threshold voltage level and blinking problem
What is the sensetive ac voltage stabilization method coming from
  voltage divider and it contains noise filter capacitor and take
  avarage?


Calculating an average by using 3/4 of the current average and 1/4 of the new measurement (exponential average) works well for me in a lot of situations. You can adjust the constants as you see fit, as long as they add to 1.0. I use powers of 2 and shifting for maximum performance:

// Exp. average: 3/4 old avg + 1/4 new data, with rounding
int16_t xpavg(int16_t newdat, int16_t avg){

   // (3 * avg + 1 * newdat) / 4
   return( (((avg&lt;&lt;2) - avg + newdat) + 2) &gt;&gt; 2 );
}