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I'm building a robot for a school project. I am currently using an Arduino Uno, two DC motors and an ultrasonic sensor. The two motors are being controlled via the Arduino Motor Shield v3. I want the robot to be autonomous so it has to be able to move around on its own using the ultrasonic sensor.

This is the latest version of my source code:

#include <Servo.h>             // include Servo library
#include <AFMotor.h>       // include DC motor Library

#define trigPin 12               // define the pins of your sensor
#define echoPin 13

AF_DCMotor motor2(7);   // set up motors.
AF_DCMotor motor1(6);


void setup() {
    Serial.begin(9600);                 // begin serial communication  
    Serial.println("Motor test!");

    pinMode(trigPin, OUTPUT); // set the trig pin to output to send sound waves
    pinMode(echoPin, INPUT);   // set the echo pin to input to receive sound waves

    motor1.setSpeed(105);           // set the speed of the motors, between 0-255
    motor2.setSpeed (105);  
}

void loop() {
    long duration, distance;              // start the scan

    digitalWrite(trigPin, LOW);  
    delayMicroseconds(2);               // delays are required for a successful sensor operation.
    digitalWrite(trigPin, HIGH);
    delayMicroseconds(10);             // this delay is required as well!
    digitalWrite(trigPin, LOW);
    duration = pulseIn(echoPin, HIGH);
    distance = (duration/2) / 29.1;    // convert the distance to centimetres.

    // if there's an obstacle ahead at less than 25 centimetres, do the following:
    if (distance < 25) {   
        Serial.println("Close Obstacle detected!" );
        Serial.println("Obstacle Details:");
        Serial.print("Distance From Robot is " );
        Serial.print(distance);
        Serial.print(" CM!");                   // print out the distance in centimeters.
        Serial.println (" The obstacle is declared a threat due to close distance. ");
        Serial.println (" Turning !");

        motor1.run(FORWARD);           // Turn as long as there's an obstacle ahead.
        motor2.run (BACKWARD);
    } else {
        Serial.println("No obstacle detected. going forward");
        delay(15);

        motor1.run(FORWARD);           // if there's no obstacle ahead, Go Forward! 
        motor2.run(FORWARD);  
    }
}

The current issue is that the wheels are rotating as expected but after a few turns they stop.

I suspect that the issue is software related, but I am not completely sure. Moreover, I believe that the motors are correctly connected to the motor shield, but I might not handle them properly in the code.

Could anyone please help me solving this issue?

Codebreaker007
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Daniël Verloop
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    Upvoted, now you have enough reputation to post an image, press the **edit** button to add it. Can we assume that you are already powering your motors with an external power source, right? – Patrick Trentin Feb 18 '17 at 22:21
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    How are you powering arduino ? if you are using battery, did you check the voltage once it stopped ? – anilkunchalaece Mar 29 '19 at 10:32
  • If there's no relation to your distance measurement, remove it from the test sketch. Can you run one or both motors for a desired and given time and direction? – datafiddler Sep 22 '19 at 10:38
  • Usually you need to run the motors for a specific time and then turn them off, instead of using a delay. – Frank Mancini Mar 22 '20 at 17:27

2 Answers2

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Simple answer - get rid of the delay in the loop

  delay(15);

in combination with the used libraries this leads after some time to no motion at all. Delay stops processing everything, so use a nonblocking time measurement to give the motor routines the processing time instead of blocking everything. See blinkwithoutdelay example in ArduinoIDE how to implement this kind of routine.
When working with robots always look into the libs (= advantage of open source) if the author uses delay() If yes either rewrite the function or ditch the lib. Especially in Arduino environment a lot of really bad libs are around - they work in simple testing cases on the desktop, but not in complex close to real time environments like robotics.

Codebreaker007
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I think you must use PWM pins for motors. Since AFMotor library has option to set speed. So please change pin 7 to pin 5 for motor2 and check.

Mhmd Az
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