Simulation for a Doorbell using Solenoid and a Thermistor Controlled Fan

AIM : Make a simulation for a Doorbell and a Thermistor Controlled Fan.

OBJECTIVES :

• Make a Simulink model of a doorbell using a solenoid and observe the movement of the plunger when the switched is closed for 2 secs and then released.
• 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.

TASK 1 :

Model Diagram:

• The following is a simplified representation of a Door-Bell.

Simulink Block Diagram :

• The following is the required Simulink Block Diagram of the Door-Bell. And each element is explained in detail in the following steps.

• A Pulse Generator is used to achieve the automatic switching mechanism for the SPST Switch , where its, closing ON for 2 seconds and released. We can see the graph from the scope linked to the Pulse generator.

• The SPST Switch has a threshold of 0.5. And it is linked to the Battery and the electric part of the Solenoid. In order to make the switch close, the external control signal (vT) generated by the pulse generator should be greater than the threshold of the switch.

• A Solenoid is a device comprised of a coil of wire, the housing and a moveable plunger (armature). When an electrical current is introduced, a magnetic field forms around the coil which draws the plunger in. The moments of the plunger can be seen graphically from a scope linked to an Ideal Translational Motion Sensor.

OUTPUT :

• The following is the output plot of the pulse generator. We can observe that, the signal is turned on for every 2 sec. Alternatively, it’s in OFF mode for 2 sec. Thus, we achieved the required input.

• The following is the output plot for the displacement of the plunger of the solenoid. The ripples at the beginning and the ending of the pulse signals are due to the electrical interference. Thus, the moments of the plunger are been observed.

TASK 2:

Simulink Block Diagram:

• The following the required Simulink block diagram for Turning ON or OFF the Fan, where a thermistor is used to sense the temperature of the heat source in-turn triggering to Turn ON or OFF the Fan. The details of the elements in the Simulink model are explained in the further steps.

• The following is the Signal Builder Plot, where our required Temperature points are achieved. The Temperature source are set to the following conditions:
  • For Time Set “ 0 to 10 “ seconds, the Temperature is “293.15K”
  • For Time Set “10 to 30” seconds, the Temperature is “300.15K”
  • For Time Set “30 to 50” seconds, the Temperature is “296.15K”

• The Simulink-PS converter converts the Simulink signals to a physical signal. As Signal Builder is a complex block unlike a constant block, we’re required to let more derivatives to be achieved. For this, the Filtering and Derivatives parameter of the Simulink-PS block is set to “Filter input, derivatives calculated” option. Otherwise, there will be an error in the output.

• After trial and errors, the Threshold of the Switch required to achieve the expected output is been noted as “0.01191”. “1” represents ON and “0” represents OFF of the switch.

OUTPUT :

• The following is the output of the Simulink Model. We can observe that, the signal reaches the TURN ON mode from the Time Range 10 to 30. This output is similar to the input given in the Signal Builder. Thus, our simulation is correct and required output is achieved.