Picture of DIY EEG (and ECG) Circuit
EEGs are a noninvasive way to look into your brain. While the brain is extremely complex, areas of it can lock into circular firing patterns, resulting in telltale brain waves that one can observe with the right equipment. Intensity of these waves change depending on your internal state. The waves we will be most easily able to distinguish are alpha and beta waves -- alpha waves occur at around 8-12 Hz and when measured from the frontal lobe provide an estimate of how relaxed a person is, while beta waves are around 12-30 Hz and correspond to how much a person is concentrating or how alert they are.

The concentration of each wave can also tell more specific things about your thought patterns depending on where you measure them from. For example, alpha concentrations on the left motor cortex increase when you think about moving your right hand. Regardless of where you're taking measurements, looking at the concentrations of waves in real time - a process called biofeedback - can give you much greater control over them.

This tutorial is an in-depth guide on how to make your own simple EEG circuit. Along with monitoring brain wave concentration, the final circuit can also be used as an ECG, as a way to see your heartbeat trace. The circuit will use 3 electrodes - 2 to measure a voltage difference across your scalp, and one as a reference to ground. Depending on how many parts you already have, the circuit could only set you back around $10.

The aim for this project is to be easily available and understood by people of every technology background. For those electronically savvy, I will include up front a finalized schematic so you can jump right into making it yourself. For those that want more guidance, I will include a detailed description / explanation of every section of the circuit, showing you what it does and why you need it. 

Then, I'll move onto the software (Processing based), which is a very important piece in actually interpreting the raw data you receive.

So - let's start!

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TimothyM71 month ago

i cant find 12ohm resistors anywhere. did u mean 120ohm?

Ebay has some

oh i also want to ask: how important are the values of the capacitors and resistors? is it ok if they are a tad off?

BoardLevel4 months ago

The electrodes go into the ad620an instrumentation amplifier at pins 2 and 3.

The written code is garbage. It does not work. everyone i have seen on this site has either used another avenue to make this circuit's raw data interpretation code work or they have purchased their own expensive software or hooked the device straight into an oscilloscope or another form of raw data interpretation.

the circuit works fine and the filters can all be made out of 741 op-amps in combination with the various listed amplifiers, capacitors, and resistors.

bit of advice, write the code first. if that doesn't work for you and you have no other form of raw data interpretation to display the actual wave forms of these readings, ABANDON the project. i have a 200 dollar eeg sitting next to me and a code that does not work so i can't use it. My coding skills are not that of a professional programmer i have had one programming in c class and this is not close enough for me to debug nearly 400 lines of code with errors popping up constantly.

the creators of this this instructible also mentioned a few years ago that they would not be answering any more questions or assisting any build. i am paraphrasing but don't expect help from them i tried.

personally i believe that this should be removed from the web sight. it is misleading and if you screw up and build the circuit first then you are left with an incomplete interpretation code.

Do you have pictures of the final circuit you built?

Theres only 2 electrodes? I thought there were 3 for the ground as well?

Have you tried the code posted by SteevAtBlueDust? Please let us know if it works after you try it out.


Sorry, I can not see the bars that I can do?

ktennisluvr20 days ago

Does anyone know if the amplifier and filters and hpf gain are included in the "complete design" schematic? Or are we supposed to add those on as next steps? Thank you.

xotikworld23 days ago

Where is a good place to buy the capacitors cheap? I can't find the tantalum ones either...


And do you want them to be polarized or not? Does it matter??

Joe.G made it!5 months ago

I do not know how can you can run the code for reading eeg signal without any error. When I run the READ_EEG in arduino, it's contain 2 errors. When i try to fix the first error, the second error appear. I do not know why. Please help me to fix it.


See my comment above and try

There is a clear error right above the highlighted braces in the first image you posted. It is a function call, and the parentheses must be closed with or without (one or more separeted by comma) parameters inside and followed by a semi-colon indicating the end of the command: timeSignal(); or timeSignal(PARAMETERS);

the second image i cannot tell because missing parts of code i must see.

i've not downloaded the code or started the project yet due to lack of time. but it's my intention for soon.

Let me know if im not being clear, beacause i'm out of pratice in english language.

Can you talk more clearly? because the author only public code file to share anyone. So, what is missing parts? i can take it from where to running correctly. Thanks

Marcos Rosa2 months ago

Does anyone got the useful code? These are full of errors! Thanks!

