Line Follower Robot

Mini project 2011

Line follower robot

ACKNOWLEDGEMENT All glory and honour to god all mighty who showered his grace on us to make this endeavor a success. We take this oppurtunity to express our heart felt gratitude and thanks to our principal Prof.P.V.SUGATHAN for Providing Provi ding the facilities fa cilities for our studies studi es and constant encouragement in all achievement. We would like to express profound gratitude to our Head of the department, Mr. RAMACHANDRAN.C, for his encouragement and for providing all facilities fo r carrying out this project. We also extend our heart felt gratitude towards our mini project coordinator Mr.Lalji cyriac and Mr.Anoop. for their valuable guidance and help towards the completion c ompletion of the projec t and providing pr oviding us with the required require d facilities facil ities for completing this project project . We express our sincere thanks to all staff members of department of electronics electr onics and communicat c ommunication ion engineering engineer ing who helped us with their t heir support. Last but not least we would like to thank our parents and friends and friends for their support and encouragement throughout the project.

1 Dept. Of Electronics and communication Engg.

College of engineering Thalassery

Mini project 2011

Line follower robot

ABSTRACT Line following robot is a robo car that can follow a path. The path can be visible like a white line on the black surface (or vice-verse). As a result of this line following property it has many applications in future and now itself. Line following robot with pick and placement capabilities are commonly used in manufacturing plants. These move on a specified path to pick the component from specified location and place them on desired locations. Basically,a line-following robot is self operating robot that detects and follows a line drawn on the floor. The path to be taken is indicated by a white line on a black surface. The control system used must sense the line and manoeuvre the robot to stay on course while constantly correcting the wrong moves using feedback mechanism,thus forming a simple yet effective closed-loop system. As a programmer you get an opportunity to µteach¶ the robot how to follow the line thus giving it a human-like property of responding to stimuli. The robot has two s ensors installed installed underneath the front part of t he body, body, and two DC motors drive wheels moving forward. A circuit inside takes an input signal from two sensors and controls the speed of wheels¶ rotation. The control is done in such a way that when a sensor senses a white line, the motor slows down or even stops. Then the difference of rotation speed makes it possible to make turns.



Mini project 2011

Line follower robot

CONTENTS 1.INTRODUCTION................. 1.INTRODUCTION....... .................... .................... .................. ................. ................. .................. .................. ........ 04 2.BLOCK DIAGRAM..................... DIAGRAM............................. .................. .................... .................... .................. ................. ......... 05 3.BLOCK DIAGRAM EXPLANATION........... EXPLANATION.................... ................... .................... ................06 ......06 4.CIRCUIT DIAGRAM..........................................................................07 5.COMPONENT STUDY.......................................................................08 6.CIRCUIT 6.CIRCUIT DESCRIPTION.............. DESCRIPTION........................ .................... ................... ................... .............. .... ..........15 ..........15 7.WORKING................. 7.WORKING........................... .................... ................... ................... ............... ..... ...................... ..............................17 ........17 8.SOFTWARE SECTION................. SECTION........................... .................. .............. ...... .................. ............................ ............19 ..19 9.HARDWARE SECTION.................... SECTION.............................. ................... ......... .................. ............................ ............22 ..22 10.CONSTRUCTION.............. 10.CONSTRUCTION...................... ............. ..... .................. .................... ........... ................. .................. .............26 ...26 11.PCB LAYOUT...................... LAYOUT.............................. .................. .................... ............. ... .................. ............................ ............27 ..27 12.COMPONENT LAYOUT.................... LAYOUT............................ ................ ........ .................. ............................ ............28 ..28 13.LIST OF TOOLS & EQUIPMENTS REQUIRED........................ REQUIRED.......................... ...29 14.COMPENENTS 14.COMPENENTS REQUIRED.................. REQUIRED............................ .......... ................. ......................... .............. ...... ..30 15.PRECAUTIONS............ 15.PRECAUTIONS...................... .................. .................. ................... ............ ... ................. ......................... .............32 .....32 16.APPLICATIONS.............. 16.APPLICATIONS...................... .................. .................... ................... ......... ................. ........................... .............33 ...33 17.LIMITATIONS............ 17.LIMITATIONS...................... .................. .................. .................. ................. ................. .......... ................. ..................34 .34 18.CONCLUSION................ 18.CONCLUSION.......................... .................. ............... ....... .......................... .................................. .................3 .........35 5 19.REFERENCE.......... 19.REFERENCE.................... .................... .................... ................. ................ ................... .................. .................. ............ .. ..36 20.APPENDIX««««««««««««««««««««««...37



