Morld Tech Gossips: Voice Based ARM Exo Skeleton

Chapter 1

INTRODUCTION

Exoskeleton can also be regarded as Wearable robots: A wearable robot is a mechatronics system that is designed around the shape and function of the human body, with segments and joints corresponding to those of the person it is externally coupled with. Tele operation and power amplification where the first application, but after resent technological advances the range of application fields has widened. Increasing recognition from the scientific community means that technology is now employed in telemanipulation, man-amplification, neuromotor control research and rehabilitation, and to assist with impaired human motor control.

A powered exoskeleton is a powered mobile machine consisting primarily of a skeleton-like framework worn by a person and a power supply that supplies at least part of the activation -energy for limb movement. This project aims to develop an Arm Exoskeleton that can be worn by a person whose arm is paralyzed. The system consists of a frame that can be worn on paralyzed arm. Three motors are used to make the arm movement -for shoulder, wrist and elbow. The controlling system is a microcontroller based embedded system that helps the user to operate the exoskeleton with the other hand. This is a voice based system that on able the user to control the motor movements. Also the user has the option of storing five patterns of movements in the memory of the system. This helps the user to move the arm in a pre-defined pattern. Stepper/Dc motors are used to control the movements.

Powered exoskeletons are designed to assist and protect the wearer. They may be designed, for example, to assist and protect soldiers and construction workers, or to aid the survival of people in other dangerous environments. A wide medical market exists in the future for providing mobility assistance for aged and infirm people. Other possibilities include rescue work, such as in collapsed buildings, in which the device might allow rescue worker to lift heavy debris, while simultaneously protecting him from falling rubble. The whole system works under the control of the microcontroller in it. The system monitors the inputs by the user, verifies it and energizes the motors. The storage of the user defined patterns is done and executed by the system.

Chapter 2

BLOCK DIAGRAM

Figure: 2.1-Block Diagram of Arm Exoskeleton

2.1 BLOCK DIAGRAM DISCRIPTION

The figure: 2.1 shows the block diagram of arm exoskeleton. The main components of an arm exoskeleton are microcontroller, driver circuit, dc motors , mic , pc and a power supply. It is control by switches. The signal from switches is given to the microcontroller, where the operations are take place. The microcontroller is programmed to do several functions. The output from the microcontroller is given to the driver circuit. The driver circuit is a 1C which gives the control signals and current to the DC motor for its function.

2.2 COMPONENTS

2.2.1MICROCONTROLLER AT89C51

Micro controller is the key part of most of the electronic equipments including toys, motorcars etc. Micro controller is the new generation of microprocessors. Microprocessor needs many extra chips to perform its proper function. But in micro controllers, it needs only a crystal oscillator and some passive components. A micro controller has two versions. One with inbuilt memory and the other is without memory. This inbuilt memory can be up to 16 Bytes. This memory is more than enough for the most of the controlling applications in the electronic industry. This type of micro controllers with inbuilt memory is known as flash micro controllers compared to microprocessors, micro controller is an independent device, which can communicate to PC via RS-232 interface. Similar to microprocessor, most of the micro controllers have 40 pins. It is available in DIP and PLCC package.

In all the flash micro controllers, there are separate address space for program memory and data memory. The logical separation of program and data memory allows, the data memory accessed by an 8-bit address, which can more quickly stored and manipulated by an 8-bit CPU.

The program memory can only be read, not written to. There can be up to 64 K bytes of program memory. In the ROM and EPROM versions of the microcontrollers, the locoest 4k, 8k, or 16k bytes of program memory are provided a chip. In the ROM less versions, the program memory is external.

The data memory occupies a separate space from the program memory. Up to 64k bytes of external RAM can be addressed in external data memory space. The CPU generates RD and WR signals as needed during external data memory access.

