EMG Biofeedback Device

1. EMG Biofeedback Device BME 200/300 Fall 2003 Department of Biomedical Engineering University of Wisconsin-Madison

2. Team Members Tom Chia - BSAC Jason Ethington - Communicator Tim Rand –BWIG Kim Treml - BSAC Brent Geiger – Team Leader

3. Client Arleigh Birchler, MDiv, BSN Brahms Addition Life and Choice Advisor John Webster, Ph.D. Professor Emeritus Biomedical Engineering – UW Madison

4. 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.

5. 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

6. 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

7. 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

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

9. 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

10. 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

11. 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

12. 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

13. 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

14. Circuit Schematic • Shows exact design of circuit • All components are named and all component values are shown

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

16. Construction • Solder SMT components to board • Connect board terminals to component

17. 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

18. 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

19. 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

20. 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

21. 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

22. Special Thanks To: Paul Victorey John Webster Jeff Schowalter