Mini project 2011

Line follower robot

1.INTRODUCTION The line following robot, operates as the name specifies. It is programmed to follow a white line on a dark background and detect turns or deviations and modify the motors appropriately. It consist of sensors,comparators,microcontroller and motor drivers.We uses darlington phototransistor as the sensor. The core of the robot is the AT89C51 microcontroller.Here it act as a decision making device. It consist of two dc motors and driver ic to steer it. The differential steering system is used to turn the robot. In this system, each back wheel has a dedicated motor while the front wheels are free to rotate. To move in a straight line, both the motors are to be rotate at same speed.To manage a turn a motor is to stop at correct circumstances according to sensor output.



Mini pro jec 2011

Line follower robot



2.B

C

R M



Mini project 2011

Line follower robot

3.BLOCK DIAGRAM EXPLANATION Fig.1 show the block diagram of automated line following robot. It consist of mainly four parts: two sensors,two comparators,one decision making device and two motor drivers. The robot is built using micro controller AT89C51,motor driver L293D,operational amplifier LM324,phototransistor and a few discrete components.In the circuit, the sensor are used to detect the white strip on a black background. The sensor output is fed to the microcontroller, which takes the decision and gives appropriate command to motor driver L293D so as to move the motor accordingly

3.1 sensor:

The sensor senses the light reflected from the surface and feeds the

output to the comparator. When the sensor is above the white background the light falling on it from the source reflects to the sensor, and when the sensor is above the black background the light from the source doesn¶t reflect to it. The sensor senses the reflected light to give an output, which is fed to the comparator.

3.2 comparator:

The comparator compares the analogue inputs from sensors

with a fixed reference voltage. If this voltage is greater than thereference voltage the comparator outputs a low voltage, and if it smaller the comparator generates a high voltage that acts as input for decision-making device(microcontroller).

3.3 microcontroller:

The micro controller is programmed to make the robot move

forward,turn right or left based on the input coming from the comparator. The outputs of the microcontroller are fed to the motor driver.

3.4 motor driver:

The current supplied by the microcontroller to drive the motor

is small. Therefore a motor driver ic is used. It provides sufficent current to drive the motor.



Mini project 2011

Line follower robot

4.CIRCUIT DIAGRAM



Mini pro ject 2011

Line follower robot

5.C M 5.1 Operati

STUDY

al ampli ier

An op amp i a hi h-ga in, di

t-coupl d di

ntial linear ampli ier whose response

character istics are externa ll controlled by nega ti e feedback from the out put to the input. OP amps, widely used in computers, can perform ma thema tical operations such as summing,

integration, and differentiation. OP amps are a lso used as video and audio amplif iers, oscillators, etc. in the communication electronics. Because of their versa tility op amps are widely used in all branches of electronics both in digital and linear circu its. OP amps lend

themselves readily to IC manufactur ing techni ues. Improved I C manufactur ing techni ues, the op amp's adap tability, and ext ensive use in the design of new equ i pment have brought t he pr ice of IC ops amps from very h igh to very reasonab le levels. These facts ensure a very substantial role for the IC op amp in electronics Fig shows the symbol for an op amp. Note that the operational amplif ier has two inputs marked (-) and (+) . The minus input is the inver ting input. A signal applied to the minus

terminal will be shif ted in phase 180° a t the out put. The plus input is the non- inver ting input. A signal app lied to the plus terminal will appear in the same phase a t the out put as at the

input. Because of the complexity of the internal circuitry of an op amp, the op amp symbo l is used exclusively in circuit diagrams.



