Question about motion sensor...

[14412104]

Currently I'm trying to get all the necessary components for my project, which is a CCTV surveillance system that will start capturing when it detects human presence, my questions are: wouldn't a fly flying pass the motion sensor still trigger it on? If not, why? Do motion sensors come with different ranges and sensitivities? If so, how can I figure out which type I need? Are there are better types of sensor I can use for my project to detect human presence? Any help would be appreciated, thanks a lot guys.

[southpaw]

You can detect motion thru software as apposed to a connected device . You can then set the threshold and the ideal area of the screen you wish to capture . I believe "motion" is a program you can use for this , possibly more options in software available nowadays .
You set the threshold and configure it to record and/or email you

[rpdom]

Install the package called "motion". This compares sequential frames from a camera (or other video source) and can trigger various events based on how many bits of the image has changed. It can be tuned to require different levels of change and to compensate for changes in light levels. It can record a sequence of still frames and start recording a short video sequence. It can also run commands, and be used as a webcam. It may take a bit of tweaking to get it working, but it is well worth it.

It works with any device that supports the V4L video driver, and as the official Pi Camera has a V4L driver it is ideal.