Gas Pressure Meter (Engineering World Health) Advisor: Professor Naomi Chesler Client: EWH and Professor John Webster Team Members: Ksenija Bujanovic- Team Leader Claire Edlebeck- Communications Mike Oldenburg- BSAC Chris Webster- BWIG

Background Information  Background on Engineering World Health  EWH Design Program  EWH specifications  Submission of design idea to EWH  If approved - build prototypes  Mass production and distribution  Limiting factor  Cost

Design Constraints  Cost less than $5 in quantities of 500  Variability of gasses  Range of pressure  Digital interface  Minimum accuracy within 10% of true value  Reusability

Current Tech  Pressure sensors built into anesthesia and ventilation machines  Break easily within the machine

Motivation Malfunctioning medical equipment in third world countries Lack of resources to fix machines Impact of device on medical care worldwide Photo with permission from Engineering World Health

Last Semester’s Work  Designed circuit that converts pressure input into voltage output  Central component – Wheatstone bridge  Testing showed accurate, linear relationship between voltage and pressure Figure 1 Figure 2

This Semester’s Work  Electrical aspects  Microcontroller  Seven-segment LED display

This Semester’s Work  Mechanical aspects  Connection between the device and the ventilator machine  Fluid mechanics

Microcontrollers  Requirements  14 pins  Low power  Inexpensive  Options  Peripheral Integrated Circuit (PIC)  Mixed Signal Microcontroller

Design Matrix Peripheral Integrated Controller (PIC) Mixed Signal Microcontroller Approximate Cost $ 1.29$ 0.99 Additional Parts  Voltage reference  A/D converter  Transistor Programming Device Currently availableMust be purchased

Design Matrix Peripheral Integrated Controller (PIC) Mixed Signal Microcontroller Approximate Cost $ 1.29$ 0.99 Additional Parts  Voltage reference  A/D converter  Transistor Programming Device Currently availableMust be purchased

Budget Part DescriptionSellerPart Number Unit Cost (per 3) Total Cost (Unit x3) Unit cost (per 500) Total Cost (Unit x500) Pressure Sensor Electronic GoldmineG15473 $ 3.91 $ $ 1.51 $ Battery HolderAll ElectronicsBH-32 $ 3.09 $ 9.27 $ 0.52 $ PCBExpress PCB $ $ $ 1.60 $ Display Electronic GoldmineG4031 $ 2.66 $ 7.98 $ 0.24 $ Microcontroller $ 3.00 $ 9.00 $ 1.75 $ Resistors (two per unit)Digikey Varies Based on Size $ 0.70 $ 2.10 $ 0.06 $ Operational Amplifier Allied ElectronicsLM358ADE4 $ 2.43 $ 7.29 $ 0.11 $ Low Battery lightDigikey ND $ 0.10 $ 0.29 $ 0.08 $ TubingUS Plastics54044 $ 2.03 $ 6.09 $ 0.09 $ ButtonAll ElectronicsPB-151 $ 0.40 $ 1.20 $ 0.25 $ Total $ $ $ 6.21 $ 3,109.43

Future Work  Proposal response  Build the prototype:  Programming the PIC  Testing several mechanical connections  Update EWH with information about the prototype and any changes

Resources  C. D. Ray, Medical Engineering, (1974) Chicago: Year Book Medical Publishers, Inc.  Keidan, H., (2001) Pressure versus volume-controlled ventilation with a laryngeal mask airway in pediatric patients. Pediatric Anesthesia ( )  Webster, J. G., Medical Instrumentation. (1998) Canada: John Wiley and Sons.

QUESTIONS?