What you need:
1 – 9V battery
1 – 12v dc buzzer (Available at Radio Shack or amazon)
1 – Aluminum foil (Available at Walmart)
1 – paper tape
1 – scissors
1 – foam board
1 – knife
1 – Dishing washing sponge
Step 1: Prepare What Is Needed
Under is estimated cost for materials:
12V dc battery - $1.50
12V dc buzzer $ 3.5
Paper tape - $1.5
Hard board $1.5
Step 2: Testing Battery and Buzzer
Test it out by just making the wire from 9V DC battery that is not hooked to buzzer touch the other wire of the buzzer.
If it makes buzzer go then buzzer and battery is working.
Step 3: Cutting the Foam Board
(Usually about 20 x 24 inches work fine for most of the door mats.)
Step 4: Cutting Aluminum Foil Into Right Size
Step 5: Drawing 3 Circles
To figure out the exact measurement, the radius of the holes should be 4 inches less than the length of the foam board(There will be three holes and they will be apart by 1 inch including the edges.) then dividing that by 3 will give you the length of the radius that should be used for the hole.
First draw a center line where all the center of the holes will be located at. Then mark the center of the hole and draw a circle with the radius obtained with a compass. Measure 1 inch from each of the dots where center line and the center circle meets and from that measure the radius obtained and place the dots for other 2 holes.
With compass draw 2 circles with the 2 center dots previously marked
Step 6: Cutting the Holes With Knife
Using scissors would help to cut the foam board faster.
Attach each 3 pieces of the sponge to middle of each 3 aluminum foils that is seen through the hole. (Either tape and glue will work.)
Step 9: Attaching Top Part of Aluminum Foil
(Make sure aluminum foils do not touch each other from each side.)
Step 10: Attaching the Buzzer and Battery
Attach the not attached part of the buzzer to the top aluminum foil which is on top of the sponge with paper tape.
Attach the other part of battery wire that is not attached to the bottom part of the aluminum foil.
Step 11: Checking Process
(If it does not work check whether aluminum foil is ripped or wire is attached right.)