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Home Made Alarm Systems?
screwBrinks! asks: "I would like to begin a new project to do during those long and boring weekends. I thought about creating an alarm system in my apartment which would be connected to my computer. Then, if there is any intrusion, it would page me or phone me. I also want to be able to see a live report from the web and some other goodies. I have no problem doing the software part, but I don't have much experience with building hardware. Have any of you ever built such a system? If so, what would be your recommendation? I know much of this may already exist prebuilt, but I really would like to make as much of it as I can, for fun. I have no problem against using prebuilt infrared detectors, prebuilt door contacts, and the like as long as they aren't X-10 products."
I know somebody who did this recently. The results are very impressive, and he managed to do it all very cheaply.
First step was picking up a mini-security camera from the local electronics store. Cost $150AUD and is the size of a bottle cap. It's a CCD based camera with 12V input and standard TV composite output. It uses a pinhole instead of a lens to get the size so small. It's only black/white but it also picks up infrared! Auto-adjusting brightness. The picture quality is quite amazing.
Run a coaxial cable + 12V power cable (low amp wire) to the camera. The cable can be really long - this guy is running it over 20 metres. Plug the other end of the coaxial cable into a BT878 TV card on the PC. The TV card was $100AUD. The PC was $300AUD. You need at least a Celeron-2 processor. The 12V power supply is $20AUD pre-built from the electronics store.
Next, install Linux! You need the "motion" software package. It records MJPEG (?) but only records changing frames. It also puts a useful highlighted rectangle around the section of the frame that moved.
Finally (and I don't think he's done this step) you write a simple script to rsync the motion/MJPEG output directory to a remote server. You can use "stat" on the directory to determine if there are new frames: record the "modified" line, compare it on subsequent stat commands, any difference means there are new frames so call rsync! You could easily stick an email in there as well to alert somebody.
The setup is very impressive. The picture quality is simply incredible. Because the CCD camera detects IR you could even use it in the dark with some IR leds to illuminate the room with "invisible light". A number of people have shown interest in building their own after hearing/seeing about the original setup.