report on wall follower by rvndr s.w

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WALL FOLLOWER ROBOT BY: TEAM VICTORY Page 1

PREFACE

Difference in the academic life & practical life is revealed when enters the real life & competitive world of industry where there is a cut throat competition & one has to forcefully follow the theory of Charles Darwin Survival of Fittest. In order to exist in the competitive world one has to be fully aware of all aspects of industrial life. To meet this requirement in our engineering curricula, provision of practical training program has been made.

The Practical Training is an essential requirement for an engineering student. The student has to take the training for the pre-described period as per the university norms. The purpose of training is to help the student to gain industrial experience. Moreover, as for the utility of training concerning, it can be said that student gets an opportunity during his training to imply the theoretical knowledge in the field work & to clear the difficulties in a better way.

This report has been written with the intention of bringing together and tying up some of the loose ends of analogue and digital circuit design, those parts that are never mentioned in the textbooks and rarely admitted elsewhere. This report is includes the circuit diagram of the various circuit like motor driver, sensors, controller etc. but it exclude the specification of the Ics. This is also comprises of the controller description & also brief description of normally used controller for the purpose of selecting any controller for our purpose. In this report some of the design issues related to the grounding of the circuit is also discuss but the detail description of the design issues of the robot design is beyond the scope of the report.

The report should be written in a clear & unambiguous language so that the reader can also objectively judge the adequacy & the validity of report. It is hoped that these will facilitate the use of the report in self study & that the upcoming practicing engineer will find the text useful in updating himself in this fast moving field.

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ACKNOWLEDGEMENT

I would like to express my deep feelings of gratitude and indebtedness to all those people who are responsible for the successful completion of my practical training. There are some individuals without whom this practical training would never reach its final outcome.

We would like to thank our mentor Er. Arun Grover and team of Victory Coaching and Training Centre, Sri Ganganagar, played a vital role in the completion of the practical training. It is with pleasure we express our deep sense of gratitude and profound thanks to our beloved for there support during our stressful times and soothed frayed nerves. We thank them for all their patience and support.

We would also like to convey our thanks to all our faculty members and our friends who have helped us directly or indirectly during the course of our report entitled Basic Embedded System Design in the field of Robotics for its successful completion.

With regards and gratitude,

RAVINDER KUMAR

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Theory

1. Introduction to Robotics

In practical usage, a Robot is a mechanical device which performs automated physical tasks, either according to direct human supervision, a pre-defined program, or a set of general guidelines using artificial intelligence techniques. Robots are typically used to do the tasks that are too dirty, dangerous, difficult, repetitive or dull for humans. This usually takes the form of industrial robots used in manufacturing lines. Other applications include toxic waste cleanup, underwater and space exploration, mining, search and rescue, and mine finding. Recently however, robots are finding their way into the consumer market with uses in entertainment, vacuum cleaning, and lawn mowing. A robot may include a feedback-driven connection between sense and action, not under direct human control, although it may have a human override function. The action may take the form of electro-magnetic motors or actuators (also called effectors) that move an arm, open and close grips, or propel the robot. The step by step control and feedback is provided by a computer program run on either an external or embeddedcomputer or a microcontroller. By this definition, a robot may include nearly all automated devices. Ask a number of people to describe a robot and most of them will answer they look like a human. Interestingly a robot that looks like a human is probably the most difficult robot to make. It is usually a waste of time and not the most sensible thing to model a robot after a human being.

Mobile Robots:

Fig 1.Mars Explorer image

Mobile robots are able to move, usually they perform task such as search areas. A prime example is the Mars Explorer, specifically designed to roam the mars surface.

Mobile robots are a great help to such collapsed building for survivors Mobile robots are used for task where people cannot go. Either because it is too dangerous of because people cannot reach the area that

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needs to be searched.

Rolling Robots: Rolling robots have wheels to move around. These are the type of robots that can quickly and easily search move around. However they are only useful in flat areas, rocky terrains give them a hard time. Flat terrains are their territory.

Fig 2. rolling robots

Can be divided in two categories:

Walking Robots: Robots on legs are usually brought in when the terrain is rocky and difficult to enter with wheels. Robots have a hard time shifting balance and keep them from tumbling. Thats why most robots with have at least 4 of them, usually they have 6 legs or more. Even when they lift one or more legs they still keep their balance. Development of legged robots is often modeled after insects or crawfish.

Stationary Robot:Robots are not only used to explore areas or imitate a human being. Most robots perform repeating tasks without ever moving an inch. Most robots are working in industry settings. Especially dull and repeating tasks are suitable for robots. A robot never grows tired; it will perform its duty day and night without ever complaining. In case the tasks at hand are done, the robots will be reprogrammed to perform other tasks.

