how to build a simple line tracer robot

8/3/2019 How to Build a Simple Line Tracer Robot

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How to build a simple Line Tracer Robot??

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Some Advanced Line Tracers


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Infrared LED

Photodiode

LM324 Comparator IC


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L293D Motordriver IC

Line Tracer or Line Follower Robot is one of the simplest bots fit for an amateur to join the

vast field of Robotics. The same bot can be made complex in Mechanical implementation if

pressure on precision is more. Lets have a look on how simply a Line Tracer can be

constructed.

Requirements:

1. Two DC Gearhead Motors: Can be 45 rpm or 100rpm or even more. 45/100 rpm

may be better for beginers.

2. Motor Driver IC L293D

3. Comparator IC LM324

4. Sensor Network : TSOP/(IR led-Photodiode) sensors may be used. Failure chance

for TSOP is more. So neglect it. Lets proceed with IR LED- Photodiode Pair. A

minimum of 2 sensor networks may be used.

5. Castor Wheel for support (Typical Reverse Rickshaw design)

Working Principle:IR LED must be forward biassed (+5V) and Photodiode reverse biassed

(-5V). The sensors must be arranged such that the radiations from IR LED must reach within

the proximity of the photodiode in case of reflections from a white surface. Ideally, the

reflectivity of white surface is 1 and that for black surfaces is 0. The Line tracer works on the

above principle for distinguishing white and black surfaces. The difference in analog between

the two surfaces must be made digital. The comparator IC LM324 is used for this purpose.

The comparator will give outputs either high or low which can be adjusted for black /white

respectively or in the reverse order by adjusting the input of the comparator

IC( inverting/non-inverting inputs).Suppose that white gives HIGH and Black LOW. The

output from comparator must be coupled to the motor driver IC L293D accordingly.


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Sensor Arrangement: Atleast there must be two sensors. I will discuss the case of two

sensors. The sensors must be arranged such that the line to be followed lies between them.

i.e, the two sensors senses the ouside of the required line.This is to facilitate the

differentiation of turns. Take the case of a black line to be traced in a white background.The

robot must be set to motion when both sensors detect white.In case if left sensor detectsblack and right sensor white, then a turn to left is detected and reverse for the case of a right

turn.As soon as a left turn is detected the left tyre( motors connected directly to tyre) must be

stopped and right motor must only rotated. Or even the left tyre (motor) may be rotated in the

reverse direction. The reverse is the case with a right turn. The direction of rotation of the

motor may be adjusted by controlling the input signals to motor driver IC.

In case of a black background with white lines, the logic must be reversed.

Some Negatives: The robot will move forward if it is kept in a white background without any

black line and it will stay still if kept in a black Background. The bot will stop at Junctions.

these defects can be eliminated by using a microcontroller chip which is programmed to our

requirements.

For any further doubts, do comment.

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how to build a simple line tracer robot

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