final year project

i´m thinking a security system that uses biometrics where for example by just touching the door Knob the system already recognises the owner and switches off the alarm

that is a good project.. well you can continue with your talk here itself. please do not create multiple posts.
Regards your project.. first you need do look for a "Biometric Module" like a thumb scanner. I think they are around 6000 to 8,000 INR. I am not sure. You can confirm from the market or some dealer.
Before that study the datasheet of that module so that will help you in selecting the right controller having the right interfacing for that module

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