Door Alarm(Links)

Sensitivity of Alarm
http://science.howstuffworks.com/innovation/science-questions/touch-sensitive-lamp.htm
This article talks about switches that are sensitive to human touch, as opposed to switches that must be flipped or pushed to make and break a mechanical connection have been around for many years. They have advantages, and the most important is the fact that dirt and moisture cannot get into the switch to gum it up or damage it. The human body is generally warmer than the surrounding air. Many elevators therefore use buttons that are sensitive to the warmth of the human finger. These buttons, of course, don't work if you have cold hands. The motion-sensitive lamps you see on people's patios also sense the heat of the human body. The human body, being made mostly of water, conducts electricity fairly well. By placing two contacts very close together, your finger can close the circuit when you touch it.

Burglar Alarm
http://www.reachoutmichigan.org/funexperiments/agesubject/lessons/burglar.html

This website talks about how to use a switch, a battery, and a buzzer switch to construct a home made door alarm. It tells you the steps to make each part. One section has steps for the buzzer. Another section has steps for the battery and circuitry. Another section has steps for using the switch. The article states that a 1.5 volt battery is requitered. A kite string is needed as well. You will probably need scissors too. They strongly recommend electrical tape. You can buy a 1.5 V buzzer from stores like radioshack. You also need super glue, and need to use it super fast because it can stick to you. It also requires a scrap piece of board or plywood.  

 

Door Alarm

http://www.wikihow.com/Make-a-Door-Alarm

This site was the most simple and easy to understand. First you have to place the battery and buzzer on the wood. Tape them down with electrical tape. Second wrap the ends of the clothes pin with bare, non-insulated wire. Third Connect one of the free ends of wire around the clothes pin to a wire coming from the battery. Fourth connect the wire around the clothes pin to the buzzer. Fifth connect the remaining free wire from the battery to the buzzer. Test the switch by opening and closing the clothes pin. When the clothes pin is closed, the buzzer should turn on. If not, check the wiring again. Place a piece of cardboard or other insulative material in the clothes pin to separate the wires so that the buzzer does not go off anymore when it closes. Glue the clothes pin to the wood, as seen in the picture. Attach the string to the piece of cardboard between the close pin things. Attach the other end of the string to your door. Place the alarm so that the string is taut between the alarm and the door. When the door opens, the string should pull the cardboard out, setting off the alarm.