See my comment above and try

createeve2 months ago

Hi, have you considered electodes like ? They are from OpenEEG project. Will they work with yours?

Anything with conductive metal and a wire should work. Im pretty sure that almost all eeg electrodes work with all eeg circuits

BoardLevel made it!5 months ago

take into consideration that this circuit requires you purchase electrodes as inputs and some sort of electrode gel that will set you back more than $10. even if bough on line.

There are a lot of parts to buy if you don't have a bunch of ICs and caps laying around you will end up buying online and paying shipping costs too. some were hard to find particularly hard to find were the tantalum capacitors.

be prepared to get the run around on ambus electrodes too. they charged me four times for my order before even sending me the right 2 products even though i only needed one set of electrodes and only wanted one. i have yet to dispute the charges due to just not wanting to deal with them any more. seeing as how i might need the electrodes when and if i ever get the code running.this project cost me closer to 100 dollars than 10.

20150126_163329 (1).jpg

are tantalum capacitors necessary? I found a few capacitors of the same values that are electrolytic. will different material capacitors alter the results alot? I'm new to circuits.


TimothyM71 month ago

Going to put in another question:

can the data be processed through audacity?


nivok1 month ago

Thanks for sharing! I'm making it out , But,i got a lot of trouble when i made it,such as in my country,the notch filter work wrong ...

THE CODE WORKS! I've made the code compile, fixed bugs involving (lack of) precision, and expanded it to read data from either Arduino (via serial) or the audio in (e.g. microphone). See README for how to switch between modes.

I haven't built the circuit yet, but at least this is further progressed than the source provided above!

diamantpl2 months ago
Can someone explain me why author decided to connect the output signal to the sound card between 22k rezistor and 220n capacitor ? Why he didnt put it at the end of the circuit ? I mean output from IC LM358 connected to the sound card like in the first notch filter
Lamanator2 months ago

Hey guys,

Does anyone know what type of capacitor C10 (25nF) should be? I don't have one and can't find one online. Thanks.

NaserA2 Lamanator2 months ago

have u figured out what capacitor should it be? is it 20nF ??

Lamanator NaserA22 months ago

For the 25nF capacitor, I think that a film capacitor should suffice. As for the 20nF capacitor, it should just be a ceramic capacitor.

SaidM2 months ago
theadi15254 months ago

Soo what with this error ?

Joe.G theadi15252 months ago

this error is same thing that i have before. I think code or file download lack the library for running correctly

yajbuilder5 months ago

Yo sup...

still at this fantastic work? I all of a sudden NEED to make an eeg machine! Another way to get low noise, high channel counts is to use some high end recording stuff, like a -real- power conditioner (used for 60hz hum, I dunno to what degree though) (furman, monster) and a many-channel audio interface (focusrite, heck go bigger get an antelope or even bigger a rme hammerfall! (like 52 channels of conversion... like a ski mask of electrodes!) . that sure isn't portable, but big readings would be a piece of cake!

I want to make something I can use to monitor sleep and euphoric caffeinated feelings, so it may come down to a larger a/d converter to get those subtleties.

Also from the software-recording type end of things, HPF and LPF and all the notch filters in the world are super easy if one was to run the raw signals (post amplified) through a simple EQ. I mean, if one was to use a interface, a copy of logic pro x or PT 12 or Reaper 4 shouldn't big a biggie. :) Plus reaper is almost free and has that stuff.

Anyway, anyone still here? support? get that software fixed? ehh? ehh?


SaidM5 months ago


SaidM5 months ago


SaidM5 months ago


rbayareh mancilla made it!1 year ago

Hi! I made this proyect. I only used a High pass filter from 8Hz to 50Hz (alpha to beta waves) just for watch the changes between the waves. I used Labview and MyDAQ to observe the changes, programming a 60Hz notch filter, a graph and FFT to observe better the frequency of alpha and beta. Here are the results:

filtro pasa banda 8-13Hz.pngfiltro pasa banda 14-30Hz.pngCapture.PNGCapture2.PNGCapture3.PNGCapture4.PNGCapture5.PNGCapture7.PNG

Thank You. It helped me a lot.

Your welcome

please can you help me i want source of simulation, code
what is the price of DAQ?

I wanna get a 50Hz notch filter one!

OK, what's the problem?
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