mems based wheel chair

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MEMS BASED WHEEL CHAIR





Technical Specifications

Title of the project : MEMS Based Wheel Chair For Handicapped People

Domain : Embedded Systems Design

Software : Embedded C, Keil

Microcontroller : AT89s52

Power Supply : +5V, 500mA Regulated Power Supply

Display : LED 5mm, 16 X 2 LCD

Crystal : 11.0592 MHz

Software : Keil, Ucflash

Developed By : CMC Limited, Dilsukhnagar

Phone : 8099050333,[email protected]




ABSTRACT

Keep Ur Abstract




INTRODUCTION TO EMBEDDED SYSTEMS

An embedded system is a computer system designed for specific control functions within

a larger system. Often with real-time computing constraints. It is embedded as part of a complete

device often including hardware and mechanical parts. By contrast, a general-purpose computer,

such as a personal computer (PC), is designed to be flexible and to meet a wide range of end-user

needs. Embedded systems control many devices in common use today.

Embedded systems contain processing cores that are typically either microcontrollers or

digital signal processors (DSP). The key characteristic, however, is being dedicated to handle a

particular task. They may require very powerful processors and extensive communication, for

example air traffic control systems may usefully be viewed as embedded, even though they

involve mainframe computers and dedicated regional and national networks between airports and

radar sites (each radar probably includes one or more embedded systems of its own).Since the

embedded system is dedicated to specific tasks, design engineers can optimize it to reduce the

size and cost of the product and increase the reliability and performance. Some embedded

systems are mass-produced, benefiting from economies of scale.

Physically, embedded systems range from portable devices such as digital watches and

MP3 players, to large stationary installations like traffic lights, factory controllers, or the systems

controlling nuclear power plants. Complexity varies from low, with a single microcontroller chip, to very high with multiple units, peripherals and networks mounted inside a large chassis or

enclosure.

In general, "embedded system" is not a strictly definable term, as most systems have

some element of extensibility or programmability. For example, handheld computers share some

elements with embedded systems such as the operating systems and microprocessors that power

them, but they allow different applications to be loaded and peripherals to be connected.

Moreover, even systems that do not expose programmability as a primary feature generally need

to support software updates. On a continuum from "general purpose" to "embedded", large

application systems will have subcomponents at most points even if the system as a whole is

"designed to perform one or a few dedicated functions", and is thus appropriate to call

embedded.




Embedded systems are especially suited for use in transportation, fire safety, safety and

security, medical applications and life critical systems as these systems can be isolated from

hacking and thus be more reliable. For fire safety, the systems can be designed to have greater

ability to handle higher temperatures and continue to operate. In dealing with security, the

embedded systems can be self-sufficient and be able to deal with cut electrical and

communication systems.

The purpose of this project is to provide the security in four ways: automatic gate

opening/closing system at track crossing, signaling for the train driver, tracking the signals, and

the tr ack protection. The railroad industry‟s own desire to maintain their ability to provide safe

and secure transport of their customers hazardous materials, has introduced new challenges in

rail security. Addressing these challenges is important, as railroads, and the efficient delivery of

their cargo, play a vital role in the economy of the country.

The automatic gate opening/closing system is provided with the IR sensors placed at a

distance of few kilometers on the both sides from the crossing road. These sensors give the train

reaching and leaving status to the embedded controller at the gate to which they are connected.

The controller operates (open/close) the gate as per the received signal from the IR sensors.

MICROCONTROLLERS FOR EMBEDDED SYSTEM

In the Literature discussing microprocessors, we often see the term Embedded System.

Microprocessors and Microcontrollers are widely used in embedded system products. An

embedded system product uses a microprocessor (or Microcontroller) to do one task only. A

printer is an example of embedded system since the processor inside it performs one task only;

namely getting the data and printing it. Contrast this with a Pentium based PC. A PC can be used

for any number of applications such as word processor, print-server, bank teller terminal, Video

game, network server, or Internet terminal. Software for a variety of applications can be loaded

and run. Of course the reason a pc can perform myriad tasks is that it has RAM memory and an

operating system that loads the application software into RAM memory and lets the CPU run it.

In an Embedded system, there is only one application software that is typically burned

into ROM. An x86 PC contains or is connected to various embedded products such as keyboard,

printer, modem, disk controller, sound card, CD-ROM drives, mouse, and so on. Each one of

these peripherals has a Microcontroller inside it that performs only one task. For example, inside




every mouse there is a Microcontroller to perform the task of finding the mouse position and

sending it to the PC.

APPLICATIONS OF EMBEDDED SYSTEMS

i. Military and aerospace

ii. Communications applications

iii. Electronics applications and consumer devices




LITERATURE SURVEY

Literature review is needed before any project is begun. The review will help to

understanding the scope of the project and also the need to build the project. The review comes

from the reading on the websites and also from the books. The information from the review will

be used to start the project with an excellent idea. The review is also obtained from the sample of

the existing project in the websites.

EXISTING SYSTEM

In order to take the old people from one particular place to another particular place any

one should accompany them or they must have any particular person in order to move them .

PROPOSED SYSTEM

In this proposed system we are implementing the wheel chair for the handicapped people

or the old age people ,an MEMS sensor is attached to that particular chair ,if the handicapped

people want to move forward, backward, left, right then if he tilts the sensor in accordance of the

directions then vehicle moves in the particular direction.




BLOCK DIAGRAM

POWER

SUPPLY

AT89s52

H-Bridge

Robotic

PlatformMEMS Sensor




BLOCK DIAGRAM DESCRIPITION

Microcontroller

The AT89S52 is a low-power, high-performance CMOS 8-bit micro controller with

8Kbytes 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 micro controller.

Power Supply

The power supply are designed to convert high voltage AC mains electricity to a suitable

low voltage supply for electronics circuits and other devices. A power supply can by broken

down into a series of blocks, each of which performs a particular function. A d.c power supply

which maintains the output voltage constant irrespective of a.c mains fluctuations or load

variations is known as “Regulated D.C Power Supply”

H-Bridge

DC motors are typically controlled by using a transistor configuration called an "H-bridge".

This consists of a minimum of four mechanical or solid-state switches, such as two NPN and two

PNP transistors. One NPN and one PNP transistor are activated at a time. Both NPN and PNP

transistors can be activated to cause a short across the motor terminals, which can be useful for

slowing down the motor from the back EMF it creates.

DC Motor

Motors are the devices that provide the actual speed and torque in a drive system. This

family includes AC motor types (single and multiphase motors, universal, servo motors,

induction, synchronous, and gear motor) and DC motors (brush less, servo motor, and gear

motor) as well as linear, stepper and air motors, and motor contactors and starters.

