OpenEEG hardware

The OpenEEG project has seen contributions from many talented hardware people over the years, resulting in several different designs which have been tested and tried by various people. Below are just a few of them. For newcomers to EEG hardware design, the issue of isolation is very important here. You can't just directly connect your brain up to your PC electrically without risking unpleasant things happening. Isolation measures (such as opto-couplers, DC-DC converters, isolation gaps, etc.) must be used in the design and construction of an EEG unit. See our WARNING for more details.

ModularEEG

The modularEEG is currently the most popular of the EEG hardware designs created by the OpenEEG hardware developers. (Andreas Robinson and Joerg Hansmann have been the most active developers on this design). There is plenty of documentation online and help available on the mailing list if needed. The modularEEG is also good for people wishing to experiment with newer ideas as it has bi-directional serial communication, microcontroller firmware that can be modified and updated, and spare analogue inputs and digital I/O pins available for custom applications. The analogue board's input circuit can also be adapted for other applications such as ECG. Olimex of Bulgaria sell the bare PCBs and also pre-assembled/tested modularEEG boards. In addition, a fully-assembled unit may be available from MindField sometime in the near future.

Active Electrodes

The modularEEG was designed to use standard passive EEG electrodes with shielded cables. However, when using active electrodes instead, no skin preparation is required and better performance can be achieved under imperfect conditions. The active electrodes described here connect directly to the modularEEG without requiring any modifications to the boards.

Soundcard EEG (scEEG)

This is a stalled project that shows promise if anyone wants to work on it. The EEG signal is converted to an audible tone using an FM encoder, which can then be passed through an opto-coupler before going to the PC soundcard for software-based FM decoding. This could potentially allow a very low-cost two channel EEG device to be created. Latest news (May-2005) is that Andreas and Jon are looking at it again now.

EEG Calibrator

The EEG Calibrator is intended for the performance measurement, confirmation and the evaluation of various EEG Neurofeedback devices and solutions. The unit can be used to measure the performance of EEG hardware, software or a combination thereof. It could also be used to evaluate neurofeedback treatment protocol design behaviour as designed in software packages such as BioExplorer, BioEra or similar.

Other designs

There have been many other hardware designs considered and/or built by the group. For more details, search the mailing list archives or ask on the mailing list. For example, Andreas Robinson built a tiny SMD-based two-channel EEG as a prototype. Joerg Hansmann has a collection of older designs (RS232EEG, 555-EEG, etc) on his site. Other possibilities considered have included USB or S/PDIF interfaces, or using linear opto-couplers to open up more design possibilities (for example, see this design by Bernd Porr of Stirling University; you can get pre-matched opto-couplers in a single package now), or using 24-bit convertors to make the system more flexible regarding DC and gain levels. Joe Street created a stand-alone electrode resistance checker, and Joerg designed an automatic electrode resistance measurement patch for the modularEEG. And so on and so on ...

If designing, building and testing this kind of electronics is your kind of thing and you have ideas you'd like to develop, then you are very welcome to join the mailing list, bring your skills and share in the knowledge that the group has built up.

EEG hardware on other sites

• Monolith EEG