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🛠️ Build Instructions: 3-in-1 Multi-Mode Robot Car

Welcome to the detailed build guide! Below you will find all the required hardware components, a detailed wiring diagram, and step-by-step instructions on how to assemble and program your robot.

🛒 Hardware Requirements

To build the robot, you will need the following components:

  • 1x Arduino Uno, Nano, or compatible microcontroller
  • 1x L298N Motor Driver
  • 2x or 4x DC Motors with Wheels
  • 1x HC-SR04 Ultrasonic Sensor
  • 1x Servo Motor (e.g., SG90)
  • 2x IR Sensors (for obstacle detection / edge drop detection)
  • 1x HC-05 or HC-06 Bluetooth Module
  • 1x Robot Chassis, battery pack (e.g., 2x 18650 cells), and jumper wires

🔌 Wiring Diagram

Follow the diagram below to connect all your components correctly.

Wiring Diagram

Hardware Pin Connections Reference:

Component Arduino Pin Other Connections
L298N ENA D6
L298N IN1 D9
L298N IN2 D10
L298N ENB D5
L298N IN3 D7
L298N IN4 D8
Ultrasonic Trig D11 VCC -> 5V, GND -> GND
Ultrasonic Echo D12
Right IR A0 VCC -> 5V, GND -> GND
Left IR A1 VCC -> 5V, GND -> GND
Servo D3 VCC -> 5V, GND -> GND
HC-05 TX RX (D0) VCC -> 5V, GND -> GND
HC-05 RX TX (D1) (Use voltage divider if needed)

⚠️ IMPORTANT WARNING: Always disconnect the TX and RX wires of the Bluetooth module from the Arduino before uploading code via USB. Failure to do so will result in an upload error!

💻 Software Setup

1. Uploading the Arduino Code

  1. Open the file located at ArduinoCode/ArduinoCode.ino using the Arduino IDE.
  2. Ensure you have the required libraries installed in the IDE:
    • NewPing (for the ultrasonic sensor)
    • Servo (built-in usually, but verify it's available)
  3. Connect your Arduino to your computer via USB.
  4. Select the correct Board and Port under the Tools menu.
  5. Click Upload. Wait for the "Done Uploading" message.

2. Setting Up the Android App

There are two ways to get the app:

Option A: Pre-compiled download (Recommended)

  1. Go to the GitHub Releases page.
  2. Download the latest .apk file to your Android phone and install it (you may need to allow "Install from unknown sources" in settings).

Option B: Build it yourself

  1. Install Android Studio.
  2. Open the AndroidApp directory as a project.
  3. Build and run the app directly onto your connected Android device.

Option C: Build it via GitHub Actions (Automated CI/CD) Since this repository includes a GitHub Action workflow, the APK is built automatically!

  1. Go to the Actions tab on your GitHub repository page.
  2. Click on the most recent successful workflow run (named "Build Android App").
  3. Scroll to the bottom to the Artifacts section.
  4. Download the RobotCarController-APK zip file, extract it, and install the .apk on your phone.

⚡ Electrical Noise Issue & Hardware Fix

Problem: During testing, DC motor electrical noise caused Arduino instability, Bluetooth disconnections, and occasional unexpected resets.

Cause: Brushed DC motors generate voltage spikes and high-frequency noise due to internal commutator sparks. These spikes travel back through the L298N motor driver and disturb the microcontroller power rails and signals.

Hardware Solution Implemented:

  • Used 0.1µF (104) ceramic capacitors for noise suppression.
  • Installed 4 capacitors directly across the motor terminals (one per motor).
  • Motors are wired in 2 parallel pairs due to the L298N having 2 channels.
  • Added 2 additional 0.1µF ceramic capacitors across the L298N motor output terminals for additional spike suppression.
  • Total capacitors used: 6x 0.1µF ceramic capacitors.

Result:

  • Significant reduction in EMI.
  • Stable Arduino behavior.
  • Stable Bluetooth communication.
  • No unexpected resets.

Recommendation for Builders

If you experience:

  • Random Arduino resets
  • Bluetooth disconnection
  • Servo jitter
  • Unstable behavior when motors start

Fix: Install 0.1µF ceramic capacitors across the motor terminals and near the driver outputs as described above.

🎮 How to Play

  1. Power up the robot using the battery pack.
  2. Enable Bluetooth on your Android smartphone.
  3. Go to your phone's Bluetooth settings and pair with the HC-05/HC-06 module. Note: The default pairing PIN is usually 1234 or 0000.
  4. Open the Controller App.
  5. Connect to the paired Bluetooth device from within the app.
  6. Use the on-screen buttons to switch between Manual, Obstacle Avoidance, and Human Following mode, and drive around!