🤖How to Control DC Motors for a Robot Car: L298N Motor Driver with Arduino (4 Experiments)

Almost every first robot is a car: two wheels, two DC motors, a battery and a microcontroller. The moment you try to plug a motor into an Arduino pin, though, you hit the first real lesson of robotics — a microcontroller can think, but it can't push much current.

This guide shows how to control DC motors properly with an H-bridge and the popular L298N motor driver, then walks through four experiments that turn two motors into a robot that drives a square. It is written for students and makers building their first robot, and for parents helping them.

Why not connect the motor straight to the Arduino?

A motor also creates voltage spikes when it switches off, because its coil resists sudden changes in current. A motor driver handles the high current and absorbs those spikes, while the Arduino only sends small control signals.

How an H-bridge reverses a motor

Close S1 + S4 for forwards, S2 + S3 for backwards. Never close S1 + S2 together — that shorts the battery.

A DC motor spins one way when current flows through it from left to right, and the other way when current flows right to left. An H-bridge is four switches arranged in the shape of the letter H with the motor in the middle:

Inside the L298N, these switches are transistors controlled by logic pins, and the chip prevents the dangerous combinations for you.

Meet the L298N module

The common red L298N module contains two H-bridges, so one board drives both wheels of a robot car.

Wiring the robot car

Arduino Uno → L298N → two gear motors. The battery negative, L298N GND and Arduino GND must all be connected.

Power the Arduino from USB while testing, or from the L298N's +5V pin once the robot runs on its own battery (keep the 5 V regulator jumper on, and the battery at 12 V or below).

The code

// Left motor
const int ENA = 5, IN1 = 7, IN2 = 8;
// Right motor
const int ENB = 6, IN3 = 9, IN4 = 10;

// speed: -255 (full reverse) ... 0 (stop) ... 255 (full forwards)
void setMotor(int en, int inA, int inB, int speed) {
  digitalWrite(inA, speed > 0 ? HIGH : LOW);
  digitalWrite(inB, speed < 0 ? HIGH : LOW);
  analogWrite(en, abs(speed));
}

void drive(int left, int right) {
  setMotor(ENA, IN1, IN2, left);
  setMotor(ENB, IN3, IN4, right);
}

void setup() {
  const int pins[] = {ENA, IN1, IN2, ENB, IN3, IN4};
  for (int i = 0; i < 6; i++) pinMode(pins[i], OUTPUT);
}

void loop() {
  drive(180, 180);   delay(2000);  // forwards
  drive(0, 0);       delay(1000);  // stop
  drive(-150, 150);  delay(600);   // spin left on the spot
  drive(0, 0);       delay(1000);
  drive(-180, -180); delay(1500);  // backwards
  drive(0, 0);       delay(2000);
}

analogWrite() produces PWM — the pin switches on and off about 490 or 980 times a second (depending on the pin), and the fraction of time it is on sets the average power. 255 is fully on, 128 is about half.

Experiment 1: one motor, both directions

Lift the car so the wheels spin freely. Upload the code and watch the left wheel. Now swap the two wires on OUT1 and OUT2. The wheel turns the other way for the same code — this is how you fix a motor that runs backwards.

What you learn: direction depends only on which way the current flows.

Experiment 2: find the "dead zone"

Change the forward speed in steps: 255, 200, 150, 100, 80, 60. Note the value where the wheels stop turning on the floor.

What you learn: motors need a minimum power to overcome friction. Your robot's slowest usable speed is just above this point.

Experiment 3: drive in a straight line

Run drive(180, 180) for 3 seconds on a smooth floor. Most cars drift to one side, because no two motors are identical. Reduce the faster side a little — for example drive(180, 170) — until it goes straight.

What you learn: real robots need calibration. Better robots use wheel encoders and feedback to correct this automatically, just like the PID control in our line-following robot guide.

Experiment 4: differential steering and the square

Two-wheel robots steer by running the wheels at different speeds

Now combine them: drive forwards for 1.5 seconds, spin right for the time that gives a 90° turn, and repeat four times. Adjust the spin time until the car comes back to where it started.

Choosing the battery

Troubleshooting

Where to go next

• Learn how stepper motors differ in our stepper motor guide.
• Control the car from your phone with our Bluetooth car build.
• Check current and resistor values with the Ohm's law calculator.
• Get the parts — motors, wheels, drivers and chassis — from our robotics kits.

Frequently asked questions

Can I use the L298N with an ESP32?

Yes. The ESP32's 3.3 V logic is high enough for the L298N's inputs. Use any GPIO for IN1–IN4 and PWM-capable pins for ENA and ENB, and connect the grounds together.

Why does my robot slow down as the battery gets older?

Battery voltage falls as it discharges, and the L298N's 2 V loss makes this more noticeable. Lithium-ion packs hold their voltage better than AA cells.

What is the difference between brake and coast?

Brake connects both motor terminals to the same voltage, so the motor stops quickly. Coast disconnects it, so it spins down slowly. In the code above, drive(0, 0) with ENA at 0 lets the motors coast.

Should I use the L298N or a newer driver?

The L298N is great for learning because it is tough and widely available. For battery-powered robots, a MOSFET driver like the TB6612FNG runs cooler and gives the motors more of the battery's voltage.