$10 DIY Alarm System That Calls Your Cellphone | Home Security Systems

cell-alarm-titleSurvival Life – by Alex Miklovic

Can’t afford expensive home security systems? Ever wanted to know how to make your own DIY alarm system? Believe it or not, you can make your own wireless home security system for about $10 with a few simple hacks to a prepaid cellphone. You can easily catch intruders who set off the tripwire, because this neat little gadget calls your cellphone right when it happens.

Imagine this…

You’re suspicious that someone is entering your shed when you aren’t there. Your birdseed definitely isn’t where you put it. Tools are missing. You NEVER forget to latch your toolbox, yet there it is. Unlatched.

The clues are subtle and you begin to wonder, maybe I did put that shovel over there where I don’t put it. Or did I? After all, it’s not like I’m going crazy…right?

If only there was a way to know for sure that someone has been groping your tools behind your back. If only you had a trip wire device that called your cell phone as it was happening so that you could catch the villain in the act and make him repay you all the birdseed he practically stole right out of your gentle hands.

Well I’m going to show you how to make such a device, and all it’s going to take are a few common tools, a couple of hours and a $10 Tracfone from Target.

How to Make a DIY Home Security System

Follow these simple steps and you will soon have an awesome little gadget that alerts you to any unwanted intruders.


You will immediately get a call on your phone alerting you that your tripwire has been activated.


Supplies  and Tools You Will Need :

  • 1 Pre-paid phone (We used a $10 Tracfone)
  • 1 Soldering Iron (You can get a cheap one at Radio Shack)
  • 60/40 Rosin-Core Solder
  • Some wire
  • 1 Box cutter
  • 1 Small phillips head screwdriver
  • 1 Hot glue gun with glue
  • Tin Foil
  • 1 Clothespin


Step 1:

Begin by following the instructions in the phone’s manual to activate the phone. We went online to activate ours, but if you don’t have an internet connection there’s a number you can call as well. All of this information can be found in the box that the phone came in.

Homemade Cellphone Security System

Step 2:

Next, we need to program the phone’s speed dial function to call your phone number when the number 8 key is held down.

First, Enter your phone number into the phone by going to: Menu >> Contacts >> Add New Contact

Once you’ve added yourself to the phone’s contact list, pair your number with the phone’s number 8 key by going to: Menu >> Contacts >> Speed Dial List 


 Select cell number 8, and then select your name from the contacts list.


 If you’ve done this correctly, it will look like this.


Step 3.

Remove the screws from the back plate and disassemble the phone. There are five screws total.


Use a small Phillips head screw driver to remove the screws.


Step 4.

Once the screws are out, you can use your box cutter to pry the back plate from the front plate. It takes a bit of force and will make a loud snapping sound as it separates, so don’t worry about breaking it because you wont. Once you’ve created some space with the box cutter, you can use your fingers to do the rest of the work.


When you’ve pried it apart, it will be in three pieces.


Step 5.

You’re going to work with the middle piece.

Locate the button that corresponds with the number 8 on the keypad by cross referencing it with the rubber keypad on the front plate. Each foil circle is a button and you’ll notice that the layouts match up. The number 8 button on our phone is the second one from the bottom of the middle row. Once you’ve found it, cut the metal foil from it with a box cutter.


This will expose a copper ring with a copper circle in the middle of it. We need to solder a wire to each of them without crossing them.



If you screw the next step up, then the phone will be ruined and you’ll have to buy another.

Don’t worry, it’s not that hard. But you’ll probably want to practice on a circuit board before proceeding.

TIP: You can buy circuit boards like this from Radio Shack for $5. They also sell wire, solder and soldering irons.

diy-photo 4-3

Once you can solder wires this close without having the solder touch, you’re ready to move on to the real deal.


Step 6.

With a soldering iron, place a small amount of solder on the tip of a wire.


Don’t go overboard. This much will do.


Now solder the wire to the copper circle in the middle of the copper ring. The solder can not touch the gold ring around it or the button will be ruined. This is why you practiced first;)


Step 7.

Repeat the same steps with another wire, this time soldering it to the outer ring. Again, make sure the ring stays separated from the circle.


Step 8.

Test your soldering by touching the two wires together. The phone should work normally as if you were pressing the number 8 key on the keypad. If you screwed it up, nothing will happen.

photo 4 copy 3

Step 9.

Use the box cutter to cut the number 8 from the keypad.


Step 10.

Thread the two wires through the keypad and then reassemble the phone.


Once the phone is assembled, drip glue from a hot glue gun into the hole to keep the wires secure.


Step 11.

Now, take a strip of aluminum foil and fold it over the end of one of the wires.

photo 2 copy 7

Using your fingers, bend the end of the wire back onto itself.


Wrap the aluminum foil around the wire to secure the fitting.


Use a clothespin to clamp the end of the wire as shown.


Fold the aluminum foil over the top of the clothespin and secure it into place with the hot glue gun.


Secure the wire onto the body of the clothespin with hot glue.

photo 2 copy 8

Step 12.

Repeat these steps with the other wire and fasten it to the other half of the clothespin.


Step 13.

Braid the two wires together by twirling the clothespin.


Step 14.

Fasten the clothespin to the back of the phone with hot glue.


And your tripwire is complete!

How to set up and activate your tripwire :

The clothespin holds the number 8 key down on the phone, and so you need to separate the two halves with a thin piece of paper. Receipts work great for this.

photo 5 copy 2

When the paper is removed, the contacts on the clothespin touch and the phone will speed dial your number.



You’re probably going to need to exit out of the door that you’re booby trapping—I mean trip wiring—and so you’ll need to set it up like this:

Tape your trip wire device to the wall and drape the string over the doorknob.


Run the string under the door and make sure to give yourself enough slack to get outside.


Once you’re outside, it will look like this.


Slowly close the door while pulling the string under the door toward you. Don’t pull it tight, but remove all the slack until you feel it tugging against the doorknob on the other side.


Just before you shut the door, tape the string to the threshold.


Now cut it and shut the door.


photo-2-1-300x225You won’t be able to see it because you’ll be outside, but this is what your beautiful craftsmanship will look like from the inside.




About Alex Miklovic

Alex is a writer and music producer by day—woodworker and amateur gadget hacker by night. When these high-stress, monochromatic professional constructs overwhelm him, he disappears for days on end, leaving no trace but a slew of high quality tutorials on various blogs around the internet.


3 thoughts on “$10 DIY Alarm System That Calls Your Cellphone | Home Security Systems

  1. how do you connect the red trip wire to the piece of paper or clothespin to remove the piece of paper? How is the piece of paper removed? I might try using a small piece of cardboard, and put a hole in it to run the red trip wire thru it maybe?
    Cool idea tho! especially if you want to put it where you have no electrical access…

    1. the string is taped to the paper. when pulled it pulls the paper out of the close pin and the two leads are then in contact with one another thus making the phone dial 8.

  2. thanks notto…best to have some good tape I think…Altho I think my idea using cardboard and putting a small hole to run the wire thru it is more reliable maybe.

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