In any electric motor, operation is based on simple electromagnetism. A current-carrying

conductor generates a magnetic field; when this is then placed in an external magnetic field, it

will experience a force proportional to the current in the conductor, and to the strength of the

external magnetic field. As you are well aware of from playing with magnets as a kid, opposite




(North and South) polarities attract, while like polarities (North and North, South and South)

repel. The internal configuration of a DC motor is designed to harness the magnetic interaction

between a current-carrying conductor and an external magnetic field to generate rotational

motion..

Basic Theory

H-bridge. Sometimes called a "full bridge" the H-bridge is so named because it has four

switching elements at the "corners" of the H and the motor forms the cross bar.

The key fact to note is that there are, in theory, four switching elements within the bridge.

These four elements are often called, high side left, high side right, low side right, and low side

left (when traversing in clockwise order).

The switches are turned on in pairs, either high left and lower right, or lower left and high

right, but never both switches on the same "side" of the bridge. If both switches




HARDWARE DESCRIPTION

MICROCONTROLLER

The AT89S52 is a low-power, high-performance CMOS 8-bit micro controller with

8Kbytes 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 micro controller. 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 one monolithic chip;

the Atmel AT89S52 is a powerful micro controller, which provides a highly flexible and

cost-effective solution to many embedded control applications.[3]

Major Features of AT89S52

Compatible with MCS-51 Products

8K Bytes of In-System Programmable (ISP) Flash Memory

Endurance: 1000 Write/Erase Cycles

4.0V to 5.5V Operating Range

Fully Static Operation: 0 Hz to 33 MHz

Three-level Program Memory Lock

256K Internal RAM

32 Programmable I/O Lines

3 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

Now we may be wondering about the non-mentioning of memory space meant for

the program storage, the most important part of any embedded controller. Originally this

8051 architecture was introduced with on-chip, „one time programmable‟ version of




Program Memory of size 4K X 8. Intel delivered all these microcontrollers (8051) with

user‟s program fused inside the device.

Architecture of microcontroller AT89S52

Block Diagram of the AT89S52.

So, very soon Intel introduced the 8052 devices with re-programmable type of

Program Memory using built-in EPROM of size 4K X 8. Like a regular EPROM, this

memory can be re-programmed many times. Later on Intel started manufacturing these

8031 devices without any on chip Program Memory.




PIN DIAGRAM & DESCRIPTION

Pin diagram of the AT89S52

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, 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 RAM contents

but freezes the oscillator, disabling all other chip functions until the next interrupt or hardware

reset.

Pin description of microcontroller 89s52

VCC - Supply voltage.

GND - Ground.




Port 0

Port 0 is an 8-bit open drain bi-directional I/O port. As an output port, each pin can sink

eight TTL 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 outputs the code bytes during

program verification. External pull-ups are required during program verification.

Port 1

Port 1 is an 8-bit bi-directional 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. 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),

respectively, as shown in the following table. Port 1 also receives the low-order address bytes

during Flash programming and verification.

Port 2

Port 2 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 2 output buffers


internal pull-ups and can be used as inputs. 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 use 8-bit addresses (MOVX @ RI),

Port 2emits the contents of the P2 Special Function Register. Port 2 also receives the high-order

address bits and some control signals during Flash programming and verification.

Port 3

Port 3 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 3 output buffers


internal pull-ups and can be used as inputs. As inputs, Port 3 pins that are externally being pulled

low will source current (IIL) because of the pull-ups. Port 3 also serves the functions of various




special features of the AT89S52, as shown in the following table. Port 3 also receives some

control signals for Flash programming and verification.

Port pins and their Alternative functions

RST

Reset input. A high on this pin for two machine cycles while the oscillator is running

resets the device.

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 of1/6 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. If desired, ALE operation can

be disabled by setting bit 0 of SFR location 8EH. with the bit set, ALE is active only during a

MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable

bit has no effect if the micro controller is in external execution mode.

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. A should be

strapped to VCC for internal program executions. This pin also receives the 12-voltProgramming

enables 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.

Oscillator Connections External Clock

REGISTERS

A number of 8052 registers can be considered "basic." Very little can be done without

them and a detailed explanation of each one is warranted to make sure the reader understands

these registers before getting into more complicated areas of




The Accumulator

If you've worked with any other assembly language you will be familiar with the concept

of an accumulator register. The Accumulator, as its name suggests, is used as a general register

to accumulate the results of a large number of instructions. It can hold an 8-bit (1-byte) value

and is the most versatile register the 8052 has due to the sheer number of instructions that make

use of the accumulator. More than half of the 8052's 255 instructions manipulate or use the

Accumulator in some way. For example, if you want to add the number 10 and 20, the

resulting 30 will be stored in the Accumulator. Once you have a value in the Accumulator you

may continue processing the value or you may store it in another register or in memory.

The “B” registers

The "B" register is very similar to the Accumulator in the sense that it may hold an 8-bit

(1-byte) value. The "B" register is only used implicitly by two 8052 instructions: MUL AB and

DIV AB. Thus, if you want to quickly and easily multiply or divide A by another number, you

may store the other number in "B" and make use of these two instructions. Aside from the MUL

and DIV instructions, the "B" register are often used as yet another temporary storage register

much like a ninth "R" register.

The Program Counter

The Program Counter (PC) is a 2-byte address that tells the 8052 where the next

instruction to execute is found in memory. When the 8052 is initialized PC always starts at

0000h and is incremented each time an instruction is executed. It is important to note that PC

isn't always incremented by one. Since some instructions are 2 or 3 bytes in length the PC will be

incremented by 2 or 3 in these cases. The Program Counter is special in that there is no way to

directly modify its value. That is to say, you can't do something like PC=2430h. On the other

hand, if you execute LJMP 2430h you've effectively accomplished the same thing.

The data pointer

The Data Pointer (DPTR) is the 8052ís only user-accessible 16-bit (2-byte) register. The

Accumulator, "R" registers, and "B" register are all 1-byte values. The PC just described is a 16-

bit value but isn't directly user-accessible as a working register. DPTR, as the name suggests, is




used to point to data. It is used by a number of commands that allow the 8052 to access external

memory.

The program counter and stack pointer

The program counter (PC) is a 2-byte address, which tells the 8051 where the next

instruction to execute is found in memory. The stack pointer like all registers except DPTR

and PC may hold an 8-bit (1-Byte) value

Addressing modes

An “addressing mode” refers that you are addressing a given memory location. In

summary, the addressing modes are as follows, with an example of each:

Each of these addressing modes provides important flexibility.

