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 Brahms Addition Life and Choice Advisor John Webster, Ph.D. Professor Emeritus Biomedical Engineering – UW Madison

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

Lissencephaly Malformation of the brain Malformation of the brain Occurs during fetal development Occurs during fetal development Variety of genetic and environmental causes Variety of genetic and environmental causes Symptoms Symptoms –Vary and range in severity –Ex. Mental retardation, poor muscle control, seizures

Design Criteria Voluntary muscle contraction will activate massage pad Voluntary muscle contraction will activate massage pad Device will be in use 24/7 Device will be in use 24/7 Easy to learn and operate Easy to learn and operate Safe for patient and operator Safe for patient and operator Patient confidentiality is maintained Patient confidentiality is maintained

Client Requirements EMG electrodes are reusable EMG electrodes are reusable Device can distinguish between voluntary and involuntary muscle contractions Device can distinguish between voluntary and involuntary muscle contractions Timer to control duration of vibration Timer to control duration of vibration

Design Constraints Device must not interfere with other equipment already in use Device must not interfere with other equipment already in use Fit the design of the patient’s unique chair Fit the design of the patient’s unique chair Patient has limited body mass and musculature Patient has limited body mass and musculature Limited access to patient Limited access to patient

Basic Circuit Design Simple analog circuit components Simple analog circuit components Analog circuit contains six stages Analog circuit contains six stages Power supplied by two 9V batteries Power supplied by two 9V batteries High input impedance High input impedance Isolated from 120V wall output for patient safety Isolated from 120V wall output for patient safety

Circuit Stages Instrumentation amplifier 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 Full Wave Rectifier –Takes absolute value of signal

Circuit Stages Passive Low Pass Filter Passive Low Pass Filter –Averages signal Comparator 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 Stages Timer Timer –Input signal triggers approximately two and half minute countdown Solid State Relay 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 Shows exact design of circuit Shows exact design of circuit All components are named and all component values are shown All components are named and all component values are shown

Printed Board No ground loop No ground loop Accessible Vcc sources Accessible Vcc sources Capacitors in parallel to Vcc sources Capacitors in parallel to Vcc sources –Physical proximity to Op Amp Custom Pads Custom Pads –Diodes –Potentiometers –Terminals

Construction Solder SMT components to board Solder SMT components to board Connect board terminals to component Connect board terminals to component

Carbon-Rubber Electrodes 3 electrodes: 2 to input signal, 1 to ground 3 electrodes: 2 to input signal, 1 to ground Non-adhesive Non-adhesive –non-invasive –reusable –gel required to increase conductivity Already being used on child for other devices Already being used on child for other devices –child’s caregivers are familiar with apparatus –child’s caregivers are comfortable with their safety Inexpensive Inexpensive

Electrode Attachment Felt strap fastens around child’s thigh 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 Electrodes attach to strap with velcro –Will allow consistent results because ensures consistent electrode placement

Massage Pad ConAIR HP08 ConAIR HP08 –24” x 11” –should not affect ergonomic fit of the chair –two vibration settings, heat option Can operate independently of circuit Can operate independently of circuit

Massage Pad Cover Removable and washable Removable and washable –maintains sanitation –reduces wear on the pad Made of material attractive to children Made of material attractive to children –aesthetic value –decreases appearance as a medical device –can be changed as child’s interests change

Future Work Measure the patient’s EMG signals Measure the patient’s EMG signals Customize the EMG amplifier to the patient Customize the EMG amplifier to the patient Test device on patient Test device on patient Monitor the patient for adaptation towards the device Monitor the patient for adaptation towards the device

Special Thanks To: Paul Victorey John Webster Jeff Schowalter