Eeg Acquisition System For Brain-computer Interface Design And Implementation

A brain–computer interface (BCI) system controls the interrelated devices based on the features extracted from the brain signals. It is a communication system that does not depend on the brain's normal output pathways of peripheral nerves and muscles. The foremost thing for the BCI is to acquire the brain signals. Nowadays the Electroencephalographic (EEG) is the optimal choice for the BCI due to its no damage, feasibility and low cost.This paper studies the EEG forming theory, the EEG lead mode and the interferences about EEG recording. Then an EEG acquisition system is designed. The system consists of master module, slave module, communication module, EEG recording module and electrode module.The master module sends the computer commands and receives the EEG data. The slave module controls the recording module for channel selection, recording startup/end and sends the data to the master module. The communication module sends wireless messages between master module and slave module. The active electrodes at the scalp surface convert the brain state into electrical signals. The signals are amplified, filtered by three stages and converted to digital data by the recording module. The techniques to reduce interferences are developed in the modules, such as the active electrodes, the driven-right-leg (DRL) circuit and a series of filter circuits.To meet the need of the practicality, a BCI system should have the following characters: long term working, stabilization, reliability, real time and convenience. Some aspects of the system exhibit the characters. For example the wireless communication module extends the user's movement area and shortens the route of the analog signals. It improves the quality of the signals except the convenience to people. Another example, the active electrodes work longer and they are more reliable. In addition, complicated pretreatments are not needed when active electrodes are used.