Arduino RC car (Android control via Bluetooth)

Arduino RC Car

The first part of the project CxemCAR is here. There are also the source code for Android (Java Eclipse) and other useful information.
In this article, I will describe the assembly CxemCAR for the Arduino. We can use any Arduino-compatible board: UNO, Nano, Mega, Leonardo, and even based on STM32 – Arduino DUE. I used Arduino Nano V3.

Wiring diagram:

Connection Diagram

In the circuit I used a jumper (in the scheme Jmp1), because with a connected Bluetooth module is impossible be load sketch to the Arduino.

Beetween BT pin RX (2) and Arduino pin TX may require level shifter. For this, you can use voltage divider: calculator 5V to 3.3V

As a platform I used a small RC DIY platform, bought on AliExpress for $ 25.

RC DIY Platform

I soldered a Bluetooth-module to the Arduino and led status light. For communication between Arduino and Bluetooth, read this article: Arduino and Bluetooth. Module HC-06 placed in heat-shrink tube 10mm. Bluetooth-state LED with current limiting resistor were also placed in heat-shrink tube.

In the breadboard platform, I drilled a hole and secure motor driver L298N. Arduino board attached with double-sided tape

Android controlled CAR

Between the car platform and breadboard I placed 3 Li-Po battery 3.7V 1100 mAh. Power to the controller and motors separately: Arduino powered by a 3.7 V battery, and the motors and driver L298N from two 3.7V batteries connected in series. There are two 2-position power switch – one position is the power from the batteries to consumers, in the other position to charging terminals.

Battery Charger


The program was written in Arduino IDE 1.01.

// CxemCAR 1.0 (06.01.2013)
// Project Page:
#include "EEPROM.h"
#define D1 2          // direction of motor rotation 1
#define M1 3          // PWM left motor
#define D2 4          // direction of motor rotation 2
#define M2 5          // PWM right motor
#define HORN 13       // additional channel 1
//#define autoOFF 2500  // milliseconds after which the robot stops when the connection
#define cmdL 'L'      // UART-command for left motor
#define cmdR 'R'      // UART-command for right motor
#define cmdH 'H'      // UART-command for additional channel (for example Horn)
#define cmdF 'F'      // UART-command for EEPROM operation
#define cmdr 'r'      // UART-command for EEPROM operation (read)
#define cmdw 'w'      // UART-command for EEPROM operation (write)
char incomingByte;    // incoming data
char L_Data[4];       // array data for left motor
byte L_index = 0;     // index of array L
char R_Data[4];       // array data for right motor
byte R_index = 0;     // index of array R
char H_Data[1];       // array data for additional channel
byte H_index = 0;     // index of array H
char F_Data[8];       // array data for  EEPROM
byte F_index = 0;     // index of array F
char command;         // command
unsigned long currentTime, lastTimeCommand, autoOFF;
void setup() {
  Serial.begin(9600);       // initialization UART
  pinMode(HORN, OUTPUT);    // additional channel
  pinMode(D1, OUTPUT);      // output for motor rotation
  pinMode(D2, OUTPUT);      // output for motor rotation
  timer_init();             // initialization software timer
void timer_init() {
  uint8_t sw_autoOFF =;   // read EEPROM "is activated or not stopping the car when losing connection"
  if(sw_autoOFF == '1'){                 // if activated
    char var_Data[3];
    var_Data[0] =;
    var_Data[1] =;
    var_Data[2] =;
    autoOFF = atoi(var_Data)*100;        // variable autoOFF ms
  else if(sw_autoOFF == '0'){         
    autoOFF = 999999;
  else if(sw_autoOFF == 255){ 
    autoOFF = 2500;                      // if the EEPROM is blank, dafault value is 2.5 sec
  currentTime = millis();                // read the time elapsed since application start
void loop() {
  if (Serial.available() > 0) {          // if received UART data
    incomingByte =;        // raed byte
    if(incomingByte == cmdL) {           // if received data for left motor L
      command = cmdL;                    // current command
      memset(L_Data,0,sizeof(L_Data));   // clear array
      L_index = 0;                       // resetting array index
    else if(incomingByte == cmdR) {      // if received data for left motor R
      command = cmdR;
      R_index = 0;
    else if(incomingByte == cmdH) {      // if received data for additional channel
      command = cmdH;
      H_index = 0;
    else if(incomingByte == cmdF) {      // if received data for EEPROM op
      command = cmdF;
      F_index = 0;
    else if(incomingByte == '\r') command = 'e';   // end of line
    else if(incomingByte == '\t') command = 't';   // end of line for EEPROM op
    if(command == cmdL && incomingByte != cmdL){
      L_Data[L_index] = incomingByte;              // store each byte in the array
      L_index++;                                   // increment array index
    else if(command == cmdR && incomingByte != cmdR){
      R_Data[R_index] = incomingByte;
    else if(command == cmdH && incomingByte != cmdH){
      H_Data[H_index] = incomingByte;
    else if(command == cmdF && incomingByte != cmdF){
      F_Data[F_index] = incomingByte;
    else if(command == 'e'){                       // if we take the line end
    else if(command == 't'){                       // if we take the EEPROM line end
    lastTimeCommand = millis();                    // read the time elapsed since application start
  if(millis() >= (lastTimeCommand + autoOFF)){     // compare the current timer with variable lastTimeCommand + autoOFF
    Control4WD(0,0,0);                             // stop the car
void Control4WD(int mLeft, int mRight, uint8_t Horn){
  bool directionL, directionR;      // direction of motor rotation L298N
  byte valueL, valueR;              // PWM M1, M2 (0-255)
  if(mLeft > 0){
    valueL = mLeft;
    directionL = 0;
  else if(mLeft < 0){     valueL = 255 - abs(mLeft);     directionL = 1;   }   else {     directionL = 0;     valueL = 0;   }      if(mRight > 0){
    valueR = mRight;
    directionR = 0;
  else if(mRight < 0){
    valueR = 255 - abs(mRight);
    directionR = 1;
  else {
    directionR = 0;
    valueR = 0;
  analogWrite(M1, valueL);            // set speed for left motor
  analogWrite(M2, valueR);            // set speed for right motor
  digitalWrite(D1, directionL);       // set direction of left motor rotation
  digitalWrite(D2, directionR);       // set direction of right motor rotation
  digitalWrite(HORN, Horn);           // additional channel
void Flash_Op(char FCMD, uint8_t z1, uint8_t z2, uint8_t z3, uint8_t z4){
  if(FCMD == cmdr){           // if EEPROM data read command
    Serial.print("FData:");       // send EEPROM data
    Serial.write(;     // read value from the memory with 0 address and print it to UART
    Serial.print("\r\n");         // mark the end of the transmission of data EEPROM
  else if(FCMD == cmdw){          // if EEPROM data write command
    EEPROM.write(0,z1);               // z1 record to a memory with 0 address
    timer_init();             // reinitialize the timer
    Serial.print("FWOK\r\n");         // send a message that the data is successfully written to EEPROM

