Published July 20, 2018 © GPL3+

Guide Your Car Model Remotely with Bluetooth

Project for creating a car model guided remotely over Bluetooth directly from your smartphone.

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Guide Your Car Model Remotely with Bluetooth

Things used in this project

Hardware components

Arduino UNO

Software apps and online services

Arduino IDE

Bluetroller, serial bluetooth controller

Story

About a year ago, I wanted to improve my Arduino skills and decided to create a car model guided directly from my smartphone via Bluetooth. I didn't want to use a pre-built application but a new one created by myself (here for the curious ones).

The Bluetooth controller sends a signal every 50 milliseconds that contains the joypad current status in the app: the angle of the cursor and the strenght of the signal (in percentage). Arduino has to decode this data from the string received through the Bluetooth communication and to distribute the power between the left and the right motor.

This is how the joypad cursor should work with the L-R DC motors:

Power distribution between L-R Motors

As we can see from the electronic schema for the project, as fundamental component I've used the L293D, with that I allowed me to have external power (up to 4.5 volt from 4 AAA batteries) for the motors and 9 volts for the arduino power supply and to control separately the direction and the power of each of the motors.

This is the flow followed by the code of the project:

After the Bluetooth Serial device setup, Arduino starts searching for commands and for each command it calculates the angle and the strength. After that it calculates the maximum speed allowed by the bluetooth command and implements the power distribuition on the 0-255 scale as the first image explains.

Code

Main code of the project

SoftwareSerial bluetooth(BLE_INPUT, BLE_OUTPUT);
String command = "";
int angle = 0;
int power_percentage = 0;
const float maxPower = 255.0;
float speedLimit;
float normAngle;
void setup() {
 bluetooth.begin(9600);
}
void loop() {
 readOneCommand();
 speedLimit = (float(power_percentage) / 100) * maxPower;
 if (angle > 180 && angle < 360) {
   setDirectionClockwise(false);
 } else  {
   setDirectionClockwise(true);
 }
 // L MOTOR
 if (angle <= 90 || angle >= 270) {
   analogWrite(MOTOR_L_POW, int(speedLimit));
 } else if (angle >= 180 && angle < 270) {
   normAngle = angle % 90;
   analogWrite(MOTOR_L_POW, int((normAngle * speedLimit) / 90));
 } else {
   normAngle = (180 - angle) % 90;
   analogWrite(MOTOR_L_POW, int((normAngle * speedLimit) / 90));
 }
 // R MOTOR
 if (angle >= 90 && angle <= 270) {
   analogWrite(MOTOR_R_POW, int(speedLimit));
 } else if (angle > 270) {
   normAngle = (180 - angle) % 90;
   analogWrite(MOTOR_R_POW, int((normAngle * speedLimit) / 90));
 } else {
   normAngle = (angle) % 90;
   analogWrite(MOTOR_R_POW, int((normAngle * speedLimit) / 90));
 }
}
void setDirectionClockwise(boolean clockwise) {
 if (clockwise) {
   digitalWrite(MOTOR_L_CTRL1, HIGH);
   digitalWrite(MOTOR_L_CTRL2, LOW);
   digitalWrite(MOTOR_R_CTRL1, HIGH);
   digitalWrite(MOTOR_R_CTRL2, LOW);
 } else {
   digitalWrite(MOTOR_L_CTRL1, LOW);
   digitalWrite(MOTOR_L_CTRL2, HIGH);
   digitalWrite(MOTOR_R_CTRL1, LOW);
   digitalWrite(MOTOR_R_CTRL2, HIGH);
 }
}
void readOneCommand() {
 if (bluetooth.available()) {
   char currentChar;
   while (true) {
     currentChar = bluetooth.read();
     if (currentChar == START_SYMBOL) {
       command = "";
     } else if (currentChar == MIDDLE_SYMBOL) {
       angle = command.toInt();
       command = "";
     } else if (currentChar == END_SYMBOL) {
       power_percentage = command.toInt();
       command = "";
       break;
     }  else {
       command += currentChar;
     }
   }
   command = "";
 }
}

Credits

bertonc96

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Guide Your Car Model Remotely with Bluetooth

Things used in this project

Hardware components

Software apps and online services

Story

Schematics

Main electronic schema

Code

Main code of the project

Credits

bertonc96

Comments

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Guide Your Car Model Remotely with Bluetooth

Guide Your Car Model Remotely with Bluetooth

Things used in this project

Hardware components

Software apps and online services

Story

Schematics

Main electronic schema

Code

Main code of the project

Credits

bertonc96

Comments

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