Auto Door Bell
A door bell that automatically rings when visitors arrive. It works as auto-door-bell for guests and warning/alert for unautorized persons/thiefs. A lots of burglar-alarm circuit based design works on beam-break technology, where an IR beam when blocked creates the alarm signal. The problem with this design is, the bell rings when the guest enters and also when they leave; creating a lot of confusion to the unware family members. The design I made relies in two IR beams (actually just two IR sensors), and based on the chronlogical sequence of thier interruption, the circuit identifies whether the person is leaving or entering. The bell rings only when visitors enter the house and not when they leave. A separate beep sound is generated when visitors leave; just for confirmation.