Testing for AC voltage under load/no-load?

[THX-1138]

I'm designing a circuit to switch a 120VAC socket with a triac driven by a low DC voltage signal through a MOC3020 opto-isolated diac. I want to be able to sense a fault, defined as

 

[math]FLT = \left(TP1\land\left(\left(\phi TP2\neq\phi TP4\right)\lor\left(\phi TP3\neq\phi TP4\right)\right)\right)\lor\left(\overline{TP1}\land\left(\left(\phi TP2 =\phi TP4\right)\lor\left(\phi TP3 = \phi TP4\right)\right)\right)[/math]

 

I know I'm probably using the wrong symbols, but the meaning is:

 

There's a fault if, whether there's anything plugged into J1 or not,

• TP1 is high and there's no signal through V01 or D1, or
  
• TP1 is low and there is a signal through the diac or triac
  

 

BTW, how does one signify 'no signal' or 'phase difference'? (Since the voltage would always be zero, it'd have no phase, and hence would have a different phase than TP4, correct?)

 

Thanks!

[THX-1138]

This is what I've gotten so far. Assuming it'll work, I've gotten all the parts figured out except the transformer. R2 is sized for a 1:1 winding giving about 5VAC at 20mA across T1's secondary. I haven't been able to locate an appropriate part for T1 yet.

 

 

Any comments or suggestions welcome..!

 

Thanks!