How to Make a Simple Mat Switch

How to Make a Simple Mat Switch

Ryan Bavetta
aka Bavetta
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By bavetta

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- Video 1 -

My homemade version of a "stomp pad" automatic mat switch made with foil, cardboard, and lots of duct-tape.

Homemade mat switches can be used for triggering an event when someone steps on the pad or other pressure is applied. They are used for automatic doors in supermarkets and you can use them to! I've used matswitches to sense when a person reaches a particular location to turn on a light, activate a tape-player, activate a pneumatic dummy for a Haunted House at Halloween, etc.

A matswitch works by putting a voltage potential across two pads and deforming a separating layer enough to let one contact touch the other and thus complete a circuit. In this case, the cardboard spacers compress and the top layer bends to allow the top foil layer to touch the bottom layer. I have made pads ranging from four inches by ten inches to 48 inches square and this technique has worked flawlessly for both.

Assembly is very simple. I start by layering two pieces of cardboard with foil. I typically use duct tape, although any insulating tape should work. Be sure to stretch the foil tight to increase the smoothness. You'll need to attach wires to the foil. Soldering the wires to the foil doesn't work (try it) but it is easy enough to spread the wire out along a long patch of foil, preferably on the back side of the pad, and tape it down. Remember, do not run high voltage through the pad, stay at 12 volts or under at low currents.

Next, it's time to cut the cardboard spacers. How wide should they be? How much space in between? It doesn't really matter, as long as the foil doesn't sag and bridge the gap when unloded. Also When the mat is assembled, it is easy to have problems with the edges permanently bending around the edge, so I try to put an edge around the perimeter of the entire pad to prevent shorting. Remember, you only need to put cardboard on one of the sides!

Now, put the foil and cardboard sandwich together with, what else, more tape. Check the continuity with a multimeter. If it never turns off, try stomping hard and repeatedly on the pad. Surprisingly, I've had some matswitches for years, and none have stopped working. I put one under the carpet in a stairway of my house and it still works after two years of abuse. Allen's Halloween Homepage has a great page describing how to make a similar pad with postarboard instead of cardboard, although it sounds as though he has encountered many more problems than I have with the cardboard. Again, make sure not to run high voltages/currents through the pad - it will heat up and catch fire from sparks/resistance. Use low voltage and a relay to trigger high voltage effects.

By nosoup4u

2006-06-25 19:06:12

so if i wanted to run lets say... 120v through the mat... i would most likely have to use a transformer to lower the power?

couldnt the amount of foil be increased (the thickness of the foil layer) and it be able to take a little more voltage?

--- on the side, i have a suggestion for ur next project, i could also use a little help, how about a wireless switch? and not cheating with the cordless phone

By bavetta

2006-06-26 22:46:13

you shouldn't run 120V through the pad because of electrocution hazard, spark hazard, and fire hazard - if you were to try it, my suspicion is that it would make a loud noise and a large spark and blow your breaker - if not, you would have a lot of heat generated and it could cause a fire.

The way to do it is to send low voltage through the pad (you could use a transformer to get the low voltage) and use that to trigger a relay that switches on/off another circuit. That other circuit can be high voltage if the relay is rated for it (most are). I'll try to throw up a circuit diagram in a day or two - although it is pretty straightforward.

What you need to know about relays: there are two basic relay types - normally open, or normally closed. Normally open means that the circuit you are switching is open when no power is applied to the relay - normally closed means the opposite. Many relays come with enough leeds to enable either type of switching. You should also look at what voltage the relay will switch (some need higher voltage than others) and how much power it can take through it on the other end.

Wireless switch? What do you have in mind? RF or optical? Allen's Halloween Page has a cool optical switch, and circuit diagrams, I'd like to try that out sometime.

By nosoup4u	2006-06-27 18:23:53
i was thinking like the page feature in a phone, but that ends up being kinda big, even if u strip it a bit

By discreet	2006-08-29 19:43:14
Is that a battery symbol (low voltage end) on the wiring diagram or is the power coming from the high voltage circuit? Thanks

By bavetta	2006-08-30 07:38:37
ya, that's some low voltage power source, battery or otherwise. You would technically need some resistance in that circuit as well to prevent against short circuiting, but the resistance of the coil in the relay should be enough.

By peer	2007-04-18 07:17:29
Any idea how to make a closed circuit mat switch? Thanks

By nick	2007-08-26 17:10:37
make it so that the relay is normally closed except when the mat is activated.

By nuf	2007-10-28 04:19:00
Hi bavetta. I'm triying to make a giant piano like the one of the "Big" movie. I build your mat switch for trying. It works fine except it triggers extra signals when I step on the matswitch and it does it when I take my foot away. What do you recommand me for fixing this? Making it with less space between cardboard spacers? making it whole bigger? Thank you! Your a super DIY inspiring source!!

By bavetta	2007-11-11 09:04:10
Sounds like you need to de-bounce the switch - you can try putting a capacitor across the switch to get rid of the noise.

By bobthebuilder	2010-06-11 06:35:18
Did you have any luck building the piano? I wanted to try building one myself.

By riley2991	2008-06-18 05:31:47
I want to use this to trigger a spotlight. Once i have connected the wires to the mat switch what do i do with them then.