Olimex EEG-SMT + Brainwave

April 2nd, 2012

MOD-EEG-SMT (http://www.olimex.com/gadgets/index.html) The Modular EEG-SMT is a ready-to-use two channel biofeedback board for electroencefalography (EEG). Compared to other medical EEG systems, this has a fairly good price. Unlike other Olimex modules, this board comes assembled in anti-static plastic box. It feeds and sends the readings through a A-B USB cable and requires 1 passive and 4 active (http://radek.superhost.pl/active_electrodes/index.php?action=theory) electrodes (or 5 passive electrodes). This EEG device is setted up only for a windows environment and needs ftdi drivers and a software such as Electric Guru or Brain Bay to Start working with it. Personally I chose to use Brain Bay, an open source, free biofeedback software.

Sources

I got the sensor directly from Olimex (http://www.olimex.com/gadgets/index.html). As I made a parchase for research purposes, the manufacturer sold me the eeg-smt with a 20% off the 99EUR price (be careful with the price, it is expressed in EUROS). I also bought from them 5 electrodes, 1 passive and 4 active, and the 1.5 mt USB cable. The total value for the complete set is 113.60 EUR or approximately 150.36 USD (+ shipping).


The detailed list of prices is as follows: MOD – EEG – SMT: 99 EUR Active Electrodes: 9 EUR Passive Electrodes: 5 EUR USB Cable: 2 EUR


Olimex doesn’t have an online store, so the way to buy its products is buy emailing them and paying, for example, with paypal. They are located in Bulgaria, so be patient if you chose the cheapest shipping mode (about two weeks for the U.S.). There are two important aspects regarding the shipping: you can take an insurance in case your package get lost or damaged, and is good to read the taxes disclaimer before you purchase if you are located in Europe. More info here (http://www.olimex.com/gadgets/index.html) and here (http://www.olimex.com/gadgets/index.html) You can also make all the questions you have through their email, they are very kind and answer very quickly.

Applications

Together with the electrodes, the SMT-EEG is a device made for sensing and amplify brain electrical activity, from the surface of the brain without surgery. It was meant to be used by people who are interested in EEGs and have not necessarily a medical or scientific background. Starting with a series of DIY EEG boards, the SMT-EEG is the newest device manufactured by Olimex, and first one to be completely assembled, calibrated and ready to use (release date: around mid November 2011).

Although I still don’t have any information about people using it for specific projects, I can list a number of common or possible applications: -Biofeedback (http://en.wikipedia.org/wiki/Biofeedback)

 --Neurofeedback (http://en.wikipedia.org/wiki/Neurofeedback)

-Real-time telemetry of brain signals -Patient monitoring

--Game interfaces --Artistic applications --etc.

An interesting place to find EEG projects is this (http://shifz.org/).

Electrical Characteristics

  • MOD-EEG-SMT:

Operating Voltages: -2.7V – 5.5V (for Atmega 16L) -4.5V – 5.5V (for Atmega 16) Power Consumption at 1 MHz, 3V, and 25ºC (for Atmega 16L) -Active: 1.1mA -Idle Mode: 0.35mA -Power down Mode: < 1uA

  • Electrodes:

Operating Voltage: -5V

MOD-EEG-SMT Datasheets / Manuals MOD-SMT-EEG Manual: http://www.olimex.com/gadgets/index.html

MOD-SMT-EEG RevB Schematic: http://www.olimex.com/gadgets/MOD-EEG-SMT/MOD-EEG-SMT-SCHEMATIC-REV-B.pdf

Inside components datasheets

ATMEL16 (inside microcontroller) http://www.atmel.com/Images/doc2466.pdf

FT232R (USB to Asynchronus Serial Data Transfer) http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf

INA114 AU (Precision Instrumentation Amplifier) http://gerard.paresys.free.fr/Projets/INA114.pdf

MCP6071 (High Precision Operational Amplifier – OpAmp) http://ww1.microchip.com/downloads/en/DeviceDoc/22142_B_MCP6071.pdf

TLC277CD (Precision Dual Operational Amplifiers) http://www.chipcatalog.com/TI/TLC277CD.htm http://www.ti.com/lit/ds/symlink/tlc277.pdf

AP432SA (Adjustable Precision Shunt regulator) http://www.diodes.com/datasheets/AP431_A.pdfTMV0505S

TMV0505S (DC / DC Converters) http://www.tracopower.com/fileadmin/medien/dokumente/pdf/datasheets/tmv.pdf

ELECTRODE Parts Datasheets / Manuals TL062CD (Op Amp) http://www.futurlec.com/Linear/TL062CD.shtml

F2594TR-ND (ESD Supressor) http://www.littelfuse.com/data/en/Data_Sheets/Littelfuse_PulseGuard-ESD_PGB1.pdf

BZV55C6V2 (Zenner Diode) http://61.222.192.61/mccsemi/up_pdf/BZV55C%20Series%28MiniMELF%29.pdf

BAV199 (Low Leackeage – Double Diode) http://www.nxp.com/documents/data_sheet/BAV199.pdf

---

Options for DIY Electrodes:

http://openeeg.sourceforge.net/doc/hw/ae.html http://openeeg.sourceforge.net/doc/hw/electrodes/passive/

Pin Descriptions

EEG-SMT I/O CH1+: Positive pole for active electrode in channel 1 CH1-: Negative pole for active electrode in channel 1 CH2+: Positive pole for active electrode in channel 2 CH1-: Negative pole for active electrode in channel 2 DRL (http://www.biosemi.com/faq/cms&drl.htm): Driven Right Leg, must be a passive electrode. All the current flows towards this ground input. USB Type-B: Universal Serial Bus for connecting EEG-SMT with computer. It works as a data and power source cable.

Atmega 16 Inside of the EEG-SMT is an 8bit Atmega with the following characteristics.

Active and Passive Electrodes -5VA: Power Input (+) -AGND: Ground (-) -OUT: Data output

Microcontroller Connections

Passive and Active Electrodes are connected to the EEG-SMT (through 3.5 plugs) which has an Atmega 16 in its circuit. To connect this device to the computer you will need an A -B USB cable. The Manufacturer recommends to use Electric Guru or BrainBay as softwares (only for Windows). I chose to use BrainBay which has really good examples for testing the board.

According to Brain Bay’s creator, there shouldn’t be any problem interfacing EEG-SMT with Processing, given that it has already an Atmega Microcontroller in it. To do so, somebody has to provide “the (or integrates the existing) code to read the signal data from the COM-port, to do something useful with it (e.g. graphical display etc.)”.

According to Olimex EEG-SMT User Manual, the Atmega16 can be re-programmed with an ICSP debugger/programmer (which is not delivered with this EEG). You can find a list of programmers from the same manufacturer in this Manual (http://www.olimex.com/gadgets/MOD-EEG-SMT/EEG-SMT-USERS%20MANUAL%20Revision%20B.pdf).

For security reasons, I haven’t done this experience yet. But I would like to test it when I get more familiar with the board.


Other words about connecting it with Arduino: “…on the other hand it would also be possible to connect an Arduino board to the EEG device, but via UART, not via USB (the EEG device is not a USB host, but also a client as the Arduino) - if you grab the UART signals (RX/TX) before the UART/USB converter you can connect the arduino via UART (http://en.wikipedia.org/wiki/Universal_asynchronous_receiver/transmitter).”

Presentation + Testing results samples

SMT EEG + Brainwave follow link text ...

Keywords:

Electroencefalography, EEG, Olimex Modular EEG-SMT, Open EEG