February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Apparatus for the Analysis of Heart Sounds

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Team Pacemaker Luke Philips, Ryan Laterza, Min Dong Bian, Sarah Makhija Electronic Stethoscope/EKG Device In collaboration with Mechanical and Software Engineering students Dr. Howard D. Weinberger –Cardiologist and Co-Director of Cardiac Imaging at the University of Colorado at Denver and Health Sciences Center –Apparatus and methods for analyzing heart sounds Patent #5,687,738

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Project Objectives Provide objective means of analyzing cardiac acoustics –Aid in diagnosis of heart murmurs Amplified signal from stethoscope, EKG Handheld device, portable memory, graphical display

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Heart Physiology and Anatomy

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Heart Murmur Pathology Heart valve(s) fail to close/open properly, causing turbulent blood through the blood vessels Turbulent blood flow causes high and low pitch sounds known as heart murmurs Heart problems caused by the malfunction of heart valves Estimates for 2003: 71,300,000 Americans have one or more forms of cardiovascular disease (CVD)

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Use Case Diagram

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Heart Rate and EKG Monitor Using Bypass Capacitors and differential amplifier

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds What is an EKG? Graphic tracing of the voltage generated by the cardiac or heart muscle during a heartbeat EKG waveform:

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Circuit Design Problem Electrical signal is very small: 1mv peak- peak The signal is noisy Solution: –Use differential amplifier and bypass capacitors to design the circuits

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Function In this case, differential amplifier will reduce the noise voltages Bypass capacitors help filter the electrical noise out of our circuit,the good default value for bypass capacitors is 0.1uF

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds The EKG Amplifier Circuit

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Output of EKG

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds The output of EKG after modified circuit

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds How to store these data? Use Secure Digital Card (SD) Two sizes: Regular, 32 × 24 × 2.1 mm Mini, 20 x 21.5 x 1.4 mm Capacity: –Regular, 128, 256, and 512 MBs, 1, 2 and 4 GBs.MBsGBs –Mini, 16MB to 2GB

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Image of Mini SD Card

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Mixed Signal Microcontroller Texas Instrument MSP430F427

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Key Features Supply Voltage Range 2.7 to 3.6 Volts (Three 16-Bit ADCs Active) Scalable Processor Frequency: 6Mhz (2.7 V) to 8Mhz (3.6 V) Ultra low-Power Consumption: –Active Mode: 400 µA at 1 MHz, 3.0 V –Standby Mode: 1.6 µA –Off Mode (RAM Retention): 0.1 µA

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Key Features (cont.) 6 µs Wake-Up From Standby Mode 16-Bit RISC Architecture 12 General Purpose 16-Bit Registers 32 kB of FLASH Program Memory 1 kB of Random Access Memory Direct Memory Access Controller Three Independent 16-Bit Sigma-Delta A/D Converters

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Key Features (cont.) One 16-Bit Timer and Two 8-Bit Timers Integrated LCD Driver for 128 Segments Serial Communication Interface (USART), Asynchronous UART or Synchronous SPI Flash Memory can be Programmed by JTAG Port, Bootstrap Loader, or In-System by the CPU Brownout Detector Instruction Set Consists of Fifty-One Instructions –Can Operate on Word and Byte –Seven Address Modes

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds TI MSP430F427 Pin Layout and Chip Dimensions 64 Pin Quad Flat Pack Chip 12.2 mm

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Analog To Digital Converters 16-Bit Sigma Delta ADC Sampling Frequencies –Low Power Mode Disabled 1Mhz –Low Power Mode Enabled 500Khz Analog Input Range with Gain = 1 –±500mV and 650 to 950 uA Gain = 1 has highest Signal to Noise Distortion Ratio Input Impedance = 200 kΩ

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Power Li-Ion Battery Charger solution using the MSP430

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Li-lon battery Features Li-Ion ideal for portable applications –High capacity-to-size ratio –low self discharge characteristic. Battery charging –power management ICs –MCU controlled –logic devices MCU controlled –safe charging –time efficient –low cost

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Battery Features (cont.) Battery capacity, C, mA hours Battery current, C-Rate –500 mA-h battery, C-Rate 500mA –1C, 500 mA –0.1C is 50 mA. Li-Ion battery charging, three stages: –Slow Charge: current of 0.1C –Fast Charge: current of 1C –Constant voltage

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Current vs Voltage for Li-lon Battery Charging

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Risks of Li-Ion batteries –explosion due to outgassing of electrolyte –Severe reduction in battery life –sensitive to overcharging final voltage, ±50 mV of 4.1 or 4.2V. Fully charged –constant voltage, current 0.1C –Observe temperature –safe timing method charging time longer than a predetermined time Typical Cell Phone Li-Ion batteries rated at ~850 mAh

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds buck converter –constant current, constant voltage –step down voltage converter –inductor as a current source –output load impedance, i.e. the battery PNP and NPN transistors switch via PWM –switch closed current flows through inductor capacitor is charged –switch open inductor maintain current flow –Inducing voltage current flows through diode inductor charges capacitor LC network –low-pass filter –PWM frequency > cut-off capacitor voltage is constant equal to the mean value of input voltage to buck converter

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Inductor at 75 mH is sufficient PWM 15 kHz PWM resolution 8-bits Capacitor is 220 mF, cutoff frequency of LC network 1.2 kHz –helps capacitor reduce the output voltage ripple –maintain DC voltage level Three channels on A/D converter on MSP430 to measure battery –battery voltage –battery temperature –battery current

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Power Thermistor connected to negative pole of battery –resistance decreases with temperature and thermistor voltage Risk of design –Complex –Fall back plan Alkaline batteries Bench Power

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Device UI - Keypad Ultralow-Power Keypad Interface With the MSP430 draws 0.1 µA waiting interrupt driven no polling Max 2 µA at 3 V if all keys are pressed and held simultaneously No crystal required Minimum external components Suitable for any MSP430 device

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Device UI - Keypad Normal mode –wait-for-press mode –rows driven high –column pins as inputs –interrupt on a rising edge 4.7 MΩ pull down resistors –inputs low –MSP430 low-power mode –MSP430 current consumption 100 nA. Maintained indefinitely until key is pressed

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Device UI - Keypad Risk of design –Moderate Complexity –Fall back plan Individual hard- wired buttons

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Use Case Diagram Revisited

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Improvement upon current methods –Range of human ear: 20 – 20kHz May be important info beyond audible range –Objective teaching tool –Time-saving –More accurate medical records and diagnoses

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Possible extensions –Diagnostic software –Analyze dependence on respiratory phase –Integrate EKG leads and stethoscope –Input patient data from computer rather than keypad Barcodes

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Division of Labor Luke – Design power source, user- interface Ryan – Systems integration leader, implement microcontroller Min Dong – Design of memory stick, EKG amplifier Sarah – Team lead, assist team in technical undertakings All – Write user’s manual

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Schedule

February 2, 2006PDR – Apparatus for the Analysis of Heart Sounds Thank you! Questions?