To answer the title question, the only way i could think of is this ? but they don't seem to be working. The AC rms voltage at the input is 33v and the reference voltage at pin 3 is 2.6v. voltage at pin 4 is 2.2. The opamp output is always high even when i change the voltage 26vac. I wanted the opamp to go low when the voltage dropped below 30vac.
The reason for the large cap is that mains voltage comes in momentarily hence a protection zener diode D2.
The reason for the large cap is that mains voltage comes in momentarily hence a protection zener diode D2.