A line follower robot is basically a robot designed to follow a “line” or a “path”
already predetermined by the user. The path or line consists of a black line on a
white surface (or it may be reverse of that). The control system must sense a line
and maneuver the robot to stay on course, thus forming a simple yet effective
closed loop system. The robot is designed to follow very tight curves.
The robot is built with a L293d (driver IC), IR sensors (LM324, POT 10K, IR pair,
LED light, Resistors), LM7805 (regulator IC). The robot is designed using two
motors controlling wheels. It has infrared sensors on the bottom for tracking
black tape. It captures the line position with the help of these optical sensors (IR
led and IR sensor) when the sensors detect the black surface, output of
comparator, LM324 is low logic and for white surface the output.
A voltage regulator (L7805) is an electrical regulator
designed to automatically maintain a constant voltage level.
It may use an electromechanical mechanism, or passive or
active electronic components. Depending on the design, it
may be used to regulate one or more AC or DC voltages.
Pin 1: It is used for input pin
Pin 2: This is ground pin for regulator
Pin 3: It is used for output pin. Through this pin we get the
IR reflective sensors have one emitter (IR LED) and one receiver (Photodiode).
If we have white surface it reflects the light and it will sensed by the receiver,
similarly if we have black surface it absorbs the light and receiver cannot sense
IC LM 324 is a comparator IC. It is the
main brain of line tracer.
The Port takes the input voltages at
positive and negative pin respectively,
compares them and gives a digital
output in a form of logical HIGH and
L293D is a dual H-bridge motor driver integrated circuit (IC). Motor drivers act as current amplifiers
since they take a low-current control signal and provide a higher-current signal. This higher current
signal is used to drive the motors.
L293D contains two inbuilt H-bridge driver circuits. In its common mode of operation, two DC motors
can be driven simultaneously, both in forward and reverse direction. The motor operations of two
motors can be controlled by input logic at pins 2 & 7 and 10 & 15. Input logic 00 or 11 will stop the
corresponding motor. Logic 01 and 10 will rotate it in clockwise and anticlockwise directions,
Enable pins 1 and 9 (corresponding to the two motors) must be high for motors to start operating.
When an enable input is high, the associated driver gets enabled. As a result, the outputs become
active and work in phase with their inputs. Similarly, when the enable input is low, that driver is
disabled, and their outputs are off and in the high-impedance state.
Robotics is an interesting subject to discuss about and in this advanced world Robots are
becoming a part of life. In this project we are going to discuss about a robot which is
capable of following a line without the help of any external source.
The Embedded Line Follower robot uses two motors to control rear wheels and the single
front wheel is free. It has 2- infrared sensors on the front for detection of black tracking
tape. When a sensor detects black color, the sensor output is given to the comparator
LM324. The output of comparator compares this sensor output with the reference voltage
and gives an output. The output of comparator will be low when it receives and input
form the sensor.
We follow a simple logic to implement this project. As we know that black color is capable of
absorbing the radiation and white color or a bright color reflects the radiation back. Here we
use 2 pairs of IR pair. The robot uses the sensors to sense the line and the arrangement is
made such that sensors face the ground. The output from the sensors is an analog signal
which depends on the amount of light reflected back and this analog signal is given to the
comparator to produce digital signal (0s and 1s).
Internally, we have a motor driver IC L293D which is used to control the rotation of the
wheels. The rotation of these wheels depends upon the response from the comparator. Let us
assume that when a sensor is on black line it reads 0 and when it is on the bright surface it
The line following robot was finally completed. A lot of effort was put into the design,
implementation and days of toil in front of the computer, writing and debugging the
information about the robot. The robot was finally running with a few glitches here and
there which were sorted in the later revisions of the firmware. The line following robot
still has a few short-comings but achieves most of the objectives.
I earned a lot of knowledge on several IC’s, a deeper & clearer view of the
architecture, ports & all functional blocks was achieved. Did a lot of research on
robotics and already have my next my next project planned.
There’s a lot of learning & yet not the end, learning is a continuous never ending
process but is definitely fun…