The hand is propelled by compressed air and explodes upward when tripped.
The trigger in this case is from a PIR motion sensor which I have showcased in another instructable.
Essentially when someone passes in front of the tombstone the hand will appear to pop out of the ground.
This will show you how to create a this kinetic zombie graveyard prop for Halloween
You can hear the air compressor running in the background during the test.
Step 1: You will need
Before you begin you will need to reference my PIR motion sensor instructable and you will need to reference an instructable on creating Styrofoam tombstones on this site.
You will need an compressed air source (an air compressor)
An air line
A 3 inch SEWER cleanout from Home Depot
A rubber glove
And an air solenoid(12V model from a HVAC supply store)
Step 2: Prepare the tombstone
I chose the name for two reasons. One for the letter "O" and the second is obvious...
The center of the first "O" is removed using a 3/4 inch hole saw to create an orifice for the motion sensing element.
The Motion sensor is aligned up with the hole in the tombstone to give an idea of optimal placement, then the lens cover is replaced and the sensor assembly is fastened in place with duct tape.
This will trigger the scary hand motion...