2.2.2 PINOUT OF AT89C51

Fig 2.2 Pinout of AT89C51

2.2.3 HARDWARE DISCRIPTION

2.2.4 ACCUMULATOR

Acc is the Accumulator register. The mnemonics for Accumulator –specific instructions, however, refer to the accumulator simply as ‘A’.

2.2.5 B REGISTER

The B register is used during multiply and divide operations. For other instructions it can be treated as another scratch pad register.

2.2.6 STACK POINTER

The stack pointer register is 8 bits wide. It is incremented before data is stored during PUSH and CALL executions.

2.2.7 DATA POINTER

The Data pointer (DTPR) consists of a high byte and a low byte. Its functions are to hold a 16-bit address. It may be manipulated as 16-bit register or as two independent 8-bit registers.

2.2.8 SERIAL DATA BUFFER

The serial data buffer is actually two separate registers, a transmit buffer and a receive buffer register. When data is moved to serial data buffer, it goes to the transmit buffer, where it is held for serial transmission. When data is moved from serial data buffer, it comes from the receive buffer.

2.2.9 TIMER REGISTERS

Register pairs (THO, TLO), (THI, TLI) and (TH_2,TL₂) are the 16-bit counter register for timer/counter 0,1 and 2 respectively.

2.2.10 CAPTURE REGISTERS

The register pair (RCAPZH, RCAPZL) is the capture registers for the timer 2 modes. In this mode, in response to a transition, TH₂ and TL₂ are copied into RCAP2H and RCAP₂ L. Timer 2 also has a 16-bit auto reload mode, and RCAP₂H and RCAP₂L hold the reload value for this mode.

2.2.11 CONTROL REGISTERS

Special function registers IP, IF, TMOD, TCON, T₂CON, T₂ MOD, SCON and PCON contain control and status bits for the interrupt system, the timer/counters and the serial port.

2.2.12 PORT STRUCTURES AND OPERATIONS

All four ports are bi-directional. Each consists of a latch, an output driver and an input buffer.

The output drives of ports) and 2, and the input buffers of port 0, are used in access to external memory. In this application, port 0 outputs the low byte of the external memory address, time-multiplexed with the byte being written or read. Port 2 outputs the high byte of the external memory address when the address is 16 bits wide. All the port 3 pins and two port 1 pins are multifunctional. They are not only port pins but also provide some special features.

2.2.13 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. When is written to port 0 pins, the pins can be used as high impedance inputs.Port 0 may also be configured to be the multiplexed low order address/data bus during access to external program and data memory. In this mode Po 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.

2.2.14 PORT 1

Port 1 is an 8-bit bi-directional I/O port with internal pull-ups. The Port 1 output buffers can sink or source four TTL inputs. When is written to port 1 pin 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 (I_SL) because of the internal pull-ups. Port 1 also receives the low-order address bytes during flash programming verification.

2.2.15 PORT 2

Port 2 is an 8-bit bi-directional I/O port with internal pull-ups. The port 2 output buffers can SINK/source four TTL inputs. When is written to Port 2 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins that are externally being pulled low will source current (I_TL) 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 use 16-bit address. In this application it uses strong internal pull-ups when emitting 1’s.

During to external data memory that uses 8 bit addresses, port 2 emits 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.

2.2.16 PORT 3

Port 3 is an 8-bit bi-directional I/O port with internal pull-ups. The port 3 output buffers could sink or source four TTL inputs. When 1’s are written to port 3 pins they are pulled high by the internal pull-ups and can be used as inputs. As inputs port 3 pins that are externally being pulled low will source current (I_IL) because of the pull-ups. Port 3 also serves the functions of some various special features.

2.2.17 RST

Reset input a high on-this pin for two-machine cycles while the oscillator is running resets the device.

2.2.18 ALE/PROG

Address latch enable output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input during flash programming. In normal operations ALE is emitted at a constant rate of 1/16 the oscillator frequency, and may be used for external timing or clocking purposes.

