problems with timing

My program is supposed to make my buzzer sound a tone whenever my ultrasonic sensor detects an object less than 5 cm away for more than 5 seconds. However, i’m having difficulties getting the program to run consistently. After fulfilling my requirement the first time, the timing of it all gets messed up. I’m new to programming so any help would be much appreciated.

this is my program:

unsigned long delaystart = 0;
unsigned long delaytime = 5000;

int trigPin = 22 ; // Trigger
int echoPin = 23; // Echo
float duration, cm; // Ultrasonic sensor measurements
int buzzer = 12 ; //buzzer to arduino pin 12

void setup()
pinMode(trigPin, OUTPUT); //ultrasonic sensor
pinMode(echoPin, INPUT); //ultrasonic sensor
pinMode(buzzer, OUTPUT);

delaystart = millis();


void loop(){

digitalWrite(trigPin, LOW);
digitalWrite(trigPin, HIGH);
digitalWrite(trigPin, LOW);

pinMode(echoPin, INPUT);
duration = pulseIn(echoPin, HIGH);
cm = ((duration/2) / 29.1);


if((millis() - delaystart) >= delaytime)
delaystart += (delaytime);
tone(buzzer, 500);


You’re pinging far too frequently.
You should limit the ping rate to around 20 - 30 Hz.

Please remember to use code tags when posting code

I don't think the ultrasonic sensor can work with distances less than 5cm. The spec says 2cm but that is cutting it close.

…And don’t cross-post.
It’s a fast-track to the sin bin

Your duplicate topic in another forum section has been deleted

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