How to make a homemade door alarm.

Three Links for house alarm

http://www.ehow.com/how_4793072_homemade-alarm-system.html#ixzz1jj7NU9s2

This video entails how to make a homemade house alarm. This video gives very bland instructions on how to make one. However it shows simple instructions on how to make one. The things youll need is
4 pieces of insulated wire to connect a circuit. You will need 1.5 volt electric alarm or buzzer to produce the sound. you will need 1.5 volt battery yo give it power. A Wooden alligator-clip or clothes pin to stabalize everything. Also lastly Scissors, Cardboard strip Pin, 3-feet of string,1 piece of plywood at least 4-inches-by-12-inches and Electrical tape or glue.

http://science.howstuffworks.com/innovation/science-questions/touch-sensitive-lamp.htm

This is a heat sensored light that would alarm you when someone comes close. Sensors 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 certainly 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. Over the years, many different properties of the human body have been used to flip touch-sensitive switches.The human body is generally warmer than the surrounding air. Many things such as elevators 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.

http://www.geeksaresexy.net/2008/03/03/how-to-create-your-own-laser-home-alarm-system-for-under-20/

The total cost of this project is about $20. This thing will not warn the cops when burglars break into your home. However it will probably send them into panic mode. This will make anyone heart pump. Hopefully this will make them run away.To make this alarm you will need 2 small project boxes. You will need 1 1000uF 35v Capacitor. You will need 1 5K Variable Resistor. You will a Photocell and IC Board. You will need a 9v battery and clip to power up the alarm. Aso for the sound  you will need a 12v DC Piezo Siren - 102dB and toggle switch.

Three videos for house alarm

http://www.howcast.com/videos/1130-How-To-Make-a-Trip-Wire-Alarm

http:/www.youtube.com/watch?v=iUPz0hXpDI4&ctbm=vid&ei=FCwYT6TlL4_btwfA1OyQCw&usg=AFQjCNFC5f7O8c1EwhNrbSiUMndhEoLr6g&sig2=NsF1xfkKw8nVgi2GNz5pDA

http:/www.youtube.com/watch?v=3pRO5Kf55PI&ctbm=vid&ei=FCwYT6TlL4_btwfA1OyQCw&usg=AFQjCNGzTi93dUlcfkU5Y2sGtFQP9Z9oIw&sig2=Brmgtt81EtNuS5A2t72_eg