AIR BAG CRASH USING MEMS

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Mini project report on
AIR BAG CRASH SENSOR DEVELOPMENT USING
MEMS
Submitted in partial fulfillment of mini project for the award of the degree of
BACHELOR OF TECHNOLOGY
IN
ELECTRONICS AND COMMUNICATION ENGINEERING
Submitted By
K.NAVYA REGD.NO:11631A0449
S.HARI KRISHNA REGD.NO:11631A0421
P.GANESH REGD.NO:11631A0418
N.RAJIV REGD.NO:11631A0458
Under the esteemed guidance of
B.SWETHA M.tech
Department of Electronics & Communication Engineering
SRI VENKATESWARA ENGINEERING COLLEGE
Amarvadi Nagar, Sponsored by the exhibition society, HYDERABAD, Approved by AICTE,
Affiliated to Jawaharlal Nehru Technological University, HYDERABAD, Suryapet-508213,
Nalgonda Dist. 2014-2015

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SRI VENKATESWARA ENGINEERING COLLEGE
Amaravadi Nagar, Sponsored by The Exhibition Society, HYDERABAD, Approved by AICTE, Affiliated to
Jawaharlal Nehru Technological University, Hyderabad Suryapet-508213, Nalgonda Dist.
2014-2015
Department of Electronics & Communication Engineering
CERTIFICATE
This is to certify that the project report titled as "AIR BAG CRASH
SENSOR DEVELOPMENT USING MEMS" being submitted by K.NAVYA
(11631A0449), S.HARIKRISHNA (11631A0421), P.GANESH (11631A0418), and
N.RAJIV (1631A0458) from IV B.Tech I semester of Electronics and Communication
Engineering is a record bonafide work carried out by us. The results embodied in this
report have not been submitted to any other University for the award of any degree.
Signature of the Guide Signature of the H.O.D
Signature of the External Signature of the Principal

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DECLARATION
We the Students of B.Tech in ELECTRONICS & COMMUNICATION
ENGINEERING of Sri Venkateswara Engineering College, Suryapet, hereby declare that
the project with title “GSM BASED WIRELESS NOTICE BOARD” Is the original
work done by us.
To the Best of us Knowledge and belief we hereby declare that this project bears
no resemblance to any other project submitted at Sri Venkateswara Engineering College,
Suryapet or any other college affiliated to Jawaharlal Nehru Technological University,
Hyderabad for the award of the degree.
Place:
Date:
Project associates
K.NAVYA - 11631A0449
S.HARI KRISHNA - 11631A0421
P. GANESH - 11631A0418
N.RAJIV - 11631A0458

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ACKNOWLEDGEMENT
we sincerely thank our principal Dr.A.SRUJANA for her timely suggestions,
which helped me to complete this work successfully.
It is my privilege to thank Mr. E.NARENDRA, Associate Professor &I/C HOD
of ECE Department for her encouragement during the progress of this project work.
we express my sincere thanks to my supervisor B. SWETHA for giving me moral
support, kind attention and valuable guidance to me throughout this project work.
we thank to both teaching and non-teaching staff members of ECE Department
for their kind cooperation and all sorts of help to bring out this project work successfully.
By
K.NAVYA - 11631A0449
S.HARI KRISHNA - 11631A0421
P. GANESH - 11631A0418
N.RAJIV - 11631A0458

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ABSTRACT
An airbag crash sensor system is a vehicle safety device. It is an occupant
restraint consisting of a flexible envelope designed to inflate rapidly during an
automobile collision, to prevent occupants from striking interior objects such as the
steering wheel or a window.
Modern vehicles may contain multiple airbags in various side and frontal
locations of the passenger seating positions, and sensors may deploy one or more airbags
in an impact zone at variable rates based on the type and severity of impact the airbag is
designed to only inflate in mild to severe frontal crashes. Airbags are normally designed
with the intention of supplementing the protection of an occupant who is correctly
restrained with a seatbelt. Air bag operation in this project is shown by tripping the relay
in which led or a DC motor turns on. When ever any accident occur means any
Disturbance caused to MEMS sensor which was arranged in critical angle detects and
sends mechanical force to controller hence the air bag release in the form of relay
tripping.

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INDEX
CONTENTS PAGE NO
CHAPTER 1: INTRODUCTION 1
1.1 EMBEDDED SYSTEM 1
1.2 CHARACTERISTICS OF EMBEDDED SYSTEM 1
1.3 APPLICATION 2
1.4 CLASSSIFICATION 2
1.4.1 RTS CLASSIFICATION 3
1.4.1.1 HARD REAL TIME SYSTEM 3
1.4.1.2 SOFT REAL TIME SYSTEM 3
CHAPTER 2: BLOCK DIAGRAM 4
CHAPTER 3: HARDWARE REQUIREMENTS 5
3.1 TRNSFORMER 6
3.1.1 IDEAL POWER EQUATION 7
3.2 VOLTAGE REGULATOR (LM7805) 8
3.2.1 INTERNAL BLOCK DIAGRAM 9
3.2.2 ABSOLUTE MAXIMUM RATINGS 9
3.3 RECTIFIER 10
3.4 FILTER 10
3.5 MICROCONTROLLER (AT89S52/C51) 11
3.5.1 BLOCK DIAGRAM OF AT89S52 13
3.5.2 PIN CONFIGURATIONS OF AT89S52 14
3.5.3 OSCILLATOR CHARACTERISTICS 16
3.6 MEMS 17
3.6.1 PIN DESCRIPTION 19
3.6.2 ELECTRO STATIC DISCHARGE (ESD) 19
3.6.3 PRINCIPLE OF OPERATION 20
3.6.4 MODES OF OPERATION 21
3.6.5 POWER SAVING FEATURES 21

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3.6.6 TESTING THE LOGIC CHAIN 22
3.6.7 TAP DETECTION 22
3.6.8 TAP DETECTION SETUP 22
3.6.9 SHAKE DETECTION 23
3.6.10 AUTO WAKE/SLEEP 23
3.6.11 START AND STP CONDITIONS 25
3.6.12 MESSAGE FORMAT FOR WRITING MMA7660FC 26
3.6.13 MESSAGE FORMAT FOR READING MMA7660FC 27
3.7LCD MODULE 27
CHAPTER 4: SOFTWARE REQUIREMENTS 31
4.1 INTRODUCTION TO KEIL MICRO VISION 31
4.2 CONCEPT OF COMPILER 31
4.3 CONCEPT OF CROSS COMPILER 32
4.4 KEIL C CROSS COMPILER 32
4.5 BUILDING AN APPLICATION UVISION2 32
4.6 CREATING YOUR OWN APPLICATION UVISION2 33
4.7 DEBUGGING AN APPLICATION IN UVISION2 33
4.8 STARTING UVISION2 & CREATING A PROJECT 33
4.9 WINDOWS_ FILES 34
4.10 BUILDING PROJECTS & CREATING HEX FILTERS 34
4.11 CPU SIMULATION 34
4.12 DATA SELECTION 35
4.13 START DEBUGGING 35
4.14 DISASSEMBLY WINDOW 35
4.15 EMBEDDED C 36
CHAPTER 5: SCHEMATIC DIAGRAM 37
5.1 OPERATION 38
CHAPTER 6: CODING 39
6.1 SOURCE CODE 39
6.2 FLOW CHART 46

