robotics guide(technogenious solutions)

7/29/2019 Robotics Guide(Technogenious Solutions)

1/48

Page1www.technogenious.com [email protected]

Chapter 1: Robots

Introduction

You must have been thinking about what a robot isthe answer is really simple..any

machine that solves your problems, works efficiently and doesnt get tired..

Then whats the difference between a simple machine and a robot. The answer is vague but

generally a robot is a machine with motion. For example you may term a JCB machine as a robot

but not a photocopy machine.

What kinds of skills robot building requires

Robot building =mechanical engg. skills +electronics engg. skills +computer engg. skilss

Mechanical engg. Skills are required mostly for the construction part of the robot. The success of

some kind of robots depend mostly on the construction part e.g. humanoid robots.Their

construction matters a lot to us.

Electronics engg. Skills are required for the circuitry part of the robots. All the robots contain a

bunch of electronic circuits and their interconnections. What components are required and how

to interconnect them is really important for making a robot and thats where electronics skills

jump in.

Computer engg. Skills are required for giving brain to the robot. Most autonomous and semi

autonomous robots require some kind of program instruction to be embedded in them using

which they can find out what they are to do whenever certain event arises.

Types of Robots

Robots are of three types

1.

Manual Robots : These are the robots which have no brain i.e. no intelligence. They justdo what you tell them to do using either a wired or wireless medium.

2. Semi-Autonomous Robots : These are the robots which do have brain but still they needour assistance to work properly.

3. Autonomous Robots: These are the robot which are wholly self contained i.e. they dontneed our assistance to work. They have their own brain and using their brain they decide


2/48


what they are to do. Although this brain is also embedded by us in the robots but after

embedding we dont need to tell them what they are to do.

We will be concerned mostly with autonomous robots and will be discussing them only

throughout the book.

Basic Parts

Now we talk about what basic parts make up a robot.

Robot =Sensor +motors +power source +microcontroller

Microcontroller may be optional in case of very simple robots but its necessary for others.

Sensors are the input devices for the robot and provide information about the environment.Motors are the output devices and are responsible for providing motion to the robot.

Microcontroller is the brain of the system and its where we embed the instructions that form the

intelligence.

Now you are familiar with what makes up a robot. Now we should discuss in detail various parts

of the robots.


3/48


Chapter 2: Sensors

Introduction

Sensors are the input devices that provide information about the environment to the robot. This

information might be related to colour, amount of light, temperature, distance of obstacles etc.

Depending on what kind of information the sensor provides there are a number of sensors. Out of

the available ones we will be discussing following.

1. IR sensor2. Light sensor3. Temperature sensor4. TSOP based obstacle detector

IR sensor

In this topic we will learn IR sensor. How to design it and how to use it? In IR sensor there is

an emitter and a detector. Emitter emits the IR rays and detector detects it. This sensor is usually

used in making a line follower robot and edge avoider robot.

Basic Principle :

In a line follower robot the basic need is to distinguish between black and white colour. The

property is that white colour reflects all the light falling on it and black colour absorbs it. So

when IR light from emitter falls on white colour it is reflected and falls on the detector whereas

in case of black colour object no light reflects back on detector.The other colours except black

also reflect light but to different proportions.


4/48


In a edge avoider robot the basic need is to distinguish whether the sensor is on the table oroutside it. The table is never of black colour.So when sensor is on the table,it reflects portion of

light falling on it and when outside the table no light is reflected back to the sensor.

Sensor behavior if it is on the table and outside the table(supposing table of blue colour)

Cicruit Diagram :

The IR LED and IR photodiode are used as follows. The resistance of the sensor(photodiode)decreases when IR light falls on it. A good sensor will have near zero resistance in presence of

light and a very large resistance in absence of light. We have used this property of the sensor to

form a potential divider. When the IR LED comes over the black line the comparator

IC(LM358N) gives 0 as output otherwise when it is over the white surface it gives 1 as output.


