Breaking a while loop

Using Arduino Programming Questions
#1

Hi,

I’m not that experienced with Arduino and have a question regarding a while loop, at least that is what I believe it is. I am trying to control two linear actuators with an ultrasonic sensor. The actuators (without position indicator) are connected to a motor controller. What I am trying to accomplish, is when an object comes within a 5 cm range of the sensor, the motors will activate for 100 milliseconds and then stop and hold their position until the sensor detects that the object is >= 5 cm’s. When this happens the motors should go back to their original position.

What I am struggling with now is that everything works except for the motors returning to their original position after the sensor detects an object that is >= 5 cm’s. I am almost certain this has something to do with the while loop.

I hope you can help me!

int enA = 5;
int enB = 3;
const int in1 = 8;
const int in2 = 7;
const int in3 = 4;
const int in4 = 2;
const int pingPin = 12;

long previousMillis = 0;    
long interval = 1000; 
long time;
long startTime = 0;
long microsecondsToCentimeters(long microseconds) {

  return microseconds / 29 / 2;
}  

void setup() {
  // initialize serial communication:
  Serial.begin(9600);
  pinMode(in1, OUTPUT);
  pinMode(in2, OUTPUT);
  pinMode(enA, OUTPUT);
  pinMode(enB, OUTPUT);
  pinMode(in3, OUTPUT);
  pinMode(in4, OUTPUT); 
}

void loop() {
  // Variabele cm
  long duration, cm;
  
time = millis();

  // Activate
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(5);
  digitalWrite(pingPin, LOW);

  // Signal read
  pinMode(pingPin, INPUT);
  duration = pulseIn(pingPin, HIGH);

  // to cm
  cm = microsecondsToCentimeters(duration);
  Serial.print(cm);
  Serial.print("cm");
  Serial.println();
 

  delay(100);
  //send pulse
 
  if (cm < 5) {
   digitalWrite(in1, HIGH);
    digitalWrite(in2, LOW);
    digitalWrite(in3, LOW);
    digitalWrite(in4, HIGH);
    analogWrite(enA, 255);
    analogWrite(enB, 255);
    delay(100);
    
    //keep position?
    while (cm < 5){
     digitalWrite(in1, LOW);
    digitalWrite(in2, LOW);
    digitalWrite(in3, LOW);
    digitalWrite(in4, LOW);
    analogWrite(enA, 255);
    analogWrite(enB, 255);   
    Serial.read();
    if (cm >= 5){
      continue;
    }
    
  }
  }
  //Back to original position
    else {
      digitalWrite(in1, LOW);
    digitalWrite(in2, HIGH);
    digitalWrite(in3, HIGH);
    digitalWrite(in4, LOW);
    analogWrite(enA, 255);
    analogWrite(enB, 255);
    }
    }
#2

What you have:

if distance smaller than 5 cm
    move for 100ms
    
    as long as distance is smaller than 5cm
        hold position

else
    go back to home position

What you want:

if distance smaller than 5 cm
    move for 100ms
    
    as long as distance is smaller than 5cm
        hold position

    go back to home position
#3

What is connected to “pingPin” that the pin mode must be changed from output to input?

How do you expect the value for cm to be updated when in the while loop in order for it to be able to get out of the loop? Ie., where in the while loop does the value of cm get updated such that cm will become greater or equal to 5?

#4

adwsystems:
What is connected to “pingPin” that the pin mode must be changed from output to input?

How do you expect the value for cm to be updated when in the while loop in order for it to be able to get out of the loop? Ie., where in the while loop does the value of cm get updated such that cm will become greater or equal to 5?

Thanks for your reply! pingPin is the ultrasonic sensor, but it only has three pins so it shares the trig and echo signal. I think your last comment might be my main question. Any suggestions maybe ?

#5

Something needs to happen in your while loop to update the value for cm. Or it'll stay the same forever and you'll never get out of the loop.

#6