1. Portable BCI Stimulator Final Presentation Group: 17 Bonnie Chen, Siyuan Wu, Randy Lefkowitz TA: Ryan May ECE 445 Monday, April 29 th, 2013

2. Overview Introduction Features BCI/EEG System Overview Design of Individual Modules Testing and Verifications Future Development Sponsors

3. Introduction Most brain computer interfaces (BCI) limited to laboratory settings We would like to help make the EEG system more portable through bluetooth Allows people to communicate without any type of movement

4. Features Portability –Wearable Size –Rechargeable Battery Wireless control –Bluetooth –Compatible with most computers Variable frequency and Intensity –Set by User

5. BCI/EEG System Overview

6. Stimulator Top Level

7. Computer/Wireless Module Overview Wireless communication between PC and Bluetooth Module through terminal Retrieve LED number, frequency and intensity level from user Check the validity of command

8. Wireless Transmitter/Receiver Built in Bluetooth 2.0 communication Standard TTL Bluetooth receiver Data sent wirelessly from PC to Arduino

9. Receiver – Arduino Diagram

10. Input Flowchart

11. Microcontroller Module Calculates Runtime Determines if each LED should toggle Sets LED values Latches values into LED driver

12. Timing Flowchart

13. Dividing Interval for On and Off Calculate LED state time (on/off) –Interval = current – previous Compare to Required Time –1/(2*frequency) Toggle if needed Save new time –Previous = current

14. TL5940 LED Driver Overview 16 Output Channels Rref = 2k ohms Intensity set by PWM Frequency controlled by Arduino TLC5940 library

15. TLC-5940 Library TLC.set(channel,intensity); –Loads TLC Register Tlc.update(); –Latches data into LED driver

16. TLC-5940 Arduino Connections

17. 7.4V Power Supply Venom 1250mAh 10C 7.4V Lithium Ion Battery

18. LED Array Powered by 5V output from Arduino Flashes at frequency values between 1-9 Hz based on Arduino Code LED Intensities based on PWM values from LED Driver 5-10 LEDs mounted on adjustable frame

19. Lilypad Micro LEDs 3.3mm long Forward Voltage of 3.2-4.0V 200mA forward current Power Dissipation of 120mW

20. PCB Schematic

21. PCB Design Top Bottom

22. Final Design

23. Demo with the EEG

24. Review of Requirements Wireless Communication Portability Sufficient Power Successful Classification over different frequencies on EEG System

25. Testing and Verifications EEG Classification Frequency Bandwidth Power Budget

26. EEG Classification Demo Frequencies –6, 7, 8, 9 Hz Classification –All 4 Frequencies classified correctly (within 0.3Hz) Intensity of 20 out of 4096 –Fast Response –Comfortable Viewing

27. Frequency Bandwidth 1.Record LED Driver Output on Oscilloscope 2.Analyze EEG data with MATLAB 3.Compare Variance with EEG Classifier Sensitivity 4.Adjust Sensitivity values of EEG Program Accordingly 5.Test user response on EEG with updated sensitivity values

28. Frequency Bandwidth Cont. 1 Hz: μ = 1.0912, σ 2 = 0.41 6 Hz: μ = 6.0694, σ 2 = 0.36 7 Hz: μ = 7.1238, σ 2 = 1.37 8 Hz: μ = 8.1937, σ 2 = 2.01 9 Hz: μ = 9.2745, σ 2 = 5.22 10 Hz: μ = 10.495, σ 2 = 10.77 Higher Frequencies produced less stable results SSVEP measurements generally 5-15 Hz Less accurate frequencies cause slower EEG response times

29. Frequency Bandwidth Cont.

30. Power Budget ComponentImax (mA)Voltage Microcontroller40 * 2 output pins7-12V (ideal) LEDs20 * (10 LEDs)3.2V (green, white) Bluetooth Module403.3V LED Driver1205V __________________________________________________ Total440----------------- Estimated Usage time = 1250 [mAh] / 440 [mA] ≅ 3 hours of charge Factors to consider: - PWM value will never be over 50% (the blinking LED is on less than half of the time) - Able to get same results using 5 LEDs instead of 10 LEDs

31. Future Development Safer operating limits for near-eye LEDs Determine ideal threshold for response time, classification, and stability of the system. Improvements on mounting frame mechanics (aesthetics and functionality) Use Feedback from the EEG to implement commands that can control a range of devices (Quadcopter, Paralysis Assistance)

32. Sponsors A special thanks to the following people who helped make this project happen James Norton (Beckman) Erik Johnson (Beckman) David Jun (Beckman) Ryan May Professor Carney The friendly folks in the ECE parts shop

33. Thanks!!