5/48


Sensitivity of IR sensor

The sensitivity of sensor means that how much effectively the sensor senses the change that is

occurring in its surrounding. The sensitivity of the IR sensor is controlled by reference voltage,

the voltage set using the variable resistance.

Large value of reference voltage less sensitive. Small value of reference voltage more sensitive.

Light Sensor

In this topic we will learn Light sensor. How to design it and how to use it? In Light sensor

there is a detector.A detector is always paired with emitter. In this case light source acts as the

emitter. The light source may be a bulb,sunlight or anything. Emitter emits the light and detector

detects it. This sensor is usually used in making a light searching robot.

Basic Principle:

The detector used in light sensor is LDR(Light Dependent Resistor). The property of LDR is that

its resistance decreases when light falls on it(although some are there that work opposite).


6/48


Ciruit Diagram:

The resistance of the LDR decreases when light falls on it. A good LDR will have near zero

resistance in presence of light and a very large resistance in absence of light. We have used this

property of the LDR to form a potential divider.When the light falls on the LDR the comparator

IC(LM358N) gives 1 as output otherwise it gives 0 as output.

Sensitivity of L ight sensor

The sensitivity of light sensor means that how much effectively the sensor senses the light that is

present in its surroundings. The sensitivity of the Light sensor is controlled by reference voltage,

the voltage set using the variable resistance.

Large value of reference voltage less sensitive. Small value of reference voltage more sensitive.

Temperature Sensor

In this topic we will learn Temperature sensor. How to interface it and how to use it? The most

commonly used temperature sensor is LM35. Its pinout is shown below.


7/48


The most used convention is connect Vcc to +5V although datasheet says you can any voltagefrom 4-20V and connect Gnd pin to ground. Now you have Out pin that provides you the

temperature output in terms of voltage.

Basic Principle:

The voltage at pin OUT varies linearly with temperature.

Variation =10 mV per degree centigrade

How to use:

Since it provides analog output and mostly we work with digital devices in case of our robots

(brains i.e. microcontrollers are digital), we connect the OUT pin of this sensor to the input of

ADC(analog to digital convertor) and then provide the output of the ADC to the microcontroller.

The microcontrollers we will be dealing with have inbuit ADCs so you dont have to use

separate ADCs.

TSOP based obstacle detector

In this topic we will learn TSOP based obstacle detector sensor. How to design it and how to use

it? In this sensor again there is an emitter and a detector. Emitter is an IR led as in case of IR

sensor and detector now is TSOP1738(other variations also exist e.g. TSOP1740/1742 etc)

instead of IR photodiode.

Limitation of IR sensor:

Although simple IR sensor can also be used to detect obstacles as in case of edge avoider robot it

is used to detect whether it is on the table or not. But the limitation is it cant be used in sunlight


8/48


since sunlight has lots of infrared radiations in it which already reduce the resistance of sensor to

near zero and the effect of light from IR led is like the effect of a drop in the sea. To avoid this

limitation TSOP based sensor is used. In this light from IR led is modulated at certain frequency(38 Khz in our case) and the detector is chosen to respond at only IR light modulated at that

frequency(TSOP1738 in our case). Since sunlight doesnt contain IR light modulated at certain

frequency it doesnt have any effect on our detector in this case.

Circuit Diagram:

The circuit has three main parts

1.TSOP1738

2. IR led3. 555 timer and associated components.

555 timer generates a square wave of 38 KHz that is used to drive IR led. In this IR led is made

to blink at 38 KHz and this light when falls on TSOP1738 acivates it and it outputs a 0.


9/48


Remember TSOP1738 is active low i.e. it outputs a 0 when light falls on it and otherwise it

outputs 1. Now I will tell you how to choose component values to generate a square wave of

certain frequency.

Astable mode of 555 timer:

To generate a square wave 555 timer must be operated in astable mode and the circuit used is

An astable circuit produces a 'square wave', this is a digital waveform with sharp transitionsbetween low (0V) and high (+Vs). Note that the durations of the low and high states may bedifferent. The circuit is called an astable because it is not stable in any state: the output iscontinually changing between 'low' and 'high'.

