STUDY AND DESIGN OF LOW COST PRESSURE SENSORS FOR PREVENTING THEFT OF VEHICLE

A Project Report Submitted in Partial Fulfillment of the Requirements

for the Degree ofBachelor of Technology

inMechanical Engineering

byGROUP M17

MECHANICAL ENGINEERINGMOTILAL NEHRU NATIONAL INSTITUTE OF TECHNOLOGY

ALLAHABAD, INDIADecember, 2011

CERTIFICATE

Certified that the work contained in this titled “STUDY AND DESIGN OF LOW COST PRESSURE SENSORS FOR PREVENTING THEFT OF VEHICLE”, has been carried out under my supervision and that this work has not been submitted elsewhere for a degree.

Asst. Prof. S.B. MISHRAMechanical EngineeringMNNIT

Contents

INTRODUCTION

MEMS

APPLICATION OF MEMS

ADVANTAGES OF MEMS

MEMES BASED PRESSURE SENSOR DESIGN

VARIOUS RESPONSE OF PIEZORESISITIVE SENSOR

MECHANICAL DESIGN

]

Chapter 1

Introduction

Mems, micro electro mechanical systems, are the integration of electronic and mechanical components on micro level. These consists of sensor to obtain signals from the environment, electronic system provides logic and manipulation of signal obtained and finally actuators produce desired output.

This technology is targeted at devices that range in size from millimeters down to microns, and involve precision mechanical components that can be manufactured using semiconductor manufacturing technologies.A diverse range of application areas has been proposed, and applications developed for these devices include a wide range of sensor, fluid mechanics, optics, RF, storage, and biotechnology applications.

1.1 APPLICATION OF MEMS

MEMS are most popular in the automotive industry as accelerometers

for airbag systems. MEMS have many other uses besides airbag

systems, and not only for the automotive market. They also have

applications in industrial, military, and consumer markets.

Automotive Market: Airbag Systems

Vehicle Security Systems

Intertial Brake Lights

Headlight Leveling

Rollover Detection

Automatic Door Locks

Active SuspensionConsumer Market: Appliances

Sports Training Devices

Computer Peripherals

Car and Personal Navigation Devices

Active SubwoofersIndustrial Market: Earthquake Detection and Gas Shutoff

Machine Health

Shock and Tilt SensingMilitary: Tanks

Planes

Equipment for Soldiers

1.2 ADVANTAGES OF MEMS

They have proven to be a key enabling technology of developments in

areas such as transportation, telecommunications and health care, but the

range of MEMS applications covers nearly every field. The most

significant advantage of MEMS is their ability to communicate easily with

electrical elements in semiconductor chips. Other advantages include small

size, lower power consumption, lower cost, increased reliability and higher

precision.

(1)　 IC Technology used: Integrated multiple and more complex

functions on a chip, to form a monolithic system(sensors+processing+

actuators), Miniaturization with no loss of functionality, Improved

Performanc.

(2)　 Batch Fabrication: Reduced Manufacturing Cost & Time.

(3) 　 Microcomponents make the system faster, more reliable, more

portable, cheaper, low power consumption, easily & massively employed,

easily maintained & replaced.

(4)　 Easy to integrate into systems or modify.

(5)　 Little harm to environment and capable of incorporating.

(6)　 Exploitation of new physics domains.

Chapter 2

MEMS BASED PRESSURE SENSEOR DESIGN

The pressure microsensors often use a thin square-shaped diaphragm as

their main sensor element. This is because of its compatibility with bulk

and surface silicon micromachining processes. A pressure applied on the

diaphragm generates an increase in its deflection until the elastic force is

balanced by the pressure. The pressure range that can be measured by the

diaphragm depends on its dimensions (surface area and thickness),

geometry, edge conditions, and material .

The diffused resistors on the silicon substrate are used to measure the

strain of the diaphragm of the pressure microsensors. This piezoresistive

microsensor generally has four piezoresistors in a Wheatstone bridge

configuration to measure the stresses in a silicon diaphragm under normal

Pressure.

‘

The deformation response of piezoresistive sensor to a pressure of 2*10^6 Pa

The stress response of piezoresistive sensor to a pressure of 2*10^6 Pa

• Data Used

• pi(t)= 71.8*10^-11 / Pa• pi(l)= - 66.3*10^-11 / Pa• E=169.8 GPa• Nu= .066

MECHANICAL DESIGN

The del(v)/v vs pressure response of piezoresistor