Spring 2015 Senior Design College of Engineering The University of Georgia DEVELOPMENT OF AN EMBEDDED SYSTEM FOR ASSESSING EXTREMITY BLOOD VOLUMES BASED ON ELECTROCARDIOGRAPHY Faculty Mentor: Zion Tsz Ho Tse Graduate Mentor: T. Stan Gregory Driftmier Annex, Room 120

GENERALIZED BIOMEDICAL INSTRUMENTATION BLOCK DIAGRAM PatientTransducer Instrumentation Amplifier (G>1) Filter Stage DC Offset Adjust + Gain Anti-Aliasing Filter ADC New Material

Remove undesired frequency content from your signal Wall socket contains Hz Can contaminate your signal (ECG) How to implement it? Software vs. Hardware Software filters must obey Nyquist (f sample >> f noise/signal ) FILTERING With 60 Hz Noise 60 Hz Filtered

Pick C that we have in lab Reverse solve for R based on f c Single Op-amp  2 pole Twice the attenuation past f c COMMON FILTER CIRCUIT Sallen Key Lowpass (pass frequencies <f c )Sallen Key Highpass (pass frequencies >f c ) Resources: psalkey1/opsalkey1.htm psalkey1/opsalkey1.htm denshi.jp/en/OPseikiLowkeisan.htm denshi.jp/en/OPseikiLowkeisan.htm

DC OFFSET + GAIN Push signal from dc offset to desired level ex: for 5Vpp sine wave, 2.5V is desired offset for digitizing using ADC in the Arduino Further amplify to use more bits (use rather than )

ANTI-ALIASING FILTER Why? Filters out all frequencies that would disobey the Nyquist thm Use Sallen Key Lowpass filter as previously described Pick f c based on Nyquist

MORE END GOAL INFORMATION Cell phone case attachment 2 modes of use Hold with 2 hands, phone measures and plots ecg, displays heart rate Hold phone against arm, phone measures mhd signal, gives perfusion information 1 st half of the semester, design part 1 (ecg)

NEXT ASSIGNMENT Ideas for the next directions to take 1 group breaks off to learn SolidWorks and begin to CAD cell phone cases Build signal conditioning hardware  read nice ECG into Arduino (Make a test Android application) Presentation for next week (Mon Jan 26) Finish Assignment #1, present all data Pick next directions for group  brief on progress Read this datasheet, brief the group on how to operate the chip (MCP4131) Tell us why it would be useful for this project (think about how you are going to create a device that can read physiological signals from different body parts) 60b.pdf 60b.pdf