pov dispaly on table fan leds ws8212

hello all, I have made a 16led rgb setup on table fan the fan speed is 1300 rpm(approx).I am using fast led library for the same with IR led as refrence point for the circum circle(connected to A5 pin arduino).
I am trying out to display just 4 dots at 1/4th of the circle from one another as shon in video below.
The code is as below:

/*
 * IRremote: IRrecvDemo - demonstrates receiving IR codes with IRrecv
 * An IR detector/demodulator must be connected to the input RECV_PIN.
 * Version 0.1 July, 2009
 * Copyright 2009 Ken Shirriff
 * http://arcfn.com
 */

#include <IRremote.h>
#include <FastLED.h>

#define LED_PIN     5
#define NUM_LEDS    16
#define BRIGHTNESS  100
#define LED_TYPE    WS2812
#define COLOR_ORDER GRB
CRGB leds[NUM_LEDS];
#define DATA_PIN 5
#define CLOCK_PIN 13
#define UPDATES_PER_SECOND 1000

int RECV_PIN = 8;  //pov receiver ir connected

IRrecv irrecv(RECV_PIN);

decode_results results;

void setup()
{
  Serial.begin(9600);
  pinMode(8,INPUT);
      FastLED.setBrightness(  BRIGHTNESS );
   FastLED.addLeds<NEOPIXEL, DATA_PIN>(leds, NUM_LEDS);
 
}
//44ms full circle complete
void loop() {
 if (analogRead(A5)>=800)   //connected ir receiver for refrence point
  {
    for(int i=0;i<=3;i++){
    delay(7);                        //waiting to complete 1/4th of circumcirle distance (90deg)
    leds[0] = CRGB::Red;
  FastLED.show();
  leds[0] = CRGB::Black;
  FastLED.show(); 
    }
  Serial.println(millis()-t1);
  }
}

The photo of the above program executed is shown
As per my assumptions for every 1/4th of the circumcirle only one led should lit as after these lines

  leds[0] = CRGB::Red;
  FastLED.show();
  leds[0] = CRGB::Black;
  FastLED.show();

nowhere I have used delays.But, still many dots of leds appear.Can someone help me out.
As per POVfinal pic(attached below) is the one I am trying to display.

WS2812 not suitable for POV displays.

Or strobe lights.

Paul__B:
WS2812 not suitable for POV displays.

Or strobe lights.

Hi,
Please explain no why?I tried with both versions of ws8212/b

dishak:
Please explain no why?I tried with both versions of ws8212/b

Two reasons.

The minor one is that it takes significant time to update the LED strip.

The major one is that the LEDs themselves generate PWM, less of significance if you use each primary - red, green, blue - as either fully on or fully off, but their switching on or off with the PWM in a fashion completely unrelated to your coding, will "chop" the traces as they move.

You cannot use any form of multiplexed or PWM colour determination for a POV display.

The dot star type LED strips multiplex at a faster rate and so are more likely to succeed with a project like this. Also if you wire them up using the SPI interface you can get the data into the chips faster.