EMG Biofeedback EMG Biofeedback DeviceDevice

BME 200/300BME 200/300

Fall 2003 Fall 2003

Department of Biomedical Department of Biomedical Engineering Engineering

University of Wisconsin-University of Wisconsin-MadisonMadison

Team MembersTeam Members

Tom Chia - BSACTom Chia - BSAC

Jason Ethington - CommunicatorJason Ethington - Communicator

Tim Rand –BWIGTim Rand –BWIG

Kim Treml - BSACKim Treml - BSAC

Brent Geiger – Team LeaderBrent Geiger – Team Leader

ClientClient

Arleigh Birchler, MDiv, BSNArleigh Birchler, MDiv, BSN

Brahms Addition Life and ChoiceBrahms Addition Life and Choice

AdvisorJohn Webster, Ph.D.John Webster, Ph.D.

Professor Emeritus Professor Emeritus

Biomedical Engineering – UW MadisonBiomedical Engineering – UW Madison

Abstract Abstract

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

Problem StatementProblem Statement

The goal of the project is to design The goal of the project is to design an EMG biofeedback device to allow an EMG biofeedback device to allow a patient with Lissencephaly to a patient with Lissencephaly to exhibit some physical control over exhibit some physical control over their life their life

Measure, amplify, and process EMG Measure, amplify, and process EMG signal to provide physical and signal to provide physical and cognitive stimulationcognitive stimulation

LissencephalyLissencephaly

Malformation Malformation of theof the brainbrain Occurs during fetal developmentOccurs during fetal development Variety of genetic and environmental Variety of genetic and environmental

causescauses SymptomsSymptoms

– Vary and range in severityVary and range in severity– Ex. Mental retardation, poor muscle control, Ex. Mental retardation, poor muscle control,

seizuresseizures

Design CriteriaDesign Criteria

Voluntary muscle contraction will Voluntary muscle contraction will activate massage padactivate massage pad

Device will be in use 24/7Device will be in use 24/7 Easy to learn and operateEasy to learn and operate Safe for patient and operatorSafe for patient and operator Patient confidentiality is Patient confidentiality is

maintainedmaintained

Client RequirementsClient Requirements

EMG electrodes are reusableEMG electrodes are reusable Device can distinguish between Device can distinguish between

voluntary and involuntary muscle voluntary and involuntary muscle contractionscontractions

Timer to control duration of Timer to control duration of vibrationvibration

Design ConstraintsDesign Constraints

Device must not interfere with Device must not interfere with other equipment already in useother equipment already in use

Fit the design of the patient’s Fit the design of the patient’s unique chairunique chair

Patient has limited body mass Patient has limited body mass and musculatureand musculature

Limited access to patientLimited access to patient

Basic Circuit DesignBasic Circuit Design

Simple analog circuit componentsSimple analog circuit components Analog circuit contains six stagesAnalog circuit contains six stages Power supplied by two 9V Power supplied by two 9V

batteriesbatteries High input impedance High input impedance Isolated from 120V wall output for Isolated from 120V wall output for

patient safetypatient safety

Circuit StagesCircuit Stages

Instrumentation amplifierInstrumentation amplifier– Amplifies voltage difference across input Amplifies voltage difference across input

electrodeselectrodes– Provides high input impedanceProvides high input impedance– Provides gain for entire circuitProvides gain for entire circuit– High and low pass filters determine High and low pass filters determine

frequency range and block DC offsetfrequency range and block DC offset

Full Wave RectifierFull Wave Rectifier– Takes absolute value of signalTakes absolute value of signal

Circuit StagesCircuit Stages

Passive Low Pass FilterPassive Low Pass Filter– Averages signalAverages signal

ComparatorComparator– Compares signal to a prescribed reference Compares signal to a prescribed reference

voltagevoltage– If input signal is greater than reference If input signal is greater than reference

voltage then signal is passed to next stagevoltage then signal is passed to next stage– Reference voltage manually adjustableReference voltage manually adjustable

Circuit StagesCircuit Stages

TimerTimer– Input signal triggers approximately two and Input signal triggers approximately two and

half minute countdownhalf minute countdown

Solid State RelaySolid State Relay– Acts as a switch between circuit and massage Acts as a switch between circuit and massage

padpad– Activates massage pad upon active input Activates massage pad upon active input

signal from timer, deactivates pad when timer signal from timer, deactivates pad when timer countdown expirescountdown expires

– Optically isolated from 120V wall voltageOptically isolated from 120V wall voltage

Circuit SchematicCircuit Schematic

Shows exact design of circuitShows exact design of circuit All components are named and all All components are named and all

component values are showncomponent values are shown

Printed BoardPrinted Board

No ground loopNo ground loop Accessible Vcc sourcesAccessible Vcc sources Capacitors in parallel to Vcc sourcesCapacitors in parallel to Vcc sources

– Physical proximity to Op AmpPhysical proximity to Op Amp Custom PadsCustom Pads

– DiodesDiodes– PotentiometersPotentiometers– TerminalsTerminals

ConstructionConstruction

Solder SMT components to boardSolder SMT components to board Connect board terminals to Connect board terminals to

componentcomponent

Carbon-Rubber Carbon-Rubber ElectrodesElectrodes

3 electrodes: 2 to input signal, 1 to 3 electrodes: 2 to input signal, 1 to groundground

Non-adhesiveNon-adhesive– non-invasivenon-invasive– reusablereusable– gel required to increase conductivitygel required to increase conductivity

Already being used on child for other Already being used on child for other devicesdevices– child’s caregivers are familiar with apparatuschild’s caregivers are familiar with apparatus– child’s caregivers are comfortable with their child’s caregivers are comfortable with their

safetysafety InexpensiveInexpensive

Electrode AttachmentElectrode Attachment

Felt strap fastens around child’s thighFelt strap fastens around child’s thigh– softsoft– easily replaceableeasily replaceable– fastens with velcro so fit can be adjustfastens with velcro so fit can be adjust– color matches massage pad covercolor matches massage pad cover

Electrodes attach to strap with velcroElectrodes attach to strap with velcro– Will allow consistent results because Will allow consistent results because

ensures consistent electrode placementensures consistent electrode placement

Massage PadMassage Pad

ConAIR HP08ConAIR HP08– 24” x 11”24” x 11”– should not affect ergonomic should not affect ergonomic

fit of the chairfit of the chair– two vibration settings, heat two vibration settings, heat

optionoption

Can operate Can operate independently of circuitindependently of circuit

Massage Pad CoverMassage Pad Cover

Removable and washableRemovable and washable– maintains sanitationmaintains sanitation– reduces wear on the padreduces wear on the pad

Made of material attractive to Made of material attractive to childrenchildren– aesthetic valueaesthetic value– decreases appearance as a medical decreases appearance as a medical

devicedevice– can be changed as child’s can be changed as child’s interestsinterests

changechange

Future WorkFuture Work

Measure the patient’s EMG Measure the patient’s EMG signalssignals

Customize the EMG amplifier to Customize the EMG amplifier to the patientthe patient

Test device on patientTest device on patient Monitor the patient for adaptation Monitor the patient for adaptation

towards the devicetowards the device

Special Thanks To:Special Thanks To:

Paul VictoreyPaul Victorey

John WebsterJohn Webster

Jeff SchowalterJeff Schowalter