The time period (T) of the square wave is the time for one complete cycle, but it is usually betterto consider frequency (f) which is the number of cycles per second.

T =0.7 x (R1 +2R2) x C1 and f =1.4/( (R1+2R2) x C1 )

T =time period in seconds (s)f =frequency in hertz (Hz)R1 =resistance in ohms ( )R2 =resistance in ohms ( )C1 =capacitance in farads (F)

The time period can be split into two parts:T =Tm +TsMark time(output high):Tm =0.7 (R1 +R2) C1Space time(output low):Ts =0.7 R2 C1

Many circuits require Tm and Ts to be almost equal; this is achieved if R2 is much larger thanR1.


10/48


Chapter 3: Motors

Introduction

Motors are the output devices that are used to provide motion to the robot. Motion may be

related to robot moving from one place to another,it may be related to movement of a robotic

arm whose base is kept stationary to pick and place objects etc. The following kind of motors are

generally used in robotics

1. DC Geared Motor2. Simple DC motor3. Stepper Motor4. Servo Motor

DC Geared Motor

A DC Geared motor has two terminals. When we apply Vs(+ve voltage) to terminal1 and

Ground to terminal2 the motor rotates in one directions and if we apply ground to terminal1 and

Vs to terminal2 it rotates in opposite direction. The function of gears is to increase the torgue andreduce the speed. See one thing speed and torgue are inversely proportional. That means if you

decrease the speed, torgue will increase and vice versa. Basically a DC geared motor has a

simple DC motor on the rear side whose speed is very high and in the front part it employs a

combination of gears that reduces the speed and increases torgue. This is the reason why when

we remove the applied voltage a DC geared motors stops at the point where voltage was


11/48


removed whereas simple DC motor continue to rotate for a second or more even after removing

the voltage applied.

Driving DC Geared Motor

A DC geared motor usually draws current more than the maximum value per pin of the

microcontrollers therefore we cannot attach their two terminal directly to two pins of

microcontroller and operate it by appliying 1 to one pin and 0 to other. If we do so

microcontroller will get damaged since motor draws more current than microcontroller pins can

provide. So some kind of driver is needed inbetween.The driver to be used depends on whether

we want unidirectional motion or bidirectional motion.

Unidirectional Motion using transistor

In the above circuit giving high voltage (e.g. 5V) on input pin motor will start rotating sincegiving high voltage on input pin will turn on the transistor which will connect the motors lower

terminal to the ground and motor will start. One more thing a diode has been used in the circuit.

Why is it needed? Normally we do not use this diode in this circuit but it is really necessary.

You know why because when we stop the motor the back current generated by it will flow

through diode instead of transistor. If it werent so our transistor would have got damaged.


12/48


Unidirectional Motion using relay

This circuit is almost same as the above one except current passing through motor now passes

through relay instead of transistor. So the transistor used in this circuit can be of low current

rating as compared to the one used in the above circuit. The circuit is shown below.

When we switch on the transistor by applying 1 to its base, current passed through the coil in therelay which causes the contact to change from NC to NO and motors one terminal now is

connected to Vs and other to ground thereby causing motor to rotate in one direction. The diode

has been used for the same reason as for the previous circuit but now for the back current

generated by the coil in the relay.


13/48


Bidirectional Motion using Hbridge

In Fig.1 simple H-bridge Connection is shown using switch. Where all the switches are open and

the motor is not receiving any potential difference V or current I and hence it is not rotating.


14/48


In Fig.2 switches S2 and S3 are open and S1 and S4 are closed which creates a potential

difference across the motor and simultaneously a current flows through the circuit which rotates

the motor shaft, lets say, in the clockwise (CW) direction.

Similarly, in Fig.3 switches S1 and S4 are open and S2 and S3 are closed which rotates the motor

in anti-clockwise direction.

These switches can be replaced with transistors as shown in fig. below


15/48


When A is 1 and B is 0, T1 and T4 are on and T2 and T3 are off so the motor rotates in

clockwise direction and if A is 0 and B is 1, the motor rotates in anticlockwise direction.