2.2.19 PSEN

Program store enable is the read strobe to external program memory, when the microcontroller is executing code from external program memory locations. EA should be strapped to vie for internal program executions.

This pin also receives the 12 VOH programming enable voltage (V_pp) during flash programming for parts that require 12 volt V_pp.

2.3 CRYSTAL OSCILLATOR

Fig 2.3 Crystal Oscillator

XTAL 1: Input to the inverting oscillator amplifier and input to the Internal clock operating circuit.

XTAL 2: Output from the inverting oscillator amplifier

XTAL 1 and XTAL 2 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.

They are no requirements on the duly cycle of the external clock 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.

2.4 Power Supply Section

Power supply is a device or system that supplies electrical or other types of energy to an output load or group of loads.

A simple AC powered linear power supply usually uses a transformer to convert the voltage from the wall outlet (mains) to a different, usually a lower voltage. If it is used to produce DC a rectifier circuit is employed either as a single chip, an array of diodes sometimes called a diode bridge or Bridge Rectifier, both for full wave rectification or a single diode yielding a half wave (pulsating) output. More elaborate configurations rectify the AC voltage at first to pulsating DC.

Then a capacitor smooth out part of the pulses giving a type of DC voltage. The smaller pulses remaining are known as ripple. Because of a full wave rectification they occur at twice the mains frequency (in USA it's 60 Hz doubled to 120 Hz - or the UK, its 50Hz, doubled to 100Hz). Finally, depending on the requirements of the load, a linear regulator may be used to reduce the ripple sometimes also allowing for adjustment of the output to the desired but lower voltage.

Fig 2.4 Power Supply Section

2.4.1 LM7805 Voltage Regulator

These are monolithic integrated circuits designed as fixed voltage regulators for a wide variety of applications including local, on card regulation. These regulators employ internal current limiting, thermal solution and safe area compensation. They can also be used with external components to obtain adjustable voltages and current.

Features are

Ø Output Current up to 1A

Ø Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24

Ø Thermal Overload Protection

Ø Short Circuit Protection

Ø Output Transistor Safe Operating Area Protection

2.4.2 MAX 232

Since RS232 is not compatible with today’s microprocessors and microcontrollers we need a line drive to convert the RS232’Ss signals to TTL voltage levels that will be acceptable to the today’s microprocessor pins. One example of such a converter is MAX232 from Maxim Corporation.

Fig 2.5 MAX 232

The MAX232 converts from RS232 voltage levels to TTL voltage levels. A MAX232 chip has long been using in many uC boards. It provides 2-channel RS232C port and requires external 10uF capacitors.

2.4.3 PIN OUT DIAGRAM

Fig 2.6 Pin out Diagram

The MAX232 from Maxim was the first IC which in one package contains The necessary drivers (two) and receivers (also two), to adapt the RS-232 signal voltage levels to TTL logic. It became popular, because it just needs one voltage (+5V) and generates the necessary RS-232 voltage levels (approx. -10V and +10V) internally. This greatly simplified the design of circuitry. Circuitry designers no longer need to design and build a power supply with three voltages (e.g. -12V, +5V, and +12V), but could just provide one +5V power supply, e.g. with the help of a simple 78x05 voltage converter.

MAX-232 includes a Charge Pump, which generates +10V and -10V from a single 5vsupply.This I.C. also includes two receivers and two transmitters in the same package. This is useful in many cases when you only want to use the Transmit and Receive data Lines. You don't need to use two chips, one for the receive line and one for the transmission.

However this convenience is expensive, but compared with the price of designing a new power supply it is very cheap. There are also many variations of these devices. Each receiver converts TIA/EIA-232 -F inputs to 5-V TTL/CMOS levels. These receivers have a typical threshold of 1.3 V, a typical hysteresis of 0.5 V, and can accept ±30-V inputs. Each driver converts TTL/CMOS input level into TIA/EIA-232-Flevels.The driver, receiver, and voltage-generator functions are available as cells in the Texas Instruments.

