Development of low cost EEG monitoring device

Abstract

The activities of our body are controlled by our brain. By observing the electrical signal generated by neurons, we can monitor brain activity. This signal is called electroencephalogram (EEG) which can be extracted by electrode and be displayed onto voltmeter, oscilloscope or on computer screen. The electrical signal produced in order of micro volts which is too small to differentiate between the amplitude of the waveform. Focus of this project is to develop an amplifying circuit which is capable to amplify the electrical signal produced by the brain. Method used to extract brain signal by using electrode cap which place onto scalp of our skin hair. The signal obtained from the electrode have amplitude of micro volts and contains frequency component near to 300 Hz and the signal needs to be amplified around a hundred thousand times. The signal gain needs to be conditioned by using instrumentation amplifier such AD620. The reason of AD620 have been used due to it low noise which is suitable for this project requirement. Then signal needs to be passed through active high pass and low pass filter stages. High pass filter used to provides gain to the signal obtained and low pass filter used to conditions the signal which smoothing more the signal. A component used to develop the high pass and low pass filter is a OP07 operational amplifier. Results show that wave produce when using OP07 is slightly better compare to Op-amp 741 because OP07 has low noise capability. ADS1299 used to convert the signal from analog to digital form. The analog amplifying circuit is interface with computer by using 8051 microcontroller.