Autonomous Obstacle-Avoiding Car with Remote Joystick Control

This project implements Raspberry Pi-based robot car that autonomously navigates using IR ground sensors, a HC-SR04 ultrasonic sensor mounted on a SG90 servo, and a L298N motor driver. The car continuously monitors obstacles and scans its surroundings with a servo sweep to determine the clearest direction before moving. A HW-504 joystick connected through a USB-PC-to-network bridge enables manual remote control, allowing users to switch between autonomous and manual driving with a double press. The system cleanly separates responsibilities: Arduino reads inputs, a computer forwards them over the network, and the Raspberry Pi executes real-time driving logic.

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Components Logic

Combining L298N+DC motors, 2xIR sensors, Ultrasonic(HC-SR04) sensor+Servo(SG90) motor code so the system works as a single program

1. IR sensors (mounted near the ground) continuously check for obstacles at ground level.
2. Ultrasonic sensor (mounted on a servo motor) continuously checks the distance in the forward direction.
3. When either:
   • the IR sensors detect an obstacle, or
   • the ultrasonic sensor detects an object closer than a defined threshold,
   • the car must stop immediately.
4. When the car has stopped, the servo motor begins a full 180° scan to search for the clearest path:
   • The servo starts at its neutral position (90°).
   • It sweeps from 90° → 0°, then 0° → 180°, and finally returns 180° → 90°.
   • The ultrasonic sensor measures the distance at each angle.
   • While sweeping back and forth, some angles are scanned twice (e.g., 90°→0° and 0°→90°).
   • Duplicate readings are avoided and only one value for each angle is kept.
5. After the sweep, the program compares all stored distances and chooses the angle with the largest distance as the direction to move towards.
6. The servo then returns to its initial 90° position, but the ultrasonic sensor continues monitoring the front direction during driving.
7. Before moving toward the chosen direction, the car should reverse slightly to create space between itself and the detected obstacle standing in the front.
8. After reversing, the car rotates/moves toward the selected direction and continues driving normally.
9. This behavior repeats:
   • The servo only performs a sweep when an obstacle is detected by either the IR sensors or the ultrasonic sensor.
   • Otherwise, the car continues driving straight with continuous distance monitoring.

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Remote Control of the Car from 2-Axis HW-504 Joystick Module

The HW-504 joystick is physically wired to an Arduino. The Arduino reads the joystick's SW, X and Y pin values and sends these coordinates/values to the computer through a USB connection. Since the Raspberry Pi cannot be connected to the Arduino in this setup (it can be connected but in this project the intention is to remotely control the car), the computer acts as a bridge as it receives joystick inputs from Arduino and then sends that data across the local network to the RPi. RPi is connected to the same subnet as the computer, hence RPi can receive these coordinate values and interpret them as control commands for the car to be remotely controlled.

To activate manual remote control, press the joystick twice (twice!, and not once, in order to avoid accidental presses). The car will stop and wait for coordinate inputs sent from the joystick to the Raspberry Pi. To exit remote control and return to autonomous mode, press the joystick twice again. The car will then resume navigating on its own(based on description defined above) using the ultrasonic sensor, IR sensors, and Servo to detect and avoid obstacles.

This architecture creates a clean separation of responsibilities:

• Arduino Uno R3 handles input acquisition,
• computer handles data transmission, and
• Raspberry Pi 3B v1.2 handles vehicle control.

Remote control diagram

Hardware Flow

HW-504 Joystick
        ↓
     Arduino
        ↓ (USB connection)
     Computer

Network Flow

Computer
     ↓ (over local subnet)
Raspberry Pi 3B v1.2
     ↓
L298N motor → DC hobby motors

Complete End-to-End Flow

HW-504 Joystick
        ↓
     Arduino
        ↓ (USB connection)
     Computer
        ↓ (sends SW, X, Y over local subnet)
   Raspberry Pi 3B v1.2
        ↓
 L298N motor → DC hobby motors

Control-Flow and Component Diagrams (for visual understanding)

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Circuit Diagram

Car chassis

Remote joystick

(OPTIONALLY) Check out how those components are assembled and connected individually, visit diagrams/circuit-diagrams/. For checking the code of individual componets, go to components-testing/individual-parts-testing

To see where each wire and pin connects, click here:

Components were connected in the order provided below.

1. L298N and DC hobby motor wires and pins:

    Red wires - IN1, IN3
    Black wires - IN2, IN4

    IN1, IN2 = GPIO7, GPIO8
    IN3, IN4 = GPIO9, GPIO10
    ENA, ENB = GPIO13, GPIO12

    12+V (VC) - Connect to Power Supply Battery 2x3.7V
    GND - GND
    5+V (VCC) - no need to connect to it, since DC motors require 6V each

    NOTE: Both RPi and L298N MUST have a COMMON ground/GND!
    Connect RPi GND to L298N GND powered from battery

2. IR sensor pins:

    GND - GND
    VCC - 5V
    OUT(right)=GPIO17, 
    OUT(left)=GPIO27

    Instead of connecting GND, VCC to each of IR sensors individually, 
    connect only a single GND, VCC from RPi to breadboard then 
    distribute from there to IR sensors which are also connected to breadboard

3. Servo SG09 motor:

    RED - VCC, 5V
    YELLOW - GPIO19; PWN enabled pins (BCM: GPIO12, GPIO13, GPIO18, GPIO19) if available.
    BROWN - GND

4. HC-SR04 Ultrasonic sensor pins:

    VCC - 5V
    GND - GND
    TRIG - GPIO16
    ECHO - GPIO26
  
    Make sure to use voltage divider with two resistors 
    for pin connected to Echo. Otherwise the program 
    will not work and Pi can be damaged!

    Instead of connecting GND and VCC individually to ultrasonic
    and servo, a single GND/VCC is connected to breadboard
    and from there distributed to ultrasonic and servo motor. 

5. HW-504 2-Axis joystick:

    GND - GND
    5V+ - 5V
    VRx - A0 (only analog pin)
    VRy - A1 (only analog pin)
    SW - digital pin 8

6. RGB LED:

   Long leg to 3.3V
   1st leg to digital pin 7 (RED)
   3rs leg leave it alone; not used
   4th lef to digital pin 6 (BLUE)

Sequential Order of locally running the program

As of now only 3 folders/files are of importance:

iot-autocar/
│
├── arduino/
│   └── hw-504-joystick-send-values.ino              # STEP 1: upload to Arduino
│
├── raspberry-pi/
│   └── pi-receiver-mode-switcher.py                 # STEP 2: run on Raspberry Pi
│
└── computer/
    └── computer-bridge.py                           # STEP 3: run on computer/PC

The order of running these files:

1. Upload hw-504-joystick-send-values.ino to Arduino.
2. Followingly, run pi-receiver-mode-switcher.py from your RPi:

python ./raspberry-pi/pi-receiver-mode-switcher.py

3. Only after than, run computer-bridge.py on your computer:

python ./computer/computer-bridge.py