Introduction: Computer Controlled RC Car With Two Arduinos

Required Parts: This project requires two Arduino boards which can be bought from
This project uses two Arduino Uno compatible boards.

An L293D or other Dual H-Bridge Motor Driver chip will be needed to drive the motors of the RC car. This can be found here:

Finally, this project requires the RF transmitter ( and receiver (ttps:// which will used for communication between the Arduinos.

A breadboard to prototype your circuit and a prototype board is also needed to solder everything together in the end. This can be bought from an electronics store like Jaycar Electronics.

Required Knowledge: A basic knowledge of electronics is required for this tutorial. If you have never worked with electronics take a look at this tutorial (at least up to lesson 4):
Knowing how to solder will also help with the final steps:
This tutorial also assumes that you have a basic knowledge of the Arduino Uno and know how to program and upload a basic sketch. For the basics of Arduino, check out the Adafruit Arduino basics lessons at:
A basic knowledge of Java is also assumed. You should know how to set up Java on your computer and create a basic Java program. This tutorial uses the Eclipse IDE. For the basics of programming Java and using Eclipse, check out this tutorial:

Tutorial Structure: This tutorial will be split up into 3 parts:
  • Sending Arduino
  • Recieving Arduino
  • Computer program

Step 1: Sending Arduino: Wiring and Building.

Pick one of your Arduinos to be the sending one and the other to be the receiver. The layout for the sending Arduino is simple. We are using a breadboard to connect the RF Transmitter to the Arduino. The four pins on the transmitter are as follows: Ground, Data in, 5V in, Antenna.
Place the transmitter in the breadboard and wire the Ground and 5V pins to the corresponding Ground and 5V on the Ardunio. The data in pin should be connected to pin 12 on the Arduino. The antenna is optional but to gain more range, you can simply attach a long wire and leave it hanging.

Step 2: Sending Arduino: the Code.

Coding the Sending Arduino is also simple. For both this and the reciever, you need to download the Virtual Wire library from
This tutorial uses version 1.20 (download link: any version should be compatible.

At the top of the sketch put:
#include <VirtualWire.h> //include the required library
In the setup function put:
void setup()
  //Begin the serial connection
  while(!Serial); //Wait till serial connection is ready
  Serial.println("Serial ready"); //Debugging
  //Initialize the IO and ISR
  vw_setup(2000); // Bits per sec
This code simply initializes the serial connection and Virtual Wire.
The Loop function should look like this:
void loop()
  //If serial input is available
    char input =; //Read input
    send(&input;); //Send input via RF transmitter
  } else {  
This reads an input character and sends it to the send function.
Finally the send function should be created to look like this:
void send (char *message)
  vw_send((uint8_t *)message, strlen(message)); //Send the message
  vw_wait_tx(); // Wait until the whole message is gone
The send function takes a character and sends it using the Virtual Wire library.
This is all that's required for the sending Arduino.

You can download the complete sketch from here:

Step 3: Receiving Arduino: Wiring and Building.

Wiring the receiving Arduino is a little more complicated.
It requires both the RF receiver and the L293D chip.

The RF receiver:
The pins on the RF receiver labelled GND are ground. DATA OUT is where the received signal will be sent out. VDD is power for the chip and ANT is for the optional antenna.
The RF receiver is connected separately from the L293D chip. The ground goes to one of the ground ports on the Arduino. The power in goes to the Arduino's 5V output and the DATA OUT should be connected to pin 13 on the Arduino. The antenna can be left loose and later connected to the RC car's antenna.

The L293D chip:
The pins on the L293D chip are shown on the diagram above. EN1 and EN2 are the motor enable pins. They act as a master on/off switch for each motor. IN1,IN2,IN3 and IN4 are the inputs that control the directions of each motor. If IN1 is powered and IN2 is not, the motor on OUT1 and OUT2 will turn one way. Likewise if the inputs are flipped, so too are the outputs and the motor will turn the other way. 0V is ground and +V is power for the chip. +Vmotor is used as a separate power source for the motors.
The wiring for the l293D chip is not as complicated as it may look. The +V and the +Vmotor pins should be connected to and external power supply. In this project we will end up connecting these to the battery pack from the RC car. The IN1, IN2, IN3 and IN4 pins will be connected to pins 3,4,5 and 6 on the Arduino. The two motor enable pins are connected to pins 9 and 10 on the Arduino. The OUT1 and 2 pins go to one motor and OUT3 and 4 go to the other. It doesn't matter which IN pins go to which pins on the Arduino or which OUT pins go to which leads on the motor as these will be defined in code.

