Disposable Mattress Cover with Wet Sheet Sensors

ECE 4884 L05Advisor: Dr. Art Koblasz

Team Members:Youn Hur

Michael WozniakPyungho Chung

Dongki Yoon

Project Overview

Improve upon previous group’s design to build a disposable mattress cover with wetness detection function

ClientHospitals, Nursing Homes, and Patient Caring Facilities

Cost$22.14 ($1.96 + $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 SpecificationMattress Cover

Cost : Less than $2 Current

Drawn from detection circuit << 0.5 mA Dimensions Materials

Technical SpecificationDetection 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 PadConnector

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 ApproachMicrocontroller

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 ApproachAC 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 ScheduleMarch

April

2weeks 1week

3days

Analog Circuit Design

Circuit Design w/ Microcontroller

Microcontroller coding

end3/21

3/10

3/19

3/24

3/31 1week 4/7 1week

Pattern Design/Assembly

Testing

end3/28

end4/4

end4/11

Current Status

Building a prototype Building analog circuit and adjusting

components Waiting for conductive ink print on PET Writing micro-controller code

Questions?