Beginner Robot Car Tutorial (Raspberry Pi 4 / Pi 5)

What you will build

A small 2WD or 4WD robot car powered by Raspberry Pi 4 or Raspberry Pi 5. It can drive forward/backward, turn left/right, and it will stop/turn when it detects an obstacle using an HC-SR04 ultrasonic sensor.

Parts list (with shopping links)

These are examples from common reputable stores. You can swap brands - just match the part type.

Build steps (detailed)

Step 1 - Assemble the chassis

1. Mount motors to the chassis.
2. Press/attach wheels firmly.
3. Install caster wheel (if included).
4. Mount the battery holder.
5. Mount the Raspberry Pi on standoffs (do not let it touch metal).

Step 2 - Wiring the motor driver (detailed)

We will use this GPIO mapping (BCM):

• IN1 → GPIO17
• IN2 → GPIO18
• IN3 → GPIO22
• IN4 → GPIO23
• Pi GND → Motor driver GND

2.1 Power & ground (do this first)

• Power the Raspberry Pi from its own USB-C power supply (official PSU recommended).
• Power the motors + motor driver from a separate motor battery pack (for example 6xAA NiMH).
• Tie all grounds together:
  • Pi GND → Motor driver GND
  • Motor battery negative → Motor driver GND

Never use the Pi's 5V pin to power the motors. Motor noise and current spikes will reboot or kill the Pi.

2.2 Driver inputs: Pi → motor driver

Wire the Pi GPIOs to the driver’s control pins:

• GPIO17 → IN1
• GPIO18 → IN2
• GPIO22 → IN3
• GPIO23 → IN4

If your board has enable pins:

• TB6612FNG: tie STBY high (to 3.3V) to enable outputs.
• L298N: tie ENA and ENB high (jumpers or 5V) so the channels are enabled.

Optional (speed control): connect PWMA/PWMB or ENA/ENB to Pi PWM-capable pins and use PWM in code. If you don’t care about speed yet, just tie them high for full power.

2.3 Motors: driver → motors

For a 2WD robot:

• Left motor + → OUTA1 (or OUT1)
• Left motor − → OUTA2 (or OUT2)
• Right motor + → OUTB1 (or OUT3)
• Right motor − → OUTB2 (or OUT4)

If a wheel spins backwards, swap the + and − wires for that motor only.

2.4 Motor battery → motor driver

• Motor battery + → VM / 12V / VIN (motor power input)
• Motor battery − → Motor driver GND

The Pi does not get power from this battery. It still uses its own USB-C power.

Step 3 - Wiring the ultrasonic sensor safely (detailed)

We’ll use an HC-SR04 ultrasonic sensor.

Target wiring:

• VCC → Pi 5V
• GND → Pi GND
• TRIG → GPIO24
• ECHO → GPIO25 through a resistor divider

3.1 Why you need a level shifter

The HC-SR04 ECHO pin outputs around 5V. Raspberry Pi GPIO pins are only safe up to 3.3V. We drop 5V down to ~3.3V using two resistors as a simple voltage divider.

3.2 Resistor divider wiring (ECHO → GPIO25)

Example values: 2 kΩ and 1 kΩ.

HC-SR04 ECHO → 2 kΩ → GPIO25
                    |
                   1 kΩ
                    |
                   GND
      

Any similar ratio around 2:1 is fine (for example 3.3 kΩ + 1.8 kΩ), but 2 kΩ / 1 kΩ is easy.

3.3 Final sensor connections

• HC-SR04 VCC → Pi 5V
• HC-SR04 GND → Pi GND
• HC-SR04 TRIG → GPIO24
• HC-SR04 ECHO → level-shifted line → GPIO25

GND for the Pi, motor driver, motor battery, and HC-SR04 must all be common.

Step 4 - Install Raspberry Pi OS

1. Flash Raspberry Pi OS (64-bit) with Raspberry Pi Imager.
2. Boot, finish setup, connect network.
3. Update: sudo apt update && sudo apt full-upgrade -y

Code

Motor test (robot_test.py)

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)

IN1, IN2, IN3, IN4 = 17, 18, 22, 23

for p in (IN1, IN2, IN3, IN4):
    GPIO.setup(p, GPIO.OUT)

def stop():
    for p in (IN1, IN2, IN3, IN4):
        GPIO.output(p, 0)

def forward():
    GPIO.output(IN1, 1); GPIO.output(IN2, 0)
    GPIO.output(IN3, 1); GPIO.output(IN4, 0)

try:
    forward()
    time.sleep(2)
    stop()
    time.sleep(1)
finally:
    stop()
    GPIO.cleanup()

Run: python3 robot_test.py

Obstacle avoidance (concept)

Loop: measure distance. If under 20cm - stop, turn, continue. Otherwise drive forward.

Videos that help (embedded)

These are external YouTube videos. If one ever disappears, the text tutorial still works.

Printable PDF

Download the printable version here: wolfieweb_pi_robot_tutorial.pdf

Open wiring-only page · Download wiring-only PDF