From: sleeper75se (sleeper75se_at_yahoo.se)
Date: 2001-12-26 18:17:39
Hi Jimmy,
--- In buildcheapeeg_at_yahoogroups.com, "JimmyB_101" <jiva_at_humboldt1.com> wrote:
> Sorry for the on going distraction of bringing up soundcards
> ... that was my hope for a very low cost, possibly 8 bit,
> 2 channel, "hobby" unit. No solutions have been proposed that
> seem easy to implement. (yet?)
The modular EEG setup is probably is as cheap as it gets. You can
replace the filters, which use a lot of resistors and capacitors,
with a switched-capacitor single-chip filter to lower the part count,
but that would make it more expensive. (They are $9 each.)
I've got some comments on other ideas that have been discussed
recently:
* Using a delta-sigma ADC with built in filter.
ADS1211 does not work the way you want it to. The filter is designed
for sampling one channel at a time, not for switching between
channels with every sample.
* Signal processor + oversampling:
Not practical unless you are prepared to solder 100-pin fine-pitch
packages that cost maybe $10-$20. Also, DSP's are very noisy and
power hungry. A microcontroller is not fast enough either.
So let's just stick to what we are working on.
You might wonder what is happening right now...
I can't speak for Joerg, but I'm working on a new analog frontend
using low noise LT1012 opamps that hopefully works with protection
resistors. It will be ready for prototyping early/mid January.
> [etc.: clueless wandering through hardware sites over the
> summer left me with the impression that an on board serial
> A>D might be the easiest, cheapest, tested method for a very
> low cost unit IF drivers can be written to retreive
> data in an accurate and timely manner for non DOS Operating
> Systems. Joerge's very low budget serial unit
> from that time period is an example of what could
> be implemented in DOS.]
If we use the standard serial protocol, that won't be a
problem. :-)
/Andreas
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:36 BST