Challenges

Week-2

1). Make a Simulink model of Doorbell using solenoid block with the following details:

In the above arrangement, when the switch is closed the electromagnet receives electrical power from the battery and pulls the metal arm to hit the bell producing sound.

Create a situation where the switch is closed for 2 seconds and then released. Observe the physical movement of the plunger.

Assume remaining parameters.

Ans).

The model has been created by Solenoid, DC Voltage Source and other supporting blocks as shown in fig.

Ideal Translational Motion sensor used to measure the plunger position and velocity and are showed by using scope block.

The results are shown in below fig. for two cases with varying the damper to get smooth movement in plunger. pulse generator is used to operate the swith for 2sec as per requirement

• Switch closed from 4 sec to 6 sec and then opened
• solenoid Air Stoke gap is 5mm and intially plunger is at 8mm far

damping coefficient = 5 N/(m/s)

• The plunger is oscillated at 6sec when swith opend because of poor daming adn it took little more time to come its intial position
• Also more swing in velocity and position of plunger as shown in figure.
• This can be avoid by providing proper damping to the system

damping coefficient = 8 N/(m/s)

• from the graph it is observed that the transition of plunger position is in smoother manner but got little bit delay to come rest positon/initial position as shown in figure.
• also velocity of plunger measured and showed in below graph

2). Use a thermistor to sense the temperature of a heater & turn on or turn off the fan as per 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

Ans). the model was built by Thermister to sense the temperature given by signal builder block through controlled temperature source and DC network used to sense the temperature variations and sensor output is used to controll the fan operating mode as shown in below figure...

at the end of simulation the fan operating conditon is OFF that can verify by Lamp colour i.e. green because of temperature 23 °C which is less than 25 °C

at 21.5 sec the lamp glows red means Fan is ON condition because of temperature is 27°C which is greater than 25°C as shown in below figure

the resulst are