From: Jim Meissner (jpmeissner_at_mindspring.com)
Date: 2002-01-14 21:41:56
Dear Doug:
> Since then you
> posted your schematics (thanks!) and also Andreas posted
> even more schematics. Now I am really confused! I have no
> idea which of these circuits to try. I like this TinyEEG
> approach a LOT (for size/mobility reasons), although I think
> it would be good to have at least some expansion capability
> to add more modules. I wonder if that same design could be
> done with the AT90 series uC on the same form factor.
Well you have your choice. The schematics that I posted actually work, so building them would be safe. If you would be interested in that, I could take some pictures of the board and shielded box, etc.
But, I suggest you wait for Andreas. He is a wiz and can make 2 sided pc boards in 2 hours. I tried to help him with some analog advice which he incorporated in the pc board design. I foresee that board as being very flexible. In the future it would be quite easy to make small changes and use that board for ECG, EMG, GSR, etc. I envision the expansion that you are interested in. But first things first. Small steps. So please be patient.
> Regarding microcontroller choices, I think Atmel is a much
> better choice than HC11.
I was hoping for the HC11 only because I know the code, but I think Andreas is looking at the Atmel?
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: Doug Sutherland
To: buildcheapeeg_at_yahoogroups.com
Sent: Monday, January 14, 2002 2:47 PM
Subject: Re: [buildcheapeeg] Analog-to-digital conversion
Hi Jim,
I am also from the school of "build and test". You can spend
a lot of time designing, but if you don't actually try it in
use, the design might not be workable for many reasons. I'm
a software guy primarily, but I do hardware stuff too, and I
always shoot for "vertical prototypes" that can demonstrate
that things work end-to-end before refining any hardware or
software.
I held back on my digikey order of parts when I heard that
the ModularEEG wasn't performing very well. Since then you
posted your schematics (thanks!) and also Andreas posted
even more schematics. Now I am really confused! I have no
idea which of these circuits to try. I like this TinyEEG
approach a LOT (for size/mobility reasons), although I think
it would be good to have at least some expansion capability
to add more modules. I wonder if that same design could be
done with the AT90 series uC on the same form factor.
Regarding microcontroller choices, I think Atmel is a much
better choice than HC11. The specs are very impressive. It
is getting hard to find HC11 chips too. The microcontroller
in ModularEEG is $6.45, and I can make my own programming
cable and download free dev tools. I like how small they
are too. Your comments on A/D resolution are interesting.
I wonder if there are Atmel uCs with 12-bit ADC? Is there
a concern with conversion time when you go to 16+ bits?
I am waiting for you hardware folks to tell me that one of
these designs is ready for building. Then I will work on
some software.
-- Doug
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