Mini project 2011

IC

Line follower robot

LM324 LM 324 is a low power quad operational amplifier which we uses in our project as

comparator. The LM124 series consists of four independent, high gain, internally frequency compensated operational amplifiers which were designed specifically to operate from a single power supply over a wide range of voltages. Operation from split power supplies is also possible and the low power supply current drain is independent of the magnitude of the power supply voltage. Application areas include transducer amplifiers, DC gain blocks and all the conventional op amp circuits which now can be more easily implemented in single power supply systems. For example, the LM124 series can be directly operated off of the standard +5V power supply voltage which is used in digital systems and will easily provide the required interface electronics without requiring the additional ±15V power supplies. features

 Internally frequency compensated for unity gain  Large DC voltage gain 100 dB  Wide bandwidth (unity gain) 1 MHz (temperature compensated)  Wide power supply range: Single supply 3V to 32V or dual supplies ±1.5V to ±16V  Very low supply current drain (700 A)-essentially independent of supply voltage  Low input biasing current 45 nA (temperature compensated)  Low input offset voltage 2 mV and offset current: 5 nA  Input common-mode voltage range includes ground  Differential input voltage range equal to the power supply voltage



Mini pro ject 2011

Line follower robot

5.2 Phototransistor We uses L14F1 pho totrans istor as the sensors in our circu it. The standard symbol of a phototransistor, which can be regarded as a conven tional trans istor housed in a case that enables its semiconduc tor junctions to be exposed to ext erna l light. The device is norma lly used with its base open c ircu it, in either of the conf igurations shown in f ig. 5.9.2, and functions as follows.

Fig. 5.9.1Phototransistor symbol.

In practice, the collector and emitter current of the transistor are vir tually identical and, since the base is open circu it, the device is not sub jected to signif icant nega tive feedback . The sensitivity of a phototrans istor is typically one hundred times great er than that of a photodiode, but is usefu l maximum operating frequency (a few hundred k iloher t ) is propor tionally lower than that of a photodiode by us ing only its base and co llector terminals



Mini pro ject 2011

Line follower robot

and ignor ing the emitter, as shown in f ig.5.10.2. Phototransistors are solid-state light detectors with interna l gain that are used to provide ana log or digital signals. They det ect visi ble, ultraviolet and near-infrared light from a var iety of sources and are more sensitive

than

photodiodes,

semiconduc tor

devices

that

require

a

pre-amplif ier .

Phototransistors feed a pho tocurrent out put into the base of a sma ll signal transistor . For each

illumination level, the area of the exposed co llector-base junction and the D C current gain of the trans istor def ine the out put.

Fig. 5.9.2. Phototransistor used in circuit

The base current from the incident photons is amplif ied by the ga in of the trans istor, resulting in current gains that range from hundreds to severa l thousands. R esponse ti me is a function of the capacitance of the collector-base junction and the va lue of the load res istance. Photodar lingtons, a common type of phototrans istor, have two stages of ga in and can prov ide net gains great er than 100,000. Because of their ease of use, low cost and compati bility with

transistor-trans istor logic (TTL), phototransistors are of ten used in applications where more than severa l hundred nano wa tts (nW) of op tical power are ava ilable. Selecting phototrans istors requ ires an ana lysis of performance spec if ications. Collector current is the

total amount of current that f lows into the collector terminal.

Collector dark curren t is t he

amount of collector current for which there is no op tical input. Typ ica lly, both collector



Mini project 2011

Line follower robot

current and collector dark current are measured in milliamps (mA). Peak wavelength, the wavelength at which phototransistors are most responsive, is measured in nanometers (nm). Rise time, the time that elapses when a pulse waveform increases from 10% to 90% of its maximum value, is expressed in nanoseconds (ns). Collector-emitter breakdown voltage is the voltage at which phototransistors conduct a specified (nondestructive) current when biased in the normal direction without optical or electrical inputs to the base. 5.3

AT89C 51 microcontroller The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with

4Kbytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmel¶s high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51 instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications. Features Compatible with MCS-51 Products 4K Bytes of In-System Reprogrammable Flash Memory Endurance: 1,000 Write/Erase Cycles Fully Static Operation: 0 Hz to 24 MHz Three-level Program Memory Lock 128 x 8-bit Internal RAM 32 Programmable I/O Lines Two 16-bit Timer/Counters



Mini project 2011

Line follower robot

Six Interrupt Sources Programmable Serial Channel Low-power Idle and Power-down Modes AT89C51 is the decision making device in our project. We uses port 3 of the controller as input and the decision is fed out through port2. We uses 12 Mhz crystal oscillator for giving clock pulse. The port 3 output is fed to motor driver and to motor to steer the robocar.

5.4

L293D DR IVER IC

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. 13 Dept. Of Electronics and communication Engg.


Mini project 2011

Line follower robot

The L293D is assembled in a 16 lead plastic package which has 4 center pins connected together and used for heat sinking.

5.5

DC MOTOR An electric motor converts electrical energy into mechanical energy. A DC motor is

an electric motor that runs on direct current (DC) electricity.

The DC electric motor generates torque directly from DC power supplied to the motor by using internal commutation, stationary permanent magnets, and rotating electrical magnets. Like all electric motors or generators, torque is produced by the principle of Lorentz force, which states that any current-carrying conductor placed within an external magnetic field experiences a torque or force known as Lorentz force. Advantages of a brushed DC motor include low initial cost, high reliability, and simple control of motor speed. Disadvantages are high maintenance and low life-span for high intensity uses. Maintenance involves regularly replacing the brushes and springs which carry the electric current, as well as cleaning or replacing the commutator . These components are necessary for transferring electrical power from outside the motor to the spinning wire windings of the rotor inside the motor.



Mini project 2011

Line follower robot

6.CIRCUIT DESCRIPTION The fig.4.1 shows the circuit of automated line following robot. When light falls on the phototransistor(say,T1), it goes into saturation and starts conducting. When no light falls on the phototransistor it is cut-off. A white LED (LED2) has been used to illuminate the white path on a black background. Phototransistor T1 and T2 are used for detecting the white path on the black background. Collector of phototransistor T1 and T2 are connected to the inverting inputs of operational amplifier A2 and A1. The signal voltage at the inverting input of the operational amplifier is compared with the fixed reference voltage, which is formed by a potential divider circuit of 5.6-kilo-ohm resistor and 10-kilo-ohm preset. This reference voltage can be adjusted by changing the value of the 10-kilo-ohm preset. When sensor T2 is above the black surface, it remains cut-off as the black surface absorbs virtually all the light falling from LED2 and no light is reflected back. The voltage at the inverting input (pin2) of operational amplifier A1 is higher than the reference voltage at its non inverting input(pin3) and therefore the amplifier output at pin1 becomes zero. When sensor T2 ia above the white line, the light gets reflected from the white surface to fall on phototransistor T2. Phototransistor T2 goes into saturation and conducts. The inverting input (pin2) of operational amplifier A1 goes below the reference voltage at its non inverting input (pin 3) of operational amplifier A1 and therefore output pin 1 goes high. This way, the comparator outputs logic µ0¶ for black surface and logic¶1¶ for white surface. Similarly, comparator A2 compares the input voltage from phototransistor T1 with a fixed reference voltage. The outputs of operational amplifier A1 and A2 are fed to microcontroller AT89C51. The AT89C51 is an 8-bit microcontroller having 4kB of flash, 128 bytes of RAM,32 I/O lines, two 16-bit timers/counters,a five-vector two level interrupt architecture, onchip oscillator and clock circuitary. A 12 Mhz crystal is used for providing the basic clock frequency. All I/O pins are reset to µ1¶ as soon as RST pin goes high. Holding RST pin for two machine cycles while oscillator is running resets the device. Power on reset is derived from resistor R5 and capacitor C1. Switch S2 is used for manual reset. The microcontroller,



Mini project 2011

Line follower robot

based on the inputs from sensor T1 (say left) and sensor T2 (say right), controls the motor to make the robot turn left, turn right or move forward. Port pins P2.0, P2.1, P2.2 and P2.3 are connected to pins 15,10,7 and 2 of motor driver L293D. Port pins P2.0 and P2.1 are used for controlling the right motor, while port pins P2.2 and P2.3 are used for controlling the left motor.