Step 4: Receiving Arduino: the Code.

At the top of this sketch, also include the Virtual Wire library:
#include <VirtualWire.h> //Include required library
We will also define some constants that we will use to control our car:
#define FORWARD '8'
#define BACKWARD '5'
#define STOP '0'
#define LEFT '4'
#define RIGHT '6'
#define STRAIGHT '/'

#define TIMEOUT 500UL
Next comes the variables for the motor pins. The value of these variables will be whatever pin the wire is connected to on the Arduino. If you wired yours up differently make sure you update your code here:
int motor1Pin1 = 5;    // pin 2 on L293D is connected to this pin on the Arduino
int motor1Pin2 = 6;    // pin 7 on L293D                  "
int enablePin1 = 9;    // pin 1 on L293D                  "
int motor2Pin1 = 3;    // pin 10 on L293D                 "int motor2Pin2 = 4;    // pin 15 on L293D                 "
int enablePin2 = 10;    // pin 9 on L293D                 "
There are two variables to control the motor speeds:
int motor1Speed = 255; //max speed 255 
int motor2Speed = 255;
The last variable is for the timeout counter:
unsigned long counter;

The setup function will set up the pins as required. It also set's up Virtual Wire:
void setup() 
    //Set pin modes
    pinMode(motor1Pin1, OUTPUT);
    pinMode(motor1Pin2, OUTPUT);
    pinMode(motor2Pin1, OUTPUT);
    pinMode(motor2Pin2, OUTPUT);
    pinMode(enablePin1, OUTPUT);
    pinMode(enablePin2, OUTPUT);
    //Set enablePin to the motors speed
    analogWrite(enablePin1, motor1Speed);
    analogWrite(enablePin2, motor2Speed);
    //Begin with motors off
    digitalWrite(motor1Pin1, LOW); 
    digitalWrite(motor1Pin2, LOW);
    digitalWrite(motor2Pin1, LOW); 
    digitalWrite(motor2Pin2, LOW);

    //Initialise the IO and ISR
    vw_set_ptt_inverted(true);    // Required for RX Link Module
    vw_setup(2000);                   // Bits per sec
    vw_set_rx_pin(13);           // We will be receiving on pin 23 (Mega) ie the RX pin from the module connects to this pin. 
    vw_rx_start();                      // Start the receiver 

The loop function will contain the following code:
void loop()
  //variables for Virtual Wire
  uint8_t buf[VW_MAX_MESSAGE_LEN];
  uint8_t buflen = VW_MAX_MESSAGE_LEN;
  //If we got a message from the serial port
  if (Serial.available())
    //Reset the timeout counter
    counter = millis();
    //Drive the requested motor
    //Otherwise check for a message from the reciever
  } else if (vw_get_message(buf, &buflen;)) // check to see if anything has been received
      //Reset timeout counter
      counter = millis();
      int i;
      Serial.println("recieved"); //Debug message
       // Message with a good checksum received.
      //For each command recieved
      for (i = 0; i < buflen; i++)
          drive(buf[i]); //Drive requested motors
      //If the counter is greater than the timeout (No signal recieved) then stop the car.
    } else if(millis()-counter >= TIMEOUT) {
Finally we need to define the Drive() function:
void drive(int dir) {
  //Check which direction is requested (same for below)
  if (dir == FORWARD) {
     Serial.println("Forward");//Used for debugging
     //Set motor accordingly (same for below)
     digitalWrite(motor1Pin1, HIGH); 
     digitalWrite(motor1Pin2, LOW);
  } else if (dir == BACKWARD) {
     digitalWrite(motor1Pin1, LOW); 
     digitalWrite(motor1Pin2, HIGH); 
  } else if (dir == STOP) {
    digitalWrite(motor1Pin1, LOW); 
    digitalWrite(motor1Pin2, LOW); 
  } else if(dir == STRAIGHT) {
    digitalWrite(motor2Pin1, LOW);
    digitalWrite(motor2Pin2, LOW);
  }else if (dir == LEFT) {
    digitalWrite(motor2Pin1, LOW);
    digitalWrite(motor2Pin2, HIGH);
  }else if (dir == RIGHT) {
    digitalWrite(motor2Pin1, HIGH);
    digitalWrite(motor2Pin2, LOW);

You can download the complete sketch from here:

Step 5: Receiving Arduino: Attaching the Car.

