G EO RGIA I NS TI TU TE O F TECHN O LOGY
School of Electrical and Computer Engineering
ECE4040 Senior Design
Design Report
Fall 2001
Mind Control Group
James Lin,
Son Phan,
Michael Oduselu
Brainwave Mind Control Design
Objective
The objective of this report is to document and report on our current design and
immediate design goals for the brainwave project. Our main goal in this stage is to find
and design a suitable biofeedback amplifier. We have chosen to design an older version
of the BrainMaster EEG monitor that was given to us by the founder. There have been
many references to the BrainMaster project and other people building their own EEG
monitor, therefore by building off something that has been tested, we hope to encounter
fewer problems.
Block Diagrams
The previous group that worked on the brainwave project came up with an overall
design represented in the block diagram below:
Figure 1. Proposed system from the previous brainwave group.
After reviewing their design and our proposed design, we have constructed a revised
block diagram.
Figure 2. Revised block diagram of new system.
The new system shows some significant changes from the previous design. The second
stage shows the amplifier and filter combined because the EEG monitor that we are
proposing to build performs both functions. The output signal is a analog signal that will
be converted into digital format through an analog/digital converter chip.
The signal is then calibrated though by adjusting the A/D circuit to get the best
range of values to be inputted into the microprocessor. This can be done with variable
resistance such as a potentiometer for each channel.
The fourth stage is the microprocessor where the signal is processed and
synchronized with the computer. This will require buying a pre-made board with a
microchip and various input ports on it that is ready for use, or building a board one by
ourselves. We propose buying a completed board or one with all the parts ready to be
assembled since designing a board will be a big task. John Peatman
john.peatman@ece.gatech.edu , a professor here at Georgia Tech, teaches a class about
microprocessors and may be of assistance. The board should then be connected to the
computer via the serial port or USB port depending on the type of microchip board being
used. Cypress Semiconductor http://www.cypress.com produces a full speed USB
microcontroller (EZ-USB) and has many different USB development kits, tools, and
example code to work with if USB desired. Code will have to be written or obtained to
interface the microchip with the computer at this stage.
During the code writing stage of the fourth stage, the next stage can be started.
During this stage a program will have to coded up to collect data from the
microcontroller and interface it with the transmitter. If a microchip development package
with code for both ends can be obtained, these steps may be simplified. This will most
likely involved C++ programming.
The transmitter is the device that will control the car’s movement. It will have to
modified to be controlled by the computer.
Current Design Step
The current step of designing the system will focus on building the EEG monitor
that will collect, amplify, and filter the brainwaves. We are using the plans for an old
version of the brainmaster http://www.brainm.com developed by the founder Thomas
Collura. The EEG circuit is a two stage amplifier shown below:
Figure 3. Amplifier Schematic.
The parts for the EEG circuit are commercially available and were obtained online from
Digikey (http://www.digikey.com) and Pioneer-Standard Electronics
(http://www.pios.com). The total cost for the parts ranges about $30 - $50 depending on
quality and extra parts. We used 1% metal film resistors and 5% polypropylene
capacitors.
The first stage of the amplifier provides a gain of 50 from the user input. Quoted
from the brainmaster plans, “The input amplifier IC-1 is an Analog Devices AD620
instrumentation amplifier, set up with a gain of 50. This gets the signal "out of the
noise," and provides high input impedance and high common-mode rejection. The "AC"
coupling due to R4 and C4, or R5 and C5, occurs with a long time-constant, and does not
limit the low-frequency response. It also does not affect the CMRR, since it is not in the
passband. It does, however, allow the inputs to IC-1 to be biased into the middle
of their common-mode range.
The amplifier IC-2 is used to provide an integrator, used as a low-pass filter
developing the reference for IC-1. This results in a baseline-correction that produces a
low-frequency cutoff at 1.6 Hz. It also allows the output of IC-1 to operate near its center,
providing good linearity.”
Stage 2 has a gain of 390 for a total gain of 19500 for the entire amplifier. In
addition the second stage provides a frequency response to 34 Hz. The schematic also
shows a input voltage of 2 volts in addition to the VSS supply voltage. This voltage is
used as a midpoint between the supplies. The circuit is specified to work with supply
voltages from 5V to 36V.
A summary of the specifications are listed below:
Type:
differential
Inputs:
(+), (-), and "ground" return
Gain:
20,000
Bandwidth:
1.7 - 34 Hz
Input Impedance: 10 Mohms
Input Range: 200 uV full-scale
Output Range: 4 volts: from 0.0 to 4.0 volts
Resolution:
0.80 uV/quantum
Input Noise: < 1.0 uV p-p
CMRR:
> 100dB
Our current progress is in the building and testing of the EEG circuit. A picture of circuit
in its current progress is pictured below:
Figure 4. EEG circuit on proto-board for testing.
The next steps in the design plan are to add on another stage for the midpoint
voltage. The circuit should be able to operate with just the two stages and two power
supplies, but one power supply is more convenient. The brainmaster plans also provide
the schematics to implement the midpoint voltage and a circuit on obtaining a clean
voltage source.
Figure 4. Midpoint voltage circuit.
Component values for Figure 4 are:
R0: 50K 1% metal film
R1: 100K 1% metal film
R2: 100K 1% metal film
C3: 0.1 uF mylar
Figure 5. Circuit to get a clean power supply.
Figure 5 shows a circuit used to obtain a clean regulated power supply. The components
included a 7805 regulator. The other components values are:
B1: 9V battery, or 6 "AA", "C", or "D" cells
C1: 10uF tantalum
C2: 0.1uF mylar
Once the circuit has been assembled, we hope to see some oscillations on the
oscilloscope. The circuit can be tested by trying to record the heartbeat from one hand to
the other. If a good signal is obtained, the circuit will be used to try to obtain a
brainwave. To improve results, the circuit can be soldered onto a pre-holed prototype
board to reduce capacitive coupling.
Using the Brainwaves
First of all, we need to know if we have or can attain a common thinking pattern.
Our patterns differ in function of geographic origin, tradition and culture and
access to current technological developments. Unfortunately, function of the native
language as well. But we can learn. And adaptation to modern technology
is learnable, so it may be possible to learn a common representation of ideas (after all, we
are the same species, so we should have similar thinking patterns and
learning capabilities).
The question is: how do we get to these common thinking patterns? Again, if we
find a way to communicate with a computer, it is doable. The computer will learn from
different groups of people and then look for similarities. Machine learning (and
reinforcement learning) can be used to discover the specifics of thinking of a group of
people or individuals.
The brain operates in different states which output different types of waves. One
possible of using the waves to navigate by controlling which state our brain is operating
in with emotions. If a person can train the way he feels, then he may have the power to
control the output the EEG to match his thoughts and emotions. Figure 6 shows a guide
of which type of brainwaves are associated with different emotions.
Figure 6. Guide to brainwave navigation.
Appendix
I. Amplifier Parts
1. AD620
FEATURES:
-
Gain Range: 1 - 1000
-
Wide Power Supply Range: (+ -) 2.3 V – (+-) 18 V
-
Available in 8-Lead DIP and SOIC Packaging
-
Low Power, 1.3 mA max Supply Current
-
For more information: www.analog.com
2. OP90
FEATURES:
-
Single Supply Operation: +1.6V to +36
-
Dual Supply Operation: (+-) 0.8V to (+-) 18V
-
Low Supply Current: 20u A Max
-
High Output Drive: 5m A Min
-
Low Input Offset Voltage: 150u V Max
-
High Open-Loop Gain: 700V/mV Min
-
Outstanding FSRR: 5.6u V/V Max
For more information: www.analog.com