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CHAPTER 7: HARDWARE TESTING 47
7.1 CONTINUITY TEST 47
7.2 POWER ON TEST 47
CHAPTER 8: CONCLUSION 48
CHAPTER 9: ADVANTAGES AND APPLICATIONS 50
CHAPTER 10: BIBILOGRAPHY 51

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LIST OF FIGURES
FIG NO NAME OF THE FIGURE PAGE NO
2.1 BLOCK DIAGRAM OF AIR BAG CRASH SENSOR 4
3.1.1 A TYPICAL TRANSFORMER 6
3.1.2 IDEAL POWER EQUATION 7
3.2.1 CIRCUIT DIAGRAM OF VOLTAGE REGULATOR 8
3.2.2 BLOCK DIAGRAM OF VOLTAGE REGULATOR 9
3.2.3 RATING OF THE VOLTAGE REGULATOR 9
3.3 BRIDGE RECTIFIER 10
3.4 FILTER OUTPUT 11
3.5 BLOCK DIAGRAM OF AT89S52 13
3.5.1 PIN DIAGRAM OF AT89S52 14
3.5.2 OSCILLATOR CONNECTIONS 17
3.5.3 EXTERNAL CLOCK DRIVE CONFIGURATION 17
3.6.1 AXIS ORIENTATION/MOTION DETECTION SENSOR 17
3.6.2 BOTTOM VIEW MMA 7660FC 18
3.6.3 PIN CONNECTIONS MMA 7660FC 18
3.6.5 MMA CONNECTIONS TO MCU 19
3.6.7 SIMPLIFIED TRANSDUCER PHYSICAL MODEL 20
3.6.11 BIT TRANSFER 25
3.6.12 ACKNOWLEDGE 26
3.6.13 SINGLE BYTE WRITE 26
3.6.14 MULTIPLE BYTES WRITE 27
3.6.15 SINGLE BYTE READ 27
3.6.16 MULTIPLE BYTES READ 27
3.7.1 2X16 LINE ALPHANUMERIC LCD DISPLAY 28
3.7.3 CONTROLLER TO LCD INTERPRETS 30
5 SCHEMATIC DIAGRAM OF AIR BAG CRUSH 37
6.2 FLOW CHART OF AIR BAG CRUSH SENSOR 46

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LIST OF TABLES
TABLE NO NAME OF THE FIGURE PAGENO
3.2.3 RATING OF THE VOLTAGE REGULATOR 9
3.6.4 PIN DESCRIPTION MMA 7660FC 19
3.6.6 ESD AND LATCH-UP PROTECTION
CHARACTERISTICS 20
3.6.8 STATE MACHINE MODES 21
3.6.9 FEATURE SUMMARY TABLE 22
3.6.10 AUTO WAKE/SLEEP TRUTH TABLE 24
3.7.2 2*16 LCD PINS 29

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ABBREVIATIONS
ADDRESS LATCH ENABLE ALE
PROGRAM STORE ENABLE PSEN
EXTERNAL ACCESS EA
MICRO-ELECTRO-MECHANICAL SYSTEM MEMS
READ/WIRTE R/W
TIMER/COUNTERS C/T
ELECTRO STATIC DISCHARGE ESD
LIQUID CRYSTAL DISPLAY LCD
INTEGRATED DEVELOPMENT ENVIRONMENT IDE
HIGH LEVEL LANGUAGE HLL
IN-SYSTEM PROGRAMMABLE ISP

AIR BAG CRASH SENSOR DEVELOPMENT USING MEMS
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CHAPTER-1
INTRODUCTION
1.1 EMBEDDED SYSTEMS
An Embedded System is a combination of computer hardware and software, and
perhaps additional mechanical or other parts, designed to perform a specific function. An
embedded system is a microcontroller-based, software driven, reliable, real-time control
system, autonomous, or human or network interactive, operating on diverse physical
variables and in diverse environments and sold into a competitive and cost conscious
market.
An embedded system is not a computer system that is used primarily for
processing, not a software system on PC or UNIX, not a traditional business or scientific
application. High-end embedded & lower end embedded systems. High-end embedded
system - Generally 32, 64 Bit Controllers used with OS. Examples Personal Digital
Assistant and Mobile phones etc.Lower end embedded systems - Generally 8,16 Bit
Controllers used with an minimal operating systems and hardware layout designed for the
specific purpose. Examples Small controllers and devices in our everyday life like
Washing Machine, Microwave Ovens, where they are embedded in.
1.2 CHARACTERISTICS OF EMBEDDED SYSTEMS
 An embedded system is any computer system hidden inside a product other than a
computer.
 They will encounter a number of difficulties when writing embedded system
software in addition to those we encounter when we write applications.
 Throughput – Our system may need to handle a lot of data in a short period of
time.
 Response–Our system may need to react to events quickly.
 Testability–Setting up equipment to test embedded software can be difficult.
 Debug ability–Without a screen or a keyboard, finding out what the software is
doing wrong (other than not working) is a troublesome problem.

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 Reliability – embedded systems must be able to handle any situation without
human intervention.
 Memory space – Memory is limited on embedded systems, and you must make
the software and the data fit into whatever memory exists.
 Program installation – you will need special tools to get your software into
embedded systems.
 Power consumption – Portable systems must run on battery power, and the
software in these systems must conserve power.
 Processor hogs – computing that requires large amounts of CPU time can
complicate the response problem.
 Cost – Reducing the cost of the hardware is a concern in many embedded system
projects; software often operates on hardware that is barely adequate for the job.
 Embedded systems have a microprocessor/ microcontroller and a memory. Some
have a serial port or a network connection. They usually do not have keyboards,
screens or disk drives.
1.3 APPLICATIONS
 Military and aerospace embedded software applications.
 Communication applications.
 Industrial automation and process control software.
 Mastering the complexity of applications.
 Reduction of product design time.
 Real time processing of ever increasing amounts of data.
 Intelligent, autonomous sensors.
1.4 CLASSIFICATION
 Real Time Systems.
 RTS is one which has to respond to events within a specified deadline.
 A right answer after the dead line is a wrong answer.

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1.4.1 RTS CLASSIFICATION
 Hard Real Time Systems.
 Soft Real Time System.
1.4.1.1 HARD REAL TIME SYSTEM
 "Hard" real-time systems have very narrow response time.
 Example: Nuclear power system, Cardiac pacemaker.
1.4.1.2 SOFT REAL TIME SYSTEM
 "Soft" real-time systems have reduced constrains on "lateness" but still must
operate very quickly and repeatable.
 Example: Railway reservation system – takes a few extra seconds the data
remains valid.

