We tend to go a little overboard for Halloween here at the Hunt household. This year, we added to our fog-machine/laser/Arduino-fueled festival with a few solenoid-driven pneumatic props. We also moved into the garage, which allowed us to hang black plastic walls and create a proper walk-through, instead of just having displays in the yard.

Here’s what we rigged up:

First, the main Arduino board:

The Arduino microcontroller board is wired over thin-gauge speaker wire to motion sensors (Passive Infrared, or “PIR”) and to solenoids. Each solenoid is connected to a pneumatic cylinder, which drives the prop when activated. The Arduino is hooked up with a WaveShield, which is a daughterboard that plays .wav files from an SD card. The code is simple: when one of the PIRs fires, it activates a relay for the solenoid, and fires off a shrieking audio sample.

Here’s one of the smaller props that we call “Sheila.” Sheila is a simple jumper that pops up from behind her tombstone and shrieks. Loudly.

Along the way there are some simple static props, like this zombie floating in midair over the cauldron.

Next, visitors encounter ghostly, green, glowing footsteps on the floor:

Simple, but effective: an LCD projector mounted to the top of a tall step ladder, projecting a video loop on the floor. The crunchy sound effects really helped — I synched those up with the animated feet using Logic.

Next up, the Cabinet of Doom. This is an old cabinet frame, fitted with a one-way mirror on the back. At first, you see just your own reflection in the back of the cabinet.

But when the prop fires, a flood light illuminates the horror within…

On our way to the graveyard, we have to file past Fred, a large-scale jumper built out of 2×4′s and a PVC frame. Early versions of Fred had a bit of a stability problem, such that it became more of a skeleton trebuchet than a scare prop. We had to keep retrieving skeletal pieces from across the room. Some cable ties and Gorilla Glue helped keep Fred a little more together.

In the graveyard, we have some standard props, including a “Bucky” skeleton that’s been modified with heat-gun shrink wrap plastic, colored with some furniture stain. And of course, some luminescent skulls (a little Woolite and blacklight works wonders).

But the best part of the graveyard is Madame Leota. I took a plain foam mannequin head ($4 from Amazon) and sanded off the nose and lips to give a smoother projection surface. Then I layered on some drywall plaster to smooth out the uneven styrofoam.

Then using one of those small micro-projectors, got a loop of the real Madame Leota from Disneyland and voila, an animated, ghostly disembodied head:

She just sits in the graveyard and recites her spiel over and over.

Exiting the garage, there’s a hallway with strobe lights and a giant prop head over the doorway, which also features two large mirrors, making an endless tunnel to your right and left.

To see it in all its dimly lit glory, check out the video here.