Introduction: Use a DIY Pressure Plate Switch to Automate Your Haunted House

About: My name is Jason Poel Smith. In my free time, I am an Inventor, Maker, Hacker, Tinker, and all around Mad Genius

When running a large haunted house, you want most of the special effects to be automated. But for this to be effective, you need to get the timing right. The best way to do this is to use sensors to detect where your guests are.

In this project, I am going to show you how to make a simple DIY pressure plate switch. This is just a pressure sensitive switch that is activated when someone steps on it. A sensor like this is really useful for effects that require someone to be in a specific location.  I also give several examples of ways that you can use it to activate special effects in a haunted house. 

Step 1: Materials

Here are the materials and tools that you will need to make your DIY pressure plate switch:

3 Large Sheets of Cardboard
Aluminum Foil
Several Feet of Insulated Wire 

Wire Strippers
A Sharp Knife

Step 2: Attach Foil to Two of the Cardboard Sheets

Tear off a piece of aluminum foil that is at least as big as the cardboard sheets. Lay it centered on the cardboard. If the foil hangs over the edge of the cardboard wrap it around to the back side. Tape one side of the foil to the cardboard. Then stretch the foil tightly and tape the opposite side. Do this for all four sides of the foil. 

Repeat this process with a second sheet of cardboard and foil.

Step 3: Attach Wires to the Foil With Tape

Take one wire and strip about one inch of insulation off of the end. Then lay it on the first sheet of cardboard so the the bare end of the wire is touching the aluminum. Apply a piece tape on top of the wire to hold it in contact with the foil. Repeat this with the second wire and the second sheet of cardboard. This isn't the most secure way of attaching the wires but it should hold together for Halloween. 

Step 4: Cut Out the Center of the Third Sheet of Cardboard

The third sheet of cardboard is used as a spacer between the other two sheets. To make this work, we need to cut out the center of the third sheet of cardboard.

Trace a rectangle on the face of the cardboard that is offset from the edge by about one inch. Then using a sharp knife, cut out this rectangle.

Step 5: Assemble the Pressure Plate Switch

Now it is time to assemble the pressure plate switch. Lay down the first piece of cardboard with foil side facing up. Then set the cutout piece of cardboard on top of it. Place the third sheet of cardboard on top of the cutout with the foil side facing down. Lastly, attach the three layers together with tape.

This is the completed pressure plate switch. When you press on the center of the cardboard, the two foil sheets will make contact and complete a circuit just like a regular switch. Now all you have to do is find some way of disguising the pressure plate so that it is not noticeable. The easiest way to do this is to put it under a light rug. 

Step 6: Use the Pressure Plate Switch to Activate an Arduino Program

One way that you can use a switch like this is to activate an Arduino program. This works just like any other external switch that you might use with an Arduino. Connect one wire to the GND pin. Then take the other wire and connect it to an input pin and also connect it to the 5V pin with a 1k resistor.

The resistor acts as a pull-up resistor. It will make the input pin read HIGH when the button is not being pressed. But when the button is pressed the switch connects the input pin to GND and the input will then read LOW. You can then use this signal to activate any kind of sequence that you like.

//Here is an example of code that you could use with this switch.
const int buttonPin = 2;     // the number of the pushbutton pin
const int ledPin =  13;      // the number of the LED pin

// variables will change:
int buttonState = 0;         // variable for reading the pushbutton status

void setup() {
  // initialize the LED pin as an output:
  pinMode(ledPin, OUTPUT);     
  // initialize the pushbutton pin as an input:
  pinMode(buttonPin, INPUT);    

void loop(){
  // read the state of the pushbutton value:
  buttonState = digitalRead(buttonPin);

  // check if the pushbutton is pressed.
  // if it is, the buttonState is LOW:
  if (buttonState == LOW) {    
    // turn LED on:   
    digitalWrite(ledPin, HIGH); 
  else {
    // turn LED off:
    digitalWrite(ledPin, LOW);

Step 7: Use the Pressure Plate Switch As an Auxiliary Switch for DC Electronics

You can also use the pressure plate switch to activate function on small DC electronics. By wiring the pressure plate switch in parallel with an existing momentary switch, you can use it to activate that function just like the original button. As an example, I am going to be using a small sound module to play sound effects when the pressure plate is stepped on.

Start by removing the housing of your electronic device. Then locate the button for the function that you want to activate. In this case it is the play button. Find a good place on both sides of the button to connect the wires from your pressure plate. In most cases one side of the button will be wired to the microchip and the other side will be connected to either ground or the positive supply voltage. On my circuit there was an open pin hole on one side of the button so I connected one wire there. The other side of the button was connected to ground so I connected the second wire to the negative terminal of the battery. 

After making these connections, any time that the pressure plate is stepped on, the sound module will play your sound effects.

Step 8: Use the Pressure Plate Switch With a Relay to Activate AC Electronics

This kind of pressures plate switch can only safely switch small DC voltages. So if you want to use it to activate AC appliances, then you need to add a relay to isolate the switch from the AC power line. To set this up, you will need the following materials:

Relay (with a 12 volt coil and contacts rated high enough for your AC appliance)
Insulated Connectors (that match the terminals of your relay)
Insulated Plastic Housing
Extension Cord
12 volt power supply or battery 

Wire Strippers
Sharp Knife

Start by cutting the extension cord into two pieces. If necessary also cut the wires coming from the power supply and the pressure plate. Then strip about 1/2 inch of insulation off the cut ends of all of the wires. Then attach insulated connector to the ends. Use one male connector for one of the wires from the power supply. The rest of the connectors should be female.

Connect one wire from the pressure plate to the power supply. Then connect the other wires from the pressure plate and power supply to the coil terminals of the relay. Connect the male end of the extension cord to the common terminals of the relay. Then connect the female end of the extension cord to either the normally open or the normally closed terminals depending on whether you want the appliance to turn on or off when the pressure plate is stepped on.

The last step is to put the relay in an insulated plastic housing. Use your knife to cut slots in the sides for all the power cords. Carefully fit the relay and power cords into the housing and close it up. 

As an example, I connected the female end of the extension cord to the normally closed terminals of the relay. Then I plugged a lamp into the plug. The lamp is normally on, but when someone walks into the room and steps on the pressure plate, the lights will suddenly turn off. 

Step 9: Alternate Designs

This pressure plate design works well in most circumstances. However, you can make a sturdier version of this design by using thin sheets of wood instead of cardboard. You can also replace the aluminum foil with thin sheet metal. Select the materials that are the most appropriate for your application.

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