Essay: Wireless multichannel EEG recording system

Abstract: This paper describes a wireless multichannel EEG recording system. EEG is a technique that reads electrical activity of the brain that is recorded from the scalp. It consists of transmitter and receiver. The transmitter consists of electrodes, preprocessing section, processing unit, switches and Zigbee module. The receiver consist of Zigbee module, display unit, processing unit, memory, switches and LCD. The captured EEG signals are amplified, filtered and are converted to digital by using A/D converter built in MSP430 microcontroller. The digital signals are transmitted via Zigbee to receiver side. Upon receiving these digital signals by Zigbee module can be displayed on PC via RS232 serial port. The features of this system are portability and low power consumption.
Index Terms: Electrodes, amplifier, MSP430, zigbee module, PC, LCD.
EEG (Electroencephalography) is a technique that reads electrical activity of the brain which is recorded directly from the scalp. It is completely non-invasive technique that can be applied to patient repeatedly. The neurologist Hans Berger in1924 has discovered the presence of electrical activity of the brain and that is represented on paper [1].
EEG signals are recorded by using electrodes that are placed on scalp according to 10-20 international system as shown in following figure.
… The amplitude of EEG signals received from above electrodes is very low i.e. from 0.5 to 100??v which is 100 times less than ECG signal. Also the noise from surrounding tissues of the body and interference from the nearby electrical sources is added to the electrode voltages. Hence, there is need for preprocessing of EEG signals [3]. So, collected electrode signals are amplified and then given to analog circuitry for removal of noise. Then signals are digitized using microcontroller and displayed on PC
The EEG signals are classified in to following five frequency types Delta (0.5-4Hz), Theta (4-7Hz), Alpha (8-13Hz), Beta (14-30Hz) and Gamma (??30Hz) [2].