Week -2

Aim - To make a simulink model of doorbell using solenoid block and use a thermistor to sense the temperature of a heater and turn on or turn off the fan.

Objective - To make a simulink model of doorbell using solenoid block with the following details-

• Create a situation where the switch is closed for 2 seconds and then released. Observe the physical movement of the plunger.

use a thermistor to sense the temperature of a heater and turn on or turn off the fan as per the below conditions

• Temperature source: 20 °C from 0 to 10 seconds, 27 °C from 10 to 30 seconds, 23 °C from 30 to 50 seconds

  Fan conditions: ON if the temperature above 25 °C, OFF otherwise

A) Doorbell - when the switch is closed the electromagnet receives electrical power from the battery and pulls the metal arm to hit the bell producing sound.

The most widely used form is the interrupter bell, which is a mechanical bell that produces a continuous sound when current is applied. The bell which is often in the shape of a cup or half-sphere, is struck by a spring-loaded arm ith a metal ball on the end called a clapper actuated by an electro-magnet In its rest position the clapper is held away from the bell a short distance by its springy arm. When the switch is closed an electric current passes from the battery through the winding of the electromagnet. It creates a magnetic field that attracts the iron arm of the clapper pulling it over to give the bell a tap. This opens a pair of electrical contacts attached to the clapper arm, interrupting the current to the electromagnet. The magnetic field of the electromagnet collapses, and the clapper springs away from the bell. This closes the contacts again, allowing the current to flow to the electromagnet again, so the magnet pulls the clapper over to strike the bell again. This cycle repeats rapidly, many times per second, resulting in a continuous ringing.

Model -

Output -

this pulse generator generate a pulse of amplitude 1 for a duration of 4 sec with 50% pulse width . phase delay is 2 sec.

Position signal-

it's position signal in which after 2 sec the circuit is closed and the doorbell rings. because of the spring stiffness the plunger oscillated for about half a second which is damping effect.

Velocity signal -

Thermistor - A thermistor was first discovered michael farraday in 1833 on a silver sulfide which showed a behaviour of decrease in resistance when temperature increased .

A thermistor is a semiconductor that has a resistance capacity more than a conducting material and less than insulating material . its electrical resistance varies with the change in the temperature or thermally sensitive resistor. there are mainly two types of thermistors namely the negative temperature coefficient (NTC) and the Positive Temperature coefficient (PTC).

Model-

Output-

here we have taken the threshold value for switch is 0.012.

RESULTS-

here 0-10s the switch is off than the input value is 0 than 10-30s the value is 1 it means the switch is on. after that it shows the velue is 0 hence the switch is off.

result -

Conclusion- the output results have been successfully achieved . the fan is on when temp is 25 degree celcius which is in between 10-30 sec.