How can i use 555 to build repite cycle timer with 15 sec on and 5 min off? Answered

For timing that long (5 minutes, specifically) it would be easier and more efficient to use a microcontroller.  I'm fairly certain that duty cycle is technically possible to do with a 555 timer, but you'll have to include a lot of trimmer resistors to get the timing just right.

If you want reliable timing, for long periods, the 555 is a very poor way of doing it.
You're better off with a processor.

Steve