From: Jim Meissner (jpmeissner_at_mindspring.com)
Date: 2002-01-17 20:00:12
Dear Joel:
> It would be very nice to build the EEG as small and cheap as
> possible......
It is my personal opinion that this project has not progressed because of the above requirement. Joerg has spent a considerable amount of time attempting to make everything as cheap as possible. He has come up with some extremely clever designs.
My view is just the opposite. Get a design that works FIRST. Build it, and then look at how to make it cheaper.
I spent a lot of time building my brain monitor and I am willing to share what I learned. Andreas is incorporating many of my suggestion with the understanding that we can "redesign" to make it cheaper. We are even putting "planned" options on the board.
> and make a separate multiplexer that can be used to
> stack multiple EEG-modules to allow for as many channels as
> one wishes.
The design that Andreas is working on right now has a built in multiplexer for 8 channels. All you need to do is hook up more boards.
> other interfaces (USB, Firewire, IrDA,
> whatever), which might be needed when increasing the number of
> channels and discovering that RS232 is not fast enough
The device that I built ran at 9600 Baud and transmitted 5 bytes at a 128 Hz rate. That worked as well or better than most machines out there. So what is this USB, Firewire, IrDA for? I thought you wanted a CHEAP brain monitor.
So as not to keep this argument going for another few months, the present goal is to transmit RS232 data at 112.2 K Baud over fiber optic isolated transmitter receiver pairs. We will be able to satisfy the safety isolation (5,000 volts ) requirement with a 2 inch length of fiber. The transmitter and receiver will be on separate boards. Andreas has picked out the chips that should just "bolt" together, and we all agree that this is not the lowest cost solution, but should work without fiddling.
Joerg is in search of a "safe" 5,000 volt isolation DC/DC converter that will eliminate the need for batteries.
> simple configurationfile could define what kind of modules
> are on each channel and applications just register themselves
> for the kind of data they can handle and doesn't have to
> know about anything else.
You want "cheap as possible" and Plug and Play windows environment? My view is: lets get something working FIRST before we get so fancy. At this point Andreas has provided 8 channels that can be addressed by the "downloaded" firmware. Later we could have a 2 way comm. link to the micro.
> Of course, all modules should be able to connect directly to
> a PC too if multiple channels are not needed.
No, even for one channel you still have to go through the "save floating isolated" A/D converter!
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: Joel Eriksson
To: buildcheapeeg_at_yahoogroups.com
Sent: Thursday, January 17, 2002 1:38 PM
Subject: Re: [buildcheapeeg] New schematic and layout
From: Joel Eriksson <jen_at_ettnet.se>
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Subject: Re: [buildcheapeeg] New schematic and layout
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On Thu, Jan 17, 2002 at 01:08:26PM -0500, Jim Meissner wrote:
> Dear Andreas:
>
> I just downloaded your latest work. Wonderful, Wonderful, Wonderful!
>
> Think the SMT TinyEEG board is great because you can use one board
> for a single channel machine, or two boards for right and left hemisphere.
It would be very nice to build the EEG as small and cheap as
possible and make a separate multiplexer that can be used to
stack multiple EEG-modules to allow for as many channels as
one wishes. Then only the multiplexer would have to be modified
when someone wishes to make other interfaces (USB, Firewire, IrDA,
whatever), which might be needed when increasing the number of
channels and discovering that RS232 is not fast enough, for example.
> My interest would be to add several more boards for EKG, GSR,
> temperature, respiration rate, etc.
That's a good idea. It would be great if the multiplexer could
handle the data from such modules too, that should not be a
problem if they communicate with equal baudrate I suppose. A
simple configurationfile could define what kind of modules
are on each channel and applications just register themselves
for the kind of data they can handle and doesn't have to
know about anything else.
It's probably obvious now that I'm more into programming than
electronics. :-) Is it at all possible / practical to use a
multiplexer as I have described? Would it be very expensive?
Of course, all modules should be able to connect directly to
a PC too if multiple channels are not needed.
-- Joel ErikssonYahoo! Groups Sponsor ADVERTISEMENT
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