Immediate Addressing MOV A, #20 H

Direct Addressing MOV A, 30 H

Indirect Addressing MOV A, @R0

Indexed Addressing

a. External Direct MOVX A, @DPTR

b. Code In direct MOVC A, @A+DPTR

Immediate Addressing:

Immediate addressing is so named because the value to be stored in memory

immediately follows the operation code in memory. That is to say, the instruction itself

dictates what value will be stored in memory. For example, the instruction:

MOV A, #20H:

This instruction uses immediate Addressing because the accumulator will be loaded

with the value that immediately follows in this case 20(hexadecimal). Immediate addressing

is very fast since the value to be loaded is included in the instruction. However, since the

value to be loaded is fixed at compile-time it is not very flexible.

Direct AddressingDirect addressing is so named because the value to be stored in memory is obtained

by directly retrieving it from another memory location.

For example:

MOV A, 30h




This instruction will read the data out of internal RAM address 30(hexadecimal) and

store it in the Accumulator. Direct addressing is generally fast since, although the value to

be loaded isn‟t included in the instruction, it is quickly accessible since it is stored in the

8051‟s inter nal RAM. It is also much more flexible than Immediate Addressing since the

value to be loaded is whatever is found at the given address which may variable.

Also it is important to note that when using direct addressing any instruction that

refers to an address between 00h and 7Fh is referring to the SFR control registers that

control the 8051 micro controller itself.

Indirect Addressing

Indirect addressing is a very powerful addressing mode, which in many cases

provides an exceptional level of flexibility. Indirect addressing is also the only way to access

the extra 128 bytes of internal RAM found on the 8052. Indirect addressing appears as

follows:

MOV A, @R0:

This instruction causes the 8051 to analyze Special Function Register (SFR)

Memory:

Special Function Registers (SFRs) are areas of memory that control specific

functionality of the 8051 processor. For example, four SFRs permit access to the 8051‟s 32

input/output lines. Another SFR allows the user to set the serial baud rate, control and access

timers, and configure the 8051‟s interrupt system.

Special Function Registers (SFRs)

SFRs are areas of memory that control specific functionality of the 8051 processor. For

example, four SFRs permit access to the 8051‟s 32 input/output lines. Another SFR allows the

user to set the serial baud rate, control and access timers, and configure the 8051‟s interrupt

system.

Interrupt RegistersThe individual interrupt enable bits are in the IE register . Two priorities can be

set for each of the six interrupt sources in the IP register

Timer 2

Timer 2 is a 16-bit Timer / Counter that can operate as either a timer or an event

counter. The type of operation is selected by bit C/T2 in the SFR T2CON . Timer 2 has




three operating Modes : capture , auto-reload ( up or down Counting ) , and baud rate

generator . The modes are selected by bits in T2CON . Timer 2 consists of two 8-bit

registers , TH2 and TL2 . In the Timer function , the TL2 register is incremented every

machine cycle . Since a machine cycle consists of 12 oscillator periods, the count rate is

1/12 of the oscillator frequency. In the Counter function , the register is incremented in

response to a 1-to-0 transition at its corresponding external input pin , T2 .When the

samples show a high in one cycle and a low in the next cycle, the count is incremented .

Since two machine cycles (24 Oscillator periods ) are required to recognize 1-to-0

transition , the maximum count rate is 1 / 24 of the oscillator frequency . To ensure that a

given level is sampled at least once before it changes , the level should be held for

at least one full machine cycle .

Capture Mode

In the capture mode , two options are selected by bit EXEN2 in T2CON . If

EXEN2 = 0, Timer 2 is a 16-bit timer or counter which upon overflow sets bit TF2 in

T2CON . This bit can then be used to generate an interrupt. If EXEN2 = 1 , Timer 2 performs

the same operation , but a 1-to-0 transition at external input T2EX also causes the

current value in TH2 and TL2 to be captured into RCAP2H and RCAP2L ,

respectively

Auto-reload (Up or Down Counter)Timer 2 can be programmed to count up or down when configured in its 16-bit

auto-reload mode. This feature is invoked by the DCEN

(Down Counter Enable) bit located in the SFR T2MOD . Upon reset , the DCEN bit is

set to 0 so that timer 2 will default to count up. When DCEN

is set , Timer 2 can count up or down , depending on the value of the T2EX pin . In

this mode , two options are selected by bit EXEN2 in T2CON . If EXEN2 = 0 , Timer 2

counts up to 0FFFFH and then sets the TF2 bit upon overflow . If EXEN2 = 1 , a 16-

bit reload can be triggered either by an overflow or by a 1-to-0 transition at external

input T2EX.

Baud Rate Generator

Timer 2 is selected as the baud rate generator by setting TCLK and/or RCLK

in T2CON . Note that the baud rates for transmit and receive can be different if Timer




2 is used for the receiver or transmitter and Timer 1 is used for the other function .The

baud rates in Modes 1 and 3 are determined by Timer 2‟s over flow rate according to the

following equation .

Modes 1 and 3 Baud Rates =Timer 2 Overflow Rate/16

The timer operation is different for Timer 2 when it is used as a baud rate

generator .Normally ,as a timer , it increments every machine cycle (at 1/12 the oscillator

frequency).As a baud rate generator , however, it increments every state time ( at 1/2 the

oscillator frequency ) .

Timer 0

Timer 0 functions as either a timer or event counter in four modes of operation .

Timer 0 is controlled by the four lower bits of the TMOD register and bits 0, 1, 4 and 5

of the TCON register

Mode 0 (13-bit Timer)

Mode 0 configures timer 0 as a 13-bit timer which is set up as an 8-bit timer

(TH0 register) with a modulo 32 prescaler implemented with the lower five bits of

the TL0 register . The upper three bits of TL0 register are indeterminate and should

be ignored . Prescaler overflow increments the TH0 register.

Mode 1 ( 16-bit Timer )

Mode 1 is the same as Mode 0, except that the Timer register is being run

with all 16 bits . Mode 1 configures timer 0 as a 16-bit timer with the TH0 and

TL0 registers connected in cascade . The selected input increments the TL0 register .

Mode 2 (8-bit Timer with Auto-Reload)

Mode 2 configures timer 0 as an 8-bit timer ( TL0 register ) that automatically

reloads from the TH0 register . TL0 overflow sets TF0 flag in the TCON register

and reloads TL0 with the contents of TH0 , which is preset by software .

Mode 3 ( Two 8-bit Timers )

Mode 3 configures timer 0 so that registers TL0 and TH0 operate as separate 8-

bit timers. This mode is provided for applications requiring an additional 8-bit timer or

counter .