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CHAPTER-2
BLOCK DIAGRAM
Figure 2.1: Block diagram of air bag crash sensor development using mems
AT89S52
MICRO
CONTROLLER
POWER SUPPLY
AIR BAG
INDICATORS
MEMS
LCD
DISPLAY

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CHAPTER-3
HARDWARE REQUIREMENTS
HARDWARE COMPONENTS
 POWER SUPPLY
 MICROCONTROLLER (AT89S52/AT89C51)
 MEMS
 LCD MODULE

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POWER SUPPLY
3.1 TRANSFORMER
Transformers convert AC electricity from one voltage to another with a little loss
of power. Step-up transformers increase voltage, step-down transformers reduce voltage.
Most power supplies use a step-down transformer to reduce the dangerously high voltage
to a safer low voltage.
Figure 3.1.1: A typical transformer
The input coil is called the primary and the output coil is called the secondary.
There is no electrical connection between the two coils; instead they are linked by an
alternating magnetic field created in the soft-iron core of the transformer. The two lines
in the middle of the circuit symbol represent the core. Transformers waste very little
power so the power out is (almost) equal to the power in. Note that as voltage is stepped
down and current is stepped up.
The ratio of the number of turns on each coil, called the turn’s ratio, determines
the ratio of the voltages. A step-down transformer has a large number of turns on its
primary (input) coil which is connected to the high voltage mains supply, and a small
number of turns on its secondary (output) coil to give a low output voltage.
TURNS RATIO = (Vp / Vs) = (Np / Ns)
Where,
Vp = primary (input) voltage.
Vs = secondary (output) voltage
Np = number of turns on primary coil

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Ns = number of turns on secondary coil
Ip = primary (input) current
Is = secondary (output) current.
3.1.1 IDEAL POWER EQUATION
Figure 3.1.2: Ideal power equation
The ideal transformer as a circuit element If the secondary coil is attached to a
load that allows current to flow, electrical power is transmitted from the primary circuit
to the secondary circuit. Ideally, the transformer is perfectly efficient; all the incoming
energy is transformed from the primary circuit to the magnetic field and into the
secondary circuit. If this condition is met, the incoming electric power must equal the
outgoing power:
Giving the ideal transformer equation
Transformers normally have high efficiency, so this formula is a reasonable
approximation.
If the voltage is increased, then the current is decreased by the same factor. The
impedance in one circuit is transformed by the square of the turn’s ratio. For example, if
an impedance Zs is attached across the terminals of the secondary coil, it appears to the
primary circuit to have an impedance of (Np/Ns)2
Zs. This relationship is reciprocal, so that
the impedance Zp of the primary circuit appears to the secondary to be (Ns/Np)2
Zp.

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3.2 VOLTAGE REGULATOR 7805
FEATURES
• Output Current up to 1A.
• Output Voltages of 5v.
• Thermal Overload Protection.
• Short Circuit Protection.
• Output Transistor Safe Operating Area Protection.
Figure 3.2.1: Circuit diagram of voltage regulator
DESCRIPTION
The LM78XX/LM78XXA series of three-terminal positive regulators are
available in the TO-220/D-PAK package and with several fixed output voltages, making
them useful in a Wide range of applications. Each type employs internal current limiting,
thermal shutdown and safe operating area protection, making it essentially indestructible.
If adequate heat sinking is provided, they can deliver over 1A output Current. Although
designed primarily as fixed voltage regulators, these devices can be used with external
components to obtain adjustable voltages and currents.

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3.2.1 INTERNAL BLOCK DIAGRAM
Figure 3.2.2: Block diagram of voltage regulator
3.2.2 ABSOLUTE MAXIMUM RATINGS
Table 3.2.3: Rating of the voltage regulator

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3.3 RECTIFIER
A rectifier is an electrical device that converts alternating current (AC), which
periodically reverses direction, to direct current (DC), current that flows in only one
direction, a process known as rectification. Rectifiers have many uses including as
components of power supplies and as detectors of radio signals. Rectifiers may be made
of solid state diodes, vacuum tube diodes, mercury arc valves, and other components. The
output from the transformer is fed to the rectifier. It converts A.C. into pulsating D.C.
The rectifier may be a half wave or a full wave rectifier. In this project, a bridge rectifier
is used because of its merits like good stability and full wave rectification. In positive half
cycle only two diodes( 1 set of parallel diodes) will conduct, in negative half cycle
remaining two diodes will conduct and they will conduct only in forward bias only.
Figure 3.3: Bridge rectifier
3.4 FILTER
Capacitive filter is used in this project. It removes the ripples from the output of
rectifier and smoothens the D.C. Output received from this filter is constant until the
mains voltage and load is maintained constant. However, if either of the two is varied,
D.C. voltage received at this point changes. Therefore a regulator is applied at the output
stage.
The simple capacitor filter is the most basic type of power supply filter. The use
of this filter is very limited. It is sometimes used on extremely high-voltage, low-current
power supplies for cathode-ray and similar electron tubes that require very little load
current from the supply. This filter is also used in circuits where the power-supply ripple

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frequency is not critical and can be relatively high. Below figure can show how the
capacitor charges and discharges.
Figure 3.4: Filter output
3.5 Microcontroller AT89S52
The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller
with 8K bytes of in-system programmable Flash memory. The device is manufactured
using Atmel’s high-density non volatile memory technology and is compatible with the
industry standard 80C51 instruction set and pin out. The on-chip Flash allows the
program memory to be reprogrammed in-system or by a conventional non volatile
memory programmer. By combining a versatile 8-bit CPU with in-system programmable
Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller which
provides a highly-flexible and cost-effective solution to many embedded control
applications. The AT89S52 provides the following standard features: 8K bytes of Flash,
256 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit
timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-
chip oscillator, and clock circuitry. In addition, the AT89S52 is designed with static logic
for operation down to zero frequency and supports two software selectable power saving
modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial
port, and interrupt system to continue functioning. The Power-down mode saves the

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RAM contents but freezes the oscillator, disabling all other chip functions until the next
interrupt or hardware reset.
FEATURES
 Compatible with MCS®-51 Products
 8K Bytes of In-System Programmable (ISP) Flash Memory Endurance: 10,000
Write/Erase Cycles
 4.0V to 5.5V Operating Range
 Fully Static Operation: 0 Hz to 33 MHz
 Three-level Program Memory Lock
 256 x 8-bit Internal RAM
 32 Programmable I/O Lines
 Three 16-bit Timer/Counters
 Eight Interrupt Sources
 Full Duplex UART Serial Channel
 Low-power Idle and Power-down Modes
 Interrupt Recovery from Power-down Mode
 Watchdog Timer
 Dual Data Pointer
 Power-off Flag
 Fast Programming Time
 Flexible ISP Programming (Byte and Page Mode)
 Green (Pb/Halide-free) Packaging Option

