 AM
Subject: [buildcheapeeg] Re: modularEEG input stage prototype
> Hi Joerg,
>
> sorry to hear that it didn't work. Does this mean we don't have a
> working input stage at the moment?
We could use the RS232EEG input stage instead (first stage gain reduced to 10
and one additional stage) and add the DRL and guarding
circuit.
However then we have no user protection against INA114 worst case failure
(inputs internally shorted to supply lines)
> A couple of questions:
>
> How is the input stage realized? A double sided board with ground
> planes and guards is much closer to how it should look than a
> breadboarded setup.
It is a single sided board (the gameport-EEG PCB) heavily patched
(traces removed, wires added)
Interference as a possible cause for the bad result has been one of my
ideas too, and I have soldered copper foil for shielding below the input
stage and finally shielded the whole pcb. This has removed 50Hz line noise
completely but not the 0.1 Hz noise.
Further I have changed all AGNG lines to star topology
to avoid possible current coupling - but that has changed nothing.
> The schematic says the protection diodes are 1N4148.
It should have been BAT48 shottkey diodes - but these I have
removed right in the beginning because they picked up voltage
variations from the DC supply line and thereby caused the whole
circuit to oscillate from rail to rail.
> What happens if
> you cover them with a piece of electricians tape?
> (They're light sensitive)
>
> Is the noise reduced/changed if you cool the input circuit (not the
> INA114) with cold-spray or something similar? I realize this is a
> shot in the dark...
I could test it.
Regards,
Joerg
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This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:35 BST