Embedded

Controller

RXD

TXD

TXD

RXD2

3

5

GND

MAX 232

Interfacing of MAX-232

INTERRUPTS

An Interrupt is a planned diversion from the program flow. Up on occurrence of an

interrupt the controller vectors the control to the Interrupt Service Routine

Interrupt Service Routine

For every interrupt, there must be an interrupt service routine (ISR), or interrupt handler.

When an interrupt is invoked, the micro controller runs theISR. For every interrupt, there is a fixed

location in memory that holds the address of its ISR. The group of memory location set aside to

hold the addresses of ISRs is interrupt vector table.

Interrupt Vector Table for the 8051

INTERRUPT ROM

(HEX)

PIN

Reset 0000 9

Interrupt 0 0003 P3.2(12)

Timers 0 interrupt (TF0) 000B

External hardware Interrupt

1(INT1)

0013 P3.3 (13)

Timers 1 interrupt (TF1) 001B

Serial COM (RI and TI) 0023

Interrupts




Six Interrupts in the 8051

In reality, only five interrupts are available to the user in the 8051, but many

manufacturers‟ data sheets state that there are six interrupts since they include reset .the six

interrupts in the 8051 are allocated as above.

1. Reset. When the reset pin is activated, the 8051 jumps to address location 0000.this is the

power-up reset.

2. Two interrupts are set aside for the timers: one for Timer 0 and one for Timer 1.Memory location

000BH and 001BH in the interrupt vector table belong to Timer 0 and Timer 1, respectively.

3. Two interrupts are set aside for hardware external harder interrupts. Pin number 12(P3.2) and

13(P3.3) in port 3 is for the external hardware interrupts INT0 and INT1, respectively. These

external interrupts are also referred to as EX1 and EX2.Memory location 0003H and 0013H in the

interrupt vector table are assigned to INT0 and INT1, respectively.

4. Serial communication has a single interrupt that belongs to both receive and transmit. The

interrupt vector table location 0023H belongs to this interrupt.




POWER SUPPLY

The power supply are designed to convert high voltage AC mains electricity to a

suitable low voltage supply for electronics circuits and other devices. A power supply can by

broken down into a series of blocks, each of which performs a particular function. A d.c power

supply which maintains the output voltage constant irrespective of a.c mains fluctuations or load

variations is known as “Regulated D.C Power Supply” For example a 5V regulated power supply

Functional Block Diagram of Power supply

TRANSFORMER

A transformer is an electrical device which is used to convert electrical power from one electrical

circuit to another without change in frequency.

Transformers convert AC electricity from one voltage to another with little loss of power.

Transformers work only with AC and this is one of the reasons why mains electricity is AC.

Step-up transformers increase in output voltage, step-down transformers decrease in output

voltage. Most power supplies use a step-down transformer to reduce the dangerously high mains




voltage to a safer low voltage. 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 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.

An Electrical Transformer

Turns ratio = Vp/ VS = Np/NS

Power Out= Power In

VS X IS=VP X IP

Vp = primary (input) voltage

Np = number of turns on primary coil

Ip = primary (input) current

RECTIFIER

A circuit, which is used to convert a.c to dc, is known as RECTIFIER. The process of

conversion a.c to d.c is called “rectification”

TYPES OF RECTIFIERS

Half wave Rectifier

Full wave rectifier

1. Center tap full wave rectifier.




2. Bridge type full bridge rectifier.

Comparison of rectifier circuits

Parameter

Type of Rectifier

Half wave Full wave Bridge

Number of diodes

1 2 3

PIV of diodes

Vm 2Vm Vm

D.C output voltage Vm/ 2Vm/ 2Vm/

Vdc, at

no-load

0.318Vm 0.636Vm 0.636Vm

Ripple factor 1.21 0.482 0.482

Ripple

frequency f 2f 2f

Rectification

efficiency 0.406 0.812 0.812

RMS voltage Vrms Vm/2 Vm/√2 Vm/√2

Comparison of rectifier circuits




Full-wave Rectifier

From the above comparisons we came to know that full wave bridge rectifier as more

advantages than the other two rectifiers. So, in our project we are using full wave bridge rectifier

circuit.

Bridge Rectifier

A bridge rectifier makes use of four diodes in a bridge arrangement to achieve full-wave

rectification. This is a widely used configuration, both with individual diodes wired as shown

and with single component bridges where the diode bridge is wired internally .

A bridge rectifier makes use of four diodes in a bridge arrangement as shown in fig(a) to

achieve full-wave rectification. This is a widely used configuration, both with individual diodes

wired as shown and with single component bridges where the diode bridge is wired internally.

Operation

During positive half cycle of secondary, the diodes D2 and D3 are in forward biased

while D1 and D4 are in reverse biased as shown in the fig(b). The current flow direction is

shown in the fig (b) with dotted arrows.




During negative half cycle of secondary voltage, the diodes D1 and D4 are in forward

biased while D2 and D3 are in reverse biased as shown in the fig(c). The current flow direction

is shown in the fig (c) with dotted arrows.

FilterA Filter is a device, which removes the a.c component of rectifier output but allows the

d.c component to reach the load.

Capacitor Filter

We have seen that the ripple content in the rectified output of half wave rectifier is 121% or

that of full-wave or bridge rectifier or bridge rectifier is 48% such high percentages of ripples is

not acceptable for most of the applications. Ripples can be removed by one of the following

methods of filtering:

(a) A capacitor, in parallel to the load, provides an easier by – pass for the ripples voltage though

it due to low impedance. At ripple frequency and leave the d.c.to appears the load.

(b) An inductor, in series with the load, prevents the passage of the ripple current (due to high

impedance at ripple frequency) while allowing the d.c (due to low resistance to d.c)

(c) various combinations of capacitor and inductor, such as L-section filter section filter,

multiple section filter etc. which make use of both the properties mentioned in (a) and (b) above.

Two cases of capacitor filter, one applied on half wave rectifier and another with full wave

rectifier.

Filtering is performed by a large value electrolytic capacitor connected across the DC

supply to act as a reservoir, supplying current to the output when the varying DC voltage from

the rectifier is falling. The capacitor charges quickly near the peak of the varying DC, and then




discharges as it supplies current to the output. Filtering significantly increases the average DC

voltage to almost the peak value (1.4 × RMS value).

To calculate the value of capacitor(C),

C = ¼*√3*f*r*Rl

Where,

f = supply frequency,

r = ripple factor,

Rl = load resistance

Note: In our circuit we are using 1000microfarads.