For this project you can use any remote control car that uses DC motors.
First, remove the casing of the car. Mine had a bunch of screws which I undid and the casing came straight off.
Next unscrew the circuit board already in the car, we wont be needing that. Cut all the wires connected as close to the circuit board as possible and remove the board. Now we are ready to wire up our car to our Arduino.
Now connect the wires from the motors to the OUT pins of the L293D chip and the wires from the battery pack to the rails that power the chip. The ground of the Arduino should also connect to the negative terminal of the battery pack. Finally, connect the car antenna to the RF receiver antenna pin.

Step 6: Computer Program: Creating the GUI.

For the computer program, create a new Java application in whatever application you are using. I recommend Eclipse.
First create a class that extends JPanel which will be used as our GUI. It will also need to implement ActionListener and KeyListener.
public class GUI extends JPanel implements ActionListener, KeyListener {

In the constructor of our class we will be setting up the GUI layout. In order to achieve the layout above, we will be using a 3 by 4 grid. Note that this does not need to be defined anywhere, we just tell the components what grid space to occupy and the grid is created accordingly. The code below is the constructor for the GUI class and contains the layout of our GUI.

	public JButton bFront, bBack, bLeft, bRight; //Define the buttons
	StyledDocument instructionsText; //This is used for the instructions
	public JTextPane instructions;	//Also used for instructions
	public GUI() {
		setLayout(new GridBagLayout()); //Set the layout to Grid Bag
		this.setPreferredSize(new Dimension(400,400));//Set the size of the window
		GridBagConstraints c = new GridBagConstraints();
		c.fill = GridBagConstraints.BOTH;
		c.gridx = 0; //This will be the position of the instructions
		c.gridy = 0;
		c.gridwidth = 4; //The instructions will span 4 tiles
                //Create the instructions text
		StyledDocument instructionsText = new DefaultStyledDocument();
		Style defaultStyle = instructionsText.getStyle(StyleContext.DEFAULT_STYLE);
		StyleConstants.setAlignment(defaultStyle, StyleConstants.ALIGN_CENTER);
		try {
			instructionsText.insertString(0, "Control the car using the keyboard.\n Change the key bindings by clicking the buttons below.", null);
		} catch (BadLocationException e) {
                //add the text to the pane
		instructions = new JTextPane(instructionsText);
		//add the pane to the window
		//Create the forward button (same for others below)
		bFront = new JButton("Forward key: " + KeyEvent.getKeyText(frontKey));

		//Set position of the forward button (same for others below)
		c.gridwidth = 1;
		c.gridx = 1;
		c.gridy = 1;
		bBack = new JButton("Backward key: " + KeyEvent.getKeyText(backKey));
		c.gridx = 1;
		c.gridy = 4;
		bLeft = new JButton("Left key: " + KeyEvent.getKeyText(leftKey));
		c.gridx = 0;
		c.gridy = 3;
		bRight = new JButton("Right key: "+ KeyEvent.getKeyText(rightKey));
	    c.gridx = 3;
		c.gridy = 3;

With our class defined we need to create the main method which will run and show our GUI:
	 public static void main(String[] args) {
		 // TODO Auto-generated method stub
		 //Create and show the GUI
		javax.swing.SwingUtilities.invokeLater(new Runnable() {
		 public void run() {
	 private static void createAndShowGUI() {
		//Create and set up the window.
		JFrame frame = new JFrame("Arduino RC Car Controller");

