possible to assemble 2 EEG-SMT to use 8 electrodes ?

[Stéphanie]

Hi All,

I have ordered an aseembled EEG-SMT on Olimex website,

Someone said to me that the only drawback of this version is that it has maximum 4 electrodes (whereas you can have 8 when assembling the OpenEEG).

So I was wondering if it's possible to assemble two EEG-SMT in order to use 8 electrodes ?

Thanks a lot,
Stéphanie

[olimex]

you can add USB hub to your computer and connect as many SMT-EEGs as you need thus having any number of electrodes

[ellecieffe]

you can add USB hub to your computer and connect as many SMT-EEGs as you need thus having any number of electrodes

ModularEEG P2 firmware can manage up to 6 bipolar channels , right?

How do you manage DRL channels? They all connected to the user, one for each EEG device? or maybe can be connected via COM, VREF and AGND? what are these?

Thanks

[LubOlimex]

Hey Stéphanie and ellecieffe,

Connecting more than one EEG-SMT to a single computer is possible and achieved as explained on page 17 of the manualhttps://www.olimex.com/Products/EEG/OpenEEG/EEG-SMT/resources/EEG-SMT.pdf. Please note that this is more of a workaround than intended feature. Basically the EEG-SMTs you have connected to the computer will work in parallel rather than being recognized as a single data stream. This is not a problem for our readings since we will place the electrodes on different spots, but might provide practicable difficulties. The main problem is that there isn't ready software for multiple inputs and you will have everything x2: two separate client programs opened, two DRL electrodes placed, two devices recognized in the computer system, etc.

ModularEEG P2 firmware can manage up to 6 bipolar channels , right?

Yes. But that doesn't affect connecting multiple EEG-SMTs to a single computer since each of them is own instance of P2 firmware.

How do you manage DRL channels? They all connected to the user, one for each EEG device? or maybe can be connected via COM, VREF and AGND? what are these?

Yes, unfortunately, each separate EEG-SMT needs to have its DRL connected to the user. By the way from my experience I've noticed the best place for the DRL is the soft tissue of the ears.

Best regards,
Lub/OLIMEX

[ellecieffe]

Thanks for the answers.

Sorry, what about COM, VREF and AGND holes near the DRL circuit? what are these?

Best Regards

[LubOlimex]

Hi ellecieffe,

The COM can be used to add additional channels on hardware level. You will have to replicate the same layout like the two channels implemented the COM has to connect to units like U5 and U6 (INA114BU/1K). Since the elements are quite specific this hasn't been tested much.

The VREF and AGND are test points. There should be 2V between them.

Best regards,
Lub/OLIMEX