It should be noted that the MAX232(A) is just a driver/receiver. It does not generate the necessary RS-232 sequence of marks and spaces with the right timing, it does not decode the RS-232 signal, it does not provide a serial/parallel conversion. All it does is to convert signal voltage levels. Generating serial data with the right timing and decoding serial data has to be done by additional circuitry.

Fig 2.7 Pin out Diagram

2.5 DC MOTOR DRIVER MODULE

The L293 and L293D are quadruple high-current half-H drivers. The L293 is designed to provide bidirectional drive currents of up to 1 A at voltages from 4.5 V to 36 V. The L293D is designed to provide bidirectional drive currents of up to600-mA at voltages from 4.5 V to 36 V. Both devices are designed to drive inductive loads such as relays, solenoids, dc and bipolar stepping motors, as well as other high-current/high-voltage loads in positive-supply applications. All inputs are TTL compatible. Each output is a complete totem-pole drive circuit, with a Darlington transistor sink and a pseudo-Darlington source. Drivers are enabled in pairs, with drivers 1 and 2 enabled by 1,2EN and drivers 3 and 4 enabled by 3,4EN. When an enable input is high.

The associated drivers are enabled and their outputs are active and in phase with their inputs. When the enable input is low, those drivers are disabled and their outputs are off and in the high-impedance state. With the proper data inputs, each pair of drivers forms a full-H (or bridge) reversible drive suitable for solenoid or motor applications.A VCC1 terminal, separate from VCC2, is provided for the logic inputs to minimize device power dissipation. The L293and L293D is characterized for operation from 0°C to 70°C.

Fig: 2.8 pin out diagram of L293D

The L293D is a 16-pin chip with a little notch cut out of the front of it. Orient the chip so its notch matches the notch in the shape of the chip on the PCB. Carefully drop the chip into the gold-plated pads, and solder it into place from the other side. To avoid any nasty punctures, clip off any excess pins that poke through the pads on the solder side.

2.6 DC MOTOR

A DC motor is designed to run on DC electric power. Two examples of pure DC designs are Michael Faraday's homopolar motor (which is uncommon), and the ball bearing motor, which is (so far) a novelty. By far the most common DC motor types are the brushed and brushless types, which use internal and external commutation respectively to create an oscillating AC current from the DC source—so they are not purely DC machines in a strict sense.

The classic DC motor design generates an oscillating current in a wound rotor, or armature, with a split ring commutator, and either a wound or permanent magnet stator. A rotor consists of one or more coils of wire wound around a core on a shaft; an electrical power source is connected to the rotor coil through the commutator and its brushes, causing current to flow in it, producing electromagnetism.

Many of the limitations of the classic commutator DC motor are due to the need for brushes to press against the commutator. This creates friction. At higher speeds, brushes have increasing difficulty in maintaining contact. Brushes may bounce off the irregularities in the commutator surface, creating sparks. (Sparks are also created inevitably by the brushes making and breaking circuits through the rotor coils as the brushes cross the insulating gaps between commutator sections.

Depending on the commutator design, this may include the brushes shorting together adjacent sections—and hence coil ends—momentarily while crossing the gaps. Furthermore, the inductance of the rotor coils causes the voltage across each to rise when its circuit is opened, increasing the sparking of the brushes.) This sparking limits the maximum speed of the machine, as too-rapid sparking will overheat, erode, or even melt the commutator.

The making and breaking of electric contact also causes electrical noise, and the sparks additionally cause RFI. Brushes eventually wear out and require replacement, and the commutator itself is subject to wear and maintenance (on larger motors) or replacement (on small motors).

Fig: 2.9DC motor

When the activation signal for forward motion is HIGH, q3 is on and in turn switches Q1 and Q6. So now the motor rotates and rover moves forward. When the signal for reversing is high, transistors Q2,Q4,Q5 are ON. This makes the rover do the reverse motion.