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Autonomous robots: Autonomous robots are self supporting or in other words self contained. In a way they rely on their own brains.

Autonomous robots run a program that gives them the opportunity to decide on the action to perform depending on their surroundings. At times these robots even learn new behavior. They start out with a short routine and adapt this routine to be more successful at the task they perform. The most successful routine will be repeated as such their behavior is shaped. Autonomous robots can learn to walk or avoid obstacles they find in their way. Think about a six legged robot, at first the legs move ad random, after a little while the robot adjust its program and performs a pattern which enables it to move in a direction.

2. Introduction to sensors

A sensor is a type of transducer. A sensor is a device that converts a physical phenomenon into an electrical signal. As such, sensors represent part of the interface between the physical world and the world of electrical devices, such as computers. The other part of this interface is represented by actuators, which convert electrical signals into physical phenomena. Sensors are used in everyday life. Applications include automobiles, machines, aerospace, medicine, industry and robotics.

The ability to trace objects is a trait that has enabled humans to manipulate the environment. Without the ability to see, we would not be able to do our work. It makes sense, then, to provide sensor to our robot creations so they can manipulate objects and use tools. Sensors are extremely important for any robot.

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We can talk about sensors in general, but in an application like Micro mouse, we can customize the discussion so the sensors are optimized for this application. There are vast numbers of sensors used in robotics. A robotic sensor is used to detect an object around him. Robotic sensors come in a variety of styles. They can be photo diodes, phototransistors, photo resistors (LDR), photocells, TSOP, piezoelectric crystals and many others.Purposes:

Sensors on a robot serve several purposes. The first purpose is to make sure the robot can detect errors. Errors are a way of life. Sensitive sensors that can detect slight errors can help the robot correct errors before errors accumulate to a level that can no longer be corrected.The second purpose of sensors on a robot is to sense the obstacle in between the path of the robot. The range of the sensor gives our robot time to stop or decrease or increase the speed save the time in the competitions.

Types of Sensor:

On the basis of signal detection method :

Different sensors require different sensing strategies. There are three modes of signal detection used by sensors:1. Through-beam detection2. Reflex detection.

Through beam detection method:

The through-beam method requires that the source and detector are positioned opposite each other and the light beam is sent directly from source to detector. When an object passes between the source and detectors, the beam is broken; signal shows the detection of an object. Through-beam detection generally provides the longest range of the three operating modes and provides high power at shorter range to penetrate steam, dirt, or other contaminants between the source and detector. Alignment of the source and detector must be accurate.

Reflex detection method:

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The reflex method requires that the source and detector are installed at the same side of the object to be detected. The light beam is transmitted from the source to a retro reflector that returns the light to the detector. When an object breaks a reflected beam, the object is detected.The reflex method is widely used because it is flexible and easy to install and provides the best cost-performance ratio of the three methods. The object to be detected must be less reflective than retro reflector.

Proximity detection method:

The proximity requires that the source and detector are installed on the same side of the object to be detected and aimed at a point in front of the sensor. When an object passes in front of source and detector, light from the source is reflected from the objects surface back to the detector, and the object is detected. The only difference between reflex detection & proximity method is reflection of signal from retro reflector and from object to be detected. Each sensor type has a specific operating range. In general through-beam sensor offer the greatest range, followed by reflex sensors, then by proximity sensors.

2.1 Some commonly used sensors

1. LED-LDR SENSOR:

An LED-LDR sensor circuit is very simple and cheap before moving to discuss the details first we understand the working of light dependent resistor. A photoresistor is made of a high-resistance semiconductor. If light falling on the device is of high enough frequency, photons absorbed by the semiconductor give bound electronsenough energy to jump into the conduction band. The resulting free electron (and its hole partner) conduct electricity, thereby lowering resistance.LDRs or Light Dependent Resistors are very useful especially in light/dark sensor circuits. Normally the resistance of an LDR is very high, sometimes as high as 1000 000 ohms, but when they are illuminated with light resistance drops dramatically.

Explation:

Transmitter: the current coming to the base of the transistor is passing through a current limiting resistor of 1K. This current made the transistor to work in the active region and the voltage at the collector is low hence LED light up and send

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light to the receiver.

Receiver: When the light level is low (no light detected) the resistance of the LDR is high. This prevents current from flowing to the base of the transistors. Consequently the LED does not light. However, when light shines onto the LDR its resistance falls and current flows into the base of the first transistor and then the second transistor. This makes the collector voltage low & indicating LED lights.

