Two years ago I added a sound activated ground breaker from Grandin Road. I like it so much that we added two more from Halloween Asylum this year. With that being said, I am wondering how I can transform these from sound activated to possibly a motion sensor. We have a FireFly 511 and either the props go off at the wrong time or they don't go off at all. I would really like to have them fire at the right time. Any thoughts would be greatly appreciated.