This is a video of the 3rd annual haunted house that my daughters (aged 7 and 8) and I put on for our neighborhood. It's a great tradition for having fun, scaring our friends, and learning how to make new things.
All of the props, except for the spectral projection, are Arduino controlled, attached to IR sensors and pushbuttons. This was the first year we introduced thunder along with the witch, and the all-new IKEA bed coffin.
Light up ghost
This was a simple Halloween prop from Christmas Tree Shop. I took it apart, found the trigger circuit, and wired that in to a breadboard. The breadboard connects up a 2N3904 transistor as the switch across the trigger circuit, a 47k-ohm resistor, and a HC-SR501 PIR sensor. See the Arduino file for all the details.
This is a looping Halloween video, projected onto a frosted clear shower curtain. There is no sensor or controller this year, though I'm thinking about making one next year because when the timing is perfect, the spectre is very scary.
Witch and thunder
This is another prop from Christmas Tree Shop that I hacked apart to be triggered from an IR sensor. I found it handy to use CAT5 cable to run lines from her head/neck where the motor was down to the Arduino on the ground. The video doesn't do it justice, but there's a cauldron with smoke from a fog machine, and flashing banks of LED lights in the cauldron controlled by DMX (the protocol, not the rapper)
Also, for the first time this year, there's a loud thunderclap produced by a second Arduino driving an amplified speaker using pulse code modulation. This high-low tech tip was extremely handy. Since this is triggered by the IR sensor, the timing is almost always perfect for a good startle.
Hall of masks
This one is pure low tech. Inspired by this blog post, we glued a bunch of plastic masks to black plastic hung from the ceiling. Add in a spooky whispers soundtrack plus black lights and this hallway becomes the freakiest part of the house. If you really want to scare your guests, dress in all black, wear a matching mask, and stand in the corner. No one will notice you until you jump out, causing lasting trauma. This has been a go-to prop for us since the first annual haunted house, so it's time to lovingly retire it.
IKEA bed coffin with reaper
We had an old IKEA bed sitting in the garage in pieces, so I decided to put it to good use. I cut apart the headboard, footboard, and bed rails and reconfigured them as a toe pincher coffin. Luckily the desire for an old, beat-up look hid my hasty woodworking.
This is the first pneumatic prop we've used in the haunted house. I had really hoped to leave the coffin laying down, but the pneumatic arm didn't deliver enough force to lift the coffin lid. So I put the coffin upright, and it did the trick. The Arduino controls both the solenoid air valve and the hacked grim reaper prop. I didn't know if I'd be able to get the coffin lid timing right, so at first I used a pushbutton as a trigger. But with some tinkering and careful placement, I was able to use a PIR sensor and coordinate a series of bangs that worked pretty well. Though the controller still supports hiding and using the pushbuttons for the perfect scare.