The code uses a library to work with EEPROM AVR-memory. Arduino board by USART from the Bluetooth module receives data ready for the left and right engine. All basic calculations are performed in the Android application.

Download INO code for Arduino IDE

24 thoughts on “Arduino RC car (Android control via Bluetooth)”

  1. i have done all connection.i used sony xperia mobile
    and downloaded the app.when i try to connect to the bluetooth it comes socket failed. pls explain me what is socket failed means.and how it can be corrected.

  2. i whanna buy a pirate 4wd kit. Can u pls tell me that each motor, in your project, can rotate, backwards and forwards, and tilt, left or right, in the same time?

  3. ENG: how can i do the same white Arduino Uno?
    ESP: como puedo hacer lo mismo con Arduino Uno?
    greetings from Chile!! 🙂

  4. Hi guys i have a problem. I make the circuit but when i press the button on the application the motor don’t run well.

    I use HC-05 Bluetooth with breackboard, and i made this pin:

    -Pin +5V to +5V of arduino
    -Pin GND to GND of arduino
    -Pin TX to pin 10 of arduino (RX)
    -Pin RX to pin 11 of arduino (TX)

    I use 10 and 11 for softwareserial becouse pin TX and RX of arduino uno don’t work with this bluetooth and the offical forum of arduino tell me this solution.

    Motor Shield:
    -M1 M2 Motor 1 6V Brushless
    -M3 M4 Motor 2 6V Brushless
    -IN1 IN2 IN3 IN4 to 2 3 4 5 of arduino

    Arduino i use 2 9V Battery, one for arduino and one for motorshield. This is the video who can help me?:


  5. Please, help me. I uploaded this program to my arduino uno and connected all things (arduino bluetooth + l298 + 2 motor) in my car. But one thing doesn’t working in my car. Sometimes my car run nicely sometimes when i touch and up my finger my car still running not stopping (and hit the wall). What do i do. Is there something wrong this car’s source code? Please, help me.

  6. Hi guys. Please help me?
    My car doesn’t good running.
    When i press and then up my finger from the button in my phone (galaxy s2) my car still running not stopping (and so hit wall). Sometimes it’s work nicely. Sometimes this kind of fail come again and again. What do i do? Please explain me this fail.
    I think my all circuit connection right (Arduino Uno R3 + Seeeduino Bluetooth + L298 + 2 motor).

  7. Hello,

    This is a great and amazing tutorial.
    Any chance to find the same app but for iPhone?

    Thanks a lot

  8. This is a superb example of how to make an RC car! The problem i’m having is that i have a L298D motor board which fits on top of arduino. How do you rewrite the rx and tx so that i came communicate with it?

  9. Can u please briefly explain me the Additional channel means? And that external circuits GND and the switch connection?

  10. Hello, I just like to ask if is it maybe possible to get android app for 2.3.6 release ? I tryed to modify existing source code but I don’t have enough experiences with Fragments, Resources and other things that should be modyfied for 320 x 480 screen resolution.

  11. Sir please help me. I buy allnthings and made the car. But when i search for that android application, it is removed from google play. But ihave to participate on a science exhibition. Please help me sir

  12. HELLO Guys
    can anybody help me plzz/////
    i don’t use Horn in this car//
    so can anyone remove the HORN coding from the SOURCE CODE plz ///
    because the Source code is too large …..thats why code doesn’t UPLOAD in Arduino UNO //

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