Using H-Bridge Motor Drivers

Understand how H-bridge motor drivers like the L298N control motor direction and speed for two-wheeled robots.

An H-bridge is a circuit that lets you control the direction of a DC motor by switching the current flow. It’s essential for robotics because it allows you to drive motors forward and backward with just a few control signals.

⚙️ How the H-Bridge Works

The H-bridge gets its name from the circuit diagram, which looks like an “H” made of transistors or switches.

H Bridge

The S1 - S4 in this diagram are Transistors that act like switches. The motors are controlled by these switches.

It allows current to flow in either direction through the motor:

• IN1 high, IN2 low → forward
• IN1 low, IN2 high → backward
• IN1 and IN2 same → brake/stop

When paired with PWM on the enable pin, you can also control the speed of the motor.

🔌 Wiring Two Motors with L298N

L298N Motor Driver

Works with up to 12v for powerful motors.

The L298N has two H-bridges inside — perfect for controlling two motors independently. Here’s a typical wiring setup:

• Motor A
  • GP0 → IN1
  • GP1 → IN2
  • GP2 (PWM) → ENA
• Motor B
  • GP3 → IN3
  • GP4 → IN4
  • GP5 (PWM) → ENB

GP pins are the GPIO pins on the Pico.

Raspberry Pi Pico Pinouts

Each of the green edge connectors are referred to as GPIO or General Purpose Input Output pins. The black are the common ground pins.

Don’t forget: Pico GND must connect to L298N GND.

🧪 Writing the Code

Here’s a MicroPython script for controlling both motors:

from machine import Pin, PWM
from time import sleep

# Motor A
in1 = Pin(0, Pin.OUT)
in2 = Pin(1, Pin.OUT)
ena = PWM(Pin(2))
ena.freq(1000)

# Motor B
in3 = Pin(3, Pin.OUT)
in4 = Pin(4, Pin.OUT)
enb = PWM(Pin(5))
enb.freq(1000)

def motor_a_forward(speed=50000):
    in1.high()
    in2.low()
    ena.duty_u16(speed)

def motor_a_backward(speed=50000):
    in1.low()
    in2.high()
    ena.duty_u16(speed)

def motor_b_forward(speed=50000):
    in3.high()
    in4.low()
    enb.duty_u16(speed)

def motor_b_backward(speed=50000):
    in3.low()
    in4.high()
    enb.duty_u16(speed)

def stop_motors():
    in1.low()
    in2.low()
    in3.low()
    in4.low()
    ena.duty_u16(0)
    enb.duty_u16(0)

# Test
motor_a_forward()
motor_b_forward()
sleep(2)

motor_a_backward()
motor_b_backward()
sleep(2)

stop_motors()

🤖 Why This Matters

With two motors under your control, you can:

• Drive forward/backward

• Turn left/right

• Rotate on the spot (tank steering)

This forms the basic movement logic for most two-wheeled robots.

🧩 Try It Yourself

Try setting different speeds for left and right motors.

• Create a function to “spin in place.”

• Add buttons to manually control each motor.

You’re now ready to add some intelligence to your robot!

Next up: Line Following with IR Sensors

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