Regulator

Voltage regulator ICs is available with fixed (typically 5, 12 and 15V) or variable output

voltages. The maximum current they can pass also rates them. Negative voltage regulators are

available, mainly for use in dual supplies. Most regulators include some automatic protection

from excessive current ('overload protection') and overheating ('thermal protection'). Many of

the fixed voltage regulator ICs have 3 leads and look like power transistors, such as the 7805

+5V 1A regulator shown on the right. The LM7805 is simple to use. You simply connect the

positive lead of your unregulated DC power supply (anything from 9VDC to 24VDC) to the

Input pin, connect the negative lead to the Common pin and then when you turn on the power,

you get a 5 volt supply from the output pin.

A Three Terminal Voltage Regulator

78XX

The Bay Linear LM78XX is integrated linear positive regulator with three terminals. The

LM78XX offer several fixed output voltages making them useful in wide range of applications.

When used as a zener diode/resistor combination replacement, the LM78XX usually results in an




effective output impedance improvement of two orders of magnitude, lower quiescent current.

The LM78XX is available in the TO-252, TO-220 & TO-263packages,

Features

• Output Current of 1.5A

• Output Voltage Tolerance of 5%

• Internal thermal overload protection

• Internal Short-Circuit Limited

• No External Component

• Output Voltage 5.0V, 6V, 8V, 9V, 10V, 12V, 15V, 18V, 24V

• Offer in plastic TO-252, TO-220 & TO-263

• Direct Replacement for LM78XX

H-BRIDGE

DC motors are typically controlled by using a transistor configuration called an "H-bridge".

This consists of a minimum of four mechanical or solid-state switches, such as two NPN and two

http://en.wikipedia.org/wiki/H-bridge







PNP transistors. One NPN and one PNP transistor are activated at a time. Both NPN and PNP

transistors can be activated to cause a short across the motor terminals, which can be useful for

slowing down the motor from the back EMF it creats.

Basic Theory

H-bridge. Sometimes called a "full bridge" the H-bridge is so named because it has four

switching elements at the "corners" of the H and the motor forms the cross bar.

The key fact to note is that there are, in theory, four switching elements within the bridge.

These four elements are often called, high side left, high side right, low side right, and low side

left (when traversing in clockwise order).

The switches are turned on in pairs, either high left and lower right, or lower left and high

right, but never both switches on the same "side" of the bridge. If both switches on one side of a bridge are turned on it creates a short circuit between the battery plus and battery minus

terminals. If the bridge is sufficiently powerful it will absorb that load and your batteries will

simply drain quickly. Usually however the switches in question melt.

To power the motor, you turn on two switches that are diagonally opposed. In the picture

to the right, imagine that the high side left and low side right switches are turned on.

The current flows and the motor begins to turn in a "positive" direction. Turn on the high

side right and low side left switches, then Current flows the other direction through the motor

and the motor turns in the opposite direction.

Actually it is just that simple, the tricky part comes in when you decide what to use for

switches. Anything that can carry a current will work, from four SPST switches, one DPDT

switch, relays, transistors, to enhancement mode power MOSFETs.

One more topic in the basic theory section, quadrants. If each switch can be controlled

independently then you can do some interesting things with the bridge, some folks call such a

bridge a "four quadrant device" (4QD get it?). If you built it out of a single DPDT relay, you can

really only control forward or reverse. You can build a small truth table that tells you for each of

the switch's states, what the bridge will do. As each switch has one of two states, and there are

four switches, there are 16 possible states. However, since any state that turns both switches on

one side on is "bad" (smoke issues forth: P), there are in fact only four useful states (the four

quadrants) where the transistors are turned on.

http://en.wikipedia.org/wiki/Electromotive_force







High Side Left High Side Right Low Side Left Low Side Right Quadrant Description

On Off Off On Forward Running

Off On On Off Backward Running

On On Off Off Braking

Off Off On On Braking

The last two rows describe a maneuver where you "short circuit" the motor which causes

the motors generator effect to work against itself. The turning motor generates a voltage which

tries to force the motor to turn the opposite direction. This causes the motor to rapidly stop

spinning and is called "braking" on a lot of H-bridge designs.

Of course there is also the state where all the transistors are turned off. In this case the

motor coasts freely if it was spinning and does nothing if it was doing nothing.

Implementation

1. Using Relays

A simple implementation of an H Bridge using four SPST relays is shown. Terminal A

is High Side Left, Terminal B is High Side Right, Terminal C is Low Side Left and

Terminal D is Low Side Right. The logic followed is according to the table above.

Warning: Never turn on A and C or B and D at the same time. This will lead to a short

circuit of the battery and will lead to failure of the relays due to the large current.




2. Using Transistors

We can better control our motor by using transistors or Field Effect Transistors (FETs).

Most of what we have discussed about the relays H-Bridge is true of these circuits. See the

diagram showing how they are connected. You should add diodes across the transistors to catch

the back voltage that is generated by the motor's coil when the power is switched on and off.

This fly back voltage can be many times higher than the supply voltage!




Transistors, being a semiconductor device, will have some resistance, which causes them

to get hot when conducting much current. This is called not being able to sink or source very

much power, i.e.: Not able to provide much current from ground or from plus voltage.

Mosfets are much more efficient, they can provide much more current and not get as hot. They

usually have the fly back diodes built in so you don't need the diodes anymore. This helps guard

against fly back voltage frying your ICs.

To use Mosfets in an H-Bridge, you need P-Channel Mosfets on top because they can

"source" power, and N-Channel Mosfets on the bottom because then can "sink" power.

It is important that the four quadrants of the H-Bridge circuits be turned on and off

properly. When there is a path between the positive and ground side of the H-Bridge, other than

through the motor, a condition exists called "shoot through". This is basically a direct short of

the power supply and can cause semiconductors to become ballistic, in circuits with large

currents flowing. There are H-bridge chips available that are much easier, and safer, to use than

designing your own H-Bridge circuit.

1. Using H-Bridge Devices

The L293 has 2 H-Bridges (actually 4 Half H-Bridges), can provide about 1 amp to each and

occasional peak loads to 2 amps.

The L298 has 2 h-bridges on board, can handle 1amp and peak current draws to about 3amps.

The LMD18200 has one h-bridge on board, can handle about 2 or 3 amps and can handle a peak

of about 6 amps. There are several more commercially designed H-Bridge chips as well.

Once a Half H-bridge is enabled, it truth table is as follows:

INPUT

A

OUTPUT

Y

L L

H H

So you just give a High level when you want to turn the Half H-Bridge on and Low level when

you want to turn it off. When the Half H-Bridge is on, the voltage at the output is equal to




Vcc2.If you want to make a Full H-Bridge, you connect the motor (or the load) between the

outputs of two Half H-Bridges and the inputs will be the two inputs of the Half H-Bridges.

