phase control

[chava]

hello
I have a pic 12c508a and I have to control the ligth intensity of a lamp using a triack and a phase control methode.
what I did is that i sampled the phase input (220VAC) .
I know that when phase input voltage<0 I will get "o" in the pic pin and when the phase input voltage>0 I will get "1".
I made a little program to ligth the triack at "t" sec after zero cros was detected.(t is a time ofcourse)
the problem is that for some reasone the point in which the pic ligth the triack changes in a cyclic form, as if every phase-cycle the pic calculate "t" differently

here is the code- main procedure:

while (1){
//the loop condition detect phase direction change
while(input(pin_phase)==mystatus.current_phase){

TMR0=0;
wait_for_pulse+=1;
if (wait_for_pulse==level) output_high(pin_out);
else output_low(pin_out);
while (TMR0<100);//wait 200 usec
}

//phase_direction_changed:
if (input(pin_phase)==1) mystatus.current_phase=1;
else mystatus1.current_phase=0;
wait_for_pulse=0;

}

[Neutone]

Here is something really basic.


While(1)
{
While(input(pin_phase));
Delay_ms(x);
output_high(pin_out);
output_low(pin_out);
While(!input(pin_phase));
Delay_ms(x);
output_high(pin_out);
output_low(pin_out);
}

The value for x has to be in the range of 1/2 of the period and less. That gives you from 0 to ~8mS at 60hZ. Thats not a lot of resolution but the method used for delay can be something different. This method requires a timer that counts for longer than 1/2 the period;

While(1)
{
While(input(pin_phase));
set_timer1(0);
while ( get_timer1() < x) ;
output_high(pin_out);
output_low(pin_out);
While(!input(pin_phase));
set_timer1(0);
while ( get_timer1() < x) ;
output_high(pin_out);
output_low(pin_out);
}

[chava]

hi
well I tryed that methode but the result was a blinking ligth. the ligth was not stable and a sence of blinking was in it.
tank you anyway,
by the way i succeeded , I did it by minimizing the period of the loop so that there is no delay between the point-in-time is which a phase-dierection-change was detected to the point-in-time when the pic respond to that detection.
thanks
chava