Ultrasonic sensor

Other Hardware Sensors
1

After struggling for few days i decided to post my problem online:
I'm using ultrasonic sensor to measure distance. My goal is to when the distance is >90 a smiley is displayed on my 8x8 led matrix display and when distance is <90 (cm) a :open_mouth: - smiley is displayed. The distance measurement works fine but the problem is when i add the if( distance <= 90 ); For some reason when ever i add the if statement my ultrasonic sensor starts displaying about 5cm (1-10) and thus showing :open_mouth: - smiley.
Can someone take a look and tell me what I'm doing wrong and why do i start getting wrong readings?

#include "LedControl.h"
 
LedControl lc=LedControl(12,11,10,2);  // Pins: DIN, CLK, CS

int echo = 3; 
int trig = 2; 
int beep = 7;  // currently not used
int led = 5;
float pingTime;    
float distance;
float speedOfSound = 1.236;

byte smiley1[]{
B00000000,
B01100110,
B01100110,
B00000000,
B00000000,
B01000010,
B00111100,
B00000000,

};

 byte smiley2[]{
B00000000,
B01100110,
B01100110,
B00000000,
B00111100,
B01000010,
B01000010,
B00111100,

};

 
void setup(){

  Serial.begin(9600);
  pinMode(echo, INPUT);
  pinMode(trig, OUTPUT);
  pinMode(beep, OUTPUT);
  pinMode(led, OUTPUT);
  
  lc.shutdown(0,false);  // Wake up display
  lc.setIntensity(0,1);  // Set intensity level
  lc.clearDisplay(0);  // Clear Display
}


void Smiley1(){ 
  for (int i = 0; i < 8; i++) {
    lc.setRow(0, i, smiley1[i]);
  }
}

void Smiley2(){
  for (int i = 0; i < 8; i++) {
    lc.setRow(0, i, smiley2[i]);
  }
}



void loop(){

  digitalWrite(trig, LOW);
  delayMicroseconds(2000);
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);

 
  pingTime = pulseIn(echo, HIGH);
  pingTime = pingTime / 1000000.;
  pingTime = pingTime / 3600.;

  distance = speedOfSound * pingTime;
  distance = distance / 2;
  distance = distance * 100000000;

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

  if( distance <= 90 ){
    Smiley2();
    digitalWrite(led, HIGH);
  }
  else{ Smiley1(); }



 
  
  delay(5);
  digitalWrite(led, LOW);


}

PS It works fine without the if statement, if i remove it i get the right distance reading.

2

How is the LED matrix powered?

3

I followed this tutorial https://brainy-bits.com/tutorials/how-to-control-max7219-led-matrix/ i used one display.

4

Copy the ling you have a scheme on the page. But anyhow, the led matrix is not the problem, the sensor is the one making problems...

5

So, until you start to use the LED matrix, everything looks OK, and after that , it's wrong, and it's not the fault of the LED matrix?

Try increasing the final delay to 50 milliseconds - 5 milliseconds is way too short.

6

Duplicate post deleted.

DO NOT CROSS-POST, CROSS-POSTING WASTES TIME.

7

I figured i posted it in the wrong category and though somebody else would help me..It is not the led matrix, what ever i put that has a delay i get multiple values from my sensor one normal (100cm) and other phantom value ( 1 - 10 cm ) and i still can't figure out why.

8

Did you try increasing the delay to 50 milliseconds?