Remember never make both A and B 1 because if you do so, all the transistors will be ON andhence there will be a short circuit.

L293D dual HBridge IC

One IC exists in market that contains two hbridges in it and can be used most of the times.

Bidirectional Motion using Relays


16/48


The circuir for each relay includes transistor as shown before. When Relay1 is ON and Relay2 is

OFF there is a potential difference across its two terminals so it rotates in one direction. When

Relay2 is ON and Relay1 is OFF there is a potential difference across its two terminals but thistime its in opposite direction so it rotates in other direction. In this way we can use relays to

control bidirectional motion of motors.

Hbridge vs Relays

The difference is in speed. The relay operates at much lower speeds than transistors, so it can not

be used in high speed applications. The other side is for the same current rating, relays are much

cheaper than the transistors of the same current rating. So what you choose depends on the kind

of application.

Simple DC Motors

This motor uses the same driving circuits as DC Geared motors but the only difference is even

after removing the potential difference across them , they continue to rotate for some time(1

second or more) they dont stop at the precise moment just like DC Geared motors do.

Stepper Motors

A stepper motor is a brushless electric motor that can divide a full rotation into a large number of

steps.Stepper motors are very different from a regular DC motors. Instead of spinning like DC

motors do, stepper motor steps at a specific resolution for each pulse.The motor that I will be

discussing needs48 steps / pulses just to complete a single revolution.

Another advantage of stepper motors is the fact that their speed of rotation can be achieved

almost instantly even if you change the spinning direction.

Stepper motor consists of a rotor - the permanent magnet that rotates inside, and stator - four

coils (north, east, south, west) that are part of the case, and which don't move. Rotor can be

moved by sequentially applying a pulsed DC voltage to one or two coils at a time.


17/48


Stepper Motor Inner Construction

Identification of wires

Stepper motors either have five or six wires...out of which one and two are for power

respectively. But how to identify which one is that. Here it is..

Isolate the Common Power wire(s) by using an multimeter to check the resistances between pairs

of wires. The Common Power wire will be the one with only half as much resistance between it

and all the others. This is because the Common Power wire only has one coil between it and each

other wire, whereas each of the other wires have two coils between them. Hence half the

resistance.

Now you need to identify in which sequence coils should be activated so that you can rotate the

motor in the direction you want.


18/48


1. Identify the wires to the coils by supplying a voltage on the Common Power wire(s) andkeeping one of the other wires grounded while grounding each of the remaining three

wires in turn and observing the results. Select one wire and ground it .Assume it'sconnected to coil 4.

2. Keeping it grounded, ground each of the other three wires one by one. Grounding onewire should make the rotor turn a little clockwise .That'll be the wire connected to Coil 3.

3. Grounding one wire should make the rotor turn a little anticlockwise . That'll be the wireconnected to Coil 1.

4. Grounding one wire should do nothing .That'll be the wire connected to Coil 2.Note:

The numbering of the coils as above is purely arbitrary - it's the order they are in that's

important.

Stepping modes

Since each coil can be programatically controlled, you can experiment with different types of

stepping modes.

1. Single Stepping - the simplest mode turns one coil ON at a time. 48 pulses are needed to

complete one revolution. Each pulse moves rotor by 7.5 degrees. The following sequence has to

be repeated 12 times for motor to complete one revolution.


19/48


PulseCoil 1Coil 2Coil 3Coil 4

1 ON

2 ON

3 ON

4 ON

This sequence rotates the motor in anticlockwise direction . To rotate the motor in clockwise

direction we have to reverse the sequence in which pulses are applied to various coils.

2. High Torque Stepping - high power / precision mode turns ON two coils on at a time. 48

pulses are needed to complete one revolution. Each pulse moves rotor by 7.5 degrees. The

following sequence has to be repeated 12 times for motor to complete one revolution.


1 ON ON

2 ON ON

3 ON ON

4 ON ON


20/48


Again this sequence rotates the motor in anticlockwise direction . To rotate the motor in

clockwise direction we have to reverse the sequence in which pulses are applied to various coils.