		//Tell the program to exit when the GUI is closed
		final GUI gui = new GUI(); //create the GUI
		gui.setOpaque(true); //Set it to visible
		frame.setContentPane(gui); //attach it to the Jframe
		//Display the window.
Next we need to add the functionality for when we click on a button:
//If a button is clicked tell the program to listen for the next key pressed
public void actionPerformed(ActionEvent e) {

	if(e.getActionCommand().equals("forward")) {
		listenKey = 1;
	} else if(e.getActionCommand().equals("backward")) {
		listenKey = 2;
	} else if(e.getActionCommand().equals("left")) {
		listenKey = 3;
	} else if(e.getActionCommand().equals("right")) {
		listenKey = 4;
We also need to handle keyboard presses:
public void keyPressed(KeyEvent e) {
	//When a key is pressed
	//if not listening for a key change the color of the corresponding button 
	//and save the state of the key
	if(listenKey <= 0)
		if(e.getKeyCode() == frontKey) {
			frontKeyPressed = true;
		} else if(e.getKeyCode() == backKey) {
			backKeyPressed = true;
		} else if(e.getKeyCode() == leftKey) {
			leftKeyPressed = true;
		} else if(e.getKeyCode() == rightKey) {
			rightKeyPressed = true;

public void keyReleased(KeyEvent e) {
	//When a key is released
	//If we are waiting for a key
	switch(listenKey) {
		//Set the control for the requred button
		case 1:
			frontKey = e.getKeyCode();
			bFront.setText("Forward key: " + KeyEvent.getKeyText(frontKey));
			listenKey = 0;
		case 2:
			backKey = e.getKeyCode();
			bBack.setText("Backward key: " + KeyEvent.getKeyText(backKey));
			listenKey = 0;
		case 3:
			leftKey = e.getKeyCode();
			bLeft.setText("Left key: " + KeyEvent.getKeyText(leftKey));
			listenKey = 0;
		case 4:
			rightKey = e.getKeyCode();
			bRight.setText("Right key: " + KeyEvent.getKeyText(rightKey));
			listenKey = 0;
			//Otherwise return the button to normal
			if(e.getKeyCode() == frontKey) {
				frontKeyPressed = false;
			} else if(e.getKeyCode() == backKey) {
				backKeyPressed = false;
			} else if(e.getKeyCode() == leftKey) {
				leftKeyPressed = false;
			} else if(e.getKeyCode() == rightKey) {
				rightKeyPressed = false;
Download the class file so far:

Step 7: Computer Program: Coding the Serial Connection.

Finally we'll add the serial port functionality to our program.
To do this we need to download the RXTX library from:
Place the rxtxSerial.dll and the RXTXcomm.jar into the project folder and add it to the build path in Project>Properties>Java Build Path.
Next we'll create a separate thread which we'll put at the bottom of the createAndShowGUI() function:
Thread t=new Thread() {
	public void run() {

		//Attempt to initialize the serial connection
		while(!gui.initialize()) {
			System.out.print("Waiting one second...");
			try {Thread.sleep(1000);} catch (InterruptedException ie) {}
		//Send data every 100ms
		while(true) {
			try {Thread.sleep(100);} catch (InterruptedException ie) {}
The sendData() function is as follows:
public void sendData(){
	try {
		//If forward key is pressed send forward etc...
		} else if(backKeyPressed){
		} else {
			//If both left and right are pressed the car will go straight
		} else if (rightKeyPressed){
		} else {
	} catch(Exception e) {
Download the complete class file here:

Step 8: Finalising Everything.

Once you are happy that your car is working you can solder the wiring permanently onto your prototype board. If you do not know how to solder, check out this tutorial:

Further improvements:
  • If your RC car has any LED lights, try hooking them up to your Arduino too. You could use a photosensitive resistor to detect when it gets dark and turn the lights on accordingly.
  • Another cool addition could be to add a wireless camera to see what the car see's while you drive it around.
  • For advanced programmers, In addition to a wireless camera try creating a web interface to control your car from anywhere in the world.
  • Try adding different sensors to the car and give it some artificial intelligence.

Share your ideas or show off your designs in the comment section below!


Pra7esh (author)2016-04-09

I have no knowledge of java but am in real need of help. could you please send the java file you made.

MahfuzH (author)2016-03-09

i am using an adafruit motor shield to run 4 dc motors..what codes should i use?

MahmoodM (author)2015-01-12

I keep getting "Could not find COM port". How to fix this thing?

azverche (author)2014-07-09

I press backward but i didn't receive anything on second arduino..

