Simulink-Doorbell and Automatic fan

Objective

1. To create a simulink model of solenid operated doorbell

2. Automatic DC motor fan operated based on room temperature using thermistor

1.SOLENOID OPERATED DOORBELL

schematic diagrtam of the doorbell

simulink model

Working

when the switch is closed the plunger moves which inturn pulls the metal arm to hit the bell producing the desired sound.

Switch on/off conditions are given as a pulse signal

Translational sensors are used to trace the position of the plunger

Simulation study is done under different damping values suchas 0 N/(m/s), 1 N/(m/s) , 10 N/(m/s)

Input signal (switch on and off conditions)-using pulse generator

solenoid properties:

solenoid with an airgap of 5mm

Result: study the plunder position in solenoid under differrent damping coefficient of plunger spring.

For damping = 0 N/(m/s) - imaginary because no such system exists in real life

change damping to 0 under mechanical section in solenoid block properties

For damping = 1 N/(m/s)

below graph shows the plunger position

For damping = 10 N/(m/s)

below graph shows the plunger position

Inference:

1.when the switch is truned on for 2 secs , plunger moves to close the air gap of 5mm

2.And when the switch is turned off, plunger returns to the original position without any oscillation when the damping value is high but if the damping value is low it undergoes several oscillations before coming to the original position.

2.THERMISTOR BASED AUTOMATIC FAN:

Simulink model:

Working:

1. A NTC thermistor is used to sense the temperature change. In a NTC thermistor if the temperatue increases the resistance decreases

2.A referance Resistor is used in series with the thermistor so as to measure the voltage drop change as temperature changes

3.Voltage sensor placed across the reference reistor sense voltage and it is given to a logic circuit which based on the fan turn on/off criteria provided ( here fan shouls turn on if temp>25'C) operates the dc motor switch.

4.Rotational sensor placed in motor measures the fan operating velocity

INPUT: Sample temperature conditions given as signal

Result:

1.voltage change across thermistor and reference Resistor

since a NTC thermistor is used as temperature increases resistance across the thermistor decreases, so the voltage drop across the thermistor aslo decreases.

As a result voltage drop across the Reference resistor increases with increase in temperature.

2. Switch on/off and Fan motor on/off

when the temperature increases above 25 degree celcius( 298 k) switch is closed else open i.e., Fan is on when the temperature is above 298K.

above graph representing the angular velocity of the dc fan motor shows that fan is running only when the temperature is above 298K.

Conclusion:

A simulink model for a solenoid operated electric bell and a thermistor controlled automatic fan is created and studied.