From: Joerg Hansmann (info_at_jhansmann.de)
Date: 2001-08-08 15:52:06
Hi,
----- Original Message -----
From: <gogol101_at_yahoo.com>
To: <buildcheapeeg_at_yahoogroups.com>
Sent: Wednesday, August 08, 2001 2:49 PM
Subject: [buildcheapeeg] Re: comADC-EEG
...
> Becose I have simple GSR meter (plan from Frans S.
> http://groups.yahoo.com/group/buildcheapeeg/message/887 )
Was that the "HUIDMETER.ZIP" ?
(see circuit.gif)
I do not have the message ID-numbers.
> I would like to know if I can use this ADC for GSR.
That should be possible.
> What is input voltage range ?
-Ub for AD=0
+Ub-3V for AD=max
BTW:
Ub could very well be +-4.5 V from a 9V battery.
> Can I lower sampling frekvency. I think for GSR I don't need too high
> sampling.
Yes. I have made a redesign (see comADC01-2_sch.png)
that uses a programmable sampling clock from the PC software.
However I would not recommend to lower the sampling clock
below 2 x line frequency (about 100 or 120Hz depending on country),
because else you have no good possibility to check, if your
circuit picks up line noise.
> I suppose when I decrease samp. frekvency I can increase output
> pulse, so increase resolution (or precision )
> I hope Im not wrong.
You are right. Simply double C8 and you get 1 bit resolution more.
If line noise detection is not a problem, you can do this doubling
lets say up to 16ms pulse time and get +4bit added to your resolution
at 1 ms.
If you had 8 bit at 1 ms you would now have 12bit.
However remember that during the pulse-time your PC
does nothing else but counting. So key, mouse etc. input
is stopped during this time and sound-output could be
problematic.
> > I have connected the comADC prototype with the amplifier
> > stage of the old gameport EEG and written a DJGPP / allegro
> > program to decode the interface data.
>
> I'v looked at DJPG and Allegro. Is there program from which screen
> shot where taken? I didnt find any.
>
> Its your own and is it available ?
I have written it in C++.
It is a quick and dirty prototype. The GUI is not finished.
All setup is via #define in the source.
So if you want to run it on your PC you probably
have to make some adjustments and recompile
it with DJGPP (and the allegro gaming library).
If you are not scared until now, I can mail you the
source code and/or the executable.
Regards,
Joerg
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:31 BST