Week -2

Question1

Aim

To make a Simulink model of Doorbell

Introduction

figure 1

An inductor is a passive electronic component which is capable of storing electrical energy in the form of magnetic energy. Basically, it uses a conductor that is wound into a coil, and when electricity flows into the coil this will generate a magnetic field.

The magnetic field is produced when the switch is closed and pulls the plunger towards the mechanical part and once the switch is opened the plunger moves to its intial position.

Blocks used

Pulse Generator

The Pulse Generator block generates square wave pulses at regular intervals. The block waveform parameters, Amplitude, Pulse Width, Period, and Phase delay, determine the shape of the output waveform. The following diagram shows how each parameter affects the waveform.

Scope

Display signals generated during simulation

Solenoid block

The Solenoid block represents the electrical characteristics and generated force for the solenoid.

Ideal Translational Motion Sensor

The Ideal Translational Motion Sensor block represents a device that converts an across variable measured between two mechanical translational nodes into a control signal proportional to velocity or position.

Mechanical Translational Reference

The Mechanical Translational Reference block represents a reference point, or frame, for all mechanical translational ports. All translational ports that are rigidly clamped to the frame (ground) must be connected to a Mechanical Translational Reference block.

Solver Configuration

Each physical network represented by a connected Simscape™ block diagram requires solver settings information for simulation. The Solver Configuration block specifies the solver parameters that your model needs before you can begin simulation.

Electrical Reference block

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

Simulink-PS Converter

The Simulink-PS Converter block converts the input Simulink signal into a physical signal. Use this block to connect Simulink sources or other Simulink blocks to the inputs of a Simscap physical network.

working of the simulink model

Simulink block

1) Pulse generator is used to generate the wave as per the requirement which is show in the table below

Generation of the wave

By generating the wave as shown above we can Create a situation where the switch is closed for 2 seconds and then released.

2) When switch is closed the current flows from the source (battery).

3) As the current flows over the coil it generates the magentic field

4) The magentic field produced pulls the pulnger towards the bell

Result

The plot shows the position of plunger

for 0-2secs the switch is in off condition

for 2-4secs the plunger is negavtive and indicates that it is towards the bell

and the Oscillation of the plunger can be reduced by increasing the damping value as show in the tabel below

Plot after increasing the damping value

Question 2

Aim

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

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.

Introduction

A thermistor is a thermal resistor - a resistor that changes its resistance with temperature.

There are two kinds of of thermistors, NTC (negative temperature coefficient) and PTC (positive temperature coefficient). In general, you will see NTC sensors used for temperature measurement. PTC's are often used as resettable fuses.

NTC Thermistor - When the temperature of a thermistor increases, its resistance decreases significantly. Typically, for every 1^oC rise in temperature, there will be a 5% decrease in their resistance. So their sensitivity is very high.

PTC thermistors- When a current flows through a PTC the heat generated raises the temperature of the PTC. When the temperature of a thermistor increases, its resistance increases.

NTC 10D-13 explained below

Blocks used

Signal Builder

The Signal Builder block allows you to create interchangeable groups of piecewise linear signal sources and use them in a model.

Controlled Temperature Source

The Controlled Temperature Source block represents an ideal source of thermal energy that is powerful enough to maintain specified temperature difference across the source regardless of the heat flow consumed by the system.

Thermistor

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

Thermal Reference

The Thermal Reference block represents a thermal reference point, that is, a point with an absolute zero temperature, with respect to which all the temperatures in the system are determined.

Resistor

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

where:

working of the simulink model

1) The input signal is given as shown below which represents 20 °C from 0 to 10 seconds, 27 °C from 10 to 30 seconds and 23 °C from 30 to 50 seconds.

all the values are converted to kelvin as all the thermal blocks are in kelvin by default.

2) The resistance of NTC thermistor will decrease as the temperature increases.

3)Resistance is connected in series with the thermistor to know the evaluate threshold voltage and also to keep the circuit in balanced way when there is sudden change in the temperature.

4)once the threshold voltage is know for 25 degree Celsius the threshold value can be mentioned in the switch.

5)switch open's if the threshold value is equal too or greater than the mentioned value

6)The signal passes to the controlled voltage source where it maintance an ideal voltage source that is powerful enough to maintain the specified voltage at its output regardless of the current passing through it.

7) The fan runs when the temperature is above 25 degree Celsius

Error encountered

Solution for the error

changing the filter and derivatives to filter input and derivatives calulated

Result

output from the switch

time vs swith open/close

If the threshold value is equal to or greater than 0.01196 then the switch opens in the below plot the switch opens between 10 to 30 secs as the incoming signal value is greater than threshold value.

output of voltage sensor

voltage vs time

The current is directly proportional to the voltage and inversely proportional to the resistance. This means that increasing the voltage will cause the current to increase, while increasing the resistance will cause the current to decrease.

The above statement we can related it with the above graph, when the temperature increases the resistance decreases and there will be increase in current and voltage which is visible in graph above.

output of the fan

rpm vs time

from the above graph we can see that the fan is turned on between 10 to 30 secs when the temperature is above 25 degree celsius.