The output of the circuit is taken from the indicating LED anode point. The preset resistor can be turned up or down to increase or decrease resistance, in this way it can make the circuit more or less sensitive. The illumination of the indicating LED is also increase by reducing the value of 470 resistor to 200. Table shows the practical parameter value.

Problem:

The main problem of using LED-LDR is the problem of its very much sensitivity to the environment light. As the environment changes (i.e. the light conditions) the variable resistance (pot) needs to be adjusted in order to maintain its proper working. By changing the value of the resistance of the pot, we change the value of voltage applied at the base of transistor BC 547 due to potential divider network and thus brings the transistor in active region. To save the LDR from the environment light cover it properly. So it is better to use IR transmitter receiver sensor circuit, which is less affected by the environment.

2 SIMPLE INFRARED LIGHT PROXIMITY SENSORS

Light may always travel in a straight line, but it bounces off nearly everything. You can use this to your advantage to build an infrared collision detection system. You can mount several infrared bumper sensors around the periphery of your robot. They can be linked together to tell the robot that something is out there, or they can provide specific details about the outside environment to a computer or control circuit. This is the simplest of all range nding sensors. An IrED shines IR to a potential wall, and a phototransistor picks up the intensity of the reected radiation. In theory, the intensity is the inverse of distance squared.

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Explation:

In the you can see the merger of the three circuit transmitter, receiver & comparator. The IR-LED transmit the light whish is not visible with the naked eyes but can see by mobile camera because it works in the infrared region. This light is absorb by the photo diode when it detect the light its resistance decrease & current get the least resistance path to the ground. Because of this phenomenon the voltage at inverting end of the comparator is low & output of the comparator is high & indicating LED off. When light is not detecting the voltage at the inverting end is high & output of the comparator is low. The output given by the comparator is fed to the controller which works on the TTL logics.

Sensitivity can be adjusted by changing the value of R2; reduce the value to increase sensitivity. An increase in sensitivity means that the robot will be able to detect objects farther away. A decrease in sensitivity means that the robot must be fairly close to the object before it is detected.

Bear in mind that all objects reflect light in different ways. Youll probably want to adjust the sensitivity so the robot behaves itself best in a room with white walls. But that sensitivity uses an infrared phototransistor.

Lists of parts for infrared proximity sensor

R1 270 resistorR2 10K resistorQ1 Infrared sensitive phototransistorLED1 Infrared light-emitting diode

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3 TSOP1738 SENSORS

The circuit designed as per the previous works fine but there is a limitation of the range of the sensors. The problem of range can be solved by using TSOP1738 as the IR receiver. This TSOP receiver normally find in the TV remote control systems.

By changing the modulation frequency of the IR LED, we can estimate the range to an object from the IR LED and TV remote control, which allows you to decide whether to take immediate evasive action or slightly alter the course of the robot. This is the normal IR receiver used in the common TV remotes. It receives a signal of 38 kHz. This device is active low i.e. when the sensor does not receive a signal its output is high while the output goes low when it receives the signal. Giving a signal of 38 kHz gives a range of 25-30 cms in the reflected signal which is sufficient for detecting an obstacle and stops the robot. Hence this is a better choice than the normal IR receivers which provide a range of not more than 5-10 cms. The circuit diagram for the IR transmitter and TSOP1738 is given as below.The opaque barrier is there between the TSOP & IR LED to ensure there is not a direct path from the IR LED to the TV remote control.

3 ULTRASONIC SENSOR:

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Ultrasonic sensing is an example of reflective sensing. The sensor usually consists of a transmitter and receiver pair and responds to variation in the amount of reflected energy detected by the receiver. The transmitter emits a high frequency sound wave, which reflects off the object and is detected by the receiver, where the Time-of-Flight (TOF) information can be calculated. The range of the object can be determined from the TOF data if the speed of the sound wave is a known constant. These sensors are accurate over distances of several meters, with their accuracy dependant on the span of the transmitted signal.

Accuracy of sensor:

Accuracy only applies to sensors that are supposed to be calibrated. For calibrated sensors of a particular make/model, the output is supposed to relate to some physical quantities regardless of the individual sensor. For example, if a sensor is sensing a wall & it gives in the output a voltage of 1.6v then we have to examine the interfacing issues because if we use a controller with TTL compatibility then for that it is logic low but we want that if sense the wall then it should be logic 1 hence we have to use interfacing logics.