Suppose we have connected Half H-Bridges 1 and 2 to form a Full H-Bridge. Now the truth table

is as follows:

INPUT

1A

INPUT

2A

OUTPUT

1Y

OUTPUT

2Y Description

L L L LBraking (both terminals

of motor are Gnd)

L H L H Forward Running

H L H L Backward Running

H H H HBraking (both terminals

of motor at Vcc2

2) L293D Motor Driver IC

Since two motors are used to drive The back wheels of the robot independently, there is a need

for Two H-bridges. Instead of implementing the above H-bridge controlCircuit twice, an

alternative is to use an integrated circuit (IC), which Provides more than one

H-bridges. One such IC is L293D, which has 2 H-Bridges in it. It can supply 600 Ma

continuous and 1.2 A peak Currents. It is suitable for switching applications up to 5 kHz. These

Features make it ideal for our application. Another option is to use IC L298, which can drive 2 A

continually and 3 A peak currents. The Diagram of L293D is shown in Figure 2It can be observed

from the figure that L293D has a similar configuration to the circuit in Figure 1.




Figure 1

3) Motor Driver Connections:

The motor driver requires 2 control inputs for each motor. Since we drive 2 motors, we need 4

controls Inputs from the microcontroller.

Since it has many pins which can be configured as outputs, there are many options for

implementation.For example, in our robot the last 4 bits of Port B (RB4, RB5, RB6,RB7 - Pins

37 to 40) are used to control the rotation direction of the motors . The enable pins of the motor

driver are connected to the PWM outputs of the microcontroller (Pins 16and 17). This is because,

as was mentioned above, by changing the width of the pulse (implying changing the enable time

of the driver) one can change the speed of the motor. The truth table for motor driver is as shown

in Table II, where H = high, L = low, and Z =high output impedance state.

Since the motors are reverse aligned, in order to have the robot Move forward they must be

configured such that one of them turns forward and the other one turns backward. In case of any

requirement for the robot to move backward, it is sufficient to just reverse the Outputs of the

control pins. For example, in our robot while moving forward, inputs of the motor driver have

states shown in the first row Of Table III, whereas for backward movement, the states shown in

the second row of Table III is applied.




TABLE II

THE TRUTH TABLE OF THE MOTOR DRIVER

Input enable output

H H H

L H L

H L z

L L z

TABLE III

DRIVER CONTROL INPUTS

Direction Input 1 Input 2 Input 3 Input 4

Forward H L L H

Backward L H H L

DC Motor

DC motors are configured in many types and sizes, including brush less, servo, and gear

motor types. A motor consists of a rotor and a permanent magnetic field stator. The magnetic

field is maintained using either permanent magnets or electromagnetic windings. DC motors are

most commonly used in variable speed and torque.

Motion and controls cover a wide range of components that in some way are used to

generate and/or control motion. Areas within this category include bearings and bushings,

clutches and brakes, controls and drives, drive components, encoders and resolves, Integrated

motion control, limit switches, linear actuators, linear and rotary motion components, linear

position sensing, motors (both AC and DC motors), orientation position sensing, pneumatics and

pneumatic components, positioning stages, slides and guides, power transmission (mechanical),seals, slip rings, solenoids, springs.

Motors are the devices that provide the actual speed and torque in a drive system. This

family includes AC motor types (single and multiphase motors, universal, servo motors,

http://dc-motors.globalspec.com/Industrial-Directory/motors

http://dc-motors.globalspec.com/Industrial-Directory/motor




















induction, synchronous, and gear motor) and DC motors (brush less, servo motor, and gear

motor) as well as linear, stepper and air motors, and motor contactors and starters.

In any electric motor, operation is based on simple electromagnetism. A current-carrying

conductor generates a magnetic field; when this is then placed in an external magnetic field, it

will experience a force proportional to the current in the conductor, and to the strength of the

external magnetic field. As you are well aware of from playing with magnets as a kid, opposite

(North and South) polarities attract, while like polarities (North and North, South and South)

repel. The internal configuration of a DC motor is designed to harness the magnetic interaction

between a current-carrying conductor and an external magnetic field to generate rotational

motion.

Let's start by looking at a simple 2-pole DC electric motor (here red represents a magnet

or winding with a "North" polarization, while green represents a magnet or winding with a

"South" polarization).

Block Diagram of the DC motor

Every DC motor has six basic parts -- axle, rotor (a.k.a., armature), stator, commutator,

field magnet(s), and brushes. In most common DC motors (and all that Beamers will see), the

external magnetic field is produced by high-strength permanent magnets1. The stator is the

stationary part of the motor -- this includes the motor casing, as well as two or more permanent

magnet pole pieces. The rotor (together with the axle and attached commutator) rotates with

respect to the stator. The rotor consists of windings (generally on a core), the windings being

electrically connected to the commutator. The above diagram shows a common motor layout --

with the rotor inside the stator (field) magnets.

The geometry of the brushes, commutator contacts, and rotor windings are such that

when power is applied, the polarities of the energized winding and the stator magnet(s) are





http://encyclobeamia.solarbotics.net/articles/current.html


http://encyclobeamia.solarbotics.net/articles/dc.html

















misaligned, and the rotor will rotate until it is almost aligned with the stator's field magnets. As

the rotor reaches alignment, the brushes move to the next commutator contacts, and energize the

next winding. Given our example two-pole motor, the rotation reverses the direction of current

through the rotor winding, leading to a "flip" of the rotor's magnetic field, and driving it to

continue rotating.

In real life, though, DC motors will always have more than two poles (three is a very

common number). In particular, this avoids "dead spots" in the commutator. You can imagine

how with our example two-pole motor, if the rotor is exactly at the middle of its rotation

(perfectly aligned with the field magnets), it will get "stuck" there. Meanwhile, with a two-pole

motor, there is a moment where the commutator shorts out the power supply (i.e., both brushes

touch both commutator contacts simultaneously). This would be bad for the power supply, waste

energy, and damage motor components as well. Yet another disadvantage of such a simple motor

is that it would exhibit a high amount of torque” ripple" (the amount of torque it could produce is

cyclic with the position of the rotor).

