I want to build a little fun "security system" for a couple doors in the house just to try stuff ive been learning. I have a board all wired that trips an alarm when a door is opened, but im having trouble finding an actual wireless sensor. The doors are too far apart to be running wires all over my house.
I would like something really simple what will transmit either a high or low signal to my board depending on the status of the door. Im having a bit of trouble find one online. Thanks for all the help or input in advance.

 

There are commercial wireless door chimes such as the first two models (19208 and 19209) here:

http://www.jascoproducts.com/products/pc/viewCategories.asp?idCategory=34

The 19208 can be found for about $15.

This type of home product usually operates at 433MHz.

 

No doubt, you will have to do some modifications to make the door chimes work and the signal range may not fix your requirements.

I suppose if you have already built one unit that works for one door, you could always just build another for the second door!

 

you can buy a wireless doorbell. place the sending battery-powered push-button so that the toor will momentarilly activate it.

 

At radioshack they have a 38kHz IR sensor and they also have a high power IR transmitter LED. You could get a 555 timer and set the frequency to 38kHz which would drive the IR emitter LED. Place the emitter and detector across from each other very close to the door. Whenever the door opened the detector wouldn't receive a signal because the door would be in the way and then you could activate the the bell. Not sure if this would be something you could do for your application but its a nifty little circuit and it introduces you to IR transmission which is fun stuff.