I don't know what your project is about, but if "15 min" is not a absolute, and you want to waste a little time on the chip....

there are approx 900 seconds in 15 minutes.

Using a long int of 32768 you can break a second down into 1/36 of a second.

Since the chances are, your main program will be screaming fast, you only need to call a "Sub routine" wherever you want, and think is appropriate.

Its simple, no big thinking of Code, no interupts...

double counter

counter=900
Main:
......
.....
ADC in...
LCD out...
Rest of program....
......
Goto "Pause and light"
goto Main

Pause and Light:
pause 30 (Pause 1000 is 1 second, and 30 is adjustable to your liking)
Counter=counter-1;

If counter==0 then
Check continuity.
flash bulb.
counter=900
endif

goto main.
end

This is a Psuedo code.

Dwayne