Introduction: Making a Motorized Secret Entrance

About: Web developer by day. Gamer by night. Halloween fanatic and DIYer, all the time! My projects tend to combine pop culture, technology, and craftsmanship to produce something that's fun, unique, and more than l…
If you're decorating along the lines of a haunted house or a superhero lair, a secret entrance is just the thing to get Halloween guests into your home. In our case, we threw a Superhero costume party and wanted to build a motorized, moving wall activated by statue - a nod to the Batman series of the 60s.

- Surprise guests with an apparently closed room as they walk in
- Give them a riddle to figure out how to open the hidden door/wall
- Keep the area this occupies to a functional minimum so it doesn't take up too much actual entertaining space

Step 1: Planning the Layout

We have a tiled area at our front door which defined a natural boundary for our fake room. The area is large enough for 2-3 guests to comfortably walk in and move around, and small enough that it doesn't occupy too much of the (real) room.

We decided that walking in from the front door, into a tiny room with only walls wouldn't seem very plausible. To help sell the illusion we hung a door in front of you as you walk in, but boarded it up, so the room appeared as a small vestibule which was no longer passable. We left the knob off this door, just to keep guests from trying to go through it (despite the boards). Which leads me to a point about safety...

Step 2: Framing and Safety

It's important to realize that guests may push on any wall, looking for a way in, and you don't want anything collapsing. Sometimes Halloween props can be flimsy and just for looks; this isn't one of those times. So I took care to build a sturdy structure framed mostly with 2x4s. Given our particular geometry, and materials used, we got away with only anchoring one top corner to the actual wall with a single screw.

For the section of the wall that makes up the secret door, we used lighter materials so the job of moving it would be easier on the motor. It consists of just one 2x4 on the edge where it hinges, a 1x3 across the top, a 1x4 across the bottom, and a lightweight 2x3 steel stud on the side that moves. Since this section was light, just two hinges were used to connect it to the other framing.

There's about an inch gap at the top and bottom of the framing of this section, so there's plenty of clearance to move. The gaps would be covered once the "walls" were added.

Step 3: Walling It In

The walls and a false ceiling were added with panels of pink insulation foamboard. It's lightweight, easy to cut, hang, and paint, plus easy to re-use for a different project later. Two inch masking tape works great to cover seams and screws - in spooky lighting it disappears nicely.

You could do any faux paint finish inside - we just painted everything white to blend with our existing doors and (real) walls.

Step 4: Adding the Wheel and Motor

A small 12 volt motor was used to motorize the door. The motor came with a gearbox with an  output (free) speed of around 60-90 rpm. A motor that's nicely geared down is what's needed here - for one, you don't want the door moving too fast, and the gearing lets you use a pretty small motor. Once everything is hooked up it takes the motor about 6-7 seconds to open the door. The slow speed helps give the illusion that the wall is very heavy, plus it's safe in case anyone is standing too close on the other side.

The wheel is a hard rubber wheelchair wheel salvaged from some past robotics projects.

The wheel and motor were mounted so the wheel extends below, and supports, the bottom of the door framing.

Step 5: Electrical Work

The motor is powered by a typical 120vac-12vdc adapter. I mounted a double pole, double throw (DPDT) switch outside of the fake room to operate the door in either direction.

To open the door from inside the room, two limit switches were mounted just under the base of a statue (see the photo). The switches are wired as "normally closed". When the statue is resting on the switches, they are open, and they become closed when the statue is tilted. Two switches (rather than one) were used because it was an easy way to tie into the existing circuit with the DPDT switch.

Step 6: Finishing Touches

Some final details really help to pull everything together. Also, the surprise of the wall opening is heightened if the lighting/decor is different on either side of the room. Inside, we added some webbing and LED candles inside for a run-down, creepy atmosphere. Outside we had different colored lighting and decorations.

We marked the swing of the door with an arc of gaffers tape on the floor. This would keep our guests aware of not standing too close as more people come in.

The final touch was a small riddle inside to give guests a clue of how to enter.
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