I'm thinking about building a security system with multiple (2-3) webcams and some lights with a few sensors around. The idea is that in the event of an incident detection, the lights are turned on (if at night) and streams from the cameras recorded to a flash memory of some description, maybe compact flash.
Webcams are preferred because they're dirt cheap but do require drivers to get the images.
I don't want to be reinventing anything as it's not aimed to be any sort of commercial product just for maybe a few friends/family so overall cost is not too much an issue but
Compact flash is probably a poor choice - they are generally small (you can get bigger devices, but they are disproportionately expensive). A small flash SSD will give more value for money, and let you store a lot more. A small hard disk could also be a good choice - if you are only making a couple of non-commercial systems, you could use second-hand drives to save money.
I think your budget here is a bit too optimistic.
Look up a project called "motion" for Linux - it tracks the input from cameras and activates recording or alarms when motion is detected.
But what about cable length ? With USB I see a problem there because normally you would have several cameras at different sides of the building. Ethernet and WLAN would be easier but of course more expensive.
My particular application only requires a small area to be covered so even with 3 cameras I could get them all within 3 or 4 metres of the central controller. It is an issue though if I wanted to expand the system.
If you opt for RS170(-ish) cameras (composite video out), you can purchase one of the ubiquitous "4 channel camera" cards for a few dollars, use a surplus PC, install the equally ubiquitous (Windows?) application that:
- monitors the 4 cameras
- allows you to define "motion regions" in the image streams
- signals an alarm when motion is detected
- begins recording video (to whatever medium you have on PC)
- exports live video feeds via web interface (assume PC has NIC) etc.
Your total out of pocket would be defined by the cost of the cameras you select.
The downside is cabling costs/hassle. (also, frame rate will vary with the horsepower you have available -- but even a *few* frames a second is usually enough for this sort of application).
You might also consider adding audio to your implementation.
I'm finishing up the design of a low cost "mote" that would allow a USB camera (or a variety of other things) to be hung on a PoE/wireless drop for exactly this sort of application (with "local intelligence" instead of just pushing bytes down a wire). However, that would require *more* work on your part (the boards are *really* small)
I will try to locate the camera card and software that I mentioned (but I am traveling so don't have easy access to the resources I would normally have :< )
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