Pr5 dd

PR5
Line Following Robot

Version 1.0
August 2008
Cytron Technologies Sdn. Bhd.

Information contained in this publication regarding device applications and the like is intended through suggestion only and may be superseded by
updates. It is your responsibility to ensure that your application meets with your specifications. No representation or warranty is given and no liability is
assumed by Cytron Technologies Incorporated with respect to the accuracy or use of such information or infringement of patents or other intellectual
property rights arising from such use or otherwise. Use of Cytron Technologies’s products as critical components in life support systems is not
authorized except with express written approval by Cytron Technologies. No licenses are conveyed, implicitly or otherwise, under any intellectual
property rights.

OVERVIEW FEATURES
PIC16F877A
This document describes the development of Cytron
- 8-bit microcontroller with 33 I/O
Technologies DIY (Do It Yourself) Project PR5. This
- operate with 5V supply
robot is able to follow the line and it is provides with
- operating speed 20MHz
LCD for display. Schematic and source code is
provided.
LINE-FOLLOWING
- Using 3 pairs of infrared sensor

Created by Cytron Technologies Sdn. Bhd. – All Rights Reserved 1

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PR5 – Line Following Robot

SYSTEM OVERVIEW

Comparator
PIC16F877A MOTOR

IR Sensor
(line follow)

GENERAL DESCRIPTION
PR5 is an open source microcontroller Do It Yourself
kit. This PIC microcontroller based project designed
for user to start develop smart robot which capable of
line following. It also provides buzzer for user to
indicate the condition or status of the robot that useful
for debugging and testing.

PIC16F877A
This powerful (200 nanosecond instruction execution)
yet easy-to-program (only 35 single word instructions)
CMOS FLASH-based 8-bit microcontroller packs
Microchip's powerful PIC® architecture into an 40- or
44-pin package and is upwards compatible with the Figure 1
PIC16C5X, PIC12CXXX and PIC16C7X devices. Figure 1 shows the pin diagram for PIC16F877A. For
Features of the device: more information about the PIC microcontroller, please
refer to the datasheet. The datasheet can be found in
• 256 bytes of EEPROM data memory
microchip web site at: http://www.microchip.com
• self programming
• 2 Comparators
• 8 channels of 10-bit Analog-to-Digital (A/D)
converter
PIC START-UP KIT SK40A
• 2 capture/compare/PWM functions
• synchronous serial port can be configured as
either 3-wire Serial Peripheral Interface
(SPI™) or the 2-wire Inter-Integrated Circuit
(I²C™) bus
• Universal Asynchronous Receiver Transmitter
(UART).
All of these features make it ideal for more advanced
PIC Start-Up Kit SK40A series is a user friendly kit
level A/D applications in automotive, industrial,
which enable plug n use feature.
appliances and consumer applications.
This kit is designed to offer:

• Compact, powerful, flexible and robust start
up platform!
• Suitable for hobbyists and expects.
• Save development and soldering time.
• No extra components required for the PIC to
function. Is ready to rock!


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• All 33 I/O pins are nicely labeled to avoid PIC Start-up Kit SK40A
miss-connection by users.
• Ready with bootloader hardware allowing
user to load program easily via PC serial port
to PIC.
• No programmer is needed to re-program the
PIC.
• No more frustrated work plugging PIC out
and back for re-programming.
• Perfectly fit to 40 pins PIC16F and PIC18F.

SK40A come with:

• 5V voltage regulator (1A max)
• 20MHz oscillator
• Reset button
Figure 3
• Bootloader button
• Bootloader hardware and bootloader serial
cable For the instruction of using this PIC SK40A
• And all the necessities to eliminate users programmer, please refer to the particular PIC
difficulty in controlling the PIC. programmer user’s manual at:
http://www.cytron.com.my/listProductCategory.asp
Users are able to utilize the function of PIC by directly ?cid=82#51
plugging in the I/O components in whatever way that is
convenient to user. With bootloader firmware on PIC, Donut board
you can start developing projects and have fun with
this kit. This kit comes WITHOUT PIC
microcontroller to provide the freedom for user to
choose PIC type.

HARDWARE
This project will require following hardware:
a. 1 x PIC16F877A
b. 1 x PIC Start-up kit SK40A
c. Related electronic components

Please refer to Appendix A for the board layout of PR5.
The source code and schematic are provided free Figure 4
therefore Cytron Technologies will not be responsible Components:
for any further modification or improvement.
1. PIC Start-up Kit SK40A x 1
Comparator (LM324) 2. PIC16F877A x 1
3. IR Receiver x 3
4. IR Emitter x 3
5. LED x 3
6. Trimmer 10K x 3
7. Resistor 330 ohm x 6
8. Resistor 4.7 kohm x 3
9. Comparator LM324 x 1
10. Motor Driver L293D x 1
11. 14 Pins IC Socket x 1
Figure 2 12. 16 Pins IC Socket x 1
The value from the IR sensor is compared with the 13. PCB Connector 2 Ways x 3
value from the preset which can be adjusted by user. 14. PCB Connector 5 Ways x 2
The output is logic 1 if IR sensor value is larger than 15. Rainbow Cable 5 Ways x 1
preset and vise versa. The LED is used to indicate logic 16. Wrapping Wire x 3
1 or logic 0. The LED will turn ON when logic 1 and 17. RC Servo Motor C36S (modified) x 2
turn OFF when logic 0. 18. Robot Base x 1


