Help with led strip on power on

Hi, i’m new to arduino and led strips and have a school project involving them. I’m running into the problem that when I power the led strip and the arduino, all the leds of the strip turn white, i partially solved this problem by doing this

for(int i = 0; i < 34; i++) {  
leds[i].setRGB( 0, 0, 0);
}
FastLED.show();

But as you can see in the video they still light up for like 2 or 3 sec then turn off because of the code.

I saw a lot of tutorials in youtube and they all seem to stay off on power on, unlike mine that turn on, when power is supplied.

There is no problem now, but i need to connect a lot more leds and the little step down that i have only supports 3A MAX, so you see the problem, on power on if i have a lot of leds they will turn on and something will go wrong.

So i need to ask you, how can i make the leds stay off when power is supplied and just light up when i say so in the code?

Here is a video of it working and the code

#include <FastLED.h>
#define NUM_LEDS 33
#define DATA_PIN A3

CRGB leds[NUM_LEDS];
unsigned long time;

String ciclos;
String intervalo;
String unoR;
String unoG;
String unoB;
String dosR;
String dosG;
String dosB;
String tresR;
String tresG;
String tresB;
char letra;
int ciclosI;
int intervaloI;
int unoIR;
int unoIG;
int unoIB;
int dosIR;
int dosIG;
int dosIB;
int tresIR;
int tresIG;
int tresIB;
int uno;
int dos;
int tres;
int check;



//////////////

void setup() { 
    
    Serial.begin(9600);  
  
    FastLED.addLeds<NEOPIXEL, DATA_PIN>(leds, NUM_LEDS);
	
	for(int i = 0; i < 34; i++) {  
	 leds[i].setRGB( 0, 0, 0);
	}
	
	FastLED.show();
}

//////////////

void loop() {
  check = 1;
  if (Serial.available() > 0) {
       delay(100);   
       while (Serial.available()) {      
     
	    ciclos = Serial.readStringUntil(',');
        Serial.read();
        intervalo = Serial.readStringUntil(',');
        Serial.read();
     
        unoR = Serial.readStringUntil(',');
        Serial.read();
        unoG = Serial.readStringUntil(',');
        Serial.read();
        unoB = Serial.readStringUntil(',');
        Serial.read();
     
        dosR = Serial.readStringUntil(',');
        Serial.read();
        dosG = Serial.readStringUntil(',');
        Serial.read();
        dosB = Serial.readStringUntil(','); 
        Serial.read();     
     
        tresR = Serial.readStringUntil(',');
        Serial.read();
        tresG = Serial.readStringUntil(',');
        Serial.read();
        tresB = Serial.readStringUntil(')');   
     
       }

       unoIR = unoR.toInt();
       unoIG = unoG.toInt();
       unoIB = unoB.toInt();
       dosIR = dosR.toInt();
       dosIG = dosG.toInt();
       dosIB = dosB.toInt();
       tresIR = tresR.toInt();
       tresIG = tresG.toInt();
       tresIB = tresB.toInt();
       intervaloI = intervalo.toFloat()/80;
	   ciclosI = ciclos.toInt();
    
    for(int c = 1; c = ciclosI; c++) { 
    for(int i = 0; i < 32; i++) {       
     if(i==0){
     uno = unoIR/40;
     dos = unoIG/40;
     tres = unoIB/40;
     }
     
     if(i==9){
     uno = dosIR/40;
     dos = dosIG/40;
     tres = dosIB/40;
     }
     
     if(i==17){
     uno = tresIR/40;
     dos = tresIG/40;
     tres = tresIB/40;
     } 
     
     if(i==0 && check == 1){ 
         for(int d = 1; d < 41; d++) { 
          leds[i].setRGB( uno*d, dos*d, tres*d);
          FastLED.show();
          time = millis();
      
          while(millis() - time < intervaloI){
           if (Serial.available() > 0) {
           letra = Serial.read();
		   }
           if(letra=='A'){ 
            break;  
           }
          }
         
		  if(letra=='A'){ 
           break;
          }
        }
	 check = 0;
     }
	 
	if(letra=='A'){ 
	 leds[i].setRGB( 0, 0, 0);
     leds[i+1].setRGB( 0, 0, 0);
     break;
    }
     
    for(int d = 1; d < 41; d++) { 
     if ( i!=9 && i!=17){
      leds[i].setRGB( uno*(40-d), dos*(40-d), tres*(40-d));
     }
     if ( i==9){
      leds[i].setRGB( unoIR*(40-d)/40, unoIG*(40-d)/40, unoIB*(40-d)/40);
     }
     if ( i==17){
      leds[i].setRGB( dosIR*(40-d)/40, dosIG*(40-d)/40, dosIB*(40-d)/40);
     }
	 if ( i==31 && (ciclos-c)!=0){
	 leds[0].setRGB( unoIR*d/40, unoIG*d/40, unoIB*d/40);	 
	 }
     leds[i+1].setRGB( uno*d, dos*d, tres*d);
     FastLED.show();
     time = millis();
	 
      
     while(millis() - time < intervaloI){
      if (Serial.available() > 0) {
       letra = Serial.read();
	  }
      if(letra=='A'){ 
       break;
      }      
     }
	 
	 if(letra=='A'){ 
      break; 
	 } 
    }
	
	if(letra=='A'){ 
	 leds[i].setRGB( 0, 0, 0);
     leds[i+1].setRGB( 0, 0, 0);
     break; 
	} 
         
    time = millis();
     if(i>0){
      while(millis() - time < intervaloI){
       if (Serial.available() > 0) {
        letra = Serial.read();
	   }
       if(letra=='A'){ 
        break;
       }
      }
     }
	 
	if(letra=='A'){ 
	 leds[i].setRGB( 0, 0, 0);
     leds[i+1].setRGB( 0, 0, 0);
     break; 
	}
    }        
    
	if(letra=='A'){
     break; 
	}
	}		
	}

              
    FastLED.show();
    intervalo="";
    letra='C';
  }

I forgot the circuit is somthing like this (its missing the bluetooth module, the step down to 5V, the battery is different and its only one led)

https://ibb.co/eRDJN5

(its missing the bluetooth module, the step down to 5V, the battery is different and its only one led)

So in other words it is useless.

1) Where is the large capacitor across the supply?

2)

when I power the led strip and the arduino, all the leds of the strip turn white,

Yes they will do that.

1) I'm waiting for it to arrive

2) So, there is no way to make them not light on start?

So, there is no way to make them not light on start?

Not that I am aware of. Sometimes they do and sometimes they don’t.

  1. I’m waiting for it to arrive

You don’t have to have physically have one before it can be placed on a diagram.

Well okey, thank you for the help!