Multimodal Bio-Signal Acquisition Platform
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Drawing -EEG/ECG Wireless Acquisition System
Drawing -Optical-Pulse Temperature Monitoring Board

Multi-Sensor Bio-Signal Platform with BLE, SD Logging, and USB Interface

EEG, ECG, PPG, and Temperature Wearable System with BLE, SD Logging, and USB-C Interface

Project Summary:
Designed and developed a modular, battery-powered biomedical signal acquisition system capable of recording EEG, ECG, PPG, and skin temperature signals. The system combines high-resolution analog front-ends, wireless BLE communication, local storage, and smart power management in a compact 4-layer PCB. It is suitable for research in neurophysiology, biofeedback, and wearable health monitoring.

🧩 System Architecture

📟 Main Acquisition Unit

  • Signal Processing Core:
    • ADS1299 – 8-channel, 24-bit analog front-end for EEG and ECG acquisition
  • Wireless MCU:
    • nRF52840 – BLE 5.0 SoC for wireless communication and system control
  • Storage & Interface:
    • MicroSD card for local data logging
    • USB Type-C for charging and USB data communication (CDC/MSC)
  • Antenna:
    • NANO mXTEND NN02-10 – BLE chip antenna

❤️‍🔥 Sensor Expansion Board

  • Optical Pulse Sensor:
    • AFE4404 – Analog front-end for PPG signal conditioning and LED control
    • SFH7050A – Integrated green/red/IR LEDs and photodiode for HR and SpO₂
  • Temperature Sensor:
    • MLX90632SLD – Calibrated non-contact IR sensor for skin temperature

🔋 Power Architecture

  • Battery Management:
    • TP4056 + DW01A + FS8205 – Safe Li-Ion charging and protection
  • Regulation:
    • TPS63020 – Buck-boost converter for regulated 3.3 V and 5 V outputs
  • Load Sharing:
    • Custom power path circuit for uninterrupted operation during charging
  • Power Source:
    • Rechargeable Li-Ion battery + USB-C charging

📐 Hardware Specs

  • Board Size: 115 mm × 100 mm
  • Layers: 4-layer PCB for analog integrity and RF optimization
  • Modular Design: Expansion board can be attached for multi-modal sensing

📲 Features

  • High-resolution EEG/ECG/PPG acquisition with low noise and accurate timing
  • BLE 5.0 for real-time streaming to mobile or desktop apps
  • SD card logging for offline high-resolution recording
  • IR temperature sensing for thermal feedback or contextual data
  • USB-C for charging and data connectivity
  • Fully portable, wearable-friendly hardware platform

🧠 Use Cases

  • Brain–computer interface (BCI) development
  • Neurofeedback and cognitive state monitoring
  • Stress and wellness tracking (HRV, temperature)
  • Medical research prototypes for multi-modal biosignal analysis
  • Sleep, attention, and cardiovascular monitoring

Description : 

This project is a fully integrated, battery-powered biomedical acquisition system composed of two custom-designed PCBs: a main board (115 mm × 100 mm, 4-layer) and a compact sensor extension board (21 mm × 10 mm). The system enables real-time and offline monitoring of multiple physiological signals, including electroencephalogram (EEG), electrocardiogram (ECG), photoplethysmography (PPG), and skin temperature. EEG acquisition requires external electrodes placed on the subject’s head, which connect to the system through a robust D-SUB 50 connector, ensuring secure and shielded multi-channel analog signal transmission. This same connector also carries the interface lines to the extension board, enabling a clean, modular integration between the two PCBs. The main board features the ADS1299, an 8-channel, 24-bit analog front-end optimized for low-noise biopotential recording, and the nRF52840 SoC, which manages all system control and Bluetooth Low Energy 5.0 communication with a companion mobile or desktop application for real-time visualization, device configuration, and firmware updates. For local data storage, the system includes a microSD card, and it supports USB Type-C for charging, USB communication (CDC/MSC), and firmware flashing. The power architecture consists of a TP4056 Li-Ion charging IC, DW01A protection circuit, FS8205 dual MOSFETs, and a TPS63020 buck-boost converter providing regulated 3.3 V and 5 V rails. A load-sharing power path circuit enables uninterrupted operation whether running on battery or charging via USB. The extension board, physically separate but connected through the D-SUB interface, integrates an AFE4404 PPG analog front-end, the SFH7050A multi-wavelength optical sensor (green/red/IR) for heart rate and potential SpO₂ measurement, and the MLX90632SLD non-contact infrared sensor for continuous skin or ambient temperature monitoring. This dual-board modular design allows ergonomic placement of head-mounted EEG electrodes and skin-contact sensors while maintaining system compactness and electrical performance. Overall, the platform is ideal for research and development in neurophysiology, brain–computer interface (BCI) systems, stress and cardiovascular monitoring, and wearable multi-sensor biofeedback technologies.