Robo Fest Document How to Build a Line

8/6/2019 Robo Fest Document How to Build a Line

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How to build a basic line following Robot

6/27/2011


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Contents

CONTENTS .......................................................................................................................................... 2

LIST OF FIGURES .............................................................................................................................. 3

INTRODUCTION ............................................................................................................................... 4

HOW TO BUILD A BASIC LINE FOLLOWING ROBOT ............................................................ 5

Required Items ................................................................................................................................................ 5

PIC 16F877A ....................................................................................................................................................... 5

DC motor Gear box............................................................................................................................................. 5

Chassis plate ....................................................................................................................................................... 6

Wheel sets .......................................................................................................................................................... 6

Trackball ............................................................................................................................................................. 6

L293D IC ............................................................................................................................................................. 7

LM324 IC ............................................................................................................................................................ 8

IR Transmitters and Receivers ............................................................................................................................ 8

L7805 voltage regulator ................................................................................................................................... 11

PIC microcontrollers ...................................................................................................................................... 11

Pic programming............................................................................................................................................ 12


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List of Figures

Figure 1 ................................................................................................................................................... 5

Figure 2 ................................................................................................................................................... 5

Figure 3 ................................................................................................................................................... 6

Figure 4 ................................................................................................................................................... 6

Figure 5 ................................................................................................................................................... 6

Figure 6 ................................................................................................................................................... 6

Figure 8 ................................................................................................................................................... 7

Figure 7 ................................................................................................................................................... 7

Figure 9 ................................................................................................................................................... 8

Figure 10 ................................................................................................................................................. 8

Figure 11 ................................................................................................................................................. 9

Figure 12 ............................................................................................................................................... 11

Figure 13 ............................................................................................................................................... 11

Figure 15 ............................................................................................................................................... 12

Figure 14 ............................................................................................................................................... 12

Figure 16 ............................................................................................................................................... 13

Figure 17 ............................................................................................................................................... 14

Figure 18 ............................................................................................................................................... 14
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Introduction

School competitors of SLIIT Robofest 2011 should develop a line following robot. This

document will give the basic guidelines to develop a line following robot.

Remember this is only a basic guide.

(You do not need to limit only these components)


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How to build a basic line following Robot

Required Items

Following items should be purchased to develop a line following robot.

Microcontrollers (Ex:- PIC 16f877A) DC Motor gear box Chassis plate Wheel sets Operational Amplifiers (Ex:- LM324 IC) Motor controllers (Ex:- L293D IC) Trackball L7805 voltage regulator IR Transmitters and Receivers

Details of these items are given bellow.

PIC 16F877A

DC motor Gear box

Figure 1

Figure 2


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Chassis plate

Wheel sets

Trackball

Figure 4

Figure 3

Figure 5

Figure 6


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L293D IC

This is a 14 pin IC which we can use to interface two DC motors. It contains two H-Bridges

which can control the direction of two dc motors (both clockwise and anti-clockwise). L293D

has output current of 600mA and peak output current of 1.2 A per channel. The output supply

(VCC2) has a wide range from 4.5 V to 36 V. Moreover for protection of circuit from back

EMF, output diodes are included within the IC.

(Further details refer data sheets)

Figure 8

Figure 7


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LM324 IC

IR Transmitters and Receivers

Infra-Red LED is used as a source of infrared rays. It comes in two packages, 3mm or 5mm.

3mm is better as it requires less space. IR sensor is nothing but a diode, which is sensitive for

infrared radiation.

This infrared transmitter and receiver are called as IR TX-RX pair. It can be obtained from

any decent electronics component shop and costs less than 40Rs. The above snap shows 3mm

and 5mm IR pairs.

Colors of IR transmitter and receiver are different. However you may come across pairs

which appear exactly same or even has opposite colors than shown in above picture and it is

not possible to distinguish between TX and RX visually. In case you will have to take help of

millimeter to distinguish between them.

You can design the IR transmitter and receiver circuit as shown in the diagram given below.

It has 4-Infrared sensors to detect black tracking path. When the some sensors detect black

color output of the associated comparators, LM324, are low logic and the other the outputs

are high. Due to this logic, when the sensor detects black color, LED is lighted up and for

other colors (such as white) it will not light up.

Figure 9

Figure 10


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Figure 11


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These are some IR sensor patterns you can use to detect the Black line. However number of

sensors can be varied.

(1)

(2)

(3)


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L7805 voltage regulator

Last two digits of LM78XX indicate output voltage. For an example assume if it is LM7805,

last two digits are 05 and they indicate that regulator IC output is 5V.

PIC microcontrollers

PIC Microcontrollers are quickly replacing computers when it comes to programming roboticdevices. These microcontrollers are small and can be programmed to carry out a number of

tasks and are ideal for school and industrial projects. A simple program is written using a

computer; it is then downloaded to a microcontroller which in turn can control a roboticdevice. Click on the sections below to view a detailed explanation

Figure 12

Figure 13


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Pic programming

Figure 15

The microcontroller executes the program loaded in its Flash memory. This is the so called

executable code comprised of seemingly meaningless sequence of zeros and ones. It is

organized in 12-, 14- or 16-bit wide words, depending on the microcontrollers architecture.

Every word is considered by the CPU as a command being executed during the operation ofthe microcontroller. For practical reasons, as it is much easier for us to deal with hexadecimal

Figure 14


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number system, the executable code is often represented as a sequence of hexadecimal

numbers called Hex code. It is used to be written by the programmer. All instructions that the

microcontroller can recognize are together called the Instruction set. As for PIC16F

microcontrollers the programming words of which are comprised of 14 bits, the instruction

set has 35 different instructions in total.

Figure 16

As the process of writing executable code was endlessly tiring, the first human friendly

programming language called assembly language was created. The truth is that it made the

process of programming more complicated, but on the other hand the process of writing

programs stopped being a nightmare. Instructions in assembly language are represented in the

form of meaningful abbreviations, and the process of their compiling into executable code is

left over to a special program on a PC called Assembler. The main advantage of this

programming language is its simplicity, i.e. each program instruction corresponds to one

machine instruction in the microcontroller. It enables a complete control of what is going on

within the chip, thus making this language commonly used today.

However, programmers have always needed a programming language close to the languagebeing used in everyday life. As a result, the higher programming languages have been

invented. One of them is C. The main advantage of these languages is simplicity of program

writing. It is no longer possible to know exactly how each command executes, but it is no

longer of interest anyway. In case it is, a sequence written in assembly language can always

be inserted in the program, thus enabling it.


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Figure 17

Similar to assembly language, a specialized program in a PC called Compiler is in charge of

compiling program into machine language. Unlike assemblers, these create an executable

code which is not always the shortest possible.

Figure 18

The above figure gives a rough illustration of what is going on during the process of

compiling the program from higher to machine language.


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Basic line following robot include three main parts.

Chassis part Motor controller part Sensor circuit part

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Robo Fest Document How to Build a Line