Week -2

1.Aim:-This challenge to make a Simulink model of doorbell using a solenoid block and make another Simulink model where a thermistor

will be used to sense the temperature of a heater & turn it on turn it off the fan.

Theory:-

Doorbell 

             A doorbell is a signalling device typically placed near a door to a building's entrance. When a visitor presses a button the bell ring 

inside a building, alerting the occupant to the presence of the visitor. The heart of a doorbell is an electromagnet. Electromagnets are coils 

of wire wrapped around a small piece of magnetic metal. when electricity passes through the wire, it creates a magnetic fields around the wire.

when you press a doorbell button, you complete an electrical circuit that allows household electricity to flow through the doorbell's internal

electromagnet. The magnetic field generated by the electromagnet is then used to power a mechanism that create the doorbell sound.

Doorbells are low-voltages devices. This means they require relatively little energy to operate. An important part of a doorbell mechanism is the

transformer. converts regular 120-volt household current to the lower voltage required by the doorbell.

Solenoid:- 

A solenoid is a 3-dimensional structure of wire. When this wire is wrapped around a metallic block in a coil and electricity is passed through it, it

has some special magnetic properties. Electromagnetic induction makes it an electromagnet that can be switched on or off. The side in which the 

current appears to be passing clockwise is the south pole, and the side in which the current appears to be passing clockwise is the south pole, and 

the side in which the current seems to be passing anticlockwise is the Northern pole. The solenoid works just like a bar magnet and therefore has

many uses. This principle is used to create valves, among other things. Where the solenoid operates an electric switch, it is a relay.

The fig attached the doorbell model is the presentation of "A doorbell operated on solenoid". In this model, some blocks are used to make the working model of the doorbell. These blocks are:

1.Pulse generator: The pulse generetor block generates square wave pulses at regular itervals. The block waveform parameters, amplitudes, pulse width, period, and phase delay, determine the shape of the output waveform.

2.Simulink-PS Converter:-Converts the Unitless simulink input signal to a physical signal.

3.Scope:-Display signals generator during simulation.

4.Switch:-Switch controlled by an external physical signal.

5.Battery:-The battery block represents a simple battery model.

6.Solenoid:-Model electrical characterictics and generated force of solenoid.

7.Ideal translational Motion Sensor:-It is a motion sensor in a mechanical translation systems.

8.PS-simulink convertor:-It converts physical converts physical signal into simulink output signal.

9.Mechanical Translational Referances:-Referance connection for for mechanical translational ports.

10.Scope:-It displays signals generator in simulation.

Model Explanation:-

. (In below dia.)

2.After that, the input signal is converted into physical form with the use of "Simulink-PS convertor" and further send to the  switch of the electrical circuit.

3.The electrical circuit consist of a solenoid, a battery, and a switch. One end of the solenoid is connected to the battery and its other ends is connected to the switch. An electrical refferance is provided in electrical circuit.

4.The mechanical Part of the solenoid is connected to an ideal translation motion sensor and mechanical translational referance.

5.The P-Port of the sensor makes a connection with the "PS-simulink Convertor" to provide the output in signal form. Further, the converter is connected with the scope to display our output signal.

6.A solver configuration is connected to an electrical circuit to solve all parameters before the beginning of the simulation.

                                                 Signal input in doorbell

Output:-

Here we can see that the switch is closed for 2 Seconds and after that switch is open. Amplitude=0 means the Switch is closed.It can also be seen that 

the plunger strikes after every 2 Seconds.

The motion of the plunger was simulated and recorded and plotted in scope. 

                                              Fig.Output of doorbell model

2. Aim:-

A thermistor is a resistance thermometer or a resistor whose resistance is dependent on temperature.

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

Theory:-A thermistor defined as a type of resistor whose electrical resistance varies with temperature changes. Although all resistor's registance will fluctuate slightly with temperature,

a thermistor is particularly sensitive to temperature changes.

Thermistor act as a passive component in a circuit. They are an accurate, cheap, and robust way to measure temperature. While thermistors do not work well in extremely hot or cold 

temperature. While thermistor do not work well in extremely hot or cold temperatures, they are the sensor choice for many different applications.

The attached fig show the represent thermistor connection which sense the temperature of a heater and passes the signal to a switch where a thresold limit is already set. If the temperature

is above or equal to the threshold limit, it gives "1" as output which is "switch on". If the temperature is below the threshold limit, then it will give "0" As output which means "switch off".The 

input signal is generator with the help of a "signal builder" block This signal is created according to the conditions given in this challange. This conditions are as following.

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.

Here the temperature is converted in kelvin from degree celcuis because the signal converter doen not take °C value as input.

I also have to set the signal unit as "kelvin" in Simulink-Ps convertor.

The formula for conversion: 1 °C=273.15 K

The signal is:

From 0-10 Sec -Temperature is 293.15K

From 10-30 Sec -Temperature is 300.15K

From 30-50 sec- Temperature is 296.15K 

 MOdel Explation:

1. At first, the signa I is created in "Signal Builder" and furth er passes to "SimuIink-PS Converter" to convert the input sign ol into the physics I signal.
2. This physical sign ol is connected to a block "Controlled Temperature Source". This block is connected to the thermistor and a "Thermal Reference"
3. The thermistor is a port of an electric circuit where a battery, a voltage sensor, a resistor connected pa ra llel to the voltage sensor, an electrics I reference are connected to make a complete circ A solver configuration is connected to that electrics I circuit to solve all pa rameters before the beginning of the simulation.
4. The voltage sensor senses the temperature in the fo rm of voltage and sends the data to its port "V". From this port, e get ouf OUtput and send it to thoo different "PS-5imulink Converter".

From converter l, the signa I is sent to the threshold switch. In the switch, the threshold limit is set to 1.lO555e

2. !f the temperature is above or equal to the threshold I imit, then it gives "J" as ou tput which is "Switch On". If the ten perature is belo e the threshold limit, then it will give "0" as output which means "Switch Off". The input signal is generated ith the her p of a "Signal Builder" block (See Fig 9).

The switch is connected to the scope    here we can see our outp ut plot.

From converter 2, it converts the physical signal into a Simulink signal and sends the voltage data from the Voltage Sensor to display. This display gives us the threshold va lue of voltage. This value is set in the switch.

Output:

It can be seen that the value of the signa I is "0" from 0 - l0 sec beca use in this time the temperature was 20°C whic h is below 25°C means "Switch off the fan". After that, the signa I value gives "I" as output from 10 - 30 sec because in this time the temperature was 27°C which is above 35°C means "Switch on the fan". The value of the signal is again goes to "0" from 30 - 50 sec becau se in this time the temperature was 23°C which is below 25°C means "switch off the fan".

Now it is clear that our model is correct and fulfills aII the input conditions.