3. Half Stepping - stepping is doubled and motor needs 96 pulses to complete one revolution.Each pulse moves rotor by approximately 3.75 degrees. Notice the mix of single stepping mode

(lighter green) and high torque mode (darker green).


1 ON

2 ON ON

3 ON

4 ON ON

5 ON

6 ON ON

7 ON

8 ON ON


21/48


Circuit Diagram

The circuit diagram used to interface the stepper motor to the microcontroller is given below

ULN 2003 IC is a 16 pin IC and is simply used as an earth switch.The function of ULN 2003 IC

is to ground huge amount of current. If HIGH signal is applied to 1,2,3 or 4 no. pin of the IC then

the windings connected to 16,15,14 or 13 no. pin get grounded respectively.


22/48


Servo Motors

Servos are the DC motors with built in gearing and feedback control loop circuitry and no motordrivers are required. They are also used for precise positioning but unlike stepper motors they

can rotate by some angle(usually in the range 0 to 180 degrees) in one step. However, servos are

unable to continually rotate, meaning they can't be used for driving wheels (unless modified), but

their precision positioning makes them ideal for robot arms,RC planes etc.

Servos usually have three wires

1. Black/Brown is for Ground2. Red is for power(usually 4.8 to 6V)3. Yellow/Orange/White is the signal wire(3-5V)

The duration of the pulse on the signal wire determines by what angle the servo will rotate. This

duration is different for different motors. So you better check datasheet of that motor before

using any. But still there is a standard that is given below


23/48



24/48


Chapter 4: Power Sources

Introduction

In case of robotic systems you mostly need two voltages

1. +5V for the microcontroller and may be other logic devices2. Higher voltages generally +12V for motors and some other devices.

All you need is a DC supply whether it be +5 or +12V. So you have two options for the supply

AC to DC conversion:

If your systems base is stationary then you can plug your system into AC socket to receive

power and convert AC to DC using bridge rectifier as shown below.

In the diagrams below, when the input connected to the left corner of the diamond is positive,

and the input connected to the right corner is negative, current flows from the upper supply

terminal to the right along the red (positive) path to the output, and returns to the lower supply

terminal via the blue (negative) path.


25/48


When the input connected to the left corner is negative, and the input connected to

the right corner is positive, current flows from the lowersupply terminal to the right alongthe red (positive) path to the output, and returns to the upper supply terminal via

the blue (negative) path.[3]

In each case, the upper right output remains positive and lower right output negative.

The output waveforms generated are shown in fig. The voltage coming from AC outlet is 230 V

AC which is converted to 12 V AC by the step down transformer and then in converted to

unidirectional voltage as shown in second part of fig which then by the use of the capacitor is

converted to almost pure DC.


26/48


DC power source:

There are a number of DC power sources available in market as given below

1. 9V radio battery : 9V radio batteries are easily available in market and they come in twomain varieties : rechargable and non-rechargable.


27/48


Whatever it be they can be used only in low current applications because generally they

are rated at 250mAh. For high current application either you can connect them in

parallel or switch to other alternatives.

2. Li-ion Batteries : Other alternative is Li-ion batteries available in market. They aregenerally rechargeable and are very light weight. So they are really appropriate for

robotic applications and their current rating is also usually high as 2000mAh. They are

mostly used as mobile phone batteries.

3. Ni-Mh Batteries : Other alternative is Ni-Mh batteries available in market. They are alsogenerally rechargeable and are light weight. So they are also appropriate for robotic

applications and their current rating is also usually high as 2000mAh. They mostly come

in the form of 1.2 V cells and so a series of them is needed to get higher voltages.


28/48


How to get +5V

Everything discussed till now says how to obtain +12V and +9V but microcontroller usuallyworks at +5V . So how to get that voltage. For that we need to use a voltage regulator as shown

below.

The current capacity of this regulator is 1A . If you need more current than that either use a

number of them in parallel or switch to another voltage regulator whose current capacity is

more.


