Didn't you just answer your own question?

Flag test - if flag "Projector is ON"
        - then page jump
        ELSE
        - delay 30 seconds
        - then page jump

or for a "cleaner" version (not that it matters)

Flag test - if flag "Projector is OFF"
         - delay 30 seconds
         ELSE
         - n/a [leave blank]
Page jump