Line Following Robot (LFR) Using L293D Motor Driver & IR Sensors

Line Follower Robot Using L293D and IR Sensors

A line follower robot is an autonomous robot that follows a visible path, usually a black line on a white surface or vice versa. It detects the line using infrared (IR) sensors and moves accordingly. This robot is simple yet powerful, commonly used in automation, education, and robotics competitions.

In this version, we design the robot without using a microcontroller like Arduino. Instead, it works using direct hardware logic—IR sensors control the motors through an L293D motor driver IC. The logic is hardwired, meaning no programming is required.

Working Principle

The IR sensor has an IR LED and a photodiode. When the IR light reflects off a surface:

• White surface reflects IR light → sensor output is HIGH (5V)
• Black surface absorbs IR light → sensor output is LOW (0V)

We use two IR sensors, placed on the left and right side of the robot. Based on the output of these sensors, we control the direction of two motors using the L293D.

The L293D IC is a dual H-bridge motor driver that allows us to control the direction of two DC motors. Each IR sensor’s output is connected to the input pins of L293D. When the sensor detects a black line (LOW output), it activates the motor on that side, and when it detects white (HIGH output), the motor turns off or changes direction.

For example:

• Both sensors LOW → both motors ON → robot moves forward
• Left sensor LOW, Right HIGH → turn left
• Left HIGH, Right LOW → turn right
• Both HIGH → robot stops or can be programmed (hardware-wise) to search

Applications

This robot can be used in:

• Industrial automation for material transport
• Warehouses for delivery systems
• Hospitals for medicine delivery
• Educational robotics projects
• Robotics competitions like RoboRace

Conclusion

A line follower robot using L293D and IR sensors without Arduino is a cost-effective and simple automation tool. It helps students learn the basics of electronics, sensors, and motor control, and can be enhanced further with more logic or advanced sensors.