Block Diagram of the DC motor having two poles only

So since most small DC motors are of a three-pole design, let's tinker with the workings of one

via an interactive animation (JavaScript required):

Block Diagram of the DC motor having Three poles






You'll notice a few things from this -- namely, one pole is fully energized at a time (but two

others are "partially" energized). As each brush transitions from one commutator contact to the

next, one coil's field will rapidly collapse, as the next coil's field will rapidly charge up (this

occurs within a few microsecond). We'll see more about the effects of this later, but in the

meantime you can see that this is a direct result of the coil windings' series wiring:

Internal Block Diagram of the Three pole DC motor

There's probably no better way to see how an average dc motor is put together, than by

just opening one up. Unfortunately this is tedious work, as well as requiring the destruction of a

perfectly good motor. This is a basic 3-pole dc motor, with 2 brushes and three commutator

contacts.

LCD MODULE

THEORY:

A liquid crystal is a material (normally organic for LCDs) that will flow like a liquid but

whose molecular structure has some properties normally associated with solids. The Liquid

Crystal Display (LCD) is a low power device. The power requirement is typically in the order of

microwatts for the LCD. However, an LCD requires an external or internal light source. It is

limited to a temperature range of about 0C to 60C and lifetime is an area of concern, because

LCDs can chemically degrade.

There are two major types of LCDs which are:

1. Dynamic-scattering LCDs and

2. Field-effect LCDs




Field-effect LCDs are normally used in such applications where source of energy is a prime

factor (e.g., watches, portable instrumentation etc.).They absorb considerably less power than the

light-scattering type. However, the cost for field-effect units is typically higher, and their hoight

is limited to 2 inches. On the other hand, light-scattering units are available up to 8 inches in

height. Field-effect LCD is used in the project for displaying the appropriate information.

The turn-on and turn-off time is an important consideration in all displays. The response time of

LCDs is in the range of 100 to 300ms.The lifetime of LCDs is steadily increasing beyond

10,000+hours limit. Since the color generated by LCD units is dependent on the source of

illumination, there is a wide range of color choice.

HARDWARE DIAGRAM:

16 x 2 Char LCD

R1

R2

GND

Vcc

Vf RSRWEN

D0 – D7

A K D0

D7

ACK

RS (Command / Data):

This bit is to specify weather received byte is command or data. So that LCD can

recognize the operation to be performed based on the bit status.




RS = 0 => Command

RS = 1 => Data

RW (Read / Write):-

RW bit is to specify weather controller wants READ from LCD or WRITE to LCD. The

READ operation here is just ACK bit to know weather LCD is free or not.

RW = 0 => Write

RW = 1 => Read

EN (Enable LCD):-

EN bit is to ENABLE or DISABLE the LCD. When ever controller wants to write some

thing into LCD or READ acknowledgment from LCD it needs to enable the LCD.

EN = 0 => High Impedance

EN = 1 => Low Impedance

ACK (LCD Ready):-

ACK bit is to acknowledge the MCU that LCD is free so that it can send new command

or data to be stored in its internal Ram locations

ACK = 1 => Not ACK

ACK = 0 => ACK




FLOWCHART:

START

Configure port pins for all hardware

connections

Copy command in to Accumulator

Is LCD Free

Wait

No

Yes

Clear RS Bit

Enable LCD

Send Command

Disable LCD

Is Command

Count Zero No

1




Copy Data in to Accumulator

Is LCD Free

Wait

No

Yes

Set RS Bit

Enable LCD

Send Data

Disable LCD

Is Data

Count Zero No

1

STOP

MEMS

Pin Name Description Pin

Status1 RESERVED Connect to AVSS Input




2 N/C No Internal Connection, leave

unconnected or connect to Ground

Input

3 AVDD Device Power Input

4 AVSS Device Ground Input

5 INT Interrupt/Data Ready Output

6 SCL I2C Serial Clock Input

7 SDA I2C Serial Data Open

Drain

8 DVSS Digital I/O Ground Input

9 DVDD Digital I/O Power Input

10 RESERVED Connect to AVSS Input

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 (poly silicon) 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.

. Orientation Detection Logic in 3-Dimensional Space




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) register ).

Tap Detection SetupIn 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 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 º angle change) which can not be detected by orientation

detection.

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, 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 -1.3




g, 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 three (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.

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 samples per second

(1 sample/second, 8 samples/second, 16 samples/second, or 32 samples/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 (1 sample/second, 2 samples/second, 4

samples/second, 8 samples/second, 16 samples/second, 32 samples/second, 64 samples/second,

and 120 samples/ 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.




SOFTWARE USED

INTRODUCTION TO EMBEDDED „C‟

Data Types

U people have already come across the word “Data types” in C- Language. Here also the

functionality and the meaning of the word is same except a small change in the prefix of their

labels. Now we will discuss some of the widely used data types for embedded C- programming.

data types

Unsigned Char

The unsigned char is an 8-bit data type that takes a value in the range of 0-255(00-FFH).

It is used in many situations, such as setting a counter value, where there is no need for signed

data we should use the unsigned char instead of the signed char. Remember that C compilers use

the signed char as the default if we do not put the key word.

Signed char

The signed char is an 8-bit data type that uses the most significant bit (D7 of D7-D0) to

represent the – or + values. As a result, we have only 7 bits for the magnitude of the signed

Data Types Size in Bits Data Range/Usage

unsigned char 8-bit 0-255

signed char 8-bit -128 to +127

unsigned int 16-bit 0 to 65535

signed int 16-bit -32,768 to +32,767

sbit 1-bit SFR bit addressable only

Bit 1-bit RAM bit addressable only

Sfr 8-bit RAMaddresses80-FFH only




number, giving us values from -128 to +127. In situations where + and – are needed to represent

a given quantity such as temperature, the use of the signed char data type is a must.

Unsigned Int

The unsigned int is a 16-bit data type that takes a value in the range of 0 to 65535 (0000-

FFFFH).It is also used to set counter values of more than 256. We must use the int data type

unless we have to. Since registers and memory are in 8-bit chunks, the misuse of int variables

will result in a larger hex file. To overcome this we can use the unsigned char in place of

unsigned int.

Signed Int

Signed int is a 16-bit data type that uses the most significant bit (D15 of D15-D0) to

represent the – or + value. As a result we have only 15 bits for the magnitude of the number or

values from -32,768 to +32,767.

Sbit (single bit)

The sbit data type is widely used and designed specifically to access single bit

addressable registers. It allows access to the single bits of the SFR registers.

I/O PROGRAMMING IN EMBEDDED “C”

In this topic we look at C- programming of the I/O ports and also both byte and bit I/O

programming.

Byte Size I/O

As we know that ports P0-P3 are byte accessible, we use the P0-P3 labels as defined in

the header file.