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19. Servo Wheel x 2 Just three simple steps
20. Screw for Wheel x 8
21. Castor BTU-720 x 2
22. 9V Battery Snap x 1 Step1
23. 4AA Battery Holder x 1
24. Donut Board x 1

SOFTWARE

Flow Chart:

Start

Initialize PIC

Step2
Follow
Start Button Yes the line
pressed?

No

Step3

For more information about the software for this
system, please refer to the source code provided. The
explanation of each instruction is provided in the
Line Following Algorithm Concept
source code as the comment of each line.
Now that we have learn about IR sensor, we will move
on to line following. In line following, you will have to
The source code is provided free and Cytron
know about IR sensor and also controlling motors. For
Technologies will not be responsible for any further
modification or improvement. this project, we will be applying what we have learnt in
PR4. But first of all you will have to learn about
controlling motor.


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1. Controlling The Motor middle sensor and right sensor. A view of the
1.1 Basic placement of the sensors is as below:

When we say motor, we actually mean D.C. motor.
This is because we are using D.C power supply for
all of our projects. As an example, the
PIC16F877A needs 5V DC to power it where else
the Bluetooth modules needs 3.3V DC.

There are different types of DC motors available in
the market such as DC geared motor, servo motor
and stepper motor, but for this project, we will be
focusing on servo motor. Typical servo motors
only allow 180° rotate which is not suitable for a
wheeled robot to move from a place to another The distance between 2 sensor depends on the width.
place. Thus, we had made some modification to the The sensor should be placed in such a way that
servo motor so that it can rotate 360° continuously. maximum distance of two sensors is equal to the width
At the remaining of the text, we only concentrate of the line as shown in figure below.
on the continuous rotating servo motor.

To move the motor, just connect the power supply
to the terminal on the motor while to move it in
opposite direction, change the polarity of the
connection between the power supply and the
terminal. For this line following robot, we will be Tuning the comparator to trigger at certain intensity of
using two motors. infrared light is called “Teaching”. We will need a
small Philips screw driver to tune the VR or preset to
1.2 Motor driver L293D desire voltage. Place the robot on a white floor with
black tape (line) as shown in picture:
In a line following robot, usually the motor is
powered by a different source from the main
circuit the motor will move faster and more
powerful. For our application, 4.8V is more
suitable.

From the schematics below, you can see that there
is 6 pins connected to the microcontroller and 2
pins to each motor. Out of which is the
microcontroller. Therefore, an additional
component is required to enable the
microcontroller to control the motors. For this
project, we will be using L293D for this purpose.
A servo motor usually needs 4.8V or 6.0V to
operate. Higher voltage will generate more power
to the motor, thus the 6 pins, 3 is for the left motor
and the other 3 is for the right motor. Now lets
concentrate on only 1 side of L293D, 3 pins for the To teach the robot for line detection, you may follow
microcontroller and 2 pins for the motor. Form the these steps:
3 pins, 2 pins is for the direction of the motor and
1 pin (connected to Pin C1 or C2) is for PWM 1. Adjust the robot so that the center infrared
which is to control the speed of the motor. If sensor is on top of white floor, make sure the
controlling of speed is not required, just provide wheels and castor of the robot touches the
this pin with 5 volt to enable it to move. The floor properly.
direction of the motors depends on the connection 2. Use the screw driver to adjust the preset of
of the terminal but can also be determined through center sensor until indicator LED (center)
the program. Therefore, the sample program has to light ON.
be modified according to your robot. 3. Now adjust the robot to move the center
sensor towards the black line where the
2. IR sensors reflection of infrared is poor.
For this project, we will be using three pairs of IR 4. At this point, make sure the indicator LED is
sensors which will be attached to the bottom of the OFF. If the LED is still on, it means you have
robot. These 3 sensors will be classified as left sensor,


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over tune the preset. Tune it back so that the 1. Get the electronic components on hand
indicator is OFF. and solder them up!
5. Repeat step a. - d. for a few time and make
sure the indicator LED ON and OFF correctly Prepare your donut board! Solder the SK40A onto
at the right spot. your donut board. Follow the schematic that is
6. Repeat step a. - e. to "teach" left sensor and shown in Appendix A. If you are not sure, you can
right sensor. test it out first on your protoboard. It is advisable
7. Now your robot has been "taught". to start with the sensor part and test it first before
soldering the motor part. This is because the
Let’s see how this robot can follow line based of the sensors can be tested without the need to program
response from each sensor. In our discussion, we will the microcontroller. Test the sensors by placing it
bypass the comparator by assuming that this robot have on a white surface and after that on a black surface,
been taught. Once a particular sensor sensed black line, If the LEDs lights when it is placed on the white
it will trigger the PIC. surface and turn off when placed on the black
surface, then your sensors are connected correctly.
Example of how the sensors function when the robot You can then proceed with your motor part. Make
follows a black line on a white floor: sure that all the polarity of the components are
according to the schematic.
Sensor
Response
Left Middle Right
W B W Go Straight
B W W Turn Left
W W B Turn Right