2.7 SOFTWARE

2.7.1 INTRODUCTION TO EMBEDDED C

Embedded C is a C language extension. Embedded C is designed to bridge the performance mismatch between Standard C and the embedded hardware and application architecture. It aims to provide portability and access to common performance- increasing features of processors used in the domain of and embedded processing. The Embedded C specification extends the C language to support freestanding embedded processors in exploiting the multiple address space functionality, user-defined named address spaces, and direct access to processor and I/O registers. These features are common for the small, embedded processors used in most consumer products.

The Embedded C specification for fixed-point, named address spaces, and named registers gives the programmer direct access to features in the target processor, thereby significantly improving the performance of applications. The hardware I/O extension is a portability feature of Embedded C. Its goal is to allow easy porting of device-driver code between systems.

2.7.2 EMBEDDED C

An embedded hardware device, depending on its size and capabilities, can have an operating system—such as embedded Linux—with limited or minimal functionality compared to a desktop version. For very small embedded devices, an OS might be entirely absent: it is not possible to write programs, compile, and run and debug the code in such small devices. In such a situation, it is necessary to use cross compilers (or assemblers), which compile programs written in a high-level language on a host system (typically a PC) and generate code for a target system (for example, an embedded device). If we write assembly programs and use an assembler running on a host to generate code for a target device, it is a cross assembler. So, we can write programs on our PC generate code for the embedded device and run it there. This solves the problem of creating executable code for embedded systems, but testing, debugging or tracing embedded programs are difficult.

2.7.3 FRONT END: VISUAL BASIC.NET:

Visual basic .NET is the next generation of the Visual Basic language from Microsoft. With Visual Basic you can build .NET applications quickly and easily. Applications made with Visual Basic are built on the services of the common language runtime and take advantage of the .NET Framework.Visual Basic has many new and improved features such as inheritance, interfaces, and overloading that make it a powerful object-oriented programming language. Other new language features include free threading and structured exception handling. Visual Basic fully integrates the .NET Framework and the common language runtime, which together provide language interoperability, garbage collection, enhanced security, and improved versioning support. Visual Basic supports single inheritance and creates Microsoft intermediate language (MSIL) as input to native code compilers.

Visual Basic is comparatively easy to learn and use, and Visual Basic has become the programming language of choice for hundreds of thousands of developers over the past decade. An understanding of Visual Basic can be leveraged in a variety of ways, such as writing macros in Visual Studio and providing programmability in applications such as Microsoft Excel, Access and Word. Visual Basic.NET, the next generation of the Visual Basic language, is a fast and easy way to create .NET-based applications. Visual Basic .NET has many new and improved features that make it a powerful object-oriented programming language, including inheritance, interfaces, and overloading. Other new language features include free threading and structured exception handling. Visual Basic .NET also fully integrates the .NET Framework and the Common Language Runtime, which provide language interoperability, garbage collection, enhanced security, and improved versioning support

Chapter 3

CIRCUIT DIAGRAM

Fig 3.1 Circuit Diagram

3.1 CIRCUIT DIAGRAM DISCRIPTION

The figure: 3.1 show the circuit diagram. MAX 232 is used for controlling the arms. The microcontroller used in arms exoskeleton is AT 8952. The signals from the MAX 232 are inputted to the AT8952 for operations. Driver circuit in this is L293D driver for controlling the motors. Three 1293D circuits are used in it. The main functions of L293D are to provide sufficient power and control signals to the DC motor.

The +5 volt supply is useful for both analog and digital circuits.TTL, and CMOS ICs will all operate nicely from a +5 volt supply. In addition, the +5 volt supply is useful for circuits that use both analog and digital signals in various ways. More importantly for our purposes, the +5 volt supply will be used as the primary reference for regulating all of the other power supplies we will build. We'll see how this works after completing the basic +5 volt supply.

