How to make a door alarm?

Answer 1

there are a few different ones you can make, depends on your exact needs. some are below in the source

Answer 2

Equipment:
9 volt battery, wire, cardboard, aluminum foil, cellophane tape, and a small electric buzzer

Method:

Cut a piece of cardboard about one and a half inches by four inches and fold lightly in half.
Tape strips of foil around the cardboard.
Tape a clip wire to each of the pieces of foil.
Join the wires in a circuit with the battery and the buzzer.
Set up the burglar alarm near a door so that anyone coming through the door will step on the cardboard and set off the buzzer.
How it works:
When the two pieces of foil are pressed together, the circuit is completed and the electricity can flow. The flow of electricity through the electric buzzer causes it to make noise.

Some ideas to try:
Replace the buzzer with a light emitting diode. Connect the positive (+) side of the diode to the cardboard switch, orÖ Connect a resistor in the circuit between the battery and the buzzer to change the sound.

Electrical engineers keep track of three quantities when they design circuits:

voltage
current
power
Voltage is electrical pressure or force. Symbolized by "V", it is measure in volts. Current is the flow of electrons passing a given point. Symbolized by the letter "l," it is measured in amperes. Power is the work performed by a current. Symbolized by the letter "P," it is measured in watts.

We generate voltage by using batteries, generators and solar cells. We get current by placing voltages across things such as buzzers, lights, resistors and other interesting devices. Using voltage to make things happen is the purpose of electronics.

Ohms Law is the relationship between voltage, current, resistance and power.
V= l x R and P = l x V.

You could read this site too, this one had diagrams so I couldn't copy paste without you missing out on alot.
http://www.reachoutmichigan.org/funexperiments/agesubject/lessons/burglar.html

I hope that I helped!

Answer 3

We got robbed once. The robber broke the lock on the door and we couldn't get it fixed until the next day. This is what the police officer who filed our report recommended as a makeshift alarm: Fill a big pot with a bunch of silverware. Balance the pot on a piece of wood wedged against the door to hold it closed. It would be impossible to open the door without creating a huge racket.

Answer 4

First you need a trigger that will be tripped when the door is opened. A magnetic switch with the magnet on the door is good. Connect the switch to a buzzer, horn, etc.

Answer 5

You'll need some string and a bell. Tie the bell to the door using the string. Voilá!

Answer 6

The easiest is a hammer over a door.
Open: boom.
A bucket with water will do as well.
In that case: flush!
More expensive: a dog or a goose.
Th

Answer 7

its very easy,, string and 5 empty cans ,, horaaa,, just married now