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...
Step 3: Make the Hand
The hand pot is a 3 inch sewer clean out from home depot. This is the solid metal plate variety for stability.
You will need to drill and tap a minimum of a 1/8 MIP hole in the base to attach the air supply.
Thread in a connector and attach the Solenoid valve, the type of valve that you use will dictate the type of connector needed. There are many flavours of connectors, just use the largest possible.
The rubber glove is will need a small hole cut into the tip of the middle finger.
The cuff of the glove is stretched over the sewer flange then taped in place with electrical tape. This will prevent the glove from flying off while the air is flowing.
Step 4: Attach the Solenoid
The power source is attached to the NO contact of the relay and the common contact of the relay is attached to one lead of the solenoid valve. The other lead of the solenoid valve is attached to ground.
Essentially when motion is sensed the trigger will allow the hand to deploy upward creating the illusion that something is digging out from the grave. In low light condition the yellow glove will reflect enough light and should startle or scare passers by, there is also an ominous hissing sound as air escapes...