Download Power Chair Securement System Ben Roedl

Brain Tissue Stimulator
N. Lewis, S. Noel, A. Phillips, S. Skroch
University of Wisconsin – Madison, Department of Biomedical Engineering
Prof. Willis Tompkins – Advisor
Dr. Mathew Jones – Client
Problem Statement
Circuit Schematic
Testing
Tested circuit with a 20 V supply & 5 V pulse
To develop a multi-channel brain tissue stimulator.
This device must generate stimulation current of 1
mA on 16 separate channels.
Filter out external electrical noise.
Allow each channel to be independently gated on/off.
Motivation
To learn the circuitry of the hippocampus to better
understand learning and memory.
Tested circuit with 120 V supply & 5 V pulse.
Failure most likely due to grounding fault.
To improve upon the current tissue stimulation
process which is not physiologically accurate.
To provide a low-cost multi-channel stimulator.
Client Specifications
Future Work
Trigger each pad independently with a 5V transistor
transistor logic (TTL) pulse.
Continue testing circuit at higher
voltages.
Deliver 1 mA of current to each channel.
Find method to cut down lag.
Deliver the same amount of current to each pad.
Active feedback to create constant
current source.
Deliver the pulse in 100 s with no lag.
Rectifier: Takes the AC input signal and transforms it
to a positive output.
Cost Analysis
Potentiometer (5 MΩ)
Potentiometers (10 kΩ)
Floating voltage source
Voltage regulator
Optical Isolator
Inverter
FET
Resistors
Total (for 16 channels)
Circuit Components
$8.37
32 @ $0.10
$73.25
$0.99
32 @ $0.44
16 @ $1.32
32 @ $5.25
48 @ $0.06
$363.34
Low-pass filter: Filters out the 60 Hz noise and
smoothes the signal from the rectifier into a constant
DC signal.
Optical isolator: Blocks any backflow of electrons to
the computer, which provides the 5V trigger pulse.
DC Power supply: Keeps the voltage seen at the gate
12 V above the voltage at the drain in order to keep
the FET open.
Field Effect Transistor: Acts as a switch. When the
gate sees the 5V pulse, it lets the supply voltage (of
up to 1000V) through.
Capacitive (Cap.) Bypass: Shortens pulse fall time.
Add large potentiometers for voltage
control.
Add more channels.
Printed circuit board in finished box.
References
http://www.superteaching.org/MINDimages/hippocampus.gif
Acknowledgements
We would like to thank Professors L. Burke O’Neal
and Jack Ma for their help this semester.