How to Build a Low-Cost EEG Brain Wave Reader From Scratch

Introduction

An electroencephalogram (EEG) measures electrical activity in the brain using electrodes placed along the scalp. EEGs allow researchers and clinicians to evaluate brain disorders, sleep disorders, dementia, epilepsy, and more. Commercial EEG machines can cost tens of thousands of dollars, putting them out of reach for hobbyists and students. However, with inexpensive off-the-shelf components, you can build your own simple EEG device to measure brain waves in real time.

In this guide, I will walk you through the entire process of constructing a budget EEG from start to finish using easy-to-find materials. With some basic skills in circuit building and coding, you can have your own DIY brain wave reader to experiment with brain-computer interfaces and neurofeedback applications.

Materials Needed

Building an EEG requires just a few core components:

• Electrodes - To detect electrical signals from the scalp. Affordable options include stainless steel discs or rings.

• Wires - For connecting electrodes to amplifier. Any thin, flexible, insulated wire will work.

• Amplifier - To boost the small electrical signals picked up by electrodes. An instrumentation amplifier or op amp circuit can be built or purchased inexpensively.

• Filter - Helps isolate brain wave frequencies. Can be built with capacitors and resistors.

• Microcontroller - Samples and digitizes the amplified signal. Arduino or Raspberry Pi boards are common choices.

• Computer - For recording and analyzing EEG data. Any PC or laptop will suffice.

• Resistors - Assorted values for building amplifier and filter circuits.

• Capacitors - For constructing filters to isolate frequency bands.

• Electrode gel/paste - Helps conduct signals from skin to electrodes. Can be purchased or made.

• Headset/cap - Comfortably holds electrodes against scalp. Can be 3D printed or sewn.

In total, building a basic 8-channel EEG with these components would likely cost between $50-150 depending on options chosen. Many parts can be reused or repurposed from other projects, keeping costs down.

Headset Design

The headset or cap holds the electrodes in position on the head. For acceptable signal quality, careful positioning of electrodes is important.

There are 10-20, 10-10, and 10-5 systems that specify standardized electrode placements. For an easy DIY headset, a simplified 3 or 4 electrode design is recommended:

• Frontal lobe site - For detecting alpha/beta waves
• Temporal lobe site - Detects theta waves
• Occipital lobe site - Gamma and delta waves
• Reference electrode

3D printing services can be used to manufacture a plastic headset with mounts for the chosen electrode sites. The headset should be adjustable to fit snugly and comfortably on the head.

Alternatively, a fabric cap with velcro straps can be sewn by hand or machine. The electrodes can be sewn into the cap or attached with snaps or velcro. Elastic bands help apply gentle pressure to keep electrodes in place.

Amplifier and Filter Circuit

The small electrical signals from the brain need to be amplified before they can be processed by the microcontroller.

An instrumentation amplifier is ideal, providing high gain while rejecting noise. The INA128 is a common choice, or you can build an instrumentation amp from op amps like the TL072. A gain of 1000x or higher is recommended.

Next, passive filters help isolate the frequency bands of interest:

• Delta waves - 0.5-4 Hz
• Theta waves - 4-8 Hz
• Alpha waves - 8-12 Hz
• Beta waves - 12-30 Hz
• Gamma waves - 30-100 Hz

First order RC filters with appropriate cutoff frequencies can be constructed using resistors and capacitors. Active filters with op amps can also be implemented for better performance.

The amplified and filtered analog signal can then be digitized by the microcontroller's ADC.

Microcontroller and Software

The Arduino is a classic choice for DIY EEG projects thanks to its ease of use and extensive documentation. The analog inputs can sample the filtered amplifier output. Apply the right resistors as voltage dividers to match the Arduino's 0-5V input range.

For better resolution, the Raspberry Pi has up to 18 bit ADCs available. Install Raspbian, then read the ADC with Python scripts. NumPy, SciPy, Matplotlib allow for signal processing and real-time plotting.

Open source software like OpenBCI can be leveraged. It handles the filtering, visualization, and data logging for EEG signals out of the box. Their Ultracortex Mark IV is an Arduino-based design you can replicate or modify.

Experiments and Applications

Once built, what can you do with a DIY EEG? Here are some fun experiments to try:

• Record signals during different activities - Record and compare your brain waves when resting, doing math, reading, meditating, etc. See how they differ.

• Neurofeedback - Try controlling a game or app using your brain waves. For example, make music by focusing hard or relaxing.

• Sleep stages - Track your sleep cycles by logging brain waves overnight. Watch for transitions between REM/non-REM.

• Brain-computer interface - Use real-time brain wave analysis to control external hardware like robots or spellers.

• Biofeedback - Detect when you are focused vs. distracted by monitoring your alpha and theta waves.

• Reaction time - Measure how long it takes for your brain to react to stimuli by correlating EEG signals with events.

Building your own portable EEG unlocks tons of possibilities for exploring brainwaves. With an understanding of the basic electronics and software involved, anyone can move from idea to functional prototype quickly and affordably using DIY techniques. What will you discover with your homemade brain scanner?

Conclusion

Constructing a budget EEG system from widely available components is achievable for makers of all skill levels. With around $100-$150 in parts and some free software, you can start measuring brainwaves for innovative neuroscience projects and experiments. By following the steps outlined here for the electrodes, amplification, filtering, and microcontroller coding, you'll gain valuable insight into EEG technology while saving thousands over expensive commercial systems. Turn your ideas into reality by building your own DIY brain wave reader from scratch.