HC-SR04 ultrasonic sensor issues with DC Motor

Other Hardware Motors, Mechanics, Power and CNC
1

Hello I am trying to control two DC motors using the HC-SR04 ultrasonic sensor. I am using Arduino uno and the Motor control shield. Bellow is my code. The motor only go forward. What am I doing wrong?

#include <AFMotor.h>

AF_DCMotor motor1(1,MOTOR12_2KHZ);
AF_DCMotor motor2(2,MOTOR12_2KHZ);
//AF_DCMotor motor3(3);
//AF_DCMotor motor4(4);
const int trigPin=9;
const int echoPin=10;

//int status=0; //0-off 1-forward 2-back

void setup()
{Serial.begin(9600);

motor1.setSpeed(200);
motor2.setSpeed(200);

}

void loop()
{
// and the distance result in centimeters

long duration,cm;
pinMode(trigPin, OUTPUT);
digitalWrite(trigPin,LOW);
delayMicroseconds(2);
digitalWrite(trigPin,HIGH);
delayMicroseconds(20);
digitalWrite(trigPin,LOW);

pinMode(echoPin, INPUT);
duration = pulseIn(echoPin,HIGH);
// convert the time into distance
// speed of sound is 340m/s or 29 microseconds per centimeter
cm = microsecondsToCentimeters(duration);
for (cm=0; cm<=100; cm++)
//if (cm<=100)
{
motor1.run(FORWARD); //go forward for cm between 0 and 100
motor2.run(FORWARD);
//println(cm);
delay(100);
}
if (cm<=10){
motor1.run(RELEASE); //Stop
motor2.run(RELEASE);
delay(100); //delay
motor1.run(BACKWARD); //go backward
motor2.run(BACKWARD);
delay(100);
}
else if (cm>10&&cm<12)
{
motor1.run(BACKWARD);// from backward 2cm then turn right
motor2.run(FORWARD);
delay(100);
}
//delay(500);

else if (cm>12&& cm<14)

{
motor1.run(FORWARD); //Left turn
motor2.run(BACKWARD);
delay(100);
//motor1.run(FORWARD); // Left Turn
//motor2.run(BACKWARD);
//delay(500);
}

{

Serial.print(cm);
Serial.print("cm");

Serial.println();

delay(100);

}
cm = microsecondsToCentimeters(duration);
}

long microsecondsToCentimeters(long microseconds)

{
// The speed of sound is 340 m/s or 29 microseconds per centimeter.

// The ping travels out and back, so to find the distance of the

// object we take half of the distance travelled.

return microseconds / 29 / 2;
}

2

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ngong123:

cm = microsecondsToCentimeters(duration);

So you have now converted the sensor reading to centimeters, so far so good.

ngong123:

for (cm=0; cm<=100; cm++)

//if (cm<=100)
{
motor1.run(FORWARD); //go forward for cm between 0 and 100
motor2.run(FORWARD);
 //println(cm);
 delay(100);
}

For no apparent reason you decide to blow away that nice sensor reading and instead count from 0 to 100, during which time you set the motors going forward every tenth of a second.

ngong123:

if (cm<=10){

motor1.run(RELEASE); //Stop
motor2.run(RELEASE);
delay(100);          //delay
motor1.run(BACKWARD); //go backward
motor2.run(BACKWARD);
delay(100);
}
else if (cm>10&&cm<12)
{
 motor1.run(BACKWARD);// from backward 2cm then turn right
 motor2.run(FORWARD);
 delay(100);
 }
//delay(500);

else if (cm>12&& cm<14)

{
 motor1.run(FORWARD); //Left turn
 motor2.run(BACKWARD);
delay(100);
//motor1.run(FORWARD); // Left Turn
//motor2.run(BACKWARD);
//delay(500);
}

Now you have some if statements, none of which will ever be true because your for loop set cm to 100.

ngong123:

  Serial.print(cm);

Serial.print("cm");

Then you print the value of cm but apparently you didn't bother to look at it, otherwise you would have noticed it's always 100.

ngong123:

 cm = microsecondsToCentimeters(duration);

Just for kicks, calculate cm again, right before it goes out of scope.