Disposable Mattress Cover with Wet Sheet Sensors ECE 4884 L05 Advisor: Dr. Art Koblasz Team Members: Youn Hur Michael Wozniak Pyungho Chung Dongki Yoon

Project Overview  Improve upon previous group’s design to build a disposable mattress cover with wetness detection function  Client Hospitals, Nursing Homes, and Patient Caring Facilities  Cost $22.14 ($ $20.18)

Mattress Parts Circuit Parts 9V DC 5V AC or Conductive Ink 32 gauge wire Deviations from Previous Designs

Technical Objectives  Safe, sanitary, comfortable and durable mattress cover  Detection function to alarm wetness and breakage in conductive pattern  AC signal testing circuit

Technical Specification Mattress Cover  Cost : Less than $2  Current Drawn from detection circuit << 0.5 mA  Dimensions Materials

Technical Specification Detection Circuit  Cost : Approximately $20  Current source 110V AC  Dimensions (Casing) 25 cm x 20 cm x 15 cm (L x W x H)  Parts Microcontroller, Opto-isolator, Rectifier, Transformer, Resistors, Wires, Circuit board, Connector, Casing, Wall plug-in

Overall Construction Power Adaptor Detection Circuit Mattress Pad Connector Output of Circuit (USB, Wireless) Computer

Mattress Conductive Pattern  Two intertwined loops to cover top surface with 10~15 cm spacing  Each loop can be checked for continuity (breakage)  AC signal sent to one loop can be read from the other loop for wetness detection

Connector & Power Adapter

Detection Circuit Schematic

Design Approach Microcontroller  Low power consumption, low cost, and self-sufficient  Arithmetic logic to detect its own AC signal that runs through mattress cover  Utilize A/D converter  Easy to manipulate

Design Approach AC Signal Testing  DC changes PH level in an electrolytic solution and leads to destruction of neurons  Electricity can be detected by sense of touch at 0.5 mA (current range should be much less)  AC does not change PH and can be healing stimulant

Testing & Demonstration  Safety test Measure AC signal strength Sit on wet cover  Durability test Pull and tear to test mechanical strength of bed sheet Fold and crumple to check breakage of conductive pattern Run higher voltage through the circuit

Problems & Issues  Providing electrical isolation between the circuit and the mattress  Keeping cost of materials low as more parts being added  Contacting material suppliers to create the prototype is time-consuming

Project Schedule

Current Status  Building a prototype Building analog circuit and adjusting components Waiting for conductive ink print on PET Writing micro-controller code

Questions?