In the some building is need to using good security. For some example is using this design circuit. The door knock alarm is a simple design for the simple security for the house. This circuit is based by sensor piezoelectric wafer for detected the alarm. This is the figure of the circuit.
Operation of the circuit is the resistor R5 determines the knock sound sensitivity. The value shown should work in most cases. The box could be hard mounted to the door or suspended at about the middle of the door, by a string from the top of the door in such a way that the box rests against the door. It is suggested that the circuit be housed in a plastic box with a 9v battery holder.
Operation of the circuit is the resistor R5 determines the knock sound sensitivity. The value shown should work in most cases. The box could be hard mounted to the door or suspended at about the middle of the door, by a string from the top of the door in such a way that the box rests against the door. It is suggested that the circuit be housed in a plastic box with a 9v battery holder.