The +5 volt power supply is based on the commercial 7805 voltage regulator IC. This IC contains all the circuitry needed to accept any input voltage from 8 to 18 volts and produce a steady +5 volt output, accurate to within 5% (0.25 volt). It also contains current-limiting circuitry and thermal overload protection, so that the IC won't be damaged in case of excessive load current; it will reduce its output voltage instead. The 1000µf capacitor serves as a "reservoir" which maintains a reasonable input voltage to the 7805 throughout the entire cycle of the ac line voltage. The two rectifier diodes keep recharging the reservoir capacitor on alternate half-cycles of the line voltage, and the capacitor is quite capable of sustaining any reasonable load in between charging pulses.

This microcontroller is used for checking the code transmitted from the switches and. In order to maximize the performance and parallelism, the area uses Harvard architecture- with separate memories and buses for program and data. Instructions in the program memory are executed with the single level pipelining. While one instruction is being executed, the instruction is pre-fetched from the program memory.

The program memory is In-System Re-Programmable Flash memory. The fast access register file contains 32 x 8 bits general purpose working registers with a single clock cycle access time. This allows single-cycle arithmetic logic unit (ALU) operations. In a typical area operation, two operands are output from the register file, the operation is executed, and the result is stored back in the register file- in one clock cycle.

Motor is a electrical device that convert electrical energy in to mechanical energy. When AC current passes through the coil the armature rotates.Here the motor is used to controll the arm movements. 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.

There are many ways to strengthen a signal so it’s strong enough to drive a large load like a motor. Transistors H-bridges circuit, buffer chips, and dedicated motor driving chips are all suitable candidates, with their own benefits and limitations. For our ‘Secret’ motor driver, we wanted something that would take standard TTL inputs and make a standard servo our slave. You see, standard servos use a “Pulse Width Modulated” signal to tell a servo where to rotate to.PWM works by sending a rapid train of high/low signals to the servo’s regular driver brains, and depending on how different the high signal is from the low signal, the servo moves to the according position. PWM is great if you don’t want to rotate much more than 180°, which is fine for actuators, but not for driving wheels. With our ‘Secret ’motor driver and a bit of servo hacking, we’ are going to lobotimize and turn a standard servo into something more useful - a small, compact, powerful gear motor! It’ll be something you can use very simple input signals to control its rotation. We’ll even throw in a 5V regulator hack if you want to clamp the voltage right at the servo.

Chapter 4

EMBEDDED MODULE

An embedded system is a special-purpose computer system designed to perform a dedicated function. Unlike a general-purpose computer, such as a personal computer, an embedded system performs one or a few pre-defined tasks, usually with very specific requirements, and often includes task-specific hardware and mechanical parts not usually found in a general-purpose computer. Since the system is dedicated to specific tasks, design engineers can optimize it, reducing the size and cost of the product.

Embedded systems are often 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. In terms of complexity embedded systems run from simple, with a single microcontroller chip, to very complex with multiple units, peripherals and networks mounted inside a large chassis or enclosure.

Mobile phones or handheld computers share some elements with embedded systems, such as the operating systems and microprocessors which power them, but are not truly embedded systems themselves because they tend to be more general purpose, allowing different applications to be loaded and peripherals to be connected.

4.1 OVERVIEW

Embedded systems run the computing devices hidden inside a vast array of everyday products and appliances such as cell phones, toys, handheld PDAs, cameras, and microwave ovens. Cars are full of them, as are airplanes, satellites, and advanced military and medical equipments. As applications grow increasingly complex, so do the complexities of the embedded computing devices. The goal of this course is to develop a comprehensive understanding of the technologies behind the embedded systems design. The students develop an appreciation of the existing capabilities and limitations of various steps in overall design methodology - modeling/specification, exploration, partitioning, synthesis (hardware/software/interface), and validation/verification of embedded systems

4.2 CHARACTERISTICS OF EMBEDDED SYSTEM

Embedded systems are designed to do some specific task, rather than be a general-purpose computer for multiple tasks. Some also have real-time Performance constraints that must be met, for reason such as safety and usability; others may have low or no performance requirements, allowing the system hardware to be simplified to reduce costs.
Embedded systems are not always separate devices. Most often they are physically built-in to the devices they control.
The software written for embedded systems is often called firmware, and is stored in read-only memory or Flash memory chips rather than a disk drive. It often runs with limited computer hardware resources: small or no keyboard, screen, and little memory.

