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EEG Machine

EEG Machine. By The All-American Boys Featuring Slo -Mo Motaz Alturayef Shawn Arni Adam Bierman Jon Ohman. High Level Block Diagram. Processor Schematic. FPGA Daughter Board. Power. A2D. JTAG. FPGA Pins. Bank 3. Bank 4. Bank 1. Bank 2. RS232. Push Buttons, Switches & LEDs.

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EEG Machine

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  1. EEG Machine By The All-American Boys Featuring Slo-Mo MotazAlturayef Shawn Arni Adam Bierman Jon Ohman

  2. High Level Block Diagram

  3. Processor Schematic

  4. FPGA Daughter Board Power A2D JTAG

  5. FPGA Pins Bank 3 Bank 4 Bank 1 Bank 2

  6. RS232

  7. Push Buttons, Switches & LEDs

  8. Sample Code using Nios II • IP Core • Ex. SPI Void A2D_T (unsigned char ch){ while (true) { if(IOWR_ALTERA_AVALON_SPI_STATUS(base, data) &0x040) { IOWR_ALTERA_AVALON_SPI_TXDATA(base, data) } }}

  9. Testing • Memory Storage • Inputs stored then flash LEDs • FFT analysis to Nios II console • RS232 • TX & RX LEDs, PC use • User Output • Flash On-board LED with Goggles

  10. Electrode Input Schematic

  11. Part Selection • Op-Amp Choice: • Burr-Brown OPA27 • Ultra low-noise amplifiers • Differential Amp Choice: • Burr-Brown INA105 • Ultra low-noise amplifiers • Resistor Choice • Using 1% tolerance, should be well matched enough • Have .1% tolerance options picked out if necessary

  12. Filter Selection • Using Sallen-Key low-pass filter • Corner at 100Hz • 40dB/dec decrease • Simple, easily expanded if necessary • Should filter out high frequency noise components to neural signal • Filter not designed to filter out all environmental noise

  13. Power • Input circuit powered separately from rest of device • Safety: • Don’t want any risk with a person attached to one end • Noise: • High frequency components of processor could infect power lines • Introduce artifacts into signal

  14. Power cont’d • Input board powered by 9V battery • Voltage inverted to provide negative voltage for amplifier operation

  15. Testing • Testing will be done on PCB • Voltage injections at specific input sites • Measure response for each stage functionality • Expect to see: • Amplification of 100x • Single summed output signal • Frequencies over 100Hz are not passed • Noise levels are minimized

  16. Design Change to Contact • No headband • Movement and friction will introduce too many artifacts • Conductive paste will be necessary • Metal/Skin interface is not good enough to conduct strong signals • Epoxy cast contact with double-sided adhesive to form “well” for paste

  17. Risks to Design/Implementation • Cannot get usable signal from head contacts • Purchase commercial contacts • Low-Pass Filter not sufficient at eliminating excess signal information • Cascade to increase effectiveness • Use Different Design • Too much noise on the signal line • Increase contact surface area • Increase signal strength • Isolate board through effective shielding

  18. Output Component Changes • Previous output components: • Audio CODEC • Monitor to display visual stimulus • Current output components: • Separate ADC and DAC • Input signal is not being output as auditory stimulus • LED mounted glasses or goggles for visual stimulus • Eliminates the need for VGA circuit

  19. ADC Architectures

  20. AnalogtoDigitalConverter 16-Bit Resolution Low Noise Performance Low Power Consumption Sigma-Delta Architecture Serial SPI Communication Constant Output

  21. Digital to Analog Converter 16 Bit Resolution Serial I2C Interface 4 Channel Output Low Power Operation Output Directly to Headphones

  22. Visual Stimulus Example of Glasses

  23. Testing • Mount ADC to through-hole adapter • Input sinusoidal signal • View output on multi-meter • Mount DAC to through-hole adapter • Input digital values from FPGA flash • View output on oscilloscope

  24. LabView code for PSD

  25. TestResults • The test used a .wav file • The left graph is the time domain • The right graph is the power spectrum.

  26. Serial interface

  27. Buck conveter Buck converter used to supply enough current to the board. (LM2676-3.3) VCCIO will power VCCIO1, VCCIO2, VCCIO3 and VCCIO4. VCC33 will power the ADC and the DAC chips. MAX232 need 3.3v so will use VCC33 Memory

  28. Power for Daughter Board

  29. Voltage Regulator and Clock Voltage regulator with 1.2v output (LM1117-1.2-0.8A) VCC12 is the input for VCCD_PLL1, VCCD_PLL2, VCCA_PLL1 and VCCA_PLLA. The clock is 50MHz

  30. Schedule

  31. Questions?

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