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.

 Soln.

        Simulink model for the above given arrangement is as shown  bellow

And the bellow graph showing position of the plunger in response with the switch operation (ON/OFF), (simulink file is attached)

2. Use 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

 Ans.

      Block diagram for the given system requirements is as bellow.

• Controlling the Switch to On/Off position using voltage drop across the 1000 ohms resistor  in series with a thermistor and a DC voltage source of 100V DC .
• In this case for an input temarature of 25degC resulting in a voltage drop of 50 across the resisotr, which is used to control the switch.
• The switch output is set to constatnt 100 which is activating the controlled voltage source to run the DC motor.
• An Ideal motion sensor is connected to the motor to sense the angular velocity and displacement.
• Gain blocks are used to convert rad/s to RPM and rad to Rev.
• Finally the scope observing the provided input is bellow.

 

From the above graph its visible that

• The fan is started to run at 10Sec and taken 2-3 sec to accelerate to full speed,
• then continuously run till temarature fall bellow 25degC (i.e 30sec) then at 30sec ,
• when the temparature falling bellow 25degC, the switch cut iff the supply and fan deceleraed in 2-3 sec to zero velocity.

Simulink files are attached.