Re: 24 channel EEG

Regarding building a 24-channel EEG system based on OpenEEG...

You should be aware that OpenEEG is two pieces: (1) the analog components with the necessary differential amplification and (2) the digital components that do the analog-to-digital conversion (ADC) and communication to the PC.  There are also critical components like the power supply with the safety-critical electrical isolation.

In OpenEEG, the key bottleneck to expanding the channel count is the number of ADCs available.  The current design uses ADCs that are built into the microprocessor that is at the heart of the digital components.  I think that it has 6 ADCs, so you could redesign OpenEEG to get up to 6 channels by simply copying and pasting the analog components and wiring them to the unused ADC inputs on the microcontroller.

To maybe make this easier, be aware that the OpenEEG processor is from the same family as the Arduino.  So, if you already use Arduino, you could focus on just the copying 6x the analog components onto a new board and then plug their outputs into the analog inputs on the Arduino.  That would be pretty sweet...but you'd be missing all of the electrical protections...so think VERY carefully about that.  As an exercise in circuit-building, though, it might be a good approach.

If you go Arduino, you could also go with an Arduino Mega and get more ADCs.  That has 16 analog input pins, so you could maybe make a 16-channel EEG system out of it.  Again, copy-paste the analog components from OpenEEG and you might get there.

Before jumping to 24 channels (or even 16 or even 8),  I'd definitely aim at a smaller goal of 4 or 6 channels.  While the copy-paste process of making more analog channels from the OpenEEG schematic is conceptually simple, doing things in the real world is always harder than you expect.  Start smaller, get experience, find success, then step up to the higher number of channels.

Another alternative is to check out OpenBCI, which is an 8-channel hacker-friendly EEG system.  It has built-in capability to be daisy-chained to get at least up to 16-channels.  The downside of OpenBCI is that it's not ready yet...it's still in its kickstarter.

Chip

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