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3.5.1 BLOCK DIAGRAM OF AT89S52
Figure 3.5 : Block diagram of AT89S52

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3.5.2 PIN CONFIGURATIONS OF AT89S52
Figure 3.5.1: Pin diagram of AT89S52
PIN DESCRIPTION
VCC
Supply voltage.
GND
Ground.
Port 0
Port 0 is an 8-bit open drain bidirectional I/O port. As an output port, each pin can
sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high-
impedance inputs. Port 0 can also be configured to be the multiplexed low-order
address/data bus during accesses to external program and data memory. In this mode, P0
has internal pull-ups. Port 0 also receives the code bytes during Flash programming and

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outputs the code bytes during program verification. External pull-ups are required during
program verification.
Port 1
Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1 output
buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are
pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 1 pins that
are externally being pulled low will source current (IIL) because of the internal pull-ups.
In addition, P1.0 and P1.1 can be configured to be the timer/counter 2 external count
input (P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX).
Port 2
are externally being pulled low will source current (IIL) because of the internal pull-ups.
Port 2 emits the high-order address byte during fetches from external program memory
and during accesses to external data memory that uses 16-bit addresses (MOVX @
DPTR). In this application, Port 2 uses strong internal pull-ups when emitting 1s. During
accesses to external data memory that uses 8-bit addresses (MOVX @ RI), Port 2 emits
the contents of the P2 Special Function Register.
Port 3
are externally being pulled low will source current (IIL) because of the pull-ups.
RST
Reset input. A high on this pin for two machine cycles while the oscillator is
running resets the device. This pin drives high for 98 oscillator periods after the
Watchdog times out. The DISRTO bit in SFR AUXR (address 8EH) can be used to
disable this feature. In the default state of bit DISRTO, the RESET HIGH out feature is
enabled.

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ALE/PROG
Address Latch Enable (ALE) is an output pulse for latching the low byte of the
address during accesses to external memory. This pin is also the program pulse input
(PROG) during Flash programming.
In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator
frequency and may be used for external timing or clocking purposes. Note, however, that
one ALE pulse is skipped during each access to external data memory.
PSEN
Program Store Enable (PSEN) is the read strobe to external program memory.
When the AT89S52 is executing code from external program memory, PSEN is activated
twice each machine cycle, except that two PSEN activations are skipped during each
access to external data memory.
EA/VPP
External Access Enable. EA must be strapped to GND in order to enable the
device to fetch code from external program memory locations starting at 0000H up to
FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on
reset. EA should be strapped to VCC for internal program executions. This pin also
receives the 12-volt programming enable voltage (VPP) during Flash programming.
XTAL1
Input to the inverting oscillator amplifier and input to the internal clock operating
circuit.
XTAL2
Output from the inverting oscillator amplifier
3.5.3 OSCILLATOR CHARACTERISTICS
XTAL1 and XTAL2 are the input and output, respectively, of an inverting
amplifier which can be configured for use as an on-chip oscillator, as shown in Figure 1.
Either a quartz crystal or ceramic resonator may be used. To drive the device from an
external clock source, XTAL2 should be left unconnected while XTAL1 is driven as
shown in Figure 6.2. There are no requirements on the duty cycle of the external clock

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signal, since the input to the internal clocking circuitry is through a divide-by-two flip-
flop, but minimum and maximum voltage high and low time specifications must be
observed.
Fig 3.5.2: Oscillator Connections Fig 3.5.3: External Clock Drive Configuration
3.6 MEMS
The MMA7660FC is a ±1.5 g 3-Axis Accelerometer with Digital Output(I2C). It
is a very low power, low profile capacitive MEMS sensor featuring a low pass filter,
compensation for 0g offset and gain errors, and conversion to 6-bit digital values at user
configurable samples per second. The device can be used for sensor data changes,
product orientation, and gesture detection through an interrupt pin (INT). The device is
housed in a small 3mm x 3mm x 0.9mm DFN package.
Fig 3.6.1: Axis Orientation/Motion Detection Sensor

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FEATURES
• Digital Output (I2C)
• 3mm x 3mm x 0.9mm DFN Package
• Low Power Current Consumption: Off Mode: 0.4 μA, Standby Mode: 3 μA, Active
Mode: 47 μA at 1 ODR
• Configurable Samples per Second from 1 to 120 samples a second.
• Low Voltage Operation:
Analog Voltage: 2.4 V - 3.6 V
Digital Voltage: 1.71 V - 3.6 V
• Auto-Wake/Sleep Feature for Low Power Consumption
• Tilt Orientation Detection for Portrait/Landscape Capability
• Gesture Detection Including Shake Detection and Tap Detection
• Robust Design, High Shocks Survivability (10,000 g)
• RoHS Compliant
• Halogen Free
• Environmentally Preferred Product
• Low Cost
Fig 3.6.2: Bottom view Fig 3.6.3: Pin connections
MMA 7660FC MMA 7660FC

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3.6.1 PIN DESCRIPTION
Table 3.6.4: Pin Description MMA 7660FC
Figure 3.6.5: MMA Connections to MCU
3.6.2 ELECTRO STATIC DISCHARGE
WARNING: This device is sensitive to electrostatic discharge. Although the Free
scale accelerometer contains internal 2000 V ESD protection circuitry, extra precaution
must be taken by the user to protect the chip from ESD. A charge of over 2000 V can
accumulate on the human body or associated test equipment. A charge of this magnitude
can alter the performance or cause failure of the chip. When handling the accelerometer,
proper ESD.

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Precautions should be followed to avoid exposing the device to discharges which may be
detrimental to its performance.
Table 3.6.6: ESD and Latch-up Protection Characteristics
3.6.3 PRINCIPLE OF OPERATION
The Free scale Accelerometer consists of a MEMS capacitive sensing g-cell and a
signal conditioning ASIC contained in a single package. The sensing element is sealed
hermetically at the wafer level using a bulk micro machined cap wafer. The g-cell is a
mechanical structure formed from semiconductor materials (polysilicon) using masking
and etching processes.
The sensor can be modeled as a movable beam that moves between two
mechanically fixed beams). Two gaps are formed; one being between the movable beam
and the first stationary beam and the second between the movable beam and the second
stationary beam.
The ASIC uses switched capacitor techniques to measure the g-cell capacitors and
extract the acceleration data from the difference between the two capacitors. The ASIC
also signal conditions and filters (switched capacitor) the signal, providing a digital
output that is proportional to acceleration.
Fig:3.6.7 Simplified Transducer Physical Model

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3.6.4 MODES OF OPERATION
Table 3.6.8: State Machine Modes
3.6.5 POWER SAVING FEATURES
The MMA7660FC includes a range of user configurable power saving features.
The device’s samples per second can be set over a wide range from 1 to 120 samples a
second; the operating current is directly proportional to samples per second. The analog
supply AVDD can be powered down to put the MMA7660FC into Off Mode, which
typically draws 0.4 μA. The Auto-Wake/Sleep feature can toggle the sampling rate from
a higher user selected samples per second to a lower user selected samples per second,
changing based on if motion is detected or not. The user can choose to use any of the
above options to configure the part and make it have the optimal power consumption
level for the desired application.

