How Does A Calling Bell Work?

The first machine that works for us is an electrical door bell. It is a simple machine used in our day to day life that fills excitement for guests for us to open the door to know whom are going to meet.

Many times people are most unaware of the simplest things, like in this case of a door bell. If we question ourselves, how many of us have ever taken a moment out to think about how a door bell works. Though we often use this electrical machine every day, we are ignorant about understanding things.   

 In this post let us learn about how this device works for us.

Science of simplicity at its best we can say when we look at this simple machine’s   actually fascinating basic principle of electromagnetism that works in an innovative way.

Working Principle

The most important part is its magnetic motor. The magnetic motor constitutes a conventional electromagnet. An electromagnet is an arrangement of a coil of wire  wrapped around magnetic material which produces magnetic field when electricity is passed through the coil.  , The higher the amplification of magnetic field required, higher should be the coiling of the wire. This magnetic field produces an immense effect on any magnetic substance when brought into its magnetic field. It means when an iron object is placed in this magnetic field, it will be attracted towards the magnetic field due to polar orientation generated by the electromagnetism.

Process

The electrical circuit is closed  when the door bell button is pressed, which leads to the flowing of electric current through the electromagnet.

This current of 120 V, when passed through a transformer   is turned into usable 10 V current. The current then passes through the electromagnetic wire winding. A magnetic field is generated as a result, which is used to drive a sound making mechanism.

Different kinds of noises require different types of sound making mechanisms. The three main types of sound making mechanisms are as follows:

1.     Buzzer

It is the simplest kind of door bell mechanism. In a buzzer, the two ends of the winding are connected to the electrical circuit that work with the help of an electromagnet. The electrical circuit is directly connected at one end of the winding while the other end of the wire is connected to a metal contact placed adjacent to a moving contact arm which is a light thin metal arm whose one end rests against the contact point and the other end is anchored and connected to the electrical circuit.

When the door bell button is pressed, the electrical circuits closes and results in the generation of an electromagnetic field. The magnetic field attracts the iron bar, which pulls the contact arm away from the metal contact. The moving away of the contact arm breaks the circuit and thus turns off the electromagnet. The contact arm snaps back to its original position. This closes the electrical circuit and reestablishes the flow of electrical current through the circuit. Once again the magnetic field is generated and the process repeats itself.

The sound is generated due to the contact arm hitting rapidly to the magnet and the stationary contact, several times in a second.

2.     Bell

The bell also runs on the same principle with the only difference that the moving arm is connected to a clapper which rests against a circular metal plate. The process takes place in the same way as in Buzzer, with the arm moving back and forth and the clapper hitting the bell repeatedly.

3                Chime

The chime door bell uses a solenoid to generate the noise. Solenoid is anelectromagnet with wire winding and a small metal piston inside it. The piston is attached to a spring assembly inside the wire winding. When electric current flows through the wire,electromagnetic field is generated which pulls the metal piston towards it. The metal piston hits the tone bar located on both the sides of the arrangement. When the door bell button is released, the spring snaps the piston back to its original position and the piston hits the tone bar on the other side of the arrangement. The two tone bars are made and arranged in such a way that the hitting action produces a ding-dong sound.