Week -2

AIM - 1.To make a Simulink model of Doorbell using solenoid block.

2.Use a thermistor to sense the temperature of a heater & turn on or turn off the fan.

STUDY 1 -

The doorbell uses a solenoid switch such that when it is closed the circuit gets completed and the electricity is passed into the solenoid which creates a electromagnetic field due to which the plunger moves and hits the bell to produce the sound.

SIMULINK MODEL -

EXPLANATION -

The input signals given are period=4sec,pulse width=50%,phase delay=0,amplitude=1.The battery is connected to the solenoid via a switch and when the pulse generator produces an input signal it closes the switch and allows the current to pass through it.The plunger part of the solenoid is connected to the motion sensor to get the position of the plunger and also a mechanical translation reference is provided for the circuit.The scope is connected in order to view the output of the motion sensor.

RESULTS -

When the pulse generator amplitude is 0 the plunger is at the original position and when it is 1 ,there is movement in the plunger position.Because of the low damping value some oscillations are produced before getting to its original position.

STUDY 2 -

A thermistor is a resistance thermometer, or a resistor whose resistance is dependent on temperature. The term is a combination of “thermal” and “resistor”. It is made of metallic oxides, pressed into a bead, disk, or cylindrical shape and then encapsulated with an impermeable material such as epoxy or glass.There are two types of thermistors: Negative Temperature Coefficient (NTC) and Positive Temperature Coefficient (PTC). With an NTC thermistor, when the temperature increases, resistance decreases. Conversely, when temperature decreases, resistance increases. This type of thermistor is used the most.A PTC thermistor works a little differently. When temperature increases, the resistance increases, and when temperature decreases, resistance decreases. This type of thermistor is generally used as a fuse.Typically, a thermistor achieves high precision within a limited temperature range of about 50ºC around the target temperature. This range is dependent on the base resistance.

SIMULINK MODEL -

EXPLANATION -

The signal builder block was used to build a signal to achieve the given temperature source(20 °C from 0 to 10 seconds, 27 °C from 10 to 30 seconds, 23 °C from 30 to 50 seconds).Input signal from the sognal builder is then passed to the controlled temperature source which is connected to the temperature source.The temperrature source is connected to the thermistor and temperature sensor.A NTC type thermistor is used to sense the change in the temperature and also a reference resistor is connected in series to measure the voltage drop as the temperature changes.The Voltage sensor is used to measure the drop in the voltage and produce a output signal to switch ON/OFF the fan.

RESULTS -

CONCLUSION -

1.A simulink model for the doorbell using solenoid was created and the results were shown when there is change in amplitude.

2. Simulink model of Thermistor to sense the temperature of the heater to turn ON/OFF the fan and is observed that the fan operates only when the temperature is above 25 deg Celsius and is OFF when the temperature drops below 25 deg celsius.