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3.6.6 TESTING THE LOGIC CHAIN
MMA7660FC can be put into Test Mode, which disables accelerometer
measurements and instead allows the user to write 6-bit values directly to the three axis
data registers, thus simulating real time accelerometer measurements. The state machine
will respond to these values according to the enabled features and functions, allowing
them to be validated.
NOTE: MMA7660FC does not include an accelerometer self test function, which is
typically an electrostatic force applied to each axis to cause it to deflect.
Table 3.6.9: Feature Summary Table
3.6.7 TAP DETECTION
The MMA7660FC also includes a Tap Detection feature that can be used for a
number of different customer applications such as button replacement. For example, a
single tap can stop a song from playing and a double tap can play a song. This function
detects a fast transition that exceeds a user-defined threshold (PDET (0x09) register) for a
set duration (PD (0x0A) registers).
3.6.8 TAP DETECTION SETUP
In order to enable Tap detection in the device the user must enable the Tap
Interrupt in the INTSU (0x06) register and AMSR[2:0] = 000 in the SR (0x08) register.
In this mode, TILT (0x03) register, XOUT (0x00), YOUT (0x01), and ZOUT (0x02)
registers will update at the 120 samples/second. The user can configure Tap Detection to

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be detected on X and/or Y and/or Z axes. The Customer can configure this by changing
the XDA, YDA, and/or ZDA bit in the PDET (0x09) register. Detection for enabled axes
is decided on an OR basis: If the PDINT bit is set in the INTSU (0x06) register, the
device reports the first axis for which it detects a tap by the Tap bit in the TILT (0x03)
register. When the Tap bit in the TILT (0x03) register is set, tap detection ceases, but the
device will continue to process orientation detection data. Tap detection will resume
when the TILT (0x03) register is read.
NOTE: Delta G is available with any AMSR setting, when XDA = YDA = ZDA = 1
(PDET = 1). When the sampling rate is less than 120 samples/second, the device can not
detect tapping, but can detect small tilt angles (30 degree angle change) which can not be
detected by orientation detection.
3.6.9 SHAKE DETECTION
The shake feature can be used as a button replacement to perform functions such
as scrolling through images or web pages on a Mobile Phone/PMP/PDA. The customer
can enable the shake interrupt on any of the 3 axes, by enabling the SHINTX SHINTX,
SHINTY, and/or SHINTZ in the INTSU (0x06) register. MMA7660FC detects shake by
examining the current 6-bit measurement for each axis in XOUT, YOUT, and ZOUT.
The axes that are tested for shake detection are the ones enabled by SHINTX, SHINTY,
and/or SHINTZ. If a selected axis measures greater that 1.3 or less than -1.3g, then a
shake is detected for that axis and an interrupt occurs. All three axes are checked
independently, but a common Shake bit in the TILT register is set when shake is detected
in any one of the selected axes. Therefore when all 3 (SHINTX, SHINTY, and/or
SHINTZ) are selected the sensor will not know what axis the shake occurred.
When the TILT register is read the Shake bit is cleared during the acknowledge bit of the
read access to that register and shake detection monitoring starts again.
3.6.10 AUTO WAKE/SLEEP
The MMA7660FC has the Auto-Wake/Sleep feature that can be enabled for
power saving. In the Auto-Wake function, the device is put into a user specified low

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samples per second (32 samples/second, 16 samples/second, 8 samples/second, or 1
sample/second) in order to minimize power consumption. When the Auto-Wake is
enabled and activity is detected such as a change in orientation, pulse event, Delta G
acceleration or a shake event, then the device wakes up. Auto-Wake will automatically
enable Auto-Sleep when the device is in wake mode and can therefore be configured to
cause an interrupt on wake-up, by configuring the part to either wake up with a change in
orientation, shake, or if using the part at 120 samples/second tap detection. When the
device is in Auto-Wake mode, the MODE (0x07) register, bit AWE is high. When the
device has detected a change in orientation, a tap shake, or Delta G (change in
acceleration), the device will enter Auto-Sleep mode. In the Auto-Sleep function, the
device is put into any of the following user specified samples per seconds (120
samples/second, 64 samples/second, 32 samples/second, 16 samples/second, 8
samples/second, 4 samples/second, 2 samples/second, and 1 sample/second). In the Auto-
Sleep mode, if no change in the orientation, shake or tap has occurred and the sleep
counter has elapsed, the device will go into the Auto-Wake mode. When the device is in
the Auto-Sleep mode, the MODE (0x07) register, bit ASE is high. The device can be
programmed to continually cycle between Auto-Wake/Sleep.
NOTE: The device can either be powered on in Wake/Sleep state depending on
ASE/AWE settings. If the AWE bit is set, the device is powered on in, in sleep state. If
the ASW bit is set, the device is powered on in, in wake state.
Table 3.6.10: Auto Wake/Sleep Truth Table

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3.6.11 START AND STP CONDITIONS
Both SCL and SDA remain high when the interface is not busy. A master signals
the beginning of a transmission with a START (S) condition by transitioning SDA from
high to low while SCL is high. When the master has finished communicating with the
slave, it issues a STOP (P) condition by transitioning SDA from low to high while SCL is
high. The bus is then free for another transmission.
Bit Transfer
One data bit is transferred during each clock tap.. The data on SDA must remain
stable while SCL is high.
Figure 3.6.11: Bit Transfer
Acknowledge
The acknowledge bit is a clocked 9th bit, which the recipient uses to handshake a
receipt of each byte of data. Thus each byte transferred effectively requires 9 bits. The
master generates the 9th clock tap, and the recipient pulls down SDA during the
acknowledge clock tap, such that the SDA line is stable low during the high period of the
clock tap. When the master is transmitting to MMA7660FC, it generates the acknowledge
bit because it is the recipient. When the device is transmitting to the master, the master
generates the acknowledge bit because the master is the recipient.

SVES ECE Dept.26
Figure 3.6.12: Acknowledge
3.6.12 Message Format for Writing MMA7660FC
A write to MMA7660FC comprises the transmission of the device’s key scan
slave address with the R/W bit set to 0, followed by at least one byte of information. The
first byte of information is the register address of the first internal register that is to be
updated. If a STOP condition is detected after just the register address is received, then
MMA7660FC takes no action. MMA7660FC clears its internal register address pointer
to register 0x00 when a STOP condition is detected, so a single byte write has no net
effect because the register address given in this first and only byte is replaced by 0x00 at
the STOP condition. The internal register address pointer is not, however, cleared on a
repeated start condition. Use a single byte write followed by a repeated start to read back
data from a register. Any bytes received after the register addresses are data bytes. The
first data byte goes into the internal register of the device selected by the register
address..
Figure 3.6.13: Single Byte Write
If multiple data bytes are transmitted before a STOP condition is detected, these
bytes are generally stored in subsequent MMA7660FC internal registers because the
register addresses generally auto-increments.

