help electroencephalograph

[jane012]

I need a little help. Someone can point me a site, components or schematics of electroencephalograph. I must know how its possible capture the low frequency and the components for it.

[Tomi Engdahl]

Here are some possibly useful links:

Electroencephalograph (EEG)
http://www.patient.co.uk/showdoc/27000326/

Electroencephalography
http://en.wikipedia.org/wiki/Electroencephalography

Building an EEG at home with the OpenEEG project
http://openeeg.sourceforge.net/buildeeg/circuits.php

EEG machine instrumentation amplifier
http://www.electro-tech-online.com/elec ... rcuit.html
http://plus1plus1plus.org/Resources/EEG ... .11x17.pdf

EKG Happy EKG Amplifier Circuit
http://home.att.net/~jnozum/EKGHappy.htm

Programmable Chip EEG
http://www.opencircuits.com/Programmable_Chip_EEG

Circuit Cellar Discussion: EEG via soundcard??
http://bbs.circuitcellar.com/phpBB2/vie ... p?p=10919&

SoundcardEEG (scEEG) prototype
http://openeeg.sourceforge.net/doc/hw/sceeg/

No Doze EEG Sleep Detector
http://courses.ece.uiuc.edu/ece445/proj ... _paper.doc

NI discussion forums: EEG (Electro Encephalo Gramme) Components
http://forums.ni.com/ni/board/message?b ... read.id=94

General notes on EEG circuits picked from those pages:
"Leakage currents greater than 20 microamps renders such hardware NOT ACCEPTABLE for medical use. Moreover, the medical profession prefers leakage currents to be no more than 10 microamps."
"ECG circuits use an instrumentation IC that has its opamps and resistors highly matched. Then it can cancel mains hum. It will be difficult to match the parts in this EEG circuit."
"If you have any doubt of any voltage spikes coming out of a computer, oscilloscope, or A/D (analog-to-digital) converter, please add opto-coupling."
"Yes, search around for ECG circuits - they have plenty of it out there, if you dig deep enough. uA741 homebrewed are very problematic - try using an instrumentation amp for this. The most recommended is the Analog Devices AD620. Also, get the real ECG electrodes first - they are important. Search around for online retailers in your place for a bag of 3M disposable or equivalent. One-cent coins isn't going to work well. And finally, isolate the inputs "
"there is several step must be applied. from the electrode --> pre-amplifier-->low pass filter-->high pass--> gain amplifier--> notch filter-->safety circuit. to desgin a EEG amplifier must have high gain, low noise and filtering. "