If we use number of sensor than each individual one is almost guaranteed to output a different voltage at the same distance from an object. Hence we have to study the design issues of that circuit or refer data sheet.

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3. Motors

Motors come in many sizes and types, but their basic function is the same. Motors of all types serve to convert electrical energy into mechanical energy. They can be found in VCR's, elevators, CD players, toys, robots, watches, automobiles, subway trains, fans, space ships, air conditioners, refrigerators, and many other places. The performance of the motor is very important in circuit design. This is because the electrics motors directly affect its speed and pushing capability. Motorperformance information is needed to select the required speed. The currentrequirements from the motor will dictate what type and size batteries will need andthey are also a factor in determining the minimum current requirements for motorspeed controllers. DC Motor:

DC motors seem quite simple. Apply a voltage to both terminals, and it willspin. DC motors are non-polarized which means that it can reverse voltage so themotor will rotate in two directions, forward and backward. Typical DC motors arerated from about 6V-12V. The larger ones are often 24V or more but for the purpose of this project, it is necessary to use 6V-12V range motor. Voltage is directly related to motor torque. The more voltage supplied, the higher the torque will be produce. Specifications of most DC motors show high revolutions per minute (rpm) and low torque.

Fig. D.C. motor

From the start, DC motors seem quite simple. Apply a voltage to both terminals, and it spins. But what if you want to control which direction the motor spins? Correct, you reverse the wires. Now what if you want the motor to spin at half that speed? You would use less voltage. But how would you get a robot to do those things autonomously? How would you know what voltage a motor should get? Why not 50V instead of 12V? What about motor overheating? Operating motors can be much more complicated than you think. DC motors are non-

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polarized - meaning that you can reverse voltage without any bad things happening. Typical DC motors are rated from about 6V-12V. The larger ones are often 24V or more. But for the purposes of a robot, you probably will stay in the 6V-12V range. So why do motors operate at different voltages? As we all know (or should), voltage is directly related to motor torque.

STEPPER MOTORS:

Stepper motors differ from standard DC motors in such a way that they have two independent coils which can be independently controlled. As a result, stepper motors can be moved by impulses to precede exactly a single step forward or backward, instead of a smooth continuous motion in a standard DC motor. A typical number of steps per revolution is 200, resulting in a step size of 1.8. Some stepper motors allow half steps, resulting in an even finer step size. There are also a maximum number of steps per second, depending on load, which limits a stepper motors speed.

Stepper motors seem to be a simple choice for building mobile robots, considering the effort required for velocity control and position control of standard DC motors. However, stepper motors are very rarely used for driving mobile robots, since they lack any feedback on load and actual speed (for example a missed step execution). In addition to requiring double the power electronics, stepper motors also have a worse weight/performance ratio than DC motors.

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4. Robot batteries

The robots are no longer limited to bulky low power non-rechargeable batteries, and today there is a large assortment to suit your robots' demands. How are batteries rated? With any battery you will see a voltage and a power rating. Battery voltages can be somewhat complicated. When fully recharged, a battery will often be 15% above its voltage rating. When fully discharged, about 15% below its rating. A fully charged battery will also immediately drop below its rating when driving heavy loads, such as a DC motor. To increase battery voltage, wire multiple of them in series. Batteries also cannot supply an infinite current. So expect batteries of different types but equal voltages to have different current outputs. To increase battery current output, wire multiple of them in parallel. This is why batteries often come in assembled packs of smaller cells. So when using a battery, make sure your circuit handles changes in battery voltage. For the power rating you will see something like 1200mAh. mAh means milliamps per hour. So if it is 1200mAh, that means the battery can supply 1.2 amps for one hour or 2.4 amps for 30 minutes or 0.6 amps for two hours.

Lithium (Li-ion) is the new standard for portable power. Li-ion batteries have the same high energy capacity as NiMHs, power output rates of NiCads, and weigh about 20%-35% less. They also have zero memory effect problems, meaning you can recharge whenever. Although lithium batteries are the most advanced for portable power, they are also the most expensive. Also, they are made out of totally non-toxic material, making them safe for cute squirrels and pretty trees. What is to be remembered is to, lithium ignites very easily, and forms large quantities of hydrogen when put in contact with water, so don't shoot at it or blow it up or anything of that nature. Also, fire extinguishers are usually water based, so dont use them on lithium battery fires.

