Motion Sensor Schematic

Where can you find a diagram for the proposed security system at home using 8051 and some temp sensors as smoke detector sensor motion detector magnetic sensor with a keyboard and LCD screen?

I do not know why you want to build a unit around an old 8051, so all the sensors to tell you about the production a "pair of potential free contacts. So it will be all on the keyboard interface and LCD.

You will surely find many schemes out there that 8051 has an LCD screen and keyboard.