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Figure 3.6.14: Multiple Bytes Write
3.6.13 Message Format for Reading MMA7660FC
MMA7660FC is read using it’s internally stored register address as address
pointer, the same way the stored register address is used as address pointer for a write.
The pointer generally auto-increments after each data byte is read using the same rules as
for a write. Thus, a read is initiated by first configuring the device’s register address by
performing a write followed by a repeated start. The master can now read 'n' consecutive
bytes from it, with the first data byte being read from the register addressed by the
initialized register address.
Figure 3.6.15: Single Byte Read
Figure 3.6.16: Multiple Bytes Read
3.7 LCD MODULE
To display interactive messages we are using LCD Module. We examine an
intelligent LCD display of two lines,16 characters per line that is interfaced to the
controllers. The protocol (handshaking) for the display is as shown. Whereas D0 to D7th
bit is the Data lines, RS, RW and EN pins are the control pins and remaining pins are

SVES ECE Dept.28
+5V, -5V and GND to provide supply. Where RS is the Register Select, RW is the Read
Write and EN is the Enable pin.
The display contains two internal byte-wide registers, one for commands (RS=0) and the
second for characters to be displayed (RS=1). It also contains a user-programmed RAM
area (the character RAM) that can be programmed to generate any desired character that
can be formed using a dot matrix. To distinguish between these two data areas, the hex
command byte 80 will be used to signify that the display RAM address 00h will be
chosen.Port1 is used to furnish the command or data type, and ports 3.2 to3.4 furnish
register select and read/write levels.
The display takes varying amounts of time to accomplish the functions as listed.
LCD bit 7 is monitored for logic high (busy) to ensure the display is overwritten.
Liquid Crystal Display also called as LCD is very helpful in providing user
interface as well as for debugging purpose. The most common type of LCD controller is
HITACHI 44780 which provides a simple interface between the controller & an LCD.
These LCD's are very simple to interface with the controller as well as are cost effective.
Figure 3.7.1: 2x16 Line Alphanumeric LCD Display
The most commonly used ALPHANUMERIC displays are 1x16 (Single Line & 16
characters), 2x16 (Double Line & 16 character per line) & 4x20 (four lines & Twenty
characters per line). The LCD requires 3 control lines (RS, R/W & EN) & 8 (or 4) data
lines. The number on data lines depends on the mode of operation. If operated in 8-bit
mode then 8 data lines + 3 control lines i.e. total 11 lines are required. And if operated in
4-bit mode then 4 data lines + 3 control lines i.e. 7 lines are required. How do we decide
which mode to use? It’s simple if you have sufficient data lines you can go for 8 bit mode
& if there is a time constrain i.e. display should be faster then we have to use 8-bit mode
because basically 4-bit mode takes twice as more time as compared to 8-bit mode.

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Pin Symbol Function
1 Vss Ground
2 Vdd Supply Voltage
3 Vo Contrast Setting
4 RS Register Select
5 R/W Read/Write Select
6 En Chip Enable Signal
7-
14
DB0-
DB7
Data Lines
15 A/Vee
Gnd for the
backlight
16 K Vcc for backlight
Table 3.7.2 : 2*16 LCD Pins
When RS is low (0), the data is to be treated as a command. When RS is high (1),
the data being sent is considered as text data which should be displayed on the screen.
When R/W is low (0), the information on the data bus is being written to the LCD. When
RW is high (1), the program is effectively reading from the LCD. Most of the times there
is no need to read from the LCD so this line can directly be connected to Gnd thus saving
one controller line.
The ENABLE pin is used to latch the data present on the data pins. A HIGH -
LOW signal is required to latch the data. The LCD interprets and executes our command
at the instant the EN line is brought low. If you never bring EN low, your instruction will
never be executed.

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Figure 3.7.3: Controller to LCD Interprets

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CHAPTER-4
SOFTWARE REQUIREMENTS
4.1 INTRODUCTION TO KEIL MICRO VISION
Keil an ARM Company makes C compilers, macro assemblers, real-time kernels,
debuggers, simulators, integrated environments, evaluation boards, and emulators for
ARM7/ARM9/Cortex-M3, XC16x/C16x/ST10, 251, and 8051 MCU families.
Keil development tools for the 8051 Microcontroller Architecture support every
level of software developer from the professional applications engineer to the student just
learning about embedded software development. When starting a new project, simply
select the microcontroller you use from the Device Database and the µVision IDE sets all
compiler, assembler, linker, and memory options for you.
Keil is a cross compiler. So first we have to understand the concept of compilers
and cross compilers. After then we shall learn how to work with keil.
4.2 CONCEPT OF COMPILER
Compilers are programs used to convert a High Level Language to object code.
Desktop compilers produce an output object code for the underlying microprocessor, but
not for other microprocessors. I.E the programs written in one of the HLL like ‘C’ will
compile the code to run on the system for a particular processor like x86 (underlying
microprocessor in the computer). For example compilers for Dos platform is different
from the Compilers for Unix platform So if one wants to define a compiler then compiler
is a program that translates source code into object code.
The compiler derives its name from the way it works, looking at the entire piece
of source code and collecting and reorganizing the instruction. See there is a bit little
difference between compiler and an interpreter. Interpreter just interprets whole program
at a time while compiler analyses and execute each line of source code in succession,
without looking at the entire program.
The advantage of interpreters is that they can execute a program immediately.
Secondly programs produced by compilers run much faster than the same programs
executed by an interpreter. However compilers require some time before an executable

SVES ECE Dept.32
program emerges. Now as compilers translate source code into object code, which is
unique for each type of computer, many compilers are available for the same language.
4.3 CONCEPT OF CROSS COMPILER
A cross compiler is similar to the compilers but we write a program for the target
processor (like 8051 and its derivatives) on the host processors (like computer of x86). It
means being in one environment you are writing a code for another environment is called
cross development. And the compiler used for cross development is called cross
compiler. So the definition of cross compiler is a compiler that runs on one computer but
produces object code for a different type of computer.
4.4 KEIL C CROSS COMPILER
Keil is a German based Software development company. It provides several
development tools like
 IDE (Integrated Development environment)
 Project Manager
 Simulator
 Debugger
 C Cross Compiler, Cross Assembler, Locator/Linker
The Keil ARM tool kit includes three main tools, assembler, compiler and linker.
An assembler is used to assemble the ARM assembly program. A compiler is used to
compile the C source code into an object file. A linker is used to create an absolute object
module suitable for our in-circuit emulator.
4.5 BUILDING APPLICATIONS IN µVISION2
To build (compile, assemble, and link) an application in µVision2, you must:
 Select Project - (for example, 166EXAMPLESHELLOHELLO.UV2).
 Select Project - Rebuild all target files or Build target.µVision2 compiles,
assembles, and links the files in your project.