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5. Microcontroller

Introduction to microcontroller

A microcontroller is a computer with most of the necessary support chips onboard. A Central Processing Unit (CPU) that executes the programs. Some random-access memory (RAM) where it can store data that is variable. Some read only memory (ROM) where programs to be executed can be stored. Input and output (I/O) devices, that enable communication to be established with the outside world i.e. connection to devices such as keyboard, mouse, monitors and other peripherals. There are a number of other common characteristics that define microcontrollers.If a computer matches a majority of these characteristics, then it can be classified as a microcontroller. Microcontrollers may be:

Embedded inside some other device (often a consumer product) so thatthey can control the features or actions of the product. Another name for microcontroller is therefore an embedded controller.

Dedicated to one task and run one specific program. The program is storedin ROM and generally does not change

. A low-power device. A battery-operated microcontroller might consume as

little as 50 mW.

A microcontroller may take an input from the device it is controlling andcontrols the device by sending signals to different components in the device.

A microcontroller is often small and low cost. The components may be chosen to minimize size and to be as inexpensive as possible.

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What is a microcontroller actually?

History of microcontroller:The first single-chip microprocessor was the 4-bit Intel 4004 released in

1971, with the Intel 8008 and other more capable microprocessors becoming available over the next several years. However, both processors required external chips to implement a working system, raising total system cost, and making it impossible to economically computerize appliances.The Smithsonian Institution says TI engineers Gary Boone and Michael Cochran succeeded in creating the first microcontroller in 1971. The result of their work was the TMS 1000, which went commercial in 1974. It combined read-only memory, read/write memory, processor and clock on one chip and was targeted at embedded systems.About 55% of all CPUs sold in the world are 8-bit microcontrollers and microprocessors. According to Semico, over four billion 8-bit microcontrollers were sold in 2006.A typical home in a developed country is likely to have only four general-purpose microprocessors but around three dozen microcontrollers. A typical mid-range automobile has as many as 30 or more microcontrollers. They can also be found in many electrical devices such as washing machines, microwave ovens, and telephones.

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Use of microcontroller in robotics:A microcontroller can be considered a self-contained system with a

processor, memory and peripherals and can be used as an embedded system.[5] The majority of microcontrollers in use today are embedded in other machinery, such as automobiles, telephones, appliances, and peripherals for computer systems. While some embedded systems are very sophisticated, many have minimal requirements for memory and program length, with no operating system, and low software complexity. Typical input and output devices include switches, relays, solenoids, LEDs, small or custom LCD displays, radio frequency devices, and sensors for data such as temperature, humidity, light level etc. Embedded systems usually have no keyboard, screen, disks, printers, or other recognizable I/O devices of a personal computer, and may lack human interaction devices of any kind.

Types of microcontrollers:Microcontrollers can be classified on the basis of internal bus width,

architecture, memory and instruction set. THE 8-BIT MICROCONTROLLER: When the ALU performs arithmetic and logical operations on a byte (8-bits) at an instruction, the microcontroller is an 8-bit microcontroller. The internal bus width of8-bit microcontroller is of 8-bit. Examples of 8-bit microcontrollers are Intel 8051 family and Motorola MC68HC11 family.

THE 16-BIT MICROCONTROLLER:When the ALU performs arithmetic and logical operations on a word (16-bits)

at an instruction, the microcontroller is a 16-bit microcontroller. The internal bus width of16-bit microcontroller is of 16-bit. Examples of 16-bit microcontrollers are Intel 8096family and Motorola MC68HC12 and MC68332 families. The performance and computing capability of 16 bit microcontrollers are enhanced with greater precision as compared to the 8-bit microcontrollers.

THE 32-BIT MICROCONTROLLER:When the ALU performs arithmetic and logical operations on a double word

(32- bits) at an instruction, the microcontroller is a 32-bit microcontroller. The internal bus width of 32-bit microcontroller is of 32-bit. Examples of 32-bit microcontrollers are Intel80960 family and Motorola M683xx and Intel/Atmel 251 family. The performance and computing capability of 32 bit microcontrollers are enhanced with greater precision as compared to the 16-bit microcontrollers.

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Introduction to 8051 microcontroller family:There are a wide range of devices available in the 8051 family, differing in

terms of memory type and capacity, number of counter/timers, types of serial interface, number of input/output ports, clock rates, frequency range, etc. However,there is a commonality among all devices in that they have been developed fromthe core 8051 device with modifications to produce the particular attributes of a different family member. Each member of the 8051 microcontroller family hasbeen designed with improved device specifications in mind and to provide thecustomer with a device to suit particular user requirements.

