In this project i am using a phase angle control and mains frequency is 50Hz. For each half of sine wave, i have 100 steps (100us).

First i tried Mr. Karas Zero Crossing circuit given in earlier but it is not having equal on/off period apart from two much rise and fall times. so now I use a circuit which works with direct 230V AC BR and a optocoupler. Now Zero crossing is O.K.

I want to have feed back for adjusting the ouput Firing Angle in case of input Voltage variations.

Can I control in this way?

1. Measure input AC Voltage by using unregulated DC.

2. Multiply the input AC with the duty cycle which know and display as calculated output voltage.

3. If input varies, then adjust the duty cycle to maintain calculated output voltage constant.

I can accept upto to +/-2V in the calculated output voltage. My idea is to avoid the feed back and related components.


By the way i am using optodiac (MOC3020) for firing the triacs.

Your views on how to control the duty cycle in order to maintain output constant will be helpful.

Thanks for your time

V.Nagararajan