SIMULINK MODEL OF A DOOR BELL

AIM:

To Make a Simulink model of Doorbell using solenoid block to create a situation where the switch is closed for 2 seconds and then released the physical movement of the plunger.

THEORY:

ELECTROMAGNET:

Electromagnets are non-permanent magnets that produce a magnetic field as long as an electric current passes through a coil. The magnetic field disappears when the current ceases.

The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be rapidly manipulated. By controlling the strength of the electric current, the magnetic field will have a wide range of values. However, a continuous supply of electrical energy is required to maintain the field in case of electromagnets.

In applications where a variable magnetic field is not required, permanent magnets are generally superior. Electromagnets are used in many situations where a rapidly- or easily-variable magnetic field is desired.

SOLENOID:

A solenoid is an electromagnet that converts electric energy into mechanical movement. When current is applied a magnetic field is generated in the coil which displaces the stell arm present inside it. The length of this movement is called stroke and the force of the stroke is measured in Newton (N).

SIMULINK MODEL:

Note that the circuit is made up of subcircuits blue circuit and green circuit.

Simulink automatically allocates blue color to any electrical circuit. Here we have a battery, solenoid, and a switch connected to a pulse generator present in the circuit.

The solenoid has a rated voltage of 50V and the rated current is 0.05A.

So we provide a controlled input of 45V through the battery and have the overall circuit resistance greater than 1550ohms by changing the closed resistance of the switch to ensure the current to the solenoid is well below the rated current.

We note that our total resistance of the circuit is 1550 ohms.

In order to activate the switch(that is initialized with a threshold of 0.5), we use a pulse generator with signal amplitude 1 and with a pulse width for a period of 2 seconds.

This input is in line with our requirement that the bell should ring for the first 2 seconds, hence we close the switch only for two seconds when the solenoid is energized and pulls the plunger towards the bell to slam it once that gives out a bell sound.

We sense the movement of the plunger via an ideal translational sensor connected to the plunger of the solenoid.

We calculated the displacement of the plunger to be 5.743849336033663e-04, hence this value was given as an initial displacement to the motion sensor so that we could ideally represent the 0 displacement as the contact value. Now the displacement of the plunger is shown via the below graph

The mechanical properties of the solenoid have been varied to ensure critical damping is at place.

`c_c=2 sqrt(k.m)`

using this formula we found that the critical damping coefficient to be 3.162. This damping has helped us to eliminate oscillations.

RESULT:

We have designed a circuit based on the stated requirement and have also demonstrated with the graph the working of the bell for a time span of 4 seconds.