4.3 ADVANTAGES OF EMBEDDED SYSTEM

Ø Higher performance: The integration of various ICs shortens the traveling route and time of data to be transmitted resulting in higher performance.

Ø Lower power consumption: The integration of various ICs eliminates buffers and other interface circuits. As the number of components is reduced, less power will be consumed.

Ø Slimmer and more compact: Housed in a single separate package, the chip is smaller in size and therefore occupies less space on the PCB. Hence products using embedded system are slimmer and more compact.

Ø Reduced design and development system: The system on a chip provides all functionality required by the system. System designers need not worry about the basic function of the system-right from the beginning of the design phase, they can focus on the development features. As a result, the time spends on research and development is reduced and this in turn reduces the time to market of their products.

Ø Lower system costs: In the past, several chips in separate packages were required to configure a system. Now, just one system on-chip can replace all of these, dramatically reducing the packaging cost.

Chapter 5

FLOW CHART

Chapter 6

PROGRAM

#include <reg51.h>

unsigned char mybyte;

sbit motor1_for=P2^0;

sbit motor1_rev=P2^1;

sbit motor2_for=P2^2;

sbit motor2_rev=P2^3;

sbit motor3_for=P2^4;

sbit motor3_rev=P2^5;

sbit motor4_for=P2^6;

sbit motor4_rev=P2^7;

sbit motor5_for=P1^0;

sbit motor5_rev=P1^1;

void delay()

{

unsigned int i;

for(i=0;i<=60000;i++)

{

;

}

void init_motor()

{

motor1_for=0;

motor1_rev=0;

motor2_for=0;

motor2_rev=0;

motor3_for=0;

motor3_rev=0;

motor4_for=0;

motor4_rev=0;

motor5_for=0;

motor5_rev=0;

}

void main(void){

TMOD=0x20; //use Timer 1, mode 2

TH1=0xFD; //4800 baud rate

SCON=0x50;

TR1=1;

while (1) {

while (RI==0); //wait to receive

mybyte=SBUF; //save value

//write value to port

RI=0;

if(mybyte=='A')

{

motor1_for=1;

motor1_rev=0;

delay();

init_motor();

}

if(mybyte=='C')

{

motor2_for=1;

motor2_rev=0;

delay();

init_motor();

}

if(mybyte=='E')

{

motor3_for=1;

motor3_rev=0;

delay();

init_motor();

}

if(mybyte=='G')

{

motor4_for=1;

motor4_rev=0;

delay();

init_motor();

}

if(mybyte=='I')

{

motor5_for=1;

motor5_rev=0;

delay();

init_motor();

}

//send('A');

//delay();

if(mybyte=='B')

{

motor1_for=0;

motor1_rev=1;

delay();

init_motor();

}

if(mybyte=='D')

{

motor2_for=0;

motor2_rev=1;

delay();

init_motor();

}

if(mybyte=='F')

{motor3_for=0;

motor3_rev=1;

delay();

init_motor();

}

if(mybyte=='H')

{

motor4_for=0;

motor4_rev=1;

delay();

init_motor();

}

if(mybyte=='J')

{

motor5_for=0;

motor5_rev=1;

delay();

init_motor();

}

SBUF=mybyte; //place value in buffer

while (TI==0);

TI=0;

}

Chapter 7

PCB DESIGN AND FABRICATION

Fig 7.1 PCB Design and Fabrication

7.1 PCB DESIGN PROCEDURES

The PCB designing procedure consists of following steps.