29/48


Chapter 5: Microcontrollers(AVR family)

Introduction

Microcontroller is the brain of your robot.This is where you embed the instructions for the robot

to follow and the intelligence of the robot depends on you. As intelligent the program written by

you is, as intelligent the robot will be. So it all depends on your skills how intelligent you can

make your robot.

Microcontroller families

Mainly three types of families exist

1. 8051 fmaily2. AVR family3. PIC family

Every family has different features. 8051 family is the oldest one. So has very few features as

compared to others. I personally find AVR family easies to work with.

AVR familyAVR stands for Advanced Virtual RISC. RISC means reduced instruction set computer. On the

other side there is a CISC architecture which stands for complex instruction set computer. In

RISC there are small number of simple instructions only that can be executed within a single

clock cycle whereas in CISC there are large number of complex instructions that generally take

more than one clock cycle. Microcontroller in this family may be 8bit or 16 bit . We will be


30/48


discussing only 8 bit microcontrollers. 8 bit means they can process only 8 bits of data at a time.

Some examples of 8 bit microcontrollers are ATmega8,Atmega16,Atmega32 etc.

Atmega8

It is a microcontroller of AVR family with

8 KB of flash memory 512 bytes EEPROM 1 KB of internal SRAM

The flash memory is used to store the program that provides the intelligence to the system.

EEPROM is used to store the data values that may need to be changed by the program written by

us but we want that to be stored permanently.

Internal SRAM is used to store the values of various variables that are not required to be stored

permanently.

Besides these some other features of this microcontroller are

Two 8 bit timer/counters One 16 bit timer/counter 6 built in ADCs Internal calibrated crystal oscillator(1,2,4 and 8 MHz) Programmable serial USART etc.


31/48


Pinout Of Atmega8

It is a 28 pin IC and its pinout is shown in fig below

VCC : It is the supply voltage for the microcontroller and for two versions of atmega8 it iso 2.7 - 5.5V (ATmega8L)o 4.5 - 5.5V (ATmega8)

Gnd : This is the ground pin for the microcontroller.

PORTB(PB0-PB7) : These are eight general purpose I/O pins with both high current and highsink capacity. Each pin has maximum current capacity of 40 milli amperes.

PORTD(PD0-PD7) : These are eight general purpose I/O pins with both high current and high

sink capacity. Each pin has maximum current capacity of 40 milli amperes.

PORTC(PC0-PC6) : These are seven general purpose I/O pins with both high current and highsink capacity. Each pin has maximum current capacity of 40 milli amperes. The pin PC0 can notbe normally used for input. ( except when RSTDISBL fuse is programmed but beware if youprogram this bit you normally wont be able to reprogram it except when you use specialprogrammers)


32/48


RXD & TXD : These two pins stand for receiver and transmitter and are used for serialcommunication using USART.

INT0 & INT1 : These are the external interrupt pins and cause the program execution to shift toa fixed point when they are activated.

XTAL 1 & XTAL2 : These are used to connect to an external crystal oscillator . When thefrequencies provided by the built in crystal oscillator are not suffiecient for you, you may need toconnect an external crytal oscillator.

SCK,MISO & MOSI : These pins are used for programming. They stand for clock, Master inslave out and master out slave in. These pins enable the transfer of program from computer to themicrocontroller.

ADC0-ADC5 : These are the input pins for the built in analog to digital converters.

AVCC : This is the supply voltage for the built in ADCs

AREF : This is the reference voltage for the built in ADCs

RESET : This pin is used to reset the microcontroller. A low on this pin resets the controller.

I think this much details are enough for you guys for the beginning. So now lets proceed to the

programming part.


33/48


Chapter 6: Making your first program(AVR Studio & WinAVR)

Introduction

Ok lets start with your first program : Blinking an LED. The complete procedure for what you

are to do is shown in fig below.

This is what you normally do when you write a program in C . Isnt it ?

The procedure for microcontroller is only little different as shown below. In the above case you

got an exe file and executed that on your PC but here you get a hex file and transfer that to

microcontroller and then the program is run in that microcontroller.

