From: sleeper75se_at_yahoo.se
Date: 2001-11-29 22:58:50
Hi Jim,
>3) I do not see that it is possible to build a usable EEG
>for $100 in parts. The HC11 board alone is $100.00.
Actually, eval-boards are damn expensive. The HC11-board is probably
obsolete by any standards, that's why it is so hard to find. The
OpenEEG project is based on a single-chip microcontoller with
internal 10-bit A/D-converters that costs around $10. Look at
www.atmel.com. The processor family is called AVR 8-bit RISC.
> 4) The 555 voltage to pulse width converter that I saw here
> is cute and well designed, but tying up the PC handshaking it
> is pennywise and pound foolish. (See my comment about not
> enough time to do all the tasks)
Actually, those problems can esily be solved with a low cost (say $2)
microcontroller that handles the handshaking.
> How can I access the current design? What is SourceForge?
The current design can be found here:
http://sourceforge.net/projects/openeeg
I'm quite new as an active participant of this group (longtime lurker
though), so I haven't got all the inside information, but someone has
built a working prototype I am sure. On the software-front, there is
very little to be found at the moment, except
http://www.realization.org/page/topics/electric_guru.htm
The program hasen't been updated for a long time. Also, there's no
source to it. My guess the biggest part of the project is software
development. So that's where we need to put the effort i think.
-------------
Doug,
that's an impressive list of links! Nice!
>
> 4) I found some really interesting specs on the
> biosemi web site. There is a schematics for
> an EEG that uses just 3 op-amps, 6 resistors,
> and 2 capacitors per channel. This design
> yields band width of 0.2-40 Hz and has a
> CMRR of 136 dB.
> http://www.biosemi.com/publications/artikel7.htm
That's basically the headstage used in the OpenEEG-design. If you
download the design from Sourceforge, you'll find that link on the
schematics. :-)
> I'm not sure close one can get to the above with a
> low-cost design, but my goal is to get as close to
> that within reason while keeping the parts cost low.
It is relatively easy to build a low-cost, hugh-quality device if you
know what you're doing. The pricetags you find on various websites
are outrageous if you just look at parts cost. A new brainmaster
costs $975. Building one for yourself would perhaps set you back $200
(educated guess). Most of the cost however, comes from the fact that
biofeedback is a low-volume specialty business and that the units are
hand built.
/Andreas
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