Week -2

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

Procedure:

1: Firstly, we need a DC voltage source and Electrical switch for operation. The electrical switch has three ports, 2 ports are connected to the positive and negative terminals and the third port is for the input to the switch. The third port accepts the PS signal, so a Simulink to PS converter is used to provide input from the Simulink environment by a pulse generator.

2: Pulse generator input is conditioned to close the switch every 2 seconds.

3:A solenoid block is connected to the battery and switch terminals of the circuit with electrical reference and solver configuration. Since at the backend, a lot of equations are used to compile the operation, we define the solver configuration for compiling Simscape blocks.

4: With the help of an ideal translation motion sensor, we measure the input of the solenoid by connecting the p and c ports of the solenoid to the sensor. A mechanical translational reference is used to ground the mechanical ports.

5: The plunger position is displayed using the scope by converting the physical output into the Simulink environment.

When the switch is closed for 2 seconds, the coil is energized and a magnetic field is created around it, resulting in the movement of the plunger.

When is switch is open, the coil demagnetizes and the plunger resets back to its original position.

This can be examined in the output graph of the plunger.

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

conditions:

The Thermistor is a thermal resistor whose resistance is dependent on the temperature it experiences. The NTC (negative temperature coefficient) type of thermistor is used in this analysis. The NTC thermistor resistance decreases with an increase in temperature.

The Thermistor-controlled fan is a model that works in a way that when the temperature of the thermistor is above a certain value, then the fan is automatically turned on. When the temperature across the thermistor is high the resistance decreases and thus the voltage from the battery used up by the thermistor is less, thus with the voltage divider principle the voltage across the sample resistor with fixed voltage is in series with the thermistor experiences high voltage.

The temperature signals are given with help of a signal builder as per the requirement (20 degrees c 0-10s, 27 degrees c 10-30s, 23 degrees c 30-50s, and additionally 25 degrees c 50-80s). The input signal is given to the controlled temperature source block, which maintains a controlled temperature difference regardless of the heat flow.

The controlled temperature source the temperature to the thermistor, which is connected to the battery and a sample resistor with a fixed voltage in series. A voltage sensor is connected in parallel to the sample resistor. The whole circuitry is grounded with electrical reference and a solver configuration is specified for the operation.

According to the condition provided, the fan should turn on when the temperature across the thermistor is above 25 degrees c. The voltage across the resistor at this temperature is determined, and it is the threshold voltage (0.01199v) to turn ON the fan.

The voltage across the resistor is fed to the switch, which acts like an if conditional statement. The switch has two optional points where if the given voltage is greater than the threshold then the condition is true, operation 1 is followed, or else no operation. A lamp from the dashboard is connected to the switch, when the condition is true, the lamp turns green indicating the fan is turned on, or turns red indicating the fan is turned off.

The output of the switch allows voltage to pass through the DC motor with help of a controlled voltage source. The rotational movement of the fan (DC motor) is sensed by an ideal rotational motion sensor, and speed and the angular displacement of the fan are observed using a scope.

The images of the fan's angular displacement and angular velocity show clearly that the fan is turned at two instances when the temperature is 27 degrees c from 10-the 30s, and again it is turned on when the temperature is 26 degrees c from 50-80s.

The fan's angular velocity at these two-time instances is 1450 rad/s which is 231 revolutions per second. Thus, when the temperature is above 25 degrees c the fan is turned ON automatically rotating with the speed of 231 rps.