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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


Client
Client

Arleigh Birchler, MDiv, BSN

Brahms Addition Life and Choice

Advisor

John Webster, Ph.D.

Professor Emeritus

Biomedical Engineering – UW Madison


Abstract
Abstract

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


Lissencephaly
Lissencephaly

  • 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


Construction
Construction

  • 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


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