Week -2

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

Ans1:

Abstract: In this Simulink model, we are using the Flemings right-hand thumb rule to demonstrate the movement of the plunger using a solenoid. To clearly see the direction of the plunger we are switching the supply using a PS switch model in the Simulink.

Design: We have designed the model using majorly 4 components which are the battery source, switch, solenoid, and motion sensor. The battery is connected to the PS switch, where the PS switch is turned on and turned off by providing the pulse to it from a pulse generator. the pulse generator is set to 2 secs off and 2 secs on the switching period. this switch is then connected to the solenoid coil. Attaching the solenoid coil is the plunger. the plunger is connected to the motion sensor, the output of which is given to the scope.

Working: When the switch is off there is no supply to the solenoid coil. But when the switch is turned on the solenoid coil is energized and due to this, there is a force acting on the plunger as per the Flemings right-hand thumb rule. The motion sensor recognizes the movement and the same is reflected in the scope. Now, the switch is kept off for 2 secs and then again is turned on and the plunger again experiences the same force in the same direction. These movements are shown in the scope.

Results: From the scope, it is very clear that there are oscillations found when the coil is energized. It also depends on the damping coefficient of the plunger. Less the damping more are the vibrations seen in the scope.

In this way, we can demonstrate the DOorbell simulation using a solenoid coil and a plunger.

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

Ans2:

Abstract: In this Simulink model we are using a thermister to sense the change in temperature. As the temperature changes, the value of resistance also changes. If the temperature is above 25 deg cel, then the FAN will turn ON, if not beyond that then the FANs will be OFF.

Design: We have designed this model using majorly 7 components which are a signal builder, a controlled temperature source, a thermistor, a battery, a resistor, and a switch. The signal builder block demonstrates the different temperature levels as defined in the question. These temperatures are sensed by a temperature sensor which is nothing but a thermistor. However, the signal furnished by the signal builder is not a temperature source, therefore we used a controlled temperature source as an input to the thermistor. Now the thermistor can sense the change in the temperature over different periods of time. A 24 V battery is connected to the thermistor and a 16-ohm resistor is used as a load. To measure the voltage across the resistor, a voltmeter is used. The output of that voltmeter is given to a three-way switch. The output of this switch is connected to an indicator lamp.

Working: The signal builder represents the temperature source for the thermistor. As per the given question, the temperature range is different for the different time periods. The circuit is simple, it has a battery, a thermistor, and a resistor. As we know as the temperature varies the value of the thermister also varies and hence, the value of voltage across the load resistor will vary. this change in voltage is observed by a voltmeter. For 25 deg cel temperature, the value of voltage coming is 1.068 V, and hence we are taking this value as a reference. The value of voltage above 1.068 V signifies that the temperature has gone beyond the 25 deg cel mark and the FAN needs to be turned ON. So to give the signal to the FAN to turn ON we are using a 3-way switch in which we have set a threshold of 1.068 V. If the value goes beyond that the switch will give "1" as an output else "0". The indication lamp used to represent the on and off position of the FAN is customized according to that, i.e. if 1 it will show a green indication and if 0 it will show a red indication.

Results: It is observed that for the time period between 10 secs to 30 secs the lamp glows in green color which indicates that the FAN is turned on. For the rest of the time, the lamp indicates red color which means the FAN is off.

ALL THE NECESSARY DOCUMENTS ARE ATTACHED HEREWITH