Where, W = White
B = Black
2. Building your robot
This is the concept of a line following robot. We can
see that when the middle sensor detects the line, the The figure below shows the components for the
robot will move forward. This is because the line is in movement of the line following robot. These
the center of the robot. But when the left sensor or the components are only recommendations. Other
right sensor detects the black line, this means that the motors, wheels, bases and castors that you like can
robot have strayed from the line. If the robot strayed to also be used. In this chapter, we will be learning
the right, the left sensor will detect the line and the how to assemble all the components shown to build
brain will react by turning left to go back to the line. the robot.
As for the right sensor, it reacts in the opposite way.

3. Coordinating the motor and sensor
Now that you know how the sensors detect a line, we
will continue to learn how the robot moves. The robot
uses the concept of two separate moving wheels. The
table below shows the combination of the wheels to
move the robot in the desired direction.

Left Wheel Right Wheel Movement
1 Forward Forward Forward
2 Backward Backward Backward
3 Forward Stop Right Turn
4 Stop Forward Left Turn
Sharp
5 Forward Backward 2.1 Assembling the motors and base
Right Turn
Sharp Left
6 Backward Forward i. First, screw the two motors on both side of the
Turn
acrylic base included. Make sure that the shaft
of the motors is positioned in the center of the
When you reach this part, you have learnt the basic
base.
concept of line following algorithm. What you have to
do now is Prepare your PCB board!


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ii. After the motor have been mounted on the
base, assemble the wheels onto the motor and
screw it using the silver small screw that is 3. Programming the microcontroller
included with the motor.
After all robot have been completed, its time
to program the microcontroller. For this
project, we will be using C programming. The
bootloader will still be used to program it
(refer to PR3). There will be some changes
when using MPLAB and Bootloader.
Download the sample source code (PR5.hex)
and try it on your robot. If the wheel does not
turn in the required direction, just download
the program (PR5.c) and change it to suit your
robot.

iii. For the castor, insert the bolts through the 3.1 MPLAB and PICC Lite
hole on the front and on the back and
tighten the nuts. • Install MPLAB
• Install PICC Lite

1. Start the MPLAB IDE program.

2. Set up a new project. Select Project-> Project
Wizard then Click Next to continue.
2.2 Completing the Assembly
3. Choose the correct device which is
PIC16F877A and click Next to continue.
Stick the completed circuit (main circuit and
sensors) and battery holders onto the base. The
arrangement of the circuit and holders are
completely dependant on your creativity.

4. Select HI-TECH PICC Toolsuite as your
language toolsuite from the Active Toolsuite
drop-down menu. Click Next to continue. .


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5. Enter a name and select the location for the
project. Click Next to continue.

7. Download the sample program to the folder
that you have created the project.

8. Right click on the Source files and select Add
Files.
6. Click Next then select Finish to complete.

9. Add the PR5.c file.

10. Now you are ready to build your project.
Select Project-> Build All or press CRTL+F10.

11. MPLAB will generate a HEX file that will be
transferred to the PIC Microcontroller using
the bootloader.


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3.2 Bootloader 3.3 Changing the program
• Please click here to review how to setup
bootloader.
• There is some changes when using C
programming:
For source code written in C language with
PICC Lite Compiler, there must be offset 200 in
the “PICC Linker” option (Please refer to the
pictures below).

The figure above is part of the program. If the robot is
not moving in the direction that is supposed to, change
the value for Port B that is circled in the program above.
The four values represent RB7, RB6, RB5 and RB4
respectively. So to change the direction of the right
wheel, change the value for RB7 and RB6 (first 2 digit)
from 01 to 10. For the left wheel, change the value for
RB5 and RB4 (next 2 digit) from 01 to 10. If the value
is 00, that means that the motor stops. The value for ‘j’
has to be the same as Port B.

WARRANTY
No warranty will be provided as this is DIY project.
Thus, user is advice to check the polarity of each
electronic component before soldering it to board.


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Appendix A:
Donut Board Layout

CytRon SK40A Comparator
LM324
LED

Motor drive
L293D LED

LED
Resistor
330Ohm


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Appendix B:
Schematic

Prepared by
Cytron Technologies Sdn. Bhd.
19, Jalan Kebudayaan 1A,
Taman Universiti,
81300 Skudai,
Johor, Malaysia.

Tel: +607-521 3178
Fax: +607-521 1861

URL: www.cytron.com.my
Email: support@cytron.com.my
sales@cytron.com.my


Pr5 dd

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