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4.6 CREATING YOUR OWN APPLICATION IN µVISION
To create a new project in µVision2, you must:
 Select Project - New Project.
 Select a directory and enter the name of the project file.
 Select Project - Select Device and select an 8051, 251, or C16x/ST10 device from
the Device Database™.
 Create source files to add to the project.
 Select Project - Targets, Groups, and Files. Add/Files, select Source Group1, and
add the source files to the project.
 Select Project - Options and set the tool options. Note when you select the target
device from the Device Database™ all special options are set automatically. You
typically only need to configure the memory map of your target hardware. Default
memory model settings are optimal for most applications.
 Select Project - Rebuild all target files or Build target.
4.7 DEBUGGING AN APPLICATION IN µVISION2
To debug an application created using µVision2, you must:
 Select Debug - Start/Stop Debug Session.
 Use the Step toolbar buttons to single-step through your program. You may enter
G, main in the Output Window to execute to the main C function.
 Open the Serial Window using the Serial #1 button on the toolbar.
Debug your program using standard options like Step, Go, Break, and so on.
4.8 STARTING µVISION2AND CREATING A PROJECT
µVision2 is a standard Windows application and started by clicking on the
program icon. To create a new project file select from the µVision2 menu Project – New
Project. This opens a standard Windows dialog that asks you for the new project file
name. We suggest that you use a separate folder for each project. You can simply use the
icon Create New Folder in this dialog to get a new empty folder. Then select this folder

SVES ECE Dept.34
and enter the file name for the new project, i.e. Project1. µVision2 creates a new project
file with the name PROJECT1.UV2 which contains a default target and file group name.
You can see these names in the Project.
4.9 WINDOW-FILES
Now use from the menu Project – Select Device for Target and select a CPU for
your project. The Select Device dialog box shows the µVision2 device data base. Just
select the microcontroller you use. We are using for our examples the Philips 80C51RD+
CPU. This selection sets necessary tool Options for the 80C51RD+ device and simplifies
in this way the tool Configuration.
4.10 BUILDING PROJECTS AND CREATING HEX FILES
Typical, the tool settings under Options – Target are all you need to start a new
application. You may translate all source files and line the application with a click on the
Build Target toolbar icon. When you build an application with syntax errors, µVision2
will display errors and warning messages in the Output Window – Build page. A double
click on a message line opens the source file on the correct location in a µVision2 editor
window. Once you have successfully generated your application you can start debugging.
After you have tested your application, it is required to create an Intel HEX file to
download the software into an EPROM programmer or simulator. µVision2 creates HEX
files with each build process when Create HEX files under Options for Target – Output is
enabled. You may start your PROM programming utility after the make process when
you specify the program under the option Run User Program #1.
4.11 CPU SIMULATION
µVision2 simulates up to 16 Mbytes of memory from which areas can be mapped
for read, write, or code execution access. The µVision2 simulator traps and reports illegal
memory accesses. In addition to memory mapping, the simulator also provides support
for the integrated peripherals of the various 8051 derivatives. The on-chip peripherals of
the CPU you have selected are configured from the Device.

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4.12 DATABASE SELECTION
You have made when you create your project target. Refer to page 58 for more
Information about selecting a device. You may select and display the on-chip peripheral
components using the Debug menu. You can also change the aspects of each peripheral
using the controls in the dialog boxes.
4.13 START DEBUGGING
You start the debug mode of µVision2 with the Debug – Start/Stop Debug
Session Command. Depending on the Options for Target – Debug Configuration,
µVision2 will load the application program and run the startup code µVision2 saves the
editor screen layout and restores the screen layout of the last debug session. If the
program execution stops, µVision2 opens an editor window with the source text or shows
CPU instructions in the disassembly window. The next executable statement is marked
with a yellow arrow. During debugging, most editor features are still available.
For example, you can use the find command or correct program errors. Program
source text of your application is shown in the same windows. The µVision2 debug mode
differs from the edit mode in the following aspects.
The “Debug Menu and Debug Commands” described on page 28 are available.
The additional debug windows are discussed in the following.
The project structure or tool parameters cannot be modified. All build commands are
disabled.
4.14 DISASSEMBLY WINDOW
The Disassembly window shows your target program as mixed source and
assembly program or just assembly code. A trace history of previously executed
instructions may be displayed with Debug – View Trace Records. To enable the trace
history, set Debug – Enable/Disable Trace Recording.
If you select the Disassembly Window as the active window all program step
commands work on CPU instruction level rather than program source lines. You can
select a text line and set or modify code breakpoints using toolbar buttons or the context
menu commands.

SVES ECE Dept.36
You may use the dialog Debug – Inline Assembly… to modify the CPU
instructions. That allows you to correct mistakes or to make temporary changes to the
target program you are debugging. Numerous example programs are included to help you
get started with the most popular embedded 8051 devices.
The Keil µVision Debugger accurately simulates on-chip peripherals (I²C, CAN,
UART, SPI, Interrupts, I/O Ports, A/D Converter, D/A Converter, and PWM Modules) of
your 8051 device. Simulation helps you understand hardware configurations and avoids
time wasted on setup problems. Additionally, with simulation, you can write and test
applications before target hardware is available.
4.15 EMBEDDED C
Use of embedded processors in passenger cars, mobile phones, medical
equipment, aerospace systems and defense systems is widespread, and even everyday
domestic appliances such as dish washers, televisions, washing machines and video
recorders now include at least one such device.
Because most embedded projects have severe cost constraints, they tend to use
low-cost processors like the 8051 family of devices considered in this book. These
popular chips have very limited resources available most such devices have around 256
bytes (not megabytes!) of RAM, and the available processor power is around 1000 times
less than that of a desktop processor. As a result, developing embedded software presents
significant new challenges, even for experienced desktop programmers. If you have
some programming experience - in C, C++ or Java - then this book and its accompanying
CD will help make your move to the embedded world as quick and painless as possible.

SVES ECE Dept.37
CHAPTER-5
SCHEMATIC DIAGRAM
Figure 5 : Schematic diagram of air bag crush

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5.1 OPERATION
Modern vehicles may contain multiple airbags in various side and frontal
locations of the passenger seating positions, and sensors may deploy one or more airbags
in an impact zone at variable rates based on the type and severity of impact the airbag is
designed to only inflate in mild to severe frontal crashes. Airbags are normally designed
with the intention of supplementing the protection of an occupant who is correctly
restrained with a seatbelt. Air bag operation in this project is shown by tripping the relay
in which led or a DC motor turns on.
When ever any accident occur means any Disturbance caused to MEMS sensor
which was arranged in critical angle detects and sends mechanical force to controller
hence the air bag release in the form of relay tripping.

