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