Build a Cheap and Easy Floor Mat Trigger

Since my home haunted house is pretty small, I don’t have a lot of room for elaborate scenes and actors… at least, not yet!  I’m mostly prop-based.  But I like to use automated props as much as I can.  To do this, I need a really good way to ensure that the props get triggered at the right time.

Historically, triggering my scenes has been the biggest problem.  The store-bought props don’t work so well in extremely dark settings (i.e. almost no light).  About the only thing that worked consistently was for me to lead groups through the house and set things off myself (e.g. clapping hands, shining a pen light, push a button, etc).

Frankly, that works and is certainly cheap.  It also works best to use actors to handle these chores.  But I wanted something more automated.

Commercial Options

Commercial motion sensors can work well – even in extremely dark situations.  But the good ones (i.e. good enough to work in total darkness) aren’t as cheap as I’d like.  FrightProps has them for around $35.

Surprisingly, floor mat triggers are even more expensive!  If you want one big enough to make sure it isn’t accidentally stepped over – you’re looking at $65 to $80.  Fortunately, I found a great way to build my own floor mat trigger for around $10!  I used two of these last year and they worked great!  Here’s how I did it.

What You’ll Need

This is what you need to build 2 floor mats:

• Utility razor or sharp knife
• Wire Cutters or sharp knife
• Aluminum foil (18" wide)
• Black Poster Board Paper (24" x 36") x 4
• Black or Brown Indoor Extension Cord (I recommend 12′.  Longer is better.) x 2
• Spray Adhesive
• Black Duck Tape – 2 inch wide
• Foam Weatherstrip Tape (1/2" x 17ft roll)

I found everything at my local Menards (including the poster board). The total cost (not counting tools) was just over $20.  You can save a little money by only building one mat.  But even if you buy the smallest sizes available you’ll have enough foil, tape, adhesive and weatherstrip to build two.  So, you might as well spring for an extra extension cord (around $1.50) and poster board (around $3 for 2 sheets) and build two mats.

Sorry I don’t have any pictures.  I’ll try to take some the next time I build one.  I’m pretty sure I’ll want more this coming Halloween.

How to Make the Floor Mat

This is one of the easiest projects I’ve done and I’d recommend it to just about anybody.  The instructions below describe the process to build one.  You’ll need a large, flat work area that is pretty well ventilated.  And be sure to cover the area with a drop cloth or newspaper.  This is for the spray adhesive.  It’s about as precise (and noxious) as spray paint.

Prepare Your Wire

• Remove ends – We don’t need either end of the extension cords.  Cut them off at the base with your wire cutters or knife. 
• Pull apart one end to about 3’  – You need to separate the two stranded wires of your cord.  On one end, use a knife to cut a slit in the flat insulation between the two wires.  You can then pull them apart.  Pull apart about 3′ of cord to work with; making a giant "Y". 
• Remove 28" of insulation – This is the hardest and most time consuming part.  I found it easiest to work in 3 to 4 inch sections.  Use your knife to cut a lengthwise slit in the insulation.  Pull it apart and then cut it off – exposing the wire.  Do this until you have about 28" exposed.  It doesn’t have to be exact.  Just hold it up to you poster board.  It should be about 6" shorter.

Prepare the Poster Board

Lay the poster board flat – Make sure you cover your area with a drop cloth or newspaper. With ONE of the stranded wires of your extension cord, do the following: Spread apart the wires – Beneath the insulation of you extension cord, you’ll find stranded copper wire that’s basically twisted together.  Carefully pull the strands apart and lay them flat on the poster board so that it looks like a giant tree.  The wire should cover most the board "reaching out" to about 4 inches from the edges. Place the base of the insulation at the bottom of the page – about 3 inches from the edge.

Should end up with something like this:

Glue Aluminum Foil to Poster Board

If you bought the sizes I suggested, you’ll note that the paper is 6" wider than the foil.  That’s perfect because we need a good border around the foil. 

• Cut two pieces of foil to 30" (or 6" less than paper if you bought a different size)
• Spray poster board and wire with a light, even coat of adhesive – avoid the edges, but don’t get concerned if you have a little over spray. From the picture above, you’re basically spraying the area outlined with the dashed border.
• Carefully center the foil on the board – this is the hardest part.  Once you place the foil, you won’t be able to pick it back up.  So be careful.  That said, it doesn’t have to be perfect.  If it’s not exactly centered or it’s crooked; it’ll probably be fine.  The important point is to have a good couple of inches of poster border around the foil.
• Keep the foil smooth – Another important factor is to keep the foil smooth.  If you have a crease or bump that’s more than a 1/4" or so deep, you’ll want to use a knife to cut it out.  Tiny bubbles and crinkles – and even holes in the foil – are fine.  Obviously, you’ll be able to see bumps from the wire.
• The foil should completely cover wire.  Don’t worry if you see a little exposed wire at the bottom (less than 1/4") near the insulation.  Otherwise, if strands are sticking out of the edges, cut them off.  They’re thin enough that scissors can handle it.
• Set aside to let any overspray dry while you work on the next board.

Apply Weatherstrip

On ONE board, we want to place strips of weatherstrip tape that are approximately 1.5" apart.  Again, don’t worry about being precise.  Just make sure you have strips on the outer-most edges.  The result will look something like the image on the right.

Note: My design is intended to sit on top of carpet or the floor.  It’s black and my haunt is always pitch black.  So, it works great for my needs.  If you plan to put this under a rug or something else, you’ll probably need to experiment with thicker stripping.

Tape the Sides Together

Once you’ve completed the above for the other side, you’re ready to tape them together.  (Remember: You only put weatherstrip on ONE of the two sides.)

• Stack both pieces so that the aluminum foil is on the inside.
• Use strips of duct tape along the outside edge to tape them together.
• This means that the duct tape will form a 1-inch border around all edges on both sides of the finished mat.
• A thin line of paper glue would probably work as well.  But I don’t recommend it.  The edges are the most likely to tear while you’re moving it around or as people step on it.  I also like to tape my mats in place and this edge is convenient to use without fear of tearing the mat when I remove it.

Using the Mat

That’s it.  You’re done!  Now, realize that your mat won’t do anything just yet.  It’s just a trigger.  So, it’s like having the trigger of a gun – but no gun.  We still need a timer, a power source and something to turn on/off (i.e. strobe or spot light).  I’ve already blogged about my favorite timer switch.  In a future post, I’ll show how I put them all together into a nice controller that can run anything you can plug into the wall.

Simple Prop Timer Switch

Most automated props and most scare zones in a haunted house depend on two critical, interdependent factors.  They need a trigger (aka signal) and a timer switch.  The trigger does very little.  It simply sends a signal to the timer switch.  The timer switch then switches power on/off for a predetermined amount of time.

Most store-bought props have a timer switch and trigger built-in.  Which is great; except that the triggers on most store bought props are complete crap.  But that’s a different topic for another time.

In my haunted houses, I use the timer switch to turn on lights, strobes or spot lights that in turn trigger my props.  It works pretty well since the haunted house is almost completely dark during the rest of the time.  Because of my space limitations, putting even a small, LED spot on a prop would announce its presence way too soon and ruin the scare.

I have yet to use the timer switch to start audio of some sort.  I may introduce it next year.

Anyway, I highly recommend the simple timer from FrightProps.  It’s inexpensive (in relative terms), flexible and reliable.  If interested, check out the link here.  FrightProps is an excellent resource for any DIY haunted houser.

If you find the electronics jargon a bit confusing, don’t be intimidated.  I was completely confused at first but found my first couple of projects to be pretty easy.  I’ll share them here in future posts.