Bit – Addressable I/O Programming

The I/O ports of P0-P3 are bit- addressable, so we can access a single bit without

disturbing the rest of the port. We use the sbit data type to access a single bit of P0-P3.the format

is Px^y where x is the port and y is the bit.

Accessing SFR addresses 80-FFH

Another way to access the SFR RAM space 80-FFH is to use the sfr data type. This is

shown in the below example .Both the bit and byte addresses for the P0-P3 ports are given in the




table. Notice in the given example that there is no #include<reg51.h> statement which allows us

to access any byte of the SFR RAM space 80-FFH.

About Software

Software‟s used are *Keil software for C programming

What's New in µVision3?

µVision3 adds many new features to the Editor like Text Templates, Quick Function Navigation,

and Syntax Coloring with brace high lighting Configuration Wizard for dialog based startup and

debugger setup. µVision3 is fully compatible to µVision2 and can be used in parallel with

µVision2.

What is µVision3?

µVision3 is an IDE (Integrated Development Environment) that helps you write, compile, and

debug embedded programs. It encapsulates the following components:

A project manager.

A make facility.

Tool configuration.

Editor.

A powerful debugger.

To help you get started, several example programs (located in the

C51\Examples\C251\Examples\C166\Examples , and \ARM\...\Examples) are provided.

HELLO is a simple program that prints the string "Hello World" using the Serial Interface.

Building an Application in µVision2

To build (compile, assemble, and link) an application in µVision2, you must:

1. Select Project -(forexample,166\EXAMPLES\HELLO\HELLO.UV2).

2. Select Project - Rebuild all target files or Build target.

µVision2 compiles, assembles, and links the files in your project.

Creating Your Own Application in µVision2

To create a new project in µVision2, you must:

1. Select Project - New Project.

2. Select a directory and enter the name of the project file.




3. Select Project - Select Device and select an 8051, 251, or C16x/ST10 device from the

Device Database

4. Create source files to add to the project.

5. Select Project - Targets, Groups, Files. Add/Files, select Source Group1, and add the

source files to the project.

6. 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.

7. Select Project - Rebuild all target files or Build target.

Debugging an Application in µVision2

To debug an application created using µVision2, you must:

1. Select Debug - Start/Stop Debug Session.

2. 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.

3. 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.

Starting µVision2 and 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 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.

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 database. Just select the micro

controller 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.

Building Projects and Creating a 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.

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.

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.

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.

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.

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.

Steps for executing the Keil programs

1. Click on the Keil uVision Icon on Desktop

2. The following fig will appear




e

3. Click on the Project menu from the title bar

4. Then Click on New Project

5. Save the Project by typing suitable project name with no extension in u r own folder

sited in either C:\ or D:\




6. Then Click on Save button above.

7. Select the com ponent for u r project. i.e. Atmel……

8. Click on the + Symbol beside of Atmel

9. Select AT89C51 as shown below




e

10. Then Click on “OK”

11. The Following fig will appear

e

12. Then Click either YES or NO………mostly “NO”

13. Now your project is ready to USE

14. Now double click on the Target1, you would get another option “Source group 1” as

shown in next page.




15. Click on the file option from menu bar and select “new”

16. The next screen will be as shown in next page, and just maximize it by double

clicking on its blue boarder.




20. Now you will get another window, on which by default “C” files will appear.

21. Now select as per your file extension given while saving the file

22. Click only one time on option “ADD”

23. Now Press function key F7 to compile. Any error will appear if so happen.




24. If the file contains no error, then press Control+F5 simultaneously.

25. The new window is as follows

26. Then Click “OK”

27. Now Click on the Peripherals from menu bar, and check your required port as shown

in fig below




28. Drag the port a side and click in the program file.

29. Now keep Pressing function key “F11” slowly and observe.

You are running your program successfully




SOURCE CODE

#include<reg52.h>

#include"mems.h"

#include"lcddisplay.h"

sbit m0a = P0^0;

sbit m0b = P0^1;

sbit m1a = P0^2;

sbit m1b = P0^3;

void motor0(unsigned char x, unsigned char y)

{m0a=x;

m0b=y;

}

void motor1(unsigned char p, unsigned char q)

{

m1a=p;

m1b=q;

}

void delay_ms(int cnt)

{

int i;

while(cnt--)

for(i=0;i<500;i++);

}

main(){

unsigned char memsdata;

lcd_init();

lcdcmd(0x01);

msgdisplay("finger based ");




lcdcmd(0xc0);

msgdisplay("wheel chair");

delay(100);

write_mems(7,0x00);

delay_ms(500);write_mems(7,0x01);

delay_ms(500);

write_mems(8,0x3F);

delay_ms(500);

while(1)

{

memsdata=read_mems(3)&0x3f;

if(memsdata == 21 || memsdata == 5)

{ lcdcmd(0x01);

msgdisplay(" **stop**");

//P2=0xf5;

// str("stable ");

motor0(0,0);

motor1(0,0);

}

if(memsdata == 10 )

{

lcdcmd(0x01);

msgdisplay(" **go left**"); //left//P2=0xf3;

motor0(0,1);

motor1(1,0);

}




if (memsdata == 6)

{

lcdcmd(0x01);

msgdisplay(" **go right**");//right

motor0(1,0);

motor1(0,1);

}

if( memsdata == 26)

{

lcdcmd(0x01);

msgdisplay(" **go front**"); //front

motor0(1,0);

motor1(1,0);

}

if( memsdata == 22 )

{

lcdcmd(0x01);

msgdisplay(" **go back**"); //back

motor0(0,1);

motor1(0,1);

}

}

}




.

CONCLUSION

The project “PROJECT CLASS” has been successfully designed and tested. It has beendeveloped 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.




BIBILOGRPAHY

[1] Furber “Arm System-On-Chip Architecture, 2/E”, Pearson Education.

[2] 8051-DATASHEET.

[3] Arm Architecture Reference Manual-David Seal

[4] Fundamentals of Micro processors and Micro computers-B.Ram

[5] Micro processor Architecture, Programming& Applications-Ramesh S.Gaonkar

[6] Electronic Components-D.V.Prasad

[7] Wireless Communications- Theodore S. Rappaport

[8] Mobile Tele Communications- William C.Y. Lee

WEBSITES[1] www.atmel.com

[2] www.wikipedia.org

[3] www.8051projects.net

[4] www.engineersgarage.com

[5] www.keil.com

[6] www.educypedia.org

[7] www.howstuffworks.com

[8] www.instructables.com

[9] www.8051projects.info

[10] www.projectguidance.com

[11] www.national.com

[12] www.microsoftsearch.com

mems based wheel chair

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