8051 Microcontroller internal Structure:

Introduction to Microcontroller AT89C2051:The 2051 is a 20 pin version of the 8051. It is a low-voltage, high-

performance CMOS 8-bit microcomputer with 2K bytes of Flash programmable and erasable read only memory. Atmel manufactures the chip using high-density nonvolatile memory technology. The 2051 and is compatible with the industry-standard MCS-51 instruction set. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel 2051 is a powerful microcontroller. It provides a very flexible, cost-effective solution to many embedded control applications.

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Operational features of the 2051:The 2051 features Compatibility with MCS-51 Products, 2K Bytes of

Reprogrammable Flash Memory with 1,000 Write/Erase Cycles. The operating range of the 2051 is 2.7V to 6V. Among these features, the 2051 alsocontains the following features:

Fully Static Operation: 0 Hz to 24 MHz Two-level Program Memory Lock 128 x 8-bit Internal RAM 15 Programmable I/O Lines Two 16-bit Timer/Counters Six Interrupt Sources Programmable Serial UART Channel Direct LED Drive Outputs On-chip Analog Comparator Low-power Idle and Power-down Modes

Pin diagram of 2051 microcontroller:

Pin Description;

Pin Name: Purpose:VCC Supplies voltage and power.

GND Ground.

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Port 1Port 1 is an 8-bit bi-directional I/O port. Port pins P1.2 toP1.7 provide

internal pull-ups. P1.0 and P1.1 require external pull-ups. P1.0 and P1.1 also serve as the positive input (AIN0) and the negative input (AIN1), respectively, of the on-chip precision analog comparator. The Port 1 output buffers can sink 20mA and can drive LED displays directly. When 1s are written to Port 1 pins, they can be used as inputs. When pins P1.2 to P1.7 are used as inputs and are externally pulled low, they will source current (IIL) because of the internal pull-ups. Port 1 also receives code data during Flash programming and verification.

Port 3:Port 3 pins P3.0 to P3.5, P3.7 are seven bi-directional I/O pins with internal

pullups.P3.6 is hard-wired as an input to the output of the on-chip comparator and is not accessible as a general purpose I/O pin. The Port 3 output buffers can sink 20mA. When 1s 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 (IIL) because of the pull-ups. Port 3 also serves the functions of various special features of the AT89C2051 as listed below: Port 3 also receives some control signals for Flash programming and verification.RST: Reset input. All I/O pins are reset to 1s as soon as RST goes high. Holding the RST pin high for two machine cycles while the oscillator is running resets the device.

Power-down Mode of 2051 microcontroller:In the power down mode the oscillator is stopped, and the instruction that

invokes power down is the last instruction executed. The on-chip RAM and Special Function Registers retain their values until the power down mode isterminated. The only exit from power down is a hardware reset. Reset redefines the SFRs but does not change the on-chip RAM. The reset should not be activated before VCC is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize.

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Circuit diagram of 2051:

Where+vcc = +5 voltGnd = 0volt

Addressing mode of 2051 microcontroller:The CPU can access data in various ways. The data could be in a register or

memory. Data can be accessed immediately. Methods of accessing data are called Addressing Modes Various addressing modes of a up are determined when it is designed and therefore cannot be changed by the programmer. The 8051 provides a total of 4 distinct addressing modes.

1. Immediate2. Register3. Direct4. Register Indirect

1. Immediate Addressing mode:

The first addressing mode is basically not an addressing mode; it is just a method to pass the value to be executed as part of the instruction. The immediate value is specified by placing a '#' character in front of the immediate value to be passed. For example look at the following instruction:Add A, #77; Add77 to the accumulator this instruction will add 77 (decimal) to the contents of the accumulator and store the result in accumulator. This method is used when we are required to pass certain integer values into calculation like multiplication and division.

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2. Direct Addressing mode:

It differs from register addressing in that any byte within the first 256 addresses can be accessed by specifying 8-bit address. When using this mode, there is few things watch out for. The first RAM addresses (080h to 0FFh, if the device you are using has RAM at these locations) cannot be accessed by direct memory addressing. If you specify an instruction like : Mov A, 088h you will load the accumulator with the contents of the TCON register located at address 088h rather than the contents of RAM byte.

3. Resistor addressing mode:

Bank addressing mode allows programmer to access a byte in the current register bank. This is most efficient (both in terms of clock cycle and control store) method of accessing data. Most register instruction executes in one register cycle and only requires one byte to execute the instruction. The 8 bytes are known as R0 through R7. For example add A, R2; add content of R2 to accumulator and store result in accumulator.

