Week -2

Simulink challenge 2

Doorbell using solenoid

Objective

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.

Working of a doorbell

The heart of a doorbell is an electromagnet. Electromagnets are coils of wire wrapped around a small piece of magnetic metal. When electricity passes through the wire, it creates a magnetic field around the wire.

When you press a doorbell button, you complete an electrical circuit that allows household electricity to flow through the doorbell's internal electromagnet. The magnetic field generated by the electromagnet is then used to power a mechanism that creates the doorbell sound.

Solenoid

A solenoid is a type of electromagnet, the purpose of which is to generate a controlled magnetic field through a coil wound into a tightly packed helix. The coil can be arranged to produce a uniform magnetic field in a volume of space when an electric current is passed through it. The term solenoid was coined in 1823 by André-Marie Ampère to designate a helical coil.

Simulink diagram

Pulse generator

Pulse generator is used to generate a pulse of 2seconds by using following parameters

This creates a signal of

Solenoid is used as an electromagnet which converts electric current to mechanical motion

Switch is used to complete the circuit

Battery provides power supply

Ideal mechanical translational motion sensor is used to measure the displacement of the solenoid spring.

Scopes and displays are used to display the output signal

Output

Simulink challenge 2

Thermistor fan model

Objective

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’

Thermistor

A thermistor is a resistance thermometer, or a resistor whose resistance is dependent on temperature. The term is a combination of “thermal” and “resistor”. It is made of metallic oxides, pressed into a bead, disk, or cylindrical shape and then encapsulated with an impermeable material such as epoxy or glass.

There are two types of thermistors: Negative Temperature Coefficient (NTC) and Positive Temperature Coefficient (PTC). With an NTC thermistor, when the temperature increases, resistance decreases. Conversely, when temperature decreases, resistance increases. This type of thermistor is used the most.

Simulink model

Blocks used

Signal builder – used to create input Simulink signal

Controlled temperature source

This block represents an ideal energy source in a thermal network that can maintain a controlled temperature difference regardless of the heat flow rate. The temperature difference is set by the physical signal port S. A positive temperature difference causes the temperature at port B to be greater than the temperature at port A.

Thermistor

This block represents an NTC thermistor using the B-parameter equation.

Resistor

This is used to create a potential difference.

Voltage sensor

Used to measure the potential difference across the resistor

Switch

The physical signal from voltage sensor is converted to Simulink signal and the connected to a switch.

The voltage for temperature of 298.15K (25C) is calculated and is 0.01196V

This is used as threshold value for the switch.

If V>threshold then switch is ON unless switch is OFF.

Observations

Input signal

Voltage sensor signal

Output signal