Can someone make this program and send me??

faizaa (author)azverche2014-11-27

can you please tell me how to input code to control the cam and projector for live recording and display direct from pc please help me in my project ...

backis (author)2013-11-19

i have problem with reaction time:( I need to push button many times and fast just to get reaction :(

malnas01 (author)backis2013-11-19

Did you copy my code exactly or modify it in any way? Try download and use my exact code. It might be an issue with your RF receiver or transmitter, have you used them before, did they work as expected?

backis (author)malnas012013-11-20

Yeah my rf transmitter is shit only works at 10cm range :DDD(with huge antenna)

malnas01 (author)backis2013-11-20

Does the rest of the project work? The RF transmitter I linked in the tutorial is the one I'm using. You can buy it from spark fun for $3.95USD

backis (author)malnas012013-11-21

Yes everything works. I'm using your code as a template to control relays.Now i'm
trying to crate working jar file :D But with my knowledge and experience with java it's taking time :D

faizaa (author)backis2014-11-27

can you tell me how to input code to control the cam and projector for live recording and display direct from pc please help me in my project ...

malnas01 (author)backis2013-11-21

ahah good luck :) let me know how it ends up going!
What are you actually doing with it ?

cgrrty (author)malnas012013-11-29

so cool

faizaa (author)2014-11-27

Can you make one car for me please i want some addition in it i need a small projector which can rotate and a camera installed inside a car which also can rotate 360 degree to see all four sides of a car and a distance meter to see how much distance did a car moved and if possible make the car 4 wheel drive please replay me as urgent you can please…

thank you…

dicki witwicky (author)2014-10-26
  • Another cool addition could be to add a wireless camera to see what the car see's while you drive it around.

    HOW??? please tell me.. =D
creasty (author)2013-11-28

hey,friend it's look like u have a great knowlage on arduino i need ur help,i m new to arduino..i want to run arduino programme which i'hv (made for leonardo board only) and check whether there is any error in programme or not..and than i want to upload this programme in programme board and acorrding to programme it'll run 2 gear motor,so how can i check it and load it..can u please tell me step wise instruction or put instructable type vedio..i'll be thankfull,thank you

malnas01 (author)creasty2013-11-28

You can find many good tutorials already on the internet. Try look here:
This will teach you the basics of programming for the Arduino. It works on the Leonardo!

To upload the program to the Arduino use the Arduino IDE here:

dicki witwicky (author)malnas012014-09-04

hey it worked.THANKS!

i have problem with reaction time, this program is taking long time to respond to the keys pressed
how can i reduce the response time in the program.


Yeah same here, I just got done with it today and the reaction time takes a while. Did you figure out a way to reduce the reaction time?


thanks.. but the problem has been solved =)

yogesh22 (author)2014-03-13

it is giving a warning during run time in console as:


WARNING: RXTX Version mismatch

Jar version = RXTX-2.2-20081207 Cloudhopper Build

native lib Version = RXTX-2.2pre2

how to resolve this??

yogesh22 (author)2014-01-25

the power led of receiver end arduino does not turns on even after all the connections shown in your figure
is there any connection missing or do i need to connect an adapter
please reply ASAP
Thank You

malnas01 (author)yogesh222014-01-25

The receiver arduino needs a power supply of its own. I used a battery pack that came with it. You could also connect the cat battery to the Vin pin on the Arduino but I recommend the separate battery pack

yogesh22 (author)malnas012014-01-26

ok nw i got it
thanks for your quick reply

malnas01 (author)yogesh222014-01-26

You're welcome. Good luck with it :)

yogesh22 (author)malnas012014-01-27

can i drive two 12 volts (0.4amp 200 rpm 4 kg torque) geared dc motors with this circuit?? or do i need to make some changes?

malnas01 (author)yogesh222014-01-27

Yes you should be able to but you may need to increase the power supply connected to the +Vmotor pin of the l293d chip. If you do increase the power supply you should probably connect the +V pin to your Arduinos 5v out instead of the external power supply so as not to damage it with to much voltage.

yogesh22 (author)malnas012014-01-31

hey it worked.THANKS!
but this program is taking long time to respond to the keys pressed
how can i reduce the response time in the program.
I think my java program is taking more time to transmit the character from pc because my circuitry is working perfectly

saberakhizada (author)2013-12-05

Can you please tell me how to make a receiver for Lanyu 5CH transmitter RC controller because I lost it or if you can contact me

saberakhizada (author)2013-12-05

Its a very cool project i like it

saberakhizada (author)2013-12-05

Hi friend

backis (author)2013-11-19

cool project :D