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This is my fourth instructable. It is on how you can make an alarm without any expensive equipment. It takes very short to set up too.

materials

wire
bar magnet(s)
reed switch
tape
paper
battery with holder
buzzer
door
Intruders:)





result
 

Step 1: Step One: Battery

attach the battery/holder to the wall with tape (see pic) attach wires flowing downwards.

Step 2: Step Two: Attaching the Reed Switch

attach the reed switch to the hanging wire from the battery close but not touching the door

Step 3: Step Three: Bar Magnet Trigger

when a reed switch comes close to a magnet both parts attract causing them to come together and continue the flow of electricity. Attach the magnet with tape to the inner part of the door so it can swing.

Step 4: Step Four: Attaching the Buzzer

add a wire flowing from the other side of the reed switch. This should then go to the buzzer. The attach an other wire flowing up (see red wire)

Step 5: Finishing Touchings

attach the final two wires so that the circuit is complete now when the bar magnet comes close to the reed switch it will buzz. To make a disarmer put a piece of tape under the magnet and reed switch (see pic). Now you can put a piece of thick paper between the magnet and reed switch from the outside and be able to walk in without it going of. You may have to adjust it to your desire. Thanks for viewing my instructable!  
<p>Hey!! Thanks for this instructable! But i want this alarm system portable like we can pu t it in a purse or on a cycle. can you give me some idea about that? :)</p>
<p>thanks^^</p>
Hey, I have a question. In your picture the bar magnets were put on the door and get taped in it, so when the door open, the bar magnets get touch with reed switch or what? <br>Thank you. Sorry for my bad english
then you just have to top that prank!
lol thats awesome
Cool. reed-switches are the best.
thanks

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Bio: [ALL INSTRUCTABLES MADE WHEN 12 YEARS OLD, DO NOT JUDGE, NEW ACCOUNT "Neon_Bible"] I love to play sports like basketball because Im a baller :). I ... More »
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