4. Register Indirect Addressing mode:

As the name indicates it is an indirect mode of addressing. It user R0 or R1 as an 8-bit index register to access a byte in the first 256 addresses of the data space. As: -Orl A, @R0The register indirect addressing mode is identified by the symbol '@' before either R0 or R1. Using any other bank (R2 to R7) will result in an error.

Instruction set for assembly programming of 2051 microcontroller:The instructions for the 8051 device are dependent on the clock frequency and are completed in a number of clock cycles. The basic 8051 device operates on minimum 12 clock cycles per instruction basis and this is reflected in the notes that follow each type of instruction described below.

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A. Mov instructionMOV A,Rn [A]MOV A,direct [A]MOV A,@Ri [A]MOV A,#dat a [A]MOV Rn,A [Rn]

MOV Rn,direct

B. Arithmetic instructionsADD A,Rn [A] < ___ [A] +[Ri]ADD A,direct [A] < ___ [A] + [direct]ADD A,#data [A] < ___ [A] +dataSUBB A,Rn [A] < ___ [A] _ [Rn] _ C_INC A [A] < ___ [A] +1

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6. H-BRIDGE

For most applications we want to be able to do two things with a motor: Run it in the forward and backward directions. Modify its speed.

An H-bridge is what is needed to enable a motor to run forward/backward. . In the next section we will discuss a method called pulse width modulation to change the motor speed. Figure 3.4 demonstrates the H-bridge setup, which received its name from its resemblance to the letter H. We have a motor with two terminals a And b and the power supply with + and -. Closing switches 1 and 2 will connect a with + and b with -: the motor runs forward. In the same way, closing 3 and 4 instead will connect a with - and b with +: the motor runs backward.

The way to implement an H-bridge when using a microcontroller is to use a power amplifier chip in combination with the digital output pins of the controller or an additional latch. This is required because the digital outputs of a microcontroller have very severe output power restrictions. They can only be used to drive other logic chips, but never a motor directly. Since a motor can draw a lot of power (for example 1A or more), connecting digital outputs directly to a motor can destroy the microcontroller.

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Working:The circuit diagram is shown in the fig 3-5 TIP 122 or TIP127 we can use for the switching purpose. These can work at a higher voltage level because these are power transistor. They require 3 V at there base for the purpose of switching then only the transistor come in the active region. For the practical point of view most of the people convert these 4 input into 2 input by combining the Q1, Q4 base & Q2, Q3 base because of that the voltage coming from the controller is divided into parts & because of that the not responds properly. So it is advised for using the 4 input insisted of two.

There are two ways shown in the table but it recommended that not to use the brake condition because it short circuit the transistors and they burn it up. The disadvantage for using that is they generally in from 4 transistor 2 transistor heat up very much you cant touch it hence we use sink for them.

Q1 Q2 Q3 Q4 Direction of rotation

1 0 0 1 Clockwise

0 1 1 0 Anticlockwise

0 0 0 0 Stop

1 1 1 1 brake

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6.1 The L293D

Description:

The Device is a monolithic integrated high voltage, high current four channel driver designed to accept standard DTL or TTL logic levels and drive inductive loads (such as relays solenoids, DC and stepping motors) and switching power transistors. To simplify use as two bridges each pair of channels is equipped with an enable input. A separate supply input is provided for the logic, allowing operation at a lower voltage and internal clamp diodes are included. This device is suitable for use in switching applications at frequencies up to 5 kHz. The L293D is assembled in a 16 lead

plastic package

which has 4 center pins

connected together and used for heat sinking The L293DD is assembled in a 20 lead surface mount which has 8 center pins connected together and used for heat sinking.

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Internal diagram of ln293d

Pin diagram of motor driver

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7. Pulse width modulation

Pulse width modulation or PWM for short is a smart method for avoiding analog power circuitry by utilizing the fact that mechanical systems have certain latency. Instead of generating an analog output signal with a voltage proportional to the desired motor speed, it is sufficient to generate digital pulses at the full system voltage level (for example 5V). These pulses are generated at a fixed frequency, for example 20 kHz, so they are beyond the human hearing range. By varying the pulse width in software (see Figure 3.6, top versus bottom), we also change the equivalent or effective analog motor signal and therefore control the motor speed. One could say that the motor system behaves like an integrator of the digital input impulses over a certain time span. The quotient Duty cycle ton/t period is called the pulse-width ratio or duty cycle.

8. Differential

Drive:

The differential drive design has two motors mounted in fixed positions on the left and right side of the robot, independently driving one wheel each. Since three grounds contact points are necessary, this design requires one or two additional passive caster wheels or sliders, depending on the location of the driven wheels. Differential drive is mechanically simpler than the single wheel drive, because it does not require rotation of a driven axis. However, driving control for differential drive is more complex than for single wheel drive, because it requires the coordination of two driven wheels.