Compiler and IDE :

The compiler that we are gonna use is WinAVR and the IDE is AVR Studio.First install

WinAVR and then AVR Studio and follow following steps.


34/48


STEP 1: Start AVR Studio 4. Go to START>All Programs>Atmel AVR Tools>AVR Studio 4.

STEP 2: On welcome screen click on New Project

STEP 3: On next screen choose AVR GCC on project type, and give project name and path

make sure create folder is checked and click on next.


35/48


STEP 4: Choose AVR Simulator as debug platform and ATmega8 as device in device list and

click on finish.


36/48


STEP 5: Now you are ready to write the program. The following screen will appear.

STEP 6: Now write this code in center code window


37/48


STEP 7: Compile the program by clicking on build.

STEP 8: You should get this on build window if u did everything CORRECT.

STEP 9: Now go to your project folder. You will find a default folder inside it. Open it, you will

see a blinkled.hex file. This is the file that you will later transfer to your microcontroller.

Program Explanation:

#define F_CPU 1000000ULThis define the clock speed. It means at what speed the microcontroller is operating. 1 MHz is

the default c lock of atmega microcontrollers. It tells the duration of one clock cycle and hence in

wat time microcontroller can process some instruction.


38/48


#include

#include

These are the header files- one for input output and the other for the delay function.

int main(void)This is the main function from where the execution starts.

DDRD=0xFF;It is used for defining whether the pins of port will be used for input or output. A pin is used as

input if its cooresponding bit in the DDR(data definition register) is 0 and it is used as output if

its cooresponding bit in the DDR(data definition register) is 1. If we connect 8 LEDs onPORTD, set it as output and send data on these pins as 1, all LEDs will glow.

DDRD is an 8 bit register for setting data direction line of PORTD. Similarly we have DDRA,

DDRB and DDRC.

Now there is an infinite loop for continued blinking. Most of the programs for robotic systems

will contain an infinite loop like this and all the code that does actual function will go inside it.

After that we have just send the data on PORTD as high on all 8 pins by command

PORTD=0xFF; Similarly we can send data 0 on all 8 pins by command PORTD=0x00; and

need to put some delay between these two commands so that we can see the blinking LEDs

otherwise they will blink very rapidly and our eyes cannot see these fast blinking LEDs.


39/48


Chapter 6: Burning the hex file(AVRDude)

Introduction

Now the time to transfer the hex file to your microcontroller(flash memory). For this you need

two things

Burner Hardware Burner software

Burner hardware is the hardware that you use to connect your microcontroller to your PC. It actsas an intermediary between your PC and microcontroller. Burner software is the software that

you use as an interface to burn the hex file into the microcontroller.

Burner Hardware

Burner hardware that I personally use for AVR microcontrollers is USBasp. It is really cheap and

easy to make. USBasp that we provide is shown below.

It has a 6 pin header at the right end which contains following pins from top to bottom

MOSI MISO SCL RESET VCC


40/48


GROUNDConnect these pins to corresponding pins of the microcontroller. If you remember we alreadydiscussed these pins in chapter on microcontrollers and now you are ready to burn the hex file.

Burner Software

The burner software that I prefer is AVRDude. It is an open source program but one limitation is

that it has a command line interface but dont worry there are a number of GUIs for it. So you

can easily use it.

1. First select the target device.2.

Then select Intel Hex as file format. Whether you want to verify after programming ornot depends on you

3. Then select the hex file you want to burn. The hex file will go into flash4. The click program and you will be done.


41/48


Chapter 7: Making a line follower

Introduction

A line follower as it name signifies is a robot that follows a line. The line is in contrast with its

background. Here we will be discussing how to make a simple line follower that can follow a

black line on a white surface.

Logic

We use two IR sensors to detect the colour beneath the sensor and we keep the distance between

the sensors to be greater than the width of the line. The following conditions can arise

Both the sensors are on white. In this case we should keep on going straight. The left sensor is on white and right sensor is on black. We should make our robot turn to

the right.

