How can I build a simple alarm that would make noise when a door is opened?

http://www.radioshack.com/category.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F006%5F002%5F004%5F000&Page=1

radioshack has it all, but in my opinion they have become less technical and more "user freindly" and in my opinion that is a bad thing. I want to be able to walk in and say "im looking for a 470ohms resistor" and i would like them to say "rightover there sir" not "uuuh... what do you mean? like a cell phone?"

but thats just my opinion, sorry for getting off topic...

You want simple?

This is simple...

You will need:

• A 9v battery
  
• The loudest 9v buzzer you can find
  
• A few old wires
  
• A push switch to make it 31137
  
• (Some tin foil)
  
• Universal bonding tape (sticky tape will also work)
  

Connect a bit of wire to the -tive termial of the battery
Connect a bit of wire between the +tive battery terminal and one of the buzzer terminals.
Connect another piece of wire from the other buzzer terminal to the push switch.
A third piece of wire to the free termainal of the switch
Place large flat pieces of tin foil to the ends of the free pieces of wire
Selotape once piece of the bits of tin foil to the door.
Position the other piece so that it touches the first piece when the door opens.

Flick the switch and hey presto... Youve got a high quality alarm!

im not quite sure that quality is the word you are looking for jo662 why not just tie a string to the doornob and the other end to your finger
anyway radio shack is a very reliable source. I am sure you would be appreciative of any help so try jo662's idea then go to radioshack if nessesary.

I sence that you have very intrusive and nosey parents nimlars, the best way to defeat that is watchfullness, and social engeneering when you get caught doing whatever it is that you dont want them to know about. Anyway good luck and keep an ear out!

im not worried about my parents, they are easy to hear around the house and can't catch me. My dad thinks he knows more about computers than me because he knows what the history folder is. I want the alarm because my brother would like it for his room, and it seems like a fun thing to get away from school with.

I think I got it figured out, thanks for the help. BTW zok, I want to make it, not just buy it.