Obstacle Avoiding Robot




Posted in TechnologyArduino

Introduction: Obstacle Avoiding Robot

About: I am an electrical engineering and physics student and I love to tinker with things.

I have seen many obstacle avoiding robot builds online including here at instructables, so I decided to do an instructable myself and provide as much visual and written detail as possible. Many of the obstacle avoiding robot projects that I have seen utilize a third servo upon which the PING))) sensor is mounted. This way, when the robot reaches its threshold distance to the obstacle in front of it, this third servo pans left and right then the robot turns to the route which has a “clearer” path and goes on. I on the other hand am just going to show you how to do it without the third panning servo. This is a better alternative for those on a tighter budget. Continue onto the next step to see the parts list.

Step 1: Gather the Parts

To build this robot you are going to need the following parts. All of these parts can be gotten separately or in a bundle (you won't need all of the parts in the bundle) at http://www.parallax.com/.

The following hardware you can get anywhere in various prices.
 • Arduino Nano (any 5v Arduino of your choosing will work).
 • Four AA batteries 
 • AA battery holder
 • Breadboard (a mini breadboard was perfect in size).
 • Wire
 • PING))) Ultrasonic Distance Sensor

Hardware from Parallax:
The following hardware you can get anywhere in various prices.
Stock #            Quantity         Product Name
700-00009              1              Tail Wheel Ball
700-00022              1              Boe-Bot Aluminum Chassis
700-00023              1              Cotter Pin-1/16" Diameter
700-00025              1              Rubber Grommet-13/32" Hole Diameter
721-00001              2              Wheel, Plastic, 2.58 Dia, .3 W
721-00002              2              Rubber Band Tire for 721-00001
900-00008              2              Continuous Rotation Servo

• Arduino IDE (my version is 1.0.5).

Phillips head screw driver
 • Computer
 • Screws and nuts

Step 2: Building the Circuit

As you can see, the circuit is very simple. Just make sure that you have the signal wire of each of the servos going to the correct pins. They are not interchangeable in regards to the code that will be running the robot. The sensor that you see there in the schematic is NOT the PING))) sensor. The software that I used to create the schematic just doesn't have the PING))) sensor in its inventory, so I used the next closes one. The connections are the same (red=power, black=ground, yellow=SIG). I believe the circuit is self-explanatory, but if you have any questions, don't hesitate to ask. Continue onto the next step for the programming part.

Step 3: Programming

The basic concept of the code is for the robot to always be monitoring for objects in front of it while moving. This is done by the PING))) sensor where it sends out a 40kHz chirp which is not audible, and retrieves the echo. The program then gets the duration it takes for the pulse to get back and converts it into distance. Once the robot detects an object where the distance forward is greater than the danger threshold - the path is clear so our program tells the robot to move forward. Otherwise the robot will turn and proceed. The code just loops in this fashion. 


> Design an obstacle avoiding robot using an Arduino NANO and Parallax PING))) Ultrasonic Distance Sensor
> Zoran M.

#include //include Servo library

const int RForward = 0;
const int RBackward = 100;
const int LForward = RBackward;
const int LBackward = RForward;
const int pingPin = 7;
const int dangerThresh = 15; //threshold for obstacles (in cm)
Servo leftMotor;
Servo rightMotor; //declare motors
long duration; //time it takes to recieve PING))) signal

void setup()

void loop()
  int distanceFwd = ping();
  if (distanceFwd>dangerThresh) //if path is clear
    rightMotor.write(RForward); //move forward
  else //if path is blocked
long ping()
  // Send out PING))) signal pulse
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  digitalWrite(pingPin, HIGH);
  digitalWrite(pingPin, LOW);
  //Get duration it takes to receive echo
  pinMode(pingPin, INPUT);
  duration = pulseIn(pingPin, HIGH);
  //Convert duration into distance
  return duration / 29 / 2;

Continue onto the last step for additional pictures and conclusion.

Step 4: Additional Pictures and Conclusion

Everything went pretty well while putting this project together. The program had no trouble whatsoever; the only thing I had some trouble with was the PING))) sensor. As I declared the threshold to be 15 cm it was picking up distances sometimes further than what I set it to be and sometimes closer than what I set it to be. A suggestion for future improvement would be to have a random method in the program where when the robot approached an object I would have no control whether it would turn left or right and by how many degrees. With this random method, both the the direction and degree of turn would be totally random; making it easier for the robot to get out of corners. Don't hesitate to post up your versions, even if you did it like I did. I would love to see them!