7.2 DRAWING THE CIRCUIT SCHEMATIC

Drawing of the circuit is done through EAGLE (Easily applicable Graphic Layout Editor) schematic capture software. It includes many libraries with thousands of component symbols. We can select the required symbols from the library and place if in the schematic. After placing the component symbols, we can complete the interconnection using wire or bus control.

The next is to assign to part reference. Each component has to be assigned footprint or PCB pattern name. The footprint gives the actual size physicals, representation of components on the PCB artwork. The component symbol and foot symbol should correspond in all respects.

7.3 DESIGN RULE CHECK AND NET LIST CREATION

After the circuit is schematic is completed with all required information such as part reference and footprints. The design rule check can be used for checking errors in the design it will check for duplicate symbol, overlapped lines and dangling lines.

After the schematic design and file passes the DRC, check, it is processed by a program called a electric rule checker (ERC), that checks for wiring errors. The final operation to be done before starting PCB artwork is the list creation.

A net creation of components and interconnection along with other information such as footprint, track width, etc. A net list software or tool can take the circuit schematic as input and generate net list. The net list can be used as an information source for the remaining stages.

7.4 CREATING THE PCB ART WORK

In automatic design, the net list obtained from the previous stages is used for getting the required footprint and interconnections. The software used for the PCB network design is the ORCAD layout.

The steps in PCB design are:

Ø Loading the net list, the net list generates has to be loaded in to the PCB software when starting a new design. Operation being with bringing all component footprints on design screen with a nest of interconnection. This interconnection indicates connection between the pins of components and which helps in routing and placing.

Ø Drawing board outline and placing component: depending upon the density of component and connections, we have to design the size the board, accordingly outline the PCB has to drawn, saves as a barrier, to limit routing only inside the board outlines. Then the components of the footprint have to be placed to in optimum position to make the routing samples spaces referring to the schematic diagram and the nest. The software automatically recalculates the minimum interconnection distance through routing. In placing, aesthetic is also a factor of consideration.

Ø Routing: It is the interconnection of component using copper track of required width. Before starting routing the following thing must be done.

7.5 ENABLING OR DISABLING THE REQUIRED LAYERS

q Enabling the no of layers used and enabling in artwork depends upon the complexity of the circuit and fabrication technology available. If the board is single sided enable only bottom as solder side layer as tracks cane only on one side of the PCB. If double sided board is required, enable bottom and component side. If the circuit is much more complex you enable the required number or inner layer considering the fabrication technique and cost.

q Assigning width to each net and route spacing we can assign a desired width for each net in the circuit depending upon the amount of flowing through it.

q Loading the strategy and technology files. These are some mechanical data, which help to adjust the routing the meet the specified technology at routing strategy. After doing the desired steps, routing can be done manually for automatically.

q Manually routing- in these cases the designed has to manually connect each track. This time consuming process, but is necessary in some cases. In this case also software checks for errors and reports them.

q Automatic routing- in this type of routing the software employs the standard routing algorithm to calculate the routing path and error checking in full digital circuits also routing can be used successfully.

7.6 PCB DESIGN ISSUES

Using capture software, there are cases when connection cannot be given by were due to complexity of interconnection. In those cases connections are given though net aliening. The link to the library manager enables to fine to footprint of the component after capture is done.

The components are placed on the board so as to form minimum interconnections. After placement they require width for track were set up power lines are provided with grater width than signal lines. Next the layer for routing and jumper are specified. Since the board is single sided, only bottom layer is enabled.

Top layer is enabled as jumper layer where vertical and horizontal jumpers are loaded.

Pad stacks were taken and width of pads changed. The pads were converted from square to round. The next step is post processing top layer, bottom layer, and component layer can be taken separately.

Chapter 8

ADVANTAGES

· It is very helpful to handicapped man.

· It helps all movement of an human hand.

· It is just like a real hand.

· It has long life.