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I know this is probably a very asked question, but I am building a fairly basic radar type thing which sweeps left and right and uses an ultrasonic sensor to determine the distance to an object and a buzzer is set off if something is detected.

The device itself works but I've noticed that because I have used delay() to allow the servo to complete its full movements, it is holding up the rest of the code, and as a result the buzzer and returning of the distance is extremely unresponsive and sluggish.

So far I have looked at simply returning a value whenever the motor reaches a certain step but it doesn't achieve exactly what I'm looking for, and I have looked into using millis() for timing asynchronously, but I'm struggling to wrap my head around it a bit in terms of how it will work for a servo.

My current working but sluggish code:

//Servo Stuff
#include <Servo.h>
int servoPin = 12; // Pin for interacting with servo defined
int servoStart = 0; //Starting position of servo motor
int servoEnd = 90; //End position of servo means it rotates 90 degrees
int waitTime = 1000; // Allows servo to fully rotate before moving again
int servoPos = 20; // For incrementing the position of the servo
int servoStep = 20; //amount to increment servo position by
Servo myServo; // Creates an instance of a servo object


//Ultrasonic stuff
int trigPin = 9;
int echoPin = 10;
long duration;
int distance;
int maxDistance = 329; // The max range of the ultrasonic sensor

//Buzzer stuff
int buzzerPin = 11;
int buzzerWait = 200;

void setup(){

//Attach the servo object to the pin and begin serial monitor with
// polling rate of 9600
Serial.begin(9600);
  myServo.attach(servoPin);
  pinMode(buzzerPin, OUTPUT);
  

    pinMode(trigPin, OUTPUT); // Trig pin set as output
    pinMode(echoPin, INPUT); // echo pin set as i
      }
    
    void loop()
    {
    
    
      // Moving servo 
      myServo.write(servoStart); //Moves servo to the starting pos
      //delay (waitTime); //allows servo to fully move before next move
      //myServo.write(servoEnd); //Moves to end position
      //delay (waitTime); // waits before reverting back to start pos
      
    //myServo.write(servoStart);
    //delay(waitTime);
    //myServo.write(20);
    //delay(waitTime);
    //myServo.write(40);
    //delay(waitTime);
    //myServo.write(60);
    //delay(waitTime);
    
     // Using ultrasonic sensor
      
      // Clears the trig pin
      digitalWrite(trigPin, LOW);
      delayMicroseconds(2);
      
    // Sets the trigPin on HIGH state for 10 microseconds
      digitalWrite(trigPin, HIGH);
      delayMicroseconds(10);
      digitalWrite(trigPin, LOW);
      
    // reads echoPin and returns the travel time of the wave in microseconds
      duration = pulseIn(echoPin, HIGH);
      
    // Calculating distance
      distance = duration*0.0343/2;
      
    //Prints the distance to the Serial Monitor
      Serial.print("Distance: ");
      Serial.println(distance);
      Serial.println(distance);
      
      if (distance < maxDistance) {
      digitalWrite(buzzerPin, HIGH);
      //delay(buzzerWait);
      //digitalWrite(buzzerPin,LOW);
      //delay(buzzerWait);
      
      }else digitalWrite(buzzerPin, LOW);
      
        
    }

Any pointers to some good resources for this would be very appreciated, thanks.

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From your code it seems like you are doing all the servo movement before you read the distance and report back. A lot of code is commented out, so it's a bit difficult to follow. What I would do is something along the line of:

[...]
int servoStart=0;
int servoEnd=90;
int servoPos=0;

[...]
void setup() {
    [usual setup stuff like you do it now]
    myServo.write(servoPos);  //start at pos 0
    // Maybe a delay here to make sure we are at pos. 0
}

void loop() {
    //Switch direction if we reach end
    if (servoPos+servoStep < servoStart || servoPos+servoStep > servoEnd)
        servoStep = -servoStep;    
    servoPos += servoStep;
    myServo.write(servoPos);
    //Small delay?
    //Read distance
    //Send distance to seraial
    //Buzz buzzer if needed
}
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  • Thank you for this, works perfectly!
    – SourOddity
    Mar 22 at 17:07

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