Mini pro ject 2011

Line follower robot

7.WOR

ING

Fig 7.1

Fig

7. 1

shows the path of line follower robot. Where µL¶ is the lef t sensor and µ R ¶ is

the r ight sensor . At the star t when the robot is at point µA¶ sensors T1 and T 2 are above the black surface and por t pins P3.0 and P3.1 of the microcontroller recieve logic¶0¶. As a result the robot moves forward in straight direction. At point µB¶, a lef t turn is encountered, and the lef t sensor comes above the whtie surface, whereas the r ight sensor rema ins above the black surface. Por t pin P3.0 of the microcontroller recieves logic¶0¶ from the r ight sensor . As a resu lt lef t motor stops and t he r ight motor rotates, to make robot turn lef t. This process con tinues until lef t sensor comes above the black background. Similr ly, at point µC¶, where a r ight turn is encountered, the same procedure for r ight



Mini project 2011

Line follower robot

turn is excecuted. When both sensors are at white surface, the robot should stop. The output of the microcontroller depends on the input recieved at its port pins P3.0 and P3.1 as shown in table below



Mini project 2011

Line follower robot

8.SOFTWARE SECTION The source program for the project is written in the Assembly language and assembled using Metalink¶s ASM51 assembler,which is freely available on the internat for download. It is well commented for easy understanding and works as per the flow-chart shown in fig.8.1



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Line follower robot

8.1 pro ram $MOD51 ORG 0000h LJMP MAIN ORG 0030h MAIN:

SETB p3.0 ;input for left sensor SETB p3.1 ;input for right sensor

AGAIN:

JB p3.0,NEXT JB p3.1,GO CLR p2.0 SETB p2.1 CLR p2.2 SETB p2.3 SJMP AGAIN

GO:

CLR p2.0 SETB p2.1 CLR p2.2 CLR p2.3 SJMP AGAIN

NEXT:

JB p3.1,go1 CLR p2.0



Mini project 2011

Line follower robot

CLR p2.1 CLR p2.2 SETB p2.3 SJMP AGAIN GO1:

CLR p2.0 CLR p2.1 CLR p2.2 CLR p2.3 SJMP AGAIN

HERE:

SJMP HERE END

The above program is of extension .ASM since it is written in assembly language. So in order to burn this program to microcontroller using burner, we need to convert this .ASM file to .HEX file. We should use a µasm to hex converter¶ which is a software freely available on internet. The generated hex code is then burnt into the microcontroller unit (MCU) usinga suitable Atmel 89 series programmer such as one from Sunrom Technologiesor Frontline Electronics. You shouldnot remove the microcontroller from the zero insertion force (ZIF) socket until the programming is complete.

Steps for installation Install ASM51 to computer-Type the program in notepad or similar editors-save the program as .ASM in the same folder where ASM51 installed-Open ASM51.EXE from the folder and type name of saved file-Then two files which have extensions .HEX and .LST generated.