The left sensor is on black and right sensor is on white. In that case we should move ourrobot to the left

Last condition is both the sensors are on black. What should we do in this case dependson the requirements but generally a high width black part is placed at the end of the trackand our robot should stop there. So we should stop our bot in such condition.

Example

Both the sensors are on whiteas shown in fig below. What we should do then? Weshould keep on going straight.


42/48


In the above fig if we kept on going straight the following condition as shown in figbelow will arise i.e. left sensor is on white and right sensor is on black. Now we

should make our robot turn to the right. Isnt it?

Now when we turn our robot to the right we will have the condition as shown below.

Again both the sensors will be on white and we will move our robot forward.


43/48


In this way the robot is able to follow the line.

Program

The code for our line follower is shown below.

#define F_CPU 8000000UL

#include #include int main(){

int left,right;

DDRB=0b11111111; //define PORTB as outputDDRC=0b0000000; //define PORTC as input

/* connect your left sensor to PC4 and right sensor to PC5. Connect your left motorhbridge terminals to PB2 & PB3 and right motor hbridge terminals to PB0 & PB1 */

while(1){


44/48


left =PINC & 0b0010000; //mask to get status of only PC4right =PINC & 0b0100000; //mask to get status of only PC5

if(left ==0b0010000 && right ==0b0100000) //both on white{

PORTB =0b00001001; //move forward

}else if(left ==0b0010000 && right ==0b0000000) //only left on white{

PORTB =0b00001000; //move right

}

else if(left ==0b0000000 && right ==0b0100000) //only right on white{PORTB =0b00000001; //move left

}else //both on black{

PORTB =0b00000000; //stop}

}}


45/48


Chapter 8: Making a cell phone controlled robot

Introduction

In many robotic application there is a need to control a machine using cell phone like starting or

activating it by cell phone or deactivating it by cell phone. So in this chapter we will see how to

design such kind of system which can be controlled by cell phone.

DTMF(Dual Tone Multi Frequency)

It is the technique for transmitting information over telecommunication lines. The DTMF system

uses eight different frequency signals transmitted in pairs to represent sixteen different numbers,symbols and letters as shown below.

So to control our robot through a cell phone what we need to do is to decode these frequencies

and find out what particular button was pressed and we are done then. To detect these

frequencies we make use of DTMF decoders ICs. There are a number of these available in

market but I will show you one that is most commonly used.


46/48


DTMF Decoder(HT9170)

The circuit diagram used for HT9170 is shown below

What happens is we give the one input from the headphone to the point termed DTMF and

connect other input from the headphone to ground. What this circuit does is provide us the digital

value of the key presses e.g.

when 1 is pressed we have D3 D2 D1 D0 =0001

when 2 is pressed we have D3 D2 D1 D0 =0010 and so on.

Connections with microcontroller

We connect these four pins termed D3 D2 D1 D0 to 4 pins of out microcontroller port which we

configure as inputs. Suppose we have connected these pins as given below


47/48


D3 ->PC.3 D2->PC.2 D1->PC.1 D0->PC.0

Now we take input from these four pins and depending upon the data present on these pins we

instruct our bot to do something.

Remember :The ICs output is sticky i.e. once you press 1 on your mobile the o/p will remain

0001 unless you press some other key.

Program

The code for cell controlled robot is given below.

/* connect D3-D0 of HT9170 to PC3-PC0 and Connect your left motor hbridge terminals to PB2& PB3 and right motor hbridge terminals to PB0 & PB1 */

#define F_CPU 8000000UL

#include int main(){

int DTMF;

DDRB=0b11111111;DDRC=0b0000000;

while(1){

DTMF =PINC & 0b0001111; //mask PD4-PD7

if(DTMF==2){

PORTB =0b00001001; //forward}

else if(DTMF==4){

PORTB =0b00000001; //left

}else if(DTMF==5){

PORTB =0b00000000; //stop


48/48

}

else if(DTMF==6){PORTB =0b00001000; //right

}else if(DTMF==8){

PORTB =0b00000110; //backward

}

}}

The code must be clear to you all is you have read the earlier part of this book.

robotics guide(technogenious solutions)

Documents