Week -2

AIM:- 1. To make Simulink model for a doorbell using solenoid block.

2. To use Thermistor to sense temperature of a heater and turn on/ off the fan.

1.Doorbell—

Blocks used in Doorbell-

1. Switch
2. Pulse generator
3. Scope
4. Solenoid
5. Battery
6. Ideal translational motor sensor
7. Mechanical translational reference.
8. Electrical Reference
9. Switch

First we provide signal to the solenoid block for 10 seconds, through pulse generator block also we can customize the signal using it. Here an Ideal Translational motion sensor is used to observe the equivalent plunger movement

Output of Scope:-

output from customized pulse generator, switch closed in circuit 10 sec time.

Scope block for Ideal translational motion sensor

Here we can clearly observe that when solenoid generate electro-magnetic field as circuit closed, the plunger instantly magnetised. After 10 sec it come to original position with some vibration.

Thermister model:-

Thermister:an electrical resistor whose resistance is greatly reduced by heating, used for measurement and control.

There are two types of thermistors. NTC (Negative Temperature Coefficient thermistors) and PTC ( Positive Temperature Coefficient thermistors). The difference is that NTC thermistors exhibit a DECREASE in resistance as body temperature increases, while PTC thermistors exhibit an INCREASE in resistance as body temperature increases.

temperature source: 20 degree celcius from 0 to 10 seconds, 27 degree celcius from 10 to 30 seconds, 23 degree celcius from 30 to 50 seconds.

fan conditions :- ON if the temperature above 25 degree celcius. OFF otherwise

Working:-

In this model signal builder block is used to get temperature Signal for the controlled temperature source. The temperature of heater is supplied to thermistor to sense it. Now in order to run the fan when temperature reaches the value of 298K we have to trigger the circuit with some external supply of battery and as there is no device to calculate the resistance value of thermistor so we have to attached another resister in parallel across the terminal. The voltage sensor is attached across the resistor to calculate the voltage Drop into it and this voltage drop value is input as threshold value to the switch to start the fan and it will go on when threshold value is more than 0.01195.

Input in Signal bulder:-

output signal:-

here zero indicate the fan is off