Mini project 2011

Line follower robot

9.HARDWARE SECTION PCB DESIGN & FABR ICATION 9.1 PCB DESIGN Designing of PCB is a major step in the production of PCB is a major. It forms a distinct factor in electronic performance and reliability. The productivity of a PCB, its assembly and service ability also depends on the design. The designing of a PCB consists of designing of the layout followed by the preparation of th e artwork. The layout should include all the relevant aspects in details of the PCB design while the art work preparation brings it to the form required for the production process. The layout can be designed with the help of anyone of the standard layout edition software such as Eagle, Orcad or Edwin XP. Hence a concept, clearly defining all the details of the circuits and partly of the equipment, is a prerequisite and the actual layout can start. Depending on the accuracy required, the artwork might be produced a 1:1 or 2:1 even 4:1 scale. It is best prepared on a 1:1 scale. You need to generate a positive (copper black) UV translucent art work film. You will never get a good board without good art work, so it is important to get the best possible quality at this stage. The most important thing is to get a clear sharp image with a very solid opaque black. Art work is done using ORCAD software. It is absolutely essential that your PCB software prints holes in the middle of pads, which will act as centre marks when drilling. It is virtually impossible to accurately hand-drill boards without these holes. If you are looking to buy PCB software at any cost level and want to do hand-protyping of boards before production, check that this facility is available when defining pad and line shapes, the minimum size recommended (through-linking holes) for reliable result is 50 mil, assuming 0.8mm drill size; 1 mil=(l/1000) th of an inch. You can go smaller drill sizes, but through linking will be harder. 65 mil round or square pads for normal components. ICs, with 0.8 mm hole, will allow a 12.5mil, down to 10mil if you really need to. Center-tocentre spacing of 12.5 mil tracks should be 25 mil-slightly less may be possible if your printer can manage it. Take care to preserve the correct diagonal track-track spacing on



Mini project 2011

Line follower robot

mitered corners; grid is 25 mil and track width 12.5mil. The art work must be printed such that the printed side is in contact with PCB surface when exposing, to avoid blurred edges. In practice, this means that if you design the board as seen from the component side, the bottom (solder side) layer should be printed the 'correct' way round, and top side of the double-sided board must be printed mirrored

9.2 ETCHING Ferric chloride etchant is a messy stuff, but easily available and cheaper than most alternatives. It attacks any metal including stainless steel. So when setting up a PCB etching area, use a plastic or ceramic sink, with plastic fitting and screws wherever possible, and seal any metal screws with silicon. Copper water pipes may be splashed or dripped-on, so sleeve or cover them in plastic; heat-shrink sieving is great if you are installing new pipes. Fume extraction is not normally required, although a cover over the tank or tray when not in use is a good idea. You should always use the hex hydrate type of ferric chloride, which should be dissolved in warm water until saturation. Adding a teaspoon of table salt helps to make the etchant clearer for easier inspection. Avoid anhydrous ferric chloride. It creates a lot of heat when dissolved. So always add the powder very slowly to water; do not add water to the powder, and use gloves and safety glasses. The solution made from anhydrous ferric chloride doesn't etch at all, so you need to add a small amount of hydrochloric acid and leave it for a day or two. Always take extreme care to avoid splashing when dissolving either type of ferric chloride, acid tends to clump together and you often get big chunks coming out of the container and splashing into the solution. It can damage eyes and permanently stain clothing. If you are making PCBs in a professional environment where time is money you should get a heated bubble-etch tank. With fresh hot ferric chloride, the PCB will etch in well under 5 mins. Fast etching produces better edge-quality and consistent line widths. If you aren't using a bubble tank, you need to agitate frequently to ensure even etching. Warm the etchant by putting the etching tray inside a larger tray filled with boiling water.



Mini project 2011

Line follower robot

9.3 DR ILLING If you have fiber glass (FR4) board, you must use tungsten carbide drill bits. Fiber glass eats normal high-speed steel (HSS) bits very rapidly, although HSS drills are alright for older larger sizes (> 2mm). Carbide drill bits are available as straight-shank or thick-shank. In straight shank, the hole bit is the diameter of the hole, and in thick shank, a standard s ize (typically about 3.5 mm) shank tapers down to the hole size. The straight-shank drills are usually preferred because they break less easily and are usually cheaper. The longer thin section provides more flexibility. Small drills for PCB use usually come with either a set of collets of various sizes or a three-jaw chuck. Sometimes the 3-jaw chuck is an optional extra and is worth getting for the time it saves on changing collets. For accuracy, however, 3-jaw chucks are not brilliant, and small drill sizes below 1 mm quickly formed grooves in the jaws, preventing good grip. Below 1 mm, you should use collets, and buy a few extra of the smallest ones; keeping one collet per drill size as using a larger drill in a collet will open it out and it no longer grips smaller drills well. You need a good strong light on the board when drilling, to ensure accuracy. A dichroic halogen lamp, under run at 9V to reduce brightness, can be mounted on a microphone gooseneck for easy positioning. It can be useful to raise the working surface above 15 cm above the normal desk height for more comfortable viewing. Dust extraction is nice, but not essential. and occasional blow does the trick! A foot-pedal control to switch the drill 'off and 'on' is very convenient, especially when frequently changing bits. Avoid hole sizes less than 0.8 mm unless you really need them. When making two identical boards, drill them both together to save time. To do this, carefully drill a 0.8 mm whole in the pad near each corner of each of the two boards, getting the center as accurately as possible. For larger boards, drill a hole near the centre of each side as well. Lay the boards on the top of each other and insert a 0.8 mm track pin in two opposite corners, using the pins as pegs to line the PCBs up. Squeeze or hammer the pins into boards, and then into the remaining holes. The two PCBs are now µnailed¶ together accurately and can be drilled together.

