Combine an ultrasonic sensor with motor control so your robot senses obstacles and steers around them on its own.
Every step includes a visual reference and a plain-language explanation, so you always know what to do next.
Fix the HC-SR04 facing forward at the front of the chassis, and mount both gear motors and wheels so the robot can drive and turn freely.
Connect the ultrasonic sensor's TRIG/ECHO to pins 9 and 10, and the L298N motor control pins to 5, 6, 9... (use free pins, e.g. 3 and 11 if 9/10 are taken by the sensor).
The robot drives forward continuously, checking distance each loop. If an obstacle is closer than 15cm, it stops, reverses briefly, then turns before continuing.
#define TRIG 9
#define ECHO 10
#define LEFT_MOTOR 5
#define RIGHT_MOTOR 6
long getDistanceCm() {
digitalWrite(TRIG, LOW);
delayMicroseconds(2);
digitalWrite(TRIG, HIGH);
delayMicroseconds(10);
digitalWrite(TRIG, LOW);
long duration = pulseIn(ECHO, HIGH);
return duration * 0.034 / 2;
}
void setup() {
pinMode(TRIG, OUTPUT);
pinMode(ECHO, INPUT);
pinMode(LEFT_MOTOR, OUTPUT);
pinMode(RIGHT_MOTOR, OUTPUT);
}
void loop() {
long distance = getDistanceCm();
if (distance > 15) {
// Path clear: go forward
analogWrite(LEFT_MOTOR, 150);
analogWrite(RIGHT_MOTOR, 150);
} else {
// Obstacle ahead: stop, back up, turn
analogWrite(LEFT_MOTOR, 0);
analogWrite(RIGHT_MOTOR, 0);
delay(200);
analogWrite(LEFT_MOTOR, 100);
analogWrite(RIGHT_MOTOR, 30);
delay(400);
}
}Power the robot on an open floor. It should drive forward and automatically turn away whenever it gets close to a wall or obstacle.
The 15cm threshold may be too generous for your room — increase it slightly, or check the sensor isn't picking up reflections from the chassis itself.
Increase the distance threshold (e.g. to 20–25cm) to give the robot more time to stop and turn before contact.
Alternate the turn direction each time an obstacle is detected, or add a second sensor to compare left/right space.
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