Published September 29, 2022 © GPL3+

Simple Bluetooth Car with Android App

Build a simple l298n enabled car with an Arduino uno and 4 DC motors and code the android app!

BeginnerFull instructions provided1,289

Things used in this project

Hardware components

HC-05 Bluetooth Module

Arduino UNO

7.4v Lipo Battery

DC motor (generic)

L298N Motor / Stepper Driver

Jumper wires (generic)

Software apps and online services

MIT App Inventor 2

Story

Welcome to the Easy Arduino Bluetooth Car

This project is designed to teach someone to build a simple Arduino enabled car, with commonly accessible parts. I wanted to bring together the learnings from my experience build a car without a readymade kit. It works with easy to find parts and requires no paid android applications to run.

It works by connecting the android app to the hc-05 and voila! The car will go left, right, forward and backwards !

Arduino Wiring

HC05

1. Connect the VCC of the HC05 to 5v of the Arduino

2. Connect the GND of HCO5 to the GND of the Arduino

3. Connect TXD to RX on the Arduino

4. Connect RXD to TX on the Arduino

L298N

1. Powering the L298N. Use a 7.4v LiPo battery. Connect the red battery wire to the 12v pin on the L298N via a male to male jumper wire. Connect a black male to male wire to GND.

2. Connecting the left motor pins to Arduino:

ENA -> Pin3
IN1 -> Pin4
IN2 -> Pin5

3. Connecting the right motor pins to Arduino:

IN3 -> Pin13
IN4 -> Pin12
ENB -> Pin11

4. Wiring the Motors into L298n: Put both red wires from the same into the same output pins. Do the same for black.

Powering the Arduino

Updated 2/4/2023

The Arduino is powered via VIN which will need a male to male jumper wire connecting VIN to 5v on L298N and GND TO GND.

Arduino IDE

To understand the concepts, there are 3 pieces that talk to each other.

Each side of the car has 2 dc motors. Both motors connect to the same 3 pins that regulate turning the motor on and off and direction.

EN pins turn motors on and off.

IN pins determine direction of motors (forward and backwards).

Output pins power the motors. They draw current from the L298N and need a 7.4v battery to work.

The Arduino code is below.

The arduino code can be understood as the receiver for the android applications commands.

The android app sends a letter to the HC05 which then talks to the arduino.

The Arduino code reads that letter then activates the pins to run the motor. If you push forward, the app sends an F to the HC05. The F is then translated by the arduino code to run the motorpins for both sides of the car.

Look at the motor pins in the Arduino code, then check the MotorPin variables to understand which letters trigger which MotorPins

Android Application

You can download this via the MIT AI Companion. Check the Blocks tab to understand the logic of the application and how it talks to the arduino, which then triggers the motors.

Very broadly, the flow is

> Forward button in Android App
> Sends an F to HC05
> Arduino Pins connected to both the and right motors run

https://gallery.appinventor.mit.edu/?galleryid=f7bd19d3-5d4e-477e-9c68-66a8afd68244

Conclusion and Thoughts

This project was born out of my desire to build a Bluetooth car and finding different tutorials solved different parts of the problem, but not the entire problem. I decided to create this once I had solved the problem for myself for an end to end Bluetooth controlled l298n Arduino with all open source components and code. I am not an expert and this was self taught. If you have feedback or ways to improve the project, please contact me. Its a work in progress and we learn by working together.

Code

Arduino UNO code to control 4 dc motors

/*
 * Control 4 DC motors with Smartphone via bluetooth
 */
 
int motor1Pin1 = 4;
int motor1Pin2 = 5; 
int enable1Pin = 3; 
int motor2Pin1 = 12; 
int motor2Pin2 = 13;
int enable2Pin = 11; 
int state;
int flag=0;        
int stateStop=0;
void setup() {
    // sets the pins as outputs:
    pinMode(motor1Pin1, OUTPUT);
    pinMode(motor1Pin2, OUTPUT);
    pinMode(enable1Pin, OUTPUT);
    pinMode(motor2Pin1, OUTPUT);
    pinMode(motor2Pin2, OUTPUT);
    pinMode(enable2Pin, OUTPUT);
    // sets enable1Pin and enable2Pin high so that motor can turn on:
    digitalWrite(enable1Pin, HIGH);
    digitalWrite(enable2Pin, HIGH);
    // initialize serial communication at 9600 bits per second:
    Serial.begin(9600);
}

void loop() {
    if(Serial.available() > 0){     
      state = Serial.read();   
      flag=0;
    }   
    // if the state is 'F' the DC motor will go forward
    if (state == 'F') {
        digitalWrite(motor1Pin1, HIGH);
        digitalWrite(motor1Pin2, LOW); 
        digitalWrite(motor2Pin1, LOW);
        digitalWrite(motor2Pin2, HIGH);
        if(flag == 0){
          Serial.println("Go Forward!");
          flag=1;
        }
    }
    
    // if the state is 'R' the motor will turn left
    else if (state == 'R') {
        digitalWrite(motor1Pin1, HIGH); 
        digitalWrite(motor1Pin2, LOW); 
        digitalWrite(motor2Pin1, LOW);
        digitalWrite(motor2Pin2, LOW);
        if(flag == 0){
          Serial.println("Turn LEFT");
          flag=1;
        }
        delay(1000);
        state=3;
        stateStop=1;
    }
    // if the state is 'S' the motor will Stop
    else if (state == 'S' || stateStop == 1) {
        digitalWrite(motor1Pin1, LOW); 
        digitalWrite(motor1Pin2, LOW); 
        digitalWrite(motor2Pin1, LOW);
        digitalWrite(motor2Pin2, LOW);
        if(flag == 0){
          Serial.println("STOP!");
          flag=1;
        }
        stateStop=0;
    }
    // if the state is 'L' the motor will turn right
    else if (state == 'L') {
        digitalWrite(motor1Pin1, LOW); 
        digitalWrite(motor1Pin2, LOW); 
        digitalWrite(motor2Pin1, LOW);
        digitalWrite(motor2Pin2, HIGH);
        if(flag == 0){
          Serial.println("Turn RIGHT");
          flag=1;
        }
        delay(1000);
        state=3;
        stateStop=1;
    }
    // if the state is 'B' the motor will Reverse
    else if (state == 'B') {
        digitalWrite(motor1Pin1, LOW); 
        digitalWrite(motor1Pin2, HIGH);
        digitalWrite(motor2Pin1, HIGH);
        digitalWrite(motor2Pin2, LOW);
        if(flag == 0){
          Serial.println("Reverse!");
          flag=1;
        }
    }
    //For debugging purpose
    Serial.println(state);
}

Credits

builder-dave

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Simple Bluetooth Car with Android App

Things used in this project

Hardware components

Software apps and online services

Story

Welcome to the Easy Arduino Bluetooth Car

Arduino Wiring

Android Application

Schematics

Arduino HC05 Fritzing Diagram

Arduino HC05 Fritzing Diagram

Code

Arduino UNO code to control 4 dc motors

Credits

builder-dave

Comments

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Simple Bluetooth Car with Android App

Simple Bluetooth Car with Android App

Things used in this project

Hardware components

Software apps and online services

Story

Welcome to the Easy Arduino Bluetooth Car

Arduino Wiring

Android Application

Schematics

Arduino HC05 Fritzing Diagram

Arduino HC05 Fritzing Diagram

Code

Arduino UNO code to control 4 dc motors

Credits

builder-dave

Comments

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