Week -2

Fl+m¨x+λ˙x+kx=Fe

where F_e is the electromagnetic force, F_l is the load force, λ is the viscous damping term and m is the plunger mass. The electromagnetic force is related to the solenoid current and inductance by

where α and β are constants. Plugging the preceding equation into the equation for electromagnetic force gives the force-stroke relationship of the solenoid for a current i₀:

The Solenoid block solves for α and β by taking the two specified force and stroke measurements and substituting them into the preceding equation. It solves the resulting equations for α and β.

A positive current from the electrical + to - ports creates a negative force (i.e., a pulling force) from the mechanical C to R ports.

• For the second part:

The Thermistor block represents an NTC thermistor using the B-parameter equation. The resistance at temperature T is

where:

The following equation describes the thermal behavior of the block:

where:

OBJECTIVE - The objective is to simulate the model of doorbell using solenoid block and have to create a situation where the switch is closed of 2s and then released and have to observe the plunger movement.

• use a thermistor to sense the temperature of a heater and turn on and off the fan as per the following condition:

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

PROCEDURE - For the first part:

The solenoid is a electromagnet. on passing current through the conducting wires a magnetic field is generated around it which attracts magnetic materials. This phenomenon is used in the bell. when the switch of the bell is presssed the current passes through the circuit, exciting the electromagnet and pulling he plunger towards the metal portion. This produces ringing sound.

• First u need to get all the things that u require from the library browser such as solenoid, battery, ideal force sensor for the input pulse generator is used a switch and make the connections.
• The simulink model is mention below

• in the model the pulse generator is such that every 2 seconds its on

• The switch has a threhold of 0.5
• The parameter of the pulse generator is mentioned below

The switch is then connected to solenoid

For observing the position of the plunger the graph is mention below. The graph is between distance vs time

in the above graph we can see that when the plunger is away from c the postion is close to -0.0425mm and when it is near c the position is 0.

For the second part:

A thermistor is a resistance thermometer, or a resistor whose resistance is dependent on temperature. The word is a combination of thermal and resistor.

For this particular operation fisrt go to the library browser of simulink and get all the blocks that is required such as thermistor, Battery, resistor, voltage sensor, controlled temperature source, signal builder block,and a switch block.

here the signal builder block is used as a input. which is mentioned below

For time 0s to 10s the temperature is 293k

For time 10s to 30s the temperature is 300k

For time 30s to 50s the temperature is 296k

• Controlled temperature source represents source of thermal energy that can maintain a controlled temperature difference regardless of heat flow.
• A resistor is used to control the current from battery
• A voltage sensor will convert the voltage into physical signal
• Finally a solver configuration is used for solving the simulation.

Mentiones below is the graph for the signal builder

The overall model is mentioned below

In the figure above a switch block is used to maintain the condition that the fan needs to be on if the temperature is above 298k otherwise off.

The threshold of the switch is kept to 0.0115 which acts as 298k

RESULT :

Mentioned below is plot for the output of the operation

From the output it is clear that between 0s to 10s the fan is off because the temperature is below 298k

But in time interval between 10s to 30s the fan is on because the temperature is above 298k

again from time interval between 30s to 50s the fan is off due to same reason.

CONCLUSION - In the first part i have created the simulation of doorbell using solenoid block and got the positions of plunger as -0.0425 and 0 when the plunger is moved away from c and moved close to c respectively.

In the second part i have simulated the thermistor model to sense the temperature of heater and turned on and off the fan as per conditions and got the results displayed.