Line Follower and Obstacle Avoiding Robot using Arduino

Autonomous navigation starts with two primitive skills: staying on a path and not hitting things. A robot that cannot follow a marked route is useless in a warehouse; one that cannot stop for an obstacle is dangerous anywhere. Students meet these as separate builds — a line follower here, an obstacle avoider there — and never face what happens when the two behaviors conflict. A line running straight into a box forces the issue: the robot must suspend path-following, maneuver around the obstruction, and re-acquire the line on the far side, all without human help. That arbitration — deciding moment to moment which behavior owns the motors — is the real lesson, and it generalizes beyond the track: every autonomous vehicle is a stack of competing behaviors under a priority scheme. A small chassis, an IR array, an ultrasonic sensor and a motor driver are enough hardware to teach it.

1. The IR sensor array continuously reads the contrast between the black line and the white floor; the Arduino computes a steering correction proportional to how far off-center the line is.
2. The L298N driver converts that correction into differential wheel speeds — slowing one side to steer — so the robot tracks the line smoothly.
3. Meanwhile the HC-SR04 pings for obstacles ahead. If something comes within the stop distance, line-following is suspended.
4. The robot backs up slightly, scans left and right with the ultrasonic sensor, and turns toward the clearer side.
5. Once the path is clear, it re-acquires the line and resumes tracking — the whole switch happens in a fraction of a second.

Dual-mode autonomy: IR line tracking with automatic ultrasonic obstacle-avoidance override
5-channel IR sensor array for stable line detection with minimal wobble on curves
HC-SR04 ultrasonic ranging (2 cm – 400 cm) for obstacle detection and sidestepping
L298N dual H-bridge motor driver with PWM speed control for smooth turns
Behavior arbitration logic — obstacle avoidance takes priority, line following resumes automatically
Adjustable IR threshold (onboard potentiometer) and code-level calibration constants
Battery-powered with onboard power switch — fully untethered track demos
Compact 2WD chassis with high-grip wheels for reliable traction on chart-paper tracks
Arduino firmware with tunable parameters (speed, turn gain, stop distance)

Assembled robot
Complete Arduino firmware (well-commented, tunable parameters)
Circuit diagram and wiring schematic
IR calibration and track-setup guide
Project report PDF (synopsis, design, algorithm, results, conclusion)
PPT presentation for final review
Viva Q&A preparation document

FAQs

1. How does the robot decide between following the line and avoiding the obstacle? Through behavior arbitration: the ultrasonic check runs every control cycle, and if an obstacle is closer than the stop distance, avoidance preempts line-following. Once clear, line tracking resumes automatically. It is a simple priority scheme.
2. What is the L298N and why is it used here? The L298N is a dual H-bridge motor driver that lets the Arduino control two DC motors' direction and speed. Direction comes from logic-level inputs; speed comes from PWM on the enable pins. It handles up to 2 A per channel, plenty for small gear motors.
3. How do I calibrate the IR sensors? Each sensor module has a threshold potentiometer, and the firmware has calibration constants. The included guide walks through setting the threshold so the array cleanly distinguishes the black line from the white floor under your room's lighting.
4. Can the ultrasonic sensor really measure distance accurately? Yes — the HC-SR04 sends a 40 kHz pulse and times the echo; distance = (echo time × speed of sound) / 2. The firmware filters readings to reject noise, giving stable ±3 mm measurements for avoidance decisions.
5. Is this a reasonable first robotics project? Yes — it is the standard first build because it combines sensors, control logic and motor driving in one package with a lively track demo: line following plus dodging obstacles.
6. Can it be extended later? Common extensions are Bluetooth/manual override mode, PID-tuned steering, maze-solving logic, or a servo-mounted scanning ultrasonic head. The firmware structure makes these additions straightforward.