I am wanting to to detect 240V mains zero crossings for a TRIAC based heater controller. I have a 240/12 Volt transformer whose output is rectified, regulated to 7.6Vdc which powers the arduino.
My question is: Will the transformer's output be phase shifted with respect to its input? I am planning to put the 12Vac lines into a comparator (op-amp) and have arduino check the comparator's output to sense the Mains zero crossing. Anti-phase is of course no problem. Unfortunately I have no oscilloscope to check directly.
Will this work, or will the transformer induce a phase-shift?