Week -2

Aim:- To make a simulink model of doorbell using solenoid block

and To sense the temperature of a heater and turn on or turn off the fan using thermistor

Question 1:-

Model of doorbell using solenoid block

Doorbell: A doorbell is a siginaling device which is placed near a door to building entrance.when a visitor press a button the bell rings inside the building alert the presence of vistor.this doorbells are low voltage devices.

When you press a doorbell button a 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 creates the doorbell sound.

Solenoid: A solenoid is a device comprised of a coil of wire, the housing and a moveable plunger.When an electrical current is introduced, a magnetic field forms around the coil which draws the plunger in. More simply, a solenoid converts electrical energy into mechanical work.

Simulink model for doorbell using solenoid:-

Blocks used in the above simulink:

1) Pluse generator : This block is used to generate square wave pulses at regular intervals.

2) switch: It is mainly used to controlled extrenal signal i.e on or off.

3) simulink-ps converter: It converters simulink input siginal into a physical signal.

4) Electrical reference: It is electrical ground connection

5)Solenoid: It indicates generated force of solenoid and electrical characteristics.

6) Battery: It gives power to the closed loop.

7) PS-simulink converter: It converts physical signal into simulink output.

8) Mechanical translational references: It is reference connection for mechincal translational ports act as ground for mechincal ports.

9) Ideal translational motion sensor: It is a motion sensor in mechincal trsnslation systems.

10)Scope: It always displays the siginals generated during simulation.

OUTPUT:

When spring constant is 20 N/m:

When spring constant is 200N/m:

• From the above graphs we obserrve that plunger is moved from its original position to some amplitude with time delay of 2 sec.
• Then it hit the bell and pause there for 2sec and comes to its initial position.

Question 2 : Using a thermistor to sense the temperature of a heater & turn on or turn off the fan as per the below conditions:

• 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

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

The thermistor works on the simple principle of change in resistance due to a change in temperature. When the ambient temperature changes the thermistor starts self-heating its elements. its resistance value is changed with respect to this change in temperature. This change depends on the type of thermistor used.

Simulink model for Thermistor:

Description:

• As per the given conditions for time and temperature assign the values to the repeating sequence as per our conditions. here the given conditions is converted into kelven.

• Simulink ps converter ,converts simulink signal into physical signal.
• then this signal is given to the controlled temperature source block which represents an ideal source of thermal energy to maintain specified temperature
• Then this signal is passed to the thermistor block which is connected to the battery and voltage sensor is connected to a resistor which is used to measure the volatge as threshold value.
• As per the condition given (fan) that ON if the temperature is above 25 c, OFF otherwise here we can use the switch to provide threshold value
• If the signal value is greater than the threshold value then it turn ON otherwise it will be turn OFF.

Threshold value:

Output:

Angular velocity:

• From the above graph we can observ that if the temperature is 20 deg,celcius(293k) the fan is off for first 10 sec.
• when the temperature is 25 deg celcius (300k) then the fan is off for next 20 sec.
• And when the temperature comes to 23 deg celcius (296k)fan gets off.

Conclusion:

• In the first part of the question we use a solenoid to convert electrical energy to mechanical and prepared a simulink model into a doorbell
• In the secound part of the question we use the thermistor to sense the tempearture based on the conditions given and we aslo added threshold value to the switch for turn on and turn off the fan.