9.4 SOLDER ING Solderin is a process in which two or more metal items are joined together by melting and

flowing a filler metal into the joint, the filler metal having a relatively low melting point. Soft 24 Dept. Of Electronics and communication Engg.


Mini project 2011

Line follower robot

soldering is characterized by the melting point of the filler metal, which is below 400 °C (752 °F). The filler metal used in the process is called solder . Soldering is distinguished from brazing by use of a lower melting-temperature filler metal. The filler metals are typically alloys that have melting temperatures below 350 °C. It is distinguished from welding by the base metals not being melted during the joining process which may or may not include the addition of a filler metal. [2] In a soldering process, heat is applied to the parts to be joined, causing the solder to melt and be drawn into the joint by capillary action and to bond to the materials to be joined by wetting action. After the metal cools, the resulting joints are not as strong as the base metal, but have adequate strength, electrical conductivity, and water-tightness for many uses.

9.41 Solders: Soldering filler materials are available in many different alloys for differing applications. In electronics assembly, the eutectic alloy of 63% tin and 37% lead (or 60/40, which is almost identical in performance to the eutectic) has been the alloy of choice. Other alloys are used for plumbing, mechanical assembly, a nd other applications. An eutectic formulation has several advantages for soldering; chief among these is the coincidence of the liquidus and solidus temperatures, i.e. the absence of a plastic phase. This allows for quicker wetting as the solder heats up, and quicker setup as the solder cools. A non-eutectic formulation must remain still as the temperature drops through the liquidus and solidus temperatures. Any differential movement during the plastic phase may result in cracks, giving an unreliable joint. Additionally, a eutectic formulation has the lowest possible melting point, which minimizes heat stress on elec tronic components during soldering. Other common solders include low-temperature formulations (often containing bismuth), which are often used to join previously-soldered assemblies without un-soldering earlier connections, and high-temperature formulations (usually containing silver ) which are used for hightemperature operation or for first assembly of items which must not become unsoldered during subsequent operations.



Mini project 2011

Line follower robot

9.42 Flux: In high-temperature metal joining processes (welding, brazing and soldering), the primary purpose of flux is to prevent oxidation of the base and filler materials. Tin-lead solder, for example, attaches very well to copper, but poorly to copper oxides (which form quickly at soldering temperatures). Flux is nearly inert at room temperature, yet becomes strongly reductive when heated. This helps remove oxidation from the metals to be joined, and inhibits oxidation of the base and filler materials. Secondarily, flux acts as a wetting agent in the soldering process, reducing the surface tension of the molten solder and causing it to better wet out the parts to be joined.

10.CONSTRUCTION Three wheels can be used fr this robot-one on the front and two at the rear. Front wheel can rotate in any direction as specified by the rear wheel. Construction also requires two side brackets for mounting motors,chasis etc. Castor wheel can be used for front wheel.



Mini project 2011

Line follower robot

11.PCB LAYOUT



Mini project 2011

Line follower robot

12.COMPONENT LAYOUT



Mini project 2011

Line follower robot

13.LIST OF TOOLS AND INTRUMENTS REQUIRED

Following tools and instruments are used for preparing the project 1.

