Electroencephalography made cheap and easy
Project base on the INA163 instrumentation amplifier for the readout of encephalographic signals
The overall cost of one device (including the INA163 and three electrodes) should be under 50€ (updated 06/2022) (yes, Aliexpress is your friend). It is also easy to build (it only requires basic soldering skills) and does not require neither special power supply nor other electronics instrumentation for it to work
- The designed PCB (schematics in this repo)
- Two 7V-12V batteries
- Electrodes (highly recommended use of either silver or gold-plated electrodes)
- 3,5mm male to male audio cable
- A PC running Matlab (Maybe python in a future, who knows) with 3,5mm mic input
- Conductive gel
Just solder the SMD components as shown in the schematic. It is highly recommended to use a stencil with solder paste. Nevertheless, the components are big enough (0603) for allowing a painless hand-soldering experience.
IMPORTANT: for safety issues, it is recommended to run this program from a laptop computer not connected to the plug of your house. I mean, this is as risky as wearing some wired headsets, but everyone warns about this online, so here I am. I'm not responsible for anything, u know.
Note: This is not an easy project for plug-n-play users. The amplifiers are highly sensitive to noise and you will surely have to debug the system in order to obtain optimal performance. In this way, I highly recommend reading some papers about how EEG really work in order to fully understand what we are trying to achieve. As a first reference, I can recommend the following video:
The connection of the electrodes can be carried out in multiple different ways. It will all depend on how many electrodes you have and what signals you want to measure. Moreover, since we are using differential amplifiers, the signal will be measured between the difference of two point, so that there will be no absolute ground. This way, you will have to decide what electrode to compare with which one in order to see the signal you are looking for. See the following great video in order to understand the different usual montages:
As a first approach, using two electrodes for measuring the left and right halfs of the frontal lobe and a third electrode as a wirtual ground behind your ear can be a good solution for measuring alfa waves and eye blinks.
Remeber to apply conductive gel between the electrode and the skull and to get the electrodes as fixed to the head as possible without hurting the patient, since loose electrodes can lead to noise in the measurements
The PCB is powered though two batteries (between 7V and 12V each) so that the operational amplifiers can work with both positive and negative voltages.
Connect the electrodes to the PCB and the PCB to the audio input of your laptop. Beware that this board is extremely noise sensitive, so stay away from low-frequency EMI sources. Also, always power it through batteries, since the 50Hz/60Hz of a power supply can dirty the ignal output
Cuando tenga tiempo escribo algo wapo, primero tengo que mriar si funciona
Due to the high sensibility of the devide, the EECutre may also be used for readout of Electrocardiographic signals as well as Electromipgraphic signals. Just connect different electrodes to the input ports of the PCB and have fun!