What is a line follower?

Line follower is a machine that can follow a path. The path can be visible like a black

line on a white surface (or vice-versa) or it can be invisible like a magnetic field.

Why build a line follower?

Sensing a line and maneuvering the robot to stay on course, while constantly correcting

Wrong moves using feedback mechanism forms a simple yet effective closed loop

system. As a programmer you get an opportunity to ‘teach’ the robot how to follow the

line thus giving it a human-like property of responding to stimuli.

Practical applications of a line follower: Automated cars running on roads with

Embedded magnets ; guidance system for industrial robots moving on shop floor etc.

This the simple line follower robot without using micro-controller

Block diagram:


SENSOR:-We used Infrared Emitter-Sensor pair for sensing the track. When the emitter passes over the white surface the light from it is reflected back to the sensor whereas on black surface light doesn’t reflect back and thus resistance of sensor goes high which intern switches off the motor.

AMPLIFIER- In this we used NPN transistor BC548 as the amplifier circuit. It amplifies the low intensity sensor signal and provides it to the input of the motor driving circuit.

CALIBRATION CIRCUIT- A preset or variable resistor of value 500K is used to adjust the sensitivity of the sensor.

MOTOR DRIVEN CIRCUIT- L293D is used as motor driving circuit which responses accordingly to the low input signal provided by the amplifier circuit.

MOTOR-In this we used the DC MOTERS which are used to move the follower ahead.

Circuit diagram

Circuit Diagram

The Circuit explanation:-

The robot uses a combination of IR Photo diode and IR-LEDs to sense the presence to a line. An IR Photo diode is a resistor whose resistance is proportional to the light falling on it- greater the light, lesser the resistance and visa-versa. The basic principle underlying this project is that objects light in colour radiate the light falling on them while dark coloured objects don’t. So when the sensors are above the black line the light emitted by the IR- LED is not radiated by the floor, hence the resistance of the Photo-diode increases. The opposite happens when the robot back on the white surface.

In our robot the IR Photo diode is used part of a voltage divider circuit.

My own robot:-

Sensor circuit are mounted on board:-

RF detector are mounted on robot:-


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