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EMG Biofeedback Device. BME 200/300 Fall 2003 Department of Biomedical Engineering University of Wisconsin-Madison. Team Members. Tom Chia - BSAC Jason Ethington - Communicator Tim Rand –BWIG Kim Treml - BSAC Brent Geiger – Team Leader. Client. Arleigh Birchler, MDiv, BSN

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emg biofeedback device

EMG Biofeedback Device

BME 200/300

Fall 2003

Department of Biomedical Engineering

University of Wisconsin-Madison

team members
Team Members

Tom Chia - BSAC

Jason Ethington - Communicator

Tim Rand –BWIG

Kim Treml - BSAC

Brent Geiger – Team Leader


Arleigh Birchler, MDiv, BSN

Brahms Addition Life and Choice


John Webster, Ph.D.

Professor Emeritus

Biomedical Engineering – UW Madison


We designed an EMG biofeedback device that will turn on a vibrating massage pad. The device will provide a child with Lissencephaly a physical stimulus triggered by their EMG signal. Through operant conditioning, the child will learn that he can use this device to create a pleasurable sensation for himself. We hope this will provide independence to the child. The design utilizes three surface electrodes to detect EMG signals from the child’s quadriceps. A six stage analog circuit processes the signal and powers the massage pad for 2.5 minutes if the EMG signal is sufficiently strong.

problem statement
Problem Statement
  • The goal of the project is to design an EMG biofeedback device to allow a patient with Lissencephaly to exhibit some physical control over their life
  • Measure, amplify, and process EMG signal to provide physical and cognitive stimulation
  • Malformation of thebrain
  • Occurs during fetal development
  • Variety of genetic and environmental causes
  • Symptoms
    • Vary and range in severity
    • Ex. Mental retardation, poor muscle control, seizures
design criteria
Design Criteria
  • Voluntary muscle contraction will activate massage pad
  • Device will be in use 24/7
  • Easy to learn and operate
  • Safe for patient and operator
  • Patient confidentiality is maintained
client requirements
Client Requirements
  • EMG electrodes are reusable
  • Device can distinguish between voluntary and involuntary muscle contractions
  • Timer to control duration of vibration
design constraints
Design Constraints
  • Device must not interfere with other equipment already in use
  • Fit the design of the patient’s unique chair
  • Patient has limited body mass and musculature
  • Limited access to patient
basic circuit design
Basic Circuit Design
  • Simple analog circuit components
  • Analog circuit contains six stages
  • Power supplied by two 9V batteries
  • High input impedance
  • Isolated from 120V wall output for patient safety
circuit stages
Circuit Stages
  • Instrumentation amplifier
    • Amplifies voltage difference across input electrodes
    • Provides high input impedance
    • Provides gain for entire circuit
    • High and low pass filters determine frequency range and block DC offset
  • Full Wave Rectifier
    • Takes absolute value of signal
circuit stages1
Circuit Stages
  • Passive Low Pass Filter
    • Averages signal
  • Comparator
    • Compares signal to a prescribed reference voltage
    • If input signal is greater than reference voltage then signal is passed to next stage
    • Reference voltage manually adjustable
circuit stages2
Circuit Stages
  • Timer
    • Input signal triggers approximately two and half minute countdown
  • Solid State Relay
    • Acts as a switch between circuit and massage pad
    • Activates massage pad upon active input signal from timer, deactivates pad when timer countdown expires
    • Optically isolated from 120V wall voltage
circuit schematic
Circuit Schematic
  • Shows exact design of circuit
  • All components are named and all component values are shown
printed board
Printed Board
  • No ground loop
  • Accessible Vcc sources
  • Capacitors in parallel to Vcc sources
    • Physical proximity to Op Amp
  • Custom Pads
    • Diodes
    • Potentiometers
    • Terminals
  • Solder SMT components to board
  • Connect board terminals to component
carbon rubber electrodes
Carbon-Rubber Electrodes
  • 3 electrodes: 2 to input signal, 1 to ground
  • Non-adhesive
    • non-invasive
    • reusable
    • gel required to increase conductivity
  • Already being used on child for other devices
    • child’s caregivers are familiar with apparatus
    • child’s caregivers are comfortable with their safety
  • Inexpensive
electrode attachment
Electrode Attachment
  • Felt strap fastens around child’s thigh
    • soft
    • easily replaceable
    • fastens with velcro so fit can be adjust
    • color matches massage pad cover
  • Electrodes attach to strap with velcro
    • Will allow consistent results because ensures consistent electrode placement
massage pad
Massage Pad
  • ConAIR HP08
    • 24” x 11”
    • should not affect ergonomic fit of the chair
    • two vibration settings, heat option
  • Can operate independently of circuit
massage pad cover
Massage Pad Cover
  • Removable and washable
    • maintains sanitation
    • reduces wear on the pad
  • Made of material attractive to children
    • aesthetic value
    • decreases appearance as a medical device
    • can be changed as child’s interests change
future work
Future Work
  • Measure the patient’s EMG signals
  • Customize the EMG amplifier to the patient
  • Test device on patient
  • Monitor the patient for adaptation towards the device
special thanks to
Special Thanks To:

Paul Victorey

John Webster

Jeff Schowalter