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Differential drive technique

9. Led blinking test code

We are giving a test code for the eight leds connected to the port p1. In common anode configuration, at random as last led off, next led on and so on .The assembly language program for led blinking is as shown below:

$ mod 52;Org #0000h;Mov p1, #00h; make port 1 as output port

Start: mov p1, #01h;Acall delay; wait for some timemov p1, #02h;Acall delay;mov p1, #04h;Acall delay;mov p1, #08h;Acall delay;mov p1, #10h;Acall delay;mov p1, #20h;Acall delay;mov p1, #40h;Acall delay;mov p1,#80h;Acall delay;

Ljmp start; repeat the above codeDelay: mov r1, #0ffh;D1: djnz r1 ,d1;

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Ret;End;

10. Wall Follower Robot

What is a wall follower?

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Wall follower is an autonomous robot which has the capability to follow a wall by keeping a constant distance from it. It takes decision automatically when the wall is detected by its sensors on the left and on the front side of the robot.

Why build a wall follower?Sensing a wall on the left and the front side of the robot, the machine can be

protected by accident with the wall or any other obstacle .so we design a robot capable to do this. Practical applications of a wall follower:

Automated machine running with the wall can avoid the accident.

Prerequisites:

Knowledge of basic digital and analog electronics. Knowledge of the microcontroller, motor driver, sensors. Sheer interest, an innovative brain and perseverance!

Background:By using the principle of the IR sensors and its application to design the line

follower, wall follower robot, I think that it is also possible to design a robot which Can protect itself from an accident. So by modifying the edge avoider robot I design this robot. Here

Sensor 1 left sensor

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Sensor 2 front sensor

Logic for wall follower robot:

We know the work of photo diode sensor (as given above) when the photo diode receives the reflected light from the surface of table then its output is logic 1 and when the light is not received by diode then the output of the sensor is logic 0. When the surface is present then the sensor will give +5 volt (logic 1) as output otherwise it give 0 volt (logic 0) at output.

Sensor 1 Sensor 2 Action taken0 0 Forward0 1 Rotate1 0 forward1 1 rotate

We give the output of these two sensors to the microcontrollers port 1 by making it an input port.The output is taken from the port p3, to control the motor driver IC l293d.The assembly program for controlling the edge avoider robot when the sensor 1 is connected to the p1.2 pin and sensor 2s output is given to p1.3.The motor driver IC is connected to port p3 as;P3.0 enable1P3.1 input 1P3.2 input2P3.3 enable2P3.4 input3P3.5 input4

Program for this is as given below;$mod52org 0000h;mov p1,#0ffh;mov p3,#00h;

main: mov r3,p1;

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cjne r3,#0f3h,case2; sjmp right;case2:cjne r3,#0f7h,case3; sjmp right;case3:cjne r3,#0fbh,case4; sjmp fw;case4:cjne r3,#0ffh,main; sjmp left;

right:mov p3,#6bh; acall delay;

acall delay;acall delay;mov p3,#00h;acall delay;

sjmp main;

left: mov p3,#58h; acall delay;

mov p3,#00h;acall delay;

sjmp main;

fw: mov p3,#5bh; acall delay;

mov p3,#00h;acall delay;mov p3,#58h;acall delay;mov p3,#43;acall delay;

sjmp main;

delay: mov r0,#10h;d2: mov r1,#0ffh;d1: djnz r1,d1;

djnz r0,d2;ret;

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end;

11.CONCLUSION

Thus we have successfully made a robot which has two degrees of freedom, & can avoid its accident with wall on left or the front side of robot without any manual monitoring.

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After some problems during the work at last I will successful to complete this project at time and it works properly according to the condition.

It is avoided to run this robot in the presence of light because the photo diodes are very sensitive to the outside light.

The above problem can be removed by using the IR sensor, or other sensors.

REFERENCES1. www.google.com

2. www.nex-robotics.com

3. www.logicbrigade.com

4. www.8052projects.com

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5. The 8051 microcontroller and Embedded Systems by M.A.Mazidi

6. Www. Wikipedia.com

7. Introduction to Microcontrollers by Unther Gridling Bettina Weiss

8. www.cs.binghamton.edu/~reckert/

9. www.bipom.com

10. www.alldatasheets4u.com

report on wall follower by rvndr s.w

Documents

purpose of training

training centre

utility of training

robot design

validity of report

academic life practical

design issues

controller description