SVES ECE Dept.39
CHAPTER-6
PROJECT CODE
6.1 SOURCE CODE
#include<reg51.h>
#include"I2C_MEM.c"
sfr ldata=0X90;//PORT 1
sbit rs=P2^6;
sbit en=P2^7;
sbit Air_Bag=P2^4;
LcdCmd(unsigned char);
LcdData_Chr(unsigned char);
LcdData_Str(char *temp);
Lcd_Init();
LcdData_Display();
Delay(unsigned int);
XY_Movements(unsigned char f_b,unsigned char l_r);
bit play_flag=1;
main()
{
Air_Bag=1;
Lcd_Init();

SVES ECE Dept.40
LcdCmd(0x80);
LcdData_Str(" I2C MEMS TEST ");
MEMS_Init();
LcdCmd(0x80);
LcdData_Str(" Mem inited ");
Delay(250);
LcdCmd(0x80);
LcdData_Str(" MEMS BASED ");
LcdCmd(0xC0);
LcdData_Str("Air Bag System");
while(1)
{
x=RrByte_MEMS(0x00);
Delay(5);
//u_x=(x%10)+48;
//t_x=(x/10)+48;
//Lcd_Data_Chr(1,2,2,&t_x);
//Lcd_Data_Chr(1,2,3,&u_x);
Delay(15);
y=RrByte_MEMS(0x01);
Delay(5);

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//u_y=(y%10)+48;
//t_y=(y/10)+48;
//Lcd_Data_Chr(1,2,8,&t_y);
//Lcd_Data_Chr(1,2,9,&u_y);
Delay(15);
XY_Movements(x,y);
}
}
XY_Movements(unsigned char f_b,unsigned char l_r)
{
if((f_b>15&&f_b<25))
{
Air_Bag=0;
LcdCmd(0x80);
LcdData_Str(" Alert! ");
LcdCmd(0xC0);
LcdData_Str("Air Bag Released");
}
if(f_b<50&&f_b>45)
{

SVES ECE Dept.42
Air_Bag=0;
LcdCmd(0x80);
LcdCmd(0xC0);
}
if(l_r>15&&l_r<25)
{
Air_Bag=0;
LcdCmd(0x80);
LcdCmd(0xC0);
}
if(l_r<50&&l_r>45)
{
Air_Bag=0;
LcdCmd(0x80);
LcdCmd(0xC0);
}

SVES ECE Dept.43
}
Lcd_Init()
{
LcdCmd(0x38);
LcdCmd(0x0E);
LcdCmd(0x01);
LcdCmd(0x80);
}
Lcddata_Chr(unsigned char value)
{
ldata=value;
rs=1;
en=1;
Delay(1);
en=0;
Delay(1);
return;
}
//Delay(unsigned int k)
// {
// int i,j;
// for (i=0;i<=k;i++)

SVES ECE Dept.44
// for (j=0;j<=1275;j++);
// }
LcdCmd(unsigned char value)
{
ldata=value;
rs=0;
en=1;
Delay(1);
en=0;
return;
}
LcdData_Str(char *temp)
{
unsigned int s;
for(s=0;temp[s]!='0';s++)
{
ldata=tem p[s];
rs=1;
en=1;
Delay(1);
en=0;

SVES ECE Dept.45
}
}
EN=0;
}

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6.2 FLOW CHART
Figure 6.2: Flow chart of air bag crush sensor
START
INITIALIZE
MICROCONTROLLER
INITIALIZE MEMS
IF MEMS=1
MONITOR MEMS
RELEASE AIR BAG
AGAIN MONITOR
CONDITIONS
STOP
NO

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CHAPTER-7
HARDWARE TESTING
7.1 CONTINUITY TEST
In electronics, a continuity test is the checking of an electric circuit to see if
current flows (that it is in fact a complete circuit). A continuity test is performed by
placing a small voltage (wired in series with an LED or noise-producing component such
as a piezoelectric speaker) across the chosen path. If electron flow is inhibited by broken
conductors, damaged components, or excessive resistance, the circuit is "open".
Devices that can be used to perform continuity tests include multi meters which
measure current and specialized continuity testers which are cheaper, more basic devices,
generally with a simple light bulb that lights up when current flows.
An important application is the continuity test of a bundle of wires so as to find the two
ends belonging to a particular one of these wires; there will be a negligible resistance
between the "right" ends, and only between the "right" ends.
This test is the performed just after the hardware soldering and configuration has
been completed. This test aims at finding any electrical open paths in the circuit after the
soldering. Many a times, the electrical continuity in the circuit is lost due to improper
soldering, wrong and rough handling of the PCB, improper usage of the soldering iron,
component failures and presence of bugs in the circuit diagram. We use a multi meter to
perform this test. We keep the multi meter in buzzer mode and connect the ground
terminal of the multi meter to the ground. We connect both the terminals across the path
that needs to be checked. If there is continuation then you will hear the beep sound.
7.2 POWER ON TEST
This test is performed to check whether the voltage at different terminals is
according to the requirement or not. We take a multi meter and put it in voltage mode.
Remember that this test is performed without microcontroller. Firstly, we check the
output of the transformer, whether we get the required 12 v AC voltage.

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CHAPTER-8
ADVANTAGES AND APPLICATIONS
ADVANTAGES
 The system is completely automatic and requires no human supervision to carry
out the necessary actions.
 The main advantage of this system is it is economical and reliable.
 The system is best for guiding the perimeter of a house or a business center the
point s where an intruder would enter the building
.
DISADVANTAGES
1. When Power Is Off, Then the Total System is Off, So always Required Battery
APPLICATIONS
 Air Craft Applications
 Accident Prevention Applications
 Medical Applications
 Military and aerospace embedded software applications
 Communication Applications
 Industrial automation and process control software
 Mastering the complexity of applications.
 Reduction of product design time.
 Real time processing of ever increasing amounts of data.

SVES ECE Dept.49
FUTURE SCOPE
Air bags are very important as it is absolutely crucial to ensure protection of
human life. Thus they must be implemented for saving precious lives and it should be
made necessary for automobile manufacturer to implement this mechanism

SVES ECE Dept.50
CHAPTER-9
CONCLUSION
The “AIR BAG CRASH SENSOR DEVELOPMENT” has been achieved
successfully using microcontroller unit. The circuit has been tested and verified.
It has been developed by integrating features of all the hardware components
used. Presence of every module has been reasoned out and placed carefully thus
contributing to the best working of the unit.
Secondly, using highly advanced IC’s and with the help of growing technology
the project has been successfully implemented.

SVES ECE Dept.51
CHAPTER-10
BIBLIOGRAPHY
TEXT BOOKS REFERED
1. “The 8051 Microcontroller and Embedded systems” by Muhammad Ali Mazidi and
Janice Gillispie Mazidi, Pearson Education.
2. ATMEL 89S52 Data Sheets.
WEBSITES
 www.atmel.com
 www.beyondlogic.org
 www.wikipedia.org
 www.howstuffworks.com
 www.alldatasheets.com

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