This paper presents a portable electroencephalography (EEG) monitoring system designed for real-time brain signal acquisition, processing, and secure data transmission. The system integrates eight Ag/AgCl electrodes configured in four channels, using low-noise instrumentation amplifiers (AD620), analog multiplexers (CD4051), and operational amplifiers (TL081) for signal conditioning. An ESP32 microcontroller manages data acquisition, processing, and visualization on a 128\(\,\times \,\)64 I2C OLEDdisplay. Secure data transmission is achieved using the ATECC608A secure element and W5500 Ethernet controller, with a tamper detection switch ensuring physical security. The system is powered by a 3.7V Li-Po battery with an isolated power module(B0505S-1W). The design spans biomedical engineering, electronics, embedded systems, signal processing, IoT, and cybersecurity. Electrode placement follows the 10–20 international system, and the system is compared with state-ofthe-art EEG systems to highlight its unique features, such as portability, security and cost-effectiveness. Detailed subsections cover instrumentation amplifier design, active filters, multiplexer design, electrode placement, hardware implementation, and security measures. Lab tests in a controlled setting showed effective detection of predicted EEG patterns like alpha waves, with minimal artifact and noise. The system maintains a balance among simplicity, performance, and portability and thus is well positioned for use in educational settings, initial neurological investigations, and brain computer interface research. This paper points to the capability of low cost hardware to make EEG technology more democratic and sets the stage for future upgrades, such as wireless connectivity and enhanced signal processing.
