Week -2

Section - A

Aim: To make a Simulink model of Doorbell using solenoid block.

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.

Solution:

Theory:

Solenoid:

• A Solenoid is a Three-Dimensional structure of wire which is wrapped around a metallic block in a coil.
• When current is passed through it, the coil shows some special properties of Electromagnetic induction, which makes it an Electromagnet that can be switched ON or OFF.
• The side in which the current appears to be passing clockwise is the South Pole and the side in which currnet seems to be passing Anti-clockwise is the North Pole.
• The Solenoid works same as like a Bar Magnet and it has many uses.

Fig.[a] Construction of Solenoid

Doorbell:

• The Doorbell is a device having both mechanical and electrical components which produces sound by pressing a switch.
• When the switch is pressed, the circuit loop is complete, which causes the current starts flowing in the circuit, while passing through the solenoid, it generates the electromagnet at desired space which allows the plunger's movement due to which it hits the bell and sound is produced.

Fig.[b] Construction of Doorbell

Input:

Fig.[c] Simulink Model of Doorbell using Solenoid Block.

Simulink Model Description:

• Pulse Generator: This block generates square wave pulses at regular intervals. The input parameters are amplitude, pulse width, period and phase delay, which determines the shape of the output waveform.

Fig.[d] Pulse Generator.

• Battery Source: It gives the power to the closed loop.
• PS-Simulink Converter: It converts physical signal into simulink signal.
• Electrical reference: It shows an electrical connection to the ground.
• Mechanical Translational References: This block is used as reference connection for mechanical translational parts.
• Soleniod: Electrical charcteristics and generated force of solenoid.
• Switch: Switch controlled by an external physical signal.
• Simulink-PS Conerter: It convetrs Simulink input signal into a physical signal.
• Ideal Translational Motion Sensor: It is a motion sensor in mechanical translational system.
• Scope block: It displays output signals generated during simulation.

Input Waveform:

Fig.[e] Input waveform.

Output Waveform:

Fig.[f] Output waveform.

Result:

• From the output results we can conclude that, when the switch is closed, electromagnet receives electrical power from the battery and pulls the metal arm to hit the bell which produces sound.
• The motion of plunger was simulated, recorded and plotted by using an ideal motion sensor and scope.

Section - B

Aim: To use a thermistor to sense the temperature of a heater.

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.

Solution:

Theory:

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 up of metallic oxides, pressed into a bead, disc or cylindrical shape and then encapsulated with an impermeable material such as an epoxy or glass.
• Thermistors are easy to use, expensive, sturdy and respond predictably to changes in temperature. While they do not work well with excessively hot or cold temperature, they are the sensor of choice for applications that measure temperature at the desired base point. They are ideal when very precise temperature are required.

Fig.[A] Different forms of construction of thermistors.

Temperature Range:

The approximate overall range of temperatures in which a sensor type can be used. Within a given temperature range, some sensors work more efficient than others.

Input:

Fig.[B] Simulink model for Fan controlled by a thermistor.

Simulink Model Desciption:

• Initialy, we have to convert the temperature degree Celcius into Kelvin (K).

Sr.No. At Position Time (second) Temp.(Kelvin)

1 At point 1 0 second 293 K

2 At point 2 10 second 293 K

3 At point 3 10 second 300 K

4 At point 4 30 second 300 K

5 At point 5 30 second 296 K

6 At point 6 50 second 296 K

• Signal Builder block is used to input the values as per given conditions.

Fig.[C] Signal Builder Block.

Controlled Temperature Source:

The Controlled Temperature Block represents an ideal source of energy that is powerfil enough to maintain specified temperature difference across the source regardless of the haet flow consumed by the system. Connections A and B are thermal conserving ports corresponding to the source Inlet and Outlet respectively. Port S is a physical signal port through which the control sigal that drives the source is applied.

Thermistor:

A thermistor is a type of resistor whose resistance is dependent on temperature more than standard resistors. The Thermistor block represents an NTC thermistor using the B-parameter equation.

NTC- Negative Temperature Coefficient.

Resistor:

The Resistor block models a linear resistor described with the following equation:

V=I * R Where,

V-Voltage.

I-Current.

R-Resistance

Voltage Sensor:

The Voltage Sensor block represents an ideal voltage sensor, a device that converts voltage measured between two points of an electrical circuit into a physical signal proportional to the voltage.

Voltage Source:

The Voltage Source block implements a voltage source with DC, AC, and noise components.

Electrical Reference:

The Electrical Reference block represents an electrical ground. Electrical conserving ports of all the directly connected blocks to the ground must be connected to an ElectricalReference block. A model with electrical elements must contain at least one Electrical Reference block.

Input Waveform:

Fig.[D] Input waveform.

Output Waveform:

Fig.[E] Output waveform

Result:

• Thus, a thermistor is used to sense the temperature of a heater & turn on or turn off the fan as per the conditions (Fan conditions: ON if the temperature above 25 "C. OFF otherwise).
• Therefore the fan conditions are executed by Switch block and plotted.