We changed our design in our voltage source. First, we turn on the switch and leave it so the device is always turned on. Second, we insert a piece of paper to make the circuit open. Third, when the hammer starts to swing, it will tug the paper out and make the circuit reconnected.
We changed the way we tied the rope on the stick by tying the rope much loosely. When the stick pull the trigger, the rope on the stick will fall off, which avoiding the stick stuck in the gun.