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    Can you pls tell me the wiringif iI use DC motors with two pins??? Just tell me the connection pin..

    Pls describe the pins of arduino that you are using for servos and ping sensor..Reply fast it is urgent

    1 reply

    Take a look at the drawing. It is very clear and easy to follow.

    Yup, you can use an Arduino Uno.

    how if i change the PING sensor with sharp GP2D12 IR Ranger sensor, is that work?

    You answered many of my questions about Arduino and Servos. Thanks.

    Is a servo necessary or can this be driven with a pair of brushless motors, such as you might find in a Tamiya gearbox?

    3 replies

    You can do it with brushless motors as well.

    Is it a direct connect? What is the connection to control the motor? In other words, if I have a 2 wire motor where do I connect which wire?

    Thanks Zoran!

    Here: https://www.instructables.com/id/Arduino-obstacle-avoiding-robot-1/ is an instructable you can follow. Thanks.

    thank you. But the error messages:

    Arduino: 1.5.5-r2 (Windows 7), Board: "Arduino Uno"

    sketch_jan28a.ino: In function 'void loop()':
    sketch_jan28a:27: error: expected initializer before 'rightMotor'
    sketch_jan28a.ino: In function 'void loop()':
    sketch_jan28a:31: error: redefinition of 'void loop()'
    sketch_jan28a:6: error: 'void loop()' previously defined here
    sketch_jan28a:34: error: 'dangerThresh' was not declared in this scope
    sketch_jan28a:36: error: 'leftMotor' was not declared in this scope
    sketch_jan28a:36: error: 'LForward' was not declared in this scope
    sketch_jan28a:37: error: 'rightMotor' was not declared in this scope
    sketch_jan28a:37: error: 'RForward' was not declared in this scope
    sketch_jan28a:41: error: 'leftMotor' was not declared in this scope
    sketch_jan28a:41: error: 'LBackward' was not declared in this scope
    sketch_jan28a:42: error: 'rightMotor' was not declared in this scope
    sketch_jan28a:42: error: 'RForward' was not declared in this scope
    sketch_jan28a.ino: In function 'long int ping()':
    sketch_jan28a:50: error: 'pingPin' was not declared in this scope
    sketch_jan28a:59: error: 'duration' was not declared in this scope

    This report would have more information with
    "Show verbose output during compilation"
    enabled in File > Preferences.

    still come up. I have a week left to do this project so it would really help if you could help me quickly. Thank you!

    3 replies

    Use this code: https://gist.github.com/anonymous/9b140e31f95be145a08a . When you hit 'verify', what do you get? Any errors, or nothing? By the way, what version of Arduino evironment are you using?

    thank you. i am using 1.5.5-r2. But with the new code the error messages:

    Arduino: 1.5.5-r2 (Windows 7), Board: "Arduino Uno"

    sketch_feb25a.ino: In function 'void setup()':
    sketch_feb25a:27: error: redefinition of 'void setup()'
    sketch_feb25a:1: error: 'void setup()' previously defined here
    sketch_feb25a.ino: In function 'void loop()':
    sketch_feb25a:33: error: redefinition of 'void loop()'
    sketch_feb25a:6: error: 'void loop()' previously defined here

    This report would have more information with
    "Show verbose output during compilation"
    enabled in File > Preferences.

    appear with the new code. Please respond as soon as possible. Thank you.

    When you go to arduino's website, download this: http://imgur.com/MDy1lfM . Try it out and let me know how it goes.

    I am in the process of making this robot. I am a student that only has a little robotic experience but my teacher knows quite a bit. The Arduino software does not recognize the word Servo and I don't know what to do. Could someone help me?

    1 reply

    Hello, LegitINSTRUCTABLES. How about if you insert <Servo.h> after #include like I have shown here: http://imgur.com/JTTTXGl ?

    can I use HCdSR04 as my sensor??can't find available PING sensor here...

    1 reply

    That will work, although you might have to change some of the code in the program to correspond to the pins of that sensor.

    The code would work on other arduinos right? I've just started to learn the language, thank you.