[dmarto]

There is also the OpenEEG project[0], the boards are way cheaper (sub 100eur[1]) and also they are both open source and open hardware.

[0] - https://openeeg.sourceforge.net/doc/index.html

[1] - https://www.olimex.com/Products/EEG/OpenEEG/

[ron_87]

is is possible measure EEG with 8 bits ADC ?

[Kiboneu]

I've been wondering about this for a while.... have you tried?

I'm not a EEG designer but I've experimenting and learning about it. Sounds like you make PiEEG? This is really cool and I appreciate the docs on the github.

After amplification, you could get the signal 0-100uV to ~0-Vanalog; so then the entire 8-bit range could ideally be used. Realistically, after filtering, due to roll-off / artifacts one could probably use 3/4ths of that space -- so ~ 192 voltage levels that can be determined by the ADC per sample. Does this sound right?

It'd probably depend on what level of control / reliability one would want from the EEG data; I imagine that you could probably cut a lot of corners if, say, you were only measuring for hemispheric coherence in a small set of frequency bands, or stages of REM sleep (and maybe ERPs like p300).

I don't know, this is in my upcoming experiments. Originally this was an attempt to build an EEG amplifier / filter circuit for an atmega328p 10-bit ADC but for my purposes I settled for a 12-bit (and possibly hardware oversampling) on an EFM32.

[dmarto]

With an active electrode, it should be good enough. After all, we are talking about hobby-grade results.

The Olimex ones are 10-bit (supporting both active and passive electrodes), while it's claimed[0] that 12-bit resolution is sufficient for EEG.

However, it's worth noting that there are obvious advantages to the higher resolution.

[0] https://www.biosemi.com/faq/24bitsystem.htm

[ron_87]

EEG in microvolts, if ADC 12 bits, then reference for ADC should be in millivolts

[mlyle]

He mentions active probes. Active probes have amplification.

As his link makes clear, your ADC just needs enough resolution to measure the signal when the (amplified) offset voltages don't saturate it.

[ron_87]

yes, I told about digital EEG device from this website. To clarify analog device, I need a little more time