Soldering iron

2.

Desoldering pump

3.

Drill Machine

4.

Multimeter

5.

Filer

6.

Tweezers

7.

Screw driver

8.

Power supply

9.

Flux

10.

Desoldering wick

11.

Petrol

12.

Brush

13.

Soldering Wire



Mini project 2011

Line follower robot

14.COMPONENTS REQUIRED SI.No

NAME OF THE COMPONENT

QUANTITY

PRICE

1.

AT89C51

1

55

2.

IC L293D

1

80

3.

IC LM324

1

18

4.

L14F1 PHOTOTRANSISTOR

2

40

5.

IN 4007 DIODE

1

2

6.

5MM LED

2

1.50

7.

RESISTOR 10K

3

.25

8.

RESISTOR 5.6K

2

.25

9.

RESISTOR 330

1

.25

10.

RESISTOR 220

1

.25

11.

RESISTOR 10K-PRESET

2

5

12.

CAPACITORS 10 F/16V ELECTROLYTIC

1

.5

13.

CAPACITORS 33 pF CERAMIC

2

.75

14.

CAPACITORS 47 F/16V ELECTROLYTIC

1

.5

15.

CAPACITORS .1F CERAMIC

1

.75

16.

ON/OFF SWITCH

1

2

17.

PUSH TO ON SWITCH

1

10

18.

CRYTAL OSCILLATOR 12 MHz

1

15

19.

6V DC GEARED MOTOR

2

20

20.

BATTERY 1.5V

4

9



Mini project 2011

Line follower robot

21.

40 PIN IC BASE

1

1

22.

16 PIN IC BASE

1

1

23.

14 PIN IC BASE

1

1

TOTAL=260



Mini project 2011

Line follower robot

15.PRECAUTION As we were dealing with a phototransistor we need to control the natural light, since our sensor is even sensitive to sun light. So we need to place our sensor under the chasis. Position of LED is quite important to us since it is the source of light to be reflected back to sensors.



Mini project 2011

Line follower robot

16.APPLICATIONS Industrial automated equipment carriers Entertainment and small household applications. Automated cars. Tour guides in museums and other similar applications. Second wave robotic reconnaissance operations. Future application:-can replaces trolleys in indudtries,road trains....



Mini project 2011

Line follower robot

17.LIMITATIONS Choice of line is made in the hardware abstraction and cannot be changed by software. Calibration is difficult, and it is not easy to set a perfect value. The steering mechanism is not easily implemented in huge vehicles and impossible for non-electric vehicles (petrol powered). Few curves are not made efficiently, and must be avoided. Lack of a four wheel drive, makes it not suitable for a rough terrain. Use of IR even though solves a lot of problems pertaining to interference, makes it hard to debug a faulty sensor. Lack of speed control makes the robot unstable at times.



Mini project 2011

Line follower robot

18.CONCLUSION

For a test, I held my robot in the air then two wheels rotated as expected and I approached a white paper to sensors. Then, corresponding wheels stopped as expected. Hence our product is working as per theory . Next, I put it down on the track, but unfortunately, it didn¶t move. I found the torque of motors not enough to drive my robot. Even though the chosen DC motor was slowest and gave highest torque among other DC motors in the lab, it wasn¶t enough. For solving this problem, I will have to find a suitable DC motor with large torque and it even moves through perfect plains. Overall, the robot project wasn¶t successful, but it was quite a fun to go through all the process. I also realized that there were many things to consider practically such as installation of motors, building up a circuit by soldering and putting all parts together. This experience hopefully would be helpful in the future work.



Mini project 2011

Line follower robot

19.REFERENCE/BIBILOGRAPHY Efy magazine september 2009 1.

[Online] // Wikipedia. - www.wikipedia.com.

2.

[Online] // circuits today. - www.circuitstoday.com.

3.

[Online] // electronics schematics. - www.electroschematic.com.

4.

[Online] // electronics for you. - www.efy.com.



Line Follower Robot

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