Week -2

Aim:-1) To make a Simulink model of Doorbell using Solenoid block, Where the switch is closed for 2 sec and observe the physical movement of Plunger.

Solenoid is a device which consist of coil of wire which is tightly wounded , A movable plunger . When the electric current flows through it , The coils are excited and it acts like a magnet dur to which there is movement of plunger in linear direction. In other way it converts electric energy into mechanical energy.

Following fig shows the arrangement of simulink model of doorbell using solenoid block.

Details of blocks which has been used in above model are as follows

• Pulse generator It is used to give a input of Square wave with all control parameter such as width, frequency and phase dalay.
• Simulink ps converter It convert simulink input signals into physical signals .
• Switch It is used to make circuit on or off .
• Scope It is used to observe the pattern of waveform in input or output side .
• Battery It has been used to given as power source . It could be Ac or DC supply .
• Electrical reference It is used to make electric circuit as ground
• Solenoid It is device which excited by electrical power and perform mechanical work. (with the help of plunger )
• Ideal translational motor sensor that converts an across variable measured between 2 mechanical translational junction into a control signal proportional to velocity and position.
• Mech Translational reference It is used to ground the mechanical cicuit.
• Solver configuration It define solver configuration used by sensor .
• Display It has been used to display the output result .
• Ps simulink convertor It has been used to convert the mechanical signal into simulink signal .

In pulse generator following changes has been made to work a model accordingly to required condition , Time period has been kept as 4 sec . Whereas pulse width kept as 50%, and phase delay has been given of 2 sec to obtain required result

The following graph shows the change in input square wave pulse when the following changes are made .

Observation:- The following graph shows the movement of plunger when as specified time the bell rungs.

Aim 2 :- Use the Thermistor to sense the temperature of heater and turn on or off as per the given conditions.
temperature source : 20 degree C from 0 to 10 sec , 27 degree C from 10 to 30 sec , 23 degree C from 30 to 50 sec
Fan conditions :- ON if the temperature above 25 degree C , OFF otherwise .

Solution:- Thermistor is a type of resistor in which the electric resistance varies with the change in temp , likely all resistor shows fluctuation slightly with temperature , But thermistor is particularly sensitive to temperature change

Use of Thermistor mainly thermistor is used to measure the thermal conductivity of electric material

It has been used in household appliances like Microwave , fridge , oven .

Basically thermistor can be classified into 2 type

1) Negative temperature coefficient (NTC) thermistor

2) Positive temperature coefficient (PTC) thermistor

1) Negative temperature coefficient :- It is a type of thermistor in which when the temperature rises then the resistance decreases , And when the resistance increases temperature decreases . There has been inverse relation between temperature and resistor .

2) Positive temperature coefficient :- In positive temperature coefficient there has been direct relation between temperature and resistance , with the rise in temperature there has been rise in resistance , And with the rise in resistance there has been rise in temperature . The best example of Positive temperature coefficient is fuse . Mostly circuit protection device are of positive temperature coefficient .

following simulink model represent the heater using thermistor

Details of block which has been used in model are as follows :-

• Repeating sequence stair it gives a repetitive signals to the circuit , Here some modification has to be made an entered the value of signal according to the give condition of temperature in kelvin as [293 300 300 296 296]

• Simulink ps converter it has been used to convert simulink signal into Physical signal i.e thermal signal ,
• Scope has been attached to the output of repeating sequence stair block to observe its pattern .
• controlled temperature source This block represents an ideal energy source in a thermal network that can maintain a controlled temperature difference .
• Thermal reference it act as ground to the thermal frame.
• solver function It Defines solver settings that use for simulation .
• Thermistor It is a type of resistor in which its value changes which the change in temperature.
• Voltage sensor It is, a device that converts voltage measured between any electrical connections into a physical signal proportional to the voltage.
• Electric reference it is used to provide ground connection to the electric circuit.
• PS-simulink converter It has been used to convert the physical signal into simulink signal.
• switch it has been used to tun on of off the circuit whenever temperature crocess the threshold value .
• lamp is used to observe the indication whenever temperature crocess the threshold value its colour changes .scope has been used to observe output result constant block has been used as 0,1 to make either turn on or off the switch .

following graph show the variation of pulse of temperature with respect to time in sec.

That is for temp 20degree for 0 to 10 sec , for temp 27degree for 10 to 30 sec and at 23 degree for 30 to 50 sec .

Output:-

Thus the output graph of Fan shows that when the temperature is 293 K that is 20 degree for first 10 sec, which is less than 25 degree the Fan remain in OFF state but when the temperature reaches at 300 k that is 27 degree the Fan became in ON state , And it continues to be in ON state for next 20 sec . Again at 30 th sec as the temperature become 296 k i.e 23 which is less than 25 degree again FAN be in OFF state .

Result:- Thus we have studied that switching Of heater using thermistor can be turn ON or OFF state can be controlled with this model .